Separation comb for avoiding misalignments of pultrusions in a spar cap

Abstract

The present invention relates to a method for manufacturing a reinforcing structure for a wind turbine blade (10), the method comprising the steps of: 1) arranging a plurality of strips (63) of fibre-reinforced material into adjacent stacks of strips (65a, b, c) forming a layered structure (61) with a plurality of fibre-reinforced layers (67), wherein adjacent fibre-reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers (66), 2) providing at least one separation comb (70) comprising: a base region (71) and a teeth region (73) comprising a plurality of teeth (74) extending from the base region (71), wherein the plurality of teeth (74) are arranged in a linear array with gaps (79) between adjacent teeth (74), the gaps (79) being configured for allowing resin to flow from one side of the separation comb (70) to the other side of the separation omb (70), and wherein the plurality of teeth (74) are configured for penetrating the interlayers (66), 3) inserting the at least one separation comb (70) between two adjacent stacks of strips (65a, b, c) and penetrating he plurality of interlayers (66) with the plurality of teeth (74), such that the plurality of strips (63) in adjacent stacks of strips (65a, b, c) are separated by the at least one separation comb (70), 4) optionally moving the layered structure (61) to a desired location, such as into a wind turbine blade shell mould, after inserting the at least one separation comb (70) between adjacent stacks of strips (65a, b, c), 5) optionally removing the at least one separation comb (70), and 6) infusing the layered structure with resin to form a reinforcing structure (78).

Description

[0001] SEPARATION COMB FOR AVOIDING MISALIGNMENTS OF PULTRUSIONS IN A SPAR CAP

[0002] FIELD OF INVENTION

[0003] The present disclosure relates to a separation comb for a reinforcing structure of a wind turbine blade, a reinforcing structure, a wind turbine blade and methods of manufacture thereof.

[0004] BACKGROUND

[0005] Wind power provides a clean and environmentally friendly source of energy. Wind turbines usually comprise a tower, generator, gearbox, nacelle, and one or more rotor blades. The wind turbine blades capture kinetic energy of wind using known airfoil principles. Modern wind turbines may have rotor blades that exceed 90 meters in length.

[0006] Wind turbine blades are usually manufactured by forming two shell parts or shell halves from layers of woven fabric or fibre and resin. Spar caps or main laminates are placed or integrated in the shell halves and may be combined with shear webs or spar beams to form structural support members. Spar caps or main laminates may be joined to, or integrated within, the inside of the suction and pressure halves of the shell.

[0007] As the size of wind turbine blades increases, various challenges arise from such blades being subjected to increased forces during operation, requiring improved reinforcing structures. In some known solutions, pultruded fibrous strips of material are used. Pultrusion is a continuous process in which fibres are pulled through a supply of liquid resin and then heated in an open chamber where the resin is cured. Such pultruded strips can be cut to any desired length.

[0008] WO 2006 / 082479 Al discloses a method for preparing a wind turbine blade shell member comprising a plurality of elements of cured fibre-reinforced sheet material. A plurality of elements of cured fibre- reinforced sheet material is provided in a mould, a resin is introduced between the elements of cured fibre-reinforced sheet material and the elements are bonded to adjacent elements by curing the resin.

[0009] However, the manufacturing of large reinforcing structures, such as spar caps or spar beams, in this way can be challenging, in particular when pultruded, carbon fibre-reinforced spar caps are used as the reinforcing members. Carbon fibres are typically lighter than glass fibres by volume and have improved tensile and compressive strength. In some known approaches, separate pultruded elements are used to form the reinforcing structure, and each element is individually positioned within the structure of the shell. This can easily lead to laminate defects, such as voids, wrinkles or misaligned fibres, that may have disadvantageous effects on mechanical properties. In other approaches, pultruded elements are laid up outside the shell and subsequently moved to the shell. This process often results in slight overlap and / or misplacement of the pultrusion layers which may also have disadvantageous effects on mechanical properties.

[0010] SUMMARY

[0011] It is an object of the present invention to provide a reinforcing structure for a wind turbine blade which is easily manufactured, handled and assembled. It is another object of the present invention to provide a reinforcing structure for a wind turbine blade which avoids or reduces the abovediscussed misalignments, overlaps and defects. It is another object of the present invention to provide a reinforcing structure for a wind turbine blade which has a simple construction and is comparatively cheap to manufacture. It is another object of the present invention to provide an improved method of manufacturing a reinforcing structure for a wind turbine blade.

[0012] It has been found that one or more of the aforementioned objects can be obtained by a method for manufacturing a reinforcing structure for a wind turbine blade, the method comprising the steps of: arranging a plurality of strips of fibre-reinforced material into adjacent stacks of strips forming a layered structure with a plurality of fibre-reinforced layers, wherein adjacent fibre-reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, providing at least one separation comb comprising: a base region a teeth region comprising a plurality of teeth extending from the base region,

[0013] - wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb to the other side of the separation comb, and wherein the plurality of teeth are configured for penetrating the interlayers, inserting the at least one separation comb between two adjacent stacks of strips and penetrating the plurality of interlayers with the plurality of teeth, such that the plurality of strips in adjacent stacks of strips are separated by the at least one separation comb, optionally moving the layered structure to a desired location, such as into a wind turbine blade shell mould, after inserting the at least one separation comb between adjacent stacks of strips, optionally removing the at least one separation comb, and infusing the layered structure with resin to form a reinforcing structure.

[0014] It has been found that insertion of at least one separation comb in between stacks of strips in a layered structure before resin infusion, greatly reduces undesired overlaps and / or misplacement of the plurality of strips in the layered structure. Importantly, the plurality of teeth of the at least one separation comb is configured for penetrating interlayers of the layered structure. The interlayers are resin flow promoting interlayers configured for facilitating resin flow between the strips of fibre- reinforced material. The teeth may e.g., be sharp or pointed such that they can be punched through the interlayers in the layered structure, which allows for eased insertion of the separation combs in an assembled layered structure. The gaps of the separation comb allow for an improved distribution of resin between adjacent stacks, e.g., in a VARTM process, while maintaining the desired structural stability. Thus, the separation comb of the present invention is advantageous in maintaining the required tolerances and positions of the strips along the length of the stacks in the layered structure before resin infusion, thus providing an improved reinforcing structure where misalignments and defects which may affect mechanical properties of the wind turbine blade may be avoided.

[0015] A wind turbine blade is usually manufactured from two shell halves, a pressure side shell half and a suction side shell half. The wind turbine blade extends in a spanwise direction between the tip and the root end of the wind turbine blade corresponding to the length of the wind turbine blade. The wind turbine blade further extends in a chordwise direction between the leading edge and the trailing edge of the wind turbine blade corresponding to the width of the wind turbine blade. The wind turbine blade further extends in a flapwise direction between the two shell halves of the wind turbine blade, corresponding to the thickness of the wind turbine blade.

[0016] Preferably, both shell halves comprise an elongate reinforcing structure, such as a spar cap or a main laminate.

[0017] In preferred embodiments, the reinforcing structure of the present invention is a spar cap or a main laminate for a wind turbine blade. In some embodiments, the reinforcing structure comprises a box spar. In other embodiments, the reinforcing structure comprises a spar beam. The reinforcing structure comprises a layered structure which is resin infused. Thus, reference to the reinforcing structure and the layered structure may sometimes be used interchangeably herein. The layered structure comprises a plurality of strips of fibre-reinforced material arranged into adjacent stacks of strips. The layered structure comprises a plurality of fibre-reinforced layers, wherein adjacent fibre- reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers. Each fibre- reinforced layer comprises a strip from each of the adjacent stacks of strips. Preferably, each interlayer extends between the stacks of strips.

