A novel metamaterial with adjustable anisotropic negative thermal expansion and negative Poisson’s ratio

Metamaterials with thermal contraction and auxetic effect can effectively prevent irreversible damage caused by thermal stress and impact in engineering applications, playing a crucial role in aerospace and other fields. Therefore, we propose a novel double-negative metamaterial structure by combining triangular arrowhead structures and triangular thermal metamaterial structures, which can achieve thermal expansion coefficient over a wide range from −167 × 10⁻⁶ to 162 × 10⁻⁶ K⁻¹, and Poisson’s ratios range from −1.7 to 1.95. Furthermore, we study the impact of the geometric parameters of the designed structures on the coefficient of thermal expansion, elastic modulus, and Poisson’s ratio of the metamaterial by using the stiffness matrix method. Results show that changing the included angle of the re-entrant triangle of the structure can change the sign of thermal expansion coefficient and Poisson’s ratio. This paper provides new ideas and methods for designing mechanical metamaterials with anisotropic adjustable thermal expansion coefficients and Poisson’s ratios.