Light silicon dioxide aerogel felt material for sound insulation and noise reduction in airplane and preparation method and application of light silicon dioxide aerogel felt material

Abstract

The invention discloses a light silicon dioxide aerogel felt material for sound insulation and noise reduction in an airplane as well as a preparation method and application of the light silicon dioxide aerogel felt material. The light silicon dioxide aerogel felt material comprises a flexible felt material serving as a matrix and silicon dioxide aerogel filled in fiber gaps of the matrix, the preparation method comprises the following steps: dipping a flexible felt material matrix in silicon dioxide sol, carrying out heating treatment to enable the silicon dioxide sol to be gelled and cured in matrix fiber gaps to form a wet gel felt, and carrying out aging, aging and hydrophobic modification on the wet gel felt, and carrying out CO2 supercritical drying to prepare a soft and flexible light silicon dioxide aerogel felt; wherein the thickness of the light silicon dioxide aerogel felt is in positive correlation with the sound insulation index, and the light silicon dioxide aerogel felt is attached to a special-shaped curved surface in an aircraft cabin in an unstressed mode. In this way, the material is low in density, light in weight, excellent in sound insulation and heat insulation performance, soft, tough, capable of being attached to the curved surface of a cabin, convenient to install, hydrophobic, free of weight increment and stable in performance and can be used for sound insulation, noise reduction and heat insulation protection of airplanes.

Description

Technical Field

[0001] This invention relates to the field of sound insulation and heat insulation materials, and in particular to a lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft, its preparation method, and its application. Background Technology

[0002] Noise during aircraft flight has long been a problem that has plagued the industry. Aircraft noise mainly comes from incident noise generated by the interaction between the engine system and the airframe structure, aerodynamic noise generated by friction between the airframe and the air, and superimposed noise from other factors such as altitude changes and the operation of onboard equipment.

[0003] Prolonged exposure to such high-intensity noise environments not only severely impacts the physical and mental health of pilots and crew, leading to increased fatigue, decreased concentration, reduced cognitive and responsiveness, and impaired command transmission, but may also cause endocrine disorders, tinnitus, hearing loss, and arrhythmia. For military aircraft, noise interference will also directly affect combat effectiveness and fighting power. At the same time, aircraft also face the challenge of regulating internal thermal conditions during flight. To effectively control internal temperature and reduce noise levels, the industry currently widely adopts a solution of applying sound and heat insulation materials to key areas such as the fuselage inner walls and engines.

[0004] Lightweight aerogel felt, as a novel functional material suitable for the aerospace field, must meet stringent performance requirements: First, it must have both excellent thermal insulation performance and significant sound insulation and noise reduction effect; Secondly, there is a strict upper limit to the takeoff weight of an aircraft for a single flight mission, so aerogel felt must be lightweight and low-density to maximize the release of effective load space. In addition, to adapt to the complex internal structure of the fuselage, the material must have good flexibility and processability to ensure convenient and efficient construction and assembly; In terms of safety performance, aerogel felt must meet fire-retardant standards and strictly control the amount of smoke and toxic emissions and smoke density to meet airworthiness standards. At the same time, it must also have excellent hydrophobic properties to effectively resist moisture penetration without increasing weight, thereby extending the service life of the material and ensuring flight safety and crew health.

[0005] Currently, the main components of traditional silica aerogel mats, both domestically and internationally, are glass fiber needled mats and silica aerogels, which have significant limitations in terms of preparation process and performance.

[0006] In terms of the substrate, the fiberglass felt substrate it uses is made of single coarse fiberglass filaments of 13-14 microns needle-punched together, with a density as high as 100-130 Kg / m³, which is difficult to meet the stringent requirements of the aerospace field for lightweight materials. Regarding aerogels, the silica aerogels used are synthesized from tetraethyl orthosilicate with a single silicon source via a sol-gel method. They are hard and brittle. The preparation process uses oxalic acid as a catalyst, ammonia as an alkaline catalyst, and a mixed solvent of alcohol and water as a solution. Although hexamethyldisilazane is used for hydrophobic treatment afterward, it produces an irritating odor. More importantly, the silica aerogel felt made by impregnating the high-density fiberglass felt with silica sol has a very high density, usually as high as 170-240 Kg / m³. Its hard, brittle and easily cracked properties result in extremely poor surface conformability, making it difficult to adapt to the complex curved surface structure of aircraft cabins.

[0007] Therefore, traditional aerogel felts, both domestically and internationally, cannot meet the numerous special requirements of aircraft manufacturing for lightweight materials, structural adaptability, and environmental friendliness in terms of weight control, flexibility, and molding adaptability. Summary of the Invention

[0008] The main technical problem solved by this invention is to provide a lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft. The material has low density and light weight, making it suitable for sound insulation, noise reduction, and heat insulation protection in aircraft. It is soft and tough, conforms to the curved surfaces of the cabin, is easy to install, flame-retardant, low in toxicity, and low in smoke, meets aviation standards, is hydrophobic and does not increase weight, has stable performance, and can be adapted to different noise scenarios by adjusting the thickness. When used in aircraft, it can reduce noise hazards, create a comfortable environment, improve crew efficiency, and enhance the aircraft's market competitiveness.