[0018] It is preferred that the reinforcing structure extends along the wind turbine blade in a spanwise direction. Typically, the reinforcing structure will extend over 60-95% of the blade length. Thus, the plurality of strips will typically extend in a spanwise direction of the blade and at least some of the strips have preferably a length corresponding to 60-95% of the blade length.

[0019] In some embodiments, the plurality of strips are pultruded planks, also called pultrusions, comprising fibre reinforced carbon fibres and / or glass fibres.

[0020] Each of the plurality of strips has a length, a thickness and a height, wherein the length is larger than the thickness and the thickness is larger than the height.

[0021] It is particularly preferred that each strip comprises a pultruded fibre material, such as a pultruded carbon fibre material. In some embodiments, the reinforced material is carbon fibre and / or glass fibre. In some embodiments, each strip contains a carbon fibre material. In other embodiments, each strip contains a glass fibre material. In other embodiments, each strip contains a glass fibre material and a carbon fibre material. In some embodiments, the strips may not contain any polymer when laying up the strips. In such embodiments, a polymer resin is typically infused into strips following the lay-up.

[0022] Each stack of strips preferably comprises between 2-30 strips, such as between 3-20 strips successively arranged on top of each other in a flapwise direction of the wind turbine blade.

[0023] Each stack will usually also extend in a spanwise direction within the blade. In a midsection between a root end and a tip end, each stack may comprise 8-15 layers of strips, whereas towards the root end and towards the tip end the number of layered strips may decrease to 1-3. Thus, the stack of strips is preferably tapered towards both the root end and the distal end. Such configuration advantageously allows for a profile that is consistent with the thickness profile of the shell. Typically, two or more or three or more stacks of strips are arranged next to each other, adjacent to each other in a substantially chordwise direction.

[0024] In some embodiments, the plurality of interlayers are resin flow promoting layers, such as a resin flow promoting fabric or mat. The interlayers are configured for facilitating resin flow between the strips of fibre-reinforced material. In some embodiments, the step of infusing resin into the layered structure comprises effecting resin flow through one or more of the interlayers from at least one of the stacks of strips to an adjacent stack of strips through the gaps between adjacent teeth of the plurality of teeth. In some embodiments, the plurality of interlayers comprises polymeric fibres and / or glass fibres and / or carbon fibres. In some embodiments, the interlayer is interleaved between the strips of each stack. A difference between the strips of fibre-reinforced material and the interlayers is that the strips comprise cured resin, whereas the interlayers does not. Thus, resin can flow through the interlayers, while resin cannot flow through the strips.

[0025] A space between adjacent stacks in the layered structure / reinforcing structure is preferably between 0.1 mm to 5.0 mm, such as between 0.5 mm to 1.0 mm, as seen in a substantially chordwise direction. The space between adjacent stacks is preferably less than 0.5 mm, or less than 0.3 mm, as seen in a substantially chordwise direction. The layered structure / reinforcing structure has a length, a thickness and a height, wherein the length is larger than the thickness and the thickness is typically larger than the height. The length of the layered structure / reinforcing structure is defined by the length of the strips, the height of the layered structure / reinforcing structure is defined by the height of a stack of strips including the interlayers arranged between the strips, and the thickness of the layered structure / reinforcing structure is defined by the combined thickness of all of the adjacent stacks of strips including the space between the adjacent stacks.

[0026] In some embodiments, the length of the layered structure / reinforcing structure is in the range of 1 m to 100 m, such as in the range of 1 m to 10 m. In some embodiments, the height of the layered structure / reinforcing structure is in the range of 5 cm to 100 cm, preferably in the range of 5 cm to 50 cm. In some embodiments, the thickness of the layered structure / reinforcing structure is in the range of 10 cm to 300 cm.

[0027] In some embodiments, the layered structure is assembled in a wind turbine blade shell mould. In such embodiments, the separation comb is inserted in the layered structure during or after the assembly of the layered structure. In other embodiments, the layered structure is assembled offline, i.e., outside the wind turbine blade shell mould, and subsequently moved to a wind turbine blade shell mould. In such embodiments, the separation comb may be inserted in the layered structure before or after moving the layered structure to the wind turbine blade shell mould. Preferably, the separation comb is inserted before moving of the layered structure, to avoid misalignments of the strips during movement. The layered structure is typically resin infused in the wind turbine blade shell mould. However, in some embodiments, the layered structure may also be resin infused outside the wind turbine blade shell mould and subsequently moved to the wind turbine blade shell mould.

[0028] Preferably, at least one separation comb is inserted vertically in the layered structure from the top, after the plurality of strips are arranged into adjacent stacks, i.e., after assembly of the layered structure, but before resin infusion. Resin infusion may, for example, be done using vacuum-assisted resin transfer moulding. In other embodiments, a prepreg material can be used for the strips, which contains a fibre material pre-impregnated with a resin system, such as an epoxy resin. The separation combs may be arranged in certain areas along the layered structure / , or at set distances.

[0029] In some embodiments, the at least one separation comb is removed before resin infusion, such that they are not part of the reinforcing structure i.e., the layered structure after resin infusion. However, the at least one separation comb may also be left in the reinforcing structure such that they form an integral part of the reinforcing structure and the wind turbine blade.

[0030] Thus, in some embodiments, the at least one separation comb are configured to be removably arranged in the layered structure.

[0031] If the separation comb is removed before the infusion step, the separation comb may be made from any suitable material, including fibre-reinforced material and / or one or more metals and / or one or more polymeric materials, such as sheet metal, extruded metal, extruded or pultruded composites or mixtures thereof. In some embodiments, the separation comb is made of a polymer material, such as a thermoplastic material. In some embodiments, the separation comb comprises, or consists of, a metal, such as steel. In some embodiments, the separation comb comprises, or consists of, a glass fibre fabric. In other embodiments, the separation comb comprises, or consists of, a carbon fibre fabric. In other embodiments, the separation comb comprises, or consists of, a carbon fibre fabric and a glass fibre fabric.

[0032] In other embodiments, the one or more separation combs are configured to be permanently arranged in the reinforcing structure. If the at least one separation comb are co-infused with the layered structure, it is preferred that the same material is used for the separation comb as for the plurality of strips to avoid stresses due to mismatch in coefficient of thermal expansion. In such embodiment, the at least one separation comb is preferably made from extruded or pultruded composites. Preferably, the at least one separation comb essentially consists of fibre-reinforced carbon fibres and / or glass fibres. This is because most reinforcing structures and wind turbine blades also essentially consist of carbon fibres and / or glass fibres. Thus, by having the same material in the reinforcing structure and the separation comb, the structural properties of the reinforcing structure and wind turbine blade are not negatively affected by the presence of the separation combs. However, the at least one separation comb may also be made of sheet metal, extruded metal, polymer material and mixtures thereof as described above for a separation comb configured to be removably arranged in the reinforcing structure. The at least one separation comb can be manufactured using an extrusion process, or a pre-designed mould or 3D printing / additive manufacturing.

[0033] The at least one separation comb has a length, a thickness and a height, wherein the length and height are larger than the thickness. The height of the at least one separation comb is equal to a height of the teeth region plus a height of the base region. The length of the at least one separation comb is equal to a length of the teeth region and / or a length of the base region.

[0034] In preferred embodiments, the at least one separation comb has a length in the range of 5 cm to 100 m, preferably in the range of 5 cm to 50 cm. In some embodiments, the at least one separation comb has a height in the range of 5 cm to 100 cm, such as in the range of 5 cm to 50 cm, preferably in the range of 10 cm to 30 cm. In some embodiments, the at least one separation comb has a thickness in the range of 0.1 mm and 10 mm, preferably in the range of 0.5 mm and 5 mm, such as 1 mm.

