Studies on Impact Performance of Gradient Lattice Structure Applied to Crash Box

The conventional crash box with thin-walled column conceals some limitations on pedestrian protection and lightweight. The metallic NPR metamaterials designed in this study are based on re-entrant lattice structures. Re-entrant structures are known to be one main class of axenic structures that display negative Poisson’s ratio (NPR), which can be manufactured by 3D printing technology. This kind of metamaterial has good designability and can be used as the filling structure of the crash box to improve the crashworthiness of the car. This paper starts from the relations between geometric parameters of the metamaterial. Considering the deformation characteristics of the crash box, the structure were designed into some gradient types. The mechanical properties of different gradient structures under the same impact conditions were compared to find the proper gradient structures. Based on the studies, the gradient lattice structure is applied to the automobile crash box. We made some simulation by the finite element software LS-DYNA of vehicle head-on collision. We compared the crashworthiness of the cars which have different crash boxes. The accelerations of some key points in the crew compartment were measured. Also, we compared the energy absorption efficiency of the boxes. We came to the conclusion that the gradient lattice structure can efficiently improve the structural crashworthiness criteria of the thin-walled column and also achieve better pedestrian protection of the vehicle structure. Because the lattice structure has good impact performance, some other vehicle structures which need to have a good impact behavior can also be replaced by it .