Patent ID: 12202214

DETAILED DESCRIPTION

Various exemplary embodiments and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

FIG.1illustrates a conventional modern upwind wind turbine according to the so-called “Danish concept” with a tower400, a nacelle600and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub800and three blades1000extending radially from the hub800, each having a blade root1600nearest the hub and a blade tip1400furthest from the hub800.

FIG.2Ashows a schematic view of a first embodiment of a wind turbine blade1000. The wind turbine blade1000has the shape of a conventional wind turbine blade and comprises a root region3000closest to the hub, a profiled or an airfoil region3400furthest away from the hub and a transition region3200between the root region3000and the airfoil region3400. The blade1000comprises a leading edge1800facing the direction of rotation of the blade1000, when the blade is mounted on the hub, and a trailing edge2000facing the opposite direction of the leading edge1800.

The airfoil region3400(also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region3000due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade1000to the hub. The diameter (or the chord) of the root region3000may be constant along the entire root area3000. The transition region3200has a transitional profile gradually changing from the circular or elliptical shape of the root region3000to the airfoil profile of the airfoil region3400. The chord length of the transition region3200typically increases with increasing distance r from the hub. The airfoil region3400has an airfoil profile with a chord extending between the leading edge1800and the trailing edge2000of the blade1000. The width of the chord decreases with increasing distance r from the hub.

A shoulder4000of the blade1000is defined as the position, where the blade1000has its largest chord length. The shoulder4000is typically provided at the boundary between the transition region3200and the airfoil region3400.

It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

FIG.2Bis a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade1000, e.g. a cross sectional view of the airfoil region of the wind turbine blade1000. The wind turbine blade1000comprises a leading edge1800, a trailing edge2000, a pressure side2400, a suction side2600, a first spar cap7400, and a second spar cap7600. The wind turbine blade1000comprises a chord line3800between the leading edge1800and the trailing edge2000. The wind turbine blade1000comprises shear webs4200, such as a leading edge shear web and a trailing edge shear web. The shear webs4200could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The spar caps7400,7600may comprise carbon fibres while the rest of the shell parts2400,2600may comprise glass fibres.

FIG.3Ais a schematic diagram illustrating a cross sectional view of an interlayer1arranged between a first element50, such as a first pultruded carbon element and a second element60, such as a second pultruded carbon element, e.g. of a conductive fibre reinforced composite material. The elements50,60and the interlayer1may form part of a spar cap100arranged in a wind turbine blade, such as the spar caps7400,7600of the wind turbine blade1000as illustrated inFIG.2.

FIG.3Bis a schematic diagram illustrating an exploded view of the interlayer1arranged between the first and second elements50,60. The interlayer1, in the illustrated example, comprises an interlayer sheet2having an upper interlayer surface3and a lower interlayer surface4. In the same way, the first element50has a first upper surface51and a first lower surface52and the second element60has a second upper surface61and a second lower surface62.

The first element50and the second element60are arranged such that the first lower surface52of the first element50is facing the second upper surface61of the second element60. The interlayer1and the interlayer sheet2is arranged between the lower surface of the first element50and the upper surface of the second element60, e.g. such that the upper interlayer surface3is in contact with the first lower surface52and the lower interlayer surface4is in contact with the second upper surface61.

FIG.3Cis a schematic diagram illustrating a cross-sectional view of a fibre reinforced composite material100, e.g. spar cap or part of a spar cap, comprising a plurality of elements, such as pultruded carbon elements, including a first element50, such as a first pultruded carbon element, and a second element60, such as a second pultruded carbon element. The plurality of elements are arranged in an array with three rows of elements arranged adjacent to each other. Each row of elements are separated by an interlayer1. The fibre reinforced composite material100may form part of a spar cap arranged in a wind turbine blade, such as the spar caps7400,7600of the wind turbine blade1000as illustrated inFIG.2. Although not specifically illustrated, interlayers may also be provided between adjacent elements in the width direction, to facilitate conductivity between elements also in this direction.

FIGS.4A and4Bis a schematic diagram illustrating a three-dimensional view of an exemplary interlayer sheet2according to two different embodiments, whereasFIGS.5A and5Bshows a cross-sectional view throughFIGS.4A and4B. InFIGS.4C and5Can exploded view of the embodiments shown inFIGS.4B and5Bis illustrated.

