Journal of Composites Science doi: 10.3390/jcs9080422

Authors: Giordano Pierozan Bernardes Matheus de Prá Andrade Matheus Poletto

Reinforcing PLA composites with natural fibres is a prominent strategy for improving PLA’s properties while benefiting from its intrinsic biodegradation. However, these composites may be susceptible to an inefficient stress-transferring process due to the weak intermolecular interactions between PLA and natural fibres. A well-known practice is to incorporate coupling agents to improve polymer–fibre adhesion, such as carboxylic acids (CAs) and grafted copolymers. CAs are a more affordable and biodegradable option for improving PLA/natural fibre interface strength, resulting in a material with superior mechanical and thermal properties. In this context, this research discusses the potential use of mono (C6 and C8) and di (CC6 and CC8) carboxylic acids as coupling agents in PLA/pecan nutshells (PN) composites. PLA/PN composites with four different CAs were processed in a twin-screw extruder and subsequently injection moulded. The results indicated an increase in the flexural strength of the PLA due to the presence of PN in the neat composite. The use of CAs increased the storage modulus of PLA/PN composites, while C6 and CC8 reduced the PLA composite tan δ peak height. The PLA’s Tg in PLA/PN composite shifted to lower temperatures after the incorporation of CAs while increasing the PLA crystallinity degree. These results strongly suggested that besides acting as efficient coupling agents, these acids also exerted roles as nucleating agents and plasticisers.

Journal of Composites Science doi: 10.3390/jcs9080421

Authors: Zimeng Guo Tianxiao He Yuqi Lou Guoxing Xu Qiong Jia

In this study, a pH-responsive molecularly imprinted polymer (MIP) drug carrier was developed utilizing boric acid-functionalized mesoporous silica nanoparticles (MSNs) as the substrate. The carrier was engineered for controlled drug release, with capecitabine (CAPE) being selected as the template molecule due to its structural characteristics and clinical relevance. In vitro drug release studies demonstrated the pH-responsive release behaviors of the fabricated carrier, highlighting its promising applicability in the controlled release of pharmaceutical compounds containing cis-diols, particularly for site-specific therapy where pH variations serve as physiological triggers.

Journal of Composites Science doi: 10.3390/jcs9080420

Authors: Imen Hamouda Masoud Tayefi Mostafa Eesaee Meysam Hassanipour Phuong Nguyen-Tri

This study examined the impact of storage and operational aging on the thermal stability, structural degradation, and electrical properties of styrene–butadiene rubber (SBR) compound by analyzing three distinct materials: a laboratory-stored sample, an operationally aged one, and an original unaged reference. Thermal degradation was analyzed through thermogravimetric analysis (TGA), which examined weight loss as a function of temperature and time at different heating rates. Results showed that the onset temperature and peak position in the 457 °C to 483 °C range remained stable. The activation energy (Ea) was determined using the Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman methods, with the original unaged sample’s (OUS) Ea averaging 203.7 kJ/mol, decreasing to 163.47 kJ/mol in the laboratory-stored sample (LSS), and increasing to 224.18 kJ/mol in the operationally aged sample (OAS). The Toop equation was applied to estimate the thermal degradation lifetime at a 50% conversion rate. Since the material had been exposed to electricity, the evolution of electrical conductivity was studied and found to have remained stable after storage at around 0.070 S/cm. However, after operational aging, it showed a considerable increase in conductivity, to 0.321 S/cm. Scanning Electron Microscopy (SEM) was employed to analyze microstructural degradation and chemical changes, providing insights into the impact of aging on thermal stability and electrical properties.

Journal of Composites Science doi: 10.3390/jcs9080419

Authors: Rafael González-Cuello Joaquín Hernández-Fernández Rodrigo Ortega-Toro

The growing interest in probiotic bacteria within the food industry is driven by their recognized health benefits for consumers. However, preserving their therapeutic viability and stability during gastrointestinal transit remains a formidable challenge. Hence, this research aimed to enhance the viability of Lactobacillus reuteri through microencapsulation using a binary polysaccharide mixture composed of low acyl gellan gum (LAG), high acyl gellan gum (HAG), and calcium for the microencapsulation of L. reuteri. To achieve this, the Box–Behnken design was applied, targeting the optimization of L. reuteri microencapsulated to withstand simulated gastrointestinal conditions. The microcapsules were crafted using the internal ionic gelation method, and optimization was performed using response surface methodology (RSM) based on the Box–Behnken design. The model demonstrated robust predictive power, with R2 values exceeding 95% and a lack of fit greater than p > 0.05. Under optimized conditions—0.88% (w/v) LAG, 0.43% (w/v) HAG, and 24.44 mM Ca—L. reuteri reached a viability of 97.43% following the encapsulation process. After 4 h of exposure to simulated gastric fluid (SGF) and intestinal fluid (SIF), the encapsulated cells maintained a viable count of 8.02 log CFU/mL. These promising results underscore the potential of biopolymer-based microcapsules, such as those containing LAG and HAG, as an innovative approach for safeguarding probiotics during gastrointestinal passage, paving the way for new probiotic-enriched food products.

Journal of Composites Science doi: 10.3390/jcs9080418

Authors: Tomislav Skrinjaric Kristina Gorseta Jelena Bagaric Petra Bucevic Bucevic Sojcic Jakov Stojanovic Luc A. M. Marks

Background. Physicomechanical properties and clinical service of bulk-fill composites depend on their adequate polymerization and depth of cure. Some manufacturers claim that these composites can be adequately cured when used in bulks exceeding 4 mm. Objective. The aim of this study was to compare Vickers microhardness (VMH) and depth of cure (DOC) of six contemporary bulk-fill resin composites at depths of 4 mm and 6 mm. Material and methods. Six bulk-fill composites were evaluated in this study: 1. Tetric EvoCeram Bulk (Ivoclar Vivadent, Schaan, Liechtenstein), (TEC); 2. Filtek Bulk Fill Posterior (3M ESPE Dental Products Division, St. Paul, MN, USA), (FBF); 3. Filtek One Bulk Fill (3M ESPE Dental Products Division, St. Paul, MN, USA, (FOB); 4. SonicFill 2 (Kerr, Orange, CA, USA), (SF2); 5. Admira Fusion X-tra (Voco, GmbH, Cuxhaven, Germany), (AFX); 6. GrandioSO X-tra (Voco, GmbH, Cuxhaven, Germany), (GSX). The 18 specimens (3 of each composite) were prepared in split Teflon moulds of 4 mm diameter and 6 mm thickness. All composites were cured in standard mode for 20 s using LED LCU (D-Light Duo, RF-Pharmaceuticals Sarl, Geneva, Switzerland; 1200–1300 mW/cm). The VMH was measured using a digital Micro Hardness Tester Shimadzu (HMV-2T E, Shimadzu Corporation, Kyoto, Japan). A 50 g (0.5 N) load force was applied for 30 s. Each specimen was measured at five places selected by chance at each level (N = 15). The hardness ratio or DOC was calculated for all samples as the ratio of bottom and surface microhardness at levels of 4 and 6 mm. Data were analysed using one-way ANOVA and Tukey’s post hoc test. Results. Significant reduction in VMH was observed for all tested materials when comparing top surface and bottom (p < 0.01). The highest VMH was obtained for GSX and AFX, and the lowest for TEC. The results show that the degree of polymerization was adequate for all tested materials at a depth of 6 mm, since the hardness ratio exceeded 0.80 in all cases. The hardness ratio at 4 mm was high for all tested composites ranging from 0.91 for TEC to 0.98 for GSX. All composites showed adequate DOC at the bottom of the 6 mm bulk samples. However, the hardness ratio was the highest for Admira Fusion X-tra (0.96) and GrandioSO X-tra (0.97). Conclusions. All tested materials showed a significant decrease in microhardness from the top surface to the bottom. The DOC was adequate for all bulk-fill composites at a depth of 6 mm cured under standard mode for 20 s. All bulk-fill resin composites evaluated in this study can be used in bulk, up to 6 mm.

Journal of Composites Science doi: 10.3390/jcs9080417

Authors: Nadarajah Vasanthan

Poly(trimethylene terephthalate) (PTT) is a thermoplastic polyester with a unique structure due to having three methylene groups in the glycol unit. PTT competes with poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) in carpets, textiles, and thermoplastic materials, primarily due to the development of economically efficient synthesis methods. PTT is widely utilized in textiles, carpets, and engineering plastics because of its advantageous properties, including quick-drying capabilities and wrinkle resistance. However, its low melting point, resistance to chemicals, and brittleness compared to PET, have limited its applications. To address some of these limitations for targeted applications, PTT nanocomposites incorporating clay, carbon nanotube, silica, and ZnO have been developed. The distribution of nanoparticles within the PTT matrix remains a significant challenge for its potential applications. Several techniques, including sol–gel blending, melt blending, in situ polymerization, and in situ forming methods have been developed to obtain better dispersion. This review discusses advancements in the synthesis of various PTT nanocomposites and the effects of nanoparticles on the isothermal and nonisothermal crystallization of PTT.

Journal of Composites Science doi: 10.3390/jcs9080416

Authors: Yan Zhou Weibo Liu Yu Feng Pengfei Shi Liqiang Wan Xufeng Hao Farong Huang Jianhua Qian Zuozhen Liu

To study the influence of curing agent structure on the properties of epoxy resin, four types of aromatic diamines with the structure of diphenyl methane (4,4′-methylenedianiline (MDA), 4,4′-methylenebis(2-ethylaniline) (MOEA), 4,4′-methylenebis(2-chloroaniline) (MOCA), and 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA)) and a high-performance epoxy resin, 3-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline (AFG-90MH), were used in this study. The resulting resin systems were designated as AFG-90MH-MDA, AFG-90MH-MOEA, AFG-90MH-MOCA, and AFG-90MH-MCDEA. After curing, these systems were named AFG-90MH-MDA-C, AFG-90MH-MOEA-C, AFG-90MH-MOCA-C, and AFG-90MH-MCDEA-C. The influence of the structure of the diamines on the processability, curing reaction activity, and thermal and mechanical properties (including flexural and tensile properties) of the epoxy resins were investigated. These systems demonstrate excellent processability with wide processing windows ranging from 30 °C to 110–160 °C while maintaining low viscosity. Consistent apparent activation energy (Ea) trends via both Kissinger and Flynn-Wall-Ozawa methods were observed. The epoxy systems exhibit the following increasing Ea sequence: AFG-90MH-MDA < AFG-90MH-MOEA < AFG-90MH-MOCA < AFG-90MH-MCDEA. The processability and curing reaction kinetic results indicate that the reactivities of the diamines decrease in the order: MDA > MOEA > MOCA > MCDEA. Polar chlorine substituents in diamines strengthen intermolecular interactions, thereby enhancing mechanical performance. The flexural strength of cured epoxy systems decreases as follows with corresponding values: AFG-90MH-MOCA-C (165 MPa) > AFG-90MH-MDA-C (158 MPa) > AFG-90MH-MCDEA-C (148 MPa) > AFG-90MH-MOEA-C (136 MPa). Diamines with substituents like chlorine or ethyl groups reduce the glass transition temperatures (Tg) of the cured resin systems. However, the cured resin systems with the diamines containing chlorine demonstrate superior thermal performance compared to those with ethyl groups. The cured epoxy systems exhibit the following descending glass transition temperature order with corresponding values: AFG-90MH-MDA-C (213 °C) > AFG-90MH-MOCA-C (190 °C) > AFG-90MH-MCDEA-C (183 °C) > AFG-90MH-MOEA-C (172 °C).

Journal of Composites Science doi: 10.3390/jcs9080415

Authors: Paschalina Terzopoulou Dimitris S. Achilias Evangelia C. Vouvoudi

Wood polymer composites (WPCs) represent a rapidly growing class of sustainable materials, formed by combining lignocellulosic fibers with thermoplastic or thermoset polymeric matrices. This review summarizes the state of the art in WPC development, emphasizing the use of recyclable (or recycled) and biodegradable polymers as matrix materials. The integration of waste wood particles into the production of WPCs addresses global environmental challenges, including plastic pollution and deforestation, by offering an alternative to conventional wood-based and petroleum-based products. Key topics covered in the review include raw material sources, fiber pre-treatments, compatibilizers, mechanical performance, water absorption behavior, thermal stability and end-use applications.

Journal of Composites Science doi: 10.3390/jcs9080413

Authors: Nataliya Alfimova Kseniya Levickaya Il’ya Buhtiyarov Ivan Nikulin Marina Kozhukhova Valeria Strokova

Phosphogypsum, a byproduct of orthophosphoric acid production, is one of the large-tonnage wastes. Since phosphogypsum mainly consists of CaSO4 2H2O, it can be considered as an alternative gypsum-bearing raw material in the production of gypsum binders. However, its features, such as particle morphology and the presence of impurities, can negatively affect the characteristics of phosphogypsum-based binders. Identification of these factors will allow us to develop methods for their minimization and increasing the efficiency of phosphogypsum use from the required source as a raw material for the production of phosphogypsum-based binders. In this regard, the manuscript contains a comprehensive and comparative analysis of phosphogypsum and natural gypsum, which makes it possible to establish their differences in chemical composition and structural and morphological features, which subsequently affect the properties of the phosphogypsum-based binder. It has been established that the key factor negatively affecting the strength of phosphogypsum-based paste (2.58 MPa) is its high water demand (0.89), which is due to the high values of the specific surface area of the particles and the presence of a large number of conglomerates with significant porosity in phosphogypsum. It has been suggested that preliminary grinding of phosphogypsum can help reduce the amount of water required to obtain fresh phosphogypsum-based paste with a standard consistency and improve its physical and mechanical properties.

Journal of Composites Science doi: 10.3390/jcs9080414

Authors: M. J. Mohammad Fikry Keisuke Iizuka Hayato Nakatani Satoru Yoneyama Vladimir Vinogradov Jun Koyanagi Shinji Ogihara

Carbon fiber-reinforced plastics (CFRPs) offer excellent in-plane mechanical performance, but their relatively low interlaminar fracture toughness makes them vulnerable to delamination, particularly around intralaminar discontinuities such as resin-rich regions or fiber gaps. This study investigates the effectiveness of polyamide (PA) mesh inserts in improving interlaminar toughness and suppressing delamination in CFRP laminates with such features. Two PA mesh configurations were evaluated: a fully embedded continuous layer and a 20 mm cut mesh strip placed between continuous and discontinuous plies near critical regions. Fracture toughness tests showed that PA mesh insertion improved interlaminar toughness approximately 2.4-fold compared to neat CFRP, primarily due to a mechanical interlocking mechanism that disrupts crack propagation and enhances energy dissipation. Uniaxial tensile tests with digital image correlation revealed that while initial matrix cracking occurred at similar stress levels, the stress at which complete delamination occurred was approximately 60% higher in specimens with a 20 mm mesh and up to 92% higher in specimens with fully embedded mesh. The fully embedded mesh provided consistent delamination resistance across the laminate, while the 20 mm insert localized strain redistribution and preserved global mechanical performance. These findings demonstrate that PA mesh is an effective interleaving material for enhancing damage tolerance in CFRP laminates with internal discontinuities.

Journal of Composites Science doi: 10.3390/jcs9080412

Authors: Nefeli Mitsopoulou Marinos Kattis

This study examines the energy behavior of a strengthening system consisting of a Fiber Reinforced Polymer (FRP) plate bonded to a rigid substrate and subjected to tensile loading, where the adhesive interface is governed by a bilinear bond–slip law with a vertical descending branch. The investigation focuses on the interaction between the elastic energy stored in the FRP and the adhesive interface, as well as the characteristic lengths that control the debonding process. Analytical expressions for the strain energy stored in both the FRP plate and the adhesive interface are derived, enabling the identification and evaluation of two critical characteristic lengths as the bond stress at the loaded end approaches its maximum value lc, at which the elastic energies of the FRP and the adhesive interface converge, signaling energy saturation; and lmax, where the adhesive interface attains its peak energy absorption. Upon reaching the energy saturation state, the system undergoes failure through the sudden and complete debonding of the FRP from the substrate. The onset of unstable debonding is rigorously analyzed in terms of the first and second derivatives of the total potential energy with respect to the bond length. It is further demonstrated that abrupt debonding may also occur in cases where the length exceeds lc when the bond stress reaches its maximum, and the bond–slip law is characterized by a vertical branch. The findings provide significant insights into the energy balance and stability criteria governing the debonding failure mode in FRP-strengthened structures, highlighting the pivotal role of characteristic lengths in predicting both structural performance and failure mechanisms.

Journal of Composites Science doi: 10.3390/jcs9080411

Authors: Rabina Acharya Vistasp M. Karbhari

Non-autoclave-cured wet layup composites are used extensively in applications ranging from civil and marine infrastructure to offshore components and in transmission power systems. In many of these applications the composites can be exposed to elevated temperatures for extended periods of time. While residual tensile characteristics have been used traditionally to assess the integrity of the composite after a thermal event/exposure, it is emphasized that fiber-dominated characteristics such as longitudinal tensile strength are not affected as much as those associated with shear. This paper reports on the investigation of shear related characteristics through off-axis and short-beam shear testing after exposure to temperatures between 66 °C and 260 °C for periods of time up to 72 h. It is shown that the use of shear test results in conjunction with tensile tests enables better assessment of the competing effects of postcure, which results in an increase in performance, and thermal degradation, which causes drops in performance. Off-axis-to-tensile strength and short-beam shear strength-to-tensile strength ratios are used to determine zones of influence and mechanisms. It is shown that temperatures up to 149 °C can lead to advantageous postcure related increases in performance whereas temperatures above 232 °C can lead to significant deterioration at time periods as low as 4 h. The use of shear tests is shown to provide data critical to performance integrity showing trends otherwise obscured by just the use of longitudinal tensile tests. A phenomenological model developed based on effects of the competing mechanisms and grouping based on phenomenon dominance and temperature regimes is shown to model data well providing a useful context for deign thresholds and determination of remaining structural integrity.

