A low temperature curing composite film and a preparation method and application thereof

Abstract

The application discloses a low-temperature curing composite film and a preparation method and application thereof. The low-temperature curing composite film comprises at least one semi-cured resin adhesive film, at least one continuous conductive copper mesh, and at least one reinforced non-woven fabric. The semi-cured resin adhesive film does not contain conductive filler particles and is configured to be completely cured at a temperature range of 80-90 DEG C. The application realizes low-temperature rapid curing, high-conductivity stable lightning protection, strong bonding structure reinforcement, and excellent weather-resistant and corrosion-resistant integrated performance of wind power blade lightning strike damage.

Description

Technical Field

[0001] This invention relates to the field of wind turbine blade repair materials, specifically to a low-temperature curing composite film, its preparation method, and its application. Background Technology

[0002] In recent years, my country's wind power sector has developed rapidly. As the core component of wind turbines, wind turbine blades are becoming increasingly larger, with blade lengths reaching 80-150 meters and tip heights exceeding 100 meters. Currently, most onshore wind turbine blades utilize all-glass fiber reinforced composite materials, significantly increasing the probability of lightning strikes. After a lightning strike, blades are prone to surface ablation, holes, glass fiber carbonization, and breakage or burning of the lightning protection copper mesh. If repairs are not timely, this can lead to blade delamination and breakage, seriously affecting power generation safety.

[0003] Currently, the main repair solutions for lightning damage to wind turbine blades are as follows: 1) Hand lay-up conductive adhesive + copper mesh + fiberglass cloth: Conductive adhesive is applied on-site by hand, copper mesh is laid, and fiberglass cloth is covered. This solution has problems such as long curing time (more than 24 hours), low bond strength, poor conductivity uniformity, reliance on manual construction, and insufficient quality stability.

[0004] 2) High-temperature curing epoxy resin + copper mesh prepreg: The copper mesh resin film is prepreged in the factory and needs to be heated to 120-170℃ on site for curing. This solution has a high curing temperature, is difficult to construct at high altitudes in the field, has high energy consumption, and the high-temperature curing process can easily damage the original substrate of the blade.

[0005] 3) Conductive coating + local copper sheet overlap: It only repairs the conductive path, lacks structural reinforcement, has poor bending resistance, and is easily damaged by lightning strikes again.

[0006] 4) Single low-temperature resin repair adhesive: It is easy to apply, but it lacks a continuous conductive skeleton, has poor lightning protection performance, low mechanical strength, and cannot meet the requirements for high-frequency lightning protection.

[0007] In summary, existing technologies cannot simultaneously meet the comprehensive requirements of low-temperature rapid curing, convenient high-altitude construction, high electrical conductivity and stability, strong structural adhesion, resistance to environmental aging, and low cost. Therefore, there is an urgent need to develop a composite material specifically adapted for lightning strike repair of wind turbine blades to overcome the shortcomings of existing technologies. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a low-temperature curing composite film, its preparation method, and its applications. This invention achieves integrated performance including low-temperature rapid curing of lightning-damaged wind turbine blades, high conductivity for stable lightning protection, strong adhesive structure reinforcement, and excellent weather resistance and corrosion resistance.

[0009] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: This invention provides a low-temperature curing composite film, comprising: At least one layer of semi-cured resin film; At least one layer of continuous conductive copper mesh; and At least one layer of reinforcing nonwoven fabric; The semi-cured resin film contains no conductive filler particles and is configured to fully cure within a temperature range of 80~90°C.

[0010] Preferably, the semi-cured resin film comprises a low-temperature curing thermosetting resin system, wherein the low-temperature curing thermosetting resin system includes a thermosetting resin, a low-temperature curing agent, an accelerator, a toughening agent, a coupling agent, and a weathering agent.

[0011] Preferably, the thermosetting resin includes at least one of epoxy resin, polyurethane resin, and acrylate resin; the low-temperature curing agent includes at least one of modified amine, imidazole, acid anhydride, and latent curing agent; the toughening agent is polyurethane or nitrile rubber; and the weathering agent includes at least one of ultraviolet absorber, light stabilizer, and antioxidant.

