An electric heating lightning protection composite film for blade deicing and a preparation method thereof

Abstract

The present application relates to a kind of electric heating lightning protection composite film for blade deicing and its preparation method, electric heating lightning protection composite film includes in turn: (1) lightning protection surface layer, including metal element and at least partially impregnated the first resin matrix of the metal element;(2) insulating resin core layer, resistance is greater than 2000MΩ;(3) heating bottom layer, including heating element and at least partially impregnated the second resin matrix of the heating element, the heating element includes at least one of carbon fiber, graphene;The first resin matrix and second resin matrix include same or different thermoplastic resin;The electric heating lightning protection composite film is formed into an integrated structure by superimposing metal net, first resin matrix, insulating resin, second resin matrix and heating element, hot-pressing molding.The present application uses thermoplastic resin system, obtains multifunctional integrated composite film by hot-pressing molding, effectively takes into account electric heating deicing and lightning protection effect by bonding on the surface of wind turbine blade.

Description

Technical Field

[0001] This invention belongs to the field of wind power technology, and specifically relates to wind turbine blade de-icing and lightning protection technology, and more specifically to an electrically heated lightning protection composite film for blade de-icing, its preparation method, and a wind turbine blade. Background Technology

[0002] Wind energy, as a new energy source, has advantages such as being clean, renewable, and inexhaustible, and has therefore been widely used. In southern my country (such as Hunan, Yunnan, and Guizhou provinces), wind farms are mostly located in high-altitude, cold mountainous areas where winter icing is severe. These areas have unique climatic characteristics of low temperatures and high humidity in winter, leading to frequent accidents such as wind turbine shutdowns and damage caused by icing on the turbine blades. At the same time, wind turbines are located at high altitudes and in open mountaintop locations, making them susceptible to direct lightning strikes, resulting in frequent blade damage accidents caused by lightning strikes.

[0003] However, while using electrothermal de-icing, the presence of metallic substances on the blade surface greatly increases the probability of the blade being struck by lightning; while using lightning arresters for lightning protection, due to the large blade area, makes it difficult to effectively attract lightning, thus increasing the risk of lightning strikes to the composite fiber material of the blade body.

[0004] Existing blade de-icing and lightning protection technologies mainly employ electrothermal de-icing and the installation of several lightning arresters on the blade surface, with lightning current being conducted to the ground via a grounding down conductor. For example, patent application CN 115898793A discloses a system for implementing lightning protection and de-icing of wind turbine blades, enabling intelligent switching between lightning protection and de-icing modes. This system includes: sensors for real-time measurement of ambient temperature, wind speed, and ice thickness; a DC de-icing power supply introduced from the nacelle hub motor, which generates a low-voltage, high-current signal via a half-bridge rectifier circuit, with the DC power output connected to a de-icing / grounding switch on the blade via a slip ring; two terminals of a lightning surge protection device connected to both ends of a metal mesh; both ends of the metal mesh connected to the de-icing / grounding switch corresponding to the positive and negative terminals of the DC de-icing power supply, and grounded via a lightning arrester down conductor; and a control unit for connecting and controlling the de-icing / grounding switch to connect the DC power cable to the blade metal mesh in de-icing mode, and disconnecting the blade metal mesh from the DC power cable and grounding the blade metal mesh when switching to lightning protection mode. However, the de-icing and lightning protection system of this invention has a complex structure, uses a large amount of metal materials, has a large load on the blades, and increases the probability of the blades being struck by lightning. Due to the large blade area and the limited number of lightning rods, it is difficult to effectively attract lightning, which significantly increases the risk of the composite fiber material of the blade body being struck by lightning.

[0005] Patent application CN110701005A discloses an integrated composite membrane for electric heating, de-icing, and lightning protection of wind turbine blades. This composite membrane includes an adhesive layer, a first adhesive reinforcement layer, an electric heating film layer, an isolation layer, a lightning protection mesh layer, a second adhesive reinforcement layer, and a protective paint layer. While this invention optimizes the structure compared to the system disclosed in patent application CN 115898793A, saving on-site operation time and reducing on-site construction costs, and can be used for both new blade manufacturing and existing wind farm blade de-icing upgrades, offering flexibility and adaptability, it primarily uses a traditional thermosetting resin system. The low insulation level of the raw materials cannot fully guarantee that the electric heating film layer is unaffected by strong lightning strikes, resulting in low reliability. Furthermore, the composite membrane structure is relatively complex, the processing technology is cumbersome, the yield is low, and recycling is difficult.

[0006] Therefore, the urgent technical problem to be solved in this field is to determine which materials and preparation methods are used to produce an electrically heated lightning protection composite film with high electric heating de-icing efficiency, good lightning protection performance, and effective insulation and isolation between the heating element and the lightning protection metal element, and to use the composite film in wind turbine blades to provide wind turbine blades that can operate stably for a long time in low temperature and high humidity climate environments. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention aims to provide an electrically heated lightning protection composite film for blade de-icing and its preparation method, and further provide a wind turbine blade having the electrically heated lightning protection composite film.

