A carbon fiber silencer

Abstract

This utility model relates to the field of silencer technology and discloses a carbon fiber silencer, comprising: an inlet pipe, a front cover, a middle isolation cover, a middle noise transmission pipe, a tail cover, an outlet pipe, a rear sound transmission porous pipe, a front sound transmission porous pipe, a sound-absorbing material, and an outer shell; one end of the front sound transmission porous pipe is inserted into an inner convex ring on the front cover, and the other end is inserted into a convex ring on one side of the middle isolation cover; one end of the rear sound transmission porous pipe is inserted into a convex ring on the other side of the middle isolation cover, and the other end of the rear sound transmission porous pipe is inserted into an inner convex ring on the tail cover; the outer shell is cylindrical, with one end inserted into an outer convex ring on the front cover and the other end inserted into an outer convex ring on the tail cover; the porous structure on the front and rear sound transmission porous pipes can reflect and scatter sound waves, effectively enhancing the sound wave resistance and weakening effect of the inner wall of the cylinder, thereby meeting the noise reduction requirements of the air compressor.

Description

Technical Field

[0001] This utility model relates to the field of silencer technology, and more specifically, to a carbon fiber silencer. Background Technology

[0002] In industrial settings such as air compressors in nitrogen generation equipment, high-frequency noise (1-4kHz band) control faces severe challenges. The peak noise level of such equipment exceeds 100dB during operation. Although traditional noise reduction solutions achieve basic noise reduction through multi-chamber structures and general sound-absorbing materials (such as glass wool), their absorption efficiency for high-frequency sound waves cannot meet the requirements.

[0003] The utility model patent application CN109057919A discloses a high-efficiency noise reduction silencer that employs a typical chamber partitioning scheme. Its core structure is as follows: The entire system consists of a silencer cylinder as the main structure, internally divided into series-connected silencer chambers by multiple radially arranged baffles. Each baffle is equipped with a silencer pipe connecting adjacent chambers, and these pipes have several silencer holes on their sidewalls for sound wave scattering. Notably, both the inlet and outlet pipes extend into the cylinder—the former extends rearward so that its outlet is located before the inlet of the first silencer pipe, and the latter extends forward so that its inlet is located after the outlet of the last silencer pipe. This design aims to prolong the residence time of the airflow within the chambers. The inner walls of all silencer chambers are covered with ultrafine glass wool as a sound-absorbing material, dissipating sound wave energy through physical absorption.

[0004] The aforementioned solution uses only sound-absorbing material on the inner wall of the anechoic chamber, but lacks a porous structure for sound wave reflection and scattering. Sound waves pass rapidly through the chamber, failing to meet the noise reduction requirements of the air compressor. Furthermore, existing structures mostly use welded connections to form rigid gaps, resulting in high-frequency sound wave penetration and leakage, severely weakening the chamber's sound absorption effect. Utility Model Content

[0005] The present invention aims to overcome at least one of the defects of the prior art and provide a carbon fiber silencer to solve the technical problems of weak sound wave resistance and attenuation effect of the inner wall of the cylinder, high frequency sound wave penetration and leakage rate of the rigid gap formed by welding assembly, which cannot meet the noise reduction requirements of air compressor.

[0006] The technical solution adopted by this utility model is a carbon fiber silencer, comprising: an inlet pipe, a front cover, a middle isolation cover, a middle noise transmission pipe, a tail cover, an outlet pipe, a rear sound transmission porous pipe, a front sound transmission porous pipe, silencing material, and an outer shell; one end of the front sound transmission porous pipe is inserted into an inner convex ring on the front cover, and the other end is inserted into a convex ring on one side of the middle isolation cover; one end of the rear sound transmission porous pipe is inserted into a convex ring on the other side of the middle isolation cover, and the other end of the rear sound transmission porous pipe is inserted into an inner convex ring on the tail cover; the outer shell is cylindrical, with one end inserted into an outer convex ring on the front cover and the other end inserted into an outer convex ring on the tail cover; the silencing material fills the gaps between the outer shell and the front sound transmission porous pipe, and the gaps between the outer shell and the rear sound transmission porous pipe; the inlet pipe is fixed on the front cover, the middle noise transmission pipe is fixed on the middle isolation cover, and the outlet pipe is fixed on the tail cover.

