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J. Compos. Sci.
Volume 9
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J. Compos. Sci., Volume 9, Issue 7 (July 2025) – 64 articles

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21 pages, 4359 KiB  
Article
Continuously Formed Fiber-Reinforced Thermoplastic Composite Rebar for Concrete Reinforcement
by Jacob C. Clark, William G. Davids, Roberto A. Lopez-Anido, Andrew P. Schanck and Cody A. Sheltra
J. Compos. Sci. 2025, 9(7), 378; https://doi.org/10.3390/jcs9070378 - 18 Jul 2025
Abstract
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 [...] Read more.
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 meter 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. Full article
(This article belongs to the Section Fiber Composites)
8 pages, 720 KiB  
Article
Microscopic Characterization of Pb10−xCux(PO4)6O by 31P and 63/65Cu NMR Measurements
by Qing-Ping Ding, Yue Sun, Qiang Hou, Wei Wei, Xin Zhou, Xinyue Wang, Zhixiang Shi and Yuji Furukawa
J. Compos. Sci. 2025, 9(7), 377; https://doi.org/10.3390/jcs9070377 - 18 Jul 2025
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Optical–Electric–Magnetic Multifunctional Composite Materials)
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18 pages, 3500 KiB  
Article
Cellulose Acetate–PHB Biocomposite from Saccharum officinarum for Ni (II) Adsorption: Equilibrium and Kinetics
by Candelaria Tejada-Tovar, Ángel Villabona-Ortíz, Oscar Toro-Madrid, Rodrigo Ortega-Toro and Humberto Bonilla Mancilla
J. Compos. Sci. 2025, 9(7), 376; https://doi.org/10.3390/jcs9070376 - 18 Jul 2025
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Sustainable Biocomposites, 3rd Edition)
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14 pages, 6629 KiB  
Article
Investigating the Mechanical and Thermal Performance of HDPE Composites Based on Nano-Graphite Particles
by Abdullah Shalwan, Hussain Ali Alenezi and Saad Ali Alsubaie
J. Compos. Sci. 2025, 9(7), 375; https://doi.org/10.3390/jcs9070375 - 17 Jul 2025
Abstract
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) [...] Read more.
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. Full article
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19 pages, 4188 KiB  
Article
Enhanced Mechanical and Electrical Performance of Epoxy Nanocomposites Through Hybrid Reinforcement of Carbon Nanotubes and Graphene Nanoplatelets: A Synergistic Route to Balanced Strength, Stiffness, and Dispersion
by Saba Yaqoob, Zulfiqar Ali, Alberto D’Amore, Alessandro Lo Schiavo, Antonio Petraglia and Mauro Rubino
J. Compos. Sci. 2025, 9(7), 374; https://doi.org/10.3390/jcs9070374 - 17 Jul 2025
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2025)
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15 pages, 3833 KiB  
Article
High-Temperature Tribological Behavior of Polyimide Composites with Dual-Phase MoS2/MXene Lubricants: A Synergistic Effect Analysis
by Xingtian Ji, Pengwei Ren, Hao Liu, Yanhua Shi, Yunfeng Yan and Jianzhang Wang
J. Compos. Sci. 2025, 9(7), 373; https://doi.org/10.3390/jcs9070373 - 17 Jul 2025
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Polymer Composites: Fiber Architecture, Interfacial Engineering, and Processing)
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22 pages, 3224 KiB  
Article
Performance Optimization of SBR-Modified Pervious Composite Incorporating Recycled Concrete Aggregates
by Abdulkader El-Mir, Perla Tannouri, Joseph J. Assaad, Dana Nasr, Maria Ghannoum, Firas Barraj and Hilal El-Hassan
