Simulation Of The Key Bearing Performance Of Fiber Reinforced Plastic Composite Pipes

In recent years,fiber-reinforced plastic composite pipes have become the main choice for oil and gas gathering pipelines due to their corrosion resistance,heat resistance,high strength,light weight,convenient transportation and installation,and low maintenance costs.However,in the pipeline transportation,installation and service process,fiber-reinforced plastic composite pipes will undergo a series of single loads and complex loads such as stretching,bending,torsion,internal pressure,etc.Therefore,the pipes are required to have excellent load-bearing performance.The load-bearing performance of the pipeline depends on its structure and production process.As a new type of composite pipe,fiber-reinforced plastic composite pipe usually adopts empirical method or trial-and-error method in the manufacturing process.There is a certain degree of blindness and the production cost is high.It is impossible to effectively determine the key factors affecting the performance of the pipe and ensure the stability of its performance.Finite element analysis technology can greatly save the loss of manpower,material resources and time in the process of test,and analyze the influence of different factors more efficiently.Therefore,this paper uses the finite element analysis method to simulate the mechanical response of the polyester fiber reinforced polyethylene composite pipe under different loads.It mainly explores the influence of composite pipe production process parameters on its different load-bearing performance,establishes the relationship between pipeline process parameters and load-bearing performance,and better guides the production and use of composite pipes.The main research contents and results are as follows:Based on the structural characteristics and material properties of the polyester fiber reinforced polyethylene composite pipe,a finite element model of the composite pipe was established using finite element analysis software and the bearing state of the pipe was simulated and calculated.Comparing with the results of the hydrostatic test and short-term blasting test of the actual pipe,it is found that the simulated value of the pipe diameter and the blasting pressure of the composite pipe under 3.75 MPa are in good agreement with the experimental data,and the relative errors are 2.6% and 3.302%,respectively.This indicates that the finite element model of the polyester fiber reinforced polyethylene composite pipe has high accuracy and can be used to simulate and study the load-bearing performance of the composite pipe under different conditions.Based on the finite element model of polyester fiber reinforced polyethylene composite pipe,the stress distribution of each structural layer of the composite pipe under different loads is analyzed,and the influence of process parameters such as fiber winding angle,pipe diameter-to-thickness ratio,and fiber laying layer number on the bearing performance is explored.The study found that the polyester fiber layer is the main load-bearing structure of the composite pipe,and its stress determines whether the composite pipe fails.Therefore,the maximum stress criterion is used as the failure criterion of the polyester fiber reinforced layer,which is the failure criterion of the composite pipe.Through simulation analysis,it is determined that the process parameters that can obtain the best pressure-bearing performance are the fiber winding angle ±56°,the pipe diameter-thickness ratio D/t<14,and the number of fiber layers is 4 layers.During the load-bearing process,appropriately increasing the fiber winding angle or reducing the pipe diameter-to-thickness ratio can improve the torsion performance and bending performance of the composite pipe.Because the composite pipe itself has good tensile properties,the process parameters have little effect on it.On the basis of single load analysis,the bearing conditions of composite pipes under complex loads of torsion and tension,internal pressure and tension are further studied.The study found that,compared with the pure torsion or pure internal pressure state,the intervention of tensile load will make the change of the stress of the polyester fiber layer tend to be gentle.Under the combined action of torsion and tensile load,the outermost fiber has the largest stress value and is prone to breakage.However,when the internal pressure and tensile load act simultaneously,the innermost fiber has the largest stress value and is prone to breakage.It shows that under combined load,the effects of torsion and internal pressure load dominate.The analysis of the process parameters on the bearing performance of the pipeline under complex loads shows that the smaller the fiber winding angle and the larger the pipe diameter-to-thickness ratio,the tensile performance of the composite pipe under combined loads can be improved.By analyzing the mutual influence of various loads under complex loads,it is found that the change of torsional load has no effect on the tensile performance of the composite pipe,and appropriate internal pressure load intervention can improve the tensile performance of the composite pipe.