DK201870879A1

DK201870879A1 - Method and Apparatus for Making a Wind Turbine Blade

Info

Publication number: DK201870879A1
Application number: DKPA201870879A
Authority: DK
Inventors: Stenbæk Nielsen Knud
Original assignee: Vestas Wind Systems A/S
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2019-12-09

Abstract

A method of making a portion of a wind turbine blade and a mould therefor, the method comprising: providing a mould having a plurality of holes located on a form surface thereof, wherein each of the plurality of holes is operatively connected to a selectively operable evacuation device; covering at least some of the plurality of holes with a gas permeable membrane, laying-up a skin surface of the wind turbine blade on the membrane, wherein the skin surface comprises a plurality of fibre layers; encapsulating the skin surface in an airtight envelope; and curing the fibre layers in a resin matrix.

Description

Method and Apparatus for Making a Wind Turbine Blade

TECHNICAL FIELD

The present disclosure relates to a method and apparatus for making a wind turbine blade. In particular, the present disclose relates to a mould for making a portion of a wind turbine blade and a method of making a portion of a wind turbine blade using the mould.

BACKGROUND

Typically, wind turbine blades are manufactured in two halves, or half shells, which are bonded together along a leading edge and a trailing edge. A shear web structure is typically provided between the half shells, where the shear web is bonded to an inner surface of each half shell.

Adhesive is used to bond the inner surfaces of the half shells to the shear web structure, and to bond the outer edges of the half shells together. It will be appreciated that the adhesive bonds provide critical connections between the various components of the blade, and that the bonds must therefore have extremely high integrity to withstand the high forces and fatigue loads experienced in operation. To this end, the process of creating the adhesive bonds during production of wind turbine blades must be highly repeatable and robust.

Each half shell is formed in a mould. Typically, the shear web is adhesively bonded to the inner surface of a first, or lower, half shell while it is still in its mould. Adhesive is then applied to the bond edges of the leading and trailing edges of the lower half shell, and also to the uppermost bond surface of the shear web. The mould containing the second, or upper, half shell is then lifted, inverted, and positioned above the mould containing the lower half shell such that the bond surfaces along the leading and training edges align. The bond surfaces are brought together by moving the upper mould towards the lower mould until the bond surfaces come together. The assembly is then cured before the complete blade is broken out of the moulds.

It will be readily apparent that it would be catastrophic for upper half shell to fall out of its mould during movement to its position above the lower half shell. Such an event would cause tremendous damage to the half shell itself, and may also damage the lower half shell, the lower mould, building installations and/or personnel. It is therefore vital that systems are provided to ensure that such an event cannot take place.

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It is known to use anti drop-out (ADO) devices to clamp the upper half shell to the mould before it is lifted and placed on top of the lower half shell in its mould. Such a device is disclosed in WO2015096839A1.

Although known ADO devices work well to prevent drop-out, they do not prevent the upper half shell from sagging under its own weight and pre-releasing from the form surface of the upper mould. Such pre-released is undesirable as it can cause the weight of the upper half shell to rest on the adhesive of the shear-web bond surface before the adhesive has fully cured. This can result in adhesive bonds which are too thin, or result in the formation of kissing bonds which are formed as a result of thermal expansion during bond line curing.

It is against this background that the present invention has been developed.

SUMMARY OF THE INVENTION

Accordingly, there is provided a method of making a portion of a wind turbine blade, the method comprising: providing a mould having a plurality of holes located on a form surface thereof, wherein each of the plurality of holes is operatively connected to a selectively operable evacuation device; covering at least some of the plurality of holes with a gas permeable membrane, laying-up a skin surface of the wind turbine blade on the membrane, wherein the skin surface comprises a plurality of fibre layers; encapsulating the skin surface in an airtight envelope; and curing the fibre layers in a resin matrix.

The method may preferably further comprise applying a vacuum to at least some of the plurality of holes, wherein the action of applying the vacuum causes the fibre layers to compact. The method may include applying a layer of gelcoat on top of the membrane so that at least a portion of the plurality of holes are covered by a layer of membrane and a layer of gelcoat. Optionally, all of the plurality of holes may be covered by a layer of membrane and a layer of gelcoat. Optionally, the plurality of holes may be arranged in a number of discrete hole arrays. Preferably, at least some of the hole arrays are covered by a discrete patch of membrane. Preferably, each hole array may have an evacuation device associated therewith.

