Experimental analysis of compressive notch strengthening in closed-cell aluminum alloy foam

The notch strengthening effect is studied experimentally in closed cell aluminum foams. The limit loads, net section strength were found for a set of double-edge-notched (DEN) and single-edge-notched (SEN) specimens loaded in compression. In addition, the evolution of the deformation is monitored through a digital image correlation procedure. The influence of independently varying the net section width, b. and the crack length to width ratio, a/W is examined. The DEN specimens showed notch-strengthening behavior, while the SEN specimens were found to be notch-insensitive. From the plastic deformation measurements the dominant deformation mode for the SEN specimens was found to be a crushing/twinning mode. The constraint imposed on this twinning mode by the DEN geometry leads to the observed notch-strengthening behavior. A phenomenological model is developed to ratiorialize the observed strength enhancement for the DEN-specimens, featuring a dependence on the ligament width to cell size ratio, b/d. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.