Effects of Microstructural Properties on Auxeticity and Negative Thermal Expansion of a Class of 2D Lattice Systems

We study auxetic lattice structures with curved bi‐material ligaments using the finite element method. The overall Poisson's ratio and coefficient of thermal expansion of the lattices can be simultaneously tuned to be negative by adjusting their microstructural geometries and constituent material parameters. The Young's modulus of ligaments plays an important role in controlling the effective Poisson's ratio and coefficient of thermal expansion. The size and Young's modulus of the joints that connect ligaments strongly affect the effective mechanical properties. When Young's modulus of the joint is given, a larger joint size gives rise to stronger auxeticity, but less negative thermal expansion. By tuning the coefficient of thermal expansion of each constituent, the overall coefficient of thermal expansion may be negative, zero, or positive. The bicamaterial auxetic structures studied here may be designed to possess desired properties for real‐world applications when their microstructural properties are appropriately tuned.