Journal of Composites Science doi: 10.3390/jcs9080410

Authors: Dora Kroisová Stepanka Dvorackova Martin Bilek Josef Skrivanek Anita Bia?kowska Mohamed Bakar

Carbon fiber (CF) and carbon fiber-reinforced polymers (CFRPs) are widely used in the aerospace, automotive, and energy sectors due to their high strength, stiffness, and low density. However, significant waste is generated during manufacturing and after the use of CFRPs. Traditional disposal methods like landfilling and incineration are unsustainable. CFRP machining processes, such as drilling and milling, produce fine chips and dust that are difficult to recycle due to their heterogeneity and contamination. This study investigates the oxidation behavior of CFRP drilling waste from two types of materials (tube and plate) under oxidative (non-inert) conditions. Thermogravimetric analysis (TGA) was performed from 200 °C to 800 °C to assess weight loss related to polymer degradation and carbon fiber integrity. Scanning electron microscopy (SEM) was used to analyze morphological changes and fiber damage. The optimal range for removing the polymer matrix without significant fiber degradation has been identified as 500–600 °C. At temperatures above 700 °C, notable surface and internal fiber damage occurred, along with nanostructure formation, which may pose health and environmental risks. The results show that partial fiber recovery is possible under ambient conditions, and this must be considered regarding the harmful risks to the human body if submicron particles are inhaled. This research supports sustainable CFRP recycling and fire hazard mitigation.

Journal of Composites Science doi: 10.3390/jcs9080409

Authors: Raghu Somanna Rudresh Bekkalale Madegowda Rakesh Mahesh Bilwa Prashanth Malligere Vishveshwaraiah Prema Nisana Siddegowda Sandeep Bagrae Madhukar Beejaganahalli Sangameshwara Girish Hunaganahalli Nagaraju Madhusudan Puttaswamy

This study investigates the mechanical, morphological, and wear properties of SiO2-filled tri-axial warp-knitted (TWK) glass fiber-reinforced vinyl ester matrix composites, with a focus on void fraction, tensile, flexural, hardness, and wear behavior. Adding SiO2 fillers reduced void fractions, enhancing composite strength, with values ranging from 1.63% to 5.31%. Tensile tests revealed that composites with 5 wt% SiO2 (GV1) exhibited superior tensile strength, Young’s modulus, and elongation due to enhanced fiber–matrix interaction. Conversely, composites with 10 wt% SiO2 (GV2) showed decreased tensile performance, indicating increased brittleness. Flexural tests demonstrated that GV1 outperformed GV2, showcasing higher flexural strength, elastic modulus, and deflection, reflecting improved load-bearing capacity at optimal filler content. Shore D hardness tests confirmed that GV1 had the highest hardness among the specimens. SEM analysis revealed wear behavior under various loads and sliding distances. GV1 exhibited minimal wear loss at lower loads and distances, while higher loads caused significant matrix detachment and fiber damage. These findings highlight the importance of optimizing SiO2 filler content to enhance epoxy composites’ mechanical and tribological performance.

Journal of Composites Science doi: 10.3390/jcs9080408

Authors: Almat Sagitov Karibek Sherov Didar Berdimuratova Ainur Turusbekova Saule Mendaliyeva Dinara Kossatbekova Medgat Mussayev Balgali Myrzakhmet Sabit Magavin

This article analyzes statistics on the failure of technological equipment, assemblies, and mechanisms of agricultural (and other) machines associated with the breakdown or failure of gear pumps. It was found that the leading causes of gear pump failures are the opening of gear teeth contact during pump operation, poor assembly, wear of bushings, thrust washers, and gear teeth. It has also been found that there is a problem related to the restoration, repair, and manufacture of parts in the conditions of enterprises serving the agro-industrial complex of the Republic of Kazakhstan (AIC RK). This is due to the lack of necessary technological equipment, tools, and instruments, as well as centralized repair and restoration bases equipped with the required equipment. This work proposes to solve this problem by applying AM technologies to the repair and manufacture of parts for agricultural machinery and equipment. The study results on the stress–strain state of support bushings under various pressures are presented, showing that a fully filled bushing has the lowest stresses and strains. It was also found that bushings with 50% filling and fully filled bushings have similar stress and strain values under the same pressure. The difference between them is insignificant, especially when compared to bushings with lower filling. This means that filling the bushing by more than 50% does not provide a significant additional reduction in stresses. In terms of material and printing time savings, 50% filling may also be the optimal option.

Journal of Composites Science doi: 10.3390/jcs9080407

Authors: Pengfei Ma Shangke Yuan Shuming Jia

This study investigates the bond behavior of fabric-reinforced cementitious matrix (FRCM) composites with three common masonry substrates—solid clay bricks (SBs), perforated bricks (PBs), and concrete hollow blocks (HBs)—using knitted polyester grille (KPG) fabric. Through uniaxial tensile tests of the KPG fabric and FRCM system, along with single-lap and double-lap shear tests, the interfacial debonding modes, load-slip responses, and composite utilization ratio were evaluated. Key findings reveal that (i) SB and HB substrates predominantly exhibited fabric slippage (FS) or matrix–fabric (MF) debonding, while PB substrates consistently failed at the matrix–substrate (MS) interface, due to their smooth surface texture. (ii) Prism specimens with mortar joints showed enhanced interfacial friction, leading to higher load fluctuations compared to brick units. PB substrates demonstrated the lowest peak stress (69.64–74.33 MPa), while SB and HB achieved comparable peak stresses (133.91–155.95 MPa). (iii) The FRCM system only achieved a utilization rate of 12–30% in fabric and reinforcement systems. The debonding failure at the matrix–substrate interface is one of the reasons that cannot be ignored, and exploring methods to improve the bonding performance between the matrix–substrate interface is the next research direction. HB bricks have excellent bonding properties, and it is recommended to prioritize their use in retrofit applications, followed by SB bricks. These findings provide insights into optimizing the application of FRCM reinforcement systems in masonry structures.

Journal of Composites Science doi: 10.3390/jcs9080406

Authors: Viviane Chaves de Souza Henrique Pina Cardim Carlos Toshiyuki Hiranobe Guilherme Pina Cardim Iago William Zapelini Leonardo Lataro Paim Gleyson Tadeu Almeida Santos Silvio Rainho Teixeira Erivaldo Ant?nio da Silva Renivaldo José dos Santos Flávio Camargo Cabrera

The incorporation of residues into rubber composites has gained attention as a sustainable strategy to address waste management challenges while replacing commercial fillers. In this study, we investigated the potential use of water filter cartridge residue after exhaustion, composed of activated carbon, as a reinforcing filler in vulcanized natural rubber composites. Samples were prepared with 5, 10, 15, and 20 phr (per hundred rubber) of residue and compared to unfilled natural rubber. Stress vs. strain tests reached 13.9 MPa of tension at rupture for composites containing 10 phr of carbon-activated residues, representing a 21.9% increase compared to natural rubber. Interestingly, the tension at rupture for NR/AC10phr reached values close to those of NR/CB5phr (with carbon black N330) attaining 14.4 MPa. These results indicate that, even at relatively low concentrations, the carbon filter can offer partial substitution for commercial fillers. Moreover, the use of activated carbon from filter cartridges as filler in rubber composites provides an environmentally favorable alternative to energy-intensive regeneration processes for activated carbon.

Journal of Composites Science doi: 10.3390/jcs9080405

Authors: Pirat Karntiang Hiroshi Ikeda Yuki Nagamatsu Hiroshi Shimizu

This study aimed to develop experimental filler-reinforced resin composites for vat-photopolymerization 3D printing and to evaluate the effects of filler addition on their mechanical, physicochemical, and bonding properties for dental restorative applications. Silanized nano- and/or micro-fillers were incorporated into acrylic resin monomers to formulate photocurable resins suitable for vat-photopolymerization. The rheological behavior of these liquid-state resins was assessed through viscosity measurements. Printed resin composites were fabricated and characterized for mechanical properties—including flexural strength, flexural modulus, and Vickers hardness—both before and after 8 weeks of water immersion. Physicochemical properties, such as water sorption, water solubility, and degree of conversion, were also evaluated. Additionally, shear bond strength to a resin-based luting agent was measured before and after artificial aging via thermocycling. A commercial dental CAD-CAM resin composite served as a reference material. Filler incorporation significantly improved the mechanical properties of the printed composites. The highest performance was observed in the composite containing 60 wt% micro-fillers, with a flexural strength of 168 ± 10 MPa, flexural modulus of 6.3 ± 0.4 GPa, and Vickers hardness of 63 ± 1 VHN, while the commercial CAD-CAM composite showed values of 152 ± 8 MPa, 7.9 ± 0.3 GPa, and 66 ± 2 VHN, respectively. Filler addition did not adversely affect the degree of conversion, although the relatively low conversion led to the elution of unpolymerized monomers and increased water solubility. The shear bond strength of the optimal printed composite remained stable after aging without silanization, demonstrating superior bonding performance compared with the CAD-CAM composite. These findings suggest that the developed 3D-printed resin composite is a promising candidate for dental restorative materials.

Journal of Composites Science doi: 10.3390/jcs9080404

Authors: Mónica Antonio-Flores Andrés Eliú Castell-Rodríguez Gabriela Pi?ón-Zárate Beatriz Hernández-Téllez Abigailt Flores-Ledesma Enrique Pérez-Martínez Carolina Sámano-Valencia Gerardo Quiroz-Petersen Katia Jarquín-Yá?ez

There is insufficient evidence regarding the cytotoxicity of restorative 3D-printing resins, used as part of the digital workflow in dentistry. This study presents a novel comparative evaluation of cell viability and adhesion using human Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs), a less commonly used but clinically relevant cell line in dental biomaterials research. The aim of this study was to evaluate the cell viability of WJ-MSCs seeded on 3D-printed resins intended for temporary restorations. Resin discs of three commercial 3D-printing resins (NextDent C&B, Leaf Dental C&B, and UNIZ Temp) and a conventional self-curing acrylic resin (NicTone) were used. WJ-MSCs were cultured on the specimens for 1, 4, and 10 days. Cell viability was assessed using the PrestoBlue assay, Live/Dead immunofluorescence staining, and 7AAD/Annexin V staining. Cell adhesion was evaluated using scanning electron microscopy. Direct exposure to the 3D-printed resins and the self-curing acrylic caused slight reductions in cell viability compared to the control group in both microscopic analyses. 7AAD/Annexin V showed the highest percentage of viable WBCs for the conventional acrylic (34%), followed by UNIZ (35%), NextDent (42%), and Leaf Dental (36%) (ANOVA p < 0.05 Tukey’s post-hoc test p < 0.05). These findings suggest that 3D-printed resins could be considered safe for use in temporary restorations.

Journal of Composites Science doi: 10.3390/jcs9080403

Authors: Norbert Sobon Michal Krasowski Karolina Kopacz Barbara Lapinska Izabela Barszczewska-Rybarek Patrycja Kula Kinga Bociong

Background: This study aimed to assess the impact of methacrylate-functionalized polyhedral oligomeric silsesquioxanes dispersed in nanosilica (MA/Ns-POSS) on the mechanical properties of light-curable dental resins and composites. The primary goal was to evaluate how different concentrations of MA/Ns-POSS (0.5–20 wt.%) affect the hardness, flexural strength, modulus, diametral tensile strength, polymerization shrinkage stress, and degree of conversion of these materials. Methods: A mixture of Bis-GMA, UDMA, TEGDMA, HEMA, and camphorquinone, with a tertiary amine as the photoinitiator, was used to create resin and composite samples, incorporating 45 wt.% silanized silica for the composites. Hardness (Vickers method, HV), flexural strength (FS), and flexural modulus (Ef) were assessed using three-point bending tests, while diametral tensile strength (DTS) polymerization shrinkage stresses (PSS), and degree of conversion (DC) analysis were analyzed for the composites. Results: The results showed that resins with 10 wt.% MA/Ns-POSS exhibited the highest Ef and FS values. Composite hardness peaked at 20 wt.% MA/Ns-POSS, while DTS increased up to 2.5 wt.% MA/Ns-POSS but declined at higher concentrations. PSS values decreased with increasing MA/Ns-POSS concentration, with the lowest values recorded at 15–20 wt.%. DC analysis also showed substantial improvement for 15–20 wt.% Conclusion: Incorporating MA/Ns-POSS improves the mechanical properties of both resins and composites, with 20 wt.% showing the best results. Further studies are needed to explore the influence of higher additive concentrations.

Journal of Composites Science doi: 10.3390/jcs9080402

Authors: Adeel Iqbal Nuha S. Mashaan Themelina Paraskeva

This paper presents a critical and comprehensive review of the application of mining waste, specifically waste rock and tailings, in asphalt pavements, with the aim of synthesizing performance outcomes and identifying key research gaps. A systematic literature search yielded a final dataset of 41 peer-reviewed articles for detailed analysis. Bibliometric analysis indicates a notable upward trend in annual publications, reflecting growing academic and practical interest in this field. Performance-based evaluations demonstrate that mining wastes, particularly iron and copper tailings, have the potential to enhance the high-temperature performance (i.e., rutting resistance) of asphalt binders and mixtures when utilized as fillers or aggregates. However, their effects on fatigue life, low-temperature cracking, and moisture susceptibility are inconsistent, largely influenced by the physicochemical properties and dosage of the specific waste material. Despite promising results, critical knowledge gaps remain, particularly in relation to long-term durability, comprehensive environmental and economic Life-Cycle Assessments (LCA), and the inherent variability of waste materials. This review underscores the substantial potential of mining wastes as sustainable alternatives to conventional pavement materials, while emphasizing the need for further multidisciplinary research to support their broader implementation.

Journal of Composites Science doi: 10.3390/jcs9080401

Authors: Héctor Herrera Hernández Carlos O. González Morán Gemima Lara Hernández Ilse Z. Ramírez-León Citlalli J. Trujillo Romero Juan A. Alcántara Cárdenas Jose de Jesus Agustin Flores Cuautle

This research focuses on designing polymer membranes as biocompatible materials using home-built electrospinning equipment, offering alternative solutions for tissue regeneration applications. This technological development supports cell growth on biomaterial substrates, including hepatocellular carcinoma (Hep-G2) cells. This work researches the compatibility of polymer membranes (fiber mats) made of polyvinylidene difluoride (PVDF) for possible use in cellular engineering. A standard culture medium was employed to support the proliferation of Hep-G2 cells under controlled conditions (37 °C, 4.8% CO2, and 100% relative humidity). Subsequently, after the incubation period, electrochemical impedance spectroscopy (EIS) assays were conducted in a physiological environment to characterize the electrical cellular response, providing insights into the biocompatibility of the material. Scanning electron microscopy (SEM) was employed to evaluate cell adhesion, morphology, and growth on the PVDF polymer membranes. The results suggest that PVDF polymer membranes can be successfully produced through electrospinning technology, resulting in the formation of a dipole structure, including the possible presence of a polar β-phase, contributing to piezoelectric activity. EIS measurements, based on Rct and Cdl values, are indicators of ion charge transfer and strong electrical interactions at the membrane interface. These findings suggest a favorable environment for cell proliferation, thereby enhancing cellular interactions at the fiber interface within the electrolyte. SEM observations displayed a consistent distribution of fibers with a distinctive spherical agglomeration on the entire PVDF surface. Finally, integrating piezoelectric properties into cell culture systems provides new opportunities for investigating the influence of electrical interactions on cellular behavior through electrochemical techniques. Based on the experimental results, this electrospun polymer demonstrates great potential as a promising candidate for next-generation biomaterials, with a probable application in tissue regeneration.

Journal of Composites Science doi: 10.3390/jcs9080399

Authors: Salvatore Brischetto Domenico Cesare Tommaso Mondino

The present paper proposes a three-dimensional (3D) spherical shell model for the magneto-electro-elastic (MEE) free vibration analysis of simply supported multilayered smart shells. A mixed curvilinear orthogonal reference system is used to write the unified 3D governing equations for cylinders, cylindrical panels and spherical shells. The closed-form solution of the problem is performed considering Navier harmonic forms in the in-plane directions and the exponential matrix method in the thickness direction. A layerwise approach is possible, considering the interlaminar continuity conditions for displacements, electric and magnetic potentials, transverse shear/normal stresses, transverse normal magnetic induction and transverse normal electric displacement. Some preliminary cases are proposed to validate the present 3D MEE free vibration model for several curvatures, materials, thickness values and vibration modes. Then, new benchmarks are proposed in order to discuss possible effects in multilayered MEE curved smart structures. In the new benchmarks, first, three circular frequencies for several half-wave number couples and for different thickness ratios are proposed. Thickness vibration modes are shown in terms of displacements, stresses, electric displacement and magnetic induction along the thickness direction. These new benchmarks are useful to understand the free vibration behavior of MEE curved smart structures, and they can be used as reference for researchers interested in the development of of 2D/3D MEE models.

Journal of Composites Science doi: 10.3390/jcs9080400

Authors: Samira Farjaminejad Rosana Farjaminejad Pedram Sotoudehbagha Mehdi Razavi

Tissue-engineered scaffolds, particularly composite scaffolds composed of polymers combined with ceramics, bioactive glasses, or nanomaterials, play a vital role in regenerative medicine by providing structural and biological support for tissue repair. As scaffold designs grow increasingly complex, the need for non-invasive imaging modalities capable of monitoring scaffold integration, degradation, and tissue regeneration in real-time has become critical. This review summarizes current non-invasive imaging techniques used to evaluate tissue-engineered constructs, including optical methods such as near-infrared fluorescence imaging (NIR), optical coherence tomography (OCT), and photoacoustic imaging (PAI); magnetic resonance imaging (MRI); X-ray-based approaches like computed tomography (CT); and ultrasound-based modalities. It discusses the unique advantages and limitations of each modality. Finally, the review identifies major challenges—including limited imaging depth, resolution trade-offs, and regulatory hurdles—and proposes future directions to enhance translational readiness and clinical adoption of imaging-guided tissue engineering (TE). Emerging prospects such as multimodal platforms and artificial intelligence (AI) assisted image analysis hold promise for improving precision, scalability, and clinical relevance in scaffold monitoring.

