Evaluation of strength anisotropy and fracture behavior of UD NITE-SiC/SiC composites with various fiber orientations

A SiC/SiC composite by Nano-infiltration and Transient Eutectic-phase (NITE) process is the attractive candidate materials for advanced energy systems, aero-space system. The NITE process is improved to the industrialization grade process from the laboratory grade process. In order to ensure reliability of products by NITE-SiC/SiC composites, understanding of the strength anisotropy is important. This paper presented the basic strength anisotropy knowledges of unidirectional (UD) type NITE-SiC/SiC composites with various fiber orientations by correlation evaluation of microstructure and mechanical properties. Also, the strength anisotropy evaluation of UD NITE-SiC/SiC composites utilizing the strength anisotropy prediction theories were discussed. The axial/off-axial mechanical properties of UD NITE-SiC/SiC composites by the industrialization grade process were evaluated by axial/off-axial tensile test. The mechanical properties of NITE-SiC/SiC composites fabricated tended to decrease with increasing of fiber orientation angle. The experiment results by axial/off-axial tensile test were consistent with the strength anisotropy prediction theories by the maximum normal stress theory and the Tsai-Hill criterion. Also, the failure mode of SiC/SiC composites fabricated with each fiber orientation angle was consistent with fracture surface observation results. The strength anisotropy of UD NITE-SiC/SiC composites was suggested to be able to predict by Tsai-Hill criterion. The basic strength anisotropy of UD SiC/SiC composites was understood.