[0007] By connecting the front sound transmission porous tube to the front cover and the middle isolation cover; the rear sound transmission porous tube to the middle isolation cover and the tail cover; and the outer shell to the front cover and the tail cover, a multi-connected assembly structure is formed, which reduces the penetration and leakage rate of high-frequency sound waves at the gaps and completely eliminates the rigid gaps of traditional welding. This solution not only includes sound-absorbing materials, but also sets up front and rear sound transmission porous tubes inside. The porous structure on the front and rear sound transmission porous tubes can reflect and scatter sound waves, which can effectively enhance the effect of the inner wall of the cylinder in hindering and weakening sound waves, thereby meeting the noise reduction requirements of the air compressor.

[0008] Furthermore, the noise inlet pipe, front cover, intermediate isolation cover, intermediate noise transmission pipe, tail cover, noise outlet pipe, rear sound transmission porous pipe, front sound transmission porous pipe, and outer shell are all made of carbon fiber composite material. Carbon fiber composite material has a high sound absorption coefficient, while also being lightweight, making it easy to move, transport, install, and maintain.

[0009] Furthermore, the sound-absorbing material is made of activated carbon fiber felt.

[0010] Furthermore, the axes of the noise input tube, the intermediate noise transmission tube, and the noise output tube are located in the same plane, the intermediate noise transmission tube is located on one side of the noise input tube axis, and the noise output tube is located on the other side of the noise input tube axis.

[0011] Furthermore, the noise inlet tube has a horn-shaped structure, with the larger diameter end located inside the muffler and having several holes, and the smaller diameter end located outside the muffler, with connecting threads on the outer circumference.

[0012] Furthermore, both the front and rear acoustic porous tubes are provided with holes, the diameter of which is 2-5 mm and the spacing between the holes is 10-20 mm.

[0013] Furthermore, the diameter of the larger end of the noise inlet tube is smaller than the diameter of the intermediate noise transmission tube and the diameter of the noise outlet tube, respectively. By increasing the cross-sectional area of ​​the channel, the airflow velocity is reduced, turbulent noise is suppressed, and the duration of sound wave action is extended.

[0014] Compared with the prior art, the beneficial effects of this utility model are as follows: by connecting the front sound transmission porous tube to the front cover and the middle isolation cover; connecting the rear sound transmission porous tube to the middle isolation cover and the tail cover; and connecting the outer shell to the front cover and the tail cover, a multi-connection assembly structure is formed, which reduces the penetration and leakage rate of high-frequency sound waves at the gaps and completely eliminates the rigid gaps of traditional welding. This solution not only has sound-absorbing materials, but also sets up front and rear sound transmission porous tubes inside. The porous structure on the front and rear sound transmission porous tubes can reflect and scatter sound waves, which can effectively enhance the effect of the inner wall of the cylinder in hindering and weakening sound waves, thereby meeting the noise reduction requirements of the air compressor. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the silencer of this utility model.

[0016] Figure 2 This is a half-sectional view of the silencer of this utility model.

[0017] Figure 3 This is a partial sectional view of the present invention.

[0018] Figure 4 This is a magnified view of a portion of the structure at point A of this utility model.

[0019] Figure 5 This is an enlarged view of a partial structure at point B of this utility model.

[0020] Figure 6 This is a schematic diagram of sound propagation in a silencer.

[0021] In the diagram: 1. Noise inlet tube; 2. Front cover; 3. Middle isolation cover; 4. Middle noise transmission tube; 5. Tail cover; 6. Noise outlet tube; 7. Rear sound transmission multi-hole tube; 8. Front sound transmission multi-hole tube; 9. Sound-absorbing material; 10. Outer shell. Detailed Implementation

[0022] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this invention. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0023] All materials and experimental apparatus used in the embodiments, comparative examples, and experimental examples of this utility model are commercially available materials and experimental apparatus. Except for some materials whose models and manufacturers are given below, the specific sources of other materials and experimental apparatus will not be repeated.

[0024] This solution discloses the following technical solutions:

[0025] Carbon fiber muffler:

[0026] like Figure 1 and 2 As shown, this solution discloses a carbon fiber silencer for use on the terminal air compressor of a nitrogen generator, including an inlet noise pipe 1, a front cover 2, a middle isolation cover 3, a middle noise transmission pipe 4, a tail cover 5, an outlet noise pipe 6, a rear sound transmission porous pipe 7, a front sound transmission porous pipe 8, a sound-absorbing material 9, and an outer shell 10.

[0027] like Figure 2 , 4 As shown in Figure 5, the front cover 2, the middle isolation cover 3, and the tail cover 5 are all circular plates; the sides of the front cover 2 and the tail cover 5 are respectively provided with a large-diameter outer convex ring and a small-diameter inner convex ring. The outer and inner convex rings on the front cover 2 extend to the same side, and the outer and inner convex rings on the tail cover 5 extend to the same side; the outer edge of the middle isolation cover 3 is provided with a convex ring, which extends to both sides of the middle isolation cover 3.

