Effects of the fiber surface characteristics on the interfacial microstructure and mechanical properties of the KD SiC fiber reinforced SiC matrix composites

SiC fiber reinforced SiC matrix (SiCf/SiC) composites, employing two types of KD SiC fibers (from National University of Defense Technology, China) with different fiber surface characteristics as reinforcements, were fabricated by precursor infiltration and pyrolysis (PIP) process. The fiber surface characteristics were evaluated by SEM, XPS and Raman analysis. The effects of fiber surface characteristics on the interfacial microstructure and mechanical properties of the KD SiCf/SiC composites were investigated. The results show that the tensile strength of the KD-2 SiC fibers (with silicon-based oxide surface layers) is about 85% that of the KD-1 SiC fibers (with pyrocarbon (PyC) surface layers), but the flexural strength of the KD-2 SiCf/SiC composite is only around 15% that of the KD-1 SiCf/SiC composite. SEM, TEM and elemental mapping analysis show that the large strength difference between the two composites is ascribed to the interfacial microstructure and the degree of fiber damage, which are arising from the different fiber surface characteristics.