J. Compos. Sci. 2025, 9(7), 372; https://doi.org/10.3390/jcs9070372 - 16 Jul 2025
Viewed by 66
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Novel Cement and Concrete Materials)
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18 pages, 20927 KiB  
Article
Numerical and Experimental Study on the Deformation of Adaptive Elastomer Fibre-Reinforced Composites with Embedded Shape Memory Alloy Wire Actuators
by Holger Böhm, Andreas Hornig, Chokri Cherif and Maik Gude
J. Compos. Sci. 2025, 9(7), 371; https://doi.org/10.3390/jcs9070371 - 16 Jul 2025
Viewed by 59
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)
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31 pages, 3523 KiB  
Article
Sustainable Tunable Anisotropic Ultrasound Medical Phantoms for Skin, Skeletal Muscle, and Other Fibrous Biological Tissues Using Natural Fibers and a Bio-Elastomeric Matrix
by Nuno A. T. C. Fernandes, Diana I. Alves, Diana P. Ferreira, Maria Monteiro, Ana Arieira, Filipe Silva, Betina Hinckel, Ana Leal and Óscar Carvalho
J. Compos. Sci. 2025, 9(7), 370; https://doi.org/10.3390/jcs9070370 - 16 Jul 2025
Viewed by 147
Abstract
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, [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Biocomposite Materials for Regenerative Medicine and Biomedical Applications)
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16 pages, 4361 KiB  
Article
Residual Stress Evolution of Graphene-Reinforced AA2195 (Aluminum–Lithium) Composite for Aerospace Structural Hydrogen Fuel Tank Application
by Venkatraman Manokaran, Anthony Xavior Michael, Ashwath Pazhani and Andre Batako
J. Compos. Sci. 2025, 9(7), 369; https://doi.org/10.3390/jcs9070369 - 16 Jul 2025
Viewed by 127
Abstract
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. [...] Read more.
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. Full article
(This article belongs to the Section Composites Modelling and Characterization)
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17 pages, 2964 KiB  
Article
Seawater Ageing Effects on the Mechanical Performance of Basalt Fibre-Reinforced Thermoplastic and Epoxy Composites
by Mohamad Alsaadi, Tomas Flanagan and Declan M. Devine
J. Compos. Sci. 2025, 9(7), 368; https://doi.org/10.3390/jcs9070368 - 15 Jul 2025
Viewed by 96
Abstract
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). [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Continuous Fiber Reinforced Thermoplastic Composites)
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15 pages, 3974 KiB  
Article
Cast Polyamide 6 Molds as a Suitable Alternative to Metallic Molds for In Situ Automated Fiber Placement
by Fynn Atzler, Ines Mössinger, Jonathan Freund, Samuel Tröger, Ashley R. Chadwick, Simon Hümbert and Lukas Raps
J. Compos. Sci. 2025, 9(7), 367; https://doi.org/10.3390/jcs9070367 - 15 Jul 2025
Viewed by 140
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Composites Manufacturing and Processing)
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16 pages, 2358 KiB  
Article
Enhancing Polycaprolactone with Levulinic Acid-Extracted Lignin: Toward Sustainable Bio-Based Polymer Blends
by Elodie Melro, Hugo Duarte, Filipe E. Antunes, Artur J. M. Valente, Anabela Romano and Bruno Medronho
J. Compos. Sci. 2025, 9(7), 366; https://doi.org/10.3390/jcs9070366 - 14 Jul 2025
Viewed by 88
Abstract
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, [...] Read more.
