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The coupling between tensile stress and water diffusion in composites represents a major issue in many marine applications. Even if these two behaviours are well documented as separate subjects, there are still very few data on fully coupled mechanisms. The aim of this study is to understand what governs the coupled behaviour, by investigating the water diffusion in carbon/epoxy. The coupling is first evaluated on neat resin samples to characterise the matrix behaviour. Then the study focuses on composites with two types of woven fibre orientation: one at ±45°, in order to understand the coupling effects on materials loaded away from the reinforcement direction and another quasi-isotropic to obtain properties along the fibres. For each material the same approach was applied: first, the tensile behaviour, damage development and water diffusion were studied uncoupled. Then, semi-coupled effects were investigated. The final part of the paper combines both behaviours as fully coupled phenomena

In order to predict the lifetime of fibre rope mooring lines it is essential to be able to predict their behaviour under tension fatigue. Creep failure is known to be a major contributor to fatigue in synthetic fibres and models to predict creep failure are well-established. We show that expansion of such models to varying loading conditions allows the prediction of the fatigue performance. However, it is difficult to design tests to quantify the fatigue performance for HMPE ropes since often premature failure occurs due to external abrasion and viscous heating due to too high testing frequencies or amplitudes. This paper presents a testing methodology which allows tensile fatigue lifetime to be evaluated by testing at higher temperature to avoid premature abrasion failure. We also show that when the temperature evolution due to viscous heating is properly accounted for the modelling framework presented can be effectively used to describe the premature failure occurring due to this heating effect. Results from tests on yarns and small ropes are presented, and a predictive model for rope fatigue lifetime has been validated.

Polyamide fibres are known to be sensitive to water, and this has limited their marine applications. However, their low stiffness and high strength could be attractive for shallow water mooring line ropes, particularly for floating wind turbines. Such applications require the influence of water on mechanical behaviour to be fully understood, and this paper presents results describing how water affects static and creep response of polyamide 6 fibre yarns. First, the effect of water on fibre Tg is quantified, then tensile behaviour is examined. Finally, a model based on Schapery's non-linear creep analysis is identified for different humidity conditions. The results show that while moisture has a small effect on short-term tensile behaviour, long term response is strongly affected and this must be considered in any marine application.