Fractal analysis of cracks in alumina–zirconia composites

The crack paths, induced by Vickers indentation in alumina–zirconia composites, were analyzed using fractal geometry. The fractal dimension nS was calculated for each crack. This parameter refers to a corresponding three-dimensional fracture surface and indicates how its geometry varies by changing the magnification. An interesting correlation between KIC and nS was found: it suggests that the samples with high percentages of alumina and also the pure zirconia are characterized by an intergranular fracture mode, while the composites with high zirconia content present a transgranular fracture mode. This result is confirmed by analyzing the energies of fracture calculated using both the classical and fractal approaches. The results obtained in this research not only made it possible to understand the fracture behavior of the analyzed composites, but also confirmed the good potential of fractal analysis to explain complex mechanisms such as those involved in the fracture of brittle materials.