Pultruded stringers, spar caps, wind turbine blades and pultrusion manufacturing processes

Abstract

A pultruded strip, a spar cap, a wind turbine blade and a pultrusion manufacturing process are disclosed. The pultruded strip comprises a pultruded core and a coated interface layer. The pultruded core is made of reinforcing fibers impregnated with a core resin. The interface layer is made of an interface resin present on at least one surface of the pultruded core, the interface layer allowing the pultruded strip to be wound for packaging after manufacture, the interface resin comprising an isocyanate resin and a polyester resin, and the mass ratio of the isocyanate resin to the polyester resin being 1:3 to 2:3. The interface layer forms a tacky surface on the pultruded strip, the tacky surface being used to form a bond between at least two pultruded strips.

Description

Technical Field

[0001] This application relates to the field of composite materials technology, and more specifically to a pultruded slat, a spar cap, a wind turbine blade, and a pultrusion manufacturing process. Background Technology

[0002] Pultruded slats are typically fiber-reinforced resin composites. For example, pultruded slats can be glass fiber or carbon fiber reinforced composite slats. The structural reinforcing fibers extend along the length of the slat, giving it high tensile strength and consequently high load-bearing capacity. Such slats can be stacked and bonded together by resin infusion to form laminated assemblies with structural properties suitable for reinforcing wind turbine blades, such as wing spars.

[0003] However, pultrusion typically results in slats with very smooth bonded surfaces, making them difficult to bond firmly. Furthermore, when slats are stacked, their smooth surfaces adhere tightly to each other, leaving virtually no gaps for resin to penetrate between adjacent slats.

[0004] Therefore, the surface of the slats usually needs to be treated before they are bonded together, such as by sanding to roughen the surface. However, this sanding often damages the reinforcing fibers near the surface, affecting the mechanical properties of the slats.

[0005] Another approach involves applying a release layer to the surface of the slats. This release layer is removed before stacking the slats, creating a rough bonded surface. However, this release layer introduces several drawbacks. For instance, during pultrusion, the release layer may become entangled in the pultrusion die, affecting the production process and increasing pultrusion costs. Furthermore, removing the release layer can damage the fibers and affect the slats' mechanical properties. Additionally, the extra release layer increases product costs, leading to higher production costs for downstream products such as spar caps.

[0006] Therefore, there is a need for a pultruded slat, spar cap, wind turbine blade, and pultrusion manufacturing process to at least partially solve the above problems. Summary of the Invention

[0007] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. This summary section is not intended to limit the key and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0008] To at least partially address the aforementioned problems, a first aspect of this application provides a pultruded slat for a spar cap on a wind turbine blade, the pultruded slat comprising:

[0009] A pultruded core, the pultruded core being made of reinforcing fibers impregnated with a core resin, the reinforcing fibers including glass fibers and / or carbon fibers;

[0010] The coated interface layer is made of an interface resin present on at least one surface of the pultruded core, the interface layer allowing the pultruded strip to be wound and packaged after manufacturing, the interface resin containing isocyanate resin and polyester resin, and the mass ratio of the isocyanate resin to the polyester resin is 1:3 to 2:3.

[0011] The surface of the interface layer forms a bonded surface on the pultruded strip, and the bonded surface is used to form an adhesive surface between at least two pultruded strips.

[0012] According to the pultruded slats of this application, without affecting the winding and packaging, a sanding-free interface layer is provided, which will not cause damage to the reinforcing fibers, thus ensuring that the pultruded slats do not lose their mechanical properties; and in the lamination and injection process for forming the spar cap, they can be directly stacked and injected without the need for additional slat surface activation treatment, and the use of consumables such as release cloth is eliminated, reducing production costs.

[0013] The pultruded core is formed by dragging reinforcing fibers impregnated with the core resin through a pultrusion die and heating and curing them.

[0014] The interface layer is obtained by coating the interface resin onto at least one surface of the pultruded core through roller coating, brush coating, spray coating or injection molding process and then hardening it.

[0015] The bonded surface, without sanding, can be used to form the bonding surface between at least two pultruded strips bonded with the injection resin during the process of forming the spar cap by stacking at least two pultruded strips and through a lamination injection process.

[0016] Furthermore, the interface layer is formed by a glue injection mold process. Along the dragging direction, the glue injection mold is located downstream of the pultrusion mold. The glue injection mold has an inlet, an outlet, and a glue injection port disposed between the inlet and the outlet. The height dimension of the cavity in the glue injection mold gradually decreases along the dragging direction, so that the outlet dimension of the glue injection mold can limit the interface layer to have a predetermined thickness.

