Carbon fiber reinforced resin matrix composite material for unmanned aircraft wing panels and method of making same

Abstract

This invention discloses a carbon fiber reinforced resin matrix composite material for UAV winglets and its preparation method, belonging to the field of carbon fiber technology. The method includes: preparing carbon fibers through electrospinning combined with stepwise pre-oxidation and carbonization processes; performing composite acidification treatment on the carbon fibers using concentrated nitric acid and hydrogen peroxide to increase surface-active functional groups; using a modifier prepared by the reaction of specific amines and methyl methacrylate, and synergistically using silane to perform surface treatment on the acidified carbon fibers to construct a strong and tough interface layer; and finally molding and curing the pretreated carbon fibers with epoxy resin prepreg. Compared with the prior art, the carbon fiber reinforced resin matrix composite material obtained by this invention is particularly suitable for UAV winglets, possessing high specific strength, high specific modulus, and excellent resistance to damp heat aging, meeting the stringent requirements of high-end equipment for lightweight, high reliability, and long service life of materials.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber technology, and in particular to a carbon fiber reinforced resin matrix composite material for drone winglets and its preparation method. Background Technology

[0002] In the field of carbon fiber preparation and composite materials, carbon fiber reinforced resin matrix composites, with their advantages of high strength and low density, are experiencing a continuous increase in demand in aerospace, drones, and other fields, especially for structural applications such as drone winglets that have stringent requirements for weight and reliability. How to effectively treat carbon fiber surfaces to improve the interfacial bonding strength and durability with the resin matrix has been a long-standing technical challenge in this field. Existing technologies typically employ methods such as nitric acid oxidation, plasma treatment, or electrolytic oxidation to activate the carbon fiber surface, increasing its oxygen-containing functional groups and improving wettability. However, while these conventional treatment methods often enhance interfacial chemical activity, they often fail to construct a stable interfacial layer on the fiber surface that can effectively transfer stress and resist humid heat aging, resulting in challenges to the interlaminar shear strength and long-term reliability of the composite material.

[0003] To address the aforementioned common problems, existing patent technologies have proposed various improvement schemes, but they still have significant limitations. For example, CN117209954A discloses a method for preparing carbon fiber composite materials, which forms a gradient coating layer on the fiber surface through pyrolysis, but the chemical bonding strength between the coating layer and the fiber body needs further improvement. Another publication, CN114262496A, discloses a method for preparing carbon fiber resin-based composite materials for umbrella ribs, which uses an organic acid solution to impregnate the precursor fibers. This treatment method is relatively simple and cannot meet the high requirements for interface durability under complex load conditions. Yet another publication, CN113604908A, discloses a method for preparing nanofibers and a nylon composite material reinforced with them, which focuses on using activated nanofibers as reinforcing fillers and fails to achieve multi-level reinforcement from the fiber body interface structure design level.

[0004] In summary, existing carbon fiber surface modification technologies still have significant shortcomings. They either struggle to simultaneously achieve high interfacial bond strength and excellent environmental aging resistance, or their process adaptability is limited, failing to provide durable and reliable interfacial protection for composite materials under complex operating conditions. Therefore, there is an urgent need to develop a new interface construction method that can establish a strong and stable transition layer between carbon fibers and resins from the perspective of combining chemical grafting and physical construction, thereby comprehensively improving the mechanical properties and service life of composite materials under harsh environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a carbon fiber reinforced resin matrix composite material for UAV winglets and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a carbon fiber reinforced resin matrix composite material for UAV winglets is as follows:

[0008] Step 1: Add carboxylated carbon nanotubes, polyvinyl butyral, polyacrylonitrile, and polyethylene glycol to N,N-dimethylformamide and stir to obtain a spinning solution; obtain electrospinning fibers by electrospinning, wash and dry them, oxidize them stepwise in air atmosphere, and then carbonize them in sections in nitrogen atmosphere to obtain carbon fibers.

[0009] Step 2: Immerse the carbon fiber obtained in Step 1 in concentrated nitric acid for acidification treatment, take it out, wash and dry it to obtain acidified carbon fiber; then immerse the acidified carbon fiber in a modification solution for treatment, and dry it to obtain pretreated carbon fiber.

[0010] Step 3: Prepare a prepreg resin by mixing bisphenol A type epoxy resin and 4-methylhexahydrophthalic anhydride, add the pretreated carbon fiber obtained in step 2 to make a prepreg, and then mold, cure and demold to obtain a carbon fiber reinforced resin matrix composite material.

