Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly ("directly driven" or "gearless") or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

The wind turbine hub may be rotatably coupled to a front of the nacelle. The wind turbine hub may be connected to a rotor shaft, and the rotor shaft may then be rotatably mounted in the nacelle using one or more rotor shaft bearings arranged in a frame inside the nacelle. The nacelle is a housing arranged on top of a wind turbine tower that may contain and protect the gearbox (if present) and the generator (if not placed outside the nacelle) and, depending on the wind turbine, further components such as a power converter, and auxiliary systems.

In order to extract more energy from the wind, the size of the rotor diameter is increased by increasing the dimensions of the wind turbine blades. The larger size of the blades introduces higher physical loads into the blade and related components. Wind turbine rotor blades generally comprise a body shell formed by two shell halves of a composite material, e.g. glass fiber composites. The shell halves are generally manufactured using molding processes and then coupled together along the corresponding edges of the rotor blade. The body shell is relatively lightweight and has structural properties that are not designed to withstand all the bending moments and other loads acting on the blade during operation. To improve the structural properties of the rotor blade such as stiffness, strength and buckling resistance, the body shell is generally reinforced with structural components, e.g. spar caps at the suction and pressure sides of the blade with one or more shear webs connecting them. The spar caps may also be called "main laminate" or "spar cap laminate" of the wind turbine blade.

The spar caps can be manufactured using several materials such as glass fiber laminate composites and carbon fiber laminate composites. Modern spar caps may be manufactured using pultruded composites. Composites manufactured by pultrusion may have a constant cross-section that can be easily stacked to form a larger composite part. Therefore, a plurality of pultruded plates may be stacked and infused together in a mold to form a larger (i.e. longer, thicker, wider) composite part, e.g. a spar cap.

The spar cap may be manufactured "offline", i.e. the spar cap may be manufactured separately from the remainder of the blade. A stack of pultruded plates may be placed in a mold, which may subsequently be infused with a thermoset resin. The infused stack of plates forms the spar cap which is then to be joined to the shells of the wind turbine blade.

If a spar cap is damaged or defective, for example if it has cracks or delaminations, or if tolerances are not met, it is generally discarded and replaced by an entirely new spar cap. Resources dedicated to the manufacturing of the spar cap, including time and materials, are thus lost, and additional time, materials and manhours are needed to manufacture the new spar cap.

A defect may occur during the aforementioned offline manufacturing process of the spar cap, or after joining the spar cap to the shells of the blade. A defect may even occur during storage or transportation or use of a manufactured wind turbine blade.

<CIT> discloses a method for removing one or more pultrusion elements.

The present disclosure aims at reducing the need for replacing a spar cap which is damaged or defective.

In an aspect of the present disclosure, a method for removing one or more thermoset pultrusion elements from a spar cap for a wind turbine blade is provided. The spar cap comprises a plurality of thermoset pultrusion elements, each of the thermoset pultrusion elements being at least partially surrounded by a thermoplastic material. The method comprises heating a portion of thermoplastic material which surrounds, at least in part, a first thermoset pultrusion element. The method further comprises removing part or all of the heated portion of thermoplastic material; and removing at least a portion of the first thermoset pultrusion element.

According to this aspect, one or more thermoset pultrusion elements such as pultruded plates and stacks of pultruded plates, or one or more portions thereof, may be removed from a spar cap by heating and removing the thermoplastic material which surrounds them at least in part. Desired thermoset pultrusion elements may therefore be removed from a spar cap in a non-destructive manner, while maintaining the structural integrity of the remaining of the spar cap. New or same thermoset pultrusion elements may then be added to the spar cap for repairing it. Throwing away the defective spar cap and starting to build one from scratch may be avoided. Material, human and time resources may be more efficiently used. A relatively fast and easy repair process may be obtained.

In the prior art, such a repair is not known and is generally not even possible because thermoset resin is generally used for infusing a stack of pultruded plates when manufacturing the spar cap. If a defect occurs at any time during or after the resin infusion process, the spar cap in general always needs to be discarded entirely.

Throughout this disclosure, the term "thermoset pultruded plate" is generally used to define reinforced materials, e.g. fibers or woven or braided strands, that are impregnated with a thermoset material such as a thermoset resin and pulled through a heated die such that the thermoset material cures or undergoes polymerization. Such pultruded plates may be stacked to form a "stack of pultruded plates". The pultruded plates comprised in a stack of pultruded plates may have same or different dimensions. For instance, different pultruded plates may have different lengths and/or widths. A pultruded plate and a stack of pultruded plates are encompassed herein by the term "pultrusion element".

