STRAIN RATE DEPENDENT DEFORMATION AND FAILURE PROCESS OF MAGNESIUM FOAMS

Lightweight closed-cell magnesium foams have the potential to dissipate impact energy in automotive and aerospace structures which are subjected to ballistic and impact loads. This work investigated the strain rate dependent compressive deformation and failure process of closed-cell Mg foams fabricated by the direct foaming process. The split-Hopkinson pressure bar technique with high speed imaging was used to characterise the dynamic response which was then compared to the measured quasi-static behaviour. The shape of the dynamic stress strain curve is similar to that at low strain rates. However, both the peak and plateau stresses increase with the strain rate. It was found that under quasi-static compression the damage evolution in the foam causes several big fragments, while at high strain rates the extensive cracking in the foam results in a large quantity of small fragments, thus dissipating more impact energy.