Analysis of flexural behaviour of reinforced thermoplastic pipes considering material nonlinearity

Reinforced thermoplastic pipes (RTPs) are considered as prospective alternatives to traditional steel pipes in different offshore oil and gas applications due to their attractive properties. The spoolable versions of these pipes can be efficiently installed by the reel-lay method with relative ease. Nonlinear flexural behaviour of RTPs composed of a liner made of pipe grade polyethylene (PE), aramid fibre reinforced PE layers and a PE outer cover is modelled and analysed using finite-element analysis (FEA) considering the material nonlinearity. The pipe is modelled as a cylindrical shell in Abaqus/Standard. Numerical algorithms reflecting strain-dependent mechanical characteristics of PE are employed to perform simulations. Advantages of the proposed modelling approach are demonstrated with numerical examples. The minimum allowable bend radii of RTPs with different ply angles are determined. The effects of diameter-to-thickness ratios and the material nonlinearity on the spoolability of RTPs have been investigated. It is shown that the spoolability of RTPs can be improved by employing a certain two angle-ply reinforcing layer system, which could reduce the installation costs.