Failure Process Investigation of Overwrapping Composite on the Pipe by Burst Test

Overwrapping structure of Glass Fiber Reinforced Polymer(GFRP) is widely used for pipeline repair and is also a promising crack arrest method, so it is worthy of further research on its failure process. For investigating failure process, a bare pipe with specially designed defect of axial slot is used for hydrostatic test, burst pressure 25.6MPa is obtained. Then, the same defected pipe wrapped with 5 layers composite is used for hydrostatic test, overwrapping composite and pipe bust simultaneously at pressure 26.2MPa, failure process cannot be observed as sudden failure. Next, the same defected pipe wrapped with 12 layers composite is utilized for hydrostatic test, progressive failure process of overwrapping GFRP structure happens at pressure 28.6MPa, while the defected pipe remains well. After overwrapping composite is wholly broken axially, the damage interface area between composite structure and pipe is distinguished by proposed strain gauge method. Subsequent hydrostatic test shows that the remaining intact interface still has obvious enforcement effect, the burst happens at pressure 30.2MPa. It implies that interface's shear strength between overwrapping composite and pipe is essential to improve ultimate burst pressure.