[0017] The pultruded core is pulled into the injection mold from the inlet, receives the interface resin through the injection port, and is then pulled through the outlet to form an ungelled interface layer of the predetermined thickness on the surface of the pultruded core. According to the above configuration, forming the interface layer using the injection mold enables continuous production and direct formation of an interface layer of the predetermined thickness, resulting in high efficiency and uniform interface layer thickness.

[0018] Furthermore, before the pultruded strip is wound and packaged, the interface layer is heated to a temperature greater than 100°C by a supplementary heating device to harden the interface layer and prevent the interface layer from sticking together during winding and packaging.

[0019] In this configuration, the supplementary heating device is located downstream of the injection mold along the dragging direction. This arrangement ensures that the interface layer forms a hardened surface before winding and packaging, preventing adhesion between the pultruded strips after winding and improving product quality.

[0020] Furthermore, the surface of the interface layer is textured, and the texture is formed by a texture application device before the interface layer gels. The texture application device is located between the injection mold and the supplementary heating device, and includes a scraper or stamp with a textured shape. According to the above configuration, the texture not only improves the surface roughness, thereby improving the interlayer adhesion, but also serves as a flow channel for the injection resin during lamination injection, thus ensuring that the injection resin fully impregnates and wets the pultruded slab and fiber fabric layers.

[0021] Furthermore, the texture can be constructed in the form of irregular stripes, grids, or scattered dots. According to this scheme, the choice of texture is diverse, offering a high degree of design freedom.

[0022] Further, the predetermined thickness of the interface layer is 0.02-0.2 mm; and / or

[0023] The thickness of the texture is the same as the predetermined thickness of the interface layer. According to the above setting, the thickness of the texture can be freely selected; having the texture with the same thickness as the interface side further improves the roughness and allows the infused resin to bond simultaneously to both the interface layer and the pultruded core, thereby also improving the reliability of the bonding.

[0024] Furthermore, the mass ratio of the isocyanate resin to the polyester resin is 1:3 to 1:2.

[0025] Further, the isocyanate resin comprises diphenylmethane diisocyanate; and / or

[0026] The polyester resin comprises bisphenol A type polyester resin and a reaction accelerator.

[0027] The second aspect of this application provides a spar cap for a wind turbine blade, the spar cap comprising the pultruded slats described in the first aspect above.

[0028] The wing cap according to this application has the above-mentioned pultruded slats, and therefore can achieve a similar technical effect to the pultruded slats of the first aspect.

[0029] A third aspect of this application provides a wind turbine blade comprising the pultruded slats described in the first aspect, or the spar cap described in the second aspect.

[0030] The wind turbine blade according to this application has the above-mentioned pultruded slats or the above-mentioned spar cap, and therefore can achieve a similar technical effect to the pultruded slats of the first aspect.

[0031] A fourth aspect of this application provides a pultrusion process for manufacturing pultruded strips for spar caps of wind turbine blades, wherein at least two pultruded strips are stacked and formed into the spar caps by a lamination casting process, the pultrusion process comprising:

[0032] In the core forming step, the reinforcing fiber is impregnated with core resin and then dragged through a pultrusion mold and heated to cure, forming the pultruded core of the pultruded strip;

[0033] The step of forming an interface layer involves coating an interface resin onto at least one surface of the pultruded core using a molding process, and defining the interface layer to have a predetermined thickness before gelation. The interface layer, after curing, allows the pultruded strip to be wound and packaged. The interface layer defines the bonded surface of the pultruded strip. The interface resin contains isocyanate resin and polyester resin, and the mass ratio of the isocyanate resin to the polyester resin is 1:3 to 2:3.

[0034] The winding step involves winding and packaging the pultruded strip after the interface layer has hardened.

[0035] According to the pultrusion process of this application, a non-grinding interface layer bonding surface can be formed without affecting the winding and packaging, and the bonding surface will not cause damage to the reinforcing fibers, thereby ensuring that the pultruded strips do not lose mechanical properties. Furthermore, the pultruded strips formed by this pultrusion process can be directly stacked and injected in the lamination and injection process for forming the spar cap, without the need for additional strip surface activation treatment, and the use of consumables such as release cloth is eliminated, reducing production costs.

[0036] Furthermore, the step of forming the interface layer further includes: applying a texture to the surface of the interface layer after the interface layer has a predetermined thickness and before the interface layer gels. According to the above configuration, the roughness of the interface layer can be increased, thereby improving the interlayer bonding force, and also allowing the resin to be fully filled between adjacent interface layers during lamination and infusion.

