Damping material, damping structure and preparation method and application thereof

Abstract

The application belongs to the field of aviation technology, and particularly relates to a damping material, a damping structure and a preparation method and application thereof. The damping material comprises the following mass ratio of each chemical raw material: ethylene vinyl acetate rubber A: ethylene vinyl acetate rubber B: ethylene vinyl acetate rubber C=(3-12):(6-14):(3-7); wherein the mass percentage content w of vinyl acetate in the ethylene vinyl acetate rubber A satisfies: 65%<=w<=75%; the mass percentage content w of vinyl acetate in the ethylene vinyl acetate rubber B satisfies: 75%<w<=85%; and the mass percentage content w of vinyl acetate in the ethylene vinyl acetate rubber C satisfies: 85%<w<92%. Each EVM rubber satisfies the above mass ratio range, the effective damping temperature range of the damping material is -10 DEG C to 50 DEG C, the damping material in the effective damping temperature range expands the effective damping temperature range of the EVM rubber, and the application also comprises adding other additives to the base material composed of each EVM rubber, which is beneficial to meeting the requirements of the aviation transport machine on flame retardancy, low smoke property and non-toxicity and other aspects under the premise of the preparation process.

Description

Technical Field

[0001] This application belongs to the field of aerospace technology, specifically relating to a damping material, damping structure, its preparation method and application. Background Technology

[0002] Modern civil aircraft are constantly evolving towards safety, efficiency, low carbon emissions, environmental friendliness, and smooth, comfortable operation. Compared to less perceptible indicators like safety and efficiency, passenger comfort is the most subjectively felt aspect of a journey, making it a key focus of optimization during aircraft design and manufacturing. Reducing cabin noise levels is a crucial means of enhancing passenger comfort. Through long-term research and design, aircraft have minimized aerodynamic noise, jet noise, and turbine vibration. Aircraft designers have focused considerable effort on the acoustic packaging of the cabin structure. For example, interior trim panels act as acoustic barriers; by constraining and damping them, vibration and sound energy transmission and radiation into the cabin can be reduced. However, good interior trim panels, in addition to excellent acoustic design, also need to meet certain requirements: a sufficiently wide effective damping temperature range, flame retardancy, low smoke emission, and non-toxicity. Therefore, providing a damping material with a wide effective damping temperature range, good performance in all aspects, and easy-to-manufacture manufacturing process is a problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0003] The technical objective of this application is to at least solve the problems that, under the premise of the manufacturing process, the interior panels of existing aviation equipment cannot achieve a relatively wide effective damping temperature range, and cannot simultaneously meet the performance requirements of materials in terms of mechanical properties, damping properties, flame retardancy, low smoke and non-toxicity.

[0004] This objective is achieved through the following technical solutions:

[0005] In a first aspect, this application provides a damping material comprising the following chemical raw materials in the following mass ratio:

[0006] Ethylene vinyl acetate rubber A: Ethylene vinyl acetate rubber B: Ethylene vinyl acetate rubber C = (3-12):(6-14):(3-7);

[0007] The mass percentage w of vinyl acetate in the ethylene vinyl acetate rubber A satisfies: 65% ≤ w ≤ 75%;

[0008] The mass percentage w of vinyl acetate in the ethylene vinyl acetate rubber B satisfies: 75% < w ≤ 85%;

[0009] The mass percentage w of vinyl acetate in the ethylene vinyl acetate rubber C satisfies: 85% < w < 92%.

[0010] This application selects to design and form the above-mentioned damping material, the effective damping temperature range of which is conducive to achieving -10℃ to 50℃. The effective damping temperature range performance index includes the conventional meaning and measurement method in the art, and it is correlated with the glass transition temperature Tg of the damping material. The damping material that meets the requirements of the effective damping temperature range expands the effective damping temperature range of EVM rubber and is suitable for the operating temperature range of interior panels of civil aircraft in aviation equipment.

[0011] In some embodiments of this application, the ratio of ethylene vinyl acetate rubber A: ethylene vinyl acetate rubber B: ethylene vinyl acetate rubber C is (4-10): (8-13): (4-6).

[0012] In some embodiments of this application, the mass percentage w of vinyl acetate in the ethylene vinyl acetate rubber A satisfies: 67% ≤ w ≤ 72%.

[0013] In some embodiments of this application, the mass percentage w of vinyl acetate in the ethylene vinyl acetate rubber B satisfies: 76% < w ≤ 83%.

[0014] In some embodiments of this application, the mass percentage w of vinyl acetate in the ethylene vinyl acetate rubber C satisfies: 88% < w < 92%.

[0015] In some embodiments of this application, the material further comprises one or more combinations of flame retardants, silane coupling agents, and crosslinking agents.

[0016] In some embodiments of this application, the flame retardant comprises a first flame retardant and a second flame retardant in a mass ratio of (4-6):(9-11), wherein the first flame retardant is an inorganic metal oxide flame retardant and the second flame retardant is a halogen-containing flame retardant.

[0017] In some embodiments of this application, the silane coupling agent is vinylsilane.

[0018] In some embodiments of this application, the crosslinking agent is an organic peroxide vulcanizing agent, which includes one or a combination of two of bis-tert-butyl peroxide dicumyl peroxide and dicumyl peroxide.

[0019] In some embodiments of this application, the effective damping temperature range of the material is -10℃ to 50℃, preferably 5℃ to 40℃, and more preferably 10℃ to 30℃.

[0020] The EVM rubber selected in this application has low smoke emission, toxicity, and smoke corrosivity, making it an ideal flame-retardant rubber. Adding various additives with different performance effects to the EVM rubber, and synergistically adjusting their dosage, ensures that the material possesses excellent mechanical and damping properties, as well as good flame retardancy, low smoke emission, and non-toxicity.

[0021] A second aspect of this application is to provide a damping structure comprising a constrained damping layer;

[0022] The constraint damping layer comprises alternately stacked constraint layers and damping layers, wherein the number of constraint layers and damping layers is the same;

[0023] The constraint damping layer also includes a pressure-sensitive adhesive layer located on the surface of the outermost damping layer;

[0024] The damping layer comprises a material made using the material described in the first aspect;

[0025] The constraint layer is obtained by surface roughening of carbon fiber reinforced epoxy resin.

[0026] In some embodiments of this application, an adhesive is further disposed between the constraint layer and the damping layer.

[0027] In some embodiments of this application, the number of alternating stacking times is 1 to 5.

[0028] In some embodiments of this application, the damping layer satisfies one or more combinations of the following properties:

[0029] (1) Rubber tensile strength ≥15MPa;

[0030] (2) Elongation at break ≥200%;

[0031] (3) Tear strength ≥18kN / m;

[0032] (4) At 23℃±2℃ and 10Hz~1000Hz, the maximum loss factor tanδmax≥1.2.

[0033] In some embodiments of this application, the flexural modulus of the carbon fiber reinforced epoxy resin is ≥40 GPa.

