This study investigates the tribological and viscoelastic performance of untreated Phoenix sp. fiber-reinforced polyester composites (PFPCs), with the objective of establishing an optimal fiber length–loading combination for sliding wear resistance and quantifying the associated viscoelastic behavior through dynamic mechanical analysis (DMA). PFPCs were fabricated via compression moulding with fiber lengths of 10, 20, and 30 mm and loadings of 5–25 wt%. Dry sliding wear tests were carried out on a pin-on-disk tribometer under varying loads (10–30 N; 0.1–0.3 MPa), sliding velocities (1–3 m/s), and sliding distances (1000–3000 m). Among the tested configurations, the 20 mm–20 wt% PFPC exhibited the lowest specific wear rate (SWR) of 13.1 × 10 −6 mm 3 /Nm, 19.1% reduction relative to the 5 wt% baseline. Six quadratic regression models developed using Box–Behnken Design (BBD) within Response Surface Methodology (RSM) described the SWR and coefficient of friction (CoF) responses with high predictive accuracy (R 2 = 0.9842–0.9989); ANOVA confirmed applied load as the dominant factor governing SWR and fiber content as the dominant factor governing CoF, with a significant interaction between the two (p < 0.05). Numerical optimization identified 22–24 mm and 24–25 wt% as the optimal range for minimum SWR, subsequently validated experimentally. DMA confirmed improved stiffness and thermal stability at the optimal configuration, and SEM revealed a transition from mild abrasive wear to severe wear mechanisms with increasing load. These findings establish the 20 mm–20 wt% PFPC as a candidate sustainable material for dynamic sliding-contact components, such as bushings and bearing liners, in automotive interior and light-duty mechanical applications.
The inclusion of nanoparticles significantly affects the physico-mechanical behavior of polymer laminates, thereby enhancing their manufacturability and machinability. To meet the growing demand for high-strength, lightweight materials in engineering applications, carbon nanomaterials are being added to carbon fiber reinforced polymer composites (CFRP). The proposed experimental work examines the effect of Multiwall carbon nanotube (CNT) loading and a novel approach on the machinability evaluation of milling via. with and without a backup plate (BP) arrangement. Adding 1 wt% of CNT resulted in better impact (43.58%), stiffness (22.61%), and flexural strength (24.97%) for the developed composite. The machinability characteristics were assessed by varying the CNT weight fraction (1–3 wt%) in the epoxy matrix and the machining speed (S), feed rate (F), and depth of cut (D). The variance analysis of machining outcomes, which included material removal rate (MRR), surface roughness (SR), and cutting force (FC), was conducted to assess trade-offs in process efficiency. The abrasive properties of CNT with a backup plate (BP) resulted in increased MRR (2.72%), decreased SR (5.47%), and decreased FC (3.04%). This study examines the machining behavior of CNT/CFRP for advanced sustainable structural components, thereby greatly improving surface integrity by reducing fiber pull-out, matrix cracking, and interfacial debonding.
Autofrettage is commonly applied to metal-lined composite pressure vessels to improve fatigue resistance by introducing compressive residual stress into the liner. However, in thin-walled Type III vessels with filament-wound carbon-fiber/epoxy overwraps, excessive autofrettage may cause irreversible matrix-dominated damage and weaken the constraint imposed by the composite overwrap. This study investigates the burst and fatigue responses of a 56 L thin-walled Type III composite pressure vessel under different autofrettage pressures using a sequential finite element framework coupled with a three-dimensional progressive damage model. Acoustic emission monitoring, hydrostatic burst tests, pressure-cycling fatigue tests, and post-fatigue microscopic observations were used to validate and interpret the predictions. Increasing autofrettage pressure intensified retained matrix tensile damage in the overwrap and promoted earlier fiber tensile damage during repressurization. Experimentally, the burst pressure decreased from 90 to 81 MPa as autofrettage pressure increased from 44 to 60 MPa, while fatigue life decreased from 740 to 575 cycles. The model captured these degradation trends with mean absolute percentage errors of 3.2 and 2.3% for burst pressure and fatigue life, respectively. The results indicate that autofrettage design should be damage-limited rather than pressure-maximized.
