A pultruded plank for reinforcing a wind turbine blade

Abstract

Herein is described a pultruded plank for reinforcing a wind turbine blade, the pultruded plank comprising reinforcing fibers and a resin, pultruded plank having a surface comprising a channel pattern for guiding infusing resin.

Description

[0001] A pultruded plank for reinforcing a wind turbine blade

[0002] Field of the Invention

[0003] The present invention relates to pultruded planks and processes for producing pultruded planks, for example pultruded planks for reinforcing wind turbine blades.

[0004] Background

[0005] It is known to use pultruded fibers, for example in the form of pultruded planks, to reinforce structural components, such as wind turbine blades or related components such as a spar cap. These structural components are often formed by laying pultruded planks into a mold, filling the mold with a resin, and curing the resin to form a structural component.

[0006] Several layers of pultruded fibers, for example in the form of pultruded planks, may be required to form a structural component, for example a section of a wind turbine blade. Due to the pultrusion process used for forming the pultruded planks, pultruded planks generally have a very smooth surface. Conventionally, a peel-ply layer is applied to the surface of the pultruded plank during manufacturing of the pultruded plank to ensure the pultruded plank has a textured surface after removal of the peel-ply layer before assembly of the pultruded planks into a structural component. The peel-ply layers are also used to leave behind a textured surface on the pultruded plank after removal of the peel-ply layer from the surface of the pultruded plank in order to attempt to aid resin infusion between stacked pultruded planks.

[0007] Previous attempts to provide pultruded planks without peel-ply layers include applying a sacrificial layer to a pultruded plank and abrading the sacrificial layer to form a roughened surface as described in WO 2018 / 206068.

[0008] There is a need to provide improved elongate reinforcing structures, such as pultruded planks, and associated processes to provide improved structural components and improvements in the production of structural components such as components of wind turbine blades, e.g., spar caps.

[0009] Summary of the Invention

[0010] At its most general, the present invention provides a pultruded plank having a surface comprising a channel pattern. The present inventors have found that providing a pultruded plank having a surface comprising a channel pattern can improve the efficiency of the production of pultruded planks for use in forming composite articles. Furthermore, the present inventors have found that the pultruded planks described herein having a surface comprising a channel pattern also provide improvements in the efficiency of producing or assembling structural components comprising a plurality of said pultruded planks (i.e., pultruded planks having a surface comprising a channel pattern), as well as providing for improvements in resin flow (e.g. resin infusion) between the layers of pultruded planks and / or layers of pultruded planks and other reinforcing fabric layers which may be employed to form a composite article such as a wind turbine blade (for example, a subcomponent of a wind turbine blade).

[0011] In an aspect, the present invention provides a pultruded plank for reinforcing a wind turbine blade, the pultruded plank comprising reinforcing fibers and a resin, the pultruded plank having a surface comprising a channel pattern for guiding infusing resin.

[0012] In an aspect, the present invention provides a pultruded plank for reinforcing a wind turbine blade, the pultruded plank comprising reinforcing fibers and a resin, the pultruded plank having a surface comprising a channel pattern for guiding infusing resin, wherein the channel pattern comprises at least one first channel running the length of the pultruded plank and at least one second channel running across the width of the pultruded plank.

[0013] In another aspect, the present invention provides a method for producing a pultruded plank for reinforcing a wind turbine blade, the method comprising: drawing reinforcing fibers and a resin through a pultrusion die to form a pultruded plank; and forming a channel pattern into a surface of the pultruded plank.

[0014] In another aspect, the present invention provides a method for producing a pultruded plank for reinforcing a wind turbine blade, the method comprising: drawing reinforcing fibers and a resin through a pultrusion die to form a pultruded plank; and forming a channel pattern into a surface of the pultruded plank, wherein the channel pattern comprises at least one channel running the length of the pultruded plank, and a plurality of channels running across the width of the pultruded plank In another aspect, the present invention provides a stack comprising a plurality of pultruded planks, the pultruded planks being as described herein.

