Method of manufacturing a wind turbine blade part

Abstract

The present disclosure relates to a method of manufacturing a wind turbine blade part which involves placing at least one open-ended hollow tube about the dry-fibre lay-up prior to resin infusion. This enables manufacturers to "bridge" regions of the dry-fibre lay-up which are likely to become locked-off during resin infusion to help ensure that such regions do not become isolated from vacuum.

Description

[0001] METHOD OF MANUFACTURING A WIND TURBINE BLADE PART

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of manufacturing a wind turbine blade part, to a fibre fabric for aiding the manufacture of a wind turbine blade part, and to a wind turbine blade part comprising said fibre fabric.

[0004] BACKGROUND OF THE INVENTION

[0005] Resin infusion , e.g. vacuum-assisted resin transfer moulding (VARTM), is a composite manufacturing process in which a lay-up (or stack) of dry-fibre plies is impregnated with a resin which is drawn through the dry-fibre lay-up under the influence of vacuum. During a VARTM process, a stack of dry-fibre plies is laid up onto a mould before a vacuum bag is applied over said mould such that a mould cavity is defined between the vacuum bag and the mould. A vacuum is then applied to said mould cavity which draws resin (from a resin source) into the mould cavity where said resin can infuse into the stack of dry-fibre plies.

[0006] It shall be appreciated that during the VARTM process, resin is typically infused into the infusion (or B) surface of the lay-up (which is the surface of the lay-up which faces to the vacuum bag) and subsequently permeates through the thickness of the lay-up towards the opposite (A) surface (which is the surface of the lay-up which is in contact with the mould) under the influence of gravity or vacuum.

[0007] As such, in conventional resin infusion processes, resin tends to be drawn across the infusion surface of the lay-up much more quickly than the mould surface of the lay-up. Furthermore, the speed at which the resin permeates through the thickness of the layup may also vary across different regions of the dry-fibre lay-up.

[0008] This can lead to areas within the lay-up becoming isolated from vacuum by the surrounding resin, thereby leading to air pockets (or dry spots) within the final composite product in which the dry-fibre plies have not been properly impregnated with resin. This phenomenon is known as “lock-off”. It is the aim of the present invention to provide a solution to this issue. SUMMARY OF THE INVENTION

[0009] According to a first aspect of the present disclosure, there is provided a method of manufacturing a wind turbine blade part comprising the steps of: a) laying up a plurality of dry-fibre plies onto a mould to form a dry-fibre stack; b) placing at least one open-ended hollow tube about the dry-fibre stack, wherein the at least one open-ended hollow tube comprises a first end, a second end and an internal conduit extending between said first and second ends; c) placing a vacuum bag onto the mould such that a mould cavity is defined between the mould and the vacuum bag; and d) applying a vacuum to the mould cavity so as to draw resin from a resin source into the dry-fibre stack, wherein, during step b), the first end of the at least one open-ended hollow tube is placed in fluid communication with a first region of the dry-fibre stack and the second end of the at least one open-ended hollow tube is placed in fluid communication with a second region of the dry-fibre stack, such that, upon application of the vacuum during step d), air is drawn out of the first region via the at least one open-ended hollow tube until the first region becomes saturated with resin.

[0010] Advantageously, the aforementioned method enables manufacturers to “bridge” regions of the dry-fibre stack which are likely to become locked-off during resin infusion to help ensure that such regions do not become isolated from the vacuum source prior to becoming fully saturated.

[0011] In other words, in the event that the first region of the dry-fibre stack becomes surrounded (or encircled) by resin as the resin is drawn across the dry-fibre stack, the internal conduit(s) of the at least one open-ended hollow tube allow air (or other gases) to continue to be drawn out of the first region, along said internal conduit(s), and into the second region and thereby help to ensure that the first region of the dry-fibre stack remains in fluid communication with the vacuum source.

[0012] As such, even if the first region becomes encircled or surrounded by resin during resin infusion, resin can continue to be drawn into and saturate the first region(s) of the dry- fibre stack and hence the likelihood of air pockets being present within the final composite product is reduced.

[0013] In some examples, the resin infusion process may be a VARTM process.

[0014] In some examples, during step d), the resin is drawn into the dry-fibre stack such that a resin flow front may advance across the dry-fibre stack; and the method may further comprise the step of predicting an area of the dry-fibre stack that will be encircled by the resin flow front before said area becomes fully saturated with resin, said area being the first region of the dry-fibre stack.

[0015] As is well understood in the art, the “resin flow front” is an advancing boundary of the resin as the resin is drawn through the dry-fibre stack. If the resin flow front moves through different parts of the dry-fibre stack at different speeds, the resin flow front may encircle an area of the dry-fibre stack. By “encircled” means that the resin surrounds and forms a closed boundary around the area of the dry-fibre stack. The term encircled does not necessarily mean a perfect circular shape, it means that the resin surrounds the area, which can be in various shapes, not necessarily a circle.

[0016] It shall be appreciated that the “first region” may alternatively be referred to as a “lock- off region” or a “dry spot”, that is a region of the dry-fibre stack behind the resin flow front that is not fully saturated with said resin.

[0017] It shall be appreciated that the “second region” may alternatively be referred to as a “non-locked-off region”, that is a region which is predicted to become saturated with resin after the first region has become fully saturated.

[0018] In a conventional resin infusion process, an area of the dry-fibre stack that is encircled by a resin flow front may result in that area being isolated from the vacuum, leading to a lock off region. However, the hollow tube(s) of the invention allow for the encircled area to be in fluid communication with the vacuum such that air (or any other gas) may be removed from the encircled area, such that the encircled area subsequently becomes saturated with the resin.

[0019] In some examples, the step of predicting the area of the dry-fibre stack that will be encircled by the resin flow front before said area becomes fully saturated with resin may be carried out by computer simulation, that is software that can model resin infusion processes. Or, in another example, the step may be carried out by manufacturing a prototype blade part and identifying those areas that are encircled by resin.

[0020] In some examples, during step b), the first end(s) of the at least one open-ended hollow tube may be placed in fluid communication with the first region of the dry-fibre stack.

[0021] It shall be appreciated that the first region corresponds to the said predicted area that will be encircled by resin and so the hollow tube(s) will be located at the necessary place to remove gas from the encircled area.

[0022] In some examples, the vacuum may be applied to the mould cavity via a vacuum port, and the second region may be located between the vacuum port and the first region. In other words, the second region of the dry-fibre stack may be downstream of the first region. In some examples, the second region is located proximate to said vacuum port.