High-performance transparent polymers are of great interest in the automotive and electronics industries, but conventional plastics lack mechanical strength, while high-performance systems are generally opaque. In this study, polyvinyl alcohol (PVA)-based transparent wood composites were fabricated from beech, maple, and poplar via delignification and vacuum-assisted infiltration. The resulting composites exhibited light transmittance values of 83.5% (beech-PVA), 20.5% (poplar-PVA), and 5.4% (maple-PVA), with corresponding haze values of 95.9%, 95.9%, and 82.9%, respectively. Linear regression models established strong correlations between optical properties and Hunter color parameters: haze versus lightness (R 2 = 0.82) and haze versus yellowness (R 2 = 0.80), enabling targeted optical design. PVA infiltration achieved the lowest yellowness (b = +11 to +13) reported for additive-free transparent wood composites, producing a near-neutral, glass-like appearance. Electron microscopy confirmed complete pore filling and nanoscale PVA penetration into the cell walls, forming a dense hydrogen-bonded network. This interaction produced exceptional viscoelastic behavior: beech-PVA achieved a glass transition temperature of 169.2°C, while maple-PVA exhibited the broadest damping among transparent wood composites (tan δ > 0.27 from 20°C to 95°C). These thermomechanical characteristics, combined with tunable haze through color control, make this material ideal for hot climates requiring heat management and visual comfort. PVA-based transparent wood functions as a natural “smart surface,” paving the way for sustainable, shock-resistant construction materials derived entirely from biological sources.
The optical anisotropy of transparent injection-molded poly (ethylene terephthalate) (PET)-based copolyesters, including a biomass-derived PET copolymer, was investigated through birefringence and retardation measurements. Injection molding simulation was also performed to predict residual stress distributions. The effects of molding conditions and copolymer composition on optical anisotropy were systematically evaluated. The average retardation decreased from 468.6 to 190.3 nm as the injection temperature increased from 260 to 280°C, whereas it increased from 226.6 to 347.6 nm as the packing pressure increased from 40 to 80 MPa. Birefringence increased in the order of PET, poly (ethylene terephthalate-co-1,4-cyclohexanedimethylene terephthalate) (PETG), poly (cyclohexanedimethylene terephthalate-co-ethylene terephthalate) (PCTG), and poly (ethylene terephthalate-co-isosorbide terephthalate-co-cyclohexanedimethylene terephthalate) (PEICT). Increasing the 1,4-cyclohexanedimethanol (CHDM) content increased birefringence, while the incorporation of isosorbide (ISB) further enhanced birefringence by restricting polymer chain mobility and stress relaxation during cooling. These results demonstrate that the optical anisotropy of transparent PET-based copolyesters can be effectively controlled through copolymer composition and injection molding conditions.
This study presents the experimental characterization of a polyphenylene sulfide (PPS) matrix reinforced with a 2D textile carbon-fiber architecture, using macroscale mechanical testing combined with microscale fractographic analysis. The purpose of this work is to investigate the mechanical behavior and damage mechanisms of CF/PPS composite laminates under tensile, compressive, and shear loading using full-field strain measurements and microstructural observations. Quasi-static tensile (ASTM D3039), compression (ASTM D6641), and shear (ASTM D7078) tests were performed in the warp and fill directions, with Digital Image Correlation (DIC) used for full-field strain measurements. Microstructural analyses of fractured specimens were carried out using optical microscopy, stereoscopy, and scanning electron microscopy (SEM). Tensile tests revealed linear-elastic behavior up to brittle failure, with elastic moduli of approximately 54 GPa and tensile strengths of approximately 733-714 MPa in the warp and fill directions. Compression tests showed nearly linear behavior with failure dominated by fiber microbuckling and progressive delamination, with compressive strengths between 523 and 545 MPa. Shear tests exhibited nonlinear behavior due to fiber reorientation and locking effects, with shear strengths of 66–67 MPa. DIC measurements enabled the identification of strain localization and damage initiation sites under all loading conditions, showing strong correlation with microstructural features such as fiber microbuckling, matrix plastic deformation, and interlaminar damage. The combined use of Digital Image Correlation and microstructural analysis provided a comprehensive understanding of the mechanical response and failure mechanisms of CF/PPS laminates under different loading conditions, highlighting the strong relationship between full-field strain evolution and the underlying microstructural damage processes.
