Effect of C/SiC interphase on interfacial and mechanical properties of SiC fiber reinforced mullite matrix composites

Continuous SiC fiber reinforced mullite (SiCf/Mu) matrix composite was fabricated via sol–gel process. The capability of fiber coatings to weaken the interfacial interaction, thus to enhance the fracture toughness of the SiCf/Mu composite was explored. The results show that the SiC interphase fabricated by chemical vapor deposition (CVD) process was columnar-grain structured. A thin carbon layer was also produced during the CVD process, forming C/SiC interphase. The interfacial shear strength of the SiCf/Mu composite was significantly reduced from ≈537 to ≈115 MPa after the introduction of C/SiC interphase, as quantified by in situ fiber push-in tests. Accordingly, the macro fracture toughness of the composite was remarkably enhanced from ≈0.9 to ≈10.5 MPa m1/2. The work highlights the efficiency of using C/SiC interphase to weaken the interfacial bonding, thus greatly toughen the SiCf/Mu composite.