Study on Microstructures of 2D and 3D Chemical Vapor Infiltration SiC/SiC Composites

The chemical vapor infiltration (CVI) SiC/SiC composites are porous materials, and the porosity affects the molten salt infiltration and may affect the mechanical properties. Therefore, the internal microstructures of the 2D and 3D silicon carbide composites are studied by synchrotron radiation micro-computed tomography (micro-CT) technology. The cross-sectional slice and 3D volume image of the composite are reconstructed, then the pores of the composites are visualized in three dimensions, and the porosity is quantitatively analyzed. The results indicate that most of small pores (micrometer) exist between filaments and larger pores (millimeter) occur between fiber bundles, and the internal pores of 2D and 3D composites are greatly influenced by the fabric structure. In contrast, the 3D braided composites have lower porosity, smaller pore distribution fluctuations, and more stable internal structure.