Industrial solid waste is an abundant but underexploited feedstock for advanced materials production. Herein, we develop a scalable strategy for the high-value utilization of flue gas desulfurization gypsum from Baotou Iron and Steel Group. We converted it into high-aspect-ratio (∼160) calcium sulfate whiskers (CSWs) via a hydrothermal route and modified their interfacial compatibility using stearic acid with an optimal concentration of 4 wt%, under which the modified CSWs exhibit an activation index of 0.618 and a water contact angle of 108°. When they are added to ultra-high-molecular-weight polyethylene (UHMWPE) as a reinforcement phase, the stiffness and toughness of the composite are enhanced, showing a maximum elongation at break of 331.16%, unchanged yield strength, improved flexural performance, and notched impact strength exceeding 70 kJ·m -2 . These results demonstrate the technical feasibility of transforming flue gas desulfurization gypsum into calcium sulfate whiskers for polymer reinforcement, offering an environmental and economical pathway for industrial solid waste valorization and advanced composite fabrication.
This study investigated the effect of the two types of polymer matrixes and different reinforcement materials and their percentage on the bending properties of wood-plastic composites in the elastic range of the force-deflection bending diagram, as well as FTIR spectroscopy. This work provides new insights into the early-stage deformation mechanisms of sawdust-reinforced polymer composites by isolating and quantifying the elastic-zone behavior, whereas the majority of studies concentrate on MOE and MOR from the whole diagram of three-point bending tests. The results demonstrated that mechanical properties in the elastic zone were significantly affected not only by reinforcement content and ratio but also by the polymer matrix. The mechanical properties showed a negative response to increased amounts of sawdust particles from 40 to 60%. According to the obtained results, the superior mechanical properties were achieved by using 50% sawdust in biodegradable polymer and 40% sawdust-rPET composites, respectively. Further effects of different types and ratios of reinforcements and polymer on the chemical composition of composites were studied via the ATR-FTIR method. Utilizing waste PET (rPET) and wood residual (sawdust) to produce high-performance reinforced composites may open new opportunities toward the production of added-value composites using 100% recycled and waste raw materials.
Nanoporous materials functionalized liquid (NMFL)-filled structures demonstrate significant potential in the field of energy absorption and cushioning. To thoroughly investigate the behavior of NMFL-filled tubes under axial loading, this study establishes an analytical model based on the ring-shaped crushing hypothesis, deriving analytical expressions for peak stress and mean crushing stress, with the accuracy of the theoretical model validated through finite element analysis. The results show that the crushing process of NMFL-filled tubes exhibits three distinct stages: elastic, yield, and strengthening. For a representative configuration, the FE-predicted peak stress and mean crushing stress in the yield stage are 20.94 MPa and 16.00 MPa, respectively, while the corresponding theoretical predictions are 23.68 MPa and 16.99 MPa. Parametric analysis reveals that the infiltration pressure of the NMFL and the wall thickness of the tube are key parameters controlling the crushing morphology, and global buckling instability occurs when the infiltration pressure exceeds 14 MPa. This study fills the gap in the theoretical modeling of axial crushing for NMFL-filled structures and provides a scientific basis for developing new high-performance cushioning and energy-absorbing materials.
