Mechanical Properties of Cochiral and Contrachiral Mechanical Metamaterials Under Different Temperatures

Cochiral and contrachiral mechanical metamaterials are designed by introducing chiral cells with different handedness to the center of the basic chiral cell. Both single-material designs and multimaterial designs are explored. The designs are fabricated via a multimaterial 3D printer, and uniaxial tension experiments are performed in a thermal chamber at two different temperatures. For single-material designs, either cochiral or contrachiral ones, the effective Poisson's ratio is independent of temperature, while for their multimaterial counterparts, the effective Poisson's ratio can change with temperature. It is found that the handedness of the core chiral cell significantly influences the rotation efficiency and the effective Poisson's ratio of the design, although it only slightly influences the effective stiffness. Cochiral designs have higher rotation efficiency than the contrachiral designs and therefore are more auxetic. While for the contrachiral designs, the effective Poisson's ratio can be tuned in a wider range and the overall fracture strain is higher.