Influence of long-term thermal aging on the microstructural and tensile properties of all-oxide ceramic matrix composites

The mechanical properties of Nextel (TM) 610-reinforced ceramic composites in the on-axis direction after a long-term thermal exposure at 1200 degrees C for 200 h are studied using tensile tests. To clarify the mechanisms underlying the effects of thermal exposure on the macromechanical properties of oxide/oxide ceramic matrix composites, variations in the microstructure and micromechanical properties of these materials (including the fibre grain size and the porosity distribution) are analyzed. Grain coarsening is the most significant feature arising from heat treatment and porosity decreases with increasing heat-treatment time. The dimensions and weight of the specimen also decrease. Given the microstructural changes observed after heat treatment, a model based on mesoscopic-scale approaches is proposed to clarify the influence of thermal exposure on the mechanical properties of the composite, including its stiffness, ultimate failure modes, and strength.