Aluminium foam—modulus of elasticity and electrical conductivity according to percolation theory

Abstract

Aluminium foam is an isotropic, highly porous aluminium in which the pores create a cellular structure. Industrial exploitation of this remarkable material will be determined by the possibility of measuring, predicting and reproducing its mechanical and physical properties. It is obvious that these properties are significantly affected by the porosity of the foam. On the macroscopic level, aluminium foam can be approximately characterized by the effective mechanical and physical properties, considering the foam as a homogeneous bulk body with a certain apparent density. However, the dependence of these effective properties on the pore structure and on the quantities which characterize the components of the foam (aluminium alloy and gas) has still not been satisfactorily explained. In reality, the foam is created by an infinite aluminium cluster. This cluster has a complicated structure, defined by the randomly distributed gas pores with various sizes in the metallic matrix. The presence of such a cluster is essential for the existence of the foam. If the cluster does not exist the foam disintegrates and the effective properties are zero. This situation agrees well with the behavior of effective properties according to percolation theory.