Anti-interference airport FOD radar antenna cover composite material and preparation method thereof

Abstract

The application discloses an anti-interference airport FOD radar antenna cover composite material and a preparation method thereof. The application adopts an epoxy functional group functionalized silica aerogel precursor solution, and introduces a nanometer aluminum foil with surface grafted epoxy groups to construct a layered structure. The silica aerogel not only forms a stable interpenetrating network structure with a cyanate-epoxy resin matrix through chemical bonding, but also forms a directional reinforcing skeleton inside the aerogel due to the two-dimensional sheet characteristics of the nanometer aluminum foil. The shrinkage stress generated during the curing process of the composite material can be effectively dispersed and absorbed, the interface defects such as micro-cracks and pores generated due to the shrinkage of the resin during curing are greatly reduced, the water absorption and environmental sensitivity of the composite material are reduced, the dielectric properties of the composite material are stabilized, the bending strength and impact toughness of the composite material are simultaneously improved, and the composite material can better resist the impact of hail, tool falling and other foreign matters in the operation of the airport.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to an anti-jamming airport FOD radar radome composite material and its preparation method. Background Technology

[0002] Airport foreign debris (FD) monitoring radars are crucial for ensuring flight safety. They typically use high-frequency electromagnetic waves to detect runways and surrounding areas in real time, and one of their core components is the radome. The radome must not only maintain high transmittance, low dielectric loss, and low reflection characteristics in terms of electromagnetic performance to avoid interfering with radar signals, but it must also possess excellent shock resistance, weather resistance, and long-term service stability in complex outdoor environments.

[0003] Traditional radomes often use glass fiber reinforced epoxy resin or cyanate ester resin composites. While these offer some wave transmission, their high dielectric constant leads to impedance mismatch with air, causing electromagnetic wave reflection at the interface and reducing radar detection sensitivity and signal-to-noise ratio. To improve impedance matching, the industry has attempted to introduce porous materials or low-dielectric fillers (such as silica aerogel) to lower the overall dielectric constant of the composite material. However, aerogels, as nanoporous materials, are rich in hydrophilic hydroxyl groups on their surface, resulting in extremely poor compatibility with hydrophobic resin matrices. Simple blending easily leads to weak interfacial bonding, forming microscopic defects and pores. This not only severely degrades the material's mechanical properties (such as impact resistance and interlaminar shear strength) but also becomes a channel for moisture intrusion, causing the dielectric properties of the composite material to deteriorate sharply in humid environments. This seriously affects the reliability of radar operation in adverse weather conditions such as rain and fog.

[0004] Therefore, it is necessary to design an anti-jamming airport FOD radar radome composite material and its preparation method to solve the above problems. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides an anti-interference airport FOD radar radome composite material and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a method for preparing an anti-interference airport FOD radar radome composite material, comprising the following steps: Step S1: Prepare a wet gel with tetraethyl orthosilicate, add a silane coupling agent for hydrophobic treatment, and obtain a silica aerogel precursor solution. Step S2: Add nano-aluminum foil to the silica aerogel precursor solution to construct a layered silica aerogel. Step S3: Mix layered silica aerogel with cyanate ester-epoxy resin in proportion to obtain several mixtures of different concentrations; Step S4: Immerse the aramid fiber skeleton in several mixed solutions of different concentrations in descending order of concentration, and perform curing treatment in sequence to form a protective layer with a gradient structure. Step S5: Cut and trim the mold obtained in step S4 to obtain the anti-interference airport FOD radar radome.

[0007] In a preferred embodiment of the present invention, in step S1, the silane coupling agent is KH-560.

[0008] In a preferred embodiment of the present invention, step S1 includes the following sub-steps: Step S11: Dissolve tetraethyl orthosilicate and silane coupling agent in an ethanol solution at a mass ratio of 3 to 4:1; Step S12: Adjust the pH of the solution in step S11 to 2-3, and react at 50-60℃ for 2-2.5 hours to complete the acidic catalytic hydrolysis; Step S13: After hydrolysis, add 25-30% ammonia solution, adjust the pH to 8-9, and age at 40-50℃ for 48-52 hours to form a wet gel. Step S14: Immerse the wet gel in an ethanol solution containing 2-5% KH-560 and treat it at 40-50℃ for 24-26 hours to obtain an epoxy-functionalized silica aerogel precursor solution.

[0009] In a preferred embodiment of the present invention, in step S2, the thickness of the nano-aluminum foil is 20-200 nm and the length is 5-20 μm.

