Nondestructive evaluation of microstructure of SiC_f/SiC composites by x-ray computed microtomography

Continuous fiber-reinforced ceramic matrix composites (CFCCs) have a complex distribution of porosity, consisting of interfiber micro pores and interbundle/interply macro pores. Owing to the complex geometry of the pores and fiber architecture, it is difficult to obtain representative microstructural features throughout the specimen volume with conventional, destructive ceramographic approaches. In this study, we introduce X-ray computed microtomography (X-ray μCT) to nondestructively analyze the microstructures of disk shaped and tubular SiC_f/SiC composites fabricated by the chemical vapor infiltration (CVI) method. The disk specimen made by stacking plain-woven SiC fabrics exhibited periodic, large fluctuation of porosity in the stacking direction but much less variation of porosity perpendicular to the fabric planes. The X-ray μCT evaluation of the microstructure was also effectively utilized to improve the fabrication process of the triple-layered tubular SiC composite.