Characterisation of mode-I fracture resistance of adhesive layers with imperfections

In this work, a novel procedure to evaluate the influence of imperfections at the interface (such as voids and interfacial failure) on the fracture resistance of adhesive joints in mode-I debonding is proposed, based on an image-processing analysis of the crack surface. Its application to the characterisation of fracture resistance of aluminium DCB specimens bonded with an epoxy adhesive leads to a more accurate evaluation of the ‘effective’ fracture resistance by taking into account the distribution of imperfections along the interface, therefore also confirming that the typical oscillations and drops in the load–displacement curve can be attributed to the imperfections. •Image-processing procedure for extracting the defect distribution in the adhesive.•Correlation between the defects in the adhesive, load–displacement plot and R-curve.•Contribution of interfacial failure and voids to the effective fracture resistance.•Finite-element model that takes into account the defects on the interface.