Apparatus and method for fiber mat deposition

Abstract

The present disclosure relates to an apparatus (100) for depositing a fibrous mat (200) on a surface, the apparatus (100) comprising a reel (101) for holding a roll (102) of fibrous mat (200), a first roller (111) at a first lateral position and a second roller (112) at a second lateral position for exerting a traction force on the fibrous mat (200), and a fibrous mat tension compensator (120) configured to adjust tension in the fibrous mat (200) in a lateral direction of the fibrous mat. The present disclosure also relates to a method for depositing a fibrous mat (200) on a surface.

Description

[0001] This application claims the benefit of European patent application No. 22161223.7 filed on March 9, 2022. Technical Field

[0002] The present disclosure relates to an apparatus and method for fiber mat deposition, and in particular to an apparatus for depositing a fiber mat in a mold for manufacturing a shell of a wind turbine blade. The present disclosure also relates in particular to an apparatus for providing a fiber mat with locally customized fiber orientation, a wind turbine blade manufactured with such a fiber mat, and a method for providing the same. Background Art

[0003] Modern wind turbines are commonly used to supply electricity to an electrical grid. Wind turbines of this type generally comprise a tower and a rotor arranged on the tower. The rotor, which generally comprises a hub and a plurality of blades, is arranged to rotate under the influence of the wind on the blades. The rotation generates a torque, which is generally transmitted to a generator via a rotor shaft, either directly ("direct drive") or by using a gearbox. In this way, the generator produces electricity that can be supplied to an electrical grid.

[0004] In order to extract more energy from the wind, the size of the rotor diameter is increased by increasing the size of the wind turbine blades. In order to reduce the overall weight of the wind turbine blades, the blades may generally comprise composite materials and are typically manufactured using resin-infused fiberglass composites. Using composite materials to manufacture wind turbine blades allows them to meet requirements with respect to size, geometry and weight. In addition, the fibers can be aligned with the load paths to generate blades with anisotropic mechanical properties and with enhanced mechanical properties. The possibilities for fiber alignment allow the fibers to be placed in precise locations and directions as required to provide the required stiffness and strength to the component. However, the desired fiber alignment is currently not a fully automated process and reproducibility is challenging.

[0005] Despite the significant benefits of composite materials compared to other structural materials, the deposition of fiber mats is a complex process. In particular, the molds for wind turbine blade shells include areas with complex curvatures, including double curved surfaces and also (almost) vertical surfaces. When depositing the fiber mats, the fiber mats will buckle and exhibit corrugations. This is inherent to the manufacturing process of many fiber reinforced composite parts and significantly affects the mechanical properties of the product, such as stiffness, strength and fatigue. Although this is a specific problem related to wind turbine blade manufacturing, similar problems may also be encountered in other technical fields.

[0006] To avoid this buckling and corrugation, the fibers need to be placed in a shear displacement. Shear means that for example a transverse fiber may not run in a transverse direction but at an angle.

[0007] In order to control the proper fiber deposition, the placement of the fibers is still usually done manually. Even if the fiber mat can be initially laid down by an automated process, a subsequent manual process is usually required to avoid the buckling mentioned above and to provide a product with the desired mechanical properties. Due to the essentially manual process, the quality and consistency of the product is difficult to ensure.

[0008] The manual process allows the fiber layers to be draped into the production tool in a variety of ways and results in composite components with reduced weight and locally optimized mechanical properties. Manual placement and / or alignment of the fiber mat into the production tool results in a very tedious and cumbersome task with limited reproducible quality and high production costs.

[0009] For these and other reasons, there is interest in improving the fiber deposition process and in doing so through an automated or semi-automated process, thereby making product quality highly reproducible and improved.

[0010] The present disclosure provides examples of systems and methods that at least partially overcome some of the shortcomings of existing wind turbine blade manufacturing processes. Summary of the invention

[0011] In a first aspect, an apparatus for depositing a fiber mat on a surface is disclosed. The fiber mat has a length extending in a lay direction and a width extending in a transverse direction. The apparatus includes a reel for holding a roll of the fiber mat, a first roller and a second roller located at corresponding first and second transverse positions, and a fiber mat tension compensator. The first roller and the second roller are configured to apply a traction force on the fiber mat to unwind the fiber mat from the reel in the lay direction. In addition, the first roller is controlled independently of the second roller. In addition, the fiber mat tension compensator is configured to adjust the tension in the fiber mat in the transverse direction.

