Abstract
The interfacial properties of three dimensional (3D) Nextel™440 fiber-reinforced silica (N440/SiO2) ceramic matrix composites containing a single layer pyrocarbon (PyC) interphase were investigated. The fiber/matrix bonding was characterized by the fiber push-in tests. The results showed that the PyC interphase can significantly weaken the interfacial bonding. The three-point bending tests indicated that the PyC interphase played a key role in the strength improvement of the composites. The fiber/matrix interface was observed by SEM and TEM in order to clarify the mechanism. Microstructure analysis revealed that the PyC interphase was chemically inert to the fiber and the matrix, and that the interfacial reaction was dramatically restrained. Moreover, the inherent layer structure of PyC proved to be very beneficial for crack deflection. Finally, the weakening occurred between the fiber and the coating, between the coating and the matrix, and within the coating.
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