Fibre fabric sheet for a wind turbine blade with shear drape marks

Abstract

A fibre fabric sheet for reinforcing a wind turbine blade part, the fibre fabric sheet comprises a plurality of fibre strands including a majority of the fibre strands oriented along a main fibre direction, and one or more shear drape marks provided on a first surface of the fibre fabric sheet, wherein the one or more shear drape marks have a first shape when the fibre fabric sheet is in a flat configuration and a second shape when the fibre fabric sheet is in a double-curved configuration.

Description

[0001] FIBRE FABRIC SHEET FOR A WIND TURBINE BLADE WITH SHEAR DRAPE MARKS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a fibre fabric sheet comprising shear drape marks, a method of manufacturing such a fibre fabric sheet, a method of manufacturing a wind turbine blade using the fibre fabric sheets, and a computer-implemented method of determining the shape of the shear drape marks.

[0004] BACKGROUND

[0005] Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor having a rotatable hub with one or more wind turbine blades. The wind turbine blades capture kinetic energy of wind using known airfoil principles. The wind turbine blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the wind turbine blades to a gearbox or, if a gearbox is not used, directly to the generator.

[0006] The wind turbine blades generally include a suction side shell and a pressure side shell each moulded in a dedicated shell mould and typically formed using moulding processes that are bonded together at bond lines along the leading and trailing edges of the blade. Further, the pressure and suction shells are relatively lightweight and have structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the wind turbine blade during operation. Thus, to increase the stiffness, buckling resistance and strength of the wind turbine blade, the body shell is typically reinforced using one or more structural components (e.g. opposing spar caps with a shear web configured therebetween) that engage the inner pressure and suction side surfaces of the shell halves. The spar caps and / or shear web may be constructed of various materials, including but not limited to glass fibre laminate composites and / or carbon fibre laminate composites.

[0007] In the manufacturing of wind turbine blades, achieving precise fibre alignment and draping on complex surfaces is important for ensuring structural integrity and performance. Particularly, the process of draping fibre fabric sheets onto blade moulds that inherently exhibit a double curvature poses significant challenges, especially draping fibre fabric sheets of the shell around regions of maximum double-curvature such as the root portion.

[0008] In the context of a wind turbine blade mould, double curvature refers to a surface geometry that exhibits curvature in two orthogonal directions simultaneously. In simple terms, it describes a mould surface that is curved both along its length, i.e. span, and across its width, i.e. chord. This double curvature is a fundamental characteristic of modern wind turbine blade moulds. The complexity of double curvature arises from the need to conform the composite materials precisely to the mould surface, requiring the fibres to be oriented in multiple directions to accommodate the changing contours. Regions of maximum curvature, such as the root portion of a blade, present particularly challenging scenarios for draping fibre fabrics due to the sharp transitions and tighter curvatures.

[0009] Dry or preimpregnated fibre fabric sheets, typically composed of carbon, glass, or other composite materials, need to conform precisely to the contours of the mould surface to create a laminate with optimal strength and stiffness properties. However, achieving correct shear draping - the process of orienting the two-dimensional fibre fabric sheets in both directions to accommodate the curvature of the mould - demands a high level of skill and attention to detail from operators. This process is inherently time-consuming and labour-intensive, requiring considerable expertise to achieve consistent results.

[0010] One of the primary challenges of insufficient shear draping is the formation of wrinkles and creases in the fabric, particularly in areas of high curvature such as the root portion of the blade mould. The presence of wrinkles can introduce weaknesses and inconsistencies in the laminate, leading to performance deficiencies and potential failure under operational loads. In contrast to other composite parts, wind turbine blades are some of the largest composite parts presently built and it is cumbersome for operators to ensure correct shear draping throughout.

[0011] However, efforts to automate draping of the fibre fabric sheets have so far disappointed, and the reliance on manual methods introduces inherent variability and the potential for human error, which can lead to inconsistencies in the quality of the finished composite parts.

[0012] SUMMARY

[0013] On this background, it may be seen as an object of the present disclosure to provide a method of providing and arranging fibre fabric sheets in a wind turbine blade mould that consistently produces high quality blade parts.

[0014] One or more of these objects may be met by aspects of the present disclosure as described in the following.

[0015] A first aspect of the present disclosure relates to a fibre fabric sheet for reinforcing a wind turbine blade part. The fibre fabric sheet comprises a plurality of fibre strands including a majority of the fibre strands oriented along a main fibre direction. Such a fibre fabric sheet may also be known as a unidirectional fibre fabric sheet. The fibre fabric sheet further comprises one or more shear drape marks provided on a first surface of the fibre fabric sheet. The one or more shear drape marks have a first shape when the fibre fabric sheet is in a flat configuration and a second shape when the fibre fabric sheet is in a double-curved configuration.

[0016] In this context, the fibre fabric sheet is in the flat configuration, for example, when the fibre fabric sheet is arranged on a flat surface. Likewise, the fibre fabric sheet is in the double-curved configuration when the fibre fabric sheet is arranged on a double-curved surface, for example, when draped on a double-curved mould surface of a mould for manufacturing the wind turbine blade part. Accordingly, each respective shear drape mark transitions from the first shape when the fibre fabric sheet is in the flat configuration to the second shape when the fibre fabric sheet is in the doublecurved configuration.

[0017] Additionally, the fibre fabric sheet may also comprise a second surface opposite of the first surface. The second surface may also comprise one or more shear drape marks similar to those provided on the first surface. The shear drape marks provided on the first surface may be visible on the second surface. However, for the purposes of the present disclosure, it is not essential that shear drape marks are visible or provided on the second surface.

[0018] Additionally or alternatively, the second shape of the one or more shear drape marks may be configured for indicating shear drape angle of the majority of fibre strands with respect to the main fibre direction of the fibre fabric sheet when the fibre fabric sheet is in the double-curved configuration and is arranged on a double-curved mould surface of a wind turbine blade part mould.

[0019] Additionally or alternatively, the one or more shear drape marks may be formed by a colourant arranged on the first surface of the fibre fabric sheet. The majority of fibre strands may have a fibre appearance and the colourant may have a first appearance. The first appearance may be different from the fibre appearance and / or the first appearance and the fibre appearance may be contrasting. For example, the fibre appearance of the majority of fibre strands may be substantially white or light grey and the first appearance may be dark grey or black or vice versa. Often the majority of fibres strands will either be glass fibres, carbon fibres, or a combination of glass and carbon fibres. In such cases, the fibre appearance is greyscale. Therefore, the first appearance of the colourant is preferably a colour, such as primary colours, e.g. red, green, or blue, or secondary colours obtained by mixing primary colours. In any case, the colour of the colourant may be selected to achieve a highly visible contrast to the fibre appearance. Additionally or alternatively, wherein at least one, preferably each, of the one or more shear drape marks, in the first shape, are oriented along a first direction.

