Multifunctional stealth protective coating for airplane surface and preparation process of multifunctional stealth protective coating

Abstract

The invention discloses a multifunctional stealth protective coating for an aircraft surface and a preparation process thereof, and relates to the technical field of aviation coatings, and the multifunctional stealth protective coating is composed of a bottom adhesive force layer, a middle stealth layer and a bionic protective outer layer. According to the multifunctional stealth protective coating, the collaborative design of the thermal response adjusting wave-absorbing powder and the modified organic silicon-epoxy hybrid resin matrix is adopted, so that self-adaptive regulation and control of a wave-absorbing structure can be realized in a high-temperature environment generated by high-speed flight of an airplane, and agglomeration of a wave-absorbing filler and softening deformation of the resin matrix are avoided; the stealth performance is kept stable in the high-temperature environment, it can be ensured that an airplane continuously deals with multi-band cooperative detection in the dynamic flight process, the problem that the stealth performance of an existing coating is degraded in the high-temperature environment is effectively solved, and the stealth capacity and task execution reliability of the airplane are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of aviation coating technology, specifically to a multifunctional stealth protective coating for aircraft surfaces and its preparation process. Background Technology

[0002] Stealth coatings are stealth materials that are permanently coated on the surface of an object. They mainly include radar stealth, infrared stealth, visible light stealth, laser stealth, sonar stealth, and multi-functional stealth coatings. By coating the surface of an aircraft, they reduce the probability of it being detected by radar, infrared, and other detection systems. The core function is to absorb or attenuate electromagnetic wave signals, thereby reducing the detectable features of the target. The coating must have wide-temperature chemical stability, low areal density, high bonding strength, and resistance to environmental changes. It achieves the stealth effect by reducing the target's electromagnetic wave reflection, infrared radiation, and other signal characteristics.

[0003] Existing full-band stealth coatings for aircraft use statically dispersed absorbing fillers and single-performance resin matrices, lacking the ability to adaptively adjust thermal response. In the high-temperature environment of 60-300℃ generated by high-speed aircraft flight, the absorbing fillers are prone to agglomeration, and the resin matrix is ​​prone to softening and deformation, leading to the failure of the absorbing structure. This results in a significant increase in the radar reflectivity of the coating, increased fluctuations in infrared emissivity, and a sharp decline in stealth performance. It is unable to cope with multi-band coordinated detection during dynamic flight, seriously affecting the aircraft's battlefield survivability and mission reliability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a multifunctional stealth protective coating for aircraft surfaces and its preparation process, thus solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a multifunctional stealth protective coating for aircraft surfaces, characterized in that the multifunctional stealth protective coating comprises a bottom adhesion layer, an intermediate stealth layer, and a biomimetic protective outer layer, the specific components by weight as follows: The underlying adhesion layer comprises: 45-55 parts of modified silicone-epoxy hybrid resin matrix, 2-4 parts of silane coupling agent KH-560, 1-3 parts of nano-alumina powder, 0.5-1 part of dispersant BYK-163, 0.3-0.8 parts of defoamer silicone emulsion, and 15-20 parts of solvent butyl acetate; The intermediate stealth layer comprises: 30-40 parts of modified organosilicon-epoxy hybrid resin matrix, 15-25 parts of core-shell structured composite functional filler, 8-12 parts of thermally responsive microwave absorbing powder, 5-8 parts of self-healing agent, 2-5 parts of nano-titanium nickel yellow, 0.3-0.6 parts of leveling agent BYK-333, and 10-15 parts of solvent butyl acetate; The biomimetic protective outer layer comprises: 50-60 parts of modified organosilicon-epoxy resin hybrid matrix, 3-6 parts of nano-tungsten carbide powder, 2-4 parts of nano-silica powder, 0.5-1 part of ultraviolet absorber UV-531, 2-5 parts of temperature and humidity sensitive composite powder, 0.5-1 part of fluorine-modified acrylate additive, and 10-15 parts of butyl acetate solvent; The core of the core-shell composite functional filler is a hollow alumina microsphere, and the shell consists of a nano-silicon carbide-carbonyl iron powder composite microwave absorbing layer and a nano-silica-polyaniline composite infrared low emissivity layer from the inside to the outside. The weight ratio of the core to the shell is 1:0.8-1.2.

[0006] Preferably, the thermally responsive microwave absorbing powder is made by combining shape memory polyurethane microspheres and nanocomposite microwave absorbing powder in a weight ratio of 2:1. The nanocomposite microwave absorbing powder is obtained by mixing nano-silicon carbide powder, nano-carbonyl iron powder and nano-graphene powder in a weight ratio of 3:3:1. The method for preparing the modified organosilicon-epoxy resin hybrid matrix is ​​as follows: Bisphenol A type epoxy resin E-51 and hydroxyl-terminated polydimethylsiloxane resin were mixed at a weight ratio of 2:1. 3%-5% of the silane coupling agent KH-560 by mass of bisphenol A type epoxy resin E-51 was added. The mixture was stirred and reacted at 60-70°C for 2-3 hours, and then cooled to room temperature to obtain the modified organosilicon-epoxy resin hybrid matrix.