Accurate prediction of lightning strike damage in composite laminates remains challenging due to oversimplified representations of current distribution and through-thickness conductivity. This study introduces a novel model that uniquely integrates an elliptical Gaussian current distribution to capture both arc expansion and non-uniform current density, and explicit representation of Interlayer resin enrichment with dielectric breakdown properties. Quantitatively, compared to the conventional uniform current model, the proposed elliptical Gaussian distribution alone reduces damage depth prediction error by 66.7% (reducing under-prediction from 3 plies to 1 ply). Crucially, further incorporating explicit interlayer modeling reduces the depth error by nearly 100%, achieving exact prediction of 5-ply damage as validated by experiment, while maintaining total Joule energy variation within 1% of the Gaussian-only model. Furthermore, unlike previous models that require subsequent mechanical analysis to predict delamination, this approach uniquely captures both in-plane ablation and interlayer delamination morphology directly from coupled thermal-electrical analysis. These findings demonstrate that explicitly modeling elliptical Gaussian current distribution and interlayer resin enrichment is not merely incremental but essential for accurate lightning strike damage prediction in composite laminates.
Environmental concerns over petroleum-based plastics have driven interest in biodegradable, bio-based composites. Polylactic acid (PLA), derived from renewable feedstocks, is valued for its biodegradability and biocompatibility. However, PLA reinforced with synthetic or inorganic fillers often shows poor interfacial adhesion and limited functional properties. Recent advances focus on incorporating natural fillers from agricultural and industrial byproducts to improve both sustainability and performance. Natural fillers derived from polysaccharides, proteins, lignocellulosic biomass, and bioceramics offer an eco-friendly route to enhance the mechanical, thermal, and functional properties of PLA. This review presents a comprehensive classification of natural fillers based on their origin and discusses environmentally benign extraction and processing methods. The effect of interfacial adhesion and bio-based surface modifiers in improving filler dispersion and matrix compatibility is critically analyzed. The influence of natural fillers on key properties such as water absorption, moisture sensitivity, optical transparency, flame retardancy, and rheological behavior is systematically evaluated. Bio-based surface modifications using natural crosslinkers, plasticizers combined with green processing techniques such as reactive extrusion, electrospinning, and supercritical CO 2 foaming, enhance filler dispersion and matrix compatibility. These strategies have led to significant improvements in mechanical strength, barrier properties, flame retardancy, and bioactivity. Consequently, PLA composites have potential applications in packaging, biomedical devices, water purification, electronics, and automotive components. This review presents an integrated, application-driven perspective, merging natural reinforcements with bio-based crosslinkers, compatibilizers, and functional additives. It explains the connections between composition, processing, and performance and highlighting current advancements in filler incorporation, surface engineering, and sustainable fabrication.
Polydiacetylene (PDA) is a conjugated polymer widely recognized for its distinct thermochromic behavior, characterized by reversible or irreversible transitions between blue and red phases upon external stimuli. These chromatic transitions arise from conformational distortions of the ene–yne conjugated backbone, which alter the effective conjugation length and shift the absorption maximum. The thermochromic response of PDA is strongly influenced by supramolecular packing, headgroup interactions, solvent environment, photopolymerization conditions, and the incorporation of metal ions or inorganic components. This review systematically discusses the molecular and structural factors governing PDA thermochromism, including solvent effects, precursor selection, photopolymerization time, pH, and metal coordination (e.g., Zn 2+ systems). Emphasis is placed on the relationship between topochemical packing constraints, backbone planarity, and phase stability. Strategies to enhance thermal reversibility—such as headgroup modification and metal-ion coordination—are critically compared in terms of structural control and practical implications. Finally, recent advances in thermochromic sensing applications are highlighted, focusing specifically on systems where temperature-dependent chromatic transitions are central to functionality. By consolidating structure–property relationships with materials design strategies, this review aims to guide the development of next-generation PDA-based thermochromic materials.
