Effects of handedness ratio and handedness distribution on the mechanical properties of Bi-chiral mechanical metamaterials

Abstract

The elastic mechanical properties of bi-chiral mechanical metamaterials are explored via systematic finite element simulations. Designs of bi-chiral mechanical metamaterials with both periodic and complete random handedness distributions for various handedness ratio and domain size and length aspect ratios were investigated. It is found that in general, because of the interactions at the ‘twinned’ intercellular boundaries between neighboring domains, the handedness ratio, handedness distribution, domain size and length aspect ratio significantly influence the overall mechanical properties of bi-chiral designs. Specifically, when handedness ratio increases and domain size decreases, the effective stiffness and the auxetic effects increases, while the effective shear modulus is much less sensitive to either the handedness ratio or the domain size. The chirality-induced normal shear coupling effect is solely determined by the handedness ratio. An empirical mechanical model was proposed to quantify the influences of ‘twinned’ intercellular boundaries on the effective stiffness and effective Poisson’s ratio of bi-chiral designs. In addition, both upper and lower limits of the effective stiffness and the effective Poisson’s ratio of bi-chiral designs are identified.