Journal of Reinforced Plastics and Composites

This work has concerned upcycling of used PET bottles by compounding with graphene nanoplatelets (GNP). The effects of antioxidants concentration on molecular weight and mechanical properties of the recycled PET sheets were examined, using ¹H-NMR spectroscopy and a universal testing machine, respectively. The optimum antioxidants concentration was found to be 1.5 phr, as it is effectively mitigated PET chain scission. When loaded with 0.2 phr of GNP, the crystallinity of the PET/GNP sheets increased from 20.11% to 25.75% while the water vapor transmission rate of the PET sheet dropped from 16.795 (g.mm/m².day) to 11.585 (g.mm/m².day) accordingly. The improvements were obtained at the expense of visible light transmittance which decreased from 77.70% to 10.76%. A similar but more pronounced effect was observed when a surface-functionalized GNP was used. For the encapsulation of organic photovoltaic (OPV) cells, PET composite sheet containing 0.025 phr of GNP was chosen. After 2 weeks, the normalized PCE of OPV cells encapsulated with recycled PET sheets were about 0.61–0.62, whereas that of the bear OPV cell dropped rapidly to 0.20. In overall, this work demonstrated a feasibility of using PET/GNP composite sheets as a cover lid for encapsulation of OPV, aiming to enhance durability and lifespan of the devices.

Graphical Abstract

Accurate identification of the damage initiation location, propagation behavior, and damage modes of metal-composite joint structures is crucial for the design of civil aircraft. Considering the differences in the mechanical properties of metals and composites, a progressive damage model is developed based on a bilinear elastic-plastic hardening model and a three-dimensional (3D) Hashin damage model, which realizes the simultaneous analysis of the damage state of heterogeneous material joint structures. Experiments on seven typical multi-bolt metal-composite joints were conducted to investigate structural failure mechanisms. The results show that the geometric configuration and composite layup design are the dominant factors influencing the load-bearing capacity and failure modes. Optimizing the joint layout from a single-row to a double-row configuration increased the ultimate load by 57.8%. For the same configuration, optimizing the composite layup design improved stress redistribution between adjacent holes, enhancing the ultimate load by 19.5%. The improved finite element model demonstrated strong agreement with scanning electron microscopy (SEM) analysis, indicating that the competitive damage behavior between metal and composite components is the fundamental cause of diverse failure modes in the joints. The error is controlled within 5% compared with the experimental results, which verifies the accuracy of the model.

Aiming at the problems of rough and porous surfaces, and poor surface appearance and mechanical properties of thermoplastic polyurethane elastomer (TPU) parts with selective laser sintering (SLS) technology. In this paper, TPU parts were coloured using dry-blended colorant powders comprising carbon black pigment and TPU matrix particles. Firstly, the colour is applied by dry colouring and then the TPU parts are modified simultaneously by solvent-induced film formation process. The final effect of colour powder dyeing is affected by many factors, such as pigment particle size, proportion of colour powder, fixing temperature, fixing time and so on. The results show that the colourfastness rating of TPU parts is 5. The surface roughness (Sa) value is reduced from 13.6 μm to 0.6 μm, and the tensile strength is increased from 2.8 MPa to 3.8 MPa, and elongation at break from 200% to 334%. The mechanism involves electrostatic adsorption of pigment and TPU particles onto the part surface and into its micropores during dry-colouring. Subsequently, the solvent dissolves the TPU particles during fixing. This dissolved TPU penetrates the micropores and forms a continuous film anchored within them. Consequently, the modified TPU parts exhibit uniform colour, high colour fastness, smooth and flat surfaces, and improved mechanical properties.

