Pure mode III fracture of U-notched specimens made of PMMA and GPPS polymers: Experimental and theoretical evaluations

Abstract

In this paper, a new set of fracture experiments are conducted on the U-notched components made of Polymethyl-methacrylate (PMMA) and general-purpose Polystyrene (GPPS) under pure out-of-plane shear (mode III) loading by using an anti-symmetric four-point bend (ASFPB) configuration. For exploring the influence of the notch tip radius, the specimens with four different radii are tested. Two well-known brittle failure criteria, namely the point stress (PS) and mean stress (MS) criteria, are then employed to assess the fracture behavior of the tested U-notched specimens. Stress analyses needed for determining the notch stress intensity factors (NSIFs) are performed by means of the finite element modeling of the test configuration. A good agreement is revealed between the predictions of the PS and MS criteria and the experimental results, confirming their suitability for estimating pure mode III fracture of U-notched components made of brittle materials. No meaningful difference is observed between the theoretical predictions of the PS and MS criteria. It is revealed that the fracture toughness enhancement of PMMA-made U-notched specimens is more sensitive to increasing the notch tip radius than that of U-notched GPPS samples.