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. Full article
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20 pages, 10209 KiB  
Article
Micro and Macro Analyses for Structural, Mechanical, and Biodegradability of a Pulp-Based Packaging Material: A Comprehensive Evaluation Using SEM, XRD, FTIR, and Mechanical Testing
by 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 and K. R. Koswattage
J. Compos. Sci. 2025, 9(7), 365; https://doi.org/10.3390/jcs9070365 - 14 Jul 2025
Viewed by 152
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Sustainable Composites and Manufacturing Innovations)
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28 pages, 5774 KiB  
Article
Data-Driven Prediction of Polymer Nanocomposite Tensile Strength Through Gaussian Process Regression and Monte Carlo Simulation with Enhanced Model Reliability
by Pavan Hiremath, Subraya Krishna Bhat, Jayashree P. K., P. Krishnananda Rao, Krishnamurthy D. Ambiger, Murthy B. R. N., S. V. Udaya Kumar Shetty and Nithesh Naik
J. Compos. Sci. 2025, 9(7), 364; https://doi.org/10.3390/jcs9070364 - 14 Jul 2025
Viewed by 200
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Characterization and Modelling of Composites, Volume III)
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18 pages, 5837 KiB  
Article
Influential Microstructural Descriptors for Predicting Mechanical Properties of Fiber-Reinforced Composites
by Jamal F. Husseini, Eric J. Carey, Farhad Pourkamali-Anaraki, Evan J. Pineda, Brett A. Bednarcyk and Scott E. Stapleton
J. Compos. Sci. 2025, 9(7), 363; https://doi.org/10.3390/jcs9070363 - 12 Jul 2025
Viewed by 249
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Editorial Board Members' Collection Series: Mechanical Analysis of Composite Materials)
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20 pages, 3537 KiB  
Article
A New Sulfur-Containing Copolymer Created Through the Thermally Induced Radical Copolymerization of Elemental Sulfur with N2,N2-Diallylmelamine Comonomer for Potential CO2 Capture
by Dharrinesh Narendiran, Nurul Hazirah Sumadi, Ali Shaan Manzoor Ghumman, Noor Ashikin Mohamad, Mohamed Mahmoud Nasef, Amin Abbasi and Rashid Shamsuddin
J. Compos. Sci. 2025, 9(7), 362; https://doi.org/10.3390/jcs9070362 - 11 Jul 2025
Viewed by 267
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Polymer Composites: Fiber Architecture, Interfacial Engineering, and Processing)
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24 pages, 2179 KiB  
Article
Time-Dependent Rheological Behavior and MPS Simulation of Cement–Bentonite Slurries with Hydration Accelerators for Borehole Backfilling Applications
by Shinya Inazumi, Kazuhiko Tazuke and Seiya Kashima
J. Compos. Sci. 2025, 9(7), 361; https://doi.org/10.3390/jcs9070361 - 10 Jul 2025
Viewed by 204
Abstract
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 [...] Read more.
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. Full article
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15 pages, 4106 KiB  
Article
Effect of Alumina Microparticle-Infused Polymer Matrix on Mechanical Performance of Carbon Fiber Reinforced Polymer (CFRP) Composite
by 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 and Kadhavoor R. Karthikeyan
J. Compos. Sci. 2025, 9(7), 360; https://doi.org/10.3390/jcs9070360 - 10 Jul 2025
Viewed by 206
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advanced Composite Materials from Natural and Synthetic Sources: Fabrication, Characterization and Practical Application, Volume II)
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28 pages, 7820 KiB  
Review
Mechanisms and Performance of Composite Joints Through Adhesive and Interlocking Means—A Review
by Khishigdorj Davaasambuu, Yu Dong, Alokesh Pramanik and Animesh Kumar Basak
J. Compos. Sci. 2025, 9(7), 359; https://doi.org/10.3390/jcs9070359 - 10 Jul 2025
Viewed by 356
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Mechanical Properties of Composite Materials and Joints)
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10 pages, 2813 KiB  
Article
The Effect of Doping with Aluminum on the Optical, Structural, and Morphological Properties of Thin Films of SnO2 Semiconductors
by Isis Chetzyl Ballardo Rodriguez, U. Garduño Terán, A. I. Díaz Cano, B. El Filali and M. Badaoui
J. Compos. Sci. 2025, 9(7), 358; https://doi.org/10.3390/jcs9070358 - 9 Jul 2025
Viewed by 199
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Optical–Electric–Magnetic Multifunctional Composite Materials)
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22 pages, 2470 KiB  
Article
