Tension-Tension Fatigue of 2.5D-SiC/SiC Ceramic Matrix Composites at Elevated Temperatures

Abstract

In order to investigate the influence of Tension-tension fatigue behavior of fiber reinforced ceramic-matrix composites, SiC/SiC composites with 2.5D fiber architecture were prepared via Precursor Infiltration and Pyrolysis (PIP) method. Tension-tension fatigue behavior of SiC/SiC composites was investigated in 1000°C and 1200°C, under fatigue stresses ranging from 70 to 120MPa at a frequency of 1.0 Hz, under oxidizing atmosphere. Fatigue life of SiC/SiC composites achieved 305, 984 cycles at 1200°C/70MPa, and 252, 988 cycles at 1200°C/108MPa, which were longer than test in 1000°C. Composite microstructure, as well as failure mechanism was investigated. The main reason that cause tension-tension fatigue failure of SiC/SiC composites are oxidation damage and stress damage. The microstructure of SiC/SiC composites demonstrated that the oxidation of interfaces and SiC fibers caused the failure of the composites. Under the load of alternating stress, the original voids and cracks in the material preparation process will be widened, and new cracks will be generated, for cracked SiC/SiC composites, oxygen in is especially serious at intermediate temperatures(∼800°C) where it can reach the SiC fiber before being sealed off by slow-glowing silica on the matrix crack surface, therefore, tension-tension fatigue life of SiC/SiC composites at 1000°C is lower than 1200°C.