Long-term Stiffness Research Of Glass Fiber Reinforced Plastic Pipeline

This article topic source: National Natural Science Foundation of China(NO. 11102142)- The theory and methods research of long-term performance prediction of GFRP pipeline under service conditions; The Fundamental Research Funds for the Central Universities(NO.2012-Ia-023)- The rheological behavior and the service life research of the polymer matrix composites.Based on viscoelastic theory of RMC and constant displacement test, this article studied on three different kinds of layer of GFRP pipeline ring under the condition of constant displacement, through systematic test got the changes of the GFRP pipeline’s stiffness with time in the different initial deflection, and set up the long-term pipe stiffness prediction expression of GFRP pipeline service at any time and under arbitrary initial deflection. This work has a positive significance to the safety and reliability for long-term use of GFRP pipeline structure.In this paper, the main results of the work are as follows:(1) From the perspective of the theory, contrast to distinguish the concept of ring stiffness and pipe stiffness, clarify this article studies on the long-term pipe stiffness. Combined with the existing research results at home and abroad, from the classical laminated plate theory and the theory of viscoelasticity of polymer matrix composites, consider the material properties of GFRP, Established a complete theory research model of GFRP pipe stiffness changed with the time and the initial deflection, From theory research model can predict the long-term performance of GFRP pipeline stiffness, and lay a theoretical foundation for the next test study.(2) On the basis of the theory, use the pure hoop winding layer and pure cross winding layer and hoop- cross winding layer, three different kinds of GFRP pipe ring as test object; Through independent design load device, with a long-term performance testing method in general international- the basis of the constant displacement test, studies the three different layer of GFRP pipe ring’s pipe stiffness changes with time under the condition of constant displacement through the test, after more than 5400 hours of long-term performance test, get a lot of experiment data.(3) Data processing and long-term stiffness prediction. Based on these experiment data obtained from long-term performance test, through the different ways of processing fitting, getting each process pipe stiffness changes with time in the initial deflection of test, and the Pipe stiffness attenuation of each process pipe after serving 50 years under any initial deflection, and get the conclusion of the hoop winding layer helps to improve the ability of resisting stiffness attenuation of pipeline. After continuous test fitting, finally the expression of pipe stiffness is established with different initial deflection change during the course of time. Namely, the long-term stiffness prediction expression of the GFRP pipe is established.(4) The prediction expression of the GFRP pipe long-term stiffness validation. By comparing the stiffness value measured in experiment and the prediction expression, the difference of the prediction expression value and experimental value is very small, proved that the prediction expression of the GFRP pipe long-term stiffness is very reasonable and accurate.