Aviation composite material paddle and preparation method thereof

Abstract

The invention discloses an aviation composite material paddle and a preparation method thereof, and the preparation method comprises the following steps: curing a carbon fiber prepreg by using a mold pressing process to prepare a carbon beam as a main bearing structure; a carbon beam and a light core material are used as internal supports through a three-dimensional weaving technology, a skin is formed through wrapping and weaving, and an integrated fiber prefabricated body is obtained; preparing a toughened resin system for RTM (resin transfer molding), wherein the toughened resin system comprises liquid resin capable of being thermally cured, a curing agent and a carbon nanotube subjected to surface chemical modification; and placing the fiber preform in a mold, closing the mold, injecting the toughened resin system into a mold cavity, curing, and demolding to obtain the aviation composite material paddle. According to the invention, the preparation of the composite material paddle with high surface precision, light overall weight and excellent impact toughness is realized, and the preparation method is good in process repeatability and suitable for batch production.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite materials technology, and in particular to an aerospace composite blade and its preparation method. Background Technology

[0002] Carbon fiber composites, with their excellent mechanical properties, high chemical stability, low density, high specific strength, high specific stiffness, fatigue resistance, and strong designability, are widely used in high-tech fields such as aerospace, military equipment, and marine vessels. In applications with stringent requirements for lightweight, high strength, and high reliability, such as satellite components, aircraft wings, and aero-engine parts, carbon fiber composites play an irreplaceable role. As a key aerodynamic component of spacecraft, the performance of propulsion blades directly affects the propulsion efficiency and overall performance of the spacecraft. Therefore, they are required to possess high precision, good elasticity and fatigue strength, high specific stiffness, and extremely light weight. Their main function is to cut through the air at high speeds to generate precise and stable thrust.

[0003] Lightweighting is a long-term strategic research priority in the aerospace field. Studies show that for every 1 kg reduction in the weight of an aircraft, the corresponding launch vehicle can be reduced by up to 500 kg. Traditional metal propeller blades suffer from inherent drawbacks such as long production cycles, low material utilization, and complex processing techniques, making it difficult to meet the urgent demands of modern aircraft upgrades for high performance and extreme lightweighting. Propeller blades manufactured using 3D printing technology generally face problems such as insufficient high-temperature resistance, weak aging resistance, and susceptibility to surface deformation under sustained aerodynamic loads, limiting their application in high-reliability scenarios. Therefore, using carbon fiber composite materials to manufacture propeller blades can meet the requirements for lightweighting and fatigue resistance.

[0004] However, carbon fiber composite propeller blades are mostly variable cross-section airfoil structures with complex aerodynamic shapes, typically requiring extremely high material properties, dimensional accuracy, and surface quality after molding. Currently, when using processes such as autoclave molding or vacuum-assisted casting molding, the cured parts often exhibit problems such as uneven surface roughness and difficulty in precisely controlling dimensional accuracy. While compression molding is more efficient, its layup process heavily relies on manual experience, resulting in poor product consistency and difficulty in meeting the quality stability requirements of mass production. The combination of three-dimensional braiding technology and resin transfer molding (RTM) provides a new approach to manufacturing high-precision propeller blades. This solution can effectively ensure the cross-sectional accuracy, torsion angle accuracy, and surface roughness of the blades, while also possessing high production efficiency.

[0005] However, with the continuous expansion of application scenarios, the requirements for damage tolerance and impact toughness of propeller blades are increasing, posing a greater challenge to the toughness of the resin matrix. Currently, thermoplastic or rubber solutions are often used to toughen the resin, but this method often leads to a sharp increase in the viscosity of the resin system, seriously affecting the resin's ability to wet the dense three-dimensional fiber preform and failing to meet the core requirements of RTM process for low resin viscosity and good flowability. Therefore, how to simultaneously resolve the contradiction between high-precision molding of the fiber preform and high-level toughening of the resin matrix through an efficient and comprehensive manufacturing method while ensuring RTM processability, and ultimately achieve the unity of high precision, lightweight, and high toughness in propeller blade products, has become a key technical bottleneck restricting the development of high-performance aerospace composite material propeller blades. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide an aerospace composite material rotor blade and its preparation method. The present invention ensures the accuracy of the main load-bearing structure through molding a carbon beam, achieves the overall molding of complex aerodynamic shapes through three-dimensional woven skin, and utilizes a carbon nanotube chemically toughened resin system to achieve good wetting and curing during the RTM process. This results in a composite material rotor blade with high surface precision, light overall weight, and excellent impact resistance and toughness, with good process repeatability, making it suitable for mass production.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: A method for preparing an aerospace composite material rotor blade includes the following steps: S1. Carbon beam preparation: Carbon fiber prepreg is cured by molding process to prepare carbon beams as the main load-bearing structure; S2. Prefabricated body integration: Through three-dimensional weaving technology, carbon beams and lightweight core materials are used as internal supports, and the weaving is wrapped to form a skin, resulting in an integrated fiber prefabricated body; S3. Resin system preparation: Prepare a toughening resin system for RTM molding, the toughening resin system comprising a thermosetting liquid resin, a curing agent and surface-chemically modified carbon nanotubes. S4, RTM molding: The fiber preform is placed in a mold, and after the mold is closed, the toughening resin system is injected into the mold cavity. After curing, the mold is demolded to obtain the aerospace composite blade.