[0015] In another aspect, the present invention provides a method of forming a wind turbine blade, the method comprising: providing a plurality of pultruded planks as described herein; stacking the pultruded planks to form a stack; and infusing the stack with resin.

[0016] In an aspect, the present invention provides a wind turbine blade (for example, a wind turbine blade or a subcomponent thereof) comprising a pultruded plank as described herein.

[0017] In an aspect, the present invention provides a pultruded plank for a wind turbine blade obtainable or obtained by a process described herein.

[0018] The present inventors have found that conventional techniques to provide a pultruded plank with a textured surface by using peel-ply layers cause difficulties in assembling structural components from pultruded planks due to the need to remove the peel-ply layers. Removal of the peel-ply layers in order to expose the textured surface of the pultruded plank surface also produces waste which the present inventors seek to avoid.

[0019] The present inventors have found that the present invention provides improvements in the efficiency of producing pultruded planks for reinforcing wind turbine blades and the assembly of structural components for wind turbine blades. In particular, the present inventors have found that the present invention removes the need for employing peel-ply layers on pultruded planks as the pultruded planks described herein are provided with a channel pattern formed on their surface. The present invention also provides a solution to the problem of the waste associated with conventional peel-ply layers.

[0020] The present inventors have also found that the pultruded planks described herein surprisingly improve the efficiency in the production of structural components, such as structural components of wind turbine blades. The pultruded planks described herein have also be found to exhibit excellent handleability, in particular the pultruded planks can be rolled, cut and stacked. Even more surprisingly, the present inventors consider that the pultruded planks described herein can provide improvements in the efficiency of the production of reinforced structural components, e.g. wind turbine blades, without detrimentally effecting the mechanical properties of the final components.

[0021] The present inventors have found that pultruded planks described herein provide advantages in relation to resin infusion. In particular, the present inventors have found that the channel pattern may be designed to control infusion speed of infusing resin. The configuration of the channel pattern of the pultruded plank may be selected in order to provide for desired resin infusion.

[0022] When a composite article such as a wind turbine blade is formed, pultruded planks as described herein may be stacked and infused with resin. The present inventors have found that the channel pattern of the pultruded plank can be adapted to control resin flow (speed of infusion) through a stack of pultruded planks. In for production of composite articles such as wind turbine blades, it may be necessary to infuse resin through layers of reinforcing fabrics (for example glass fibers fabrics) and / or pultruded planks such as those described herein. The present inventors have found that the channel pattern of the pultruded plank can be adapted to control resin flow (speed of infusion) through all of the reinforcing materials (e.g., reinforcing fabrics and pultruded planks) making up a reinforcing component of a composite article such as a wind turbine blade. Therefore, the present inventors have surprisingly found that by providing a pultruded plank comprising a channel pattern as described herein, control of resin flow during the production of a composite article can be straightforwardly provided, for example by allowing control of the configuration of the channel pattern of the pultruded plank. This provision of control of resin flow during the production of a composite article, by the provision of pultruded planks as described herein provides advantages in terms of the mechanical properties of the final composite article.

[0023] Furthermore, the present inventors have found that a channel pattern may be formed in a surface of the pultruded plank by molding during the formation of the pultruded plank. For example, the channel pattern may be formed by the pultrusion die which may be a shaped pultrusion die configured to form a channel pattern in the pultruded plank. For example, the pultrusion die may have at least one surface with a wavy shape to form a channel pattern in the surface of the pultruded plank, the channel pattern comprising at least a first channel running along the length of the pultruded plank, or a plurality of first channels running along the length of the pultruded plank. The present inventors expect that pultruded planks as described herein formed by molding may provide further improvements, particularly in relation to the mechanical properties of components formed using the pultruded planks. As a pultruded plank is exits from a pultrusion die, the temperature of the die may cause polymerisation of the resin such that following exit from the die the pultruded plank cools and retains the shape imparted by the pultrusion die.

