ABSTRACT The transverse mechanical integrity of unidirectional fiber‐reinforced polymer (UD‐FRP) composites is critical for structural performance yet remains difficult to predict due to complex nonlinear couplings among microstructural features, fiber transverse modulus, and interfacial properties. This study establishes a unified, data‐driven micromechanical framework to systematically investigate transverse failure mechanisms across a broad parametric space spanning these critical variables. A high‐fidelity database comprising 648 Finite Element Analysis (FEA) simulations on Representative Volume Elements (RVEs) was generated. The interpretable tree‐based Machine Learning (ML) architecture achieved a prediction accuracy of R 2 > 0.91, and Symbolic Regression (SR) subsequently extracted explicit algebraic equations (R 2 > 0.81). SHapley Additive exPlanations (SHAP) analysis quantified distinct failure regimes governed by modulus mismatch: (i) under transverse tension, a “modulus‐mismatch penalty” was identified: fiber transverse modulus beyond 60 GPa causes high interfacial strength to compromise global capacity by intensifying matrix stress; and (ii) under transverse compression, a “rigid obstacle effect” was revealed, where high‐modulus fibers ( E f > 50 GPa) deflect shear bands to enhance strength, effectively compensating for weaker interfaces. These findings culminate in quantitative design maps and explicit analytical formulas, demonstrating how integrating interpretable ML with Symbolic Regression accelerates composite optimization beyond traditional trial‐and‐error.

ABSTRACT The investigation evaluates the erosion behavior of carbon fiber (CF) reinforced epoxy laminates, protected with an epoxy‐based coating system incorporating synthesized molybdenum disulfide (MoS 2 ) functionalized multiwalled carbon nanotubes (MWCNTs) hybrid nanoparticles. The nanocomposite coating with 0.5 wt% MoS 2 ‐MWCNTs hybrid demonstrated a superior resistance to severe erosive wear conditions and exhibited clear deviation in erosion response as compared to conventional epoxy/CF composites. The epoxy hybrid nanocomposite coated epoxy/CF laminates displayed a semi‐ductile erosion characteristic, with a maximum erosion rate of 1132 mg/kg, occurring at a 30° impact angle, and the minimum erosion rate of 600 mg/kg occurring at a 90° impact angle. Morphological analysis of the eroded surface by FESEM revealed that micro‐plowing and micro‐cutting mechanisms were predominant at the hybrid nanocomposite coated regions, whereas fiber cutting mechanisms were primarily observed in the epoxy/CF laminates.

ABSTRACT Ultraviolet Cured‐In‐Place Pipe (UV‐CIPP) technology is an efficient and environmentally friendly trenchless pipeline rehabilitation method. The flexural performance of its rehabilitation materials directly affects the long‐term service reliability of the repaired pipelines. This study focuses on curved glass fiber‐reinforced UV‐CIPP liners, systematically investigating their circumferential thickness non‐uniformity and spatial distribution of circumferential and longitudinal flexural performance. The failure mechanisms were revealed using acoustic emission (AE) monitoring and microstructural characterization. The results show that due to resin flow during curing, the circumferential thickness of the UV‐CIPP liner increases from the crown (0°) to the invert (180°), while flexural strength and modulus decrease symmetrically. The longitudinal flexural performance exhibits a non‐monotonic trend of increasing first and then decreasing. AE analysis identifies three damage phases: matrix micro‐cracking (50–80 dB), fiber‐resin interface debonding (80–100 dB), and unstable fiber fracture with large energy release. Scanning electron microscopy (SEM) observations confirm that the main failure modes are fiber pull‐out, resin debonding, and interlayer delamination. This study systematically quantifies the direct influence of curvature effects on the flexural performance degradation of UV‐CIPP materials through combined experimental and theoretical analysis, establishing a theoretical foundation for optimizing UV‐CIPP curing processes and material performance.