[0034] In some embodiments of this application, the pressure-sensitive adhesive layer is selected as a PET pressure-sensitive adhesive layer, and the adhesive strength of the PET pressure-sensitive adhesive layer is ≥70kPa.

[0035] In some embodiments of this application, the thickness of the constraint damping layer is ≤3.0 mm;

[0036] In some embodiments of this application, the thickness of the damping layer is greater than the thickness of the constraint layer, which is greater than the thickness of the pressure-sensitive adhesive layer.

[0037] A third aspect of this application is to provide a method for preparing a damping structure, the method comprising:

[0038] The materials described in the first aspect are mixed to form a compound, and the compound is calendered and preformed to form a damping layer preform.

[0039] The carbon fiber reinforced epoxy resin is subjected to surface roughening treatment, and an adhesive is applied to at least one side of the treated surface to provide a restraint layer;

[0040] Preheat the mold used to form the damping structure;

[0041] The coated constraint layer and damping layer blanks are alternately stacked into the mold and vulcanized to form a damping structure semi-finished product;

[0042] A pressure-sensitive adhesive layer is formed on the outermost damping layer surface of the semi-finished damping structure to obtain the damping structure.

[0043] In some embodiments of this application, the calendering and preform preparation are carried out in a rubber mixing mill, and the process is as follows:

[0044] Adjust the roller gap of the rubber mixing mill to meet the preset size of the constraint layer;

[0045] The compounded rubber is placed on the rubber mixing mill and re-mixed until the rubber sheet is soft and has a smooth surface;

[0046] After remelting, the rubber sheet is wrapped around the rollers to form a rubber sheet with uniform thickness. The thickness of the rubber sheet is tested. If the thickness of the rubber sheet does not meet the preset thickness of the damping layer, the roller gap of the rubber mixing mill is adjusted to meet the preset thickness.

[0047] This application selects to first pre-treat the surface of the constraint layer material (carbon fiber reinforced epoxy resin) to roughen the bonding surface, then apply a hot-curing adhesive using spraying technology, and precisely control the thickness and uniformity of the rubber layer compound using a calendering process. Next, by designing the mold position, the edges of each layer of carbon fiber reinforced epoxy resin are fixed and positioned with locating pins. The calendered blank is then cut, and a constraint layer coated with hot-curing adhesive on both sides is laid in the preheated mold. A locating frame is added, followed by a complete layer of rubber, then another constraint layer coated with hot-curing adhesive on both sides, and another locating frame is added. This process is repeated until the appropriate thickness is achieved, at which point the mold is closed and finally secured with locating pins. This design effectively controls the thickness of each layer in the vulcanized lightweight composite damping material and ensures that the lightweight multi-layer composite damping material does not warp during the molding process. Then, by matching the vulcanization conditions of the rubber layer (including vulcanization temperature, vulcanization pressure, and vulcanization time), the hot vulcanizing adhesive reacts chemically with the rubber layer and the constraint layer during the molding process, achieving a strong bond between the constraint layer and the rubber layer. Ultimately, the precision molding of the stacked constraint damping material can be achieved, and the excellent sound insulation, noise reduction, flame retardancy, low smoke, and non-toxic properties of the constraint damping material can be brought into play.

[0048] The fourth aspect of this application is to provide the use of the material described in the first aspect, or the structure described in the second aspect, or the structure obtained by the method described in the third aspect, in the manufacture of aerospace equipment, the aerospace equipment comprising interior panels of a civil transport aircraft;

[0049] Preferably, the interior trim panel includes any one or more of the following: ceiling, side wall panel, partition, kitchen structure, large cabinet, and storage box. Attached Figure Description

[0050] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0051] Figure 1 A schematic diagram of the structure of the constraint damping layer according to an embodiment of this application is shown.

[0052] Figure 2 A schematic flowchart illustrating the process for preparing the constrained damping layer according to an embodiment of this application is shown.

[0053] Figure 3 A schematic diagram of the structure of the constraint damping layer according to an embodiment of this application is shown.

[0054] The labels in the attached diagram are as follows:

[0055] 100. Constrained damping layer;

[0056] 101. Constraint Layer;

[0057] 102. Damping layer;

[0058] 103. Pressure-sensitive adhesive layer. Detailed Implementation

[0059] Currently, the constraint damping products of foreign manufacturer SMAC have been used in the foreign civil aircraft market for more than 20 years. After analyzing the composition of SMAC's constraint damping products for interior panels, it was found that the matrix component is butyl rubber, and the other fillers are difficult to analyze with testing instruments.

[0060] In recent years, China has also reported on the preparation of constrained damping materials by rubber blending. This method aims to broaden the glass transition range of polymer damping materials to achieve the goal of expanding the operating temperature range and frequency range of damping materials. However, conventional blending methods are not only complex and difficult to operate, but also sometimes fail to achieve the best performance of all aspects of the material.

[0061] Ethylene vinyl acetate rubber (EVM) is a copolymer of ethylene and vinyl acetate. EVM rubber possesses excellent aging resistance (maximum operating temperature up to 175℃), ozone / UV resistance, oil resistance, and good processability. It is commonly used in cable insulation, electrical components, sealing materials, medical devices, automotive parts, shock-absorbing materials, and interior and exterior automotive trim. The vinyl acetate (VA) content in EVM rubber ranges from approximately 40% to 90% by mass. Different VA contents result in different glass transition temperatures (Tg). Generally, the higher the VA content, the higher the Tg shifts. For example, EVM rubber with 70% VA content has a Tg of approximately -12℃, EVM rubber with 80% VA content has a Tg of approximately 5℃, and EVM rubber with 90% VA content has a Tg of approximately 25℃. The question remains whether it is possible to expand the effective damping temperature range of EVM rubber by blending it with different VA contents, and to regulate its properties to make it suitable for interior systems in civil aircraft.

[0062] Based on the above concept, the applicant finally designed the damping material of this application. The effective damping temperature range of the damping material is -10℃ to 50℃, which is suitable for the operating temperature range of interior panels of civil aircraft in aviation equipment. This application also selects to add other additives, such as flame retardants, silane coupling agents, crosslinking agents, etc., to EVM rubber with different VA contents, to ensure the excellent damping characteristics, flame retardancy, low smoke and non-toxicity of the damping material. Moreover, the molding process of this damping material to prepare the damping structure is not complicated, which is conducive to the precise molding of the damping structure.

[0063] To achieve the above design effect, the first aspect of this application is to provide a damping material comprising chemical raw materials in the following mass ratio: ethylene vinyl acetate rubber A: ethylene vinyl acetate rubber B: ethylene vinyl acetate rubber C = (3-12):(6-14):(3-7); wherein, the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber A satisfies: 65% ≤ w ≤ 75%; the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber B satisfies: 75% < w ≤ 85%; and the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber C satisfies: 85% < w < 92%.

