Numerical study of the effect of the composite patches on the stress intensity factors for a circumferential fully crack in pipes

The purpose of this paper is to reinforce the pressurized pipe containing a fully circumferential crack (internal and external) using composite patches due to their remarkable properties. In the research procedure, in order to validate the proposed models, firstly, a cylindrical pipe with a circumferential crack subjected to the uniform tension was modeled and the results of stress intensity factors were compared with an existing paper. Then, in order to examine the modeling process of composite patch and adhesive, a damaged plate with a central crack was considered and the results of stress intensity factors were investigated and evaluated. Stress intensity factor at the crack tip was calculated using the J-integral. In this regard, using the 3D finite element method, the stress intensity factors in the crack before and after the pipe repair were evaluated with boron/epoxy, carbon/epoxy and glass/epoxy composite patches. The crack geometries correspond to different relative depths from 0.4 to 0.8. The results showed that the use of composite patches significantly decreased the stress intensity factors, and this reduction in the external circumferential cracks is more than the internal ones. Also, in the research process, the effect of the patch thickness, the angle of the fiber and the adhesive material on the stress intensity factors has been investigated.