[0009] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft, comprising: Flexible felt material matrix; Silica aerogel that fills and solidifies within the gaps between the matrix fibers; By impregnating flexible felt material matrices of different densities with silica sols of varying solid contents to achieve gel solidification and matching, and then aging and hydrophobically modifying them before supercritical CO2 drying, lightweight silica aerogel felts of different densities can be formed, with a density ≤360 kg / m³. 3 .

[0010] In a preferred embodiment of the present invention, the flexible felt material matrix is ​​a low-density flexible felt material. A low-density flexible felt material matrix is ​​impregnated in silica sol. Heat treatment causes the low-solids silica sol to gel and solidify within the interfiber spaces of the matrix, forming a wet gel felt. After aging and hydrophobic modification, it is dried using supercritical CO2 to achieve a density ≤95 kg / m³. 3 A lightweight silica aerogel felt with a thickness of ≤50mm that is soft and rollable; the thickness of the lightweight silica aerogel felt is positively correlated with the sound insulation, and it can be stress-free and fits into irregular curved surfaces inside the aircraft cabin.

[0011] In a preferred embodiment of the present invention, the original thickness of the flexible felt material matrix is ​​≤50mm.

[0012] In a preferred embodiment of the present invention, the solid content in the low-solids silica sol is controlled at 18-30 wt%.

[0013] In a preferred embodiment of the present invention, the thermal conductivity of the finished lightweight silica aerogel felt is ≤0.03W / (m·k).

[0014] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is: a method for preparing a lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft, comprising the following steps: S1. Preparation of flexible felt material matrix: S11. Raw material processing: Using reinforcing fiber substrate with a diameter of 5-11μm as raw material, it is processed into fluffy fiber by an opening machine; S12, Web Forming: The opened fibers are layered and laid out using a web forming machine to form a fluffy three-dimensional fiber web structure; S13. Needle Punching Reinforcement: The fiber web is repeatedly needled using a needle punching machine with barbed needles. The needle angle is 25-45°, the puncture frequency is 500-800 times / min, and the needle penetration depth is 60-80% of the fiber web thickness. It includes at least three gradient needle punching processes: the first needle punching: needle density of 50-80 needles / cm², penetration depth of 60-70%; the second needle punching: needle density of 80-120 needles / cm², penetration depth of 70-75%; and the third needle punching: needle density of 120-150 needles / cm², penetration depth of 75-100%. This causes the fibers in the fiber web to become entangled with each other, forming fiber bundles that are "pins" driven into the fiber web to produce low-density needle-punched felt. S2. Preparation of alkyd solution: Weigh deionized water and add it to a sealed hydrolysis stirring vessel. Add an appropriate amount of dilute hydrochloric acid and an appropriate amount of 95% ethanol. Stir well to form an alkyd solution for silane hydrolysis. S3. Preparation of low solid content silica sol: Add silane to a closed hydrolysis stirring vessel with a prepared alkyd solution, start the stirring vessel, and stir and hydrolyze for 5-8 hours to obtain a nano-sized hydrolyzed silica sol liquid with abundant silica molecular groups, i.e., low solid content silica sol, and transport it to the microwave curing wet gel mat production line for later use. S4. Preparation of alkaline catalyst solution: Weigh deionized water and add it into a closed hydrolysis stirring vessel. Add an appropriate amount of sodium hydroxide and caustic soda, and then add 95% ethanol. Stir for 1-4 hours until uniform to form an alkaline catalyst solution. Transfer the solution to the microwave curing wet gel felt production line for later use. S5. Formation of wet gel composite: The low-solid-content silica sol obtained in step S3 is impregnated with the low-density needle-punched felt obtained in step S1, and the wet gel composite is formed by gelation treatment using the alkaline catalyst solution prepared in step S4. S6. Microwave-assisted rapid gel curing: Place the fiberglass mat impregnated with low solid content silica sol in a microwave production line. Use microwave energy to accelerate the sol-gel conversion. The microwave curing time is 0.5-15 minutes, so that the rapid gelation and solidification can be formed into a wet gel mat. S7. Aging and Solvent Replacement: Fix the wet gel mat in a special fixture and suspend it in an aging chamber for 12-24 hours for gel aggregation reaction; then soak it in 95% ethanol in the aging chamber for 12-24 hours to fully replace the water produced by the gel reaction. S8. Hydrophobic modification treatment: The wet gel felt is subjected to hydrophobic modification treatment for 12-48 hours in the aging chamber to perform surface hydrophobic modification. S9. The modified wet aerogel mat is fixed in a special fixture and suspended in a supercritical drying vessel. It is then dried using supercritical CO2 fluid extraction to obtain a lightweight silica aerogel mat with a density ≤95 kg / m³. 3 .

