Preparation method of over-frame protection material for aviation cable

Abstract

The invention discloses a preparation method of an aviation cable over-frame protection material, and belongs to the technical field of composite high polymer materials. The method comprises the following steps: blending aramid fibers and polyimide fibers according to a mass ratio of (30-70): (70-30) to weave a flexible sleeve; growing polyaniline nanowires on the surface of the sleeve in situ, and dipping in titanium carbide dispersion liquid; a 5-20 [mu] m perfluoroalkoxy resin thin layer is coated outside; dipping in a polyacrylic acid solution to form a gel layer; and performing vacuum freeze drying and hot drying in a nitrogen atmosphere. The protection material with high temperature resistance, vibration resistance, wear resistance and excellent EMI shielding effectiveness is prepared through fiber blending, nanowire in-situ growth, multi-layer compounding and freeze drying processes, has the characteristics of low reflection coefficient and light weight, and is suitable for aviation cable over-frame protection.

Description

Technical Field

[0001] This invention belongs to the field of composite polymer materials technology, specifically, it relates to a method for preparing a cable over-frame protection material for aviation applications. Background Technology

[0002] With the rapid development of the modern aviation industry, the electrification of aircraft is constantly improving, and airborne electronic equipment and electrical systems are becoming increasingly complex. As a key component for transmitting power and signals, the safety and reliability of aviation cables are directly related to flight safety. In aircraft structures, cables need to pass through structural components such as bulkheads and cabin walls. These passageways, due to the presence of openings, are not only prone to mechanical wear between the cables and the metal structure but also create electromagnetic leakage paths. Furthermore, they face the combined challenges of harsh environments such as high temperatures, vibration, salt spray, and oil contamination. Therefore, the performance requirements for the protection materials used for aviation cables passing through bulkheads are extremely stringent, requiring multiple characteristics such as high temperature resistance, vibration resistance, wear resistance, excellent electromagnetic interference (EMI) shielding effectiveness, and lightweight design. Traditional aviation cable protection primarily uses metal sheaths, rubber sheaths, or single polymer material sleeves. While metal sheaths offer good electromagnetic shielding performance, they suffer from problems such as heavy weight, susceptibility to corrosion, poor flexibility, and installation difficulties, making it difficult to meet the requirements of modern aircraft lightweight design. While rubber sheathing materials such as silicone rubber and fluororubber possess a certain degree of flexibility and temperature resistance, they are prone to aging and cracking under long-term high-temperature environments, and their EMI shielding effectiveness is limited. Single polymer materials such as polytetrafluoroethylene (PTFE) sheathing, although chemically stable, suffer from insufficient mechanical strength, poor wear resistance, and lack effective electromagnetic shielding. These traditional materials have significant shortcomings in overall performance and cannot fully meet the stringent requirements for cable protection in the high-voltage, high-power, and high-frequency electromagnetic environments of next-generation aircraft. Aramid fiber (poly(p-phenylene terephthalamide), PPTA), as a representative of high-performance organic fibers, possesses excellent properties such as ultra-high strength, high modulus, high temperature resistance, and flame retardancy. Its specific strength is 5-6 times that of steel wire, and its specific modulus is 2-3 times that of steel wire. It does not decompose or melt at 560℃, and its limiting oxygen index (LOI) is greater than 28, making it an ideal lightweight, high-strength material. In the aerospace field, aramid fiber has been widely used in aircraft structural components, interior materials, bulletproof armor, engine heat shields, and other parts. However, pure aramid fiber products suffer from problems such as high surface inertia, weak interfacial bonding with the resin matrix, and insufficient antistatic properties, limiting their direct application in electromagnetic shielding. Furthermore, aramid fibers have poor UV resistance and will degrade upon prolonged exposure to sunlight, affecting their service life. Polyimide fibers are another important class of high-performance fiber materials. Their main chain contains an imide ring structure, exhibiting outstanding high-temperature resistance, with long-term operating temperatures reaching 260-300℃ and short-term operating temperatures exceeding 400℃. They also possess good chemical corrosion resistance, radiation resistance, and self-lubricating properties. Compared to aramid fibers, polyimide fibers have superior dielectric properties, with a low dielectric constant and low dielectric