[0012] According to this first aspect, by independently controlling the rollers, the apparatus allows to locally vary the alignment of the fibers in the fiber mat, while at the same time producing a fiber mat deposit that is substantially free of wrinkles and other surface defects. This is achieved by means of a combination of the rollers and a fiber mat tension compensator, which limits the accumulation of fibers downstream of the rollers. This results in a significant reduction in manufacturing time compared to known approaches for depositing fiber mats on three-dimensional surfaces. In addition, the apparatus significantly reduces the need for manual post-deposition assistance, which at the same time promotes a highly repeatable final product.

[0013] In another aspect, a method of depositing a fiber mat having a length and a width on a surface is provided. A roll of the fiber mat is arranged on a reel, and the method includes rotating two or more rollers to apply traction to the fiber mat and pull the fiber mat from the reel in a laydown direction. During the rotation of the rollers, one of the rollers has a different speed than at least one of the other rollers to obtain a shear angle in the fiber mat. In addition, the method includes depositing the fiber mat on the surface, and adjusting a tension along the width of the fiber mat in a portion of the fiber mat between the rollers and the reel.

[0014] Throughout this disclosure, a fiber mat may be considered to encompass any piece of fabric comprising fibers. The fibers may be arranged in strands or rovings. The fibers may be natural or synthetic fibers, and in particular may be any type of fiber suitable for use in fiber reinforced composites, and more particularly may be glass fibers or carbon fibers. The fibers may have various orientations, for example the fiber mat may be uniaxial, biaxial, multiaxial or different. The fibers may be woven using different types of weaving, or may be non-woven.

[0015] Throughout this disclosure, the term "shear angle" is understood to be the angle defined between the fibers of the mat and their original intended orientation. For example, transverse fibers may have a shear angle that is the deviation between the original orientation of the fiber (i.e., oriented at 90° to the length of the fiber mat, oriented at 45° to the length of the fiber mat, or other) and the actual orientation of the fiber. As an example, the shear angle of fibers arranged in a 45° orientation relative to the length of the fiber mat may be defined as the actual orientation of the fiber relative to the 45° orientation.

[0016] Since the fibers in the fiber mat may not be tightly connected, in examples, the shear angle may vary across the fiber mat. A positive shear angle may be understood as a local rotation of the fibers in a counterclockwise direction relative to the intended orientation, while a negative shear angle may be understood as a local rotation of the fibers in a clockwise direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Non-limiting examples of the present disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of a wind turbine according to one example; Figure 2A is a schematic diagram showing a wind turbine blade according to one example; Figure 2B The internal structure of a wind turbine blade is schematically shown; Figure 2C A molding system that can be used to manufacture wind turbine blades is shown; Figure 3 schematically illustrates an apparatus according to an example in a first configuration; Figure 4A schematically shows a top view of a portion of a fiber mat and a roller in a first example; Figure 4B schematically shows a top view of a portion of a fiber mat and a roller in a first example; Figure 4C schematically shows a top view of a portion of a fiber mat and a roller in a first example; Figure 4D schematically shows a top view of a portion of a fiber mat and a roller in a first example; Figure 5 schematically illustrates a fiber mat tension compensator according to one example, acting on a portion of the fiber mat between a roller and a reel; Figure 6 Schematically shows Figure 5 A corresponding top view of the fiber mat and roller of the example shown in ; Figure 7 is a flow chart of a method for depositing a fiber mat on a surface according to one example; and Figure 8 is a flow chart of another method of depositing a fiber mat on a surface according to one example. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to embodiments of the present disclosure, one or more examples of which are shown in the accompanying drawings. Each example is provided by way of explanation only and not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present disclosure. For example, a feature shown or described as a part of an embodiment may be used in conjunction with another embodiment to produce yet another embodiment. Therefore, it is expected that the present disclosure covers such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0019] Figure 1 A conventional modern upwind wind turbine 2 according to the so-called "Danish concept" is shown, having a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor axis. The rotor comprises a hub 8 and three blades 10 extending radially from the hub 8, the blades each having a blade root 16 closest to the hub and a blade tip 14 farthest from the hub 8.