[0015] In a preferred embodiment of the present invention, the reinforcing fiber substrate in step S11 includes at least one of glass fiber, chopped strands of electronic yarn, seaweed fiber, high silica fiber, quartz fiber, basalt fiber, pre-oxidized fiber, carbon fiber, polyester fiber, electrospun fiber, and glass fiber meltblown cotton.

[0016] In a preferred embodiment of the present invention, the silane used in the low-solids silica sol in step S3 is at least one of methyltrimethoxysilane, tetraethyl orthosilicate, and dimethyldimethoxysilane.

[0017] In a preferred embodiment of the present invention, the ethanol is industrial ethanol with a purity ≥95.0 wt%, the CO2 has a purity ≥99.0 wt%, the dilute hydrochloric acid is industrial synthetic hydrochloric acid with a mass fraction of 31.0 ± 0.5 wt% based on hydrochloric acid, the sodium hydroxide is industrial sodium hydroxide with a purity ≥97.0 wt%, and the deionized water has a resistivity ≥12.0 MΩ·cm at 25°C.

[0018] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide an application of lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft. The lightweight silica aerogel felt material can also be used for sound insulation, noise reduction and heat insulation engineering in rotorcraft, flying cars, seaplanes and turbofan engine aircraft.

[0019] The beneficial effects of this invention are: With a density of ≤95Kg / m³, it is significantly lightweight, and its sound insulation, noise reduction, and thermal insulation performance far exceed those of traditional materials; It is flexible and bendable, with high strength, and can closely fit the curved surfaces of the aircraft cabin, making it easy to install and providing excellent fit. In terms of safety, the flame retardancy, toxicity, smoke density, and flammability of the radiant panels all meet aviation standards, ensuring flight safety. At the same time, its high water repellency ensures that it does not increase in weight over long-term use and maintains stable performance; Furthermore, the material can be adapted to different noise scenarios in different parts of the aircraft by adjusting its thickness. When applied to the interior walls of the aircraft cabin, it has a good sound insulation and noise reduction effect. After being applied to the aircraft, the material can significantly reduce noise hazards, provide a comfortable environment for the crew and passengers, improve the crew's work efficiency and flight mission performance, and enhance the aircraft's market competitiveness. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a flowchart of the preparation method of the lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft, according to the present invention. Figure 2 This is a cross-sectional view of a preferred embodiment of the lightweight silica aerogel felt for sound insulation and noise reduction in aircraft. Figure 3This is an electron scanning microscope image of the lightweight silica aerogel felt prepared in Example 2 of the present invention, with a scale bar of 200 μm and a magnification of 290x. Figure 4 This is an electron scanning microscope image of the lightweight silica aerogel mat prepared in Example 2 of the present invention, with a scale bar of 5 μm and a magnification of 15,000x. Figure 5 This is an electron scanning microscope image of the lightweight silica aerogel mat prepared in Example 2 of the present invention, with a scale bar of 100 nm and a magnification of 500,000 times. Figure 6 This is a sound insulation curve of a lightweight silica aerogel felt with a thickness of T8mm according to Embodiment 2 of the present invention. Figure 7 This is a sound insulation curve of a lightweight silica aerogel felt with a thickness of T12mm according to Embodiment 3 of the present invention. The components in the attached diagram are labeled as follows: 1. Flexible felt material matrix; 2. Low solid content silica sol. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] This invention addresses the specific application needs of aircraft by providing a lightweight silica aerogel felt and its series of products. When applied to the sound insulation and noise reduction of aircraft cabin interior walls, actual verification tests show that the material exhibits excellent sound insulation and noise reduction effects, meeting the stringent requirements of aircraft cabins for sound insulation and noise reduction.

[0024] Please see Figure 1-7 : Example 1:

[0025] A lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft includes: a flexible felt material matrix and silica aerogel filling the gaps between the fibers of the matrix.

[0026] By impregnating flexible felt material matrices of different densities with silica sols of varying solid contents to achieve gel solidification and matching, and then aging and hydrophobically modifying them before supercritical CO2 drying, lightweight silica aerogel felts of different densities can be formed, with a density ≤360 kg / m³. 3 .

[0027] The flexible felt material matrix is ​​preferably made of low-density flexible felt material. The low-density flexible felt material matrix is ​​impregnated in silica sol, and then heated to allow the low-solids silica sol to gel and solidify within the interfiber spaces of the matrix, forming a wet gel felt. After aging and hydrophobic modification, it is dried using supercritical CO2 to form a density ≤95Kg / m³. 3 A soft, rollable, lightweight silica aerogel felt with a thickness of ≤50mm.

[0028] Among them, the thickness of lightweight silica aerogel felt is positively correlated with the sound insulation, and it can be stress-free and fits into the irregular curved surfaces inside the aircraft cabin.

