Design and energy absorption of star-shaped nesting cells and gradient lattice structures with negative Poisson’s ratio effect

Star-shaped lattice structures with negative Poisson’s ratio (NPR) effect have a prospective application in the fields of aerospace, vehicle and civil protection due to their excellent capabilities of energy absorption. However, existing gradient lattice structures with NPR effect require significant deformation, making them unsuitable for small space deformation collision buffers in equipment like aircraft and automobiles. To address this issue, this study designs several new star-shaped cell structures (r1, r2, r3), homogeneous structures (R1, R2, R3), and gradient structures (“X”, “V”, “Λ”, “O”). Then the NPR effect, stress–strain curves, specific energy absorption of these structures are studied by the means of quasi-static compression experiments and finite element analysis. The results indicate that among the cell structures, r3 shows the best equivalent elastic modulus, NPR effect, and energy absorption effect, particularly for small deformation. In the case of homogeneous lattice structures, R3 exhibits the highest compressive strength and energy absorption. For gradient lattice structures, the type of gradient has minimal impact on the mechanical properties, but the stress strength and energy absorption improve with an increase in the number of layers. These results could provide a theoretical guidance for the application of NPR structures in buildings, vehicle, and other security protection fields to meet practical engineering needs.