[0024] The invention includes the combination of the aspects and preferred features described herein except where such a combination is clearly impermissible or expressly avoided.

[0025] Brief Description of the Figures

[0026] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0027] Figure 1 is a plan view of a pultruded plank according to an embodiment described herein; and

[0028] Figure 2 is a side view of a stack of pultruded planks according to an embodiment described herein.

[0029] Detailed Description

[0030] Aspects and embodiments of the present invention will now be discussed. Further aspects and embodiments will be apparent to those skilled in the art.

[0031] Pultruded planks are produced by drawing reinforcing fibers and a resin through a pultrusion die. For example, pultruded planks may be produced by drawing reinforcing fibers and a thermosetting resin through a pultrusion die.

[0032] Pultruded planks contain reinforcing fibers arranged substantially parallel to the length of the pultruded plank.

[0033] Examples of reinforcing fibers include glass fibers, carbon fibres, polymer fibers and natural fibers. In preferred embodiments, the reinforcing fibers of the pultruded planks comprise, consist essentially of, or consist of glass fibers.

[0034] In embodiments, the pultruded plank comprises, consists essentially of, or consists of reinforcing fibers and a resin. In embodiments, the pultruded plank comprises, consists essentially of, or consists of reinforcing fibers and a thermoset resin.

[0035] A pultruded plank has a length, a width and a thickness, wherein the length is greater than the width and the thickness, and the width is greater than the thickness. In embodiments, the reinforcing fibers (e.g., glass fibers) constitute from about 55 wt.% to about 95 wt.% by total weight of the pultruded plank, and the resin (e.g., the thermoset resin) constitutes from about 5 wt.% to about 45 wt.% of the pultruded plank. For example, the reinforcing fibers (e.g., glass fibers) may constitute from about 70 wt.% to about 90 wt.% by total weight of the pultruded plank, and the resin (e.g., the thermoset resin) may constitutes from about 10 wt.% to about 30 wt.% of the pultruded plank.

[0036] The term "glass fibers" is used herein to refer to a plurality of continuous glass filaments (the term "continuous" as used here is used to refer to a fiber / filament that has a length many times longer than its diameter, for example at least about 5000 times longer than its diameter, e.g., at least about 10 000 times longer than its diameter). The glass fibers used in the fabrics described herein may be provided as glass fiber strands (or tows). The glass fibers may be formed by a continuous manufacturing process in which molten glass passes through the holes of a "bushing," the streams of molten glass thereby formed are solidified into filaments / fibers. The glass fibers described herein may include a sizing on their surface, e.g., a sizing applied on the glass fibers during formation of the fibers. The sizing can include components such as a film former, lubricant, coupling agent (to promote compatibility between the glass fibers and the resin used to form a composite article comprising the hybrid fabric described herein), etc. that facilitate formation of the glass fibers and / or use thereof in a matrix resin. In some embodiments, the glass fibers include a polyester compatible sizing, an epoxy compatible sizing, or a vinyl-ester compatible sizing.

[0037] The term "glass fiber strand" or "glass fiber tow" as used herein, refers to a bundle of continuous glass filaments. In embodiments the glass fiber strands or tows are bundles of untwisted glass filaments.

[0038] In embodiments, glass fiber strands or glass fiber tows are provided from glass fiber direct rovings. Glass fiber direct rovings are made up of a bundle of continuous untwisted (i.e., substantially parallel, or parallel) glass filaments bonded (as the glass filaments are formed) into a single strand and wound onto a bobbin.

