Printability and mechanical performance of fused deposition modeling-printed composites reinforced with coconut shell powder

In recent developments for producing fiber-reinforced polymer matrix composites, the fused deposition modeling method has emerged as a prominent technique. While carbon and glass fibers traditionally constitute these composites, the non-recyclable nature of these fibers has prompted a shift towards utilizing natural fibers. This transition offers several advantages for matrix reinforcement, including reduced production costs, minimized waste generation, enhanced mechanical properties, decreased part density, and the renewable nature of the materials. This study examines the influence of three key printing parameters—layer thickness, printing speed, and infill percentage—on the mechanical properties of composite parts reinforced with natural fibers. A composite filament, comprising a 60% polylactic acid (PLA) matrix and 40% coconut shell powder (CSP) reinforcement, was extruded using a laboratory setup. Subsequently, the filament was employed to print samples that underwent tensile testing. The experiments were designed and analyzed using response surface methodology to optimize the printing parameters and understand their interactive effects on tensile strength and elongation. The results highlight the pronounced influence of printing speed and infill percentage on the tensile strength of the printed samples. In contrast, the layer thickness exhibited a negligible impact on tensile strength. The sample with optimal printing conditions—featuring a layer thickness of 0.2 mm, a printing speed of 30 mm/s, and a 100% infill percentage—demonstrated the highest tensile strength of 25.1 MPa. Finally, scanning electron microscopy images captured from fractured samples revealed that the presence of CSP particles within the PLA matrix contributes to the formation of internal voids and premature, brittle failures in the samples.