[0023] Advantageously, locating the second region between the vacuum port and the first region helps to draw air from first region in a downstream direction towards the vacuum port.

[0024] In some examples, the at least one open-ended hollow tube may be formed of an electrically insulating material. It shall be appreciated that following the resin infusion process, the at least one hollow tube becomes incorporated into the wind turbine blade part. As such, the use of at least one hollow tube which is formed of an electrically insulating material helps to ensure that lightening protection is maintained when the at least one hollow tube becomes incorporated into the wind turbine blade part.

[0025] In some examples, the internal conduit of the at least one open-ended hollow tube may comprise an inner diameter of no more than 1mm. In some examples, the internal conduit may comprise an inner diameter of no more than 0.5mm. In other examples, the internal conduit may comprise an inner diameter of no more than 0.3mm.

[0026] Advantageously, using a hollow tube having an inner diameter of no more than 1mm helps to prevent significant volumes of resin from being drawn through the hollow tube during resin infusion. In some examples, the at least one open-ended hollow tube may comprise an outer diameter of no more than 2mm, and preferably no more than 1mm.

[0027] Advantageously, using a hollow tube having an outer diameter of no more than 2mm helps to reduce the magnitude of stresses which may be introduced into the dry-fibre stack as the respective ply layers are laid on top of the at least one open-ended hollow tube. For example, wrinkles in the dry-fibre stack can be avoided.

[0028] In some examples, the at least one open-ended hollow tube may be formed of glass. In other examples, the at least one open-ended hollow tube may be formed of a polyamide material.

[0029] It shall be appreciated that following the resin infusion process, the at least one open- ended hollow tube become incorporated into the wind turbine blade part. As such, since composite laminates used in wind turbine blade parts are typically glass fibre reinforced polymeric composites, the use of hollow glass fibres helps to improve the compatibility between the hollow tubes and the wind turbine blade part.

[0030] In some examples, the at least one open-ended hollow tube may comprise a plurality of said open-ended hollow tubes. Advantageously, using a plurality of open-ended hollow tubes allows more gas to be removed from the first region, and over a larger area.

[0031] In some examples, during step b), the plurality of open-ended hollow tubes may be arranged in a staggered array.

[0032] It shall be appreciated that prior to resin infusion the plurality of open-ended hollow tubes will be laid down in areas in which the manufacturer predicts that a lock-off may occur, which will be within a tolerance window. For example, the predicted lock-off region may change depending on the ambient temperature or the viscosity of the resin for example. The use of a staggered array of hollow tubes allows the tubes to cover a larger lateral area and hence provides manufacturers with a greater tolerance window when placing the tubes. In some examples, the plurality of open-ended hollow tubes may be incorporated into a fibre fabric. In some examples, the fibre fabric may become incorporated into the wind turbine blade part. Advantageously, incorporating the plurality of open-ended hollow tubes into a fibre fabric makes the tubes easier to handle and therefore makes it easier for such tubes to be placed about the dry-fibre stack.

[0033] In some examples, during step b), the plurality of open-ended hollow tubes may be embedded between one or more of the dry fibre ply layers which make up the dry-fibre stack.

[0034] In some examples, during step b), the plurality of open-ended hollow tubes may be placed between an A-surface of the dry-fibre stack and a surface of the mould.

[0035] In some examples, during step b), the plurality of open-ended hollow tubes may be embedded between one or more of the dry fibre ply layers proximate to an A-surface of the dry-fibre stack. Preferably, the plurality of open-ended hollow tubes may be embedded between one or more of the dry fibre ply layers proximate to the A-surface of the dry-fibre stack such that the open-ended hollow tubes are within 30% of the dryfibre stack thickness measured from the A-surface, and wherein no open-ended hollow tubes are embedded within 70% of the dry-fibre stack thickness measured from a B- surface of the dry-fibre stack. Preferably, the plurality of open-ended hollow tubes may be embedded between one or more of the dry fibre ply layers proximate to the A- surface of the dry-fibre stack such that the open-ended hollow tubes are within 20% of the dry-fibre stack thickness measured from the A-surface, and wherein no open-ended hollow tubes are embedded within 80% of the dry-fibre stack thickness measured from the B-surface of the dry-fibre stack. More preferably, the plurality of open-ended hollow tubes may be embedded between one or more of the dry fibre ply layers proximate to the A-surface of the dry-fibre stack such that the open-ended hollow tubes are within 10% of the dry-fibre stack thickness measured from the A-surface, and wherein no open-ended hollow tubes are embedded within 90% of the dry-fibre stack thickness measured from the B-surface of the dry-fibre stack.

[0036] The A-surface may be the last area to be saturated during resin infusion because resin enters from the B-surface and moves downward towards the A-surface. Placing the tubes at or near the A-surface ensures that any lock-off region near the mould (where air pockets are most likely) remains connected to the vacuum source until fully saturated. By not placing the tubes in other regions of the stack reduces costs and complexity.

[0037] According to a second aspect of the present disclosure, there is provided a fibre fabric for resin infusion comprising: a plurality of fibres; and a plurality of open-ended hollow tubes, wherein each tube comprises a first end, a second end and an internal conduit extending between said first and second ends for allowing gases to traverse over at least a portion of the fibre fabric during resin infusion.

[0038] In some examples, at least some of the plurality of open-ended hollow tubes may extend continuously across the width of the fibre fabric from a first edge thereof to a second edge thereof.

[0039] In some examples, the plurality of open-ended hollow tubes may be spaced apart in the longitudinal direction by a distance of at least 50mm.

[0040] In some examples, at least some of the plurality of open-ended hollow tubes may extend continuously along a length of the fibre fabric from a first end thereof to a second end thereof.

[0041] In some examples, the plurality of open-ended hollow tubes may be spaced apart in the lateral direction by a distance of at least 50mm.

[0042] In some examples, the plurality of open-ended hollow tubes may extend obliquely across the fibre fabric.

[0043] In some examples, the plurality of open-ended hollow tubes are interspersed between the plurality of fibres.

[0044] Advantageously, interspersing the plurality of opened-ended hollow tubes between the fibres helps to better embed the hollow tubes within the fibre fabric and hence helps to prevent said tubes from being damaged or pulled-off of the fibre fabric during handling and / or lay-up. In some examples, the fibre fabric may comprise a plurality of weft fibres extending transversely across the fibre fabric and at least one warp fibre extending along a length of the fibre fabric, substantially perpendicular to the plurality of weft fibres. In some examples, the fibre fabric may comprise a plurality of warp fibres.

