Wind turbine blade spar cap and method of manufacturing wind turbine blade spar cap

Abstract

A wind turbine blade spar cap comprises a fiber reinforced resin structure, such as a pultrusion element, comprising fiber bundles wherein each of at least some of the fiber bundles comprises: a first set of longitudinally aligned first filaments, each of the first set of longitudinally aligned first filaments defining a first cross-section; and a second set of longitudinally aligned second filaments, each of the second set of longitudinally aligned second filaments defining a second cross-section. The first cross-section is different from the second cross-section. The method also relates to a method for manufacturing a wind turbine blade spar cap.

Description

Technical Field

[0001] The present invention relates to a wind turbine blade spar cap, in particular a wind turbine blade spar cap for a horizontal axis wind turbine. The present invention also relates to a method for manufacturing a wind turbine blade spar cap, for example for a horizontal axis wind turbine. Background Art

[0002] As part of the worldwide transition to renewable energy, there is a need for wind turbines of increasing size and efficiency. However, the mechanical properties of wind turbine blades limit the size of the blades and thus the power output of the wind turbine. During use, wind turbine blades are subject to static and dynamic loads (i.e., aerodynamic loads) caused by the wind acting on the blades, as well as gravity loads.

[0003] The loads caused by wind acting on a wind turbine blade are generally referred to as flapping loads, and the loads caused by gravity are generally referred to as shimmy loads. During use of a blade, its pressure side is generally subject to tension, and its suction side is generally subject to compression. The flapping loads may be resisted by internal shear webs in the blade, while the leading and trailing edges of the blade carry the shimmy bending loads.

[0004] The spar caps may be embedded in or attached to the suction side shell and the pressure side shell at the attachment area of ​​the shear web. The spar caps may provide enhanced tensile or compressive strength. The spar caps may include longitudinally aligned filaments incorporated in, for example, a pultruded element that may be designed to handle certain predetermined levels of tensile and compressive loads. The tensile properties of the filaments are higher than their compressive properties, so compressive strength may be a limiting property in the design of the spar caps. To date, the development of spar caps comprising fiber reinforced resin structures has focused on the geometric configuration of multiple fiber reinforced elements, such as sandwich structures, optimization of the interface between the spar caps and the shear webs, and maximizing the volumetric fiber filament content in the fiber reinforced elements. Summary of the invention

[0005] Against the above background, it is an object of a preferred embodiment of the present invention to provide a wind turbine blade spar cap having improved properties, such as improved compressive strength. Another object of a preferred embodiment of the present invention is to provide a spar cap that balances the compressive and tensile properties of the spar cap. Another object of a preferred embodiment of the present invention is to provide a simple and efficient method for manufacturing such a spar cap.

[0006] In a first aspect, the present invention provides a wind turbine blade spar cap, the wind turbine blade spar cap comprising a fiber reinforced resin structure, the fiber reinforced resin structure comprising fiber bundles, wherein at least some of the fiber bundles include:

[0007] a first set of longitudinally aligned first filaments, each of the first set of longitudinally aligned first filaments defining a first cross-section; and

[0008] a second set of longitudinally aligned second filaments, each of the second set of longitudinally aligned second filaments defining a second cross-section,

[0009] The first cross section is different from the second cross section.

[0010] The present invention proceeds from the insight that the compressive and tensile properties of a spar cap are affected by the geometrical configuration of the filaments themselves. Providing separate groups of different filaments in one or more fiber bundles may provide improved compressive properties of a wind turbine blade spar cap without compromising tensile properties to an unacceptable degree.

[0011] According to the present invention, within a single fiber bundle, there is a group of first filaments and a group of second filaments. The cross-section of the first group of filaments has a different cross-section than that of the second group of filaments.

[0012] Since the compressive properties of the spar caps may impose restrictions on the spar cap structure, a certain proportion of the tensile properties may be sacrificed to improve the compressive properties to obtain an overall balance of improvements in the compressive and tensile properties.

[0013] Preferably, the fiber bundle is a carbon bundle, and the first filaments are carbon filaments, and the second filaments are carbon filaments.

[0014] Providing filaments with different cross-sections within a bundle can increase the threshold for fracture and other severe failures. More specifically, in a carbon bundle having carbon filaments of equal cross-section, once fracture of an individual filament begins, fracture may occur throughout the carbon bundle. In a bundle including carbon filaments of different cross-sections, fractures that begin to develop in individual filaments of the bundle are less likely to propagate through the bundle and / or the fiber reinforcement structure before the fracture becomes severe.

