Study On Mechanical Properties Of Continuous Glass Fiber Reinforced Polyethylene Pipe

Continuous glass fiber reinforced polyethylene composite pipe(CGF-RTP)is a new kind of reinforced thermoplastics pipe.The inner tube and outermost layer of the composite pipe are made of high density polyethylene.CGFR-PECT,as enhancement layer,is wound around the inner tube in the opposite direction.All the layers of pipeline are integrated with special process.The composite pipe has high pressure resistance performance,excellent physical performance and reliable connection performance,and the application space and market prospect are very broad.However,as a new kind of composite pipe,there are few literatures about its related technologies at home and abroad.This paper analyzes and studies the mechanical properties of CGF-RTP,which is of great significance to the safety use,structure optimization design and cost reduction of the composite pipe.In order to highlight the main factors and simplify the mathematical model,this paper first makes basic assumptions about the pipeline structure and materials of CGF-RTP.The elastic parameters of CGFR-PECT were obtained by using the elastic parameter formula,and the tensile strength was calculated according to the proportion of glass fiber and HDPE in the composite belt.The accuracy of the tensile strength of the composite belt is verified by the tensile test,and the contribution of glass fiber to the tensile load of the composite belt is analyzed.Based on the structural characteristics of CGF-RTP,a mathematical model of mechanical properties was established based on the basic equations of elastic mechanics.Using the finite element analysis software ANSYS,the stress state of CGF-RTP was simulated and analyzed.The stress analysis of CGF-RTP was performed under different pressure loads,the study found that the main stress of the reinforced layer increases linearly with the increase of internal pressure load,and the main stress of the inner layer increases faster than the outer layer.Stress analysis was carried out on the CGF-RTP at the same under internal pressure loading,and the study found that the stress of the reinforced layer is greater than internal and external layer,and the stress of the inner layer is greater than that of the outer layer,and the annular stress and axial stress are linearly decreasing from inside to outside.As a failure mode that the failure of the inner reinforcement layer results in the failure of the outer reinforcement layer,the failure criterion of CGF-RTP is proposed.As a failure mode that the failure of the reinforcement layer at the same time causes failure of the pipeline,the theoretical formula of the burst pressure of CGF-RTP is derived.The normal temperature blasting test of CGF-RTP is carried out.The result of the test is compared with the pressure value of the pipeline by the failure criterion and the theoretical formula of the blasting pressure.It is found that the blasting pressure value obtained by the failure criterion is in good agreement with the test result,which proves the reasonableness of the proposed failure criterion and the related failure mode.The theoretical formula of blasting pressure of CGF-RTP is modified,and the accuracy of the modified formula is verified.The ring stiffness of CGF-RTP is defined,and the experimental method of ring stiffness test is put forward.ANSYS is used to simulate the ring stiffness of CGF-RTP,and on this basis,the ring stiffness of the polyethylene pipe with the same geometry and CGF-RTP is compared and analyzed,and the influence of the number of different layers and winding angle on the ring stiffness of the pipe is analyzed.The research shows that the composite belt can effectively improve the ring stiffness of the pipe,and with the increase of the number of reinforced layers,the ring stiffness becomes larger and larger.With the increase of the winding angle of the reinforcing layer in the range of 45 to 55 degrees,the ring stiffness becomes smaller and has a linear relationship.The ring stiffness test of CGF-RTP verified the reliability of the finite element analysis results and related conclusions.