On the fracture behaviour of CFRP bonded joints under mode I loading: Effect of supporting carrier and interface contamination

This paper addresses the fracture behaviour of bonded composite plates featuring a kissing bond along the crack growth path. Double cantilever beam (DCB) experiments are carried out under a displacement controlled loading condition to acquire the load response. The experimental data are collected and analysed analytically for specimens with and without kissing bond. The following aspects are observed and discussed: effect of the adhesive carrier film, non-smooth crack growth and rising R curve. An analytical model taking into account the aforementioned effects is proposed. The kissing bond leads to unstable crack growth resulting in a loss of the load carrying capacity. The presence of the knit carrier in the adhesive film results in the crack growth process characteristic for the stick-slip phenomena and a significant increase of the resistance to fracture of the bondline by triggering a bridging phenomenon. The model shows a very good agreement with the experimental data. A sound understanding of the fracture process is gained enabling analysis and prediction of the effects of kissing bonds and supporting carrier.