[0037] Furthermore, the step of forming the interface layer also includes: supplementing the pultruded strip with additional heating before winding and packaging, wherein the additional heating temperature is greater than 100°C. According to the above settings, the interface layer can form a hardened surface, preventing the pultruded strips from sticking together during winding. Attached Figure Description

[0038] The following drawings, which are incorporated herein by reference and are used to understand this application, illustrate embodiments of the invention and their descriptions to explain the principles of the invention.

[0039] In the attached image:

[0040] Figure 1 This is a schematic diagram of a wind turbine blade structure according to one embodiment of this application;

[0041] Figure 2 This is a schematic diagram of the structure of a pultruded strip according to one embodiment of this application;

[0042] Figure 3 This is a schematic diagram of the texture of a pultruded strip according to one embodiment of this application;

[0043] Figure 4 This is a schematic diagram of the preparation process of a pultruded slab according to one embodiment of this application;

[0044] Figure 5 for Figure 4 A schematic diagram of the injection mold section;

[0045] Figure 6 A schematic flow diagram of a pultrusion preparation process according to one embodiment of this application; and

[0046] Figure 7 A more detailed flow diagram of the pultrusion preparation process according to one embodiment of this application; and

[0047] Figure 8 This is a schematic diagram illustrating a lamination casting process for a pultruded slab according to one embodiment of this application.

[0048] Explanation of reference numerals in the attached figures:

[0049] 10: Wind turbine blade 11: Windward casing 12: Leeward casing

[0050] 13: Mezzanine area; 14: Shear beam; 20: Wing beam cap

[0051] 100: Pultruded slab; 110: Pultruded core; 111: Fiber

[0052] 120: Interface layer 1: Fiber yarn bundle 2: Core resin tank

[0053] 3: Pultrusion die; 4: Injection die; 5: Texture application device

[0054] 6: Supplementary heating device; 7: Traction machine 100R: Pultruded slab coil

[0055] 41: Inlet; 42: Outlet; 43: Glue Inlet

[0056] 15: Shell fabric; 8: Flow guiding fabric Detailed Implementation

[0057] The following description provides numerous specific details to offer a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with this application.

[0058] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof.

[0059] The ordinal numbers such as “first” and “second” used in this application are merely identifiers and have no other meaning, such as a specific order. Furthermore, for example, the term “first component” does not imply the existence of a “second component,” and the term “second component” does not imply the existence of a “first component.” It should be noted that the terms “upper,” “lower,” “front,” “back,” “left,” “right,” “inner,” “outer,” and similar expressions used herein are for illustrative purposes only and are not intended to be limiting.

[0060] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings.

[0061] like Figure 1As shown, this application provides a wind turbine blade 10, which typically has an outer shell composed of two half-shells (such as a windward shell 11 and a leeward shell 12). Each half-shell may have a sandwich region 13 and a non-sandwich region 13. The sandwich region 13 includes a skin layer made of fiber-reinforced resin composite material (such as glass fiber reinforced plastic) and a lightweight foam core (such as a polyurethane foam core) sandwiched between the two skin layers.

[0062] A spar cap 20 can be installed in the non-mezzanine region 13, i.e., the spar cap 20 is arranged between the two mezzanine regions 13. Furthermore, the spar cap 20 can form an integral unit with the mezzanine region 13. The spar cap 20 on the windward shell 11 and the spar cap 20 on the leeward shell 12 are arranged opposite each other, and a shear beam 14 is preferably provided between them. The shear beam 14 and the spar caps 20 on the two half-shells form an I-shaped structure, thereby effectively transferring the load from the wind turbine blades 10 to the wind turbine hub. The spar cap 20 can transfer tensile and compressive bending loads, while the shear beam 14 can transfer shear stress.

[0063] The spar cap 20 is made of several stacked pultruded slats 100. (Reference) Figure 8 For example, multiple pultruded slats 100 can be stacked, spliced, and bundled together to form a prefabricated assembly of an integral or partial spar cap 20. During stacking, fiber guiding fabric 8 is laid between the slat layers, and a shell fabric 15 is laid on the outermost layer. The shell fabric 15 can be made of the same material as the skin layer of the interlayer region 13, or the two can be integrated. The prefabricated slats and other components for making the blade are placed together in a casting mold. Then, by applying a vacuum to the mold and injecting infusion resin, the vacuum pressure fills the gaps between the slat layers and between the parallel spliced ​​slats with the infusion resin. Subsequently, the spar cap 20 is formed by curing the infusion resin.