[0035] The exact dimensions of the at least one separation comb depends on the dimensions of the layered structure into which the separation comb is to be arranged. Thus, the dimensions of a separation comb are predetermined based on the dimension of the layered structure into which the separation comb is to be arranged.

[0036] Preferably, the one or mor separation combs are inserted vertically between two adjacent stacks of strips and the plurality of interlayers are penetrated with the plurality of teeth, such that the plurality of strips in adjacent stacks of strips are separated by the at least one separation comb along the whole height of the layered structure. In this way, overlaps of strips in adjacent stacks can be avoided. By vertical insertion is meant that the at least one separation comb is inserted into the layered structure at an angle perpendicular or substantially perpendicular to the plurality of fibre- reinforced layers.

[0037] The thickness of the at least one separation comb depends on the desired separation between adjacent stacks of strips in the layered structure. Thus, the thickness of the at least one separation comb is configured to correspond to a predetermined spacing between two adjacent stacks in the layered structure / reinforcing structure. Said distance usually extends in a substantially chordwise direction when arranged between adjacent stacks in the wind turbine blade shell member.

[0038] The length of the at least one separation comb is preferably much smaller than the length of the layered structure / reinforcing structure. This is because it is not necessary to separate the stacks of strips along their whole length, to avoid overlaps or misalignments. Also, a shorter separation comb is easier to insert in the layered structure / reinforcing structure, easier to transport and cheaper to manufacture. Instead of having one long separation comb, one or more, such as one, two or three, smaller separation combs may be arranged between two adjacent stacks to avoid overlap and misalignments between the strips in the adjacent stacks along their whole length.

[0039] The height of the at least one separation comb is defined between tips of the plurality of teeth and an edge of the base region most distal to the tips of the teeth. The preferred height of the at least one separation comb depends on the height of the layered structure / reinforcing structure.

[0040] In preferred embodiments, the height of the at least one separation comb is configured to be the same or substantially the same as a stack of the layered structure / reinforcing structure in which the separation comb is configured to be inserted, including the height of the plurality of interlayers. Thus, preferably, the separation comb has a height which is equal the height of the layered structure, such that when inserting the at least one separation comb between two adjacent stacks of strips and penetrating the plurality of interlayers with the plurality of teeth, the plurality of strips in adjacent stacks of strips are separated by the at least one separation comb along the whole height of the layered structure. In this way, a separation comb can efficiently separate two stacks of strips in the reinforcing structure without pultruding from the reinforcing structure. Preferably, the separation comb should be flush or substantially flush with an upper surface of the reinforcing structure when inserted between adjacent stacks in the reinforcing structure. Particularly if the separation comb is to be permanently inserted in the reinforcing structure. In this way, the separation comb does not have any negative effects on the mechanical properties of the reinforcing structure.

[0041] However, in some embodiments, the separation comb has a height which is greater than the height of the layered structure, such that when inserting the at least one separation comb between two adjacent stacks of strips and penetrating the plurality of interlayers with the plurality of teeth, the plurality of strips in adjacent stacks of strips are separated by the at least one separation comb along the whole height of the layered structure and the separation comb protrude from the layered structure. This is advantageous if the separation comb is to be removed from the layered structure before resin infusion, since the protruding part of the separation comb will allow it to be easily identified and removed e.g., by grabbing the protruding part of the separation comb. Alternatively, the separation comb may comprise a handle or another protruding element connected to the base region of the separation comb on a surface opposite the plurality of teeth, configured to protrude from the upper surface of the layered structure to allow easy removal of the separation comb from the layered structure. In less preferred embodiments, the separation comb has a height which is smaller than the layered structure / reinforcing structure. In such embodiments, the height of the base region is reduced, not the height of the teeth region and / or the plurality of teeth. This is because it is not preferred that the base region of the at least one separation comb covers the interface where resin can flow between two stacks of strips, i.e., through the interlayers.

[0042] Thus, in preferred embodiments, the teeth region of the at least one separation comb has a height which is equal to the height of the layered structure minus a height of an uppermost fibre-reinforced layer of the plurality of fibre-reinforced layers. If it is desired that the separation comb is flush with an upper surface of the layered structure, the base region of the at least one separation comb has a height which is equal to a height of an uppermost fibre-reinforced layer of the layered structure. If it is desired that the separation comb protrudes from an upper surface of the layered structure, the base region of the at least one separation comb has a height which is greater than a height of an uppermost fibre-reinforced layer of the layered structure.

[0043] However, in some embodiments, the teeth region of the at least one separation comb has a height which is greater than the height of the layered structure minus a height of an uppermost fibre- reinforced layer and / or in some embodiments the base region of the at least one separation comb has a height which is smaller than a height of an uppermost fibre-reinforced layer of the layered structure.

[0044] In some embodiments, the base region is substantially rectangular.

[0045] In some embodiments, the base region has a thickness corresponding to a predetermined spacing between two adjacent stacks in the reinforcing structure. In some embodiments, the thickness of the base region is constant or substantially constant. In some embodiments, the thickness of the base region is in the range of 0.1 mm to 1 mm, preferably in the range of 0.5 mm to 5 mm, such as around 1 mm.

[0046] In some embodiments, the plurality of teeth includes between 2 and 100 teeth, such as between 2 and 50 teeth, preferably between 5 and 10 teeth.

[0047] In some embodiments, all of the plurality of teeth extends substantially parallelly. The height of the plurality of teeth is defined between the tips of the plurality of teeth and an edge of the base region most proximal to the tips of the teeth. In some embodiments, all of the plurality of teeth have substantially the same height.

[0048] In some embodiments, all of the plurality of teeth have substantially the same length and thickness.

[0049] In some embodiments, the plurality of teeth are identical or substantially identical in shape and size.

[0050] In some embodiments, the plurality of teeth has a pointed or sharp tip. This is advantageous for penetration of the interlayers.

[0051] In some embodiments, the length and / or thickness of the plurality of teeth decrease from the base to the tip. In some embodiments, all of the plurality of teeth have sharp or pointed edges along their height. This is particularly advantageous for penetration of the interlayers, in case the length and / or thickness of the plurality of teeth decrease from the base to the tip.

[0052] In some embodiments, the thickness of the plurality of teeth is substantially constant along the height of the teeth.

[0053] In some embodiments, the length of the plurality of teeth is in the range of 0.1 mm to 10mm, such as between 0.5 mm and 5 mm, such as 1 mm. In some embodiments, the thickness of the plurality of teeth is in the range of 0.1 mm to 10 mm, such as between 0.5 mm and 5mm, such as 1 mm.

[0054] In some embodiments, the maximum thickness of the plurality of teeth is the same as the thickness of the base region.

[0055] In some embodiments, the plurality of teeth have a circular or elliptical cross-section along their height. In such embodiments, the diameter of the plurality of teeth is in the range of 0.1 mm to 10 mm, such as between 0.5 mm and 5 mm, such as 1 mm. In some embodiments, the diameter of the plurality of teeth decreases from the base to the tip. In some embodiments, the maximum diameter of the plurality of teeth is the same as the thickness of the base region. In some embodiments, the diameter at the tips of the plurality of teeth is between 0.5 mm and 5 mm, such as 1 mm.

[0056] In a preferred embodiment, each of the separation combs comprises a plurality of gaps for allowing resin to flow from one side of the separation combs to the other side of the separation combs. The gaps are defined between two adjacent teeth in the teeth region of the separation comb. Each separation comb may comprise between 2-100 gaps, preferably between 10-50 gaps. The gaps allow for resin migration from one stack of strips to another stack of strips even in the presence of at least one separation comb in a reinforcing structure. The gaps can be slits, slots or channels, such as spanwise extending slots.

