Sspar cap and production method thereof

Abstract

The invention relates to a method (100) for producing a spar cap for a rotor blade of a wind turbine, the method comprising the steps of: providing a plurality of pultruded sheets (110), the pultruded sheets being a thermoplastic composite comprising 45% or less by volume of a polymer matrix comprising a (meth) acrylic polymer and at least 55% by volume of fibers, preferably carbon fibers; stacking the pultruded sheets into a pre-spar cap shape (130); and joining the stacked pultruded sheets (140) in order to produce the spar cap. The invention also relates to a spar cap, a rotor blade, a method for producing a rotor blade and a wind turbine.

Description

Technical Field

[0001] The present invention relates to the field of wind turbines, in particular blades of wind turbines, and more particularly to spar caps made of thermoplastic polymer composites. The present invention relates to a method for producing a spar cap, a spar cap, a rotor blade comprising a spar cap, and a method for producing a rotor blade comprising a spar cap. Background Art

[0002] Currently, wind turbine blades are made of composite materials that are both light and durable. In fact, wind turbine blades are subject to bending, torsion or tensile stresses. This is mainly due to the fact that the blades of a wind turbine must support significant mechanical loads during the operation of the wind turbine, especially in the presence of strong gusts.

[0003] In order to strengthen their structure, spar caps are integrated into wind turbine blades. The spar caps may, among other things, transfer the main aerodynamic bending loads from the rotor blade to the hub. The spar caps are incorporated into the blade and typically extend over a majority of the total length of the blade.

[0004] These spar caps are often designed with glass fiber and / or carbon fiber reinforced plastic (CFRP). As the wind energy industry evolved, CFRP gave way to pultruded unidirectional fiber composites with unidirectional fibrous reinforcements.

[0005] In particular, the spar cap may include a unidirectional fiber layer infused into a thermosetting polymer resin to form a pre-spar cap. The pre-spar cap is then positioned in a mold together with other components of the wind turbine blade to form a blade including the spar cap. For example, the spar cap may be manufactured by a vacuum infusion process (VIP) and in particular vacuum assisted resin infusion (VARI). In this technique, once a full vacuum state is reached, the resin is applied. Then, the liquid resin is infused inside the mold.

[0006] In other embodiments, the spar caps may also be manufactured by resin transfer molding (RTM) and, for example, vacuum assisted resin transfer molding (VARTM). RTM uses a closed mold into which a fiber layup is placed. The mold is closed, sealed, and heated. Heated resin is injected into the mold to impregnate the fiber layup. The mold is then maintained at a temperature sufficient to cure the resin (often an epoxy resin). Current RTM technology produces lightweight parts with excellent mechanical properties. With regard to these qualities, composite materials are widely used in a variety of structural and non-structural applications common in aerospace and aviation.

[0007] VARTM differs from RTM in that the fibrous reinforcements and materials are laid out on the mould and vacuum bagged. Liquid resin is introduced through ports in the mould and vacuum drawn through the reinforcements via designed channels and an infusion medium that facilitates fibre wetting. Subsequent curing does not require high temperatures or pressures.

[0008] However, these techniques result in difficult and uneven impregnation, leading to imperfections. These defects can spread over large areas and can significantly reduce the reliability of the final product. In addition, their repair is particularly time-consuming and expensive.

[0009] Therefore, techniques are being developed to improve the manufacture of spar caps.

[0010] For example, EP3569394 proposes a spar cap made by stacking carbon fiber layers and including adhesive film layers between the carbon fiber layers. These different layers are assembled together by different techniques, such as pressure, heat, vacuum in a mold. The spar cap is then incorporated into the blade of a wind turbine. These spar caps include carbon fibers impregnated with epoxy resin.

[0011] Another solution disclosed in document WO2010 / 083840 proposes to combine uncured resin pre-impregnated fiber layers with cured fiber reinforced resin layers, the cured layers having a stiffness greater than the uncured layers and thus increasing the stiffness of the spar cap. These layers comprise carbon fibers, glass fibers or aramid fibers, and epoxy, polyester, vinyl ester or phenolic resins.

[0012] Document EP3501810 proposes a spar cap made of a pultruded composite layer comprising abutment surfaces to facilitate the flow of resin and thus better resin infusion between the strips compared to conventionally known strips. Composite materials are, however, also made of glass or carbon fibers and thermosetting polymers such as epoxy, vinyl ester, polyurethane or polyester type resins.

[0013] At present, spar caps are mainly composed of polymer composites, in which fibrous reinforcements are incorporated into a thermosetting polymer matrix. The fibers of the fibrous reinforcements can typically consist of glass fibers, carbon fibers or ceramic fibers, but also of natural fibers. The polymer matrix, which is mainly composed of polymers, holds the fibers together, transmits tension between the fibers, and protects the fibers from external mechanical and chemical influences. The polymer matrix is ​​often thermosetting, and the thermosetting polymer composite parts are linked together using thermosetting resins (for example, epoxy resins or polyester or polyurethane adhesives).

[0014] However, thermosetting composite materials have several disadvantages, such as high costs when recycling these materials, or if recycling is not possible, large amounts of waste are accumulated. In addition, when wind turbine blades are constructed from polymer composites (e.g., by low-pressure injection molding or infusion molding), the use of thermosetting resins generally results in long cycle times. In addition, these polymer composite parts are then assembled during industrial processes before being shipped to the installation site. Given the long cycle times observed when using thermosetting polymer matrices during both part manufacturing and assembly, there is a need to identify polymers and / or resins that will be able to reduce cycle times and, therefore, reduce wind turbine production times.

[0015] Additionally, production of spar caps may include the use of peel plies for better adhesion which is expensive and slows production.

[0016] Furthermore, it is very difficult to remove the peeling sheets over large surfaces, for example for turbine blades which can be about 100 meters long. This constitutes a real industrial challenge in terms of technical difficulty and time. Furthermore, the presence of the peeling sheets increases the number of steps during recycling and, in particular, for removing the peeling sheets, and therefore the time and costs.

[0017] Wind turbine blades incorporating thermoplastic materials are proposed, for example, in application WO2010025830; however, the proposed thermoplastics are essentially proposed for forming the bonds between the various parts of the wind turbine blade and they have a relatively high sensitivity to moisture or a high melting point.

[0018] Application US2017 / 0058864 describes an adjustable wind turbine blade made of thermoset and / or thermoplastic material. The thermoset-thermoplastic interface is welded; however, the blade contains a large portion of thermoset material.

[0019] Document EP2497945 discloses at least one spar cap on each side of the blade and therefore within each half-blade. Each part is glued together so as to obtain a glued laminate type structure forming the spar cap. However, gluing two parts together introduces the risk of failures and defects. Moreover, the mechanical properties are not optimal. Moreover, the bonding resin is of epoxy type, which does not allow easy recycling of the spar cap.

[0020] In document WO2018172656, the applicant proposes to manufacture wind turbine blades from thermoplastic polymer composites having mechanical properties suitable for the field of wind power generation and being mainly recyclable. Such wind turbine blades may include a reinforcing element comprising a thermoplastic polymer composite and comprising a low-density structure arranged in a sandwich-type structure. However, such wind turbine blades may include thermosetting and may be connected by epoxy resin or polyester or polyurethane adhesives.

[0021] Document US2020 / 095978 discloses a joint interface for wind turbine rotor blade components. One component is a pair of longitudinally extending spar caps, which may have a shear web disposed therebetween.

[0022] Document US2017 / 082089 relates to a wind turbine motor blade component formed by pultruding a mixed resin fiber reinforced composite. The document discloses a pultruded plate having different parts formed by thermosetting resin material and thermoplastic material, respectively.

[0023] Document US2017 / 080648 relates to a method for manufacturing a spar cap for a wind turbine rotor blade using a thermoplastic matrix composite plate. Each plate is pultruded and includes a thermoplastic resin material.

[0024] Therefore, there is a need for a spar cap that comprises thermoplastic and is therefore easily recyclable, while providing mechanical and chemical properties that meet the requirements of the wind energy industry, and reduces cycle time and cost to solve industry problems. Summary of the invention

[0025] For the purpose of providing a basic understanding of the present invention, a brief summary of selected aspects, embodiments and examples of the present invention is set forth below. However, the summary does not constitute an extensive review of all aspects, embodiments and examples of the present invention. The sole purpose of the summary is to present selected aspects, embodiments and examples of the present invention in a concise form as an introduction to a more detailed description of aspects, embodiments and examples of the present invention that follows the summary.