[0011] Preferably, the method for preparing the carbon fiber reinforced resin matrix composite material for UAV winglets is as follows, in parts by weight:

[0012] Step 1: Add 0.3-0.8 parts of carboxylated carbon nanotubes, 1-2 parts of polyvinyl butyral, 10-20 parts of polyacrylonitrile, and 0.3-0.8 parts of polyethylene glycol to 75-85 parts of N,N-dimethylformamide, stir for 2-6 hours to ensure uniform mixing, and allow to stand to remove bubbles to obtain a spinning solution; spin under the conditions of relative humidity 30-40%, temperature 20-25℃, voltage 15-20KV, receiving distance 15-20cm, and spinning solution extrusion speed 0.5-1mL / h to obtain electrostatic fibers; wash with water 1-3 times, dry at 50-70℃ for 5-15 hours; then oxidize in steps in air atmosphere to obtain pre-oxidized fibers; place the pre-oxidized fibers in a nitrogen atmosphere for segmented heating and carbonization, cool and remove to obtain carbon fibers;

[0013] Step 2: Immerse the carbon fibers prepared in Step 1 in 60wt%-67wt% concentrated nitric acid and mix. Treat at 50-70℃ for 1-5 hours, then remove and wash with water and dry at 50-70℃ for 2-6 hours to obtain acidified carbon fibers. Immerse the acidified carbon fibers in a modification solution and stir at 60-80℃ for 1-5 hours. Remove and dry at 60-80℃ for 1-5 hours to obtain pretreated carbon fibers.

[0014] Step 3: Prepare a prepreg resin by mixing bisphenol A type epoxy resin and 4-methylhexahydrophthalic anhydride in a mass ratio of 15-20:3-8; add the pretreated carbon fiber prepared in step 2 to the prepreg resin to obtain a prepreg; the mass ratio of the pretreated carbon fiber to the prepreg resin is 10-15:5-10; lay the obtained prepreg in a molding die and cure it under a molding press; after molding, demold to obtain a carbon fiber reinforced resin matrix composite material.

[0015] The stepwise heating oxidation in step 1 involves first maintaining the temperature at 180-220℃ for 10-30 minutes, and then increasing the temperature at 1-3℃ / min to 280-320℃ and maintaining it for 40-60 minutes.

[0016] The segmented heating carbonization in step 1 involves raising the temperature at 5-10℃ / min to 900-1000℃ and holding it for 80-120 minutes, then raising it at 5-15℃ / min to 1200-1300℃ and holding it for 20-40 minutes.

[0017] The molding and curing process in step 3 involves first maintaining the temperature at 110-130℃ for 1-3 hours; then raising the temperature to 150-170℃ and maintaining it for 1-2 hours; and finally curing at 180-220℃ for 0.5-2 hours, with the pressure set at 4-8 MPa.

[0018] The modified liquid is prepared as follows:

[0019] Methyl methacrylate was added to anhydrous ethanol to prepare a 20wt%-30wt% functional solution. The functional solution was then added to an amine under a nitrogen atmosphere at a mass ratio of 1-3:0.5-2. The mixture was stirred at 30-40℃ for 10-30 hours, and the solvent was removed by vacuum distillation to obtain the precursor. The precursor was then added to anhydrous ethanol to prepare a 15wt%-25wt% precursor solution. The mixture was stirred with the amine under a nitrogen atmosphere at 30-40℃ for 10-30 hours at a mass ratio of 15-25:0.5-2. The solvent was removed by vacuum distillation to obtain the modifier. The modifier was added to toluene to prepare an 8wt%-12wt% modification solution. (3-glycidyloxypropyl)trimethoxysilane was added at 0.2%-0.5% of the modification solution mass and stirred until homogeneous to obtain the modified solution.

[0020] The amine is at least one of diethylenetriamine, triethylenetetramine, ethylenediamine, 1,3-propanediamine, N-(2-aminoethyl)piperazine, and polyetheramine.

[0021] Preferably, the amine is composed of diethylenetriamine and polyetheramine in a mass ratio of 5-10:2-4.

[0022] The preparation method in step 2 can also be the following method:

[0023] The carbon fibers prepared in step 1 are immersed in a mixture of 60wt%-67wt% concentrated nitric acid and treated at 50-70℃ for 1-5 hours. After treatment, the carbon fibers are removed and washed with water 1-3 times. Then, they are immersed in 1-5wt% hydrogen peroxide and treated at 30-50℃ for 10-30 minutes. After that, they are removed, washed with water, and dried at 50-70℃ for 2-6 hours to obtain acidified carbon fibers. The acidified carbon fibers are immersed in a modification solution and stirred at 60-80℃ for 1-5 hours. After that, they are removed and dried at 60-80℃ for 1-5 hours to obtain pretreated carbon fibers.

