Mixed-mode I/II fracture study of polymer composites using Single Edge Notched Bend specimens

Fracture behavior of polymer composites was investigated using Single Edge Notched Bending (SENB) specimens. The basic idea of this research was to check the ability of the SENB test method for generating mixed-mode I/II loading conditions by introducing an inclined notch as initial crack. For this purpose, SENB specimens containing a notch inclined at different angles were tested under static loading at room temperature. Three-dimensional finite element models were developed for simulating the mechanical response of the SENB test specimens. The test data were analyzed using methods of linear-elastic fracture mechanics. In order to validate the models, the predicted load-displacement responses were compared to the measured ones at different inclinations of the notch. From the experimentally measured crack growth initiation loads critical strain energy release rates at various mixed-mode I/II loading conditions were computed using the virtual crack closure technique. Non-uniform distribution of the critical strain energy release rate mode components along the crack front was obtained. It was found that besides modes I and II, there was also insignificant mode III component of the critical strain energy release rate. The simulations revealed that the relative amount of mode II component of the critical strain energy release decreased with increasing the notch inclination. It was shown that SENB specimens with inclined notch can be used for investigating fracture behavior of fiber reinforced polymer composites under various mixed-mode I/II crack loading conditions.