[0020] Figure 2AA schematic diagram of an exemplary wind turbine blade 10 is shown. 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 includes a root region 30 closest to the hub, a profile or airfoil region 34 farthest from the hub, and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 includes a leading edge 18 facing the direction of rotation of the blade 10 when the blade is mounted on the hub, and a trailing edge 20 facing in the opposite direction of the leading edge 18.

[0021] The airfoil region 34 (also referred to as the profile region) has an ideal or almost ideal blade shape with respect to generating lift, while the root region 30 has a substantially circular or elliptical cross section for structural considerations, for example, which makes it easier and safer to mount the blade 10 to the hub. The diameter (or chord) of the root region 30 may be constant along the entire root region 30. The transition region 32 has a transition profile that gradually changes 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 generally 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.

[0022] The shoulder 40 of the blade 10 is defined as the location where the blade 10 has its maximum chord length. The shoulder 40 is generally provided at the boundary between the transition region 32 and the airfoil region 34.

[0023] It should be noted that the chords of the different sections of the blade generally do not lie in a common plane, because the blade may be twisted and / or bent (i.e., pre-bent), thus providing a corresponding twisted and / or bent course to the chord plane, which is to compensate for the most common case of the local velocity of the blade depending on the radius from the hub. The wind turbine blade 10 comprises a blade shell, which comprises two blade shell parts or half shells, typically made of fiber reinforced polymer: a first blade shell part 24 and a second blade shell part 26. The wind turbine blade 10 may include additional shell parts, such as a third shell part and / or a fourth shell part. The first blade shell part 24 is typically a pressure side or windward blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together using an adhesive such as glue along a bond line or glue joint 28 extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 have a semicircular or semi-elliptical outer cross-sectional shape.

[0024] Figure 2Bis a schematic diagram showing a cross-sectional view of an exemplary wind turbine blade 10, such as a cross-sectional view of an airfoil region of the wind turbine blade 10. The wind turbine blade 10 includes a leading edge 18, a trailing edge 20, a pressure side 24, a suction side 26, a first spar cap 74, and a second spar cap 76. The wind turbine blade 10 includes a chord line 38 between the leading edge 18 and the trailing edge 20. The wind turbine blade 10 includes a shear web 42, such as a leading edge shear web and a trailing edge shear web. Alternatively, the shear web 42 may be a spar box having a spar side, such as a trailing edge spar side and a leading edge spar side. The spar caps 74, 76 may include carbon fiber, while the remainder of the shell portions 24, 26 may include glass fiber.

[0025] Figure 2C 30 is a schematic diagram showing an exemplary mold system for molding a blade shell of a wind turbine blade. The mold system 301 includes a first mold 302 and a second mold 312. The first mold 302 is configured for manufacturing a first blade shell portion of a wind turbine blade, such as a windward shell portion of a wind turbine blade (forming a pressure side). The second mold 312 is configured for manufacturing a second blade shell portion of a wind turbine blade, such as a downwind shell portion of a wind turbine blade (forming a suction side). Surfaces 304 and 314 are mold surfaces for depositing fibers.

[0026] Figure 3 Schematically illustrated is an apparatus 100 for depositing a fiber mat 200 on a surface according to an example. The apparatus 100 comprises a reel 101 for holding a roll 102 of the fiber mat 200. The fiber mat 200 has a length extending in a laying direction and a width extending in a transverse direction. In addition, the apparatus 100 comprises a first roller 111 located at a first transverse position and a second roller 112 located at a second transverse position. The first roller 111 and the second roller 112 are configured to apply a traction force on the fiber mat 200 to unwind the fiber mat 200 from the reel 101 in the laying direction. In addition, the first roller 111 is controlled independently of the second roller 112. The apparatus 100 further comprises a fiber mat tension compensator 120, which is configured to adjust the tension in the fiber mat 200 in the transverse direction.

[0027] In order to control the shear angle, the rollers 111 and 112 may be independently controlled, in particular the rotational speeds may be independently controlled. If one of the rollers rotates faster than the other, the faster roller may exert more traction on the fiber, thus creating a shear angle. If one of the rollers rotates faster than the other, fiber material may accumulate between the other roller and the reel 101. If the rollers have different speed profiles, a tension compensator 120 may be used to adjust the tension in the transverse direction caused by the previous difference in the rotational speed of each of the rollers 111, 112. In the example shown, the fiber mat tension compensator 120 may be used to adjust the length of the track between the reel and the roller to avoid material accumulation at one of the rollers.