[0015] Additionally, providing different cross-sections allows the individual filaments in the fiber bundle to be packed more densely, as the spaces between filaments of large cross-section can be filled with filaments of smaller cross-section. Thus, the volumetric filament content of the bundle can be increased compared to a bundle comprising filaments of equal cross-section. The diameter of the fiber bundle can therefore be reduced, which in turn can lead to reduced spar cap size and savings in resin, and mechanical properties can be enhanced due to the higher filament content in the bundle and, therefore, in the fiber reinforced resin structure.

[0016] Furthermore, filaments with different cross-sections can advantageously ensure that the filaments have different degrees of carbonization, which in turn can further improve the mechanical properties and breaking properties of the fiber bundle.

[0017] The present invention is not limited to fiber bundles with only two groups of filaments. Generally, embodiments of the present invention can have any number of filament groups. Each of such several groups can, for example, have different cross-sections, such as cross-sections of different shapes and / or different sizes. For example, in an embodiment of the present invention, each of at least some of the fiber bundles includes a third group of longitudinally aligned third filaments, each of which defines a third cross-section, wherein the third cross-section is different from the first cross-section and the second cross-section. More than two filament groups can further improve the mechanical properties and fracture properties of the fiber bundle. Preferably, the third filament is a carbon filament.

[0018] In the present context, the term "longitudinally aligned" refers to the longitudinal direction of the fiber bundle, ie the direction of its length. The fiber-reinforced resin structure can be provided in the form of a pultruded element and / or as a woven or non-woven structure.

[0019] Typically, according to embodiments of the present invention, each fiber bundle may, for example, include 100 to 200,000 filaments, such as 12,000 to 50,000 filaments.

[0020] The filaments may alternatively be referred to as fiber filaments. The carbon fibers may include or consist of carbon fibers. Thus, a structure reinforced by carbon filaments may be understood as a fiber reinforced structure or a carbon reinforced structure.

[0021] In an embodiment of the invention, the first cross-section defines a first cross-sectional area, and the second cross-section defines a second cross-sectional area, wherein the first cross-sectional area is greater than the second cross-sectional area.

[0022] In this case, the first cross-sectional area can be understood as the area of ​​the first cross section of the first wire of the first group. Similarly, the second cross-sectional area can be understood as the area of ​​the second cross section of the second wire of the second group.

[0023] Generally, providing different cross-sectional areas is a simple and efficient way to achieve different cross-sections.Such different areas can in particular ensure further improved mechanical properties and fracture properties of the bundle.

[0024] In an embodiment of the present invention, the first cross-sectional area is 50 square microns to 200 square microns, such as 55 square microns to 100 square microns, such as 60 square microns to 120 square microns. The second cross-sectional area may be 10 square microns to 50 square microns, such as 20 square microns to 45 square microns, such as 30 square microns to 40 square microns.

[0025] The above exemplary combinations of cross-sectional areas may ensure a proper balance of mechanical properties of the fiber bundle, as well as improved packing of the filaments.

[0026] In an embodiment of the invention, the first cross-section defines a first cross-sectional shape and the second cross-section defines a second cross-sectional shape, wherein the first cross-sectional shape is different from the second cross-sectional shape.

[0027] As an alternative or supplement to different cross-sectional areas, different groups of silk can have different cross-sectional shapes. The different shapes of the groups can be, for example, any one of a circle, an ellipse, a bean shape, an irregular shape, and a polygon. The polygonal shape can be, for example, a triangle, a quadrilateral, a pentagon, a hexagon, etc. The cross-sections of different shapes can help improve the accumulation of silk in the fiber bundle.

[0028] In an embodiment of the invention, said first group of longitudinally aligned first filaments accounts for at least 30%, such as at least 35%, such as at least 40%, such as at least 45% of the total cross-sectional area of ​​each fiber bundle.

[0029] In an embodiment of the invention, said second group of longitudinally aligned second filaments accounts for at least 30%, such as at least 35%, such as at least 40%, such as at least 45% of the total cross-sectional area of ​​each fiber bundle.

[0030] Note that the above total cross-sectional area relates to the portion of the cross-section of the fiber bundle that is formed by the filaments. It therefore does not include the gaps between the filaments of the fiber bundle. In a wind turbine blade spar cap, the fiber bundle is saturated with resin, which may at least partially fill such gaps. In this context, such gaps should not be considered as part of the total cross-sectional area of ​​the fiber bundle. In other words, only the filaments contribute to the "total cross-sectional area".

[0031] The respective percentages of the first and second sets of filaments may be tailored to meet a desired balance between tensile and compressive properties.