[0064] In this application, the ethylene vinyl acetate rubber includes any type conventionally used in the art, and the mass percentage w of vinyl acetate is provided by the supplier or obtained by a person skilled in the art using conventional measurement and calculation methods. The ethylene vinyl acetate rubber protected in this application includes, but is not limited to, the components with different VA contents mentioned above. Other EVM rubber types with different VA contents that adopt the design concept of this application should also be within the scope of protection of this application. For example, ethylene vinyl acetate rubber A and / or ethylene vinyl acetate rubber B and / or ethylene vinyl acetate rubber B may include a single type of rubber with a specific VA content, or may include mixed rubbers with different VA contents satisfying the above range, achieving an effective damping temperature range of -10℃ to 50℃ for the damping material.

[0065] Meanwhile, the mass ratio between ethylene vinyl acetate rubber A, ethylene vinyl acetate rubber B, and ethylene vinyl acetate rubber C satisfies any one of the above-mentioned range values. Within this range, the effective damping temperature range of the damping material is conducive to achieving -10℃ to 50℃. The effective damping temperature range performance index includes the conventional meaning and measurement method in this field, and it is correlated with the glass transition temperature Tg of the damping material. The damping material that meets this effective damping temperature range expands the effective damping temperature range of EVM rubber and is applicable to the operating temperature range of interior panels of civil aircraft in aviation equipment.

[0066] In some embodiments, this application selects ethylene vinyl acetate rubber A and ethylene vinyl acetate rubber B as single types of rubber with a specific VA content. However, this application does not exclude other combinations. For ease of study, this application will use single types of rubber with a specific VA content as examples in the following discussion. In some embodiments, the ratio of ethylene vinyl acetate rubber A: ethylene vinyl acetate rubber B: ethylene vinyl acetate rubber C is (4-10): (8-13): (4-6). By controlling the amount of each EVM rubber, this application achieves an effective damping temperature range of 5-40°C within this range.

[0067] In some embodiments, the ratio of ethylene vinyl acetate rubber A: ethylene vinyl acetate rubber B: ethylene vinyl acetate rubber C is 3:5:2. By controlling the amount of each EVM rubber, within this mass ratio, the effective damping temperature range of the damping material can achieve relatively optimal matching with the operating temperature of the interior panels of aerospace equipment.

[0068] In some embodiments, the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber A satisfies: 67% ≤ w ≤ 72%.

[0069] In some embodiments, the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber B satisfies: 76% < w ≤ 83%.

[0070] In some embodiments, the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber C satisfies: 88% < w < 92%.

[0071] In the actual preparation of damping materials, this application includes specific research based on the type of ethylene vinyl acetate rubber provided by the supplier.

[0072] In some embodiments, the damping material, in addition to containing various types of EVM rubber with the above-mentioned mass ratio, also contains one or more combinations of flame retardants, silane coupling agents, and crosslinking agents. When flame retardants, silane coupling agents, and crosslinking agents are contained simultaneously, their effect on improving the performance of the damping material is relatively superior.

[0073] The flame retardant accounts for 39.39% to 141.7% of the total mass of the EVM rubber, and can also be any one of 39.39% to 108.3%, 39.39% to 51.5%, 51.5% to 108.3%, 51.5% to 141.7%, or 108.3% to 141.7%.

[0074] The flame retardant contains a first flame retardant and a second flame retardant in a mass ratio of (4-6):(9-11). The first flame retardant is an inorganic metal oxide flame retardant, such as antimony trioxide, aluminum hydroxide, magnesium hydroxide, and zinc borate. The second flame retardant is a halogen-containing flame retardant, such as a chlorine-containing flame retardant or a bromine-containing flame retardant, such as chlorinated paraffin and decabromodiphenyl ether.

[0075] Meanwhile, the mass of the silane coupling agent is 0.61% to 3.33% of the total mass of the EVM rubber, or any one of the following: 0.61% to 1.21%, 0.61% to 1.67%, 1.21% to 1.67%, 1.21% to 3.33%, or 1.67% to 3.33%. Examples of silane coupling agents include vinyltriethoxysilane A151 and γ-aminopropyltriethoxysilane KH-550.

[0076] The crosslinking agent comprises 0.61% to 3.33% of the total mass of the EVM rubber, and can be any one of the following: 0.61% to 1.21%, 0.61% to 1.67%, 1.21% to 1.67%, 1.21% to 3.33%, or 1.67% to 3.33%. The crosslinking agent is an organic peroxide-based vulcanizing agent, specifically including di-tert-butyl peroxide, dicumyl peroxide, etc.

[0077] In addition, the damping material also contains conventional additives used to improve rubber properties, such as reinforcing agents, plasticizers, activators, and accelerators. The dosage of each additive includes any amount conventionally used in the field. For example, the mass of the reinforcing agent may be any one of the following: 9.09%–41.66%, 9.09%–15.15%, 9.09%–25%, 15.15%–25%, 15.15%–41.66%, or 25%–41.66% of the total mass of the EVM rubber. Reinforcing agents include carbon black, silica, nano-titanium dioxide, talc, precipitated calcium carbonate, and organic substances such as phenolic resin may also be used.

[0078] The plasticizer accounts for any one of the following percentages by mass: 2.42%–13.33%, 2.42%–4.85%, 2.42%–6.67%, 4.85%–6.67%, 4.85%–13.33%, and 6.67%–13.33% of the total mass of EVM rubber. The plasticizer comprises a first plasticizer and a second plasticizer in a mass ratio of (1–3):(3–5). The first plasticizer is a stearic acid-based plasticizer, including stearic acid, zinc stearate, and stearate esters. The second plasticizer is an ester-based plasticizer, including dioctyl sebacate, dioctyl phthalate, dibutyl phthalate, alkyl sulfonates, and polyol esters.

[0079] The activator's mass is any one of the following: 1.21%–6.67%, 1.21%–2.42%, 1.21%–3.33%, 2.42%–3.33%, 2.24%–6.67%, or 3.33%–6.67% of the total EVM rubber mass. Furthermore, the types of activators include activated magnesium oxide, zinc oxide, etc.

[0080] The accelerator's mass is any one of the following: 0.61%–5%, 0.61%–1.67%, 0.61%–1.82%, 1.67%–5%, 1.67%–1.82%, or 1.82%–5% of the total EVM rubber mass. Types of accelerators include triallyl isocyanurate and triallyl cyanurate.

[0081] In some embodiments, for example, the content of each chemical raw material is as follows, calculated by parts by mass:

[0082] Ethylene vinyl acetate rubber A: 15-60 parts;

[0083] Ethylene vinyl acetate rubber B: 30-70 parts;

[0084] Ethylene vinyl acetate rubber C: 15-35 parts;

[0085] First flame retardant: 20-30 parts;

[0086] Second flame retardant: 45-55 parts;

[0087] Silane coupling agent: 1-2 parts;

[0088] Crosslinking agent: 1-2 parts;

[0089] Reinforcing agent: 15-25 parts;

[0090] First plasticizer: 1-3 parts;

[0091] Second plasticizer: 3-5 parts;

[0092] Surfactant: 2-4 parts;

[0093] Accelerator: 1-3 parts.

