Tribological Characteristics of Periwinkle Shell/Raffia Palm Seed Reinforced Epoxy Hybrid Composites

Abstract

Environmentally friendly and sustainable brake pad materials have attracted increasing attention due to the health and environmental concerns associated with asbestos-based friction materials. This study developed and characterized hybrid epoxy composites reinforced with periwinkle shell (PWS) and raffia palm seed (RPS) particles as potential eco-friendly brake pad materials. Unlike previous investigations that considered PWS or RPS individually, the present work examined their combined use in a hybrid system to evaluate the synergistic effects of agro-waste reinforcements on brake pad performance. Four composite formulations (Samples A–D) containing 4.41–17.71 wt.% PWS and 3.41–13.77 wt.% RPS were produced using epoxy resin as the matrix through molding and curing under a pressure of 18.25 kN/m². The composites were characterized by evaluating density, water absorption, hardness, wear depth, wear rate, and coefficient of friction. Results showed that increasing the reinforcement content significantly enhanced composite performance. Density increased from 2.60 to 3.28 g/cm³, while water absorption decreased from 0.1214% to 0.0388%. Hardness improved from 33.40 HV to 72 HV. Tribological evaluation revealed a reduction in wear depth from 257.859 µm to 140.297 µm and a decrease in wear rate from 0.00000893 to 0.00000819 mm³/(N·m). The coefficient of friction decreased from 0.70–0.75 to 0.57–0.60, indicating improved friction stability. Sample D exhibited the best overall performance. The findings demonstrate that hybrid PWS/RPS epoxy composites are promising low-cost, environmentally friendly brake pad materials that enhance performance while promoting agricultural waste valorization and sustainable manufacturing.