[0045] In some examples, the plurality of open-ended hollow tubes may be orientated substantially parallel to the plurality of weft fibres.

[0046] In some examples, the plurality of open-ended hollow tubes may be orientated substantially parallel to the at least one warp fibre.

[0047] In some examples, the plurality of open-ended hollow tubes may be orientated at an angle of approximately + / - 45 degrees relative to the weft and / or warp fibres.

[0048] In some examples, the plurality of open-ended hollow tubes may be interwoven into the fibre fabric via the at least one warp fibre.

[0049] Advantageously, interweaving the hollow tubes into the fibre fabric helps to reduce the risk of rupturing the hollow tubes during manufacture of the fibre fabric.

[0050] In some examples, the first and / or second ends of at least some of the plurality of open- ended hollow tubes may protrude beyond an edge of the fibre fabric.

[0051] It shall be appreciated that prior to resin infusion the fibre fabric will be laid down in areas in which the manufacturer predicts that a lock-off may occur, which will be within a tolerance window. For example, the predicted lock-off region may change depending on the ambient temperature or the viscosity of the resin for example.

[0052] The use of a fibre fabric in which at least some of the plurality of open-ended hollow tubes protrude beyond an edge of the fibre fabric allows the tubes to cover a larger lateral area and hence provides manufacturers with a greater tolerance window when placing the tubes.

[0053] In some examples, the plurality of open-ended hollow tubes may be arranged in a staggered array. It shall be appreciated that prior to resin infusion the fibre fabric will be laid down in areas in which the manufacturer predicts that a lock-off may occur, which will be within a tolerance window. For example, the predicted lock-off region may change depending on the ambient temperature or the viscosity of the resin for example. The use of a staggered array of hollow tubes allows the tubes to cover a larger lateral area and hence provides manufacturers with a greater tolerance window when placing the tubes.

[0054] In some examples, the plurality of open-ended hollow tubes may comprise a first colour, and the plurality of fibres may comprise a second colour which is different to the first colour. Advantageously, the use of different colours for the hollow tubes and the fibres enables manufacturers to more easily identify the position of the hollow tubes within the fibre fabric which helps to prevent manufacturers from inadvertently severing the hollow tubes when cutting the fibre fabric to a desired size.

[0055] In some examples, the fibre fabric may comprise a first fabric layer and a second fabric layer, and the plurality of open-ended hollow tubes may be sandwiched between the first and second fabric layers. Advantageously, sandwiching the plurality of hollow tubes between the first and second fabric layers helps to better embed the hollow tubes within the fibre fabric and hence helps to prevent said tubes from being damaged or pulled-off of the fabric during handling and / or lay-up.

[0056] In some examples, the plurality of open-ended hollow tubes may be bonded to a surface of the first and / or second fabric layers. In other examples, the plurality of open- ended hollow tubes may be stitched to a surface of the first and / or second fabric layers.

[0057] In some examples, the fibre fabric may be a non-woven fabric. In some examples, the plurality of fibres are glass fibres. It shall be appreciated that following the resin infusion process, the fibre fabric becomes incorporated into the wind turbine blade part. As such, since wind turbine blade parts are typically formed of glass fibre reinforced polymeric composites, the use of glass fibres helps to improve the compatibility between the fibre fabric and the wind turbine blade part.

[0058] In some examples, the plurality of open-ended hollow tubes may be formed of a polyamide material. In other examples, the plurality of open-ended hollow tubes may be formed of glass. Advantageously, the use of a polyamide material helps make the hollow tubes more resistant to puncture (e.g., during handling or stitching). According to a third aspect of the present disclosure, there is provided a wind turbine blade part comprising the fibre fabric according to the second aspect of the present disclosure.

[0059] The term “hollow” is defined herein to mean that the at least one tube defines an internal conduit (or cavity) which contains a gas (e.g., air).

[0060] The term “open-ended” is defined herein to mean that the respective ends of the at least one tube comprise an opening in fluid communication with the internal conduit.

[0061] The term “electrically insulating material” is defined herein to mean that the at least one open-ended hollow tube has an electrical resistance greater than 1Mohm / meter.

[0062] The term “A-surface” (or mould surface) is defined herein to mean the surface of the dry-fibre stack which is facing or in contact with the mould.

[0063] The term “B-surface” (or infusion surface) is defined herein to mean the surface of the dry-fibre stack which is facing the vacuum bag and hence is not facing or in contact with the mould.

[0064] BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0066] FIG. 1 shows a front view of a wind turbine;

[0067] FIG. 2 shows a section view of a wind turbine blade of the wind turbine illustrated in FIG. 1 ;

[0068] FIG. 3 shows a schematic illustration of an apparatus for manufacturing a wind turbine blade part via VARTM;

[0069] FIG. 4 shows a flow diagram of a method of manufacturing a wind turbine blade part according to an example of the present disclosure; FIG. 5 shows a schematic illustration of a stack of dry-fibre ply layers undergoing resin infusion;

[0070] FIG. 6A shows a top (or plan) view of a fibre fabric according to an example of the present disclosure;

[0071] FIG. 6B shows a side view of the fibre fabric illustrated in FIG. 6A;

[0072] FIG. 7 shows a side view of a fibre fabric according to an alternative example of the present disclosure;

[0073] FIG. 8 shows a top (or plan) view of a fibre fabric according to another example of the present disclosure;

[0074] FIG. 9 shows a top (or plan) view of a fibre fabric according to yet another example of the present disclosure; and

[0075] FIG. 10 shows a side view of a fibre fabric according to a further example of the present disclosure.

[0076] DETAILED DESCRIPTION OF EMBODIMENT(S)

[0077] FIG. 1 shows a wind turbine 1 according to an example of the present disclosure.

[0078] The wind turbine 1 includes a nacelle 2 supported on a tower 3 that is mounted on a foundation 4. The wind turbine 1 depicted here is an onshore wind turbine such that the foundation 4 is embedded in the ground, but the wind turbine 1 could be an offshore installation in which case the foundation 4 would be provided by a suitable marine platform, such as a monopile or jacket.

[0079] The nacelle 2 supports a rotor 5 comprising a rotor hub 6 to which a plurality of blades 7 are attached. The blades 7 which make up the rotor 5 of the wind turbine 1 each comprise a tip end, which is located distal from the rotor hub 6, a root end, which is located proximal to the rotor hub 6, and leading and trailing edges 8, 9 which extend in a spanwise direction between the root and tip ends of the blades 7. It will be noted that the wind turbine 1 illustrated in FIG. 1 is the common type of horizontal axis wind turbine (HAWT) such that the rotor 5 is mounted at the nacelle 2 to rotate about a substantially horizontal axis defined at the centre at the rotor hub 6. However, it shall be appreciated that in an alternative example, the wind turbine 1 may be a vertical axis wind turbine (VAWT).