Cupuaçu husk was used as vegetal filler in polystyrene, aiming to investigate its influence on the properties of the polymer. The chemical characterization of the residue was carried out using FTIR and FRX. The thermal behavior was studied by TG/DSC. Surface morphology was observed by SEM. The particle size distribution was evaluated by laser scattering. Four types of test samples were fabricated: a sample containing only pure polystyrene and other ones filled with 1, 2, and 3% of residue. Furthermore, samples were subjected to thermal aging in an oven. 30-day oven-aged and unaged samples were characterized mechanically (tensile test), thermally (TG/DSC) and chemically (FTIR). In addition, fracture region was evaluated by SEM. The filler incorporation affected positively the mechanical behavior of the polymer. The degradation temperatures presented some increase along with the incorporation of the filler. Also, DSC curves suggested that the filler incorporation might have inhibited the formation of low molecular weight molecules detected in curve of pure-PS sample. It suggests that the residue can be a viable option as a thermal stabilizer. These results imply that the incorporation of the cupuaçu residue may have some positive influence in the performance of mechanical and thermal properties of the polystyrene.

Natural medical latex products commonly encounter critical challenges during application, including poor tensile performance, inadequate strength, and insufficient biocompatibility. Additionally, their usage environments are often contaminated with pathogenic bacteria. Traditional antibacterial strategies typically rely on materials like pentachlorophenol and N-methylolacrylamide, but these substances increase user risks of allergies and other diseases. To address these limitations, this study synthesizes polymethyl methacrylate-polystyrene (PMMA-PS) and polymethyl methacrylate-chitosan oligosaccharide (PMMA-COS) nanoparticle emulsions via emulsion polymerization. Under conventional direct deposition methods, poor interfacial compatibility between the membrane materials causes extensive delamination of the deposited layer from the natural latex surface during long-term use, thereby deteriorating overall mechanical performance. To mitigate this, PMMA-PS is first blended with pre-vulcanized natural rubber latex (SPNR). The addition of PMMA-PS enhances film mechanical properties due to the excellent compatibility between PMMA-PS and PMMA-COS emulsions, which fosters a more stable phase structure during blending and deposition. Leveraging COS’s ability to improve surface antibacterial property, PMMA-COS dispersion is deposited onto PMMA-PS∼SPNR blend films, yielding PMMA-COS/PMMA-PS∼SPNR composite films with enhanced mechanical properties, physical stability, and reduced safety concerns. This research provides scientifically valuable findings and quantitative evidence for improving the antibacterial and mechanical performance of natural medical latex products (e.g., condoms, medical gloves) and the stability of nanocoatings on their surfaces.

The integrated overmolding of fiber-reinforced thermoplastic composite laminates has emerged as an innovative manufacturing process. The laminate temperature uniformity is the main factor affecting product quality. In this paper, the temperature of continuous glass fiber-reinforced polypropylene (CGFRPP) laminate was measured using a thermal imaging camera. A finite element model was established according to the heat transfer equation to analyze the temperature distribution of the laminate. The Grey wolf optimization (GWO) algorithm and chaos mapping were used to optimize the BP neural network. The CIGWOBP temperature prediction model was established. By independently controlling the heating power of the heating tubes, the temperature field of the laminate became uniform. The maximum temperature gradient was 9.4°C and the optimized efficiency was 51%. The laminate structure was optimized with a preheating time of 30 s. These results are expected to guide future efforts in achieving temperature uniformity in heated composite laminates during the integrated over-molding process in the automotive industry.

In this study, a quasi-static compression experiment system was employed to investigate the enhancing mechanism for polyurethane foam filling on the mechanical properties of paper honeycomb structures. Based on the comparative analysis of single-cell and honeycomb plate samples, it is revealed that cell side length, wall thickness, foam strength, and interfacial bonding force exert synergistic regulatory effects on out-of-plane load-carrying capacity. Experimental results indicate that reducing the cell side length and increasing the wall thickness can significantly improve the structural properties, while the peak stress, plateau stress, and energy absorption of foam-filled paper honeycomb increases by 25% to 450% compared with those of unfilled honeycomb. Notably, the cooperative load-bearing capacity exceeds the simple superposition effect of foam and bare honeycomb. Finally, a predictive model for the plateau force of foam-filled paper honeycomb is proposed, with experimental verification errors below 10%. This model provides a theoretical framework for optimal design of lightweight composite honeycomb structures.