[0028] like Figure 2 and 3 As shown, one end of the front acoustic porous tube 8 is inserted into the smaller diameter inner convex ring on the front cover 2, and the other end is inserted into the convex ring on one side of the middle isolation cover 3. One end of the rear acoustic porous tube 7 is inserted into the convex ring on the other side of the middle isolation cover 3, and the other end is inserted into the smaller diameter inner convex ring on the tail cover 5. The outer shell 10 is cylindrical and fits over the rear acoustic porous tube 7 and the front acoustic porous tube 8. One end is inserted into the larger diameter outer convex ring on the front cover 2, and the other end is inserted into the larger diameter outer convex ring on the tail cover 5. The space between the outer shell 10 and the front acoustic porous tube 8, and between the outer shell 10 and the rear acoustic porous tube 7, is filled with sound-absorbing material 9.

[0029] The noise inlet tube 1 is concentrically fixed on the front cover 2, the intermediate noise transmission tube 4 is eccentrically fixed on the intermediate isolation cover 3, and the noise outlet tube 6 is eccentrically fixed on the tail cover 5. The axis of the noise inlet tube 1, the axis of the intermediate noise transmission tube 4, and the axis of the noise outlet tube 6 are in the same plane. When viewed axially from the end of the muffler, the intermediate noise transmission tube 4 is located on one side of the noise inlet tube 1, and the noise outlet tube 6 is located on the other side of the noise inlet tube 1.

[0030] The noise inlet tube 1 has a horn-shaped structure, with the larger diameter end located inside the muffler and several holes on the horn-shaped structure. The smaller diameter end is located outside the muffler, and the outer circumference is threaded for connecting equipment. The intermediate noise transmission tube 4 and the noise outlet tube 6 have ordinary tubular structures.

[0031] After the plug-in assembly, the outer surfaces of the front sound transmission multi-hole tube 8, the middle isolation cover 3, and the rear sound transmission multi-hole tube 7 are exactly within the same cylindrical surface; the outer circular surface of the front cover 2, the outer peripheral surface of the outer shell 10, and the outer circular surface of the tail cover 5 are also within the same cylindrical surface. This coherent interlocking design can maximally impede the propagation of sound to the outside. After assembly, the noise inlet tube 1, the middle noise transmission tube 4, and the noise outlet tube 6 are not concentric, which can further impede the propagation of sound to the outside of the silencer. The specific sound transmission diagram is as follows: Figure 6 As shown.

[0032] Among them, the noise inlet tube 1, front cover 2, front and rear sound transmission porous tubes 7, middle isolation cover 3, middle noise transmission tube 4, rear sound transmission porous tube 7, tail cover 5, noise outlet tube 6 and outer shell 10 are all solidified parts made of carbon fiber composite material and machined, and the sound-absorbing material 9 is made of activated carbon fiber felt.

[0033] Carbon fiber composite materials and their preparation methods are as follows:

[0034] The carbon fiber composite material mentioned above includes the following components in parts by weight: 40-60 parts carbon fiber cloth, 30-50 parts epoxy resin, 1-10 parts curing agent, 1-3 parts plasticizer, 5-15 parts diluent, 10-25 parts coal fly ash nanoparticles, 5-20 parts toughening agent, 1-5 parts filler, 1-5 parts flame retardant, 0.5-1 part thixotropic agent, and 0.5-1 part defoamer.

[0035] Among them, the carbon fiber cloth is made of resin-based carbon fiber, which has a sound absorption coefficient of about 0.9 at high frequencies and has good sound absorption performance.

[0036] Epoxy resins that can be used include bisphenol A type epoxy resin, bisphenol F type epoxy resin, or phenolic epoxy resin. The advantages and disadvantages of different material choices are as follows:

[0037] Bisphenol A type epoxy resins (such as E-51 and E-44) have the advantages of balanced overall performance, low cost, and easy processing. Their limitations include moderate resistance to damp heat and a tendency to soften at high temperatures. They are suitable for medium and low temperature environments, and their damping performance can be optimized with toughening agents.

[0038] Bisphenol F type epoxy resin (such as YD-128): Advantages: low viscosity, resistance to damp heat, and low curing shrinkage. Limitations: low mechanical strength and high cost.

[0039] Phenolic epoxy resin (such as DEN431) has the advantages of high temperature resistance, high rigidity, and good flame retardancy. Its limitation is that it is brittle and requires a high proportion of toughening agent.

