Fracture Toughness Measurements of Two Specimen Geometries Considering Stability in Brittle Materials.

It has been shown that a lack of stable crack extension can influence the critical stress intensity factor SIF measured for brittle materials. Previously performed stability analyses of two specimen geometries were used to design experiments, which would make it possible to observe the transition from unstable to stable fracture as a function of the specimen compliance. This transition was observed to be in agreement with the predictions. The lack of stability gave higher critical SIF values for the material with the higher fracture toughness, while this difference was lost in the experimental scatter for the other materials.