[0039] Any suitable glass reinforcing fibers may be employed, for example, fibers made from E glass, E-CR glass (such as Advantex™ glass fibers available from Owens Corning), C glass, H glass, S glass, and AR glass types can be used. In embodiments, the glass fibers referred to herein have a linear mass density in the range of about 50 Tex to about 5000 Tex, for example about 200 Tex to about 4800 Tex, about 500 Tex to about 4800 Tex, aboutlOOO Tex to about 4800 Tex, or about 2000 Tex to about 4800 Tex.

[0040] In embodiments, the pultruded planks described herein may comprise additional fibers in addition to glass fibers. Examples of other fibers which may be included include carbon fibres and / or polymer fibers and / or natural fibers.

[0041] In embodiments, the resin is a thermoplastic resin or a thermoset resin. In embodiments, the resin is a thermoset resin, for example suitable thermoset resin. Examples of suitable resins include an epoxy resin, a polyester resin or a vinyl-ester resin.

[0042] The pultruded planks described herein have a length, a width and a thickness. Figures 1 and 2 show pultruded planks 1, and la and lb respectively, having a length L, a width W, and a thickness T, sides 2 and upper surface 2. Typically, the length of the pultruded plank is greater than the width of the pultruded plank and the thickness of the pultruded plank, and typically the width of the pultruded plank is greater than the thickness of the pultruded plank. The pultruded planks shown in figures 1 and 2 have a surface 2, which may be referred to as an upper surface.

[0043] The pultruded plank may have a length in the range of about 1 m to about 1000 m, for example about 2 m to about 500 m, about 5 m to about 250 m, or about 10 m to about 100 m.

[0044] The pultruded plank may have a width in the range of about 2 cm to about 50 cm, for example about 5 cm to about 20 cm, or about 5 cm to about 15 cm.

[0045] The pultruded plank may have a thickness in the range of about 1 mm to about 10 mm, for example about 2 mm to about 8 mm, or about 3 mm to about 5 mm.

[0046] The pultruded plank described herein has a surface comprising a channel pattern. The pultruded plank may be described as comprising an upper surface and a lower surface. In embodiments, one surface of the pultruded plank comprises the channel pattern, i.e., the upper surface and / or the lower surface. In embodiments, both surfaces of the pultruded plank, i.e., the upper surface and the lower surface, comprise a channel pattern. In embodiments in which both surfaces of the pultruded plank comprises a channel pattern, the channel pattern of the upper surface may be the same or different to the channel patter of the lower surface. In embodiments, both surfaces of the pultruded plank, i.e., the upper surface and the lower surface, comprise a channel pattern and the channel pattern of the upper surface is different to the channel pattern of the lower surface, for example to provide for improved control of resin infusion speed. In embodiments, only one surface of the pultruded plank, i.e., either the upper surface or the lower surface, comprises a channel pattern.

[0047] The channel pattern of a surface (for example, the upper and or lower surface) of the pultruded plank may be selected to provide a desired resin infusion speed, for example a desired resin infusion speed during the production of a composite article formed from the, or a plurality of the, pultruded plank(s).

[0048] The channel pattern of the pultruded plank is for guiding infusing resin. Pultruded planks as described herein may be stacked, and stacks of pultruded planks infused a resin to form a structural component. The channel pattern of the pultruded planks allows resin to infuse between pultruded planks stacked on one another. In embodiments, the channel pattern is formed on a surface of the pultruded plank as a pattern ground into a surface of the pultruded plank. In embodiments, the channel pattern may be formed into a surface of the pultruded plank during formation of the pultruded plank, e.g., during extrusion from a pultrusion die. For example, the pultrusion die may be shaped (or molded) to form a channel pattern in a surface of the pultruded plank.

[0049] The channel pattern may comprise at least one first channel running along the length of the pultruded plank. The first channel may be straight. The first channel may not be straight, for example follow a curved path along the length of the pultruded plank.

[0050] The channel pattern may comprise at least one first channel oriented in a direction substantially parallel to the length of the pultruded plank, for example a first channel oriented in a direction substantially parallel to the length of the pultruded plank and running the length of the pultruded plank.