Throughout this disclosure, a thermoset material generally encompasses a plastic material or polymer that, once cured, cannot be easily remolded or returned to a liquid state. As such, after initial forming, thermoset materials are generally resistant to heat, corrosion, and/or creep. Examples of thermoset materials may generally include, but are not limited to, some polyesters, esters, or epoxies.

Throughout this disclosure, a thermoplastic material generally encompasses a plastic material or polymer that typically becomes pliable or moldable when heated to a certain temperature and solidify upon cooling. Further, thermoplastic materials may include amorphous thermoplastic materials and/or semi-crystalline thermoplastic materials.

For example, some amorphous thermoplastic materials may generally include, but are not limited to, styrenes, vinyls, cellulosics, polyesters, acrylics, polysulphones, and/or imides. More specifically, exemplary amorphous thermoplastic materials may include polystyrene, acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), glycolised polyethylene terephthalate (PET-G), polycarbonate, polyvinyl acetate, amorphous polyamide, polyvinyl chlorides (PVC), polyvinylidene chloride, polyurethane, or any other suitable amorphous thermoplastic material. In addition, exemplary semi-crystalline thermoplastic materials may generally include, but are not limited to polyolefins, polyamides, fluropolymer, ethyl-methyl acrylate, polyesters, polycarbonates, and/or acetals. More specifically, exemplary semi-crystalline thermoplastic materials may include polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polypropylene, polyphenyl sulfide, polyethylene, polyamide (nylon), polyetherketone, or any other suitable semi-crystalline thermoplastic material.

In a further aspect of the disclosure, a method for removing one or more thermoset pultrusion plates from a spar cap for a wind turbine blade is provided. The spar cap comprises a plurality of thermoset pultruded plates, the thermoset pultruded plates being separated by a thermoplastic material. The method comprises removing a top thermoset pultruded plate; heating and removing thermoplastic material surrounding a thermoset pultruded plate below the top thermoset pultruded plate; and removing the next thermoset pultruded plate.

Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

<FIG> illustrates a conventional modern upwind wind turbine <NUM> according to the so-called "Danish concept" with a tower <NUM>, a nacelle <NUM> and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub <NUM> and three blades <NUM> extending radially from the hub <NUM>, each having a blade root <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>.

The airfoil region <NUM>, also called the profiled region, has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region <NUM>, due to structural considerations, has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade <NUM> to the hub. The chord length of the transition region <NUM> typically increases with increasing distance from the hub. The width of the chord decreases with increasing distance from the hub.

The wind turbine blade <NUM> comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part <NUM> and a second blade shell part <NUM>, typically made of fiber-reinforced polymer. The wind turbine blade <NUM> may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part <NUM> is typically a pressure side or upwind blade shell part. The second blade shell part <NUM> is typically a suction side or downwind blade shell part. The first blade shell part <NUM> and the second blade shell part <NUM> are fastened together with adhesive, such as glue, along bond lines or glue joints <NUM> extending along the trailing edge <NUM> and the leading edge <NUM> of the blade <NUM>. Typically, the root ends of the blade shell parts <NUM>, <NUM> have a semi-circular outer cross-sectional shape.

<FIG> is a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade <NUM>, e.g. of the airfoil region <NUM> of the wind turbine blade <NUM>. The wind turbine blade <NUM> comprises a leading edge <NUM>, a trailing edge <NUM>, a pressure side <NUM>, a suction side <NUM>, a first spar cap <NUM>, and a second spar cap <NUM>. The wind turbine blade <NUM> comprises a chord line <NUM> between the leading edge <NUM> and the trailing edge <NUM>. The wind turbine blade <NUM> comprises shear webs <NUM>, such as a leading edge shear web and a trailing edge shear web. The shear webs <NUM> could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The spar caps <NUM>, <NUM> may comprise carbon fibers while the rest of the shell parts <NUM>, <NUM> may comprise glass fibers.

<FIG> is a schematic diagram illustrating an exemplary mold system for molding a blade shell of a wind turbine blade. The mold system <NUM> comprises a first mold <NUM> and a second mold <NUM>. The first mold <NUM> is configured for manufacturing a first blade shell part of a wind turbine blade, such as an upwind shell part of the wind turbine blade (forming the pressure side), and has a mold surface <NUM> for depositing fibers. The second mold <NUM> is configured for manufacturing a second blade shell part of the wind turbine blade, such as a downwind shell part of the wind turbine blade (forming the suction side), and has a mold surface <NUM> for depositing fibers.