[0057] In some embodiments, the gaps between the tips of adjacent teeth of the plurality of teeth are between 3 mm and 200 mm, preferably between 3 mm and 50 mm, more preferably between 3 mm and 10 mm, such as 5 mm. The gaps should be at least 3 mm, such as at least 4 mm, such as at least 5 mm, to allow resin flow from one stack of strips to another stack of strips. If the gaps are too narrow, resin flow will be disturbed by the separation comb, which may result in uneven resin distribution in the areas where separation combs are inserted. This is not desirable.

[0058] In preferred embodiments, the gaps are located adjacent to interfaces between two neighbouring strips within a stack of strips, when the separation comb is arranged in a layered structure. In preferred embodiments, at least one of the gaps, preferably several or all of the gaps, is located adjacent to an interlayer arranged in between neighbouring strips. This has been found to enable a particularly advantageous resin distribution process within and across the stacks of strips.

[0059] In another aspect, the present invention relates to a reinforcing structure for a wind turbine blade, the reinforcing structure comprising a plurality of strips of fibre-reinforced material arranged into adjacent stacks of strips forming a layered structure with a plurality of fibre-reinforced layers, a plurality of interlayers arranged between the plurality of fibre-reinforced layers, such that adjacent fibre-reinforcing layers are separated by an interlayer, and at least one separation comb arranged between adjacent stacks of strips, wherein the at least one separation comb comprises: a base region a teeth region comprising a plurality of teeth extending from the base region,

[0060] - wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb to the other side of the separation comb, and

[0061] - wherein the plurality of teeth penetrates the plurality of interlayers.

[0062] In preferred embodiments, the plurality of strips, the plurality of interlayers and the at least one separation comb, are embedded in a cured resin. In some embodiments, the resin is epoxy resin, or vinyl ester resin. In some embodiments, a plurality of separation combs, such as two, three, four, five, six or even more than six separation combs are arranged in the reinforcing structure between adjacent stacks of strips. If more than two adjacent stacks of strips are present, such as three adjacent stacks of strips including a first, second and third stack, the reinforcing structure preferably comprise at least two separation combs, one for separating the first and second stack and one for separating the second and third stack. In some embodiments, the reinforcing structure comprises two separation combs for each number of adjacent stacks of strips. For example, if the reinforcing structure comprises three adjacent stacks of strips, including a first, second and third stack, the reinforcing structure preferably comprise at least four separation combs, two for separating the first and second stack and two for separating the second and third stack.

[0063] In another aspect, the present invention relates to a method for manufacturing a reinforcing structure for a wind turbine blade, the method comprising the steps of: arranging a plurality of strips of fibre-reinforced material into adjacent stacks of strips forming a layered structure with a plurality of fibre-reinforced layers, wherein adjacent fibre-reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, providing at least one separation structure comprising one or more teeth, such as a plurality of teeth, configured for penetrating the interlayers, inserting the one or more teeth between two adjacent stacks of strips and penetrating the plurality of interlayers with the one or more teeth, such that the plurality of strips in adjacent stacks of strips are separated by the one or more teeth, optionally moving the layered structure to a desired location, such as into a wind turbine blade shell mould, after inserting the one or more teeth between adjacent stacks of strips, optionally removing the one or more teeth, and infusing the layered structure with resin to form a reinforcing structure.

[0064] In yet another aspect, the present invention relates to a reinforcing structure for a wind turbine blade, the reinforcing structure comprising a plurality of strips of fibre-reinforced material arranged into adjacent stacks of strips forming a layered structure with a plurality of fibre-reinforced layers, a plurality of interlayers arranged between the plurality of fibre-reinforced layers, such that adjacent fibre-reinforcing layers are separated by an interlayer, and at least one separation structure arranged between adjacent stacks of strips, wherein the at least one separation structure comprises one or more teeth, such as a plurality of teeth, wherein each of the plurality of teeth separate two adjacent stacks of strips and penetrate the plurality of interlayers. All relevant features and embodiments discussed above with respect to the method of manufacturing a reinforcing structure comprising a separation comb and the reinforcing structure comprising the separation comb, likewise apply to the method of manufacturing a reinforcing structure comprising a separation structure comprising one or more teeth and the reinforcing structure comprising a separation structure comprising one or more teeth. Even though it is preferred that the separation structure is a separation comb, due to the stability and eased handling provided by the base region, one or more teeth may sufficiently separate the adjacent stacks of strips.

[0065] In yet another aspect, the present invention relates to a wind turbine blade comprising a reinforcing structure with at least one separation comb or separation structure as described herein.

[0066] In some embodiments, the wind turbine blade has a profiled contour including a pressure side and a suction side, and a leading edge and a trailing edge with a chord having a chord length extending therebetween, the wind turbine blade extending in a spanwise direction between a root end and a tip end.

[0067] In yet a further aspect, the present invention relates to a method of manufacturing a wind turbine blade comprising a reinforcing structure, the wind turbine having a profiled contour including a pressure side and a suction side, and a leading edge and a trailing edge with a chord having a chord length extending therebetween, the wind turbine blade extending in a spanwise direction between a root end and a tip end, the method comprising the steps of: providing a blade shell mould, arranging a plurality of blade shell components in the blade shell mould, assembly of a layered structure in the blade shell mould or assembly of the layered structure at a location different from the blade shell mould and subsequently moving of the layered structure to the blade shell mould, wherein assembly of the layered structure comprises: arranging a plurality of strips of fibre-reinforced material into adjacent stacks of strips forming a layered structure with a plurality of fibre-reinforced layers, wherein adjacent fibre-reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, providing at least one separation comb comprising:

[0068] - a base region

[0069] - a teeth region comprising a plurality of teeth extending from the base region, - wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb to the other side of the separation comb, and wherein the plurality of teeth are configured for penetrating the interlayers, inserting the at least one separation comb between two adjacent stacks of strips and penetrating the plurality of interlayers with the plurality of teeth, such that the plurality of strips in adjacent stacks of strips are separated by the at least one separation comb along the whole height of the layered structure, optionally removing the at least one separation comb, and infusing resin into the blade shell mould to form a resin-infused reinforcing structure in a wind turbine blade shell, and combining two wind turbine blade shells to form a wind turbine blade.

[0070] In yet a further aspect, the present invention relates to wind turbine blade comprising a reinforcing structure comprising at least one separation comb as described herein.

[0071] In some embodiments, the step of infusing resin into the stacks of strips comprises effecting resin flow from at least one of the stacks of strips to an adjacent stack of strips through the gaps between adjacent teeth of the plurality of teeth. Such resin flow is typically in a substantially chordwise direction within the blade mould. In some embodiments, resin can be infused into the stack closest to the leading edge or closest to the trailing edge of the blade, wherein resin flow is effected from that stack to the other stacks of the reinforcing structure through the gaps, e.g., in a chordwise direction towards the trailing edge or towards the leading edge. In other embodiments, resin can be infused into a stack located at the centre of the reinforcing structure, seen in a chordwise direction, wherein resin flow is effected from that stack to the other stacks of the reinforcing structure through the gaps, i.e., towards the leading edge and towards the trailing edge.

[0072] In a preferred embodiment, the pressure side shell half and the suction side shell half of the blade are manufactured in respective mould halves, preferably by vacuum-assisted resin transfer moulding. According to some embodiments, the pressure side shell half and the suction side shell half each have a longitudinal extent of 50-150 m, preferably 60-80 m. In a preferred embodiment, the pressure side shell half and the suction side shell half each comprise one or more layers of carbon fibres.

