Variability in mechanical properties of a metal foam

Abstract

Mechanical properties of cellular materials depend on their relative densities. In this paper, variability in elastic modulus, plastic strength, and energy absorption of a closed-cell Al foam, ALPORAS, and their connection with the variability in the density was examined. It was found that the tangent modulus in initial loading is considerably lower and has higher variability vis-à-vis the unloading modulus, a result of the higher sensitivity of the former to morphological defects in the cellular structure. The variability in the plastic strength and energy absorption are found to be similar, because of their interdependence. Within the range of the specimen volumes examined, no size-scaling of properties was observed. The variance in modulus and plastic strength are correlated with that in the density with the aid of the scaling relationships and error propagation techniques. Furthermore, the variability in plastic strength is related to the variance in the cell-size by considering the micromechanism of deformation in closed-cell foams, which is the collective collapse of 5–6 cells. Implications of these results in the context of manufacturing and testing strategies are discussed.