[0007] Preferably, the self-healing agent is a microcapsule of a two-component epoxy repair agent coated with urea-formaldehyde resin, wherein the microcapsule has a particle size of 5-10 μm and a shell wall thickness of 0.5-1 μm; The two-component epoxy repair agent is prepared by mixing bisphenol A type epoxy resin E-44 and polyamide 650 curing agent in a weight ratio of 1:1.

[0008] Preferably, the temperature and humidity sensitive composite powder is prepared by mixing temperature-sensitive powder and humidity-sensitive powder in a weight ratio of 1:1; The temperature-sensitive powder is poly(N-isopropylacrylamide) grafted nano-silica powder, and the humidity-sensitive powder is montmorillonite-polyethylene glycol composite powder.

[0009] Preferably, the preparation method of the core-shell structured composite functional filler is as follows: Hollow alumina microspheres were ultrasonically cleaned in a 5% (v / v) dilute hydrochloric acid solution for 10-15 minutes, rinsed with deionized water until neutral, and dried at 80°C for later use. The dried hollow alumina microspheres were dispersed in an ethanol-water mixture, and a mixture of nano-silicon carbide powder and nano-carbonyl iron powder was added. The nano-silicon carbide-carbonyl iron powder composite microwave absorbing layer was formed by coating the surface of the microspheres using the sol-gel method. The microwave absorbing layer microspheres were then dried. The microwave-absorbing microspheres were dispersed in a polyaniline aqueous dispersion emulsion, and nano-silica powder was added. The mixture was ultrasonically coated for 30-40 minutes, filtered, and dried at 100-120℃ to obtain the core-shell structured composite functional filler.

[0010] Preferably, the performance indicators of the multifunctional stealth protective coating are: The radar reflectivity is ≤-15dB in the 2-18GHz band, and the reflectivity fluctuation is ≤2dB in the incident angle range of 0°-60°. The infrared emissivity is ≤0.3 in the 3-14μm band, and the visible light camouflage color difference ΔE is ≤1.0. The coating exhibits excellent high and low temperature resistance, with no cracking or peeling after 50 cycles of -80℃ to 300℃. It also demonstrates excellent salt spray resistance, with no rust after 1500 hours of salt spray testing with a 5% sodium chloride solution. Furthermore, its self-healing properties are such that when the scratch width is ≤50μm, the radar reflectivity of the coating recovers to over 95% of its original performance after repair, and the surface water contact angle is ≥120°.

[0011] A process for preparing a multifunctional stealth protective coating for aircraft surfaces includes the following steps: S1. The aircraft metal substrate to be sprayed is successively ground, degreased and derusted. Then, a low-temperature plasma surface treatment instrument is used to activate the surface of the aircraft metal substrate. The plasma power is 150-200W, the treatment time is 5-8min, and the vacuum degree is 10-20Pa. S2. The modified organosilicon-epoxy hybrid resin matrix, the silane coupling agent KH-560, the nano alumina powder, the dispersant BYK-163, the defoamer organosilicon emulsion, and the solvent butyl acetate are mixed evenly and coated onto the pretreated aircraft metal substrate surface using an air spraying method. The dry film thickness is controlled to be 10-15 μm, and the mixture is allowed to stand until the surface is dry to form the bottom adhesion layer. S3. After the bottom adhesion layer is sprayed, the modified silicone-epoxy hybrid resin matrix, the core-shell structure composite functional filler, the thermal response regulating microwave absorbing powder, the self-healing agent, the nano titanium nickel yellow, the leveling agent BYK-333, and the solvent butyl acetate are mixed evenly and coated onto the surface of the bottom adhesion layer after it has dried using a high-pressure airless spraying method. The dry film thickness is controlled to be 30-40μm. After standing until it is surface dry, the intermediate stealth layer is formed. S4. After the intermediate stealth layer is sprayed, the modified organosilicon-epoxy resin hybrid matrix, the nano tungsten carbide powder, the nano silica powder, the ultraviolet absorber UV-531, the temperature and humidity sensitive composite powder, the fluorinated modified acrylate additive, and the butyl acetate solvent are mixed evenly and coated onto the surface of the intermediate stealth layer after it has dried by electrostatic spraying. The dry film thickness is controlled to be 5-10 μm. After standing until it is surface dry, the biomimetic protective outer layer is formed. Immediately after spraying, a template imprinting process is used to assist in solvent evaporation. S5. After the bottom adhesion layer, the intermediate stealth layer, and the biomimetic protective outer layer are sequentially sprayed, the coating surface is first irradiated with ultraviolet light with a wavelength of 365nm and a light intensity of 800-1000mW / cm². 2 The irradiation time is 5-10 minutes; S6. After ultraviolet irradiation, the coated aircraft metal substrate is placed in an electric heating drying oven and cured in stages: 40℃ for 1 hour, 60℃ for 1 hour and 80℃ for 2 hours. After curing, it is naturally cooled to room temperature to obtain the multifunctional stealth protective coating.

