Dynamic crushing behavior of a novel bi-directional gradient lattice structure under axial and oblique impact loadings

To meet the crashworthiness requirement of lightweight structures under different impact directions, a series of novel bi-directional gradient lattice structures (BD-GLSs) are proposed to improve their oblique impact resistance performance. In this paper, four types of BD-GLSs with both symmetric and asymmetric gradient topology configurations are constructed by varying the side lengths of lattice unit cells in xy-plane, and their crushing behavior under axial and oblique impact loadings are numerically investigated. The dynamic crushing behaviors are highlighted by comparing with the traditional uniform and uni-directional gradient lattice structures, which is validated via experiment studies. It is demonstrated that the specific energy absorption of the BD-GLSs with symmetric gradient topology configuration can achieve an increment of 42.26 % as compared to the uniform lattice structure. Moreover, the specific energy absorption of BD-GLSs with symmetric gradient topology configuration is 47.63 % higher than that of the uni-directional gradient lattice structure under oblique impact, which suggests that the bi-directional gradient topology can provide better crashworthiness performance under the oblique impact conditions. The symmetrical gradient topology configuration has greater bearing capacity and better crashworthiness under both axial and oblique impact loadings by comparing with other gradient topology configurations. The proposed bi-directional gradient topology configuration provides an optimal design strategy for the crashworthiness design of lightweight structures, especially in the case of unknown impact load directions, which has a great competitive advantage in crashworthiness applications.