[0010] In a preferred embodiment of the present invention, step S2 includes the following sub-steps: Step S21: Silanize the nano-aluminum foil and graft epoxy groups onto the surface of the nano-aluminum foil; Step S22: Add the silanized aluminum foil to the silica aerogel precursor solution and stir evenly. The mass ratio of the aluminum foil to silica is 1 to 4:10. Step S23: Freeze the solution from step S23 at a temperature of -40℃±5℃ for 3 to 4 hours; Step S24: After freezing, the ice crystals are removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel.

[0011] In a preferred embodiment of the present invention, in step S3, the mass ratio of cyanate ester resin to epoxy resin in the cyanate ester-epoxy resin is 6-7:3-4.

[0012] In a preferred embodiment of the present invention, step S3 includes the following sub-steps: Step S31: Break up the layered silica aerogel and control the particle size to 50-80 μm; Step S32: Add the crushed layered silica aerogel to several portions of the same cyanate ester-epoxy resin in different proportions, and stir at 2000-3000 rpm for 10-20 min to obtain several portions of mixed solution with different concentrations.

[0013] In a preferred embodiment of the present invention, in step S32, the proportion of layered silica aerogel in several portions of mixed liquid of different concentrations decreases by 5% to 8% in turn, wherein the highest proportion of layered silica aerogel is 30% to 33%.

[0014] In a preferred embodiment of the present invention, step S4 includes the following sub-steps: Step S41: Preheat the aramid fiber to 50-70°C; Step S42: Immerse the preheated aramid fiber into the mixture with the highest concentration and cure it at a temperature range of 80-85℃ for 0.5-1h. Then, immerse it in other mixtures with different concentrations in descending order of concentration and cure it at a temperature range of 100-105℃ for 1-1.5h to form a protective layer with a gradient structure.

[0015] An anti-jamming airport FOD radar radome composite material, based on the aforementioned preparation method of the anti-jamming airport FOD radar radome composite material.

[0016] This invention addresses the shortcomings of the prior art and has the following beneficial effects: The present invention provides a method for preparing an anti-interference airport FOD radar radome composite material. This method utilizes an epoxy-functionalized silica aerogel precursor solution, and introduces surface-grafted epoxy group-containing nano-aluminum foil to construct a layered structure. The silica aerogel not only forms a stable interpenetrating network structure through chemical bonding with the cyanate ester-epoxy resin matrix, but the two-dimensional sheet-like properties of the nano-aluminum foil also create a directional reinforcing skeleton within the aerogel. This effectively disperses and absorbs the shrinkage stress generated during the curing process of the composite material, greatly reducing interface defects such as microcracks and pores caused by resin curing shrinkage. It also lowers the water absorption rate and environmental sensitivity of the composite material, enabling it to maintain stable dielectric properties even in harsh environments such as airport humidity and salt spray. Simultaneously, the flexural strength and impact toughness of the composite material are improved, allowing it to better resist impacts from external objects such as hail and dropped tools that may be encountered during airport operations.

[0017] The present invention provides a method for preparing an anti-jamming airport FOD radar radome composite material. By introducing KH-560 silane coupling agent, epoxy functional groups are grafted onto the surface of silica aerogel, resulting in a hydrophobic epoxy functionalized silica aerogel. This allows the silica aerogel to be fully compatible with cyanate ester-epoxy resin and to undergo a ring-opening reaction with the amine groups in the cyanate ester-epoxy resin to form a covalently bonded interpenetrating network structure. This not only effectively improves the wettability and coating properties of the resin on the surface of the silica aerogel, but also eliminates interfacial micropores and defects through chemical bonding, giving the composite material higher interfacial strength and stability, thus exhibiting a high-strength toughness enhancement effect when subjected to external impact.

[0018] The present invention provides a method for preparing an anti-jamming airport FOD radar radome composite material, which combines epoxy-functionalized silica aerogel with surface-silanized nano-aluminum foil to jointly construct a layered composite structure. Through chemical bonding, a strong bond is achieved between the aerogel particles, the resin, and the aluminum foil surface. The pinning and deflecting effect of the sheet-like aluminum foil on cracks significantly weakens the brittle failure mode of the aerogel itself, enabling the composite material to disperse external forces step by step when subjected to impact, avoiding brittle fracture and delamination failure at the interface. This not only improves the interfacial bonding strength and energy dissipation capacity of the protective layer, but also provides excellent thermal conductivity and moisture barrier properties through the aluminum foil layer, further avoiding performance degradation caused by damp heat. Thus, the radar radome possesses wave transmission, impact resistance, and anti-jamming performance during long-term service.

