Alumina-mullite-zirconia composites obtained by reaction sintering Part II. R-Curve behavior

Applying Linear Elastic Fracture Mechanics equations and sample compliance variation to quantify the instantaneous crack length, the R-curve behavior of alumina-mullite-zirconia composites obtained by reaction sintering, was evaluated as a function of zirconia and mullite content. Changes in the R-curve profile as a function of the notch geometry (Chevron and straight-through notch) was observed and discussed, based on the analysis of the y() function applied to each notch type. The influence of the y() function in the R-curve shape was observed in both the initial and the final crack propagation region where, in the latter, the R-curves presented a sharp increase. In order to suppress these effects, the R-curve values for pure alumina were deducted from those obtained for the different composites produced. The analysis of the resulting curves highlights the influence of the amount of zirconia and mullite inclusions in these composites.