MECHANICAL MODELLING AND CHARACTERIZATION OF CLOSED-CELL METALLIC FOAMS

Abstract

This thesis focusses on characterizing the yield properties of closed-cell aluminium foams through numerical and experimental investigations. As it is difficult to carry out comprehensive experimental investigations of such materials under complex stress states, a direct approach to generate irregular 3D micromechanical models, adequately characterizing the geometrical characteristics, is presented. The generated micromechanical models can well predict the macroscopic behaviour of closed-cell aluminium foams under uniaxial and hydrostatic compression. The numerical response is further validated using custom designed experimental investigations, under uniaxial and biaxial stress states in compression, tension, and a combination of tension-compression loading conditions. The initial yield surface, plotted using the comprehensive set of yield data obtained from both experimental and numerical investigations, is observed to be considerably shifted towards the positive mean stress axis in the mean stress – effective stress space. Finally, a yield criterion is proposed for isotropic closed-cell aluminium foams with minimum necessary parameters.