Journal of Composites Science doi: 10.3390/jcs9080398

Authors: Jo?o Queirós Hernani Lopes Luís Mour?o Viriato dos Santos

This study comprehensively compares the performance of two non-destructive testing (NDT) techniques—active thermography (AT) and digital shearography (DS)—for identifying various damage types in composite structures. Three distinct composite specimens were inspected: a carbon-fiber-reinforced polymer (CFRP) plate with flat-bottom holes, an aluminum honeycomb core sandwich plate with a circular skin-core disbond, and a CFRP plate with two low-energy impacts damage. The research highlights the significant role of post-processing methods in enhancing damage detectability. For AT, algorithms such as fast Fourier transform (FFT) for temperature phase extraction and principal component thermography (PCT) for identifying significant temperature components were employed, generally making anomalies brighter and easier to locate and size. For DS, a novel band-pass filtering approach applied to phase maps, followed by summing the filtered maps, remarkably improved the visualization and precision of damage-induced anomalies by suppressing background noise. Qualitative image-based comparisons revealed that DS consistently demonstrated superior performance. The sum of DS filtered phase maps provided more detailed and precise information regarding damage location and size compared to both pulsed thermography (PT) and lock-in thermography (LT) temperature phase and amplitude. Notably, DS effectively identified shallow flat-bottom holes and subtle imperfections that AT struggled to clearly resolve, and it provided a more comprehensive representation of the impacts damage location and extent. This enhanced capability of DS is attributed to the novel phase map filtering approach, which significantly improves damage identification compared to the thermogram post-processing methods used for AT.

Journal of Composites Science doi: 10.3390/jcs9080397

Authors: Mojtaba Jafari Kermanipour Mohammad Hossein Bagheripour Ehsan Yaghoubi

This study investigates the effectiveness of geopolymer-based binders for the stabilization of silty sand, aiming to improve its strength and durability under cyclic environmental conditions. A composite binder consisting of Ground Granulated Blast-furnace Slag (GGBS) and Recycled Glass Powder (RGP), modified with nano poly aluminum silicate (PAS), was used to treat the soil. The long-term performance of the stabilized soil was evaluated under cyclic wetting–drying (W–D) conditions. The influence of PAS content on the mechanical strength, environmental safety, and durability of the stabilized soil was assessed through a series of laboratory tests. Key parameters, including unconfined compressive strength (UCS), mass retention, pH variation, ion leaching, and microstructural development, were analyzed using field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Results revealed that GGBS-stabilized specimens maintained over 90% of their original strength and mass after eight W–D cycles, indicating excellent durability. In contrast, RGP-stabilized samples exhibited early strength degradation, with up to an 80% reduction in UCS and 10% mass loss. Environmental evaluations confirmed that leachate concentrations remained within acceptable toxicity limits. Microstructural analysis further highlighted the critical role of PAS in enhancing the chemical stability and long-term performance of the stabilized soil matrix.

Journal of Composites Science doi: 10.3390/jcs9080396

Authors: Vasil M. Garamus D. C. Florian Wieland Julian P. Moosmann Felix Beckmann Lars Lottermoser Maria Serdechnova Carsten Blawert Mohammad Fazel Eshwara P. S. Nidadavolu Wolfgang Limberg Thomas Ebel Regine Willumeit-R?mer Berit Zeller-Plumhoff

Hybrid implants composed of magnesium and titanium are a promising direction in orthopaedics, as these implants combine the stability of titanium with the biological activity of magnesium. These partly soluble implants require careful investigation, as the degradation of magnesium releases hydrogen, which can enter the Ti matrix and thus alter the mechanical properties. To investigate this scenario and quantify the hydrogen uptake along with its structural impacts, we employed inert gas fusion, scanning electron microscopy, X-ray diffraction, and a combination of synchrotron absorption and X-ray diffraction tomography. These techniques enabled us to investigate the concentration and distribution of hydrogen and the formation of hydrides in the samples. Titanium hydride formation was observed in a region approximately 120 µm away from the titanium surface and correlates with the amount of absorbed hydrogen. We speculate that the degradation of magnesium at the magnesium/titanium implant interface leads to the penetration of hydrogen due to a combination of electrochemical and gaseous charging.

Journal of Composites Science doi: 10.3390/jcs9080395

Authors: Parham Joolaei Ahranjani Hamed Sadatfaraji Kamine Dehghan Vaibhav A. Edlabadkar Prasant Khadka Ifeanyi Nwobodo VN Ramachander Turaga Justin Disney Hamid Rashidi Nodeh

Wax deposition, driven by the crystallization of long-chain n-alkanes, poses severe challenges across industries such as petroleum, oil and natural gas, food processing, and chemical manufacturing. This phenomenon compromises flow efficiency, increases energy demands, and necessitates costly maintenance interventions. Wax inhibitors, designed to mitigate these issues, operate by altering wax crystallization, aggregation, and adhesion over the pipelines. Classic wax inhibitors, comprising synthetic polymers and natural compounds, have been widely utilized due to their established efficiency and scalability. However, synthetic inhibitors face environmental concerns, while natural inhibitors exhibit reduced performance under extreme conditions. The advent of nano-based wax inhibitors has revolutionized wax management strategies. These advanced materials, including nanoparticles, nanoemulsions, and nanocomposites, leverage their high surface area and tunable interfacial properties to enhance efficiency, particularly in harsh environments. While offering superior performance, nano-based inhibitors are constrained by high production costs, scalability challenges, and potential environmental risks. In parallel, the development of “green” wax inhibitors derived from renewable resources such as vegetable oils addresses sustainability demands. These eco-friendly formulations introduce functionalities that reinforce inhibitory interactions with wax crystals, enabling effective deposition control while reducing reliance on synthetic components. This review provides a comprehensive analysis of the mechanisms, applications, and comparative performance of classic and nano-based wax inhibitors. It highlights the growing integration of sustainable and hybrid approaches that combine the reliability of classic inhibitors with the advanced capabilities of nano-based systems. Future directions emphasize the need for cost-effective, eco-friendly solutions through innovations in material science, computational modeling, and biotechnology.

Journal of Composites Science doi: 10.3390/jcs9080394

Authors: Yang Wan Benlong Su Guochang Lin Youshan Wang Gege Huang Jian Wu

Optimisation of the anti-skid properties of tyres is a significant area of composite applications. For investigating the wet slip friction characteristics, the wet slip friction test of tread rubber and road surface was carried out using the comprehensive tire friction testing machine. The wet slip properties of different formulated rubbers under various working conditions such as different slip speeds, water film thicknesses and vertical loads were compared through the test. Subsequently, an orthogonal test programme was designed to investigate the degree of significant influence of each factor on the wet slip performance. A three-dimensional finite element model of tread rubber and road surface with water film was established in order to facilitate analysis of the wet slip properties. The simulation results were utilised to elucidate the pattern of the effects of different loads on the wet slip friction characteristics. Results indicate that the wet slip friction coefficient is subject to decrease in proportion to the magnitude of the vertical load; the friction coefficient of rubber block in wet slip condition exhibits a decline of approximately 26% in comparison with that of dry condition; the factor that exerts the most significant influence on the coefficient of friction is the vertical load, while the water film thickness exerts the least influence. The results obtained can serve as a reference source for the design of tire anti-skid performance enhancement.

Journal of Composites Science doi: 10.3390/jcs9080393

Authors: Nicolas Candau Guillaume Corvec Noel León-Albiter Miguel Mudarra Lopez

This paper investigates the interplay between rubber network damage, carbon black (CB) network damage, heat exchange, and voiding mechanisms in filled Styrene-butadiene rubber (SBR) under cyclic loading. To do so, three carbon black filled SBR composites, SBR5, SBR30 and SBR60 are studied. The study aims to quantify molecular damage and its role in inducing reversible or irreversible heat flow and voiding behavior to inform the design of more resilient rubber composites with improved fatigue life and thermal management capabilities. The study effectively demonstrated how increasing carbon black content, particularly in SBR60, leads to a shift from mostly reversible to irreversible and cumulative damage mechanisms during cyclic loading, as evidenced by thermal, volumetric, and electrical resistivity changes. In particular, we identify a critical mechanical energy of 7 MJ.m−3 associated with such transition. These irreversible changes are strongly linked to the damage and re-arrangement of the carbon black filler network, as well as the rubber chains network and the formation/growth of voids, while reversible mechanisms are likely related to rubber chains alignment associated with entropic elasticity.

Journal of Composites Science doi: 10.3390/jcs9080392

Authors: Sijan Adhikari Braiden M. Myers Bryce L. Tuck Courtney Dawson Joey R. Cipriano Jules F. Ahlert Menziwokuhle Thwala Mia A. Griffin Omar Yadak Osama A. Alfailakawi Micah S. Ritz Seth M. Wright Jeffery Volz Shreya Vemuganti

Epoxy resins are widely used as protective coatings in civil infrastructure, yet sulfate-rich environments accelerate their deterioration. This study evaluates the effectiveness of multi-walled carbon nanotubes (MWCNTs) in enhancing the sulfate resistance of epoxy resins. Neat and MWCNT-reinforced epoxy specimens (0.25 wt.% and 0.5 wt.%) were fabricated, heat cured at 100 °C and exposed to a solution of sulfuric acid and sodium chloride maintaining a pH of less than 3 for 0, 30, and 60 days. Analytical techniques, including scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), revealed distinct degradation patterns: the neat epoxy exhibited puncture damage and extensive salt deposition, while the MWCNT-reinforced specimens showed crack propagation mitigated by nanotube bridging. Heat curing introduced micro-voids that exacerbated sulfate ingress. The salt deposition surged to 200 times for the MWCNT-reinforced specimens compared to the neat ones, whereas crack width was higher in the MWCNT reinforced specimen compared to their neat counterparts, given that crack-bridging was observed. These findings highlight the potential of MWCNTs to improve epoxy durability in sulfate-prone environments, though the optimization of curing conditions and dispersion methods is critical.

Journal of Composites Science doi: 10.3390/jcs9080391

Authors: Rafah R. Abdulmajid Dillshad K. Bzeni Farid H. Abed Hussein M. Hamada

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Journal of Composites Science doi: 10.3390/jcs9080390

Authors: Mortada Sabeh Whwah Hajir A Al-Hussainy Anmar Dulaimi Luís Filipe Almeida Bernardo Tiago Pinto Ribeiro

This study investigates the influence of varying water-to-cement (W/C) ratios and fine aggregate compositions on the performance of concrete incorporating expanded perlite aggregate (EPA) as a lightweight alternative to natural sand. A total of eighteen concrete mixes were produced, each with different W/C ratios and fine-to-coarse aggregate (FA/CA) ratios, and evaluated for workability, compressive strength, flexural and tensile strength, water absorption, density, and thermal conductivity. Perlite was used to fully replace natural sand in half of the mixes, allowing a direct assessment of its effects across low-, medium-, and high-strength concrete formulations. The results demonstrate that EPA can improve workability and reduce both density and thermal conductivity, with variable impacts on mechanical performance depending on the W/C and FA/CA ratios. Notably, higher cement contents enhanced the internal curing effect of perlite, while lower-strength mixes experienced a reduction in compressive strength when perlite was used. These findings suggest that expanded perlite can be effectively applied in structural and non-structural concrete with optimized mix designs, supporting the development of lightweight, thermally efficient concretes. Mixture W16-100%EPS was considered the ideal mix because its compressive strength at the age of 65 days 44.2 MPa and the reduction in compressive strength compared to the reference mix 14% and the reduction in density 5.4% compared with the reference mix and the reduction in thermal conductivity 14% compared with the reference mix.

Journal of Composites Science doi: 10.3390/jcs9080389

Authors: Maciej Sydor Grzegorz Pinkowski Agata Bonenberg

Mycelium-bonded composites (MBCs), or myco-composites, represent a novel engineered material that combines natural lignocellulosic substrates with a fungal matrix. As a sustainable alternative to plastics, MBCs are gaining increasing interest; however, their large-scale industrial adoption remains limited, partly due to low social acceptance resulting from their unattractive appearance. Laser engraving provides a promising method for fabricating intricate patterns and functional surfaces on MBCs, minimizing tool wear, material loss, and environmental impact, while enhancing esthetic and engineering properties. This study investigates the influence of CO2 laser parameters on the material removal rate during the engraving of myco-composites, focusing on the effects of variable laser power, beam defocus, and head feed rate on engraving outcomes. The results demonstrate that laser power and beam focus significantly impact material removal in mycelium-bonded composites. Specifically, increasing the laser power results in greater material removal, which is more pronounced when the beam is focused due to higher energy density. In contrast, a beam defocused by 1 mm produces less intense material removal. These findings highlight the critical role of beam focus—surpassing the influence of power alone—in determining engraving quality, particularly on irregular or uneven surfaces. Moreover, reducing the laser head feed rate at a constant power level increases the material removal rate linearly; however, it also results in excessive charring and localized overheating, revealing the low thermal tolerance of myco-composites. These insights are essential for optimizing laser processing techniques to fully realize the potential of mycelium-bonded composites as sustainable engineering materials, simultaneously maintaining their appearance and functional properties.

Journal of Composites Science doi: 10.3390/jcs9080386

Authors: T. Pavan Rahul P. S. Rama Sreekanth

Sophisticated energy-harvesting technologies have swiftly progressed, expanding energy supply distribution and leveraging advancements in self-sustaining electronic devices. Despite substantial advancements in friction nanomotors within the last decade, a considerable technical obstacle remains for their flawless incorporation using printed electronics and autonomous devices. Integrating advanced triboelectric nanogenerator (TENG) technology with the rapidly evolving field of composite material 3D printing with has resulted in the advancement of three-dimensionally printed TENGs. Triboelectric nanogenerators are an important part of the next generation of portable energy harvesting and sensing devices that may be used for energy harvesting and artificial intelligence tasks. This paper systematically analyzes the continual development of 3D-printed TENGs and the integration of composite materials. The authors thoroughly review the latest material combinations of composite materials and 3D printing techniques for TENGs. Furthermore, this paper showcases the latest applications, such as using a TENG device to generate energy for electrical devices and harvesting energy from human motions, tactile sensors, and self-sustaining sensing gloves. This paper discusses the obstacles in constructing composite-material-based 3D-printed TENGs and the concerns linked to research and methods for improving electrical output performance. The paper finishes with an assessment of the issues associated with the evolution of 3D-printed TENGs, along with innovations and potential future directions in the dynamic realm of composite-material-based 3D-printed TENGs.

Journal of Composites Science doi: 10.3390/jcs9080388

Authors: Jianyong Tu Xingmiao Duan Xingang Luan Dianwei He Laifei Cheng

Continuous SiC fiber-reinforced SiC matrix composites (SiC/SiC), as structural heat protection integrated materials, are often used in parts for large-area heat protection and sharp leading edges, and there are a variety of low-velocity impact events in their service. In this paper, a drop hammer impact test was conducted using narrow strip samples to simulate the low-velocity impact damage process of sharp-edged components. During the test, different impact energies and impact times were set to focus on investigating the low-velocity impact damage characteristics of 2.5D SiC/SiC composites. To further analyze the damage mechanism, computed tomography (CT) was used to observe the crack propagation paths and distribution states of the composites before and after impact, while scanning electron microscopy (SEM) was employed to characterize the differences in the micro-morphology of their fracture surfaces. The results show that the in-plane impact behavior of a 2.5D needled SiC/SiC composite strip samples differs from the conventional three-stage pattern. In addition to the three stages observed in the energy–time curve—namely in the quasi-linear elastic region, the severe load drop region, and the rebound stage after peak impact energy—a plateau stage appears when the impact energy is 1 J. During the impact process, interlayer load transfer is achieved through the connection of needled fibers, which continuously provide significant structural support, with obvious fiber pull-out and debonding phenomena. When the samples are subjected to two impacts, damage accumulation occurs inside the material. Under conditions with the same total energy, multiple impacts cause more severe damage to the material compared to a single impact.

Journal of Composites Science doi: 10.3390/jcs9080387

Authors: Saurabh Gupta Mahmood Haq Konstantin Cvetkovic Oleksii Karpenko

Modern aerospace engineering places increasing emphasis on materials that combine low weight with high mechanical performance. Fiber metal laminates (FMLs), which merge metal layers with fiber-reinforced composites, meet this demand by delivering improved fatigue resistance, impact tolerance, and environmental durability, often surpassing the performance of their constituents in demanding applications. Despite these advantages, inspecting such thin, layered structures remains a significant challenge, particularly when they are difficult or impossible to access. As with any new invention, they always come with challenges. This study examines the effectiveness of the fundamental anti-symmetric Lamb wave mode (A0) in detecting weak interfacial defects within Carall laminates, a type of hybrid fiber metal laminate (FML). Delamination detectability is analyzed in terms of strong wave dispersion observed downstream of the delaminated sublayer, within a region characterized by acoustic distortion. A three-dimensional finite element (FE) model is developed to simulate mode trapping and full-wavefield local displacement. The approach is validated by reproducing experimental results reported in prior studies, including the author’s own work. Results demonstrate that the A0 mode is sensitive to delamination; however, its lateral resolution depends on local position, ply orientation, and dispersion characteristics. Accurately resolving the depth and extent of delamination remains challenging due to the redistribution of peak amplitude in the frequency domain, likely caused by interference effects in the acoustically sensitive delaminated zone. Additionally, angular scattering analysis reveals a complex wave behavior, with most of the energy concentrated along the centerline, despite transmission losses at the metal-composite interfaces in the Carall laminate. The wave interaction with the leading and trailing edges of the delaminations is strongly influenced by the complex wave interference phenomenon and acoustic mismatched regions, leading to an increase in dispersion at the sublayers. Analytical dispersion calculations clarify how wave behavior influences the detectability and resolution of delaminations, though this resolution is constrained, being most effective for weak interfaces located closer to the surface. This study offers critical insights into how the fundamental anti-symmetric Lamb wave mode (A0) interacts with delaminations in highly attenuative, multilayered environments. It also highlights the challenges in resolving the spatial extent of damage in the long-wavelength limit. The findings support the practical application of A0 Lamb waves for structural health assessment of hybrid composites, enabling defect detection at inaccessible depths.

Journal of Composites Science doi: 10.3390/jcs9080385

Authors: Pavan Hiremath Srinivas Shenoy Heckadka Gajanan Anne Ranjan Kumar Ghadai G. Divya Deepak R. C. Shivamurthy

This study presents a multi-modal investigation into the wear behavior of bio-based epoxy composites reinforced with multi-walled carbon nanotubes (MWCNTs) at 0–0.75 wt%. A Taguchi L16 orthogonal array was employed to systematically assess the influence of MWCNT content, load (20–50 N), and sliding speed (1–2.5 m/s) on wear rate (WR), coefficient of friction (COF), and surface roughness (Ra). Statistical analysis revealed that MWCNT content contributed up to 85.35% to wear reduction, with 0.5 wt% identified as the optimal reinforcement level, achieving the lowest WR (3.1 mm3/N·m) and Ra (0.7 µm). Complementary morphological characterization via SEM and AFM confirmed microstructural improvements at optimal loading and identified degradation features (ploughing, agglomeration) at 0 wt% and 0.75 wt%. Regression models (R2 > 0.95) effectively captured the nonlinear wear response, while a Random Forest model trained on GLCM-derived image features (e.g., correlation, entropy) yielded WR prediction accuracy of R2 ≈ 0.93. Key image-based predictors were found to correlate strongly with measured tribological metrics, validating the integration of surface texture analysis into predictive modeling. This integrated framework combining experimental design, mathematical modeling, and image-based machine learning offers a robust pathway for designing high-performance, sustainable nanocomposites with data-driven diagnostics for wear prediction.