[0020] Additionally or alternatively, the first direction may be transverse or even substantially perpendicular to the main fibre direction. For example, the first direction may be oriented perpendicular to the main fibre direction within at most ±1°, preferably within at most ±0.5°, or more preferably within at most ±0.1°. As the first direction approaches to be perpendicular with main fibre direction, the precision by which the one or more shear drape marks indicate the true shear drape angle of the fibre fabric sheet is improved. Thus, an operator will more easily achieve the desired shear drape angle to avoid wrinkles and thus improve the quality of a composite part comprising the fibre fabric sheet.

[0021] Additionally or alternatively, at least one, preferably each, of the one or more shear drape marks may comprise a line extending, in the first shape, along the first direction. Further, at least two, preferably each, of the one or more shear drape marks extend in parallel. The line may optionally be dashed, dotted, dash-dotted, or have any other suitable shape known to the skilled person.

[0022] In a first embodiment, the line may extend, in the first shape, substantially straight and the line may, in the second shape, curve. Thus, the line may, in the second shape, indicate a local shear drape angle of the majority of fibre strands with respect to a main fibre direction of the fibre fabric sheet. Accordingly, an operator can inspect the local shear angle by measuring the angle between the line, in the second shape, and a reference line. For example, if the line in the first shape is provided as perpendicular to the main fibre direction and the fibre fabric sheet is draped so that the main fibre direction is parallel to, for example, a mould edge or a lateral side of the fibre fabric sheet, then the shear drape angle can be inspected by measuring the angle between the line in the second shape and the mould edge or a lateral side of the fibre fabric sheet.

[0023] In a second embodiment, the line may, in the first shape, curve along the first direction, and the line may extend, in the second shape, substantially straight. The line may, in the second shape, indicate a local shear drape angle of the majority of fibre strands with respect to a main fibre direction of the fibre fabric sheet. The one or more shear drape marks are provided so that when the fibre fabric sheet is arranged on a predetermined location of the double-curved portion of the mould surface, the second shape comprises a substantially straight line.

[0024] The inventors have found that by configuring the shear drape marks so that the line in the second shape is substantially straight within the plane of the fibre fabric sheet, the desired shear drape angle of the fibre fabric sheet is intuitively communicated to the operator and, thus, feedback on correct draping is provided simultaneously with the actual draping of the fibre fabric sheet. Furthermore, a correctly draped fibre fabric sheet can be readily inspected by inspecting the straightness of the line in the second shape. The inspection of the shear drape angle and straightness may also be easily automated, for example, by visual recognition, and can thus be used in a feedback loop if draping of the fibre fabric sheet is automated, e.g. by a robot.

[0025] Additionally, the shear drape marks may comprise a first shear drape mark and a second shear drape mark. The first shear drape mark may comprise a first line curving in the first shape. The second shear drape mark comprises a second line curving in the first shape. The second line in the first shape is different from the first line in the first shape. By providing two shear drape marks having differently curving lines in the first shape, the shear drape marks can be tailored to the specific local double-curvature of respective shear drape marks at the predetermined location of the mould surface. For example, the local double-curvature of the mould surface at the first shear drape mark may be different than the local double-curvature of the mould surface at the second shear drape mark. Accordingly, the first and second shear drape marks provide the operator with the ability to inspect and verify that the fibre fabric sheet is correctly shear draped at multiple locations further reducing the risk of wrinkling.

[0026] Additionally or alternatively, the fibre fabric sheet of the first aspect may comprise a first lateral side and a second lateral side, wherein the first direction extends between the first lateral side and the second lateral side. The lateral sides may extend along the main fibre direction. The first lateral side may be oriented towards a leading edge of the wind turbine blade part and the second lateral side may be oriented towards a trailing edge of the wind turbine blade part. At least one, preferably each, of the one or more shear drape marks may extend between the first lateral side and the second lateral side, preferably from the first lateral side to the second lateral side.

[0027] Additionally or alternatively, the fibre fabric sheet of the first aspect may comprise a proximal side and a distal side, wherein the main fibre direction extends between the proximal side and the distal side. The proximal and distal sides may extend along the first direction. The proximal side may be oriented towards a root end of the wind turbine blade part and the distal side may be oriented towards a tip end of the wind turbine blade part.

[0028] Additionally or alternatively, the one or more shear drape marks of the fibre fabric sheet of the first aspect may comprise a plurality of shear drape marks distributed, preferably regularly or even substantially equidistantly, along the main fibre direction. In particular, the one or more shear drape marks may comprise a plurality of shear drape marks spaced by 1-10 metres, preferably 1-5 metres along the main fibre direction. Additionally or alternatively, the one or more first shear drape marks may be provided as a line, a dashed line, a dotted line, a dash-dotted line, a grid, a shape, a polygon, such as a triangle, or a rectangle.

[0029] Additionally or alternatively, the plurality of fibre strands comprises or consists essentially of glass fibre strands, carbon fibre strands, a combination of glass fibre strands and carbon fibre strands, wood strands, or metal strands. Preferably, the plurality of fibre strands consists essentially of glass fibre strands.

[0030] Additionally or alternatively, the fibre fabric sheet may be semi-cured (for example as a preimpregnated fibre fabric sheet which may also be known as a prepreg sheet) or be uncured (for example be provided as dry fibre strands or devoid of a resin material). In this regard, the fibre fabric sheet may at least be uncured before being incorporated into a wind turbine blade part. Accordingly, the fibre fabric sheet may be a dry fibre fabric sheet or a preimpregnated fibre fabric sheet. Thus, the plurality of fibre strands may be dry fibre strands or provided with a semi cured resin for being subsequently cured. In any case, the fibre fabric sheet is shear flexible so as to allow being draped onto a double-curved mould surface.

[0031] Additionally or alternatively, the fibre fabric sheet may be provided as at least part of a roll. For example, the fibre fabric sheet may have a supply configuration in which the fibre fabric sheet is provided as a roll.

[0032] Additionally or alternatively, the fibre fabric sheet of the first aspect may comprise a minority of fibre strands that are oriented at a secondary fibre direction transverse to the main fibre direction. Further, such a minority of fibre strands may have a colour which is different from the colour of the majority of fibre strands and may be known as tracer strands, tracer yarns, or similar. In the context of the present disclosure, such a coloured tracer strand does not represent a shear drape mark since the orientation with respect to the longitudinal axis are often arranged off slightly normal to main fibre direction, such as 85-89 degrees, and this angle may further vary along its length. Further tracer strands do not necessarily follow the individual fibre strand of the majority of fibre strand as the fabric shear (strands moving relative to each other) and does therefore not represent an accurate measure for shear drape angle. Thus, such a tracer strand does not reliably indicate the shear drape angle of the majority of fibre strands aligned in the longitudinal axis.

