Observation of microcrack damage in Al2O3-ceramics by scanning acoustic microscopy and small angle x-ray scattering

The microcrack model yields an increase JR in crack-resistance. Considering the value of the observed increase of the crack resistance, it appears that JR is too small to explain the whole R-curve. Therefore, also other effects must play a role suchas the contribution to the energy dissipation by the friction of the rough intercrystalline broken crack walls. In our opinion both models describe parts of the reality. In this paper we have concentrated our discussion only on one aspect of increasing crack resistance. I a previous paper, we have also reported effects which are in line with the crack wall interaction model.