Microstructure and mechanical properties of carbon fibre-reinforced alumina composites fabricated from sol

Alumina matrix composites reinforced with the laminated and stitched carbon fibre cloth preform were fabricated through the infiltration–drying–heating route using the ${\text{Al}}_2{\text{O}}_3$ sol with a high solid content as raw materials. The investigation was focussed on the characteristics of sol and the mechanical properties and high-temperature resistance of $\text{C}/{\text{Al}}_2{\text{O}}_3$ composites. $\alpha {\text{-Al}}_2{\text{O}}_3$ with favourable sintering activity can be obtained after heat treatment of sol at $1200{}^{\circ }\text{C}$. The as-received $\text{C}/{\text{Al}}_2{\text{O}}_3$ composites with a total porosity of 16.8% exhibit a flexural strength of 271.3 MPa and a notch toughness of 13.0 MPa ${\text{m}}^{1/2}$, respectively. As a result of the evolution of interface and matrix, the flexural strength of $\text{C}/{\text{Al}}_2{\text{O}}_3$ composites is decreased by 28.5% after heat treatment at $1600{}^{\circ }\text{C}$ for 1 h under inert atmosphere. At the same time, fracture mode of composites is transformed from tough to brittle behaviour.