Mechanical strengthening and fracture surface morphology of sustainable epoxy composites reinforced with tamarind seed powder

The main objective of this work is to experimentally evaluate the physical and mechanical characteristics of an epoxy/tamarind seed powder (TSP) composite by varying the TSP composition at 0%, 5%, 10%, 15%, and 20% by weight. TSP is added as a novel sustainable bio-filler in epoxy, with a dual role as a micro-reinforcement and a crack-arresting agent. Physical characteristics such as density and void content were examined, and the results showed that both increased as TSP composition increased. The TSP substantially influences the flexural, impact, and tensile characteristics of the composite. In comparison to neat epoxy, the tensile strength improved by almost 4.8 times, the flexural strength by 2.7 times, and the impact strength by 1.85 times at 10% TSP, indicating the best overall performance among the evaluated weight fractions. Scanning electron microscopy shows a direct correlation between particle morphology, interfacial bonding, and fracture mechanisms. Tensile fracture samples were analyzed, which confirmed the mechanical results. At 10% TSP, the rougher fracture morphology and changes in crack path were observed. At 15–20% compositions, the existence of particle clusters and voids favored unstable fracture growth. The proposed composites are suitable for secondary structural applications requiring moderate stiffness and sustainable bio-filler substitution.