ABSTRACT Continuous carbon fiber‐reinforced polymers (CCFRPs) exhibit superior mechanical properties compared with short‐fiber‐reinforced composites, while additive manufacturing (AM) enables the fabrication of complex geometries. Among various material systems, continuous carbon fiber‐reinforced polyethylene terephthalate glycol (CCF/PETG) produced by AM is particularly attractive due to its good processability and chemical resistance. In this work, a custom melt‐impregnation setup was developed to manufacture CCF/PETG prepreg filaments. The filament properties were systematically tuned by adjusting key processing parameters, especially impregnation temperature, impregnation pressure, and winding speed. By increasing the impregnation temperature and pressure while reducing the winding/stretching speed, stable forming and enhanced impregnation quality were achieved. Under optimized conditions, the prepared filaments reached a peak tensile strength of 1103.25 MPa, with a fiber volume fraction of 39.13%, a dense microstructure (porosity < 1%), and good geometric fidelity (circularity of 0.95). The practical printability of these filaments in fused deposition modeling (FDM) was further demonstrated: printed CCF/PETG components achieved a tensile strength of 715.16 MPa and a flexural strength of 457.44 MPa along the fiber direction. These results confirm that the proposed melt‐impregnation route can produce high‐quality continuous‐fiber thermoplastic feedstocks and enable the fabrication of high‐performance composites by AM.

ABSTRACT This study presents a hierarchical reinforcement strategy utilizing reduced graphene oxide (rGO) that concurrently functionalizes basalt fiber surfaces and the epoxy matrix in a basalt/epoxy composite. Electrophoretic Deposition (EPD) provided uniform rGO fiber coating, while ultrasonication–high‐shear mixing enabled stable, exfoliated rGO dispersion in the matrix. This dual‐phase methodology creates continuous three‐dimensional reduced graphene oxide networks that connect fiber‐matrix interfaces and bulk resin regions. The composites' tensile strength improved by 23.5%, interlaminar shear strength by 22.1%, mode‐I fracture toughness by 86%, storage modulus by 44% (7800 MPa at 30°C), and glass transition temperature rose to 95°C. Due to stress wave dissipation and crack deflection at rGO‐modified surfaces, high‐speed ballistic tests show a 26.7% increase in energy absorption (131.4 J) and specific energy absorption (2577 J/kg) over unmodified basalt/epoxy. The interconnected hierarchical rGO structure provides a broadband electromagnetic interference shielding effectiveness of approximately 40 dB (8–18 GHz), primarily due to absorption (SEA = 29 dB) resulting from multiple internal reflections and improved electrical percolation. This synergistic dual‐phase graphene functionalization approach produces lightweight structural composites that exhibit an outstanding blend of mechanical strength, impact resistance, and electromagnetic properties, rendering them highly suitable for aerospace, defense, and electronic enclosure applications.

ABSTRACT Polyphenylene sulfide (PPS) was compounded with recycled carbon fibers (rCF) and thermal black (TB) particles, followed by injection molding (IM) and extrusion of the compounded composites into filaments for fused filament fabrication (FFF). The effect of rCF and TB contents on the microstructure, crystallization kinetics, and mechanical performance of the PPS composites was evaluated and analyzed. At the incorporation of 20 wt.% rCF, the tensile strength of IM specimens increased from 73 MPa up to 151 MPa, and the tensile modulus increased from ~3.5 GPa up to ~20 GPa, respectively. FFF printed specimens with 20 wt.% of rCF showed a tensile strength of 86 MPa and a tensile modulus of 6 GPa, higher when compared to IM neat PPS. Crystallization kinetics of extruded pellets, IM, and FFF printed PPS composites were investigated. The results revealed that the incorporation of rCF and TB significantly hindered the crystallization of PPS. The microstructural characterization provided quantitative results for porosity content and the length distribution and deviation angle of rCF. These characterizations helped to analyze the mechanical performance of IM and FFF printed parts, providing quantitative results to explain the differences in mechanical properties of specimens fabricated through the two methods.