[0051] The channel pattern may comprise a plurality of first channels running the length of the pultruded plank. The plurality of first channels may be aligned with one another.

[0052] The channel pattern may comprise a plurality of first channels, the first channels spaced from one another by at least about 0.1 cm, for example, at least about 0.5 cm, or at least about 1 cm. The channel pattern may comprise a plurality of first channels, the first channels spaced from one another by up to about 10 cm, for example, up to about 5 cm. The channel pattern may comprise a plurality of first channels, the first channels spaced from one another by about 0.1 cm to about 10 cm, for example about 0.5 cm to about 5 cm, or about 1 cm to about 5 cm. The distance between first channels may be determined by measuring to the mid-point of adjacent first channels along a line oriented substantially perpendicular to the orientation of the first channels, for example a line oriented substantially perpendicular to the length of the pultruded plank.

[0053] The channel pattern may comprise at least one second channel running across the width of the pultruded plank. The second channel may be straight. The second channel may not be straight, for example follow a curved path across the width of the pultruded plank.

[0054] The channel pattern may comprise at least one second channel oriented in a direction substantially perpendicular to the length of the pultruded plank, for example a second channel oriented in a direction substantially perpendicular to the length of the pultruded plank and running across the pultruded plank.

[0055] The channel pattern may comprise a plurality of second channels running across the width of the pultruded plank.

[0056] The channel pattern may comprise a plurality of second channels, the second channels spaced from one another by at least about 0.1 cm, for example, at least about 0.5 cm, or at least about 1 cm. The channel pattern may comprise a plurality of second channels, the second channels spaced from one another by up to about 10 cm, for example, up to about 5 cm. The channel pattern may comprise a plurality of second channels, the second channels spaced from one another by about 0.1 cm to about 10 cm, for example about 0.5 cm to about 5 cm, or about 1 cm to about 5 cm. The distance between second channels may be determined by measuring to the mid-point of adjacent second channels along a line oriented substantially perpendicular to the orientation of the second channels, for example a line oriented substantially parallel to the length of the pultruded plank.

[0057] The channel pattern may comprise a first channel and a plurality of second channels. The first and second channels may have the configuration described above.

[0058] The channel pattern may comprise a plurality of first channels and a second channel. The first and second channels may have the configuration described above.

[0059] The channel pattern may comprise a plurality of first channels and a plurality of second channels. The first and second channels may have the configuration described above.

[0060] The channels of the channel pattern, for example the or each first channel and the or each second channel, may have a U-shaped, V-shaped, square-shaped, or rectangular-shaped cross section. The channels of the channel pattern, for example the or each first channel and / or the or each second channel, may have a depth of up to about 2mm, for example a depth of up to about 1 mm, or a depth of up to about 0.5 mm. The channels of the channel pattern, for example the or each first channel and the or each second channel, may have a depth of at least about 0.1 mm, for example at least about 0.2 mm, at least about 0.3 mm, at least about 0.4 mm, or at least about 0.5 mm. For example, the channels of the channel pattern, for example the or each first channel and / or the or each second channel, may have a depth in the range of about 0.1 mm to about 2mm, about 0.2 mm to about 2 mm, about 0.5 mm to about 1 mm, or about 0.1 mm to about 1 mm.

[0061] The channels of the channel pattern, for example the or each first channel and / or the or each second channel, may have a width of at least about 0.5 mm, or at least about 1 mm. The channels of the channel pattern, for example the or each first channel and / or the or each second channel, may have a width of up to about 5 mm, for example up to about 3 mm, up to about 2 mm or up to about 1 mm. The channels of the channel pattern, for example the or each first channel and / or the or each second channel, may have a width in the range of about 0.5 mm to about 5 mm, for example about 1 mm to about 5 mm, or about 1 mm to about 2 mm. The wide of the channels of the pattern may be measured as the distance across the channel in a direction perpendicular to the channel length.