[0064] It should be noted that several pultruded slats 100 can be stacked first and infused with resin, allowing the resin to cure and form a finished spar cap 20. Then, the finished spar cap 20 is placed into a mold for half a wind turbine blade (or half shell) and infused with resin, filling the gaps between the spar cap 20 and other components and the fiber layers of the outer shell with resin. Subsequently, the infused resin is cured to form half a blade.

[0065] Alternatively, the pultruded slats 100 and other components can be fixed into prefabricated components, and then resin can be injected during the overall blade fabrication to form a complete half-blade.

[0066] The above-mentioned pultruded slab 100 can be used as a reference. Figures 2 to 5The pultruded slat 100 includes a pultruded core 110 and an interface layer 120. The interface layer 120 is located on at least one surface of the pultruded core 110 to define a bonded surface of the pultruded slat 100. This bonded surface, without sanding, can be used to form an adhesive surface between at least two pultruded slats bonded to the injection resin during the formation of the spar cap 20 by the aforementioned lamination injection process.

[0067] The pultruded core 110 includes a core resin and fibers 111 disposed within the core resin. The pultruded core 110 is manufactured by dragging the fibers 111 impregnated with the core resin through a pultrusion die 3 and heating and curing them in the pultrusion die 3.

[0068] The interface layer 120 is composed of an interface resin, which is a curable resin that is fluid before curing and has a dry, hardened surface after curing. Preferably, the interface resin can be a compound resin. Since the pultruded core 110 produced by the pultrusion die 3 can be partially or nearly fully cured, a low-viscosity, high-polarity, and high-flexibility primer resin can be selected as the interface layer to ensure the adhesion between the interface resin and the core.

[0069] The interface layer 120 is obtained by applying an interface resin to at least one surface of the pultruded core 110 via roller coating, spraying, brushing, or injection molding and then curing it. The interface layer 120 is defined to have a predetermined thickness of 0.02-0.2 mm, preferably 0.03-0.09 mm, before gelation or before curing, and the interface layer 120, after curing, allows the pultruded slab 100 to be wound and packaged. The surface of the cured interface layer 120 forms the bonded surface of the pultruded slab 100. The thickness of the cured interface layer 120 is 0.02-0.2 mm, preferably 0.03-0.09 mm. Optionally, the predetermined thickness can be defined by the wire rod roller coating or the exit size of the injection mold 4.

[0070] According to the pultruded slats 100 of this application, without affecting the winding and packaging, a sand-free interface layer 120 is provided on the bonding surface, which will not cause damage to the reinforcing fibers, thereby ensuring that the pultruded slats 100 do not lose their mechanical properties; and in the lamination and injection process for forming the wing cap 20, they can be directly stacked and injected without the need for additional slat surface activation treatment, and the use of consumables such as release cloth is eliminated, reducing production costs.

[0071] As one implementation, the surface of the interface layer 120 can be a rough surface. For example, a texture can be formed on the surface of the interface layer 120. This not only improves adhesion through higher surface roughness but also provides flow channels for the injection resin through the gaps created by the texture, allowing the injection resin to fill the spaces between the pultruded strips 100. Optionally, the texture can be irregularly striped, grid-like, or dotted. For example, Figure 3 Image (a) shows a striped texture. Figure 3 (b) shows a scattered texture.

[0072] Furthermore, the texture thickness can be 0.02-0.2 mm, preferably 0.03-0.09 mm. Specifically, the texture thickness can be less than the thickness of the interface layer 120. Alternatively, the texture thickness can be the same as the predetermined thickness of the interface layer 120, that is, by applying the texture, the surface of the pultruded core 110 can be exposed. In this way, not only is the roughness further improved, but the infused resin can also bond to both the interface layer 120 and the pultruded core 110 simultaneously, thereby improving the reliability of the bonding.

[0073] For the specific preparation process of pultruded slab 100, please refer to [reference needed]. Figure 4 The pultruded core 110 is formed by the pultrusion process. First, the fiber 111 is drawn from the fiber yarn 1 using the traction machine 7 and passed through the resin tank 2 to impregnate the core resin. Then, after being heated by the pultrusion mold 3, the core resin is cured to form the pultruded core 110.

[0074] Subsequently, the pultruded core 110 is further dragged by the traction machine 7 to the injection mold 4 located downstream of the pultrusion die 3 to perform the injection molding process and form an uncured or ungelled interface layer 120 of a predetermined thickness. Reference Figure 5 The injection mold 4 has an inlet 41, an outlet 42 and an injection port 43 disposed between the inlet 41 and the outlet 42, and the height dimension of the cavity in the injection mold 4 gradually decreases along the dragging direction, so that the size of the outlet 42 of the injection mold 4 can limit the predetermined thickness of the interface layer 120.