[0012] Preferably, the continuous conductive copper mesh is made of copper, with a thickness of 0.05~1mm and an areal density of 50~1500g / m³. 2 The resistance of the copper mesh is 1~10mΩ.

[0013] Preferably, the reinforcing nonwoven fabric is a high-temperature resistant nonwoven fabric with a temperature resistance of ≥200℃, a thickness of 0.05~0.2mm, and a basis weight of 5~30g / m². 2 .

[0014] Preferably, the low-temperature curing composite film is a multi-layer composite structure, including two layers of semi-cured resin film, a reinforcing non-woven fabric disposed between the two layers of semi-cured resin film, and a continuous conductive copper mesh located on the outer surface of at least one layer of semi-cured resin film.

[0015] Preferably, the surface of the continuous conductive copper mesh is subjected to a surface modification treatment, which includes at least one of chemical oxidation, silane coupling agent modification, and plasma treatment.

[0016] Preferably, the total thickness of the low-temperature curing composite film is 0.2~1.5mm, and the basis weight is 200~2000g / m³. 2 After curing, the composite film has a tensile strength ≥20MPa and a peel strength ≥1kN / m.

[0017] Another aspect of the present invention provides a method for preparing a low-temperature curing composite film, which includes the following steps: (1) The components of the low-temperature curing thermosetting resin system are heated and mixed evenly according to the formula and then degassed under vacuum to obtain the resin solution. (2) The resin liquid is heated and then cast onto a release film, and after cooling and setting, a semi-cured resin film is obtained; (3) The reinforced nonwoven fabric is arranged on at least one layer of the semi-cured resin film, and then the continuous conductive copper mesh is covered on top. The layers are bonded by hot pressing and then cooled and shaped. (4) Cutting and rolling.

[0018] The present invention further provides an application of a low-temperature curing composite film in the repair of wind turbine blades after lightning strikes. Specifically, the low-temperature curing composite film is directly applied to the lightning-damaged area of ​​the wind turbine blade and cured at 80~90℃ for 1-4 hours. The continuous conductive copper mesh serves as the lightning current conduction path, and the semi-cured resin film serves as a reinforcement layer for the blade structure after curing.

[0019] The beneficial effects of this invention are as follows: (1) The composite film of the present invention comprises at least one layer of semi-cured resin film without conductive filler particles, and the film is configured to cure rapidly in a temperature range of 80°C to 90°C. Compared with the traditional high temperature curing scheme, the curing temperature is greatly reduced, the requirements for heating equipment are low, the field high-altitude construction operation is simple, the energy consumption is low, and the low temperature curing process is less likely to damage the original substrate of the blade, while shortening the repair cycle and improving the convenience and safety of construction.

[0020] (2) The composite membrane of the present invention contains at least one layer of continuous conductive copper mesh. The copper mesh serves as the only continuous conductive skeleton, which avoids the resistance fluctuation and discontinuity problems caused by the agglomeration of conductive filler particles, thereby providing a stable and low-resistance lightning current conduction path, ensuring efficient lightning protection performance, and maintaining conductive reliability under blade bending load.

[0021] (3) The composite membrane of the present invention comprises at least one layer of reinforcing nonwoven fabric, which works synergistically with the semi-cured resin film to form a strong adhesive reinforcing layer with the blade substrate after curing, thereby improving the overall tensile strength and bending resistance of the composite membrane, effectively repairing lightning-induced ablation holes and delamination damage, and restoring the structural strength of the blade.

[0022] (4) The semi-cured resin film of the present invention does not contain conductive filler particles, which avoids the damage of the resin continuity to the filler, and ensures that the resin fully wets the copper mesh and blade substrate and the interface bonding, thereby achieving high bonding strength and long-term use stability without relying on conductive particles. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the low-temperature curing composite film of Embodiment 1 of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides a low-temperature curing composite film, comprising at least one layer of semi-cured resin film, at least one layer of continuous conductive copper mesh, and at least one layer of reinforcing nonwoven fabric. The semi-cured resin film contains no conductive filler particles (e.g., silver powder, nickel powder, carbon black, graphene, etc.) and is configured to rapidly and completely cure within a temperature range of 80–90°C.

