Modelling and verification of a novel bi-material mechanical metamaterial cellular structure with tunable coefficient of thermal expansion

The tunable thermal expansion characteristic of metamaterials is beneficial to solve the problems caused by drastic temperature changes. Here, we propose a novel bi-material mechanical metamaterial cellular structure (NBMCS) that can adjust the coefficient of thermal expansion (CTE). Under some parameters restrictions, the structure can realize the regulation of its CTE in a wide range from -115 ppm/celcius to 83.6 ppm/celcius with Al alloy/ Low carbon steel combination. A general thermoelasticity equation that builds the relationship among the temperature, the external force, and the displacement is derived, which is then assembled into a theoretical model of NBMCS. Through theoretical analysis and numerical simulations, the underlying mechanism among the CTE of NBMCS, geometric parameters, elastic modulus ratio, and CTE ratio is revealed. Experiments are carried out based on industrial camera and DIC method, which verify the theoretical modelling. Finally, the tunable range of CTE and elastic modulus for three different material combinations are compared.