Biaxial cyclic analysis of Al(2)O(3)p-6061 Al composite

Proportional and non-proportional biaxial cyclic tests were carried out on cylindrical specimens of 20% Al(2)O(3)p 6061 aluminum alloy metal matrix composite in the TO (annealed) and T6 (quenched and artificially aged) conditions. These results were then compared to those found using a three-dimensional (3D) finite element analysis on a representative unit cell. A special material model, capable of accurately describing the behaviour of metals under multiaxial and non-proportional loads was used to simulate the elastic-plastic aluminum matrix. Comparison of unit cell results using sphere and cube shaped reinforcements shows that the unit cell using a spherical inclusion produces less hardening and lower yield stresses but agrees well with experimental values. Under cyclic equibiaxial loading the modulus of the annealed specimen was found to drop rapidly with increasing numbers of cycles. While the model was able to predict the initial hysteresis loops it could not represent the decrease in stiffness without the addition of further damage parameters. This change in the modulus is attributed to decohesion at the matrix-reinforcement interface. The model is much more accurate than the conventional kinematic and isotropic hardening models and predicts the overall composite behaviour fairly accurately.