Fracture assessment of U-notched PMMA under mixed mode I/II loading conditions by means of local approaches.

The paper investigates the fracture behaviour of U-notched specimens made of polymethylmethacrylate at room temperature under mixed mode loading conditions. The specimens are flat and double notched. The notches bisectors lie on the same line that forms an angle β with the loading direction; this specimen shape allows to consider mixed mode loading conditions. With changing β, different contributions of mode I and mode II loading are achieved. The specimens net section, calculated perpendicularly to the load application direction, is maintained constant while the notch fitting radius changes ranging from 1 to 4 mm. The results have been analysed through both the averaged strain energy density method and the theory of critical distance assessing the use of coarse free mesh models for the application of these methods