Experimental and FEM study on the in-plane and out-plane loaded reversible dual-material bio-inspired lattice structures with improved energy absorption performance

In the current study, bio-inspired lattice structures are derived from the architecture of the Euplectella aspergillum (sea sponge). All the lattice structures are fabricated using the fused filament fabrication (FFF) process. The fabricated structures are subjected to quasi-static uni-axial compressive in-plane and out-plane loading condi-tions. The results shows that energy absorption performance of lattice structures also depends on the structure's stiffness. When used in lattice structures, soft material like thermoplastic polyurethane (TPU) has good energy absorbing performance. However, the stiffness of soft materials is not good enough to increase energy absorption. Here an attempt has been made to increase the energy absorption capacity of lattice structures by using a combination of hard (PLA) and soft phase (TPU) material in the fabrication of structures. Overall, the mechanical properties and deformation behavior in the experimental and finite element studies are quite similar. Structures under in-plane loading conditions showed a shorter linear elastic region and longer plateau region, whereas the structures subjected to out-plane loading conditions showed longer nonlinear elastic regions and a shorter plateau region. Overall, the structures loaded in the in-plane condition have a more stable response, whereas those loaded in the out-plane loading conditions have higher mean plateau stress, higher energy absorption and better efficiency. In both in-plane and out-plane loaded structures, dual-material fabricated structures showed higher efficiency; in-plane structures showed the highest experimental efficiency of 0.453 whereas out-plane structures showed the highest efficiency of 0.470. Combination of dual-material showed improved perfor-mance without compromising the reversibility of the energy absorbers. Hence this study opens a field for the design and fabrication of better energy absorbers.