In an aspect of the present disclosure, a method <NUM> for removing one or more thermoset pultrusion elements <NUM> from a spar cap <NUM>, <NUM> for a wind turbine blade <NUM> is provided. The spar cap <NUM>, <NUM> comprises a plurality of thermoset pultrusion elements <NUM> wherein each of the thermoset pultrusion elements <NUM> is at least partially surrounded by a thermoplastic material <NUM>. The method <NUM> is schematically shown in the flow chart of <FIG>.

The method comprises, at block <NUM>, heating a portion of thermoplastic material <NUM> which surrounds, at least in part, a first thermoset pultrusion element <NUM>. Any suitable heating tool <NUM> allowing selective heating may be used. For instance, a torch or a heater which may be moved over a spar cap may be used. In this way, a certain specific region of the thermoplastic material may be heated in a controlled manner. The method further comprises, at block <NUM>, removing part or all of the heated portion of the thermoplastic material. The method further comprises, at block <NUM>, removing at least a portion of the first thermoset pultrusion element <NUM>. The spar cap may be arranged in a spar cap mold in some examples. In other examples, the spar cap may be supported, held and/or secured by any suitable supporting or securing element such as cranes, cradles, conveyor belts and others. Lifting elements such as cranes or others may be used to remove one or more thermoset pultrusion elements.

Heating the portion of thermoplastic material may comprise heating a top or a bottom portion of the spar cap <NUM>. <FIG> schematically illustrates a cross-section of an example of a spar cap <NUM>. The spar cap <NUM> would extend lengthwise perpendicular to the plane of the figure. The spar cap <NUM> comprises four thermoset pultrusion elements <NUM>, e.g. carbon fiber reinforced thermoset pultrusion elements. In this example, the thermoset pultrusion elements <NUM> are pultruded plates <NUM>, e.g. carbon fiber reinforced pultruded plates. Each of the pultruded plates <NUM> is totally surrounded, in cross-section, by a thermoplastic material <NUM>. In this and other examples, the thermoplastic material <NUM> may e.g. comprise a thermoplastic reinforced prepeg. Specifically, at least a top surface and a bottom surface of each pultruded plate <NUM> is surrounded by thermoplastic material <NUM>. A heating tool <NUM> is used to heat a top portion of the spar cap. The thermoplastic material surrounding the top pultruded plate <NUM> is heated and at least a portion of it is removed. This allows access to the top pultruded plate <NUM>, which is also removed. The removal of the top pultruded plate <NUM> is schematically represented in <FIG>. The remaining spar cap keeps its structural integrity.

A spar cap may comprise more or less than four pultruded plates in other examples. If necessary, one or more of the remaining pultruded plates <NUM> may be removed in the same way, by heating and removing a suitable amount of thermoplastic material <NUM>, e.g. from top to bottom. In this and other examples, it may also be possible to remove the bottom pultruded plate <NUM> first, and then if required, to remove one or more further pultruded plates <NUM> from bottom to top.

Even though in all the depicted examples the pultruded plates <NUM> are shown as thin, wide and long plates which are stacked on top of each other, it is noted that this is done for illustration purposes only. in any of the depicted examples, a single pultruded plate <NUM> may in reality comprise a plurality of pultruded plates or "strips" next to each other. Each pultruded plate or strip may, in cross-section, have e.g. a width between <NUM> and <NUM>, and a height between <NUM> and <NUM>.

In the example of <FIG>, instead of removing the entire top pultruded plate, it may be possible to remove only a portion of the top pultruded plate. An example of this is schematically illustrated in <FIG>. In this example, the top pultruded plate <NUM>, or a portion thereof, may be exposed by heating and removing thermoplastic material <NUM>. A first portion <NUM> of the pultruded plate, e.g. a damaged portion, may be separated from the pultruded plate and removed. The location and size of the portion <NUM> to be separated may for instance depend on the extent of the damage of the top pultruded plate <NUM>. Separation may be performed by cutting, sawing or other. A second portion <NUM> of the pultruded plate may remain as part of the spar cap <NUM>. The removal of a portion <NUM> of a pultruded plate <NUM> is applicable in general to any pultruded plate. For instance, a portion of the bottom pultruded plate <NUM> or of other pultruded plate <NUM> may be removed. In general, a portion of a pultrusion element <NUM> may be removed. For instance, a portion of a pultruded stack <NUM> of pultruded plates may be cut away and removed.

