A method of manufacturing a thermoplastic wind turbine blade

Abstract

The application belongs to the technical field of thermoplastic composite materials, and provides a manufacturing method of thermoplastic wind power blades, and the specific process is as follows: pouring a pouring resin into a mold, then covering a circulating cooling system on the upper surface of the mold; and performing temperature change treatment on the mold to complete the manufacturing of the thermoplastic wind power blade. In the application, MAA is added to a PMMA / MMA mixed solution, and MAA and MMA form a hydrogen bond, thereby enhancing the mechanical properties of the thermoplastic pouring resin. The full paving of the circulating cooling liquid channel above the product and the cooling program of the mold can effectively reduce the polymerization exothermic temperature of the acrylic resin and improve the quality of the blade. The obtained blade is directly connected with the leeward shell, the windward shell, the web plate and the like of the thermoplastic wind power blade by using ultrasonic welding technology, thereby avoiding the need of embedding conductive materials in induction welding and resistance welding, increasing the raw material and process cost, and causing the fatigue resistance of the wind power blade to be reduced.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic composite materials technology, and in particular to a method for manufacturing thermoplastic wind turbine blades. Background Technology

[0002] Currently, wind turbine blades use epoxy resin, which is thermosetting and non-recyclable, posing a significant environmental challenge. Wind turbine blades are currently manufactured using a vacuum infusion process, producing the leeward shell, windward shell, and web separately, which are then bonded together using thermosetting structural adhesives. However, this bonding process suffers from weak adhesion and long construction cycles. Thermoplastic wind turbine blades can utilize fusion welding technology, thus solving these problems. Currently, domestic and international engineers have developed several thermoplastic resins for wind turbine blades, such as thermoplastic polyurethane infusion resin. However, it is highly sensitive to moisture, which does not meet the current manufacturing environment and processes for wind turbine blades. Cyclic butylene terephthalate (CBT) is a thermoplastic liquid resin, but it requires high heating temperatures (150℃) and is sensitive to moisture, limiting its application in wind turbine blades. Polymethyl methacrylate (PMMA) has excellent weather resistance and is a thermoplastic resin with recyclability, making it advantageous for manufacturing recyclable wind turbine blades. However, PMMA is thermoplastic, and its mechanical properties are inferior to those of thermosetting epoxy resin. The heat of polymerization of monomer MMA into PMMA is 57.8 kJ / mol, which is three times that of epoxy resin. Excessive heat of polymerization can lead to problems such as burning of the core material and resin inside wind turbine blades.

[0003] Chinese patent CN 115612427 discloses a thermoplastic resin, its preparation method, and a wind turbine blade. The method uses 65-85 parts of methyl methacrylate, 10-30 parts of polymethyl methacrylate resin, 0.02-0.1 parts of polymerization inhibitor, and 0.05-0.5 parts of odor masking agent. While this invention utilizes thermoplastic PMMA, enabling the green recycling of wind turbine blades, its thermoplastic resin, containing only PMMA, has poor mechanical properties. Furthermore, it fails to consider the heat dissipation issues associated with thick laminates or sandwich panels like wind turbine blades, resulting in poor quality of the final product.

[0004] Therefore, a new process is urgently needed to improve upon the problems existing in the current technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the deficiencies in the prior art and provide a method for manufacturing thermoplastic wind turbine blades.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for manufacturing a thermoplastic wind turbine blade, comprising the following steps: (1) Pour the injection resin into the mold, and then cover the upper surface of the mold with a circulating cooling system; (2) The mold is subjected to temperature change treatment to complete the manufacturing of thermoplastic wind turbine blades.

[0007] Preferably, the resin instillation in step (1) comprises methyl methacrylate slurry, methacrylic acid and an initiator; The methyl methacrylate slurry has a mass fraction of 70-95 parts, and the methacrylic acid has a mass fraction of 5-20 parts. The viscosity of methyl methacrylate slurry is 30~500 mPa·s.

[0008] Preferably, the initiator comprises an oxidizing agent and a reducing agent; The oxidizing agents include one or more of benzoyl peroxide, dodecyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide; The mass of the oxidant is 0.5-5% of the sum of the masses of methyl methacrylate slurry and methacrylic acid; The reducing agent includes one or more of N,N-dimethylaniline, N,N-dimethyl-p-toluidine, and N,N-diethylaniline; The mass of the reducing agent is 0.01~3% of the combined mass of methyl methacrylate slurry and methacrylic acid.