[0008] Furthermore, the carbon beam has a symmetrical layup structure with a layup sequence of [±45 / 0 / (0 / 90) / 0]s, and the length direction of the carbon beam is 0° fiber direction.

[0009] Preferably, the lightweight core material is foam.

[0010] Furthermore, in step S2, the three-dimensional weaving begins at the root of the blade and the root is treated with dry yarn thickening, and then extends to the upper and lower surfaces of the blade and the blade tip, finally forming a closed three-dimensional fabric structure that wraps the carbon beam and the lightweight core material; wherein, the three-dimensional weaving preferably uses carbon fiber yarn or tow.

[0011] Further, in step S3, the surface chemical modification process of the carbon nanotubes is as follows: first, the silane coupling agent undergoes a self-condensation reaction in the presence of an amine curing agent, and then it undergoes a grafting reaction with the carboxylated carbon nanotubes.

[0012] Furthermore, the toughening resin system also includes an accelerator.

[0013] Further, by weight, the toughening resin system comprises the following components: 70-80 parts of liquid resin, 10-20 parts of curing agent, 3-7 parts of accelerator, and 3-7 parts of surface-chemically modified carbon nanotubes.

[0014] Preferably, in the toughening resin system, the liquid resin is a liquid epoxy resin, the curing agent is an amine curing agent, and the accelerator is a urea accelerator. The liquid epoxy resin is preferably one or a mixture of bisphenol F type epoxy resin, bisphenol A type epoxy resin, and glycidylamine epoxy resin. The amine curing agent is preferably one or more of diethylenetriamine, triethylenetetramine, hexamethylenediamine, and dicyandiamide. The urea accelerator is preferably one or more of UR500, UR200, U-35M, and U-52M.

[0015] Further, in step S4, before injecting the toughening resin system, the following pretreatment is performed: the mixed toughening resin system is subjected to vacuum degassing treatment until no bubbles are released; and the mold cavity containing the fiber preform is subjected to vacuum treatment after mold closing.

[0016] Another aspect of the present invention provides an aerospace composite blade prepared by the above-described preparation method, comprising: The carbon beam serves as the main load-bearing structure, the lightweight core material surrounds the carbon beam, and the skin is formed and wrapped around the carbon beam and the lightweight core material through a three-dimensional weaving process. The carbon beam, lightweight core material, and skin are integrally formed into a composite material structure by curing a toughened resin system containing surface-modified carbon nanotubes.

[0017] The beneficial effects of this invention are as follows: This invention utilizes a molded carbon beam as the main load-bearing skeleton of the blade, ensuring the dimensional accuracy and fiber orientation accuracy of the main load-bearing components of the blade. Combined with the shaping effect of the three-dimensional woven skin in the RTM mold, the aerodynamic profile accuracy and surface smoothness of the blade are effectively improved. The combination of carbon fiber composite materials and lightweight foam core materials achieves extreme lightweighting and significantly improves the specific strength and specific stiffness of the product. In this invention, chemically grafted carbon nanotubes form a nanoscale reinforcing network in the resin matrix, thereby toughening the resin matrix and significantly improving the impact toughness and damage tolerance of the blades. Furthermore, the improved toughened resin system can maintain good fluidity, ensuring full wetting of the high-density three-dimensional woven preform during RTM injection, successfully resolving the contradiction between high toughness and RTM processability.

[0018] In terms of production process, this method shows significant advantages: molding and three-dimensional weaving reduce the variation of traditional manual laying and ensure high product consistency; while the process design of "prefabricated integration + RTM integrated molding" efficiently integrates multiple manufacturing links, shortens the production cycle, and is conducive to mass production.

