Role of fiber-matrix adhesion at CFRP stage on microstructure and mechanical properties of C/C-SiC composite

In order to understand the role of fiber-matrix adhesion (FMA) at carbon fiber-reinforced polymer (CFRP) stage on the microstructure and mechanical properties of C/C-SiC composite via liquid silicon infiltration (LSI) process, the FMA was adjusted by thermal treatment of carbon fibers at different temperatures and evaluated by means of single fiber push-out technique. The microstructure was characterized by optical microscopy and scanning electron microscopy. The mechanical properties were measured by the double-notched shear test, three-point flexural test, and single edge-notched beam test, respectively. Results indicated that the microstructure and mechanical properties of C/C-SiC composite via LSI were closely associated with the FMA at CFRP stage. The microstructure of C/C-SiC composite fabricated by using the CFRP with high FMA presented nonhomogeneous distribution and concentration of SiC matrix. In contrast, the C/C-SiC composite fabricated by using the CFRP with low FMA, the high content of SiC distributed homogeneously and surrounded the fiber, which resulted in a strong bonded C-SiC interface. The strong C-SiC interface is detrimental to the fracture toughness, but it is beneficial to the improvement of oxidation resistance. To obtain desired mechanical properties of C/C-SiC composite, the control of interface bonding is important, which can be realized by modifying the FMA at CFRP stage.