Multi-objective optimization on mechanical properties of cocoa pod husks and tamarind shell reinforced poly (lactic acid) biocomposites using extreme mixture design

This study presents the development of PLA-based biocomposites reinforced with cocoa pod husk powder (CPHP) and tamarind shell powder (TSP) as renewable natural fillers. A mixture design approach was used to optimize the proportions of CPHP, TSP and PLA, and their effects on tensile, flexural and impact properties. Biocomposites were prepared via twin-screw extrusion and injection molding. SEM and SEM-EDS analyses revealed that excessive CPHP or TSP content caused particle agglomeration, voids and poor interfacial adhesion, while the optimized formulation (5 wt% CPHP, 15 wt% TSP, 80 wt% PLA) showed well-dispersed fillers and strong matrix–filler bonding. Multi-objective optimization predicted maximum mechanical properties, including tensile strength of 35.20 MPa, tensile modulus of 1,802 MPa, flexural strength of 60.52 MPa, flexural modulus of 4,575 MPa, and Izod impact strength of 33.17 kJ/m². The optimized biocomposites were successfully processed into injection-molded pots, demonstrating structural integrity and eco-friendly applicability. This work highlights the potential of CPHP and TSP as biodegradable reinforcements, offering a sustainable route for high-performance, environmentally friendly composites.