Journal of Composites Science doi: 10.3390/jcs9080384

Authors: Naomi Bouman Sofia Salles Lantyer Marques Naiara Poli Veneziani Sebbe Antoine Gerritse Heide Heloise Bernardi William Marcos Muniz Menezes Francisco José Gomes da Silva Jorge Tadao Matsushima Lucas Giovanetti Rita de Cássia Mendon?a Sales-Contini

The aerospace industry is increasingly turning to composite materials due to their exceptional strength, stiffness, and beneficial physical properties. However, increased reliance on carbon fibre composites has substantial environmental implications, particularly concerning waste management. Recycling these materials is a potential solution to these sustainability issues, provided the recycled fibres retain adequate mechanical strength and durability. This study evaluates the mechanical capabilities of recycled carbon fibres in a scaled-down aircraft spar model (AMT-600 GURI), contrasting them with the capabilities of conventional spars. The primary objective is to ascertain whether recycled composites can fulfil the stringent structural requirements of aerospace applications, employing both simulation and experimental validation methods. The recycled carbon fibre composites were manufactured using hand lay-up and vacuum bagging techniques, and their properties were validated through rigorous tensile and compressive strength testing. These validated results were then used to inform a finite element model developed in HyperWorks software. Simulations revealed that the recycled spar achieved maximum stress values of 3.87 MPa under lift forces, a slight increase of +8.95% compared to the original spar, and 55.05 MPa under drag forces, a significant improvement of +36%. Aerodynamic evaluations further confirmed the structural resilience of the recycled spar, with displacement measurements of 141.4 mm for lift and 504.8 mm for drag, closely aligning with the original spar’s performance. In summary, this study demonstrates that recycled carbon fibre composites can serve as effective substitutes for traditional aerospace materials, thereby supporting sustainability initiatives without compromising performance. The outlined approach provides a reliable framework for incorporating recycled materials.

Journal of Composites Science doi: 10.3390/jcs9080383

Authors: Juan José Valenzuela Expósito Elena Picazo Camilo Francisco Antonio Corpas Iglesias

This study explores the development and optimization of TiO2-based photoactive coatings enhanced with silver (Ag)—to boost photocatalytic performance—for application on glass-fiber-reinforced polyester (GFRP) and epoxy (GFRE) composites. The influence of Ag content on the structural, physicochemical, and functional properties of the coatings was evaluated. The TiO2-Ag coating showed the best performance and was tested under UV-A irradiation and visible light (Vis), with high efficiency in VOC degradation, self-cleaning, and microbial activity. The tests were repeated in multiple runs, showing high reproducibility in the results obtained. In GFRP, pollutant and microorganism removal ratios of more than 90% were observed. In contrast, GFRE showed a lower adhesion and stability of the coating. This result is attributed to incompatibility problems with the epoxy matrix, which significantly limited its functional performance. The results highlight the feasibility of using the TiO2-Ag coating on GFRP substrates, even under visible light. Under real-world conditions for 351 days, the coating on GFRP maintained its stability. This type of material has high potential for application in modular building systems using sandwich panels, as well as in facades and automotive components, where self-cleaning and contaminant-control properties are essential.

Journal of Composites Science doi: 10.3390/jcs9080382

Authors: Cédric-Olivier Turrin Valérie Maraval Anne-Marie Caminade

Dendrons, also named dendritic wedges, are a kind of molecular tree, having a branched structure linked to a functional core. The functional core can be used in particular for the functionalization of materials. Different types of dendrons are known, synthesized either by a convergent process, from the external part to the core, or by a divergent process from the core to the external part. Polyphosphorhydrazone (PPH) dendrons are always synthesized by a divergent process, which enables a fine-tuning of both the core function and the external functions. They have been used for the functionalization of diverse materials such as silica, titanium dioxide, gold, graphene oxide, or different types of nanoparticles. Nanocomposites based on materials functionalized with PPH dendrons have been used in diverse fields such as catalysts, chemical sensors, for trapping pollutants, to support cell cultures, and against cancers, as will be emphasized in this review.

Journal of Composites Science doi: 10.3390/jcs9080381

Authors: Jian Wang Xinyue Guo Haomin Gong Wanggang Zhang Yiming Liu Bo Li

The Mo:BiVO4/FeOOH photoelectrode was synthesized through the deposition of FeOOH onto the surface of the Mo:BiVO4 photoelectrode. The composite photoelectrode demonstrated a photocurrent of 1.8 mA·cm−2, which is three times greater than that observed for pure BiVO4. Furthermore, the glycerol conversion rate was recorded at 79 μmol·cm−2·h−1, approximately double that of pure BiVO4, while the selectivity for glyceraldehyde reached 49%, also about twice that of pure BiVO4. The incorporation of Mo has been shown to enhance the stability of the BiVO4. Additionally, Mo doping improves the efficiency of electron-hole transport and increases the carrier concentration within the BiVO4. This enhancement leads to a greater number of holes participating in the formation of iron oxyhydroxide (FeOOH), thereby stabilizing the FeOOH co-catalyst within the glycerol conversion system. The FeOOH co-catalyst facilitates the adsorption and oxidation of the primary hydroxyl group of glycerol, resulting in the cleavage of the C−H bond to generate a carbon radical (C). The interaction between the carbon radical and the hydroxyl group produces an intermediate, which subsequently dehydrates to form glyceraldehyde (GLAD).

Journal of Composites Science doi: 10.3390/jcs9070379

Authors: Artem Igorevich Bogdanov Vitaliy Pavlovich Kulevich Roman Evgenevich Novikov Victor Georgievich Shmorgun

An approach for the formation of intermetallic coatings on the titanium surface based on titanium aluminides is proposed. The approach involves producing a layered steel-aluminum-titanium metal composite via explosive welding, followed by heat treatment to form a diffusion zone at the steel–aluminum interface with a thickness of more than 30 μm, sufficient for the spontaneous separation of the steel layer. As a result, an aluminum layer approximately 0.3 mm thick remains on the titanium surface. Subsequent heating at temperatures of 700–850 °C, below the allotropic transformation temperature of titanium, results in the transformation of the aluminum layer into titanium aluminides. The formation of the intermetallic coating structure occurs as a result of the upward transportation of TiAl3 fragments separated from the reaction zone by circulating melt flows. With increasing heat treatment time, these fragments become separated by the Al2O3 oxide phase.

Journal of Composites Science doi: 10.3390/jcs9070380

Authors: Muhammad Ali Rostampour Davood Mostofinejad Hadi Bahmani Hasan Mostafaei

This study investigates the cracking behavior of high-performance calcium oxide-activated concrete incorporating basalt and synthetic macro fibers under compressive and flexural loading. Acoustic emission (AE) monitoring was employed to capture real-time crack initiation and propagation, offering insights into damage evolution mechanisms. A comprehensive series of uniaxial compression and four-point bending tests were conducted on fiber-reinforced and plain specimens. AE parameters, including count, duration, risetime, amplitude, and signal energy, were analyzed to quantify crack intensity and classify fracture modes. The results showed that tensile cracking dominated even under compressive loading due to lateral stresses, while fiber inclusion significantly enhanced toughness by promoting distributed microcracking and reducing abrupt energy release. Basalt fibers were particularly effective under flexural loading, increasing the post-peak load-bearing capacity, whereas synthetic macro fibers excelled in minimizing tensile crack occurrence under compression.

Journal of Composites Science doi: 10.3390/jcs9070378

Authors: Jacob C. Clark William G. Davids Roberto A. Lopez-Anido Andrew P. Schanck Cody A. Sheltra

Despite the strength and ductility of steel reinforcing bars, their susceptibility to corrosion can limit the long-term durability of reinforced concrete structures. Fiber-reinforced polymer (FRP) reinforcing bars made with a thermosetting matrix offer corrosion resistance but cannot be field-bent, which limits flexibility during construction. FRP reinforcing bars made with fiber-reinforced thermoplastic polymers (FRTP) address this limitation; however, their high processing viscosity presents manufacturing challenges. In this study, the Continuous Forming Machine, a novel pultrusion device that uses pre-consolidated fiber-reinforced thermoplastic tapes as feedstock, is described and used to fabricate 12.7 mm nominal diameter thermoplastic composite rebars. Simple bend tests on FRTP rebar that rely on basic equipment are performed to verify its ability to be field-formed. The manual bending technique demonstrated here is practical and straightforward, although it does result in some fiber misalignment. Subsequently, surface deformations are introduced to the rebar to promote mechanical bonding with concrete, and tensile tests of the bars are conducted to determine their mechanical properties. Finally, flexural tests of simply-supported, 6 m long beams reinforced with FRTP rebar are performed to assess their strength and stiffness as well as the practicality of using FRTP rebar. The beam tests demonstrated the prototype FRTP rebar’s potential for reinforcing concrete beams, and the beam load–deformation response and capacity agree well with predictions developed using conventional structural analysis principles. Overall, the results of the research reported indicate that thermoplastic rebars manufactured via the Continuous Forming Machine are a promising alternative to both steel and conventional thermoset composite rebar. However, both the beam and tension test results indicate that improvements in material properties, especially elastic modulus, are necessary to meet the requirements of current FRP rebar specifications.

Journal of Composites Science doi: 10.3390/jcs9070376

Authors: Candelaria Tejada-Tovar ángel Villabona-Ortíz Oscar Toro-Madrid Rodrigo Ortega-Toro Humberto Bonilla Mancilla

This research work focused on the development of an adsorbent biocomposite material based on polyhydroxybutyrate (PHB) and cellulose acetate derived from sugarcane (Saccharum officinarum) fibre, through cellulose acetylation. The resulting material represents both an accessible and effective alternative for the treatment and remediation of water contaminated with heavy metals, such as Ni (II). The biocomposite was prepared by blending cellulose acetate (CA) with the biopolymer PHB using the solvent-casting method. The resulting biocomposite exhibited a point of zero charge (pHpzc) of 5.6. The material was characterised by FTIR, TGA-DSC, and SEM analyses. The results revealed that the interaction between Ni (II) ions and the biocomposite is favoured by the presence of functional groups, such as –OH, C=O, and N–H, which act as active adsorption sites on the material’s surface, enabling efficient interaction with the metal ions. Adsorption kinetics studies revealed that the biocomposite achieved an optimal adsorption capacity of 5.042 mg/g at pH 6 and an initial Ni (II) concentration of 35 mg/L, corresponding to a removal efficiency of 86.44%. Finally, an analysis of the kinetic and isotherm models indicated that the experimental data best fit the pseudo-second-order kinetic model and the Freundlich isotherm.

Journal of Composites Science doi: 10.3390/jcs9070377

Authors: Qing-Ping Ding Yue Sun Qiang Hou Wei Wei Xin Zhou Xinyue Wang Zhixiang Shi Yuji Furukawa

The report of the first room-temperature, ambient-pressure superconductivity in copper-doped lead apatite Pb10−xCux(PO4)6O has attracted lots of attention. However, subsequent studies revealed the presence of numerous impurity phases in the polycrystalline sample, and the sharp superconducting-like transition is not due to a superconducting transition but most likely due to a reduction in resistivity caused by the first-order structural phase transition of Cu2S at around 385 K from the β phase at high temperature to the γ phase at low temperature. Before now, only bulk measurements have been performed on a Pb10−xCux(PO4)6O powder sample, which could be affected by the impurity phases, masking the intrinsic properties of Pb10−xCux(PO4)6O. In this study, 31P and 63/65Cu nuclear magnetic resonance (NMR) measurements have been performed on a Pb10−xCux(PO4)6O powder sample to investigate its physical properties from a microscopic point of view. Our NMR data evidence the non-magnetic insulating nature of Pb10−xCux(PO4)6O without any trace of electron correlation effects. Furthermore, the 63/65Cu NMR results suggest that no copper or very little copper is substituted for Pb in Pb10(PO4)6O prepared by sintering Pb2SO5 and Cu3P.

Journal of Composites Science doi: 10.3390/jcs9070375

Authors: Abdullah Shalwan Hussain Ali Alenezi Saad Ali Alsubaie

High-density polyethylene (HDPE) is a widely used polymer known for its excellent mechanical properties and chemical resistance. This study investigated the impact of incorporating varying percentages of nano-graphene particles (NGP) into HDPE on its thermal, mechanical, and tensile properties. Differential scanning calorimetry (DSC) analysis revealed that the addition of NGP enhanced the thermal stability and crystallization behavior of HDPE, with optimal performance observed at a 5% NGP concentration. Mechanical property evaluations indicated that small additions of NGP initially reduced zero-shear viscosity from 114,667 Pa·s to 44,045 Pa·s at 1% NGP, but higher concentrations improved the material’s rigidity and strength, with the best results at 3% NGP, where the flexural modulus reached 980 MPa. Tensile tests showed that while small amounts of NGP may decrease tensile strength from 26.4 MPa to 23.5 MPa at 1% NGP, higher concentrations significantly enhanced these properties, with tensile strength at break reaching 27 MPa and tensile elongation peaking at 20.8% at 7% NGP. The findings highlight the potential of NGP to enhance the performance of HDPE composites, making them suitable for a wide range of industrial applications. These enhanced composites are particularly important for the bottling industry, where improved material properties can lead to lighter, stronger, and more efficient packaging solutions.

Journal of Composites Science doi: 10.3390/jcs9070374

Authors: Saba Yaqoob Zulfiqar Ali Alberto D’Amore Alessandro Lo Schiavo Antonio Petraglia Mauro Rubino

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) have attracted significant interest as hybrid reinforcements in epoxy (Ep) composites for enhancing mechanical performance in structural applications, such as aerospace and automotive. These 1D and 2D nanofillers possess exceptionally high aspect ratios and intrinsic mechanical properties, substantially improving composite stiffness and tensile strength. In this study, epoxy nanocomposites were fabricated with 0.1 wt.% and 0.3 wt.% of CNTs and GNPs individually, and with 1:1 CNT:GNP hybrid fillers at equivalent total loadings. Scanning electron microscopy of fracture surfaces confirmed that the CNTGNP hybrids dispersed uniformly, forming an interconnected nanostructured network. Notably, the 0.3 wt.% CNTGNP hybrid system exhibited minimal agglomeration and voids, preventing crack initiation and propagation. Mechanical testing revealed that the 0.3 wt.% CNTGNP/Ep composite achieved the highest tensile strength of approximately 84.5 MPa while maintaining a well-balanced stiffness profile (elastic modulus ≈ 4.62 GPa). The hybrid composite outperformed both due to its synergistic reinforcement mechanisms and superior dispersion despite containing only half the concentration of each nanofiller relative to the individual 0.3 wt.% CNT or GNP systems. In addition to mechanical performance, electrical conductivity analysis revealed that the 0.3 wt.% CNTGNP hybrid composite exhibited the highest conductivity of 0.025 S/m, surpassing the 0.3 wt.% CNT-only system (0.022 S/m), owing to forming a well-connected three-dimensional conductive network. The 0.1 wt.% CNT-only composite also showed enhanced conductivity (0.0004 S/m) due to better dispersion at lower filler loadings. These results highlight the dominant role of CNTs in charge transport and the effectiveness of hybrid networks in minimizing agglomeration. These findings demonstrate that CNTGNP hybrid fillers can deliver optimally balanced mechanical enhancement in epoxy matrices, offering a promising route for designing lightweight, high-performance structural composites. Further optimization of nanofiller dispersion and interfacial chemistry may yield even greater improvements.

Journal of Composites Science doi: 10.3390/jcs9070373

Authors: Xingtian Ji Pengwei Ren Hao Liu Yanhua Shi Yunfeng Yan Jianzhang Wang

Polyimide (PI), owing to its high heat resistance and low density, is often employed as a substitute for metallic materials in high-temperature environments, such as aircraft engines, bearings, and gears. However, the relatively high friction coefficient of pure PI limits its application under harsh conditions. Therefore, this study synthesized a composite lubricant with binary fillers to improve this performance. This study employed the hydrothermal method to synthesize MoS2/MXene composite lubricating fillers and systematically investigated the high-temperature tribological properties of PI composites reinforced with these fillers. The results demonstrated that the optimal PI composite containing 5% MoS2/MXene exhibited a 14 °C increase in initial decomposition temperature compared to pure PI. Additionally, its thermal conductivity was enhanced by 36%, while the hardness (0.398 GPa) and elastic modulus (6.294 GPa) were elevated by 12.4% and 18.6%, respectively, relative to the pure PI. In terms of tribological behavior, all composite formulations displayed typical temperature-dependent friction characteristics. It is worth noting that MXene’s high hardness and thermal conductivity inhibited the occurrence of abrasive wear. At the same time, the substrate was strengthened, and thermal resistance was enhanced, thereby delaying the plastic deformation of the material at high temperatures.

Journal of Composites Science doi: 10.3390/jcs9070372

Authors: Abdulkader El-Mir Perla Tannouri Joseph J. Assaad Dana Nasr Maria Ghannoum Firas Barraj Hilal El-Hassan

This study aimed to optimize the performance of pervious concrete (PC) while promoting sustainability using recycled concrete aggregates (RCAs), styrene butadiene rubber (SBR) waste, and silica fume (SF). The mixtures were developed using the Taguchi approach with four mix design factors, each at three levels: the water-to-binder ratio (w/b), RCA replacement percentage by weight of natural aggregates, the cement substitution rate with SF, and the SBR addition rate by binder mass. Thus, a total of nine mixes were prepared and tested for density, porosity, permeability, compressive strength, splitting tensile strength, abrasion resistance, and resistance to freezing and thawing. The results revealed that incorporating RCA and SBR decreased density and compressive strength but increased porosity and permeability. The performance of PC enhanced with SF addition and reduced w/b. TOPSIS was then employed to find the optimum mixture design proportions by considering multiple performance criteria. The results indicated that a high-performing sustainable PC mixture, with enhanced strength and durability characteristics, was formulated with a w/b ratio of 0.30, 25% RCA, 5% SF replacement, and 4% SBR addition.

