Study on the mechanical properties of the thin-walled double circular tube filled with a novel NPR lattice core based on the concave rotating mechanism

This study presents a thin-walled double circular tube filled with a novel negative Poisson’s ratio (NPR) lattice core based on the concave rotating mechanism. The unit cell of the NPR lattice core is constructed by replacing each inclined side of a concave hexagon with a smaller concave hexagon with an identical geometry aspect ratio. The single cell is arrayed to obtain a two-dimensional honeycomb structure, and then curling and mirroring operations are utilized to get a circular tube structure. Compressive deformation and load–displacement response of NPR lattice core with different concave angles are analyzed by FEM. To validate with numerical results, the NPR lattice core samples are prepared using 3D printing technology and subjected to quasi-static uniaxial compression experiments. Then, the thin-walled double circular tube filled with the NPR lattice core (FDCT) is established. The load–displacement relationship and energy absorption characteristics are analyzed, and the effects of two angle parameters on the specific energy absorption of the structure are discussed. The results show that an increase in the concave angle decreases the rigidity of the NPR lattice core. When subject to compression, all models show NPR effects, with minimum and maximum Poisson’s ratios of −0.29 and −0.5, respectively. For FDCT, it is found that the interaction between the core layer and the tube wall enhances the structure’s energy absorption performance. Changes in the core layer angle parameters affect the energy absorption of the FDCT structure, where increasing the concave angle improves the energy absorption efficiency of the structure. In contrast, the effect of the rotational angle is not significant.