Size effects and the shear response of aluminum foam

Aluminum foam samples produced by the melt route were subjected to static and quasi-static low-rate shear deformation using a specially designed loading fixture. Characteristic response curves are presented for a range of relative densities (3.1-15%). For the range of densities examined, the shear modulus shows a linear dependence on relative density, while the ultimate strength follows a non-linear power law. Over the range of strain rates examined, the aluminum foam shear response is shown to have no rate dependence in the linear regime, while the ultimate strength and energy absorption are strain rate dependent, increasing by 24% and 63%, respectively. Size effects in shear deformation are examined with optical techniques through which the average shear strain is calculated over sub-regions of the sample. The strain in these sub-regions deviates significantly from the global applied strain for regions smaller than 18 mean cell diameters, indicating a critical specimen size, below which certain bulk properties are no longer representative.