This study presents a novel approach that explores the impact of both volume fraction and particle size of biosilica on the mechanical properties, wear resistance, load-bearing capacity, and time-dependent behaviour of Polylactic acid (PLA)-biosilica hybrid nanocomposites developed through Fused Deposition Modelling (FDM), a 3-dimensional (3D) printing technique. Using sustainably extracted biosilica from agricultural waste (corncob) as a filler, this study enhances the environmental sustainability of the composite while providing a robust, durable, and eco-friendly material suitable for various applications. The optimized specimen, A3, containing 99% PLA and 1 vol.% of 20 nm biosilica, exhibited the best mechanical performance. Moreover, specimen A4, which contains 98% PLA and 2 vol.% 20 nm biosilica, demonstrated outstanding wear qualities with a specific wear rate of 0.015 mm 3 /Nm and a coefficient of friction (COF) of 0.22. Scanning Electron Microscopic (SEM) analysis further confirmed the dispersion and adhesion characteristics within the PLA matrix. A3 displayed a uniform dispersion of biosilica particles, enhancing load transfer and crack deflection, while A4 and A7 demonstrated filler agglomeration at higher biosilica volumes, which could create weak points under mechanical loading. Thus the optimized PLA–biosilica composite (A3) is well suited for load-bearing biomedical components such as patient-specific orthotic supports and prosthetic sockets, where moderate strength, fatigue resistance, and biocompatibility are essential. Additionally, it can be effectively used in lightweight structural and tribological components such as gears, bushings, and housings in automotive and consumer applications, where enhanced wear resistance and durability are required.

This study develops and validates a strain rate dependent constitutive model for uncured highly aligned discontinuous fiber (ADF) prepregs in the fiber direction. Uniaxial tensile and stress-relaxation experiments were conducted at room temperature on 3 mm carbon fiber/epoxy prepreg specimens over three orders of magnitude in strain rate, revealing nonlinear hardening up to a rate-dependent peak stress followed by pronounced strain softening and rapid viscous relaxation. Based on these experimental observations, a phenomenological continuum model was formulated with separate hardening and softening regimes together with a time-dependent relaxation behavior. Model parameters were calibrated against normalized experimental data and shown to accurately reproduce the measured stress-strain response across all tested strain rates. An incremental formulation was derived to accommodate arbitrary strain rate histories, enabling direct implementation in finite element forming simulations. Implementation in Abaqus/Explicit reproduced the measured stress-strain response for constant and variable strain rate tensile loading with high fidelity. Experimental validation under variable strain rate histories confirms the high predictive accuracy of the proposed phenomenological continuum model. The proposed framework provides a practical methodology for converting experimental data into a constitutive model that can be used in forming simulations of ADF composites. The method can be applied to other ADF composites and establishes a foundation for future extensions to multiaxial and non-isothermal conditions.

This work investigates the mechanical, impact, shear, and morphological properties of epoxy-based composites reinforced with 40 vol.% Pterospermumacerifolium stem fiber and Hordeumvulgare husk-derived silicon oxynitride. The addition of fibers increased the tensile strength from 53 MPa (neat epoxy) to 109 MPa and flexural strength from 68 MPa to 128 MPa, while the incorporation of silicon oxynitride as a nano-filler further enhanced the properties. Among the composites, EPS2 (3 vol.% silicon oxynitride) exhibited the highest mechanical performance, with tensile strength of 145 ± 4.4 MPa, flexural strength of 161 ± 5.1 MPa, and Izod impact strength of 4.6 ± 0.14 J, demonstrating optimal fiber-matrix interaction and reinforcement efficiency. In high-velocity impact testing, EPS2 absorbed 6.8 ± 0.24 J with an extended impact duration of 14.3 ± 0.6 ms, while total energy absorption reached 38.7 ± 1.3 J with a deflection of 3.8 ± 0.14 mm. EPS2 also displayed the highest V-Notch shear strength (21.4 ± 0.8 MPa) and rail shear strength (22.4 ± 0.9 MPa), confirming enhanced shear load-bearing capacity. SEM analysis revealed uniform filler dispersion and strong fiber-matrix adhesion, minimizing voids and enhancing mechanical stability, whereas excessive filler content in EPS3 led to agglomeration and reduced performance. Overall, EPS2 demonstrated the best balance of strength, toughness, and impact resistance, showing minimal perforation, negligible delamination, and superior energy dissipation, making it the most suitable composition for structural applications requiring high mechanical integrity.

