Optimisation and characterisation of epoxy-kenaf composites filled with nano copper and zirconia for improved structural performance

This study evaluates the mechanical and thermal performance of epoxy and epoxy-Kenaf fibre composites reinforced with nano copper (Cu) and nano zirconia (ZrO2) fillers at 2–10 wt%. The objective is to enhance tensile strength, Young’s modulus, and thermal conductivity through synergistic reinforcement using natural fibres and nanoparticles. The neat epoxy matrix exhibits a tensile strength of 24.3 MPa, a Young’s modulus of 1.20 GPa, and a thermal conductivity of 0.23 W/m·K. With nano-filler incorporation, significant improvements are observed, with optimum performance at 4–6 wt%. ZrO2-filled epoxy achieves a maximum tensile strength of 31.6 MPa and a modulus of 1.57 GPa, corresponding to ~30% and ~31% increases compared to neat epoxy, while Cu-filled epoxy exhibits the highest thermal conductivity of 0.37 W/m·K, representing an enhancement of ~61%. The addition of Kenaf fibre further amplifies performance, with epoxy-Kenaf/ZrO2 composites reaching 46 MPa tensile strength and 3.8 GPa modulus, corresponding to ~89% and ~217% improvements, along with a thermal conductivity of 0.36 W/m·K at 6 wt% filler loading. These enhancements arise from improved interfacial adhesion, nanoparticle dispersion, and efficient stress and heat transfer mechanisms. The findings demonstrate the potential of hybrid natural fibre composites with optimised nano-filler content for structural and thermal applications.