[0075] In this way, the pultruded core 110 is pulled into the injection mold 4 from the inlet 41, receives the interface resin through the injection port 43, and is then pulled through the outlet 42, thus forming an uncured or ungelled interface layer 120 of predetermined thickness on the surface of the pultruded core 110. Using the injection mold 4 to form the interface layer 120 enables continuous production and direct formation of the interface layer 120 of predetermined thickness, resulting in high efficiency and uniform thickness of the interface layer 120.

[0076] The aforementioned traction machine 7 can be positioned between the injection mold 4 and the pultrusion mold 3, or downstream of the injection mold 4 or at the very downstream end of the production line. Figure 4 In the illustrated embodiment, the traction machine 7 is positioned between the injection mold 4 and the pultrusion mold 3. Therefore, the power source for the forward movement of the slats downstream of the traction machine 7 can be a winding and packaging device.

[0077] Next, the pultruded core 110 with the interface layer 120 applied is dragged to the texture application device 5 located downstream of the injection mold 4, and the texture application device 5 is used to apply texture to the uncured or ungelled interface layer 120. Optionally, the texture application device 5 includes a squeegee or stamp with a texture shape (such as irregular stripes, grids, or scattered dots as described above).

[0078] Next, the pultruded core 110 is dragged to the supplementary heating device 6 located in the texture application device 5. In one example, since the interface layer 120 requires 5-30 minutes to harden at room temperature, in order to improve production efficiency and avoid adhesion in subsequent processes, the supplementary heating device 6 can be used to apply a temperature greater than 100°C to the interface layer 120 for supplementary heating, so that the interface layer 120 hardens to have a non-sticky hardened surface. The supplementary heating device 6 can be an oven or a heating lamp.

[0079] The pultruded slab is then dragged to the downstream winding and packaging device to form a pultruded slab roll 100R for easy transport and use. Since the surface of the interface layer 120 has been hardened, the interface layer 120 will not stick together during winding.

[0080] In a preferred embodiment, fiber 111 can be a continuous fiber such as glass fiber, polyester fiber, or carbon fiber. The core resin can be at least one of commercially available or homemade epoxy resin, vinyl ester resin, or polyurethane resin, and the interface resin is preferably a commercially available or homemade resin having isocyanate groups, unsaturated bonds, and / or unsaturated groups.

[0081] For example, the interface resin can be a compound having isocyanate groups, unsaturated bonds and / or unsaturated groups, or the interface resin can be a combination of a compound having isocyanate groups and a compound having unsaturated bonds and / or unsaturated groups.

[0082] In one specific example, the compounds having unsaturated bonds and / or unsaturated groups may include alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; glycidyl (meth)acrylate, polyethylene glycol mono(meth)acrylate with 2 to 14 ethylene oxide groups, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate with 2 to 14 ethylene oxide groups, polyethylene glycol di(meth)acrylate with 2 to 14 propylene oxide groups, polypropylene glycol di(meth)acrylate with 2 to 14 propylene oxide groups, trimethylolpropane di(meth)acrylate, and bisphenol A. Compounds obtained by esterification of polyols such as diglycidyl ether acrylate adduct, phthalic acid diester of diethyl methacrylate, toluene diisocyanate adduct of diethyl methacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and dipentaerythritol tri(meth)acrylate with α, β-diunsaturated carboxylic acids, and acrylic adducts of glycidyl groups such as trimethylolpropane triglycidyl ether acrylate adduct, can be used individually or in combination.

[0083] In one specific example, the compounds having isocyanate groups may include aliphatic, alicyclic, aryliphatic, and / or aromatic isocyanates. Preferred diisocyanates include, for example, trimethyl, tetramethyl, pentamethyl, hexamethyl, heptamethyl, or octamethylmethylene diisocyanate, 2-methyl-pentamethylene-1,5-diisocyanate, 2-ethyl-butylene-1,4-diisocyanate, pentamethyl-1,5-diisocyanate, butylene-1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), hydrogenated phenyl diisocyanate (HXDI), cyclohexane 1,4-diisocyanate, diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), toluene diisocyanate (TDI), diphenylmethylene diisocyanate, 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate, phenylene diisocyanate, etc. They can be used individually or in combination of two or more.