InFIGS.4A and5A, the interlayer sheet2comprises one fibre layer i.e. the first fibre layer10. In this case, the first upper fibre surface11is also the upper interlayer surface3and the first lower fibre surface12is also the lower interlayer surface4.

InFIGS.4B,4C,5B and5Cthe interlayer sheet2comprises three fibre layers including a first fibre layer10, a second fibre layer20and a third fibre layer30.

The first fibre layer10have a first upper fibre surface11and a first lower fibre surface12. The second fibre layer have a second upper fibre surface21and a second lower fibre surface22and the third fibre layer30have a third upper fibre surface31and a third lower fibre surface32.

The first fibre layer10is arranged between the second fibre layer20and the third fibre layer30. In this case, the third lower fibre surface32is also the lower interlayer surface4and the second upper fibre surface21is also the upper interlayer surface3.

The first fibre layer10comprise a first plurality of fibres, the second fibre layer20comprise a second plurality of fibres and the third fibre layer30comprise a third plurality of fibres. The first plurality of fibres may comprise a first plurality of glass fibres and/or a first plurality of polymeric filaments, such as polyester filaments, preferably thermoplastic polyester filaments or polypropylene filaments or polyethylene filaments and/or a first plurality of carbon fibres (and/or another conductive fibre, e.g. metal fibre, such as copper fibre and/or steel fibre). In the same way the second plurality of fibres may comprise a second plurality of glass fibres and/or a second plurality of polymeric filaments, such as polyester filaments, preferably thermoplastic polyester filaments or polypropylene filaments or polyethylene filaments and/or a second plurality of carbon fibres (or another conductive fibre, e.g. metal fibre, such as copper fibre or steel fibre) and the third plurality of fibres may comprise a third plurality of glass fibres and/or a third plurality of polymeric filaments, such as polyester filaments, preferably thermoplastic polyester filaments or polypropylene filaments or polyethylene filaments and/or a third plurality of carbon fibres (or another conductive fibre, e.g. metal fibre, such as copper fibre or steel fibre).

The interlayer sheet2comprises a plurality of carbon fibres6(not illustrated inFIG.4or5) forming part of the upper interlayer surface3as well as the lower interlayer surface4. Thus, the plurality of carbon fibres6extends through the interlayer sheet2, including the one or more layers10,20,30in one way or another. Reference is made toFIGS.6-9illustrating a plurality of different embodiments where the plurality of carbon fibres6form part of the upper interlayer surface3as well as the lower interlayer surface4of an interlayer sheet2. The presence of the plurality of carbon fibres6extending through the interlayer sheet2, is that the plurality of carbon fibres6may facilitate the transfer of electrons between two elements, e.g. two carbon elements, sandwiching the interlayer sheet2, by providing indirect contact between such two elements. In this way, the interlayer sheet2protects the elements, e.g. containing conductive fibres, against lightning strikes. While embodiments are described with reference to carbon fibres6, these may in alternative embodiments, within the scope of the present disclosure, be replaced by or mixed with other conductive fibres, e.g. metal fibres, such as copper fibres or steel fibres.

Preferably, the interlayer comprises 10-45 wt % carbon fibres, 5-50 wt % polymeric filaments and 15-50 wt % glass fibres. The polymeric filaments provide good surface properties to the interlayer sheet, such as good adherence properties. The glass fibres add stability and reinforcement to the interlayer sheet and the carbon fibres add conductivity.

FIG.6Ais a schematic diagram showing a top view of an embodiment of an interlayer sheet2.FIG.6Bis a schematic diagram showing a cross-sectional view of the interlayer sheet2ofFIG.5Aas well as a close-up of part C of the cross-sectional view of the interlayer sheet2.

The interlayer sheet2comprises one fibre layer i.e. a first fibre layer10. Thus, the first upper fibre surface11is also the upper interlayer surface3and the first lower fibre surface12is also the lower interlayer surface4.

The first fibre layer10may be a non-woven fabric layer, e.g. essentially consisting of a first plurality of polymeric filaments, such as polyester filaments. Such a layer has good surface properties, including good adherence properties. For example, the first fibre layer10may be a polyester surface veil.

