Innovative 3D chiral metamaterials under large deformation: Theoretical and experimental analysis

In this paper, making use of the coupled deformation features of reentrant and tetrachiral lattices, innovative 3D chiral metamaterials are designed, in which their mechanical properties and deformation mechanisms are explored in details. Firstly, three types of innovative 3D chiral metamaterials are designed based on geometry topology in the x¯y¯ plane, namely: tetrachiral, anti-tetrachiral and hybrid-tetrachiral, respectively. Secondly, the coupled tension and rotation deformation mechanisms of innovative 3D chiral metamaterials are investigated based on large deformation theories of representative unit cell. The theoretical formulas for extension stress, Poisson's ratio and rotation angle of the square loop are derived, it is found that wide range of negative Poisson's ratio can be obtained with the proposed 3D chiral metamaterials. Afterwards, tensile experiments are performed, and good agreements between theoretical, finite element and experimental results are presented, verifying the reliability of the theoretical models. Finally, influences of the geometry parameters on the mechanical behaviors of the proposed 3D auxetic metamaterials are also studied.