Volume 33, Issue 5 (September 2005)
Hoop Tensile Properties of Ceramic Matrix Composite Cylinders
Tensile stress-strain properties in the hoop direction were obtained for 100-mm diameter ceramic matrix composite cylinders using ring specimens machined from the cylinder ends. The silicon carbide fiber-reinforced silicon carbide matrix composite (SiC/SiC) cylinders were fabricated from 2D balanced SiC fabric with several material variants, including wall thickness (6, 8, and 12 plies), SiC fiber type (Sylramic, Sylramic-iBN, Hi-Nicalon, and Hi-Nicalon S), fiber sizing type, and matrix type (full CVI SiC, and partial CVI SiC plus slurry cast + melt-infiltrated SiC-Si). Cloth ply splices existed in all the hoops. Tensile hoop measurements were made at room temperature and 1200°C using hydrostatic ring test facilities. Room temperature hoop strengths for the various cylinders were generally similar and at 1200°C, ultimate strengths and strains of the hoops were about 70 % of their room temperature values, and elastic moduli were about 90–100 % of their room temperature values. The hoop properties are compared with in-plane data measured on flat panels using same material variants, but containing no splices. A lower strength and failure strain of hoops compared to panels was observed and was due to a stress concentration associated with the cloth splice geometry. The failure mode of the hoops, determined through microstructural examination, revealed that a fracture surface always existed at the cloth ply splice on the inner diameter of the failed specimens.