Mold assembly for perfusion of spar caps and related methods

Abstract

The present disclosure relates to a method for manufacturing a spar cap of a wind turbine blade, the spar cap comprising a stack of pultruded plates (211). The method comprises laying a stack of pultruded plates (211) on a mold (220) between first and second side walls (222, 221), infusing the stack of pultruded plates with a resin, and demolding (303) the infused stack of pultruded plates from the mold (220). Furthermore, at least one of the side walls is adjusted in a transverse direction relative to the stack of pultruded plates (211) at least after laying the stack of pultruded plates or before demoulding (303) the stack of pultruded plates. The present disclosure also relates to an infused pultrusion stack.

Description

[0001] This application claims priority from European patent application EP 22159824.6 “Mold assembly for infusing a spar cap and related methods” filed on March 2, 2022. Technical Field

[0002] The present disclosure relates to a die assembly for infusing a spar cap comprising a layup of pultruded panels and a method for infusing a spar cap. Background Art

[0003] Modern wind turbines are often used to supply electricity to an electrical grid. This type of wind turbine usually comprises a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is arranged to rotate under the influence of the wind on the blades. The torque generated by said rotation is usually transmitted to a generator via the rotor shaft directly ("direct drive") or by using a gearbox. In this way, the electricity generated by the generator 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. The larger the size of the blades, the higher physical loads are introduced to the blades and related components. A wind turbine rotor blade typically comprises a main body shell formed from two shell halves of a composite material. The main body shell is relatively lightweight and has structural properties that are not designed to withstand the bending moments and other loads acting on the blade during operation. In order to improve the structural properties of the rotor blade, such as stiffness and strength, the blade is typically reinforced with structural components, for example, one or more spar caps at the suction and pressure sides of the blade, with shear webs connecting them.

[0005] Spar caps can be manufactured using several materials, such as glass fiber laminate composites and carbon fiber laminate composites. Modern spar caps can be manufactured using pultruded composites, particularly carbon fiber based pultruded composites. Composites manufactured by pultrusion can have a constant cross-section, which can be easily stacked to form larger composite parts. They can be referred to as pultruded "sheets". Multiple pultruded sheets can be stacked and poured together in a mold to form larger (i.e., longer, thicker, wider) composite parts, such as spar caps.

[0006] Due to the cost and other benefits of using pultruded sheets for manufacturing composite parts, the industry is developing new methods to integrate them into the composite manufacturing process. Known methods include placing the pultruded sheets in a mold in order to later infuse them. However, the pultruded sheets can be difficult to align relative to each other and relative to the mold, and this can lead to defects in the final product. In order to mitigate the above-mentioned misalignment, a considerable amount of manual labor is required, which leads to an increase in the average cost of the composite part and a decrease in the overall yield of composite manufacturing.

[0007] Furthermore, methods known in the art use supports located in the mold to guide the pultruded sheet from, for example, a lifting device such as a crane or the like. After resin infusion and demolding, the stack of resin-infused pultruded sheets may need to be processed by a qualified operator to improve the quality of the product and, for example, to remove excess resin. This results in a time-consuming and complex task that requires manual labor and hinders productivity and the quality of the final product.

[0008] The present disclosure provides examples of assemblies and methods that at least partially overcome some of the shortcomings of existing molds for spar cap manufacturing and methods for manufacturing spar caps including pultruded panels. Summary of the invention

[0009] In a first aspect, a die assembly is provided. The die assembly is configured for manufacturing a spar cap comprising a layup of pultruded panels. The die assembly comprises a die surface having a longitudinal direction and a transverse direction and at least two side walls. The side walls are substantially arranged along the longitudinal direction. Furthermore, at least one of the side walls is configured to be adjusted along the transverse direction of the die surface.