[0026] The object of the present invention is to overcome the disadvantages of the prior art. In particular, the present invention proposes a method for producing a spar cap for a rotor blade of a wind turbine, the method comprising the following steps: - providing a plurality of pultruded sheets, the pultruded sheets being a thermoplastic composite comprising 45% by volume or less of a polymer matrix comprising a (meth)acrylic polymer, and at least 55% by volume of fibers, preferably carbon fibers; - stacking the pultruded sheets into a pre-spar cap shape; and - Joining of stacked pultruded sheets to produce spar caps.

[0027] The advantage of the method is that the spar caps comprise thermoplastics. The method according to the invention allows providing a recyclable solution for the spar caps and preferably pultruded spar caps and thus the rotor blades of a wind turbine. Each pultruded sheet does not need to be glued to each other. In addition, thermoplastic spar caps bring similar mechanical properties compared to thermosetting resins.

[0028] Furthermore, the method according to the invention allows reducing waste and facilitating the pultrusion process.

[0029] Furthermore, due to the thermoplastic content and in order to improve the mechanical properties of the produced spar caps, it is possible to design the pattern directly on the pultruded sheet without using, for example, peel plies.

[0030] The method according to the invention also allows saving time and reducing cycle times.

[0031] According to other optional features of the method according to the present invention, the method may optionally include one or more of the following features alone or in combination: - the step of providing a plurality of pultruded sheets comprises a step of surface texturing, preferably said textured surface having a Ra between 3 μm and 30 μm according to standard ISO 4287:1997, - pultruded sheet has a thickness from 2 mm to 8 mm, - the method further comprises a step for providing a plurality of interlayers, - the stacking step further comprises a thermoforming step, - The joining step is performed in the spar cap mould. - the joining step is performed in the rotor blade mould and wherein the stacked pultruded sheets of the spar cap are joined when the rotor blade is formed, preferably by infusion and / or thermoplastic adhesive, - The step of providing a plurality of pultruded sheets comprises the following steps: Provide roving fibers; impregnating the fibers with a polymer resin comprising a polymer matrix comprising a (meth)acrylic polymer; Heating impregnated fibers; Cooling the heated composite, and optionally calendering; and Pull out pultruded sheet; - the polymer matrix comprises at least one multifunctional (meth)acrylic monomer comprising at least two (meth)acrylic functional groups, -Pultruded sheets do not include peeling plies.

[0032] According to another aspect, the invention may also relate to a spar cap for a wind turbine, which spar cap is obtainable by the method according to the invention.

[0033] According to other optional features of the spar cap according to the present invention, the spar cap may optionally include one or more of the following features alone or in combination: - the spar cap comprises a plurality of pultruded sheets being a thermoplastic composite comprising 45% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 55% by volume of fibers, preferably carbon fibers, the plurality corresponding to at least two. The pultruded sheet has at least one textured surface having a Ra between 3 μm and 30 μm according to standard ISO 4287:1997. - Pultruded sheets can be separated by one or more interlayers.

[0034] According to another aspect, the invention may also relate to a rotor blade comprising a spar cap according to the invention.

[0035] According to another aspect of the present invention, a wind turbine is provided, comprising a spar cap according to the present invention or a rotor blade according to the present invention.

[0036] According to another aspect, the invention may also relate to a method for producing a rotor blade comprising a spar cap according to the invention, said method comprising associating the spar cap with a shell and a shear web, and joining them by gluing, welding and / or infusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: [ Figure 1 ] Figure 1 is a schematic diagram of a method according to an embodiment of the present invention. [ Figure 2 ] Figure 2 is a schematic diagram of steps of providing a plurality of pultruded sheets according to an embodiment of the present invention. [ Figure 3 ] Figure 3 Pultruded sheet samples before (left) and after (right) the embossing process after the die by calendering on the pultrusion line.

[0038] Several aspects of the present invention are disclosed with reference to flowcharts and / or block diagrams of methods and apparatus according to embodiments of the invention.

[0039] In the figures, flow charts and / or block diagrams show the architecture, functionality, and possible implementations of devices or systems or methods according to several embodiments of the present invention.

[0040] For this purpose, each block in the flowchart or block diagram may represent a system, device, or module.

[0041] In some implementations, the functionality associated with the blocks may occur in a different order than indicated in the figures.

[0042] For example, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

[0043] Each block of the flowchart or block diagrams, and combinations of blocks in the flowchart or block diagrams, may be implemented by a particular system that performs a particular function or action or performs a combination of particular equipment. DETAILED DESCRIPTION

[0044] The following is a description of exemplary embodiments of the present invention.

[0045] "Polymer" means a copolymer or a homopolymer or a block copolymer. The term "copolymer" means a polymer that aggregates several different monomer units, and the term "homopolymer" means a polymer that aggregates the same monomer units. "Block copolymer" means a polymer that includes one or more uninterrupted blocks of each of different polymer species, the polymer blocks being chemically different from each other and linked together by covalent bonds. These polymer blocks are also called polymer blocks.

[0046] Within the meaning of the present invention, the expression "polymer composite" denotes a multicomponent material comprising at least two immiscible components, wherein at least one component is a polymer and the other component may, for example, be a fibrous reinforcement.

[0047] Within the meaning of the present invention, "fibrous reinforcement" or "fibrous matrix" or "fibers" means a number of fibers, unidirectional fibers or fibers of a braid, or a continuous filament mat, fabric, felt or nonwoven, which may be in the form of a tape, web, braid, core or sheet.

[0048] The term "matrix" may refer to a material that acts as a binder and is capable of transmitting forces to the fibrous reinforcement. A "polymer matrix" includes polymers and may include other compounds or materials. Thus, a "(meth)acrylic polymer matrix" refers to all types of compounds, polymers, oligomers, copolymers or block copolymers, acrylics and methacrylics. However, if the (meth)acrylic polymer matrix includes up to 10% by weight, preferably less than 5% by weight, of other non-acrylic monomers, it will not depart from the scope of the present invention that the other non-acrylic monomers are selected from, for example, the following group: butadiene, isoprene, styrene, substituted styrenes (such as α-methylstyrene or tert-butylstyrene), cyclosiloxanes, vinylnaphthalene and vinylpyridine.

[0049] In the meaning of the present invention, the term "resin" may refer to a liquid slurry used as a binder, capable of transmitting force to the fibers. A "resin" may contain a polymer, but also other compounds, such as monomers and / or oligomers. Preferably, the resin according to the present invention is polymerizable.

[0050] Within the meaning of the present invention, the term "initiator" may refer to a compound that can start / initiate / continue the polymerization of one or more monomers.

[0051] Within the meaning of the present invention, the term "polymerization" may refer to the process of converting a monomer or a mixture of monomers into a polymer.

[0052] Within the meaning of the present invention, the term "monomer" may refer to a molecule that can undergo polymerization.

[0053] For the purposes of the present invention, the term "thermoplastic polymer" may refer to a polymer that is substantially solid at room temperature, which may be crystalline, semi-crystalline or amorphous, and which softens during temperature increase (in particular after exceeding its glass transition temperature (Tg), and flows at higher temperatures and / or can observe a distinct melting when exceeding its so-called melting temperature (Tf) (when it is semi-crystalline)), and becomes solid again when the temperature drops below its melting point and below its glass transition temperature. This also applies to thermoplastic polymers that are slightly crosslinked by the presence of multifunctional monomers or oligomers in the formulation of the "syrup" (meth)acrylate, the mass percentage of which is preferably less than 10%, preferably less than 5%, and thus preferably less than 2%, and may be at least 0.5%, which thermoplastic polymers can be thermoformed when heated above the softening temperature.

[0054] The term "thermoplastic composition" may refer to a thermoplastic syrup or a thermoplastic resin or a thermoplastic resin precursor, and to a mixture of a thermoplastic resin or a thermoplastic resin precursor, respectively, and a monomer. The term "thermoplastic resin precursor" refers to a prepolymer, which already includes several polymerized monomers as monomer units in the prepolymer chain, which prepolymer is capable of further polymerization once fully polymerized in order to reach a higher molecular weight, or in other words, can continue to polymerize.

