Mixed-mode I+II fracture characterisation of composite bonded joints

Abstract

This work addresses fracture characterisation of composite bonded joints under mixed-mode I+II loading. A proper strategy, including only two different loading conditions applied to five tests, is performed to obtain the fracture law describing the mixed-mode fracture behaviour. The peel test loading condition is employed to characterise fracture under pure mode I loading considering a symmetrical double-cantilever beam specimen and under mixed-mode I+II with mode I supremacy with an asymmetrical double-cantilever beam specimen. Three-point bending loading condition was also employed. The end-notched flexure test was used to characterise fracture under pure mode II, while the asymmetric single-leg bending tests were performed to cover mixed-mode I+II loading with mode II predominance up to a mode-mixity with moderate mode I prevalence. A methodology using cohesive zone modelling was applied to perform loading mode partition, which is crucial for an appropriate identification of the criterion describing the fracture behaviour of these joints.