[0010] According to this first aspect, the die assembly allows to place the pultruded sheet relative to the die surface and to align the pultruded sheet by adjusting the position of at least one side wall in the transverse direction. Thus, the die assembly significantly reduces manual supervision and labor during the positioning and alignment of the pultruded sheet. This results in an at least partially automated process with high reproducibility. At the same time, the production costs are reduced and the productivity of the composite parts is increased. Furthermore, the draft angles usually used for demoulding the part for placing the pultruded sheet and for resin infusion can be reduced or eliminated. Thus, the resin excess on the sides of the part will be reduced and the labor required afterwards will also be reduced.

[0011] Furthermore, the fact that at least one side wall can be adjusted allows the same mould assembly to be used for pultruded panels of different sizes. Furthermore, the side wall facilitates the demoulding step after resin infusion, for example, the side wall can be moved away from the spar caps to facilitate collection of the spar caps.

[0012] In another aspect, a method for manufacturing a spar cap including a stack of pultruded sheets is provided. The method includes laying up the stack of pultruded sheets on a mold surface between a first sidewall and a second sidewall. Furthermore, the method includes infusing the stack of pultruded sheets with a resin and demolding the infused stack of pultruded sheets from the mold. Furthermore, at least after laying up the stack of pultruded sheets or before demolding the stack of pultruded sheets, at least one of the sidewalls is adjusted in a transverse direction relative to the stack of pultruded sheets.

[0013] According to this aspect, the method allows placing the stack of pultruded sheets in a mould and then displacing the side walls relative to the stack of pultruded sheets. Thus, alignment of the pultruded sheets can occur during translation of the side walls. Furthermore, the fact that the side walls can be moved allows manufacturing spar caps with different dimensions (e.g. width) and the draft angles typically used for demoulding can be reduced. The side wall(s) can be translated after infusing the stack of pultruded sheets with resin, which greatly simplifies the demoulding process and reduces the risk of damaging the spar caps during removal.

[0014] Throughout this disclosure, the terms "pultruded composite," "pultruded sheet," "pultrusion," or similar terms are generally used to define a reinforcement material (eg, fibers or woven or braided strands) that is impregnated with a resin and pulled through a heated die to cure the resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Non-limiting examples of the present disclosure will be described below 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 may be used in the manufacture of wind turbine blades is shown; Figure 3 schematically illustrates a mold assembly according to one example; Figure 4 schematically illustrates a cross-sectional view of another example of a mold assembly in a first configuration; Figure 5 Schematically shows the second configuration Figure 4 mold components; Figure 6 Two examples of lay-ups of resin-infused pultruded panels are schematically shown; Figure 7 is a flow chart of a method for manufacturing a spar cap according to one example. DETAILED DESCRIPTION

[0016] 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 only as an explanation 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 part of one embodiment may be used together with another embodiment to produce yet another embodiment. Therefore, the present disclosure is intended to cover such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0017] 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, each blade having a blade root 16 closest to the hub and a blade tip 14 farthest from the hub 8.

[0018] Figure 2A A 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 having a root end 17 and a tip end 15, and includes a root region 30 closest to the hub, a profiled 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 and a trailing edge 20, the leading edge 18 facing the direction of rotation of the blade 10 when the blade is mounted on the hub, and the trailing edge 20 facing the opposite direction of the leading edge 18.

[0019] The airfoil region 34 (also referred to as the shaping region) has an ideal or nearly ideal blade shape with respect to the generation of lift, while the root region 30 has a substantially circular or elliptical cross section due to structural considerations, which, for example, makes it easier and safer to mount the blade 10 on the hub. The diameter (or chord) of the root region 30 can 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 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.

[0020] 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 typically disposed at the boundary between the transition region 32 and the airfoil region 34.

[0021] It should be noted that the chords of different sections of the blade do not usually lie in a common plane, as the blade may be twisted and / or bent (i.e. pre-bent), thereby providing a chord plane with a correspondingly twisted and / or bent line, which is the most common case, to compensate for the local speed 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, a first blade shell part 24 and a second blade shell part 26, typically made of fiber reinforced polymer. 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 with an adhesive (such as glue) along a join line or glue joint 28, which extends along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root end of the blade shell part 24, 26 has an outer cross-sectional shape that is semi-circular or semi-elliptical.