[0026] The semi-cured resin film comprises a low-temperature curing thermosetting resin system. This system may include a thermosetting resin, a low-temperature curing agent, an accelerator, a toughening agent, a coupling agent, and a weathering agent. Preferably, the thermosetting resin is selected from at least one of epoxy resin, polyurethane resin, and acrylate resin, with epoxy resins (such as bisphenol A type epoxy resin and bisphenol F type epoxy resin) being particularly suitable due to their good adhesion and mechanical properties. The low-temperature curing agent is selected from at least one of modified amines, imidazoles, acid anhydrides, and latent curing agents, such as modified aliphatic amines or imidazole adducts. The accelerator is used to accelerate the curing reaction at low temperatures, and may be, for example, a tertiary amine or an organometallic salt. The toughening agent is preferably a polyurethane elastomer or nitrile rubber to improve the impact resistance and crack resistance of the cured resin. The coupling agent is preferably a silane coupling agent (e.g., γ-aminopropyltriethoxysilane) to enhance the interfacial adhesion between the resin and the copper mesh, and between the resin and the wind turbine blade substrate. The weathering agent may include at least one of ultraviolet absorbers, hindered amine light stabilizers, and antioxidants to delay the aging and degradation of materials during long-term outdoor use.

[0027] In a preferred formulation example, the low-temperature curing thermosetting resin system may comprise, by weight: 20-40 parts bisphenol A epoxy resin, 10-20 parts aliphatic epoxy resin, 15-25 parts modified amine curing agent, 0.5-2 parts imidazole accelerator, 5-15 parts polyurethane toughening agent, 1-3 parts silane coupling agent, 0.5-1 part ultraviolet absorber, and 0.1-0.5 parts defoamer. This formulation can achieve rapid curing in 1-4 hours within the range of 80-90°C.

[0028] The continuous conductive copper mesh is preferably made of copper, with a thickness of 0.05~1mm and an areal density of 50~1500g / m³. 2The resistance of the copper mesh is 1~10mΩ. The advantage of using a continuous copper mesh instead of a conductive particle filling system is that the copper mesh itself forms a complete conductive path, avoiding resistance fluctuations and discontinuities caused by particle agglomeration, while also having good flexibility.

[0029] To improve the interfacial bonding strength between the copper mesh and the resin, as well as the anti-aging properties of the copper mesh itself, the surface of the copper mesh can be modified. For example, the surface modification treatment may include one or more combinations of chemical oxidation (e.g., micro-oxidation to form a cuprous oxide layer), silane coupling agent impregnation treatment, and plasma surface activation treatment. After modification, the adhesion between the copper mesh surface and the resin is significantly improved, and the copper mesh's resistance to oxidation and corrosion is enhanced, thereby extending the service life of the composite film in harsh environments such as salt spray and humid heat.

[0030] The reinforcing nonwoven fabric is preferably a high-temperature resistant nonwoven fabric with a temperature resistance ≥200℃, a thickness of 0.05~0.2mm, and a basis weight of 5~30g / m². 2 The nonwoven fabric serves as the intermediate reinforcing layer of the composite film. After hot-pressing, it is wrapped by two layers of resin film and cured to form a "sandwich" structure, which significantly improves the overall tensile strength and tear resistance of the composite film.

