Fracture assessment of VO-notches under mode II loading: Experiments and theories

• Mode I and mode II fracture tests were performed on the VO-BD PMMA specimens.
• The new VO-MTS and VO-MS brittle fracture criteria were used in theoretical study.
• The results were obtained in terms of the critical notch stress intensity factors.
• Both the criteria provide very good estimates to the experimental results.
• Using the critical distances of sharp crack for VO-notches is permissible.

In the present investigation, two brittle fracture criteria were suggested to predict the onset of brittle fracture in engineering components weakened by V-notches with end holes (VO-notches) under pure mode II loading. These criteria, called VO-MTS and VO-MS were developed based on the two well-known failure concepts of the maximum tangential stress (MTS) and the mean stress (MS), respectively. In order to evaluate the accuracy of the criteria, 72 new brittle fracture tests were conducted at room temperature on the new disk type specimen containing a central slit, called the VO-notched Brazilian disk (VO-BD) specimen, made of PMMA. First, the experimental fracture loads were converted to the corresponding mode I and mode II notch fracture toughness (NFT) values and the important ratio mode II NFT/mode I NFT was experimentally achieved. Then, the theoretical values of the ratio were predicted by means of the VO-MTS and the VO-MS criteria. It was found that both the criteria could provide very good predictions to the experimental results of the ratio mode II NFT/mode I NFT, as well as those of the fracture initiation angle. Also, found in this research was that one can utilize the critical distances of sharp crack in the fracture predictions of VO-notches.