[0022] Figure 2B is a schematic diagram showing a cross-sectional view of an exemplary wind turbine blade 10, for example, 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 components 24, 26 may include glass fiber.

[0023] Figure 2C 1 is a schematic diagram illustrating an exemplary mold system for molding a blade shell of a wind turbine blade. The mold system 100 includes a first mold 102 and a second mold 112. The first mold 102 is configured for manufacturing a first blade shell component of a wind turbine blade, such as a windward shell component of a wind turbine blade (forming a pressure side). The second mold 112 is configured for manufacturing a second blade shell component of a wind turbine blade, such as a downwind shell component of a wind turbine blade (forming a suction side). The mold system 100 further includes surfaces 104, 114 for depositing fibers.

[0024] Figure 3A top perspective view of a die assembly 200 according to an example is schematically shown. The die assembly 200 is configured to manufacture a spar cap comprising a stack of pultruded sheets 211. The die assembly 200 comprises a die surface 210 having a longitudinal direction and a transverse direction. Furthermore, the die assembly 200 comprises at least two side walls 221, 222 arranged substantially in the longitudinal direction. At least one of the side walls 221, 222 is configured to be adjusted in the transverse direction of the die surface 210. This allows for precise adjustment of the distance between the side walls 211, 222, which is used both for guiding the stack of pultruded sheets 211 when they are laid on the die surface 210 and for pushing the stack of pultruded sheets 211 in the transverse direction and aligning them relative to each other and relative to the die surface 210.

[0025] In the example shown, only one sidewall 221 can be adjusted, but in other examples, both sidewalls 221, 222 can be adjustable. Note that in this example, the stack of pultruded sheets 211 is shown elevated relative to the die surface 210, as if the stack of pultruded sheets 211 were still being lowered into the die 200. Once the pultruded sheets 211 are positioned in the die, (final) adjustment of the sidewalls of the die can occur.

[0026] Also refer to Figure 3 In some examples, the mold assembly 200 may include a guide 225 extending in a transverse direction. The guide 225 may be configured to guide at least one of the side walls 221. The connection between the guide 225 and the side walls 221, 222 may be a male-female connection. The guide 225 may define a female connection and the side wall 221 may define a male connection, or vice versa. In addition, the guide 225 may be embedded in the mold surface 210. In addition, the guide 225 may include a sealing cap to at least partially seal the guide opening located below the stack of pultruded sheets 211 and avoid accumulation of resin.

[0027] In an example, the side walls of the mould may be substantially parallel to each other, ie the draft angle may be 0°.After resin infusion, the adjustable side wall(s) may be displaced in a lateral direction to allow demoulding.

[0028] In an example, at least one of the side walls 211 may include a sliding element configured to slide along the guide 225 in a lateral direction. The sliding element and the guide 225 may define a low friction coupling to facilitate smooth adjustment. In addition, the side wall 211 may also include a clamping or fixing element to fix the position of the side wall 211 along the guide, for example, a locking rod. The clamping (or fixing) element may be manual or automatic.

[0029] In another example, the die assembly 200 may further include a drive unit configured to adjust at least one of the side walls 221 in the transverse direction. The drive unit may be automatically operated or may be operated by a qualified operator. The drive unit may include pneumatic, and / or hydraulic and / or electronic components, such as, for example, pistons, pumps, encoders, stepper motors, etc. Therefore, before laying the stack of pultruded boards, the drive unit may displace the side walls 221, 222 to provide more space for their descent. In other examples, the drive unit may displace the side walls 221, 222 after laying the stack of pultruded boards to fix them and align them relative to each other and relative to the die 220. In addition, the die assembly 200 may include a sensor unit configured to determine the pressure applied by at least one of the side walls 221, 222 to the stack of pultruded boards 211. The sensor unit may feed the drive so that it stops displacing after reaching a given pressure threshold. Furthermore, the sensor unit may also comprise a processing and control unit which processes the data from the sensor and provides control parameters to the drive.