[0019] This invention overcomes the technical bottlenecks in precision, weight, toughness, and production efficiency of high-performance blades, and has outstanding industrial application value. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the aerospace composite material propeller blade of Embodiment 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the cross-sectional structure of the aerospace composite material blade of Embodiment 1 of the present invention. Detailed Implementation

[0022] 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.

[0023] This invention provides a method for preparing aerospace composite material rotor blades, comprising the following steps: S1. Carbon beam preparation: Carbon fiber prepreg is cured by molding process to prepare carbon beams as the main load-bearing structure; The carbon beam has a symmetrical layup structure with a layup sequence of [±45 / 0 / (0 / 90) / 0]s, and the length direction of the carbon beam is 0° fiber direction. The symmetrical layup effectively avoids warping deformation caused by asymmetry in the layup during curing, ensuring the dimensional accuracy of the carbon beam; while laying high-strength, high-modulus 0° fibers along the main load-bearing direction maximizes the performance of unidirectional fibers, enabling the carbon beam to efficiently withstand the main bending and tensile loads during blade operation.

[0024] S2. Prefabricated body integration: Through three-dimensional weaving technology, carbon beams and lightweight core materials are used as internal supports, and the weaving is wrapped to form a skin, resulting in an integrated fiber prefabricated body; The lightweight core material is preferably foam; the three-dimensional weaving begins at the root of the blade and the root is treated with dry yarn thickening, and then extends to the upper and lower surfaces of the blade and the blade tip, finally forming a closed three-dimensional fabric structure that wraps the carbon beam and the lightweight core material; the dry yarn thickening treatment at the root directly enhances the strength and rigidity of the connection between the blade and the hub, and the reliability of this most critical stress-bearing part is greatly improved. Among them, three-dimensional weaving preferably uses carbon fiber yarn or tow.

[0025] S3. Resin system preparation: Prepare a toughening resin system for RTM molding, the toughening resin system comprising a thermosetting liquid resin, a curing agent and surface-chemically modified carbon nanotubes. The surface chemical modification process of carbon nanotubes involves: first, a silane coupling agent undergoes a self-condensation reaction in the presence of an amine curing agent, followed by a grafting reaction with carboxylated carbon nanotubes. This process, involving the self-condensation of the silane coupling agent followed by grafting with carboxylated carbon nanotubes, achieves the grafting of flexible long chains that can bond well with the resin matrix onto the surface of carbon nanotubes, thus realizing chemical toughening.

[0026] The toughening resin system also includes accelerators.

[0027] Furthermore, by weight, the toughening resin system comprises the following components: 70-80 parts of liquid resin, 10-20 parts of curing agent, 3-7 parts of accelerator, and 3-7 parts of surface-chemically modified carbon nanotubes.

[0028] In the toughening resin system, the liquid resin is a liquid epoxy resin, the curing agent is an amine curing agent, and the accelerator is a urea accelerator. The liquid epoxy resin is preferably one or a mixture of bisphenol F type epoxy resin, bisphenol A type epoxy resin, and glycidylamine epoxy resin. The amine curing agent is preferably one or more of diethylenetriamine, triethylenetetramine, hexamethylenediamine, and dicyandiamide. The urea accelerator is preferably one or more of UR500, UR200, U-35M, and U-52M.

[0029] S4, RTM molding: The fiber preform is placed in a mold, and after the mold is closed, the toughening resin system is injected into the mold cavity. After curing, the mold is demolded to obtain the aerospace composite blade. In step S4, before injecting the toughening resin system, the following pretreatment is performed: the mixed toughening resin system is subjected to vacuum degassing until no bubbles are released; and the mold cavity containing the fiber preform is vacuumed after molding. Vacuum degassing and vacuuming of the resin and mold cavity before resin injection effectively remove gases introduced during resin mixing and air between fibers in the mold cavity, fundamentally preventing defects such as bubbles and dry spots in the finished product. This ensures the composite material is dense and flawless, thereby guaranteeing the full utilization of its mechanical properties and service life.

[0030] like Figure 1 and Figure 2 As shown, the aerospace composite blade prepared by the above method includes: The carbon beam 1 serves as the main load-bearing structure, the lightweight core material 2 surrounds the carbon beam 1, and the skin is formed and wrapped around the carbon beam 1 and the lightweight core material 2 by a three-dimensional weaving process. The carbon beam 1, lightweight core material 2, and skin 3 are integrally formed into a composite material structure by curing a toughened resin system containing surface-modified carbon nanotubes.