[0031] In a preferred multilayer composite structure, the low-temperature curing composite film comprises two layers of semi-cured resin films, a reinforcing nonwoven fabric disposed between the two semi-cured resin films, and a continuous conductive copper mesh located on the outer surface of at least one layer of semi-cured resin film. That is, the composite film has a three-layer sandwich structure of "resin film-nonwoven fabric-resin film," with the continuous conductive copper mesh attached to the outer surface of one side of the resin film; alternatively, continuous conductive copper mesh can be disposed on both outer surfaces to meet higher conductivity redundancy requirements. The typical total thickness of this structure is 0.2~1.5 mm, and the basis weight is 200~2000 g / m³. 2 After curing, the tensile strength of the composite film can reach ≥20MPa, and the peel strength (with the fiberglass matrix of the wind turbine blade) is ≥1kN / m.

[0032] This invention also provides a method for preparing the above-mentioned low-temperature curing composite film, the method comprising the following steps: Step (1): Resin solution preparation. The components of the low-temperature curing thermosetting resin system (e.g., the epoxy resin, curing agent, accelerator, toughening agent, coupling agent, weathering agent, defoamer, etc.) are added to a mixing device according to the formulation ratio, and heated to 40-60℃ until homogeneous. For example, a double planetary mixer can be used for high-speed mixing at a speed of 800-1500 rpm for 10-20 minutes to ensure thorough and uniform mixing of all components. Subsequently, vacuum degassing is performed, preferably at a vacuum degree of -0.08 to -0.1 MPa for 5-10 minutes, to remove air bubbles from the resin solution and obtain a homogeneous, bubble-free resin solution.

[0033] Step (2): Cast coating to form a film. The resin solution obtained in step (1) is heated to 40-60℃ and then coated onto release paper by casting. The coating thickness can be adjusted according to the thickness requirements of the final composite film, for example, 0.05~0.3mm. After coating, the release paper with the resin coating is cooled and shaped to partially cure the resin solution, resulting in a semi-cured resin film. The degree of curing of the resin film is preferably controlled within the range of 10%~20% to maintain appropriate tack and workability, while avoiding complete curing and loss of adhesion.

[0034] Step (3): Hot-pressing composite molding. The semi-cured resin film, reinforcing nonwoven fabric, and continuous conductive copper mesh obtained in step (2) are assembled according to a preset layered structure. In a preferred embodiment, two semi-cured resin films are peeled off, and the reinforcing nonwoven fabric is sandwiched between the two resin films to form a sandwich pre-stacked layer of "resin film-nonwoven fabric-resin film"; then, a continuous conductive copper mesh is covered on at least one outer surface of the sandwich layer. The assembled multilayer stack is fed into a hot-pressing composite equipment (e.g., a hot press roller or a flatbed hot press) and hot-pressed at a temperature of 50~70°C for 15~30 seconds to tightly bond the layers together through the adhesiveness of the resin. After hot pressing, cooling and shaping are performed (e.g., natural cooling, air cooling, or water cooling) to stabilize the composite film structure.

[0035] It should be noted that the stacking order in step (3) is not limited to the above method. For example, the continuous conductive copper mesh can be hot-pressed together with a layer of semi-cured resin film first, and then the non-woven fabric and the second layer of resin film can be stacked.

[0036] Step (4): Cutting and winding. Cut the continuous length of composite film obtained in step (3) into predetermined widths (e.g., 50mm, 100mm, 200mm, etc.) according to actual needs, then wind it up and seal it with moisture-proof packaging for easy storage and transportation. Since the semi-cured resin film will still slowly cure at room temperature, it is recommended to store it under refrigeration (e.g., -18℃).

[0037] This invention further provides the application of the aforementioned low-temperature curing composite film in the repair of wind turbine blades after lightning strikes. Exemplarily, the application process is as follows: First, the lightning-damaged area of ​​the wind turbine blade is cleaned, polished, and dried to remove the ablated carbonized layer and loose debris. Then, according to the shape and size of the damaged area, a suitable size of low-temperature curing composite film is cut, the release film is removed, and the resin film side of the composite film is directly adhered to the damaged area, gently pressed by hand or a rubber roller to ensure that the continuous conductive copper mesh forms electrical contact with the original lightning protection copper mesh or metal lightning arrester of the blade (e.g., through overlapping or pressing). After adhesion, the composite film is heated to 80-90°C for curing, typically for 1-4 hours. After curing, the continuous conductive copper mesh serves as a lightning current conduction path, smoothly transmitting the lightning current to the original lightning protection system; the semi-cured resin film cures to form a dense and tough reinforcing layer, firmly bonding to the blade's glass fiber or carbon fiber matrix, repairing ablated holes and delamination damage; the non-woven fabric reinforcement layer provides additional tensile and impact resistance. In addition, the weather-resistant agent in the resin system and the antioxidant treatment of the copper mesh ensure long-term stable operation of the repaired area in harsh environments such as high salt spray at sea and high ultraviolet radiation on land.

