Applicability of VCCT in mode I loading of yielding adhesively bonded joints—a case study

Abstract

Virtual Crack Closure Technique (VCCT) is a fracture analysis method that is typically utilised when plastic dissipation does not exist. This paper studies the applicability of VCCT for crack growth analyses of an adhesively bonded joint with a ductile adhesive and self-similar crack growth. Analyses were performed for a Double Cantilever Beam (DCB) specimen with epoxy adhesive. Reference data for the analysis case existed. The precrack cycle of the DCB test was first analysed assuming linear elastic behaviour of the adhesive and by using the measured average fracture energy as a critical value. The computed force–displacement curve was noted to match well with the experimental data. In the next step, a nonlinear analysis was performed by using a linear elastic – ideally plastic material model for the adhesive and by selecting the critical energy release rate value so that the computed force–displacement curve fit the experimental and linear analysis data. The approach allowed for extracting plastic dissipation from the measured fracture energy to obtain an estimate for the critical energy release rate. The nonlinear analysis results were further studied using the Energy Derivate Technique (EDT) as a post-processing tool. The EDT analysis results confirmed that plastic dissipation remains at a constant level for the entire crack propagation phase of the precrack cycle analysis.