Foam core sandwich structures are widely used in lightweight engineering applications due to their high specific stiffness and energy absorption capability. However, under critical loading conditions such as compression, bending, and impact, their performance is often constrained by limited core strength, weak face-core interfacial bonding, and poor damage tolerance. These structural and performance limitations significantly restrict their application in demanding service environments. To address these challenges, various foam-core reinforcement strategies have been developed to enhance the mechanical performance and failure resistance of sandwich panels. This review systematically summarizes recent advances in particle-reinforced, fiber-reinforced, and composite or structural foam core sandwich structures. Particular emphasis is placed on how different reinforcement concepts improve compressive strength, shear and flexural performance, resistance to delamination, and impact energy absorption. By comparatively analyzing the reinforcement mechanisms, mechanical property enhancements, and inherent limitations of each strategy, this review provides a comprehensive overview of current research progress and identifies key directions for the design of high-performance foam-based sandwich structures.
The strength ratio of composite pressure vessels is a critical measure of their structural performance and reliability, both of which are highly dependent on the effective allocation of design parameters. In this study, a three-dimensional elasticity-based theoretical model is developed for composite cylinders subjected to uniform internal pressure. An improved Gaussian quantum-behaved particle swarm optimization-differential evolution (GQPSO-DE) algorithm is employed to simultaneously optimize the winding angle and ply thickness. By maximizing the strength ratio of the weakest ply, the overall structural strength and load-carrying capacity of the vessel are significantly improved. Two representative composite cylinders with different radial ratios are subsequently investigated, and the corresponding optimal combinations of winding angle and ply thickness are obtained. The results demonstrate that the proposed method is effective in enhancing the strength ratio of the weakest ply.
Maleic anhydride (MAH) grafting effectively enhances the interfacial compatibility between hydrophobic high-density polyethylene (HDPE) and hydrophilic graphene oxide (GO). In this study, HDPE-g-MAH/GO nanocomposites were prepared by melt blending and investigated using experimental techniques (FTIR, DSC, and TGA) combined with molecular dynamics (MD), density functional theory (DFT), and COSMO-RS analyses. MD simulations showed that MAH grafting increased the polymer–GO binding energy from about 455 to nearly 2000 kcal·mol −1 , indicating significantly improved interfacial adhesion. Hydrogen bonding between GO oxygenated groups and MAH functionalities was identified with an average O···H distance of ∼2.15 Å and an interaction energy of −4.8 kcal·mol −1 . DFT calculations revealed a reduction in the HOMO–LUMO energy gap from 9.16 eV for PE to 0.56 eV for the PE-g-MAH/GO system, suggesting enhanced charge transfer and interfacial interaction. Experimentally, MAH grafting reduced HDPE crystallinity from 41.4% to 32.1%, while GO incorporation partially restored crystallinity up to 36.2% due to its nucleating effect. TGA results showed slight improvements in thermal stability. COSMO-RS analysis further confirmed the enhanced affinity of MAH-grafted PE toward GO, demonstrating the compatibilizing role of MAH in improving nanocomposite performance.
This review provides a state-of-the-art overview of carbon fiber reinforced polymers composites manufactured by fused deposition modeling (FDM), one of the leading additive manufacturing technologies. The principal focus is put in evaluating the fatigue behavior of such composites. As CFRP materials become increasingly vital for functional and structural applications, it is essential to determine their fatigue strength at representative cyclic stress levels for successful application in engineering systems. The review covers how mechanical strength are influenced by fiber content, orientation, layer thickness, and infill density parameters. The aim of this study is to synthesize existing knowledge, present existing problems, and offer future research directions for developing the structural reliability character of CFRP composites in additive manufacturing.
To investigate the dynamic damage response of fiber-reinforced polymer composites under explosion load, an improved explosion damage model of FRP was proposed. By introducing the dynamic enhancement factor to characterize the material strengthening at high strain rates, Hashin-Strain criterion is optimized to capture interfacial debonding and delamination damage mechanisms under multi-axial stress coupling, and a nonlinear exponential stiffness degradation model is proposed to describe the rapid accumulation and energy dissipation process of damage under explosion load. Based on ABAQUS/VUMAT subroutine, the prediction accuracy of five damage calculation schemes is compared and analyzed. The near-field explosion test of composite sandwich panel is carried out, and the optimized damage calculation method is extended to the near-field explosion damage prediction of composite sandwich panel. The results show that the optimized model significantly improves the prediction ability of damage morphology and fracture size. The area error of delamination damage and perforation damage predicted against Gargano , s test simulation are all within 10%, and the damage energy dissipation curve agree well with the test results. The corresponding results provide theoretical and experimental support for the anti-explosion design and evaluation of fiber reinforced composites in marine armor and other protection projects.
