Interfacial Stress Singularities at Free Edge of Hybrid Metal Matrix Composites

Novel hybrid-matrix composites with alternating metallic matrices of different plastic flow resistance offer excellent potential for a superior strength and toughness combination than traditional monomatrix composites. The local stress concentrations in this class of composites can be controlled by proper tailoring of the metal matrices. The free edge accentuated stress state which govern inter-matrix interfacial cracking in such hybrid metal matrix composites has been solved. Determined through asymptotic expansion and numerical methods, the local decohesion stress, σ_θθ, is found to be always positive for far field tensile loading. The power of the stress singularity is found to depend on the ratio of the plastic resistances of the two matrix metals. A larger difference in resistance to onset of plastic flow between the two matrix metals leads to stronger stress singularity. The work hardening behavior of the matrices also affects the power of the stress singularity. At the limit, the interfacial stress becomes nonsingular for non-workhardening matrices. Detailed results of both the power of the stress singularity, and its angular variation have been determined for a range of matrix combinations.