Abstract
Cell wall material properties of Al-alloy foams have been derived by a combination of nanoindentation experiment and numerical simulation. Using the derived material properties in FE (finite element) modeling of foams, the existing constitutive models of closed-cell Al-alloy foams have been evaluated against experimental results. An improved representative model has been proposed for FE analysis of closed-cell Al-alloy foams. The improved model consists of a combination of spherical and cruciform-shaped cells similar to those of Meguid et al.'s cruciform-hemisphere model (Finite Elem. Anal. Design: 2002, 38, 631). However, the spherical cells, which are smaller in size, are made of thicker cell walls in the new improved model compared to the cruciform-shaped cells, based on observation of the underlying Al-alloy foams. The compressive mechanical properties of Al-3wt.%Si-2wt.%Cu-2wt.%Mg alloy foams of relative density 12%–20% have been obtained by simulation using the improved representative model. While the traditional foam models overpredict the foam strength, the new weaker-cruciform-stronger-hemisphere model is found to predict the foam properties with much better accuracy. It is found that the proposed new model is capable of producing all three different types of deformation pattern of closed-cell metal foams, namely, uniform deformation, layerwise deformation, and the progressive deformation from the locations of lowest densities and highest impurities to those of higher densities and lower impurities.
Highlights
Light weight metallic foams can be used in the construction of composite panels, foam-filled shells and tubes, and many other lightweight composite structures [1] with high structural efficiency
As pointed out by Santosa and Wierzbicki [18], the major difficulty in predicting the crushing strength of closedcell aluminum foams through numerical simulation lies in obtaining their cell wall material properties
Results showed that the FE simulations using conventional foam models over predict elastic modulus and crushing strength of foams when the real cell wall material properties are applied to the models
Summary
Light weight metallic foams can be used in the construction of composite panels, foam-filled shells and tubes, and many other lightweight composite structures [1] with high structural efficiency. As pointed out by Santosa and Wierzbicki [18], the major difficulty in predicting the crushing strength of closedcell aluminum foams through numerical simulation lies in obtaining their cell wall material properties. For example, see [5], it has been shown that the material properties of Al-foam cell wall can be identified by performing nanoindentation test on the cell wall and simulating the test results using numerical FE codes. A numerical study of closed-cell Al-alloy foams has been performed using the cell wall material properties obtained by a combination of nanoindentation test and FE simulation with various existing numerical models of foams. Results showed that the FE simulations using conventional foam models over predict elastic modulus and crushing strength of foams when the real cell wall material properties are applied to the models. An improved model, named weaker-cruciform-stronger-hemisphere model, has Advances in Materials Science and Engineering been developed which is shown to be able to predict behaviors of closed-cell Al-alloy foams in much better agreement with the experimental results
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