[0032] The above-mentioned percentages of filaments in the cross-sections of the first and second groups may be advantageous in compensating for the smaller area of ​​the individual cross-sections of the filaments of one group, ie by including relatively more filaments in the other group.

[0033] In an embodiment of the invention, the fiber bundle forms part of a pultruded element of the wind turbine blade spar cap. Pultrusion is a process known per se, in which the bundle is pulled through a die while being saturated with resin. Thereby a perfect longitudinal alignment of the filaments is achieved, resulting in improved mechanical properties.

[0034] In an embodiment of the invention, all fiber bundles have the same total cross-sectional area.

[0035] Although all fiber bundles may have the same cross-sectional area, the cross-sections of individual filaments within a fiber bundle may still be different. Providing fiber bundles with equal cross-sectional areas may facilitate processing of the bundles in subsequent manufacturing steps, such as pultruding the bundles to form pultruded components, and / or laying up the filaments to form preforms or woven fabrics. Providing fiber bundles with equal cross-sectional areas may further facilitate achieving uniform compression and tensile properties. In the case of pultrusion, it is beneficial for the fiber bundles to have the same cross-sectional area so that they can be easily drawn into the pultrusion die.

[0036] In a second aspect, the present invention provides a method for manufacturing a spar cap for a wind turbine blade, the method comprising the following steps:

[0037] transferring liquid through a first set of nozzle holes to form a first set of filaments, and transferring liquid through a second set of nozzle holes to form a second set of filaments, wherein each of the first set of nozzle holes has a first cross-sectional opening, and each of the second set of nozzle holes has a second cross-sectional opening, wherein the first cross-sectional opening and the second cross-sectional opening have different sizes and / or different shapes;

[0038] processing the first group of filaments and the second group of filaments to form a first group of filaments and a second group of filaments;

[0039] bundling the first group of filaments and the second group of filaments to form a fiber bundle including the first group of filaments and the second group of filaments, wherein the first group of filaments and the second group of filaments are longitudinally aligned; and

[0040] The fiber bundles are incorporated into a resin structure of the wind turbine blade spar cap.

[0041] The method provides a simple and efficient process for manufacturing a wind turbine blade spar cap according to the first aspect of the invention.

[0042] The method particularly provides a procedure for manufacturing a multicomponent fiber bundle from a single raw material source (i.e., liquid). The fiber bundle can be manufactured using a single nozzle plate (i.e., spinneret) in which multiple groups of nozzle holes are provided. Thus, bundles of filaments of different cross-sections can be manufactured in a cheap and fast manner.

[0043] Preferably, the fiber bundle is a carbon bundle, and the first group of filaments are carbon filaments and the second group of filaments are carbon filaments.

[0044] The liquid is the raw material that is transferred through the nozzle orifice to form the filament. For the manufacture of carbon or natural filaments, the liquid is called a "dope" or "precursor." For the manufacture of glass filaments, the liquid is called a "melt."

[0045] In the case of carbon filaments, examples of suitable precursors include polyacrylonitrile, rayon, petroleum pitch, and combinations thereof.

[0046] In the case of carbon filaments, the processing step preferably comprises carbonizing the precursor in a manner known per se. During carbonization, the precursor can be drawn into a filament which is heated without allowing the precursor to come into contact with oxygen. In the absence of oxygen, the filament does not burn. As a result of the heating, a filament consisting of long, interlocking chains of carbon atoms remains, with no or only a small amount of non-carbon atoms remaining.

[0047] The cross-sectional area and shape of the filaments of the bundle are parameters that can be varied to optimize one or more properties of the fiber bundle, and thereby optimize one or more properties of the wind turbine blade spar cap manufactured by the method according to the invention. These parameters can be controlled by appropriately selecting the size and shape of the nozzle hole. The exact area and shape of the nozzle hole may not completely match the area and shape of the filaments manufactured therefrom, because carbonization generally involves the removal of material. However, the size and shape changes of the holes are at least partially translated into different sizes and shapes of the filaments in the resulting fiber bundle. Compensation for changes in the size and / or shape of the filaments due to carbonization can be compensated by selecting the size and / or shape of the nozzle hole.

[0048] Embodiments of the present invention may employ any number of nozzle hole groups. Such groups of nozzle holes may, for example, define different cross-sectional dimensions and / or shapes. For example, in one embodiment of the present invention, liquid is transferred through a third set of nozzle holes to form a third group of filaments, wherein the third set of nozzle holes has a third cross-sectional dimension and / or shape that is different from the cross-sectional shape and / or dimensions of the first set of nozzle holes and / or the second set of nozzle holes. Therefore, the first cross-sectional opening, the second cross-sectional opening, and the third cross-sectional opening may have different dimensions and / or different shapes, and the processing step may accordingly include processing the third group of filaments to form the third group of filaments, in which case the bundling step may include bundling the first group of filaments, the second group of filaments, and the third group of filaments to form the fiber bundle, wherein the first group of filaments, the second group of filaments, and the third group of filaments are longitudinally aligned. Preferably, the third group of filaments is carbon filaments.