[0038] Example 1

[0039] Take 30 parts by weight of bisphenol A type epoxy resin (E-51), 15 parts by weight of aliphatic epoxy resin (CY179), 20 parts by weight of modified amine curing agent (ANCAMINE 2337S), 1 part by weight of imidazole accelerator (2-ethyl-4-methylimidazolium), 10 parts by weight of polyurethane toughening agent (PU-610), 2 parts by weight of silane coupling agent (KH-550), 0.8 parts by weight of ultraviolet absorber (UV-531), and 0.3 parts by weight of defoamer (BYK-066N), add them to a double planetary mixer, heat to 60°C, stir at 1000 rpm for 15 minutes, and then degas under a vacuum of -0.09 MPa for 8 minutes to obtain a uniform resin solution.

[0040] The adhesive liquid is heated to 60°C and cast onto release paper with a coating thickness of 0.12 mm. After cooling and setting, a semi-cured resin film with a semi-curing degree of about 15% is obtained.

[0041] Take two layers of the above semi-cured resin film, and then add a layer of reinforcing nonwoven fabric (polyester nonwoven fabric, temperature resistant 220℃, thickness 0.15mm, basis weight 25g / m²). 2 The resin film is sandwiched between two layers of resin film, and then a continuous conductive copper mesh (copper mesh, 0.1 mm thick, surface density 195 g / m²) is covered on the outer surface of the top layer of resin film. 2 (with a resistance of 5mΩ), then the laminate is fed into a hot press roller, hot-pressed at 70℃ for 20 seconds, cooled and shaped, cut to a width of 100mm, rolled up and sealed for packaging, thus obtaining a low-temperature curing composite film.

[0042] like Figure 1 As shown, the composite film prepared in Example 1 comprises two semi-cured resin films 10, a reinforcing nonwoven fabric 20 disposed between the two semi-cured resin films 10, and a continuous conductive copper mesh 30 located on the outer surface of one of the semi-cured resin films 10. The total thickness of the resulting composite film is 0.35 mm, and the basis weight is approximately 350 g / m³. 2 .

[0043] The prepared low-temperature curing composite film was peeled off from the release film and adhered to a cleaned, polished wind turbine blade fiberglass-reinforced epoxy resin substrate test plate (200mm×100mm×5mm), with the continuous conductive copper mesh facing outwards. Air bubbles were removed by pressing with a rubber roller. The test plate was heated to 80~90℃ and cured for 1.5 hours for tensile strength, flexural life, and resistance testing. Separately, a composite film from the same batch was adhered to a substrate test plate of the same specifications for peel strength testing.

[0044] Test method: Tensile strength: Carefully peel the cured composite film from the substrate test plate, cut dumbbell-shaped specimens (gauge length width 10mm), and test according to GB / T 1040.3-2006, with a tensile rate of 5mm / min.

[0045] Peel strength: Cut a 25mm wide sample from the substrate and perform a 180° peel test according to GB / T 2791-1995, with a peel rate of 100mm / min.

[0046] Bending life: Cut a 20mm×100mm strip sample from the cured composite film and bend it 180° repeatedly at a bending radius of 2mm and a frequency of 60 times / min. The failure criterion is the appearance of visible cracks in the continuous conductive copper mesh.

[0047] Resistance: The resistance of the conductive copper mesh was tested using the four-probe method.

