Experimental and stress-based theoretical studies on mixed mode I/III fracture of round-tip V-notched Polystyrene specimens

A series of fracture experiments are carried out on the round-tip V-notched GPPS (general-purpose Polystyrene) specimens under various combinations of tension and out-of-plane shear (mixed mode I/III loadings). The test samples are prepared with three different notch opening angles of 30°, 60°, and 90° and four different notch tip radii of 0.5, 1, 2, and 4 mm. Two stress-based fracture criteria entitled mean stress (MS) and point stress (PS) are employed to predict the fracture resistance and fracture initiation angle of the V-notched rectangular specimens. An acceptable consistency is observed between the theoretical predictions and the experimental values of the fracture resistance and fracture initiation angle attained for all the considered notch tip radii and notch opening angles. No meaningful preference is found between the two criteria from the aspect of accuracy of predicting the brittle fracture of V-notched GPPS components. It is also shown that the out-of-plane fracture initiation angles due to mixed mode I/III loading cases are slightly larger for the V-notched members with smaller notch tip radii.