<FIG> schematically illustrates a cross-section of another example of a spar cap <NUM>. The spar cap <NUM> comprises two pultrusion elements <NUM>. In this example, the pultrusion elements <NUM> are stacks of pultruded plates <NUM>. Each stack <NUM> may comprise a plurality of pultruded plates which were previously molded together using a thermoset resin.

Each stack <NUM> is completely surrounded, in cross-section, by a thermoplastic material <NUM>. In this example, each stack of pultruded plates <NUM> comprises four pultruded plates <NUM>. Each plate of the stack is adjacent to at least another plate of the stack. The thermoplastic material surrounding the top stack of pultruded plates <NUM> may be heated and at least a portion of it may be removed. This allows access to the top stack of pultruded plates <NUM>, which may be removed. A stack of pultruded plates <NUM> may comprise more or less than four pultruded plates in other examples. In this and in other examples, a spar cap <NUM> may comprise stacks of pultruded plates <NUM> with a same or a different number of plates. All the stacks <NUM> of the spar cap <NUM> may comprise a same number of pultruded plates, or one or more stacks may have a different number of pultruded plates. Similarly to the example of <FIG>, it may be possible to remove a bottom stack of pultruded plates <NUM> first.

In some examples, the method may comprise, before heating the portion of the thermoplastic material, removing a second thermoset pultrusion element <NUM>. The second thermoset pultrusion element may be removed in different ways. In some examples, see e.g. <FIG> and <FIG>, the second thermoset pultrusion element may be a top <NUM> or a bottom <NUM> thermoset pultrusion element and the first thermoset element may be below or above, e.g. immediately below or above, the second thermoset pultrusion element <NUM>, <NUM>, respectively.

<FIG> schematically illustrates a cross-section of another example of a spar cap <NUM>. The spar cap <NUM> comprises four pultrusion elements. In this example, the pultrusion elements are pultruded plates <NUM>. A top surface and a bottom surface of the middle pultruded plates <NUM>, <NUM>, i.e. the pultruded plates between the top <NUM> and the bottom <NUM> pultruded plates, is surrounded by thermoplastic material <NUM>. A top surface of the top pultruded plate <NUM> and a bottom surface of the bottom pultruded plate <NUM> are not surrounded by thermoplastic material <NUM> in this example.

In the example of <FIG>, removal of the second thermoset pultrusion element <NUM> may be performed by scarfing. Scarfing may be understood herein as an abrasive process in which a thermoset element <NUM> may be thinned and ultimately disintegrated. Suitable tools for scarfing may include for example grit wheels, grind wheels and sand paper. The top pultruded plate <NUM> may therefore be scarfed, e.g. grinded, and the next pultruded plate <NUM> be removed after heating and removing at least part of the thermoplastic material <NUM> surrounding the plate <NUM>. In other examples, the pultruded plates of <FIG> may be stacks of pultruded plates. Scarfing of an external thermoset pultrusion element such as the top pultruded plate <NUM> of <FIG> may also be performed in other examples. In some of these examples, both scarfing and heating a thermoplastic material <NUM> may be performed to remove an external thermoset pultrusion element.

As the external thermoset pultrusion elements <NUM>, <NUM> are easier to access than the middle thermoset pultrusion elements <NUM>, <NUM>, using a thermoplastic material <NUM> to cover the top and bottom surfaces of the middle thermoset pultrusion elements <NUM>, <NUM> may help to remove them faster and more easily. Using a thermoplastic material <NUM> to also cover the top and the bottom surfaces of an external pultrusion element <NUM>, <NUM> may further help to ease and speed the process of separation of one or more external thermoset pultrusion elements <NUM>, <NUM> from a spar cap <NUM>, <NUM> as processes such as grinding may be avoided.

The second thermoset pultrusion element may also be removed in a similar manner as the first thermoset pultrusion element. In the example of <FIG>, the first and second thermoset pultrusion elements may be e.g. any two pultruded plates <NUM> next to each other. , the first thermoset element may be above or below the second thermoset pultrusion element. The second thermoset pultrusion element may e.g. be the top pultruded plate <NUM> and the first thermoset pultrusion element may e.g. be the top middle pultruded plate <NUM>. Removing the second pultrusion element may therefore comprise heating a portion of thermoplastic material which surrounds, at least in part, the second thermoset pultrusion element, and removing part or all of the heated portion of the thermoplastic material <NUM>.