[0028] The apparatus 100 allows the fiber mat 200 to be deposited on a surface in a fast and efficient manner and allows the fiber mat deposition to be replicated during different runs. Thus, the apparatus 100 can improve the reproducibility of the results achieved during the manufacture of composite components. Furthermore, since the first roller 111 is controlled independently of the second roller 112, the apparatus 100 can modify the shear angle between the fibers in a continuous manner during deposition. This allows the shear angle between the fibers to be adjusted according to the particularities of the surface used to deposit the fibers and greatly reduces fiber defects such as wrinkles. Furthermore, due to the reduction of fiber defects during deposition, the operator may not need to brush the deposited fibers, or deposit less than before, and thus also avoid other defects caused by the operator standing on the fiber mat.

[0029] Figure 3 The example in FIG. 1 shows that the apparatus 100 may further include a frame 300 for carrying the reel 101, the first roller 111 and the second roller 112, and the fiber mat tension compensator 120. The frame 300 may be displaceable along the laying direction to facilitate the fiber mat deposition. Similarly, the frame 300 may include a sub-frame for each component (i.e., the reel 101, the first roller 111 and the second roller 112, and the fiber mat tension compensator 120), and the sub-frames may be at least partially displaceable between each other.

[0030] in addition, Figure 3 It is shown that the fiber mat tension compensator 120 may be arranged between the reel 101 and the first and second rollers 111 and 112. The variation in shear angle achievable when depositing the fiber mat depends inter alia on the distance between the reel and the rollers and the tension that the fiber mat tension compensator 120 may apply.

[0031] exist Figure 3In the example shown in , the fiber mat tension compensator 120 includes a fiber mat contact surface 121 and an actuator. The actuator is configured to change the position of at least a portion of the fiber mat contact surface 121 in a vertical direction. In some examples, the actuator may include several independent components to locally modify the position of the fiber mat contact surface 121. Figure 3 In the example shown in , the actuator comprises two movable connections respectively located at the two ends of the fiber mat contact surface 121. The fiber mat contact surface 121 in this example is the outer surface of a cylinder.

[0032] Figure 3 The movable connection in is connected to a corresponding spring-type element. The length of the spring can be controlled to determine the vertical position of the end of the cylinder, and thereby determine the inclination of the cylinder. However, other arrangements may also be used. For example, the movable connection may be arranged in a vertical guide, or may be directly connected to a guide system that can be operated by an actuator. The movable connection may be located substantially below or above the fiber mat, and may allow either end of the cylinder to be moved upward or downward, and limit the inclination of the cylinder, and thereby limit the tension in the transverse direction. In other examples, the actuator may include a hydraulic piston, a pneumatic piston, a servo motor, a cam or a worm assembly to control the position of the fiber mat contact surface 121. In addition, other quantities and distributions may also be applied.

[0033] In some examples, the fiber mat tension compensator 120 may include a cylinder as the fiber mat contact surface 121. The cylinder may be a freely rotating cylinder, a fixed cylinder, or a cylinder with controlled rotation. Other types of surfaces may be used as the fiber mat contact surface 121. In some examples, the fiber mat contact surface 121 may include two or more parts whose heights are independently adjustable. In some other examples, the fiber mat contact surface 121 may be a compliant surface that can change the shape of the surface. The compliant surface may integrate the actuator under the surface to reduce space.

[0034] In the present disclosure, the vertical direction should be understood as a direction substantially perpendicular to the laying direction and the transverse direction.

[0035] In an example, the surface on which the fiber mat may be deposited may be the inner surface of a mold for manufacturing a shell of a wind turbine blade, but it is clear that the systems and methods disclosed herein may be used to manufacture other products, in particular fiber reinforced composite products, namely spar caps. After the mat is deposited into the mold, other mats are deposited beside and on top of the mat. Depending on the shape and, for example, the curvature of the mold, an appropriate shear angle may be defined. Using the method according to Figure 3 An apparatus of the example can use corresponding shear angles to perform deposition in an automated and precise manner.

[0036] Figure 3It is also shown that the fiber mat tension compensator 120 can adjust the fiber mat tension in the cross direction in response to a change in the speed of at least one of the rollers 111, 112. Thus, by adjusting the fiber mat tension locally (i.e., in a portion of the fiber mat 200), the fiber mat tension compensator 120 avoids accumulation of fibers behind the rollers 111, 112. As previously described, the tension compensation can be actuated to change the changing speed of the rollers 111, 112.