[0024] The preparation method in step 2 can also be the following method:

[0025] The carbon fibers prepared in step 1 are immersed in a mixture of 60wt%-67wt% concentrated nitric acid and treated at 50-70℃ for 1-5 hours. After treatment, the carbon fibers are removed and washed with water 1-3 times. Then, they are immersed in 1-5wt% hydrogen peroxide and treated at 30-50℃ for 10-30 minutes. After that, they are removed, washed with water, and dried at 50-70℃ for 2-6 hours to obtain acidified carbon fibers. The acidified carbon fibers are immersed in a modification solution and stirred at 60-80℃ for 0.5-2 hours. Then, 0.2%-0.5% of (3-glycidyloxypropyl)trimethoxysilane is added according to the mass of the modification solution, and stirring is continued at 60-80℃ for 1-3 hours. After that, they are removed and dried at 60-80℃ for 1-5 hours to obtain pretreated carbon fibers.

[0026] This invention employs a progressive process design, gradually enhancing the overall performance of the composite material from spinning raw materials to interface modification. First, carboxylated carbon nanotubes, polyethylene glycol, and polyvinyl butyral are added to the electrospinning precursor to optimize spinning stability and fiber microstructure, preparing high-performance carbon fibers. Then, acidification with concentrated nitric acid followed by light oxidation with low-concentration hydrogen peroxide significantly increases the oxygen-containing groups on the fiber surface, improving the adsorption and grafting efficiency of subsequent modifiers. Subsequently, modifiers obtained by the interaction of amines and methyl methacrylate are grafted onto the fiber surface. Furthermore, a synergistic ratio of diethylenetriamine and polyetheramine provides both high-density chemical crosslinking sites and a flexible energy-dissipating layer, enhancing initial bonding strength and fracture energy. Finally, (3-glycidyloxypropyl)trimethoxysilane is introduced in situ during the modification process to form an organic-inorganic bridging network, further densifying the interface and preventing moisture intrusion. Each step takes into account the adjustability of process parameters to achieve a balance between production efficiency and performance improvement, facilitating large-scale application.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] 1) This invention significantly improves the overall mechanical properties of composite materials, especially the interfacial shear strength and fracture toughness, through synergistic optimization from spinning materials to carbonization process and interfacial chemical crosslinking reinforcement, thereby meeting the high strength and high toughness structural requirements of UAV winglets and helping to reduce component weight.

[0029] 2) This invention constructs a dense interface through hydrogen peroxide pre-oxidation, organic grafting and in-situ silane bridging, which effectively inhibits moisture penetration and interface hydrolysis, and greatly improves the performance retention and service life after damp heat aging.

[0030] 3) The materials and modification processes used in this invention are compatible with the commonly used epoxy composite material molding process, and the process parameters are adjustable, making it easy to promote and apply on existing production lines. At the same time, the material properties are improved through interface enhancement. Detailed Implementation

[0031] Some material parameters and their sources:

[0032] Polyethylene glycol, number average molecular weight 2000.

[0033] Carboxylated carbon nanotubes with a carboxyl content of 5 wt%, a length of 520 μm, and a diameter of 5-15 nm.

[0034] Polyvinyl butyral, acetal degree 70%, number average molecular weight 150,000.

[0035] Polyacrylonitrile, weight average molecular weight 150,000-250,000.

[0036] Bisphenol A type epoxy resin, grade: DER 331, brand: Dow Chemical.

[0037] Polyetheramine, brand name: Polyetheramine D230 M, brand: BASF, Germany.

[0038] In the embodiments and comparative examples of this invention, all raw materials are commercially available products.

[0039] Example 1

[0040] A method for preparing a carbon fiber reinforced resin matrix composite material for UAV winglets is as follows, in parts by weight:

[0041] Step 1: Add 0.5 parts of carboxylated carbon nanotubes, 1.5 parts of polyvinyl butyral, 16 parts of polyacrylonitrile, and 0.5 parts of polyethylene glycol to 81.5 parts of N,N-dimethylformamide. Mechanically stir for 4 hours to ensure uniform mixing and allow to stand to remove bubbles to obtain a spinning solution. Spinning is carried out under the conditions of relative humidity 35%, temperature 22℃, voltage 18KV, receiving distance 18cm, and spinning solution extrusion speed 0.6mL / h to obtain electrostatic fibers. Wash with water 3 times and dry in a drying oven at 60℃ for 10 hours. Then, oxidize in air by stepwise heating: first, hold at 200℃ for 20 minutes, then increase to 300℃ at 2℃ / min and hold for 50 minutes to obtain pre-oxidized fibers. Place the pre-oxidized fibers in a nitrogen atmosphere and heat and carbonize in stages, increasing to 950℃ at 8℃ / min and holding for 100 minutes, then increasing to 1300℃ at 10℃ / min and holding for 30 minutes. Cool and remove to obtain carbon fibers.

