Comput.Mater.Sci. 16, 61-69, 1999


T.Daxner, H.J. Böhm and F.G. Rammerstorfer

Institute of Lightweight Structures and Aerospace Engineering and
Christian Doppler Laboratory for Micromechanics of Materials,
TU Wien, Vienna, Austria

Abstract - The subject of this work is metallic foams under crush and crash loading, the focus being on the influence of inhomogeneities of the apparent density on the maximum stresses and the energy absorption behavior during compressive deformation. Based on an analytical description of the uniaxial stress-strain relationship of cellular materials, which is fitted to experimental results, a relation between the effective density and the static compression behavior of a certain brand of metallic foams can be obtained. This relation is implemented into a mathematical model, which represents the material as an array of point masses connected by longitudinal, nonlinear springs and transversal, rigid cross-bridges, which can be opened or closed as required. Several distributions of mesoscale inhomogeneities are studied and assessed with respect to their influence on the energy absorption and impact damage protection potential. It is shown that only a mesoscopically homogeneous foam fully exploits the energy absorption potential of a foam of a given apparent density. The effects of inertia are shown by simulating impact events. The stress waves propagated and reflected in the homogenized foam material and their influence on the impact response are described.