[0008] Specifically, the present invention provides an electrically heated lightning protection composite membrane for blade de-icing, comprising the following layers in sequence:

[0009] (1) A lightning protection surface layer comprising a metal element and a first resin matrix at least partially impregnated with the metal element;

[0010] (2) Insulating resin core layer with a resistance greater than 2000MΩ;

[0011] (3) A heating substrate comprising a heating element and a second resin matrix at least partially impregnated with the heating element, wherein the heating element comprises at least one of carbon fiber and graphene;

[0012] The first resin matrix and the second resin matrix contain the same or different thermoplastic resins;

[0013] The electrically heated lightning protection composite film is formed into an integral structure by superimposing a metal mesh, a first resin matrix, an insulating resin, a second resin matrix, and a heating element.

[0014] To optimize the structure of multilayer films, reduce processing steps, and effectively control film thickness, this invention uses thermoplastic resin instead of the thermosetting resin commonly used in existing technologies. This not only enables the thermoplastic resin to impregnate and fix the metal mesh and heating element, but also allows the layers to be melted and bonded together. Furthermore, leveraging the recyclability of thermoplastic resin, waste films can be recycled and reused, reducing costs and being more environmentally friendly.

[0015] The resin used in the insulating resin core layer of this invention must have excellent insulation properties. Optionally, the insulation properties of the layer can be further improved by adding insulating fillers to ensure that it provides insulation and isolation to the lightning protection surface layer and the heating bottom layer on both sides, thereby achieving the effects of heating de-icing and lightning protection safety.

[0016] Carbon fiber and its fabrics or other forms are currently widely used electric heating materials on the market. Graphene materials have the advantages of faster heating and higher efficiency, and the products are thinner, but the cost is slightly higher than that of carbon fiber. Therefore, depending on the weight and thickness requirements of multilayer films, the differences in the icing area of ​​blades, and the risk of lightning strikes, it is of great significance to use the two alone or in combination for practical production applications.

[0017] The thickness of the composite film is 1-5 mm, preferably 1-3 mm, wherein the thickness of the lightning protection surface layer is 0.5-1.0 mm, the thickness of the heating layer is 0.2-1.0 mm, and the thickness of the insulating resin core layer is 0.1-1.0 mm, preferably 0.1-0.5 mm.

[0018] Furthermore, the metal element comprises either a copper mesh or an aluminum alloy mesh, the copper / aluminum alloy mesh being connected to the lightning arrester of the blade; the heating element is connected to a power source. The metal element in the lightning protection layer can have various choices in terms of metal type and structural form, such as using metal foil, metal mesh, metal fiber, or metal particles with good conductivity. Considering factors such as overall cost and process complexity, metal mesh is preferred, especially with a basis weight of 850 g / m². 2 The preferred value is 800g / m³. 2 The following copper or aluminum alloy mesh, the copper / aluminum alloy mesh connected to the lightning arrester of the blade, is grounded through the lightning protection system in the blade via the down conductor.

[0019] The heating element has two electrodes, which are connected to the positive and negative terminals of the power supply, respectively, and connected to the electric heating control cabinet. Based on the monitored icing condition on the blade surface, heating is activated to remove the ice, thereby achieving intelligent de-icing operation.

[0020] Furthermore, the insulating resin comprises at least one of thermoplastic polyimide resin and polyolefin resin.

[0021] Both the first and second resin matrices contain ethylene-vinyl acetate copolymer (EVA). Using the same thermoplastic resin makes it easier to determine the melting temperature range during hot pressing. EVA resin melts when heated, exhibiting excellent adhesion, effectively impregnating and bonding the metal components of the lightning protection layer and the heating elements of the heating layer into a single structure. Specifically, a hot pressing platform is used to integrally hot press the stacked raw materials, raising the hot pressing temperature above the softening temperature of EVA to leverage its adhesive properties. This approach offers simple process control, continuous production capability, and high production efficiency.

[0022] Furthermore, the first resin matrix, insulating resin, and second resin matrix are pre-formed into a pre-made film, which is then stacked between the metal mesh and the heating element and hot-pressed as a whole to obtain an electrically heated lightning protection composite film with a thickness of 1-5 mm.

[0023] Optionally, on the side of the heating substrate opposite to the insulating resin core layer, an adhesive layer is also included. The adhesive layer comprises at least one of EPDM rubber, nitrile rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, and chloroprene rubber. The adhesive layer can be bonded to the heating substrate by coating, bonding, or other methods after the aforementioned integral hot pressing molding. More preferably, the raw materials of the adhesive layer are stacked outside the heating element, i.e., stacked as follows: metal mesh / first resin matrix / insulating resin / second resin matrix / heating element / adhesive layer raw materials, and then integrally hot pressed molding is performed to form the above layers into an integral structure.