[0048] Salt spray aging: After curing, the test plate with the composite film is subjected to a 1000-hour neutral salt spray test according to ASTM B117. After drying at room temperature, the appearance is visually inspected and the peel strength and resistance are tested according to the above method.

[0049] The test results are shown in Table 1.

[0050] Table 1

[0051] Example 2

[0052] 40 parts by weight of polyurethane resin (Bayer Desmodur N100), 25 parts by weight of blocked polyurethane curing agent (Vestagon B1530), 1.5 parts by weight of amine accelerator (DABCO 33-LV), 8 parts by weight of polyurethane toughening agent (Desmocap 11), 2 parts by weight of silane coupling agent (KH-560), 1 part by weight of ultraviolet absorber (Tinuvin 1130), and 0.2 parts by weight of defoamer (BYK-088) were prepared according to the same steps as in Example 1. A semi-cured resin film was obtained by casting and coating at a thickness of 0.15 mm, heating at 50°C for 20 minutes. Hot-pressing was performed at 60°C for 25 seconds, with the remaining steps the same as in Example 1. A low-temperature curing composite film was obtained with a total thickness of 0.38 mm and a basis weight of approximately 370 g / m³. 2 .

[0053] The prepared composite film was laminated onto a fiberglass-reinforced epoxy resin substrate test plate for wind turbine blades in the same manner as in Example 1, and cured at 80-90°C for 1.5 hours. After curing, the cured composite film was peeled off from the test plate, and samples were cut for tensile strength and flexural life testing. Another composite film from the same batch was laminated onto a substrate test plate of the same specifications, cured under the same conditions, and directly used as a substrate for peel strength testing. Resistance testing was performed before peeling off the film. The methods for tensile strength, peel strength, flexural life, and resistance testing were the same as in Example 1. Damp heat aging was performed at 85°C / 85%RH for 500 hours. The test results are shown in Table 2.

[0054] Table 2

[0055] Comparative Example 1 Commercially available two-component epoxy conductive silver paste (containing silver powder), copper mesh (specifications same as in Example 1), and 200g / m² were used. 2 Unidirectional fiberglass cloth. In the area damaged by lightning strikes on wind turbine blades, operators manually apply conductive silver paste (approximately 0.3mm thick), then lay a copper mesh, cover with fiberglass cloth, and heat to cure. This method is an on-site hand lay-up wet process, and the construction quality is highly dependent on manual operation. It is prone to defects such as localized insufficient adhesive, copper mesh floating, and uneven thickness, making it impossible to form a pre-formed standardized composite membrane.

[0056] The testing method is the same as in Example 1. The test results are shown in Table 3.

[0057] Table 3

[0058] Comparative Example 1 uses a field hand lay-up wet process, which relies on manual labor and has poor quality stability. After being flexed 1000 times at 80°C, the resistance of the sample increased to 45mΩ, and the peel retention rate was only 52% after 1000 hours of salt spray treatment. Compared with Comparative Example 1, the composite film of Example 1 of this invention has significantly improved in terms of curing speed, adhesive strength, electrical conductivity stability, and salt spray resistance.

[0059] Comparative Example 2 A conductive particle-filled pre-formed film was prepared by mixing 60 parts by weight of epoxy resin, 40 parts by weight of silver-coated copper conductive particles (10 μm particle size), and 20 parts by weight of modified amine curing agent, and then coating the mixture into a film with a thickness of 0.2 mm. No non-woven fabric reinforcement layer was used, and no continuous conductive copper mesh was included. Although this film is pre-formed, its conductivity relies on the point contact between conductive particles to form a conductive path. Lacking a continuous conductive framework, the contact between particles is prone to failure after bending or aging.

[0060] The adhesive film was adhered to a fiberglass-reinforced epoxy resin substrate test board for wind turbine blades and cured and tested under the following conditions: Heating and curing at 80℃ for 2 hours (ensuring full curing), used for peel strength, flexural life, electrical resistance, and damp heat aging tests. The testing method was the same as in Example 1. The test results are shown in Table 4.

