Research On Degradation Law And Mechanism Of Ultimate Bending Bearing Capacity Of Corroded Marine Pipeline Repaired By CFRP

Composite repair technology has the advantages of simple repair process,short time and low cost,and is widely used in the repair of corroded pipes.However,under the influence of long-term load and harsh environment,the effect of composite material repairing pipe will be greatly affected.In this paper,composite material repaired corroded pipes are selected as the research object,The effect of seawater environment and bending moment on the repair effect of composite materials is studied by experimental method.Based on that,the bending failure mode and competition mechanism of the pipe is analyzed and the parametric comparison is studied through the finite element method.Finally,the durability verification analysis is carried out.The specific research contents are as follows:(1)Through the experimental method,the bending performance of the corroded pipes repaired by CFRP is studied under the conditions of seawater immersion and bending moment load.By applying 0% and 30% pre-bending moment to the pipes.And put them into artificial seawater with concentration of 5 times for 200 hours,400 hours,600 hours and 800 hours for soaking acceleration test,and the durability test of bending performance is taken out.On this basis,the durability coefficient of CFRP repair pipe was proposed,and according to the test results,the reasons for the decrease of bending load of CFRP repair pipe were analyzed.(2)Through the experimental method,the CFRP plate and the CFRP-steel plate are put into the artificial seawater for 200 hours,400 hours,600 hours and 800 hours for accelerated test.Then,the CFRP is tested on the universal tensile testing machine,and the single shear tensile test is carried out on the CFRP-steel plate.The change law of the tensile properties of CFRP and the interfacial bonding properties of CFRP steel plate with time under seawater immersion is studied.The relationship between the durability coefficient of CFRP and the durability coefficient of CFRP-steel interface bond strength and the durability coefficient of CFRP repaired pipe are compared.(3)A new model of CFRP repaired corroded pipes is established,and the accuracy of the model is verified by comparing the experimental results with the finite element results.On this basis,the failure mode and competition mechanism of CFRP repaired pipe under bending load are studied.The influence of different thickness of pipe,different thickness of CFRP and different thickness of adhesive on the ultimate bending load of CFRP repaired pipe are studied.Finally,to simulate the environmental effect of seawater immersion on the ultimate load of CFRP repaired pipe,the properties of CFRP and adhesive are calculated by multiplying the original material properties with the decline factor of materials obtained in the experimental results,so that to verify the durability.