[0012] Preferably, in steps S2, S3 and S4, the spraying pressure of the air spraying is 0.3-0.5MPa, the spraying pressure of the high-pressure airless spraying is 15-20MPa, and the voltage of the electrostatic spraying is 60-80kV.

[0013] Preferably, in step S4, the template imprinting uses a porous polytetrafluoroethylene template, the pore size of the template imprinting is 1-5 μm, the imprinting pressure is 0.1-0.2 MPa, and the imprinting time is 1-2 min.

[0014] Preferably, in step S1, the surface roughness Ra of the aircraft metal substrate after polishing is controlled to be 1.6 μm; The degreasing treatment uses acetone solvent for ultrasonic degreasing, and the ultrasonic time is 10 minutes. The rust removal process involves wiping the surface with a phosphate-based rust remover.

[0015] This invention provides a multifunctional stealth protective coating for aircraft surfaces and its preparation process. It offers the following advantages: (1) The multifunctional stealth protective coating adopts the synergistic design of thermal response-adjustable absorbing powder and modified organosilicon-epoxy hybrid resin matrix. It can achieve adaptive control of the absorbing structure in the high temperature environment generated by the high speed flight of the aircraft, avoid the agglomeration of absorbing filler and the softening and deformation of resin matrix, and maintain the stealth performance in the high temperature environment. It can ensure that the aircraft can continuously cope with multi-band collaborative detection during dynamic flight, effectively reduce the problem of the stealth performance decay of existing coatings in the high temperature environment, and ensure the stealth capability and mission execution reliability of the aircraft.

[0016] (2) The coating is applied through a layered spraying structure. The bottom adhesion layer strengthens the bonding stability between the coating and the substrate. The middle stealth layer and the biomimetic protective outer layer form a synergistic protection system, which reduces the structural damage such as peeling and cracking of the coating under high temperature environment, improves the overall environmental adaptability and structural integrity of the coating, extends the service life of the coating in extreme flight environment, reduces the maintenance frequency caused by coating failure, and ensures the continuity and safety of the aircraft in long-term missions.

[0017] (3) The modified silicone-epoxy hybrid resin matrix selected for the coating has excellent high and low temperature resistance and structural stability. Combined with the synergistic effect of each functional layer component, it reduces the problem of insufficient high temperature performance of the existing single resin matrix coating. At the same time, it realizes the simultaneous guarantee of stealth function and protection performance, and further realizes the effect of stealth and protection performance without conflict in high temperature environment. It can broaden the applicable flight scenarios of the coating, so that the aircraft can maintain stable comprehensive performance under different high temperature conditions, and further improve its adaptability to complex flight environment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the preparation steps of the multifunctional stealth protective coating for aircraft surfaces and its preparation process according to the present invention. Figure 2 Line graphs showing the visible light camouflage color difference test results of embodiments and comparative examples of the present invention; Figure 3 Line graphs showing the self-healing performance results of embodiments and comparative examples of the present invention; Figure 4 This is a line graph showing the surface water contact angle results for embodiments and comparative examples of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0020] Please see Figure 1 This invention provides a multifunctional stealth protective coating for aircraft surfaces and its preparation process. To achieve the above objectives, this invention utilizes the following technical solution: The multifunctional stealth protective coating comprises a bottom adhesion layer, an intermediate stealth layer, and a biomimetic protective outer layer, with the following specific components by weight: The bottom adhesion layer comprises: 45-55 parts of modified silicone-epoxy hybrid resin matrix, 2-4 parts of silane coupling agent KH-560, 1-3 parts of nano-alumina powder, 0.5-1 part of dispersant BYK-163, 0.3-0.8 parts of defoamer silicone emulsion, and 15-20 parts of solvent butyl acetate; The intermediate stealth layer comprises: 30-40 parts of modified organosilicon-epoxy hybrid resin matrix, 15-25 parts of core-shell structured composite functional filler, 8-12 parts of thermally responsive microwave absorbing powder, 5-8 parts of self-healing agent, 2-5 parts of nano-titanium nickel yellow, 0.3-0.6 parts of leveling agent BYK-333, and 10-15 parts of solvent butyl acetate; The biomimetic protective outer layer comprises: 50-60 parts of modified organosilicon-epoxy resin hybrid matrix, 3-6 parts of nano-tungsten carbide powder, 2-4 parts of nano-silica powder, 0.5-1 part of ultraviolet absorber UV-531, 2-5 parts of temperature and humidity sensitive composite powder, 0.5-1 part of fluorine-modified acrylate additive, and 10-15 parts of butyl acetate solvent; Among them, the core of the core-shell structure composite functional filler is a hollow alumina microsphere, and the shell layer consists of a nano-silicon carbide-carbonyl iron powder composite microwave absorbing layer and a nano-silica-polyaniline composite infrared low emissivity layer from the inside to the outside. The weight ratio of the core to the shell is 1:0.8-1.2.