[0019] The present invention provides a method for preparing an anti-interference airport FOD radar radome composite material. By constructing a gradient structure protective layer, a smooth transition of the dielectric constant of the protective layer is achieved. This prevents strong reflection and signal distortion of radar waves during penetration due to dielectric abrupt changes, thus ensuring the high transmittance and low loss performance of the radome. At the same time, the gradient distribution avoids stress concentration and brittle fracture caused by the concentration of hard and brittle fillers in traditional homogeneous composite layers. When the composite material is subjected to external impacts such as hail, bird strikes, or tool drops, it can suppress crack propagation and interlayer delamination by dissipating energy at different levels, significantly improving the overall impact resistance and toughness. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a flowchart of a method for preparing an anti-interference airport FOD radar radome composite material according to the present invention; Figure 2 This is a waveform representation of the preferred embodiment of the present invention without a shield at 92GHz. Figure 3 This is a waveform transmission performance characterization diagram of a preferred embodiment of the present invention with a shield at 92GHz. Figure 4 This is a waveform representation of the preferred embodiment of the present invention without a shield at 93 GHz. Figure 5 This is a waveform transmission performance characterization diagram of a preferred embodiment of the present invention with a shield at 93GHz. Figure 6 This is a waveform representation of the preferred embodiment of the present invention without a shield at 94 GHz. Figure 7 This is a waveform representation of the preferred embodiment of the present invention with a shield at 94GHz. Detailed Implementation

[0021] 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.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0023] like Figure 1 As shown, a method for preparing an anti-jamming airport FOD radar radome composite material includes the following steps: Step S1: Prepare a wet gel with tetraethyl orthosilicate, add a silane coupling agent for hydrophobic treatment, and obtain a silica aerogel precursor solution. Step S2: Add nano-aluminum foil to the silica aerogel precursor solution to construct a layered silica aerogel. Step S3: Mix layered silica aerogel with cyanate ester-epoxy resin in proportion to obtain several mixtures of different concentrations; Step S4: Immerse the aramid fiber skeleton in several mixed solutions of different concentrations in descending order of concentration, and perform curing treatment in sequence to form a protective layer with a gradient structure. Step S5: Cut and trim the mold obtained in step S4 to obtain the anti-interference airport FOD radar radome.

[0024] In this invention, the silane coupling agent in step S1 is KH-560.

[0025] In this invention, step S1 includes the following sub-steps: Step S11: Dissolve tetraethyl orthosilicate and silane coupling agent in an ethanol solution at a mass ratio of 3 to 4:1; Step S12: Adjust the pH of the solution in step S11 to 2-3, and react at 50-60℃ for 2-2.5 hours to complete the acidic catalytic hydrolysis; Step S13: After hydrolysis, add 25-30% ammonia solution, adjust the pH to 8-9, and age at 40-50℃ for 48-52 hours to form a wet gel. Step S14: Immerse the wet gel in an ethanol solution containing 2-5% KH-560 and treat it at 40-50℃ for 24-26 hours to obtain an epoxy-functionalized silica aerogel precursor solution.

[0026] Using tetraethyl orthosilicate as the silicon source and ethanol as the medium to reduce the viscosity of the system and facilitate the dispersion of water and silane, KH-560 can be pre-introduced to make it uniformly distributed near the silanol network during hydrolysis / condensation, creating conditions for subsequent surface grafting. After hydrolysis, silane generates silanol groups that can covalently bond with the siloxane network, while retaining the epoxy side chain. The pH of the obtained solution was adjusted to 2-3. This is an acid-catalyzed hydrolysis treatment. Tetraethyl orthosilicate undergoes rapid hydrolysis to generate silanol (Si-OH). Acidic conditions can inhibit premature condensation and form more dispersed oligomeric silanol species, which makes the final gelation more uniform and the pore size distribution controllable. At the same time, KH-560 also undergoes partial hydrolysis at this stage to generate silanol groups that can be grafted with silanol, but its epoxy side chains remain intact. Adding ammonia to adjust the pH to 8-9 is the alkaline catalytic stage, which promotes further cross-linking of the network structure and maturity of the skeleton. Aging helps to compensate for incomplete condensation in the network, improve the skeleton strength and reduce the risk of drying shrinkage cracks. The wet gel obtained in the alkaline catalysis stage is immersed in an ethanol solution containing 2-5% KH-560 and treated at 40-50℃ for 24-26 hours to allow silane to be grafted onto the surface of the aerogel through silanol condensation while retaining epoxy groups, thereby obtaining an epoxy-functionalized silica aerogel precursor with hydrophobic tendency. Specifically, the Si-OH formed by the hydrolysis of KH-560 forms a Si-O-Si covalent bond with the Si-OH on the surface of the aerogel through a condensation reaction. At the same time, its epoxy groups exist on the surface in a free or semi-connected form, providing active sites for subsequent reactions with resins or amines. This grafting can improve the wettability and compatibility between silica and cyanate ester-epoxy resin, and also increase hydrophobicity.