[0094] EVM rubber itself has low smoke emission, toxicity, and smoke corrosivity, making it an ideal flame-retardant rubber. Adding additives with different performance effects to EVM rubber, and synergistically adjusting their dosage, ensures excellent mechanical and damping properties while also providing good flame retardancy. Therefore, the damping material provided in this application is suitable for relevant airworthiness standards for transport aircraft and has promising applications in civil aircraft, such as interior panels, specifically ceilings, sidewalls, partitions, galley structures, large cabinets, and storage boxes.

[0095] In some embodiments, the effective damping temperature range of the damping material is 10–30°C, which enables a better match between the effective damping temperature range and the operating temperature of the interior panels of civil aircraft in aviation equipment transport aircraft.

[0096] The damping material provided in the first aspect of this application is used to prepare a damping layer, which is then used to further prepare a damping structure. Therefore, the second aspect of this application is to provide a damping structure comprising... Figure 1 The constrained damping layer 100 shown comprises alternating layers of constrained layer 101 and damping layer 102, with the number of layers of constrained layer 101 and damping layer 102 being equal, ensuring that the alternating layering process ends with damping layer 102. A pressure-sensitive adhesive layer 103 is then formed on the surface of the outermost damping layer. The constrained layer 101 is made of the damping material described in the first aspect above. The damping layer 102 is obtained by surface roughening of carbon fiber reinforced epoxy resin, and the carbon fiber reinforced epoxy resin can be any type of material conventional in the art, the surface roughening method can be a conventional method in the art, and the pressure-sensitive adhesive layer 103 can be a conventional pressure-sensitive adhesive in the art. This application adopts... Figure 1 The constrained damping layer shown in the diagram is beneficial for synergistically utilizing the properties of each layer, thereby improving the damping characteristics, flame retardancy, low smoke emission, and non-toxicity of the damping structure.

[0097] In some embodiments, an adhesive is further disposed between the constraint layer and the damping layer. The adhesive is formed by coating the damping layer (carbon fiber reinforced epoxy resin) during surface roughening treatment, and the coating method includes any method conventional in the art, preferably spraying. The adhesive includes a hot-curing adhesive, which, together with subsequent processes, facilitates the vulcanization molding of the constraint damping layer with an alternating layered structure.

[0098] In some embodiments, the alternating layering is performed 1 to 5 times, preferably 3 to 5 times. This is because the damping structure needs to be adapted to the interior panel, and its thickness should not be too thick. Otherwise, various problems such as uneven shrinkage and dimensional deformation may occur during manufacturing, ultimately leading to a deterioration in the performance of the molded product. For example, the typical thickness of conventional constraint damping components is 2 mm to 3 mm, while the thickness of the constraint damping layer in this application is ≤3.0 mm. This range excludes the case where the value is zero.

[0099] In some embodiments, the damping layer satisfies one or more of the following properties:

[0100] (1) Rubber tensile strength ≥15MPa; the test standard for this property meets: GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0101] (2) Elongation at break ≥200%; the test standard for this property meets: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0102] (3) Tear strength ≥18kN / m; the test standard for this property meets the requirements of GB / T 529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber.

[0103] (4) At 23℃±2℃ and 10Hz~1000Hz, the maximum loss factor tanδmax≥1.2; the test standard for this performance meets: GJB 981 Forced Non-Resonant Dynamic Test Method for Viscoelastic Damping Materials

[0104] In some embodiments, the flexural modulus of carbon fiber reinforced epoxy resin is ≥40 GPa; the test standard for this property meets the requirements of GB-T 1449-2005 Test method for flexural properties of fiber reinforced plastics.

[0105] In some embodiments, the pressure-sensitive adhesive layer is selected as a PET pressure-sensitive adhesive layer, wherein the adhesive strength of the PET pressure-sensitive adhesive layer is ≥70kPa, and the test standard for this performance meets the standard test method of ASTM C 297 / C 297M-2004 for the straight tensile strength of sandwich structures.

[0106] In some embodiments, the thickness of the damping layer is greater than the thickness of the constraint layer and the thickness of the pressure-sensitive adhesive layer. For example, in this application, the thickness of the damping layer is less than or equal to 0.4 mm, the thickness of the constraint layer is about 0.2 mm, and the length and width of the constraint layer are not less than 500 mm (assuming the constraint layer is a regular cuboid). The thickness of the pressure-sensitive adhesive layer is 0.08 mm to 0.12 mm.

[0107] To obtain a damping structure comprising the aforementioned constrained damping layer, a third aspect of this application provides a method for preparing a damping structure. The method includes: mixing the materials described in the first aspect to form a compound; calendering and preforming the compound to form a damping layer blank; roughening the surface of a carbon fiber reinforced epoxy resin; coating at least one side of the treated surface with an adhesive to provide a constrained layer; preheating a mold for forming the damping structure; alternately layering the coated constrained layer and damping layer blank into the mold and vulcanizing to form a damping structure semi-finished product; and forming a pressure-sensitive adhesive layer on the outermost surface of the damping layer of the damping structure semi-finished product to obtain the damping structure.

[0108] For constrained damping structures with large aspect ratios, thin thickness, and multiple layers, conventional blanking and vulcanization processes are quite challenging. This is because producing blanks with a thickness of less than 0.4 mm from rubber sheets is inherently difficult. On one hand, the prepared blanks are prone to shrinkage, leading to increased thickness; on the other hand, ensuring uniform thickness over large areas is difficult. Typical constrained damping components are 2 mm to 3 mm thick, and vulcanization processes suffer from uneven shrinkage and dimensional deformation. These problems can lead to deterioration in the performance of multi-layered composite damping materials after molding, and the inherent internal stress may cause warping in the vibration damping components, reducing reliability. This application selects to first pre-treat the surface of the constraint layer material (carbon fiber reinforced epoxy resin) to roughen the bonding surface, then apply a hot-curing adhesive using spraying technology, and precisely control the thickness and uniformity of the rubber layer compound using a calendering process. Next, by designing the mold position, the edges of each layer of carbon fiber reinforced epoxy resin are fixed and positioned with locating pins. The calendered blank is then cut, and a constraint layer coated with hot-curing adhesive on both sides is laid in the preheated mold. A locating frame is added, followed by a complete layer of rubber, then another constraint layer coated with hot-curing adhesive on both sides, and another locating frame is added. This process is repeated until the appropriate thickness is achieved, at which point the mold is closed and finally secured with locating pins. This design effectively controls the thickness of each layer in the vulcanized lightweight composite damping material and ensures that the lightweight multi-layer composite damping material does not warp during the molding process. Then, by matching the vulcanization conditions of the rubber layer (including vulcanization temperature, vulcanization pressure, and vulcanization time), the hot vulcanizing adhesive reacts chemically with both the rubber layer and the constraint layer during the molding process, achieving a strong bond between the constraint layer and the rubber layer. Ultimately, this allows for the precise molding of the stacked constraint damping material. Here, and in the context, "rubber layer" refers to the damping layer or damping material, etc.