[0021] The thermally responsive microwave absorbing powder is made by combining shape memory polyurethane microspheres and nanocomposite microwave absorbing powder in a weight ratio of 2:1; the nanocomposite microwave absorbing powder is obtained by mixing nano silicon carbide powder, nano carbonyl iron powder and nano graphene powder in a weight ratio of 3:3:1. The modified organosilicon-epoxy resin hybrid matrix is ​​prepared as follows: Bisphenol A type epoxy resin E-51 and hydroxyl-terminated polydimethylsiloxane resin are mixed at a weight ratio of 2:1, and 3%-5% of silane coupling agent KH-560 by mass of bisphenol A type epoxy resin E-51 is added. The mixture is stirred and reacted at 60-70℃ for 2-3 hours, and then cooled to room temperature to obtain the modified organosilicon-epoxy resin hybrid matrix.

[0022] The self-healing agent is a microcapsule of a two-component epoxy repair agent encapsulated in urea-formaldehyde resin. The microcapsule has a particle size of 5-10 μm and a shell wall thickness of 0.5-1 μm. The two-component epoxy repair agent is made by mixing bisphenol A type epoxy resin E-44 and polyamide 650 curing agent in a weight ratio of 1:1.

[0023] The temperature and humidity sensitive composite powder is made by mixing temperature-sensitive powder and humidity-sensitive powder in a weight ratio of 1:1; the temperature-sensitive powder is poly(N-isopropylacrylamide) grafted nano-silica powder, and the humidity-sensitive powder is montmorillonite-polyethylene glycol composite powder.

[0024] The specific preparation method of the core-shell structured composite functional filler is as follows: Hollow alumina microspheres are placed in a 5% (v / v) dilute hydrochloric acid solution and ultrasonically cleaned for 10-15 min, rinsed with deionized water until neutral, and dried at 80℃ for later use. The dried hollow alumina microspheres were dispersed in an ethanol-water mixture, and a mixture of nano-silicon carbide powder and nano-carbonyl iron powder was added. The nano-silicon carbide-carbonyl iron powder composite microwave absorbing layer was formed by coating the surface of the microspheres using the sol-gel method. The microwave absorbing layer microspheres were then dried to obtain microwave absorbing layer microspheres. The microwave absorbing layer microspheres were dispersed in a polyaniline aqueous dispersion emulsion, and nano-silica powder was added. The mixture was ultrasonically coated for 30-40 minutes, filtered, and dried at 100-120℃ to obtain a core-shell structured composite functional filler.

[0025] The performance indicators of the multi-functional stealth protective coating are as follows: radar reflectivity ≤ -15dB in the 2-18GHz band, reflectivity fluctuation ≤ 2dB in the incident angle range of 0°-60°, infrared emissivity ≤ 0.3 in the 3-14μm band, and visible light camouflage color difference ΔE ≤ 1.0. The coating exhibits excellent high and low temperature resistance, with no cracking or peeling after 50 cycles of -80℃ to 300℃. It also demonstrates excellent salt spray resistance, with no rust after 1500 hours of salt spray testing with a 5% sodium chloride solution. Furthermore, its self-healing properties are such that when the scratch width is ≤50μm, the radar reflectivity of the coating recovers to over 95% of its original performance after repair, and the surface water contact angle is ≥120°.

[0026] The preparation process of the multifunctional stealth protective coating includes the following steps: S1. The aircraft metal substrate to be sprayed is successively ground, degreased and derusted. Then, a low-temperature plasma surface treatment instrument is used to activate the surface of the aircraft metal substrate. The plasma power is 150-200W, the treatment time is 5-8min, and the vacuum degree is 10-20Pa. S2. Mix the modified organosilicon-epoxy hybrid resin matrix, silane coupling agent KH-560, nano alumina powder, dispersant BYK-163, defoamer organosilicon emulsion and solvent butyl acetate evenly, and apply it to the pretreated aircraft metal substrate surface by air spraying, controlling the dry film thickness to be 10-15μm, and let it stand until the surface is dry to form the bottom adhesion layer; S3. After the bottom adhesion layer is sprayed, the modified silicone-epoxy hybrid resin matrix, core-shell structure composite functional filler, thermal response regulating microwave absorbing powder, self-healing agent, nano titanium nickel yellow, leveling agent BYK-333 and solvent butyl acetate are mixed evenly and coated on the surface of the bottom adhesion layer after surface drying using high pressure airless spraying method. The dry film thickness is controlled to be 30-40μm. Let it stand until surface dry to form the intermediate stealth layer. S4. After the intermediate stealth layer is sprayed, the modified organosilicon-epoxy resin hybrid matrix, nano tungsten carbide powder, nano silica powder, UV absorber UV-531, temperature and humidity sensitive composite powder, fluorinated modified acrylate additive and butyl acetate solvent are mixed evenly and coated onto the surface of the intermediate stealth layer after it has dried by electrostatic spraying. The dry film thickness is controlled to be 5-10μm. After standing until it is dry, a biomimetic protective outer layer is formed. Immediately after spraying, the solvent evaporation process is used to assist the solvent evaporation process by template imprinting. After the S5 layer, the bottom adhesion layer, the intermediate stealth layer, and the biomimetic protective outer layer are applied in sequence, the coating surface is first irradiated with ultraviolet light at a wavelength of 365nm and an intensity of 800-1000mW / cm². 2 The irradiation time is 5-10 minutes; S6. After UV irradiation, the coated aircraft metal substrate is placed in an electric heating drying oven and cured in stages: 40℃ for 1 hour, 60℃ for 1 hour and 80℃ for 2 hours. After curing, it is naturally cooled to room temperature to obtain a multifunctional stealth protective coating.