[0073] According to some embodiments, the method further comprises a step of arranging one or more shear webs in at least one of the shell halves, usually at the location of the reinforcing structure. Each shear web may comprise a web body, a first web foot flange at a first end of the web body, and a second web foot flange at a second end of the web body. In some embodiments, the shear webs are substantially I-shaped. Alternatively, the shear webs may be substantially C-shaped.

[0074] In yet another aspect, the present invention relates to a separation comb configured for separating adjacent stacks of strips forming a spar cap for a wind turbine blade with a plurality of fibre- reinforced layers, wherein adjacent fibre-reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, the separation comb comprising: a base region a teeth region comprising a plurality of teeth extending from the base region, wherein the teeth region has a height which is equal to or greater than a height of the spar cap minus a height of an uppermost fibre-reinforced layer of the plurality of fibre-reinforced layers,

[0075] - wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb to the other side of the separation comb, and

[0076] - wherein the plurality of teeth is configured for penetrating the interlayers.

[0077] In yet another aspect, the present invention relates to a separation structure comprising at least two separation combs as described herein, wherein the at least two separation combs are connected by a connecting element.

[0078] In some embodiments, the connecting element is a plate and is connected to the base region of the least two separation combs, such that it is configured to be arranged on top of the layered structure when the separation combs are inserted between adjacent stacks of strips.

[0079] In some embodiments, the connecting element comprises a handle or protruding element allowing easy removal of the separation structure from the layered structure.

[0080] In some embodiments, the separation structure is substantially rack-shaped.

[0081] In some embodiments, the connecting element of the separation structure extends throughout the entire spanwise and / or chordwise extent of the layered structure in the wind turbine blade.

[0082] According to another aspect, the present invention relates to a part for a wind turbine blade, said part comprising a separation comb and a plurality of stacked fibre-reinforced layers, wherein the separation comb comprises a base region and a teeth region, the teeth region comprising a plurality of teeth extending from the base region, and wherein the plurality of teeth of the teeth region of the separation comb penetrates the plurality of stacked fibre-reinforced layers.

[0083] In a preferred embodiment, the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb to the other side of the separation comb.

[0084] According to another preferred embodiment, the plurality of stacked fibre-reinforced layers comprise adjacent stacks of fibre-reinforced layers forming a spar cap for a wind turbine blade, wherein the fibre-reinforced layers within each of the stacks are separated by interlayers, and wherein the teeth region has a height which is equal to or greater than a height of the spar cap minus a height of an uppermost fibre-reinforced layer of the plurality of stacked fibre-reinforced layers. In an advantageous embodiment, the plurality of teeth is configured for penetrating the interlayers.

[0085] According to another preferred embodiment, the part comprises at least two separation combs according to any of the preceding claims, wherein the at least two separation combs are connected by a connecting element.

[0086] According to yet another aspect, the present invention relates to a wind turbine blade obtainable by the method described herein. The embodiments and features described above for the method of manufacturing a reinforcing structure likewise apply to the other aspects of the invention, including the aspects related to the separation comb, the separation structure, the reinforcing structure, the wind turbine blade and the method for manufacturing a wind turbine blade and vice versa.

[0087] BRIEF DESCRIPTION OF THE FIGURES

[0088] Embodiments of the disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present disclosure and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0089] Fig. 1 is a schematic illustration of a wind turbine,

[0090] Fig. 2 is a schematic illustration of a three-dimensional and a cross-sectional view of a wind turbine blade, Fig. 3 is a schematic illustration of a top view of a reinforcing structure in a wind turbine blade and cross-sectional views of a reinforcing structure according to the prior art illustrating misalignments of strips in the reinforcing structure,

[0091] Fig. 4 is a is a schematic illustration of a front view of a separation comb according to different embodiments of the present invention,

[0092] Fig. 5 is a schematic illustration of a three-dimensional view of the dimensions of a separation comb according to an embodiment of the present invention, relative to a reinforcing structure in the form of a spar cap,

[0093] Fig. 6 is a schematic illustration of cross-sectional views of a reinforcing structure comprising a separation comb according to different embodiments of the present invention, and

[0094] Fig. 7 is a schematic illustration of a separation structure and a reinforcing structure comprising a separation structure according to an embodiment of the present invention.

[0095] DETAILED DESCRIPTION

[0096] 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.

[0097] Fig. 1 illustrates a conventional modern upwind wind turbine according to the so-called "Danish concept" with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 farthest from the hub 8. The rotor has a radius denoted R.

[0098] Fig. 2A shows a schematic view of a wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 farthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0099] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0100] A shoulder 40 of the blade 10 is defined as the position where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34. Fig. 2A also illustrates the longitudinal extent, length or longitudinal axis of the blade.

[0101] 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.

[0102] The blade is typically made from a pressure side shell part 36 and a suction side shell part 38 that are glued to each other along bond lines at the leading edge 18 and the trailing edge of the blade 20.

[0103] Fig. 2B shows a schematic view of a cross section of the blade along the line I-I shown in Fig. 2A. As previously mentioned, the blade 10 comprises a pressure side shell part 36 and a suction side shell part 38. The pressure side shell part 36 comprises a spar cap 45, also called a main laminate, which constitutes a load-bearing part of the pressure side shell part 36. The spar cap 45 comprises a plurality of fibre layers 42 mainly comprising unidirectional fibres aligned along the longitudinal direction of the blade in order to provide stiffness to the blade. The suction side shell part 38 also comprises a spar cap 45 comprising a plurality of fibre layers 46. The pressure side shell part 36 may also comprise a sandwich core material 43 typically made of balsawood or foamed polymer and sandwiched between a number of fibre-reinforced skin layers. The sandwich core material 43 is used to provide stiffness to the shell in order to ensure that the shell substantially maintains its aerodynamic profile during rotation of the blade. Similarly, the suction side shell part 38 may also comprise a sandwich core material 47.

[0104] The spar cap 45 of the pressure side shell part 36 and the spar cap 45 of the suction side shell part 38 are connected via a first shear web 50 and a second shear web 55. The shear webs 50, 55 are in the shown embodiment shaped as substantially I-shaped webs. The first shear web 50 comprises a shear web body and two web foot flanges. The shear web body comprises a sandwich core material 51, such as balsawood or foamed polymer, covered by a number of skin layers 52 made of a number of fibre layers.

[0105] The blade shells 36, 38 may comprise further fibre-reinforcement at the leading edge and the trailing edge. Typically, the shell parts 36, 38 are bonded to each other via glue flanges.

[0106] Fig. 3A is a schematic top view of a shell half 38 of a wind turbine blade comprising a reinforcing structure 62 according to the prior art. The reinforcing structure 62 is in the form of a spar cap, arranged within the shell half 38. In the illustrated embodiment, the reinforcing structure 62 comprises three adjacent stacks 65a, 65b, 65c of strips of fibre-reinforced material arranged adjacent to each other. Only the uppermost strip 64a, 64b, 64c of each stack 65a, 65b, 65c can be seen in fig. 3A.

[0107] Fig. 3B is a schematic cross-sectional view of the reinforcing structure 62 of fig. 3A through the cross-section a-a illustrated in Fig. 3A. As can be seen in Fig. 3B, each stack 65a, 65b, 65c of the reinforcing structure 62 comprises three strips 63a, 64a, 63b, 64b, 63c, 64c. The nine strips 63a, 64a, 63b, 64b, 63c, 64c of fibre-reinforced material are arranged into adjacent stacks 65a, 65b, 65c of strips forming a layered structure 61 with three fibre-reinforced layers 67, 68, including an uppermost fibre-reinforced layer 68, wherein each fibre-reinforced layer 67, 68 comprises a strip 63a, 64a, 63b, 64b, 63c, 64c from each of the adjacent stacks 65a, 65b, 65c of strips. Furthermore, the reinforcing structure 62 of Fig. 3B comprises two interlayers 66 arranged between the three fibre-reinforced layers 67, 68, such that adjacent fibre-reinforced layers 67, 68 are separated by an interlayer 66.

