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A method of strengthening a wind turbine blade Disclosure Number: IPCOM000199112D
Publication Date: 2010-Aug-26
Document File: 15 page(s) / 67K

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A method of strengthening a wind turbine blade is described. The blade comprises a shell body comprising a fibre-reinforced polymer material. The blade is strengthened by use of a UV curable prepreg material having a first side and a second side. The method comprises the steps of: a) applying the UV curable, fibre-reinforced prepreg material to an area of application on an outer surface or an inner surface of the wind turbine blade with the first side of the prepreg material facing the area of application, and b) exposing the prepreg material to UV radiation for a predetermined amount of time so as to allow the prepreg to cure.

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A method of strengthening a wind turbine blade

   The present invention relates to a method of strengthening a wind turbine blade com- prising a shell body comprising a fibre-reinforced polymer material.

Vacuum infusion or VARTM is a process used for moulding fibre composite mouldings, where uniformly distributed fibres are layered in one of the mould parts, the fibres being rovings, i.e. bundles of fibre bands, bands of rovings, or mats, which are either felt mats made of individual fibres or woven mats made of fibre rovings. The second mould part is often made of a resilient vacuum bag, and is subsequently placed on top of the


fibre material. By generating a vacuum, typically 80% to 95% of the total vacuum, in the mould cavity between the inner side of the mould part and the vacuum bag, the liquid polymer can be drawn in and fill the mould cavity with the fibre material contained herein. So-called distribution layers or distribution tubes, also called inlet channels, are used between the vacuum bag and the fibre material in order to obtain as sound and


efficient a distribution of polymer as possible. In most cases, the polymer applied is polyester or epoxy, and the fibre reinforcement is most often based on glass fibres or carbon fibres.

During the process of filling the mould, a vacuum, which in this connection is to be un-


derstood as an under-pressure or negative pressure, is generated via vacuum outlets in the mould cavity, whereby liquid polymer is drawn into the mould cavity via the inlet channels in order to fill said mould cavity. From the inlet channels, the polymer dis- perses in all directions in the mould cavity due to the negative pressure as a flow front moves towards the vacuum channels. Thus, it is important to position the inlet channels


and vacuum channels optimally in order to obtain a complete filling of the mould cavity. Ensuring a complete distribution of the polymer in the entire mould cavity is, however, often difficult, and accordingly this often results in so-called dry spots, i.e. areas with fibre material not being sufficiently impregnated with resin. Dry spots are thus areas where the fibre material is not impregnated, and where there can be air pockets, which


are difficult or impossible to remove by controlling the vacuum pressure and possibly an overpressure at the inlet side. In connection with vacuum infusion, employing a rigid mould part and a resilient mould part in the form of a vacuum bag, the dry spots can be repaired after the process of filling the mould by for example puncturing the bag in the respective locations and by drawing out air for example by means of a syringe needle.


Liquid polymer can optionally be injected in the respective locations, and this can for

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example be done by means of a syringe needle as well. This is a time-consuming and tiresome process.

Prepreg moulding is a method in which reinforcement fibres are pre-impregnated with a pre-cat...