Characterization and modeling of the viscoelastoplastic behavior of polyester mooring lines

This study presents a model for describing the viscoelastic and viscoplastic behavior of a full-size polyester (PET) subrope, which can be used to determine the medium- and long-term response of synthetic cables used in floating wind turbines. While this material is well established in offshore oil and gas applications, it is also currently being considered for marine renewable energy (MRE) station-keeping. The determination of constitutive laws, using models such as Schapery’s, remains complex and is usually limited to yarns or small ropes. In our case, the viscoelastic model is fitted in its incremental form using optimization methods, based on simple creep and relaxation tests at different stress levels. Each step of the approach is described in detail, leading to a constitutive law that can be implemented in finite element method (FEM) software. The model demonstrates good agreement with experimental data, highlighting its potential to accurately simulate the response of synthetic mooring lines in a marine environment.