Damage resistance, R-curve behavior and toughening mechanisms of ZrB2-based composites with SiC whiskers and ZrO2 fibers

The damage tolerance and R-curve behavior of ZrB2-based composites with SiC whiskers and ZrO2 fibers were investigated by using the envelope method. Obvious R-curve behavior was further observed in these composites, as a result of the combined effect of whisker toughening and transformation toughening. The SiC whiskers with high aspect ratio exhausted more fracture energy by deflection, bridging and pull-out during failure, and promoted the transformation toughening of ZrO2 fibers. It was found that these interactions produced a notable increase in toughness to 8.2 MPa m1/2. The relatively contribution of each toughening mechanism was estimated. This calculated value was in good agreement with the experimental results (8.0±0.5 MPa m1/2) and the predictions of R-curve behavior (8.026 MPa m1/2).