Three-dimensional bi-metallic lattice with multi-directional zero thermal expansion

Metamaterials with zero coefficient of thermal expansion (CTE) are of increasing interest with the rapid development in aerospace applications. Despite numerous two-dimensional (2D) metamaterials with high thermal stability have been investigated, studies on three-dimensional (3D) zero CTE structures are still limited by the complexity of fabrication and geometric connections. In this study, novel 3D bi-metallic lattices with multi-directional zero CTEs are designed, fabricated and experimentally validated. A theoretical method has been developed to predict the effective CTE of the lattice with different materials and geometric parameters and illustrated by comparison with experimental results and numerical simulation results. The 3D lattice had identical effective CTEs along three orthogonal directions and the CTE results were extreme close to zero (0.62 ppm/ degrees C), which is the first time to achieve nearly zero CTE over a wide temperature range in 3D metallic lattice. In addition, the mechanical performance and the effect of geometric parameters of the lattice has been investigated using finite element analysis (FEA). Different thermal deformation mechanisms in the lattice are revealed by different selections of materials for connection bar. The proposed design method and thermal mechanisms are promising for the design of the bearing platform with zero CTE in aerospace engineering.