Effect of Shore A hardness and process parameters on the impact behaviour of SLA printed polymers

Stereolithography (SLA) enables the fabrication of polymer components with exceptional dimensional accuracy; however, their resistance to impact loading is highly sensitive to material and processing parameters. In this study, the impact behaviour of SLA-printed polylactic acid (PLA) specimens was systematically investigated by evaluating the combined effects of Shore A hardness, layer height, and post-curing time. Specimens with hardness values of 50 A, 60 A, and 70 A were fabricated at layer heights of 20, 30, and 40 μm and subjected to post-curing durations of 30, 45, and 60 min. Charpy impact testing revealed that lower material hardness and finer layer resolution significantly enhance impact energy absorption, while extended post-curing improves interlayer bonding and fracture resistance. The highest impact performance was achieved at 50 A Shore hardness, 20 μm layer height, and 60 min of post-curing. In addition, fracture patterns indicated a semi-ductile failure mechanism characterized by progressive deformation and delayed crack propagation.