[0040] Commonly used curing agents such as HY91 or K6 are used:

[0041] HY91 curing agent: It is a modified amine curing agent (low toxicity, low temperature curing type). Specifically, Huntsman's HY91 series or domestic alternatives (such as Shanghai Dianyang Chemical's DY-91) are selected. It has moderate reactivity with epoxy resin and is suitable for systems containing nanofillers (such as coal fly ash nanoparticles).

[0042] K6 curing agent: Anhydride curing agent (high temperature curing, high heat resistance type). Specifically, choose K6 series from Japan Kayaku (KAYAKU), or domestic alternatives (such as Jiaxing Guanghua K6 anhydride). It requires high temperature curing (140-180℃), has excellent heat resistance (Tg can reach above 150℃), low volatility, and is suitable for high-filler systems (such as composite materials containing 25 parts of coal fly ash).

[0043] Plasticizers, either rubber or polyether, are used to improve the flexibility and impact resistance of composite materials. In this case, rubber-based plasticizers are preferred. Recommended options include liquid nitrile rubber (LNBR) or hydroxyl-terminated polybutadiene rubber (HTPB); specifically, Hycar1300X43 (Zeon Corporation, USA): a liquid nitrile rubber with 33% acrylonitrile content, exhibiting good compatibility with epoxy resin and improving flexibility (the preferred choice in this case). Alternatively, Krasol LBH-3000 (Covestro, Germany): a hydroxyl-terminated polybutadiene rubber with low viscosity, enhancing low-temperature crack resistance. The role of rubber-based plasticizers is to lower the glass transition temperature (Tg) of the resin system, improving the material's deformation capacity under dynamic loads. They also synergistically disperse with coal fly ash nanoparticles (50nm) to reduce stress concentration.

[0044] Polyether plasticizers: Recommended: Polypropylene glycol diglycidyl ether (PPGDE) or polyether amine; specifically, Epodil 748 (Huntsman, USA): an epoxy-terminated polypropylene glycol ether that combines plasticizing and diluting functions. Or Jeffamine D-400 (Huntsman, USA): a polyether amine that can participate in curing as a reactive plasticizer, improving toughness. Functions of polyether plasticizers: Improve resin flowability, reduce viscosity (synergistically with diluents), while maintaining the flexibility of the cured network structure. Reduce brittleness caused by high filler content (10-25 parts coal fly ash).

[0045] The diluent, either phenyl acrylate or butyl styrene acrylate, is used to reduce the viscosity of the epoxy resin for easier processing. Recommended phenyl acrylates include phenoxyethyl acrylate (PHEA) or phenoxyethyl acrylate (PEA). Specifically, SR-339 (Sartorma, USA): phenoxyethyl acrylate, highly reactive, reduces viscosity while participating in curing; or Laromer PEA (BASF, Germany): phenoxyethyl acrylate, with excellent compatibility with epoxy resins. Function: The diluent content (5-15 parts) can adjust the resin viscosity to 200-500 mPa·s (suitable for prepreg impregnation). The phenyl structure provides rigidity, partially offsetting the modulus reduction caused by plasticizers.

[0046] Butylbenzene acrylate (preferred in this case), recommended: Butyl acrylate-styrene copolymer (BA-St) or isooctyl acrylate (EHA); specific options: Ebecryl 168 (Belgium Zynx): Isobornyl methacrylate, highly hydrophobic, suitable for humid environments. Or Actilane 421 (France Arkema): Isooctyl acrylate, low volatility, low shrinkage. Function: Long-chain alkyl groups (butyl / isooctyl) improve the material's hydrolysis resistance, suitable for silencers (contact with moisture environments), and are compatible with the hydrophobic surface of coal fly ash nanoparticles (silane modified), reducing interfacial defects.

[0047] Coal fly ash nanoparticles, with an average diameter of 50 nm (measured by a laser particle size analyzer), can enhance the impact strength, flexural strength, and hardness of epoxy resin, and also have noise reduction function.

[0048] This case study prioritizes Ningxia Dongfang's coal fly ash nanoparticles. Reasons for selection:

[0049] 1. Acoustic performance optimization

[0050] Reduce impurity interference: Impurities in coal fly ash (such as Fe2O3, CaO, unburned carbon, etc.) can be introduced into heterogeneous interfaces, causing sound waves to be randomly scattered inside the material, reducing the sound transmission loss (TL) in the target frequency band (1-4kHz).

[0051] 2. Enhanced Interface Integration

[0052] Impurities (such as CaO) readily react with the hydroxyl groups in epoxy resin, forming a weak interfacial layer. After modification with KH-550, high-purity coal fly ash exhibits more complete chemical bonding between its surface epoxy groups and the resin, reducing interfacial defects and improving load transfer efficiency.