[0030] In an alternative example, adjusting the sidewall(s) may be a manual process.

[0031] Figure 4 and Figure 5 A cross-sectional view of a mold assembly according to another example of the present disclosure is shown.

[0032] Figure 4 Schematically illustrated is a die assembly 200 with a stack of pultruded sheets 221 at a given height prior to deposition onto a die surface 210. In addition, Figure 4 At least one of the side walls 221, 222 is shown to include a side wall surface 226 configured to contact a side surface of the stack of pultruded sheets 211 ( Figure 6 212 in the figure). In an example, the side wall surface 226 may be rotatable around the longitudinal direction of the mold surface 210. Thus, the rotation of the side wall surface 226 allows for defining a variable draft angle that defines the distribution of the resin during infusion.

[0033] also, Figure 4 It is also shown that the mold surface 210 can include one or more receiving portions 224 to receive the side wall fasteners 223. Having multiple receiving portions distributed in the transverse direction allows the side wall 221 to be positioned at discrete locations depending on, for example, the size of the pultruded board or the stage of the molding process. It will be apparent that multiple receiving portions and fasteners can also be provided in the longitudinal direction.

[0034] The receiving portion 224 and the corresponding fastener 223 may provide a threaded connection, but other coupling methods may also be used. In some examples, the side walls 221, 222 may have an elongated hole to receive the side wall fastener 223. The elongated hole may provide a variable positioning of the side wall 211 relative to the mold surface 210. In other examples, the receiving portion in the mold 220 may be elongated, and the fastener 223 may be introduced therein at a desired lateral position.

[0035] Figure 5 The die assembly 200 is schematically shown, wherein a stack of pultruded sheets 221 has been deposited on top of the die surface 210. Figure 5 In the example, one of the side walls 221 is located next to the stack of pultruded sheets 221 and is fixed to the die 220. In this example, the die assembly 200 also includes a fastener 223 that matches the internal geometry of the receiving portion 224 in the die 220. Figure 4 As discussed, the side walls 221, 222 may include a side surface 226 that is rotatable about the longitudinal direction of the die 220. As shown, this may result in the side surface 226 being substantially parallel to the side surfaces of the stack of pultruded sheets 211.

[0036] Note that while the side walls 221 , 222 are shown as L-shaped profiles, the side walls may have any other suitable cross-section.

[0037] Figure 6 Two infused pultrusion stacks 201 are shown. The infused pultrusion stacks 201 define a longitudinal direction and a transverse direction. In addition, the infused pultrusion stacks 201 define two side surfaces 212 that bound the infused pultrusion stacks 201 in the transverse direction. The two side surfaces 212 extend in the longitudinal direction and are substantially parallel to each other.

[0038] In an example, the infused stack 201 includes a plurality of pultruded sheets 211 infused with resin. The stack of pultruded sheets 211 may include carbon fiber, glass fiber, aramid fiber, or other suitable fibers. In addition, the infused stack 201 of pultruded sheets may include epoxy resin, polyester resin, vinyl ester resin, or other suitable resins.

[0039] like Figure 6 As shown in the figure, the infused pultrusion stack 201 can have a rectangular cross-section (left embodiment), or it can have a curved cross-section (right embodiment). Therefore, the outer surface 213 of the infused pultrusion stack 201 can be flat or curved. The size and geometry of the infused pultrusion stack 201 can be adjusted according to the geometry or mechanical requirements of the composite product.

[0040] In both examples, the draft angle of the sidewalls can be 0° or close to 0°. Thus, resin buildup on the sides of the stack can be avoided. This can reduce the weight of the product and can also reduce the need for post-processing. In addition, a draft angle of 0° or close to 0° can also reduce the cost of other components adjacent to the pultrusion stack 201. For example, a core panel configured to be assembled next to the pultrusion stack 201 can be cut to a right angle that substantially matches the sidewalls of the pultrusion stack 201. This can result in a faster and cheaper manufacturing process.

[0041] In some examples, the infused pultrusion stack 201 may be formed by combining Figure 7 Further discussion of the method to obtain.