[0062] The channels of the channel pattern, for example the or each first channel and / or the or each second channel, may have a width to depth ratio in the range of about 5:1 to about 1:5, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1.5:1 to about 1:1.5.

[0063] The channel pattern may comprise at least one first channel and at least one second channel, for example at least one first channel and a plurality of second channels or a plurality of first channels and a plurality of second channels, the first channel oriented in a first direction and the second channel oriented in a second direction. In embodiments, the first direction is different to the second direction. In embodiments, the second direction is within about 10° to about 90° of the first direction, for example the second direction is within about 20° to about 90° of the first direction, the second direction is within about 30° to about 90° of the first direction, the second direction is within about 40° to about 90° of the first direction, or the second direction is within about 45° to about 90° of the first direction. In embodiments, the first direction is substantially parallel to the length of the pultruded plank and the second direction is within about 10° to about 90° of the first direction, for example the second direction is within about 20° to about 90° of the first direction, the second direction is within about 30° to about 90° of the first direction, the second direction is within about 40° to about 90° of the first direction, or the second direction is within about 45° to about 90° of the first direction. In embodiments, the second direction is substantially perpendicular to the first direction.

[0064] The channel pattern may be formed in the surface of the pultruded plank by grinding. For example, the channel pattern may be ground into the surface of the pultruded plank after formation of the pultruded plank.

[0065] In embodiments, the channel pattern ground into a surface of the pultruded plank comprises a first channel oriented in a first direction and a plurality of second channels oriented in a second direction. The first and second channels may be as described herein.

[0066] The channel pattern may be formed in the surface of the pultruded plank by shaping (or molding) the pultruded plank, for example shaping the pultruded plank by a pultrusion die to form a channel pattern in a surface of the pultruded plank. In embodiments, the pultrusion die is a shaped pultrusion die configured to form the channel pattern in the pultruded plank, and forming a channel pattern in a surface of the pultruded plank comprises shaping the pultruded plank to form a channel pattern in a surface of the pultruded plank.

[0067] The terms "substantially parallel" and "substantially perpendicular" used herein, may be used to refer to a direction oriented within about ±10° of the reference direction, for example about ±5° of the reference direction.

[0068] Examples of pultruded planks as described herein are shown in figures 1 and 2. The pultruded planks shown in figures 1 and 2 have an upper surface 2 comprising a channel pattern comprising a first channel 4 oriented in a first direction (the first direction being substantially parallel to the length of the pultruded plank) and a plurality of second channels 6 oriented in a second direction (the second direction being substantially perpendicular to the first direction). The depth D of one of the second channels 6 in the pultruded plank of figure 2 is shown on figure 2.

[0069] The channel pattern in the surface of the pultruded plank may have a depth which is at least about 10% of the thickness of the pultruded plank, for example at least about 20% of the thickness of the pultruded plank, or at least about 30% of the thickness of the pultruded plank. The channel pattern in the surface of the pultruded plank may have a depth which is up to about 80% of the thickness of the pultruded plank, for example up to about 75 %, up to about 70%, or up to about 65% of the thickness of the pultruded plank. The channel pattern in the surface of the pultruded plank may have a depth which is in the range of about 10% to about 80% of the thickness of the pultruded plank, for example about 20% to about 75%, or about 30% to about 70% of the thickness of the pultruded plank.

[0070] In embodiments, the or each channel oriented in the first direction may have the same or different depth as the or each channel oriented in the second direction. In embodiments, when the pattern comprises a plurality of channels oriented in a first direction, each of the channels may have the same depth or different depths. In embodiments, when the pattern comprises a plurality of channels oriented in a second direction, each of the channels may have the same depth or different depths.

[0071] The channel pattern in the surface of the pultruded plank may comprise a plurality of channels oriented in different directions. For example, the channel pattern in the surface of the pultruded plank may comprise a first channel oriented in a first direction, a second channel oriented in a second direction and a third channel oriented in a third direction wherein the first, second and third directions are all different to each other.

