Effects of defect dimensions and putty properties on the burst performances of steel pipes wrapped with CFRP composites

Externally wrapped carbon fiber reinforced polymer (CFRP) composites are effective to repair a defective steel pipe. In the present study, the pipes of defects with different hoop lengths were repaired with CFRP and different putty was used to fill the defects. The effects of defect dimensions and putty mechanical properties on the burst performances of the repaired pipes were investigated through burst tests and finite element (FE) analysis. If the putty failed before the CFRP, CFRP continued to bear the load when the hoop length of the defect was less than 20% of the pipe diameter, while it was inactive when the length was greater. The rupture strain of the putty should be greater than CFRP to avoid the putty fails firstly. According to the burst performances of the repaired defective steel pipe with CFRP, the design methods based on allowable stress in the pipe substrate (LAStress) or allowable strain of the repair laminates (LAStrain) in ISO/TS 24817 were compared quantitatively. A method to predict the burst pressure of the repaired pipes was proposed based on the failure mechanism of the repaired pipes.