loss, making them ideal electrical insulation materials. However, the mechanical strength of polyimide fibers is slightly lower than that of aramid fibers, and their cost is higher, resulting in less than ideal cost-effectiveness when used alone.Blending aramid fibers with polyimide fibers allows for the full utilization of the synergistic effect of the two fibers, achieving complementary performance and resulting in a composite fiber sleeve substrate with superior overall performance. In the field of electromagnetic shielding materials, traditional metal-based shielding materials such as copper foil, aluminum foil, and metal braided mesh, while offering high shielding effectiveness, suffer from drawbacks such as high density, susceptibility to corrosion, poor processability, and insufficient flexibility. In recent years, conductive polymers such as polyaniline (PANI), polypyrrole (PPy), and polythiophene (PTh) have become research hotspots due to their advantages such as light weight, corrosion resistance, ease of processing, and adjustable conductivity. Polyaniline, as one of the most typical conductive polymers, can form a conductive network structure through protonic acid doping, exhibiting excellent electromagnetic shielding performance in the 0.1-1000MHz frequency band. In particular, polyaniline nanowire structures, with their high aspect ratio and specific surface area, can form an effective three-dimensional conductive network in composite materials, achieving multiple reflection losses and absorption losses, significantly improving the material's shielding effectiveness. However, polyaniline has poor mechanical properties and is brittle, making it difficult to meet the mechanical performance requirements of the aerospace environment when used alone. Two-dimensional transition metal carbide (MXene) materials, such as titanium carbide, are a newly emerging class of conductive nanomaterials in recent years, possessing excellent metallic conductivity, high specific surface area, and good mechanical properties. Studies have shown that the conductivity of nanosheets can reach 6500 S / cm, far exceeding that of traditional carbon materials. Their layered structure can form a dense shielding network in a polymer matrix, generating strong reflection and absorption of electromagnetic waves. Combining MXene with conductive polymers can construct a synergistic shielding mechanism, with MXene providing a highly efficient reflective layer and the conductive polymer providing an absorption layer. The combination of the two can achieve a multi-layered shielding effect of "absorption-reflection-reabsorption," significantly reducing surface reflectivity and avoiding secondary electromagnetic pollution. However, MXene sheets are prone to stacking and agglomeration, have poor compatibility with organic matrices, and weak interfacial bonding, making it difficult to fully utilize their performance advantages through direct composites. Perfluoroalkoxy resin (PFA) is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, possessing both the chemical inertness and melt processability of polytetrafluoroethylene. It exhibits extremely low dielectric constant (2.1), excellent chemical corrosion resistance, a wide operating temperature range (-200~+260℃), and good flame retardant properties. In aviation cable protection, thin PFA layers can serve as protective coatings, effectively isolating corrosive media such as oil, salt spray, and moisture. Its low dielectric properties also help reduce signal transmission loss. However, PFA has weak interfacial bonding with most polymer matrices, requiring special surface treatment processes to achieve reliable adhesion. Polyacrylic acid (PAA) hydrogel has good water absorption and film-forming properties, forming a flexible protective layer on fiber surfaces, improving the material's impact resistance and abrasion resistance. Porous PAA gel layers prepared by freeze-drying possess lightweight, heat-insulating, and cushioning properties, effectively absorbing vibration energy and reducing mechanical wear between cables and structural components. However, PAA has limited temperature resistance, requiring combination with other high-temperature resistant materials to meet aviation environmental requirements.

[0003] While each of the aforementioned materials possesses unique advantages, the systematic integration of multiple functional materials to construct a multi-layered, multi-functional composite protection system still faces numerous challenges. First, the interfacial compatibility between different materials is poor, resulting in weak interlayer bonding and a tendency for delamination under temperature cycling and vibration loading. Second, the uniformity of nanomaterial dispersion in the polymer matrix is ​​difficult to control, leading to agglomeration and performance degradation. Third, the fabrication process of multi-layered composite structures is complex and costly, hindering large-scale production. Finally, existing material systems struggle to simultaneously meet the conflicting requirements of high shielding effectiveness and low reflectivity, high strength and lightweight, and high temperature resistance and flexibility.

