Experimental analysis of deformation mechanisms in a closed-cell aluminum alloy foam

The evolution of plastic deformation in a cellular Al alloy upon axial compression is monitored through a digital image correlation procedure. Three stages in the deformation response have been identified. The first involves localized plastic straining at cell nodes, It occurs uniformly and leads to a nominal loading modulus appreciably lower than the stiffness, The second comprises discrete bands of concentrated strain containing cell membranes that experience plastic buckling, elastically constrained by surrounding cells. In this phase, as the loading increases, previously formed bands harden, giving rise to new bands in neighboring regions. The localized bands exhibit a long-range correlation with neighboring bands separated by 3-4 cells along the loading direction. This length scale characterizes the continuum limit. Thirdly, coincident with a stress peak, sigma(o), one of the bands exhibits complete plastic collapse. As the strain increases, this process repeats, subject to small stress oscillations around sigma(o). (C) 2000 Elsevier Science Ltd. All rights reserved.