[0033] Additionally or alternatively, at least 90%, preferably at least 95%, or more preferably at least 99% of the plurality of fibre strands may be oriented in the main fibre direction. Additionally or alternatively, the one or more fibre fabric sheets may comprise an area weight of 200 g to 4000 g per square metre, more preferably 400 g to 2000 g per square metre. Alternatively, the one or more fibre fabric sheets may comprise an area weight at least 100 g, at least 150 g, or most preferably at least 200 g per square metre. Alternatively, the one or more fibre fabric sheets may comprise an area weight at most 4000 g, at most 3000 g, or most preferably at most 2000 g per square metre.

[0034] The inventors have found that a dry, glass, unidirectional fibre fabric sheet exhibits a maximum achievable shear drape angle between 5-14° making such a material especially suited for being provided with shear drape marks according to the present disclosure. Limited shear drape ability for fibre materials is mostly found in unidirectional fibre fabrics. Biaxial fibre fabrics, such as those with fibres arranged in ±45°, can usually be shear draped to a much larger degree.

[0035] A second aspect of the present disclosure relates to a method of manufacturing a fibre fabric sheet for being draped in mould for manufacturing a wind turbine blade part, the method comprising the steps of: providing a fibre fabric sheet preferably in a flat configuration; and marking one or more shear drape marks with a first shape on a first surface of the fibre fabric sheet to obtain a fibre fabric sheet according to the first aspect of the present disclosure.

[0036] Additionally, the one or more shear drape marks may be marked by a printing process, such as an ink printing process or a laser printing process. Preferably the colourant deposited by the printing process is insoluble with the resin used in the manufacturing process of the wind turbine blade part to allow for post-curing quality inspection of the shear drape marks.

[0037] Additionally or alternatively, the first shape of the one or more shear drape marks may be substantially oriented in a first direction transverse to the main fibre direction.

[0038] Additionally or alternatively, the first shape of the one or more shear drape marks may be provided by a method according to a sixth aspect of the present disclosure.

[0039] Additionally or alternatively, the fibre fabric sheet may be provided as part of a fibre fabric roll and the method may further comprise unrolling a part of the fibre fabric roll, and cutting the fibre fabric sheet from the unrolled part of the fibre fabric roll. A third aspect of the present disclosure relates to a method of manufacturing a wind turbine blade part, such as a suction-side and / or pressure shell part. The wind turbine blade part may preferably be according to a fourth aspect of the present disclosure. The method may further comprise the steps of: providing a wind turbine blade part mould having a mould surface with a double-curved portion; and

[0040] - draping a fibre fabric sheet according to the first aspect of this disclosure or a fibre fabric sheet provided by a method according to the second aspect of this disclosure on the doublecurved portion of the wind turbine blade part mould so that the fibre fabric sheet is in the double-curved configuration and so that the first surface of the fibre fabric sheet including the one or more shear drape marks form the top surface of the fibre fabric sheet.

[0041] In the context of the present disclosure, the double-curved portion of the mould surface is understood as a surface portion having a curvature in two perpendicular directions, for example in a spanwise direction and a chord-wise direction. The curvature in the chord direction is provided to allow the manufacture of a wind turbine blade having an airfoil portion with a desired airfoil crosssection while the curvature in the spanwise direction is provided to allow the manufacture of the wind turbine blade having a root portion with a constant outer diameter for a certain spanwise distance and a transition portion that transitions this constant outer diameter to the airfoil portion having the desired airfoil cross-section. Accordingly, the transition portion of the wind turbine blade often exhibits the greatest degree of double curvature and thus resulting in that this area of the mould is critical during draping or lay up of fibre fabric sheets.

[0042] Additionally, the first shape may comprise a substantially straight line extending along the first direction and the second shape of the line curves so as to indicate a local shear drape angle of the majority of fibre strands with respect to a main fibre direction of the fibre fabric sheet. Optionally, at least two, preferably each, of the one or more shear drape marks extend in parallel. The method may, in this case, further comprise the steps of: inspecting, such as measuring, at least one shear drape angle between a reference line, such as a mould edge or a lateral side of the fibre fabric sheet, and at least one of the shear drape mark(s); and determining whether the at least one inspected shear drape angle is within a predetermined tolerance of an expected shear drape angle. The predetermined tolerance may be ±2° but preferably be ±1°.

[0043] Further, the method may comprise a step of: in accordance with a determination that the at least one measured shear drape angle is not within the predetermined tolerance of the expected shear drape angle, redraping the fibre fabric sheet and repeating the measurement and determination steps. The at least one expected shear drape angle is determined in accordance with a method according to the sixth aspect of the present disclosure.

[0044] In this context, redraping the fibre fabric sheet may involve an operator stretching and shearing the fibre fabric sheet so as to conform the shape of the fibre fabric sheet to the double-curved portion of the mould surface.

[0045] Alternatively, the first shape may comprise a curved line, and the second shape comprises a substantially straight line. The one or more shear drape marks are configured so that, when the fibre fabric sheet is arranged on a predetermined location of the double-curved portion of the mould surface, the second shape comprises the substantially straight line. Optionally, the first shape of a first shear drape mark comprises a first curved line, and the first shape of a second shear drape mark comprises a second curved line different from the first curved line while the second shape of the second shear drape mark is also a substantially straight line not necessarily parallel to the second shape of the first shear drape mark.

[0046] The method may, in this case, further comprise the steps of: inspecting, such as measuring, the straightness of at least one of the shear drape mark(s) and / or a shear drape angle between a reference line, such as a mould edge or a lateral side of the fibre fabric sheet, and at least one of the shear drape mark(s); and determining whether the inspected straightness of at least one of the shear drape mark(s) is within a predetermined straightness tolerance and / or the inspected shear drape angle is within a predetermined angle tolerance. The predetermined straightness tolerance may define that the respective shear drape mark must lie between two parallel lines separated by at most 10 mm, 5 mm, 4 mm, 3 mm, 2 mm or even 1 mm. This predetermined straightness tolerance may be preferable for a fibre fabric sheet with a width in the range of 20 cm to 200 cm. The predetermined angle tolerance may be the same as previously discussed. The at least one expected shear drape angle may be determined in accordance with a method according to the sixth aspect of the present disclosure.

[0047] The inventors have found that by configuring the fibre fabric sheet so that the second shape of the shear drape marks is a substantially straight line within the plane of the fibre fabric sheet, the desired shear drape angle of the fibre fabric sheet is simultaneous feedback is intuitively communicated to the operator during draping of the fibre fabric sheet. Furthermore, a correctly draped fibre fabric sheet can be readily inspected by inspecting the straightness of the second shape of each respective shear drape mark.

[0048] Further, the method may comprise a step of: in accordance with a determination that the at least one measured shear drape angle is not within the predetermined tolerance of the expected shear drape angle, redraping the fibre fabric sheet and repeating the measurement and determination steps.