[0053] 3. Long-term stability

[0054] Resistance to damp heat is crucial; impurities (such as CaO) absorb moisture and trigger micro-region hydrolysis, leading to expansion and cracking of the composite material. High-purity coal fly ash can avoid such problems and extend the service life of the silencer in humid environments.

[0055] Unsaturated polyester is used as a toughening agent to improve the toughness and impact resistance of the composite material. Recommended types are as follows:

[0056] Polylite 31032 (Chang Hsing Chemical, Taiwan): A phthalic unsaturated polyester with low cost and significantly improved toughness after curing. It was the preferred choice in this case.

[0057] Atlac 580 (Ineos, USA): An isophthalic unsaturated polyester with excellent chemical and heat resistance. When blended with epoxy resin, it can form an interpenetrating network (IPN).

[0058] The filler uses inorganic fillers such as calcium carbonate or talc to improve the physical and mechanical properties of epoxy resin and reduce costs.

[0059] The flame retardant used is the halogen-free flame retardant Exolit EP150, which is specifically designed for thermosetting epoxy resins and has excellent flame retardant properties.

[0060] The thixotropic agent is one of fumed silica (also known as white carbon black), organobentonite, and hydrogenated castor oil.

[0061] Defoamers include one of the following: silicone oils and organosilicones. Defoamers are used in the epoxy resin processing to reduce the generation of bubbles, thereby improving product quality.

[0062] Essential components for noise reduction purposes:

[0063] Carbon fiber cloth: The core reinforcement provides stiffness and an acoustic reflection interface.

[0064] Epoxy resin: a matrix material that acts as a bonding and reinforcing phase and transfers stress.

[0065] Coal fly ash nanoparticles: core noise reduction filler that improves TL through damping and scattering mechanisms.

[0066] Curing agent: Ensures the resin cross-links and cures to form a stable network structure.

[0067] Plasticizers: used to adjust the flexibility of resins, but excessive amounts will reduce the modulus and affect the high-frequency sound wave reflection efficiency.

[0068] Diluent: Used to reduce the viscosity of epoxy resin to facilitate processing.

[0069] Non-essential components:

[0070] Toughening agents: used to improve the toughness and impact resistance of composite materials.

[0071] Defoamer: Defoamers are used in the epoxy resin processing to reduce the generation of bubbles, thereby improving product quality.

[0072] Flame retardants: Flame retardant properties are not directly related to noise reduction.

[0073] While toughening agents, defoamers, and flame retardants can enhance other functions of carbon fiber composites, they do not directly contribute to noise reduction.

[0074] Filler: A process aid that does not directly contribute to noise reduction and can be adjusted according to the production process.

[0075] Thixotropic agents: process aids that do not directly contribute to noise reduction and can be adjusted according to the production process.

[0076] Technical basis for the proportion range:

[0077] Example 1:

[0078] The necessary components include: 40 parts carbon fiber cloth, 30 parts bisphenol A type epoxy resin E-51, 10 parts modified amine curing agent, 3 parts rubber plasticizer, 15 parts phenyl acrylate diluent, and 10 parts Ningxia Dongfang coal fly ash.

[0079] Non-essential components: 20 parts unsaturated polyester toughening agent, 1 part silicone oil defoamer, 5 parts calcium carbonate filler, 5 parts ExolitEP150 flame retardant, and 1 part atmospheric silica thixotropic agent.

[0080] Example 2:

[0081] The necessary components include: 50 parts carbon fiber cloth, 40 parts bisphenol A type epoxy resin E-514, 10 parts modified amine curing agent, 3 parts rubber plasticizer, 15 parts phenyl acrylate diluent, and 18 parts Ningxia Dongfang coal fly ash.

[0082] Non-essential components: 20 parts unsaturated polyester toughening agent, 1 part silicone oil defoamer, 5 parts calcium carbonate filler, 5 parts ExolitEP150 flame retardant, and 1 part atmospheric silica thixotropic agent.

[0083] Example 3:

[0084] The necessary components include: 60 parts carbon fiber cloth, 150 parts bisphenol A type epoxy resin E-515, 10 parts modified amine curing agent, 3 parts rubber plasticizer, 15 parts phenyl acrylate diluent, and 25 parts Ningxia Dongfang coal fly ash.

[0085] Non-essential components: 20 parts unsaturated polyester toughening agent, 1 part silicone oil defoamer, 5 parts calcium carbonate filler, 5 parts ExolitEP150 flame retardant, and 1 part atmospheric silica thixotropic agent.

