The present paper highlights results from the priority program "Cellular Metals" of the Deutsche Forschungsgemeinschaft (DFG SPP 1075). The aim of the present study is to present the possibilities of a statistically secured approach to estimate the compression plateau strength of aluminium foams and to correlate its values with the hierarchical foam structure. The paper describes the foam structure investigations which were carried out on different aluminium foams (alloys AlMgSi0.5 and AlSi7) produced according to a powder-metallurgical route (patented by the Fraunhofer-Institute in Bremen), and also the corresponding compression tests. The macroscopic pore structure formation was studied by using stochastic methods of quantitative metallography. The microstructure of the cells walls was examined by means of optical microscopy and high-resolution scanning electron microscopy. The plateau stress is primarily determined by the global density of the foam linked to the average pore size which decreases with increasing density. Under compression, the upper plateau stress is reached when collapse inside of a deformation band formed in the early stress/strain response occurs for the first time. The collapse originates from a weak spot in a pore understood as a volume dependent inhomogeneity. For this reason the plateau stress is also volume dependent. This correlation advises the application of Weibull statistics determining the characteristic value of the plateau stress.
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