Limit curves for brittle fracture in key-hole notches under mixed mode I/III loading based on stress-based criteria

Abstract

In this research, with the aim to estimate the onset of fracture in key-hole notched components, made of brittle materials and subjected to combined tension-tear loading, the fracture limit curves are developed in terms of the notch stress intensity factors (NSIFs) based on the maximum tangential stress (MTS) and mean stress (MS) criteria. In order to verify the curves developed, a series of fracture tests are carried out on key-hole notched specimens made of PMMA using an improved loading configuration. The samples are prepared with three various notch tip radii for the sake of evaluating the influence of the notch tip radius on the fracture toughness of the key-hole notched samples. It is shown that for all notch tip radii, the fracture limit curves for both MTS and MS criteria are in very good consistency with the experimental data. No meaningful difference is found between the curves of MTS and MS criteria, especially under plane-stress conditions. It is also observed that the notch fracture toughness of the PMMA specimens could be well estimated under both plane-stress and plan-strain conditions.