[0037] Figure 3 The example in also shows that one or more of the first roller 111 and the second roller 112 can be arranged on the shaft 113. In the example, the rollers 111, 112 and the shaft 113 define a rotatable connection. In addition, the shaft 113 can be substantially perpendicular to the laying direction and the transverse direction. This allows to modify the angle defined between the laying direction and the rotation direction of the rollers 111, 112. The change of this angle can improve the deposition of the fiber mat, for example in a configuration where the device 100 is tilted and the gravity acting on the fiber mat 200 interferes with achieving a uniform fiber mat distribution.

[0038] Furthermore, in some examples, one or more of the first roller 111 and the second roller 112 can be configured to translate in the transverse direction. This allows the apparatus 100 to be used with fiber mats having different widths. Furthermore, translating the rollers 111, 112 in the transverse direction allows the point of maximum shear angle to be controlled, such as in examples with three or more rollers, where the apparatus 100 generates a non-constant shear angle in the transverse direction of the fiber mat 200.

[0039] In an example, the reel 101 may include a drive for rotating the shaft of the reel 101 to control the tension of the fiber mat 200 on the reel 101. Figures 4A to 4D As discussed, this allows for more precise fiber mat deposition.Other methods for controlling the tension in the fiber mat roll 102 on the reel 101 are also contemplated, for example rollers or other elements applying pressure on the outer surface of the fiber mat roll.

[0040] exist Figure 3 In the example of , the total tension on the fiber mat 200 is kept substantially constant between the two rollers 111, 112 and the reel 101. In addition, Figure 3 It is shown that an additional roller 130 may be employed to limit the transfer of the shear angle caused by the two rollers 111, 112. Thus, the additional roller 130 may comprise a relatively high friction surface to prevent any spanwise variation in the fiber mat 200 from reaching the reel 101. In addition, the apparatus 100 may comprise two side rollers 140, 141, which are respectively located at either side of the fiber mat tension compensator 120 and are configured to limit the vertical displacement of the fiber mat 200 caused by the fiber mat tension compensator 120 in the longitudinal direction.

[0041] Figures 4A to 4DFour different examples of the two rollers 111, 112 exerting traction on the fiber mat 200 are shown. Figures 4A to 4D In the embodiment of the present invention, the first fiber mat end 201 corresponds to the fiber portion closest to the reel 101, and the second fiber mat end 202 corresponds to the fiber portion closest to the deposition surface. Figure 4A A first example is shown, in which the pre-tension applied by the reel 101 and the fiber mat tension compensator 120 is balanced with the traction force generated by the rollers 111, 112. Figure 4A In , both rollers rotate at the same speed and therefore the shear angle 203 is zero.

[0042] Figure 4B A second example is shown where the pre-tension applied by the reel 101 and the fiber mat tension compensator 120 is too high compared to the traction force generated by the rollers 111, 112. This causes the fibers directly below the rollers 111, 112 to advance faster in the lay direction than the rest of the fibers and contributes to an undesirable pattern in the fiber mat 200 by having negative and positive shear angles 203 in the cross direction.

[0043] Figure 4C A third example is shown where the pre-tension applied by the reel 101 and the fiber mat tension compensator 120 is too low and the material has a high longitudinal stiffness. In this case, the rollers may appear to be pulling on the fiber mat and this again results in an undesirable pattern in the fiber mat 200.

[0044] at last, Figure 4D A fourth example is shown, where the pre-tension applied by the reel 101 and the fiber mat tension compensator 120 is unbalanced in the transverse direction. In this example, the tension may be balanced with the traction force generated by the second roller 112, but is too high compared to the traction force generated by the first roller 111. This results in a portion of the fiber mat being deposited at a desired shear angle 203 (zero in this case), and a portion of the fiber mat being deposited at an undesired shear angle 203.

[0045] Figure 5 The schematic diagram shows the effect on the rollers 111, 112 and the reel 101 ( Figure 5 4, the first fiber mat end 201 corresponds to the fiber mat portion closest to the reel 101, and the second fiber mat end 202 corresponds to the fiber mat portion closest to the rollers 111, 112 and the deposition surface. Figure 5 In the example shown in FIG. 1 , the fiber mat tension compensator 120 is of the type Figure 3The type shown in Fig. 1 is substantially the same, although the following discussion is also valid for other alternatives that may be applied. The fact that the rollers 111, 112 can be controlled independently means that if a different speed profile is assigned to each of the rollers 111, 112, the fiber mat portion under each of the rollers will travel at a different speed. Therefore, at a given time after operation, a certain amount of fiber mat may accumulate behind the rollers 111, 112 rotating at a lower average speed.