[0084] For example, when the interface resin is composed of a compound resin, the compound resin may be composed of isocyanate resin, polyester resin, vinyl ester resin, epoxy resin, modifying components (modifiers that can improve polarity and toughness), and monomers.

[0085] For example, the interface resin preferably comprises an isocyanate resin (i.e., the compound having isocyanate groups as described above) and a polyester resin (i.e., the compound having unsaturated bonds and / or unsaturated groups as described above). The isocyanate resin may preferably contain diphenylmethane diisocyanate. In this embodiment, the commercially available isocyanate resin selected is from Wanhua Chemical. PM-200. Alternatively, commercially available Covestro isocyanate resins can also be used. 44C

[0086] 44CP24, or Huntsman Surprasec 1051, etc.

[0087] The polyester resin can be a bisphenol A polyester resin. In this embodiment, the polyester resin selected is a commercially available bisphenol A type unsaturated polyester of grade 3301. Alternatively, the polyester resin can also be a commercially available UP197, UP197A, or Atlac382 type polyester.

[0088] As one implementation method, the polyester resin also contains a reaction accelerator. For example, metal-based reaction accelerators include tin-based accelerators such as dibutyltin dilaurate, stannous octanoate, and stannous chloride; iron-based accelerators such as ferric chloride and ferrocene; cobalt-based accelerators such as cobalt naphthenate and cobalt isooctanoate; and zinc-based accelerators such as zinc isooctanoate. Alternatively, the reaction accelerator can also be an ammonium-based accelerator. Optionally, the reaction accelerator can be included in the polyester resin component.

[0089] These reaction accelerators can not only accelerate the curing of polyester resins, but also act as reaction catalysts for isocyanate resins, thus eliminating the need for a curing agent component in typical two-component polyurethane coatings. Furthermore, since polyester resins do not contain initiators, the aforementioned reaction accelerators can be pre-mixed into the polyester resin.

[0090] In one implementation, the mass ratio of isocyanate resin to polyester resin is 1:3 to 2:3. Preferably, the mass ratio of isocyanate resin to polyester resin is 1:3 to 1:2. More preferably, the mass ratio of isocyanate resin to polyester resin is 1:3 to 7:13. Even more preferably, the mass ratio of isocyanate resin to polyester resin is 3:7 to 7:13.

[0091] Furthermore, within the aforementioned mass ratio range, the ratio of isocyanate resin to polyester resin can be adjusted according to process conditions and environment, so that the viscosity of the interface resin before gelation or curing is in the range of 80-800 cps, so as to limit the thickness of the interface layer 120 and apply texture.

[0092] According to the interface resin of this application, the formed interface layer can achieve two-stage bonding: a primary bonding between the pultruded strip and the interface layer, and a secondary bonding between the strip containing the interface layer and the injection resin.

[0093] Specifically, the -NCO groups in the isocyanate resin can absorb water from the air and react to generate highly polar extended chain segments. When the interfacial resin is coated onto the pultruded core, the hydroxyl groups on the surface of the isocyanate resin and the pultruded strip can react to form hydrogen bonds and covalent bonds, thereby forming a primary bond. At the same time, some covalent bonds break to generate some free radicals, which are used to initiate crosslinking of the polyester resin.

[0094] The use of polyester resin can increase the crosslinking density of the interface layer in three dimensions, improve the strength and chemical corrosion resistance of the interface layer, and give the strips resistance to friction and resistance to swelling and corrosion of solvents and small molecule components in the injection resin during transportation.

[0095] During the formation of the interface layer, the -NCO groups react to generate -NH2. -NH2 can react with -NCO to form urea and polyurea. These are highly polar groups that can form chemical bonds with the subsequently infused epoxy resin, thereby forming a secondary bond between the interface layer and the infused resin. For example, the curing conditions for epoxy resin infusion are generally a temperature greater than 50°C for 6 hours, while some typical epoxy resin infusion curing conditions are 60-80°C for 10-12 hours, which can meet the chemical reaction conditions between the active groups in the isocyanate resin and the epoxy resin.

[0096] Therefore, the interface resin of the interface layer in this application can form chemical bonds with the core material of the pultruded strip and the injection resin in the lamination process through primary and secondary bonding, thereby giving the interface layer a high bonding strength with both the core material of the pultruded strip and the injection resin.

[0097] The following uses isocyanate resins from interface resins ( Examples 1-6 use PM-200 and polyester resin (Bisphenol A type unsaturated polyester, grade 3301) in different mass ratios as interface resins. Examples 1-3 use other types of adhesives as interface resins as comparative examples.

