External surface cracked offshore steel pipes reinforced with composite repair system subjected to cyclic bending: An experimental investigation. (October 2020)

• Record Type: Journal Article
• Authors: Li, Zongchen; Jiang, Xiaoli; Hopman, Hans; Zhu, Ling; Liu, Zhiping
• Is Part Of: Theoretical and applied fracture mechanics. Volume 109(2020)
• Publication Date: 2020-10
• Subjects: Composite repair system -- Offshore steel pipes -- External surface crack -- Experimental investigation -- Fatigue crack growth rate -- Structural integrity; Fracture mechanics -- Periodicals; 620.1126
• DOI: 10.1016/j.tafmec.2020.102703
• Languages: English
• ISSNs: 0167-8442

Abstract

Highlights: CRS reinforcement on surface cracked pipes under cyclic bending was experimental studied. CRS significantly decreased the FCGR and prolonged residual fatigue lives. No bond failure occurred on each reinforced specimens during fatigue tests. The reinforcement effect mainly came from the decreasing of the deformation in pipes. Crack-bridging effect played an important role towards the reinforcement effect. Abstract: In this paper, we experimentally studied the external surface crack growth in steel pipes reinforced with Composite System Repaired (CRS). CRS reinforced surface cracked API 5L X65 pipes were tested, containing three initial notch sizes and four reinforcement schemes. During the tests, the crack growth results, as well as the strain on the external mid-bottom composite laminate around the cracked area, and the vertical deflection of the specimens were recorded. The results showed that within the surface crack growth stage, the composite laminates were adequately bonded on the steel substrate, which significantly decreased the crack growth rate and prolonged the residual fatigue life. In addition, CRS reinforcement has increased the stiffness of the surface cracked pipes. Through the analysis on applying different reinforcement schemes, we indicated that increasing the amount of composite layers evidently facilitated the reinforcement effectiveness, while increasing the bond length did not; and the inversely diagonal wrapping pattern performance less effective.