Strength of dissimilar adhesively bonded DCB joints and its connection with the failure pressure of composite repair systems

The application of adhesively bonded joints in petroleum industry over other traditional joining methods has increased significantly in recent years mainly because of the potential for light weight structures, fast repairing systems and low temperature applications. The principal benefits are design flexibility and joining of dissimilar materials. Therefore, accurate analysis and study about the mechanical behavior of dissimilar materials joints are fundamentally required since composite materials are widely used as repair systems for metallic pipelines with localized flaws or damage that prejudice the serviceability. Experimental analyses were performed on dissimilar adhesively bonded DCB joints, similar to a composite repair applied to a pipeline, to investigate the design factors that affect the joint behavior. This study shows that the critical energy release rate obtained in dissimilar DCB joints tests can be correlated with the one obtained in hydrostatic tests performed in pipelines with though-wall defects repaired with composite sleeves. It is proposed an approximated theoretical framework that allows obtaining an estimate of critical fracture parameters that arise in composite repair standards only using simpler and less expensive DCB tests in the place o hydrostatic test.