Enhanced energy absorption performance of 3D printed 2D auxetic lattices

Auxetic lattices have attracted increasing attention due to their unusual mechanical behavior and potential for an array of applications. However, a narrow window of stiffness realizable for a given cell topology limits their applications. In this study, a pair of novel 2D re-entrant auxetic lattices capable of exhibiting enhanced stiffness and energy absorption is proposed by introducing vertical ligaments into conventional re-entrant structures. These modified re-entrant auxetic lattices were realized via fused deposition additive manufacturing. The deformation patterns and the energy absorption characteristics of 3D printed auxetic lattices under quasi-static compression were investigated both via Finite Element (FE) simulations and experiments. The effective elastic stiffness of the proposed lattices was theoretically estimated. The FE results corroborated by experiments, elucidate the role of different sub-cells on the effective mechanical properties of the proposed auxetic lattices. The results indicate that the proposed structures - Type A and B variants, exhibit enhanced stiffness (+355%) and superior energy absorption (+165%) in comparison to conventional 2D re-entrant lattices of the same mass. Furthermore, the findings of the study suggest that the strength, stiffness, energy absorption capacity and Poisson's ratio of 2D auxetic lattices can be tailored by tuning the sub-cell properties and cell wall thickness.