ON THE EFFECTS OF FRICTION, ROUGHNESS AND TOUGHNESS ON INTERFACIAL SLIDING IN BRITTLE COMPOSITES

This computational analysis investigates the interaction between frict ion, roughness and toughness at interfaces with regard to sliding leng ths which proceed from the tip of an impinging matrix fracture. Slidin g lengths at interfaces are important to the fracture behavior of brit tle fibrous composites. The computer model uses a two dimensional surf ace integral formulation to model a crack perpendicular to a nominally planar interface. The tractions at the interface satisfy a Coulomb re lationship and are found through an iterative process involving the st ress induced by the matrix crack, the stress induced by the developing slip and an initial normal compressive stress (presumed to result fro m setting and/or thermal coefficient mismatch). The interfacial roughn ess is simulated using surface integral elements arranged in a periodi c, triangular array. The toughness of the interface is represented via a specialization of the surface integral formulation to embed the nea r-tip, elastic asymptotic solution. The results indicate that there ar e significant interaction effects between friction and the other param eters, i.e. the friction dictates the sensitivity of the sliding lengt hs to changes in interfacial toughness and roughness. Also, to achieve 'long' sliding lengths, which may be desirable in reducing the stress concentration in the medium across the interface, the magnitude of th e interfacial critical energy release rate must be significantly less than the magnitude required to ensure crack deflection. (C) 1998 Elsev ier Science Ltd.