Correlation of Microstructure and Compressive Strength of C/C Composite Using X-ray Tomography

For the control rod element of a Very High Temperature Reactor, carbon fiber reinforced carbon matrix composite (C/C composite) is one of the major candidate materials for its high strength and thermal stability. In this study, in order to correlate the microstructure of the C/C composite to its compressive strength, the X-ray tomography was applied to visualize the internal microstructure of the C/C composite. The relationship between change in the compressive strength and that in the microstructure was also investigated. This study showed that the pore distribution in the C/C composite could be confirmed visually and the volume and shape of the pores could be evaluated by the X-ray tomography in three-dimension. Moreover, since the matrix was gradually lost and transverse cracks became large with increasing the oxidation, the bonding strength between fiber bundles became weak and the compressive strength of parallel to lamina decreased.