The concrete facing slabs of rockfill dams exhibit heightened susceptibility to plastic shrinkage cracking, a phenomenon aggravated by harsh environmental conditions during construction that significantly compromises structural durability. This study systematically investigates the plastic shrinkage characteristics of basalt fiber concrete under simulated harsh environmental conditions, with particular emphasis on critical infrastructure applications. A free plastic shrinkage test setup and the restrained slab method were employed to quantify free shrinkage strain and evaluate the severity of restrained plastic cracking. The results indicated that increasing the basalt fiber content to 0.10% resulted in a cracking area reduction rate of 89%. Further increases in basalt fiber content resulted in a notably slower rate of reduction in the cracking area. When the W/C (water to cement ratio) was reduced from 0.5 to 0.3, the cracking area reduction rate of basalt fiber concrete relative to plain concrete increased from 55% to 89%. The crack mitigation capacity of basalt fiber demonstrates enhanced efficacy in lower W/C ratio matrices.

Resin-mineral composite materials, as a class of important engineering materials, possess excellent mechanical properties and broad application prospects. The accurate prediction of their equivalent elastic constants is crucial for the design and application of these materials. This paper aims to delve into the equivalent elastic constants of resin-mineral composite materials, providing new insights for the design of these composites by combining theoretical analysis and experimental investigation. Initially, the homogenization concept of composite materials and Eshelby’s equivalent inclusion theory are employed to theoretically analyze the internal stress field of the composites, yielding explicit expressions for the equivalent elastic constants of resin-mineral composite materials. Subsequently, a series of resin-mineral composite specimens with varying volume fractions of constituent materials are fabricated and subjected to elastic property tests. The results indicate that the discrepancy between the experimental and theoretical equivalent elastic constants is approximately 10%, which substantiates the reliability of the theoretical analysis process. Finally, the influence of steel fiber and aggregate volume fractions on the equivalent elastic constants of resin-mineral composite materials is analyzed. These findings are of significant importance for optimizing the design of composite materials and enhancing their application performance.

Glass-fiber reinforced polymer (GFRP) composites offer significant advantages, including high performance, light weight, excellent insulation, and corrosion resistance. It is an ideal material for transmission towers as a replacement for steel. Understanding the performance of GFRP composites in service environments is a key issue to promote the application. In this paper, the influence of low temperature on the static and fatigue properties of GFRP plates for composite transmission towers is investigated through tests conducted at room temperature (RT, 20°C) and low temperature (LT, −40°C). The results show that the elastic modulus, ultimate strength, and fatigue life of GFRP plates are substantially enhanced at LT. The effect of temperature on Poisson’s ratio is limited. The S-N-T model with reference to the Arrhenius model can accurately describe the relationship between stress level, fatigue life, and test temperature of GFRP plates. In addition, the relationship between the normalized fatigue stiffness and the normalized fatigue life of GFRP plates is described using a three-stage fatigue damage prediction model. The results show that the fatigue stiffness degradation trend predicted by the model aligns closely with the test results.

Carbon fiber reinforced polymer (CFRP) composites are widely used in aerospace and other advanced engineering fields due to their exceptional mechanical properties and performance advantages. However, during machining, CFRP is prone to defects such as burrs, tearing, and delamination. Modifying the tool rake face geometry and adding micro-textures on the tool surface can reduce machining damage to CFRP. The underlying mechanisms of these effects remain to be further investigated. First, the unique “crescent-shaped concave” structure of the bamboo rat’s lower incisors is utilized and applied to the rake face of the cutting tool for biomimetic tool design. The variable curvature configuration of the “crescent-shaped concave” structure can effectively reduce cutting forces, thereby mitigating subsurface damage. Furthermore, based on the depth data of the “crescent-shaped groove,” a depth-varying micro-texture is applied to the biomimetic rake face of the cutting tool. The study investigates the fracture and failure modes of fibers and matrices under cutting load conditions. A combined approach of finite element simulation and experiments is employed to explore the subsurface damage suppression mechanisms during the machining of unidirectional fiber-reinforced plates at 45°, 90°, and 135° orientations. Using the micro-textured cutting tool proposed in this study to machine unidirectional fiber-reinforced plates at 45°, 90°, and 135° orientations, the subsurface damage was reduced by 40.83%, 11.94%, and 43.62%, respectively, compared to conventional tools. While subsurface damage was reduced at all orientations, a significant reduction in subsurface damage was observed in the 135° unidirectional fiber-reinforced plate.

