ROTOR BLADE WITH BELTS COMPRISING PULTRUDED PRODUCTS

Abstract

A method for producing a component of a rotor blade, by providing a production mould (2) with a curved support surface (1), at least one flexible pultrudate (4) being laid onto the support surface (1), the at least one flexible pultrudate (4) being covered with a vacuum film (6), a vacuum being generated and the at least one flexible pultrudate (4) being pressed entirely onto the curved support surface (1) of the production mould (2) by the vacuum.

Claims

1. A method for producing a component of a rotor blade, by providing a production mould (2) with a curved support surface (1), at least one flexible pultrudate (4) being laid onto the support surface (1), the at least one flexible pultrudate (4) being covered with a vacuum film (6), a vacuum being generated and the at least one flexible pultrudate (4) being pressed entirely onto the curved support surface (1) of the production mould (2) by the vacuum.

2. The method according to claim 1, characterised in that if the at least one flexible pultrudate (4) is initially straight in a cross-section and while it is pressed by the formation of the vacuum onto the curved support surface (1), it is kept continuously at a temperature below the glass transition temperature (Tg).

3. The method according to claim 1, characterised in that the component is infused with resin (8) and the resin (8) and the at least one pultrudate (4) are cured.

4. The method according to claim 1, characterised in that the at least one pultrudate (4) is curved along a cross-section and along a longitudinal section.

5. The method according to claim 1, characterised in that the at least one pultrudate (4) is heated to a temperature below a glass transition temperature (Tg) and at that temperature is pressed onto the curved support surface (1).

6. The method according to claim 1, characterised in that two to five pultrudates (4) are laid alongside one another and up to ten pultrudates (4) are laid one above the other on the curved support surface (1) and an infusion process is carried out and a girder is produced.

7. Arrangement for producing a component of a rotor blade with a production mould (2) having a curved support surface (1) and at least one flexible pultrudate (4) which lies entirely on the support surface (1) and has a glass transition temperature (Tg) and is at a temperature below the glass transition temperature (Tg).

8. Arrangement according to claim 7, characterised in that a vacuum film (6) is laid over the at least one uncured pultrudate (4).

Description

[0025] The invention is described with reference to an exemplary embodiment in three drawings, in which:

[0026] FIG. 1 shows a cross-sectional view of a flat pultrudate laid onto a curved support surface of a production mould,

[0027] FIG. 2 shows a cross-sectional view of a pultrudate drawn onto the curved surface of the production mould,

[0028] FIG. 3 shows a longitudinal section of a pultrudate laid on the curved surface before the drawing on.

[0029] A curved support surface 1 of a production mould 2 for a girder of a rotor blade is shown in FIG. 1 in a cross-section perpendicular to a longitudinal direction L.

[0030] The girders according to the invention have a number of pultrudates 4 which can be arranged in the longitudinal direction alongside one another and one above the other. The cross-section of a pultrudate 4 for producing the girder is shown in FIG. 1. A girder cross-section would comprise a number of pultrudates 4, for example three to five pultrudates 4 laid alongside one another and up to ten laid one above the other.

[0031] The production mould 2 illustrated in FIG. 1 serves for the separate production of girders. The girders are finished separately as components of a rotor blade and then laid as a finished component onto an inner wall of a rotor blade half-shell. The rotor blade half-shell is not yet laminated as a finished component but, at the time at which the finished girder is laid onto it, comprises a stack of woven and laid fabric layers including sandwich core materials, balsa wood or the like. The laminated girder is laid onto the stack of layers and is laminated into the rotor blade half-shell in a subsequent lamination process.

[0032] Since the rotor blade shell is curved both in cross-section and also in longitudinal section along the support surface of the pultrudate 4, the pultrudate 4 must already incorporate the curvatures in its own shape in order to lie as entirely as possible, at least over a large area on the inner wall of the rotor blade half-shell. Therefore the support surfaces 1 of the production mould 2 of the girder which are illustrated in FIG. 1 and also in FIG. 3 are curved both in cross-section and also in longitudinal section. The illustrated curvature is not true to scale, but is illustrated exaggeratedly.

