Fracture assessment of Brazilian disc specimens weakened by blunt V-notches under mixed mode loading by means of local energy

The main purpose of this research is to re-analyse experimental results of fracture loads from blunt V-notched samples under mixed mode (I + II) loading considering different combinations of mode mixity ranging from pure modes I to II. The specimens are made of polymethyl-metacrylate (PMMA) and tested at room temperature. The suitability of fracture criterion based on the strain energy density (SED) when applied to these data is checked in the paper. Dealing with notched samples, characterized by different notch angles and notch root radii, the SED criterion used in combination with the concept of local mode I, valid in the proximity of the zone of crack nucleation, permits to provide a simple approximate but accurate equation for the SED in the control volume. This proposal unifies predictions for the experimental results obtained under modes I, II and mixed mode loading.

Research highlights
► Brittle fracture of blunt V-notched samples under mixed mode loading is investigated.
► 160 data are provided from Brazilian discs (mode I, mixed-mode and mode II loadings).
► A criterion based on the strain energy density is applied for the fracture assessment.
► The local mode I concept is proved to be valid for blunt V-notches.
► A final synthesis of the new data in terms of local energy is reported.