Slurry material extrusion of chopped carbon fiber reinforced silicon carbide ceramic matrix composites (CMCs)

Silicon carbide (SiC) is a useful high temperature ceramic due to its excellent mechanical properties and oxidation resistance. In this study, monolithic SiC and chopped carbon fiber reinforced (Cf)/SiC ceramic matrix composites (CMCs) were additively manufactured via direct ink writing (DIW). Samples employing five different print paths were prepared from SiC and 10 vol.% Cf/SiC inks. All parts were pressurelessly sintered, with relative densities of 96% measured for samples prepared from both inks. Electron and optical microscopy were used to show a high degree of fiber alignment parallel to the direction of the print. Thus, CMC architectures consistent with the print paths were created when printing the 10 vol.% Cf/SiC inks. Characteristic flexure strengths for monolithic SiC and 10 vol.% Cf/SiC CMC samples were the same for the 0 degrees print path, measuring 360-375 MPa. Fiber pullout was observed on the fracture surface of the 10 vol.% Cf/SiC CMCs. The Weibull modulus for the 10 vol.% Cf/SiC CMC samples (10.7) was greater than the monolithic SiC samples (7.4); the trend of fibers narrowing the distribution of failure strengths was consistent for the other print paths investigated.