[0027] It should be noted that cyanate ester-epoxy resin is hydrophobic. During the mixing process with hydrophilic silica, the cyanate ester-epoxy resin will have difficulty spreading and penetrating to the surface of silica particles, resulting in a large wetting angle and the presence of weak layers or voids at the interface. The unwetted voids cannot be filled by the resin during the curing and shrinkage process and will be magnified into micropores or microcracks. Crack sources are easily formed at the stress concentration points around the filler. Therefore, the long-chain organosilicon structure in KH-560 molecules is chemically bonded to the surface of the aerogel to form a hydrophobic layer, which matches the surface of the cyanate ester-epoxy resin. This completely solves the wettability problem between heterogeneous materials, allowing the resin to completely coat the aerogel particles, eliminating the micropores caused by incomplete wetting, and eliminating the physical channels for water adsorption from the source. Secondly, the introduction of KH-560 silane coupling agent causes epoxy functional groups to be grafted onto the surface of silica aerogel and undergo a ring-opening reaction with the amine groups in cyanate ester-epoxy resin to form a covalently bonded interpenetrating network structure, which transforms the physical bonding of silica into chemical bonding in a three-dimensional cross-linked network. Furthermore, when the material is subjected to external impact, the pinning and deflecting effect of the sheet aluminum foil on the cracks significantly weakens the brittle failure mode of the aerogel itself. This allows the composite material to disperse the external force step by step when impacted, and effectively transfer it to the entire network structure of the aerogel through chemical bonds, avoiding stress concentration at the interface and delamination. At the same time, the nanoporous structure of the aerogel can absorb impact energy through plastic deformation, thereby improving the impact toughness of the composite material.

[0028] The dense organosilicon layer not only blocks the contact between water molecules and the silanol groups inside the aerogel, but its low surface energy also prevents water from spreading on the material surface, thus reducing the saturated water absorption rate of the composite material. This effectively avoids the problem of the protective layer formed by silica aerogel and cyanate ester-epoxy resin absorbing water under heavy rain conditions, which would lead to a change in dielectric constant.

[0029] In this invention, in step S2, the thickness of the nano-aluminum foil is 20-200 nm and the length is 5-20 μm.

[0030] In this invention, step S2 includes the following sub-steps: Step S21: Silanize the nano-aluminum foil and graft epoxy groups onto the surface of the nano-aluminum foil; Step S22: Add the silanized aluminum foil to the silica aerogel precursor solution and stir evenly. The mass ratio of the aluminum foil to silica is 1 to 4:10. Step S23: Freeze the solution from step S23 at a temperature of -40℃±5℃ for 3 to 4 hours; Step S24: After freezing, the ice crystals are removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel.

[0031] In step S21, the nano-aluminum foil is ultrasonically cleaned in ethanol or isopropanol for 5-15 min to remove organic residues and loose oxides. It is then immersed in 1-2% acetic acid for 30-120 s to rapidly etch and promote the formation of a uniform thin oxide layer on the surface. After that, it is washed with ethanol and dried. The cleaned nano-aluminum foil is dispersed in ethanol, and KH-560 is added to make the mass concentration range of 2-5%. The mixture is stirred and reacted at 40-60℃ for 12-24 h, thereby grafting epoxy groups onto the surface of the nano-aluminum foil, so that the originally chemically inert aluminum foil surface can acquire the ability to form covalent bonds with the resin matrix. After functionalizing the aluminum foil surface, it is added to the epoxy-functionalized silica aerogel precursor liquid and stirred to promote silica to adhere to the aluminum foil surface. The solvent crystals are induced to grow in an orderly manner by cooling the precursor liquid. After freezing, the solvent crystals are removed by sublimation under freeze-drying conditions to retain the layered channels formed by the ice crystal template and the aluminum foil interlayer.

