Brittle fracture of sharp and blunt V-notches in isostatic graphite under pure compression loading

Abstract

Brittle failure of isostatic polycrystalline graphite under pure compression loading is investigated experimentally by using prismatic specimens weakened by sharp and rounded-tip V-notches. The notched samples are characterised by different geometry parameters, i.e. notch opening angle and notch root radius, with the aim to provide a complete set of static strength data. While there are a number of papers dealing with compression of unnotched specimens made of different materials, very few results are available from notched components under compression and, in particular, no data can be found for isostatic graphite.After the description of the experimental activity, a criterion based on the strain energy density (SED) is proposed for the fracture assessment of notched graphite components under compression. The criterion, which averages SED over a control volume surrounding the notch tip, is an extension of what the present authors have proposed in previous papers dealing with the cases of in-plane tension-shear loading and torsion loading in notched graphite specimens. Good agreement is shown to exist between the experimental results and the theoretical predictions obtained for the fracture loads.