A study of deformation mechanisms for a two-dimensional metamaterial

This paper presents a numerical study of a two-dimensional tetrachiral metamaterial and the effect of unit cell parameters on its mechanical behavior. Finite element simulations are performed using independently varied geometric parameters of the chiral unit cell. Chiral structures can induce the compression-torsion effect and the deflection in mechanical metamaterials. The sample deflection is affected by the following factors: ring deformation, ligament deformation, and structure twisting. The highest strain estimated by the deflection of the metamaterial sample from the initial position is observed at an optimal ratio of ligament length to ring size. The effect of structural parameters on the deformation, stress distribution, and effective elastic properties of a two-dimensional metamaterial sample under uniaxial compression is studied and analyzed. For all variable parameters, a qualitatively similar nature of the equivalent stress distribution is revealed. It is found that a decrease in the volume of the main material in the metamaterial sample entails a decrease in effective Young's modulus. The parameters accounting for the auxetic properties of the metamaterial are obtained. Effective Poisson's ratio is determined in the range from $-$0.1 to 0.95.