Energy absorption characteristics of TPMS-filled square tubes under quasi-static axial crushing

Taking advantages of thin-walled tubes and triply periodic minimal surface (TPMS) lattices on improving crashworthiness performances, the axial crushing behaviors of square tubes (ST) filled with three types of TPMS lattices (Diamond, Gyroid, and Primitive) were investigated in this study. Specimens made of 316 L stainless steel including the empty ST, TPMS lattice fillers, and TPMS-filled ST were additively manufactured and tested under quasi-static axial crushing loads. Meanwhile, the finite element (FE) simulations were verified by the quasi-static experiments, which showed that the experimental curves were well consistent with the simulations. The experimental results also showed that the TPMS-filled ST had more energy absorption capacities (22 - 33.7 %) compared to the sum of empty ST and TPMS lattice fillers. Furthermore, the influences of relative density ( rho ), density gradient, unit cell height and multi-morphology hybrid design of TPMS lattice fillers on the energy absorption capacities of TPMS-filled tubes were systematically studied using the validated FE models. The rho gradient and hybrid design could lead to substantially lower initial peak crushing force ( F p ), comparable specific energy absorption ( SEA ), and larger crushing force efficiency ( CFE ) compared to uniform counterparts. The TPMS-filled tube with hybrid design of Diamond and Gyroid had at least 16.3 % higher SEA compared with other hybrid designs, with the best energy absorption capability. The findings of this paper provided a guidance for the design of thin-walled square tubes filled with TPMS lattices.