ABSTRACT Boundary conditions are receiving increasing attention in the overall design of composite structures. This study explores the influence of two typical bottom support boundaries on the impact response and residual properties of thick‐ply and ply‐level hybrid laminates. Low‐velocity impact (LVI) tests were conducted to compare the structural response of laminates under two different bottom support conditions. Finite element (FE) models using the LaRC05 failure criterion were developed to further investigate the influence mechanism of boundary constraints. Compression after impact (CAI) tests were also performed to evaluate the effect of support boundaries on the residual properties. Results reveal that, the bottom support boundary significantly influences the impact response of laminated composites. Although the small open‐window support boundary limits out‐of‐plane deflection, it increases local relative deformation and amplifies impact damage, thereby leading to reduced residual stiffness and strength in laminated composites. Furthermore, hybrid laminates demonstrate superior impact damage resistance and CAI strength compared to thick‐ply laminates under both support conditions. These findings suggest that compliant support boundaries offer an effective means of enhancing impact resistance in laminated composites.

ABSTRACT Structural batteries based on woven carbon fabrics are typically established on lithium ion phosphate (LFP) and graphite. While this method proved viable from the manufacturing perspective, the resulting structural batteries exhibited suboptimal electrochemical performance. This underperformance is primarily attributed to the electrochemical interference between the graphite coating and the underlying carbon fibers, where lithium ions can partially intercalate into the fibers' turbostratic graphitic structure. This parasitic reaction alters the anode's effective capacity and accelerates degradation, ultimately limiting the battery's overall performance. To address this issue, the present work replaces graphite with lithium titanate (LTO) to eliminate such interference and enhance the electrochemical stability of the structural battery. Specifically, graphite is replaced with LTO, a material known for its high stability and superior electrochemical properties, to produce a fabric anode. The lithium titanate would not interfere with carbon fibers, so the capacity of the structural batteries can be significantly improved. LTO also possesses several other advantages, such as a stable voltage plateau, low volume expansion during charge/discharge cycles and excellent cycle life, all of which are critical for maintaining the structural integrity and longevity of the battery. A liquid electrolyte is adopted in this proof‐of‐concept study to ensure stable electrochemical performance; the structural functionality is achieved through the carbon‐fabric‐reinforced encapsulation layers, demonstrating the material‐level integration of mechanical and energy‐storage functions.

ABSTRACT The use of carbon fiber reinforced polymers (CFRPs) is limited by their susceptibility to low‐velocity impact (LVI) damage. This study investigates the effect of incorporating 0.75 wt.% carbon nanofibres (CNFs) into the epoxy matrix of carbon fiber fabric laminates on their impact performance and post‐impact mechanical properties. LVI tests were performed with energies ranging from 1 to 9 J, followed by an evaluation of residual bending strength, stress relaxation, and creep properties. At an impact energy of 9 J, the CNFs‐enhanced laminates exhibited a 9.2% higher maximum impact load and a 9.0% lower maximum displacement compared to the control laminates with neat matrix. Elastic energy restored after impact was also considerably higher, with an improvement of 21.06% at 9 J. Consequently, the addition of CNFs increased the laminate's penetration threshold by 9.4%, from 12.94 to 14.15 J. Following impact, the residual bending strength and stiffness of the nano‐reinforced laminates were consistently higher than the control group; at an impact energy of 9 J, both properties were 5.3% greater. Impact damage was found to accelerate viscoelastic effects, with a 9 J impact increasing the creep displacement by 2.4 times compared to unimpacted samples. While CNFs did not substantially alter the inherent viscoelastic behavior of the material, they mitigated damage by creating bridging mechanisms that delay crack propagation. This resulted in a slight reduction in stress relaxation for impacted samples. The findings confirm that incorporating CNFs is an effective strategy for enhancing the damage tolerance and structural integrity of composite laminates.