[0031] Example I. Carbon Beam Preparation Raw materials: T700SC-12K-50C carbon fiber fabric prepreg and USN02001 unidirectional tape prepreg produced by Toray Industries, Inc. of Japan are used, and the resin matrix is ​​an epoxy resin system.

[0032] Ply design: The carbon beam ply structure is symmetrical, with a specific sequence of [±45 / 0 / (0 / 90) / 0]s, for a total of 8 layers. The length direction of the carbon beam is defined as the 0° direction, where unidirectional strip prepreg is mainly used to optimize load transfer.

[0033] Molding process: The above layup was simulated and analyzed using Siemens Fibersim software, and the optimized layup data was exported. In a constant temperature and humidity chamber (temperature 23±2℃, humidity <40%), the prepreg was laid on a pre-treated mold according to the layup sequence and angle. After laying, the upper and lower molds were closed, and the mold was moved into a hot press. The temperature was increased from room temperature to 125℃ at a rate of 3℃ / min, with a pressure of 0.8MPa, and held for 90 minutes; then the temperature was increased to 180℃, the pressure increased to 1.2MPa, and held for 120 minutes. After curing, the temperature was allowed to cool naturally to below 60℃, the pressure was released, the mold was opened, and the carbon beam component was removed.

[0034] II. Prefabricated Body Integration (Three-Dimensional Weaving) Lightweight core material: PVC structural foam from Diab is used, which is machined into core material blocks that are roughly consistent with the internal contour of the blade using CNC machine tools.

[0035] Pre-weaving fixation: The carbon beams obtained in step one and the processed foam core material are precisely positioned and temporarily fixed on a special assembly fixture using high-temperature tape to form a "carbon beam-foam" core prefabricated body.

[0036] 3D weaving: Yarn: 12K carbon fiber dry yarn.

[0037] Weaving equipment: Large-scale three-dimensional weaving machines are used.

[0038] Weaving process: The fixed core prefabricated body serves as the internal support skeleton. Weaving begins at the root of the blade, and the root is locally thickened by increasing the number of yarns and the weaving density. Subsequently, the weaving trajectory extends to the upper and lower surfaces of the blade and towards the blade tip, ultimately forming a continuous, closed, integral three-dimensional fabric structure (i.e., an integrated fiber prefabricated body) that wraps around the carbon beam and foam core material.

[0039] III. Formulation of RTM Resin System raw material: Liquid epoxy resin: NPEL-128 (Bisphenol A type liquid epoxy resin); Amine curing agents: diethylenetriamine; Urea accelerator: UR500; Carboxylated carbon nanotubes: purity >95%, carboxyl group content 3.5wt%; Silane coupling agent: KH-792.

[0040] Preparation of modified carbon nanotubes: In a 500 mL round-bottom flask equipped with a stirrer and condenser, 10 parts by weight of anhydrous ethanol, 5 parts by weight of KH-792, 5 parts by weight of ammonium bicarbonate, 10 parts by weight of diethylenetriamine curing agent, and 60 parts by weight of deionized water were added sequentially. A magnetic stir bar was placed in the flask, and the mixture was heated in a water bath to 90°C. The mixture was stirred at 100 rpm for 20 minutes to allow KH-792 to complete its self-condensation polymerization. Subsequently, 10 parts by weight of carboxylated carbon nanotubes were added to the system, and the reaction was continued at the same temperature for 140 minutes. During this period, the carboxyl groups on the surface of the carbon nanotubes underwent a grafting reaction with the amino groups on the self-condensed KH-792 and the amine curing agent. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain surface-modified carbon nanotubes (modified carbon nanotubes).

[0041] Preparation of toughening resin system: Take 75 parts by weight of NPEL-128 epoxy resin, add 5 parts by weight of the modified carbon nanotubes prepared above, and disperse at 3000 rpm for 30 minutes using a high-speed shear disperser to ensure uniform dispersion of the modified carbon nanotubes. Then add 5 parts by weight of UR500 accelerator and 15 parts by weight of diethylenetriamine curing agent, and mix at low speed under vacuum (-0.095 MPa) for 15 minutes using a planetary mixer to obtain a homogeneous toughened resin system.

