Effects of Disordered Circular Nodes Dispersion and Missing Ligaments on the Mechanical Properties of Chiral Structures

Abstract

Auxetics with negative Poisson's ratio (NPR) can expand dimensions along the direction perpendicular to the tensile direction, such as rigid rotation, reentrant and chiral structures, etc. The mechanical performances of chiral metastructures are closely related to internal defects and interactions between defects. In this paper, two types of irregular chiral structures with Gaussian dispersion of circular node positions and missing ligaments are designed, namely: antitetrachiral metastructure and tetrachiral hybrid metastructure. These two types of chiral metastructures are characterized by node radius, ligament thickness, ligament length, the circular node center dispersion range, and missing ligament percentages. Effects of random node distribution range and cell wall missing percentage on the elastic modulus and Poisson's ratio of chiral metastructures are investigated through experimental tests and finite element (FE) simulation systematically. Through dimensionless analysis, it is found that ligament thickness has remarkable influence on the negative Poisson's ratio. Effect of missing ligament on the mechanical properties of the structure is greater than effect of random node center dispersion. With the increase of ligament missing percentage, the resultant modulus of chiral metastructures decreases, and the corresponding NPR increases.

In-plane compression behavior of meta-tetrachiral and common auxetic structures

“…Li et al [52] established an analytical expression for the in-plane modulus of meta-tetrachiral structure and tested its in-plane tensile properties through experiments and finite element simulations. Niu et al [53] investigated the effect of different missing ligament ratios on the elastic modulus and Poisson's ratio of the meta-tetrachiral material system. Qi et al [54] designed a three-dimensional re-entrant structure based on the meta-tetrachiral, and investigated the coupled tension and rotation deformation mechanisms.…”