There is also proposed a method of making a wind turbine blade, the method comprising: making a first wind turbine blade portion in a first mould using the method defined above; and: providing a second wind turbine blade portion located in a second mould; applying adhesive to bond surfaces of the second wind turbine blade shell; applying a vacuum to at least some of the plurality holes such that the first wind turbine blade shell is sucked towards the form

DK 2018 70879 A1 surface of the first mould and held in place; manipulating the first mould so that that first wind turbine blade portion is positioned above the second wind turbine blade portion; locating the bond surfaces of the first wind turbine blade portion with bond surfaces of the second wind turbine blade portion; curing the adhesive; and stopping the application of the vacuum to the plurality of holes.

Still further there may be provided a method of making a wind turbine blade, the method comprising: providing a mould having a plurality of hole arrays located on a form surface thereof, wherein each of the plurality of hole arrays is operatively connected to a selectively operable evacuation device; laying-up a skin surface of a first blade portion of the wind turbine blade on the form surface, wherein the skin surface comprises a plurality of fibre layers; encapsulating the skin surface in an airtight envelope; curing the fibre layers in a resin matrix to form a first wind turbine blade portion; providing a second wind turbine blade portion located in a second mould; applying adhesive to bond surfaces of the second wind turbine blade portion; applying a vacuum to at least some of the plurality holes such that the first wind turbine blade portion is sucked towards the form surface of the first mould and held in place; manipulating the first mould so that that first wind turbine blade portion is positioned above the second wind turbine blade portion; locating the bond surfaces of the first wind turbine blade portion with bond surfaces of the second wind turbine blade portion; curing the adhesive; and stopping the application of the vacuum to the plurality of holes.

There is further proposed a mould for forming a portion of a wind turbine blade, the mould comprising: a form surface for shaping the wind turbine blade skin; and at least one discrete hole array located on the form surface, wherein the or each hole array comprises a plurality of holes, and wherein the or each hole array is arranged to be operatively connected to an evacuation device in use. Optionally, a periphery of the or each hole array may be substantially in the shape of a parallelogram, a rhomboid, a circle, a semi-circle, an oval, or a triangle. Optionally, the or each hole array may be substantially in the shape of a line or a curve. Still further optionally, the or each hole array may comprise a line located substantially at a centreline of the mould. Optionally there may be provided an evacuation box on an underside surface of the mould, wherein a periphery of the evacuation box surrounds at least a portion of the plurality of holes of at least one hole array.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

DK 2018 70879 A1

Figure 1 shows a schematic view of mould for forming a wind turbine blade half shell;

Figures 2a - 2h show example hole array patterns for use with the mould of Figure 1; and

Figure 3 shows a schematic side view of a detail of the mould of Figure 1.

DETAILED DESCRIPTION

Figure 1 illustrates a blade mould 1 for forming a wind turbine blade half shell. The mould 1 comprises a form surface 3 which is shaped to impart the required shape and size to the finished half shell.

The form surface 3 of the mould 1 comprises a plurality of holes 5 arranged in a number of hole arrays 4. In this embodiment, the holes 5 have a diameter of Xmm and are arranged in a regular pattern with the spacing between hole centres being Ymm. The hole arrays 4 extends in the spanwise direction S of the mould 1 and in the width wise direction W as shown in Figure 1.

The perimeter of the hole arrays 4 are substantially rectangular in shape, extending for Amm in the spanwise direction, and Bmm in the width direction. Of course, due to the curved shape of the form surface 3, the hole arrays 4 will have a curved profile. It will be understood that the dimensions given above refer to a rectangular shape that would be obtained were the array of holes to be provided on a flat surface.

