Advanced analysis of cross-sectional properties in unbonded flexible risers with composite layers

Unbonded flexible risers can undergo large deflection bending deformation, which is a key equipment for deep-sea oil and gas resource development. In this paper, firstly, a theoretical method for composite cylindrical and armour layers under axisymmetric load and bending moment is deduced by function principle and structural deformation characteristics. Then, the corresponding numerical model is established within ABAQUS/Explicit. After verified through experimental results, the axial compressive stiffness of the unbonded flexible riser with composite layers is studied. Furthermore, several related characteristics, including the corresponding tensile stiffness, bending stiffness of unbonded flexible riser and fibre proportion of composite layer are discussed. Finally, taking the bearing axial compression capacity of cylindrical layer into consideration, the compressive failure is studied.