Investigation On Mechanisms Of Filament-wound Fiber-reinforced Composite Pipe Under Axisymmetric Loads

Pipe is widely used in oil and gas transportation. Application of pipes increases with the exploitation of oil and gas resources in China. Filament-wound fiber-reinforced composite pipe (RTP) is a new choice for oil and gas transportation due to its advantages of corrosion resistance, pressure resistance and flexibility. RTP is a complex construction as a combination of high-strength fiber and thermoplastic material. During installation and operation, RTP may be subjected to various loads and load combinations. Thus investigation on mechanical behavior of RTP is important and necessary.Both theoretical method and numerical simulation are presented in this paper to study the mechanical behavior of RTP under axisymmetric loads, including tension, internal pressure and tension combined with internal pressure. The main works in this paper are summarized as follows:(1) A theoretical method to study the behavior of RTP under three kinds of axisymmetric loads is proposed based on a cable model under tension and torsion. In the theoretical model, material nonlinearity is considered. The pipe cross section is simplified. Then the deformation of fibers and cross section is analyzed. Equilibrium equations are derived based on the principle of stationary potential energy. Using Newton-Raphson method, the problem is solved by iterative procedure.(2) Finite element models are built to simulate the behavior of RTP under three axisymmetric loads. The boundary conditions and loading method are the same with those in theoretical method. By comparing and analyzing results from both methods, the results of theoretical method are verified by numerical method.(3) Sensitivity study is conducted to study the influence of important parameters on the behavior of RTP. The related parameters include diameter-radius ratio, lay angle, amount of wires, etc.From the theoretical method and numerical simulation, the relation between load and deformation of RTP, deformation of the pipe cross section and helical fibers as well as the stress distribution of fibers are derived. Profound understanding of function of different material in RTP is achieved when the pipe is subjected to axisymmetric loads. Through sensitivity study, factors influencing the behavior of RTP are obtained, thus valuable advice for RTP design and application is provided.