[0033] Pultrudates 4 are usually produced in a pultrusion process. For this purpose rovings, which are carbon fibre and/or glass fibre bundles stored on coils, are unrolled alongside one another and one above the other and are drawn alongside one another in the longitudinal direction through a resin bath or surrounded by a liquid resin, which is then heated together with the rovings in a furnace. During the heating the resin cures, and a solid pultrudate 4 is produced which is flexible with difficulty. However, the pultrudates according to the invention are more easily flexible by comparison with the conventional pultrudates. For this purpose, during the process of producing the pultrudate 4, first of all in a conventional manner rovings are unwound from coils, arranged alongside one another and covered with liquid resin. The rovings with the resin are moved through a furnace, wherein, however, the residence time and/or the temperature of the furnace are shortened or lowered respectively by comparison with the conventional curing step, so that the resulting pultrudate is not completely cured. Because the complete pultrudate is not completely cured, thus it is more flexible and softer, it can be used for the production method according to the invention.

[0034] FIG. 1 shows the unbent conventional pultrudate 4, which is laid onto the curved support surface 1 of the production mould 2. For the production of a girder a plurality of pultrudates 4 are usually laid alongside one another and one above the other. The problem which arises in this case is illustrated in principle in FIG. 1, that is to say that in specific regions, in this case between the support surface 1 and an underside of the pultrudates 4, a space 7 is formed in which resin 8 collects during an infusion process. After the curing operation at the end of the infusion process a solid girder is indeed produced, but along the space 7 it includes a considerable amount of resin 8 which does not have the tensile strength of the pultrudates 4 as it has no fibre structure. Therefore it is preferably provided that a girder is produced which has the fewest possible spaces 7 filled with resin 8 and consists predominantly of a homogeneous pultrudate structure with fibres running in the longitudinal direction.

[0035] According to the invention the incompletely cured pultrudates 4 according to FIG. 2 are laid onto the support surface 1 of the production mould 2 and the dry construction of the girder is covered with a vacuum film 6 in a conventional manner. The vacuum film 6 is sealed at its edges, and a vacuum is generated between the vacuum film 6 and the support surface 1. Due to the generated vacuum the surrounding air pressure presses the pultrudates 4 against the support surface 1 of the production mould 2. Since the pultrudate 4 is not completely cured, but is soft, the pultrudate 4 according to FIG. 2 adheres to the support surface 1, i. e. it forms a contact with the support surface over the entire underside facing the support surface 1.

[0036] The production mould 2 can be heated during the infusion process, so that as a result an additional softening of the pultrudate 4 is possible.

[0037] After the vacuum is produced or simultaneously, resin 8 is infused into the pultrudate structure and the pultrudates 4 are adhered to one another. During subsequent heating the resin 8 is completely cured, and a girder is produced for a rotor blade half-shell, wherein the pultrudates 4 of the girder are optimally adapted to the curvature of the support surface 1 and nevertheless no internal tension is built up in the pultrudates 4 during the infusion process, since the soft pultrudates 4 can curve easily, i.e. without a great application of force against the support surface 1 and no tension or opposing force has to be overcome.

[0038] A longitudinal section through the production mould of FIG. 1 and FIG. 2 is shown in FIG. 3. In the longitudinal direction L the pultrudate 4 also conventionally has portions which do not lie entirely on the support surface 1 of the production mould 2 and therefore form the spaces 7 in which resin 8 can collect below the pultrudate 4. In order to avoid the spaces 7, the pultrudates 4 according to the invention which are not completely cured are used as mentioned above, and during the vacuum infusion process the pultrudate 4 in longitudinal section is also drawn entirely onto the support surface 1 due to the generation of the vacuum, so that during the subsequent resin infusion process no spaces 7 are formed which fill with resin 8. After the infusion process and the curing, in the longitudinal direction L the laminated girder is also built up homogeneously of pultrudates 4 which are merely adhered to one another by the resin 8. The girder is advantageously completely cured and then, with its curvature formed in cross-section and in longitudinal section, it is laid into the rotor blade half-shell with full contact.

[0039] It is also conceivable that the entire girder is not completely cured, that is to say during the infusion process, by comparison with conventional infusion processes, the temperature of the production mould 2 is raised for a shorter time and/or to a lower curing temperature, so that after the infusion process the girder is not completely cured, but remains soft and, in an analogous manner to the above-mentioned pultrudate 4, is laid into the rotor blade half-shell where in an infusion process it is drawn onto the support surface 1 of the rotor blade half-shell.

LIST OF REFERENCE NUMERALS

[0040] 1 support surface [0041] 2 production mould [0042] 4 pultrudates [0043] 6 vacuum film [0044] 7 space [0045] 8 resin [0046] L longitudinal direction [0047] Tg glass transition temperature