Enhanced Mechanical and Tribological Performance of Casuarina Fiber-reinforced Epoxy Composites Using ZnO and ZrO₂ Nanoparticles

Natural fiber composites are increasingly explored as eco-friendly and lightweight alternatives to synthetic materials, though their limited mechanical and tribological performance hinders industrial use. In this work, epoxy composites reinforced with casuarina fiber were fabricated and modified with ZnO and ZrO2 nanoparticles to enhance their properties. Four composites, S1 (epoxy/casuarina fiber), S2 (epoxy/casuarina fiber/ ZrO2), S3 (epoxy/casuarina fiber/ZnO), and S4 (epoxy/casuarina fiber/ ZrO2/ZnO), were prepared with a resin-to-fiber ratio of 70:30 and 4 wt% nanoparticle loading. Mechanical (tensile, flexural, impact, hardness) and tribological (wear loss, coefficient of friction) tests revealed that nanoparticle incorporation significantly improved performance, with the ZnO-filled S3 composite showing the best results, achieving a tensile strength of 85 MPa, flexural strength of 125 MPa, impact strength of 7.5 kJ/m², and hardness of 92 Shore D. Wear studies further confirmed minimal wear loss (0.27052 g) and the lowest coefficient of friction (1.91) under 15 N load, 3 m/s velocity, and 1500 m sliding distance. The SEM analysis of worn surfaces supported these findings, displaying severe cracks and debris in the unmodified composites, moderate damage in ZrO2-filled samples, and smoother surfaces with shallow grooves in ZnO-filled composites, validating their superior load transfer and wear resistance. These results highlight the potential of ZnO and ZrO2 enhancing the strength and durability of casuarina fiber-reinforced epoxy composites for automotive and structural applications.