DETERMINATION OF INTERFACIAL PROPERTIES FROM OBSERVATIONS OF PROGRESSIVE FIBER DEBONDING AND PULLOUT

The characterization of the fiber/matrix interface or interphase regio n is important in accurately modeling the behavior of composites. Push out and pullout testing on single fibers are the two primary methods f or examining interfacial properties such as the coefficient of frictio n, residual stresses, interfacial strength or toughness, and the fiber roughness. In this study, single fiber pullout tests were performed o n silicon carbide fibers (SCS-2) embedded in a barium boro-silicate gl ass matrix. The samples were made by first passing the silicon carbide fibers through a flame and then sandwiching them between two pieces o f glass. The sandwich was then heated in air for 75 min at 850 degrees C under slight pressure. Relations between the length of the debond a nd the applied load (during progressive debonding) and between the emb edded length and the applied load during pullout were determined from the pullout tests. The transparency of the glass allowed the propagati on of the debond crack to be observed using an optical microscope. The roughness of the interface caused significant wearing during pullout.