Keywords: aluminium foam, micromechanical properties, discretization, compressive behaviour, closed-cell geometry, microCT.

In this paper an evaluation of microstructural finite element (micro-FE) models of closed-cell aluminium metal foam is given. A comparison of results for models generated on the basis of two different discretization schemes defined for open-cell and closed-cell materials is presented. Discretization is based on regular network of elementary cells having cubic form as defined by Gibson et al. Results are studied with respect to characteristics of the reference Alporas aluminium closed-cell foam. An open-cell discretization scheme is here considered intentionally to evaluate its capability to describe deformation mechanisms and to estimate the compressive elastic modulus of the reference material. The influence of geometrical parameters of the elementary cells is assessed prior to determination of the dependence of the elastic modulus on material porosity. The closed-cell scheme contribution of the cell-wall thickness to the overall stiffness of the material is analysed.

A virtual uniaxial compression test is simulated to obtain the elastic modulus from both open-cell and closed-cell models. With respect to the computational requirements of the closed-cell models, values of the yield stress are calculated only from simulations using the open-cell models. The material model used in the finite element (FE) simulations is based on the results obtained by nanoindetation testing of the base material used for production of the reference foam as well as on results obtained by inverse FE simulations of the nanoindentation experiments.

The elastic constants obtained and the yield stress from the FE simulations of the open-cell models for the respective porositites are in the general range for such values of the reference material. Analysis of the closed-cell models show an increase in the overall stiffness linearly related to the thickness of the cell-wall which is in agreement with analytical relations describing the deformation mechanisms of such structures. However seeing the computational requirements of the closed-cell models the considered closed-discretization offers only minor benefits over microtomography derived models that are even able to describe the internal structure including all of its irregularities and defects.

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