[0029] Furthermore, the flexible felt material matrix 1 preferably uses reinforcing fibers as the substrate. The reinforcing fiber substrate includes at least one of glass fiber, chopped strands of electronic yarn, seaweed fiber, high-silica fiber, quartz fiber, basalt fiber, pre-oxidized fiber, carbon fiber, polyester fiber, electrospun fiber, and glass fiber meltblown cotton. In this embodiment, glass fiber is preferably used as the substrate.

[0030] The preferred filler material is silica sol 2 with a low solid content, which is controlled within the range of 18-30 wt%.

[0031] The thermal conductivity of the above-mentioned lightweight silica aerogel felt material is ≤0.03W / (m·k), and more preferably ≤0.024W / (m·k).

[0032] The original thickness of the aforementioned lightweight silica aerogel felt material is ≤50mm.

[0033] The sound insulation of the aforementioned lightweight silica aerogel felt increases with the thickness of the material. By adjusting the thickness to suit different noise scenarios, it can be used in aircraft interior sound insulation and heat insulation design engineering applications.

[0034] The raw materials used in the preparation process may also include: methyltrimethoxysilane, tetraethyl orthosilicate, industrial ethanol, dimethyldimethoxysilane, industrial liquid carbon dioxide (CO2), industrial synthetic hydrochloric acid, industrial sodium hydroxide, and deionized water.

[0035] The materials used in the above preparation process are required to have the following purity: methyltrimethoxysilane ≥ 99.0 wt%, silica content in tetraethyl orthosilicate ≥ 28.0 ± 0.5 wt%, industrial ethanol ≥ 95.0 wt%, dimethyldimethoxysilane ≥ 95.0 wt%, industrial liquid carbon dioxide (CO2) ≥ 99.0 wt%, industrial synthetic hydrochloric acid ≥ 31.0 ± 0.5 wt% (based on hydrochloric acid content), industrial sodium hydroxide ≥ 97.0 wt%, and deionized water ≥ 12.0 MΩ·cm at 25°C.

[0036] Methyltrimethoxysilane meets the chemical purity standard of GB / T 35501-2017, tetraethyl orthosilicate meets the chemical purity standard of HG / T5461-2018, industrial ethanol meets the chemical purity standard of GB / T 394.1-2008, dimethyldimethoxysilane meets the chemical purity standard of T / FSI 072-2021, industrial liquid carbon dioxide (CO2) meets the chemical purity standard of GB / T 6052-2011, industrial synthetic hydrochloric acid meets the chemical purity standard of GB 320-2006, industrial sodium hydroxide meets the chemical purity standard of GB / T 209-2006, fiberglass mat meets the standard of GB / T26733 2011, and the resistivity of deionized water is tested according to the standard GB11446-1-2013.

[0037] The lightweight silica aerogel felt material of this embodiment can meet the requirements of sound insulation and heat insulation engineering on aircraft, and is an aerogel inorganic material that meets the requirements of aerospace.

[0038] The low-frequency characteristics of lightweight silica aerogel felt make it an ideal acoustic delay or high-efficiency sound insulation material. Its internal structure is rich in interconnected pores that penetrate the surface: when sound waves are incident, some are reflected at the surface, while others propagate into the material. During propagation, the vibration of the sound waves causes air movement within the pores or gaps, generating friction with the pore walls. Air near the pore walls and fiber surface is less prone to movement due to viscosity; under the combined action of friction and viscosity, a large amount of acoustic energy is converted into heat and dissipated.

[0039] Crucially, the micropore size of lightweight silica aerogel mats (typically smaller than the mean free path of air molecules, approximately 75 nm) endows them with unique acoustic properties; silica aerogels possess a maximum acoustic impedance of 10⁻⁶. 6 kg / (m 2 ⋅s).

[0040] At this scale, the air molecules within the pores almost completely lose their convective heat conduction capabilities and are in a relatively "static" state. The energy of the incident noise wave is largely consumed by these confined air molecules, which are unable to effectively transfer heat, through a strong viscosity effect, thus exhibiting excellent sound insulation and noise reduction effects on a macroscopic scale.

[0041] Table 1: Test data of lightweight silica aerogel felt material:

[0042] Table 2: Performance comparison between traditional aerogel felt and lightweight silica aerogel felt, using fiberglass as the substrate:

[0043] According to Tables 1 and 2: The lightweight silica aerogel felt material of this invention has good flame retardant properties, meets the requirements of HB 5469-2014 for 60-second vertical burning, meets the requirements of HB 7066-2022 for material toxicity, meets the requirements of Part V of Appendix F of Civil Aviation Regulation CCAR 25, and meets the requirements of Part VI of Appendix F of Regulation CCAR 25 for flammability of the radiant panel. The lightweight silica aerogel felt has met customer requirements in terms of 60-second vertical burning, smoke toxicity, smoke density, and flammability of the radiant panel, as tested by the Civil Aviation Administration of China Testing Center. With a hydrophobicity >99% (GB / T 10299-2011), the material has a high hydrophobicity and its closed-cell nanostructure effectively blocks liquid water from penetrating. The material does not absorb water and does not increase the weight of the aircraft during long-term use. Using finer glass fiber reinforced fibers as raw materials, the structural characteristics of the base felt are optimized. The flexible felt material matrix formed by opening, web laying and gradient needle punching processes has a significantly reduced unit volume mass, laying a core foundation for the lightweight of the finished product. At the same time, by combining precise impregnation with low solid content silica sol and microwave gel curing process, the amount of aerogel filling is effectively reduced, and the aerogel solid content is controlled at 21-30Wt%, achieving a balance between lightweight substrate and aerogel loading. The final lightweight silica aerogel felt has a density as low as ≤95kg / m³, which is far lower than that of conventional aerospace noise reduction materials, meeting the stringent requirements for lightweight design.