[0086] Reasons for setting the dosage range for each component:

[0087] Viscosity control: If there is too little epoxy resin (<30 parts), the resin matrix cannot fully impregnate the carbon fiber cloth (40-60 parts) and coal fly ash nanoparticles (10-25 parts), resulting in excessively high viscosity of the prepreg (>1000 mPa·s), making it difficult to uniformly impregnate the fibers, forming dry spots or pores, and affecting noise reduction performance and mechanical strength. If there is too much resin (>50 parts), it will dilute the volume ratio of the reinforcing phase, reduce the overall modulus of the composite material (the reinforcing effect of carbon fiber and coal fly ash is weakened), and at the same time, the curing shrinkage rate will increase, which can easily cause interfacial debonding.

[0088] Mechanical property optimization: As a continuous phase, epoxy resin needs to provide sufficient shear strength and toughness to transfer loads. Experiments show that when the resin content is <30 parts, the interlaminar shear strength (ILSS) is <40 MPa; while with 50 parts of resin, the ILSS can reach 60-70 MPa, but the flexural modulus decreases by 10%-15%. The 30-50 part range can balance strength and stiffness.

[0089] Curing speed matching: The stoichiometric ratio of epoxy resin to curing agent (1-10 parts) must meet the requirements for complete cross-linking. 30-50 parts of resin corresponds to 1-10 parts of curing agent (such as HY91 amine curing agent), which can ensure a moderate curing reaction rate (gel time 30-60 minutes) and avoid nanoparticle agglomeration or carbon fiber damage due to excessively high exothermic peak (>150℃).

[0090] The addition amount of 10-25 parts of coal fly ash nanoparticles balances the enhancement effect and process feasibility.

[0091] 1. Noise reduction enhancement effect

[0092] Damping performance: Coal fly ash nanoparticles (50nm) improve acoustic transmission loss (TL) through the following three mechanisms:

[0093] Interfacial friction: Microscopic slippage occurs between particles and resin / carbon fiber due to acoustic vibration, converting acoustic energy into heat energy.

[0094] Local strain energy dissipation: The resin matrix surrounding the nanoparticles undergoes viscoelastic deformation under alternating stress, dissipating energy.

[0095] Resonant scattering: The 50nm particle size matches the 1-4kHz sound wave wavelength (λ≈85-340mm), triggering resonant damping.

[0096] When 10-25 parts are added, the TL increases by 3.2dB; after more than 25 parts, the increase in TL slows down (due to particle aggregation leading to a reduction in the effective interface).

[0097] 2. Limitations on process feasibility

[0098] Dispersibility threshold: When the fly ash content is >25 parts, even with high-speed shear dispersion (3000 rpm), nanoparticle agglomeration (particle size >100 nm) will still occur, resulting in a sharp increase in the viscosity of the prepreg solution (>800 mPa·s) and uneven impregnation.

[0099] Curing inhibition risk: High content of coal fly ash (especially when it contains acidic impurities) may adsorb curing agents (such as amine HY91), prolonging the gel time or causing incomplete curing.

[0100] 3. Economic considerations

[0101] When the amount of coal fly ash added is greater than 25 parts, the amount of surface modification (KH-550) and dispersant (such as BYK-111) needs to be increased, which increases the cost by about 20%, but the marginal benefit of performance improvement is diminishing.

[0102] Mechanism of action of coal fly ash nanoparticles:

[0103] 1. Nanosize effect

[0104] High specific surface area (50-80 m² / g): provides a large interfacial area, enhancing the interaction between sound waves and materials (increased energy dissipation interface density).

[0105] Quantum confinement effect: At the nanoscale, the lattice vibration modes of SiO2 / Al2O3 in coal fly ash change, enhancing phonon scattering.

[0106] 2. Interface Collaboration Mechanism

[0107] Chemical bonding: The surface of KH-550 modified coal fly ash contains epoxy groups, which form covalent bonds (Si-OC) with the resin matrix, improving the interfacial load transfer efficiency (interfacial shear strength is increased by 30%).

[0108] Physical anchoring: Nanoparticles are embedded in the resin-carbon fiber interface to inhibit crack propagation through the "pinning effect" (increasing fatigue life by 25%).

[0109] 3. Damped dynamic model

[0110] According to the Maxwell-Voigt composite damping theory, the total damping coefficient of the coal fly ash-resin system is... η It can be represented as:

[0111]

[0112] in η m For resin matrix damping. Φ p This refers to the volume fraction of fly ash from coal. η pFor particle damping, ν is Poisson's ratio, add 10-25 parts of coal fly ash ( Φ p When ≈5%-12%, η p It increases sound energy dissipation by 2-3 times.

