Investigation of fatigue crack propagation in steel pipeline repaired by glass fiber reinforced polymer

The failure analysis of cracked steel pipe repaired by glass fiber reinforced polymer (GFRP) was investigated in this study.3-dimensional elastic-plastic finite element method (FEM) was used to examine the GFRP composite patch with different orientation of fiber, [0 degrees](8s) and [0 degrees/90 degrees](4s). The development of various inclined stationary cracks under static and cyclic internal pressures in steel pipe was simulated using Extended-FEM. The findings showed that the path of inclined crack changed to be pure mode I crack. The crack path is not affected by fiber orientation. However, crack initiation pressure is affected by fiber orientation. [0 degrees](8s) fiber orientation showed the best orientation for arresting crack in pipelines subjected to inner pressure. The reductions in the values of J-integral, crack mouth opening displacement, and monotonic plastic zone Delta(m) of stationary crack were observed in GFRP composite repaired steel pipes. It was found that these reductions in GFRP composite repaired steel pipe are mainly dependent on the fibers orientation, the length and the angle of stationary crack