[0108] Figs. 3C and 3D illustrate how the strips 63a, 64a, 63b, 64b, 63c, 64c can move within the reinforcing structure 62 and cause misalignments and overlaps of the strips 63a, 64a, 63b, 64b, 63c, 64c. In Fig. 3C, the strips 63b, 63c have moved horizontally, whereas in fig. 3D, the strips 63b, 64b, 63c, 64c have overlapped. As can be seen in figs. 3C and 3D, such misalignments and overlaps affect the final shape of the reinforcing structure 62, which is not desired. This problem is addressed by the present invention which has been found to result in greatly improved properties of the final reinforcing structure 62 with virtually no misalignments or related structural defects of the reinforcing structure 63.

[0109] Figs. 4A-4C are schematic front view illustrations of different embodiments of a separation comb 70 according to the present invention. The separation combs 70 are configured to be inserted between adjacent stacks 65a, 65b, 65c of strips of a layered structure, before it is resin infused to form a reinforcing structure 62 of a wind turbine blade 10 as illustrated in Figs. 5 and 6.

[0110] As can be seen in figs. 4A-4C, the separation comb 70 of the present invention comprises a base region 71 and a teeth region 73. The teeth region 73 comprises a plurality of teeth 74 extending from the base region 71 and being arranged in a linear array with gaps 79 between adjacent teeth 74. The gaps 79 are configured for allowing resin to flow from one side of the separation comb 70 to the other side of the separation comb 70, whereas the teeth 74 are configured for penetrating a sheet of material, such as a plurality of interlayers 66 of a layered structure, before it is resin infused to form a reinforcing structure 62.

[0111] The separation comb 70 has a length 701, a thickness 70t and a height 70h, wherein the length 701 and height 70h are larger than the thickness 70t. Only the length 701 and height 701 of the separation comb 70 can be seen in figs. 4A-4C.

[0112] The base region 71 is substantially rectangular and has a length 711 defining the length of the separation comb 701. However, the base region 71 could also have another shape, as long as it is structurally stable and can support the plurality of teeth 71.

[0113] The height 71 h of the base region 71 depends on the height of an uppermost strip 64a, 64b, 64c of a reinforcing structure 62 in which the separation comb 70 is to be arranged. This is further discussed in relation to fig. 5A.

[0114] In fig. 4A, the separation comb 70 comprises seven teeth 74 and six gaps 79. In fig. 4B, the separation comb 70 comprises twelve teeth 74 and eleven gaps 79. In fig. 4C, the separation comb 70 comprises eight teeth 74 and seven gaps 79.

[0115] Each of the teeth 74 has a height 74h, a length 741 and a thickness 74t. Only the height 75h and the length 741 can be seen in figs. 4A-4C. The height 74h of each tooth 74 is defined between the tips 75 of the plurality of teeth 74 to an edge 80 of the base region most proximal to the tips 75 of the teeth 74. As can be seen in figs. 4A-4C, the plurality of teeth 74 and the gaps 79 of the teeth region 73 may have many different shapes. The teeth 74 may have a sharp or pointed tip 75, to facilitate penetration of the interlayers 66. It is important that the teeth 74 are structurally stable i.e., do not easily break. Finally, it is important that the gaps 79 are large enough for resin to wet all or substantially all parts of the interlayers 66 of a layered structure into which the separation comb 70 is inserted, when the layered structure is infused with resin. In case the gaps 79 are too narrow at some points between adjacent teeth 74, such as very narrow proximal to the base region 71 as seen in fig. 4B, the gaps 79 may not be large enough to allow resin to efficiently flow from one side of the separation comb 70 to the other side of the separation comb 70 in that area.

[0116] In figs. 4A-4C, all of the plurality of teeth 74 of the separation combs 70 extend parallelly and have the same height 74h, length 741 and thickness 74t. However, it is not essential that all of the teeth 74 extend parallelly and have the same height 74h, length 741 and thickness 74t.

[0117] Preferably, the height of the teeth region 73h and the height of the plurality of teeth 74h are equal to or greater than the height 65h of a stack 65a, 65b, 65c of strips e.g., the height of the layered structure into which the separation comb 70 is to be inserted, minus the height 64h of the uppermost strip 64a, 64b, 64c of the stack 65a, 65b, 65c or minus the height 68h of the uppermost fibre- reinforced layer 68, respectively. This is discussed in more detail in relation to figs. 5 and 6.

[0118] In figs. 4A and 4B, all of the plurality of teeth 74 are substantially identical. This may facilitate even resin distribution throughout a reinforcing structure 62, but it is not essential for even resin distribution. For example, as can be seen in fig. 4C, the outermost teeth 74 of the separation comb 70 does not have the same shape as the remaining teeth 74. In other embodiments, teeth 74 other than the outermost teeth 74 could have different shapes than the remaining teeth 74.

[0119] In some embodiments, the plurality of teeth 74 also have sharp or pointed edges along their height 74h. This may facilitate better penetration of interlayers 66 in a reinforcing structure 62, particularly if the length of the teeth 74 decreases from the base region 71 toward the tip 75 of the teeth 74.

[0120] In fig. 4A, the length 741 of the plurality of teeth 74 is constant along the height 74h of the plurality of teeth 74. However, in figs. 4B and 4C, the length 741 of the teeth 74 decreases from the base region 71 toward the tips 75 of the teeth 74. In the same way, the thickness 74t of the teeth 74 may be constant along the height 74h of the teeth 74 or it may decrease from the base region 71 towards the tips 75. Preferably, the maximum thickness 74t of the plurality of teeth 74 is the same as the thickness 71t of the base region 71. In some embodiments, the plurality of teeth 74 may have a circular or elliptical cross-section.

[0121] Fig. 5A is a schematic perspective view of a separation comb 70 arranged next to a stack 65 of strips 63, 64, to illustrate the relative dimensions of the separation comb 70 compared to the stack 65 of strips 63, 64.

[0122] As can be seen in fig. 5A, the stack 65 of strips comprises three strips 63, 64 including an uppermost strip 64. Each of the strips 63, 64 has a length 631, 641, a thickness 63t, 64t, and a height 63h, 64h, wherein the length 631, 641 is larger than the thickness 63t, 64t and the thickness 63t, 64t is larger than the height 63h, 64h. The length 651 and thickness 65t of the stack 65 is the same as the length 631, 641 and thickness 63t, 64t of each strip. However, the height 65h of the stack 65 is the combined height 63h, 64h of the three strips plus the height of the two interlayers 66 arranged between the strips 63, 64.

[0123] As can be seen in fig. 5A, the separation comb 70 comprises a base region 71 and a teeth region 73 comprising a plurality of teeth 74. The features of the separation comb 70 is described in more detail in relation to figs. 4A-4C.

[0124] As can be seen in fig. 5A, but also in figs. 5B, 6A and 6B, the height 74h of the teeth region 73 and the plurality of teeth 74 are equal to the height 65h of a stack of strips, including interlayers, minus the height of the uppermost strip 64 of the stack 65. This allows for optimal separation of adjacent stacks 65 of strips and optimal resin flow between the adjacent stacks 65 through the interlayers 66. However, the teeth region 73 and the plurality of teeth 74 may also be higher than a stack 65 of strips minus the height of the uppermost strip 64h. It is however preferred, that it is not lower, since this would either impair optimal separation of adjacent stacks or impair resin flow between adjacent stacks.