[0080] As is known, the blades 7 are acted on by the wind which causes the rotor 5 to rotate about its axis thereby operating generating equipment through a gearbox (not shown) that is housed in the nacelle 2. The generating equipment is not shown in FIG. 1 since it is not central to the examples of the invention.

[0081] FIG. 2 shows a section view of a respective one of the wind turbine blades 7 illustrated in FIG. 1.

[0082] It shall be appreciated that the wind turbine blades 7 are of a substantially identical construction and so, for conciseness, only one of the respective wind turbine blades 7 shall be described herein.

[0083] The wind turbine blade 7 comprises a windward shell portion 10 which defines the pressure surface 10a of the wind turbine blade 7 and a leeward shell portion 12 which defines the suction surface 12a of the wind turbine blade 7.

[0084] The two shell portions 10,12 may be manufactured as a pair of half-shells which, when the wind turbine blade 7 is installed in a wind turbine 1 as illustrated in FIG. 1 , are joined along the leading edge 8 and along the trailing edge 9 of the wind turbine blade 7.

[0085] It shall be appreciated that each of the shell portions 10, 12 extend in a chordwise direction between the leading edge 8 and the trailing edge 9 of the wind turbine blade 7, and also in a spanwise direction between the root end and the tip end of the wind turbine blade 7.

[0086] The chordwise direction is indicated in FIG. 2 by a horizontal arrow and the letter “C”. A thickness direction perpendicular to the chordwise direction is also indicated by a vertical arrow and the letter “T”. The respective shell portions 10, 12 are typically made of a composite laminate material comprising a plurality of fibre reinforcements which are infused with a polymeric resin.

[0087] FIG. 3 shows a schematic illustration of an apparatus 100 for manufacturing a wind turbine blade part via VARTM.

[0088] In the example illustrated in FIG. 3, the apparatus 100 is configured for manufacturing one of the respective shell portions 10, 12 of the wind turbine blade 7 illustrated in FIG. 2.

[0089] However, it shall be appreciated that in other examples, the apparatus 100 may be used for manufacturing other types of wind turbine blade part, such as a shear web.

[0090] As shown in FIG. 3, the apparatus 100 comprises a rigid mould 102 having a surface onto which a plurality of dry-fibre plies can be laid and a vacuum bag 110.

[0091] The vacuum bag 110 is made up of a fluid-impermeable membrane 112 (e.g., a disposable film) and can be laid over and sealed against the rigid mould 102 such that a fluid-tight mould cavity 105 is defined between the mould 102 and the vacuum bag 110.

[0092] In the illustrated example, the rigid mould 102 is a female mould and hence defines a recess 104 which has a shape corresponding to a desired outer surface shape of at least one of the respective shell portions 10, 12. However, it shall be appreciated that in other examples, the rigid mould 102 may be a male mould and hence the recess 104 may be omitted in some examples.

[0093] The rigid mould 102 may also comprise a pair of flanges 106 which extend around the periphery of the rigid mould 102 to which the vacuum bag 110 can be secured.

[0094] As shown in FIG. 3, the apparatus 100 also comprises at least one resin port 116 which is in fluid communication with an associated resin source 122 to allow resin to be introduced into the space (or cavity) 105 defined between the rigid mould 102 and the vacuum bag 110, and at least one vacuum port 118 which is in fluid communication with an associated vacuum source (not shown) to allow air present within the mould cavity 105 to be drawn out (or evacuated) from the cavity 105. The resin port 116 may be attached to the resin source 122 via a suitable resin conduit 124.

[0095] In the illustrated example, the apparatus 100 comprises a single resin port 116, which is provided at a central portion of the fluid-impermeable membrane 112, and a pair of vacuum ports 118 which are provided at the periphery of the fluid-impermeable membrane 112, adjacent to the flanges 106 of the rigid mould 102.

[0096] However, it shall be appreciated that in other examples, the resin and / or vacuum ports 116, 118 may be provided at other locations about the apparatus 100. It shall also be appreciated that in other examples, a different number of resin and / or vacuum ports 116, 118 may be provided.

[0097] A method of manufacturing a wind turbine blade part according to an example of the present disclosure shall now be described with reference to FIG. 4 and FIG. 5.

[0098] As alluded to above, during a first step 130 of the method, a plurality of individual dryfibre ply layers (or plies) 109 are laid onto a surface of the mould 102 one atop the other to form a dry-fibre stack 108 having a desired shape and thickness.

[0099] The plies may comprise unidirectional, biaxial or triaxial fibres, for example.

[0100] In some examples, the dry-fibre ply layers 109 may comprise glass-fibres. In other examples, the dry-fibre ply layers 109 may comprise other types of fibre such as carbon fibres. It shall also be appreciated that in some examples, the dry-fibre stack 108 may comprise a mixture of different types of dry-fibre ply layer 109 (e.g., some glass-fibre ply layers and some carbon-fibre).

[0101] As shown in FIG. 5, the lowermost ply layer 109a of the dry-fibre stack 108 contacts the mould 102 and hence defines a mould (or “A”) surface 108a of the dry-fibre stack 108.

[0102] Meanwhile, the uppermost ply layer 109b faces the vacuum bag 110 during resin infusion and hence is not in direct contact with the mould 102. As such, the uppermost ply layer 109b defines an infusion (or “B”) surface 108b of the dry-fibre stack 108. Referring still to FIG. 5, it shall be appreciated that since the uppermost ply layer 109b is located closest to the resin port(s) 116, during resin infusion resin 120 will first infuse into and saturate the uppermost ply layer 109b of the dry-fibre stack 108 before permeating through the thickness (T) of the dry-fibre stack 108 under the influence of gravity until it ultimately reaches the lowermost ply layer 109a.

[0103] Meanwhile, as well as permeating through the thickness (T) of the dry-fibre stack 108, during resin infusion, the resin 120 will also be simultaneously drawn outwardly towards the periphery of the dry-fibre stack 108 (i.e. , towards the respective vacuum ports 118) by the suction forces applied onto the mould cavity 105 by the vacuum source (not shown).

[0104] In FIG. 5, the direction of resin flow across the dry-fibre stack 108 is indicated by a horizontal arrow and the letter “R”.

