Valorization of Peepal and Neem Tree Waste Fibers with Silica Nanoparticle Reinforcement for Environmentally Durable Epoxy Composites

<p>In this study, waste biomass derived from Peepal (<em>Ficus religiosa</em>) and Neem (<em>Azadirachta indica</em>) trees—commonly discarded through municipal pruning or natural shedding—was repurposed as sustainable fiber reinforcement in epoxy composites. These natural fibers, when combined with silica nanoparticles, offer a green alternative to synthetic reinforcements while enhancing both mechanical strength and moisture resistance. The work contributes to environmental sustainability by converting underutilized lignocellulosic biomass into value-added materials suitable for eco-friendly structural and packaging applications. This study investigates the mechanical, physical, and water absorption properties of epoxy composites reinforced with hybrid natural fibers (Peepal and Neem) and varying concentrations of silica (SiO₂) nanoparticles. Epoxy composites were fabricated using different stacking sequences of Neem and Peepal fibers—specifically N/P/N and P/N/P—and further modified with 1–3 wt% SiO₂ nanoparticles. The mechanical properties, including tensile, flexural, impact strength, and surface hardness, showed notable improvements with fiber hybridization and optimal nanoparticle loading. Among the tested configurations, the N/P/N arrangement reinforced with 2 wt% SiO₂ exhibited the highest tensile strength (70 MPa), flexural strength (74 MPa), impact strength (5.0 kJ/m²), and hardness (70 Shore D), demonstrating the superior reinforcement efficiency of Neem fibers and the strengthening effect of well-dispersed silica nanoparticles. Water absorption tests revealed a significant reduction in moisture uptake with increased nanoparticle loading, with the N/P/N + 3 wt% SiO₂ composite showing the lowest absorption (52%). Density and void analysis confirmed enhanced matrix packing and reduced porosity at higher SiO₂ contents, contributing to the improved structural integrity. These results underscore the synergistic benefits of natural fiber hybridization and nanoparticle incorporation in developing high-performance, moisture-resistant epoxy composites suitable for structural and environmental applications.</p>