Sea Water Ageing of Composites for Ocean Energy Conversion Systems: Influence of Glass Fibre Type on Static Behaviour
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Sea Water Ageing of Composites for Ocean Energy Conversion Systems: Influence of Glass Fibre Type on Static Behaviour Amélie Boisseau & Peter Davies & Frédéric Thiebaud
Received: 12 June 2011 / Accepted: 29 June 2011 / Published online: 7 July 2011 # Springer Science+Business Media B.V. 2011
Abstract Composite material components will be an essential part of ocean energy recovery devices, and their long term durability in sea water must be guaranteed. Despite extensive experience for boat structures and wind turbines few data exist to design structures subjected to a combination of mechanical loads and sea water immersion. This paper presents the first results from an experimental study, performed jointly with fibre manufacturers, and a resin supplier, to fill this gap. The experimental study is completed by numerical modelling to simulate the coupling between water absorption and mechanical behaviour. Sea water ageing is shown to result in a drop in quasi–static mechanical properties and a change in flexural mode from compression to tension at longer ageing times, which is consistent with results from the numerical simulations. Keywords Composite material . Sea water ageing . Failure mechanism . Flexure . Tidal turbine
1 Introduction Ocean energy is one of the most promising renewable energy resources, and it can be broadly split into five groups [1–3]: tides, waves, tidal currents, temperature gradients and salinity gradients. Several recent evaluations of these resources suggest that their potential is of the same order as that of the present capacity of electricity generation worldwide [3]. Interest in ocean energy is not new, tidal barrage plants have been operating for many years such as the installation on the Rance estuary, in Brittany, which has been producing A. Boisseau : P. Davies (*) IFREMER Centre de Brest, Materials and Structures group, 29280 Plouzané, France e-mail: [email protected] F. Thiebaud Université de Franche-Comté, DMA/FEMTO-ST, 25000 Besançon, France F. Thiebaud MAHYTEC, 39100 Dole, France
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electricity since 1966 [4]. What is new is the level of current development and investment, several demonstration projects in the 0.5 to 1.5 MW range are either being evaluated or will shortly be deployed, particularly wave and tidal current systems. Many devices have been proposed for wave and tidal energy conversion [1–3] but one feature of all the systems is that long term durability is essential [5]. Maintenance free–operation is a prerequisite if these systems are to be economically viable. This, together with light weight is one of the main reasons for considering composites rather than metallic structures for these applications. Fortunately there is extensive experience of composites in marine structures and in the next section a brief overview of this experience will be presented. Many studies of composites in water are also available and these will be briefly reviewed. 1.1 Composite Marine Structures Glass fibre reinforced polymers have been th
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