Crack Arrestment of Bonded Composite Joints

This paper describes current results of an ongoing program to develop a test verified analysis method for crack arrestment of bonded structures. Bonded specimens have been tested with and without fasteners, which to-date include a bonded double cantilever beam (DCB) (Mode I), double shear (Mode II), and a DCB-like pi-joint (Mode I) specimen. Finite element models utilizing the Virtual Crack Closure Technique (VCCT) for crack progression have been constructed and correlated to the tests, utilizing fracture toughness data measured using all zero and bonded layup fracture toughness tests. Utilizing the VCCT capability within ABAQUS, fasteners have been shown to arrest a crack growing in the DCB and double shear specimens, as well as cracks in the DCB pi-joint specimen. Tests of the DCB and Double Shear specimens verified these results, but further investigations are needed to resolve fastener pre-load force and crack face friction effects, especially for the Double Shear. Promising comparisons were achieved between the pi-joint DCB model and test data. This project is ongoing, and additional pi-joint Mode I and Mode II specimens are planned for future evaluations.