In some examples, the plurality of thermoset elements <NUM> may be arranged in two or more columns. In some of these examples, the first thermoset element may be removed from a first column, and the second thermoset element may be removed from the same first column. <FIG> schematically illustrates another example of a cross-section of a spar cap <NUM> comprising a plurality of pultruded plates <NUM>. In this example, the pultruded plates are arranged in two columns <NUM>, <NUM> and in a plurality of rows (there are <NUM> rows in the example of <FIG>). The first thermoset element may e.g. be the pultruded plate of the second row (starting from the top) and the left column <NUM>, and the second thermoset element may e.g. be the top pultruded plate of the left column <NUM>.

In other examples, the first thermoset pultrusion element may be removed from a first column, and the second thermoset pultrusion element may be removed from a second different column. For instance, in <FIG>, the first thermoset pultrusion element may e.g. be the top pultruded plate of the left column <NUM> and the second thermoset pultrusion element may e.g. be the top pultruded plate of the right column <NUM>.

In general, the first and second thermoset pultrusion elements may be any two thermoset pultrusion elements of a spar cap that are to be removed. They may be next to each other e.g. vertically or laterally, or there may be one or more other thermoset pultrusion elements between them.

<FIG> schematically illustrates another example of a cross-section of a spar cap <NUM>. In this example, the thermoset pultrusion elements <NUM> are stacks <NUM> of pultruded plates. The spar cap <NUM> comprises two rows <NUM>, <NUM> and three columns <NUM>, <NUM>, <NUM> of stacks <NUM> of pultruded plates.

In examples where the plurality of thermoset pultrusion elements <NUM> is arranged in two or more columns, e.g. in <FIG>, the first column, e.g. column <NUM> in <FIG>, may be removed in a single operation. This may mean that a certain column, e.g. an external column, is removed at once, instead of removing the thermoset pultrusion elements <NUM> of the column at different times. For instance, in the example of <FIG>, the left column <NUM> may be removed entirely before start to remove a stack <NUM> from the other columns. Removal of thermoset pultrusion elements may be performed column by column of thermoset pultrusion elements in some examples. This may accelerate the removal process. If the first and second thermoset pultrusion elements are in a same column, this column may be removed in a single operation. If the first and second thermoset pultrusion elements are in a different column, each of the columns may be removed in a single operation, or if the columns are adjacent, both columns may be removed at once, in a single operation.

In examples where the plurality of thermoset pultrusion elements <NUM> is arranged in two or more rows, e.g. in <FIG>, one or more rows may be removed in a single operation. For instance, in the example of <FIG>, the top row may be removed entirely before start to remove a pultruded plate <NUM> from the other rows of to remove another row. The first and the second thermoset pultrusion elements <NUM> may be in a same row or in different rows. The row comprising the first thermoset pultrusion element may be removed in a single operation, and the row comprising the second thermoset pultrusion element may be remove in a single operation. If both rows are adjacent, the two rows may be removed together in a single operation. Removal of thermoset pultrusion elements may be performed row by row of thermoset pultrusion elements. Depending on the configuration, e.g. number and arrangement, of the thermoset pultrusion elements, removing row by row or column by column may be appropriate. In other examples, different strategies for removing thermoset pultrusion element may be used.

In some examples, the method may further comprise adding one or more thermoset pultrusion elements <NUM> and/or one or more portions of thermoset pultrusion elements to the spar cap <NUM>, <NUM>, and joining them to the spar carp by using a thermoplastic material. If a portion of a thermoset pultrusion element is added, it may be further joined to a corresponding portion of a thermoset pultrusion element of the spar cap, e.g. by gluing or in any suitable manner. In this way, after removing one or more thermoset pultrusion elements <NUM> or portions thereof, the same and/or new thermoset pultrusion elements may be added and joined to the spar cap for manufacturing a spar cap with the desired specifications and properties. If a thermoset pultrusion element or a portion thereof is damaged, it may be replaced. If there are thermoset pultrusion elements that are not damaged, but they needed to be removed e.g. for accessing damaged thermoset pultrusion elements or for adjusting their position, the same thermoset pultrusion elements may be used. In this way, at least a portion of the existing spar cap may still be used, and less materials and time may be wasted than if a new spar cap needs to be built.

