Mechanical, water absorption, and flammability behavior of coconut shell and jackfruit skin powder-reinforced bio-composites fabricated through fused deposition modeling

This study investigates the development of biodegradable bio-composites made from polylactic acid (PLA) reinforced with farm waste materials, specifically coconut shell powder and jackfruit skin powder. The bio-composite filaments were fabricated using a filament extruder, and the samples were created through fused deposition modeling (FDM). Mechanical strength, water absorption, and flammability were evaluated. The results revealed that incorporating coconut shell (CBC) and jackfruit skin (JBC) powders into the PLA matrix significantly enhanced the mechanical properties, water resistance, and flame retardancy of the composites. The hybrid bio-composite (HBC) showed a 73.7 % improvement in water absorption resistance, with a water absorption rate of 9.06 +/- 0.02 %. CBC and JBC demonstrated 70.8 % and 67.2 % reductions in water absorption, respectively, compared to pure PLA. The HBC bio composite also exhibited superior flame retardancy, with a 60.9 % increase in ignition delay (8.43 +/- 0.21 s), 30.5 % reduction in flame spread rate (43.21 +/- 1.42 mm min-1), and 50.5 % increase in after-flame duration (13.14 +/- 1.05 s). In terms of tensile properties, HBC outperformed all other composites with an ultimate tensile strength (UTS) of 59.2 +/- 1.8 MPa, representing a 44.2 % improvement compared to pure PLA. The CBC and JBC showed 24.7 % and 10.7 % increases in UTS, respectively. The HBC also showed a 40.2 % improvement in flexural strength, with the lowest deflection at 4.0 +/- 0.1 mm, compared to 23 % and 20.8 % improvements for CBC and JBC, respectively.