[0049] Additionally or alternatively, the method according to the third aspect may further comprise the steps of: infusing the one or more fibre fabric sheets with a resin in a resin infusion process, preferably a vacuum assisted resin transfer infusion process; and allowing or causing the resin to cure to form the wind turbine part.

[0050] The resin may for example be polyester, epoxy, or any other suitable alternative known to the skilled person.

[0051] The fourth aspect of the present disclosure relates to a wind turbine blade part, such as a suctionside and / or pressure shell part, comprising one or more fibre fabric sheets according to the first aspect of the present disclosure. The one or more fibre fabric sheets forming a double-curved portion of the wind turbine blade part.

[0052] Additionally, the wind turbine blade part may extend in a longitudinal direction from a root end and in a chord direction between a leading edge and a trailing edge. The one or more fibre fabric sheets form part of a root region and / or a transition region of the wind turbine blade part, in particular, adjacent to the trailing edge. The main fibre direction of the one or more fibre fabric sheets may be aligned with the longitudinal direction.

[0053] Additionally or alternatively, the wind turbine blade part may comprise an airfoil region having additional fibre fabric sheets without shear drape marks. The inventors have found that while the airfoil region may exhibit some double-curvature, the most benefit is achieved by using the fibre fabric sheets according to the first aspect in the root region and / or transition region. Therefore, it may not be necessary to use marked fibre fabric sheets in the airfoil and / or tip region of the wind turbine blade part.

[0054] A fifth aspect of the present disclosure relates to a wind turbine blade extending in a longitudinal direction between a root end and a tip end and in a transverse direction between a leading edge and a trailing edge, wherein the wind turbine blade comprises at least one wind turbine blade part according to the fourth aspect of the present disclosure respectively forming a suction side shell part and / or a pressure side shell part, preferably the wind turbine blade further comprising a longitudinally extending bond line between the suction side shell part and the pressure side shell part.

[0055] The sixth aspect of the present disclosure relates to a computer-implemented method of determining a geometric mapping between a fibre fabric sheet in a flat configuration and the fibre fabric sheet in a double-curved configuration in which the fibre fabric sheet is draped on a double-curved surface of the wind turbine blade mould, wherein the method is preferably performed for obtaining the fabric fibre sheet according to the first aspect, the method comprising the steps of: receiving a geometric representation of a mould surface for a wind turbine blade part, the mould surface comprising a double-curved portion; and determining a location of the fibre fabric sheet on the double-curved portion of the mould surface to obtain a predetermined location.

[0056] Additionally, the computer-implemented method may further comprise the step of: determining one or more expected shear drape angles of the fibre fabric sheet.

[0057] Additionally or alternatively, the fibre fabric sheet may comprise one or more shear drape marks having a second shape when the fibre fabric sheet is in the double-curved configuration on the predetermined location on the double-curved portion of the mould surface, preferably the one or more shear drape marks in the second shape comprise a substantially straight line, the method further comprising a step of: transforming the second shape to a first shape of the one or more shear drape marks when the fibre fabric sheet is in a flat configuration; and

[0058] - outputting the first shape of the one or more shear drape marks.

[0059] Preferably, the method of the sixth aspect is performed as part of the method of the second aspect. In particular, the method of the second aspect may comprise a step of marking the one or more shear drape marks with the first shape outputted by the method of the sixth aspect on a first surface of the fibre fabric sheet.

[0060] The inventors have found that by determining such a geometric mapping, a correct subsequent draping of the fibre fabric sheet can be readily inspected. This can for example be achieved by measuring shear drape angles and comparing these with the expected shear drape angles but can also be achieved by employing the geometric mapping to provide shear drape marks on the fibre fabric material that allows easy inspection of the actual shear drape angle compared with an expected shear drape angle.

[0061] Additionally or alternatively, the computer-implemented method may comprise the steps of:

[0062] - segmenting the predetermined location to be occupied by the fibre fabric sheet into a plurality of spanwise lines, preferably corresponding to the course of the majority of fibre strands when arranged on the mould surface; determining the length of each one of the plurality of lines; wherein the one or more shear drape angles may be determined by comparing the length of each line of the plurality of spanwise lines to an adjacent line of the plurality of spanwise lines and thereby deriving a shear drape angle.

[0063] BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Embodiments of this 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 invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0065] Fig. 1 is a schematic perspective view of a wind turbine.

[0066] Fig. 2 is a schematic perspective view of a wind turbine blade for a wind turbine as shown in Fig. 1. Fig. 3 is a schematic perspective view of a root region and transition region of a mould for moulding a wind turbine blade part, such as the suction side or pressure side shell part shown in Fig. 2.

[0067] Fig. 4 is a plane view of a fibre fabric sheet according to a first embodiment shown in a flat configuration and having two shear drape marks in a first straight shape.

[0068] Fig. 5 is a plane view of the fibre fabric sheet of Fig. 4 in a double-curved configuration having the two shear drape marks in a second curved shape.

[0069] Fig. 6A is a plane view of a fibre fabric sheet according to a second embodiment shown in a flat configuration and having six shear drape marks in various first curved shapes.

[0070] Fig. 6B is a plane view of the fibre fabric sheet of Fig. 6A shown in a double-curved configuration and having the six shear drape marks in second straight shapes.

[0071] Fig. 7 is a schematic perspective illustration of a manufacturing setup for providing the fibre fabric sheet according to the present disclosure.

[0072] DETAILED DESCRIPTION

[0073] In the following figure description, the same reference numbers refer to the same elements and may thus not be described in relation to all figures. Fig. 1 illustrates a conventional modern upwind wind turbine 2 according to the so-called "Danish concept" with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft which may include a tilt angle of a few degrees. 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 furthest from the hub 8.

[0074] Fig. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade with a root end 17 and a tip end 15 and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest 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 8, and a trailing edge 20 facing the opposite direction of the leading edge 18. The wind turbine blade 10 comprises a suction side shell part 24 and a pressure side shell part 26 and a longitudinally extending bond line 28 between the suction side shell part 24 and the pressure side shell part 26.

[0075] 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 region 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. A shoulder 38 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 38 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0076] 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.

[0077] Typically, the suction side shell part 24 and the pressure side shell part 26 are each moulded in a dedicated mould 100 and subsequently bonded together along the bond line shown in Fig. 2 to obtain the wind turbine blade 10. Turning to Fig. 3, the root region 30 and transition region 32 of such a mould 100 is shown. These regions 30, 32 of the mould surface 102 often exhibit the greatest double-curvature of any region of the wind turbine blade, especially at the trailing edge 20, due to these regions defining the transition between the root end 17 which are circular to allow attachment to the hub of the wind turbine as shown in Fig. 1 and the airfoil region 32 which has an airfoil cross-sectional shape. During lay up in these regions, operators conform the fibre fabric sheets 40 to the double-curved mould surface 102 to avoid wrinkling that would otherwise result in a low-quality part. The fibre fabric sheets 40 can be shear draped in contrast to, for example, ordinary printer paper which can only be conformed to a single curvature surface.