[0109] Specifically, the preparation method provided in this application includes the following steps, and the process flow diagram is shown below. Figure 2 Indication:

[0110] S1: Mixing; According to the dosage relationship between the components described in the first aspect, EVM rubber with different VA contents is placed in an internal mixer for mixing. After heating to 60℃~70℃, plasticizer, reinforcing agent, activator and flame retardant are added in multiple batches. When the temperature is raised to 80℃~90℃ again, the material is discharged and thinly passed through a two-roll mill 4~6 times to form sheets. After drying for more than 2 hours, the initial mixed rubber sheets are obtained.

[0111] S2: Add vulcanizing agent; place the initial mixed rubber sheet in a two-roll mill and pass it through 3 to 5 times, then add silane coupling agent, accelerator and crosslinking agent. After the filler is completely mixed into the compound, pass it through 6 to 8 times and then sheet it.

[0112] S3: Surface roughening treatment of carbon fiber reinforced epoxy resin; degreasing treatment of carbon fiber reinforced epoxy resin in trichloroethylene vapor, sandblasting with diamond abrasive of 120 mesh or higher, and then steam degreasing in trichloroethylene.

[0113] S4: Apply adhesive to the surface of the treated carbon fiber reinforced epoxy resin; thoroughly stir the hot vulcanizing adhesive, apply the adhesive to the surface of the treated carbon fiber reinforced epoxy resin using spraying technology, and after spraying, dry at room temperature for no less than 30 minutes, and then place in an oven at 130℃ for 5 to 10 minutes.

[0114] S5: Mold preheating; Assemble the middle mold, upper mold and lower mold of the constraint damping mold together and fix them on the lower template of the vulcanizing molding machine. The temperature of the upper and lower templates of the vulcanizing molding machine is set to 170℃; Close the mold and preheat the mold for a time of not less than 30 minutes. Each mold includes any model and type of equipment conventional in this field.

[0115] S6: Calendering and blanking; adjusting the roll gap of the rubber mixing mill to meet the preset size of the constraint layer; placing the mixed rubber on the rubber mixing mill for re-mixing until the rubber sheet is soft and has a smooth surface; wrapping the re-mixed rubber sheet around the rolls to form a rubber sheet of uniform thickness, testing the thickness of the rubber sheet, and if the thickness of the rubber sheet does not meet the preset thickness of the damping layer, adjusting the roll gap of the rubber mixing mill to meet the preset thickness. In this application, the preset size (length and width) of the constraint layer is not less than 500 mm, and the preset thickness of the damping layer is less than or equal to 0.4 mm, such as 0.3 mm to 0.4 mm. Specifically, the rubber sheet is calendered on a two-roll (double-roll) rubber mixing mill. The roll gap of the two-roll rubber mixing mill is adjusted to be no less than 500mm. The mixed rubber sheet after being sheeted is placed on the two-roll rubber mixing mill for reprocessing until the rubber sheet is soft and has a smooth and flat surface. The reprocessed mixed rubber sheet is placed at the feed position of the two-roll rubber mixing mill and made to wrap around the rolls to form a uniform rubber sheet. The thickness of the rubber sheet is tested with a thickness gauge. If it is not within the target value range, the roll gap is readjusted and the thickness is measured again until the target thickness of 0.3mm to 0.4mm is reached. After the surface of the rubber sheet is flat, it is cut with a cutter. The sheet is laid on a plastic film and left to stand for no less than 5 minutes before being cut into blanks with a side length of 485mm ± 15mm. The remaining rubber edge is put into an open rubber mixing mill for re-sheeting and to form blanks again.

[0116] S7: Laying out the constraint layer and damping layer; When the temperature of the upper and lower mold plates of the vulcanizing molding machine reaches 170℃, turn on the vulcanizing molding machine, separate the upper mold and the middle mold (multi-layer positioning frame), remove the lower mold and the middle mold (multi-layer positioning frame), after reaching the limit position, remove the middle mold (multi-layer positioning frame), lay the constraint layer coated with adhesive in the lower mold cavity, install the positioning frame to fix the edge of the constraint layer, then completely lay a layer of rubber, then lay another layer of constraint layer coated with hot vulcanizing adhesive on both sides, install the positioning frame, then completely lay another layer of rubber, when the appropriate thickness is reached, fix the position with positioning pins, then install the upper mold and close the mold.

[0117] S8: Vulcanization treatment; perform venting operation, with the venting pressure gauge set to 10MPa±2MPa, and the number of venting cycles being 6 to 10; after venting is completed, the vulcanization pressure gauge set to 15MPa±2MPa, and the vulcanization time being 20min±3min, with timed vulcanization.

[0118] S9: Demolding and trimming. After vulcanization, separate the upper mold and the middle mold. Once they reach the specified position, use a copper rod to pry the middle mold and the lower mold apart and remove the constraint damping. During the demolding process, avoid damaging the positioning pins. Cut off any excess rubber material from the edges of the constraint damping product and avoid scratching the damping layer (rubber) with the blade.

[0119] S10: Adhesive layer is formed by bonding; the damping layer is placed in the laminating machine with the damping layer side facing up. The laminating machine completely adheres the pressure-sensitive adhesive layer to the surface of the damping layer. The laminating machine then cuts off the excess pressure-sensitive adhesive layer to obtain the damping structure.

[0120] Exemplary embodiments of this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art. Furthermore, the chemical reagents used in the following embodiments comprise any type, purity, etc., conventional in the art, and the equipment used comprises any type conventional in the art.

[0121] Example 1

[0122] A constrained damping layer is disclosed, the structure of which is as follows: Figure 3 As shown in Table 1, the composition of the damping material in this constrained damping layer is as follows:

[0123] Table 1. List of Component Types and Contents

[0124]

[0125] The specific preparation method of this constraint damping layer is as follows:

[0126] (1) Using conventional mass measuring instruments, such as electronic scales or electronic balances, weigh each component according to the mass fractions in Table 1. Place the EVM rubber in a mixer and mix. When the temperature inside the mixer reaches 65°C, open the dust cover and pressure cover of the mixer. Add zinc stearate, dioctyl sebacate (DOS), carbon black N330, magnesium oxide active 60, antimony trioxide, and decabromodiphenyl ether in three batches. Put down the dust cover and pressure cover. When the temperature inside the mixer reaches 85°C again, open the dust cover and pressure cover of the mixer, discharge the material, and transfer the mixed rubber to a two-roll mill. Slide the mixture through the two-roll mill 5 times to form sheets and let it air dry for 2.5 hours.