[0055] The term "thermoset polymer" may refer to a plastic material that is irreversibly transformed by polymerization.

[0056] The term "(meth)acrylic monomer" may refer to any type of acrylic and methacrylic monomers.

[0057] The term "(meth)acrylic polymer" may refer to a polymer mainly including a (meth)acrylic monomer, which accounts for at least 50% by weight or more of the (meth)acrylic polymer.

[0058] Within the meaning of the present invention, the term "PMMA" may refer to homopolymers and copolymers of methyl methacrylate (MMA), wherein the weight proportion of MMA in PMMA is preferably at least 70% by weight of the MMA copolymer.

[0059] The expression "reinforcement element" as used may refer to an element which is used in / with a structure in order to strengthen the structure, support the structure, solidify the structure, consolidate the structure, improve its mechanical properties (reinforcement, tension, stretch, etc.), its thermal properties, electrical properties and / or chemical properties.

[0060] The abbreviation "phr" may refer to parts by weight per hundred parts of the composition. For example, 1 phr of initiator in the composition means 1 kg of initiator is added to 100 kg of the composition.

[0061] The abbreviation "ppm" may refer to parts per million by weight of a composition. For example, 1000 ppm of a compound in a composition means that 0.1 kg of the compound is present in 100 kg of the composition.

[0062] As used herein, the term "about" can allow for a certain degree of variability in values ​​or ranges, for example, within 10%, within 5%, or within 1% of a stated value or limit of a stated range.

[0063] The terms "wind turbine blade" or "rotor blade" may be used interchangeably. Within the meaning of the present invention, a rotor blade may correspond to an air airfoil rotating about an axis.

[0064] The term "wind turbine" may refer to all elements corresponding to a fully constructed wind turbine. A wind turbine as used herein may refer to a device that converts kinetic energy of wind into mechanical energy.

[0065] The term "recyclable" may refer to a resin that can be recycled at 90%, preferably greater than 90%, and more preferably greater than or equal to 95%.

[0066] As mentioned, wind turbine blades are subjected to mechanical and chemical stresses during their operation. In addition, wind turbine blades are not fully recyclable and their manufacturing time is long. Current methods propose composite materials consisting mainly of thermosetting polymers to manufacture spar caps, which are then assembled with wind turbine blades. In addition, in order to improve the performance of wind turbine blades and spar caps, texturing including peel plies is introduced into the manufacturing. However, peel plies are difficult to recycle and time consuming.

[0067] Current spar cap production brings different industrial technologies that do not allow for recycling and solve field constraints. In addition, these technologies and current recycling of spar caps are too long and too expensive for the industry.

[0068] Therefore, there is a need for new spar caps and new spar cap manufacturing technologies that can be easily produced and recycled while providing mechanical and chemical properties that meet the requirements of the wind energy field and reduce production time and costs.

[0069] According to a first aspect, the invention proposes a method for producing a spar cap for a rotor blade of a wind turbine, such as e.g. Figure 1 As shown in .

[0070] The method 100 for producing a spar cap for a rotor blade of a wind turbine includes providing a plurality of pultruded sheets 110 , stacking the pultruded sheets 130 , and joining the stacked pultruded sheets 140 .

[0071] The method according to the present invention may further include a surface texturing step 115 , a step 120 of providing a plurality of interlayers, and a thermoforming step 160 .

[0072] like Figure 1 , a method 100 for producing a spar cap for a rotor blade of a wind turbine according to the present invention, as shown in , comprises a step 110 of providing a plurality of pultruded sheets. Preferably, the pultruded sheet is a thermoplastic composite comprising 45% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 55% by volume of fibers (preferably carbon fibers). More preferably, the thermoplastic composite comprises 40% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 60% by volume of fibers, and even more preferably, the thermoplastic composite comprises 35% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 65% by volume of fibers. The pultruded sheet is a thermoplastic composite comprising at least 25% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 75% by volume of fibers. Preferably, the thermoplastic composite comprises at least 27% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 73% by volume of fibers. More preferably, the thermoplastic composite comprises at least 30% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 70% by volume of fibers. The pultruded sheet is a thermoplastic composite comprising between 25% and 45% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 55% and 75% by volume of fibers. Preferably, the thermoplastic composite comprises between 27% and 40% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 60% and 73% by volume of fibers. More preferably, the thermoplastic composite comprises between 30% and 35% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 65% and 70% by volume of fibers.

[0073] like Figure 2 As shown in FIG. 1 , the step 110 of providing a plurality of pultruded sheets may include the following steps: providing roving fibers 111; impregnating the fibers 112 with a thermoplastic composition (preferably, a polymer resin comprising a polymer matrix including a (meth)acrylic polymer); heating the impregnated fibers 113; cooling the heated composite 114, and optionally texturing 115 (i.e., surface texturing) (preferably, calendering); and drawing a pultruded sheet 116.

[0074] like Figure 2As shown in FIG. 1 , the method according to the invention may comprise a step 111 of providing roving fibers. The step 111 is preferably implemented by a fiber feeding device.

[0075] The step 111 of providing roving fibers allows providing the fibers in the direction of the pultrusion path.

[0076] The fibers may be made of several fibers, unidirectional rovings or continuous filament mats, fabrics, felts or nonwovens, which may be in the form of strips, loops, braids, locks or sheets. The fiber material of the composite may be of various forms and sizes (one-dimensional, two-dimensional or three-dimensional).

[0077] One-dimensional form corresponds to linear long fibers. Fibers may be discontinuous or continuous. Fibers may be arranged randomly or parallel to each other in the form of continuous filaments. Fibers are defined by their aspect ratio, which is the ratio between the length and diameter of the fiber. Preferably, the fiber used in the present invention is a long fiber or a continuous fiber. Fibers may have an aspect ratio of at least 1000, preferably at least 1500, more preferably at least 2000, advantageously at least 3000 and more advantageously at least 5000, even more advantageously at least 6000, more advantageously at least 7500, and most advantageously at least 10000.

[0078] Two-dimensional forms correspond to nonwoven or woven fiber mats or reinforcements or fiber bundles, which may also be woven. Even if a two-dimensional form has a certain thickness, and therefore in principle a third dimension, it is considered to be two-dimensional according to the invention.

[0079] The three-dimensional form corresponds to, for example, a nonwoven fiber mat or reinforcement or stacked or folded fiber bundles or mixtures thereof, an assembly of the two-dimensional form in the third dimension.

[0080] The origin of the fiber material can be natural or synthetic. As natural materials, one can mention plant fibers, wood fibers, animal fibers or mineral fibers.

[0081] Natural fibers are, for example, sisal, jute, hemp, flax, cotton, coconut fibers and banana fibers. Animal fibers are, for example, wool or hair.

[0082] As synthetic material, mention may be made of polymer fibers chosen from thermosetting polymer fibers, thermoplastic polymer fibers, polyamide (aliphatic or aromatic) fibers, polyester fibers, polyvinyl alcohol fibers, polyolefin fibers, polyurethane fibers, polyvinyl chloride fibers, polyethylene fibers, unsaturated polyester fibers, epoxy resin fibers and vinyl ester fibers and / or carbon fibers or mixtures thereof.

[0083] The mineral fibers may also be chosen from glass fibers, in particular glass fibers of the E, R or S2 type, boron fibers, basalt fibers or silica fibers.

[0084] The fibers of the present invention may be selected from plant fibers, wood fibers, animal fibers, mineral fibers, synthetic polymer fibers, glass fibers and carbon fibers, and mixtures thereof.

[0085] Preferably, the fibers are mineral fibers. More preferably, the fibers are glass fibers or carbon fibers.

[0086] In a first more preferred embodiment, the fibers are glass fibers.

[0087] In a second more preferred embodiment, the fibers are carbon fibers.

[0088] The fibers may have a diameter between 0.005 μm and 100 μm, preferably between 1 μm and 50 μm, more preferably between 5 μm and 30 μm and advantageously between 10 μm and 25 μm.

[0089] Preferably, the fibers of the present invention are selected from continuous fibers for one-dimensional form (meaning that the aspect ratio does not necessarily apply to long fibers), or long fibers or continuous fibers for fibrous reinforcements in two-dimensional or three-dimensional form.

