Influence of tungsten carbide reinforcement on the mechanical properties, fatigue life, and fracture morphology of kevlar/S2-Glass/epoxy hybrid laminates

Fiber-reinforced polymer composites (FRPCs) have gained considerable traction in high-performance engineering owing to their high specific strength, corrosion resistance, and tuneable mechanical behaviour, making them well-suited for lightweight structural and protective applications. Kevlar, an aramid fiber renowned for its elevated tensile strength, impact resistance, and energy-absorbing capacity, finds extensive use in ballistic and aerospace applications. S2-glass fibers, compared with conventional E-glass, offer superior rigidity, thermal stability, and fatigue endurance under high-stress service conditions. Tungsten carbide (WC), a hard ceramic particulate, acts as a secondary reinforcement capable of enhancing wear resistance and surface hardness without disproportionately increasing composite density. Contemporary hybrid composites incorporate multiphase reinforcements to achieve synergistic performance in defence-critical applications such as lightweight structural and protective components and vehicle structures; however, challenges related to interfacial toughness, delamination under cyclic loading, and production scalability persist. In the present study, seven hybrid laminates were fabricated via hot-press compression moulding incorporating varying WC content (0–20 wt%) within a Kevlar/S2-glass/epoxy matrix at a fixed resin fraction (35 wt%). Mechanical characterisation encompassed tensile, flexural, fatigue, and hardness tests, while microstructural and elemental distribution analyses were conducted using field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS). The unfilled hybrid laminate (32.5 wt% Kevlar and 32.5 wt% S2-glass) yielded the highest tensile strength of 268.62 MPa 52% and 273% greater than pure Kevlar and pure S2-glass laminates, respectively and the highest flexural strength of 365.81 MPa 88% and 138% greater than the respective baselines. While fatigue life under tension–tension cyclic loading (R = 0.1, 70% UTS) reached a maximum of 2335 cycles at 15 wt% WC approximately 10.6 times (957%) higher than pure Kevlar and approximately 292% above the unfilled hybrid baseline,beyond 15 wt%, WC particle agglomeration and micro-void formation degraded tensile ductility, as confirmed by EDS mapping. Tungsten distribution was homogeneous at 10–15 wt% WC, whereas pronounced particle clustering at 20 wt% correlated directly with the observed decline in tensile ductility and the associated reductions in fatigue life and flexural strength. Future investigations could explore nano-scale WC dispersions, optimized stacking sequences, and ballistic impact testing to further assess the potential of these hybrids for lightweight protective structures.