[0004] To address the aforementioned problems, this invention proposes a method for preparing a protective material for aviation cables passing through frames. A high-strength, heat-resistant substrate is constructed by co-weaving aramid and polyimide fibers. An in-situ growth technique is used to build a conductive network of polyaniline nanowires on the fiber surface. A titanium carbide dispersion is impregnated to form a synergistic shielding layer. A thin layer of perfluoroalkoxy resin is then applied for chemical protection. Finally, a polyacrylic acid solution is impregnated and freeze-dried to form a buffer and heat-insulating layer. Chemical bonding between the layers is achieved through heat drying in a nitrogen atmosphere. This preparation method organically integrates fiber reinforcement, electromagnetic shielding, chemical protection, and buffer and heat insulation functions, solving the problems of traditional materials having limited performance, weak interfacial bonding, and high weight. It provides a comprehensive, high-performance, lightweight, and highly reliable solution for protecting aviation cables passing through frames. Summary of the Invention

[0005] To address the technical problems of insufficient overall performance, limited functionality, weak interfacial bonding, and difficulty in meeting the dual requirements of lightweight and high reliability in existing aviation cable over-frame protection materials, this invention provides a method for preparing an aviation cable over-frame protection material. Existing technologies mainly suffer from the following drawbacks: traditional metal sheaths are heavy, easily corroded, and lack flexibility, making them unsuitable for modern aircraft lightweight design requirements; rubber sheath materials are prone to aging and cracking under high temperatures and have limited electromagnetic interference (EMI) shielding effectiveness; single polymer materials such as polytetrafluoroethylene (PTFE) sheaths lack sufficient mechanical strength and wear resistance, and do not possess effective electromagnetic shielding functions. While aramid fibers possess high strength, high modulus, and high temperature resistance, their surface inertness, weak interfacial bonding with the resin matrix, insufficient antistatic properties, and poor UV resistance are significant drawbacks. Although polyimide fibers exhibit excellent high temperature resistance and dielectric properties, their mechanical strength is lower than that of aramid fibers, and their cost is higher, making their cost-effectiveness unsatisfactory when used alone. While conductive polymers such as polyaniline possess excellent electromagnetic shielding properties, their poor mechanical properties and brittleness fail to meet the mechanical performance requirements of aerospace environments. Two-dimensional transition metal carbide (MXene) materials exhibit excellent conductivity, but their layers tend to aggregate, resulting in poor compatibility with organic matrices and weak interfacial bonding. Perfluoroalkoxy resins (PFA) have weak interfacial bonding with most polymer matrices, requiring special surface treatments for reliable adhesion. Polyacrylic acid (PAA) hydrogels have limited temperature resistance and must be used in combination with other high-temperature resistant materials. Furthermore, existing multilayer composite structures suffer from poor interfacial compatibility, weak interlayer bonding, and easy delamination under temperature cycling and vibration loading. The uniform dispersion of nanomaterials within the polymer matrix is ​​difficult to control, and the preparation process is complex and costly, making it difficult to simultaneously meet the conflicting requirements of high shielding effectiveness and low reflectivity, high strength and lightweight, and high-temperature resistance and flexibility.

[0006] The present invention adopts the following technical solution: a method for preparing a cable over-frame protection material for aviation, comprising the following steps by weight: (1) preparation of blended fiber braided sleeve: aramid fiber (poly(p-phenylene terephthalamide, also known as aramid 1414) and polyimide fiber are blended at a mass ratio of (30-70): (70-30) and braided into a flexible sleeve with an inner diameter matching the cable; (2) in-situ growth of nanowires: the sleeve obtained in step (1) is immersed in an aqueous solution containing aniline monomer and p-toluenesulfonic acid, and then 10-50 parts of polyaniline (CAS No.: 25233-30-1) are added, and an ice bath reaction is performed to obtain polyaniline in-situ. Aniline nanowires are then immersed in titanium carbide dispersion and dried to obtain a flexible sleeve with a modified layer; (3) Coating with a thin layer: The flexible sleeve with a modified layer from step (2) is immersed in a perfluoroalkoxy resin solution with a thickness controlled at 5-20 μm and dried to obtain a flexible sleeve with a thin layer; (4) Reinforcing impregnation: The flexible sleeve with a thin layer obtained in step (3) is immersed in a polyacrylic acid (CAS No.: 9003-01-4) solution to form a flexible sleeve with a gel layer; (5) Freeze-drying: The flexible sleeve with a gel layer obtained in step (4) is freeze-dried under vacuum and then heat-dried under a nitrogen atmosphere to obtain a cable frame protection material for aviation.

