Static Analysis Of Non-metallic Bonded Flexible Riser Under Tensile Load

Deep water is an important area for the exploration and development of oil and gas resources.It is inseparable from the support of marine equipment in the development process.Pipeline as an important conveying equipment has been concerned by all aspects.With the increase of water depth,the development bottleneck of traditional steel pipeline exists because of its own defects,so it is imperative to develop a new type of pipeline.In flexible pipes,nonmetallic bonded composite pipes with thermoplastic material as matrix and fiber as reinforcement stand out among many new types of pipes with the advantages of light weight,corrosion resistance and good flexibility.However,its key technology has been monopolized by foreign companies.At present,the research on basic theory in China is relatively rare.This paper studies the mechanical properties of thermoplastic fiber-wound composite flexible pipe under tension and temperature.In this paper,the flexible pipe of thermoplastic fiber-wound composite material is taken as the research object.By analyzing the geometric deformation of the pipe during the tension process,the pipe section is simplified.The section of the pipe is divided into several ring structures according to the number of layers.The overall stress-strain relationship is constructed by continuous displacement conditions,and the constitutive relationship of elastic-plastic material is used to construct the mechanical model under tension.The symbolic solver of MATLAB and the powerful numerical ability are used to solve the problem.The influence of parameters such as the number of reinforcement layers,fiber angle and fiber number was analyzed,and the mechanical properties of the pipe during the whole tensile process were obtained.Under the action of temperature,the temperature distribution and temperature gradient of the pipeline are determined by heat conduction equation.The temperature stress is introduced into the overall stress-strain relationship of the model.Considering the properties of the thermoplastic matrix material at different temperatures,the influence of temperature on the overall tensile properties of the pipeline is obtained.It is found that the main factor affecting the tensile properties of filament-wound composite pipes is the winding angle of the fibers.The smaller the winding angle,the better the tensile performance of the composite pipe.Reducing the fiber winding angle or increasing the layer content of the small winding angle can significantly improve the tensile capacity of the composite pipe.In this paper,two methods to improve the tensile capacity of pipelines are proposed.When the winding angle is greater than ±45°,the improvement effect of increasing the thickness of the inner liner layer is better than increasing the number of reinforcement layers.When the winding angle is less than ±45°,the improvement effect of increasing the number of reinforcing layers is better than increasing the thickness of the inner liner layer,and the effect of the small angle reinforcing layer is far more obvious than the large angle.Temperature has a significant effect on the tensile properties.The overall temperature has a linear inverse relationship with the tensile load.The lower the overall temperature,the stronger the tensile strength of the pipe,but it will enter the yield stage earlier.The temperature difference between the inner and outer surfaces of the pipe has a very significant effect on the fiber.