Interfacial load-transfer inefficiency between carbon fibers and epoxy matrices limits the mechanical reliability of carbon fiber–reinforced polymer composites. This study treats Triton X-100 surfactant concentration as a controlled interfacial design variable and evaluates its effect on the mechanical behavior of short carbon fiber–epoxy composites. Fibers were surface-modified at 1, 2, and 3 wt.% Triton X-100 and incorporated into compression-molded epoxy composites at ∼40% fiber volume fraction. Tensile and compressive properties were measured per ASTM D3039 and D695; wettability, surfactant uptake, void fraction, and fracture morphology were characterized by contact angle goniometry, gravimetric analysis, Archimedes densitometry (ASTM D792), and scanning electron microscopy. The 1 wt.% composite exhibited tensile strength of 116.00 MPa (∼40.3% above untreated: 82.67 MPa) and a comparable compressive strength gain, while elastic modulus remained constant at ∼2.0 GPa across all conditions. Gravimetric analysis confirmed monolayer adsorption at 1 wt.% and excess deposition at 2 wt.%, consistent with the observed mechanical optimum. SEM revealed reduced fiber pull-out (64 ± 9 μm to 22 ± 4 μm) and suppressed debonding in the optimally treated composite. Controlled surfactant treatment provides a scalable, non-destructive route to enhance interfacial efficiency and mechanical performance in short carbon fiber–epoxy systems.

Accurately predicting the Depth of Penetration (DOP) is essential for understanding the impact behavior of Functionally Graded Composite Materials (FGCMs) under high-velocity conditions. However, the nonlinear dynamic behavior governing FGCMs, coupled with the high cost and time-consuming nature of experimental tests, make precise DOP estimation a challenging task. This study proposes an efficient predictive framework that combines finite element (FE) simulations with artificial neural networks (ANNs) to overcome the constraints of conventional numerical and experimental approaches. This work focuses on applying the Whale Optimization Algorithm (WOA) and the Arithmetic Optimization Algorithm (AOA) as independent optimization strategies to improve the control parameters during the initiation phase, avoid convergence to local optima, and accelerate the learning process. Finite Element (FE) simulations were used to generate input-output datasets, which were used to train three ANN models: conventional back-propagation (BP), WOA-ANN, and AOA-ANN. The optimized ANNs accurately captured the nonlinear mapping between impact velocity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>V</mml:mi> <mml:mrow> <mml:mi>i</mml:mi> <mml:mi>m</mml:mi> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) and DOP. Results confirm that WOA-ANN model outperformed both AOA-ANN and BP models, achieving lower mean square error (MSE) and higher correlation coefficients. Moreover, the optimized ANNs provide reliable predictions with a limited number of FE simulations, considerably reducing computational effort while maintaining accuracy.

Carbon fiber-reinforced aluminum laminates (CARALL), a hybrid composite, hold significant promise for use in aircraft structures. However, the distinct behaviors of the materials in this multi-layered configuration pose considerable challenges during drilling. High drilling forces and elevated temperatures can cause various forms of damage, potentially compromising the performance of CARALL structures in service. This research involved performing drilling experiments on CARALL samples produced inhouse, examining various combinations of cutting speeds (30, 60, and 90 m/min) and axial feed rates (0.05, 0.15, and 0.25 mm/rev) to assess their impact on thrust force, drilling torque, machining temperature, and the quality of the hole surface. Increasing the cutting speed from 30 m/min to 90 m/min while reducing the axial feed from 0.25 mm/rev to 0.05 mm/rev resulted in a 40.4% reduction in thrust force and a 59.8% decrease in drilling torque, but also caused a 70.4% rise in machining temperature. At elevated cutting speeds, the rise in temperature leads to a decrease in cutting force, demonstrating the relationship between force and temperature. An increase in axial feed led to rougher bore surfaces. Although the surface finish initially improved with increasing cutting speed, a further increase caused degradation once the machining temperature exceeded the glass transition temperature of the epoxy resin. An acceptable surface finish ( R a ) of 1.93 µm was achieved when an intermediate cutting speed of 60 m/min and a lower feed rate of 0.05 mm/rev were employed. Typical defects observed in the drilled holes included grooves, fiber bending, fiber exposure, matrix degradation, material smearing, adhesion, and delamination. The observed delamination was mainly due to matrix degradation at temperatures beyond the glass transition temperatures.