[0009] Preferably, the cooling medium of the circulating cooling system in step (1) is one or more of water, ethylene glycol aqueous solution and propylene glycol aqueous solution; The cooling medium has a cooling temperature of -10~20℃.

[0010] Preferably, the temperature change treatment in step (2) is performed sequentially as polymerization, preliminary curing, and curing; The polymerization temperature is 25~60℃ and the time is 10~40min.

[0011] Preferably, the initial curing temperature is provided by a circulating cooling system; The initial curing temperature is -10~20℃, and the time is 10~90min.

[0012] Preferably, the curing temperature is 80~120℃ and the curing time is 1~5h.

[0013] This invention provides a method for manufacturing thermoplastic wind turbine blades, comprising the following steps: injecting resin into a mold, then covering the upper surface of the mold with a circulating cooling system; subjecting the mold to variable temperature treatment to complete the manufacturing of the thermoplastic wind turbine blade. This invention adds methacrylic acid (MAA) to a PMMA / MMA mixed solution, where MAA forms hydrogen bonds with MMA, enhancing the mechanical properties of the thermoplastic injection resin. The use of a circulating cooling liquid channel covering the product and a cooling process in the mold effectively reduces the exothermic polymerization temperature of acrylic resins, improving blade quality. This invention uses ultrasonic welding technology to directly connect the leeward shell, windward shell, and web of the thermoplastic wind turbine blade, avoiding the need for pre-embedded conductive materials required by induction welding and resistance welding, which increases raw material and process costs and reduces the fatigue resistance of the wind turbine blade. Detailed Implementation

[0014] This invention provides a method for manufacturing a thermoplastic wind turbine blade, characterized by comprising the following steps: (1) Pour the injection resin into the mold, and then cover the upper surface of the mold with a circulating cooling system; (2) The mold is subjected to temperature change treatment to complete the manufacturing of thermoplastic wind turbine blades.

[0015] In this invention, the resin infusion in step (1) comprises methyl methacrylate slurry, methacrylic acid and an initiator.

[0016] In this invention, the mass fraction of methyl methacrylate slurry is preferably 70-95 parts, more preferably 75-90 parts, and even more preferably 80-85 parts; the mass fraction of methacrylic acid (MAA) is preferably 5-20 parts, more preferably 10-15 parts, and even more preferably 12-13 parts.

[0017] In this invention, the viscosity of the methyl methacrylate slurry is preferably 30~500 mPa·s, more preferably 100~400 mPa·s, and even more preferably 200~300 mPa·s.

[0018] In this invention, the methyl methacrylate slurry is a PMMA / MMA mixed solution, wherein the PMMA can be commercial PMMA particles or powder, or it can be obtained by prepolymerization of MMA monomers.

[0019] In this invention, the initiator is an oil-soluble redox initiation system, which includes an oxidant and a reducing agent.

[0020] In this invention, the oxidant comprises one or more of benzoyl peroxide, dodecyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide.

[0021] In this invention, the mass of the oxidant is preferably 0.5-5% of the combined mass of methyl methacrylate slurry and methacrylic acid, more preferably 1-4%, and even more preferably 2-3%.

[0022] In this invention, the reducing agent comprises one or more of N,N-dimethylaniline, N,N-dimethyl-p-toluidine, and N,N-diethylaniline.

[0023] In this invention, the mass of the reducing agent is preferably 0.01-3% of the combined mass of methyl methacrylate slurry and methacrylic acid, more preferably 1-2%, and even more preferably 1.4-1.6%.

[0024] In this invention, the resin is vacuum-infused at room temperature.

[0025] In this invention, the cooling medium of the circulating cooling system in step (1) is one or more of water, ethylene glycol aqueous solution and propylene glycol aqueous solution.

[0026] In this invention, the cooling temperature of the cooling medium is preferably -10~20℃, more preferably 0~10℃, and even more preferably 5~8℃.

