R-CURVE BEHAVIOR AND THERMAL SHOCK RESISTANCE FOR Al_2O_3 CERAMIC MATRIX COMPOSITES

The crack growth resistance behaviors(R curve ) of Al 2O 3 SiC W and Al 2O 3 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 Al 2O 3 SiC W composite showed better damage tolerance and higher thermal shock resistance than Al 2O 3 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.