Mixed mode I/III brittle fracture in round-tip V-notches

• Two stress-based criteria are extended to mixed mode I/II/III fracture in blunt V-notches.
• The criteria are based on the point stress (PS) and the mean-stress (MS) concepts.
• The results of both criteria are verified in mixed mode I/III by existing test data.
• Good agreement exists between the MS criterion and the experimental results.
• In mixed-mode I/III, the PS criterion is generally less accurate than the MS one.

Two stress-based failure criteria, presented in the past to study brittle fracture in engineering components weakened by a blunt V-notch under mixed mode I/II loading, are extended in the present study to general mixed mode I/II/III loading. As a reduced case, two brittle fracture criteria are developed for mixed mode I/III loading conditions based on the two well-known failure concepts of the maximum tangential stress (MTS) and the mean-stress (MS) which both have been frequently used for predicting mixed-mode I/II brittle fracture in notched components. In order to verify the validity of the criteria, the theoretical predictions are compared with a bulk of new experimental results recently reported in the open literature on mixed-mode I/III fracture of round graphite bars weakened by circumferential blunt V-notches. The results of the criteria are represented in the form of fracture curves in terms of the notch stress intensity factors. Good agreement is shown to exist between the mixed-mode I/III results of the MS criterion and the experimental results for different notch tip radii and various notch opening angles. Conversely, the results show that the MTS criterion provides weaker estimates compared to the MS criterion.