[0127] (2) Tighten the roller gap, pass the mixed rubber sheet at room temperature through the open mill 3 times, adjust the roller gap of the two-roll mill so that the rubber material wraps around the rollers and keeps a small amount of residual rubber between the two rollers, add vinyltriethoxysilane A151, triallyl isocyanurate TAIC and di-tert-butyl peroxide BIPB, wait for the additives to be completely mixed into the rubber, pass through the thin sheet 6 times.

[0128] (3) The carbon fiber reinforced epoxy resin was degreased in trichloroethylene vapor, sandblasted with diamond abrasive of about 120 mesh, and then degreased in trichloroethylene vapor; the flexural modulus of the carbon fiber reinforced epoxy resin was ≥40GPa; the test standard for this performance met the requirements of GB-T 1449-2005 Test Method for Flexural Properties of Fiber Reinforced Plastics. (4) The hot vulcanizing adhesive T-715A was thoroughly stirred, and the adhesive was applied to the upper and lower surfaces of the treated carbon fiber reinforced epoxy resin by spraying. After spraying, it was dried at room temperature for 40 minutes, and then placed in an oven at 130℃ for 5 minutes.

[0129] (5) Assemble the upper, middle and lower molds of the constraint damping mold together and fix them on the lower template of the vulcanizing molding machine. Set the temperature of the upper and lower templates of the vulcanizing molding machine to 170℃; preheat the mold for 50 minutes.

[0130] (6) Adjust the roller gap of the two-roll mill to 510mm. Place the sheeted rubber compound on the two-roll mill and re-mill 6 times. After re-milling, roll the rubber compound into a uniform sheet. When the sheet surface is smooth and flat, and the thickness of the sheet reaches 0.3mm as measured by a thickness gauge, cut the sheet with a cutter. Lay the sheet on a plastic film and let it rest for 10 minutes before cutting. The side length is 485mm ± 15mm. The performance of this sheet meets the following requirements:

[0131] (1) Rubber tensile strength ≥15MPa; the test standard for this property meets: GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0132] (2) Elongation at break ≥200%; the test standard for this property meets: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0133] (3) Tear strength ≥18kN / m; the test standard for this property meets the requirements of GB / T 529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber.

[0134] (4) At 23℃±2℃ and 10Hz~1000Hz, the maximum loss factor tanδmax≥1.2; the test standard for this performance meets the requirements of GJB 981 Forced Non-Resonant Dynamic Test Method for Viscoelastic Damping Materials.

[0135] (7) When the temperature of the upper and lower mold plates of the vulcanizing molding machine reaches 170℃, turn on the vulcanizing molding machine, separate the upper mold and the middle mold (multi-layer positioning frame), remove the lower mold and the middle mold, and after reaching the limit position, remove the middle mold (multi-layer positioning frame), place the constraint layer with adhesive on it in the lower mold cavity, install the positioning frame to fix the edge of the constraint layer, then completely apply a layer of rubber, then apply another layer of constraint layer, install the positioning frame, then completely apply another layer of rubber, and apply a total of 4 constraint layers and 4 rubber layers, fix them with positioning pins, install the upper mold and close the mold;

[0136] (8) Set the gauge pressure to 10MPa, vent 6 times, and after venting, set the gauge pressure to 15MPa and the vulcanization time to 20min, and vulcanize by timing.

[0137] (9) After vulcanization, separate the upper mold and the middle mold, then use a copper rod to pry open the middle mold and the lower mold, and remove the constraint damper.

[0138] (10) Place the rubber-coated side of the constraint damping layer into the laminating machine. The laminating machine completely adheres the PET pressure-sensitive adhesive tape to the rubber layer. Then, the laminating machine cuts off the excess pressure-sensitive adhesive to obtain the constraint damping layer. The thickness of the constraint damping layer is 2.5 mm. It consists of four stacked constraint layers and damping layers, with each constraint layer having a thickness of 0.2 mm, each damping layer having a thickness of 0.4 mm, and each pressure-sensitive adhesive layer having a thickness of 0.10 mm. The adhesive strength of the PET pressure-sensitive adhesive layer is ≥70 kPa, and the test standard for this performance meets the standard test method for the straight tensile strength of sandwich structures, ASTM C 297 / C 297M-2004.

[0139] Performance testing:

[0140] 1. Sound insulation test: according to ASTM E2249 standard;

[0141] 2. Damping loss factor test: The standard test method for measuring the vibration reduction characteristics of materials is ASTM E756-05.

[0142] 3. Flame retardant performance test: The material ignition test shall be conducted in accordance with CCAR25.

[0143] 4. Toxicity testing: In accordance with the HB / Z 277 aircraft cabin material fireability design guidelines;

[0144] The specific test results are shown in Tables 2 to 8 below;

[0145] Table 2 List of sound insulation test results

[0146]

[0147] In Table 2, the typical interior panel has dimensions of 1.2m x 1.2m; the constraint damping thickness is 2.5mm (of which the constraint layer is 0.2mm thick, with 4 layers; the rubber layer is 0.4mm thick, with 4 layers; and the pressure-sensitive adhesive is 0.10mm thick). First, the sound insulation of the typical interior panel was tested, and then the constraint damping layer was completely applied to the surface of the typical interior panel for further sound insulation testing. As shown in Table 2, the sound insulation of the interior panel after applying the constraint damping layer is higher than that of the interior panel itself, with an average insertion loss of 4.65dB in the 500Hz–5000Hz range. While current sound insulation testing methods are mainly limited to room temperature environments, it is reasonable to predict that the constraint damping layer protected by this application should also possess good sound insulation performance at low temperatures. For example, the sound insulation performance from -10℃ to room temperature is lower than at room temperature, but importantly, the application temperature of the constraint damping layer protected by this application is extended to low-temperature environments, improving its application range.

[0148] The constrained damping layer prepared above was applied to the surface of the base beam, and a cantilever beam test was conducted on the base beam. The base beam was made of oil-hardened steel with the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 1.6mm ± 0.05mm; the constrained damping layer had the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 2.5mm.

[0149] The specific testing process includes: first, conducting a cantilever beam test on the base beam, then removing the release paper from the constraint damper, and finally attaching the constraint damper to the base beam for another cantilever beam test;

[0150] Test conditions: 23±2℃, 50Hz~1000Hz.

[0151] The test results are shown in Tables 3 and 4 below;

[0152] Table 3. Test Results of Damping Loss Factor for Hardened Steel (Without Restraining Damping Layer)

[0153]

[0154] Table 4. List of test results for damping loss factor of constrained damping.

[0155]

[0156] As shown in Table 3, the hardened steel has three modal frequencies in the range of 50Hz to 1000Hz, and the damping loss factor calculated using formula 2b in ASTM E756-05 is very low. The composite beam with the hardened steel bonded with the constrained damping layer has two modal frequencies in the range of 50Hz to 1000Hz, and the damping loss factor of the constrained damping layer calculated using formula 2b in ASTM E756-05 is at least two orders of magnitude higher than that of the hardened steel. Therefore, the damping effect of the constrained damping in this application is improved.

