DEBONDING MECHANISMS IN THE PRESENCE OF AN INTERPHASE IN COMPOSITES

The debonding mechanism of an interphase in layered and fiber-reinforc ed composites was investigated with an emphasis on crack deflection an d penetration. A single-edged notched model consisting of three phases was analyzed by the boundary element method. The dependence of elasti c fields involved in the model on elastic constant combinations was re vealed. Interfacial debonding other than the competition between crack deflection and penetration may be initiated due to the high tensile a nd shear stress concentration before a main crack propagates to meet t he next interface. The ratio of energy release rates for infinitesimal deflecting and penetrated cracks, defined as R = G(d)/G(p). was compu ted when a main crack reached an interphase interface. The results obt ained modified those for two-phase models. Discussion regarding fractu re sequences observed in Ti-15-3 alloy reinforced with unidirectionall y aligned SCS-6 fiber was made. (C) 1998 Acta Metallurgica Inc. Publis hed by Elsevier Science Ltd. All rights reserved.