[0049] In an embodiment of the present invention, the treating step comprises: heating the first group of filaments and the second group of filaments to obtain different carbonization degrees of the first group of filaments and the second group of filaments, respectively.

[0050] The first group of filaments and the second group of filaments may be subjected to the same or different temperatures during the treating step.Different degrees of carbonization may result in different relative fractions of carbon atoms in the resulting filaments.

[0051] If a wire having a large cross-sectional area and a wire having a small cross-sectional area are subjected to the same heating process, the wire having the large cross-sectional area generally has a smaller degree of carbonization than the wire having the small cross-sectional area.

[0052] Heating, especially simultaneous heating, is a simple and more efficient process for obtaining different degrees of carbonization of carbon filaments of different sizes and / or shapes in the carbon bundle, which in turn can advantageously provide improved mechanical and fracture properties of the resulting carbon bundle and wind turbine blade spar cap.

[0053] In an embodiment of the invention, each of the first cross-sectional openings defines a first cross-sectional area, and the second cross-sectional openings define a second cross-sectional area, wherein the first cross-sectional area is greater than the second cross-sectional area.

[0054] Advantageously, different cross-sectional openings may be employed to efficiently manufacture fiber bundles having filaments of different sizes in a wind turbine blade spar cap in order to achieve the effects disclosed herein in the context of the spar cap of the first aspect of the invention.

[0055] In an embodiment of the present invention, the first set of nozzle holes and the second set of nozzle holes are arranged in the nozzle head, wherein the second set of nozzle holes accounts for at least 30%, for example at least 35%, for example at least 40%, such as at least 45% of the total opening area provided by the first cross-sectional opening and the second cross-sectional opening.

[0056] In an embodiment of the invention, the first set of nozzle holes accounts for at least 30%, such as at least 35%, such as at least 40%, such as at least 45% of the total opening area.

[0057] The ratio of gained silk group in the fiber bundle produced by the treatment step approximately equals above-mentioned corresponding opening percentage.Therefore, by being designed in the nozzle hole in for example spinneret, can realize the ratio of each group of fiber bundle easily.

[0058] The wind turbine blade spar cap manufactured by the method of the second aspect of the invention may be a spar cap according to the first aspect of the invention and may comprise any of the features thereof as disclosed herein.

[0059] In a third aspect, the present invention provides a use of at least one fiber bundle for balancing compression and tension properties in a spar cap of a wind turbine blade, wherein the at least one fiber bundle comprises: a first set of longitudinally aligned filaments, each of the first set of longitudinally aligned filaments having a first cross-section; and a second set of longitudinally aligned filaments, each of the second set of longitudinally aligned filaments having a second cross-section, wherein the first cross-section is different from the second cross-section. Preferably, the fiber bundle is a carbon fiber bundle and the filaments are carbon filaments.

[0060] In a fourth aspect, the present invention provides a use of a first set of longitudinally aligned filaments and a second set of longitudinally aligned filaments in a fiber bundle in a resin structure of a wind turbine blade spar cap for reducing filament gaps between filaments of the fiber bundle, wherein the first set of longitudinally aligned filaments each have a first cross-section and the second set of longitudinally aligned filaments each have a second cross-section, wherein the first cross-section is different from the second cross-section. Preferably, the fiber bundle is a carbon fiber bundle and the filaments are carbon filaments.

[0061] In a further independent aspect, the present invention provides a nozzle head for fiber bundle manufacturing, the nozzle head comprising:

[0062] a first set of nozzle holes, each of the first set of nozzle holes having a first cross-sectional opening; and

[0063] a second set of nozzle holes, each of the second set of nozzle holes having a second cross-sectional opening,

[0064] wherein the first cross-sectional openings are each larger than the second cross-sectional opening, wherein the second set of nozzle holes accounts for at least 30%, such as at least 35%, such as at least 40%, such as at least 45% of the total opening area of ​​the first cross-sectional opening and the second cross-sectional opening.

[0065] In the example of the exemplary nozzle tip described above, the first set of nozzle holes accounts for at least 30%, such as at least 35%, such as at least 40%, such as at least 45% of the total opening area.

