Mechanical behaviors of three-dimensional chiral mechanical metamaterials.

Chiral and achiral mechanical metamaterials are designed via spherical tiling. The 3D chiral designs show an interesting coupled compression-twisting behavior, while the 3D achiral designs show auxetic behavior. Also, besides the cellular-type chiral and achiral designs, composite-type of each design are created by adding soft matrix to the cellular designs. The designs are fabricated via multi-material 3D printing. Mechanical uni-axial compression experiments are performed on the 3D printed specimens and the experimental results are compared with finite element (FE) simulations. By jointly tailoring the chiral geometry and material combination, the effective mechanical properties and the deformation mechanisms can be tuned in a large range. In addition, a continuum-level material model was developed to predict the constitutive relationship. The results show that the material model can well predict the effective mechanical properties of the chiral 3D mechanical metamaterials. [ABSTRACT FROM AUTHOR]