Microstructure and mechanical properties of ALPORAS closed-cell aluminium foam

In recent years, closed-cell foam has drawn increasing attention in applications ranging from energy absorption devices to serving as the core material of light-weight structures. Although closed-cell foams are critical in many applications, the microstructural characteristics and mechanical properties of these foams are not fully understood. In this paper, we performed a comprehensive study on the commercially available ALPORAS closed-cell aluminium foam by means of experiment. First, inspection of the foam microstructure was systematically performed. Based on this inspection, the geometric features of the foam were characterised. Crushing experiments were subsequently conducted on specimens under various conditions to examine the effect of each of the testing parameters such as the specimen size and geometry as well as the loading direction, on the mechanical response of closed-cell foam. We found that the cells were irregular polyhedra with approximately 14 faces and that each face had approximately 5 sides. The cell wall was thinnest in the middle section, became increasingly thicker towards the edges, and eventually formed circular fillets as it intersected with neighbouring walls. The foam was geometrically and mechanically anisotropic. The factors that most influenced the mechanical properties were the loading direction and relative density. In this paper, we also compare the experimental results on the foam mechanical properties with existing equations from the literature.