[0066] In the examples of the exemplary nozzle tips described above, the first cross-sectional opening and the second cross-sectional opening have different shapes.

[0067] In a further independent aspect, the present invention provides the use of the above exemplary nozzle head in the manufacture of a fiber bundle. The fiber bundle thus manufactured can be used for a wind turbine blade spar cap, in particular a wind turbine blade spar cap according to the present invention.

[0068] An additional aspect of the invention relates to a wind turbine blade comprising a wind turbine blade spar cap, wherein the wind turbine blade spar cap comprises a fiber reinforced resin structure comprising fiber bundles, wherein each of at least some of the fiber bundles comprises:

[0069] a first set of longitudinally aligned first filaments, each of the first set of longitudinally aligned first filaments defining a first cross-section; and

[0070] a second set of longitudinally aligned second filaments, each of the second set of longitudinally aligned second filaments defining a second cross-section,

[0071] The first cross section is different from the second cross section.

[0072] The spar cap of the exemplary wind turbine blade described above may be any one of the spar caps of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Embodiments of the present invention will now be further described with reference to the accompanying drawings, in which:

[0074] Figure 1 A horizontal axis wind turbine comprising three wind turbine blades is shown;

[0075] Figure 2 shows a perspective view of a wind turbine blade;

[0076] Figure 3 shows a cross section of a wind turbine blade including a wind turbine blade spar cap;

[0077] Figure 4 A wind turbine blade spar cap according to an embodiment of the present invention is shown;

[0078] Figure 5 A portion of a fiber bundle is shown,

[0079] Figure 6a and Figure 6b shows an exemplary cross section of a fiber bundle according to the present invention;

[0080] Figure 7 The method steps according to the embodiment of the present invention are shown; and

[0081] Figure 8 An exemplary nozzle head is shown which may be used, for example, in manufacture according to the present invention. DETAILED DESCRIPTION

[0082] Figure 1 A horizontal-axis wind turbine 100 including three wind turbine blades 108 is shown. Figure 2 A perspective view of a single wind turbine blade 108 is shown.

[0083] The blades 108 constitute the rotor of the wind turbine, which is connected to the main shaft at the hub 110. The wind turbine 100 includes a tower 102 and a nacelle 104 at the upper end of the tower. Each blade 108 has a root end 118, a tip end 116, a leading edge 112, and a trailing edge 114. The blade has an overall length l from the root 118 to the tip 116. At any position between the root 118 and the tip 116, the chord length c is defined as the shortest straight-line distance between the leading edge 112 and the trailing edge 114. As shown in FIG. Figure 2As shown, the chord length can vary along the length of the blade to take into account the fact that aerodynamic and internal mechanical forces vary along the length of the blade 108. In addition, the blade can be twisted along its length, and the aerodynamic profile of the blade in a chord-wise cross-sectional view can vary along the length of the blade. At the root 118, the profile is generally circular, and in the longitudinal direction away from the root, the cross-section of the blade smoothly transitions to the aerodynamic profile. At its root 118, the blade can be mounted to a pitch adjustment device, which is used to control the pitch of the blade, that is, its rotation around a longitudinal axis extending in the length direction of the blade.

[0084] During operation of wind turbine 100, gravity pull and aerodynamic forces induce loads on wind turbine blades 108. Additionally, in a pitch-controlled wind turbine, varying pitch angles induce varying loads on blades 108. These loads dictate certain tensile and compressive properties of each blade that are considered in the manufacture of blades 108.

[0085] Figure 3 A cross section of a wind turbine blade is shown including wind turbine blade spar caps 134, 138. These spar caps 134, 138 are load-bearing structures that are incorporated in the wind turbine blade for example for structural robustness. The blade has a suction side 120 and a pressure side 124 with a suction side shell 122 and a pressure side shell 126, respectively. These shells 122, 126 are joined at the leading edge 112 and the trailing edge 114.

[0086] In this exemplary wind turbine blade, one wind turbine blade spar cap 134 is incorporated into the suction side shell 122, and another spar cap 138 is incorporated into the pressure side shell 126. The incorporation of spar caps is not limited to these exemplary locations. Furthermore, a wind turbine blade may have more than two spar caps, such as three spar caps, four spar caps, five spar caps, six spar caps, or even more than six spar caps.

[0087] Internally, the two spar caps 134 , 138 are interconnected by a shear web 128 , 130 , which at least partially carries the blade loads.

[0088] The cross-section of a wind turbine blade typically varies along the longitudinal axis of the blade, e.g. Figure 2 as indicated in the diagram.

