Mechanical and physical performance of hybrid epoxy composites reinforced with palm kernel shell and Bilinga <i>(Nauclea diderrichii)</i> sawdust

Abstract

The accumulation of agro-forestry biomass wastes such as Bilinga ( Nauclea diderrichii ) sawdust (SD) and palm kernel shell (PKS), generated from wood processing and palm oil extraction, presents serious environmental degradation and depletion of ozone layer and leads to global warming in Cameroon due to indiscriminate dumping and open burning. This study evaluates the effect of PKS–SD hybrid filler ratios on the physical, while; moisture content, apparent density, specific gravity, particle size distribution, and mechanical properties; compressive, flexural, and impact tests, and microstructural performance of epoxy composites. Raw fillers were characterized for moisture content, density, and specific gravity, while PKS was alkali-treated (5 wt% NaOH) to improve interfacial compatibility. Composites were fabricated with 40 wt% epoxy resin and PKS/SD ratios of 20/40, 25/35, and 30/30 wt%. Mechanical testing showed compressive strengths of 11.58–15.77 MPa, flexural strengths of 8.03–10.99 MPa, and impact energy of 2.49–2.58 × 10 8 kJ/m 2 , with water absorption ranging from 13.22 to 64.79%. The 30/30 hybrid exhibited optimal performance, combining high compressive (15.77 MPa) and flexural strength (10.99 MPa) with moderate water uptake (∼34.5%). SEM/EDX analyses revealed good filler dispersion and strong interfacial bonding. The novelty lies in demonstrating a synergistic dual-biofiller system where PKS enhances rigidity and SD improves dispersion, yielding balanced stiffness and toughness. The optimized 30/30 hybrid composite offers a viable route to produce low-cost, eco-efficient, composite suitable for non-structural applications like interior walls, ceiling boards, acoustic elements, and low-load building tiles, supporting bio-economy principles by valorizing local waste resources as a source of revenue and reducing pollution.