[0032] It should be noted that silica aerogel is attached to sheet-like nano-aluminum foil, and a layered aerogel structure is formed by silanizing and grafting epoxy groups onto the surface of the aluminum foil and then performing a low-temperature freezing-sublimation process. From a chemical perspective, the surface of silanized aluminum foil can provide active sites for covalent bonding with epoxy-functionalized silica and epoxy / cyanate matrix, which pins silica particles that may otherwise be free or weakly bonded to the metal sheet, thereby reducing interfacial voids, inhibiting particle agglomeration and significantly improving the filler-matrix interface strength. From the perspective of microstructure and mechanical behavior, the layered aluminum foil, as a continuous or semi-continuous sheet embedded in the aerogel layer, on the one hand, achieves crack deflection and pinning energy dissipation through mechanical pinning and interlayer friction, preventing large-scale crushing and interlayer peeling of brittle aerogel particles. On the other hand, it provides high modulus support in the planar direction while maintaining local elasticity in the thickness direction, so that when the composite system is subjected to hail, bird strikes or tool impacts, it can dissipate impact energy step by step through the interlayer energy gradient and exert the plastic energy absorption effect of the aramid skeleton. In terms of thermal and moisture stability, the metal layer and the dense chemically bonded interface together form an effective thermal conductivity and moisture resistance path. The aluminum foil increases the local thermal conductivity rate, reduces hot spot accumulation, and promotes heat diffusion outward. Combined with the Si-O-Si framework and covalent cross-linked network, it improves the decomposition temperature and char residue. At the same time, the metal layer and dense interface significantly reduce the moisture diffusion channels, thereby greatly suppressing the expansion and interface degradation caused by moisture absorption.

[0033] In this invention, in step S3, the mass ratio of cyanate ester resin to epoxy resin in the cyanate ester-epoxy resin is 6-7:3-4.

[0034] In this invention, step S3 includes the following sub-steps: Step S31: Break up the layered silica aerogel and control the particle size to 50-80 μm; Step S32: Add the crushed layered silica aerogel to several portions of the same cyanate ester-epoxy resin in different proportions, and stir at 2000-3000 rpm for 10-20 min to obtain several portions of mixed solution with different concentrations.

[0035] In this invention, in step S32, the proportion of layered silica aerogel in several portions of mixed liquid of different concentrations is reduced by 5-8% in turn, wherein the highest proportion of layered silica aerogel is 30-33%, and preferably three layers are used, for example, 30%, 25%, and 20%, and this type of reduction is adopted.

[0036] In this invention, step S4 includes the following sub-steps: Step S41: Preheat the aramid fiber to 50-70°C; Step S42: Immerse the preheated aramid fiber into the mixture with the highest concentration and cure it at a temperature range of 80-85℃ for 0.5-1h. Then, immerse it in other mixtures with different concentrations in descending order of concentration and cure it at a temperature range of 100-105℃ for 1-1.5h to form a protective layer with a gradient structure.

[0037] Considering that the reflection and transmission of electromagnetic waves when penetrating the interface of different materials are determined by the impedance mismatch at the interface; if the dielectric constant of the material changes abruptly at the interface, it will produce significant reflection and waveform distortion, thereby reducing the transmittance of the radome and introducing signal distortion. Therefore, by gradually or continuously transitioning the dielectric constant and loss factor in the thickness direction, the incident electromagnetic wave only encounters a small impedance difference on each thin layer, which is equivalent to an impedance matching network as a whole, significantly reducing reflection and smoothing phase delay. Furthermore, because air has a low dielectric constant, a mixture of aerogel with a low dielectric constant and cyanate ester-epoxy resin is used as a protective layer to further reduce the abrupt changes that occur when electromagnetic waves enter the medium from the air.

[0038] Therefore, by constructing a gradient structure for the protective layer, a smooth transition in the dielectric constant of the protective layer is achieved, preventing strong reflection and signal distortion of radar waves during penetration due to dielectric abrupt changes. This ensures the high transmittance and low loss performance of the radome. At the same time, the gradient distribution avoids stress concentration and brittle fracture caused by the concentration of hard and brittle fillers in traditional homogeneous composite layers. When subjected to external impacts such as hail, bird strikes, or falling tools, the composite material can suppress crack propagation and interlayer delamination by dissipating energy at different levels, significantly improving the overall impact resistance and toughness.

