A novel re-entrant honeycomb of negative thermal expansion

By strengthening the pore with material different from that of matrix, a new type of negative thermal expansion materials with the re-entrant hexagonal honeycomb is designed in this paper. The equivalent Young's modulus, Poisson's ratio and the coefficient of thermal expansion (CTE) are studied by using Timoshenko beam theory and the analytical formulas of these equivalent parameters are derived. The results of analytical formulas and numerical simulation indicate that the CTE of the material can be controlled from positive to negative by changing the geometry features and material properties of the structure. Meanwhile, the negative Poisson's ratio effect of the original re-entrant honeycomb can be preserved. Moreover, this method for designing new metamaterials has also been generalized to three-dimensional materials.