On crack, rigid-line fiber, and interface interactions

Interactions among cracks, rigid-line fibers, and the interface between dissimilar materials is the focus of this paper. The interface may also include point defects. An integral equation formulation capable of handling general crack-fiber-interface interactions is developed here. It is observed that an interface can significantly alter the nature of interactions among cracks and rigid-line fibers. As an example, the inner-tip stress intensity factors (SIFs) for a collinear crack system may be reduced, in the presence of an interface, to less than the outer-tip SIFs. Mixing of Mode-I and Mode-II behaviors due to interactions and their effects on stress amplification and retardation are also investigated. The effects of fiber reinforcements on crack propagation are investigated on two different scales, using a detailed local analysis as well as a micromechanical approach. The results suggest that detailed local analyses are necessary for an accurate understanding of crack-tip behaviors. A bi-material interface is assumed in the present analysis. Thus, it is suitable for composite materials with relatively large-scale inhomogeneity, where cracks and fibers can coexist, or with sublevel microcracking near reinforcements.