Multi-Objective Optimisation of Hybrid Banana/Sisal/Red Mud Composites Using Taguchi–Grey Relational Analysis
by Karthick Rasu, Vigneshwaran Shanmugam and Joao Paulo Davim
J. Compos. Sci. 2025, 9(7), 357; https://doi.org/10.3390/jcs9070357 - 8 Jul 2025
Viewed by 282
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Recent Progress in Hybrid Composites)
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24 pages, 1711 KiB  
Review
Hybridization of Lignocellulosic Biomass into Aluminum-Based Materials: Comparing the Cases of Aluminum Matrix Composites and Fiber Metal Laminates
by Cristiano Fragassa and Carlo Santulli
J. Compos. Sci. 2025, 9(7), 356; https://doi.org/10.3390/jcs9070356 - 8 Jul 2025
Viewed by 317
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Collection Editorial Board Members’ Collection Series: Fibre Composite Materials)
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21 pages, 9386 KiB  
Article
Structural Characterization and Segmental Dynamics Evaluation in Eco-Friendly Polymer Electrospun Fibers Based on Poly(3-hydroxybutyrate)/Polyvinylpyrrolidone Blends to Evaluate Their Sustainability
by 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 and Alexey L. Iordanskii
J. Compos. Sci. 2025, 9(7), 355; https://doi.org/10.3390/jcs9070355 - 8 Jul 2025
Viewed by 265
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advanced Composite Materials from Natural and Synthetic Sources: Fabrication, Characterization and Practical Application, Volume II)
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16 pages, 2400 KiB  
Article
Modeling Piezoresistive Behavior of Conductive Composite Sensors via Multi-State Percolation Theory
by Nathan S. Usevitch, Emily V. White, Anton E. Bowden, Ulrike H. Mitchell and David T. Fullwood
J. Compos. Sci. 2025, 9(7), 354; https://doi.org/10.3390/jcs9070354 - 8 Jul 2025
Viewed by 214
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Characterization and Modelling of Composites, Volume III)
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28 pages, 1259 KiB  
Review
Perspective on Sustainable Solutions for Mitigating Off-Gassing of Volatile Organic Compounds in Asphalt Composites
by Masoumeh Mousavi, Vajiheh Akbarzadeh, Mohammadjavad Kazemi, Shuguang Deng and Elham H. Fini
J. Compos. Sci. 2025, 9(7), 353; https://doi.org/10.3390/jcs9070353 - 8 Jul 2025
Viewed by 269
Abstract
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 [...] Read more.
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 Full article
(This article belongs to the Special Issue Composites: A Sustainable Material Solution)
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15 pages, 1464 KiB  
Article
Evaluation of Color Stability of UDMA-Based Dental Composite Resins After Exposure to Conventional Cigarette and Aerosol Tobacco Heating System
by Maria G. Mousdraka, Olga Gerasimidou, Alexandros K. Nikolaidis, Christos Gogos and Elisabeth A. Koulaouzidou
J. Compos. Sci. 2025, 9(7), 352; https://doi.org/10.3390/jcs9070352 - 8 Jul 2025
Viewed by 308
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Composites Applications)
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25 pages, 6538 KiB  
Article
Polymer–Filler Interactions in Graphite-Infused Polypropylene: Experimental Design, a Fundamental and Applied Study
by Rabindra Dharai, Yubaraj Chakraborty, Rabiranjan Murmu, Pragyan Senapati, Harekrushna Sutar and Debashis Roy
J. Compos. Sci. 2025, 9(7), 351; https://doi.org/10.3390/jcs9070351 - 7 Jul 2025
Viewed by 341
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Functional Composites: Fabrication, Properties and Applications)
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18 pages, 3197 KiB  
Article
The Progressive Damage Modeling of Composite–Steel Lapped Joints
by Alaa El-Sisi, Ahmed Elbelbisi, Ahmed Elkilani and Hani Salim
J. Compos. Sci. 2025, 9(7), 350; https://doi.org/10.3390/jcs9070350 - 7 Jul 2025
Viewed by 281
Abstract
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; [...] Read more.
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. Full article
(This article belongs to the Special Issue Characterization and Modelling of Composites, Volume III)
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12 pages, 11822 KiB  
Article
Thermal Degradation and Fire Behavior of Posidonia oceanica Epoxy Composites
by Maria Rosaria Ricciardi and Vincenza Antonucci
J. Compos. Sci. 2025, 9(7), 349; https://doi.org/10.3390/jcs9070349 - 7 Jul 2025
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Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Fire Safety of Structural Composites, 2nd Edition)
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