[0007] Preferably, the preparation method of polyimide fiber in step (1) is as follows: Under nitrogen protection, add 200-400 parts of solvent N-methylpyrrolidone (CAS No.: 872-50-4) to a three-necked flask, cool to below 10°C in an ice-water bath, add 20-40 parts of 4,4'-oxodiphenylamine (CAS No.: 101-80-4), stir until completely dissolved, then add 15-30 parts of pyromellitic dianhydride (CAS No.: 89-32-7) and 1-5 parts of pyridine (CAS No.: 110-86-1) in an ice bath. Add 2-8 parts of acetic anhydride (CAS No.: 108-24-7), stir at 80-100 rpm for 1-3 hours, remove the ice bath, add 5-10 parts of lithium chloride (CAS No.: 7447-41-8), continue stirring at room temperature for 24 hours to obtain a transparent solution, then adjust the liquid-solid content of the transparent solution to 15-25 wt%, then perform electrospinning, wherein the electrospinning voltage is 15-25 kV, the spraying distance is 10-20 cm, the relative humidity is 40-60%, and after electrospinning, dry and set at 60-80℃.

[0008] Preferably, the linear density of the aramid fiber in step (1) is 1.5-3.0 dtex; the linear density of the polyimide fiber in step (1) is 1.0-2.5 dtex; the mass ratio between the aramid fiber and the polyimide fiber in step (1) is (30-70):(70-30); the weaving method in step (1) is as follows: the aramid fiber and the polyimide fiber are subjected to surface activation treatment respectively, wherein the aramid fiber is treated with low-temperature plasma at a power of 400W, an oxygen flow rate of 100sccm, and a treatment time of 90s, and the polyimide fiber is treated with ultraviolet irradiation at a wavelength of 254nm and an irradiation intensity of 100mW / cm. 2 The processing time is 15 minutes. The treated aramid fibers and polyimide fibers are then blended and twisted according to a specific mass ratio. The twisting process parameters are as follows: 50-150 twists / meter for the S-direction pre-twist of the aramid fibers, 30-100 twists / meter for the Z-direction pre-twist of the polyimide fibers, a total twist of 80-200 twists / meter after alternating S-direction / Z-direction plying, a twisting tension of 0.1-0.5 cN / dtex, and a speed of 20-50 m / min. The resulting blended yarn has a linear density of 200-500 tex. The blended yarn is then warped with a warping tension of 0.2-0.6 cN / dtex, a warp yarn density of 20-40 yarns / cm, a warping speed of 30-60 m / min, a warp width of 50-200 mm based on the sleeve circumference, and a warp yarn count of 100-400 yarns calculated based on the weaving density. Finally, the yarn is braided... The sleeve is formed on a loom. The number of spindles on the loom should be 32-48, the surface roughness Ra≤0.4μm, and a 0.1mm thick silicone oil release agent should be applied. The weaving process parameters are controlled as follows: weaving angle: 30-60° relative to the sleeve axis; weaving pitch: 2-8mm, pitch deviation ±0.2mm; weaving speed: 20-60rpm; traction speed: 0.5-2.0m / min; yarn tension: 0.15-0.35cN / dtex; weaving density: 200-400 threads / cm. The completed sleeve is then heat-set using a segmented heating process: first stage: 80-100℃ for 30-60min; second stage: 150-180℃ for 30-45min; third stage: 200-250℃ for 15-30min. After heat setting, the sleeve wall thickness is 0.2-1.0mm.

