Creep-rupture behaviour of notched oxide/oxide ceramic matrix composite in combustion environment

Creep-rupture tests were performed in the combustion environment on double-edge notch and centre hole oxide/oxide ceramic matrix composite specimens. The specimens were exposed to the maximum temperature of 1250 ± 50°C in the notch region where the combustion flame directly impinged. Specimens were loaded to the desired creep load levels and the loads were sustained till either the specimens ruptured or a run-out time of 25 h was achieved. Optical and scanning electron microscopes were used to characterise specimen damage. The test results were compared to its counterparts in 1200°C (isothermal) laboratory air environment. At a given creep life, the applied creep stress for both the notch types was generally lower in the combustion environment than the laboratory air environment. Finite element simulations attributed lower applied creep stress in the combustion environment to the presence of thermal gradient stresses, which were not present in the isothermal laboratory air environment.