[0098] The performance evaluation of pultruded strips was carried out by electronic pull-out tester. The tensile and shear strength performance evaluation was carried out after the pultruded strips were laminated and poured. The results are shown in Table 1.

[0099] Table 1

[0100]

[0101] Wherein, "p" indicates failure within the pultruded strip, "b" indicates failure at the interface layer, "i" indicates failure at the infused laminate (for tensile-shear tests only), and "h" indicates failure at the structural adhesive layer (for pull-out tests only).

[0102] In addition, taking Example 3 as an example, "20%b" means that 20% of the sample failure occurred in the interface layer, "40%h" means that 40% of the sample failure occurred in the structural adhesive layer, "40%p" means that 40% of the sample failure occurred within the pultruded strip, and so on.

[0103] Furthermore, considering the pull-out failure mode, the higher the percentage of structural adhesive layer failure (h%) and the higher the percentage of failure within the pultruded strip (p%), the more ideal the interface layer bonding mode.

[0104] The interfacial layer comprising isocyanate resin and polyester resin in this application exhibits excellent adhesion to both the pultruded strips and the resin used for base layer infusion. In contrast, other types of adhesives used as comparative examples either lack sufficient strength or only exhibit good adhesion to one of the pultruded strips or the infusion resin.

[0105] The following uses Example 4 from this application, along with a pultruded strip with a release fabric, as Comparative Example 4. Various mechanical properties were tested and compared with standard requirements. The results are shown in Table 2. Interlaminar shear strength testing was conducted according to standard ISO 14130, tensile shear strength testing according to standard EN 1465, and G1C interlaminar fracture toughness testing according to standard ASTM D5528.

[0106] Table 2

[0107]

[0108] Therefore, the pultruded slab 100 with an interface layer 120 comprising isocyanate resin and polyester resin in this application exhibits superior mechanical properties compared to pultruded slabs with release fabric. Furthermore, the pultruded slab 100 with interface layer 120 ensures the structural integrity of the pultruded core 110, preventing a decrease in mechanical properties. Moreover, compared to pultruded slabs with release fabric, the pultruded slab 100 with interface layer 120 in this application not only meets standard requirements but also offers significant advantages in raw material and / or production costs.

[0109] This application also provides a pultrusion preparation process for manufacturing pultruded slabs 100, with reference to... Figure 6 and Figure 7 The pultrusion process includes the steps of forming a pultruded core, forming an interface layer, and winding.

[0110] In the step of forming the pultruded core, the fiber 111 is impregnated with core resin and then dragged through the pultrusion mold 3. After being heated and cured by the pultrusion mold 3, the pultruded core 110 of the pultruded strip 100 is formed.

[0111] In the interface layer formation step, interface resin is applied to at least one surface of the pultruded core 110 using a molding process. The interface layer 120 is defined to have a predetermined thickness before it hardens or gels. After the unhardened or ungelled interface layer 120 has reached the predetermined thickness, a texture is applied to the surface of the interface layer 120. Following texture formation, the pultruded slab 100 is further heated to harden the surface of the interface layer 120 at a temperature greater than 100°C. After hardening, the interface layer 120 allows the pultruded slab 100 to be wound and packaged, defining the bonded surface of the pultruded slab 100.

[0112] In the winding step, the pultruded strip 100 is wound and packaged after the interface layer 120 has hardened.

[0113] According to the pultrusion process of this application, a non-grinding interface layer 120 bonding surface can be formed without affecting the winding and packaging, and the bonding surface will not cause damage to the reinforcing fibers, so that the pultruded strip 100 will not lose its mechanical properties; and the pultruded strip formed by this pultrusion process can be directly stacked and injected in the lamination and injection process to form the wing cap 20 without the need for additional strip surface activation treatment, and the use of consumables such as release cloth is eliminated, reducing production costs.

[0114] The processes and steps described in all the preferred embodiments above are merely examples. Unless adverse effects occur, various processing operations can be performed in a different order than the above-described processes. The order of steps in the above processes can also be added, combined, or deleted according to actual needs.

[0115] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for descriptive purposes only and is not intended to limit the scope of this application. Features described in one embodiment may be applied, alone or in combination with other features, to another embodiment, unless that feature is not applicable in that other embodiment or is otherwise stated.

