Structural integrity of deepwater composite pipes under combined thermal and mechanical loading

Thermoplastic composite pipe (TCP) is an ideal candidate to replace traditional steel pipes in deepwater applications where high specific strengths and moduli and corrosion resistance are desirable. TCP consists of three layers: an inner thermoplastic liner; structural fibre-reinforced multi-ply laminate; and an outer thermoplastic liner. During deepwater operation the pipe is subjected to thermal gradient, arising from the mismatch between internal fluid and external ocean temperatures, in combination with mechanical loads. In the present work, a 3D finite element (FE) model is used to investigate structural integrity of TCP under combined pressures, tension and thermal gradient by considering yielding of isotropic liners and failure of the laminate at ply-level according to existing stress-based criteria. Different orientations of reinforcing fibres are investigated.