[0024] Furthermore, by weight percentage, the heating element comprises:

[0025] Carbon fiber fabric 40-90%

[0026] Graphene 10-60%;

[0027] The carbon fiber fabric and graphene undergo the following composite treatment:

[0028] S1: Prepare an ethanol-water solution of 1-3% by mass of silane coupling agent, then add acetic acid to adjust the pH to 3-4.5, and pre-hydrolyze at 45-75℃ for later use;

[0029] S2: Add graphene to a pre-hydrolyzed silane coupling agent solution, sonicate for 2-4 hours, filter, and wash with anhydrous ethanol to obtain surface-treated graphene.

[0030] S3: Surface-treated graphene is dispersed in anhydrous ethanol to obtain a suspension;

[0031] S4: Impregnate the carbon fiber fabric with the suspension, filter, and vacuum dry to attach the graphene to the carbon fiber fabric.

[0032] In addition to using carbon fiber fabric and graphene material alone, a combination of the two can also be used. In particular, using carbon fiber fabric as a framework and attaching graphene to the fabric can effectively reduce the amount of carbon fiber used, further reducing weight, and can also take advantage of the electrical conductivity and heating properties of graphene, saving the amount of graphene used and reducing costs.

[0033] Furthermore, the carbon fiber fabric undergoes low-temperature plasma surface treatment, including the following steps:

[0034] (1) The carbon fiber fabric was ultrasonically treated in anhydrous ethanol and deionized water, and then dried for later use.

[0035] (2) Using argon as the reaction gas, the carbon fiber fabric is subjected to low-temperature plasma surface activation treatment on both sides.

[0036] Carbon fibers have low surface energy and are chemically inert, resulting in poor wettability and interfacial bonding with resin matrices. Surface treatment can increase the number of polar functional groups, such as carboxyl groups, on the carbon fiber surface and / or increase the surface area, thereby improving wettability and bonding strength with the resin matrix. This invention uses low-temperature plasma to treat both sides of carbon fiber fabrics, reducing the amount of chemical agents used and simplifying the processing. It is suitable for rapid processing of large-area, continuous carbon fiber fabrics. This effectively improves the compatibility between carbon fiber fabrics and resin matrices, which not only enhances the overall mechanical properties and stability of the composite membrane but also efficiently conducts the heat generated by the carbon fiber fabric when electrically conductive, improving de-icing efficiency.

[0037] Furthermore, the preformed film is prepared by three-layer co-extrusion;

[0038] The insulating resin core layer also includes an insulating filler, the mass ratio of the insulating filler to the insulating resin being (2-5):(95-98); the insulating filler is selected from at least one of talc, light calcium carbonate, boron nitride, and boehmite; optionally, the insulating filler is surface treated.

[0039] Furthermore, the insulating filler is composed of small-particle-size fillers with a particle size of 1-4 μm, medium-particle-size fillers with a particle size of 10-20 μm, and large-particle-size fillers with a particle size of 30-40 μm in a mass ratio of (10-20):(60-70):(10-30).

[0040] Based on the characteristics of thermoplastic resins, a pre-formed film is prepared by co-extruding a first resin matrix, an insulating resin, and a second resin matrix in three layers. During use, the pre-formed film is unwound and stacked with a metal mesh and heating elements for rapid hot pressing. Compared to traditional thermosetting resins which use a pre-impregnated resin in a solid-liquid form, using a thermoplastic resin matrix ensures that each layer is solid before hot pressing, facilitating transportation and storage. Feeding during production is convenient, and simple stacking allows for hot pressing, which is beneficial for stable, automated, and large-scale production. Furthermore, composite film products using thermoplastic resin systems exhibit better flexibility and shape adaptability than thermosetting resin systems, demonstrating better adhesion to non-planar surfaces.

[0041] In addition to using polyimide (PI) and polyolefin (POE) with good temperature resistance and high insulation level, the insulating resin core layer can also use insulating fillers. These insulating fillers undergo surface treatment, resulting in good dispersibility and compatibility in the resin matrix, which helps to further improve the insulation level of the insulating resin core layer. On the other hand, the insulating fillers also have good thermal conductivity. In particular, the use of insulating fillers with a mixture of large, medium and small particle sizes allows for a hybrid effect, increasing the probability of contact between fillers and making it easier to form thermal conductive pathways. This improves the thermal conductivity of the system more than that of particles with a single microscopic morphology, which is beneficial for fully transferring the heat from the heated bottom layer to the surface of the composite film, improving de-icing efficiency and reducing energy consumption.