[0078] As shown in Fig. 3, a fibre fabric sheet 40 (illustrated by the hatched area, the hatching is merely for illustrative purposes and does not indicate the fibre direction of the fibre fabric sheet) is positioned at the location of greatest double curvature in the root region 30 and the transition region 32 adjacent to the mould edge 104 which defines the trailing edge 20. The double-curvature of the mould surface 102 is indicated by the mould edge 104 and a contour line 105. The fibre fabric sheet 40 comprises a first lateral side 62 and a second lateral side 64 oriented along the mould edge 104 and further comprises a proximal side 66 adjacent to the root end 17 and a distal side 68 arranged towards a tip end. The fibre fabric sheet 40 comprises shear drape marks 50 that indicate the local shear angle of the fibre fabric sheet. This allows the operator to readily inspect the local shear angle and compare this with an expected shear angle of the given wind turbine blade part design as will be discussed in the following. Once all fibre fabric sheets 40 as well as the remaining layers, such as additional fibre layers, and / or components, such as core parts and one or more spar caps, the mould 100 may be closed and resin infused and cured, for example, in a vacuum assisted resin transfer infusion process to provide a wind turbine blade part such as pressure side or suction side shell part.

[0079] As best seen in Fig. 4, the fibre fabric sheet 40 comprises a plurality of fibre strands including a majority of fibre strands oriented along a main fibre direction 46 and a minority of fibre strands oriented along a secondary fibre direction 48. Accordingly, the fibre fabric sheet 40 is a unidirectional fibre fabric sheet. In the shown example, the majority of fibre strands comprises about 75% of the plurality of fibre strands but in other embodiments this fraction may also be lower or preferably even higher. The fibre fabric sheet 40 shown in Fig. 4 is in the flat configuration and comprises a first shear drape mark 50A and a second shear drape mark 50B which, accordingly, are in the first shape. The first shape of the shear drape marks 50A, 50B is a dashed line extending along a first direction which forms substantially a perpendicular angle 47A, 47B to the main fibre direction 46. Accordingly, the shear drape marks 50A, 50B provide a clear visual indication of a direction perpendicular to the main fibre direction 46. The first direction is not the same as the secondary fibre direction 48 since the secondary fibre direction 48 is not necessarily perpendicular to the main fibre direction 46 due to the minority of fibre strands possibly being displaced or otherwise misaligned during draping. Accordingly, the shear drape marks 50A, 50B are provided on a first surface 41 of the fibre fabric sheet 40. In the present case, the plurality of fibre strands are glass fibres which are white or light grey, and the shear drape marks are provided by a deposited black colourant but may have any colour, for example yellow or red, with sufficient contrast to the appearance of the plurality of fibre strands.

[0080] Fig. 5 shows the fibre fabric sheet 40 of Fig. 4 in its double-curved configuration, for example, when draped on the mould surface 102 as shown in Fig. 3. As can be seen, the dashed lines of the shear drape marks 50A', 50B' which were previously perpendicular to the main fibre direction 46 are now in their second shape (as denoted by the prime suffix) and curve, for example, due to the fibre fabric sheet 40 being shear draped on the double-curved portion of the mould surface 102. An operator can thus inspect the shear drape angle 47A, 47B for example by measuring the angle between the shear drape marks 50A', 50B' and the main fibre direction 46 or a direction with a known orientation relative to the main fibre direction 46. An example could be the mould edge 104 of Fig. 3 if the fibre fabric sheet 40 is draped in alignment with this mould edge 104. The operator can then compare the inspected shear drape angles 47A, 47B with the respective expected shear drape angles and determine whether the inspected shear drape angles 47A, 47B are within a predetermined tolerance. If this is not the case, the operator can then redrape the fibre fabric sheet until the inspected shear drape angles meet the predetermined tolerance. Accordingly, potential defects can be identified and corrected during draping, leading to a higher quality part.

[0081] Turning to Fig. 6A, a fibre fabric sheet 40 is also shown in its flat configuration similar to Fig. 4 and thus shows the shear drape marks 50C, 50D, 50E, 50F, 50G, 50H according to their first shape. However, the fibre fabric sheet 40 of Fig. 6A differs from the one shown in Fig. 4 in that the shear drape marks 50C, 50D, 50E, 50F, 50G, 50H in the first shape are no longer straight but instead each shear drape mark 50C, 50D, 50E, 50F, 50G, 50H is represented by a distinct curved line. The curvature of each shear drape mark 50C, 50D, 50E, 50F, 50G, 50H is selected so that when the fibre fabric sheet is arranged on a predetermined location on the double-curved portion of a mould surface 102, for example, as shown in Fig. 3, and the correct shear draping is achieved, the shear drape marks 50C', 50D', 50E', 50F', 50G', 50H' are now in their second shape (again as denoted by the prime suffix) as shown in Fig. 6B and are substantially straight. Thus, an operator can intuitively and visually inspect whether the correct shear draping of the fibre fabric sheet has been achieved by visually inspecting or even measuring the straightness of each shear drape mark 50C', 50D', 50E', 50F', 50G', 50H'. Turning to Fig. 7, a process of manufacturing the fibre fabric sheet 40 is illustrated. A roll 80 may be provided and a part of this roll 80 can be unrolled and cut to obtain a fibre fabric sheet 40 of a desired length. The roll 80 may already comprise shear drape marks 50 provided on a first surface 41. This would for example be advantageous when the shear drape marks are straight in the first shape as shown in Fig. 3, i.e. the flat configuration of the fibre fabric sheet 40. However, when the shear drape marks are not straight in the first shape as shown in Fig. 6A, a subsequent process can provide the shear drape marks 50 as shown in Fig. 7. This process can involve a marking device 70 configured for marking curved lines. The marking device 70 deposits a colourant on the first surface 41, for example using an ink printing process, according to a predetermined curved course of the shear drape mark 50 that corresponds to a desired shear drape angle at the predetermined location of the particular fibre fabric sheet 40. The cut fibre fabric sheet 40 may for example be intended to be placed on the location shown in Fig. 3 and this location involves distinct local shear drape angles that are represented by the predetermined curved course of the shear drape mark 50.

[0082] In the following, a method of determining a mapping between the fibre fabric sheet in the flat configuration and the fibre fabric sheet in the double-curved configuration in which the fibre fabric sheet is draped on a double-curved surface of the wind turbine blade mould is described. The method comprises the steps of: receiving a geometric representation of a mould surface for a wind turbine blade part, the mould surface comprising a double-curved portion; determining a location of the fibre fabric sheet on the double-curved portion of the mould surface to obtain a predetermined location.

[0083] The geometric representation may be a numerical representation, such as a point cloud, or a parametric representation. Accordingly, an operator may thus shear drape the fibre fabric sheet on the predetermined location.

