Thermal and mechanical properties of polylactic acid reinforced with surface-treated hemp composites for automotive applications

Thermal and mechanical properties are important in the automotive industry for manufacturing reliable and durable vehicle components. Hence, this work examines the thermal and mechanical properties of polylactic acid (PLA) reinforced with surface-treated hemp composites for automotive interior components. The composites were prepared using the additive manufacturing technique, while response surface methodology (RSM) was utilized to identify the optimal processing parameters, thus reducing wastage of material from many experimental trials. The optimum parameters were identified as: 1% volume fraction, 40 mm/s print velocity, 1 mm nozzle diameter, and 45° printing direction. These conditions together with surface treatment significantly improved the tensile elastic modulus to 2607.27 MPa and impact strength to 16.66 MPa of the composite when compared to 2353.27 and 21.01 MPa of pure PLA, respectively. Surface morphology from atomic force microscopy and scanning electron microscopy showed an increased surface roughness and complex surface topography on the composite, while differential scanning calorimetry and thermogravimetry analysis revealed an enhanced crystallization behavior and thermal stability. The composite had a sharper crystallization peak at a lower temperature and decomposed more gradually than pure PLA. This study demonstrates the effectiveness of using RSM to optimize three-dimensional printed natural fiber-reinforced polymer composite materials for interior automotive components, achieving a good desirability function analysis score of 0.782.