Superior energy absorption characteristics of additively-manufactured hollow-walled lattices

Designing innovative lightweight architected materials with enhanced mechanical properties and superior energy absorption is a long-term pursuit to protect against impact-induced damage. Compared with dense-walled lattices, innovative engineering designs indicate that hollow-walled lattices exhibit unprecedented combinations of mechanical properties and functionalities with minimal weight. This paper proposed a novel hollow-walled lattice structure with variable cross-sections that can improve energy absorption significantly. A series of hollow-walled lattices were additively manufactured by the selective laser melting technique with the twinning-induced plasticity steel. The quasi-static uniaxial compressive tests were conducted to study the mechanical property and energy absorption capacity. Experimental results indicated that the hollow-walled lattices with a constant cross-section and those with a variable cross-section can improve the specific energy absorption by 29.2% and 135.6% compared with the conventional dense-walled lattices. Besides, finite element models of hollow-walled lattices were established by using the FE package LS-DYNA to investigate the effects of various structural parameters on mechanical properties and energy absorption capacity. A comprehensive parametric analysis based on the validated finite element models shows that the maximal ratio of the diameter to thickness in hollow-walled lattices leads to the optimal energy absorption capacity for the lattices with the same relative density. In addition, three typical tailored parameters, including the necking ratio, the necking local coefficient and the ratio of the thickness to diameter of variable struts, were tailored to achieve a better energy absorption capacity of hollow-walled lattice structures. Finally, the novel proposed hollow-walled lattice with a variable cross-section was also applicable in other lattices to enhance energy absorption capacity.