Temperature dependency of strength of a unidirectional Sic fiber-reinforced (BaSr)Al2Si2O8 celsian composite

Temperature dependency of strength of a high Nicalon-(BaSr)Al2Si2O8 (BSAS) celsian composite was studied between room temperature and 1100 degrees C by the three-point bend test. Test results showed that there is a definite transition in the failure mode with temperature. Up to about 800 degrees C, tensile was the dominant failure mode. Above 800 degrees C, however, the shear failure became prominent. It was shown that mode shift and rapid degradation of shear strength is due to the softening of the untransformed glassy phase in microstructure. The failure mode also exhibited a strong dependency on the L/h ratio of test specimen; large Lih ratio favored the tensile failure, while small L/h ratio promoted the shear failure.