[0027] In steps S2, S3 and S4, the spraying pressure for air spraying is 0.3-0.5MPa, the spraying pressure for high-pressure airless spraying is 15-20MPa, and the voltage for electrostatic spraying is 60-80kV.

[0028] In step S4, the template imprinting uses a porous polytetrafluoroethylene template with a pore size of 1-5 μm, an imprinting pressure of 0.1-0.2 MPa, and an imprinting time of 1-2 min.

[0029] In step S1, the surface roughness Ra of the aircraft metal substrate after grinding is controlled to be 1.6 μm; the degreasing treatment uses acetone solvent for ultrasonic degreasing, and the ultrasonic time is 10 min; the rust removal treatment uses phosphate-based rust remover for surface wiping treatment.

[0030] Example 1 Raw materials for multi-functional stealth protective coating: Underlying adhesion layer: 50 parts modified silicone-epoxy hybrid resin matrix, 3 parts silane coupling agent KH-560, 2 parts nano alumina powder, 0.8 parts dispersant BYK-163, 0.5 parts defoamer silicone emulsion, and 18 parts solvent butyl acetate; Intermediate stealth layer: 35 parts modified organosilicon-epoxy hybrid resin matrix, 20 parts core-shell structure composite functional filler, 10 parts thermal response regulating microwave absorbing powder, 6 parts self-healing agent, 3 parts nano titanium nickel yellow, 0.5 parts leveling agent BYK-333, and 12 parts solvent butyl acetate. Bionic protective outer layer: 55 parts modified organosilicon-epoxy resin hybrid matrix, 5 parts nano tungsten carbide powder, 3 parts nano silica powder, 0.8 parts ultraviolet absorber UV-531, 3 parts temperature and humidity sensitive composite powder, 0.8 parts fluorine modified acrylate additive, and 12 parts butyl acetate solvent. Preparation process of multifunctional stealth protective coating: Aluminum alloy substrate for aircraft was selected, and the surface roughness Ra=1.6μm was polished. Acetone was used for ultrasonic degreasing for 10 minutes, followed by rust removal with phosphate-based rust remover. Then, the substrate was activated by a low-temperature plasma surface treatment instrument with a power of 180W, a time of 6 minutes, and a vacuum degree of 15Pa. Mix all components of the bottom adhesion layer evenly, apply by air spraying at a pressure of 0.4 MPa, achieve a dry film thickness of 12 μm, and allow to dry on the surface. The components of the intermediate stealth layer are mixed evenly and coated using a high-pressure airless spraying method. The spraying pressure is 18MPa, the dry film thickness is 35μm, and the coating is allowed to dry on the surface. The components of the biomimetic protective outer layer were mixed evenly and coated by electrostatic spraying at a voltage of 70kV and a dry film thickness of 8μm. Immediately after spraying, the coating was imprinted with a porous polytetrafluoroethylene template with a pore size of 3μm at a pressure of 0.15MPa for 1.5min and then allowed to stand to dry. Irradiation with ultraviolet light at a wavelength of 365nm and an intensity of 900mW / cm² 2 The curing time is 8 minutes; then it is placed in an electric heating drying oven for segmented curing, kept at 40℃ for 1 hour, 60℃ for 1 hour, and 80℃ for 2 hours, and then naturally cooled to room temperature to obtain a multifunctional stealth protective coating.

[0031] Example 2 Multifunctional stealth protective coating raw materials: Underlying adhesion layer: 45 parts modified silicone-epoxy hybrid resin matrix, 2 parts silane coupling agent KH-560, 1 part nano alumina powder, 0.5 parts dispersant BYK-163, 0.3 parts defoamer silicone emulsion, and 15 parts solvent butyl acetate.

[0032] Intermediate stealth layer: 30 parts modified organosilicon-epoxy hybrid resin matrix, 15 parts core-shell structure composite functional filler, 8 parts thermal response regulating microwave absorbing powder, 5 parts self-healing agent, 2 parts nano titanium nickel yellow, 3 parts leveling agent BYK-3330, and 10 parts solvent butyl acetate. Bionic protective outer layer: 50 parts modified organosilicon-epoxy resin hybrid matrix, 3 parts nano tungsten carbide powder, 2 parts nano silica powder, 0.5 parts ultraviolet absorber UV-531, 2 parts temperature and humidity sensitive composite powder, 0.5 parts fluorine modified acrylate additive, and 10 parts butyl acetate solvent. Preparation process of multifunctional stealth protective coating: The preparation process involved plasma treatment with a power of 150 W for 5 min, a vacuum of 10 Pa, an air spraying pressure of 0.3 MPa, a high-pressure airless spraying pressure of 15 MPa, an electrostatic spraying voltage of 60 kV, a template imprinting aperture of 1 μm, a pressure of 0.1 MPa, a time of 1 min, and an ultraviolet light intensity of 800 mW / cm². 2 The time is 5 minutes, and the remaining steps are the same as in Example 1.