[0042] On the other hand, the present invention provides a method for preparing an electrically heated lightning protection composite film for blade de-icing, comprising the following steps:

[0043] Step 1: The first resin matrix, insulating resin, and second resin matrix are pre-formed into a pre-made film comprising a three-layer structure;

[0044] Step 2: Place the metal mesh on the outside of the first resin matrix of the preformed film, and place the heating element on the outside of the second resin matrix of the preformed film;

[0045] Step 3: Heat press at 120-150℃ for 5-15 minutes to obtain an electrically heated lightning protection composite film with an integrated structure and a thickness of 1-5mm.

[0046] Thirdly, this invention provides a wind turbine blade with the aforementioned electrically heated lightning protection composite film. Several electrically heated lightning protection composite films are discontinuously arranged on the surface of the wind turbine blade. The length and width dimensions of the electrically heated lightning protection composite film are (200-800mm) × (5000-7000mm). This invention cuts the composite film according to the blade size and specific bonding location. Besides the selection of length and width dimensions, the thickness of the electrically heated lightning protection multilayer film at different locations can also be selected and adjusted. For example, at the blade tip, the degree of icing and the risk of lightning strikes are both greater, but excessive film thickness will result in a larger centrifugal load on the blade and increased energy consumption. Therefore, the thickness of the multilayer film in the blade tip region is preferably below 3.5mm, more preferably below 2.5mm. To obtain a thinner thickness, the heating element preferably has increased graphene content, or uses only graphene.

[0047] The advantages of this invention are as follows:

[0048] 1. This invention uses a thermoplastic resin system to integrate impregnation and bonding simultaneously, improving the continuity and flexibility of the molding process, reducing production difficulty, and effectively solving the problems of thick and hard film, complex structure, low production efficiency, and high cost of recycling caused by the use of thermosetting resin systems in existing technologies.

[0049] 2. The insulating resin core layer of this invention uses PI or polyolefin material with a resistivity greater than 2000MΩ, which can enhance the insulation effect between the lightning protection surface layer and the heating bottom layer, providing better protection for the heating bottom layer. In particular, adding a small amount of insulating filler not only improves the insulation level but also helps to reduce the thickness of the insulating resin core layer and improve the thermal conductivity of the insulation layer, allowing the heat released from the heating bottom layer to be better conducted to the composite film surface layer, thus improving the de-icing efficiency.

[0050] 3. The heating element flexibly utilizes carbon fiber fabric and graphene, and is designed to take into account factors such as thickness, heating efficiency and cost. The composite film is scientifically arranged on the surface of the wind turbine blade to achieve the effect of de-icing and lightning protection. Attached Figure Description

[0051] The above and other objects, features, and advantages of exemplary embodiments of the present disclosure will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the present disclosure are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0052] Figure 1 This is a schematic diagram of the process flow of the electrically heated lightning protection composite film of the present invention;

[0053] Figure 2 This is a partial schematic diagram of a wind turbine blade comprising several electrically heated lightning protection composite films according to the present invention.

[0054] Explanation of reference numerals in the attached drawings: 10. Lightning protection surface layer, 11. Metal component, 20. Insulating resin core layer, 30. Heating bottom layer, 31. Heating element, 40. Adhesive layer, 50. Hot press, 100. Electric heating lightning protection composite film, 200. Wind turbine blade. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings.

[0056] The electrically heated lightning protection composite membrane 100 for blade de-icing of the present invention has a thickness of 1-5 mm and comprises the following layers in sequence:

[0057] (1) A lightning protection surface layer 10 with a thickness of 0.5-1.0 mm includes a metal element 11 and a first resin matrix at least partially impregnated with the metal element 11; the metal element 11 includes one of a copper mesh and an aluminum alloy mesh, wherein the copper mesh / aluminum alloy mesh is connected to the lightning arrester of the blade; the first resin matrix preferably includes EVA;

[0058] (2) An insulating resin core layer 20 has a thickness of 0.1-1.0 mm, preferably 0.1-0.5 mm, and a resistance greater than 2000 MΩ; the insulating resin in the insulating resin core layer 20 includes at least one of thermoplastic polyimide resin and polyolefin resin; optionally, the insulating resin core layer 20 also includes an insulating filler, the mass ratio of the insulating filler to the insulating resin is (2-5):(95-98); the insulating filler is selected from at least one of talc, light calcium carbonate, boron nitride, and boehmite; the insulating filler undergoes physical and / or chemical surface treatment, such as plasma surface treatment, coupling agent surface treatment, etc.; the insulating filler is compounded by small particle size filler with a particle size of 1-4 μm, medium particle size filler with a particle size of 10-20 μm, and large particle size filler with a particle size of 30-40 μm in a mass ratio of (10-20):(60-70):(10-30);

[0059] (3) Heating substrate 30, with a thickness of 0.2-1.0 mm, includes heating element 31 and a second resin matrix at least partially impregnated with heating element 31. Heating element 31 includes at least one of carbon fiber and graphene. The ratio of carbon fiber / graphene is specifically selected according to the thickness of the composite film, the application location, and other conditions. Heating element 31 is connected to a power source. The second resin matrix preferably includes EVA.