[0090] The method according to the present invention may include a step 112 of wetting (i.e., impregnating) the fibers. The step is preferably implemented by an impregnation device. The wetting step allows the fibers to be impregnated with the thermoplastic composition, in other words, the penetration of the thermoplastic composition with respect to the fibers. The step of wetting the fibers may include passing the fibers through the thermoplastic composition. For example, the fibers are guided through a bath or injection chamber comprising the thermoplastic composition. The thermoplastic composition may be a polymer resin and / or a polymer resin precursor. The thermoplastic composition may include at least 50% by weight of the monomers of the thermoplastic composite. The thermoplastic composition may include up to 90% by weight of the monomers of the thermoplastic composite. The thermoplastic composition may include a polymer resin comprising a polymer matrix. The polymer matrix may include a (meth) acrylic polymer. The thermoplastic composition may include a polymer and a monomer.

[0091] Preferably, the monomers of the thermoplastic compound are selected from alkyl acrylic acid monomers, alkyl methacrylic acid monomers, hydroxyalkyl acrylic acid monomers and hydroxyalkyl methacrylic acid monomers, and mixtures thereof.

[0092] Preferably, the polymer of the thermoplastic composite is selected from all types of compounds, polymers, oligomers, copolymers or block copolymers, acrylic and methacrylic. However, if the (meth)acrylic polymer matrix comprises up to 10% by weight, preferably less than 5% by weight, of other non-acrylic monomers, it will not depart from the scope of the invention if the other non-acrylic monomers are selected, for example, from the group consisting of butadiene, isoprene, styrene, substituted styrenes (such as α-methylstyrene or tert-butylstyrene), cyclosiloxanes, vinylnaphthalene and vinylpyridine.

[0093] The thermoplastic composition according to the present invention may include between 10wt% and 50wt% of (meth) acrylic polymer (PI) and between 50wt% and 90wt% of (meth) acrylic monomer (Ml). Preferably, the thermoplastic composition includes between 10wt% and 40wt% of (meth) acrylic polymer (PI) and between 60wt% and 90wt% of (meth) acrylic monomer (Ml); and more preferably, between 10wt% and 30wt% of (meth) acrylic polymer (PI) and between 70wt% and 90wt% of (meth) acrylic monomer (Ml).

[0094] The dynamic viscosity of the thermoplastic composition is in the range from 10 mPa*s to 10000 mPa*s, preferably from 20 mPa*s to 7000 mPa*s, and advantageously from 20 mPa*s to 5000 mPa*s, and more advantageously from 20 mPa*s to 2000 mPa*s, and even more advantageously between 20 mPa*s and 1000 mPa*s. The viscosity of the thermoplastic composition can be easily measured using a rheometer or a viscometer. The dynamic viscosity is measured at 25°C. If the thermoplastic composition has Newtonian behavior, meaning no shear thinning, the dynamic viscosity is independent of the shear in the rheometer or the moving speed in the viscometer. If the thermoplastic composition has non-Newtonian behavior, meaning shear thinning, the dynamic viscosity is measured at 25°C with a speed of 1 s. -1 The dynamic viscosity is measured at a shear rate of 1.

[0095] As for the thermoplastic composition of the present invention, it comprises (meth) acrylic acid monomer (M1) and (meth) acrylic acid polymer (PI). Once polymerized, (meth) acrylic acid monomer (M1) is converted into (meth) acrylic acid polymer (P2), which comprises monomer units of (meth) acrylic acid monomer (M1) and other possible monomers (M2).

[0096] Preferably, the dynamic viscosity of the (meth)acrylic composition MCI is also in the range of from 10 mPa*s to 10000 mPa*s, preferably from 20 mPa*s to 7000 mPa*s, and advantageously from 20 mPa*s to 5000 mPa*s, and more advantageously from 20 mPa*s to 2000 mPa*s, and even more advantageously between 20 mPa*s and 1000 mPa*s.

[0097] As the (meth)acrylic polymer (PI), mention may be made of polyalkyl methacrylates or polyalkyl acrylates. According to a preferred embodiment, the (meth)acrylic polymer (PI) is polymethyl methacrylate (PMMA).

[0098] According to one embodiment, the methyl methacrylate (MMA) homopolymer or copolymer comprises at least 70% by weight, preferably at least 80% by weight, advantageously at least 90% by weight, and more advantageously at least 95% by weight of methyl methacrylate.

[0099] According to another embodiment, PMMA is a mixture of at least one MMA homopolymer and at least one MMA copolymer, or a mixture of at least two MMA homopolymers or two MMA copolymers having different average molecular weights, or a mixture of at least two MMA copolymers having different monomer compositions.

[0100] The methyl methacrylate (MMA) copolymer comprises from 70 to 99.9 weight percent of methyl methacrylate and from 0.1 to 30 weight percent of at least one monomer comprising at least one ethylenic unsaturation, the at least one monomer being copolymerizable with methyl methacrylate.

[0101] These monomers are well known and mention may in particular be made of acrylic acid and methacrylic acid and alkyl (meth) acrylates in which the alkyl group contains from 1 to 12 carbon atoms. Mention may be made, by way of example, of methyl acrylate and ethyl, butyl or 2-ethylhexyl (meth) acrylate. Preferably, the comonomer is an alkyl acrylate in which the alkyl group contains from 1 to 4 carbon atoms.

[0102] According to a first preferred embodiment, the copolymer of methyl methacrylate (MMA) comprises from 80% to 99.9% by weight, advantageously from 90% to 99.9% by weight, and more advantageously from 90% to 99.9% by weight of methyl methacrylate, and from 0.1% to 20% by weight, advantageously from 0.1% to 10% by weight, and more advantageously from 0.1% to 10% by weight of at least one monomer containing at least one ethylenic unsaturation, which at least one monomer is copolymerizable with methyl methacrylate. Preferably, the comonomer is chosen from methyl acrylate and ethyl acrylate, and mixtures thereof.

[0103] The weight average molecular weight of the (meth)acrylic polymer (PI) should be high, which means greater than 50,000 g / mol, and preferably greater than 100,000 g / mol.

[0104] The weight average molecular weight can be measured by size exclusion chromatography (SEC).

[0105] The (meth)acrylic polymer (PI) can be completely dissolved in the (meth)acrylic monomer (Ml) or the mixture of (meth)acrylic monomers. It enables the viscosity of the (meth)acrylic monomer (Ml) or the mixture of (meth)acrylic monomers to increase. The obtained solution is a liquid composition, which is generally referred to as a "slurry" or a "prepolymer". The dynamic viscosity value of the liquid (meth)acrylic slurry is between 10mPa.s and 10000mPa.s. The viscosity of the slurry can be easily measured using a rheometer or a viscometer. The dynamic viscosity is measured at 25°C.

[0106] Advantageously, the liquid (meth)acrylic composition or syrup contains no additional voluntarily added solvent.

[0107] As for the (meth)acrylic monomer (M1), the monomer is selected from alkyl acrylic monomers, alkyl methacrylic monomers, hydroxyalkyl acrylic monomers and hydroxyalkyl methacrylic monomers, and mixtures thereof.

[0108] Preferably, the (meth)acrylic acid monomer (M1) is selected from hydroxyalkyl acrylic acid monomers, hydroxyalkyl methacrylic acid monomers, alkyl acrylic acid monomers, alkyl methacrylic acid monomers, and mixtures thereof, and the alkyl group contains from 1 to 22 linear, branched or cyclic carbons; the alkyl group preferably contains from 1 to 12 linear, branched or cyclic carbons.

[0109] More preferably, the (meth)acrylic monomer (M1) is selected from alkyl acrylic monomers or alkyl methacrylic monomers, and mixtures thereof, the alkyl group containing from 1 to 22 linear, branched or cyclic carbons; the alkyl group preferably contains from 1 to 12 linear, branched or cyclic carbons.

[0110] Advantageously, the (meth)acrylic monomer (M1) is selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, hydroxyethyl acrylate and hydroxyethyl methacrylate, and mixtures thereof.

[0111] More advantageously, the (meth)acrylic monomer (M1) is selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, and mixtures thereof.

[0112] According to a preferred embodiment, at least 50% by weight and preferably at least 60% by weight of the (meth)acrylic monomers (M1) are methyl methacrylate.

[0113] According to a first more preferred embodiment, at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, advantageously at least 80% by weight and even more advantageously 90% by weight of the monomer (M1) is a mixture of methyl methacrylate and optionally at least one other monomer. For example, at least one other monomer may be a multifunctional (meth) acrylic monomer (M2).