[0033] Example 3 Multifunctional stealth protective coating raw materials: Underlying adhesion layer: 55 parts modified silicone-epoxy hybrid resin matrix, 4 parts silane coupling agent KH-560, 3 parts nano alumina powder, 1 part dispersant BYK-163, 0.8 parts defoamer silicone emulsion, and 20 parts solvent butyl acetate; Intermediate stealth layer: 40 parts modified organosilicon-epoxy hybrid resin matrix, 25 parts core-shell structure composite functional filler, 12 parts thermal response regulating microwave absorbing powder, 8 parts self-healing agent, 5 parts nano titanium nickel yellow, 0.6 parts leveling agent BYK-333, and 15 parts solvent butyl acetate. Bionic protective outer layer: 60 parts modified organosilicon-epoxy resin hybrid matrix, 6 parts nano tungsten carbide powder, 4 parts nano silica powder, 1 part ultraviolet absorber UV-531, 5 parts temperature and humidity sensitive composite powder, 1 part fluorine modified acrylate additive, and 15 parts butyl acetate solvent. The preparation process involved plasma treatment at a power of 200 W for 8 min and a vacuum of 20 Pa; air spraying pressure of 0.5 MPa; high-pressure airless spraying pressure of 20 MPa; electrostatic spraying voltage of 80 kV; template imprinting aperture of 5 μm; pressure of 0.2 MPa; time of 2 min; and ultraviolet light intensity of 1000 mW / cm². 2 The time is 10 minutes, and the remaining steps are the same as in Example 1.

[0034] Comparative Example 1 The coating formulation is the same as in Example 1, except that the thermal response-adjusting microwave-absorbing powder in the intermediate stealth layer is removed, while the amounts of the remaining components remain unchanged, and the preparation process is completely the same as in Example 1.

[0035] Comparative Example 2 In the coating formulation, the core-shell structure composite functional filler of the intermediate stealth layer is replaced with a mixture of nano silicon carbide powder, nano carbonyl iron powder, nano silica powder, and polyaniline powder (weight ratio 1:1:1:1), with the amount still being 20 parts. The rest of the formulation and preparation process are the same as in Example 1.

[0036] Comparative Example 3 The formulation is completely consistent with that of Example 1. The template imprinting auxiliary solvent evaporation process in step S4 is omitted in the preparation process, and the remaining steps are the same as those in Example 1.

[0037] Test case The coatings prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests according to the following methods, with each test repeated 3 times and the average value taken: Radar reflectivity test: A vector network analyzer was used, with a test frequency band of 2-18GHz and an incident angle of 0°-60°. The reflectivity values ​​and fluctuation range were recorded. Infrared emissivity test: An infrared emissivity meter was used, with a test band of 3-14μm, to test the emissivity at room temperature (25℃) and high temperature (200℃). Visible light camouflage color difference test: The color difference ΔE between the coating and the standard camouflage substrate was tested using a colorimeter; High and low temperature resistance test: Place the coating sample in a high and low temperature test chamber and cycle it 50 times in the range of -80℃ to 300℃ (each cycle: 2 hours of low temperature holding, 1 hour of heating, 2 hours of high temperature holding, and 1 hour of cooling), and observe whether the coating cracks or peels off; Salt spray resistance test: A salt spray test chamber with 5% sodium chloride solution was used in a neutral salt spray environment for 1500 hours of continuous spraying. The coating was then observed for rust and blistering. Self-healing performance test: A 50μm wide scratch was made on the coating surface with a blade. After being placed at room temperature for 24 hours, the radar reflectivity at the scratch was tested, and the recovery rate with the original coating reflectivity was calculated. Surface water contact angle test: The contact angle between the coating surface and deionized water was tested using a contact angle measuring instrument; The coatings produced in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests based on the above tests. The test results are shown in the table below: Table 1 shows the test results of the stealth performance of the coating (refer to...). Figure 2 ):

[0038] Table 2 shows the test results of the protective performance of the coating (refer to...). Figure 3 , 4 ):