[0039] An anti-jamming airport FOD radar radome composite material, based on the aforementioned preparation method of the anti-jamming airport FOD radar radome composite material. Example 1

[0040] Tetraethyl orthosilicate and silane coupling agent were dissolved in an ethanol solution at a mass ratio of 3:1. The pH of the solution was adjusted to 2, and the reaction was carried out at 60°C for 2 hours to complete acidic catalytic hydrolysis. After hydrolysis, 30% ammonia water was added, the pH was adjusted to 9, and the mixture was aged at 50°C for 48 hours to form a wet gel. The wet gel was then immersed in an ethanol solution containing 2% KH-560 and treated at 50°C for 24 hours to obtain an epoxy-functionalized silica aerogel precursor solution. The nano-aluminum foil was silanized and epoxy groups were grafted onto its surface. The silanized nano-aluminum foil was then added to a silica aerogel precursor solution and stirred uniformly. The mass ratio of nano-aluminum foil to silica was 1:10. The solution was then frozen at -40°C for 3 hours. After freezing, the ice crystals were removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel. The crushed layered silica aerogel was added to three identical cyanate ester-epoxy resins in different proportions and stirred at 2000 rpm for 20 min to obtain a mixture with layered silica aerogels of 30%, 25% and 20% respectively, wherein the mass ratio between cyanate ester resin and epoxy resin was 7:3. Aramid fibers are preheated to 70°C and then immersed in the mixture with the highest concentration. The mixture is cured at 80°C for 1 hour. Then, the fibers are immersed in other mixtures with different concentrations in descending order of concentration and cured at 100°C for 1 hour in each case to form a protective layer with a gradient structure. Example 2

[0041] Tetraethyl orthosilicate and silane coupling agent were dissolved in an ethanol solution at a mass ratio of 3:1. The pH of the solution was adjusted to 2, and the reaction was carried out at 60°C for 2 hours to complete acidic catalytic hydrolysis. After hydrolysis, 30% ammonia water was added, the pH was adjusted to 9, and the mixture was aged at 50°C for 48 hours to form a wet gel. The wet gel was then immersed in an ethanol solution containing 2% KH-560 and treated at 50°C for 24 hours to obtain an epoxy-functionalized silica aerogel precursor solution. The nano-aluminum foil was silanized and epoxy groups were grafted onto its surface. The silanized nano-aluminum foil was then added to a silica aerogel precursor solution and stirred uniformly. The mass ratio of nano-aluminum foil to silica was 2:10. The solution was then frozen at -40°C for 3 hours. After freezing, the ice crystals were removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel. The crushed layered silica aerogel was added to three identical cyanate ester-epoxy resins in different proportions and stirred at 2000 rpm for 20 min to obtain a mixture with layered silica aerogels of 30%, 25% and 20% respectively, wherein the mass ratio between cyanate ester resin and epoxy resin was 7:3. Aramid fibers are preheated to 70°C and then immersed in the mixture with the highest concentration. The mixture is cured at 80°C for 1 hour. Then, the fibers are immersed in other mixtures with different concentrations in descending order of concentration and cured at 100°C for 1 hour in each case to form a protective layer with a gradient structure. Example 3

[0042] Tetraethyl orthosilicate and silane coupling agent were dissolved in an ethanol solution at a mass ratio of 3:1. The pH of the solution was adjusted to 2, and the reaction was carried out at 60°C for 2 hours to complete acidic catalytic hydrolysis. After hydrolysis, 30% ammonia water was added, the pH was adjusted to 9, and the mixture was aged at 50°C for 48 hours to form a wet gel. The wet gel was then immersed in an ethanol solution containing 2% KH-560 and treated at 50°C for 24 hours to obtain an epoxy-functionalized silica aerogel precursor solution. The nano-aluminum foil was silanized and epoxy groups were grafted onto its surface. The silanized nano-aluminum foil was then added to a silica aerogel precursor solution and stirred uniformly. The mass ratio of nano-aluminum foil to silica was 3:10. The solution was then frozen at -40°C for 3 hours. After freezing, the ice crystals were removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel. The crushed layered silica aerogel was added to three identical cyanate ester-epoxy resins in different proportions and stirred at 2000 rpm for 20 min to obtain a mixture with layered silica aerogels of 30%, 25% and 20% respectively, wherein the mass ratio between cyanate ester resin and epoxy resin was 7:3. Aramid fibers are preheated to 70°C and then immersed in the mixture with the highest concentration. The mixture is cured at 80°C for 1 hour. Then, the fibers are immersed in other mixtures with different concentrations in descending order of concentration and cured at 100°C for 1 hour in each case to form a protective layer with a gradient structure. Example 4