[0089] Figure 4 A wind turbine blade spar cap 134 is shown according to an embodiment of the present invention.

[0090] The spar cap 134 may have a flat rectangular shape and it may have a slight curvature to correspond to the surface / shell curvature of the wind turbine blade.The spar cap 134 extends longitudinally in the length direction of the blade.

[0091] The spar cap 134 comprises a fiber reinforced resin structure including fiber bundles 142. In this particular embodiment, the spar cap 134 comprises a plurality of pultruded elements formed from the fiber bundles 142. In another embodiment, the spar cap comprises woven or non-woven fiber bundles stacked on top of each other in a direction transverse to the chord-wise direction of the blade (vertical direction in the illustration).

[0092] The scope of the present invention is not limited to any particular type of arrangement of the fiber bundles.In general, the fiber bundles may be provided in any suitable manner, such as as pultruded elements, in the form of woven or non-woven mats / fabrics, or as unidirectional filaments.

[0093] The filaments provide reinforcement to the cured resin 140 , whereby the spar caps 134 provide the desired mechanical stability and strength.

[0094] In the illustrated embodiment, each fiber bundle 142 includes a first group of longitudinally aligned first filaments and a second group of longitudinally aligned filaments. Each of the first filaments has a first cross-section, and each of the second filaments has a second cross-section, wherein the first cross-section is different from the second cross-section. In particular, the first cross-section has a first cross-sectional area, and the second cross-section has a second cross-sectional area, and in this embodiment, the first cross-sectional area is greater than the second cross-sectional area.

[0095] Such different cross-sectional areas may ensure a proper balance of mechanical properties of the fiber bundles and, thereby, the spar caps.

[0096] The fiber bundle is preferably a carbon fiber bundle, and the first and second filaments are preferably carbon filaments. However, in other examples, the bundle may be formed of, for example, glass, basalt or natural fibers.

[0097] In one embodiment, the first cross-sectional area is 80 square microns and the second cross-sectional area is 35 square microns, corresponding to diameters of approximately 10 microns and 7 microns, respectively, given a circular cross-section. Each fiber bundle includes approximately 12,000 first filaments and 20,000 second filaments. The filaments may be based on a polyacrylonitrile precursor.

[0098] Figure 5 A portion of a fiber bundle 142 is shown, for example Figure 4 The fiber bundle 142 includes different groups of filaments, which are all aligned along the longitudinal direction 144 of the fiber bundle 142.

[0099] In a typical fiber bundle, the cross-sectional shape of the entire bundle is not perfectly circular, but rather resembles a highly eccentric ellipse (ie, a flattened oval).The fiber bundle may have any cross-sectional shape.

[0100] Figure 5 A cross-section of the fiber bundle 142 is further shown, as shown in FIG. Figure 6a and Figure 6b As shown in detail in .

[0101] Figure 6a and Figure 6b Different examples of fiber bundles with different groups of longitudinally aligned filaments are shown. A typical fiber bundle includes thousands of individual filaments. In addition, in a typical fiber bundle, the individual filaments are usually smaller than Figure 6a and Figure 6b The schematic depicted in Figure 2 is more irregularly ordered.

[0102] exist Figure 6a In the example of, the cross section shown in the fiber bundle has the first filament 146 and the second filament 148. Each of the first filament 146 has a first cross section 150, and the first cross section 150 has a first cross-sectional area and a first cross-sectional shape, and each of the second filament 148 has a second cross section 152, and the second cross section 152 has a second cross-sectional area and a second cross-sectional shape. The first cross-sectional area is greater than the second cross-sectional area. The first cross-sectional shape and the second cross-sectional shape are both circular. In addition, in this example, compared with the number of the first filament 146, the number of the second filament 148 is approximately twice as much. The whole fiber bundle can for example include 5,000 first filaments and 10,000 second filaments.

[0103] exist Figure 6b In the example of, the cross section of the fiber bundle has a first filament 146 and a second filament 148. Each of the first filaments 146 has a first cross section 150, and the first cross section 150 has a first cross-sectional area and a first cross-sectional shape, and each of the second filaments 148 has a second cross section 152, and the second cross section 152 has a second cross-sectional area and a second cross-sectional shape. The first cross-sectional shape is a rectangle, and the second cross-sectional shape is a circle. The entire fiber bundle can, for example, include 15,000 first filaments and 15,000 second filaments.

[0104] Figure 7 Method steps S1 to S4 according to an embodiment of the invention are shown.The invention relates to a method of manufacturing a spar cap for a wind turbine blade.