Journal of Composites Science doi: 10.3390/jcs9070371

Authors: Holger B?hm Andreas Hornig Chokri Cherif Maik Gude

In this work, a finite element modelling methodology is presented for the prediction of the bending behaviour of a glass fibre-reinforced elastomer composite with embedded shape memory alloy (SMA) wire actuators. Three configurations of a multi-layered composite with differences in structural stiffness and thickness are experimentally and numerically analysed. The bending experiments are realised by Joule heating of the SMA, resulting in deflection angles of up to 58 deg. It is shown that a local degradation in the structural stiffness in the form of a hinge significantly increases the amount of deflection. Modelling is fully elaborated in the finite element software ANSYS, based on material characterisation experiments of the composite and SMA materials. The thermomechanical material behaviour of the SMA is modelled via the Souza–Auricchio model, based on differential scanning calorimetry (DSC) and isothermal tensile experiments. The methodology allows for the consideration of an initial pre-stretch for straight-line positioned SMA wires and an evaluation of their phase transformation state during activation. The results show a good agreement of the bending angle for all configurations at the activation temperature of 120 °C reached in the experiments. The presented methodology enables an efficient design and evaluation process for soft robot structures with embedded SMA actuator wires.

Journal of Composites Science doi: 10.3390/jcs9070370

Authors: Nuno A. T. C. Fernandes Diana I. Alves Diana P. Ferreira Maria Monteiro Ana Arieira Filipe Silva Betina Hinckel Ana Leal óscar Carvalho

Medical phantoms are essential to imaging calibration, clinician training, and the validation of therapeutic procedures. However, most ultrasound phantoms prioritize acoustic realism while neglecting the viscoelastic and anisotropic properties of fibrous soft tissues. This gap limits their effectiveness in modeling realistic biomechanical behavior, especially in wave-based diagnostics and therapeutic ultrasound. Current materials like gelatine and agarose fall short in reproducing the complex interplay between the solid and fluid components found in biological tissues. To address this, we developed a soft, anisotropic composite whose dynamic mechanical properties resemble fibrous biological tissues such as skin and skeletal muscle. This material enables wave propagation and vibration studies in controllably anisotropic media, which are rare and highly valuable. We demonstrate the tunability of damping and stiffness aligned with fiber orientation, providing a versatile platform for modeling soft-tissue dynamics and validating biomechanical simulations. The phantoms achieved Young’s moduli of 7.16–11.04 MPa for skin and 0.494–1.743 MPa for muscles, shear wave speeds of 1.51–5.93 m/s, longitudinal wave speeds of 1086–1127 m/s, and sound absorption coefficients of 0.13–0.76 dB/cm/MHz, with storage, loss, and complex moduli reaching 1.035–6.652 kPa, 0.1831–0.8546 kPa, and 2.138–10.82 kPa. These values reveal anisotropic response patterns analogous to native tissues. This novel natural fibrous composite system affords sustainable, low-cost ultrasound phantoms that support both mechanical fidelity and acoustic realism. Our approach offers a route to next-gen tissue-mimicking phantoms for elastography, wave propagation studies, and dynamic calibration across diverse clinical and research applications.

Journal of Composites Science doi: 10.3390/jcs9070369

Authors: Venkatraman Manokaran Anthony Xavior Michael Ashwath Pazhani Andre Batako

This study investigates the fabrication and residual stress behavior of a 0.5 wt.% graphene-reinforced AA2195 aluminum matrix composite, developed for advanced aerospace structural applications. The composite was synthesized via squeeze casting, followed by a multi-pass hot rolling process and subsequent T8 heat treatment. The evolution of residual stress was systematically examined after each rolling pass and during thermal treatments. The successful incorporation of graphene into the matrix was confirmed through Energy-Dispersive Spectroscopy (EDS) analysis. Residual stress measurements after each pass revealed a progressive increase in compressive stress, reaching a maximum of −68 MPa after the fourth hot rolling pass. Prior to the fifth pass, a solution treatment at 530 °C was performed to dissolve coarse precipitates and relieve internal stresses. Cold rolling during the fifth pass reduced the compressive residual stress to −40 MPa, and subsequent artificial aging at 180 °C for 48 h further decreased it to −23 MPa due to recovery and stress relaxation mechanisms. Compared to the unreinforced AA2195 alloy in the T8 condition, which exhibited a tensile residual stress of +29 MPa, the graphene-reinforced composite in the same condition retained a compressive residual stress of −23 MPa. This represents a net improvement of 52 MPa, highlighting the composite’s superior capability to retain compressive residual stress. The presence of graphene significantly influenced the stress distribution by introducing thermal expansion mismatch and acting as a barrier to dislocation motion. Overall, the composite demonstrated enhanced residual stress characteristics, making it a promising candidate for lightweight, fatigue-resistant aerospace components.

Journal of Composites Science doi: 10.3390/jcs9070368

Authors: Mohamad Alsaadi Tomas Flanagan Declan M. Devine

This research paper employed the recently developed Elium thermoplastic resin and basalt fabrics as an alternative to thermoset/synthetic fibre composites to reduce their environmental impact. Elium® 191 XO/SA and Epoxy PrimeTM 37 resin were reinforced with mineral-based semi-unidirectional basalt fibre (BF). Physical, chemical, tensile, and flexural performance was investigated under the effect of hydrothermal seawater ageing at 45 °C for 45 and 90 days. The results show that the BF/Elium composite exhibited superior tensile and flexural strength, as well as good stiffness, compared with the BF/Epoxy composite. Digital images and scanning electron microscope images were used to describe the fracture and failure mechanisms. The tensile and flexural strength values of the BF/Elium composite were 1165 MPa and 1128 MPa, greater than those of the BF/Epoxy composite by 33% and 71%, respectively. The tensile and flexural modulus values of the BF/Elium composite were 44.1 GPa and 38.2 GPa, which are 30% and 12% greater than those of the BF/Epoxy composite. The result values for both composites were normalised with respect to the density of each composite laminate. Both composites exhibited signs of resin decomposition and fibre surface degradation under the influence of seawater ageing, resulting in a more recognisable reduction in flexural properties than in tensile properties.

Journal of Composites Science doi: 10.3390/jcs9070367

Authors: Fynn Atzler Ines M?ssinger Jonathan Freund Samuel Tr?ger Ashley R. Chadwick Simon Hümbert Lukas Raps

Thermoplastic in situ Automated Fiber Placement (AFP) is an additive manufacturing method currently investigated for its suitability for the production of aerospace-grade composite structures. A considerable expense in this process is the manufacturing and preparation of a mold in which a composite part can be manufactured. One approach to lowering these costs is the use of a 3D-printable thermoplastic mold. However, AFP lay-up on a 3D-printed mold differs from the usage of a traditional metallic mold in various aspects. Most notable is a reduced stiffness of the mold, a lower thermal conductivity of the mold, and the need for varied process parameters of the AFP process. This study focuses on the investigation of the difference in mechanical and morphological characteristics of laminates produced on metallic and polymeric molds. To this end, the tensile strength and the interlaminar shear strength of laminates manufactured on each substrate were measured and compared. Additionally, morphological analysis using scanning electron microscopy and differential scanning calorimetry was performed to compare the crystallinity in laminates. No statistically significant difference in mechanical or morphological properties was found. Thus, thermoplastics were shown to be a suitable material for non-heated molds to manufacture in situ AFP composites.

Journal of Composites Science doi: 10.3390/jcs9070366

Authors: Elodie Melro Hugo Duarte Filipe E. Antunes Artur J. M. Valente Anabela Romano Bruno Medronho

The growing demand for sustainable materials has intensified the search for biodegradable polymers. Poly(ε-caprolactone) (PCL), though biodegradable, is fossil-derived. In this study, a novel lignin extracted from pine wood using a green solvent was incorporated into PCL and compared with commercial lignins (dealkaline, alkaline, and lignosulfonate). The lignin additions imparted antioxidant properties, enhanced thermal stability, and promoted circular economy goals through lignin valorization. Notably, the green-extracted lignin showed superior compatibility with PCL when compared with commercial lignins, as evidenced by lower water uptake and solubility, and improved surface hydrophobicity (higher contact angle). Although the addition of lignin reduced the tensile strength and elongation at break, it greatly increased the PCL radical scavenging activity (DPPH) from 8 ± 1% of neat PCL to 94.8 ± 0.3% when 20 wt% of lignin-LA was added. Among the tested lignins, lignin-LA stands out as the most promising candidate to be applied as a functional additive in biodegradable polymer blends and composites for advanced sustainable applications. Not only given its intrinsically higher sustainability but also due to its capacity for improving the thermal properties of PCL–lignin blends.

Journal of Composites Science doi: 10.3390/jcs9070365

Authors: H. M. D. U. Sewwandi J. D. Chathuranga W. G. C. M. Kulasooriya D. K. A. Induranga S. V. A. A. Indupama G. D. C. P. Galpaya M. K. D. M. Gunasena H. V. V. Priyadarshana K. R. Koswattage

The extensive accumulation of plastic waste causes serious environmental problems, leading to growing interest in biodegradable alternatives. In this study, the structural, chemical, and crystalline characteristics of a pulp-based material incorporating sugarcane bagasse ash (SCBA) were investigated using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Mechanical properties of the materials were investigated through compression, tensile, and bending tests in order to assess their strength and flexibility, while biodegradability was evaluated through soil burial tests. The results indicate that SCBA addition enhances compressive strength, with optimal performance obtained at 15% SCBA content, while tensile and bending strengths showed an enhancement at 5% content. FTIR and XRD analyses suggested an increase in amorphous regions and notable microstructural interactions between SCBA particles and cellulose fibers, particularly at a 10% concentration. SEM images further confirmed effective particle dispersion and improved porosity in the composite materials. Furthermore, samples incorporating SCBA exhibited superior biodegradability compared to pure pulp. Overall, these findings highlight that incorporating 10–15% SCBA provides a promising balance between mechanical integrity and environmental sustainability, offering a viable strategy for developing eco-friendly, high-performance packaging materials.

Journal of Composites Science doi: 10.3390/jcs9070364

Authors: Pavan Hiremath Subraya Krishna Bhat Jayashree P. K. P. Krishnananda Rao Krishnamurthy D. Ambiger Murthy B. R. N. S. V. Udaya Kumar Shetty Nithesh Naik

This study presents a robust machine learning framework based on Gaussian process regression (GPR) to predict the tensile strength of polymer nanocomposites reinforced with various nanofillers and processed under diverse techniques. A comprehensive dataset comprising 25 polymer matrices, 22 surface functionalization methods, and 24 processing routes was constructed from the literature. GPR, coupled with Monte Carlo sampling across 2000 randomized iterations, was employed to capture nonlinear dependencies and uncertainty propagation within the dataset. The model achieved a mean coefficient of determination (R2) of 0.96, RMSE of 12.14 MPa, MAE of 7.56 MPa, and MAPE of 31.73% over 2000 Monte Carlo iterations, outperforming conventional models such as support vector machine (SVM), regression tree (RT), and artificial neural network (ANN). Sensitivity analysis revealed the dominant influence of Carbon Nanotubes (CNT) weight fraction, matrix tensile strength, and surface modification methods on predictive accuracy. The findings demonstrate the efficacy of the proposed GPR framework for accurate, reliable prediction of composite mechanical properties under data-scarce conditions, supporting informed material design and optimization.

Journal of Composites Science doi: 10.3390/jcs9070363

Authors: Jamal F. Husseini Eric J. Carey Farhad Pourkamali-Anaraki Evan J. Pineda Brett A. Bednarcyk Scott E. Stapleton

Fiber-reinforced composites contain microscale features such as variations in local fiber volume fraction, fiber clusters, and resin-rich regions, which may impact mechanical properties. Microscale models need to be large enough to capture these features while maintaining high fidelity to capture the localized fiber-to-fiber interactions. This makes it difficult to efficiently model regions with equivalent fiber morphologies to as-manufactured scans and to perform large statistical studies to examine how these features drive mechanical performance. This study uses a novel microstructure generator and an efficient micromechanical model along with a characterization method that measures the geometry of these features to simulate a wide range of microstructures for strength and stiffness. After understanding how the mechanical properties are affected by morphology through correlation matrices, equivalent microstructures were generated to regions of an as-manufactured composite. The generation of microstructures based on different morphological descriptors allows for an understanding of which features are valuable when modeling these materials. In comparing microstructures with different equivalent descriptors to the case with all six descriptors, it was found that only using local fiber volume fraction median resulted in over predictions of strength and stiffness. Once two descriptors or more were introduced, such as local fiber volume fraction median and inter-quartile range, there was no significant difference in strength and stiffness. This suggests that at least two descriptors should be considered when generating equivalent microstructures for mechanical properties.

Journal of Composites Science doi: 10.3390/jcs9070362

Authors: Dharrinesh Narendiran Nurul Hazirah Sumadi Ali Shaan Manzoor Ghumman Noor Ashikin Mohamad Mohamed Mahmoud Nasef Amin Abbasi Rashid Shamsuddin

Sulfur-containing polymers are unique sustainable materials with promise for the development of various adsorbents for environmental remediation. However, they have not been explored for CO2 capture despite reports on its ability to decontaminate various aqueous pollutants. This study reports on the single-step synthesis of a diamine-functionalized sulfur-containing copolymer by the thermally induced radical copolymerization of N2,N2-Diallylmelamine (NDAM), a difunctional monomer, with sulfur and explores its use for CO2 capture. The influence of reaction parameters such as the weight ratios of sulfur to NDAM, reaction temperature, time, and the addition of a porogen on the properties of aminated copolymer was investigated. The resulting copolymers were characterized using FTIR, TGA, DSC, SEM, XRD, and BET surface area analyses. The incorporation of NDAM directly imparted amine functionality while stabilizing the polysulfide chains by crosslinking, leading to a thermoset copolymer with an amorphous structure. The addition of a NaCl particle porogen to the S/NDAM mixture generated a mesoporous structure, enabling the resulting copolymer to be tested for CO2 adsorption under varying pressures, leading to an adsorption capacity as high as 517 mg/g at 25 bar. This work not only promotes sustainable hybrid materials that advance green chemistry while aiding CO2 mitigation efforts but also adds value to the abundant amount of sulfur by-products from petroleum refineries.

Journal of Composites Science doi: 10.3390/jcs9070361

Authors: Shinya Inazumi Kazuhiko Tazuke Seiya Kashima

This study investigates cement–bentonite slurries with hydration accelerators for borehole backfilling applications in infrastructure reconstruction projects. Two formulations with different accelerator dosages (5 and 10 kg/m3) were evaluated through combined experimental testing and Moving Particle Semi-implicit (MPS) numerical modeling to optimize material performance. The research focuses on time-dependent rheological evolution and its impact on construction performance, particularly bleeding resistance and workability retention. Experimental flow tests revealed that both formulations maintained similar initial flowability (240–245 mm spread diameter), but the higher accelerator dosage resulted in 33% flow reduction after 60 min compared to 12% for the lower dosage. Bleeding tests demonstrated significant improvement in phase stability, with bleeding rates reduced from 2.5% to 1.5% when accelerator content was doubled. The MPS framework successfully reproduced experimental behavior with prediction accuracies within 3%, enabling quantitative analysis of time-dependent rheological parameters through inverse analysis. The study revealed that yield stress evolution governs both flow characteristics and bleeding resistance, with increases several hundred percent over 60 min while plastic viscosity remained relatively constant. Critically, simulations incorporating time-dependent viscosity changes accurately predicted bleeding behavior, while constant-viscosity models overestimated bleeding rates by 60–130%. The higher accelerator formulation (10 kg/m3) provided an optimal balance between initial workability and long-term stability for typical borehole backfilling operations. This integrated experimental–numerical approach provides practical insights for material optimization in infrastructure reconstruction projects, particularly relevant for aging infrastructure requiring proper foundation treatment. The methodology offers construction practitioners a robust framework for material selection and performance prediction in borehole backfilling applications, contributing to improved construction quality and reduced project risks.

Journal of Composites Science doi: 10.3390/jcs9070360

Authors: Ganesh Radhakrishnan Teodora Odett Breaz Abdul Hamed Hamed Al Hinai Fisal Hamed Al Busaidi Laqman Malik Al Sheriqi Mohammed Ali Al Hattali Mohammed Ibrahim Al Rawahi Mohammed Nasser Al Rabaani Kadhavoor R. Karthikeyan

In recent times, fiber reinforced polymer composite materials have become more popular due to their remarkable features such as high specific strength, high stiffness and durability. Particularly, Carbon Fiber Reinforced Polymer (CFRP) composites are one of the most prominent materials used in the field of transportation and building engineering, replacing conventional materials due to their attractive properties as mentioned. In this work, a CFRP laminate is fabricated with carbon fiber mats and epoxy by a hand layup technique. Alumina (Al2O3) micro particles are used as a filler material, mixed with epoxy at different weight fractions of 0% to 4% during the fabrication of CFRP laminates. The important objective of the study is to investigate the influence of alumina micro particles on the mechanical performance of the laminates through characterization for various physical and mechanical properties. It is revealed from the results of study that the mass density of the laminates steadily increased with the quantity of alumina micro particles added and subsequently, the porosity of the laminates is reduced significantly. The SEM micrograph confirmed the constituents of the laminate and uniform distribution of Al2O3 micro particles with no significant agglomeration. The hardness of the CFRP laminates increased significantly for about 60% with an increase in weight % of Al2O3 from 0% to 4%, whereas the water gain % gradually drops from 0 to 2%, after which a substantial rise is observed for 3 to 4%. The improved interlocking due to the addition of filler material reduced the voids in the interfaces and thereby resist the absorption of water and in turn reduced the plasticity of the resin too. Tensile, flexural and inter-laminar shear strengths of the CFRP laminate were improved appreciably with the addition of alumina particles through extended grain boundary and enhanced interfacial bonding between the fibers, epoxy and alumina particles, except at 1 and 3 wt.% of Al2O3, which may be due to the pooling of alumina particles within the matrix. Inclusion of hard alumina particles resulted in a significant drop in impact strength due to appreciable reduction in softness of the core region of the laminates.

