Experimental Investigation on the Influence of Coconut Shell Powder on the Mechanical Properties of Sustainable Basalt/Epoxy Composites

This study investigates the use of coconut shell powder (CSP), an agricultural bio-waste, as a natural filler in basalt-fabric-reinforced epoxy composites. A neat laminate and laminates containing 1.5, 3, 4.5, and 6 wt.% CSP were fabricated by hand lay-up followed by compression molding. These low filler concentrations were selected to identify the optimum loading and the onset of adverse effects associated with excessive CSP. Tensile, flexural, and Charpy impact properties were evaluated, and fracture morphologies were examined using scanning electron microscopy. Tensile strength increased from 299 MPa for the neat (0 wt.% CSP) laminate to a maximum of 427 MPa at 4.5 wt.% CSP, representing a 42.8% improvement. At the same loading, flexural strength increased from 192.41 to 238.95 MPa, while impact strength increased from 158.00 to 216.29 kJ/m2, corresponding to improvements of approximately 24% and 37%, respectively. SEM observations revealed reduced void formation, matrix cracking, and fiber pull-out in CSP-modified composites. By correlating CSP concentration with the mechanical and fracture behavior of basalt-fabric-reinforced epoxy composites, the study addresses a relatively unexplored application of coconut-shell-derived filler. The results identify 4.5 wt.% CSP as the optimum loading within the investigated range.