Tensile strength of chemical vapor infiltrated advanced SiC fiber composites at elevated temperatures

SiC/SiC composites composed of high-crystalline, near-stoichiometric SiC fiber, like Hi-NicalonTM Type-S and TyrannoTM-SA, are promising structural materials for fusion and other high-temperature applications, because of their excellent chemical, physical and mechanical stabilities at high-temperature. In order to explore show the excellent performance of recently developed advanced SiC/SiC composites under severe environment and to identify the key issues for the further material development, room- and high-temperature tensile tests were conducted under the mild oxidizing environment at 1300degC for TyrannoTM-SA fiber reinforced SiC matrix composites with two kinds of the fiber and matrix (F/M) interphase: pyrolytic carbon (PyC) and SiC/PyC, fabricated by the forced-flow/thermal-gradient chemical vapor infiltration (F-CVI) method. Tensile strength of both composites was significantly stable to high-temperature exposure up to 1300degC in mild oxidizing environment, with no clear difference for two interfacial structures. Also there was no dependence of PyC thickness on tensile strength for both interphase systems. In order words, the rough surface of TyrannoTM-SA fiber had the same role with the SiC pre-coating. (author)