In the example of Figure 1, three hole arrays 4 are shown. Additional hole arrays 4 may be provided on the form surface 3 in areas hidden in, or excluded from, Figure 1. Each hole array 4 occupies a discrete location on the form surface 3. The hole arrays 4 may be positioned in any location as desired by a mould designer. It is desirable to have one or more hole arrays 4 located on a centreline 10 of the form surface 3 as it is along the centreline that the half shell is most likely to sag and pre-release during bond curing. However, it is not essential that hole arrays 4 be provided along the centreline 10. In one embodiment, only one hole array 4 is provided along the centreline 10 of the mould 1.

Figures 2a to 2h show example configurations for the hole arrays 4. For simplicity, like numerals are used throughout to identify like elements. The hole array 4 of Figure 2a has a perimeter which is substantially square, the hole array 4 of Figure 2b has a perimeter which

DK 2018 70879 A1 is substantially circular, the hole array 4 of Figure 2c has a perimeter which is substantially triangular, the hole array 4 of Figure 2d has a perimeter which is substantially rhomboid, and the hole array 4 of Figure 2e has a perimeter which is substantially a parallelogram.

Figures 2f to 2h illustrate other arrangements for the hole arrays 4 wherein the hole array 4 of Figure 2f is substantially linear, the hole array 4 of Figure 2g is substantially semi-circular, and the hole array 4 of Figure 2h is substantially ovoid. It will be understood that many more shapes and arrangements for the hole arrays 4 are possible including shapes having no defined or regular shape. Furthermore, it is not necessary that the holes 5 be equally or regularly spaced within the hole array 4. It is envisaged that the array 4 may have any arrangement of holes 5 as desired by the mould designer. Furthermore, the holes 5 of a hole array 4 need not all be the same size. Hole arrays 4 having different perimeter shapes and hole 5 sizes and spacing may be provided on the form surface 3 of a mould 1.

Figure 3 shows a schematic side view of a section of the form surface 3 of the mould 1. Holes 5 are shown extending through the depth of the mould 1 from the form surface 3 to an underside surface 7 of the mould 1. An evacuation box 12 is attached to the underside surface 7. The evacuation box 12 is substantially hollow and has a closed end 13 and an open end 14. The open end 14 is attached to the underside surface 7 of the mould 1 and is provided with a substantially airtight seal (not shown). A hose 14 is attached to the closed surface 13 of the evacuation box 12 via a connection piece 16 so that fluidic communication is provided between the interior of the evacuation box 12 and the hose 15. The hose is connected to a selectively operable evacuation device (not shown), such as a vacuum pump or other source of under-pressure.

As shown in Figure 3, the periphery of the open end 14 of the evacuation box 12 surrounds the hole array 4. Although not shown in Figure 3, the periphery of the open end 14 of the evacuation box 12 surrounds the entire hole array 4 such that all of the holes 5 of the hole array 4 are in fluidic communication with the interior of the evacuation box 12. Each of the hole arrays 4 of Figure 1 has an evacuation box 12 associated therewith. It is not essential that every hole array 4 has an associated evacuation box 12, or that all of the holes 5 of the hole arrays 4 are in fluidic communication with the interior of the evacuation box 12. In some embodiments, only some of the hole arrays 4 of a mould 1 have an associated evacuation box 12.

In one embodiment, each evacuation box is connected to its own discrete evacuation device. In an alternative embodiment, two or more evacuation boxes may be attached to the same

DK 2018 70879 A1 evacuation device. In a further alternative embodiment, the entire underside of the mould 1 is covered by a substantially airtight cover, which may comprise a flexible material, which is sealed at its edges to the underside surface 7 of the mould 1 and connected to an evacuation device. In this way, substantially the entire underside surface 7 of the mould 1 may be exposed to an under pressure. The evacuation box 12 of Figure 5 is shown as a rectilinear box. However, the evacuation box 12 may be of any suitable shape and may comprise any suitable material, including flexible materials.

Use of the mould 1 to manufacture a wind turbine blade will now be described. The form surface 3 of the mould 1 is first covered in a release agent which is typically painted onto the form surface 3. The release agent is provided to assist with separating the cured half shell from the mould 1 when the wind turbine blade is broken out from the moulds after bond line curing is complete. Release agents are well known in the art and their use is not discussed in detail here.

