Mechanical degradation mechanisms of 2D-C/SiC composites: Influences of preloading and oxidation

In this paper, mechanical degradation of a pre-stressed 2D-C/SiC composite subjected to high temperature oxidation was studied experimentally and theoretically. The experimental results show that the retained properties were closely related with the preload induced damage and the oxidation time. During high temperature oxidation, specimen with relatively large residual strain lost much of its stiffness and strength, becoming soft and weak, and its fiber pullout was quite long. Through SEM observations, interfacial degradation mechanisms involving two factors were found as interphase fusion and interfacial stress relaxation. Micromechanical model based on the oxidation mechanisms was developed to predict the residual modulus and strength, and accurate simulated results were obtained. The correlation between the retained properties and fiber pullout modes reveals that interfacial degradation in C/SiC composites is one of the potential issues in its industrial applications.