[0116] This application has been described through the above embodiments. However, it should be understood that the above embodiments are only for illustrative purposes. This application is not limited to the above embodiments. Many variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A pultruded slat for a spar cap on a wind turbine blade, characterized in that, The pultruded strip includes: A pultruded core, the pultruded core being made of reinforcing fibers impregnated with a core resin, the reinforcing fibers including glass fibers and / or carbon fibers; The coated interface layer is made of an interface resin present on at least one surface of the pultruded core, the interface layer allowing the pultruded strip to be wound and packaged after manufacturing, the interface resin containing isocyanate resin and polyester resin, and the mass ratio of the isocyanate resin to the polyester resin being 1:3 to 2:3, the interface layer being obtained by coating the interface resin onto at least one surface of the pultruded core using a roller coating, brush coating, spray coating or injection molding process and then curing it; The surface of the interface layer forms a bonded surface on the pultruded strip, and the bonded surface is used to form an adhesive surface between at least two pultruded strips.

2. The pultruded strip according to claim 1, characterized in that, The pultruded core is formed by dragging reinforcing fibers impregnated with the core resin through a pultrusion die and heating and curing them. The bonded surface, without sanding, can be used to form the bonding surface between at least two pultruded strips bonded with the injection resin during the process of forming the spar cap by stacking at least two pultruded strips and through a lamination injection process.

3. The pultruded strip according to claim 2, characterized in that, The interface layer is formed by a glue injection mold process. Along the dragging direction, the glue injection mold is located downstream of the pultrusion mold. The glue injection mold has an inlet, an outlet, and a glue injection port disposed between the inlet and the outlet. The height dimension of the cavity in the glue injection mold gradually decreases along the dragging direction, so that the outlet dimension of the glue injection mold can limit the interface layer to have a predetermined thickness. The pultruded core is dragged into the injection mold from the inlet, receives the interface resin through the injection port, and is then dragged through the outlet to form an ungelled interface layer with the predetermined thickness on the surface of the pultruded core.

4. The pultruded strip according to claim 3, characterized in that, Before the pultruded strip is wound and packaged, the interface layer is heated to a temperature greater than 100°C by a supplementary heating device to harden the interface layer and prevent the interface layer from sticking together during winding and packaging. The supplementary heating device is located downstream of the injection mold along the dragging direction.

5. The pultruded strip according to claim 4, characterized in that, The surface of the interface layer is textured, and the texture is formed by a texture application device before the interface layer is gelled. The texture application device is located between the injection mold and the supplementary heating device, and the texture application device includes a scraper or stamp with a textured shape.

6. The pultruded strip according to claim 5, characterized in that, The texture is constructed in the form of irregular stripes, grids, or scattered dots.

7. The pultruded strip according to claim 5, characterized in that, The predetermined thickness of the interface layer is 0.02-0.2 mm; and / or The thickness of the texture is the same as the predetermined thickness of the interface layer.

8. The pultruded strip according to claim 1, characterized in that, The mass ratio of the isocyanate resin to the polyester resin is 1:3 to 1:

2.

9. The pultruded strip according to any one of claims 1-8, characterized in that, The isocyanate resin comprises diphenylmethane diisocyanate; The polyester resin comprises bisphenol A type polyester resin and a reaction accelerator.

10. A spar cap for a wind turbine blade, characterized in that, The spar cap comprises a pultruded slat according to any one of claims 1-9.

11. A wind turbine blade, characterized in that, It includes the pultruded slats according to any one of claims 1-9, or the spar cap according to claim 10.

12. A pultrusion manufacturing process for producing pultruded strips for spar caps of wind turbine blades, characterized in that, At least two pultruded strips are stacked and formed into the spar cap by a lamination casting process, wherein the pultrusion process includes: In the core forming step, the reinforcing fiber is impregnated with core resin and then dragged through a pultrusion mold and heated to cure, forming the pultruded core of the pultruded strip; The step of forming an interface layer involves coating an interface resin onto at least one surface of the pultruded core using a molding process, and defining the interface layer to have a predetermined thickness before gelation. The interface layer, after curing, allows the pultruded strip to be wound and packaged. The interface layer defines the bonded surface of the pultruded strip. The interface resin contains isocyanate resin and polyester resin, and the mass ratio of the isocyanate resin to the polyester resin is 1:3 to 2:

3. The winding step involves winding and packaging the pultruded strip after the interface layer has hardened.

13. The pultrusion process according to claim 12, characterized in that, The step of forming the interface layer further includes: applying a texture to the surface of the interface layer after the interface layer has a predetermined thickness and before the interface layer is gelled.

14. The pultrusion process according to claim 12 or 13, characterized in that, The step of forming the interface layer further includes: supplementing the pultruded strip with heating before winding and packaging, wherein the supplementary heating temperature is greater than 100°C.

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