[0042] Step 2: Immerse the carbon fiber prepared in Step 1 in 65wt% concentrated nitric acid and mix. Treat at 60°C for 3 hours, then remove and wash with water and dry at 60°C for 4 hours to obtain acidified carbon fiber. Immerse the acidified carbon fiber in the modification solution and stir at 70°C for 3 hours. Remove and dry at 80°C for 2 hours to obtain pretreated carbon fiber.

[0043] Step 3: Prepare a prepreg resin by mixing bisphenol A epoxy resin and 4-methylhexahydrophthalic anhydride in a mass ratio of 18:5; add the pretreated carbon fiber prepared in Step 2 to the prepreg resin to obtain a prepreg; the mass ratio of the pretreated carbon fiber to the prepreg resin is 13:7. Lay the obtained prepreg in a molding die and cure it under a molding press. First, maintain the temperature at 120℃ for 2 hours; then raise the temperature to 160℃ and maintain it for 1.5 hours; finally, cure it at 200℃ for 1 hour. The pressure is set to 6 MPa. After molding, demold to obtain a carbon fiber reinforced resin matrix composite material.

[0044] The modified liquid is prepared as follows:

[0045] Methyl methacrylate was added to anhydrous ethanol to prepare a 25 wt% functional solution. The functional solution was then added to an amine under a nitrogen atmosphere at a mass ratio of 2:1. The mixture was stirred at 35°C for 20 h, and the solvent was removed by vacuum distillation to obtain a precursor. The precursor was then added to anhydrous ethanol to prepare a 20 wt% precursor solution. The mixture was stirred with the amine under a nitrogen atmosphere at 35°C for 20 h at a mass ratio of 20:1. The solvent was removed by vacuum distillation to obtain a modifier. The modifier was added to toluene to prepare a 10 wt% modification solution. 0.3% (3-glycidyloxypropyl)trimethoxysilane was added to the modification solution by mass, and the mixture was stirred until homogeneous to obtain a modified solution.

[0046] The amine is diethylenetriamine.

[0047] Example 2

[0048] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine substance is triethylenetetramine.

[0049] Example 3

[0050] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine is ethylenediamine.

[0051] Example 4

[0052] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine is 1,3-propanediamine.

[0053] Example 5

[0054] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine substance is N-(2-aminoethyl)piperazine.

[0055] Example 6

[0056] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine substance is polyetheramine.

[0057] Example 7

[0058] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine substance is composed of diethylenetriamine and polyetheramine in a mass ratio of 7:3.

[0059] Example 8

[0060] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine is composed of ethylenediamine and 1,3-propanediamine in a mass ratio of 7:3.

[0061] Example 9

[0062] A method for preparing a carbon fiber reinforced resin matrix composite material for UAV winglets is as follows, in parts by weight:

[0063] Step 1: Add 0.5 parts of carboxylated carbon nanotubes, 1.5 parts of polyvinyl butyral, 16 parts of polyacrylonitrile, and 0.5 parts of polyethylene glycol to 81.5 parts of N,N-dimethylformamide. Mechanically stir for 4 hours to ensure uniform mixing and allow to stand to remove bubbles to obtain a spinning solution. Spinning is carried out under the conditions of relative humidity 35%, temperature 22℃, voltage 18KV, receiving distance 18cm, and spinning solution extrusion speed 0.6mL / h to obtain electrostatic fibers. Wash with water 3 times and dry in a drying oven at 60℃ for 10 hours. Then, oxidize in air by stepwise heating: first, hold at 200℃ for 20 minutes, then increase to 300℃ at 2℃ / min and hold for 50 minutes to obtain pre-oxidized fibers. Place the pre-oxidized fibers in a nitrogen atmosphere and heat and carbonize in stages, increasing to 950℃ at 8℃ / min and holding for 100 minutes, then increasing to 1300℃ at 10℃ / min and holding for 30 minutes. Cool and remove to obtain carbon fibers.

[0064] Step 2: Immerse the carbon fiber prepared in Step 1 in 65wt% concentrated nitric acid and treat it at 60℃ for 2h. After treatment, take out the carbon fiber and wash it with water 3 times. Then immerse it in 3wt% hydrogen peroxide and treat it at 40℃ for 20min. After that, take it out, wash it with water and dry it at 60℃ for 4h to obtain acidified carbon fiber. Immerse the acidified carbon fiber in the modification solution and stir it at 70℃ for 3h. Take it out and dry it at 80℃ for 2h to obtain pretreated carbon fiber.

