Three-dimensional enhanced star-shaped honeycombs with negative thermal expansion

In this work, three kinds of three-dimensional enhanced star-shaped honeycombs (3D-ESSH) with enhanced effective Young's modulus and negative Poisson's ratio are proposed. Finite element simulations and uniaxial compression experiments are carried out to study the influence of the main parameters on the effective mechanical properties of the structures. The numerical results fit well with the experimental results. Compared with the three-dimensional star-shaped honeycomb (3D-SSH), the negative Poisson's ratio effect and effective Young's modulus of the 3D-ESSH are significantly enhanced. Comparison among the proposed novel honeycombs indicate that the effective mechanical performance of the structure can be improved more obviously if the reinforcing rods are only added in the loading direction. In addition, the impact of reinforcing rods on the effective thermal expansion coefficient of the novel 3D-ESSH is investigated. It's noticed that adding reinforcing rods can realize the negative thermal expansion in corresponding direction when combined with proper bi-materials.