Stiff, strong zero thermal expansion lattices via the Poisson effect

Abstract

Designing structures that have minimal or zero coefficients of thermal expansion (CTE) are useful in many engineering applications. Zero thermal expansion is achievable with the design of porous materials. The behavior is primarily stretch-dominated, resulting in favorable stiffness. Two and three-dimensional lattices are designed using ribs consisting of straight tubes containing two nested shells of differing materials. Differential Poisson contraction counteracts thermal elongation. Tubular ribs provide superior buckling strength. Zero expansion is achieved using positive expansion isotropic materials provided axial deformation is decoupled by lubrication or segmentation. Anisotropic materials allow more design freedom. Properties of two-dimensional zero expansion lattices, of several designs, are compared with those of triangular and hexagonal honeycomb nonzero expansion lattices in a modulus-density map. A three-dimensional, zero expansion, octet-truss lattice is also analyzed. Analysis of relative density, mechanical stiffness, and Euler buckling strength reveals high stiffness in stretch-dominated lattices and enhanced strength due to tubular ribs.