The demand for advanced polymer matrix composites with superior strength, wear resistance, stiffness, and reduced weight is increasing. This study introduces a novel hybrid laminate architecture in which carbon and glass fiber yarns are alternately hand-woven over stainless steel 304 wire mesh (SSWM) and embedded in a carbon fiber-reinforced polymer (CFRP) matrix. Unlike conventional CFRP or mesh-reinforced composites, this design integrates metallic mesh with woven fiber yarns to achieve enhanced load transfer and damage tolerance. Four composites with yarn orientations of 30°, 45°, 60°, and 90° were fabricated using the hand layup method. Pin-on-disc wear tests revealed that CFWM 60° exhibited the lowest wear rate (41 mm³/Nm at 10 N), a 70.3% reduction compared to CFWM 90°. Erosion tests at 75 m/s and a 90° impingement angle using alumina particles showed that CFWM 45° had the best performance (0.142 g/g), 36.88% lower than CFWM 60°. The orientation-driven improvements were attributed to superior interfacial bonding, controlled crack deflection, and optimized load distribution. Fractography using Field Emission Scanning Electron Microscopy (FESEM) analysis confirmed reduced fiber pull-out and matrix degradation in CFWM 60° and 45° configurations. This study demonstrates the tribological performance of woven CF/GF-SSWM hybrid laminates.

Reinforced concrete (RC) frames infilled with brick masonry are widely used in construction due to their improved lateral resistance. However, their behavior under lateral loading is complex due to the interaction between the frame and the infill. Modifying the interface materials has shown potential in improving the overall performance under lateral loads. However, the influence of interface material type and thickness on structural response needs further exploration. Limited research exists on the effect of interface materials and their thicknesses on the non-linear behavior of infilled frames, particularly when using flexible materials. This study evaluates the static lateral performance of Y-joint with brick masonry infill using three interface materials—cement mortar, bitumen, and rubber—across varying thicknesses. The interaction is analyzed for displacement, stress concentration, and failure load in ABAQUS. Rubber interfaces increase displacement by 80–90% compared to cement mortar and bitumen interface, while bitumen interfaces show negligible variation in stiffness across different thicknesses. Rubber interface with 20 mm thickness reduces stress concentration by 34.3% compared to 5, 10, and 15 mm. Cement mortar presents bonding issues at increased thicknesses for 20 mm thick model, with maximum debonding of 58.9% was found. These findings demonstrate that selecting appropriate interface materials and thicknesses can significantly enhance structural resilience. ANN-based approaches can efficiently identify optimal configurations, reducing dependence on computational simulations. The regression (R) value among the training, testing and validation for all cases reaches above 0.9 for stress distribution, stiffness, and contact area.

This study constructs four functionalized graphene/nitrile-butadiene rubber (FGNS/NBR) molecular dynamics (MD) models under the COMPASS force field to evaluate mechanical properties and abrasion rates. For each composite, 50 independent shear simulations (200 samples) were run; averages of force-field energy components over the post–steady-state segment built a bonded/non-bonded energy-fingerprint library. Feature screening relied on the consensus across multiple importance measures, yielding 17 descriptors. A Random Forest regressor (RFR) was trained, and mechanistic interpretation combined SHapley Additive explanations with mutual information. The MD analyses indicate that functionalization generally enhances mechanical properties and improves wear resistance. Subsequently, the RFR explanatory model further revealed three principal determinants of wear performance—Fe layer van der Waals energy, total bond length after shearing, and the torsion–stretch energy of FGNS—and indicated that the interplay between chain extension and interfacial adsorption constitutes the dominant anti-wear pathway. Overall, the study introduces an interpretable comparative method focused on relative trends across functionalizations, offering a useful analytic perspective for small-difference systems and for considering functional group and grafting choices.

