The Progressive Damage Analysis Of Carbon Fiber Tensile Layer In Deep Water Flexible Riser

The un-bonded flexible riser is a flexible pipe with a multi-layer structure and is one of the key equipments for connecting underwater wellheads and offshore floating oil production equipment in marine oil and gas fields.With the advancement of deepwater stratification in the development of marine oil and gas resources,the weight of steel armor layers restricts the development of deepwater oil and gas.The carbon fiber reinforced spiral belt is used to replace the steel armor layer in the flexible riser to realize the lightweight design of the flexible riser,which can effectively solve the contradiction between the flexible riser bearing capacity and the self-weight in the deepwater oil and gas development process.Due to the complexity of the failure mode of carbon fiber composites,the analysis of the mechanical behavior of carbon fiber tensile armor layer has become the focus of current research.This paper intends to use the progressive damage analysis method for the carbon fiber tensile armor layer under axial tension.Failure behavior was studied.The main research contents are as follows:(1)Using the numerical method and the finite element method to analyze and calculate the tensile stiffness of the carbon fiber armor layer.In the theoretical calculation,the anisotropy of carbon fiber composites is neglected,and the same theoretical calculation model is used for the analysis of steel armor layers.The finite element model is established by ABAQUS software,and the consistency of theoretical results and finite element results indicates that this paper selects The finite element model is correct.The results show that the tensile stiffness of the steel armor layer and the carbon fiber armor layer is basically the same as the axial displacement load increases,and the finite element results of the steel armor layer are larger than the theoretical calculation results.The finite element results of the layer are all smaller than the theoretical calculation results.When the structural dimensions are the same,the stiffness coefficient of the carbon fiber armor layer is slightly smaller than that of the steel armor layer,but its weight is only about 1/5 of the latter.When the materials are all carbon fiber reinforced structures,the tensile stiffness of the defective armor layer is less than the tensile stiffness of the defect-free armor layer.(2)Progressive damage analysis and experimental verification of composite perforated laminates.The Hashin criterion and the stiffness degradation method proposed by Tan are selected for finite element simulation.The ABAQUS user subroutine VUMAT is used for programming.The structure is modeled by solid element,and the C3D8 R element type is meshed.The hole-shaped laminate under axial tension is applied.Progressive damage analysis,axial tensile test of perforated laminates with universal tensile testing machine,verifying the correctness of finite element model by comparison of results(3)Progressive damage analysis of the carbon fiber tensile armor layer containing defects.The same failure criterion and stiffness degradation criterion as the laminate analysis were selected to analyze the failure of the carbon fiber tensile armor layer with defects under axial tension,and the conditions of different winding angles,different defect sizes and different defect locations were analyzed.The failure condition under.The results show that the larger the winding angle and the larger the defect,the more likely the armor layer to fail and the smaller the ultimate load;the larger the deviation of the defect position from the center of the armor layer,the smaller the ultimate load.