[0065] Step 3: Prepare a prepreg resin by mixing bisphenol A epoxy resin and 4-methylhexahydrophthalic anhydride in a mass ratio of 18:5; add the pretreated carbon fiber prepared in Step 2 to the prepreg resin to obtain a prepreg; the mass ratio of the pretreated carbon fiber to the prepreg resin is 13:7. Lay the obtained prepreg in a molding die and cure it under a molding press. First, maintain the temperature at 120℃ for 2 hours; then raise the temperature to 160℃ and maintain it for 1.5 hours; finally, cure it at 200℃ for 1 hour. The pressure is set to 6 MPa. After molding, demold to obtain a carbon fiber reinforced resin matrix composite material.

[0066] The modified liquid is prepared as follows:

[0067] Methyl methacrylate was added to anhydrous ethanol to prepare a 25 wt% functional solution. The functional solution was then added to an amine under a nitrogen atmosphere at a mass ratio of 2:1. The mixture was stirred at 35°C for 20 h, and the solvent was removed by vacuum distillation to obtain a precursor. The precursor was then added to anhydrous ethanol to prepare a 20 wt% precursor solution. The mixture was stirred with the amine under a nitrogen atmosphere at 35°C for 20 h at a mass ratio of 20:1. The solvent was removed by vacuum distillation to obtain a modifier. The modifier was added to toluene to prepare a 10 wt% modification solution. 0.3% (3-glycidyloxypropyl)trimethoxysilane was added to the modification solution by mass, and the mixture was stirred until homogeneous to obtain a modified solution.

[0068] The amine is composed of diethylenetriamine and polyetheramine in a mass ratio of 7:3.

[0069] Example 10

[0070] A method for preparing a carbon fiber reinforced resin matrix composite material for UAV winglets is as follows, in parts by weight:

[0071] Step 1: Add 0.5 parts of carboxylated carbon nanotubes, 1.5 parts of polyvinyl butyral, 16 parts of polyacrylonitrile, and 0.5 parts of polyethylene glycol to 81.5 parts of N,N-dimethylformamide. Mechanically stir for 4 hours to ensure uniform mixing and allow to stand to remove bubbles to obtain a spinning solution. Spinning is carried out under the conditions of relative humidity 35%, temperature 22℃, voltage 18KV, receiving distance 18cm, and spinning solution extrusion speed 0.6mL / h to obtain electrostatic fibers. Wash with water 3 times and dry in a drying oven at 60℃ for 10 hours. Then, oxidize in air by stepwise heating: first, hold at 200℃ for 20 minutes, then increase to 300℃ at 2℃ / min and hold for 50 minutes to obtain pre-oxidized fibers. Place the pre-oxidized fibers in a nitrogen atmosphere and heat and carbonize in stages, increasing to 950℃ at 8℃ / min and holding for 100 minutes, then increasing to 1300℃ at 10℃ / min and holding for 30 minutes. Cool and remove to obtain carbon fibers.

[0072] Step 2: Immerse the carbon fibers prepared in Step 1 in 65wt% concentrated nitric acid and treat at 60℃ for 2h. After treatment, remove the carbon fibers and wash them with water 3 times. Then immerse them in 3wt% hydrogen peroxide and treat at 40℃ for 20min. After that, remove them, wash them with water, and dry them at 60℃ for 4h to obtain acidified carbon fibers. Immerse the acidified carbon fibers in a modification solution and stir at 70℃ for 1h. Then add (3-glycidyloxypropyl)trimethoxysilane at 0.3% of the modification solution mass and continue stirring at 70℃ for 2h. Remove them and dry them at 80℃ for 2h to obtain pretreated carbon fibers.

[0073] Step 3: Prepare a prepreg resin by mixing bisphenol A epoxy resin and 4-methylhexahydrophthalic anhydride in a mass ratio of 18:5; add the pretreated carbon fiber prepared in Step 2 to the prepreg resin to obtain a prepreg; the mass ratio of the pretreated carbon fiber to the prepreg resin is 13:7. Lay the obtained prepreg in a molding die and cure it under a molding press. First, maintain the temperature at 120℃ for 2 hours; then raise the temperature to 160℃ and maintain it for 1.5 hours; finally, cure it at 200℃ for 1 hour. The pressure is set to 6 MPa. After molding, demold to obtain a carbon fiber reinforced resin matrix composite material.

