An approximate representation of fiber-matrix debonding in nonperiodic metal matrix composites

This paper presents a fiber-matrix debonding model for metal matrix composites based on a modified Needleman (1987) type cohesive zone model. In this model the fiber-matrix interface is fully described by its strength and ductility under normal and shear loading. Debonding initiates when a quadratic interaction of the interfacial tractions attains a critical value (the interfacial strength). Complete interfacial separation occurs when the magnitude of the resultant interfacial displacement exceeds the ductility of the interface. The debonding model is implemented in the method of cells micromechanical model of Aboudi (1987). The response of composites having nonperiodic microstructures is predicted by taking an alternate view of the representative volume element. That is, the interface must be representative of the conglomerate of interfaces throughout the composite. Nonperiodicity is described by a single parameter that accounts for the distribution of stress concentrations at various interfaces throughout the composite. The effects of nonperiodicity are illustrated and predictions presented for transverse tensile and axial shear loadings, then compared with experimental results. The model is observed to accurately predict the 3-stage deformation response typical of silicon carbide/titanium composites subjected to transverse tensile loading.