[0044] This aerogel felt is lightweight, soft, and rollable, conforming to surface changes and offering excellent fit. It can closely follow the complex curved contours of the aircraft interior, ensuring a seamless fit with the airframe structure and effectively preventing noise reduction performance degradation due to installation gaps.

[0045] Its comprehensive performance makes it suitable not only for the internal sound insulation and noise reduction engineering of traditional turbofan engine aircraft, but also for new aviation equipment such as rotorcraft, flying cars, and seaplanes, as well as cabin sound insulation of large ships, providing efficient and lightweight solutions for acoustic environment management in multiple scenarios.

[0046] Example 2: In this embodiment, a lightweight silica aerogel felt with a thickness of T8 mm is prepared according to the following preparation method: S1. Preparation of flexible felt material matrix: S11. Raw material processing: Select glass fiber with a diameter of 7μm as raw material and prepare it into fluffy fiber by opening machine; S12, Web Forming: The opened fibers are layered and laid out using a web forming machine to form a fluffy three-dimensional fiber web structure with an initial thickness of 12mm, leaving a compression allowance; S13. Needle Punching Reinforcement: The fiber web is repeatedly needled using a needle punching machine with a hook angle of 30°. The puncture frequency is set to 600 times / min, and the needle penetration depth is controlled to 70% of the fiber web thickness. Three gradient needle punches are performed. For the first acupuncture, the needle density was set at 60 needles / cm², the penetration depth was 65%, and it was compressed to about 8mm. The second acupuncture was performed with a needle density of 100 needles / cm², a penetration depth of 72%, and compressed to approximately 7mm. The third acupuncture session increased the needle density to 130 needles / cm², achieving a penetration depth of 78%, which was reduced to approximately 5mm. By repeatedly needle-punching, the fibers in the fiber web become entangled with each other, forming fiber bundles that are then driven into the fiber web to create a low-density needle-punched felt. At this point, the initial thickness is about 5mm, with space reserved for expansion by sol filling.

[0047] S2, Preparation of alcoholic acid solution: Weigh deionized water and add it to a sealed hydrolysis stirred tank. Add an appropriate amount of dilute hydrochloric acid and an appropriate amount of 95% ethanol. Stir well to form an alcoholic acid solution for silane hydrolysis.

[0048] S3. Preparation of low-solids-content silica sol: In a sealed hydrolysis stirred tank containing a pre-prepared alkyd solution, methyltrimethoxysilane with a purity ≥99.0wt% is added. The stirred tank is started and hydrolysis is carried out for 6 hours to obtain a nano-sized hydrolyzed silica sol liquid rich in silica molecular groups, i.e., a low-solids silica sol with a solid content of 21-30%. This sol is then transported to a microwave-cured wet gel mat production line for later use.

[0049] S4. Preparation of alkaline catalyst solution: Deionized water was weighed and added to a sealed hydrolysis stirring vessel, along with an appropriate amount of sodium hydroxide and caustic soda, and then 95% ethanol. The mixture was stirred for 2 hours until homogeneous to form an alkaline catalyst solution. This solution was then transferred to a microwave-cured wet gel felt production line for later use.

[0050] S5, Formation of wet gel complex: The low-solids silica sol obtained in step S3 is used to impregnate the low-density needle-punched felt obtained in step S1, ensuring that the sol fully penetrates into the fiber gaps. After impregnation, the thickness is restored to 8±0.5 mm. Then, the alkaline catalyst solution prepared in step S4 is used for gelation treatment, and the reaction is carried out at room temperature for 1 hour to form a wet gel composite.

[0051] S6. Microwave-assisted rapid gel curing: Fiberglass mat impregnated with low-solids silica sol was placed in a microwave production line and microwave treatment time was set to 10 minutes. Microwave energy was used to accelerate the sol-gel conversion, quickly gelled and solidified into a wet gel mat with a stable thickness of 8±0.3 mm.

[0052] S7, Aging and Solvent Replacement: The wet gel mat is fixed in a special clamp and suspended in an aging chamber for 12-24 hours for gel aggregation reaction; then it is soaked in 95% ethanol in the aging chamber for 18 hours to fully replace the water produced by the gel reaction.

[0053] S8, hydrophobic modification treatment: The wet gel felt was subjected to hydrophobic modification treatment in an aging chamber for 12-48 hours. An appropriate amount of hydrophobic agent was added to the aging chamber, and the surface was treated at 60℃ for 24 hours to perform surface hydrophobic modification.

