Extraction of mix-mode cohesive laws of a unidirectional composite undergoing delamination with large-scale fibre bridging

A novel method is proposed for extracting the mixed-mode cohesive laws of composite materials undergoing delamination with large-scale fibre bridging. In the approach, the mixed-mode cohesive laws are derived from a potential function expressed in cylindrical coordinates with the magnitude and phase angle between the normal and tangential end-openings. The potential function is mapped using experimental R-curves in terms of the J-integral and the end-openings. The mixed-mode cohesive laws describe both the crack tip (high tractions, small separations) and bridging region (small tractions, high separations). The extracted mixed-mode cohesive tractions are fully coupled, i.e., both the normal and shear traction depend on the normal and tangential openings. The peak normal and shear tractions were found to be at a mixed mode opening.