Micropolar homogenization of wavy tetra-chiral and tetra-achiral lattices to identify axial–shear coupling and directional negative Poisson's ratio

Abstract

Chiral lattices are generally considered to possess auxetic properties with negative Poisson's ratios and high compressibility. However, the effects of anisotropy and handedness (chirality) on their mechanical properties, such as directional moduli, Poisson's ratio, and other coupling effects, are not clearly understood due to the lack of analytical methods to handle both anisotropy and chirality. Herein, we construct a generalized micropolar homogenization method to characterize the elastic constants of tetra-chiral and tetra-achiral lattices having different joint types. The developed method can identify the directional moduli and Poisson's ratio and coupling effects in the anisotropic wavy lattices. The generalized micropolar homogenization of the wavy square lattices reveals i) the axial–shear coupling effect of tetra-chiral structures, ii) the weak correlation of the chirality of tetra-chiral lattices to auxeticity, and iii) the directional positive and negative Poisson's ratio of tetra-achiral lattices. This work offers a powerful platform for metamaterials' design via geometric reconfiguration of lattice structures to adjust both anisotropy and chirality.

Keywords

• Chiral lattices
• Achiral lattices
• Micropolar elasticity
• Mechanical metamaterials
• Geometric reconfiguration
• Negative Poisson's ratio