ABSTRACT This study reports the fabrication and characterization of PVDF/Ni nanowire (NW) composite films for thermoelectric (TE) applications. The composite films were prepared with varying Ni NW concentrations (30–90 wt. %) by dispersing them in PVDF using dimethylformamide (DMF) as a solvent, followed by a drying process to form uniform films. X‐ray diffraction (XRD) and fourier‐transform infrared spectroscopy (FTIR) analyses confirmed the presence of α and β crystalline phases in the PVDF matrix, while scanning electron microscopy (SEM) showed uniform dispersion of Ni NWs, forming conductive pathways. X‐ray photoelectron spectroscopy (XPS) analysis provided insights into the chemical states and interactions within the composites. Electrical characterization revealed that increasing Ni NW content enhanced electrical conductivity, while maintaining consistent n‐type Seebeck behavior. The composite with 90 wt. % Ni exhibited the highest power factor of 15.1 μW/m·K 2 at room temperature and reached an optimized value of 120 μW/m·K 2 at 400 K outperforming similar PVDF‐based materials reported in the literature. Furthermore, a flexible thermoelectric generator (TEG) was developed using p‐type PEDOT and n‐type PVDF/Ni NW composites, achieving a maximum power output ( P max ) of 230 nW at a temperature difference (ΔT) of 25 K. These findings demonstrate the potential of PVDF/Ni NW composites for use in flexible, wearable thermoelectric energy‐harvesting devices.

ABSTRACT The production of composite particleboards with agricultural waste has been the focus of many studies that aim to address environmental problems due to waste disposal. This study aimed to evaluate the potential of using castor waste as a raw material for particleboard production with a view to its application as thermal insulation for buildings. Particleboards were composed of pinewood and castor waste particles at ratios of wt. equal to 100/0, 75/25, 50/50, 25/75, and 0/100, and were evaluated for water absorption and thickness swelling, internal bonding, static bending, scanning electron microscopy (SEM), and thermal conductivity. The addition of 100% castor waste reduced water absorption from 106.97% to 78.27% after 24 h of immersion. The replacement of pinewood particles with castor waste provided better dimensional stability to the panels because of the higher content of extractives in the castor waste. The values of the modulus of rupture (MOR) were four to eight times greater than the values recommended by standards for medium‐density particleboards (MDP). The thermal conductivity of the composites with 100% castor waste was reduced from 0.078 to 0.065 W/m K. It was concluded that castor waste, as a raw material used in the manufacture of particleboard, is an alternative and sustainable diversification.

ABSTRACT Recycling glass fibers for structural applications involves reusing, repurposing, and recovering materials rather than discarding them after a single use, thereby reducing waste generation and supporting a circular economy model. This study investigates the recyclability of vitrimer‐based glass fiber‐reinforced polymer composites (GFRPs) and their ability to retain the strength of recycled composites as primary structural components. An epoxy–anhydride vitrimer matrix was used to fabricate GFRPs, and a chemical recycling process was employed to recover glass fibers by depolymerizing the vitrimer matrix in a mixed solvent system of dimethylformamide and ethylene glycol. The clean surface observed in the SEM micrograph and similar Raman spectral trends for both the virgin and recycled fibers confirm the effective recyclability. The GFRP laminates fabricated from these recycled glass fibers retained flexural and tensile strengths of approximately 95% and 98%, respectively, compared to the virgin glass fiber vitrimer composite. To enhance the strength retention, multi‐walled carbon nanotubes (MWCNTs) were incorporated into the vitrimer matrix which increased the strength retention to 99% and 103%, respectively. The results demonstrate effective recycling of glass fiber and retention of maximum strength, which ensures the use of recycled glass fibers for high‐end applications.

ABSTRACT Hybrid fiber‐reinforced polymer (HFRP) matrix composites are widely employed in aerospace and other fields owing to their excellent mechanical properties. However, their performance is often limited by interlaminar failures such as fiber fracture, matrix cracking, and delamination. This study proposes an interlaminar toughening strategy based on a synergistic combination of aramid pulp (AP) and carbon nanotubes (CNTs). Four AP/CNT systems with different areal densities were designed to construct a multi‐scale flexible bridging network, enabling a systematic investigation into their toughening mechanisms on the low‐velocity impact response and residual flexural strength of unidirectional carbon/aramid HFRP. Impact tests indicated that the resistance to impact increased with toughener concentration. The optimal impact performance was achieved at an AP areal density of 3.0 g/m 2 and a CNT density of 4.5 g/m 2 , with a peak load of 10.1 kN—an 11.2% improvement over the untoughened baseline. Conversely, post‐impact three‐point bending tests revealed that the optimal residual flexural strength of 232 MPa was reached with an AP/CNT areal density of 2.0/3.0 g/m 2 , representing a 69% enhancement. Microstructural analysis identified interfacial delamination and fiber fracture as the primary failure modes and confirmed that the AP/CNT system creates effective fiber‐bridging structures between heterogeneous layers. This suppresses interlaminar failure and significantly improves the overall structural stability. In summary, the synergistic AP/CNT toughening system effectively enhances both the impact resistance and post‐impact flexural performance of HFRP composites.