The interlayer sheet2further comprises a plurality of carbon fibres6and a plurality of glass fibres7, including short and/or continuous fibres with varying sizes. The plurality of carbon fibres6and the plurality of glass fibres7each comprise several parts, including a first part6a,7aand a second part6b,7b. The second part6b,7bof each of the plurality of carbon fibres6and the plurality of glass fibres7are randomly arranged at the first upper surface11of the first fibre layer10and forms part of the upper interlayer surface3, whereas a first part6a,7aof each of the plurality of carbon fibres6extends through the first layer10and thereby also forms part of the lower interlayer surface4.

For example, the plurality of carbon fibres6and/or the plurality of glass fibres7may be provided by spraying them onto the first fibre layer10in a direction substantially perpendicular to the surface of the first fibre layer, e.g. using pressurised air. Thereby at least some of the ends of the carbon and/or glass fibres may upon impact with the layer extend into and through the layer.

FIG.6Billustrates how a first part6a,7aof each of the plurality of carbon fibres6and glass fibres7extends from the upper interlayer surface3through the first layer10and thereby also forms part of the lower interlayer surface4. The glass fibres7extending through the first fibre layer10adds stability and reinforcement to the interlayer sheet2. Due to the plurality of carbon fibres6extending through the first layer10, the interlayer sheet2is conductive when arranged between two elements, such as carbon elements, such as between two pultruded carbon elements, of a spar cap arranged in a wind turbine blade shell.

FIG.7Ais a schematic diagram showing a top view of an embodiment of an interlayer sheet2.FIG.7Bis a schematic diagram showing a cross-sectional view of the interlayer sheet2ofFIG.7A.

The interlayer sheet2comprises three fibre layers including a first fibre layer10, a second fibre layer20and a third fibre layer30. The first fibre layer10have a first upper fibre surface11and a first lower fibre surface12. The second fibre layer have a second upper fibre surface21and a second lower fibre surface22and the third fibre layer30have a third upper fibre surface31and a third lower fibre surface32.

The first fibre layer10is arranged between the second fibre layer20and the third fibre layer30. In this case, the third lower fibre surface32is also the lower interlayer surface4and the second upper fibre surface21is also the upper interlayer surface3.

The first fibre layer10may be a non-woven fabric layer essentially consisting of a first plurality of glass fibres. The glass fibres7adds stability and reinforcement to the interlayer sheet2.

The second fibre layer and third fibre layers20,30are also non-woven fabrics. Preferably, the second fibre layer20essentially consist of a first plurality of polymeric filaments, such as polyester filaments. Such a layer adds good surface properties to the interlayer sheet2, including good adherence properties. Furthermore, the third fibre layer30essentially consist of a first plurality of polymeric filaments, such as polyester filaments. As a result, both outer surfaces of the interlayer sheet2have good adherence properties.

The interlayer sheet2further comprise a plurality of carbon fibres6. The plurality of carbon fibres6may be short and/or continuous fibres with varying sizes. The plurality of carbon fibres6each comprises several parts, including a first part6aand a second part6b. The second part6bof each of the plurality of carbon fibres6are randomly arranged at the second upper surface21of the second fibre layer20and forms part of the upper interlayer surface3, whereas a first part6aof each of the plurality of carbon fibres6extends through the first, second and third fibre layers10,20,30, such that the carbon fibres6also forms part of the lower interlayer surface4.

FIG.7Billustrates how a first part6aof each of the plurality of carbon fibres6extends from the upper interlayer surface3through the first, second and third fibre layer10,20,30, such that the carbon fibres6also forms part of the lower interlayer surface4. Due to the plurality of carbon fibres6, extending through the first layer10, the interlayer sheet2is conductive in the direction perpendicular to the plane of the interlayer sheet2. Thus, when arranged between two elements, e.g. carbon elements, such as between two pultruded carbon elements, of a spar cap arranged in a wind turbine blade shell, the interlayer sheet2prevents or reduce build up of a voltage potential between the elements.