[0054] S9, Supercritical Drying: The modified wet aerogel felt was fixed in a special fixture and suspended into a supercritical drying kettle. It was then dried by supercritical CO2 fluid extraction. The drying temperature was set at 35℃, the pressure at 7.5MPa, and the drying time at 6h. The final product, lightweight silica aerogel felt, had a thickness of 8±0.2mm, a density of ≤95kg / m³, and a thermal conductivity of ≤0.024W / (m·k).

[0055] Example 3: In this embodiment, a lightweight silica aerogel felt with a thickness of T12 mm is prepared according to the following preparation method: S1. Preparation of flexible felt material matrix: S11. Raw material processing: Select glass fiber with a diameter of 10μm as raw material and prepare it into fluffy fiber by opening machine; S12. Web Forming: The opened fibers are layered and laid out using a web forming machine to form a fluffy three-dimensional fiber web structure with an initial thickness of 18mm, leaving a compression allowance. S13. Needle Punching Reinforcement: The fiber web is repeatedly needled using a needle punching machine with a hook angle of 30°. The puncture frequency is set to 600 times / min, and the needle penetration depth is controlled to 70% of the fiber web thickness. Three gradient needle punches are performed. For the first acupuncture, the needle density was set at 70 needles / cm², the penetration depth was 65%, and it was compressed to about 16mm. The second acupuncture was performed with a needle density of 110 needles / cm², a penetration depth of 72%, and a compression to approximately 12mm. The third acupuncture session increased the needle density to 140 needles / cm², achieving a penetration depth of 78%, which was reduced to approximately 10mm. By repeatedly needle-punching, the fibers in the fiber web become entangled with each other, forming fiber bundles that are "pins" driven into the fiber web to produce low-density needle-punched felt. At this point, the initial thickness is about 10mm, leaving space for expansion filled by sol.

[0056] S2, Preparation of alcoholic acid solution: Weigh deionized water and add it to a sealed hydrolysis stirred tank. Add an appropriate amount of dilute hydrochloric acid and an appropriate amount of 95% ethanol. Stir well to form an alcoholic acid solution for silane hydrolysis.

[0057] S3. Preparation of low-solids-content silica sol: In a sealed hydrolysis stirred tank containing a pre-prepared alkyd solution, dimethyldimethoxysilane with a purity of 95.0 wt% was added. The stirred tank was started and the hydrolysis was carried out for 6 hours to obtain a nano-sized hydrolyzed silica sol liquid rich in silica molecular groups, i.e., a low-solids silica sol with a solid content of 21-30%. This sol was then transported to a microwave-cured wet gel mat production line for later use.

[0058] S4. Preparation of alkaline catalyst solution: Deionized water was weighed and added to a sealed hydrolysis stirring vessel, along with an appropriate amount of sodium hydroxide and caustic soda, and then 95% ethanol. The mixture was stirred for 2 hours until homogeneous to form an alkaline catalyst solution. This solution was then transferred to a microwave-cured wet gel felt production line for later use.

[0059] S5, Formation of wet gel complex: The low-solids silica sol obtained in step S3 is used to impregnate the low-density needle-punched felt obtained in step S1, ensuring that the sol fully penetrates into the fiber gaps. After impregnation, the thickness is restored to 12±0.5 mm. Then, the alkaline catalyst solution prepared in step S4 is used for gelation treatment, and the reaction is carried out at room temperature for 1 hour to form a wet gel composite.

[0060] S6. Microwave-assisted rapid gel curing: Fiberglass mat impregnated with low-solids silica sol was placed in a microwave production line and microwave treatment time was set to 10 minutes. Microwave energy was used to accelerate the sol-gel conversion, quickly gelled and solidified into a wet gel mat with a stable thickness of 12±0.3 mm.

[0061] S7, Aging and Solvent Replacement: The wet gel mat is fixed in a special clamp and suspended in an aging chamber for 12-24 hours for gel aggregation reaction; then it is soaked in 95% ethanol in the aging chamber for 18 hours to fully replace the water produced by the gel reaction.

[0062] S8, hydrophobic modification treatment: The wet gel felt was subjected to hydrophobic modification treatment in an aging chamber for 12-48 hours. An appropriate amount of hydrophobic agent was added to the aging chamber, and the surface was treated at 60℃ for 24 hours to perform surface hydrophobic modification.

[0063] S9, Supercritical Drying: The modified wet aerogel felt was fixed in a special fixture and suspended into a supercritical drying kettle. It was then dried by supercritical CO2 fluid extraction. The drying temperature was set at 35℃, the pressure at 7.5MPa, and the drying time at 24h. The final product, lightweight silica aerogel felt, had a thickness of 12±0.2mm, a density of ≤95kg / m³, and a thermal conductivity of ≤0.024W / (m·k).

[0064] Samples were taken from the lightweight silica aerogel felts with thicknesses of T8mm and T12mm in Examples 2 and 3, respectively, and the sound insulation was tested.

