Experimental Study on the Effects of Hierarchical Handedness on Auxetic Chiral Mechanical Metamaterial under Different Temperatures

Periodic mechanical metamaterials with hierarchical handedness are designed. Specifically, four hierarchical representative volume elements (RVE) are developed: design A has a right-handed chiral core in the center of a left-handed chiral cell; design B has a left-handed chiral core in the center of a left-handed chiral cell; designs C and D are the multi-material versions of design A and design B, respectively, by adding soft corners at critical locations. Specimens of the four designs are fabricated via a multi-materials 3D printer (Stratasys Connex3). Uniaxial tension experiments are conducted under various temperatures in a thermal chamber. The effective mechanical properties including the effective stiffness, the effective Poisson’s ratio, rotation efficiency, ultimate strength, and fracture strain of the designs are obtained from the mechanical experiments. In addition, 3D finite element models of the designs are developed in ABAQUS to support the experiments. Design guidelines for desired properties related to auxeticity, rotation efficiency, effective stiffness, and the shear-normal coupling effects will be provided. The experimental and numerical results show that the core handedness and stiffness ratio can significantly influence the effective mechanical properties of hierarchical chiral designs.