[0039] From Table 1 and Table 2, we can see that: The performance of Example 1 is superior to that of Example 2 and Example 3. It has lower radar reflectivity and the smallest incident angle fluctuation. It has the best infrared emissivity stability under high and low temperature conditions. It has no defects in salt spray resistance and high and low temperature resistance. It has the highest self-healing rate and water contact angle, indicating that the raw materials of Example 1 are the optimal ratio. Compared with Comparative Example 1, Comparative Example 1 showed a sharp deterioration in radar reflectivity and infrared emissivity at high temperatures due to the lack of thermal response-adjustable absorbing powder. This indicates that the powder can adaptively adjust the absorbing structure through thermal response, thus solving the core problem of the degradation of the high-temperature stealth performance of existing coatings. Comparing Example 1 and Comparative Example 2, Comparative Example 2 uses a simple mixed filler, which significantly increases radar reflectivity and infrared emissivity, and shows pitting corrosion in salt spray resistance. This proves that the core-shell structure can achieve the synergistic effect of the filler, improve the stealth performance and protection performance across the entire frequency band, and is superior to the simple mixed method. Comparing Example 1 and Comparative Example 3, Comparative Example 3, lacking the stencil imprinting process, showed a significant decrease in the surface water contact angle to 95°, resulting in the loss of superhydrophobic properties. This demonstrates that stencil imprinting can form biomimetic micro-nano structures, endowing the coating with excellent hydrophobic and antifouling capabilities.

[0040] The performance of Examples 1-3 all meet the requirements of stealth coating indicators and are significantly better than the comparative examples, proving that the multilayer structure design, functional component matching and preparation process have outstanding creativity and applicability, and can effectively solve the problem of existing aircraft full-band stealth coatings.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A multi-functional stealth protective coating for aircraft surfaces, characterized in that: The multi-functional stealth protective coating consists of a base adhesion layer, an intermediate stealth layer, and a biomimetic protective outer layer. The specific components by weight are as follows: The underlying adhesion layer comprises: 45-55 parts of modified silicone-epoxy hybrid resin matrix, 2-4 parts of silane coupling agent KH-560, 1-3 parts of nano-alumina powder, 0.5-1 part of dispersant BYK-163, 0.3-0.8 parts of defoamer silicone emulsion, and 15-20 parts of solvent butyl acetate; The intermediate stealth layer comprises: 30-40 parts of modified organosilicon-epoxy hybrid resin matrix, 15-25 parts of core-shell structured composite functional filler, 8-12 parts of thermally responsive microwave absorbing powder, 5-8 parts of self-healing agent, 2-5 parts of nano-titanium nickel yellow, 0.3-0.6 parts of leveling agent BYK-333, and 10-15 parts of solvent butyl acetate; The biomimetic protective outer layer comprises: 50-60 parts of modified organosilicon-epoxy resin hybrid matrix, 3-6 parts of nano-tungsten carbide powder, 2-4 parts of nano-silica powder, 0.5-1 part of ultraviolet absorber UV-531, 2-5 parts of temperature and humidity sensitive composite powder, 0.5-1 part of fluorine-modified acrylate additive, and 10-15 parts of butyl acetate solvent; The core of the core-shell composite functional filler is a hollow alumina microsphere, and the shell consists of a nano-silicon carbide-carbonyl iron powder composite microwave absorbing layer and a nano-silica-polyaniline composite infrared low emissivity layer from the inside to the outside. The weight ratio of the core to the shell is 1:0.8-1.

2.

2. The multifunctional stealth protective coating for aircraft surfaces according to claim 1, characterized in that: The thermally responsive microwave absorbing powder is made by combining shape memory polyurethane microspheres and nanocomposite microwave absorbing powder in a weight ratio of 2:

1. The nanocomposite microwave absorbing powder is obtained by mixing nano-silicon carbide powder, nano-carbonyl iron powder and nano-graphene powder in a weight ratio of 3:3:

1. The method for preparing the modified organosilicon-epoxy resin hybrid matrix is ​​as follows: Bisphenol A type epoxy resin E-51 and hydroxyl-terminated polydimethylsiloxane resin were mixed at a weight ratio of 2:

1. 3%-5% of the silane coupling agent KH-560 by mass of bisphenol A type epoxy resin E-51 was added. The mixture was stirred and reacted at 60-70°C for 2-3 hours, and then cooled to room temperature to obtain the modified organosilicon-epoxy resin hybrid matrix.

3. The multifunctional stealth protective coating for aircraft surfaces according to claim 1, characterized in that: The self-healing agent is a microcapsule of a two-component epoxy repair agent coated with urea-formaldehyde resin. The microcapsule has a particle size of 5-10 μm and a shell wall thickness of 0.5-1 μm. The two-component epoxy repair agent is prepared by mixing bisphenol A type epoxy resin E-44 and polyamide 650 curing agent in a weight ratio of 1:

1.

4. The multifunctional stealth protective coating for aircraft surfaces according to claim 1, characterized in that: The temperature and humidity sensitive composite powder is prepared by mixing temperature sensitive powder and humidity sensitive powder in a weight ratio of 1:1; The temperature-sensitive powder is poly(N-isopropylacrylamide) grafted nano-silica powder, and the humidity-sensitive powder is montmorillonite-polyethylene glycol composite powder.