Next, individual patches of gas permeable membrane material 6 are positioned over each of the hole arrays 4. A suitable membrane material is GORE-TEX (RTM). However, any suitable gas permeable material may be used.

The entire exposed surface of form surface 3, and the exposed upper surfaces of the membrane patches 6, are then covered by a gelcoat layer. The gelcoat is typically painted on using a roller applicator. Next, the skin of the half shell is built up, or laid-up, using any combination of glass fibre matting, carbon fibre pulltrusions, balsa wood, expanded polyurethane foam, or any other suitable material as dictated by the wind turbine blade design. The glass fibre matting may be pre-impregnated with resin, or may be dry.

Once the components making up the skin of the half shell have been placed in the mould 1, if necessary, the half shell lay-up is covered with a gas tight bag and a vacuum is used to draw resin into the fibres of the lay-up. As is well known in the art, this is only necessary if dry fibres are used in the lay-up.

Following resin impregnation if using dry fibre matting, or after completion of the lay-up if using pre-impregnated fibre matting, the half shell is cured. This causes the resin and gelcoat to harden to consolidate the materials of the half shell into a single composite component. As a part of this process, the patches of membrane 6 become integrated onto the outer surface of the half shell.

DK 2018 70879 A1

Once cured, the underside surface 7 of the mould 1 is exposed to an under pressure in the region of the hole arrays 4 by operation of an evacuation device (not shown) attached to the hoses 15 of evacuation boxes 12. This causes a vacuum to be applied to the outer surface of the half shell which is still in contact with the form surface 3 of the mould 1. The vacuum serves to suck the half shell onto the form surface 3 thereby keeping the half shell firmly in place in the mould 1 during the subsequent manoeuvring and curing steps described below.

Once the vacuum has been applied, the mould 1 is lifted by a crane and inverted so that the inner surface of the half shell faces downwards. During this phase, the vacuum applied to the outer surface of the half shell provides a critical holding force keeping the half shell firmly in place within the mould 1 and in contact with the form surface 3.

The mould 1 is manoeuvred until it is above a lower shell half which has been manufactured separately in a separate mould (not shown), and which is ready to receive an upper shell half in order to form a complete wind turbine blade. The mould 1 is lowered so that the bond edges located at the leading and trailing edges of the shell halves are brought into contact. This, in turn, causes an upper spar cap of a shear web, which has been fixed to the inner surface of the lower half shell, to come into contact with the inner surface of the upper half shell. Adhesive is applied to the bond edges and spar cap before the upper shell half is lowered onto the lower shell half.

The assembly is then cured to form the adhesive bonds between the two half shells. It is vital that the half shells do not move during this process to ensure the integrity of the adhesive bonds. In particular, it is important that the upper half shell does not become detached from the form surface 3 of the mould 1, thereby applying pressure to the adhesive before it has cured. As discussed above, such pre-release of the upper half shell can cause adhesive bonds which are too thin, or can cause kissing bonds caused by thermal expansion of the half shell during the bond cure. The vacuum applied to the outer surface of the upper half shell ensures that the upper half shell remains firmly held onto the form surface 3 of the mould 1 throughout the bond cure process. Once the adhesive bonds have properly formed, the vacuum is turned off so that the shell can be broken out of the mould 1.

In an alternative method, no membrane patches 6 are placed over the hole arrays 4. It should be noted that this method is not suitable for use with dry fibre lay-ups as resin can enter into the evacuation system during the resin infusion step if no membranes are provided. However, if pre-impregnated fibre lay-ups are used, it is not necessary to use the membranes. In this method, the hole arrays 4 are utilised before the half shell curing step to

DK 2018 70879 A1 compact the fibres of the pre-impregnated layers. Once the component materials have bed laid-up in the mould 1, the lay-up is covered with a gas tight bag and a vacuum is applied to the underside of the hole arrays 4 by operation of the evacuation device. This causes the lay-up to compact thus reducing the occurrence of voids in the finished structure. Once the fibres are sufficiently compacted, the vacuum source is turned off and the half shell is cured. The method then proceeds as described above.