[0105] As such, since resin 120 is first introduced at the infusion surface 108b of the dry-fibre stack 108, meaning that the resin 120 will often infuse into and saturate the uppermost ply layer 109b before it has reached the lowermost ply layer 109a, during resin infusion, resin 120 tends to be drawn across the infusion surface 108b of the stack 108 much more quickly than the mould surface 108a of the stack 108.

[0106] Furthermore, the speed at which the resin 120 permeates through the thickness (T) of the stack 108 may also vary across different regions of the dry-fibre stack 108, for example where there is a change in thickness of the stack.

[0107] As such, some regions 126 of the dry-fibre stack 108 may take a longer time to saturate (e.g., thicker regions or more solid / compacted regions) and hence may become encircled by the advancing resin flow front 121 , thereby isolating such regions 126 from the vacuum source (not shown) before they have become fully saturated.

[0108] As is well understood in the art, a “resin flow front” 121 is an advancing boundary of the resin 120 as the resin 120 is drawn through the dry-fibre stack 108. If the resin flow front 121 moves through different parts of the dry-fibre stack 108 at different speeds, the resin flow front 121 may encircle one or more regions 126 of the dry-fibre stack 108 which, in a conventional resin infusion process, may result in that area being isolated from the vacuum. This phenomenon, which is illustrated in FIG. 5, is known as “lock-off” and is undesirable as it can lead to air pockets being present within the finished wind turbine blade part which are regions or areas of the finished product in which the dry-fibre plies 109 have not been fully saturated with resin 120.

[0109] As such, in order to address this issue, during step 131 , at least one open-ended hollow tube 220 is placed about the dry-fibre stack 108 so as to “bridge” regions of the dryfibre stack 108 which are likely to become encircled (or “locked-off’) by the advancing resin flow front 121 during resin infusion.

[0110] In the following description, the at least one open-ended hollow tube comprises a plurality of open-ended hollow tubes. However, it will be appreciated that, in some examples, a single open-ended hollow tube may also bridge regions of the dry-fibre stack which are likely to become encircled by the advancing resin flow front during resin infusion.

[0111] As shown in FIG. 5, the plurality of open-ended hollow tubes 220 each comprise a first end 222, a second end 224 and an internal conduit (not shown) which extends between the first 222 and second 224 ends.

[0112] Furthermore, since the aforementioned tubes 220 are open-ended, the first 222 and second 224 ends of each tube 220 also comprise a respective opening 226 which is in fluid communication with the internal conduit (not shown) such that gases (e.g., air) can pass into and / or out of the internal conduit (not shown).

[0113] During step 131 of the method, the first ends 222 of the plurality of open-ended hollow tubes 220 are placed in fluid communication with a first (or lock-off) region 126 of the dry-fibre stack 108 which is an area of the dry-fibre stack 108 which is predicted to become encircled by the advancing resin flow front 121 prior to said area becoming fully saturated.

[0114] The step of predicting the area of the dry-fibre stack 108 that will be encircled by the resin flow front 121 may be carried out by computer simulation, that is software that can model resin infusion processes, or, in another example, may be carried out by manufacturing a prototype blade part and identifying those areas 126 that are encircled by resin 120.

[0115] It shall be appreciated that the first (or lock-off) region 126 may alternatively be referred to as a dry-spot, that is a region of the dry-fibre stack 108 (located behind the advancing resin flow front 121) that is not saturated with resin 120.

[0116] Meanwhile, the second ends 224 of the plurality of open-ended hollow tubes 220 are placed in fluid communication with a second (or non-locked-off) region 128 of the dryfibre stack 108, that is a region of the dry-fibre stack 108 which is predicted to become saturated with resin 120 after the first region 126 has become fully saturated.

[0117] The second (or non-locked-off) region 128 may be a region of the dry-fibre stack 108 which is located downstream of the first (or locked-off) region 126. For example, the second region 128 may be located between one of the respective vacuum ports 118 and the first region 126. In some examples, the second region 128 may be located proximate (or adjacent) to one of the respective vacuum ports 118.

[0118] In some examples, the plurality of open-ended hollow tubes 220 may be placed about the dry-fibre stack 108 after the dry-fibre ply layers 109 have been fully laid up.

[0119] In the example illustrated in FIG. 5, the plurality of open-ended hollow tubes 220 are placed between the A (or mould) surface 108a of the dry-fibre stack 108 and the surface of the mould 102.

[0120] However, in other examples, the plurality of open-ended hollow tubes 220 may instead be embedded between one or more of the dry-fibre ply layers 109 as the dry-fibre stack 108 is being laid up onto the surface of the mould 102.

[0121] For example, the plurality of open-ended hollow tubes 220 may be embedded between one or more of the dry-fibre ply layers 109 proximate to the A (or mould) surface 108b of the dry-fibre stack 108.

[0122] The plurality of open-ended hollow tubes 220 may be formed of glass or, alternatively, may be formed of a different material (such as polyamide). As shall be described in greater detail later within this application, the open-ended hollow tubes 220 of the present disclosure are designed to become incorporated into the finished wind turbine blade part following resin infusion.

[0123] As such, since wind turbine blade parts are typically formed of glass-fibre reinforced composite materials, forming the plurality of open-ended hollow tubes 220 from the same material (i.e. , glass) helps to improve the compatibility between the hollow-tubes 220 and the finished wind turbine blade part.

[0124] It shall also be appreciated that in examples in which the aforementioned method is being used for the manufacture of wind turbine blade shells, such as the shell portions 10,12 illustrated in FIG. 2, it is also preferable for the plurality of open-ended hollow tubes 220 to be formed of an electrically insulating material.

[0125] This helps to ensure that lightning protection is maintained upon incorporation of said hollow tubes 220 into the shell portion 10, 12.

[0126] Referring back to FIG. 4, it shall be appreciated that during step 131 , the plurality of open-ended hollow tubes 220 may be placed individually about the dry-fibre stack 108 or, alternatively, may be incorporated into a fibre fabric 200 which is either laid onto a surface of the dry-fibre stack 108 or embedded between one or more of the dry-fibre ply layers 109.

[0127] Referring now to FIG. 6A and FIG. 6B, a fibre fabric 200 is depicted for aiding the manufacture of a wind turbine blade part during resin infusion.

[0128] It shall be appreciated that the use of a fibre fabric 200 is beneficial since it enables multiple pre-positioned tubes 220 to be laid down simultaneously and therefore avoids wind turbine blade part manufacturers having to handle, position and lay individual tubes 220 which can require significant amounts of dexterity and can hence become very time consuming.

