Adjustment of multi-directional elastic properties of chiral metamaterial via a 3D printing-based soft-hard bi-material strategy

Chiral metamaterial is widely used to design morphing wings with multi-directional elastic requirements. To take into account both bearing stiffness and bending capacity, this paper proposed a soft-hard bi-material strategy to adjust the multi-directional elastic properties of 3D printed chiral metamaterial. In the elastic segment of the large deformation, the numerical was in good agreement with the tests. The ligament deformation and node rotation were obtained by image processing, which showed good consistency with the theory study. It was found that the elastic properties of chiral cells could be adjusted by varying the location, size, and amount of adjusting modules (ADMs). An optimal cell with ADMs was obtained through systematical numerical. Compared with the hard-material cell, the equivalent compression and bending stiffness of the optimal cell were decreased by 12.4% and 70.88% respectively, and the equivalent elastic ratio was increased by 3 times. The good similarity of deformation between chiral metamaterial and cell proved the representative of the former by the latter. The deformation symmetry was studied by comparing the nodes' rotation of the metamaterial. In summary, this strategy could help develop a metamaterial with comprehensive advantages, that could be a solution for the design of practical morphing wings.