Crack bifurcation in sharp V-notches

In this paper, the crack initiation angle is studied experimentally and theoretically in sharp V-notched specimens subjected to mode I loading. Some experiments are performed on the V-notched compact tension (CT) and double cantilever beam (DCB) specimens made of polymethylmetacrylate (PMMA) with two different notch opening angles. It is demonstrated that although symmetry exists in both geometry and loading of the specimens, the initiated crack would not be necessarily along the notch bisector line. Hence, a proper theory is necessary for predicting the crack initiation angle. An attempt is then made to generalize the conventional strain energy density (SED) criterion by considering the first non-singular term in the fracture model. It is shown that the first non-singular stress term has a significant role in predicting both the crack initiation angle and the notch fracture resistance. Moreover, the results of theoretical predictions when the first non-singular term is taken into account have reasonable consistency with the experimental data