[0129] The fibre fabric 200 is made up of a plurality of fibres 210 and a plurality of open-ended hollow tubes 220. As specified above, the plurality of open-ended hollow tubes 220 each comprise a first end 222, a second end 224 and an internal conduit extending therebetween for allowing gases (e.g., air) to traverse across the fibre fabric 200 during resin infusion (as shall be described in greater detail later within this application).

[0130] In some examples, the fibre fabric 200 may comprise a plurality of weft fibres 212 which extend transversely (or laterally) across a width (X) of the fibre fabric 200 and at least one warp fibre 214 which extends longitudinally along a length (Y) of the fibre fabric 200, substantially perpendicular to the plurality of weft fibres 212.

[0131] The plurality of weft fibres 212 may extend continuously between a first (or left hand) edge 202 of the fibre fabric 200 and a second (or right hand) edge 204 of the fibre fabric 200.

[0132] The at least one warp fibre 214 may extend continuously between a first (or top) end 206 of the fibre fabric 200 and a second (or bottom) end 208 of the fibre fabric 200.

[0133] In the illustrated example, the fibre fabric 200 comprises a plurality of warp fibres 214 extending between the first 206 and second 208 ends of the fibre fabric 200 such that substantially all of the warp fibres 214 extend in a direction which aligns with a longitudinal axis (Y) of the fibre fabric 200.

[0134] It shall be appreciated that in the illustrated example, the fibre fabric 200 is a nonwoven (or non-crimp) fabric and hence the warp 214 and weft 212 fibres are provided in separate layers which are bonded or stitched together to form the fibre fabric 200.

[0135] However, in other examples (such as the example depicted in FIG. 7), the fibre fabric 200 may be a woven fabric and hence the at least one warp fibre 214 may cross under and over the respective weft fibres 212 to form a weave.

[0136] It shall be appreciated that the fibre fabric 200 illustrated in FIG. 7 has many features in common with the fibre fabric 200 depicted in FIG. 6 and so, for the sake of conciseness, only the differences shall be described herein.

[0137] Referring back to FIG. 6B, in the illustrated example, the plurality of fibres 210 which make up the fibre fabric 200 are glass fibres. As mentioned above, it shall be appreciated that following the resin infusion process, the plurality of open-ended hollow tubes 220 (and hence the fibre fabric 200) become incorporated into the finished wind turbine blade part.

[0138] As such, since wind turbine blade shells are typically formed of glass-fibre reinforced composite materials, the use of glass fibre fabrics 200 helps improve the compatibility between the fibre fabric 200 and the finished wind turbine blade part.

[0139] However, it shall be appreciated that in other applications, the fibre fabric 200 may instead comprise a different fibre type such as polyester, nylon, acrylic, natural fibre etc.

[0140] Referring now to FIG. 6A, in the illustrated example, the plurality of open-ended hollow tubes 220 extend continuously across the width of the fibre fabric 200 starting from the first edge 202 of the fibre fabric 200 and terminating at the second edge 204 of the fibre fabric 200.

[0141] In other words, the plurality of open-ended hollow tubes 220 extend in the X-axis direction and are orientated substantially parallel to the plurality of weft fibres 212.

[0142] However, it shall be appreciated that in other examples, the plurality of open-ended hollow tubes 220 may only extend partially across the width of the fibre fabric 200.

[0143] It shall also be appreciated that, in further examples, the plurality of open-ended hollow tubes 220 may extend continuously along the length of the fibre fabric 200 starting from the first end 206 of the fibre fabric 200 and terminating at the second end 208 of the fibre fabric 200.

[0144] In other words, the plurality of open-ended hollow tubes 220 may extend in the Y-axis direction and hence may be orientated substantially parallel to the at least one warp fibre 214.

[0145] It shall also be appreciated that, in some examples, the plurality of open-ended hollow tubes 220 may only extend partially along the length of the fibre fabric 200. It shall also be appreciated that in further examples, the plurality of open-ended hollow tubes 220 may be orientated in other directions.

[0146] A fibre fabric 200 according to such an alternative example is depicted in FIG. 8.

[0147] It shall be appreciated that the fibre fabric 200 illustrated in FIG. 8 has many features in common with the fibre fabric 200 depicted in FIG. 6 and so, for the sake of conciseness, only the differences shall be described herein.

[0148] Notably, in the fibre fabric 200 illustrated in FIG. 8, rather than extending transversely across the fibre fabric 200 as is the case in FIG. 6A, the plurality of open-ended hollow tubes 220 extend obliquely across the fibre fabric 200 at an angle of approximately + / - 45 degrees relative to the plurality of warp / weft fibres.

[0149] Referring back to FIG. 6A, the plurality of open-ended hollow tubes 220 are spaced apart by a distance (S).

[0150] In the illustrated example, the plurality of open-ended hollow tubes 220 are spaced apart in the longitudinal (Y-axis) direction but in other examples, the plurality of open- ended hollow tubes may be spaced in the lateral (X-axis) direction.

[0151] In the illustrated example, the plurality of open-ended hollow tubes 220 are spaced apart by a distance of approximately 50mm. However, it shall be appreciated that in other examples the plurality of open-ended hollow tubes 220 may be spaced apart by different distances.

[0152] It shall be appreciated that prior to resin infusion the fibre fabric 200 will be laid down in areas in which the manufacturer predicts that a lock-off may occur, which will be within a tolerance window. However, the predicted lock-off region 126 may change depending on the ambient temperature or the viscosity of the resin 120 for example.

[0153] As such, spacing the open-ended hollow tubes 220 in this manner allows the open- ended hollow tubes 220 to cover a larger area, and therefore provides users with a greater tolerance window when placing the fibre fabric 200 about the dry-fibre stack 108 prior to resin infusion. Furthermore, the aforementioned spacing also enables this benefit to be achieved without increasing the number of tubes required per square meter of fabric, and hence does not significantly increase the unit cost of the fibre fabric 200.

[0154] It shall also be appreciated that in some examples, the plurality of open-ended hollow tubes 220 may be placed (or arranged) in a staggered array during step 131.

[0155] As with the aforementioned spacing, the use of a staggered array of hollow tubes 220 allows the tubes 220 to cover a larger area and hence provides manufacturers with a greater tolerance window when placing the tubes about the dry-fibre stack 108.

[0156] A fibre fabric 200 according to another example of the present disclosure in which the plurality of open-ended hollow tubes 220 are arranged in such a staggered array is depicted in FIG. 9.

