Finite element modelling of residual stresses and strength differential effect in discontinuously reinforced metal matrix composites

A finite element analysis is carried out on the development of residual stresses during the cooling process from the fabrication temperature in discontinuously reinforced metal matrix composites. The strength differential in subsequent compression and tension from the residual stress state is also analysed. The analysis employs three-dimensional models within the framework of unit cell assumptions with spherical, ellipsoidal and cylindrical SiC fibres in an Al matrix as test cases. The effect of morphology, aspect ratio, volume fraction and end-to-end spacing of the fibres on microscopic stress and strain distribution, plastic zone development at the matrix-particle interface and macroscopic mechanical properties of the composite is studied. The magnitude of the strength differential is shown to be highest for cylindrical fibre morphology and increases with fibre aspect ratio and volume fraction and to some extent with fibre end-to-end spacing. The results are compared with the available experimental data and an analytical model.