Using blister test to predict the failure pressure in bonded composite repaired pipes

The design and qualification of composite repairs for pipelines usually requires hydrostatic tests for the determination of the failure pressure. In this work, the use of a shaft blister test to assess the failure pressure of composite repairs is proposed. Blister tests were conducted to investigate the interfacial debonding of a cornposite plate bonded to steel substrate. The blister test specimen represents a composite repair applied to a pipeline with a defect. The onset debonding load is used to predict the failure pressure. A 3D digital image correlation (DIC) has been used to follow up the debonding propagation and evaluate the blister shape. 3D finite element model with a cohesive zone model has been used to simulate loaded shaft blister test. A good correlation between blister tests results and finite element simulation results was obtained. The validated finite element model was used to predict failure pressure in bonded composite repaired pipes with different values of defect diameter and repair thickness. The results show that the blister test could replace hydrostatic tests for the analysis of the composite repairs performance.