[0060] (4) Optional adhesive layer 40, with a thickness of 0.2-1.0 mm, includes at least one of EPDM rubber, nitrile rubber, natural rubber, isoprene rubber, styrene-butadiene rubber, and chloroprene rubber.

[0061] The first resin matrix and the second resin matrix contain the same or different thermoplastic resins, preferably both of which are EVA, so as to facilitate the selection of a more consistent processing temperature during prefabrication and hot pressing processes.

[0062] The electrically heated lightning protection composite film 100 is formed by stacking a metal mesh, a first resin matrix, an insulating resin, a second resin matrix, a heating element 31, and an optional adhesive layer 40, placing them in a hot press 50, and hot-pressing them into an integral structure; preferably, it specifically includes the following steps:

[0063] Step 1: The first resin matrix, the insulating resin, and the second resin matrix are pre-formed into a pre-film with a three-layer structure by three-layer co-extrusion.

[0064] Step 2: Place the metal mesh on the outside of the first resin matrix of the preformed film, and place the heating element 31 on the outside of the second resin matrix of the preformed film; preferably, place the raw material of the adhesive layer 40 outside the heating element 31, that is, stack it as: metal mesh / first resin matrix / insulating resin / second resin matrix / heating element 31 / adhesive layer 40 raw material.

[0065] Step 3: At a temperature of 120-150℃, hot press for 5-15 minutes to obtain an electrically heated lightning protection composite membrane 100 with an integrated structure and a thickness of 1-5mm.

[0066] The carbon fiber fabric and graphene undergo the following composite treatment:

[0067] S1: Prepare an ethanol-water solution of 1-3% by mass of silane coupling agent. Mix ethanol and pure water at a mass ratio of 1:(7-10), then add acetic acid to adjust the pH to 3-4.5, and pre-hydrolyze at 45-75℃ for later use.

[0068] S2: Add graphene to a pre-hydrolyzed silane coupling agent solution, sonicate for 2-4 hours, filter, and wash with anhydrous ethanol to obtain surface-treated graphene.

[0069] S3: Surface-treated graphene is dispersed in anhydrous ethanol to obtain a suspension with a solid content of 30-50 wt%.

[0070] S4: Impregnate the carbon fiber fabric with the suspension, filter, and vacuum dry to attach the graphene to the carbon fiber fabric.

[0071] When using only graphene, the graphene can also be surface-treated with a silane coupling agent (such as by steps S1 and S2). Preferably, after surface treatment, the suspension in step S3 is used to form a film and dry it to obtain a graphene film material. Two-dimensional graphene film materials are more convenient for subsequent hot pressing than one-dimensional graphene materials.

[0072] The carbon fiber fabric undergoes surface treatment, including the following steps:

[0073] (1) The carbon fiber fabric was ultrasonically treated in anhydrous ethanol and deionized water for 5-10 minutes, and then dried for later use.

[0074] (2) Low-temperature plasma surface activation treatment was performed on both sides of the carbon fiber fabric using argon as the reaction gas. The distance between the carbon fiber fabric and the plasma nozzle was 1-1.5 cm, the argon gas flow rate was 2-5 L / min, the discharge voltage was 20-30 kV, the current was 1-1.5 mA, the frequency was 5-15 kHz, and each side was treated for 1-3 min.

[0075] This invention provides a wind turbine blade 200 with efficient de-icing and lightning protection effects, comprising a plurality of the aforementioned electrically heated lightning protection composite films 100. The electrically heated lightning protection composite films 100 are discontinuously arranged on the surface of the wind turbine blade 200. After design and cutting, the length and width dimensions of the electrically heated lightning protection composite films 100 are (200-800mm) × (5000-7000mm). In addition to the selection of length and width dimensions, the thickness of the electrically heated lightning protection multilayer films at different locations can also be selected and adjusted. For example, at the blade tip, the degree of icing and the risk of lightning strikes are both greater, but excessive film thickness will result in a greater centrifugal load on the blade and increased energy consumption. Therefore, the thickness of the multilayer film in the blade tip region is preferably below 3.5mm, more preferably below 2.5mm. To obtain a thinner thickness, the heating element 31 preferably incorporates or uses only graphene.

[0076] Example 1

[0077] The electrically heated lightning protection composite membrane 100 provided in this embodiment has a thickness of 3mm and comprises, in sequence:

[0078] (1) Lightning protection surface layer 10, with a thickness of 0.8±0.05mm, including EVA resin and its encapsulation, with a basis weight of 800±10g / m³. 2 A copper mesh; the copper mesh can be connected to the lightning arrester at the corresponding position of the blade;

[0079] (2) Insulating resin core layer 20, with a thickness of 0.5±0.05mm, containing polyimide resin PI, with a resistance greater than 2000MΩ;

[0080] (3) Heating bottom layer 30, with a thickness of 1.0 mm, contains EVA resin and carbon fiber fabric therein, the carbon fiber fabric leads out two electrodes, which are respectively connected to the positive and negative terminals of the power supply;

[0081] (4) Adhesive layer 40.