[0157] The flame retardant properties of the constrained damping layer prepared above were tested, and the test results are shown in Tables 5, 6, 7 and 8.

[0158] Table 5. List of 12s Vertical Combustion Test Results

[0159]

[0160] Table 6 List of Smoke Density Test Results

[0161]

[0162] Table 7 List of Toxicity Test Results

[0163]

[0164]

[0165] Table 8. List of Flame Spread Test Results

[0166]

[0167] As can be seen from Tables 5 to 8, the constraint damping layer protected by this application meets the relevant and corresponding test standards.

[0168] Example 2

[0169] A constrained damping layer is disclosed, comprising five stacked layers, and the composition of the damping material in the constrained damping layer is shown in Table 9 below:

[0170] Table 9. List of Component Types and Contents

[0171]

[0172] The material containing the above-mentioned types and amounts of components was prepared using the process illustrated in Example 1.

[0173] The thickness of the constraint damping layer is 2.58 mm, which consists of three stacked constraint layers and damping layers, wherein the thickness of each constraint layer is 0.2 mm, the thickness of each damping layer is 0.3 mm, and the thickness of each pressure-sensitive adhesive layer is 0.08 mm.

[0174] (1) The constraint damping layer was completely applied to the surface of a typical interior panel component, which was 1.2m x 1.2m in length and width. A sound insulation test was conducted, and according to ASTM E2249 standard, the average insertion loss was 5.05dB in the range of 500Hz to 5000Hz. Since the amount of 70% VA-content EVM rubber A used was reduced compared to Example 1, while the amount of 90% VA-content EVM rubber A used was increased compared to Example 1, it can be reasonably expected that the effective damping temperature range of the constraint damping in Example 1 is wider than that in Example 2.

[0175] (2) The constrained damping layer prepared above is applied to the surface of the base beam, and a cantilever beam test is performed on the base beam. The base beam is made of oil-hardened steel with the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 1.6mm ± 0.05mm; the constrained damping layer has the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 2.5mm.

[0176] The specific testing process includes: first, conducting a cantilever beam test on the base beam, then removing the release paper from the constraint damper, and finally attaching the constraint damper to the base beam for another cantilever beam test;

[0177] Test conditions: 23±2℃, 50Hz~1000Hz, the loss factor of the constrained damping layer under the ASTM E756-05 standard was 0.532~0.974; Test conditions: -10℃, 50Hz~1000Hz, the loss factor of the constrained damping layer under the ASTM E756-05 standard was 0.123~0.338. The results obtained under two different test environments, room temperature and low temperature, show that the loss factor is higher at room temperature than at low temperature. It is speculated that this may be because the content of EVM rubber with 80% and 90% VA content is increased, while the content of EVM rubber with 70% VA content is decreased. Therefore, in order to take into account the low temperature damping performance of the material, it is advisable to appropriately increase the content of EVM rubber with 70% VA content.

[0178] (3) In accordance with the provisions of the CCAR25 standard for airworthiness of transport category aircraft, the flame retardant performance of the constraint damping layer was tested. The test items included 12s vertical combustion, smoke density, toxicity and flame spread. The constraint damping was required to pass the tests of 12s vertical combustion, smoke density, toxicity and flame spread. The test results showed that all met the relevant standards.

[0179] Example 3

[0180] A constrained damping layer is disclosed, comprising three stacked layers, and the composition of the damping material in the constrained damping layer is shown in Table 10 below:

[0181] Table 10 List of Component Types and Contents

[0182]

[0183]

[0184] The material containing the above-mentioned types and amounts of components was prepared using the process illustrated in Example 1.

[0185] The thickness of the constraint damping layer is 1.92 mm, which consists of three stacked constraint layers and damping layers, wherein the thickness of each constraint layer is 0.2 mm, the thickness of each damping layer is 0.4 mm, and the thickness of each pressure-sensitive adhesive layer is 0.12 mm.

[0186] (1) The constrained damping layer was completely applied to the surface of a typical interior panel component, which measures 1.2m x 1.2m. Sound insulation tests were conducted according to ASTM E2249, and the average insertion loss was 3.83dB between 500Hz and 5000Hz. The sound insulation performance of the constrained damping in this embodiment at room temperature is lower than that of Examples 1 and 2, presumably due to the increased EVM rubber content (approximately 70% VA). However, it is expected that the low-temperature performance of the constrained damping in this embodiment will improve.

[0187] (2) The constrained damping layer prepared above is applied to the surface of the base beam, and a cantilever beam test is performed on the base beam. The base beam is made of oil-hardened steel with the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 1.6mm ± 0.05mm; the constrained damping layer has the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 2.5mm.

[0188] The specific testing process includes: first, conducting a cantilever beam test on the base beam, then removing the release paper from the constraint damper, and finally attaching the constraint damper to the base beam for another cantilever beam test;

[0189] Test conditions: 23±2℃, 50Hz~1000Hz, the loss factor of the constraint damping layer under the ASTM E756-05 standard was 0.431~0.668; Test conditions: -10℃, 50Hz~1000Hz, the loss factor of the constraint damping layer under the ASTM E756-05 standard was 0.636~0.988; According to the above research approach, it can be seen that the loss factor of the constraint damping in this embodiment is higher in the low temperature environment than in the room temperature environment.

[0190] (3) In accordance with the provisions of the CCAR25 standard for airworthiness of transport category aircraft, the flame retardant performance of the constraint damping layer was tested. The test items included 12s vertical combustion, smoke density, toxicity and flame spread. The constraint damping was required to pass the tests of 12s vertical combustion, smoke density, toxicity and flame spread. The test results showed that all met the relevant standards.

[0191] Although this application has selected specific types and contents of reinforcing agents, first flame retardants, second flame retardants, first plasticizers, second plasticizers, activators, silane coupling agents, accelerators, and crosslinking agents in Examples 1 to 3, it is reasonable to infer that other types and contents within the scope of this application can also achieve the same or similar effects as those in Examples 1 to 3, and this application will not elaborate further.

[0192] Comparative Example 1

[0193] A constraint damping layer is provided:

[0194] The damping layer contains only the same EVM rubber A and EVM rubber B, or EVM rubber B and EVM rubber C, or EVM rubber A and EVM rubber C as in Example 1, and everything else remains the same as in Example 1.

[0195] The constraint damping layer is 2.5 mm thick and consists of four stacked constraint and damping layers, with each constraint layer being 0.2 mm thick, each damping layer being 0.4 mm thick, and each pressure-sensitive adhesive layer being 0.10 mm thick.

[0196] (1) The constraint damping layer was completely applied to the surface of a typical interior panel component, which was 1.2m x 1.2m in length and width. Sound insulation tests were conducted according to ASTM E2249 to obtain the average insertion loss at frequencies from 500Hz to 5000Hz. The average insertion loss test results showed that the BC combination > the AC combination > the AB combination, and the overall performance was inferior to that of Examples 1 to 3.

