Asymmetric behaviour of fibrous metal matrix composites

Experimental investigations have illustrated that unidirectional metal matrix composites (MMCs) show asymmetric behaviour under uniaxial tensile and compressive loading. This asymmetry occurs when the material is loaded along the fibre direction and also when loaded in the transverse direction. In this paper, results from finite element micromechanical models are presented. The models were used to study the asymmetric behaviour of unidirectional fibre reinforced MMCs subjected to longitudinal and transverse loading. The effects of the thermal residual stresses arising from the manufacturing process were included in the study. Also, the influence of the degree of bonding of fibre to matrix was examined, from perfectly bonded to completely debonded. Results reveal that thermal residual stresses are responsible for the asymmetric behaviour of the MMCs in the longitudinal direction. In transverse loading, both the degree of interface bonding and residual stresses account for the asymmetric behaviour. The predicted stress - strain response of the M M C shows good agreement with the available experimental data for both both tensile and compressive loading. Results also suggest that in order to predict accurately the yielding behaviour of MMCs, the current symmetric yield criteria require modification.