Auxetic structures, characterized by a negative Poisson’s ratio, expand laterally under axial loading and offer superior energy absorption and deformation capacity, making them promising candidates as core materials in sandwich structures. In this study, sandwich panels with three auxetic core geometries (star-4, re-entrant, and honeycomb) were fabricated using fused filament fabrication (FFF). The cores were produced using three thermoplastic materials: polylactic acid (PLA), polyethylene terephthalate glycol (PETG), and carbon fiber-reinforced polyamide (ePAHT-CF). PLA was also used for the face sheets, printed in three orientations (0°, 0/90°, and ±45°) to evaluate anisotropy effects. Mechanical performance was assessed through three-point bending tests, focusing on peak load, energy absorption (EA), and specific energy absorption (SEA). The honeycomb core with PLA face sheets at 0° yielded the highest peak load (702.97 N), a 351% increase compared to the lowest-performing specimen (star-4/ePAHT-CF at 155.76 N). The highest EA (9.64 J) and SEA (0.52 J/g) were achieved by the honeycomb/ePAHT-CF core with ±45° orientation. ANOVA results confirmed that core geometry and material type significantly affect peak load. Overall, the mechanical behavior is governed by the synergistic effects of geometry, material, and printing parameters.

Traditional damage detection methods for carbon fiber-reinforced polymer (CFRP) composites primarily rely on manual operations, resulting in low efficiency and accuracy. This study proposes a high-precision and rapid damage detection approach for CFRP composites based on machine vision. First, three common types of CFRP damage specimens were prepared through controlled experiments, and ultrasonic C-scan imaging was employed to acquire damage images. A dataset comprising 6650 annotated images was constructed through data augmentation techniques. Subsequently, the Mask RCNN model was enhanced in two key aspects: (1) integrating the Sim-AM attention mechanism to improve feature extraction capability, and (2) replacing the conventional Non-Maximum Suppression (NMS) algorithm with Soft-NMS. This study employs an improved Mask RCNN model to train and test the dataset. Experimental results demonstrate that the model achieves significant enhancements in detecting CFRP (carbon fiber-reinforced polymer) damage, with Precision, Recall, and mAP (mean Average Precision) reaching 97.2%, 94.5%, and 95.1%, respectively. The detection speed attains 4.9 FPS (frames per second). These metrics indicate that the proposed model outperforms both the standard Mask RCNN and other mainstream object detection models, exhibiting superior detection accuracy to meet industrial requirements. Additionally, this work provides a novel research approach for damage detection in this field.

Deeper understanding of damage propagation in continuous fiber reinforced polymer composites is required to design safer composites. The process of sample preparation imparts sufficient damage to the free edges and can be easily considered as precursor to failure. This study examines the low-cycle fatigue (LCF) behavior and damage progression in woven angle-ply laminates under static and fatigue loading. Laminates with ply orientations of (0°/90°), ±15°, ±30°, and ±45° were tested with a load-controlled fatigue at 0.1 Hz and a stress ratio (R) of 0.1. Internal and free-edge damage were monitored using Transmitted Light Photography (TLP) and optical recording. Weibull statistics is used to generate S-N curve for reliability levels of 0.95, 0.99, 0.999, and 0.9999 and to find mean-time-to-failure (MTTF), standard deviations, and coefficient of variance (CV) in the fatigue life. TLP images showed delamination promoted by free-edge damage, while compressive face damage was caused by the loading cylinder. On-axis laminates developed fewer cracks, failing with a single through-thickness crack, while off-axis laminates exhibited multiple cracks that coalesced without a single fracture. Fiber orientation significantly influenced internal debonding, and damage from sample preparation could not be fully eliminated.

