Elastic properties of two novel auxetic 3D cellular structures

Based on a 2D cross chiral structure, two novel 3D cross chiral structures (structure-1 and structure-2) with negative Poisson's ratios were proposed in this paper. Structure-1 could be evolved into structure-2 by adding a star structure. Analytical models of the two auxetic cellular structures were established based on the Timoshenko beam theory. The Young's modulus and Poisson's ratio of the cellular structures were obtained in all principal directions, which were verified by finite element method (FEM). Structure-1 exhibits anisotropic auxetic behavior while structure-2 shows uniform auxetic behavior in all three principal directions with all on-axis Poisson's ratios closer to the limit of -1. Additionally, the extra addition of star structure can enhance the Young's modulus of structure-2 significantly in the case of same relative density, compared to structure-1. Moreover, the effect of parameter variation on elastic properties of two structures and the comparison with other classical 3D auxetic structures were also thoroughly studied and discussed in detail. These results are expected to eventually contribute to the advance of research and the application of new 3D auxetic structures in the future.