[0072] Also described herein is a stack of pultruded planks, the stack comprising a plurality of pultruded planks as described herein, wherein each of the plurality of pultruded planks is disposed directly on another of the plurality of pultruded planks. The stack of pultruded planks may comprise at least 2, at least 3, at least 4, or at least 5 pultruded planks. In embodiments in which the plurality of pultruded planks have only one surface comprising a channel pattern as described herein, the plurality of pultruded planks may be stacked such that a surface of a pultruded plank without a channel pattern is stacked facing a surface of another of the plurality of pultruded planks which comprises a channel pattern. The plurality of pultruded planks forming a stack as described herein may be stacked directly on one another such that at least one surface comprising a channel pattern as described herein is provided between each layer of the stack of pultruded planks. Stacking a plurality of pultruded planks in this way has been found to provide for improved resin flow between layers of pultruded planks.

[0073] Also described herein is a composite article comprising a stack of pultruded planks as described herein infused with resin. The plurality of pultruded planks of the composite article may be described as being stacked directly on one another, with resin infused between the pultruded planks. Also described herein is a method for producing a pultruded plank for reinforcing a wind turbine blade, the method comprising: drawing reinforcing fibers and a resin through a pultrusion die to form a pultruded plank; and forming a channel pattern into a surface of the pultruded plank.

[0074] A conventional pultrusion process and apparatus may be used to provide the pultruded plank onto which a pattern is ground.

[0075] The channel pattern may be formed in the surface of the pultruded plank by grinding a channel pattern in the surface of the pultruded plank after the pultruded plank exits the pultrusion die. The channel pattern may be ground into a surface of the pultruded plank using any suitable mean.

[0076] In embodiments, the method comprises cooling the pultruded plank exiting the pultrusion die to a temperature of less than about 200 °C, for example less than about 150 °C, or less than about 100 °C, before grinding the channel pattern into a surface of the pultruded plank.

[0077] In embodiments, the method comprises selecting a suitable channel pattern, for example a channel pattern as described above, and forming the channel pattern into a surface of the pultruded plank.

[0078] In embodiments, the pultrusion die may be a shaped pultrusion die configured to form a channel pattern in the surface (or each surface) of the pultruded plank. In embodiments, the pultrusion die has a surface with a wavy shape to form a channel pattern in the surface of the pultruded plank, the channel pattern comprising at least a first channel running along the length of the pultruded plank, or a plurality of first channels running along the length of the pultruded plank.

[0079] In embodiments, the method comprises shaping the pultruded plank to form a channel pattern in a surface of the pultruded plank. In embodiments, the pultruded plank may be shaped (or molded) by the pultrusion die to form the channel pattern.

[0080] Also described herein is a method of forming a wind turbine blade, the method comprising: providing a plurality of pultruded planks as described herein; stacking the pultruded planks directly on one another to form a stack; and infusing the stack with resin.

[0081] Examples The following illustrates examples of the fabrics and related aspects described herein. Thus, these examples should not be considered to restrict the present disclosure, but are merely in place to teach how to carry out the processes and obtain the products of the present disclosure.

[0082] Example 1

[0083] A pultruded plank was formed by drawing glass fibers and a thermosetting resin through a pultrusion die. A channel pattern as shown in figure 1 was ground into the surface of the pultruded plank. The pultruded plank had a thickness of around 3mm and the depth of the channels ground into the pultruded planks was about 1 mm. The channel pattern was made up of a first channel 4 and a plurality of second channels 6, the first channel running the length of the pultruded plank in a direction substantially parallel to the length of the plank and positioned in the centre of the plank, the second channels being regularly spaced and oriented substantially perpendicular to the direction of the first channel. The first and second channels had a U-shaped cross-section.

