Interfacial bond strength in SiC/C/SiC composite materials, as studied by single-fiber push-out tests

The interfacial characteristics of SiC/C/SiC composites with different fiber-coating bond strengths have been investigated using single-fiber push-out tests. Previous studies have shown that weak or strong bonds can be obtained by using as-received or treated fibers, respectively, and that the stress-strain behavior is improved with the treated fibers. This effect results from multiple branching of the cracks within the interphase. The model used to extract interfacial characteristics from nanoindentation and microindentation tests does not consider the presence of an interphase. However, the results highlight the significant effect of the interphase on the interfacial parameters, as well as the effect of roughness along the sliding surfaces. For the composite with treated fibers, the uncommon upward curvature of the push-out curves is related to different modes of crack propagation in the interphase. Different techniques are required to analyze the interfacial properties, such as nanoindentation and microindentation with pushout and push-back tests.