Failure analysis of thermoplastic composite pipe (TCP) under combined pressure, tension and thermal gradient for an offshore riser application

Useful characteristics of fibre-reinforced thermoplastics, including high specific strengths and moduli and excellent corrosion resistance, make them ideal candidates for offshore riser pipe applications. When in operation, risers are subjected to combined mechanical and thermal loading. In the present paper, a 3D finite element (FE) model is used to analyse stress state in a section of thermoplastic composite pipe (TCP), consisting of a fibre-reinforced thermoplastic laminate fully bonded between inner and outer thermoplastic liners, under conditions illustrative of a deepwater riser application. The effects of varying combinations of pressure and thermal differentials on the distribution of stress-based failure coefficient are examined. Failure responses under different axial tensions at low/high pressures and temperatures are assessed for configurations with different laminate ply stacking sequences. Temperature-dependent material properties are considered in the thermomechanical analysis.