[0065] I. Test Method: The sound insulation characteristics of aerogel felt were determined by the standing wave tube test method according to GB / T18696.2-2002.

[0066] II. Testing Standard: Based on GB / T18696.2-2002 "Measurement of Sound Absorption Coefficient and Acoustic Impedance in Acoustic Impedance Tubes, Part 2: Transfer Function Method". III. Test Description: 1. Sample preparation: Prepare two sample sizes, with diameters of φ100mm and φ30mm respectively; 2. Test frequency range: φ100mm specification sample: test frequency range 50-1600Hz, used for low frequency sound insulation performance analysis; φ30mm specification sample: The test frequency range is 800-6300Hz, covering the mid-to-high frequency band acoustic response characteristic testing.

[0067] The sound insulation test results for lightweight silica aerogel felts with thicknesses of 8mm and 12mm are shown in Tables 3 and 4, respectively. The sound insulation data curves for these two thicknesses are shown in the figures below. Figure 6 and Figure 7 .

[0068] Table 3. Sound insulation test record of lightweight silica aerogel felt with a thickness of 8mm:

[0069] Table 4. Sound insulation test record of lightweight silica aerogel felt with a thickness of T12mm:

[0070] Based on the above, we can conclude that: Low-frequency advantage (<200Hz): T12mm achieves a sound insulation of 15.8dB at 100Hz, which is significantly higher than T8mm (8.5dB), indicating that thickening can improve low-frequency isolation capability. This characteristic can be used for controlling rumbling noise in aircraft cabins. Mid-to-high frequency stability (500-6300Hz): The sound insulation of both is maintained at 12-19dB, and T12mm still reaches 18.7dB at 6300Hz, which meets the requirements of wideband noise reduction. The T12mm thickness provides an average sound insulation improvement of 2-4dB compared to the T8mm thickness (e.g., 18.492dB vs. 15.627dB at 5000Hz), demonstrating that adjusting the thickness allows for flexible adaptation to different noise scenarios and provides space for customization of different parts of the aircraft (such as cabin walls and engine compartments).

[0071] The beneficial effects of the lightweight silica aerogel felt material of this invention for sound insulation and noise reduction in aircraft are: Extremely low density: The material density is ≤95Kg / m³, with significant lightweight characteristics, which is suitable for the stringent weight reduction requirements of the aviation industry. It can be directly applied to aircraft sound insulation and heat insulation projects. Its sound insulation and heat insulation performance far exceeds that of traditional materials such as melamine foam board, polyimide foam material, and glass wool. The material is soft and bendable, and it does not break when bent. It has excellent strength and can adapt to the curved surface changes of the aircraft cabin. There is no internal stress release problem. It has a high degree of fit with the curved surface of the cabin, which facilitates the construction of interior curved surfaces, reduces the difficulty and cost of installation, and has excellent installation fit. The 60S vertical combustion performance meets the requirements of the HB 5469-2014 standard, has excellent fire resistance, low toxicity and low smoke density, the flammability of the radiant panel meets the requirements of CCAR25 Appendix F Part VI, and the radiant flame retardancy meets aerospace requirements. The material has a high hydrophobicity and does not absorb water, thus avoiding weight increase due to water absorption during long-term use of the aircraft and maintaining performance stability. It was used for sound insulation and noise reduction of the interior walls of aircraft cabins. Verification tests have shown that it has achieved good sound insulation and noise reduction effects, meeting the requirements for sound insulation and noise reduction of aircraft. By adjusting the thickness, it can be flexibly adapted to different noise scenarios, providing space for customization of different parts of the aircraft (such as cabin walls and engine compartments). Enhancing aircraft competitiveness: When this material is applied to the engineering of sound insulation and noise reduction in the aircraft interior, it will significantly reduce the harm of noise to pilots and passengers, ensuring the physical and mental health of pilots and passengers and a comfortable flight environment experience. This enables flight crew members to carry out their work efficiently with good hearing, concentration, clear communication of commands, and quick response, significantly improving crew work efficiency and flight mission execution effectiveness.

[0072] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft cabins, characterized in that, include: Flexible felt material matrix; Silica aerogel that fills and solidifies within the gaps between the matrix fibers; By impregnating flexible felt material matrices of different densities with silica sols of varying solid contents to achieve gel solidification and matching, and then aging and hydrophobically modifying them before supercritical CO2 drying, lightweight silica aerogel felts of different densities can be formed, with a density ≤360 kg / m³. 3 .

2. The lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft as described in claim 1, characterized in that, The flexible felt material matrix is ​​made of low-density flexible felt material. A low-density flexible felt material matrix is ​​impregnated in silica sol. Heat treatment causes the low-solids silica sol to gel and solidify within the interfiber spaces of the matrix, forming a wet gel felt. After aging and hydrophobic modification, it is dried using supercritical CO2 to achieve a density ≤95 kg / m³. 3 Lightweight, flexible silica aerogel felt with a thickness of ≤50mm; Among them, the thickness of lightweight silica aerogel felt is positively correlated with the sound insulation, and it can be stress-free and fits into the irregular curved surfaces inside the aircraft cabin.

