Triaxial Failure of Aluminium Foams
Aluminium foam is a type of cellular materials and offers potential for lightweight structures and energy absorbers in automotive and aerospace industries. They may be subject to multiaxial loads in these applications and it is essential to have a failure criterion in terms of the stresses which cause yield. Three criteria have been proposed so far. Gibson and Ashby deduced a yield surface by using dimentional arguments for ideal, isotropic, homogenous foams. Miller’s yield surface was based on the model of Drucker and Prager, which was originally proposed as a model for soil. It incorporated a linear and quadratic dependence on the pressure. Deshpande and Fleck modified the yield criterion of solid metals to account for the effect of porosity on the yield criterion for a metallic foam. In this paper, triaxial tests of CYMAT aluminium foams were conducted by using MTS (Mechanical Test System) with a Hoek Cell to investigate their yield surfaces experimentally. Five types of aluminium foams with nominal relative densities. of 5%, 10%, 15%, 17% and 20% were tested for a range of axisymmetric compressive stress states. Experimental results were compared with three theoretical criteria. Triaxial tests at various strain rates (from 10−4 to 10+1 s−1) were also performed in this paper to investigate the influence of strain rate on the yield surface.