Burst Pressure Of Glass Fiber Reinforced Composite Pipe With Delamination Defect

Glass fiber reinforced pipes(GFRP)have become a new choice for longdistance oil and gas transportation pipeline because of their advantages,such as corrosion resistance and high strength.The safety of GFRPs are drawing more attention from industry as more and more GFRPs are put into application in crucial fields such as long-distance oil and gas transportation and marine engineering.GFRPs belong to the typical laminated structure and are easy to generate delamination defects in the process of production and service,which can bring hidden dangers to the safe operation of the pipe.However,the mechanical model of GFRPs are complex,and the cost of making the test pipe is high.At present,there are few reports about the pipe research aiming at the delamination defect,so it is necessary to study the influence of the delamination defect on the burst pressure of GFRPs.The study is supported by China Petroleum Pipeline Engineering Co.,Ltd.The main work of this paper is following:(1)The progressive damage analysis method and cohesive interface model are introduced to establish finite element modeling.And the UMAT subroutine is compiled by adopting FORTRAN language to establish the constitutive relationship of glass fiber reinforced materials.The mechanical parameters of the materials are obtained through experiments and literatures.(2)Considering the distribution of interlaminar shear stress,sample pipes are made and short-time hydraulic burst experiment are carried out.It is found that delamination can weaken the load-carrying capacity of GFRPs,and the factors that affect the burst pressure of GFRPs include defect width and defect axial position.At the same time,it is verified that the influence of delamination defect on the burst pressure of GFRPs is related to the interlaminar shear stress.(3)A three-dimensional finite element model of GFRPs with delamination defect is established.The predicted results of the model are in good agreement with the experimental results.Then,progressive failure process of GFRPs under internal pressure is studied.The finite element analysis shows that the fiber tensile damage of the glass fiber layers occurs after that of the matrix.The stress distribution between layers is obtained and the effect of the delamination defect on burst pressure of GFRPs is explained in the respect of interlaminar shear stress.