Carbon fiber reinforced silicon carbide (C/C-SiC) is a non-oxide ceramic matrix composite that is applied, e.g., in engine nozzles for space applications or automotive brake discs. C/C-SiC is produced via the liquid silicon infiltration process, in which a carbon fiber reinforced polymer (CFRP) is first manufactured, then pyrolyzed under inert conditions at temperatures above 1000 °C to a carbon fiber reinforced carbon (C/C), and eventually siliconized under vacuum above 1420 °C.

To obtain a C/C-SiC with favorable mechanical properties, it is crucial to create a CFRP with a good fiber bundle infiltration (FBI). Thermosets such as phenolic resin are usually used as matrix materials. This is because of their low melt viscosity, which allows the resin to infiltrate even thick carbon fiber bundles.  However, thermosets show several disadvantages such as pore formation due to gas evolution during the crosslinking process. In addition, thermoset materials are not recyclable. Thus, the use of thermoplastics such as polyether ether ketone (PEEK) is of interest. Nevertheless, the high melt viscosity of thermoplastics leads to problems regarding the FBI.

To overcome this problem, in this study C/C-SiC based on a novel developed short fiber hybrid yarn is investigated. It is shown for the first time that C/C-SiC can be fabricated from hybrid yarn. The fiber bundles of the yarn consist of C- and PEEK fibers. The yarn is warm pressed at about 400 °C to a CFRP, pyrolyzed and infiltrated with silicon. Microstructural analyses show a desired FBI with PEEK in the CFRP, a low amount of silicon and a homogenous SiC-network in the C/C-SiC state. The microstructure of the C/C, analyzed by using µ-CT and Hg-porosity, showed a fine and homogeneous crack network with a median pore diameter of 11.9 µm. Phase analyses by XRD confirmed the low Si (11 vol. %) and high SiC content (26 vol. %). Three point bending tests revealed a pseudo-ductile behavior with a Young’s modulus of 28 ± 5 GPa, a strain to failure of 0.4 ± 0.1 % and a flexural strength of 97 ± 13 MPa. Furthermore, SEM images were conducted to investigate the fracture surface of the three point bending tested sample and to explain the results gained from the mechanical testing.