In the context of global efforts toward carbon neutrality and lightweighting, advanced composite materials are in urgent demand. The fiber/matrix interface, as a critical factor determining the overall performance of composites, the interfacial characteristics of the fiber/matrix affect the performance of composite materials, has thus become a focal point of research. To improve the performance of the fiber/matrix interface, this study examines the influence of nano-titanium dioxide (TiO₂) surface modification on the tensile and fatigue properties of Three-dimensional (3D) orthogonal glass fiber/epoxy composites. Quasi-static and fatigue tensile tests were conducted to evaluate the mechanical behavior and damage mechanisms of unmodified and modified specimens along 0°, 45°, and 90° directions. Results indicate that TiO₂ modification significantly improves resistance to matrix cracking, fiber breakage, and delamination. The application of nano-TiO₂ coating on 3D orthogonal glass fiber/epoxy composites provides preliminary experimental data and theoretical insights for optimizing tensile and fatigue performance, offering a potential strategy to enhance fatigue resistance in advanced composite materials.

The increasing use of polymer-based composites and fiber metal laminates in structural applications necessitates improved joint design strategies. This study investigates the effects of bolt layout and washer type on the failure behavior of double-lap bolted joints in polypropylene-based nanocomposite plates. Experimental tests were conducted using a GOTECH AM-20 machine, and numerical simulations were performed with ABAQUS/CAE 2016. The Sb522 configuration with a flat washer showed the most severe rupture, while Sb311, Sb312, Sb511, and Sb512 exhibited strength improvements of up to 9.94% when flat washers were used instead of spring washers. Load-displacement curves and failure patterns showed strong agreement between experimental and finite element results, confirming the reliability of the simulation approach. The maximum Von Mises stress in the bolts (excluding plates) reached 2364 Pa, indicating that the bolts carried over 50% of the load. An artificial neural network model was also developed to predict joint performance parameters, demonstrating high accuracy and complementing experimental and numerical results. This hybrid approach enables efficient evaluation and optimization of nanocomposite joint configurations.

Carbon fiber reinforced polymer (CFRP) laminates, when enhanced with graphene nanoplatelets, exhibit superior stiffness, strength-to-weight ratio, and thermal conductivity, making them attractive for aerospace applications. However, in high-speed micro-drilling, the presence of graphene also alters tribological behavior, increases abrasiveness, and modifies thermal transport, intensifying the risks of delamination, matrix degradation, and tool wear. This work develops an integrated experimental–statistical framework that couples Response Surface Methodology (RSM) with variance-based Sobol global sensitivity analysis and a Desirability Function Approach (DFA) to systematically optimize spindle speed, feed rate, drill diameter, and graphene content. Sobol analysis distinguished feed rate (52.2%) and drill diameter (46.7%) as the principal determinants of thermal loading, while spindle speed governed thrust generation (80.4%), entry delamination (95.7%), and exit delamination (60.7%). Multi-objective optimization yielded an operating window (18000 rpm, 25.35 mm/min feed, 0.40 mm drill diameter, neat CFRP) that simultaneously reduced peak drilling temperature by 18%, cutting force by 22%, and delamination damage at entry and exit by 27% and 21%, respectively. These improvements are mechanistically attributed to the minimization of interlaminar shear stresses, controlled heat flux at the tool–workpiece interface, and improved chip evacuation dynamics at the optimal parameter combination. Beyond statistical modeling, this study establishes a predictive–diagnostic methodology capable of guiding industrial high-speed micro-drilling operations toward balanced thermal–mechanical performance in nano-reinforced composite systems.