[0113] 4. Theory of Acoustic Transmission Loss (TL)

[0114] According to the mass-spring-damping model, the relationship between TL and the material impedance Z and the damping coefficient η is as follows:

[0115]

[0116] TL is the transmission loss (unit: dB), ω is the angular frequency (unit: rad / s (radians / second)), η is the damping coefficient, and Z is the material impedance (unit: Pa·s / m (Rayleigh)).

[0117] The addition of coal fly ash achieves a directional boost (3.2dB) in TL in the 1-4kHz frequency band by increasing η and adjusting Z (impedance matching).

[0118] The preparation method of carbon fiber composite materials is as follows:

[0119] Raw material pretreatment:

[0120] 1. Surface treatment of carbon fiber cloth: Immerse the resin-based carbon fiber cloth in nitric acid solution (concentration 10%, 60℃) for 30 minutes for oxidation treatment, wash with water until neutral, and dry to enhance the interfacial bonding force with epoxy resin.

[0121] 2. Mixing of resin mixture: Mix according to the above proportions of components, and use a high-speed mixer (2000 rpm, 30 minutes) to ensure uniform dispersion. After uniform mixing, degas under vacuum (-0.1 MPa, 15-30 minutes, preferably 20 minutes).

[0122] The order of addition of each component when preparing the resin mixture is as follows:

[0123] (1) Premix epoxy resin and curing agent to form a basic system.

[0124] (2) Add diluent to reduce the viscosity of the system and facilitate the dispersion of subsequent additives.

[0125] (3) Add plasticizer and toughening agent. Plasticizer is used to improve flexibility and toughening agent is used to improve impact resistance. They need to be added in the early stage to ensure full compatibility with resin.

[0126] (4) Addition of coal fly ash nanoparticles: Particle size: average diameter 50 nm (measured by laser particle size analyzer). Surface modification: The coal fly ash nanoparticles are treated with silane coupling agent KH-550 to improve compatibility with epoxy resin. The surface modification method is a publicly available technology and will not be described in detail here; ultrasonic dispersion is used during addition to ensure uniform distribution.

[0127] (5) Add fillers and flame retardants. Fillers should be added in batches to avoid agglomeration or equipment overload caused by adding them all at once. Flame retardants and fillers should be added at the same time, especially powdered flame retardants, which need to be dispersed by high-speed shearing.

[0128] (6) Add thixotropic agent. The thixotropic agent is used to adjust the rheological properties (to prevent sagging). It should be added after the filler is dispersed and at a reduced speed. High-speed shearing will destroy its network structure and affect the thixotropic effect. It is recommended to mix at 500-1000 rpm for 5-10 minutes.

[0129] (7) Add defoamer. The defoamer (such as silicone) should be added before vacuum degassing and mixed briefly (5 minutes).

[0130] There are no specific requirements for the mixing time in the above steps, as long as the mixture is evenly mixed.

[0131] Vacuum degassing: After all additives are mixed, vacuum degassing (-0.1MPa, 15-30 minutes, preferably 20 minutes) is performed to completely remove air bubbles.

[0132] After degassing, the carbon fiber cloth is impregnated with the resin mixture and stacked. Finally, different cured parts are obtained through different molding and curing processes depending on the desired product. For example, in this scheme, the final product to be prepared is a carbon fiber muffler. The basic components of the carbon fiber muffler (i.e., the cured parts) can be divided into two categories: plates and cylindrical parts. The plates are formed by compression molding, while the cylindrical parts are formed by winding molding, as detailed below:

[0133] Winding molding (inlet noise tube 1, intermediate noise transmission tube 4, outlet noise tube 6, front sound transmission porous tube 8, rear sound transmission porous tube 7, and outer shell 10):

[0134] Impregnation: Immerse the pretreated carbon fiber cloth strip into the resin mixture at 25°C for 5 minutes.

[0135] Other conditions that need to be specified.

[0136] (1) Resin viscosity: The viscosity of the epoxy resin mixture must match the impregnation process (the viscosity at 25℃ is usually 200-1000 mPa·s, which meets the requirements). Too high a viscosity will lead to insufficient wetting, while too low a viscosity may cause resin loss or fiber slippage; the viscosity can be adjusted by adding diluent or adjusting the temperature.

[0137] (2) Fiber tension: The tension of the carbon fiber cloth needs to be controlled during impregnation (usually 1%-5% of the fiber strength) to avoid damage to the internal fibers or excessive stretching that leads to uneven distribution.