[0009] Preferably, the concentration of aniline monomer (CAS No.: 62-53-3) in step (2) is 0.1-1 mol / L; the concentration of p-toluenesulfonic acid in step (2) is 0.1-0.5 mol / L; the ice bath reaction time in step (2) is 2-6 h; the concentration of titanium carbide (CAS No.: 12363-89-2) dispersion in step (2) is 20-30%; and the drying temperature in step (2) is 80-90 °C.

[0010] Preferably, the solid content of the perfluoroalkoxy resin solution in step (3) is 5-15 wt%; the immersion temperature in step (3) is 60-80℃ and the immersion time is 6-12h; the drying temperature in step (3) is 150-180℃.

[0011] Preferably, the concentration of polyacrylic acid in step (4) is 15-30 wt%; the parameters for impregnation in step (4) are: temperature 80-90℃, time 2-6h.

[0012] Preferably, the freeze-drying time in step (5) is 24-48h; the heat-drying temperature in step (5) is 100-150℃, and the heat-drying time is 4-8h.

[0013] Compared with existing technologies, this invention achieves EMI shielding effectiveness of 44-72dB by introducing a synergistic conductive network of polyaniline nanowires (1D) and MXene (2D) and a porous fiber skeleton structure, while significantly reducing the reflection coefficient (R) to below 0.23. Attached Figure Description

[0014] Figure 1 This is a physical image of the flexible sleeve prepared in Example 1 of this invention.

[0015] Figure 2 This is a scanning electron microscope image of the polyimide fiber prepared in Example 1 of this invention.

[0016] Figure 3 This is a scanning electron microscope image of the polyaniline nanowires prepared in Example 1 of this invention. Detailed Implementation

[0017] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to restrict the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Also, for mass ratios not explicitly stated or mentioned, the mass ratio after addition generally refers to the mass ratio. Furthermore, in the present invention, the unit of mass is grams (g).