The multi-stage fatigue characteristics of ceramic matrix composites (CMCs) are of significant importance for the design and evaluation of reusable thermal structures. This study investigates the low-cycle static fatigue behavior, damage-evolution mechanism and lifetime of plain-woven C/SiC composites under axial multi-stage tensile loading conditions. Experimental results show that 2D-C/SiC materials exhibit remarkable anisotropic and nonlinear behaviors: the unloading modulus demonstrates a three-stage degradation trend of “fast-slow-fast” with the increase of cycle numbers, and meanwhile the residual strain accumulates progressively. Scanning Electron Microscope (SEM) analysis reveals that the fracture morphologies of specimens show matrix micro-cracks, interface debonding and fiber pull-out. Based on the shear-lag theory, this study also simulated the cyclic stress-strain behavior through a hysteresis constitutive model and proposed a shear-lag theory based residual strength model. The static fatigue life is predicted by calculating the interface slip stress and matrix crack spacing under different peak loading stresses. The predicted values by the fatigue life model and the strength model are in good agreement with the experimental results. This research supplements original data for 2D C/SiC composites in the field of axial static tensile fatigue properties under multi-stage loading mode and extends the life prediction methods.

Reinforced concrete structures in marine environments suffer from severe rebar corrosion. Basalt fiber reinforced polymer (BFRP) bars, which have better mechanical properties and corrosion resistance comparable to rebars, are a promising alternative. This study compares the durability of these two materials in concrete pore fluid simulating a marine environment. Through 0–100 days immersion experiments, it examines the mass and tensile property (tensile strength, elastic modulus, and ultimate strain) changes of the two types of bars, and uses the Arrhenius model, power function model, and exponential model to predict their long-term performance. Testing showed that after 100 days of immersion, BFRP bars had a mass loss rate of just 0.99%, compared to 3.83% for rebars. The minimum tensile strength retention rate of BFRP bars was 98.24%, versus 91.00% for rebars. The minimum elastic modulus retention rate of BFRP bars was 95.27%, while rebars only retained 92.25%. Thus, BFRP bars exhibited 7.24% and 3.02% higher tensile strength and elastic modulus retention rates, respectively, than rebars. Experimental results demonstrated that BFRP bars possess superior corrosion resistance to rebars in concrete pore fluids simulating a marine environment. Long-term predictions suggest BFRP bars last five times longer than rebars. This study shows that BFRP bars with excellent corrosion resistance and stable mechanical properties can replace rebars in marine concrete structures to effectively address corrosion issues.

Transparent wood composite (TWC) is a novel bio-based material with potential applications in architecture, electronics, and sustainable engineering. However, the limitation of TWC to deliver substantial mechanical strength and thermal stability has often hindered its large-scale applicability. This work offers a novel method for improving these qualities by using chopped strand mat (CSM) to reinforce TWC. In order to create hybrid composites, delignified rubberwood veneers were first impregnated with unsaturated polyester resin (UPR). Subsequently, CSM layers were integrated onto the layer of TWC to form hybrid composites. Mechanical, thermal, and optical properties of the one-layer and double-layer reinforced TWC versions were evaluated. The results demonstrated significant improvements in mechanical performance, with the MoE and MoR increasing by up to 59% and 78%, respectively, in CSM-incorporated TWC as compared to typical TWC. According to thermogravimetric analysis, CSM-reinforced TWC had greater thermal stability. The addition of CSM resulted in a drop in optical transmittance, indicating a trade-off between optical property and mechanical strength in TWC. Notably, the use of CSM had a minimal impact on the thermal insulating performance of TWC. This study presents an initial attempt to develop a scalable and cost-effective approach for producing mechanically strong TWC, demonstrating significant potential for superior structural and energy-efficient uses.

