Mechanical meta-sheets with independently tunable Poisson’s ratio and coefficient of thermal expansion

Abstract

Mechanical metamaterials with tunable Poisson’s ratio (PR) and coefficient of thermal expansion (CTE) have received great attention due to their unique responsive behaviors under mechanical and thermal stimuli useful in a wide range of applications. But, in most designs, they are often coupled to each other, limiting the range of their values to be achieved and their independent controllability. Here, we present mechanical meta-sheets whose PR and CTE can be independently modulated by using rotating rectangular units consisting of alternated bi-material beams. Design principles for these mechanical meta-sheets are provided and verified through simulations and experiments. Both isotropic and anisotropic thermal deformations can be realized and diverse reconfigurations are possible under thermo-mechanical loads for sandwich panels utilizing these meta-sheets as skins. The proposed design principle would be powerful in a broad range of applications requiring shape morphing, stress mitigation, and smart actuation under a thermo-mechanical environment.