Short and long term creep behaviour of polyamide ropes for mooring applications

Polyamide 6 fibres are of interest for mooring lines of floating wind turbines and these are continuously loaded throughout their service life. Such applications require the long term response of polyamide 6 ropes in water to be characterized. This paper presents results describing the long term creep behaviour of polyamide 6 sub-ropes with tests that lasted 2 years. A specially designed experimental set-up for long term creep test in water is presented first. Then, a kinetic study comparing creep and recovery is performed using a logarithmic identifi-cation of the strain rate. The need for performing long term creep tests is evaluated by comparing the long term creep results to those from short term creep tests lasting 3 h. The results show that a 3 h long creep test provides a reasonable prediction of long term creep strain using a single logarithmic linear law. Finally, a latch-based Weibull model is compared to a single linear logarithmic law to describe and predict creep and recovery response. It is shown that the Weibull model allows a better description of the recovery behaviour of polyamide 6 but is less well adapted for the description of creep.

Automated summary

This paper investigates the long term creep behavior of polyamide 6 ropes in water and performs a kinetic study on creep and recovery. The results show that short term creep tests can reasonably predict long term creep strain. Additionally, a latch-based Weibull model is proposed to describe and predict the creep and recovery response of polyamide 6.