3. The lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft as described in claim 1, characterized in that, The original thickness of the flexible felt material matrix is ​​≤50mm.

4. The lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft as described in claim 2, characterized in that, The solid content in the low-solids silica sol is controlled at 18-30 wt%.

5. The lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft as described in claim 1, characterized in that, The thermal conductivity of the finished lightweight silica aerogel felt is ≤0.03W / (m·k).

6. The method for preparing the lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft according to claim 1, characterized in that, Includes the following steps: S1. Preparation of flexible felt material matrix: S11. Raw material processing: Using reinforcing fiber substrate with a diameter of 5-11μm as raw material, it is processed into fluffy fibers by an opening machine; S12, Web Forming: The opened fibers are layered and laid out using a web forming machine to form a fluffy three-dimensional fiber web structure; S13. Needle-punching reinforcement: The fiber web is repeatedly needle-punched using a needle-punching machine with barbed needles, causing the fibers in the fiber web to entangle with each other and form fiber bundles. These "pins" are then driven into the fiber web to produce low-density needle-punched felt. S2, Preparation of alcoholic acid solution: Weigh deionized water and add it to a sealed hydrolysis stirring vessel. Add an appropriate amount of dilute hydrochloric acid and an appropriate amount of 95% ethanol. Stir well to form an alcoholic acid solution for silane hydrolysis. S3. Preparation of low-solids-content silica sol: In a closed hydrolysis stirred tank with a pre-prepared alkyd solution, silane is added, the stirred tank is started, and the mixture is stirred and hydrolyzed for 5-8 hours to obtain a nano-sized hydrolyzed silica sol liquid with abundant silica molecular groups, i.e., a low-solids silica sol, which is then transported to a microwave-cured wet gel mat production line for later use. S4. Preparation of alkaline catalyst solution: Weigh deionized water and add it to a sealed hydrolysis stirring vessel. Add an appropriate amount of sodium hydroxide and caustic soda, then add 95% ethanol. Stir for 1-4 hours until homogeneous to form an alkaline catalyst solution. Transfer the solution to the microwave-cured wet gel felt production line for later use. S5, Formation of wet gel complex: The low-solid-content silica sol obtained in step S3 is impregnated with the low-density needle-punched felt obtained in step S1, and then gelled using the alkaline catalyst solution prepared in step S4 to form a wet gel composite. S6. Microwave-assisted rapid gel curing: Fiberglass mat impregnated with low-solids silica sol is placed in a microwave production line. Microwave energy is used to accelerate the sol-gel conversion, so that the sol and gel can be rapidly gelled and solidified into a wet gel mat. The microwave curing process takes 0.5-15 minutes. S7, Aging and Solvent Replacement: The wet gel mat is fixed in a special clamp and suspended in an aging chamber for a gel aggregation reaction of 12-24 hours; then it is soaked in 95% ethanol in the aging chamber for 12-24 hours to fully replace the water produced by the gel reaction. S8, hydrophobic modification treatment: The wet gel mat was subjected to hydrophobic modification treatment in the aging chamber for 12-48 hours to perform surface hydrophobic modification. S9, Supercritical Drying: The modified wet aerogel mat was fixed in a special fixture and suspended in a supercritical drying vessel. It was then dried using supercritical CO2 fluid extraction to obtain a lightweight silica aerogel mat with a density ≤95 kg / m³. 3 .

7. The method for preparing lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft according to claim 6, characterized in that, The reinforcing fiber substrate in step S11 includes at least one of glass fiber, chopped strands of electronic yarn, seaweed fiber, high silica fiber, quartz fiber, basalt fiber, pre-oxidized fiber, carbon fiber, polyester fiber, electrospun fiber, and glass fiber meltblown cotton.

8. The method for preparing lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft according to claim 6, characterized in that, The silane used in the low-solids silica sol in step S3 is at least one of methyltrimethoxysilane, tetraethyl orthosilicate, and dimethyldimethoxysilane.

9. The method for preparing the lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft according to claim 8, characterized in that, The ethanol is industrial ethanol with a purity ≥95.0 wt%, the CO2 has a purity ≥99.0 wt%, the dilute hydrochloric acid is industrial synthetic hydrochloric acid with a mass fraction of 31.0 ± 0.5 wt% (based on hydrochloric acid), the sodium hydroxide is industrial sodium hydroxide with a purity ≥97.0 wt%, and the deionized water has a resistivity ≥12.0 MΩ·cm at 25°C.

10. The application of the lightweight silica aerogel felt material for sound insulation and noise reduction in aircraft as described in claim 1, characterized in that, Lightweight silica aerogel felt material can also be used for sound insulation, noise reduction, and heat insulation projects inside rotorcraft, flying cars, seaplanes, and turbofan engine aircraft.

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