FIG.7Cillustrates that the plurality of carbon fibres6may be punched through the interlayer sheet2, e.g. using pressurised air, and thus extend through the first, second and third fibre layer10,20,30in random directions. Alternatively, as illustrated inFIG.7D, the fibre layers10,20,30may be stitched together by the plurality of carbon fibres6, forming a controlled pattern of carbon fibres6extending through the interlayer sheet2. In the later embodiment, the plurality of carbon fibres6holds the three fibre layers10,20,30together and at the same time adds conductivity to the interlayer sheet2.

FIG.8Ais a schematic diagram showing a top view of an embodiment of an interlayer sheet2.FIG.8Bis a schematic diagram showing a cross-sectional view of the interlayer sheet2ofFIG.8A.

The interlayer sheet2comprises one fibre layer i.e. a first fibre layer10comprising a first upper fibre surface11and a first lower fibre surface12. Thus, the first upper fibre surface11is also the upper interlayer surface3and the first lower fibre surface12is also the lower interlayer surface4of the interlayer sheet2.

The first fibre layer10may be a non-woven fabric and comprises a first plurality of fibres, including a first plurality of carbon fibres6(illustrated by a black thin line), a first plurality of glass fibres7(illustrated by a grey thin line) and a first plurality of polymeric filaments8(illustrated by a black thick line). The first fibre layer10may further comprise a binding agent, preferably a binding agent being dissolvable by a resin, maintaining arrangement of the first plurality of fibres relative to each other. Alternatively or in addition, the first plurality of fibres may be stitched together, optionally with a carbon fibre thread, to maintain arrangement of the first plurality of fibres relative to each other.

The first plurality of fibres6,7,8are randomly oriented within the first fibre layer10. Due to the random arrangement of fibres in a single layer, at least a plurality6of the first plurality of carbon fibres will form part of the upper interlayer surface3as well as the lower interlayer surface4, making the interlayer sheet2conductive when arranged between two elements, e.g. carbon elements, such as between two pultruded carbon elements, of a spar cap arranged in a wind turbine blade shell.

FIGS.9A and9Bare schematic illustrations of two different embodiments of an interlayer sheet2comprising a first layer10being a woven fabric.

The first fibre layer10comprises a first upper fibre surface11and a first lower fibre surface12. Thus, the first upper fibre surface11is also the upper interlayer surface3and the first lower fibre surface12is also the lower interlayer surface4of the interlayer sheet2.

The first fibre layer10comprises a first plurality of fibres including a first plurality of carbon fibres6, a first plurality of glass fibres7and a first plurality of polymeric filaments8. The first plurality of fibres6,7,8are woven together.

The first plurality of glass fibres7is arranged in a plurality of glass fibre bundles and the first plurality of carbon fibres6are arranged in a plurality of carbon fibre bundles.

Each of the first plurality of carbon fibres6is arranged along a first length direction, each of the first plurality of glass fibres7are arranged along a second length direction and each of the first plurality of polymeric filaments8are arranged along a third length direction.

InFIG.9A, the first plurality of carbon fibres6and the first plurality of polymeric filaments8are arranged parallelly and both extend in a first direction X, whereas the first plurality of glass fibres7extend in a second direction Y, which is perpendicular to the first direction X. Thus, the first and third length directions are parallel, i.e. parallel with the first direction X, and the second length direction is perpendicular to the first and third length directions. Hence, the second length direction is parallel with the second direction Y. In an alternative embodiment (not illustrated) a number of carbon fibres may be added in the first direction X along the first plurality of glass fibres7to further enhance electrical conductivity through the plane.

InFIG.9B, the first plurality of carbon fibres6and the first plurality of glass fibres7are arranged parallelly and extend in the second direction Y, whereas the first plurality of polymeric filaments8extend in the first direction X, which is perpendicular to Y. Thus, the first length direction and second length direction are parallel, i.e. parallel with the second direction Y, and the third length direction is perpendicular to the first and second length directions. Hence, the third length direction is parallel with the first direction X.

InFIG.9B, the first plurality of carbon fibres6and the first plurality of glass fibres7are arranged parallelly and extend in the second direction Y, whereas the first plurality of polymeric filaments8extend in the first direction X, which is perpendicular to Y.

FIG.10Ais a schematic diagram illustrating an exemplary interlayer1, such as the interlayer1as described, e.g. with reference toFIG.3.FIG.10illustrates that the interlayer1may comprise a top sheet70and/or a bottom sheet72, e.g. in addition to the interlayer sheet2as described with respect toFIGS.4-9.