ABSTRACT 3D‐printed continuous carbon fiber‐reinforced polyamide (CCF/PA) composites suffered challenges in achieving strong interfacial adhesion due to rapid melting‐cooling and limited impregnation pressure during layer‐by‐layer deposition. To address this, a thermal oxidation activation strategy was proposed to enhance the mechanical properties of 3D‐printed composites by precisely controlling the interfacial evolution behavior of carbon fibers (CF). The interaction between the physical structure and chemical polarity of CF and their effects on the mechanical properties of 3D‐printed CCF/PA composites were systematically examined. The results indicate that the mechanical properties of 3D‐printed composites are collectively governed by the interfacial morphology of CF and graphite‐induced microdefects. Under the constrained thermal and pressure conditions of 3D printing, the surface chemical polarity critically influenced interfacial construction efficiency. The controlled oxidation has introduced surface defects, altering the stress‐transmission pathways and their effectiveness. Furthermore, the orientation and content of the graphite structure on the carbon fiber surface determine the conversion efficiency of the mechanical properties in 3D‐printed composites. This study illustrates the mechanism by which CF interfacial evolution contributes to the mechanical behavior of 3D‐printed CCF/PA composites, providing insights for interfacial design in additive manufacturing of high‐performance composites.

ABSTRACT Minimizing environmental impact and adopting renewable alternatives are essential in sustainable construction materials development. This research investigates the effectiveness of hemp fiber‐reinforced polymer (HFRP) with halloysite nanotube (HNT) incorporation utilizing epoxy resin as a matrix for concrete cylinder confinement. FRP composites were fabricated using the manual lay‐up method, and incorporation of 1% by weight (wt.%) of HNT yielded significant enhancement in mechanical properties. Marked improvements were witnessed in the composite laminates' ultimate tensile strength, resistance to cracking and bending. Epoxy multiscale composites demonstrated a 5°C increase in glass transition temperature ( T g ) with respect to hemp fiber composites. Compressive stress and ultimate axial strain of 1% HNT‐incorporated three‐layer HFRP confinement were found 22% and 9% higher, respectively, than those of a three‐layer HFRP confined cylinder. Confinement is carried out on pre‐loaded reinforced concrete (RC) cylinders in order to analyze the real‐time behavior. When compared to a three‐layer HFRP confined pre‐loaded RC cylinder, the HNT‐incorporated HFRP confined RC cylinder exhibited 15% and 28% higher axial stress and strain, respectively. The HNT‐incorporated three‐layer HFRP confinement system manifests excellent energy absorption and ductility.

ABSTRACT Although conventional two‐dimensional fiber‐reinforced polymer composites are commonly used in ballistic protection, they frequently suffer from delamination and poor in‐plane shear performance. Herein, we developed a three‐dimensional angle‐interlocked (3DAI) aramid/epoxy composite for bulletproof vehicle applications. The ballistic performance of the 3DAI composites is critically influenced by their programmable fabric structure, laying methods (unidirectional, orthogonal, symmetric, and sandwich), and gradient structures utilizing stacking layers with varying weft densities. The 3DAI aramid/epoxy composite exhibits superior ballistic performance, structural design flexibility, delamination resistance, and a smaller damage area, along with a reduction in the number of layers required compared to plain weave composites. The high‐weft‐density composites demonstrated the best overall ballistic performance and the highest resistance to impact deformation. The orthogonal configuration strategy was found to be the most effective in dissipating energy and provided the optimal ballistic protection. Moreover, the graded structure integrating high‐ and low‐weft‐density layers exhibited superior ballistic performance relative to the uniform design. The best anti‐denting performance was achieved when the high‐weft‐density layer was placed on the bullet‐facing side and the low‐weft‐density layer on the back side. These findings provide new insights into the armor‐grade composite and advanced ballistic composites.