Mechanical and oxidation resistance properties of 3D carbon fiber-reinforced mullite matrix composites prepared by sol–gel process

The 3D carbon fiber-reinforced mullite matrix (3D-Cf/mullite) composites were fabricated via sol–gel process, using mullite sols with high solid content as precursor. The mullitizaiton process of mullite sols was investigated with XRD and TEM. The results showed that the sol was transformed into orthorhombic mullite at 1300 °C with a trace of amorphous SiO2 between crystals of mullite. The flexural strength, fracture toughness and interlaminar shear strength of 3D-Cf/mullite composites were 277.6 MPa, 12.3 MPa m1/2 and 36.3 MPa, respectively. The 3D-Cf/mullite composites exhibited a significant tough fracture behavior. The oxidation resistance of 3D-Cf/mullite composites was examined. It can be found that the strength retentions of 3D-Cf/mullite composites were 62.9%, 84.8% and 13.6% after oxidation at 1300 °C, 1500 °C and 1700 °C, respectively. The strength transformation was interpreted with the microstructure analysis of oxidized 3D-Cf/mullite composites at different temperatures.