[0114] As far as the (meth)acrylic monomer (M2) is concerned, the monomer is multifunctional. Preferably, the (meth)acrylic monomer (M2) is selected from compounds comprising at least two (meth)acrylic functionalities. The (meth)acrylic monomer (M2) may also be selected from a mixture of at least two compounds (M2a) and (M2b), each of which comprises at least two (meth)acrylic functionalities.

[0115] The (meth)acrylic monomer (M2) may be selected from 1,3-butanediol dimethacrylate; 1,4-butanediol dimethacrylate; 1,6-hexanediol diacrylate; 1,6-hexanediol dimethacrylate; diethylene glycol dimethacrylate; dipropylene glycol diacrylate; ethoxylated (10) bisphenol A diacrylate; ethoxylated (2) bisphenol A dimethacrylate; ethoxylated (3) bisphenol A diacrylate; ethoxylated (3) bisphenol A dimethacrylate; ethoxylated (4) bisphenol A diacrylate; ethoxylated (4) bisphenol A dimethacrylate; ethoxylated bisphenol A dimethacrylate; ethoxylated (10) bisphenol dimethacrylate; ethylene glycol dimethacrylate; polyethylene glycol (200) diacrylate; polyethylene glycol (400) diacrylate; polyethylene glycol (400) dimethacrylate; polyethylene glycol (400) dimethacrylate; polyethylene glycol (600) diacrylate; polyethylene glycol (600) dimethacrylate; polyethylene glycol 400 diacrylate; propoxylated (2) neopentyl glycol diacrylate; tetraethylene glycol diacrylate; tetraethylene glycol dimethacrylate; tricyclodecane dimethanol diacrylate; tricyclodecane dimethanol dimethacrylate; triethylene glycol diacrylate; triethylene glycol dimethacrylate; tripropylene glycol diacrylate; ethoxylated (15) trimethylolpropane triacrylate; ethoxylated (3) trimethylolpropane triacrylate; ethoxylated (6) trimethylolpropane triacrylate; ethoxylated (9) trimethylolpropane triacrylate; ethoxylated 5 pentaerythritol triacrylate; ethoxylated (20) trimethylolpropane triacrylate; propoxylated (3) glycerol triacrylate; trimethylolpropane triacrylate; propoxylated (5.5) Glycerol triacrylate; Pentaerythritol triacrylate; Propoxylated (3) glycerol triacrylate; Propoxylated (3) trimethylolpropane triacrylate; Trimethylolpropane triacrylate; Trimethylolpropane trimethacrylate; Tris(2-hydroxyethyl)isocyanurate triacrylate; Ditrimethylolpropane tetraacrylate; Dipentaerythritol pentaacrylate; Ethoxylated (4) pentaerythritol tetraacrylate; Pentaerythritol tetraacrylate; Dipentaerythritol hexaacrylate; 1,10-decanediol diacrylate; 1,3-butanediol diacrylate; 1,4-butanediol diacrylate; 1,9-nonanediol diacrylate; 2-(2-ethyleneoxyethoxy)ethyl acrylate; 2-butyl-2-ethyl-1,3-propanediol diacrylate; 2-methyl-1,3-propanediol diacrylate; 2-methyl-1,3- Propylene glycol ethoxy acrylate; 3-methyl-1,5-pentanediol diacrylate; alkoxylated cyclohexanedimethanol diacrylate; alkoxylated hexanediol diacrylate; cyclohexanedimethanol diacrylate; ethoxylated cyclohexanedimethanol diacrylate; diethylene glycol diacrylate; dioxane glycol diacrylate; ethoxylated dipentaerythritol hexaacrylate; ethoxylated glycerol triacrylate; ethoxylated neopentyl glycol diacrylate; hydroxy neopentyl hydroxypivalate diacrylate; neopentyl glycol diacrylate; poly(tetramethylene glycol) diacrylate; polypropylene glycol 400 diacrylate; polypropylene glycol 700 diacrylate; propoxylated (6) ethoxylated bisphenol A diacrylate; propoxylated ethylene glycol diacrylate; propoxylated (5) pentaerythritol tetraacrylate; and propoxylated trimethylolpropane triacrylate.

[0116] Preferably, the (meth)acrylic monomer (M2) is selected from ethylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, triethylene glycol dimethacrylate, tricyclodecane dimethanol dimethacrylate and triethylene glycol diacrylate, or a mixture thereof.

[0117] The (meth)acrylic monomer (M2) may be present in the (meth)acrylic composition MCI in an amount between 0.01 and 10 phr by weight, preferably between 0.1 and 9.5 phr, more preferably between 0.1 and 9 phr, even more preferably between 0.1 and 8.5 phr, and advantageously between 0.1 and 8 phr, based on 100 parts of liquid (meth)acrylic syrup.

[0118] In a first more preferred embodiment, the (meth)acrylic monomer (M2) is present in the (meth)acrylic composition MCI between 0.01 and 9 phr and is chosen from compounds comprising two (meth)acrylic functions.

[0119] In a second more preferred embodiment, the (meth)acrylic monomer (M2) is present in the (meth)acrylic composition MCI between 0.01 and 9 phr and is chosen from a mixture comprising two (meth)acrylic functional compounds.

[0120] In a third more preferred embodiment, the (meth)acrylic monomer (M2) is present in the (meth)acrylic composition MCI between 0.01 and 9 phr and is chosen from a mixture comprising at least two (meth)acrylic functional compounds.

[0121] In a fourth more preferred embodiment, the (meth)acrylic monomer (M2) is present in the (meth)acrylic composition MCI at between 0.01 and 9 phr and is selected from a mixture of compounds comprising at least two (meth)acrylic functionalities. At least one compound of the mixture comprises only two (meth)acrylic functionalities and represents at least 50 wt %, preferably at least 60 wt % of the mixture of (meth)acrylic monomers (M2). Another compound of the mixture comprises more than two (meth)acrylic functionalities.

[0122] According to another embodiment of the wetting step, the thermoplastic composition may be a polymer resin precursor. The polymer resin precursor is not fully polymerized. The composition of the polymer resin precursor includes a polymerizable or curable component. In order to complete the polymerization, an initiator is preferably present or added.

[0123] The initiator (Ini) will be able to start the polymerization of the (meth)acrylic monomers (M1) and (M2) and is selected from free radical initiators.

[0124] Preferably, the initiator (Ini) is activated thermally.

[0125] The free radical initiator (Ini) may be selected from compounds comprising a peroxide group or compounds comprising an azo group, and is preferably selected from compounds comprising a peroxide group.

[0126] Preferably, the compound comprising a peroxide group comprises from 2 to 30 carbon atoms.

[0127] Preferably, the compound comprising a peroxy group is selected from diacyl peroxides, peroxyesters, peroxydicarbonates, dialkyl peroxides, peroxyacetals, hydroperoxides or peroxyketals.

[0128] The initiator (Ini) is selected from diisobutyryl peroxide, isopropyl peroxyneodecanoate, di(3-methoxybutyl) peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, isopropyl peroxyneoheptanoate, di-n-propyl peroxydicarbonate, tert-amyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, di-n-butyl peroxydicarbonate, hexadecyl peroxydicarbonate, Dimyristyl peroxide, 1,1,3,3-tetramethylbutyl peroxypivalate, tert-butyl peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, di-(3,5,5-trimethylhexanoyl)-peroxide, dilauroyl peroxide, didecanoyl peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)-hexane, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate, dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxydiethyl acetate, tert-butyl peroxyisobutyrate, 1,1-di-( tert-Butyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butyl peroxy)cyclohexane, 1,1-di-(tert-butyl peroxy)-cyclohexane, tert-amyl peroxy-2-ethylhexyl carbonate, tert-amyl peroxyacetate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 2,2-di-(tert-butyl peroxy)-butane, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxy-2-ethylhexyl carbonate, tert-amyl peroxybenzoate, tert-butyl peroxyacetate, butyl 4,4-di(tert-butyl peroxy)valerate, tert-butyl peroxybenzoate, di-tert-amyl peroxide, diisopropylbenzene peroxide, di-(2-tert-butyl) tert-butylperoxide, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-(2-methylbutyronitrile), azobisisobutyramide, 2,2'-azobis(2,4-dimethylvaleronitrile), 1,1'-azobis(hexahydrobenzonitrile), or 4,4'-azobis(4-cyanovaleric acid), or a mixture thereof.

