Creep as a design tool for HMPE ropes in long term marine and offshore applications

HMPE fibers show an elongation and creep behavior that is substantially different from e.g. polyester fibers. Both fibers have a reversible elastic elongation however for polyester it is much higher than for HMPE. Both fibers also show primary creep behavior; for polyester this is the main creep contribution. A very important difference is that only HMPE shows a pronounced secondary creep. This component is irreversible and not only dependent on load but also on temperature. This secondary creep component results in much higher achievable elongations for HMPE based ropes without substantial loss in strength. In this paper a model for the creep of Dyneema HMPE on fiber level will be introduced and it is shown that the adaptation of the model for calculations on ropes is possible, regardless of the rope construction. The calculation model for creep of Dyneema ropes can be used as design tool for long-term conditions that are present in offshore operations.