Due to its outstanding specific strength, corrosion resistance, and fabrication flexibility, Fiber Reinforced Plastic (FRP) presents considerable potential as an alternative to conventional reinforcement materials in the strengthening and rehabilitation of concrete structures. However, the issue of premature debonding at the FRP–concrete interface poses a critical challenge, significantly affecting the stability and reliability of its strengthening performance. To address this problem, researchers have proposed a variety of connection configurations aimed at mitigating interfacial failure, leading to the development of representative systems such as externally bonded (EB), near-surface mounted (NSM), and hybrid bonded (HB) techniques. This paper systematically reviews the developmental trajectories and structural evolution of these typical FRP connection technologies, compares their differences in load-bearing capacity, interfacial behavior, applicable scenarios, and durability performance, and summarizes key advances in experimental investigations and theoretical developments. The main challenges in mechanistic understanding and standardized application are identified. Finally, future research directions are proposed, including interface regulation, environmental adaptability assessment, and integration into engineering systems. This study provides a comprehensive understanding and forward-looking perspective for advancing the theoretical foundation and practical implementation of FRP connection technologies.

Graphical Abstract

The fiber patch placement (FPP) technology enables the automated manufacturing of complex-shaped components. However, placement defects such as bridging and wrinkling may occur during the deposition of patches onto the tool surface, which are typically unacceptable in high-performance applications. To analyze and prevent such defects, this study investigated the patch placement process using finite element (FE) simulations. Various obstacle geometries were designed to deliberately induce wrinkling, and these scenarios were subsequently simulated. Furthermore, simulations and experimental placements were carried out on an aerospace demonstrator. The simulation results were validated using 3D scan data, and typical placement defects were successfully replicated in the numerical model. The maximum deviation between scanned and simulated patches was 4.49 mm, corresponding to only 3% of the patch’s short edge length. This confirms the suitability of the approach for capturing key defect mechanisms. The placement behavior of the FPP technology has not yet been investigated using simulations validated with 3D scan data. The findings contribute to a deeper understanding of defect formation mechanisms—particularly wrinkling and bridging—under defined placement conditions. This work provides a foundation for predictive process optimization and the development of defect-preventing placement strategies for complex geometries.

The increasing usage of laminated composite structures in aviation has raised the critical need to understand their behavior under bird-strike events, which pose severe safety risks. This review uniquely focuses on the hybrid Smoothed Particle Hydrodynamics–Finite Element Method (SPH-FEM) approach for simulating bird impacts on laminated composite panels. This area has not been comprehensively addressed in prior literature. Unlike traditional modeling methods, the SPH-FEM technique enables accurate simulation of fluid-like bird behavior alongside detailed structural damage mechanisms such as delamination, fiber fracture, and matrix cracking. This work highlights key insights into the influence of bird geometry, impact velocity, and composite layup on damage progression and energy dissipation. Notably, this review identifies critical research gaps in bird homogenization and the validation of high-velocity failure criteria. Recent developments in bio-inspired helicoidal laminates and hybrid models are also examined to inform future design and simulation standards. Through this focused analysis, the review provides a forward-looking framework to advance the reliability, efficiency, and accuracy of bird-strike simulations in aerospace applications.

Using pineapple fiber, coir fiber, and banana fiber as a polymer reinforcement to develop sustainable composites reduces environmental pollution. This review emphasized the progress in development of composite materials based on pineapple fiber, coir fiber, and banana fiber and critically examined the influence of fiber loading and fiber size, fiber modification, micro and nanofillers, and hybridization on the properties of composite materials fabricated with several polymer matrices. This review has been specifically categorized according to the type of matrix materials used, which include conventional polymers, bio degradable polymers, and recycled polymers. The mechanical performance of hybrid composites based on pineapple fiber, coir fiber, and banana fiber fabricated with other natural and synthetic fiber composites was better than the individual fiber. Incorporation of filler materials such as alumina, SiC, nanoclay, eggshell powder, and nano-cellulose provided a significant enhancement in mechanical properties of composites. Alkaline and silane treatment of fiber is the most commonly used treatment method, and this treatment significantly enhances mechanical, thermal, and water resistance properties of composites. Life cycle assessment analysis and long-term durability analysis of composites, optimization of fiber treatment parameters for better performance of composites, and 3D printer filament development based on nano-cellulose extracted from banana, coir, and pineapple are future directions for developing sustainable materials.