[0042] IV. RTM Molding Mold preparation: Place the integrated fiber preform obtained in step two into the cleaned RTM mold cavity, ensuring accurate positioning, close the mold and lock it; Pretreatment: The toughening resin system mixed in step three is further degassed in a storage tank by vacuuming (-0.1 MPa) for 25 minutes until no bubbles emerge from the observation window. At the same time, the mold cavity after molding is vacuumed (-0.09 MPa) and maintained for 30 minutes to remove air from inside the fiber preform.

[0043] Injection and Curing: The mold is preheated to 60℃, and the toughening resin system is injected into the mold cavity under an injection pressure of 0.5MPa. After injection, the temperature is increased to 80℃ at 2℃ / min and held for 60 minutes; then increased to 135℃ at 1.5℃ / min and held for 120 minutes for curing. After curing, the temperature is allowed to cool naturally to below 50℃, and the mold is opened to remove the part. Post-processing, such as grinding, is performed on the part to obtain the final aerospace composite blade.

[0044] like Figure 1 and Figure 2 As shown, the aerospace composite material blade of this embodiment includes: The carbon beam 1 serves as the main load-bearing structure, the lightweight core material 2 surrounds the carbon beam 2, and the skin 3 is formed by a three-dimensional weaving process and wraps the carbon beam 1 and the lightweight core material 2. The carbon beam 1, lightweight core material 2, and skin 3 are integrally formed into a composite material structure by curing a toughened resin system containing surface-modified carbon nanotubes.

[0045] 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.

[0046] 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 method for preparing an aerospace composite material rotor blade, characterized in that, Includes the following steps: S1. Carbon beam preparation: Carbon fiber prepreg is cured by molding process to prepare carbon beams as the main load-bearing structure; S2. Prefabricated body integration: Through three-dimensional weaving technology, carbon beams and lightweight core materials are used as internal supports, and the weaving is wrapped to form a skin, resulting in an integrated fiber prefabricated body; S3. Resin system preparation: Prepare a toughening resin system for RTM molding, the toughening resin system comprising a thermosetting liquid resin, a curing agent and surface-chemically modified carbon nanotubes. S4, RTM molding: The fiber preform is placed in a mold, and after the mold is closed, the toughening resin system is injected into the mold cavity. After curing, the mold is demolded to obtain the aerospace composite blade.

2. The method for preparing aerospace composite blades according to claim 1, characterized in that, The carbon beam has a symmetrical layup structure with a layup sequence of [±45 / 0 / (0 / 90) / 0]s, and the length direction of the carbon beam is 0° fiber direction.

3. The method for preparing aerospace composite blades according to claim 1, characterized in that, The lightweight core material is foam.

4. The method for preparing aerospace composite blades according to claim 1, characterized in that, In step S2, the three-dimensional weaving begins at the root of the blade and the root is treated with dry yarn thickening. Then it extends to the upper and lower surfaces of the blade and the blade tip, eventually forming a closed three-dimensional fabric structure that wraps the carbon beam and the lightweight core material.

5. The method for preparing aerospace composite blades according to claim 1, characterized in that, In step S3, the surface chemical modification process of the carbon nanotubes is as follows: first, the silane coupling agent undergoes a self-condensation reaction in the presence of an amine curing agent, and then it undergoes a grafting reaction with the carboxylated carbon nanotubes.

6. The method for preparing aerospace composite material blades according to claim 1, characterized in that, The toughening resin system also includes an accelerator.

7. The method for preparing aerospace composite blades according to claim 1, characterized in that, By weight, the toughening resin system comprises the following components: 70-80 parts liquid resin, 10-20 parts curing agent, 3-7 parts accelerator, and 3-7 parts surface-chemically modified carbon nanotubes.

8. The method for preparing aerospace composite material blades according to claim 7, characterized in that, In the toughening resin system, the liquid resin is liquid epoxy resin, the curing agent is an amine curing agent, and the accelerator is a urea accelerator.

9. The method for preparing aerospace composite blades according to claim 1, characterized in that, In step S4, before injecting the toughening resin system, the following pretreatment is performed: the mixed toughening resin system is subjected to vacuum degassing treatment until no bubbles are released; and the mold cavity containing the fiber preform is subjected to vacuum treatment after molding.

10. An aerospace composite blade prepared by the preparation method according to any one of claims 1-9, characterized in that, include: The carbon beam serves as the main load-bearing structure, the lightweight core material surrounds the carbon beam, and the skin is formed and wrapped around the carbon beam and the lightweight core material through a three-dimensional weaving process. The carbon beam, lightweight core material, and skin are integrally formed into a composite material structure by curing a toughened resin system containing surface-modified carbon nanotubes.

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