Depending on the type of spar cap, this step may be performed in different ways. For example, the thermoset pultrusion elements <NUM> and the thermoplastic material <NUM> may be added into a spar cap mold and cured. In other examples, a thermoset pultrusion element may be at least partially surrounded with the thermoplastic material, thereby forming a block, and it may be joined to another block via thermoplastic welding. Using other ways of adding and joining thermoset pultrusion elements and thermoplastic material to the spar cap may be possible.

Method <NUM> may be used while a spar cap <NUM>, <NUM> is being manufactured, for example if a defect or problem is detected already before finishing the spar cap, or after its manufacture, e.g. after a defect of problem is detected once the spar cap has been removed from its mold. Method <NUM> may also be used after the spar cap has been assembled with a shell of a wind turbine blade, e.g. after a wind turbine blade <NUM> of a wind turbine has been damaged. One or more spar caps of the damaged wind turbine blade may be recovered and refurbishes may be processed as explained herein for using them in wind turbine blades. The method may further comprise removing a portion of the shell of the wind turbine blade.

In some examples, the method may further comprise determining that the spar cap <NUM>, <NUM> includes one or more defects before starting to remove one or more thermoset pultrusion elements <NUM> from the spar cap. Determining the presence of one or more defects may include detecting cracks, delaminations, erosion, distortion, unsuitable positioning of one or more thermoset pultrusion elements, or others. Determination may occur in one or more of a manufacturing site, a wind farm site and during transportation.

Therefore, although in the illustrated examples in <FIG> the spar cap has been shown as a separate unit, i.e. not attached to other wind turbine blade components such as a shell of the wind turbine blade, it should be clear that similar methods may be used at later stages. For example, if a defect occurs or is detected after joining the spar cap to a shell of a wind turbine blade, in the prior art the whole assembly would normally be discarded. However, using examples of the methods and systems disclosed herein, part of the spar cap or blade assembly may be salvaged. A defect may even occur or be noticed after storage or during transportation. In some examples, repair may require removing part of a blade shell or substituting part of a blade shell.

In a further aspect of the disclosure, a method <NUM> for removing one or more thermoset pultruded plates <NUM> from a spar cap <NUM>, <NUM> for a wind turbine blade <NUM> is provided. The spar cap comprises a plurality of thermoset pultruded plates <NUM> separated by a thermoplastic material <NUM>. Method <NUM> is illustrated in the flow chart of <FIG>. This method may be applied for example to the spar caps of <FIG>, <FIG>, <FIG>. The description and explanations of the spar caps <NUM>, <NUM> and pultruded plates <NUM> regarding method <NUM> also apply to method <NUM>, and vice versa.

The method comprises, at block <NUM>, removing a top thermoset pultruded plate. The top thermoset pultruded plate may be removed by grinding in some examples. If the top pultruded plate is surrounded by a thermoplastic material <NUM>, the top thermoset pultruded plate may be removed by heating and removing the thermoplastic material <NUM> surrounding the top thermoset pultruded plate.

The method further comprises, at block <NUM>, heating and removing thermoplastic material surrounding a thermoset pultruded plate below the top thermoset pultruded plate. The method further comprises, at block <NUM>, removing the next thermoset pultruded plate, i.e. the plate that was below the top thermoset pultruded plate.

Once the necessary thermoset pultruded plates have been removed, the necessary thermoset pultruded plates, e.g. new thermoset pultruded plates, may be added to the spar cap. The method may further comprise completing the spar cap by joining missing thermoset pultruded plates to the spar cap by using thermoplastic material <NUM>.

The spar cap <NUM>, <NUM> may be repaired after having detected a defect in the spar cap upon its manufacturing.

Claim 1:
A method (<NUM>) for removing one or more thermoset pultrusion elements (<NUM>) from a spar cap (<NUM>, <NUM>) for a wind turbine blade (<NUM>), the spar cap (<NUM>, <NUM>) comprising a plurality of thermoset pultrusion elements (<NUM>) wherein each of the thermoset pultrusion elements is at least partially surrounded by a thermoplastic material (<NUM>), the method comprising:
heating (<NUM>) a portion of thermoplastic material (<NUM>) which surrounds, at least in part, a first thermoset pultrusion element (<NUM>);
removing (<NUM>) part or all of the heated portion of thermoplastic material (<NUM>); and
removing (<NUM>) at least a portion of the first thermoset pultrusion element (<NUM>).