A general constitutive model for the numerical simulation of different synthetic fibres used in offshore mooring

The offshore industry faces continuous challenges as new applications (such as floating wind turbines, wave energy converters, etc.) are being proposed and old applications (such as offshore oil and gas floating units) are being installed in deeper waters. Mooring systems are among those that have faced the greatest evolution, mostly due to the recent successful use of synthetic fibre ropes. The complex mechanical loads to which these systems are subjected during service, in combination with their inherent nonlinear mechanical behaviour, call for the use of numerical techniques for the prediction of their stress and strain response. Although there can be found a considerable amount of proposed models in the specialised literature, it is noted that the great majority of them is developed to be used with very specific materials, or to model few specific phenomenon, such as creep, relaxation, or monotonic load, for instance. With that in mind, the major contribution of the present paper is that it proposes a constitutive framework that accurately predicts the stress-strain response under cyclic load of four of the most used fibres in synthetic mooring ropes, namely, polyester, high modulus polyethylene, polyamide and aramid. A polyester subrope was also modelled, which shows the robustness of the proposed methodology.