Hierarchical structure of aluminium foams and relation to compression behaviour
The present study examines the possibilities of a statistically secured approach to estimate the plateau stress of compression loaded aluminium foams. Density-normalised plateau stress values were correlated with the hierarchical foam structure to evaluate the influence of pore size distribution and microstructural features as well as matrix alloy composition on level and scatter of mechanical properties. Foam structure investigations and compression tests were performed on three closed-cell aluminium foams (alloys AlMgSi0.5, cast AlSi7 and modified AlSi7) manufactured by powder-metallurgical technology. Plateau strength levels are primarily controlled by the global density, with the strength of samples with the same global density varying by about +/- 20%. This scatter of compression strength is caused by imperfections (large pores, density fluctuations, cracks etc.) in the foam structure. Such imperfections Act as weak spots in the pore structure, and thus the plateau stress can be understood as a volume depending inhomogeneity.