[0125] As can be seen in fig. 5A, but also in figs. 5B and 6A, the height 70h of the separation comb 70 is the same or substantially the same as the height 65h of the stack 65 of strips 63, 64, including the height of the interlayers 66. The height 71h of the base region 71 is the same as the height 64h of the uppermost strip 64 of the stack 65 of strips 63, 64. In this way, the base region 71 does not block resin flow through interlayers 66 between adjacent stacks 65 of strips 63, 64, when the layered structure 61 is resin infused to form a reinforcing structure 62 for a wind turbine blade. This can also be achieved if the height 71 h of the base region 71 is smaller than the uppermost strip 64. However, the base region 71 provides structural stability to the separation comb 70. Thus, a base region 71 with a smaller height 71h may be more likely to break. In some embodiments, the height 71h of the base region 71 may also be greater than the height 64h of the uppermost strip 64. However, in such embodiments, the base region 71 would protrude from the layered structure 61 when inserted, as illustrated in fig. 6C.

[0126] The maximum thickness 70t of the separation comb is configured to correspond to a predetermined spacing between two adjacent stacks 65 in a layered structure 61. The thickness 70t of the separation comb 70 may be constant or may vary. In figs. 5A, 5B, 6A and 6B, the thickness 70t of the separation comb 70 is constant.

[0127] Fig. 5B is a schematic perspective view of a layered structure 61 in the form of a spar cap before resin infusion, wherein two separation combs 70 are about to be inserted between adjacent stacks 65a, 65b, 65c of strips.

[0128] As can be seen in Fig. 5B, the layered structure 61 comprises three stacks 65a, 65b, 65c of strips, where each stack 65a, 65b, 65c comprises three strips 63a, 64a, 63b, 64b, 63c, 64c. The nine strips 63a, 64a, 63b, 64b, 63c, 64c are arranged into adjacent stacks 65a, 65b, 65c of strips to form the layered structure 61 with three fibre-reinforced layers 67, 68, including an uppermost fibre- reinforced layer 68. Each fibre-reinforced layer 67, 68 comprises a strip 63a, 64a, 63b, 64b, 63c, 64c from each of the adjacent stacks 65a, 65b, 65c. Furthermore, the layered structure 61 comprises two interlayers 66 arranged between the three fibre-reinforced layers 67, 68.

[0129] Fig. 6A is a cross-sectional view of the layered structure 61 of fig. 5B, after insertion of two separation combs 70 between adjacent stacks of strips. When the layered structure is resin infused, it is a reinforced structure 62 configured to be a spar cap for a wind turbine blade. Fig. 6B is a close-up of two stacks 65a, 65b of the layered structure 61, and fig. 6C is a close-up of two stacks 65a, 65b of the layered structure 61 comprising a separation comb 70 inserted between adjacent stacks of strips and penetrating the interlayers with the plurality of teeth, such that the plurality of strips in adjacent stacks of strips are separated by the separation combs 70 along their whole height. The height of the separation comb 70h is greater than the height of the layered structure 61h and the height of the base region 71 h is greater than the height 64h of an uppermost strip 64a, 64b of the stack 65a, 65b of strips and the height of the uppermost fibre-reinforced layer 68h of the layered structure 61. As can be seen in both embodiments, and as described in relation to fig. 5A, the height 74h of the teeth region 73 and the plurality of teeth 74 is preferably equal to or greater than a stack 65a, 65b of the layered structure 61 minus the height 64h of the uppermost strip 64a, 64b of the stack 65a, 65b and the height of the uppermost fibre-reinforced layer 68h of the layered structure 61. This allows for optimal separation of adjacent stacks 65a, 65b of strips and optimal resin flow between the adjacent stacks 65a, 65b through the interlayers 66. Fig. 6B illustrates an embodiment where the height 71 h of the base region 71 is greater than the height 64h of the uppermost strips 64a, 64b. Such an embodiment may be preferred if the separation comb 70 is to be removed again before resin infusion. In such embodiments, the protruding part 76 of the base region 71 may be used to identify and grab the separation comb 70 and remove it from the layered structure 61 before resin infusion. Alternatively, a separate protruding element or handle 76 may be attached to the base region 71 to achieve the same effect.

[0130] Fig. 7A is a schematic illustration of a separation structure 78 comprising two separation combs 70 connected by a connecting element 77 in the form of a plate arranged on top of the layered structure 61. The separation structure 78 in the illustrated embodiment is substantially rack-shaped. Fig. 7B is a schematic cross-sectional view of a layered structure 61wherein the separation structure 78 is arranged. The features of the separation combs 70 are the same as described in relation to the above embodiments. The connecting element 77 can be used to connect several separation combs 70 for easy handling and / or removal from the layered structure 61 before resin infusion. However, the separation structure may also be resin infused with the layered structure 61.

[0131] 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.

[0132] LIST OF REFERENCES

[0133] 4 tower

[0134] 6 nacelle

[0135] 8 hub

[0136] 10 blades

[0137] 14 blade tip

[0138] 16 blade root

[0139] 18 leading edge

[0140] 20 trailing edge

[0141] 30 root region

[0142] 32 transition region

[0143] 34 airfoil region

[0144] 36 pressure side shell part

[0145] 38 suction side shell part

[0146] 40 shoulder

[0147] 42 fibre layers

[0148] 43 sandwich core material

[0149] 45 spar cap

[0150] 46 fibre layers

[0151] 47 sandwich core material

[0152] 50 first shear web

[0153] 51 core member

[0154] 52 skin layers

[0155] 55 second shear web

[0156] 56 sandwich core material of second shear web

[0157] 57 skin layers of second shear web

[0158] 60 filler ropes

[0159] 61 layered structure

[0160] 61h height of layered structure

[0161] 62 reinforcing structure

[0162] 62h height of reinforcing structure

[0163] 62t thickness of reinforcing structure

[0164] 621 length of reinforcing structure

[0165] 63 strip

[0166] 63h height of strip

[0167] 63t thickness of strip 631 length of strip

[0168] 64a, b, c uppermost strip

[0169] 64h height of uppermost strip

[0170] 64t thickness of uppermost strip

[0171] 641 length of uppermost strip

[0172] 65a, b, c stack of strips

[0173] 65h height of stack of strips

[0174] 65t thickness of stack of strips

[0175] 651 length of stack of strips

[0176] 66 interlayer

[0177] 67 fibre-reinforced layer of reinforcing structure

[0178] 68 uppermost fibre-reinforced layer

[0179] 68h height of uppermost fibre-reinforced layer

[0180] 70 separation comb

[0181] 70h height of separation comb

[0182] 70t thickness of separation comb

[0183] 701 length of separation comb

[0184] 71 base region

[0185] 71 h height of base region

[0186] 7 It thickness of base region

[0187] 711 length of base region

[0188] 72 edge of base region most distal to teeth tip

[0189] 73 teeth region

[0190] 73h height of teeth region

[0191] 731 length of teeth region

[0192] 74 teeth

[0193] 74h height of teeth

[0194] 74t thickness of teeth

[0195] 741 length of teeth

[0196] 75 teeth tip

[0197] 76 handle or pultruding element

[0198] 77 connecting element

[0199] 78 separation structure

[0200] 79 gap of separation comb

[0201] 80 edge of base region most proximal to teeth tip r distance from hub

Claims

CLAIMS1. A method for manufacturing a reinforcing structure (62) for a wind turbine blade, the method comprising the steps of: arranging a plurality of strips (63, 64) of fibre-reinforced material into adjacent stacks (65) of strips forming a layered structure with a plurality of fibre-reinforced layers, wherein adjacent fibre- reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, providing at least one separation comb (70) comprising: a base region (71) a teeth region (73) comprising a plurality of teeth (74) extending from the base region (71),- wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb (70) to the other side of the separation comb (70), and wherein the plurality of teeth are configured for penetrating the interlayers, inserting the at least one separation comb (70) between two adjacent stacks (65) of strips (63, 64) and penetrating the plurality of interlayers with the plurality of teeth, such that the plurality of strips (63, 64) in adjacent stacks of strips (63, 64) are separated by the at least one separation comb (70), optionally moving the layered structure to a desired location, such as into a wind turbine blade shell mould, after inserting the at least one separation comb (70) between adjacent stacks of strips (63, 64), optionally removing the at least one separation comb (70), and infusing the layered structure with resin to form a reinforcing structure (62).