[0084] The method can then comprise a step of determining one or more expected shear drape angles of the fibre fabric sheet, for example, by predicting the shear drape angles when conforming a flat two- dimensional fibre fabric sheet to the three-dimensional and double-curved mould surface. In practice, this may be done by segmenting the predetermined location to be occupied by the fibre fabric sheet into a plurality of spanwise lines corresponding to the course of the majority of fibre strands when arranged on the mould surface. The length of each one of the plurality of spanwise lines are determined. The length of such lines would be identical if the predetermined location was single curved or flat. However, when a double-curved location, the length of such lines differs on the degree of double-curvature. Accordingly, the one or more shear drape angles can be determined by comparing the length of each line of the plurality of spanwise lines to an adjacent line of the plurality of spanwise lines and thereby deriving the shear drape angle. Since the fibres are placed in a resting position, i.e. not elongated, the shear angle can be determined by comparing two points along a given length of two adjacent lines. The operator can thus inspect the shear drape angles and compare these inspected angles with the expected angles and adjust the draping accordingly.

[0085] When the predetermined location has been selected for the fibre fabric sheet 40 and it is desired that the second shape of the shear drape marks (i.e. when the fibre fabric sheet 40 is shear draped on the double-curved predetermined location of the mould surface) is straight, the method can include the steps of transforming the second shape to a first shape of the one or more shear drape marks when the fibre fabric sheet is in a flat configuration; and

[0086] - outputting the first shape of the one or more shear drape marks.

[0087] The step of transforming the second shape to the first shape may thus be performed by a transformation operator, such as a transformation matric and / or a transfer function.

[0088] The following items define exemplary embodiments of the present disclosure:

[0089] 1. A fibre fabric sheet for reinforcing a wind turbine blade part, the fibre fabric sheet comprises a plurality of fibre strands including a majority of the fibre strands oriented along a main fibre direction, and one or more shear drape marks provided on a first surface of the fibre fabric sheet, wherein the one or more shear drape marks have a first shape when the fibre fabric sheet is in a flat configuration and a second shape when the fibre fabric sheet is in a double-curved configuration.

[0090] 2. A fibre fabric sheet according to item 1, wherein the one or more shear drape marks, in the second shape, are configured for indicating shear drape angle of the majority of fibre strands with respect to the main fibre direction of the fibre fabric sheet when the fibre fabric sheet is in the double-curved configuration and is arranged on a double-curved mould surface of a wind turbine blade part mould.

[0091] 3. A fibre fabric sheet according to any one of the previous items, wherein the one or more shear drape marks are formed by a colourant arranged on the first surface of the fibre fabric sheet, wherein the majority of fibre strands has a fibre appearance and the colourant has a first appearance.

[0092] 4. A fibre fabric sheet according to item 3, wherein the first appearance is different from the fibre appearance and / or the first appearance and the fibre appearance are contrasting.

[0093] 5. A fibre fabric sheet according to any one of items 3-4, wherein the first appearance and the fibre appearance are contrasting. 6. A fibre fabric sheet according to any one of the previous items, wherein at least two, preferably each, of the one or more shear drape marks extends in parallel.

[0094] 7. A fibre fabric sheet according to any one of the previous items, wherein at least one, preferably each, of the one or more shear drape marks, in the first shape, are oriented along a first direction.

[0095] 8. A fibre fabric sheet according to item 7, wherein the first direction is transverse to the main fibre direction.

[0096] 9. A fibre fabric sheet according to any one of items 7-8, wherein the first direction is substantially perpendicular to the main fibre direction.

[0097] 10. A fibre fabric sheet according to any one of items 7-9, wherein the first direction is oriented perpendicular to the main fibre direction within at most ±1°, more preferably within at most ±0.5°, or more preferably within at most ±0.1°.

[0098] 11. A fibre fabric sheet according to any one of items 7-10, wherein at least one, preferably each, of the one or more shear drape marks comprises a line extending, in the first shape, along the first direction.

[0099] 12. A fibre fabric sheet according to item 11, wherein the line extends, in the first shape, substantially straight and wherein the line, in the second shape, curves so as to indicate a local shear drape angle of the majority of fibre strands with respect to a main fibre direction of the fibre fabric sheet.

[0100] 13. A fibre fabric sheet according to item 11, wherein the line, in the first shape, curves along the first direction, and wherein the line extends, in the second shape, substantially straight so as to indicate a local shear drape angle of the majority of fibre strands with respect to a main fibre direction of the fibre fabric sheet.

[0101] 14. A fibre fabric sheet according to item 13, wherein the one or more shear drape marks are provided so that when the fibre fabric sheet is arranged on a predetermined location of the double-curved portion of the mould surface, the second shape comprises the substantially straight line.

[0102] 15. A fibre fabric sheet according to any one of items 13-14, wherein the shear drape marks comprises a first shear drape mark and a second shear drape mark, wherein the first shear drape mark comprises a first line curving in the first shape, and wherein the second shear drape mark comprises a second line curving in the first shape, wherein the second line in the first shape is different from the first line in the first shape.

[0103] 16. A fibre fabric sheet according to any one of items 7-15, further comprising a first lateral side and a second lateral side, wherein the first direction extends between the first lateral side and the second lateral side.

[0104] 17. A fibre fabric sheet according to item 16, wherein at least one, preferably each, of the one or more shear drape marks extends between the first lateral side and the second lateral side, preferably from the first lateral side to the second lateral side.

[0105] 18. A fibre fabric sheet according to any one of the previous items, wherein comprises a proximal side and a distal side, wherein the main fibre direction extends between the proximal side and the distal side.

[0106] 19. A fibre fabric sheet according to any one of the previous items, wherein the one or more shear drape marks comprise a plurality of shear drape marks distributed, preferably regularly or even substantially equidistantly, along the main fibre direction.

[0107] 20. A fibre fabric sheet according to any one of the previous items, wherein the one or more shear drape marks comprise a plurality of shear drape marks spaced by 1-10 metres, preferably 1-5 metres along the main fibre direction.

[0108] 21. A fibre fabric sheet according to any one of the previous items, wherein the one or more first shear drape marks are provided as a line, a dashed line, a dotted line, a dash-dotted line, a grid, a shape, a polygon, such as a triangle, or a rectangle.

[0109] 22. A fibre fabric sheet according to any one of the previous items, wherein the plurality of fibre strands comprises glass fibre strands, carbon fibre strands, a combination of glass fibre strands and carbon fibre strands, wood strands, or metal strands.

[0110] 23. A fibre fabric sheet according to any one of the previous items, wherein the fibre fabric sheet is uncured.

[0111] 24. A fibre fabric sheet according to any one of the previous items configured for being provided on a roll.

[0112] 25. A fibre fabric sheet according to any one of the previous items, wherein a minority of fibre strands is oriented at a secondary fibre direction transverse to the main fibre direction. 26. A fibre fabric sheet according to any one of the previous items, wherein at least 90%, preferably at least 95%, or more preferably at least 99% of the fibre strands are oriented in the main fibre direction.