The top sheet70is arranged adjacent the upper interlayer surface3and the bottom sheet72is arranged adjacent the lower interlayer surface4. The interlayer sheet2may be sandwiched between the top sheet70and the bottom sheet72.

FIG.10Bis a cross-sectional view of the interlayer1illustrated inFIG.10A.

The top sheet70and/or bottom sheet72may for example be carbon veils, since such veils facilitates electrical conductivity through the plane. Furthermore, a carbon veil has high permeability, promotes resin infusion and have good adhesion properties. Alternatively, the top sheet70and/or bottom sheet72may be polyester veils, since such veils have good adhesion properties. In such case the top sheet70and/or bottom sheet72may comprise conductive elements, such as conductive fibres, such as carbon fibres. The presence of conductive fibres, such as carbon fibres, in the top sheet70and/or bottom sheet72facilitates the electrical connection through the interlayer, such as facilitates electron flow between elements, such as pultruded elements, when sandwiched therebetween.

FIG.11illustrates a cross-sectional view of an embodiment of an interlayer sheet2, wherein the interlayer sheet2comprises a first fibre layer10, a second fibre layer20and a third fibre layer30. The first fibre layer10comprises a plurality of polymeric fibres8and carbon fibre bundles6arranged along a first length direction. The carbon fibre bundles6are illustrated as black dots, whereas the polymeric filaments8are illustrated as white dots. As can be seen inFIG.11, every 4th fibre bundle is a carbon fibre bundle6, whereas the remaining fibres are polymeric filaments8. In other exemplary embodiments, there may be more or less polymeric filaments between each carbon fibre bundle.

The second fibre layer20and/or the third fibre layer30are preferably polyester surface veils or carbon surface veils. The first fibre layer10, the second fibre layer20and the third fibre layer30are stitched or woven together. The thick black line illustrates a thread64, e.g. a fibre, such as a glass fibre or a carbon fibre, extending along the second length direction and stitching or weaving the carbon fibres6and polymeric filaments8arranged along the first length direction together with the second fibre layer20and the third fibre layer30. The thread64may be a conductive fibre and in this way, the interlayer sheet2may have conductive properties, even though the second fibre layer20and/or the third fibre layer30essentially consist of a non-conductive material. In some exemplary embodiments, a plurality of threads64may be used along the length of the interlayer sheet2, and in such situation the plurality of threads64may comprise some conductive threads and some non-conductive threads, e.g. every 10th thread may be a conductive thread while the remaining threads may be non-conductive.

The disclosure has been described with reference to a preferred embodiment. However, the scope of the invention is not limited to the illustrated embodiment, and alterations and modifications can be carried out without deviating from the scope of the invention.

Throughout the description, the use of the terms “first”, “second”, “third”, “fourth”, “primary”, “secondary”, “tertiary” etc. does not imply any particular order or importance but are included to identify individual elements. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

REFERENCE SIGNS

1interlayer2interlayer sheet3upper interlayer surface4lower interlayer surface5fibre layer plane6plurality of carbon fibres6aFirst part6bSecond part7plurality of glass fibres7afirst part7bsecond part8plurality of polymeric filaments10first fibre layer11first upper fibre surface12first lower fibre surface13first plurality of carbon fibres14first plurality of glass fibres15first plurality of polymeric filaments18Third length direction20second fibre layer21second upper fibre surface22second lower fibre surface23second plurality of carbon fibres24second plurality of glass fibres25second plurality of polymeric filaments30third fibre layer31third upper fibre surface32third lower fibre surface33third plurality of carbon fibres34third plurality of glass fibres35third plurality of polymeric filaments40spar cap50first element51first upper surface52first lower surface60second element61second upper surface62second lower surface64thread70top sheet72bottom sheet100spar cap200wind turbine400tower600nacelle800hub1000blade1400blade tip1600blade root1800leading edge2000trailing edge2200pitch axis2400pressure side2600suction side3000root region3200transition region3400airfoil region3800chord line4000shoulder/position of maximum chord4200shear webs7400first spar cap7600second spar capX first directionY second direction