[0018] Example 1

[0019] The preparation method of the cable over-frame protection material for aviation includes the following steps: (1) Preparation of blended fiber braided sleeve: Aramid fiber (poly(p-phenylene terephthalamide, also known as aramid 1414) and polyimide fiber are blended at a mass ratio of 50:50 (total mass is 100g, i.e., 50g of aramid fiber and 50g of polyimide fiber) and braided into a flexible sleeve with an inner diameter matching the cable, such as Figure 1 As shown; among them, polyimide fibers (such as...) Figure 2 The preparation method of (shown) is as follows: Under nitrogen protection, 300g of N-methylpyrrolidone solvent was added to a three-necked flask and cooled to below 10℃ in an ice-water bath. 30g of 4,4'-oxodiphenylamine was added and stirred until completely dissolved. Then, under ice bath conditions, 22.5g of pyromellitic dianhydride, 3g of pyridine, and 5g of acetic anhydride were added and stirred at 90 rpm for 2 hours. The ice bath was removed, and 7.5g of lithium chloride was added. Stirring continued at room temperature for 24 hours to obtain a transparent solution. The liquid-to-solid content of the transparent solution was then adjusted to 20wt%, followed by electrospinning. The voltage for electrospinning was [voltage value missing]. 20kV, spray distance 15cm, relative humidity 50%, electrospinning followed by drying and setting at 70℃; aramid fiber linear density is 2.25dtex; polyimide fiber linear density is 1.75dtex; the weaving method is as follows: aramid and polyimide fibers are subjected to surface activation treatments separately. Aramid fibers are treated with low-temperature plasma at 400W power, 100sccm oxygen flow rate, and 90s treatment time. Polyimide fibers are treated with ultraviolet irradiation at 254nm wavelength and 100mW / cm² irradiation intensity. 2The processing time was 15 minutes. The treated aramid fibers and polyimide fibers were then blended and twisted according to a specific mass ratio. The twisting parameters were as follows: 100 twists / meter in the S-direction pre-twist of the aramid fibers, 65 twists / meter in the Z-direction pre-twist of the polyimide fibers, a total twist of 140 twists / meter after alternating S / Z-direction plying, a twisting tension of 0.3 cN / dtex, and a speed of 35 m / min. The resulting blended yarn had a linear density of 350 tex. The blended yarn was then warped with a warping tension of 0.4 cN / dtex, a warp yarn density of 30 yarns / cm, a warping speed of 45 m / min, a warp width of 125 mm based on the sleeve circumference, and a warp yarn count of 250 yarns calculated based on the weaving density. Then, a braiding machine was used to form the sleeve. The number of spindles in the braiding machine was selected as 40, the surface roughness Ra≤0.4μm, and a 0.1mm thick silicone oil release agent was applied. The braiding process parameters were controlled as follows: braiding angle: 45° relative to the sleeve axis, braiding pitch: 5mm, pitch deviation ±0.2mm, braiding speed: 40rpm, traction speed 1.25m / min, yarn tension: 0.25cN / dtex, braiding density: 300 threads / cm. The braided sleeve was then heat-set using a segmented heating process: first stage: 90℃ for 45min, second stage: 165℃ for 37min, third stage: 225℃ for 22min. After heat setting, the wall thickness of the sleeve was 0.6mm. (2) In-situ growth of nanowires: The sleeve obtained in step (1) was immersed in an aqueous solution containing aniline monomer and p-toluenesulfonic acid (the concentration of aniline monomer was 0.55 mol / L and the concentration of p-toluenesulfonic acid was 0.3 mol / L), and then 30 g of polyaniline was added. The reaction was carried out in an ice bath for 4 h, and polyaniline nanowires were grown in situ (e.g. Figure 3(as shown), then impregnate in titanium carbide dispersion (concentration of titanium carbide dispersion is 25%), and dry (drying temperature is 85℃) to obtain a flexible sleeve with a modified layer. (3) Outer thin layer: Immerse the flexible sleeve with modified layer from step (2) in perfluoroalkoxy resin solution (solid content of perfluoroalkoxy resin solution is 10wt%, immersion temperature is 70℃, immersion time is 9h), control the thickness at 12.5μm, and dry (drying temperature is 165℃) to obtain a flexible sleeve with a thin layer. (4) Reinforced impregnation: Immerse the flexible sleeve with thin layer obtained in step (3) in polyacrylic acid solution (concentration of polyacrylic acid is 22.5wt%, immersion parameters: temperature 85℃, time 4h) to form a flexible sleeve with a gel layer. (5) Freeze-drying: The flexible sleeve containing the gel layer obtained in step (4) is freeze-dried under vacuum (freeze-drying time is 36h), and then heat-dried under a nitrogen atmosphere (heat drying temperature is 125℃, heat drying time is 6h) to obtain the aviation cable over-frame protection material. The obtained aviation cable over-frame protection material is suitable for high temperature (>200℃), vibration (10-100Hz), wear and EMI (>50dB shielding, low reflection <0.3) conditions, and has the lightweight characteristics of low reflection R≈0.2-0.3 and weight reduction of 30-50%.

[0020] The specific parameters for Examples 2-8 and Comparative Examples 1-8 are listed in the following tables. The tables are designed according to the progression of the steps, with each table reflecting different parameter values ​​for the examples / comparative examples, covering all endpoint and intermediate values. Only the parameters that have changed from those in Example 1 are listed in the tables; the descriptions of the remaining parameters are the same as in Example 1.

[0021] Table 1: Preparation parameters of the blended fiber braided sleeve in step (1) (mass ratio of aramid fiber to polyimide fiber and total mass g, relevant parameters for polyimide fiber preparation)

[0022]

[0023] Table 2: Step (1) Preparation parameters of blended fiber braided sleeve (aramid fiber linear density dtex, polyimide fiber linear density dtex, twisting process parameters, etc.)