[0197] (2) The constrained damping layer prepared above is applied to the surface of the base beam, and a cantilever beam test is performed on the base beam. The base beam is made of oil-hardened steel with the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 1.6mm ± 0.05mm; the constrained damping layer has the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 2.5mm.

[0198] The specific testing process includes: first, conducting a cantilever beam test on the base beam, then removing the release paper from the constraint damper, and finally attaching the constraint damper to the base beam for another cantilever beam test;

[0199] Test conditions: 23±2℃, 50Hz~1000Hz, to obtain the loss factor of the constrained damping layer under the ASTM E756-05 standard. The damping loss factor test results show that: BC combination > AC combination > AB combination, and the overall performance is worse than that of Examples 1 to 3 in this paper.

[0200] Therefore, in order to take into account the excellent performance of the constraint damping in different high and low temperature environments, various types of EVM rubber with different VA content ranges should be selected.

[0201] Comparative Example 2

[0202] A constraint damping layer is provided:

[0203] The rolling and blanking steps are missing during the preparation process;

[0204] The constraint damping layer is 2.5 mm thick and consists of four stacked constraint and damping layers, with each constraint layer being 0.2 mm thick, each damping layer being 0.4 mm thick, and each pressure-sensitive adhesive layer being 0.10 mm thick.

[0205] (1) The constraint damping layer was completely applied to the surface of a typical interior panel, wherein the length × width of the typical interior panel is 1.2m × 1.2m. The sound insulation test was conducted, and the average insertion loss of 500Hz to 5000Hz was 1.92dB to 3.94dB according to ASTM E2249 standard.

[0206] (2) The constrained damping layer prepared above is applied to the surface of the base beam, and a cantilever beam test is performed on the base beam. The base beam is made of oil-hardened steel with the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 1.6mm ± 0.05mm; the constrained damping layer has the following dimensions: length 280mm ± 1mm, width 12.5mm ± 0.2mm, and thickness 2.5mm.

[0207] The specific testing process includes: first, conducting a cantilever beam test on the base beam, then removing the release paper from the constraint damper, and finally attaching the constraint damper to the base beam for another cantilever beam test;

[0208] Test conditions: 23±2℃, 50Hz~1000Hz, the loss factor of the confined damping layer under the ASTM E756-05 standard was 0.257~0.315.

[0209] As can be seen from Comparative Example 2 above, the calendering and preforming processes are of great significance to the performance of the constraint damping layer. If the calendering and preforming processes are missing, the uniformity and surface flatness of the constraint damping layer product will deteriorate, and the damping layer may become thicker, thinner, or missing in some areas. These defects will have a significant impact on the vibration reduction and noise reduction performance. At the same time, uneven shrinkage of the compound rubber will cause the constraint damping layer to warp, reducing its reliability.

[0210] In summary, the damping material provided in this application can simultaneously meet the requirements of mechanical properties, damping properties, flame retardancy, low smoke emission, and non-toxicity. At the same time, the preparation method provided in this application solves the problems of uneven shrinkage and dimensional deformation of each layer during vulcanization molding, reducing the probability of material warping. Furthermore, by matching the corresponding vulcanization conditions during the molding process, the composite between each layer is effectively achieved, ultimately realizing the precise molding of the constraint damping layer.

[0211] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0212] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A damping structure, characterized in that, Includes a constrained damping layer; The constraint damping layer comprises alternating layers of constraint layers and damping layers, wherein the number of constraint layers and damping layers is the same; the number of alternating layers is 1 to 5. The constraint damping layer also includes a pressure-sensitive adhesive layer located on the surface of the outermost damping layer; The damping layer is made of a damping material; The constraint layer is obtained by surface roughening treatment of carbon fiber reinforced epoxy resin; An adhesive is also disposed between the constraint layer and the damping layer; the thickness of the constraint damping layer is ≤3.0mm; The damping layer has a rubber tensile strength ≥15MPa; at 23℃±2℃ and 10Hz~1000Hz, the maximum loss factor tanδmax ≥1.

2. The damping material comprises chemical raw materials in the following mass ratio: ethylene vinyl acetate rubber A: ethylene vinyl acetate rubber B: ethylene vinyl acetate rubber C = (4~10): (8~13): (4~6); the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber A satisfies: 67% ≤ w ≤ 72%; the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber B satisfies: 76% < w ≤ 83%; the mass percentage w of vinyl acetate in ethylene vinyl acetate rubber C satisfies: 88% < w < 92%. The material also includes one or more of flame retardants, silane coupling agents, and crosslinking agents; The flame retardant comprises a first flame retardant and a second flame retardant in a mass ratio of (4~6):(9~11), wherein the first flame retardant is an inorganic metal oxide flame retardant and the second flame retardant is a halogen-containing flame retardant. The silane coupling agent is vinylsilane; The crosslinking agent is an organic peroxide-based vulcanizing agent; The effective damping temperature range of the damping material is 10℃~30℃; The method for preparing the damping structure includes: The damping material is mixed to form a compound, and the compound is calendered and formed into a damping layer blank. The carbon fiber reinforced epoxy resin is subjected to surface roughening treatment, and an adhesive is applied to at least one side of the treated surface to provide a restraint layer; Preheat the mold used to form the damping structure; The coated constraint layer and damping layer blanks are alternately stacked into the mold and vulcanized to form a damping structure semi-finished product; A pressure-sensitive adhesive layer is formed on the outermost damping layer surface of the damping structure semi-finished product to obtain the damping structure. The calendering and preform preparation are carried out in a rubber mixing mill, and the process is as follows: Adjust the roller gap of the rubber mixing mill to meet the preset size of the constraint layer; The compounded rubber is placed on the rubber mixing mill and re-mixed until the rubber sheet is soft and has a smooth surface; After remelting, the rubber sheet is wrapped around the rollers to form a rubber sheet with uniform thickness. The thickness of the rubber sheet is tested. If the thickness of the rubber sheet does not meet the preset thickness of the damping layer, the roller gap of the rubber mixing mill is adjusted to meet the preset thickness.

2. The structure according to claim 1, characterized in that, The damping layer satisfies one or more of the following properties: (1) The tensile strength of the rubber is ≥15MPa; (2) Tear strength ≥ 18 kN / m; The flexural modulus of the carbon fiber reinforced epoxy resin is ≥40 GPa; The pressure-sensitive adhesive layer is selected from PET pressure-sensitive adhesive layers, and the adhesive strength of the PET pressure-sensitive adhesive layer is ≥70kPa.

3. The structure according to claim 1 or 2, characterized in that, The thickness of the damping layer is greater than the thickness of the constraint layer, which is greater than the thickness of the pressure-sensitive adhesive layer.

4. The application of the structure according to any one of claims 1 to 3 in the manufacture of aerospace equipment, characterized in that; The aviation equipment includes interior panels for civil transport aircraft; The interior trim panels include any one or more of the following: ceiling, side wall panels, partitions, kitchen structure, large cabinets, and storage boxes.

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