Formulation and Predicted Properties of Carbonized Palm Kernel Shell, Stone Dust, and Coconut Fiber Hybrid Reinforced Epoxy Composites

Abstract

The development of sustainable composite materials using natural-mineral reinforcements has received considerable scrutiny as an alternative to conventional or synthetic fillers. In this short communication, epoxy-based hybrid composites were formulated using carbonized palm kernel shell (CPKS), stone dust, and coconut fiber as reinforcing materials. Two sets of formulations were developed: a binary hybrid system (CPKS-stone dust) and a ternary hybrid system (CPKS-stone dust-coconut fiber), with reinforcement weight fractions varied from 2 wt.% to 10 wt.%, while the polymer matrix content decreased correspondingly from 98 wt.% to 90 wt.%. This short research communication aimed to predict the influence of reinforcement type and loading on the mechanical, wear, and thermal properties of the composites based on established strengthening and toughening mechanics. Results from theoretical and mechanistic analyses indicate that low to moderate reinforcement levels (4–6 wt.%) are expected to enhance tensile, flexural, and impact strength due to good filler dispersion and improved interfacial adhesion. Oladele and his team conducted this research in 2025. CPKS and stone dust contribute to stiffness, hardness, and wear resistance, while coconut fiber improves ductility and energy absorption through fiber pull-out and crack-bridging effects. Higher reinforcement levels (8 wt.% and above) may lead to agglomeration, void formulation, and reduced tensile strength (Adeyanju et al., 2025; Lamidi et al., 2025). Overall, the ternary hybrid system demonstrates a synergistic balance of strength and toughness compared to the binary composite, potentially suitable for structural and automotive applications.