Keywords: Ni/Al hybrid metal foam, microtensile test, nanoindentation, molecular dynamic simulation, open-cell metal foam, composites.

Metal foams are bio-inspired cellular materials used for lightweight construction or as energy absorbers. As a result of their microstructure, the mechanical properties strongly depend on the properties of the strut material. In this paper, the properties of the so-called Ni/Al hybrid foams, consisting of pure aluminium foams electrochemically coated with nanocrystalline nickel, are evaluated on different hierarchical levels. The mechanical properties of Ni/Al hybrid foams are characterised by experiments and numerical modeling at different scales. The local mechanical properties of both the nickel coating and the aluminium alloy are measured by means of nanoindentation coupled with electron backscatter diffraction to gain information on the grain structure. Molecular dynamic simulations of nanoindentation on different structured nickel atom clusters were performed to attain a deeper understanding of the measured and identified properties. Furthermore, microindentation tests were performed to compare the results with the localised nanoindentation. Microtensile tests on real struts were performed to achieve a homogeneous elastic-plastic behaviour of the Ni/Al composite. Hence, we compare the local properties of the Ni coating and the Al strut at nanoscale with the global stress-strain behaviour of the Ni/Al composite at microscale. The results obtained from the microtensile experiments were compared with finite element simulations on single struts.

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