[0105] In a first step S1 of the method, a liquid (e.g., a stock solution or a precursor) is transferred through a first set of nozzle holes to form a first set of filaments, and transferred through a second set of nozzle holes to form a second set of filaments. Each of the first set of nozzle holes has a first cross-sectional opening, and each of the second set of nozzle holes has a second cross-sectional opening. The first cross-sectional opening and the second cross-sectional opening have different sizes and / or different shapes.

[0106] In the next step S2, the first group of filaments and the second group of filaments are processed to form the first group of filaments and the second group of filaments. The processing step may, for example, include heating the first group of filaments and the second group of filaments to complete the carbonization of the filaments to produce carbon filaments. The heating may, for example, be carried out at a temperature of 200 degrees Celsius to 3,000 degrees Celsius, for example, at 1,000 degrees Celsius, preferably in an oxygen-free environment. The processing may include several different heating steps, for example, a stable heating step at 250 degrees Celsius for 60 minutes to obtain a thermally stable ladder-bonded filament, followed by a carbonization heating step at 2,000 degrees Celsius in an oxygen-free environment.

[0107] In the next step S3, the first group of filaments and the second group of filaments are bundled to form a fiber bundle including the first group of filaments and the second group of filaments. The first group of filaments and the second group of filaments are bundled in the fiber bundle so that the first group of filaments and the second group of filaments are longitudinally aligned in the bundle.

[0108] In a next step S4, the fiber bundles are incorporated into a resin structure of a wind turbine blade spar cap. In some embodiments, the incorporation step is performed by pultrusion of a plurality of fiber bundles, which are pulled through a resin bath and a heated mold for curing the resin. Alternatively, the fiber bundles may be molded into the resin. In such an example, typically 50 to 250 fiber bundles may be used, for example 150 fiber bundles for a pultrusion having a transverse dimension of 100 mm x 5 mm.

[0109] The method according to the invention is not limited to the above-exemplified steps of the production method. In some embodiments, the manufacture may further comprise the step of subjecting the filaments to one or more substances in gaseous or liquid form to impart various additional properties to the final filaments, to ensure, for example, chemical or mechanical bonding of the filaments, or to protect them during winding or braiding. In some embodiments, the manufacture may further comprise the step of braiding the fiber bundles with other fiber bundles to form a fiber bundle mat before incorporating the fiber bundles in the resin structure of the wind turbine blade spar cap.

[0110] Figure 8 An exemplary nozzle head (ie, "spinneret") 154 for making a fiber bundle is shown.

[0111] The nozzle tip 154 ​​is flat and rounded with edges for incorporation into a fiber tow making apparatus.

[0112] The nozzle head 154 includes nozzle holes 156, 160, which are small holes through which liquid can be transferred to form filaments for the fiber bundle. The nozzle head 154 has a first set of nozzle holes 156 and a second set of nozzle holes 160, and the first set of nozzle holes 156 and the second set of nozzle holes 160 have a first cross-sectional opening 158 and a second cross-sectional opening 162, respectively. The first cross-sectional openings are each larger than the second cross-sectional openings. However, there are more second nozzle holes 160 than first nozzle holes. Therefore, the first set of nozzle holes accounts for about 50% of the total opening area of ​​the first cross-sectional openings, and the second set of nozzle holes accounts for about 50% of the total opening area. Here, the total opening area is the sum of all cross-sectional openings 158, 162 of the first set of nozzle holes and the second set of nozzle holes of the nozzle head 154.

[0113] The nozzle head can be made of, for example, a metallic material, a non-metallic material or a combination thereof. For example, steel, a ceramic material or a plastic material can be used. The number and size of the holes can be selected to match the properties of the fiber bundle that needs to be manufactured via the nozzle plate.

[0114] For the purpose of illustrating rather than limiting, various versions and elements of the present invention have been illustrated. Known details of methods and systems have been omitted to avoid redundantly obscuring the contents of the present disclosure. The present invention and various elements and features of the present disclosure may be combined in any possible manner within the scope of the claims.

Claims

1. A wind turbine blade spar cap, the wind turbine blade spar cap comprising a fiber reinforced resin structure, the fiber reinforced resin structure comprising fiber bundles, wherein: At least some of the fiber bundles include: a first set of longitudinally aligned first filaments, each of the first set of longitudinally aligned first filaments defining a first cross-section; and a second set of longitudinally aligned second filaments, each of the second set of longitudinally aligned second filaments defining a second cross-section, The first cross section is different from the second cross section.

2. The wind turbine blade spar cap according to claim 1, wherein: The first cross-section defines a first cross-sectional area, and wherein the second cross-section defines a second cross-sectional area, wherein the first cross-sectional area is greater than the second cross-sectional area.