5. The multifunctional stealth protective coating for aircraft surfaces according to claim 1, characterized in that: The specific preparation method of the core-shell structured composite functional filler is as follows: Hollow alumina microspheres were ultrasonically cleaned in a 5% (v / v) dilute hydrochloric acid solution for 10-15 minutes, rinsed with deionized water until neutral, and dried at 80°C for later use. The dried hollow alumina microspheres were dispersed in an ethanol-water mixture, and a mixture of nano-silicon carbide powder and nano-carbonyl iron powder was added. The nano-silicon carbide-carbonyl iron powder composite microwave absorbing layer was formed by coating the surface of the microspheres using the sol-gel method. The microwave absorbing layer microspheres were then dried. The microwave-absorbing microspheres were dispersed in a polyaniline aqueous dispersion emulsion, and nano-silica powder was added. The mixture was ultrasonically coated for 30-40 minutes, filtered, and dried at 100-120℃ to obtain the core-shell structured composite functional filler.

6. The multifunctional stealth protective coating for aircraft surfaces according to claim 1, characterized in that: The performance indicators of the multifunctional stealth protective coating are as follows: The radar reflectivity is ≤-15dB in the 2-18GHz band, and the reflectivity fluctuation is ≤2dB in the incident angle range of 0°-60°. The infrared emissivity is ≤0.3 in the 3-14μm band, and the visible light camouflage color difference ΔE is ≤1.

0. The coating exhibits excellent high and low temperature resistance, with no cracking or peeling after 50 cycles of -80℃ to 300℃. It also demonstrates excellent salt spray resistance, with no rust after 1500 hours of salt spray testing with a 5% sodium chloride solution. Furthermore, its self-healing properties are such that when the scratch width is ≤50μm, the radar reflectivity of the coating recovers to over 95% of its original performance after repair, and the surface water contact angle is ≥120°.

7. A preparation process for a multifunctional stealth protective coating for aircraft surfaces as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The aircraft metal substrate to be sprayed is successively ground, degreased and derusted. Then, a low-temperature plasma surface treatment instrument is used to activate the surface of the aircraft metal substrate. The plasma power is 150-200W, the treatment time is 5-8min, and the vacuum degree is 10-20Pa. S2. The modified organosilicon-epoxy hybrid resin matrix, the silane coupling agent KH-560, the nano alumina powder, the dispersant BYK-163, the defoamer organosilicon emulsion, and the solvent butyl acetate are mixed evenly and coated onto the pretreated aircraft metal substrate surface using an air spraying method. The dry film thickness is controlled to be 10-15 μm, and the mixture is allowed to stand until the surface is dry to form the bottom adhesion layer. S3. After the bottom adhesion layer is sprayed, the modified silicone-epoxy hybrid resin matrix, the core-shell structure composite functional filler, the thermal response regulating microwave absorbing powder, the self-healing agent, the nano titanium nickel yellow, the leveling agent BYK-333, and the solvent butyl acetate are mixed evenly and coated onto the surface of the bottom adhesion layer after it has dried using a high-pressure airless spraying method. The dry film thickness is controlled to be 30-40μm. After standing until it is surface dry, the intermediate stealth layer is formed. S4. After the intermediate stealth layer is sprayed, the modified organosilicon-epoxy resin hybrid matrix, the nano tungsten carbide powder, the nano silica powder, the ultraviolet absorber UV-531, the temperature and humidity sensitive composite powder, the fluorinated modified acrylate additive, and the butyl acetate solvent are mixed evenly and coated onto the surface of the intermediate stealth layer after it has dried by electrostatic spraying. The dry film thickness is controlled to be 5-10 μm. After standing until it is surface dry, the biomimetic protective outer layer is formed. Immediately after spraying, a template imprinting process is used to assist in solvent evaporation. S5. After the bottom adhesion layer, the intermediate stealth layer, and the biomimetic protective outer layer are sequentially sprayed, the coating surface is first irradiated with ultraviolet light at a wavelength of 365nm and a light intensity of 800-1000mW / cm². 2 The irradiation time is 5-10 minutes; S6. After ultraviolet irradiation, the coated aircraft metal substrate is placed in an electric heating drying oven and cured in stages: 40℃ for 1 hour, 60℃ for 1 hour and 80℃ for 2 hours. After curing, it is naturally cooled to room temperature to obtain the multifunctional stealth protective coating.

8. The preparation process of the multifunctional stealth protective coating for aircraft surfaces according to claim 7, characterized in that: In steps S2, S3 and S4, the spraying pressure of the air spraying is 0.3-0.5MPa, the spraying pressure of the high-pressure airless spraying is 15-20MPa, and the voltage of the electrostatic spraying is 60-80kV.

9. The preparation process of the multifunctional stealth protective coating for aircraft surfaces according to claim 7, characterized in that: In step S4, the template imprinting uses a porous polytetrafluoroethylene template with a pore size of 1-5 μm, an imprinting pressure of 0.1-0.2 MPa, and an imprinting time of 1-2 min.

10. The preparation process of the multifunctional stealth protective coating for aircraft surfaces according to claim 7, characterized in that: In step S1, the surface roughness Ra of the aircraft metal substrate after polishing is controlled to be 1.6 μm; The degreasing treatment uses acetone solvent for ultrasonic degreasing, and the ultrasonic time is 10 minutes. The rust removal process involves wiping the surface with a phosphate-based rust remover.

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