[0074] The modified liquid is prepared as follows:

[0075] Methyl methacrylate was added to anhydrous ethanol to prepare a 25 wt% functional solution. The functional solution was then added to an amine under a nitrogen atmosphere at a mass ratio of 2:1. The mixture was stirred at 35°C for 20 h, and the solvent was removed by vacuum distillation to obtain a precursor. The precursor was then added to anhydrous ethanol to prepare a 20 wt% precursor solution. The mixture was stirred with the amine under a nitrogen atmosphere at 35°C for 20 h at a mass ratio of 20:1. The solvent was removed by vacuum distillation to obtain a modifier. The modifier was added to toluene to prepare a 10 wt% modification solution. 0.3% (3-glycidyloxypropyl)trimethoxysilane was added to the modification solution by mass, and the mixture was stirred until homogeneous to obtain a modified solution.

[0076] The amine is composed of diethylenetriamine and polyetheramine in a mass ratio of 7:3.

[0077] Comparative Example 1

[0078] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the amine substance is 3-dimethylaminopropylamine.

[0079] Comparative Example 2

[0080] The preparation method of a carbon fiber reinforced resin matrix composite material for UAV winglets is basically the same as that in Example 1, except that the pretreated carbon fiber used in step 3 is replaced with an equal amount of carbon fiber prepared in step 1.

[0081] Test Example 1

[0082] Short beam shear strength test:

[0083] The short beam shear strength test procedure is performed in accordance with the ASTM D2344 test standard.

[0084] Sample preparation: Samples were cut from the carbon fiber reinforced resin matrix composites prepared in each example and comparative example. The dimensions were b=15mm wide, t=2mm thick, and 20mm long. Five parallel samples were prepared per group. The support span was L=4×t=8.0mm according to the short beam shear standard.

[0085] The testing machine and fixtures are made of Instron universal testing machine, with three-point support clamping. The diameter of the loading head and the radius of the support are in accordance with the standard.

[0086] Loading rate: 1.0 mm / min; record maximum load P. max (N), calculate the shear strength of the short beam using the formula:

[0087] τ=0.75×P max / (b×t) (Unit: MPa; b and t are in mm, Pmax is in N)

[0088] The shear strength was taken as the average value, and the test results are shown in Table 1.

[0089] Table 1

[0090] Example 1 56.1 Example 2 57.2 Example 3 54.8 Example 4 55.5 Example 5 55.0 Example 6 53.5 Example 7 62.5 Example 8 55.0 Example 9 65.3 Example 10 66.5 Comparative Example 1 52.9 Comparative Example 2 48.5

[0091] Test Example 2

[0092] Damp heat aging performance test:

[0093] The retention rate of short beam shear strength before and after damp heat aging was used to evaluate the damp heat aging performance.

[0094] The carbon fiber reinforced resin matrix composites prepared in each embodiment and comparative example were cut into identical samples according to the method of Test Example 1, with 5 samples in each group. The samples were then placed in a water bath and completely immersed in water at 70°C for 168 hours. Subsequently, the samples were removed, the surfaces were wiped dry, and the samples were left at room temperature for 24 hours to recover.

[0095] The shear strength of the short beam was then tested under the same short beam shear test conditions as in Test Example 1.

[0096] Calculate the shear strength retention rate R (%) of the short beam = (τ 湿热老化后 / τ 湿热老化前 )×100%.

[0097] The average value was taken, and the relevant test data are summarized in Table 2.

[0098] Table 2

[0099] Example 1 86.1 Example 2 87.1 Example 3 84.5 Example 4 85.2 Example 5 84.8 Example 6 83.0 Example 7 89.5 Example 8 84.6 Example 9 91.3 Example 10 94.4 Comparative Example 1 80.5 Comparative Example 2 75.0

[0100] The modifying solution is prepared by reacting amines with methyl methacrylate to obtain a modifier containing reactive functional groups. The modifier is grafted onto the carbon fiber surface to form an organic layer, which can covalently bond with epoxy resin to improve interfacial energy dissipation, thereby enhancing adhesion and improving hygrothermal stability.

[0101] The triethylenetetramine molecule used in Example 2 contains more amino groups and has a moderate number of chain segments, which allows the organic layer grafted onto the carbon fiber surface after treatment with methyl methacrylate to provide a higher density of chemical crosslinking sites, forming a denser covalent network with the epoxy resin, thereby improving the interfacial bonding strength and improving the interfacial stability under humid and hot conditions.