[0157] It shall be appreciated that the fibre fabric 200 illustrated in FIG. 9 has many features in common with the fibre fabric 200 depicted in FIG. 6 and so, for the sake of conciseness, only the differences shall be described herein.

[0158] Notably, in the example illustrated in FIG. 9, the plurality of open-ended hollow tubes 220 are arranged such that the first and / or second ends of at least some of the open- ended hollow tubes 220 protrude beyond an edge of the fibre fabric 200.

[0159] As shown in FIG. 9, the fibre fabric 200 comprises two sets of open-ended hollow tubes 220a and 220b which are arranged in an alternating manner between the first 206 and second 208 ends of the fibre fabric 200.

[0160] The first set 220a of open-ended hollow tubes 220 are arranged in the same fashion as the hollow tubes 220 illustrated in FIG. 6A and hence extend continuously across the width of the fibre fabric 200 starting from the first edge 202 of the fibre fabric 200 and terminating at the second edge 204 of the fibre fabric 200.

[0161] However, unlike the previous examples, the second set 220b of open-ended hollow tubes 220 are laterally offset from the first set 220a of open-ended hollow tubes 220. As such, the second set 220 of open-ended hollow tubes 220 start at a location which is laterally inboard of the first edge 202 of the fibre fabric 200 and terminate at a point beyond the second edge 204 of the fibre fabric 200.

[0162] In other words, the at least a portion of the second set 220b of open-ended hollow tubes 220 protrude beyond the second edge 204 of the fibre fabric by a distance (D).

[0163] In the illustrated example, the distance (D) is approximately 50mm. However, it shall be appreciated that in other examples, the open-ended hollow tubes 220 may protrude beyond the second edge 204 of the fibre fabric 200 by a different distance.

[0164] It shall also be appreciated that in some examples, the plurality of open-ended hollow tubes 220 may protrude beyond the first edge 202 of the fibre fabric 200 instead of, or in addition to, the second edge 204 and / or may protrude beyond the first 206 and / or second 208 ends of the fibre fabric 200 in examples in which the plurality of open- ended hollow tubes 220 are longitudinally orientated.

[0165] It shall also be appreciated that the plurality of open-ended hollow tubes 220 may not protrude beyond either the first 202 or second 204 edges or beyond the first 206 or second 208 ends of the fibre fabric 200 in some examples. In other words, in some examples, the plurality of open-ended hollow tubes 220 may not protrude at all.

[0166] Referring back to FIG. 6A and 6B, in some examples, the plurality of open-ended hollow tubes 220 may be interspersed within the layer of weft fibres 212 which make up the fibre fabric 200 via substituting out some of the weft fibres 212 and replacing them with the open-ended hollow tubes 220.

[0167] It has been found that interspersing the plurality of open-ended hollow tubes 220 between the plurality of weft fibres 212 helps to better embed the hollow tubes 220 within the fibre fabric 200 and hence helps to prevent said tubes 220 from being damaged or pulled off of the fibre fabric 200 during handling or lay-up.

[0168] The plurality of open-ended hollow tubes 220 can then be secured to the layer of warp fibres 214 via bonding or stitching. In some examples, the plurality of open-ended hollow tubes 220 may comprise a colour which is different to that of the plurality of fibres 210.

[0169] This helps users more easily identify the respective positions (or locations) of the open- ended hollow tubes 220 within the fibre fabric 200 to help prevent users from inadvertently severing the hollow tubes 220 when cutting the fibre fabric 200 down to a desired size.

[0170] It shall also be appreciated that in examples in which the plurality of open-ended hollow tubes 220 are secured to the layer of warp fibres 214 via stitching, it is generally preferable for the plurality of open-ended hollow tubes 220 to be formed of a relatively hard polymeric material (such as polyamide) since such materials are less prone to becoming punctured by the sewing needle during the stitching processes.

[0171] It shall also be appreciated that in some examples, the plurality of open-ended hollow tubes 220 may be secured to the fibre fabric 200 in a different manner. For example, as illustrated in FIG. 7, the plurality of open-ended hollow tubes 220 may be interwoven into the fibre fabric 220 via the at least one warp fibre 214.

[0172] Advantageously, interweaving the plurality of open-ended hollow tubes 220 into the fibre-fabric 200 is particularly beneficial since it does not require the use of a stitching needle and hence helps to reduce the risk of rupturing the hollow tubes 220 during manufacture.

[0173] It shall also be appreciated that in some examples, the plurality of open-ended hollow tubes 220 may be secured to a surface of the fibre fabric 200 rather than being embedded.

[0174] A fibre fabric 200 according to such an example of the present disclosure is depicted in FIG. 10.

[0175] It shall be appreciated that the fibre fabric 200 illustrated in FIG. 10 has many features in common with the fibre fabric 200 depicted in FIG. 6 and so, for the sake of conciseness, only the differences shall be described herein. Notably, in the example illustrated in FIG. 10, the fibre fabric 200 comprises a first fabric layer 232 and a second fabric layer 234 each comprising a plurality of fibres (not shown).

[0176] It shall be appreciated that the first 232 and second fabric 234 layers may be woven fabric layers or may be non-woven fabric layers.

[0177] As alluded to above, the plurality of open-ended hollow tubes 220 are secured to a surface 233 of the first fabric layer 232 (via bonding or stitching) before being overlaid with a second fabric layer 234 such that the plurality of open-ended hollow tubes 220 are sandwiched between the first 232 and second 234 fabric layers respectively.

[0178] It has been found that sandwiching the plurality of open-ended hollow tubes 220 between first 232 and second 234 fabric layers also helps to prevent said tubes 220 from being damaged or pulled off of the fibre fabric 200 during handling or lay-up.

[0179] It shall also be appreciated that in some examples, the plurality of open-ended hollow tubes 220 may be stitched or bonded to a corresponding surface 235 of the second fabric layer 234 in addition to, or in place of, the first fabric layer 232.

[0180] Referring back to FIG. 4, once the plurality of open-ended hollow tubes 220 have been placed about the dry-fibre stack 108 (either individually or as part of a fibre fabric 200 such as those described above), during step 132, the vacuum bag 110 is laid over the rigid mould 102 and is sealed against the flanges 106 of the mould 102 via sealant tape 114 such that a fluid-tight mould cavity 105 is defined between the mould 102 and the vacuum bag 110.

