Mixed mode I-II-III fracture criterion and its application to cement mortar

Abstract

To study crack behaviour of brittle and slightly ductile materials under pure mode III loading, the closure analysis of an infinitesimal crack extension has been carried out, and relationship between the stress intensity factor and energy release rate established. On the basis of the unified model, which specifies the in-plane crack behaviour under mixed mode I-II loading, a three-dimensional mixed mode Ia??IIa??III fracture criterion has been derived, by adopting the conversion of pure to mixed mode loading energy, in the ratio of their corresponding fracture energies.In verifying the criterion, various experimental methods have been designed using cement mortar specimens, in order to conduct three-dimensional mixed mode, as well as the corresponding pure mode, fracture tests. The stress intensity factors of the respective modes of deformation were evaluated numerically by finite element analysis. As a result, reasonable agreement was obtained between the proposed criterion and the experimental results.