[0024]

[0025] Table 3: Preparation parameters of blended fiber braided sleeve in step (1) (braiding process parameters, heat setting parameters, wall thickness in mm)

[0026]

[0027] Table 4: Step (1) Comparative parameters (based on Example 1, missing, replaced, or abnormal parameters)

[0028]

[0029] Table 5: Preparation parameters for in-situ growth of nanowires in step (2)

[0030]

[0031] Table 6: Preparation parameters of the outer coating layer in step (3)

[0032]

[0033] Table 7: Parameters for enhancing impregnation in step (4)

[0034]

[0035] Table 8: Parameters for freeze-drying in step (5)

[0036]

[0037] To verify the performance of the aviation cable over-frame protection material described in this invention, multi-dimensional tests were conducted on the products prepared in Examples 1-8 and Comparative Examples 1-8. The tests included high-temperature resistance (high-temperature exposure time), vibration resistance (vibration fatigue cycles), wear rate (wear test), EMI shielding effectiveness (dB), reflection coefficient (R-value), and weight reduction percentage (%). The test methods are as follows: High-temperature resistance test: According to GB / T2423.2 standard, a high-temperature test chamber (model: GDW-100) was used, exposed to 220℃, and the time until material failure was recorded (h). Vibration resistance test: According to GB / T2423.10 standard, a vibration testing machine (model: EV-200) was used, with a frequency of 50Hz and an amplitude of 2mm, and the number of cycles until structural damage was recorded. Wear rate test: According to GB / T3960 standard, a friction and wear testing machine (model: MM-200) was used, with a load of 100N, a rotation speed of 200r / min, and a time of 30min, and the wear rate (mg / cm²) was calculated. 2 EMI shielding effectiveness test: Shielding effectiveness (dB) was tested using a vector network analyzer (model: E5071C) according to GB / T12190 standard. Reflectance coefficient test: R-value was tested using a reflectivity meter (model: UV-3600). Weight reduction percentage test: The weight reduction percentage (%) was calculated compared with that of traditional materials (pure aramid tubing).

[0038] Table 9: Performance Test Results

[0039]

[0040] Table 10: Performance Test Results II

[0041]

[0042] The test results show that the high-temperature resistance time of the products in the examples ranges from 118.7 to 132.9 hours, the vibration fatigue cycle ranges from 8200.5 to 8800.1 cycles, and the wear rate ranges from 0.22 to 0.35 mg / cm³. 2 The EMI shielding effectiveness is 58.6-65.9 dB, the reflection coefficient is 0.21-0.28, and the weight reduction is 35.4-45.7%, demonstrating excellent performance. In contrast, the comparative examples showed a significant decrease in performance due to missing components or parameter deviations (e.g., the high-temperature resistance time decreased to 62.8-68.4 h, and the EMI shielding effectiveness decreased to 36.4-40.1 dB). This proves the superiority of the preparation method of this invention.

[0043] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A method for preparing a cable over-frame protection material for aviation applications, characterized in that: The process, by weight, includes the following steps: (1) Preparation of blended fiber braided sleeve: aramid fiber and polyimide fiber are blended at a mass ratio of (30-70):(70-30) and braided into a flexible sleeve with an inner diameter matching cable; (2) In-situ growth of nanowires: the sleeve obtained in step (1) is immersed in an aqueous solution containing aniline monomer and p-toluenesulfonic acid, followed by the addition of 10-50 parts of polyaniline, and an ice bath reaction is performed to grow polyaniline nanowires in situ. Then, the nanowires are immersed in a titanium carbide dispersion and dried to obtain a modified nanowire. (2) Flexible sleeve with modified layer; (3) Thin outer layer: Immerse the flexible sleeve with modified layer in step (2) into perfluoroalkoxy resin solution, with the thickness controlled at 5-20 μm, and dry to obtain flexible sleeve with thin layer; (4) Reinforced impregnation: Immerse the flexible sleeve with thin layer obtained in step (3) in polyacrylic acid solution to form flexible sleeve with gel layer; (5) Freeze-drying: Freeze-dry the flexible sleeve with gel layer obtained in step (4) under vacuum, and then heat-dry under nitrogen atmosphere to obtain aviation cable frame protection material.

2. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: The preparation method of polyimide fiber in step (1) is as follows: Under nitrogen protection, add 200-400 parts of solvent N-methylpyrrolidone to a three-necked flask, cool to below 10°C in an ice-water bath, add 20-40 parts of 4,4'-oxodiphenylamine, stir until completely dissolved, then add 15-30 parts of pyromellitic dianhydride, 1-5 parts of pyridine and 2-8 parts of acetic anhydride in an ice bath, stir at 80-100 rpm for 1-3 hours, remove the ice bath, add 5-10 parts of lithium chloride, continue stirring at room temperature for 24 hours to obtain a transparent solution, then adjust the liquid-solid content of the transparent solution to 15-25 wt%, then perform electrospinning, wherein the electrospinning voltage is 15-25 kV, the spraying distance is 10-20 cm, the relative humidity is 40-60%, and after electrospinning, dry and set at 60-80°C.

3. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: In step (1), the linear density of aramid fiber is 1.5-3.0 dtex; the linear density of polyimide fiber is 1.0-2.5 dtex; the mass ratio between aramid fiber and polyimide fiber in step (1) is (30-70):(70-30).

4. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: The weaving method in step (1) is as follows: aramid fibers and polyimide fibers are subjected to surface activation treatments respectively. The aramid fibers are treated with low-temperature plasma at a power of 400W, an oxygen flow rate of 100sccm, and a treatment time of 90s. The polyimide fibers are treated with ultraviolet irradiation at a wavelength of 254nm and an irradiation intensity of 100mW / cm. 2 The processing time is 15 minutes. The treated aramid fibers and polyimide fibers are then blended and twisted according to a specific mass ratio. The twisting process parameters are as follows: 50-150 twists / meter for the S-direction pre-twist of the aramid fibers, 30-100 twists / meter for the Z-direction pre-twist of the polyimide fibers, a total twist of 80-200 twists / meter after alternating S-direction / Z-direction plying, a twisting tension of 0.1-0.5 cN / dtex, and a speed of 20-50 m / min. The resulting blended yarn has a linear density of 200-500 tex. The blended yarn is then warped with a warping tension of 0.2-0.6 cN / dtex, a warp yarn density of 20-40 yarns / cm, a warping speed of 30-60 m / min, a warp width of 50-200 mm based on the sleeve circumference, and a warp yarn count of 100-400 yarns calculated based on the weaving density. Finally, the yarn is braided... The sleeve is formed on a loom. The number of spindles on the loom should be 32-48, the surface roughness Ra≤0.4μm, and a 0.1mm thick silicone oil release agent should be applied. The weaving process parameters are controlled as follows: weaving angle: 30-60° relative to the sleeve axis; weaving pitch: 2-8mm, pitch deviation ±0.2mm; weaving speed: 20-60rpm; traction speed: 0.5-2.0m / min; yarn tension: 0.15-0.35cN / dtex; weaving density: 200-400 threads / cm. The completed sleeve is then heat-set using a segmented heating process: first stage: 80-100℃ for 30-60min; second stage: 150-180℃ for 30-45min; third stage: 200-250℃ for 15-30min. After heat setting, the sleeve wall thickness is 0.2-1.0mm.

5. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: The concentration of aniline monomer in step (2) is 0.1-1 mol / L; the concentration of p-toluenesulfonic acid in step (2) is 0.1-0.5 mol / L; the ice bath reaction time in step (2) is 2-6 h; the concentration of titanium carbide dispersion in step (2) is 20-30%; and the drying temperature in step (2) is 80-90℃.

6. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: The solid content of the perfluoroalkoxy resin solution in step (3) is 5-15 wt%; the immersion temperature in step (3) is 60-80℃ and the immersion time is 6-12h; the drying temperature in step (3) is 150-180℃.

7. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: The concentration of polyacrylic acid in step (4) is 15-30 wt%; the parameters for impregnation in step (4) are: temperature 80-90℃, time 2-6h.

8. The method for preparing the aviation cable over-frame protection material according to claim 1, characterized in that: The freeze-drying time in step (5) is 24-48h; the heat-drying temperature in step (5) is 100-150℃, and the heat-drying time is 4-8h.

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