[0129] Preferably, the initiator (Ini) is selected from isopropyl peroxyneodecanoate, di(3-methoxybutyl) peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, isopropyl peroxyneoheptanoate, di-n-propyl peroxydicarbonate, tert-amyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate di-n-butyl peroxide, hexadecyl peroxydicarbonate, dimyristyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, di-(3,5,5-trimethylhexanoyl)-peroxide, dilauroyl peroxide, didecanoyl peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)-hexane or 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, or mixtures thereof.

[0130] The thermoplastic composition may include between 0.1 phr and 5 phr of an initiator (Ini) to start the polymerization of the (meth)acrylic monomer (M1) and the (meth)acrylic comonomer (M2).

[0131] The method 100 according to the invention may comprise a heating step 113. Preferably, the heating step is carried out by a heating device. The heating step allows triggering and initiating the polymerization of the thermoplastic composition with the impregnated fibers.

[0132] Heating also allows to increase the space between molecules, which allows to improve the flexibility of the thermoplastic composite. As explained, the thermoplastic composite has the property of being substantially solid at room temperature and at the same time softening during temperature rise, in particular after exceeding its glass transition temperature (Tg) or melting temperature (Tf), and becoming solid again when the temperature drops below its melting point and below its glass transition temperature. Preferably, the (meth) acrylic thermoplastic polymer forming the (meth) acrylic thermoplastic polymer matrix has a glass transition temperature (Tg) between 50°C and 160°C, preferably between 70°C and 140°C, and even more preferably between 90°C and 120°C. This aspect gives it an advantage over other thermoplastic polymers such as polyamines. In fact, polyamines generally have very high melting points, i.e., 200°C and higher, which is not convenient for the process. The glass transition temperature or melting point can be measured by methods known to those skilled in the art. Preferably, these temperatures are measured by differential scanning calorimetry according to the conditions specified for Tg in standard ISO 11357-2 / 2013 and for Tm in standard ISO 11357-3 / 2011. In addition, the (meth)acrylic thermoplastic polymer or the portion of the (meth)acrylic thermoplastic polymer has a melt flow index (MFI) of less than 20 g / 10 min according to ISO 1133 (230° C. / 3.8 kg). Preferably, the melt flow index is less than 18 g / 10 min, more preferably less than 16 g / 10 min, advantageously less than 13 g / 10 min.

[0133] The heating step may include heating by convection, by conduction, by IR (infrared) including NIR and MIR (near and mid-infrared), by microwaves, by UV (ultraviolet) and / or by induction.

[0134] According to an embodiment of the heating step 113, polymerization may occur at a temperature typically below 140°C, preferably below 130°C and even more preferably below 125°C.

[0135] According to an embodiment of the heating step, the polymerization may take place at a temperature of at least 40°C, preferably at least 50°C and more preferably at least 60°C.

[0136] Preferably, the polymerisation may take place at a temperature between 40°C and 140°C, preferably between 50°C and 130°C, even more preferably between 60°C and 125°C.

[0137] Advantageously, the heating step can be carried out continuously or discontinuously.

[0138] The heating step and the polymerization allow the transition from a thermoplastic composition that impregnates the fibers (polymer resin or polymer resin precursor) and is liquid to a thermoplastic composite.

[0139] Preferably, the heated thermoplastic composite is not limited in its geometry.

[0140] Preferably, the heated thermoplastic composite is not limited in its dimensions (eg, its length).

[0141] Preferably, the pultruded sheet from the thermoplastic composite is obtained from a pultrusion process, and more preferably from a reaction pultrusion process. Pultrusion and reaction pultrusion processes are known to those skilled in the art. In these processes, the fibers are guided through a resin bath or an injection chamber comprising a composition or a slurry. The fibers as fibrous reinforcement are, for example, in the form of unidirectional rovings or continuous filament mats. After being impregnated in the resin, the wet fibers are pulled through a heated device in which polymerization can occur.

[0142] Advantageously, the method 100 according to the present invention may include a thermoforming step. The pultruded sheet may be shaped. The shape may be a bend, curvature, twist, fold, compression, a complex shape, or a combination of any of the above shapes. According to an embodiment, the pultruded sheet includes a change in its form in at least a portion of the entire pultruded sheet.

[0143] Preferably, the thermoforming step is performed by pulling the heated pultruded sheet through a shaping device. Due to the heated thermoplastic composite, the heated portion can be shaped into different geometries. The thermoforming step allows to change the form of the pultruded sheet. The thermoforming step can be achieved due to a fixed tool, weights on both sides of the thermoplastic composite, a rotating motor or using a die. The thermoforming step can include applying pressure to the pultruded sheet, preferably to the heated pultruded sheet.

[0144] The method according to the invention may include a cooling step 114. In a particular embodiment, the cooling step may be implemented by a cooling device. In addition, the cooling step may be implemented at a given cooling temperature and / or for a given cooling duration. The cooling step allows switching from a heated composite (i.e., pultruded sheet) to a cooled composite that is easier to handle.

[0145] According to an embodiment, the cooling temperature and / or cooling duration may be selected according to the glass transition temperature (Tg) and / or melting temperature of the heated thermoplastic composite. Preferably, the cooling step is at a cooling temperature below the glass transition temperature of the heated thermoplastic composite. For example, Tg may be below 130°C, preferably below 120°C, and more preferably below 110°C.

[0146] The method according to the invention may comprise a step 116 of drawing out the pultruded sheet. In a particular embodiment, the drawing out step may be performed manually or automatically. The drawing out step may be performed by mechanical cutting to a desired length.

[0147] The pulling out step allows recovery of the pultruded sheet.

[0148] The pulling step may be performed so that the pultruded sheet has a thickness of from 2 mm to 8 mm, preferably from 3 mm to 7 mm, more preferably from 4 mm to 6 mm.

[0149] Each pultruded sheet may have a lower surface and an upper surface extending in the longitudinal direction. The upper surface and the lower surface may be defined as two longest surfaces of the pultruded sheet, and the upper surface is opposite to the lower surface.

[0150] The pultruded sheet may have different geometric shapes, such as oval, flat, rectilinear, circular. Preferably, a plurality of pultruded sheets have the same geometric shape. More preferably, the pultruded sheet may have a constant cross-section.

[0151] According to the invention, the step of providing a plurality of pultruded sheets may include other optional steps. For example, the step of providing a pultruded sheet may include a surface texturing step 115. This step allows to improve the roughness, and therefore the adhesion.

[0152] Preferably, the textured surface may have a Ra between 3 μm and 30 μm according to standard ISO 4287: 1997. Advantageously, the surface of the pultruded sheet may have a rough outer surface for more grip later for better adhesion to the wind turbine blade.

[0153] The textured surface may comprise channels having a depth of at least 0.04 mm and at most 0.5 mm.

[0154] The surface texturing step may include texturing at least one surface (ie, the upper surface and / or the lower surface) of the pultruded sheet.

[0155] The surface texturing step may be selected from sandblasting, scraping, chemical pickling, lamination and / or calendaring. Advantageously, the surface texturing step does not include a peeling sheet. More preferably, the pultruded sheet does not include a peeling sheet. Preferably, the surface texturing step includes Figure 3 The advantage of pultruded sheet material is its thermoplastic properties which allow, among other things, the design of patterns. In addition, calendering allows the replacement of peeling sheets which are expensive and slow down production. Advantageously, calendering allows the design of patterns, the addition of roughness and rapid implementation.

[0156] Back to Figure 1 And according to an embodiment, the method according to the invention may comprise a step 120 of providing a plurality of interlayers.

[0157] The interlayer may comprise fibres, preferably glass fibres or carbon fibres. The fibres may correspond to the fibres as described above. The fibres in each interlayer may be stitched together, held together by a binder, stitched and / or woven together.

[0158] The interlayer may be a texture or fabric, preferably a glass fabric, and more preferably a permeable glass fabric.

[0159] The interlayer may consist of a thermoplastic layer.

[0160] Preferably, the thermoplastic layer may be a thermoplastic composition. The thermoplastic composition may be a thermoplastic polymer and / or a thermoplastic polymer alloy.

[0161] The thermoplastic layer may comprise at most 10% by volume, preferably at most 5% of fibres.