2. A method according to any of the preceding claims, wherein the plurality of teeth (74) includes between 2 and 100 teeth, such as between 2 and 50 teeth, preferably between 5 and 10 teeth.

3. A method according to any of the preceding claims, wherein the gaps between the adjacent teeth of the plurality of teeth are between 3 mm and 200 mm, preferably between 3 mm and 50 mm, more preferably between 3 mm and 10 mm, such as 5 mm.

4. A method according to any of the preceding claims, wherein the layered structure has a height and wherein the teeth region (73) of the at least one separation comb (70) has a height which is equal to or greater than the height of the layered structure minus a height of an uppermost fibre- reinforced layer of the plurality of fibre-reinforced layers.

5. A method according to any of the preceding claims, wherein the at least one separation comb (70) has a height which is defined by the height of the teeth region (73) plus a height of the base region (71) and wherein the height of the at least one separation comb (70) is equal to or greater than the height of the layered structure, such that when inserting the at least one separation comb between two adjacent stacks (65) of strips (63, 64) and penetrating the plurality of interlayers with the plurality of teeth, the plurality of strips (63, 64) in adjacent stacks of strips (63, 64) are separated by the at least one separation comb along the whole height of the layered structure.

6. A method according to any of the preceding claims, wherein the at least separation comb (70) is made from one or more fibre-reinforced materials and / or one or more metals and / or one or more thermoplastic materials.

7. A method according to any of the preceding claims, wherein the at least one separation comb (70) essentially consists of fibre-reinforced carbon fibres and / or glass fibres.

8. A method according to any of the preceding claims, wherein the interlayers are resin flow promoting interlayers configured for facilitating resin flow between the strips (63, 64) of fibre- reinforced material and wherein the step of infusing resin into the layered structure comprises effecting resin flow through one or more of the interlayers from at least one of the stacks (65) of strips (63, 64) to an adjacent stack of strips (63, 64) through the gaps between adjacent teeth of the plurality of teeth.

9. A method according to any of the preceding claims, wherein the reinforcing structure (62) is a spar cap for a wind turbine blade and the plurality of strips (63, 64) of fibre-reinforced material are pultruded planks comprising fibre reinforced carbon fibres and / or glass fibres.

10. A method of manufacturing a wind turbine blade comprising a reinforcing structure (62), the wind turbine having a profiled contour including a pressure side and a suction side, and a leading edge and a trailing edge with a chord having a chord length extending therebetween, the wind turbine blade extending in a spanwise direction between a root end and a tip end, the method comprising the steps of: providing a blade shell mould, arranging a plurality of blade shell components in the blade shell mould,assembly of a layered structure in the blade shell mould or assembly of the layered structure at a location different from the blade shell mould and subsequently moving of the layered structure to the blade shell mould, wherein assembly of the layered structure comprises: arranging a plurality of strips (63, 64) of fibre-reinforced material into adjacent stacks (65) of strips (63, 64) forming a layered structure with a plurality of fibre-reinforced layers, wherein adjacent fibre-reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, providing at least one separation comb (70) comprising:- a base region (71)- a teeth region (73) comprising a plurality of teeth (74) extending from the base region,- wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb (70) to the other side of the separation comb, and wherein the plurality of teeth are configured for penetrating the interlayers, inserting the at least one separation comb between two adjacent stacks of strips and penetrating the plurality of interlayers with the plurality of teeth, such that the plurality of strips (63, 64) in adjacent stacks of strips are separated by the at least one separation comb along the whole height of the layered structure, optionally removing the at least one separation comb, and infusing resin into the blade shell mould to form a resin-infused reinforcing structure (62) in a wind turbine blade shell, and combining two wind turbine blade shells to form a wind turbine blade.

11. A reinforcing structure (62) for a wind turbine blade, the reinforcing structure (62) comprising a plurality of strips (63, 64, 65) of fibre-reinforced material arranged into adjacent stacks (66) of strips forming a layered structure with a plurality of fibre-reinforced layers, a plurality of interlayers arranged between the plurality of fibre-reinforced layers, such that adjacent fibre-reinforcing layers are separated by an interlayer, and at least one separation comb (70) arranged between adjacent stacks of strips, wherein the at least one separation comb (70) comprises: a base region (71) a teeth region (73) comprising a plurality of teeth (74) extending from the base region,- wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow fromone side of the separation comb (70) to the other side of the separation comb (70), and- wherein the plurality of teeth penetrates the plurality of interlayers.

12. A reinforcing structure according to claim 11, wherein the plurality of strips, the plurality of interlayers and the at least one separation comb (70), are embedded in a cured resin.

13. A wind turbine blade comprising one or more reinforcing structures according to any of claims 11 or 12.

14. A separation comb (70) configured for separating adjacent stacks of strips (63, 64) forming a spar cap for a wind turbine blade with a plurality of fibre-reinforced layers, wherein adjacent fibre- reinforced layers of the plurality of fibre-reinforced layers are separated by interlayers, the separation comb (70) comprising: a base region (71) a teeth region (73) comprising a plurality of teeth (74) extending from the base region, wherein the teeth region has a height which is equal to or greater than a height of the spar cap minus a height of an uppermost fibre-reinforced layer of the plurality of fibre- reinforced layers,- wherein the plurality of teeth is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowing resin to flow from one side of the separation comb (70) to the other side of the separation comb (70), and- wherein the plurality of teeth is configured for penetrating the interlayers.

15. A separation structure comprising at least two separation combs according to any of the preceding claims, wherein the at least two separation combs are connected by a connecting element.

16. A part (62) for a wind turbine blade, said part comprising a separation comb (70) and a plurality of stacked fibre-reinforced layers, wherein the separation comb (70) comprises a base region (71) and a teeth region (73), the teeth region comprising a plurality of teeth (74) extending from the base region (71), and wherein the plurality of teeth of the teeth region of the separation comb (70) penetrates the plurality of stacked fibre-reinforced layers.

17. A part for a wind turbine blade according to claim 16, wherein the plurality of teeth (74) is arranged in a linear array with gaps between adjacent teeth, the gaps being configured for allowingresin to flow from one side of the separation comb (70) to the other side of the separation comb (70).

18. A part for a wind turbine blade according to claims 16 or 17, wherein the plurality of stacked fibre-reinforced layers comprises adjacent stacks of fibre-reinforced layers forming a spar cap for a wind turbine blade, wherein the fibre-reinforced layers within each of the stacks are separated by interlayers, and wherein the teeth region (73) has a height which is equal to or greater than a height of the spar cap minus a height of an uppermost fibre-reinforced layer of the plurality of stacked fibre-reinforced layers.

19. A part for a wind turbine blade according to claim 18, wherein the plurality of teeth is configured for penetrating the interlayers.

20. A part for a wind turbine blade according to any of claims 16-19, wherein the part comprises at least two separation combs according to any of the preceding claims, wherein the at least two separation combs are connected by a connecting element.

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