R-CURVE BEHAVIOR AND THERMAL SHOCK RESISTANCE FOR Al₂O₃ CERAMIC MATRIX COMPOSITES

The crack growth resistance behaviors(R-curve ) of Al₂O₃-SiC_W and Al₂O₃-TiC_P ceramic matrix composites were determined by the indentation-strength method. The properties of the thermal shock resistance of the two materials were also estimated. The relationship between the R-curve and the thermal shock resistance of the materials was discussed. The properties of the thermal shock resistance increased with the increasing steepness of the R-curve gradient. Both materials exhibited rising R-curve behavior and improved thermal shock resistance. The Al₂O₃-SiC_W composite showed better damage tolerance and higher thermal shock resistance than Al₂O₃-TiC_P composites. SEM observation and theoretical analysis indicate that these phenomena can be attributed mainly to the principle toughening mechanism of pull-out and bridging of the SiC whiskers.