3. A wind turbine blade spar cap according to claim 1 or 2, wherein: The first cross-sectional area is 50 to 200 square microns, for example 55 to 100 square microns, such as 60 to 120 square microns, and wherein the second cross-sectional area is 10 to 50 square microns, for example 20 to 45 square microns, such as 30 to 40 square microns.

4. A wind turbine blade spar cap according to any one of the preceding claims, wherein: The first cross-section defines a first cross-sectional shape, wherein the second cross-section defines a second cross-sectional shape, wherein the first cross-sectional shape is different than the second cross-sectional shape.

5. A wind turbine blade spar cap according to any one of the preceding claims, wherein: The first set of longitudinally aligned first filaments accounts for at least 30%, such as at least 35%, for example at least 40%, such as at least 45% of the total cross-sectional area of ​​the fiber bundle.

6. A wind turbine blade spar cap according to any one of the preceding claims, wherein: The second set of longitudinally aligned second filaments accounts for at least 30%, such as at least 35%, for example at least 40%, such as at least 45%, of the total cross-sectional area of ​​the fiber bundle.

7. A wind turbine blade spar cap according to any one of the preceding claims, wherein: The fiber bundle forms part of a pultruded element of the wind turbine blade spar cap.

8. A wind turbine blade spar cap according to any one of the preceding claims, wherein: All of the fiber bundles have the same total cross-sectional area.

9. A wind turbine blade spar cap according to any one of the preceding claims, wherein: The fiber bundle is a carbon bundle, and the first filaments are carbon filaments, and the second filaments are carbon filaments.

10. A method for manufacturing a wind turbine blade spar cap, the method comprising the steps of: transferring liquid through a first set of nozzle holes to form a first set of filaments and transferring liquid through a second set of nozzle holes to form a second set of filaments, wherein each of the first set of nozzle holes has a first cross-sectional opening and each of the second set of nozzle holes has a second cross-sectional opening, wherein the first cross-sectional opening and the second cross-sectional opening are different sizes and / or different shapes; processing the first group of filaments and the second group of filaments to form a first group of filaments and a second group of filaments; bundling the first group of filaments and the second group of filaments to form a fiber bundle including the first group of filaments and the second group of filaments, wherein the first group of filaments and the second group of filaments are longitudinally aligned; and The fiber bundles are incorporated into a resin structure of the wind turbine blade spar cap.

11. The method according to claim 10, wherein: The processing step includes heating the first group of wires and the second group of wires to obtain different carbonization degrees of the first group of wires and the second group of wires, respectively.

12. The method according to claim 11, wherein: The first group of filaments and the second group of filaments are subjected to the same temperature during the processing step.

13. The method according to any one of claims 10 to 12, wherein: Each of the first cross-sectional openings defines a first cross-sectional area, and the second cross-sectional openings define a second cross-sectional area, wherein the first cross-sectional area is greater than the second cross-sectional area.

14. The method according to any one of claims 10 to 13, wherein: The first and second sets of nozzle holes are arranged in the nozzle head, wherein the second set of nozzle holes accounts for at least 30%, such as at least 35%, such as at least 40%, such as at least 45% of the total opening area of ​​the first and second cross-sectional openings.

15. The method according to any one of claims 10 to 14, wherein: The first set of nozzle holes accounts for at least 30%, for example at least 35%, for example at least 40%, such as at least 45% of the total opening area.

16. The method according to any one of claims 10 to 15, wherein: The fiber bundle is a carbon bundle, and the first group of filaments are carbon filaments, and the second group of filaments are carbon filaments.

17. The method according to any one of claims 10 to 16, wherein: The wind turbine blade spar cap is a wind turbine blade spar cap according to any one of claims 1 to 9.

18. Use of at least one fiber bundle for balancing compression and tension properties in a spar cap of a wind turbine blade, wherein: The at least one fiber bundle comprises a first group of longitudinally aligned filaments, each of the first group of longitudinally aligned filaments having a first cross-section, and a second group of longitudinally aligned filaments, each of the second group of longitudinally aligned filaments having a second cross-section, wherein the first cross-section is different from the second cross-section.

19. Use of a first set of longitudinally aligned filaments and a second set of longitudinally aligned filaments in a fiber bundle in a resin structure of a spar cap of a wind turbine blade for reducing the filament gaps between the filaments of the fiber bundle, in, The first set of longitudinally aligned filaments each have a first cross-section and the second set of longitudinally aligned filaments each have a second cross-section, wherein the first cross-section is different from the second cross-section.

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