[0102] In Example 7, diethylenetriamine provides a large number of reactive amine groups on the fiber surface, which covalently crosslink with the epoxy resin during curing, thus improving the initial bond strength. Adding polyetheramine to the system introduces flexible polyether segments at the interface. These flexible segments absorb energy and passivate crack propagation under stress or hydrothermal conditions, slowing down the initiation and propagation rate of interfacial cracks. The synergistic effect of both results in an interface with both a high density of chemical crosslinking sites and an energy-dissipating buffer layer, thus significantly improving the shear strength of the short beam and exhibiting better moisture and heat retention than when using only a single amine.

[0103] While prolonged treatment with concentrated nitric acid can better activate carbon fibers, it can also damage their structure. The improvement in Example 9 significantly increases the number of oxygen-containing functional groups, such as hydroxyl and carboxyl groups, on the carbon fiber surface by subjecting it to a low-concentration hydrogen peroxide treatment after concentrated nitric acid acidification. More oxygen-containing groups improve the adsorption and chemical grafting efficiency of the modifier on the fiber surface, resulting in a denser organic grafted layer that is more firmly bonded to the fiber. This dense grafted layer not only improves the chemical adhesion between the fiber and the resin but also reduces interfacial porosity and moisture channels. Therefore, it significantly improves the short beam shear strength and retention rate after damp heat aging compared to the sample without this treatment.

[0104] Example 10, building upon Example 9, further incorporates (3-glycidyloxypropyl)trimethoxysilane in situ during the carbon fiber modification process, promoting the formation of an inorganic network on the fiber surface and reducing the risk of silane interference with modifier adsorption present in Example 9. This inorganic network forms a covalent or strongly interacting bridging structure with the organic graft layer and resin matrix through silicon-oxygen bonds. This increases interfacial covalent bonding sites, enhancing bond strength, and creates a continuous inorganic barrier, reducing moisture penetration and interfacial hydrolysis rates. Consequently, Example 10 exhibits higher short beam shear strength and superior moisture and heat retention.

Claims

1. A method for preparing a carbon fiber reinforced resin matrix composite material for UAV winglets, characterized in that, The method is as follows: Step 1: Add carboxylated carbon nanotubes, polyvinyl butyral, polyacrylonitrile, and polyethylene glycol to N,N-dimethylformamide and stir to obtain a spinning solution; obtain electrospinning fibers by electrospinning, wash and dry them, oxidize them stepwise in air atmosphere, and then carbonize them in sections in nitrogen atmosphere to obtain carbon fibers. Step 2: Immerse the carbon fiber obtained in Step 1 in concentrated nitric acid for acidification treatment, take it out, wash and dry it to obtain acidified carbon fiber; then immerse the acidified carbon fiber in a modification solution for treatment, and dry it to obtain pretreated carbon fiber. Step 3: Prepare a prepreg resin by mixing bisphenol A type epoxy resin and 4-methylhexahydrophthalic anhydride, add the pretreated carbon fiber obtained in step 2 to make a prepreg, and after molding, curing and demolding, obtain carbon fiber reinforced resin matrix composite material. The modified liquid is prepared as follows: Methyl methacrylate was added to anhydrous ethanol to prepare a 20wt%-30wt% functional solution. The functional solution was then added to an amine under a nitrogen atmosphere at a mass ratio of 1-3:0.5-2. The mixture was stirred at 30-40℃ for 10-30 hours, and the solvent was removed by vacuum distillation to obtain the precursor. The precursor was then added to anhydrous ethanol to prepare a 15wt%-25wt% precursor solution. The mixture was stirred with the amine under a nitrogen atmosphere at 30-40℃ for 10-30 hours at a mass ratio of 15-25:0.5-2. The solvent was removed by vacuum distillation to obtain the modifier. The modifier was added to toluene to prepare an 8wt%-12wt% modification solution. (3-glycidyloxypropyl)trimethoxysilane was added at 0.2%-0.5% of the modification solution mass and stirred until homogeneous to obtain the modified solution. The amine is at least one of diethylenetriamine, triethylenetetramine, ethylenediamine, 1,3-propanediamine, N-(2-aminoethyl)piperazine, and polyetheramine.

