The Effects of Handedness Distribution on the Anisotropy Chiral Mechanical Metamaterial

Chiral mechanical metamaterial has broad applications in designing stretchable electronics, soft robotics, and smart and responsive materials and devices. The chiral geometry often introduces anisotropy which is not well understood due to the lack of an appropriate constitutive model. In addition, because of the overall handedness, chiral mechanical metamaterials show a unique property that under uniaxial stress/deformation, a shear deformation/stress will be generated simultaneously. Few efforts were made on understanding this unique property of normal/shear coupling, therefore, an integrated analytical-numerical method is developed to systematically quantify the overall mechanical properties of chiral mechanical metamaterials via a monoclinic constitutive model. By varying the distribution of local handedness in the chiral cells, a family of chiral mechanical metamaterials with hybrid local handedness are designed. The overall mechanical properties of them are quantified and compared via finite element simulations together with the monoclinic model. We will show that by programming the handedness in each chiral cell, the overall mechanical properties including stiffness, Poisson’s ratio, the normal/shear coupling effects, and the anisotropy can be tuned in a wide range.