Effects of SiC sub-layer on mechanical properties of Tyranno-SA/SiC composites with multiple interlayers

SiC/SiC composites with single pyrolytic carbon (PyC) interlayer generally show significant strength degradations in oxidation/irradiation environments due to the poor oxidation/irradiation resistance of the PyC interlayer. Incorporating SiC sub-layers in the PyC interlayer (SiC-PyC)n multilayers has been proved effective on improving the oxidation/irradiation resistance of the materials. However, it remains unclear whether such stiff SiC sub-layer will cause decrease of the mechanical properties of a SiC/SiC composite, especially for newly developed advanced Tyranno-SA fibers reinforced one. In this study, two plain-woven Tyranno-SA/SiC composites with designed fiber/matrix interlayers of 100 nm PyC and 50 nm PyC + 150 nm SiC + 50 nm PyC, respectively, were fabricated to investigate the effects of the stiff SiC sub-layer on the mechanical properties. The results showed that the SiC sub-layer caused much higher interfacial shear strength (ISS) in the composite. However, the two composites exhibited a similar level of proportional limit stress and ultimate flexural strength.