[0043] Tetraethyl orthosilicate and silane coupling agent were dissolved in an ethanol solution at a mass ratio of 3:1. The pH of the solution was adjusted to 2, and the reaction was carried out at 60°C for 2 hours to complete acidic catalytic hydrolysis. After hydrolysis, 30% ammonia water was added, the pH was adjusted to 9, and the mixture was aged at 50°C for 48 hours to form a wet gel. The wet gel was then immersed in an ethanol solution containing 2% KH-560 and treated at 50°C for 24 hours to obtain an epoxy-functionalized silica aerogel precursor solution. The nano-aluminum foil was silanized and epoxy groups were grafted onto its surface. The silanized nano-aluminum foil was then added to a silica aerogel precursor solution and stirred uniformly. The mass ratio of nano-aluminum foil to silica was 4:10. The solution was then frozen at -40°C for 3 hours. After freezing, the ice crystals were removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel. The crushed layered silica aerogel was added to three identical cyanate ester-epoxy resins in different proportions and stirred at 2000 rpm for 20 min to obtain a mixture with layered silica aerogels of 30%, 25% and 20% respectively, wherein the mass ratio between cyanate ester resin and epoxy resin was 7:3. Aramid fibers are preheated to 70°C and then immersed in the mixture with the highest concentration. The mixture is cured at 80°C for 1 hour. Then, the fibers are immersed in other mixtures with different concentrations in descending order of concentration and cured at 100°C for 1 hour in each case to form a protective layer with a gradient structure.

[0044] Transmission performance testing: The radome obtained in the examples was tested in a microwave anechoic chamber using a 92-94 GHz horn antenna with a width of 3*0.25 degrees as the feed and a standard gain horn antenna as the receiving antenna. The changes were measured with and without the radome, as shown in Table 1. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown.

[0045] Table 1:

[0046] In summary, comparing Examples 1 to 4, it can be concluded that as the proportion of aluminum foil increases, the nano-aluminum foil, being a two-dimensional sheet structure, can be uniformly dispersed in the silica aerogel matrix after modification with epoxy groups. Its sheet structure forms a directional arrangement inside the aerogel, reducing multiple scattering and reflection of electromagnetic waves at the porous interface, making the overall dielectric constant of the composite material tend to be stable, and avoiding local dielectric abrupt changes. The nano-aluminum foil is firmly embedded in the aerogel skeleton through chemical bonding, playing a bridging and reinforcing role, and significantly reducing porosity and microcracks caused by the brittleness of aerogel. However, as the proportion of aluminum foil becomes too large, the wave transmission performance of the prepared radome will decrease. This is mainly because the sheet aluminum foil may overlap or overlap, forming local conductive paths. This micro-conductive network will produce a strong reflection and shielding effect on high-frequency electromagnetic waves, resulting in a significant decrease in wave transmission performance. In addition, high-content aluminum foil is prone to agglomeration during the dispersion process, forming local enrichment areas. Agglomeration areas will cause abrupt changes in dielectric properties, becoming hotspots for electromagnetic wave scattering and reflection, thus reducing the overall wave transmission performance.

[0047] Experimental tests were conducted on the water absorption rate, mechanical properties, impact loss, and other properties of Examples 1 to 4.

[0048] Water absorption: According to ASTM D570, the sample was immersed in distilled water for 24 hours and the weight change was measured.

[0049] Bending strength: Three-point bending test, according to ASTM D790, sample size 80mm×10mm×4mm.

[0050] Impact resistance test: Falling ball impact test, according to ASTM D3763, using a steel ball with a diameter of 12.7 mm dropped from the same height to impact the center of the sample (sample size 100 mm × 100 mm × 4 mm). Record the impact energy and damage diameter that produce visible cracks.

[0051]

[0052] Comparing Examples 1 to 4, it can be concluded that the performance of the resulting radome is enhanced with the increase of the nano-aluminum foil content. This is mainly because the nano-aluminum foil, after epoxy functionalization treatment, is uniformly dispersed in the resin matrix and, together with silica aerogel and aramid fiber skeleton, constructs a layered composite structure. On the one hand, the aluminum foil layers act as a barrier in the resin, significantly shortening the water penetration path and gradually reducing the water absorption rate of the composite material. On the other hand, the morphology of the aluminum foil layers and the chemical bonding with the resin enable stress to be transmitted more uniformly between interfaces, resulting in a significant improvement in flexural strength and modulus. Simultaneously, under impact loads, the aluminum foil layers guide crack deflection or bifurcation, lengthening the crack propagation path and dissipating more energy. This manifests as a reduction in damage diameter, a decrease in delamination area, and a significant enhancement in impact toughness.