[0042] Figure 7 is a flow chart of a method 300 for manufacturing a spar cap according to one example, wherein the spar cap of the method 300 includes a stack of pultruded panels 211. The method 300 includes laying up 301 the stack of pultruded panels 211 in a mold 220 between a first sidewall 221 and a second sidewall 222. Furthermore, at block 302, the method 300 includes infusing the stack of pultruded panels 211 with a resin. The method 300 then also includes demolding 303 the infused stack of pultruded panels 201 from the mold 220.

[0043] During the method 300, at least one of the side walls 221, 222 may be adjusted in a transverse direction relative to the stack of pultruded sheets 211. This may occur at least after layup 301 of the pultruded sheets 211 or before demolding 303 of the stack of pultruded sheets 211.

[0044] Adjustment of at least one of the side walls 221 , 222 may be accomplished according to any of the examples previously described herein.

[0045] As discussed previously, the fact that at least one of the side walls 221, 222 is adjusted in the transverse direction greatly simplifies the placement (by potentially guiding the descent and by providing more space for the plates) and demolding of the stack of pultruded sheets 211. In fact, in some examples, adjusting at least one of the side walls 221, 222 is performed by moving said side walls 221, 222 in the transverse direction and then fastening said side walls 221, 222 to a receiving portion in the mold 220 before infusing 302 the stack of pultruded sheets 211 with resin.

[0046] In some examples, the method 300 includes laying 301 a stack of pultruded sheets 211 substantially adjacent to a first sidewall 222, the first sidewall 222 being fixed in the mold 220, and the method 300 further includes adjusting the second sidewall 221 in a transverse direction to contact the stack of pultruded sheets 211. This results in improved alignment of the pultruded sheets 211 and thus improves the quality of the final product. In addition, the sidewalls 221, 222 can define a draft angle of less than 1 degree, specifically less than 0.5 degrees, and more specifically, the draft angle is about 0 degrees. This draft angle limits the accumulation of resin between the sidewalls 221, 222 and the side surface of the pultruded sheet 211, which greatly reduces the amount of post-molding surface treatment that may be required. In other examples, the sidewalls 221, 222 can be fixed at a given position in the mold and define a large draft angle to facilitate guiding the stack of pultruded sheets 211. Then, before pouring 302, the draft angle can be reduced by rotating the sidewall surface 226.

[0047] In an example, the sidewalls 221, 222 can be substantially parallel to each other. Since the die 220 can have a curved geometry and the sidewalls 221, 222 can be displaced along the surface of the die 210, the sidewalls 221, 222 can be further adjusted by rotating the sidewall surface 226 configured to contact the stack of pultruded sheets 211. The rotation of the sidewall surface 226 can be about the longitudinal direction of the die surface 210.

[0048] As about Figure 6 As discussed, the stack of plies of pultruded sheet 211 may include carbon fibers, glass fibers, aramid fibers, or other suitable fibers, and the resin may include epoxy resin, polyester resin, vinyl ester resin, or other suitable resin.

[0049] In yet another aspect of the present disclosure, a wind turbine blade is provided. The wind turbine blade comprises a shear web and a spar cap, wherein the spar cap comprises a stack 201 of infused pultruded panels according to any example shown herein and / or manufactured according to any example shown herein. The windward and downwind shells of the wind turbine blade may be manufactured, for example, according to the process shown in FIG.

[0050] Note that some of the technical features described with respect to the die assembly 200 and the infused pultrusion layup 201 may be included in the method 300 for manufacturing a spar cap, and vice versa.

[0051] Although in all depicted examples, the pultruded sheets 211 are shown as thin, wide, and long sheets that are stacked on top of each other, it is noted that this is done for illustration purposes only. That is, in any depicted example, a single pultruded sheet 211 may actually include multiple sheets (or "strips") adjacent to each other.