Journal of Composites Science doi: 10.3390/jcs9070359

Authors: Khishigdorj Davaasambuu Yu Dong Alokesh Pramanik Animesh Kumar Basak

Conventional adhesively bonded joints, such as single-lap, curved-lap, wavy-lap, double-lap, stepped-lap, and scarf joints, are widely used for aerospace, automotive, and medical applications. These adhesively bonded joints exhibit different load transfer mechanisms and stress distributions within adhesive layers, which depend primarily on their geometries and mechanical properties of bonded materials. As such, joint geometry and material properties play a critical role in determining the capability of the joints to withstand high loads, resist fatigue, and absorb energy under impact loading. This paper investigates the effects of geometry and material dissimilarity on the performance of both conventional bonded and interlocking joints under tensile loading based on the information available in the literature. In addition, bonding and load transfer mechanisms were analysed in detail. It was found that stress concentration often occurs at free edges of the adhesive layer due to geometric discontinuities, while most of the load is carried by these regions rather than its centre. Sharp corners further intensify resulting stresses, thereby increasing the risk of joint failure. Adhesives typically resist shear loads better than peel loads, and stiffness mismatches between adherents induce an asymmetric stress distribution. Nonetheless, similar materials promote symmetric load sharing. Among conventional joints, scarf joints provide the most uniform load distribution. In interlocking joints such as dovetail, T-slot, gooseneck, and elliptical types, the outward bending of the female component under tension can lead to mechanical failure.

Journal of Composites Science doi: 10.3390/jcs9070358

Authors: Isis Chetzyl Ballardo Rodriguez U. Gardu?o Terán A. I. Díaz Cano B. El Filali M. Badaoui

There is considerable interest in broadband nanomaterials, particularly transparent semiconductor oxides, within both fundamental research and technological applications. Historically, it has been considered that the variation in dopant concentration during the synthesis of semiconductor materials is a crucial factor in activating and/or modulating the optical and structural properties, particularly the bandgap and the parameters of the unit cell, of semiconductor oxides. Recently, tin oxide has emerged as a key material due to its excellent structural properties, optical transparency, and various promising applications in optoelectronics. This study utilized the ultrasonic spray pyrolysis technique to synthesize aluminum-doped tin oxide (ATO) thin films on quartz and polished single-crystal silicon substrates. The impact of varying aluminum doping levels (0, 2, 5, and 10 at. %) on morphology and structural and optical properties was examined. The ATO thin films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmittance spectroscopy. SEM images demonstrated a slight reduction in the size of ATO nanoparticles as the aluminum doping concentration increased. XRD analysis revealed a tetragonal crystalline structure with the space group P42/mnm, and a shift in the XRD peaks to higher angles was noted with increasing aluminum content, indicating a decrease in the crystalline lattice parameters of ATO. The transmittance of the ATO films varied between 75% and 85%. By employing the transmittance spectra and the established Tauc formula the optical bandgap values of ATO films were calculated, showing an increase in the bandgap with higher doping levels. These findings were thoroughly analyzed and discussed; additionally, an effort was made to clarify the contradictory analyses present in the literature and to identify a doping range that avoids the onset of a secondary phase.

Journal of Composites Science doi: 10.3390/jcs9070357

Authors: Karthick Rasu Vigneshwaran Shanmugam Joao Paulo Davim

In response to the rising demand for sustainable engineering materials and waste valorisation strategies, this study investigates the multi-objective optimisation of eco-friendly hybrid composites reinforced with natural fibres and industrial waste. Sixteen composite specimens were fabricated using compression moulding by varying sisal fibre from 0 to 45 wt.%, banana fibre from 0 to 45 wt.%, NaOH alkali treatment from 0 to 6%, and red mud filler from 1 to 4 wt.%. Mechanical properties were evaluated following ASTM standards D256 for impact strength, D790 for flexural strength, D638 for tensile strength, D5379 for shear strength, and E18 for hardness. The Taguchi method combined with grey relational analysis was employed to identify optimal processing conditions. The best mechanical performance, with an impact strength of 6.57 J, flexural strength of 72.58 MPa, and tensile strength of 65.52 MPa, was achieved with 30 to 45 wt.% sisal fibre, 15 wt.% banana fibre, 6% NaOH, and 3 to 4 wt.% red mud. ANOVA revealed that NaOH treatment had the most significant influence on mechanical properties, with high F values and p values close to 0.05. Grey relational analysis proved more effective for multi-objective optimisation, with the highest grey grade of 0.894 observed in the specimen containing 45 wt.% sisal fibre, 6% NaOH, and 2 wt.% red mud. These findings highlight the critical role of fibre treatment and hybrid reinforcement in enhancing performance. The optimised composites demonstrate strong potential for use in automotive interior panel applications, offering a sustainable alternative with balanced strength and reduced environmental impact.

Journal of Composites Science doi: 10.3390/jcs9070356

Authors: Cristiano Fragassa Carlo Santulli

Introducing and compacting lignocellulosic biomass in aluminum structures, though recommendable in terms of higher sustainability, the potential use of agro-waste and significant weight reduction, still represents a challenge. This is due to the variability of biomass performance and to its limited compatibility with the metal. Another question may concern possible moisture penetration in the structure, which may reduce environmental resistance and result in local degradation, such as wear or even corrosion. Despite these limitations, this hybridization enjoys increasing success. Two forms are possibly available for this: introduction into metal matrix composites (MMCs), normally in the form of char from biomass combustion, or laminate reinforcement as the core for fiber metal laminates (FMLs). These two cases are treated alongside each other in this review, first because they may represent two combined options for recycling the same biomass into high-profile structures, aimed primarily at the aerospace industry. Moreover, as discussed above, the effect on the aluminum alloy can be compared and the forces to which they are subjected might be of a similar type, most particularly in terms of their hardness and impact. Both cases considered, MMCs and FMLs involved over time many lignocellulosic residues, starting from the most classical bast species, i.e., flax, hemp, sisal, kenaf, etc., and extending also to less diffuse ones, especially in view of the introduction of biomass as secondary, or residual, raw materials.

Journal of Composites Science doi: 10.3390/jcs9070355

Authors: Svetlana G. Karpova Anatoly A. Olkhov Ivetta A. Varyan Ekaterina P. Dodina Yulia K. Lukanina Natalia G. Shilkina Anatoly A. Popov Alexandre A. Vetcher Anna G. Filatova Alexey L. Iordanskii

Ultrafine fibers from poly(3-hydroxybutyrate) (PHB) and polyvinylpyrrolidone (PVP) and their blends with different component ratios in the range of 0/100 to 100/0 wt.% were obtained, and their structure and dynamic properties were studied. The polymers were obtained via electrospinning in solution mode. The structure, morphology, and segmental dynamic behavior of the fibers were determined using optical microscopy, SEM, EPR, DSC, and IR spectroscopy. The low-temperature maximum on the DSC endotherms provided information on the state of the PVP hydrogen bond network, which made it possible to determine the enthalpies of thermal destruction of these bonds. The PHB/PVP fiber blend ratio significantly affected the structural and dynamic parameters of the system. Thus, at low concentrations of PVP (up to 9%) in the structure of ultra-fine fibers, the distribution of this polymer occurs in the form of tiny particles, which are crystallization centers, which causes a significant increase in the degree of crystallinity (χ) activation energy (Eact) and slowing down of molecular dynamics (τ). At higher concentrations of PVP, loose interphase layers were formed in the system, which caused a decrease in these parameters. The strongest changes in the concentration of hydrogen bonds occurred when PVP was added to the composition from 17 to 50%, which was due to the formation of intermolecular hydrogen bonds both in PVP and during the interaction of PVP and PHB. The diffusion coefficient of water vapor in the studied systems (D) decreased as the concentration of glassy PVP in the composition increased. The concentration of the radical decreased with an increase in the proportion of PVP, which can be explained by the glassy state of this polymer at room temperature. A characteristic point of the 50/50% mixture component ratio was found in the region where an inversion transition of PHB from a dispersion material to a dispersed medium was assumed. The conducted studies made it possible for the first time to conduct a comprehensive analysis of the effect of the component ratio on the structural and dynamic characteristics of the PHB/PVP fibrous material at the molecular scale.

Journal of Composites Science doi: 10.3390/jcs9070354

Authors: Nathan S. Usevitch Emily V. White Anton E. Bowden Ulrike H. Mitchell David T. Fullwood

Flexible strain sensors, fabricated from high-elongation polymers and conductive filler particles, are proving an essential tool in the study of biomechanics using wearable technology. It has been previously shown that the resistive response of such composites, relative to the amount of conductive filler material, can be reasonably modeled using a standard percolation-type model. Once a certain critical fraction of filler material is reached, a conductive network across the sample is established and resistance rapidly decreases. However, modeling the more subtle resistance changes that occur while deforming the sensors during operation is more nuanced. Conductivity across the network of particles is dominated by tunneling mechanisms at the interfaces between the filler materials. Small changes in strain at these interfaces lead to relatively large, but nevertheless continuous, changes in local resistance. By assigning some arbitrary value of resistance as a dividing line between ‘low’ and ‘high’ resistance, one might model the piezoresistive behavior using a standard percolation model. But such an assumption is likely to lead to low accuracy. Our alternative approach is to divide the range of potential resistance values into several bins (rather than the usual two bins) and apply a relatively novel multi-state percolation theory. The performance of the multi-state percolation model is assessed using a random resistor model that is assumed to provide the ground truth. The model is applied to predict resistance response with both changes in relative amount of conductive filler (i.e., to help design the initial unstrained sensor) and with applied strain (for an operating sensor). We find that a multi-state percolation model captures the behavior of the simulated composite sensor in both cases. The multicomponent percolation theory becomes more accurate with more divisions/bins of the resistance distribution, and we found good agreement with the simulation using between 10 and 20 divisions.

Journal of Composites Science doi: 10.3390/jcs9070353

Authors: Masoumeh Mousavi Vajiheh Akbarzadeh Mohammadjavad Kazemi Shuguang Deng Elham H. Fini

This perspective explores the use of biochar, a carbon-rich material derived from biomass, as a sustainable solution for mitigating volatile organic compounds (VOCs) emitted during asphalt production and use. VOCs from asphalt contribute to ozone formation and harmful secondary organic aerosols (SOAs), which negatively impact air quality and public health. Biochar, with its high surface area and capacity to adsorb VOCs, provides an effective means of addressing these challenges. By tailoring biochar’s surface chemistry, it can efficiently capture VOCs, while also offering long-term carbon sequestration benefits. Additionally, biochar enhances the durability of asphalt, extending road lifespan and reducing maintenance needs, making it a promising material for sustainable infrastructure. Despite these promising benefits, several challenges remain. Variations in biochar properties, driven by differences in feedstock and production methods, can affect its performance in asphalt. Moreover, the integration of biochar into existing plant operations requires the further development of methods to streamline the process and ensure consistency in biochar’s quality and cost-effectiveness. Standardizing production methods and addressing logistical hurdles will be crucial for biochar’s widespread adoption. Research into improving its long-term stability in asphalt is also needed to ensure sustained efficacy over time. Overcoming these challenges will be essential for fully realizing biochar’s potential in sustainable infrastructure development

Journal of Composites Science doi: 10.3390/jcs9070352

Authors: Maria G. Mousdraka Olga Gerasimidou Alexandros K. Nikolaidis Christos Gogos Elisabeth A. Koulaouzidou

This study evaluated the effects of conventional cigarette smoke compared to aerosol from a heat-non-burn tobacco product on the color stability of two UDMA-based dental composite resins, namely a monochromatic (Omnichroma) and a polychromatic (Vittra APS) resin. Twenty disc-shaped specimens were prepared, divided into two groups of ten, and exposed to 105 cigarettes or 105 aerosol tobacco sticks via a custom-made smoking chamber. Puff duration was 2 s, with a 60 s interval between puffs in which smoke saturated the chamber for 30 s; then, clean air was introduced into the chamber for 30 s. Six puffs and six intervals were simulated. Color parameters were measured before and after exposure and following brushing of each specimen with 15 strokes. Color differences were determined based on the CIEDE2000 formula. Significant color change was found in all specimens exposed to cigarette and tobacco aerosol. The highest color-change mean value was obtained from composite resin exposed to cigarette smoke. Although both cigarette and thermal heating systems cause discoloration, the aerosol causes reduced composite resin discoloration, which compromises aesthetics and increases patient dissatisfaction, impacting the overall dental care. Color stability is the hallmark of success, as it is the main reason for replacing dental restorations.

Journal of Composites Science doi: 10.3390/jcs9070351

Authors: Rabindra Dharai Yubaraj Chakraborty Rabiranjan Murmu Pragyan Senapati Harekrushna Sutar Debashis Roy

In this study, micrographite (μG)-reinforced polypropylene (PP) composites were fabricated using melt compounding, with μG contents varying from 3 to 15 wt%. The composites were evaluated for mechanical, electrical, and thermal performance, addressing a relatively underexplored area among carbon-based fillers. Tensile testing across elongation speeds (10–50 mm/min) showed up to ~30% strength improvement at 6 wt% μG due to good dispersion and stress transfer, while ≥9 wt% led to agglomeration, reduced ductility, and increased melt resistance. SEM fractography confirmed matrix–filler debonding and brittle behavior at higher loadings, with ductility improving at higher elongation rates. A sharp drop in resistivity near 6 wt% indicated the formation of a conductive network, and thermal conductivity improved by nearly 80%. Taguchi optimization identified 12 wt% μG and 50 mm/min as optimal for tensile strength, with filler content having a stronger influence than testing speed. The novelty of this work lies in its integrated structure–property investigation across a broad μG range, offering a scalable, multifunctional PP composite system suitable for semi-structural, conductive, and thermal management applications.

Journal of Composites Science doi: 10.3390/jcs9070350

Authors: Alaa El-Sisi Ahmed Elbelbisi Ahmed Elkilani Hani Salim

In advanced structural applications—aerospace and automotive—fiber-laminated composite (FRP) materials are increasingly used for their superior strength-to-weight ratios, making the reliability of their mechanical joints a critical concern. Mechanically fastened joints play a major role in ensuring the structural stability of FRP Composite structures; however, accurately predicting their failure behavior remains a major challenge due to the anisotropic and heterogeneous nature of composite materials. This paper presents a progressive damage modeling approach to investigate the failure modes and joint strength of mechanically fastened carbon fiber-laminated (CFRP) composite joints. A 3D constitutive model based on continuum damage mechanics was developed and implemented within a three-dimensional finite element framework. The joint model comprises a composite plate, a steel plate, a steel washer, and steel bolts, capturing realistic assembly behavior. Both single- and double-lap joint configurations, featuring single and double bolts, were analyzed under tensile loading. The influence of clamping force on joint strength was also investigated. Model predictions were validated against existing experimental results, showing a good correlation. It was observed that double-lap joints exhibit nearly twice the strength of single-lap joints and can retain up to 85% of the strength of a plate with a hole. Furthermore, double-lap configurations support higher clamping forces, enhancing frictional resistance at the interface and load transfer efficiency. However, the clamping force must be optimized, as excessive values can induce premature damage in the composite before external loading. The stiffness of double-bolt double-lap (3DD) joints was found to be approximately three times that of single-bolt single-lap (3DS) joints, primarily due to reduced rotational flexibility. These findings provide useful insights into the design and optimization of composite bolted joints under tensile loading.

Journal of Composites Science doi: 10.3390/jcs9070349

Authors: Maria Rosaria Ricciardi Vincenza Antonucci

The thermal stability and flammability behavior of an epoxy resin, modified by the addition of Posidonia oceanica (PO) at three concentration levels (8%, 10%, 12% wt.), were investigated by performing thermogravimetric and cone calorimetry tests. The plant was preliminarily dried and milled to obtain a powder with an average size of 80 μm, then dispersed within the resin prior to curing. Scanning electron microscopy and spectroscopic FT-IR analysis on both PO and hybrid composites were carried out to verify the dispersion and the mechanisms of action of the plant within the resin. Results from TGA and cone calorimetry tests showed that the incorporation of PO reduced the thermal degradation rate by simultaneously increasing the residual weight and significantly affected the flammability of the epoxy resin, with a strong reduction in PHHR of up to 52%. Thus, the PO-modified resin at 12% wt was used to realize basalt laminate composites that demonstrated an improvement in fire performance with respect to the neat resin composites.

Journal of Composites Science doi: 10.3390/jcs9070348

Authors: Siok Wei Tay Inez Lau Liang Hong

This research investigates a novel hybrid E-glass fiber coated with a thin amorphous carbon (coke) layer, referred to as GF@C, designed to enhance the affinity of fiber with a polymer matrix. Acrylonitrile butadiene styrene (ABS), an engineering thermoplastic, was selected as the matrix to form the composite. The carbon coating was produced by pyrolyzing a lubricant oil (Lo) layer applied to the glass fiber strands. To promote the formation of graphite crystallites during carbonization, a small amount (x wt.% of Lo) of coronene (Cor) was added to Lo as a dopant. The resulting doped fibers, denoted GF@CLo-Cor(x%), were embedded in ABS at 70 wt.%, leading to significant improvements in mechanical properties. At the optimal doping level (x = 5), the composite achieved a Young’s modulus of 1.02 GPa and a tensile strength of 6.96 MPa, substantially higher than the 0.4 GPa and 3.81 MPa observed for the composite with the pristine GF. This enhancement is attributed to a distribution of graphite crystallites and their graphitization extent in the carbon coating, which improves interfacial bonding and increases chain entanglement. Additionally, GF@CLo-Cor(x%)–ABS composites (x = 0 and 5) exhibit significantly higher dielectric constant–temperature profiles than GF–ABS, attributed to the formation of diverse chain adsorption states on the C-coating.