ABSTRACT This study explores the performance of Roselle fiber‐epoxy composites reinforced with biosilica from Paddy straw, emphasizing the effects of silane treatment on the morphology, mechanical properties, dynamic behavior, thermal degradation, wear resistance, and hydrophobicity. Silane treatment enhanced fiber‐matrix adhesion, as confirmed by Scanning Electron Microscopy and Energy Dispersive X‐ray Spectroscopy analyses, which improved the interfacial bonding and increased fiber roughness. Biosilica particles (80–90 nm) reinforced the composite, leading to improved mechanical properties. The 3% biosilica composite (ERB3) achieved the highest tensile strength (103.25 MPa), flexural strength (193.3 MPa), and a balanced combination of fiber reinforcement and biosilica content. The 5% biosilica composite (ERB5) showed higher impact strength and ductility but had slightly lower tensile and flexural strength due to particle agglomeration. Dynamic Mechanical Analysis indicated that ERB3 had the best storage modulus (E′), indicating increased stiffness and rigidity, with less energy dissipation and better load‐bearing capacity. Hydrophobicity decreased as biosilica content increased, with ERB5 displaying the lowest contact angle (65°), though all composites maintained water resistance suitable for moisture‐resistant applications. Thermal degradation tests revealed that ERB5 had the highest thermal stability, with a peak degradation temperature of 480°C and the highest char residue (8.2%). Wear tests demonstrated that biosilica‐reinforced composites significantly outperformed pure epoxy (EP) in wear resistance, with ERB1 showing the best results. In summary, ERB3 provides the best overall performance with superior mechanical and tribological properties, while ERB5 excels in impact strength and thermal stability.

ABSTRACT Curing‐induced distortion (CID) in carbon fiber‐reinforced polymer (CFRP) composite parts presents a significant challenge in the manufacturing of high‐precision parts. While mold compensation techniques have been widely employed for relatively simple geometries like C‐shaped or V‐shaped parts, their applicability to more complex forms, particularly enclosed, rotational structures, remains inadequately investigated. The intricate CID behavior of these geometries poses substantial challenges to effective mold compensation. This study investigates a global mesh‐based mold compensation strategy tailored for enclosed and rotational CFRP parts. The global mesh‐based compensation (GMC) method is defined as a global deviation correction technique, enabling precise and continuous adjustment of each mesh node via a global compensation factor, k . To address the frequent issue of coordinate system reference drift during the compensation of such geometries, an iterative closest point algorithm is integrated into the GMC framework. Numerical simulations and mold compensation procedures are conducted across several representative configurations, demonstrating notable reductions in CID. Further experimental validation on an air‐intake part confirms the method's efficacy, yielding a 69.4% reduction in maximum CID when compared to an uncompensated mold. The results substantiate the proposed mesh‐based compensation method as a robust, accurate, and practical solution for manufacturing high‐precision enclosed and rotational CFRP parts.

ABSTRACT Carbon fiber reinforced polymer composites (CFRPs) have emerged as pivotal structural materials in aerospace, defense, and rail transportation sectors due to their outstanding specific strength, and tailorable mechanical properties. This study adopts an innovative vibration‐microwave curing process. To verify the feasibility of the process, a comprehensive characterization protocol was implemented for the first time, utilizing universal testing machines, scanning electron microscopy (SEM), and drop‐weight impact test systems to evaluate the tensile/compressive properties, fracture morphology, and impact resistance of processed specimens, with systematic comparisons made against autoclave‐cured counterparts. The experimental results demonstrate that the vibration‐microwave cured composites exhibit comparable mechanical properties to autoclave‐processed ones. Specifically, at the 0° orientation, the tensile strength and modulus of the vibration‐microwave cured composites (1708 MPa and 160 GPa, respectively) closely match the autoclave‐cured results (1773 MPa and 162 GPa). A similar trend is observed at the 90° orientation, where the tensile strength (36 vs 39 MPa) and modulus (8.3 GPa for both) are nearly identical between the two curing methods. Comparable results are also observed in the compression tests. Fracture analysis indicates fiber‐dominated failure in the 0° tension orientation and brittle fracture in the 90° tension orientation, while compression shows matrix shear/fiber buckling (in the 0° orientation) and matrix‐dominated failure (in the 90° orientation), both of which match the autoclave failure modes. Impact tests confirm nearly identical energy absorption. The experimental results validate the technical viability of employing vibration‐microwave curing as a sustainable substitute for conventional autoclave processing.