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Davies P.,French Research Institute for Exploitation of the Sea | Germain G.,French Research Institute for Exploitation of the Sea | Gaurier B.,French Research Institute for Exploitation of the Sea | Boisseau A.,French Research Institute for Exploitation of the Sea | Perreux D.,MaHyTec
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2013

The long-term reliability of tidal turbines is critical if these structures are to be cost effective. Optimized design requires a combination of material durability models and structural analyses. Composites are a natural choice for turbine blades, but there are few data available to predict material behaviour under coupled environmental and cycling loading. The present study addresses this problem, by introducing a multi-level framework for turbine blade qualification. At the material scale, static and cyclic tests have been performed, both in air and in sea water. The influence of ageing in sea water on fatigue performance is then quantified, and much lower fatigue lives are measured after ageing. At a higher level, flume tank tests have been performed on threeblade tidal turbines. Strain gauging of blades has provided data to compare with numerical models. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source

Delobelle B.,MaHyTec | Perreux D.,University of Franche Comte | Delobelle P.,University of Franche Comte
Sensors and Actuators, A: Physical | Year: 2014

As shown in a previous paper (Delobelle et al. (2013)) if synthetic flaws are generated on the surface or in the core of optical fibers thanks to single-shot femtosecond laser procedure, the rupture strength of these modified fibers can be controlled. In this paper, numerous new experiments have been conducted to show the potentialities of the embedded structured fibers within composite materials to act as a strain safety fuse sensor. The choice of a multimode optical fiber with polyimide coating has been validated. New Weibull's statistics on short fibers have been determined for two kinds of structuration, flaws on the surface or in the core of the silice fibers and in the failure strains range consistent with sensor applications on composite materials. Long structured fibers have been embedded within plane specimens of two components materials (glass fibers composite (16-20 plane sheets, 0°) and carbon fibers composite (4 sheets, ±45°)) and the comparison between the failure strains of these fibers with those issued from the Weibull's statistics of short fibers shows, at least for the superficial structuration, the possibility to use these structured fibers as strain fuse sensor. A very simple phenomenological model has been proposed. © 2014 Elsevier B.V. All rights reserved. Source

Avril C.,MaHyTec | Bailly P.A.,MaHyTec | Njuguna J.,Cranfield University | Nassiopoulos E.,Cranfield University | De Larminat A.,Citi Technologies
ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials | Year: 2012

The present study was led in the frame of the ECOSHELL European-funded project which aims at developing fully renewable composite materials for the manufacturing of high-load bearing parts in automotive applications. As a first step, three different flax reinforcements (non-woven thick mat, balanced fabric and unidirectional fabric) were combined with a bio-sourced epoxy resin for the characterization of their mechanical capabilities. This paper describes the manufacturing processes of each material with an emphasis on the handling specificities inherent in the vegetal fibers. Numerous laminates were produced and specimens were machined in order to carry out tensile, compression shear and impact tests following the requirements of ASTM standards in force. This work allowed to identify the most suitable material and opened very promising industrial perspectives. Source

Zhu J.,Cranfield University | Njuguna J.,Cranfield University | Njuguna J.,Robert Gordon University | Abhyankar H.,Cranfield University | And 9 more authors.
Industrial Crops and Products | Year: 2013

Flax reinforced tannin-based composites have a potential to be used in vehicle applications due to the environmental advantages and good mechanical properties. In this paper, the effects of fibre configuration on mechanical properties of flax/tannin composites were investigated for nonwoven and woven fabric lay-up angles (UD, [0°, 90°]2 and [0°, +45°, 90°, -45°]2). The tannin/flax composites were prepared by compression moulding. The manufactured specimens were then characterized for quasi-static tensile properties, dynamic mechanical properties and low-energy impact performance. Failure mechanism was further investigated using microscopy and demonstrated the need for further adhesion improvements. The study shows that the UD fabric reinforced composite performs better in tensile strength and modulus whereas [0°, +45°, 90°, -45°]2 composite provides the best impact energy absorption performance. © 2013 Elsevier B.V. Source

Davies P.,French Research Institute for Exploitation of the Sea | Boisseau A.,French Research Institute for Exploitation of the Sea | Choqueuse D.,French Research Institute for Exploitation of the Sea | Thiebaud F.,MaHyTec | And 3 more authors.
Materiaux et Techniques | Year: 2012

Composites will play an essential role in the development of ocean energy conversion systems, and their long term durability is critical to the success of these structures. Composites have been widely used in marine applications and in structures highly loaded in fatigue such as wind turbine blades. However, very few data are available to evaluate their performance under conditions which combine long term immersion in sea water and sustained cyclic loading. In this study composites reinforced with three different types of glass fibre and the same epoxy resin have been tested under these conditions, and the influence of aging on both static and fatigue behaviour has been quantified. Fibre type, resin and fibre/resin interface all influence the fatigue behaviour of these materials in sea water. © 2012 EDP Sciences. Source

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