Controllable design of bi-material metamaterials with programmable thermal expansion and Poisson's ratio

Abstract

Metamaterials possess superior acoustic, thermal, and mechanical properties, making them potential candidates for scientific and engineering applications. Previous studies were mainly limited to single counterintuitive property, while current applications of high-precision machines often necessitate a combination of advanced properties, such as negative thermal expansion (NTE), light-weight and negative Poisson's ratio (NPR). In this work, two bi-material missing rib-type anti-chiral metamaterials were devised and analyzed to integrate the programmable coefficient of thermal expansion (CTE), Poisson’s ratios (PR) and light-weight. The analytical solutions for the proposed metamaterials were then derived to provide guidelines for determining the geometries with targeted mechanical properties. It is shown that the proposed designs exhibit a range of special properties, including light-weight, widely programmable CTE with isotropy and stable PR performance. The analytic solutions of the CTE were further validated by numerical simulations and experimental tests. Finally, the coupling relationships among the CTE, PR and relative density were elucidated. Such an analysis of the coupled relationships is anticipated to have profound implications for the engineering community, where there is a pressing demand for materials that can meet stringent requirements of light-weight and programmable properties.