Microstructure and Mechanical Properties of a Three‐Dimensional Oxide/Oxide Composite after Long‐Term Thermal Exposure

Herein, a three‐dimensional (3D) oxide fiber reinforced oxide matrix (oxide/oxide) composite is fabricated via slurry infiltration and sintering process. Subsequently, the effects of thermal aging on the microstructure and mechanical properties of the 3D oxide/oxide composite at 900 and 1100 °C are investigated. Experimental results indicate that the thermal aging affects the matrix microstructures and fiber/matrix interface. The elastic modulus of the matrix and interfacial shear strength increases with aging temperature and time. Aging treatment at 900 °C for 100 and 300 h results in a moderate decrease in the flexural strength and fracture toughness but improves the delamination resistance, whereas that at 1100 °C for 100 h lead to a significant decrease in the flexural strength and fracture toughness. The changes in mechanical properties might be attributed to matrix densification and enhanced interfacial bonding. A three‐dimensional oxide/oxide composite was prepared via slurry infiltration sintering process and thermally aged at 900 and 1100 °C. Thermal aging strengthened the local matrix and interface while increased the matrix microcracks. Interlaminar shear strength increased but flexural strength and fracture toughness decreased. The decrease in fracture toughness was attributed to the lower elastic modulus ratio and increased interfacial bonding.