Journal of Composites Science doi: 10.3390/jcs9070347

Authors: Mohamad Alsaadi Aswani Kumar Bandaru Tomas Flanagan Declan M. Devine

A fabric orientation angle has a significant influence on the failure mechanisms at the lamina level. Any change in this angle can lead to a sudden reduction in strength, potentially resulting in catastrophic failures due to variations in load-carrying capacity. This study examined the impact of off-axis fabric orientation angles (0°, 15°, 30°, 45°, 60°, and 90°) on the flexural properties of non-crimp basalt-fibre-reinforced acrylic thermoplastic composites. The basalt/Elium® composite panels were manufactured using a vacuum-assisted resin transfer moulding technique. The results show that the on-axis (0°) composite specimens exhibited linear stress–strain behaviour and quasi-brittle failure characterised by fibre dominance, achieving superior strength and failure strain values of 1128 MPa and 3.85%, respectively. In contrast, the off-axis specimens exhibited highly nonlinear ductile behaviour. They failed at lower load values due to matrix dominance, with strength and failure strain values of 144 MPa and 6.0%, respectively, observed at a fabric orientation angle of 45°. The in-plane shear stress associated with off-axis angles influenced the flexural properties. Additionally, the degree of deformation and the fracture mechanisms were analysed.

Journal of Composites Science doi: 10.3390/jcs9070346

Authors: Pengtao Cao Jian Wu Tenglong She Juqiao Su Naichi Weng Benlong Su Youshan Wang

Aiming at the heat generation behavior of rubber products such as tires under complex loads, the thermal behavior of tread rubber materials under tensile and compressive loads is investigated by using a torsional fatigue testing machine to comparatively analyze the temperature difference between the inside and outside of the rubber cylinders and the heating history under different torsion angles and rotational speeds. Results demonstrate that during the initial rotation phase under cyclic loading, the external surface temperature of the rubber material exceeds internal measurements. However, with the continuation of cyclic loading, the internal temperature progressively escalates beyond surface temperatures. Furthermore, the temperature rise exhibited significant correlations with both imposed torsional angles and operational rotational speeds. This study provides valuable insights into heat generation patterns of rubber materials under complex working conditions.

Journal of Composites Science doi: 10.3390/jcs9070345

Authors: Awiruth Klaisiri Tool Sriamporn Nantawan Krajangta Niyom Thamrongananskul

The objective of this study was to evaluate the effect of morpholine on saliva-contaminated resin-based composite (RBC)-CAD/CAM material repaired with resin composite. Fifty RBC-CAD/CAM materials were fabricated and assigned to five groups and surface-treated with saliva, phosphoric acid (PHR), morpholine (MRL), and a universal adhesive agent (Scotchbond universal plus, SCP) based on the following techniques: group 1, saliva; group 2, SCP; group 3, saliva + SCP; group 4, saliva + PHR + SCP; and group 5, saliva + MRL + SCP. An ultradent model was placed on the specimen center, and then the resin composite was pressed and light-cured for 20 s. A mechanical testing device was used to evaluate the samples’ shear bond strength (SBS) scores. The debonded specimen areas were inspected under a stereomicroscope to identify the failure mechanisms. The data were analyzed using one-way ANOVA, and the significance level (p < 0.05) was set with Tukey’s test. The highest SBS values were in groups 2, 4 and 5, with values of 21.43 ± 1.93, 20.93 ± 1.46, and 22.02 ± 1.77 MPa, respectively. However, they were not statistically different (p > 0.05). Group 1 had the lowest SBS value by a significant amount (1.88 ± 1.01 MPa). All specimens in group 1 showed adhesive failures. Moreover, groups 2–5 found cohesive and mixed failures. In conclusion, morpholine and phosphoric acid effectively enhance bond strength. These results indicate that alternative surface modifications with morpholine for saliva-contaminated RBC-CAD/CAM materials can significantly improve the outcome.

Journal of Composites Science doi: 10.3390/jcs9070344

Authors: Weixiao Gao Shuai Yu Buntong Tan Fei Ren

This study investigates the application of additive manufacturing (AM) in fabricating transverse thermoelectric (TTE) composites, demonstrating the feasibility of this methodology for TTE material synthesis. Zinc oxide (ZnO), a wide-bandgap semiconductor with moderate thermoelectric performance, and copper (Cu), a highly conductive metal, were selected as base materials. These were formulated into stable paste-like feedstocks for direct ink writing (DIW). A custom dual-nozzle 3D printer was developed to precisely deposit these materials in pre-designed architectures. The resulting structures exhibited measurable transverse Seebeck effects. Unlike prior TE research primarily focused on longitudinal configurations, this work demonstrates a novel AM-enabled strategy that integrates directional compositional anisotropy, embedded metal–semiconductor interfaces, and scalable multi-material printing to realize TTE behavior. The approach offers a cost-effective and programmable pathway toward next-generation energy harvesting and thermal management systems.

Journal of Composites Science doi: 10.3390/jcs9070343

Authors: Thomas Allsop Mohammad W. Tahir

Over the last three decades, composite structures have become increasingly more common in everyday life, such as in wind turbines as part of the solution to produce clean energy, and their use in the aerospace industry due to their advantages over conventional materials. Most of these advantages are dependent upon the reliability and quality of the manufacturing process to ensure that there are no defects/faults or imperfections during manufacturing. Thus, it is critical to monitor the enclosed environment of moulds during fabrication in real time. This need has caused many researchers—past and present—to create or apply many sensing technologies to achieve real-time monitoring of the manufacturing processes of composite structures to ensure that the structures can meet their requirements. A consequence of these research activities is the myriad of sensing schemes, (for example, optical, electrical, piezo, and nanomaterial schemes and the use of digital twins) available to consider, and the investigations all of them have both strengths and weaknesses for a given application, with no apparent option having a distinct advantage. This review reveals that the best possible sensing solution depends upon a large set of parameters, the geometry of the composite structure, the required specification, and budget limits, to name a few. Furthermore, challenges remain for researchers trying to find solutions, such as a sensing scheme that can directly detect wrinkles/waviness during the laying-up procedure, real-time detection of the resin flow front throughout the mould, and the monitoring of the resin curing spatially, all at a spatial resolution of ~1 cm with the required sensitivity along with the need to obtain the true interpretation of the real-time data. This review offers signposts through the variety of sensing options, with their advantages and failings, to readers from the composite and sensing community to aid in making an informed decision on the possible sensing approaches to help them meet their composite structure’s desired function and tolerances, and the challenges that remain.

Journal of Composites Science doi: 10.3390/jcs9070342

Authors: Qi An Jingjie Zhang Guangchun Xiao Chonghai Xu Mingdong Yi Zhaoqiang Chen Hui Chen Chengze Zheng Guangchen Li

During the machining of unidirectional carbon fiber-reinforced polymers (UD-CFRPs), their anisotropic characteristics and the complex cutting conditions often lead to defects such as delamination, burrs, and surface/subsurface damage. This study systematically investigates the effects of different fiber orientation angles (0°, 45°, 90°, and 135°) on cutting force, chip formation, stress distribution, and damage characteristics using a coupled macro–micro finite element model. The model successfully captures key microscopic failure mechanisms, such as fiber breakage, resin cracking, and fiber–matrix interface debonding, by integrating the anisotropic mechanical properties and heterogeneous microstructure of UD-CFRPs, thereby more realistically replicating the actual machining process. The cutting speed is kept constant at 480 mm/s. Experimental validation using T700S/J-133 laminates (with a 70% fiber volume fraction) shows that, on a macro scale, the cutting force varies non-monotonically with the fiber orientation angle, following the order of 0° < 45° < 135° < 90°. The experimental values are 24.8 N/mm < 35.8 N/mm < 36.4 N/mm < 44.1 N/mm, and the simulation values are 22.9 N/mm < 33.2 N/mm < 32.7 N/mm < 42.6 N/mm. The maximum values occur at 90° (44.1 N/mm, 42.6 N/mm), while the minimum values occur at 0° (24.8 N/mm, 22.9 N/mm). The chip morphology significantly changes with fiber orientation: 0° produces strip-shaped chips, 45° forms block-shaped chips, 90° results in particle-shaped chips, and 135° produces fragmented chips. On a micro scale, the microscopic morphology of the chips and the surface damage characteristics also exhibit gradient variations consistent with the experimental results. The developed model demonstrates high accuracy in predicting damage mechanisms and material removal behavior, providing a theoretical basis for optimizing CFRP machining parameters.

Journal of Composites Science doi: 10.3390/jcs9070341

Authors: Hawraa F. Jabbar Miami M. Hilal Mohammed Y. Fattah

This study investigates the performance improvement of asphalt binders through the incorporation of two polymers, polyvinyl chloride (PVC) and styrene–butadiene–styrene (SBS), with asphalt grade (60–70), to address the growing demand for durable and climate-resilient pavement materials, particularly in areas exposed to high temperatures like Iraq. The main objective is to improve the mechanical characteristics, thermal stability, and workability of typical asphalt mixtures to extend pavement lifespan and lessen maintenance costs. A thorough set of rheological, physical, morphological, and workability tests was performed on asphalt binders modified with varying content of PVC (3%, 5%, 7%, and 9%) and SBS (3%, 4%, and 5%). The significance of this research lies in optimizing binder formulations to enhance resistance to deformation and failure modes such as rutting and thermal cracking, which are common in extreme climates. The results indicate that PVC enhances performance grade (PG), softening point, and viscosity, although higher contents (7% and 9%) exceeded penetration grade specifications. SBS-modified binders demonstrated marked improvements in softening point, viscosity, and rutting resistance, with PG values increasing from PG64-x (unmodified) to PG82-x at 5% SBS. Fluorescence microscopy confirmed optimal polymer dispersion at 5% concentration for both SBS and PVC, ensuring compatibility with the base asphalt. Workability testing revealed that SBS-modified mixtures exhibited higher torque requirements, indicating reduced workability compared to both PVC-modified and unmodified binders. These findings offer valuable insights for the design of high-performance asphalt mixtures suitable for hot-climate applications and contribute to the development of more durable and cost-effective road infrastructure.

Journal of Composites Science doi: 10.3390/jcs9070340

Authors: Jose Alfonso Prieto Palomo Juan Esteban Herrera Zabala Joaquín Alejandro Hernández Fernández

The persistent contamination of aquatic environments by heavy metals, particularly Pb2+, Cd2+, and Cu2+, poses a serious global threat due to their toxicity, persistence, and bioaccumulative behavior. In response, low-cost and eco-friendly adsorbents are being explored, among which CaCO3-based biocomposites derived from mollusk shells have shown exceptional performance. In this study, a hybrid biocomposite composed of poly(vinyl alcohol) (PVA) and oyster shell-derived CaCO3 was computationally investigated using Density Functional Theory (DFT) to elucidate the electronic and structural basis for its high metal-removal efficiency. Calculations were performed at the B3LYP/6-311++G(d,p), M05-2X/6-311+G(d,p), and M06-2X/6-311++G(d,p) levels using GAUSSIAN 16. Among them, B3LYP was identified as the most balanced in terms of accuracy and computational cost. The hybridization with CaCO3 reduced the HOMO-LUMO gap by 20% and doubled the dipole moment (7.65 Debye), increasing the composite’s polarity and reactivity. Upon chelation with metal ions, the gap further dropped to as low as 0.029 eV (Cd2+), while the dipole moment rose to 17.06 Debye (Pb2+), signaling enhanced charge separation and stronger electrostatic interactions. Electrostatic potential maps revealed high nucleophilicity at carbonate oxygens and reinforced electrophilic fields around the hydrated metal centers, correlating with the affinity trend Cu2+ > Cd2+ > Pb2+. Fukui function analysis indicated a redistribution of reactive sites, with carbonate oxygens acting as ambiphilic centers suitable for multidentate coordination. Natural Bond Orbital (NBO) analysis confirmed the presence of highly nucleophilic lone pairs and weakened bonding orbitals, enabling flexible adsorption dynamics. Furthermore, NCI/RDG analysis highlighted attractive noncovalent interactions with Cu2+ and Pb2+, while FT-IR simulations demonstrated the formation of hydrogen bonding (O–H···O=C) and Ca2+···O coordination bridges between phases.

Journal of Composites Science doi: 10.3390/jcs9070339

Authors: Hong Pan Yuxiao Wang Guangzhong Xie Chunxu Chen Haozhen Li Fang Wu Yuanjie Su

Fibrous structure is a promising building block for developing high-performance wearable piezoresistive sensors. However, the inherent non-conductivity of the fibrous polymer remains a bottleneck for highly sensitive and fast-responsive piezoresistive sensors. Herein, we reported a polyaniline/reduced graphene oxide @ polydopamine/poly (vinylidene fluoride) (PANI/rGO@PDA/PVDF) nanofiber piezoresistive sensor (PNPS) capable of versatile wearable biomonitoring. The PNPS was fabricated by integrating rGO sheets and PANI particles into a PDA-modified PVDF nanofiber network, where PDA was implemented to boost the interaction between the nanofiber networks and functional materials, PANI particles were deposited on a nanofiber substrate to construct electroactive nanofibers, and rGO sheets were utilized to interconnect nanofibers to strengthen in-plane charge carrier transport. Benefitting from the synergistic effect of multi-dimensional electroactive materials in piezoresistive membranes, the as-fabricated PNPS exhibits a high sensitivity of 13.43 kPa−1 and a fast response time of 9 ms, which are significantly superior to those without an rGO sheet. Additionally, a wide pressure detection range from 0 to 30 kPa and great mechanical reliability over 12,000 cycles were attained. Furthermore, the as-prepared PNPS demonstrated the capability to detect radial arterial pulses, subtle limb motions, and diverse respiratory patterns, highlighting its potential for wearable biomonitoring and healthcare assessment.

Journal of Composites Science doi: 10.3390/jcs9070338

Authors: Mirela Roxana Apsan Ana Maria Mitu Nicolae Pop Tudor Sireteanu Vicentiu Marius Maxim Adrian Musat

This paper analyzed the behavior of polymer composite materials reinforced with randomly oriented short natural fibers (hemp, flax, etc.) subjected to external stresses under quasistatic contact conditions with dry Coulomb friction. We presumed the composite body, a 2D flat rectangular plate, being in frictional contact with a rigid foundation for the quasistatic case. The manuscript proposes the finite element method approximation in space and the finite difference approximation in time. The problem of quasistatic frictional contact is described with a special finite element, which can analyze the state of the nodes in the contact area, and their modification, between open, sliding, and fixed contact states, in the analyzed time interval. This finite element also models the Coulomb friction law and controls the penetrability according to a power law. Moreover, the quasi-static case analyzed allows for the description of the load history using an incremental and iterative algorithm. The discrete problem will be a static and nonlinear one for each time increment, and in the case of sliding contact, the stiffness matrix becomes non-symmetric. The regularization of the non-differentiable term comes from the modulus of the normal contact stress, with a convex function and with the gradient in the sub-unit modulus. The non-penetration condition was achieved with the penalty method, and the linearization was conducted with the Newton–Raphson method.

Journal of Composites Science doi: 10.3390/jcs9070337

Authors: Mohammed Islam Tamjid Mulat Alubel Abtew Caroline Kopot

Soft body armor (SBA) remains an essential component of first responder protection. However, most SBA design concepts do not adequately address the unique performance, morphological, and psychological needs of women as first responders. In this review, female-specific designs of ballistic-resistant panels, material systems, and SBA performance testing are critically examined. The paper also explores innovations in shaping and design techniques, including darting, dartless shape construction, modular assembly, and body scanning with CAD integration to create contoured and structurally stable panels with improved coverage, reduced bulk, and greater mobility. In addition, the review addresses broadly used and emerging dry textile fabrics and fiber-reinforced polymers, considering various innovations, such as 3D warp interlock weave, shear thickening fluid (STF) coating, nanomaterials, and smart composites that improve energy dissipation and impact tolerance without sacrificing flexibility. In addition, the paper also examines various emerging ballistic performance testing standards and their revisions to incorporate gender-specific standards and measures their ability to decrease trauma effects and maintain flexibility and practical protection. Finally, it identifies existing challenges and areas of future research, such as optimizing multi-layer systems, addressing fatigue behavior, and improving multi-angle and low-velocity impact performance while providing avenues for future sustainable, adaptive, and performance-optimized body armor.

Journal of Composites Science doi: 10.3390/jcs9070336

Authors: Sujoy Saha Sabita Acharya Sidharth Menon Rao Bidthanapally Michael R. Page Menka Jain Gopalan Srinivasan

This report is on Co and Ti substituted M-type barium and strontium hexagonal ferrites that are reported to be single phase multiferroics due to a transition from Neel type ferrimagnetic order to a spiral spin structure that is accompanied by a ferroelectric polarization in an applied magnetic field. The focus here is the nature of magnetoelectric (ME) interactions in the bilayers of ferroelectric PZT and Co and Ti substituted BaM and SrM. The ME coupling in the ferrite-PZT bilayers arise due to the transfer of magnetostriction-induced mechanical deformation in a magnetic field in the ferrite resulting in an induced electric field in PZT. Polycrystalline Co and Ti doped ferrites, Ba (CoTi)x Fe12−2xO19, (BCTx), and Sr (CoTi)x Fe12−2xO19 (SCTx) (x = 0–4) were found to be free of impurity phases for all x-values except for SCTx, which had a small amount of α-Fe2O3 in the X-ray diffraction patterns for x ≤ 2.0. The magnetostriction for the ferrites increased with applied filed H to a maximum value of around 2 to 6 ppm for H~5 kOe. BCTx/SCTx samples showed ferromagnetic resonance (FMR) for x = 1.5–2.0, and the estimated anisotropy field was on the order of 5 kOe. The magnetization increased with the amount of Co and Ti doping, and it decreased rapidly with x for x > 1.0. Measurements of ME coupling strengths were conducted on the bilayers of BCTx/SCTx platelets bonded to PZT. The bilayer was subjected to an AC and DC magnetic field H, and the magnetoelectric voltage coefficient (MEVC) was measured as a function of H and frequency of the AC field. For BCTx-PZT, the maximum value of MEVC at low frequency was ~5 mV/cm Oe, and a 40-fold increase at electromechanical resonance (EMR). SCTx–PZT composites also showed a similar behavior with the highest MEVC value of ~14 mV/cm Oe at low frequencies and ~200 mV/cm Oe at EMR. All the bilayers showed ME coupling for zero magnetic bias due to the magnetocrystalline anisotropy field in the ferrite that provided a built-in bias field.

