Effects of thermal gradient on failure of a thermoplastic composite pipe (TCP) riser leg

Thermoplastic composite pipe (TCP), consisting of a fibre-reinforced thermoplastic laminate fully bonded between homogeneous thermoplastic liners, is an ideal candidate to replace traditional steel riser pipes in deepwater where high specific strengths and moduli and corrosion resistance are advantageous. During operation, risers are subjected to combined mechanical and thermal loads. In the present paper, a 3D finite element (FE) model is developed to analyse stress state in a section of TCP under combined pressure, axial tension and thermal gradient, illustrative of a single-leg hybrid riser (SLHR) application. From the obtained stresses, through-thickness failure coefficient is evaluated based on appropriate failure criteria. The effects of increasing the internal-to-external thermal gradient are investigated considering temperature dependent material properties. The influence of varying the thickness of the isotropic liners with respect to the laminate is examined.