Polymer concrete (PC) is an advanced composite whose engineered combination of synthetic resins and aggregates yields markedly improved mechanical performance and durability versus ordinary Portland cement systems. This review synthesises findings to (1) trace the historical development of PC, (2) categorise common resin classes (epoxy, polyester, vinyl ester, furan, polyurethane), (3) consolidate mix-design principles and additive/fibre strategies, and (4) quantify static and dynamic mechanical behaviour (compressive, tensile, flexural strength, fracture toughness, damping and strain-rate sensitivity) under varied curing and environmental exposures. Key outcomes include identification of an optimal resin-content window (≈12–17 wt%) that balances strength and cost, documented trade-offs between resin type and thermal/chemical durability, and the pronounced superiority of PC in impact and vibration-damping applications. The review critically examines sustainability challenges (embodied energy, recyclability, and life cycle impacts) and surveys mitigation pathways such as recycled fillers, bio-based resins, and circular economy practices. Finally, it maps future research priorities: standardised testing protocols for structural use, development of low-carbon and recyclable polymer matrices, and deployment of machine learning for mix design and property prediction. This integrated roadmap informs engineers and researchers seeking to deploy PC in structural, marine, transportation and defence applications while guiding research toward sustainable, data-driven innovation.
Tires are difficult to recycle since they are composed of different materials such as rubber, carbon black, steel, and polymers. A patented tire-recycling process developed by a local company separates rubber and steel from used tires and yields two textile fiber by-products. The aim of this study was to characterize the fibers and to evaluate their effect on the shrinkage cracking potential of concrete. Commercial microfibers were also included in the tests for comparison. A dosage of 0.1% F1 fibers reduced cracking by 87%, while 1% F2 fibers achieved up to a 97% reduction in cracking under severe environmental conditions, while a dosage of 0.1% by weight of commercial fibers achieved full cracking control. Large cracks (above 3 mm) and medium cracks (surrounding 2 mm) were fully controlled using the recycled fibers. It was concluded that these byproducts have excellent performance in mitigating restrained shrinkage cracking of cement composite materials. This has beneficial implications on the durability of concrete. Additionally, this recycling alternative could contribute to closing the material loop of tires.
Rattan fiber is emerging as a sustainable reinforcement in polymer composites due to its light weight, flexibility, and mechanical strength. Rattan fiber reinforced composites (RFRC) are thoroughly studied in this review, having a focus on surface treatment, fabrication techniques, characterization, hybridization, and prospective applications. Maximum enhancement of tensile strength and Young’s modulus were observed in fibers treated with 5% NaOH which were 35.17% and 111.5%, respectively, whereas fibers underwent through Benzoylation treatment showed 12.5% and 85.6% increment in tensile strength and Young’s modulus, respectively. Thermal stability was improved with degradation onset temperatures rising by 13–25°C. Mechanical, thermal and physical properties of RFRCs are analyzed in characterization studies, and their strength, modulus, and durability are significantly increased when hybridized with synthetic or other natural fibers. Applications in the furniture, packaging, construction, and automotive sectors are reviewed, highlighting RFRC’s possibility as an eco-friendly alternative to traditional composites. With a significant 269% increase in flexural strength and 88% increase in tensile strength, the rattan-glass hybrid composite provides exceptional mechanical performance appropriate for demanding automotive applications. To direct future advancements in sustainable rattan-based composite technology, this study reviews the existing body of knowledge and highlights important research gaps.
