Out-of-plane shear fracture analysis of PMMA and GPPS polymers weakened by round-tip V-notches

To investigate the fracture resistance of V-notched components made of Polymethyl-metacrylate (PMMA) and general-purpose Polystyrene (GPPS) under pure out-of-plane shear (mode III) loading, several new fracture tests are first conducted. 48 rectangular test samples with different notch opening angles and notch tip radii are prepared and broken using an anti-symmetric four-point bend (ASFPB) test configuration. Then, two fracture criteria, namely the mean stress (MS) and point stress (PS) criteria, are employed to estimate the mode III notch fracture toughness values experimentally obtained. It is demonstrated that there is a good consistency between the PS and MS criteria predictions and the experimental results achieved. No noteworthy difference is found between the theoretical predictions of the PS and MS criteria for fracture resistance under pure mode III loading. Moreover, it is shown that the improving effect of larger notch tip radii on the fracture resistance of the PMMA and GPPS polymers under pure out-of-plane shear is more significant for smaller notch opening angles.