Energy absorption of PLA (Polylactic Acid) - based metamaterials manufactured by material extrusion: dynamic loads and shape recovery

Abstract

An investigation of the behaviour of solid cell structures made of Polylactic Acid (PLA) by material extrusion was conducted. The studied structures are Strut-Based, TPMS (Triply Periodic Minimal Surfaces) and Spinodal. To evaluate the performance of the different structures, impact tests were carried out. Through failure tests, the structures were divided into three macro-categories according to their capacity to absorb the impact energy: low, medium and high. Subsequently, the samples that showed a lower deformation for each macro-category were selected for a second step. In the second step, cyclic loads of the deformation by impact were applied to the samples. Immediately after, the deformed samples were submitted to shape recovery by dipping them in a thermostatic bath at a temperature (70°C) higher than the glass transition of the PLA. Based on the experimental evidence, the most performing geometries were the TPMS, both for high and medium impact energies, exhibiting few internal defects. Conversely, the Spinodal structures exhibited good behaviour at low impact energies, but they were less suitable for cyclic tests due to their geometric features. The "Strut-based" structures, despite having the same density as the TPMS, were not suitable for cyclic tests due to their overall poor mechanical strength.