[0162] Preferably, the interlayer may have the same size and / or geometry as the pultruded sheet. Likewise, each interlayer may have a lower surface and an upper surface extending in the longitudinal direction. The upper surface and the lower surface may be defined as the two longest surfaces of the interlayer, and the upper surface is opposite to the lower surface.

[0163] According to an embodiment, the interlayer may have a thickness from 0.05 mm to 0.5 mm.

[0164] The method according to the invention may comprise a step of stacking the pultruded sheets into a pre-spar cap shape 130. Preferably, this step is performed in a mould.

[0165] The stacking step may include a thermoforming step.

[0166] According to an embodiment, the interlayer may be arranged between lower and upper surfaces of two pultruded sheets, such as the upper or lower interlayer surface facing the lower surface of the first pultruded sheet and the upper or lower interlayer surface facing the upper surface of the second pultruded sheet.

[0167] Alternatively, the pultruded sheets may be separated by one or more interlayers.

[0168] The stacking step may be performed until the desired thickness is reached, preferably according to the thickness of the intended spar cap. Preferably, the maximum strain is less than the breaking strain of the fiber, and more preferably, for carbon fiber, is 1.8% or less. The thickness may be calculated in this regard.

[0169] According to an embodiment, the stacking step may include at least two pultruded sheets.

[0170] According to another embodiment, the stacking step may include at least one interlayer between two pultruded sheets.

[0171] The method according to the invention may comprise a step 140 of joining the stacked pultruded sheets. This step allows forming and eventually producing the spar caps. According to an embodiment, pre-spar cap shapes may be joined with spar caps.

[0172] The joining step may be performed in a spar cap mould. This mould may be the same as the one used to stack the pultruded sheets.

[0173] Alternatively, the stacked pultruded sheets of the spar caps are joined in a spar cap mould, and the spar caps will be joined in a rotor blade, for example using a rotor blade mould.

[0174] According to an embodiment, the joining step 140 may be performed in a rotor blade mould.

[0175] According to an embodiment, the stacked pultruded sheets of the spar cap are joined when the rotor blade is formed, preferably by infusion and / or a thermoplastic adhesive.

[0176] The joining step 140 may include plastic joining, plastic welding, infusion and preferably thermoplastic infusion, ultrasonic welding, induction welding, resistance wire welding, laser welding, heating by infrared or ultraviolet radiation and / or gluing. Plastic welding may include heating. The heating may be selected among conductive heating, radial heating and / or volumetric heating. Preferably, the joining step may include welding. In fact, thermoplastic spar caps may be welded instead of using adhesives, which allows the production of easily recyclable spar caps and, therefore, rotor blade turbines that do not require any material separation. Preferably, the welded interface may have a thickness greater than or equal to 0.05 mm, preferably greater than or equal to 0.5 mm. The thickness of the welded interface may be measured by conventional methods, for example from a vertical section of the welded interface.

[0177] The method may further include an infusion step. The joining step 140 may include infusing a polymer resin between the pultruded sheets and curing the polymer resin to form a spar cap. The joining step 140 may include infusing a polymer resin between the pultruded sheets and curing the polymer resin to form a spar cap, for example, when forming a rotor blade.

[0178] The step 140 of joining may include applying at least one deforming force to the spar cap. Applying deformation to the spar cap may cause it to assume the shape of the mold and match the shape of the wind turbine blade. The deformation may be applied due to passing force, sub-vacuum force, weight, and / or heat of the mold.

[0179] The method for producing a spar cap according to the invention may further comprise a thermoforming step 150. The thermoforming step 150 may correspond to the thermoforming step as disclosed above.

[0180] Compared to conventional thermoplastic pultrusion, the method according to the invention is faster and energy efficient to produce by using in particular reactive pultrusion. In addition, as shown, the method allows the production of spar caps with the same (or better) properties as thermoset spar caps.

[0181] The method frees up the use of expensive and production slowing peel plies by calendaring at least one surface of the pultruded sheet material for improved surface roughness. The method also frees up the welding of the entire spar cap.

[0182] Additionally, the method allows for the production of recyclable spar caps and wind blades.

[0183] Finally, the method according to the invention allows reducing waste, time and costs while meeting the needs and requirements of the field.

[0184] According to another aspect, the invention proposes a spar cap for a wind turbine obtainable, preferably obtained, by the method according to the invention.

[0185] A spar cap for a wind turbine may comprise a plurality of joined pultruded sheets, the pultruded sheets being a thermoplastic composite comprising 45% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 55% by volume of fibers. Preferably, the thermoplastic composite comprises 40% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 60% by volume of fibers, and even more preferably, the thermoplastic composite comprises 35% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 65% by volume of fibers. The pultruded sheet is a thermoplastic composite comprising at least 25% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 75% by volume of fibers. Preferably, the thermoplastic composite comprises at least 27% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 73% by volume of fibers. More preferably, the thermoplastic composite comprises at least 30% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 70% by volume of fibers. The pultruded sheet is a thermoplastic composite comprising between 25% and 45% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 55% and 75% by volume of fibers. Preferably, the thermoplastic composite comprises between 27% and 40% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 60% and 73% by volume of fibers. More preferably, the thermoplastic composite comprises between 30% and 35% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 65% and 70% by volume of fibers.

[0186] When the fibers are glass fibers, the fiber and resin content are measured according to ISO 1172: 1996, and when the fibers are carbon fibers, the fiber and resin content are measured according to ISO 14127: 2008. Using the density of the corresponding material, % volume can be converted to % weight, and vice versa.

[0187] According to an embodiment, the pultruded sheet may have at least one textured surface. According to standard ISO 4287:1997, the textured surface may have a Ra between 3 μm and 30 μm.

[0188] The pultruded sheets may be separated by one or more interlayers.The spar caps according to the invention may comprise interlayers as disclosed above.

[0189] Preferably, the spar caps according to the present invention do not comprise thermoset.

[0190] Preferably, the spar cap according to the present invention comprises no peeling plies.

[0191] The spar cap for a wind turbine according to the present invention can be easily recycled. In addition, the spar cap of the present invention has high strength and light weight. It also brings very good UV resistance and impact resistance.

[0192] The spar caps according to the invention are also easy to thermoform, bond, weld and / or overmould.

[0193] Compared to thermosetting resins, the spar caps according to the invention bring similar mechanical properties.In addition, the spar caps according to the invention meet the specifications required in the art.

[0194] According to another aspect, the invention relates to a rotor blade comprising a spar cap according to the invention.

[0195] The rotor blade may comprise a cross-sectional form varying between a tip of the rotor blade and a root corresponding to an attachment zone. The rotor blade may comprise a shell defining a lower surface and an upper surface and a leading edge and a trailing edge. For example, the shell is more particularly formed with a spar cap.

[0196] Preferably, the spar cap extends along the wind turbine blade and between at least the leading edge and / or at least the trailing edge.The spar cap allows for improved stability and local stiffness compared to rotor blades of thermoplastic polymer composite only.

[0197] The invention based on the use of thermoplastic polymer composites makes it possible to produce new rotor blades. The rotor blades according to the invention can be easily recycled and are more recyclable than current rotor blades. In addition, the rotor blades according to the invention bring similar mechanical properties compared to current rotor blades and more particularly compared to thermoset rotor blades and thermoset-thermoplastic rotor blades.

[0198] According to another aspect, the invention relates to a method for producing a rotor blade comprising a spar cap according to the invention. The method may comprise the step of associating the spar cap with the shell and the shear web. The method may also comprise the step of joining them by gluing, welding or infusion.

[0199] With regard to the associated steps, different processes can be used. Mention may be made of vacuum assisted resin infusion (VARI), vacuum assisted resin transfer molding (VARTM), pultrusion, vacuum infusion molding, pressure infusion molding, autoclave molding, resin transfer molding (RTM) and their variants, such as (HP-RTM, C-RTM, I-RTM), reaction injection molding (RIM), reinforced reaction injection molding (R-RIM) and their variants, press molding, compression molding, liquid compression molding (LCM) or sheet molding (SMC) or block molding (BMC). Preferably, the rotor blade made of polymer composite is manufactured by low-pressure injection molding, infusion molding or by molding of (meth)acrylic thermoplastic polymer composites.

[0200] A first preferred manufacturing process for manufacturing a wind turbine blade is a process according to which the thermoplastic composition is transferred to the fibrous reinforcement by impregnating the fibrous reinforcement in a mould.