[0082] The sample in this embodiment was prepared through the following steps:

[0083] Step 1: EVA resin and PI resin are fed into an extruder and then into a co-extrusion die to co-extrude and form a pre-made film with a three-layer structure of EVA / PI / EVA.

[0084] Step 2: Place the copper mesh on the outside of the pre-formed EVA layer used to form the lightning protection surface layer 10, and place the carbon fiber fabric on the outside of the pre-formed EVA layer used to form the heating bottom layer 30; place the EPDM rubber forming the adhesive layer 40 on the outside of the carbon fiber fabric, i.e., the stacking is: copper mesh / EVA layer / PI layer / EVA layer / carbon fiber fabric / EPDM rubber;

[0085] Step 3: At a temperature of 145±1℃, hot press for 12 minutes to obtain an electrically heated lightning protection composite membrane 100 with an integral structure and a thickness of 3mm.

[0086] The carbon fiber fabric undergoes surface treatment, including the following steps:

[0087] (1) The carbon fiber fabric was ultrasonically treated in anhydrous ethanol and deionized water for 8 minutes in succession, and then dried for later use.

[0088] (2) Low-temperature plasma surface activation treatment was performed on both sides of the carbon fiber fabric using argon as the reaction gas. The distance between the carbon fiber fabric and the plasma nozzle was 1.2±0.1cm, the argon gas flow rate was 3.5L / min, the discharge voltage was 25kV, the current was 1mA, the frequency was 10kHz, and each side was treated for 2min.

[0089] Example 2

[0090] The electrically heated lightning protection composite membrane 100 provided in this embodiment has a thickness of 2.6 mm and comprises, in sequence:

[0091] (1) Lightning protection surface layer 10, with a thickness of 0.7±0.05mm, including EVA resin and its encapsulation, with a basis weight of 800±10g / m². 2 Copper mesh;

[0092] (2) Insulating resin core layer 20, with a thickness of 0.5±0.05mm and a resistance greater than 2000MΩ; the insulating resin core layer 20 includes polyimide resin PI and insulating filler, with a mass ratio of insulating filler to PI of 2:98. The insulating filler is selected by mixing boron nitride and aluminum oxide in a mass ratio of 2:3. The insulating filler is surface treated with low-temperature plasma similar to that used for carbon fiber fabric. The distance between the composite insulating filler and the plasma nozzle is about 1.5cm, the argon gas flow rate is 3L / min, the discharge voltage is 2kV, the current is 1mA, the frequency is 10kHz, and the treatment is carried out for 0.5min. After stirring, the treatment is repeated 4 times.

[0093] (3) Heating bottom layer 30, with a thickness of 0.8mm, contains EVA resin, carbon fiber fabric and graphene therein, with a mass ratio of carbon fiber fabric to graphene of 4:1. The carbon fiber fabric leads out two electrodes, which are respectively connected to the positive and negative terminals of the power supply.

[0094] (4) Adhesive layer 40.

[0095] The sample in this embodiment was prepared through the following steps:

[0096] Step 1: EVA resin and PI resin are fed into an extruder separately, insulating filler is added to the PI resin in steps, and the mixture is fed into a co-extrusion die and co-extruded to form a pre-made film with a three-layer structure of EVA / PI / EVA.

[0097] Step 2: Place the copper mesh on the outside of the pre-formed EVA layer used to form the lightning protection surface layer 10, and place the carbon fiber fabric and graphene composite on the outside of the pre-formed EVA layer used to form the heating bottom layer 30; place the EPDM rubber forming the adhesive layer 40 on the outside of the carbon fiber fabric and graphene, i.e., the stacking is: copper mesh / EVA layer / PI layer / EVA layer / carbon fiber fabric graphene composite / EPDM rubber;

[0098] Step 3: At a temperature of 143±1℃, hot press for 12 minutes to obtain an electrically heated lightning protection composite membrane 100 with an integral structure and a thickness of 2.6mm.

[0099] The carbon fiber fabric undergoes surface treatment, including the following steps:

[0100] (1) The carbon fiber fabric was ultrasonically treated in anhydrous ethanol and deionized water for 8 minutes in succession, and then dried for later use.

[0101] (2) Low-temperature plasma surface activation treatment was performed on both sides of the carbon fiber fabric using argon as the reaction gas. The distance between the carbon fiber fabric and the plasma nozzle was 1.2±0.1cm, the argon gas flow rate was 3.5L / min, the discharge voltage was 25kV, the current was 1mA, the frequency was 10kHz, and each side was treated for 2min.