[0113] 27. A method of manufacturing a fibre fabric sheet for being draped in mould for manufacturing a wind turbine blade part, the method comprising the steps of: providing a fibre fabric sheet preferably in a flat configuration; and marking one or more shear drape marks with a first shape on a first surface of the fibre fabric sheet to obtain a fibre fabric sheet according to any one of items 1-26, wherein the first shape is preferably obtained by a method according to any one of items 45-47.

[0114] 28. A method according to item 27, wherein the one or more shear drape marks are marked by a printing process, such as an ink printing process or a laser printing process.

[0115] 29. A method according to any one of items 27-28, wherein the one or more shear drape marks are marked by depositing a colourant on the first surface, preferably by the marking device.

[0116] 30. A method according to any one of items 27-29, wherein the first shape of the one or more shear drape marks is substantially oriented in a first direction transverse to the main fibre direction.

[0117] 31. A method according to any one of items 27-30, wherein the first shape of the one or more shear drape marks is provided by a method according to any one of items 45-47.

[0118] 32. A method according to any one of items 27-31, wherein the fibre fabric sheet is provided as part of a fibre fabric roll and the method comprises: unrolling a part of the fibre fabric roll; and cutting the fibre fabric sheet from the unrolled part of the fibre fabric roll.

[0119] 33. A method of manufacturing a wind turbine blade part, such as a suction-side and / or pressure shell part, the wind turbine blade part preferably being according to any one of items 41- 43, wherein the method comprises the steps of: providing a wind turbine blade part mould having a mould surface with a double-curved portion; and draping a fibre fabric sheet according to any one of items 1-26 or a fibre fabric sheet provided according to the method of any one of items 27-32 on the double-curved portion of the wind turbine blade part mould so that the fibre fabric sheet is in the double-curved configuration and so that the first surface of the fibre fabric sheet including the one or more shear drape marks forms the top surface of the fibre fabric sheet. A method according to item 33, wherein the fibre fabric sheet may be according to item 12, the method further comprising the steps of: inspecting, such as measuring, at least one shear drape angle between a reference line, such as a mould edge or a lateral side of the fibre fabric sheet, and at least one of the shear drape mark(s); and determining whether the at least one inspected shear drape angle is within a predetermined tolerance of an expected shear drape angle. A method according to item 34, further comprising a step of: in accordance with a determination that the at least one measured shear drape angle is not within the predetermined tolerance of the expected shear drape angle, redraping the fibre fabric sheet and repeating the measurement and determination steps. A method according to any one of items 34-35, wherein the at least one expected shear drape angle is determined in accordance with a method according to any one of items 45- 47. A method according to item 33, wherein the fibre fabric sheet may be according to any one of items 13-15, the method further comprising the steps of: inspecting, such as measuring, the straightness of at least one of the shear drape marks and / or a shear drape angle between a reference line, such as a mould edge or a lateral side of the fibre fabric sheet, and at least one of the shear drape marks; and determining whether the inspected straightness of the at least one of the shear drape marks and / or the inspected shear drape angle is within a predetermined tolerance. A method according to item 37, further comprising: in accordance with a determination that the at least one measured shear drape angle is not within the predetermined tolerance of the expected shear drape angle, redraping the fibre fabric sheet and repeating the measurement and determination steps. A method according to any one of items 37-38, wherein the at least one expected shear drape angle is determined in accordance with a method according to any one of items 45- 47. A method according to any one of items 33-39, comprising the steps of: infusing the one or more fibre fabric sheets with a resin in a resin infusion process, preferably a vacuum assisted resin transfer infusion process; and allowing or causing the resin to cure to form the wind turbine part.

[0120] 41. A wind turbine blade part, such as a suction-side and / or pressure shell part, comprising one or more fibre fabric sheets according to any one of items 1-26 forming a double-curved portion of the wind turbine blade part.

[0121] 42. A wind turbine blade part according to item 41 extending in a longitudinal direction from a root end and in a chord direction between a leading edge and a trailing edge, wherein the one or more fibre fabric sheets at least partly form part of a root region of the wind turbine blade part and wherein the main fibre direction of the one or more fibre fabric sheets are aligned with the longitudinal direction.

[0122] 43. A wind turbine blade part according to any one of items 41-42, wherein the one or more fibre fabric sheets at least partly form part of the root region adjacent to the trailing edge.

[0123] 44. A wind turbine blade extending in a longitudinal direction between a root end and a tip end and in a transverse direction between a leading edge and a trailing edge, wherein the wind turbine blade comprises at least one wind turbine blade part according to any one of items 41-43 respectively forming a suction side shell part and / or a pressure side shell part, preferably the wind turbine blade further comprising a longitudinally extending bond line between the suction side shell part and the pressure side shell part.

[0124] 45. A computer-implemented method of determining a geometric mapping between a fibre fabric sheet in a flat configuration and the fibre fabric sheet in a double-curved configuration in which the fibre fabric sheet is draped on a double-curved surface of the wind turbine blade mould, wherein the method is preferably performed obtaining the fabric fibre sheet according to any one of items 1-26, the method comprising the steps of: receiving a geometric representation of a mould surface for a wind turbine blade part, the mould surface comprising a double-curved portion; and predetermining a location of the fibre fabric sheet on the double-curved portion of the mould surface.

[0125] 46. A computer-implemented method according to item 45, further comprising the step of: determining one or more expected shear drape angles of the fibre fabric sheet.

[0126] 47. A computer-implemented method according to any one of items 45-46, wherein the fibre fabric sheet comprises one or more shear drape marks having a second shape when the fibre fabric sheet is in the double-curved configuration on the predetermined location on the double-curved portion of the mould surface, the second shape comprising a substantially straight line, the method further comprising a step of:

[0127] - transforming the second shape to a first shape of the one or more shear drape marks when the fibre fabric sheet is in a flat configuration; and

[0128] - outputting the first shape of the one or more shear drape marks, preferably for obtaining the fibre fabric sheet according to any one of items 1-26 or for performing the method according to any one of items 27-32, for example the method comprising a step of marking the one or more shear drape marks with the outputted first shape on a first surface of the fibre fabric sheet.