[0181] Then, during step 133, a vacuum is applied to the mould cavity 105 via activating the vacuum source (not shown) which subsequently draws out (or evacuates) any gases that are present within the mould cavity 105. After the mould cavity 105 has been evacuated, resin 120 is supplied to the mould cavity. In particular, under the influence of the vacuum, resin 120 is drawn from the resin source 122 into the mould cavity 105 (via the resin port 116) so that the resin 120 can begin to infuse into and saturate the respective dry-fibre ply layers 109 which make up the dry-fibre stack 108. As shown in FIG. 5, the resin 120 begins to saturate the uppermost ply layer 109b of the dry-fibre stack 108 before being drawn outwardly towards the peripheral regions of the dry-fibre stack 108 (proximate to the vacuum ports 118) via the vacuum.

[0182] However, in the event that the advancing resin flow front 121 starts to encircle (and hence isolate) the first (or lock-off) region 126 of the dry-fibre stack 108 from the vacuum source (as shown in FIG. 5), the plurality of open-ended hollow tubes 220 are able to provide a bridge across the advancing resin flow front 121 which enables air (or other gases) present within the first region 126 to be drawn out of the first region 126, across the advancing resin flow front 121 via the internal conduits provided in the plurality of open-ended hollow tubes 220 and into the second region 128 where said gases can be evacuated from the dry-fibre stack 108.

[0183] The effect of air (or other gases) being drawn out from the first region 126 by the vacuum applied during step 133 also causes resin 120 from the surrounding saturated regions of the dry-fibre stack 108 to be drawn into the first region 126 such that the first region 126 becomes fully saturated and infused with resin 120, thereby avoiding the formation of a dry-spot. Furthermore, once the first region 126 has become fully saturated, resin 120 will also start to be drawn into the open-ended hollow tubes 220, via the vacuum source, thereby blocking the first ends 222 of the tubes 220 and hence preventing any further resin from being drawn out of the first region 126.

[0184] As such, the provision of the plurality of open-ended hollow tubes 220 helps to ensure that resin 120 is drawn into and saturates the first region 126 of the dry-fibre stack 108 during resin infusion and hence helps to reduce the likelihood of air pockets being present within the final wind turbine blade part.

[0185] Finally, the resin-infused wind turbine blade part is cured during step 134 to obtain a finished wind turbine blade part into which the plurality of open-ended hollow tubes (and optionally the fibre fabric 200) is incorporated.

[0186] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1 . A method of manufacturing a wind turbine blade part comprising the steps of: a) laying up a plurality of dry-fibre plies onto a mould to form a dry-fibre stack; b) placing at least one open-ended hollow tube about the dry-fibre stack, wherein the at least one open-ended hollow tube comprises a first end, a second end and an internal conduit extending between said first and second ends; c) placing a vacuum bag onto the mould such that a mould cavity is defined between the mould and the vacuum bag; and d) applying a vacuum to the mould cavity so as to draw resin from a resin source into the dry-fibre stack, wherein, during step b), the first end of the at least one open-ended hollow tube is placed in fluid communication with a first region of the dry-fibre stack and the second end of the at least one open-ended hollow tube is placed in fluid communication with a second region of the dry-fibre stack, such that, upon application of the vacuum during step d), air is drawn out of the first region via the at least one open-ended hollow tube until the first region becomes saturated with resin.

2. The method according to claim 1 , wherein during step d) the resin is drawn into the dry-fibre stack such that a resin flow front advances across the dry-fibre stack; and the method further comprises the step of predicting an area of the dry-fibre stack that will be encircled by the resin flow front before said area becomes fully saturated with resin, said area being the first region of the dry-fibre stack.

3. The method according to claim 1 or 2, wherein the vacuum is applied to the mould cavity via a vacuum port, and wherein the second region is located between the vacuum port and the first region, and preferably wherein the second region is located proximate to said vacuum port.

4. The method according to any of claims 1 , 2 or 3, wherein the at least one open- ended hollow tube is formed of an electrically insulating material.

5. The method according to any preceding claim, wherein the internal conduit of the at least one open-ended hollow tube comprises an inner diameter of no more than 1 mm, optionally wherein the internal conduit comprises an inner diameter of no morethan 0.5mm, and further optionally wherein the internal conduit comprises an inner diameter of no more than 0.3mm.

6. The method according to claim any preceding claim, wherein the at least one open-ended hollow tube comprises an outer diameter of no more than 2mm, and preferably no more than 1 mm.

7. The method according to any preceding claim, wherein the at least one open- ended hollow tube is formed of glass.

8. The method according to any preceding claim, wherein the at least one open- ended hollow tube comprises a plurality of said open-ended hollow tubes.

9. The method according to claim 8, wherein, during step b), the plurality of open- ended hollow tubes are arranged in a staggered array.

10. The method of claim 8 or claim 9, wherein the plurality of open-ended hollow tubes are incorporated into a fibre fabric, and wherein the fibre fabric becomes incorporated into the wind turbine blade part.

11. A fibre fabric for resin infusion comprising: a plurality of fibres; and a plurality of open-ended hollow tubes, wherein each tube comprises a first end, a second end and an internal conduit extending between said first and second ends for allowing gases to traverse over at least a portion of the fibre fabric during resin infusion.

12. The fibre fabric according to claim 11 , wherein at least some of the plurality of open-ended hollow tubes extend continuously across the width of the fibre fabric from a first edge thereof to a second edge thereof.

13. The fibre fabric according to claims 11 or 12, wherein the plurality of open- ended hollow tubes are interspersed between the plurality of fibres.

14. The fibre fabric according to any of claims 11 to 13, wherein the fibre fabric comprises a plurality of weft fibres extending transversely across the fibre fabric and atleast one warp fibre extending along a length of the fibre fabric, substantially perpendicular to the plurality of weft fibres.

15. The fibre fabric according to any of claims 11 to 14, wherein the first and / or second ends of at least some of the plurality of open-ended hollow tubes protrude beyond an edge of the fibre fabric.

16. The fibre fabric according to any of claims 11 to 15, wherein the plurality of open-ended hollow tubes comprise a first colour, and wherein the plurality of fibres comprise a second colour which is different to the first colour.

17. The fibre fabric according to any of claims 11 to 16, wherein the fibre fabric comprises a first fabric layer and a second fabric layer, and wherein the plurality of open-ended hollow tubes are sandwiched between the first and second fabric layers.

18. The fibre fabric according to any of claims 11 to 17, wherein the fibre fabric is a non-woven fabric.

19. The fibre fabric according to any of claims 11 to 18, wherein the plurality of fibres are glass fibres.

20. The fibre fabric according to any of claims 11 to 19, wherein the plurality of open-ended hollow tubes are formed of a polyamide material.

21. A wind turbine blade part comprising the fibre fabric according to any of claims11 to 20.

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