Evaluation of Bridging Stress from R?Curve Behavior for Nontransforming Ceramics

Bridging stresses at the crack interface behind the crack tip are calculated for nontransforming ceramics which show increasing toughness with crack extension (R?curve behavior). With this approach, bridging stresses can be related analytically to the experimental R curve. Sample calculations for SiC?whisker?reinforced Al2O3, with a bridging?zone length of >0.5 mm, are shown in the present study. The results indicate that the bridging stress has a maximum value within a short distance (<0.01 mm) behind the crack tip and then decreases to 0 or levels off to a finite value at the end of the bridging zone depending upon the nature of the R?curve behavior. Copyright ? 1988, Wiley Blackwell. All rights reserved