[0201] A second preferred manufacturing process for manufacturing wind turbine blades is a process according to which the thermoplastic composition is used in a pultrusion process. According to the invention, the fibers are guided via batches or in an injection chamber of a thermoplastic composition comprising the composition. The fibers in the form of a fibrous reinforcement are, for example, in the form of unidirectional rovings or continuous filament mats. After impregnation, the wet fibers are pulled through a heated mold in which polymerization occurs.

[0202] A third preferred manufacturing process is Vacuum Assisted Resin Infusion (VARI).

[0203] The method for producing a rotor blade may further comprise a subsequent treatment aimed at strengthening the outer shell and improving its mechanical and chemical properties. For example, the treatment may be specifically located in certain areas of the outer surface of the rotor blade, such as along the leading edge. In this case, the treatment may comprise the deposition of a plastic or metal protective layer covering the leading edge.

[0204] The method for producing a rotor blade may further comprise a post-forming step. Post-forming involves bending and modifying the shape of the composite part. The process for manufacturing a rotor blade may further comprise a rolling step.

[0205] According to another aspect, the invention proposes a wind turbine comprising a spar cap according to the invention and / or a rotor blade according to the invention.

[0206] The wind turbine according to the invention brings the same advantages as the spar cap according to the invention and / or the rotor blade according to the invention.In fact, the wind turbine according to the invention can be easily recycled while providing mechanical and chemical properties that meet the requirements of the wind energy industry.

[0207] [Example]

[0208] Pultruded sheet is produced by pultrusion. Carbon fiber ( CT50-4.0 / 240) was impregnated with a thermoplastic composition. The thermoplastic composition was a (meth)acrylic syrup S1. The syrup S1 was prepared by dissolving 20 parts by weight of PMMA (BS520, a copolymer of MMA including ethyl acrylate as a comonomer) in 80 parts by weight of methyl methacrylate stabilized with MEHQ (hydroquinone monomethyl ether), adding 2 parts by weight of 1,4-butanediol dimethacrylate and a mixture of 1 part each of three different initiators (Ini1), (Ini2) and (Ini3), the three different initiators being: di(4-tert-butylcyclohexyl)peroxydicarbonate (P16-from Akzo Nobel) 16) Didecanoyl peroxide (DEC- from Arkema DEC) and 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (Tx141-from Akzo Nobel 141).

[0209] The impregnated fibers were heated to 110° C. during the pultrusion process in order to polymerize the thermoplastic composition. The pultrusion die was configured in order to obtain a sheet with a thickness of 5 mm and a width of 100 mm. The sheet had the following properties summarized in Table 1.

[0210] Table 1 - Properties of a pultruded sheet material complying with the specification for a wind turbine spar cap.

[0211] The invention allows to propose a spar cap comprising a thermoplastic, preferably without thermosetting properties, and which is therefore easily recyclable, while providing mechanical and chemical properties meeting the requirements of the wind energy industry.

[0212] The present invention allows to provide a recyclable solution to spar caps and preferably pultruded spar caps and therefore to rotor blades and wind turbines. Each pultruded sheet does not need to be glued to each other. In addition, thermoplastic spar caps bring similar mechanical properties compared to thermosetting resins and are therefore used for rotor blades and wind turbines.

[0213] Additionally, the present invention allows for reduced waste and facilitates the pultrusion process.

[0214] Furthermore, due to the thermoplastic properties, it is possible to design the pattern directly without using, for example, a release sheet.

[0215] The invention also allows time saving and reduces cycle time and costs.

[0216] In addition to those described above, the present invention may be the subject of a variety of variations and applications. In particular, unless otherwise indicated, the different structural and functional features of each of the above-described implementations should not be considered to be combined with each other and / or closely and / or inseparably associated, but rather to be considered as simple juxtapositions. In addition, the structural and / or functional features of the various embodiments described above may be the subject of any different juxtapositions or any different combinations, in whole or in part.

Claims

1. A method (100) for producing a spar cap for a rotor blade of a wind turbine, the method The following steps are involved: - providing a plurality of pultruded sheets (110), the pultruded sheets being a thermoplastic composite comprising 45% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 55% by volume of fibers, preferably carbon fibers; - stacking the pultruded sheets into a pre-spar cap shape (130); and - Joining the stack of pultruded sheets (140) in order to produce the spar cap.

2. The method (100) for producing a spar cap according to claim 1, in, The pultruded sheet is a thermoplastic composite comprising 35% by volume or less of a polymer matrix comprising a (meth)acrylic polymer, and at least 65% by volume of fibers.

3. A method (100) for producing a spar cap according to claim 1 or claim 2, in, The pultruded sheet is a thermoplastic composite comprising at least 25% by volume of a polymer matrix comprising a (meth)acrylic polymer, and at most 75% by volume of fibers.

4. A method (100) for producing a spar cap according to any one of the preceding claims, in, The pultruded sheet is a thermoplastic composite comprising between 25 and 45 volume % of a polymer matrix comprising a (meth)acrylic polymer, and between 55 and 75 volume % of fibers.

5. Method (100) for producing a spar cap according to any one of the preceding claims, in, The pultruded sheet is a thermoplastic composite comprising between 30% and 35% by volume of a polymer matrix comprising a (meth)acrylic polymer, and between 65% and 70% by volume of fibers.

6. Method (100) for producing a spar cap according to any one of the preceding claims, in, The step (110) of providing a plurality of pultruded sheets comprises a step (115) of surface texturing, preferably said textured surface having a Ra between 3 μm and 30 μm according to standard ISO 4287:1997.

7. Method (100) for producing a spar cap according to any one of the preceding claims, in, The pultruded sheet has a thickness of from 2 mm to 8 mm.

8. Method (100) for producing a spar cap according to any one of the preceding claims, in, The method further comprises a step (120) for providing a plurality of interlayers.

9. Method (100) for producing a spar cap according to any one of the preceding claims, in, The stacking step (130) further includes a thermoforming step.

10. Method (100) for producing a spar cap according to any one of the preceding claims, in, The joining step (140) is performed in a spar cap mould.

11. A method (100) for producing a spar cap according to claim 1 to claim 10, in, The joining step (140) is performed in a rotor blade mould and wherein the stacked pultruded sheets of the spar cap are joined when the rotor blade is formed, preferably by infusion and / or thermoplastic adhesive.

12. Method (100) for producing a spar cap according to any one of the preceding claims, in, The step (110) of providing a plurality of pultruded sheets comprises the following steps: - providing roving fibers (111); - impregnating the fibers (112) with a polymer resin comprising a polymer matrix comprising a (meth)acrylic polymer; - heating the impregnated fibers (113); - cooling the heated composite (114), and optionally calendering; and - Pulling out the pultruded sheet (116).

13. The method (100) for producing a spar cap according to claim 12, in, The temperature during the heating step is between 40°C and 140°C.

14. A method (100) for producing a spar cap according to claim 1 to claim 5, in, The method includes a surface texturing step (115).

15. Method (100) for producing a spar cap according to any one of the preceding claims, in, The pultruded sheet does not include a release sheet.

16. A method (100) for producing a spar cap according to claim 1 to claim 15, in, The fibers are glass fibers.

17. A method (100) for producing a spar cap according to claim 1 to claim 15, in, The fibers are carbon fibers.

18. A spar cap for a wind turbine obtainable by a method according to any one of the preceding claims.

19. The spar cap according to claim 18, in, The spar cap comprises a plurality of pultruded sheets, the pultruded sheets being a thermoplastic composite comprising 45% or less by volume of a polymer matrix comprising a (meth)acrylic polymer, and at least 55% by volume of fibers, preferably carbon fibers, the plurality may correspond to at least two.

20. The spar cap according to claim 19, in, The pultruded sheet has at least one textured surface having a Ra between 3 μm and 30 μm according to standard ISO 4287:1997.

21. The spar cap according to claim 19, in, The pultruded sheets may be separated by one or more interlayers.

22. A rotor blade comprising a spar cap according to claim 18.

23. A wind turbine comprising a spar cap according to claim 18 or a rotor blade according to claim 22.

24. A method for producing a rotor blade comprising a spar cap according to claim 18, the method comprising associating the spar cap with a shell and a shear web and joining them by gluing, welding or infusion.

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