2. The method for preparing carbon fiber reinforced resin matrix composite material for UAV winglets as described in claim 1, characterized in that, The method is as follows, by weight: Step 1: Add 0.3-0.8 parts of carboxylated carbon nanotubes, 1-2 parts of polyvinyl butyral, 10-20 parts of polyacrylonitrile, and 0.3-0.8 parts of polyethylene glycol to 75-85 parts of N,N-dimethylformamide, stir for 2-6 hours to ensure uniform mixing, and allow to stand to remove bubbles to obtain a spinning solution; spin under the conditions of relative humidity 30-40%, temperature 20-25℃, voltage 15-20KV, receiving distance 15-20cm, and spinning solution extrusion speed 0.5-1mL / h to obtain electrostatic fibers; wash with water 1-3 times, dry at 50-70℃ for 5-15 hours; then oxidize in steps in air atmosphere to obtain pre-oxidized fibers; place the pre-oxidized fibers in a nitrogen atmosphere for segmented heating and carbonization, cool and remove to obtain carbon fibers; Step 2: Immerse the carbon fiber prepared in Step 1 in 60wt%-67wt% concentrated nitric acid and mix. Treat at 50-70℃ for 1-5 hours, then take it out, wash it with water, and dry it at 50-70℃ for 2-6 hours to obtain acidified carbon fiber. The acidified carbon fiber is immersed in the modification solution and stirred at 60-80℃ for 1-5 hours. It is then removed and dried at 60-80℃ for 1-5 hours to obtain pretreated carbon fiber. Step 3: Prepare a prepreg resin by mixing bisphenol A type epoxy resin and 4-methylhexahydrophthalic anhydride in a mass ratio of 15-20:3-8; add the pretreated carbon fiber prepared in step 2 to the prepreg resin to obtain a prepreg; the mass ratio of the pretreated carbon fiber to the prepreg resin is 10-15:5-10; lay the obtained prepreg in a molding die and cure it under a molding press; after molding, demold to obtain a carbon fiber reinforced resin matrix composite material.

3. The method for preparing carbon fiber reinforced resin matrix composite material for UAV winglets as described in claim 1 or 2, characterized in that, The stepwise heating oxidation in step 1 involves first maintaining the temperature at 180-220℃ for 10-30 minutes, then increasing it at 1-3℃ / min to 280-320℃ and maintaining it for 40-60 minutes; the segmented heating carbonization in step 1 involves increasing the temperature at 5-10℃ / min to 900-1000℃ and maintaining it for 80-120 minutes, then increasing it at 5-15℃ / min to 1200-1300℃ and maintaining it for 20-40 minutes.

4. The method for preparing carbon fiber reinforced resin matrix composite material for UAV winglets as described in claim 1 or 2, characterized in that, The molding and curing process in step 3 involves first maintaining the temperature at 110-130℃ for 1-3 hours; then raising the temperature to 150-170℃ and maintaining it for 1-2 hours; and finally curing at 180-220℃ for 0.5-2 hours, with the pressure set at 4-8 MPa.

5. The method for preparing carbon fiber reinforced resin matrix composite material for UAV winglets as described in claim 1, characterized in that, The amine is composed of diethylenetriamine and polyetheramine in a mass ratio of 5-10:2-4.

6. The method for preparing carbon fiber reinforced resin matrix composite material for UAV winglets as described in claim 1 or 2, characterized in that, The preparation method in step 2 can also be the following method: The carbon fibers prepared in step 1 are immersed in 60wt%-67wt% concentrated nitric acid and treated at 50-70℃ for 1-5h. After treatment, the carbon fibers are taken out and washed with water 1-3 times. Then, they are immersed in 1-5wt% hydrogen peroxide and treated at 30-50℃ for 10-30min. After that, they are taken out, washed with water, and dried at 50-70℃ for 2-6h to obtain acidified carbon fibers. The acidified carbon fiber is immersed in the modification solution and stirred at 60-80℃ for 1-5 hours. It is then removed and dried at 60-80℃ for 1-5 hours to obtain pretreated carbon fiber.

7. The method for preparing carbon fiber reinforced resin matrix composite material for UAV winglets as described in claim 1 or 2, characterized in that, The preparation method in step 2 can also be the following method: The carbon fibers prepared in step 1 are immersed in 60wt%-67wt% concentrated nitric acid and treated at 50-70℃ for 1-5h. After treatment, the carbon fibers are taken out and washed with water 1-3 times. Then, they are immersed in 1-5wt% hydrogen peroxide and treated at 30-50℃ for 10-30min. After that, they are taken out, washed with water, and dried at 50-70℃ for 2-6h to obtain acidified carbon fibers. Immerse the acidified carbon fiber in the modification solution and stir at 60-80℃ for 0.5-2h. Then add (3-glycidyloxypropyl)trimethoxysilane at 0.2%-0.5% of the modification solution mass and continue stirring at 60-80℃ for 1-3h. Remove and dry at 60-80℃ for 1-5h to obtain pretreated carbon fiber.

8. A carbon fiber reinforced resin matrix composite material for unmanned aerial vehicle (UAV) winglets, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.