[0046] In order to mitigate the effects of such fiber accumulation, the fiber mat tension compensator 120 may use one or more actuators, such as pistons, which have more than one independent member to adjust the tension of the fiber mat in the transverse direction, and more specifically, the fiber mat tension compensator 120 balances the tension difference between the reel 101 and the first roller 111 and the second roller 112. Figure 5 1, wherein a first independent member (not shown) lifts a portion of the fiber mat contact surface to compensate for differences in fiber mat length behind the rollers 111, 112. In doing so, the fiber mat tension compensator 120 adjusts the path length of the fiber mat 200 between the reel 101 and the first and second rollers 111, 112 depending on the lateral position.

[0047] Figure 6 A portion of a fiber mat 200 is schematically shown below rollers 111, 112. Note that this diagram may be similar to the diagram previously described. Figure 5 In this figure, the second roller 112 rotates at a higher speed than the first roller 111. This can be deduced from the orientation of the fibers, and more precisely, from the positive magnitude of the shear angle 203 of the fibers.

[0048] Figure 7 8 is a flow chart of an example of a method 800 for depositing a fiber mat 200 on a surface. The fiber mat 200 of the method 800 has a length and a width, and a roll 102 of the fiber mat 200 is arranged on a reel 101. In particular, Figure 7 The method 800 is shown to include rotating two or more rollers 111, 112 to apply traction to the fiber mat 200 and pull the fiber mat 200 from the reel 101 in the lay direction at block 801. In addition, at block 801 of the method 800, one of the rollers 111, 112 has a different speed than at least one of the other rollers 111, 112 to obtain a shear angle 203 in the fiber mat 200. In addition, the method 800 also includes depositing the fiber mat 200 on a surface at block 802. In addition, the method also includes adjusting a tension along the width of the fiber mat 200 in a portion of the fiber mat 200 between the rollers 111, 112 and the reel 101 at block 803.

[0049] In some examples, the deposition 802 of the fiber mat is performed in a mold for manufacturing a shell of a wind turbine blade 22. In addition, in some examples, the method 800 may further include brushing the deposited fiber mat 200 to reduce fiber mat surface irregularities. The brushing step may be performed manually or automatically.

[0050] In some further examples, the rollers 111 , 112 at block 801 of method 800 rotate according to separate speed profiles, and the separate speed profiles are determined in a simulation of the laying process.

[0051] Furthermore, the method 800 may further comprise infusing the fiber mat 200 with resin and curing the resin. Specifically, vacuum assisted resin transfer molding may be used. After curing, a half blade shell may be obtained.

[0052] Figure 8 9 is a flow chart of an example of another method 900 for laying a fiber mat 200 in a mold of a shell of a wind turbine blade 22. The method 900 includes determining a desired shear angle 203 in the fiber mat 200 at box 901. Furthermore, the method 900 includes unwinding 902 the fiber mat 200 from the reel 101 as the reel 101 is displaced along the mold. Furthermore, the method also includes depositing the fiber mat 200 in the mold at a first transverse position along a layup direction and applying a second traction force at a second transverse position along the layup direction to obtain the desired shear angle 203 in the fiber mat 200 at box 903. Furthermore, the method 900 also includes at least partially compensating 904 for tension in the fiber mat 200 along the transverse direction.

[0053] In some examples, at block 902 of method 900, first and second traction forces may be applied by first and second rollers 111 and 112, respectively. In addition, first roller 111 may have a first rotational speed, and second roller 112 may have a second rotational speed, and the two rotational speeds may be different from each other.

[0054] In some further examples, block 904 of method 900 may include adjusting a length of a path of the fiber mat 200 between the reel 101 and the first and second rollers 111 , 112 .

[0055] In any of the examples disclosed herein, the fiber mat can include glass fibers or carbon fibers.