[0129] LIST OF REFERENCES

[0130] 2 wind turbine 104 mould edge

[0131] 4 tower 105 contour line

[0132] 6 nacelle 40 106 predetermined location

[0133] 8 hub L longitudinal direction

[0134] 10 blade T first direction

[0135] 13 shell C chord direction

[0136] 14 blade tip

[0137] 15 tip end

[0138] 16 blade root

[0139] 17 root end

[0140] 18 leading edge

[0141] 20 trailing edge

[0142] 24 pressure side shell part

[0143] 26 suction side shell part

[0144] 28 bond line

[0145] 30 root region

[0146] 32 transition region

[0147] 34 airfoil region

[0148] 36 tip region

[0149] 38 shoulder

[0150] 40 fibre fabric sheet

[0151] 41 first surface

[0152] 42 majority of fibre strands

[0153] 44 minority of fibre strands

[0154] 46 main fibre direction

[0155] 47 shear drape angle

[0156] 48 secondary fibre direction

[0157] 50 shear drape mark

[0158] 62 first lateral side

[0159] 64 second lateral side

[0160] 66 proximal side

[0161] 68 distal side

[0162] 70 marking device

[0163] 80 roll

[0164] 100 mould

[0165] 102 mould surface

Claims

CLAIMS1. A fibre fabric sheet (40) for reinforcing a wind turbine blade part, the fibre fabric sheet comprises a plurality of fibre strands including a majority (42) of the fibre strands oriented along a main fibre direction (46), and one or more shear drape marks (50) provided on a first surface (41) of the fibre fabric sheet, wherein the one or more shear drape marks have a first shape (52) when the fibre fabric sheet is in a flat configuration and a second shape (54) when the fibre fabric sheet is in a double-curved configuration.

2. A fibre fabric sheet according to claim 1, wherein the one or more shear drape marks, in the second shape, are configured for indicating a shear drape angle of the majority of fibre strands with respect to the main fibre direction of the fibre fabric sheet when the fibre fabric sheet is in the double-curved configuration and is arranged on a double-curved mould surface of a wind turbine blade part mould.

3. A fibre fabric sheet according to any one of the previous claims, wherein the one or more shear drape marks are formed by a colourant arranged on the first surface of the fibre fabric sheet, wherein the majority of fibre strands has a fibre appearance, and wherein the colourant has a first appearance different from the fibre appearance.

4. A fibre fabric sheet according to any one of the previous claims, wherein at least one, preferably each, of the one or more shear drape marks, in the first shape, is oriented along a first direction transverse to the main fibre direction, preferably the first direction is substantially perpendicular to the main fibre direction.

5. A fibre fabric sheet according to claim 4, wherein at least one, preferably each, of the one or more shear drape marks comprises a line extending along the first direction.

6. A fibre fabric sheet according to claim 5, wherein the line extends, in the first shape, substantially straight along the first direction and wherein the line, in the second shape, curves so as to indicate a local shear drape angle (47) of the majority of fibre strands with respect to the main fibre direction of the fibre fabric sheet.

7. A fibre fabric sheet according to claim 5, wherein the line, in the first shape, curves along the first direction, and wherein the line extends, in the second shape, substantially straight so as to indicate a local shear drape angle (47) of the majority of fibre strands with respect to a main fibre direction of the fibre fabric sheet.

8. A fibre fabric sheet according to claim 7, wherein the shear drape marks comprises a first shear drape mark and a second shear drape mark, wherein the first shear drape markcomprises a first line curving in the first shape, and wherein the second shear drape mark comprises a second line curving in the first shape, wherein the second line in the first shape is different from the first line in the first shape.

9. A method of manufacturing a fibre fabric sheet for being draped in mould for manufacturing a wind turbine blade part, the method comprising the steps of: providing a fibre fabric sheet in a flat configuration; and marking one or more shear drape marks with a first shape on a first surface of the fibre fabric sheet to obtain a fibre fabric sheet according to any one of previous claims, wherein the first shape is preferably obtained by a method according to claim 15.

10. A method according to claim 9, wherein the one or more shear drape marks are marked by depositing a colourant on the first surface, preferably by a marking device.

11. A method of manufacturing a wind turbine blade part, such as a suction-side and / or pressure shell part, the wind turbine blade part preferably being according to claim 14, wherein the method comprises the steps of: providing a wind turbine blade part mould having mould surface with a double-curved portion; and draping a fibre fabric sheet according to any one of claims 1-8 or a fibre fabric sheet provided according to the method of any one of claims 9-10 on the double-curved portion of the wind turbine blade part mould so that the fibre fabric sheet is in the double-curved configuration and so that the first surface of the fibre fabric sheet including the one or more shear drape marks forms the top surface of the fibre fabric sheet.

12. A method according to claim 11, wherein the fibre fabric sheet is according to claim 6, the method further comprising the steps of: inspecting, such as measuring, at least one shear drape angle between a reference line, such as a mould edge or a lateral side of the fibre fabric sheet, and at least one of the shear drape marks; determining whether the at least one inspected shear drape angle is within a predetermined tolerance of an expected shear drape angle, wherein the at least one expected shear drape angle is preferably determined in accordance with a method according to claim 15; amd preferably in accordance with a determination that the at least one measured shear drape angle is not within the predetermined tolerance of the expected shear drape1 angle, redraping the fibre fabric sheet and repeating the measurement and determination steps.

13. A method according to claim 11, wherein the fibre fabric sheet is according to any one of claims 7-8, the method further comprising the steps of: inspecting, such as measuring, the straightness of at least one of the shear drape mark(s) and / or a shear drape angle between a reference line, such as a mould edge or a lateral side of the fibre fabric sheet, and at least one of the shear drape marks; determining whether the inspected straightness of the at least one of the shear drape marks and / or the inspected shear drape angle is within a predetermined tolerance, wherein the at least one expected shear drape angle is preferably determined in accordance with a method according to claim 15; and preferably in accordance with a determination that the at least one measured shear drape angle is not within the predetermined tolerance of the expected shear drape angle, redraping the fibre fabric sheet and repeating the measurement and determination steps.

14. A wind turbine blade part, such as a suction-side and / or pressure shell part, for a wind turbine blade, the wind turbine blade part comprising one or more fibre fabric sheets according to any one of claims 1-9 forming a double-curved portion of the wind turbine blade part, wherein, preferably, the one or more fibre fabric sheets at least partly form part of the root region adjacent to the trailing edge.

15. A computer-implemented method of determining a geometric mapping between a fibre fabric sheet in a flat configuration and the fibre fabric sheet in a double-curved configuration in which the fibre fabric sheet is draped on a double-curved surface of the wind turbine blade mould, the method comprising the steps of: receiving a geometric representation of a mould surface for a wind turbine blade part, the mould surface comprising a double-curved portion; determining a location of the fibre fabric sheet on the double-curved portion of the mould surface to obtain a predetermined location; and optionally determining one or more expected shear drape angles of the fibre fabric sheet, wherein, optionally, the fibre fabric sheet comprises one or more shear drape marks having a second shape when the fibre fabric sheet is in the double-curved configuration on the predetermined location on the double-curved portion of the mould surface, preferably the one or more shear drape marks in the second shape comprise a substantially straight line, the method further optionally comprising the steps of:- transforming the second shape to a first shape of the one or more shear drape marks when the fibre fabric sheet is in a flat configuration; and outputting the first shape of the one or more shear drape marks for obtaining the fibre fabric sheet according to any one of claims 1-8 or for performing the method according to any one of claims 9-10.

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