[0102] The carbon fiber fabric and graphene undergo the following composite treatment:

[0103] S1: Prepare an ethanol-water solution with a mass fraction of 2.5% silane coupling agent. Mix ethanol and pure water at a mass ratio of 1:8, then add acetic acid to adjust the pH value to about 4, and pre-hydrolyze at 60°C for later use.

[0104] S2: Add graphene to a pre-hydrolyzed silane coupling agent solution, sonicate for 2.5 h, filter, and wash with anhydrous ethanol to obtain surface-treated graphene.

[0105] S3: Surface-treated graphene is dispersed in anhydrous ethanol to obtain a suspension with a solid content of 40 wt%.

[0106] S4: Impregnate the carbon fiber fabric with the suspension, filter, and vacuum dry to attach the graphene to the carbon fiber fabric.

[0107] Example 3

[0108] The electrically heated lightning protection composite membrane 100 provided in this embodiment has a thickness of 2.0 mm and includes, in sequence:

[0109] (1) Lightning protection surface layer 10, with a thickness of 0.6±0.05mm, including EVA resin and its encapsulation, with a basis weight of 800±10g / m². 2 Copper mesh;

[0110] (2) Insulating resin core layer 20, with a thickness of 0.4±0.05mm and a resistance greater than 2000MΩ; the insulating resin core layer 20 includes polyimide resin PI and insulating filler, with the mass ratio of insulating filler to PI being 4:96. The insulating filler is selected from boron nitride and alumina mixed in a mass ratio of 2:3 and screened. The insulating filler includes small particle size filler with a particle size of about 3μm, medium particle size filler with a particle size of about 15μm, and large particle size filler with a particle size of about 35μm, which are compounded in a mass ratio of 20:70:10. The above insulating filler is then subjected to low-temperature plasma surface treatment, that is, the distance between the compounded insulating filler and the plasma nozzle is about 1.5cm, the argon gas flow rate is 3L / min, the discharge voltage is 2kV, the current is 1mA, the frequency is 10kHz, and the treatment is carried out for 0.5min and then stirred. This process is repeated 4 times.

[0111] (3) Heating bottom layer 30, with a thickness of 0.5 mm, containing EVA resin and graphene therein, wherein the graphene forms a graphene film layer and leads out two electrodes, which are respectively connected to the positive and negative terminals of the power supply.

[0112] (4) Adhesive layer 40.

[0113] The sample in this embodiment was prepared through the following steps:

[0114] Step 1: EVA resin and PI resin are fed into an extruder separately, insulating filler is added to the PI resin in steps, and the mixture is fed into a co-extrusion die and co-extruded to form a pre-made film with a three-layer structure of EVA / PI / EVA.

[0115] Step 2: Place the copper mesh on the outside of the pre-formed EVA layer used to form the lightning protection surface layer 10, and place the graphene on the outside of the pre-formed EVA layer used to form the heating bottom layer 30; place the EPDM rubber forming the adhesive layer 40 on the outside of the graphene, i.e., the stacking is: copper mesh / EVA layer / PI layer / EVA layer / graphene / EPDM rubber;

[0116] Step 3: At a temperature of 140±1℃, hot press for 10 minutes to obtain an electrically heated lightning protection composite membrane 100 with an integral structure and a thickness of 2mm.

[0117] The graphene undergoes the following surface treatment:

[0118] S1: Prepare an ethanol-water solution with a mass fraction of 2.5% silane coupling agent. Mix ethanol and pure water at a mass ratio of 1:8, then add acetic acid to adjust the pH value to about 4, and pre-hydrolyze at 60°C for later use.

[0119] S2: Add graphene to a pre-hydrolyzed silane coupling agent solution, sonicate for 2.5 h, filter, and wash with anhydrous ethanol to obtain surface-treated graphene.

[0120] S3: Surface-treated graphene is dispersed in anhydrous ethanol to obtain a suspension with a solid content of 30-50 wt%; the suspension is cast into a film and dried to obtain a graphene film material.

[0121] The samples from Examples 1-3 were tested, and the test results are shown in Table 1:

[0122] Table 1 Performance test results of Examples 1-3

[0123]

[0124]

[0125] Application example:

[0126] Several electrically heated lightning protection composite films from Examples 1-3 were bonded to wind turbine blades. Specifically, the sample from Example 1 was primarily used in the blade root to middle region, with a cut size of (500-800mm) × (6000-7000mm); the sample from Example 2 was primarily used in the middle to tip region, with a cut size of (300-600mm) × (5500-6500mm); and the sample from Example 3 was primarily used in the tip region, with a cut size of (200-400mm) × (5000-6000mm). Each copper mesh was electrically connected to its corresponding lightning arrester, and grounded via a down conductor through the lightning protection system within the blade. Two electrodes were led out from the heating element and connected to the positive and negative terminals of the power supply, respectively, and connected to the electric heating control cabinet. Heating was activated to de-ice the blade based on the monitored icing condition on the blade surface, thus achieving intelligent de-icing operation.