[0053] However, as the content of nano-aluminum foil increases excessively, the high content of nano-aluminum foil filler can easily lead to uneven dispersion and agglomeration of nano-aluminum foil in the matrix. Agglomerates are no longer uniformly distributed reinforcing units, but instead become local stress concentration points, becoming the source of preferential crack initiation and rapid propagation, which weakens the mechanical properties of the material.

[0054] In summary, Example 3 is the optimal solution of the present invention.

[0055] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a composite material for an anti-jamming airport FOD radar radome, characterized in that, Includes the following steps: Step S1: Prepare a wet gel with tetraethyl orthosilicate, add a silane coupling agent for hydrophobic treatment, and obtain a silica aerogel precursor solution. Step S2: Add nano-aluminum foil to the silica aerogel precursor solution to construct a layered silica aerogel. Step S3: Mix layered silica aerogel with cyanate ester-epoxy resin in proportion to obtain several mixtures of different concentrations; Step S4: Immerse the aramid fiber skeleton in several mixed solutions of different concentrations in descending order of concentration, and perform curing treatment in sequence to form a protective layer with a gradient structure. Step S5: Cut and trim the mold obtained in step S4 to obtain the anti-interference airport FOD radar radome.

2. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: In step S1, the silane coupling agent is KH-560.

3. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: Step S1 includes the following sub-steps: Step S11: Dissolve tetraethyl orthosilicate and silane coupling agent in an ethanol solution at a mass ratio of 3 to 4:1; Step S12: Adjust the pH of the solution in step S11 to 2-3, and react at 50-60℃ for 2-2.5 hours to complete the acidic catalytic hydrolysis; Step S13: After hydrolysis, add 25-30% ammonia solution, adjust the pH to 8-9, and age at 40-50℃ for 48-52 hours to form a wet gel. Step S14: Immerse the wet gel in an ethanol solution containing 2-5% KH-560 and treat it at 40-50℃ for 24-26 hours to obtain an epoxy-functionalized silica aerogel precursor solution.

4. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: In step S2, the thickness of the nano-aluminum foil is 20–200 nm and the length is 5–20 μm.

5. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: Step S2 includes the following sub-steps: Step S21: Silanize the nano-aluminum foil and graft epoxy groups onto the surface of the nano-aluminum foil; Step S22: Add the silanized aluminum foil to the silica aerogel precursor solution and stir evenly. The mass ratio of the aluminum foil to silica is 1 to 4:

10. Step S23: Freeze the solution from step S23 at a temperature of -40℃±5℃ for 3 to 4 hours; Step S24: After freezing, the ice crystals are removed by sublimation under a vacuum of <10 Pa to obtain a layered silica aerogel.

6. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: In step S3, the mass ratio of cyanate ester resin to epoxy resin in the cyanate ester-epoxy resin is 6-7:3-4.

7. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: Step S3 includes the following sub-steps: Step S31: Break up the layered silica aerogel and control the particle size to 50-80 μm; Step S32: Add the crushed layered silica aerogel to several portions of the same cyanate ester-epoxy resin in different proportions, and stir at 2000-3000 rpm for 10-20 min to obtain several portions of mixed solution with different concentrations.

8. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 7, characterized in that: In step S32, the proportion of layered silica aerogel in several mixed solutions of different concentrations decreases by 5% to 8% in turn, with the highest proportion of layered silica aerogel being 30% to 33%.

9. The method for preparing an anti-jamming airport FOD radar radome composite material according to claim 1, characterized in that: Step S4 includes the following sub-steps: Step S41: Preheat the aramid fiber to 50-70°C; Step S42: Immerse the preheated aramid fiber into the mixture with the highest concentration and cure it at a temperature range of 80-85℃ for 0.5-1h. Then, immerse it in other mixtures with different concentrations in descending order of concentration and cure it at a temperature range of 100-105℃ for 1-1.5h to form a protective layer with a gradient structure.

10. An anti-jamming airport FOD radar radome composite material, based on the preparation method of the anti-jamming airport FOD radar radome composite material according to any one of claims 1-9.

Images