BRENNAN: INTERFACIAL CHARACTERIZATION BN=B Fig 10 Crack propagation and subsequent oxidation for 815C tensile fatigue of Sylramic fiber MI SiC/SiC composite above the matrix microcrack stress(186 MPa, 54 h to failure) tn entire to Porosity concentrated in center of fibers Porosity is actually free carbon Fig. 11. Microstructural analysis of MI SiC/SiC composite with porous Sylramic SiC fibers(porosity actually of the Sylramic fibers went to completion. This cern was the potential moisture susceptibility of the appeared to solve the problem of rough surface Syl- BN interface between the Sylramic SiC fibers and the ramic fibers leading to poor composite properties MI SiC matrix at elevated temperatures. High-tem Since the goal of the HSCT/EPM SiC/SiC com- perature gas turbine combustor environments can posite program was the development of a high-tem- contain very high moisture contents under very high rature gas turbine combustor liner result of the fuel/air combustio4626 BRENNAN: INTERFACIAL CHARACTERIZATION Fig. 10. Crack propagation and subsequent oxidation for 815°C tensile fatigue of Sylramic fiber MI SiC/SiC composite above the matrix microcrack stress (186 MPa, 54 h to failure). Fig. 11. Microstructural analysis of MI SiC/SiC composite with porous Sylramic SiC fibers (porosity actually free carbon). of the Sylramic fibers went to completion. This appeared to solve the problem of rough surface Syl￾ramic fibers leading to poor composite properties. Since the goal of the HSCT/EPM SiC/SiC com￾posite program was the development of a high-tem￾perature gas turbine combustor liner, an area of con￾cern was the potential moisture susceptibility of the BN interface between the Sylramic SiC fibers and the MI SiC matrix at elevated temperatures. High-tem￾perature gas turbine combustor environments can contain very high moisture contents under very high pressures as a result of the fuel/air combustion pro-