[0027] In this invention, after vacuum injection of the shell and web of the thermoplastic wind turbine blade, a circulating cooling liquid channel is fully laid above the product. After resin polymerization, the circulating cooling is activated to dissipate heat from the resin polymerization. To improve efficiency and facilitate heat dissipation during resin polymerization, the mold heating process no longer uses a single continuous heating method, but is optimized into a staged alternating heating and cooling procedure.

[0028] In this invention, the temperature change process in step (2) is a sequential process of polymerization, preliminary curing, and curing.

[0029] In this invention, the polymerization temperature is preferably 25~60℃, more preferably 30~55℃, and even more preferably 40~50℃; the time is preferably 10~40min, more preferably 15~35min, and even more preferably 20~30min; under these conditions, polymerization can be initiated quickly, shortening the construction period.

[0030] In this invention, the initial curing temperature is provided by a circulating cooling system.

[0031] In this invention, the initial curing temperature is preferably -10~20℃, more preferably 0~10℃, and even more preferably 5~8℃; the time is preferably 10~90min, more preferably 20~70min, and even more preferably 30~50min; after the initial curing is completed, the circulating cooling liquid is turned off for further curing.

[0032] In this invention, the curing temperature is preferably 80~120℃, more preferably 90~110℃, and even more preferably 95~105℃; the curing time is preferably 1~5h, more preferably 1.5~4.5h, and even more preferably 2~4h.

[0033] In this invention, ultrasonic welding technology is used to weld the various components of the wind turbine blade. Ultrasonic welding technology is used to connect the leeward shell, windward shell, web, etc. of the wind turbine blade, avoiding the need for pre-embedded conductive materials in induction welding and resistance welding, which would reduce the fatigue resistance of the wind turbine blade.

[0034] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] The blade shell and web consist of the following main steps: Lay-up: After applying a release agent to the blade mold, lay up the main blade materials, including fiber fabric, fiber felt, core material, main beam, lightning protection and conductive material, etc. Then lay up the auxiliary materials to establish a vacuum system, including release cloth, isolation film, flow guide net, resin flow guide tube, glue injection port, vacuum bag film, sealing tape, and one-way breathable membrane.

[0037] Preparation of infusion resin and vacuum infusion: At room temperature, in a nitrogen-protected reactor, PMMA particles were added to MMA to prepare a resin with a viscosity of 150 mPa. A methyl methacrylate slurry (90 parts by weight of methyl methacrylate slurry and 10 parts by weight of methyl methacrylate) was first prepared, followed by the addition of methacrylic acid. N,N-dimethylaniline (0.3 wt% of the acrylic resin) and benzoyl peroxide (0.7 wt% of the acrylic resin) were then added as reducing agents. The mixture was stirred to dissolve the materials. After thorough dissolution and mixing, the prepared injection resin was fed into a dispensing machine for room temperature degassing. After degassing, the injection resin was introduced into each layer of the blade through the injection port under vacuum. The mold was not heated during the injection process. A circulating cooling water strip was then installed.

[0038] Polymerization and Curing: After all the resin has been poured, the mold temperature is raised to 35°C and maintained for 20 minutes. This initial temperature increase quickly initiates the polymerization of the resin, shortening the production cycle. Afterward, the mold temperature is lowered to 0°C. Simultaneously, the circulating cooling system above the product is activated. The cooling liquid is an aqueous ethylene glycol solution, with a cooling temperature of 0°C. Curing is carried out for 30 minutes. Once the resin is completely cured, the circulating cooling liquid system is withdrawn, the mold temperature is set to 100°C, and an insulation blanket is placed over the product for post-curing of the resin for 3 hours.

[0039] Welding: After the blade components have cured, they are demolded and cleaned. Then, they are joined together. Ultrasonic welding technology is used to connect the leeward shell, windward shell, and web of the thermoplastic wind turbine blade. After grinding, polishing, and painting, a complete wind turbine blade is formed.

[0040] Example 2

[0041] The blade shell and web consist of the following main steps: Lay-up: After applying a release agent to the blade mold, lay up the main blade materials, including fiber fabric, fiber felt, core material, main beam, lightning protection and conductive material, etc. Then lay up the auxiliary materials to establish a vacuum system, including release cloth, isolation film, flow guide net, resin flow guide tube, glue injection port, vacuum bag film, sealing tape, and one-way breathable membrane.