[0061] Table 4

[0062] Comparative Example 2 used a conductive particle-filled pre-formed film, which lacked a continuous conductive framework and reinforcing nonwoven fabric. After curing at 80℃ for 2 hours and bending 500 times, the resistance of the sample increased to 180 mΩ, and the peel retention rate was only 45% after 1000 hours of salt spray treatment. This invention, through the synergistic design of a continuous conductive copper mesh + nonwoven fabric reinforcement + filler-free resin system, achieves a substantial improvement in curing speed, mechanical properties, conductivity reliability, and aging resistance.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0064] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A low-temperature curing composite film, characterized in that, include: At least one layer of semi-cured resin film; At least one layer of continuous conductive copper mesh; as well as At least one layer of reinforcing nonwoven fabric; The semi-cured resin film contains no conductive filler particles and is configured to fully cure within a temperature range of 80~90°C.

2. The low-temperature curing composite film according to claim 1, characterized in that, The semi-cured resin film comprises a low-temperature curing thermosetting resin system, which includes a thermosetting resin, a low-temperature curing agent, an accelerator, a toughening agent, a coupling agent, and a weathering agent.

3. The low-temperature curing composite film according to claim 2, characterized in that, The thermosetting resin includes at least one of epoxy resin, polyurethane resin, and acrylate resin; the low-temperature curing agent includes at least one of modified amine, imidazole, acid anhydride, and latent curing agent; the toughening agent is polyurethane or nitrile rubber; and the weathering agent includes at least one of ultraviolet absorber, light stabilizer, and antioxidant.

4. The low-temperature curing composite film according to claim 1, characterized in that, The continuous conductive copper mesh is made of copper, with a thickness of 0.05~1mm and an areal density of 50~1500g / m³. 2 The resistance of the copper mesh is 1~10mΩ.

5. The low-temperature curing composite film according to claim 1, characterized in that, The reinforcing nonwoven fabric is a high-temperature resistant nonwoven fabric with a temperature resistance of ≥200℃, a thickness of 0.05~0.2mm, and a basis weight of 5~30g / m². 2 .

6. The low-temperature curing composite film according to claim 1, characterized in that, The low-temperature curing composite film is a multi-layer composite structure, including two layers of semi-cured resin film, a reinforcing non-woven fabric disposed between the two layers of semi-cured resin film, and a continuous conductive copper mesh located on the outer surface of at least one layer of semi-cured resin film.

7. The low-temperature curing composite film according to claim 1, characterized in that, The surface of the continuous conductive copper mesh is subjected to surface modification treatment, which includes at least one of chemical oxidation, silane coupling agent modification, and plasma treatment.

8. The low-temperature curing composite film according to claim 1, characterized in that, The total thickness of the low-temperature curing composite film is 0.2~1.5mm, and the basis weight is 200~2000g / m³. 2 After curing, the composite film has a tensile strength ≥20MPa and a peel strength ≥1kN / m.

9. A method for preparing a low-temperature curing composite film according to any one of claims 1-8, characterized in that, Includes the following steps: (1) The components of the low-temperature curing thermosetting resin system are heated and mixed evenly according to the formula and then degassed under vacuum to obtain the resin solution. (2) The resin liquid is heated and then cast onto release paper, and after cooling and setting, a semi-cured resin film is obtained; (3) The reinforced nonwoven fabric is arranged on at least one layer of the semi-cured resin film, and then the continuous conductive copper mesh is covered on top. The layers are bonded by hot pressing and then cooled and shaped. (4) Cutting and rolling.

10. The application of the low-temperature curing composite film according to any one of claims 1 to 8 in the repair of wind turbine blades after lightning strikes, characterized in that, The low-temperature curing composite film is directly bonded to the lightning-damaged area of ​​the wind turbine blade and cured at 80~90℃ for 1-4 hours; the continuous conductive copper mesh serves as the lightning current conduction path, and the semi-cured resin film serves as a blade structural reinforcement layer after curing.

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