Compression Characterization of Multi-Shore and Functionally Graded Silicone-Infilled Kelvin-Cell Lattices

In this study, Kelvin-cell lattices fabricated via vat polymerization were combined with RTV-2 silicone infill to create hybrid and functionally graded architectures. Four silicone Shore hardness levels were investigated to quantify the influence of infill hardness, followed by functionally graded designs using the hardness level that yielded the highest mean compressive performance. Compression tests revealed monotonic increases in compressive force, maximum stress, and energy absorption with increasing Shore hardness, with Shore 50A silicone providing the highest performance. At 60% strain, the Shore 50A infilled lattice exhibited a ~704% increase in load capacity and a ~3.66 times improvement in energy absorption. Based on these results, functionally graded specimens with varying silicone filling heights (2–5 cells) were tested up to 60% strain using stress–strain analysis to capture the full deformation regime. The functionally graded lattices showed a sequential deformation mechanism, where Kelvin-cell collapse preceded silicone densification in partially filled configurations, enabling delayed densification and smoother stress evolution. The results demonstrate that silicone hardness and infill grading are effective design parameters for tuning the compressive properties of Kelvin-cell lattices.