In a further alternative method, the hole arrays 4 are covered with membrane patches 6 but no gelcoat is applied to the exposed surface of the membrane patches 6 so that they remain 10 gas permeable. If this method is adopted, and pre-impregnated fibre mats are used, the method of fibre compaction using a vacuum applied via the hole arrays 4 described above can still be used.

In an alternative mould configuration (not shown), A plurality of substantially equally spaced holes 5 may be provided over substantially the entire form surface 3 of the mould 1. A mould such as this is ideally covered by a single gas permeable membrane after release agent application. However, separate patches 6 of membrane material may be used to cover the whole form surface 3 of the mould 1, or only parts thereof (if pre-impregnated resin is being used).

Claims

1. A method of making a portion of a wind turbine blade, the method comprising: providing a mould having a plurality of holes located on a form surface thereof, wherein each of the plurality of holes is operatively connected to a selectively operable evacuation device;

covering at least some of the plurality of holes with a gas permeable membrane, laying-up a skin surface of the wind turbine blade on the membrane, wherein the skin surface comprises a plurality of fibre layers;

encapsulating the skin surface in an airtight envelope; and curing the fibre layers in a resin matrix.

2. The method of claim 1, comprising applying a vacuum to at least some of the plurality of holes, wherein the action of applying the vacuum causes the fibre layers to compact.

3. The method of claim 1, wherein a layer of gelcoat is applied on top of the membrane so that at least a portion of the plurality of holes are covered by a layer of membrane and a layer of gelcoat.

4. The method of claim 3, wherein all of the plurality of holes are covered by a layer of membrane and a layer of gelcoat.

5. The method of any preceding claim, wherein the plurality of holes are arranged in a number of discrete hole arrays.

6. The method of claim 5, wherein at least some of the hole arrays are covered by a discrete patch of membrane.

7. The method of claim 5 or 6, wherein each hole array has an evacuation device associated therewith.

8. A method of making a wind turbine blade, the method comprising:

making a first wind turbine blade portion in a first mould using the method according to any one of claims 1 to 7;

providing a second wind turbine blade portion located in a second mould; applying adhesive to bond surfaces of the second wind turbine blade shell;

DK 2018 70879 A1 applying a vacuum to at least some of the plurality holes such that the first wind turbine blade shell is sucked towards the form surface of the first mould and held in place;

manipulating the first mould so that that first wind turbine blade portion is positioned above the second wind turbine blade portion;

locating the bond surfaces of the first wind turbine blade portion with bond surfaces of the second wind turbine blade portion;

curing the adhesive; and stopping the application of the vacuum to the plurality of holes.

9. A method of making a wind turbine blade, the method comprising:

providing a mould having a plurality of hole arrays located on a form surface thereof, wherein each of the plurality of hole arrays is operatively connected to a selectively operable evacuation device;

laying-up a skin surface of a first blade portion of the wind turbine blade on the form surface, wherein the skin surface comprises a plurality of fibre layers;

encapsulating the skin surface in an airtight envelope;

curing the fibre layers in a resin matrix to form a first wind turbine blade portion; providing a second wind turbine blade portion located in a second mould; applying adhesive to bond surfaces of the second wind turbine blade portion; applying a vacuum to at least some of the plurality holes such that the first wind turbine blade portion is sucked towards the form surface of the first mould and held in place;

10. A mould for forming a portion of a wind turbine blade, the mould comprising:

a form surface for shaping the wind turbine blade skin; and at least one discrete hole array located on the form surface, wherein the or each hole array comprises a plurality of holes, and wherein the or each hole array is arranged to be operatively connected to an evacuation device in use.

11. A mould according to claim 10, wherein a periphery of the or each hole array is substantially in the shape of a parallelogram, a rhomboid, a circle, a semi-circle, an oval, or a triangle.

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12. A mould according to claim 10, wherein the or each hole array is substantially in the shape of a line or a curve.

5

13. A mould according to claim 10, wherein the or each hole array comprises a line located substantially at a centreline of the mould.

14. A mould according to any one of claims 10 to 13, further comprising an evacuation box provided on an underside surface of the mould, wherein a periphery of the evacuation box 10 surrounds at least a portion of the plurality of holes of at least one hole array.