[0052] This written description uses examples to disclose the present teachings, including preferred embodiments, and also enables any person skilled in the art to practice it, 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 one skilled in the art. These other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims. A person of ordinary skill in the art may mix and match aspects of the various embodiments described, as well as other known equivalents of each such aspect, to construct additional embodiments and techniques in accordance with the principles of the present application. If reference symbols relating to the drawings are placed in parentheses in the claims, they are used only to attempt to increase the intelligibility of the claims and should not be interpreted as limiting the scope of the claims.

Claims

1. A method (300) for manufacturing a spar cap for a wind turbine blade, the spar cap comprising a stack of pultruded sheets (211), the method comprising: Laying (301) the stack of pultruded sheets (211) on a mold (220) between the first side wall and the second side wall (222, 221); infusing (302) the stack of pultruded sheets (211) with resin; and The stack of infused pultruded sheets is demolded (303) from the mold (220), wherein At least after laying (301) the stack of pultruded sheets (211) or before demolding (303) the stack of pultruded sheets, at least one of the side walls (221, 222) is adjusted in a transverse direction relative to the stack of pultruded sheets (211).

2. The method (300) according to claim 1, wherein: Laying (301) the stack of pultruded sheets comprises laying the stack of pultruded sheets substantially adjacent to the first side wall (222), the first side wall (222) being secured in the mould (220), and the method further comprises subsequently adjusting the second side wall (221) in the transverse direction to contact the stack of pultruded sheets (211).

3. The method (300) according to claim 1 or 2, wherein: The sidewalls (222, 221) define a draft angle of less than 1 degree, specifically less than 0.5 degrees, and more specifically, a draft angle of about 0 degrees.

4. The method (300) according to any one of claims 1 to 3, wherein: The side walls (222, 221) are substantially parallel to each other.

5. The method (300) according to any one of claims 1 to 4, wherein: The sidewalls (222, 221) are further adjusted by rotating a sidewall surface (226) configured to contact the stack of pultruded sheets (211).

6. The method (300) according to any one of claims 1 to 5, wherein: At least one of the side walls (222, 221) is adjusted by sliding the side wall (222, 221) along a guide (225) in the mold (220).

7. The method (300) of claim 1, wherein: At least one of the side walls is attached via a fastener disposed in a hole in the side wall and a receiver in the mold.

8. The method according to claim 7, wherein: At least one of the holes in the side walls (222, 221) is an elongated hole, or at least one of the receiving portions is an elongated receiving portion.

9. A die assembly (200) for manufacturing a spar cap comprising a laminate of pultruded sheet (211), the die assembly (200) comprising: a mold surface (210) having a longitudinal direction and a transverse direction, and At least two side walls (222, 221) are arranged substantially along the longitudinal direction, wherein at least one of the side walls (222, 221) is configured to be adjusted along a transverse direction of the mold surface (210).

10. The mold assembly (200) according to claim 9, wherein: The two side walls are substantially parallel to each other.

11. The mold assembly (200) according to claim 9 or 10, wherein: The mold surface (210) includes a receiving portion (224) configured to receive a sidewall fastener (223), and at least one of the sidewalls (222, 221) includes one or more elongated holes.

12. The mold assembly (200) according to any one of claims 9 to 11, wherein: The mold surface (210) includes a guide (225) extending along the transverse direction, the guide being configured to guide at least one of the side walls (222, 221).

13. The mold assembly (200) according to any one of claims 9 to 12, further comprising a driving unit, wherein the driving unit is configured to adjust at least one of the side walls (222, 221) along the lateral direction.

14. The mold assembly (200) according to any one of claims 9 to 13, wherein: The die assembly (200) further comprises a sensor unit configured to measure a pressure applied to the stack of pultruded sheets (211) by at least one of the side walls (222, 221).

15. An infused pultrusion stack (201) obtained by the method according to any one of claims 1 to 7 and defining a longitudinal direction and a transverse direction, the infused pultrusion stack (201) comprising carbon fibers defining two side surfaces (212) which confine the infused pultrusion stack (201) along the transverse direction, wherein The two side surfaces (212) extend along the longitudinal direction and are substantially parallel to each other.

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