[0084] The present inventors expect that pultruded planks according to Example 1 may be stacked and infused with resin, the channel pattern guiding infusing resin between the pultruded planks and ensuring that the pultruded planks are adhered successfully such that a structural component formed from the pultruded planks has excellent mechanical properties and is not prone to delamination.

[0085] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0086] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0087] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations. Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0088] If a standard test is mentioned herein, unless otherwise stated, the version of the test to be referred to is the most recent at the time of filing this patent application. Throughout this specification, including the claims which follow, unless the context requires otherwise, the word "comprise" and "include", and variations such as "comprises", "comprising", and "including" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0089] It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means for example + / - 10%.

Claims

Claims1. A pultruded plank for reinforcing a wind turbine blade, the pultruded plank having a length, a width and a thickness and comprising reinforcing fibers and a resin, the pultruded plank having a surface comprising a channel pattern for guiding infusing resin, wherein the channel pattern comprises at least one first channel running the length of the pultruded plank and at least one second channel running across the width of the pultruded plank.

2. A pultruded plank according to claim 1, wherein the channel pattern comprises a plurality of first channels and / or a plurality of second channels.

3. A pultruded plank according to any of the preceding claims, wherein the channel pattern comprises channels having a depth in the range of about 0.5 mm to about 2mm.

4. A pultruded plank according to any of the preceding claims, wherein the channel pattern comprises channels having a width in the range of about 0.5 mm to about 2mm.

5. A pultruded plank according to any of the preceding claims, wherein the at least one first channel and the at least one second channel have a depth in the range of about 0.5 mm to about 2 mm.

6. A pultruded plank according to any of the preceding claims, wherein channels of the channel pattern have a width to depth ratio in the range of about 1.5:1 to about 1:1.5.

7. A pultruded plank according to any of the preceding claims, wherein the channel pattern comprises at least a first channel oriented in a first direction and a plurality of second channels, the second channels oriented in a second direction, wherein the second direction is within about 30° to about 90° of the first direction.

8. A pultruded plank according to any of the preceding claims, wherein the channel pattern comprises at least one first channel running the length of the pultruded plank, and a plurality of second channels running across the width of the pultruded plank, wherein the plurality of second channels are spaced from one another by about 0.1 cm to about 10 cm.

9. A pultruded plank according to any of the preceding claims, wherein the channel pattern comprises a plurality of first channels running the length of the pultruded plank, and a plurality of second channels running across the width of the pultruded plank, wherein the plurality of second channels are spaced from one another by a distance of about 0.5 cm to about 5 cm, and the plurality of first channels are spaced from one another by a distance of about 0.5 cm to about 10 cm.

10. A pultruded plank according to any of the preceding claims consisting essentially of reinforcing fibers and a thermoset resin.

11. A method for producing a pultruded plank for reinforcing a wind turbine blade, the method comprising: drawing reinforcing fibers and a resin through a pultrusion die to form a pultruded plank; and forming a channel pattern in a surface of the pultruded plank, wherein the channel pattern comprises at least one channel running the length of the pultruded plank, and a plurality of channels running across the width of the pultruded plank.

12. A method according to claim 11, wherein forming a channel pattern in a surface of the pultruded plank comprises grinding a channel pattern into a surface of the pultruded plank.

13. A method according to claim 11 or claim 12, wherein the pultrusion die is a shaped pultrusion die configured to form the channel pattern in the pultruded plank, and forming a channel pattern in a surface of the pultruded plank comprises shaping the pultruded plank to form a channel patter in a surface of the pultruded plank.

14. A stack of pultruded planks, the stack comprising a plurality of pultruded planks according to any of claims 1 to 10, wherein each of the plurality of pultruded planks is disposed directly on another of the plurality of pultruded planks.

15. A method of forming a wind turbine blade, the method comprising: providing a plurality of pultruded planks according to any of claims 1 to 10; stacking the pultruded planks to form a stack; and infusing the stack with resin.

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