[0127] The above embodiments and application examples are preferred implementation schemes. In practical applications, certain adjustments and combinations are required based on the specific size of the wind turbine blades and the application scenario. This approach provides long-term, stable protection for wind turbine blades while considering comprehensive performance factors such as heating and de-icing efficiency, lightning protection, low composite film weight and thickness, and mechanical and aging properties.

[0128] The preferred embodiments of the present invention have been described above to make the spirit of the present invention clearer and easier to understand, and are not intended to limit the present invention. All modifications, substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope summarized by the appended claims.

Claims

1. An electrically heated lightning protection composite membrane for blade de-icing, characterized in that, The following layers are included in sequence: (1) A lightning protection surface layer comprising a metal element and a first resin matrix at least partially impregnated with the metal element; (2) The insulating resin core layer has a resistance greater than 2000MΩ; (3) A heating substrate comprising a heating element and a second resin matrix at least partially impregnated with the heating element, wherein the heating element comprises at least one of carbon fiber and graphene; The first resin matrix and the second resin matrix contain the same or different thermoplastic resins, wherein both the first resin matrix and the second resin matrix contain ethylene-vinyl acetate copolymer resin. The insulating resin comprises at least one of thermoplastic polyimide resin and polyolefin resin, and the insulating resin core layer further comprises an insulating filler, wherein the insulating filler is boron nitride, or a mixture of boron nitride and boehmite; The first resin matrix, insulating resin, and second resin matrix are pre-formed into a pre-film through three-layer co-extrusion. After the pre-film is stacked between the metal element and the heating element, it is hot-pressed into an integral structure of the electric heating lightning protection composite film.

2. The electrically heated lightning protection composite membrane as described in claim 1, characterized in that, The metal element comprises one of a copper mesh and an aluminum alloy mesh, the copper mesh / aluminum alloy mesh being connected to the lightning arrester of the blade; the heating element is connected to a power source.

3. The electrically heated lightning protection composite membrane as described in claim 1, characterized in that, The thickness of the electrically heated lightning protection composite membrane is 1-5mm.

4. The electrically heated lightning protection composite membrane as described in claim 1, characterized in that, The heating element comprises, by weight percentage: Carbon fiber fabric 40-90% Graphene 10-60%; The carbon fiber fabric and graphene undergo the following composite treatment: S1: Prepare an ethanol-water solution of 1-3% by mass of silane coupling agent, then add acetic acid to adjust the pH to 3-4.5, and pre-hydrolyze at 45-75℃ for later use; S2: Add graphene to a pre-hydrolyzed silane coupling agent solution, sonicate for 2-4 hours, filter, and wash with anhydrous ethanol to obtain surface-treated graphene. S3: Surface-treated graphene is dispersed in anhydrous ethanol to obtain a suspension; S4: Impregnate the carbon fiber fabric with the suspension, filter, and vacuum dry to attach the graphene to the carbon fiber fabric.

5. The electrically heated lightning protection composite membrane as described in claim 4, characterized in that, The carbon fiber fabric undergoes surface treatment, including the following steps: (1) The carbon fiber fabric was ultrasonically treated in anhydrous ethanol and deionized water, and then dried for later use; (2) Using argon as the reaction gas, the carbon fiber fabric is subjected to low-temperature plasma surface activation treatment on both sides.

6. The electrically heated lightning protection composite membrane as described in any one of claims 1-5, characterized in that, The mass ratio of insulating filler to insulating resin is (2-5):(95-98); The insulating filler undergoes surface treatment.

7. The electrically heated lightning protection composite membrane as described in claim 6, characterized in that, The insulating filler is composed of small-particle-size fillers with a particle size of 1-4 μm, medium-particle-size fillers with a particle size of 10-20 μm, and large-particle-size fillers with a particle size of 30-40 μm in a mass ratio of (10-20):(60-70):(10-30).

8. A method for preparing the electrically heated lightning protection composite film according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: The first resin matrix, insulating resin, and second resin matrix are pre-formed into a pre-made film comprising a three-layer structure; Step 2: Stack the metal components on the outside of the first resin matrix of the preformed film, and stack the heating elements on the outside of the second resin matrix of the preformed film; Step 3: Heat press at 120-150℃ for 5-15 minutes to obtain an electrically heated lightning protection composite film with an integrated structure and a thickness of 1-5mm.

9. A wind turbine blade having the electrically heated lightning protection composite membrane according to any one of claims 1-7, characterized in that, Several electrically heated lightning protection composite films are discontinuously arranged on the surface of the wind turbine blades. The length and width of the electrically heated lightning protection composite film are (200-800mm) × (5000-7000mm).

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