In Situ measurement of the si-infiltration process of C/C-preforms and 3-D analysis of the resulting C/SiC microstructure

The quality of carbon-fibre reinforced silicon carbide (C-SiC) ceramic matrix composites (CMC) manufactured in the liquid silicon infiltration process (LSI) not only depends on the composition of the greenbody preform micro-structure, but is also influenced by the conditions during the melt infiltration process. Using the novel thermo optical in-situ measurement method TOM by Fraunhofer ISC, several changes during the infiltration process itself can be studied. These include variations in both the mass and temperature of the sample, as well as an observation of the advancing silicon front inside the specimens. During the infiltration process, the sample temperature increases due the exothermic formation of SiC, ultimately leading to a change of infiltration velocity. The in-situ observations are improved by the use of high-resolution X-Ray micro-computed tomography analysis. All specimens are analyzed before and after melt infiltration. The three-dimensional micro-structure permits detecting closed and open porosity as well as the damages occurring within the specimens.