This study investigates the impact of fiber reinforcement, specifically carbon and glass fibers, on the flexural behavior and fracture performance of cementitious composites with varying strengths The strength grades of the composites were designated as high-strength, medium-strength, and low-strength. The composites were reinforced with woven glass and carbon fibers at different length/span ratios and subjected to flexural testing to evaluate key parameters such as strength, strain, and modulus. High, medium, and low-strength prism specimens were prepared using specific cement dosages (634.26 kg/m 3 for high strength, 535.26 kg/m 3 for medium strength, and 432.65 kg/m 3 for low strength) with corresponding water-to-cement ratios of 0.3, 0.4, and 0.65, respectively. The results indicate that fiber reinforcement significantly enhances the flexural properties of all composite categories, with the most notable improvements observed in the medium-strength and high-strength composites. Among the composites, the carbon fiber-reinforced high-strength composite (HS-CFRC-4/7) demonstrated the highest flexural strength (10.00 MPa), a 73% improvement over the control specimen. However, a diminishing return in strength gain was observed in high-strength composites, suggesting weaker anchorage bond between woven fiber and the specimen where the matrix strength becomes the dominant factor. Additionally, carbon fibers exhibited a higher strain capacity than glass fibers, with consistent increases in ductility across all composite groups. Fracture analysis revealed distinct failure modes, including flexural cracks, diagonal shear cracks, and delamination, especially in high-strength composites.

With the rapid development of transportation and aerospace industries, the increasing emphasis on lightweighting has created a demand for advanced metal/polymer joining technologies. Underwater welding is an optimization way to reduce excessive heat effects of joints and improve welding efficiency. To mitigate the overflow of molten polymer matrix during the welding process of carbon fiber reinforced thermoplastic (CFRP) and aluminum alloy, process optimization experiments of water medium-assisted CFRP/aluminum alloy friction stir lap welding (FSLW) are carried out. For this purpose, a welding tool with water circulation function is designed and developed. The influences of water medium on material interface behavior, flow characteristics, and defect control are analyzed. By observing the joint boundary thickness and the interweaving combination of dissimilar materials under different water temperatures, the regulatory effects of water temperature on the microstructure and mechanical properties of the joint are studied. As the water temperature increases, the aluminum alloy is embedded into the CFRP in a plastically deformed state, and the thickness of the aluminum alloy at the joint bottom gradually increases, which enhances the load-bearing capacity of the dissimilar joint. The lap shear strength of the joint reaches 43.3 MPa at the 80°C water temperature.

This study investigates the tensile behavior of single strap-scarf adhesive bonded joints reinforced with carbon nanotube (CNT)-modified epoxy, using a combined experimental-numerical approach. The originality of this work lies in the systematic assessment of CNT reinforcement and geometric parameters-including scarf angle (30°,45°, 60°, 90°), strap length and thickness-on the strength and failure behavior of AA6061-T6/WEICON F2 adhesive joints. Adhesives containing 0, 0.5, 1.0, and 1.5 wt.% CNTs were prepared, with the 0.5 wt.% formulation exhibiting superior mechanical performance. Experimental tests were performed under static tensile loading, while finite element (FE) analyses employing a cohesive zone model (CZM) predicted stress distribution and failure initiation. Results demonstrated that the addition of 0.5 wt.% CNTs increased joint strength by 17.8%. Increasing patch length and thickness enhanced strength by 28.6% and 37.8%, respectively. Moreover, the single strap-scarf joint showed 33.7% higher load capacity than the single strap joint and 234% higher than the scarf joint. Failure was predominantly cohesive within the adhesive layer and correlated well with FE predictions.

The interfacial performance of carbon fiber reinforced polymer composites (CFRPs) is critically determined by the fiber-matrix adhesion. Recent advances highlight that polyamine molecules, such as diethylenetriamine (DETA), with multiple active sites, can form covalent bonds with resin molecules, effectively establishing a covalent-bonded interphase and thereby enhancing interfacial adhesion. However, the grafting efficiency of DETA is often constrained by its inherent steric hindrance and low reactivity, which limit its electrochemical grafting onto the relatively inert carbon fiber (CF) surfaces. Herein, an ultrasound-assisted electrochemical method was developed that can achieve efficient DETA grafting onto CF in 90 s. The U-o-CF@DETA exhibits superior surface properties, attaining a high nitrogen content of 21.03 at.% and optimal surface energy of 54.50 mN m −1 . When incorporated into epoxy resin (EP) matrix, the composite has an outstanding interlaminar shear strength (ILSS) of 121.24 ± 2.52 MPa. Mechanistic investigations conclusively demonstrate that the introduction of ultrasound, through its cavitation energy and the provision of OH radicals, is pivotal in boosting the extent of polyamine grafting onto the CF surface. This work provides an efficient and mild strategy of preparing surface-aminated carbon fibers (CFs) for the fabrication of high-performance CFRPs with superior interfacial properties.