[0042] Preparation of infusion resin and vacuum infusion: At 50°C, in a nitrogen-protected reactor, azobisisobutyronitrile (0.2 wt% of MMA) was added to MMA to prepolymerize MMA to prepare a viscosity of 100 mPa. A methyl methacrylate slurry was first prepared, followed by the addition of methacrylic acid, wherein the methyl methacrylate slurry comprised 85 parts by mass and the methacrylic acid comprised 15 parts by mass. A reducing agent, N,N-dimethyl-p-toluidine, comprising 0.4 wt% of the acrylic resin, and an oxidizing agent, dodecyl peroxide, comprising 0.9 wt% of the acrylic resin, were added. The mixture was stirred to dissolve the raw materials. After thorough dissolution and mixing, the prepared injection resin was conveyed to a dispensing machine for room temperature degassing. After degassing, the injection resin was introduced into each layer of the blade through the injection port under vacuum. The mold was not heated during the injection process. A circulating cooling water strip was then installed.

[0043] Polymerization and Curing: After all the resin has been poured, the mold temperature is raised to 50°C and maintained for 18 minutes. This initial temperature increase quickly initiates resin polymerization, shortening the production cycle. Afterward, the mold temperature is lowered to 10°C. Simultaneously, the circulating cooling system above the product is activated. The cooling liquid is water, and the cooling temperature is 8°C. Curing time is 45 minutes. Once the resin is fully cured, the circulating cooling liquid system is withdrawn, the mold temperature is set to 90°C, and an insulation blanket is placed over the product for post-curing of the resin for 4 hours.

[0044] Welding: After the various blade components have cured, they are demolded and cleaned. Then, they are joined together. Ultrasonic welding technology is used to connect the leeward shell, windward shell, and web of the thermoplastic wind turbine blade. After grinding and polishing, the blade is assembled into a complete wind turbine blade.

[0045] Example 3

[0046] This embodiment provides a method for detecting the heat release temperature of the root component of a thermoplastic wind turbine blade.

[0047] Lay-up: At the root of the shell mold on the leeward side of the blade, lay a 100mm layer with a density of 1250g / m² from the root tip. 2 of Biaxial fiberglass cloth, 2 meters in length. A type K thermocouple is placed in the middle of the 50 layers to detect the highest temperature. An isolation membrane, flow guide net, flow guide tube, glue injection port, and vacuum bag film are then laid to establish a vacuum system.

[0048] Preparation of infusion resin and vacuum infusion: At room temperature, PMMA particles were added to MMA in a reactor to prepare a resin with a viscosity of 60 mPa. A methyl methacrylate slurry was first prepared, followed by the addition of methacrylic acid, wherein the methyl methacrylate slurry comprised 88 parts by mass and the methacrylic acid comprised 12 parts by mass. A reducing agent, N,N-dimethyl-p-toluidine, comprising 0.5 wt% of the acrylic resin, and an oxidizing agent, tert-butyl hydroperoxide, comprising 1.2 wt% of the acrylic resin, were added. The mixture was stirred to dissolve the raw materials. After thorough dissolution and mixing, the resin was poured into a dispensing machine for room temperature degassing. After degassing, the resin was injected into each layer of the blade through the injection port under vacuum. The mold was not heated during the injection process. A circulating cooling water strip was then installed.

[0049] Polymerization and Curing: At room temperature (23℃), after all resin has been poured, the mold temperature is raised to 60℃ and maintained for 30 minutes. Afterward, the mold temperature is lowered to 5℃. Simultaneously, the circulating cooling system above the sheet is activated. The cooling liquid is an aqueous ethylene glycol solution with a cooling temperature of 10℃. The highest temperature during the resin polymerization process is recorded using thermocouples. Once the resin is completely cured, recording is stopped, and the circulating cooling liquid system is withdrawn.

[0050] Comparative Example 1

[0051] This comparative example serves as a comparison with Example 3.

[0052] The layup steps are the same as in Example 3.

[0053] The resin injection and vacuum injection are the same as in Example 3, but no circulating cooling water belt is laid after injection.