Journal of Composites Science doi: 10.3390/jcs9070335

Authors: Calin-Octavian Miclosina Remus Belu-Nica Costel Relu Ciubotariu Gabriela Marginean

This study signifies the development and characterization of a composite material with a metallic matrix of aluminum reinforced with a steel mesh, utilizing centrifugal casting technology. An evaluation was conducted to ascertain the influence of the formulation process and the presence of the insert on the mechanical behavior with regard to tensile strength. The aluminum matrix was obtained from commercial and scrap alloys, elaborated by advanced methods of degassing and chemical modification. Meanwhile, the steel mesh reinforcement was cleaned, copper plated, and preheated to optimize wetting and, consequently, adhesion. The structural characterization was performed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analyses (EDX), which highlighted a well-defined interface and uniform copper distribution. The composite was produced by means of horizontal-axis centrifugal casting in a fiberglass mold, followed by cold rolling to obtain flat specimens. A total of eight tensile specimens were examined, with measured ultimate tensile strengths ranging from 78.5 to 119.8 (MPa). A thorough examination of the fractured specimens revealed a brittle fracture mechanism, devoid of substantial plastic deformation. The onset of failures was frequently observed at the interface between the aluminum matrix and the steel mesh. The use of SEM and EDX investigations led to the confirmation of the uniformity of the copper coating and the absence of significant porosity or interfacial defects. A bimodal distribution of tensile strength values was observed, a phenomenon that is likely attributable to variations in mesh positioning and local differences in solidification. A correlation was established between the experimental results and an analytical polynomial model, thereby confirming a reasonable fit. In sum, the present study provides a substantial foundation for the development of metal matrix composites with enhanced performance, specifically designed for challenging structural applications. This method also demonstrates potential for recycling aluminum scrap into high-performance composites with controlled microstructure and mechanical integrity.

Journal of Composites Science doi: 10.3390/jcs9070334

Authors: Nuchnapa Tangboriboon Nitchakarn Malichai Guytawan Wantaha

Bio-nanocomposite films were prepared using chitosan, gelatin, and varying concentrations (0, 0.5, 1.0, 2.0, and 5.0 wt%) of titanium dioxide (TiO2) nanoparticles in acetic acid via a casting method. The incorporation of TiO2 nanoparticles into the bio-chitosan matrix enhanced ultraviolet (UV) absorption and improved the films’ physical, mechanical, and electrical properties. Additionally, the TiO2-loaded films exhibited antimicrobial activity, contributing to the extended preservation of packaged products by inhibiting microbial growth. Notably, the bio-nanocomposite films containing 1.0 wt% TiO2 exhibited an electroactive response, bending under relatively low electric field strength (250 V/mm), whereas the control film without TiO2 required higher field strength (550 V/mm) to achieve bending. This indicates potential applications in electroactive actuators requiring precise movement control. Among the tested concentrations, films containing 0.5 wt% and 1.0 wt% TiO2 (Formulas 7 and 8) demonstrated optimal performance. These films presented a visually appealing appearance with no tear marks, low bulk density (0.91 ± 0.04 and 0.85 ± 0.18 g/cm3), a satisfactory electromechanical response at 250 V/m (17.85 ± 2.58 and 61.48 ± 6.97), low shrinkage percentages (59.95 ± 3.59 and 54.17 ± 9.28), high dielectric constant (1.80 ± 0.07 and 8.10 ± 0.73), and superior UV absorption compared with pure bio-chitosan films, without and with gelatin (Formulas 1 and 6).

Journal of Composites Science doi: 10.3390/jcs9070333

Authors: Jesus D. Escalante-Tovar Joaquin Abellán-García Jaime Fernández-Gómez

Predicting the flexural behavior of fiber-reinforced ultra-high-performance concrete (UHPC) remains a significant challenge due to the complex interactions among numerous mix design parameters. This study presents a machine learning-based framework aimed at accurately estimating the modulus of rupture (MOR) of UHPC. A comprehensive dataset comprising 566 distinct mixtures, characterized by 41 compositional and fiber-related variables, was compiled. Seven regression models were trained and evaluated, with Random Forest, Extremely Randomized Trees, and XGBoost yielding coefficients of determination (R2) exceeding 0.84 on the test set. Feature importance was quantified using Shapley values, while partial dependence plots (PDPs) were employed to visualize both individual parameter effects and key interactions, notably between fiber factor, water-to-binder ratio, maximum aggregate size, and matrix compressive strength. To validate the predictive performance of the machine learning models, an independent experimental campaign was carried out comprising 26 UHPC mixtures designed with varying binder compositions—including supplementary cementitious materials such as fly ash, ground recycled glass, and calcium carbonate—and reinforced with mono-fiber (straight steel, hooked steel, and PVA) and hybrid-fiber systems. The best-performing models were integrated into a hybrid neural network, which achieved a validation accuracy of R2 = 0.951 against this diverse experimental dataset, demonstrating robust generalizability across both material and reinforcement variations. The proposed framework offers a robust predictive tool to support the design of more sustainable UHPC formulations incorporating supplementary cementitious materials without compromising flexural performance.

Journal of Composites Science doi: 10.3390/jcs9070332

Authors: Ajith Kuriakose Mani Aju Zachariah Mani Abin Varghese Jacob Anantha Krishnan Alen Shibu Paul Akash V. Krishnan Sivasubramanian Palanisamy Sathiyalingam Kannaiyan Song-Jeng Huang

The pressing issue of global warming has prompted industries to seek sustainable and renewable materials that can reduce the use of petroleum-based products. Natural fibers, as bio-based and environmentally friendly materials, offer a promising solution. In this study, ramie fiber, which is one of the strongest natural fibers, is used as reinforcement, and the mechanical properties of natural rubber composites are evaluated. The composites were fabricated using a vulcanizing technique at 150 °C, and the fibers were cut into different lengths (5 mm, 10 m, and 15 mm) and weights (15 g, 30 g, and 60 g). Mechanical performance tests, including tensile and tear strength and hardness, were conducted. The results showed that as fiber concentration increased, so did the curing time. Moreover, the composites with higher fiber concentration had higher strength. The composite with a 10 mm fiber length and 60 g weight showed the highest tensile strength (10.35 MPa). Maximum tear strength (52.51 kN/m) was achieved with 5 mm fiber length and 60 g weight. Hardness values reached up to 88 Shore A (10 mm fiber length and 60 g weight), indicating excellent wear resistance. The specimen with the highest tensile strength was subjected to scanning electron microscope analysis. The SEM analysis revealed that the composite had a ductile type of fracture with appreciable plastic deformation, confirming good fiber–matrix interaction. These findings underscore the potential of ramie fiber–reinforced natural rubber composites as sustainable, high-performance alternatives to petroleum-based materials in structural and vibration-damping applications.

Journal of Composites Science doi: 10.3390/jcs9070331

Authors: Cristiano Fragassa Francesca Conticelli Beatrice Francucci Giacomo Seccacini Carlo Santulli

This review explores the latest developments in the study of friction, wear, and degradation mechanisms in the case of biocomposites, including either natural fibers or bio-based matrices or both, intended for marine applications. Biocomposites are increasingly favored, especially for their environmental benefits and sustainability potential. However, they often exhibit inferior mechanical properties compared to traditional composites, especially under demanding conditions. In marine environments, their performance is further challenged by factors such as high humidity, saltwater exposure, fluctuating temperatures, and biofouling. All of the above significantly impact their durability and functionality. This paper examines the performance and degradation characteristics of biocomposites subjected to seawater exposure, especially considering aspects such as friction, wear, and degradation. Additionally, it discusses the recent advancements in surface treatments and material formulations aimed at enhancing the resistance of biocomposites under marine conditions. The review also highlights the critical role of testing methodologies in simulating real-life conditions to better predict the material behavior. By providing a detailed analysis of current research and emerging trends, this paper aims to guide future studies and technological innovations in the field of marine biocomposites.

Journal of Composites Science doi: 10.3390/jcs9070330

Authors: Ismael Romero-Oca?a Miriam Herrera Natalia Fernández-Delgado Sergio I. Molina

This study presents the development of a sustainable composite material by incorporating by-products from the cork industry into acrylonitrile butadiene styrene (ABS), with the aim of reducing the environmental impact of plastic composites while maintaining their performance. ABS, a petroleum-based polymer, was used as the matrix, and maleic anhydride (MAH) with dicumyl peroxide (DCP) served as a compatibilizing system to improve interfacial adhesion with cork microparticles. Composites were prepared with 10% w/w cork in various particle sizes and characterized via FTIR, X-ray computed tomography, SEM, mechanical testing, and thermal analysis. The best performing formulation (CPC-125) showed a reduction of only ~16% in tensile modulus and ~7% in tensile strength compared with ABS-g-MAH, with a more pronounced decrease in strain at break (3.23% vs. 17.47%) due to the cork’s inherent rigidity. Thermogravimetric and calorimetric analysis confirmed that thermal stability and processing temperatures remained largely unaffected. These results demonstrate the feasibility of incorporating cork microparticles as a bio-based reinforcing filler in ABS composites, offering a promising strategy to reduce the use of virgin plastics in applications compatible with conventional injection molding.

Journal of Composites Science doi: 10.3390/jcs9070329

Authors: Rafah R. Abdulmajid Dillshad K. Bzeni Farid H. Abed Hussein M. Hamada

The aim of this work is to investigate the effect of curing temperature and time on the development of compressive strength in geopolymer mortars produced using ground granulated blast-furnace slag (GGBFS) and fly ash (FA). Considering curing circumstances, both the activation energy and the reference temperature could be used properly to build a reliable anticipated model for predicting the compressive strength of geopolymer-based products (mortar and concrete) using maturity-based techniques. In this study, the compressive strength development of geopolymer mortar made from (FA) and (GGBFS) under varying curing conditions. The mortar was prepared using an alkali solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) in a 1:1 ratio, with NaOH molarity of 12. Specimens were cast following ASTM C109 standards, with a binder/sand ratio of 1:2.75, and compacted for full densification. FA-based mortar was cured at 40 °C, 80 °C, and 120 °C, while GGBFS-based mortar was cured at 5 °C, 15 °C, and 40 °C for durations of 0.5 to 32 days. Compressive strength was evaluated at each curing period, and data were analyzed using ASTM C1074 procedures alongside a computational model to determine the best-fit datum temperature and activation energy. The Nurse-Saul maturity method and Arrhenius equation were applied to estimate the equivalent age and maturity index of each mix. A predictive model was developed for geopolymer concrete prepared at an alkali-to-binder ratio of 0.45 and NaOH molarity of 12. The final equation demonstrated high accuracy, offering a reliable tool for predicting geopolymer strength under diverse curing conditions and providing valuable insights for optimizing geopolymer concrete formulations.

Journal of Composites Science doi: 10.3390/jcs9070328

Authors: Bharathiraja Parasuraman Ashwath Pazhani Anthony Xavior Michael Sudhagar Pitchaimuthu Andre Batako

This study examines the mechanical and microstructural properties of graphene-reinforced AA2219 composites developed for hydrogen storage tank inner liner applications. A novel processing route combining high-energy ball milling, ultrasonic-assisted stir casting, and squeeze casting was used to achieve homogeneous dispersion of 0.5 wt.% graphene nanoplatelets and minimise agglomeration. The composites were subjected to T6 and T8 ageing treatments to optimize their properties. Microstructural analysis revealed refined grains, uniform Al2Cu precipitate distribution, and stable graphene retention. Mechanical testing showed that the as-cast composite exhibited a UTS of 308.6 MPa with 13.68% elongation. After T6 treatment, the UTS increased to 353.6 MPa with an elongation of 11.24%. T8 treatment further improved the UTS to 371.5 MPa, with an elongation of 8.54%. Hardness improved by 46%, from 89.6 HV (as-cast) to 131.3 HV (T8). Fractography analysis indicated a shift from brittle to ductile fracture modes after heat treatment. The purpose of this work is to develop lightweight, high-strength composites for hydrogen storage applications. The novelty of this study lies in the integrated processing approach, which ensures uniform graphene dispersion and superior mechanical performance. The results demonstrate the suitability of these composites for advanced aerospace propulsion systems.

Journal of Composites Science doi: 10.3390/jcs9070327

Authors: Athanasia K. Tolkou Ioannis A. Katsoyiannis George Z. Kyzas

Among the pollutants that affect water quality, being also a problem in water treatment facilities, is natural organic matter (NOM), the largest percentage of which is humic acid (HA). In the present work, a new aluminum-modified graphene oxide adsorbent (henceforth abbreviated GO-Al) was produced for the elimination of HA. The factors affecting the adsorption process, such as pH, adsorbent dosage, initial HA concentration and contact time were examined. It was revealed that at pH 2.0 ± 0.1, by applying 1.0 g L−1 GO-Al to 5 mg L−1 HA, 91% was removed after 24 h, but equilibrium was almost reached after 30 min (82% removal). Comparable results with GO exhibited that the modification with AlCl3⋅6H2O enhanced the removal. The relative results associated slightly more with the pseudo-second-order kinetic model (PSO), and the Langmuir isotherm model, indicating that the process was closer to chemisorption. The maximum adsorption capacity (Qm) conferring to the Langmuir model was considered to be 5.91 mg g−1. Thermodynamics revealed that the process occurred spontaneously, while a adsorption–regeneration study up to 10 cycles confirmed the effectiveness of GO-Al material.

Journal of Composites Science doi: 10.3390/jcs9070326

Authors: Natalia Drakopoulou Tatiana Giannakopoulou Christos Trapalis Petroula A. Tarantili

In this work, the critical properties of epoxy resin reinforced with carbon-based nanoparticles were examined in order to improve its performance in protective coating applications. Epoxy resin composites with commercial multi-walled carbon nanotubes (MWCNTs) and graphene (GP) nanoplates were prepared via solution mixing. In addition, hybrid composites with 50:50 w/w MWCNTs/GP were also examined. The characterization of the EMI shielding effectiveness revealed that epoxy resin composites reinforced with MWCNTs presented the best performance. Composites with the same content of graphene exhibited much lower shielding results. As confirmed by electrical conductivity measurements, this outcome can be explained by the fact that the electrical percolation threshold in the composites reinforced with MWCNTs was met (around 5 phr), while the conductive network in the composites with graphene was not completely developed. An analysis of the mechanisms that contributed to EMI shielding for each type of specimen showed that, in the case of MWCNT composites, the main mechanism that determined the response of the material was reflection rather than absorption. It was also observed that by increasing the MWCNT content, the shielding efficiency of the composites was enhanced. In the case of graphene composites, the absorption and reflection remained at low levels, resulting in high transmission and therefore poor shielding. Regarding the examined hybrid composites (MWCNTs:GP at 50:50 w/w), it seemed that the MWCNT content determined their shielding performance.

Journal of Composites Science doi: 10.3390/jcs9070325

Authors: Yuan Liang Xin Xin Xuzhao He Wenjian Weng Chengwei Wu Kui Cheng

Both biochemical cues and the electrophysiological microenvironment play a pivotal role in influencing cell behaviors. In this study, collagen/polypyrrole biomimetic electroactive composite coatings with a fiber network structure were constructed on the surface of titanium substrates by hot alkali treatment and stepwise electrochemical deposition. Materialistic characterization and electrochemical performance tests demonstrated that the titanium electrodes modified with collagen/polypyrrole composite coatings exhibited the surface morphology of a collagen film layer, and their electroactivity was significantly enhanced. Cellular experiments demonstrated that the collagen in the composite coatings could provide good biomimetic biochemical cues as a main extracellular matrix component, which have a substantial effect in promoting cell adhesion, proliferation, and osteogenic differentiation. Furthermore, under exogenous electrical signals, the polypyrrole coating has the capacity to facilitate an appropriate electrophysiological microenvironment, thereby promoting osteogenic differentiation. The collagen/polypyrrole composite coating exhibited a better effect in promoting osteogenic differentiation among all samples by simultaneously providing the appropriate biochemical cues and electrophysiological microenvironments. This work demonstrates the feasibility of synergistic pro-osteogenesis by biochemical cues and an electrophysiological microenvironment, which is instructive for the field of bone tissue engineering.

Journal of Composites Science doi: 10.3390/jcs9070323

Authors: Takeshi Yabutsuka Kota Nakanishi Shigeomi Takai

If a method for developing organic polymer/apatite core–shell microspheres encapsulating organic polymer microspheres with apatite shells can be constructed, it is possible to establish a fundamental methodology to fabricate apatite capsules for drug delivery carriers. In this study, polystyrene (PS) microspheres were used as model substances in organic polymer microspheres, and the effects of the surface functional groups on the PS microspheres on the amount of Ca2+ ions introduced onto the PS microspheres were investigated. The PS/apatite core–shell microspheres were prepared by immersing Ca2+-incorporated PS microspheres in a reaction solution containing Ca2+, HPO42−, and Mg2+ to coat the surface of PS microspheres with apatite. Particle characterization of the prepared PS/apatite core–shell microspheres was performed, and the relationships among the surface functional groups, surface potential, Ca2+ adsorption, and apatite shell formation in the aqueous solution on the PS microspheres were investigated.

Journal of Composites Science doi: 10.3390/jcs9070324

Authors: Xinnuo Yu Maria Pilar Melo Sofia Folguera Carmen Llena

Objective: To evaluate the color stability and microhardness of resin-based bioactive composites after brushing with over-the-counter whitening toothpastes. Methods: A conventional resin (Luna 2) and two bioactive resins (Stela Mix and Activa Presto) were tested. Four toothpastes were used: Colgate Fresh Gel (control), Colgate Max White, Yotuel, and Crest 3D White. Forty disks of each material were prepared and divided into four subgroups. The disks were brushed to simulate three months of daily brushing. Microhardness and color changes were measured before and after brushing. Color variation was calculated using the ΔEab, ΔE00, and ΔWID indexes. Wilcoxon and two-way ANOVA tests were performed (p < 0.05). Results: In the Luna 2 and Stela groups, the b* parameter decreased significantly with all toothpastes (p < 0.05), while lightness and a* remained stable with no significant differences (p > 0.05). Stela Mix and Activa Presto exhibited color changes within the “moderately unacceptable” range according to ΔE00 (>1.8 and ≤3.6). Based on the ΔWID index, Luna 2 showed the highest variation when treated with Colgate Max (2.14 ± 1.33) and the lowest in the control group (1.08 ± 0.56A), remaining within acceptable margins with all treatments. The microhardness values before/after treatment remained for Luna 2 between 77.44 and 76.97; for Stela Mix between 76.24 and 74.13; and for Activa presto between 74.5 and 71.33. Differences were not significant for any of the pastes within each composite (p > 0.05). Conclusions: The evaluated bioactive resins exhibited color changes within the moderately unacceptable range. Colgate Max White induced the most significant color changes. Microhardness was not affected by treatment with whitening toothpastes.