Effect of friction between fiber and matrix on the fracture toughness of the composite interface

A method of evaluating the interfacial fracture toughness using a single-fi bre composite test is proposed. In contrast with the existing techniques, t he method takes into account the phenomenon of friction between the fibre a nd matrix in the debonding zone. A general mathematical solution of the pro blem and modelling of the friction phenomenon are presented. Finite-element analysis using a "contact" statement is utilized for numerical evaluation of the stress-strain state. The influence of the coefficient of friction an d interfacial debonding length is analysed in detail. It is shown that the friction reduces the calculated value of the elastic strain energy release rate for a given debonding length, relative to that obtained when friction is neglected. The magnitude of the difference depends on the coefficient of friction, the elastic properties of the fibre and matrix, and the characte ristics of the debonding mechanism. Experimental data on debonding in a ser ies of glass-epoxy single-fibre composites are analysed using the proposed numerical technique to obtain the effects of fibre surface treatments and f ibre strain-to-break on the interfacial fracture toughness. (C) Kluwer Acad emic Publishers.