C/C-SiC is conventionally fabricated by gaseous or liquid based routes. That means, a gaseous or liquid carbon precursor is required to impregnate C-fiber bundles or preforms.
Within this study, a new approach show, the possibility to integrate a solid C-matrix-precursor (as powder and/or fibers) into a carbon fiber bundle, which ease the impregnation, especially for > 12k significantly. The obtained, so called hybrid yarn, is known from organic fibers and was transferred some years ago to CFRP with matrices like PA 6.
The advantages of this approach are, e.g. the adding of the required amount of the solid matrix into a C-fiber bundle. Furthermore, powdered additives could be evenly distributed within the hybrid bundles. Furthermore, this method enable the rework of irregular shaped recycled carbon fiber qualities (rCF), and the following fabrication of endless C-yarns that may include the new matrix polymer.
In this work, PEEK matrix fibers were selected for a suitable carbon residue after the pyrolysis, a part of the applied LSI-process. 12k-carbon fiber rovings were chopped to about 60-80 mm length, mechanically opened and mixed in a complex textile technique with 60 vol. % PEEK-fibers (length: 60 mm). Finally, the continuous hybrid roving was wrapped by a nylon 6 filament, in order to gain the hybrid yarn.
The obtained hybrid yarn was again chopped into 12 mm long sticks. Several plates with 100x100x3 mm^3 were fabricated, with applying these chopped hybrid yarns. Additionally, 30x10x3 mm^3 samples with endless hybrid yarns were fabricated.
The CFRP plates were warm pressed up to 350 °C, subsequently pyrolyzed > 900 °C (nitrogen resp. vacuum) and afterwards infiltrated with liquid silicon > 1420 °C (vacuum). Finally, the microstructure by optical microscopy, the densities, porosities, the flexural and tensile strength of the obtained materials were studied and potential of this approach discussed.