[0056] This written description uses examples to disclose the present teachings, including preferred embodiments, and also enables any person skilled in the art to implement them, including making and using any device or system and performing any combined method. The patentable scope is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples have structural elements that are not different from the written language of the claims, or if they include equivalent structural elements that are not substantially different from the written language of the claims, such other examples are expected to be within the scope of the claims. Aspects from the various embodiments described and other known equivalents of each such aspect can be mixed and matched by those skilled in the art to constitute additional embodiments and techniques according to the principles of the present application. If reference marks related to the drawings are placed in brackets in the claims, they are only used to try to increase the understandability of the claims and should not be interpreted as limiting the scope of the claims.

Claims

1. An apparatus (100) for depositing a fiber mat (200) on a surface, the apparatus (100) comprising: a reel (101) for holding a roll (102) of a fiber mat (200), the fiber mat (200) having a length and a width, wherein the length extends in a lay-down direction and the width extends in a transverse direction; a first roller (111) at a first lateral position and a second roller (112) at a second lateral position for applying a traction force on the fiber mat (200) to unwind the fiber mat (200) from the reel (101) in the laying direction, wherein the first roller (111) is configured to be controlled independently of the second roller (112); and A fiber mat tension compensator (120) is configured to adjust tension in the fiber mat (200) along the transverse direction.

2. The apparatus (100) according to claim 1, wherein the fiber mat tension compensator (120) is arranged between the reel (101) and the first roller (111) and the second roller (112).

3. An apparatus (100) according to any one of claims 1 or claim 2, wherein the fiber mat tension compensator (120) comprises a fiber mat contact surface (121) and an actuator, wherein the actuator is configured to change the position of at least a portion of the fiber mat contact surface (121) along a vertical direction, wherein the vertical direction is substantially perpendicular to the laying direction and the transverse direction.

4. The apparatus (100) according to claim 3, wherein the fiber mat contact surface (121) comprises two or more parts whose heights can be adjusted independently.

5. The apparatus (100) according to any one of claims 1 to 4, wherein the surface is a surface of a mould for manufacturing a shell of a wind turbine blade or a surface of a mould for manufacturing a spar cap of a wind turbine blade.

6. The apparatus (100) according to any one of claims 1 to 5, wherein the fiber mat tension compensator (120) is configured to adjust the fiber mat tension along the transverse direction in response to a change in the speed of at least one of the rollers (111, 112).

7. The apparatus (100) according to any one of claims 1 to 6, wherein the reel (101) comprises a drive for rotating an axis of the reel (101) to control the tension of the fiber mat (200) on the reel (101).

8. The apparatus (100) according to any one of claims 1 to 7, wherein one or more of the first roller (111) and the second roller (112) are rotatably arranged on an axis (113), wherein the axis (113) is substantially perpendicular to the laying direction and the transverse direction.

9. The apparatus (100) according to any one of claims 1 to 8, wherein at least one of the first roller (111) and the second roller (112) is configured to translate in the transverse direction.

10. The apparatus (100) according to any one of claims 1 to 9, further comprising a frame (300) for carrying the reel (101), the first roller (111) and the second roller (112) and the fiber mat tension compensator (120), and wherein the frame (300) is displaceable along the laying direction.

11. A method (800) for depositing a fiber mat (200) having a length and a width onto a surface, wherein a roll (102) of the fiber mat (200) is arranged on a reel (101), the method comprising: Rotating (801) two or more rollers (111, 112) to apply traction to the fiber mat (200) and pull the fiber mat (200) from the reel (101) in a lay-down direction, wherein one of the rollers (111, 112) has a different speed than at least one of the other rollers (111, 112) to obtain a shear angle in the fiber mat (200); depositing (802) the fiber mat (200) on the surface; as well as The tension along the width of the fiber mat (200) is adjusted (803) in the portion of the fiber mat (200) between the rollers (111, 112) and the reel (101).

12. The method (800) of claim 11, wherein the fiber mat (200) is deposited in a mold for manufacturing a shell of a wind turbine blade (22).

13. The method (800) of any one of claims 11 or 12, further comprising brushing the deposited fiber mat (200) to reduce fiber mat surface irregularities.

14. The method (800) according to any one of claims 11 to 13, wherein the rollers (111, 112) rotate according to individual speed profiles, and wherein the individual speed profiles are determined in a simulation of a laying process.

15. The method (800) of any one of claims 11 to 14, wherein the method further comprises determining a desired shear angle (203) in the fiber mat (200) prior to depositing the fiber mat.

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