Notch effects in metal foams

The effect of notches on the macroscopic strength of a closed cell Al alloy foam is studied experimentally and numerically. The macroscopic strength of the foam showed a dependence on the crack length to width ratio (a/W). The observed behavior is compared with 2-D finite element simulations, employing pressure sensitive constitutive relations. The numerical model was shown to predict no notch strengthening for a range of practically relevant parameters of closed cell Al foams. To predict the experimentally-observed notch strengthening an approximate analytical relation is proposed, which relates the strengthening behavior to a strain gradient effect.