[0054] Polymerization and curing: At room temperature of 23℃, after all the resin has been poured in, the mold is not heated. The highest temperature during the resin polymerization process is recorded using a thermocouple. Recording is stopped after the resin has completely cured.

[0055] Comparative Example 2

[0056] This comparative example provides a casting resin without methacrylic acid, and compares the mechanical properties of the casting with those of Example 1.

[0057] Preparation of the infusion resin: At room temperature, in a nitrogen-protected reactor, PMMA particles were added to MMA to prepare a resin with a viscosity of 150 mPa. Methyl methacrylate slurry was mixed with N,N-dimethylaniline as a reducing agent (0.3 wt% of the acrylic resin) and benzoyl peroxide as an oxidizing agent (0.7 wt% of the acrylic resin). The mixture was stirred to dissolve the raw materials. After thorough dissolution and mixing, the prepared injection resin was transported to a dispensing machine for room temperature degassing.

[0058] The degassed injection resins from Examples 1, 2, and Comparative Example 2 were poured into a flat mold and cured at room temperature (25°C) for 12 hours. After curing, the temperature was raised to 80°C for post-curing for 4 hours. After cooling and demolding, the resins were cut into strips using a laser cutter according to GB / T2567 and subjected to tensile and bending tests. The results are shown in Table 1.

[0059] Table 1 Results of performance tests on injection resin

[0060] As can be seen from Table 1, the addition of MAA to the PMMA / MMA mixed solution can enhance the mechanical properties of the infusion resin due to the hydrogen bonding between MAA and MMA.

[0061] The highest temperatures of Example 3 and Comparative Example 1 are shown in Table 2.

[0062] Table 2. Heat dissipation temperature of wind turbine blade root components in Example 3 and Comparative Example 1.

[0063] As can be seen from Table 2, the present invention can effectively reduce the exothermic temperature of acrylate infusion resin by laying a circulating cooling liquid channel on the top of the product and using a phased heating and cooling process alternately, thus ensuring good quality of the thick-walled wind turbine blades.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a thermoplastic wind turbine blade, characterized in that, Includes the following steps: (1) Pour the injection resin into the mold, and then cover the upper surface of the mold with a circulating cooling system; (2) The mold is subjected to temperature change treatment to complete the manufacturing of thermoplastic wind turbine blades.

2. The method for manufacturing the thermoplastic wind turbine blade as described in claim 1, characterized in that, The resin infusion in step (1) comprises methyl methacrylate slurry, methacrylic acid, and an initiator; The methyl methacrylate slurry has a mass fraction of 70-95 parts, and the methacrylic acid has a mass fraction of 5-20 parts. The viscosity of methyl methacrylate slurry is 30~500 mPa·s.

3. The method for manufacturing the thermoplastic wind turbine blade as described in claim 2, characterized in that, The initiator comprises an oxidizing agent and a reducing agent; The oxidizing agents include one or more of benzoyl peroxide, dodecyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide; The mass of the oxidant is 0.5-5% of the sum of the masses of methyl methacrylate slurry and methacrylic acid; The reducing agent includes one or more of N,N-dimethylaniline, N,N-dimethyl-p-toluidine, and N,N-diethylaniline; The mass of the reducing agent is 0.01~3% of the combined mass of methyl methacrylate slurry and methacrylic acid.

4. The method for manufacturing the thermoplastic wind turbine blade as described in claim 3, characterized in that, In step (1), the cooling medium of the circulating cooling system is one or more of water, ethylene glycol aqueous solution, and propylene glycol aqueous solution; The cooling medium has a cooling temperature of -10~20℃.

5. The method for manufacturing the thermoplastic wind turbine blade as described in claim 4, characterized in that, In step (2), the temperature-changing treatment is carried out sequentially as polymerization, preliminary curing, and curing; The polymerization temperature is 25~60℃ and the time is 10~40min.

6. The method for manufacturing the thermoplastic wind turbine blade as described in claim 5, characterized in that, The initial curing temperature is provided by a circulating cooling system; The initial curing temperature is -10~20℃, and the time is 10~90min.

7. The method for manufacturing the thermoplastic wind turbine blade as described in claim 6, characterized in that, The curing temperature is 80~120℃ and the time is 1~5h.

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