Mechanical Properties of Semi-expanded Hollow Sphere Structures

Abstract

Recently, technologies for the production of cellular materials have been proposed that allow for a seamless change of the geometries of such materials from being similar to sintered hollow sphere structures to resembling comparatively regular polyhedra. In order to investigate, how the linear elastic properties of such materials are effected by this change in geometry, analyses of the expansion process are carried out by the finite element method for obtaining cell wall thickness distributions. These material distributions are then transferred to finite element unit cell models that are suitable for predicting the effective, macroscopic elastic properties. It is found that Young’s modulus, as well as the shear modulus increase monotonically with increasing degree of expansion. Furthermore, negative Poisson’s ratios are predicted for configurations that are comparable to sintered hollow sphere structures, while positive Poisson’s ratios are observed for highly expanded configurations.