Joint Design And Numerical Simulation Of Reinforced Thermoplastic Composite Pipe

Continuous glass fiber reinforced polyethylene plastic composite pipe(GFT-RTP)is a new type of reinforced thermoplastic composite pipe.The composite pipe is divided into three layers.The inner layer is high density polyethylene(HDPE).The middle layer is reinforced by continuous glass fiber reinforced polyethylene composite strip winding in both positive and negative directions,and the outer layer is covered by high density polyethylene(HDPE).The composite pipe retains good flexibility and high pressure resistance,and has broad application prospects.However,there is still a lack of reliable and convenient connection mode for this kind of composite pipe at this stage.In this paper,according to the structural characteristics of GFT-RTP pipes,different connection schemes are designed for pipes with different diameters and different operating pressures,which is of great significance for the safe use and promotion of composite pipes.According to the structural characteristics of GFT-RTP pipe,the structure of butt-welding hot-melt joint is designed for large diameter and low pressure GFT-RTP pipe,and the formula for calculating the expansion length of butt-welding hot-melt joint is deduced.This connection scheme makes the large diameter GFT-RTP pipe keep a larger diameter at the joint,and makes the macromolecule material contact the medium in the pipe,which effectively solves the corrosion problem of the joint.For small caliber medium and high pressure GFT-RTP pipes,a butt-welding armoured connection scheme is proposed,in which armoured parts are installed on the basis of butt-welding hot-melt joints to enhance the connection.This connection scheme enhances the strength of pure HDPE joints with the strength of metal armor,solves the problem that the expansion height of butt welded hot melt joints is too high when the internal pressure of pipe is too high,and effectively reduces the production cost.In order to solve the connection problem of small diameter and high pressure GFT-RTP pipe,two connection schemes of integral spinning joint and Harvard buckling joint are proposed in this paper.In the two schemes,the unique groove structure is designed and the relative optimum size is given.The existence of the groove structure shortens the length of the metal inner tube inserted into the pipe,improves the installation efficiency and reduces the cost of the joint.In addition,the connection scheme realizes the equal diameter of the joint and the pipe,and greatly improves the transportation efficiency of the pipeline system.Based on ANSYS finite element software,the finite element model of GFT-RTP pipe and butt-welded hot-melt joint is established.The stress distribution of joint and pipe under the limit internal pressure load is analyzed and compared,and the rationality of theoretical analysis and design is verified.The validity and reliability of theoretical analysis and finite element simulation are verified by hydrostatic and explosive experiments on butt welded hot melt joint,butt welded armoured joint,integral joint and Harvard joint.