Interfacial debonding and sliding in brittle-matrix composites measured using an improved fiber pullout technique

A modified fiber pullout technique has been developed which allows direct experimental evaluation of the force-displacement relation for a crack-bridging fiber. The technique allows a continuous, accurate measurement of stable, progressive interfacial debonding and frictional sliding. Coupled with an appropriate analysis, the test provides a quantitative determination of interfacial properties relevant to the toughening of brittle materials through fiber-reinforcement. The technique has been used to measure interfacial debonding and sliding in three SiC fiber/glass composite systems. The fibers differ primarily in diameter and surface roughness characteristics allowing a unique evaluation of the effects of these parameters. The results indicate that fiber surface roughness plays a significant role in the interfacial debonding and sliding behavior. Load fluctuations observed during both monotonic and cyclic loading are explained by invoking the concept of asperity-asperity interaction during sliding at a rough interface.