[0138] (3) Ambient humidity: Epoxy resin is sensitive to humidity. It is recommended to control the ambient humidity at 40%-60%RH (temperature 20-30℃) to avoid moisture affecting the curing reaction.

[0139] (5) Fiber surface treatment: The surface of carbon fiber needs to be sized (such as epoxy compatibility coating) to improve the interfacial bonding strength with resin.

[0140] (6) The ratio of the thickness of the impregnation layer on the carbon fiber surface to the thickness of the carbon fiber: Fiber volume fraction (FVF): In general, the FVF in composite materials needs to be controlled at 50%-60%. If the resin layer is too thick (FVF<50%), the material strength will decrease; if the resin is insufficient (FVF>65%), dry fibers or pores are likely to appear. The resin content can be controlled by adjusting the impregnation pressure or the rolling process.

[0141] Impregnation layer thickness ratio: The thickness of a single layer of carbon fiber cloth is usually 0.1-0.3mm. After impregnation, the total thickness increases by about 20%-30% (depending on the fiber weaving density). As a rule of thumb, the ratio of resin mixture layer thickness to fiber thickness is recommended to be 1:3 to 1:5 to ensure sufficient impregnation without over-impregnation.

[0142] Winding: Take out the soaked carbon fiber cloth, use a five-axis winding machine, preheat the mandrel to 50°, wind at an angle of ±55°, with 6 layers, tension controlled at 20N, and a winding speed of 0.5m / min.

[0143] Curing: Curing in stages (curing at 80℃ for 2 hours, curing at 120℃ for 3 hours, and curing at 150℃ for 1 hour).

[0144] CNC machining: After curing, the tube is demolded and then CNC machine tools are used to machine holes on the noise inlet tube 1, the front sound transmission multi-hole tube 8, the rear sound transmission multi-hole tube 7, the middle noise transmission tube 4, and the noise outlet tube 6. The holes on the front sound transmission multi-hole tube 8 and the rear sound transmission multi-hole tube 7 have a diameter of 1-3mm and a hole spacing of 8-12mm.

[0145] Compression molding (front cover 2, middle isolation cover 3, tail cover 5):

[0146] Step 1: Preprocessing:

[0147] 1. Wipe the working surface of the mold with acetone or alcohol to ensure that the mold surface is clean and free of grease.

[0148] 2. Saturate a clean, lint-free cloth with sealant FK-86 and wipe the surface systematically to form a smooth film. Apply approximately 1 to 3 coats, ensuring the coating is as thin as possible for even surface coverage. Allow to cure and seal in a dry environment for 15-30 minutes. After air drying, gently wipe clean. Apply another layer of FK-86, and after it dries, gently wipe clean.

[0149] 3. Apply the sealing agent three times, and wait for the solvent to evaporate before proceeding to the next step.

[0150] 4. Apply 3-5 coats of release agent EASY-LEASE-150TM, preferably 4 coats. Use a clean, lint-free cloth dampened with release agent to wipe the coating. When applying each coat, use a direction perpendicular to the application path of the previous coat to ensure complete coverage. Each coat should be applied by wiping or brushing in a single direction. Allow at least 15-20 minutes between coats.

[0151] Step Two: Lamination and Pressing

[0152] Lay out 4 layers of prepreg (carbon fiber cloth impregnated with resin mixture), with a molding pressure of 10 MPa, and cure conditions the same as the winding process (curing conditions depend on the resin, so the curing conditions are the same).

[0153] Step 3: Demolding and Machining

[0154] Remove the mold from the molding machine, wait for it to cool, then disassemble it and machine it to produce a round plate.

[0155] Fabrication of carbon fiber mufflers: bonding and assembly:

[0156] To ensure the connection between the parts, high-temperature resistant epoxy resin AB glue is used for bonding. The bonding sequence is as follows: the noise inlet tube 1 is bonded to the front cover 2, the front sound transmission multi-hole tube 8, the rear sound transmission multi-hole tube 7, and the middle noise transmission tube 4 are bonded to the middle isolation cover 3 respectively, and the tail cover 5 is bonded to the noise outlet tube 6.

[0157] Assemble all the bonded parts except for the tail cover 5 and the noise output tube 6 into one piece (using high-temperature resistant epoxy resin AB glue), wrap the outside with sound-absorbing material 9, and after wrapping, wrap the outer shell 10 on the outside of the sound-absorbing material 9 (or you can assemble the outer shell 10 first and then fill with sound-absorbing material 9). Finally, bond and assemble the tail cover 5 with the noise output tube 6, the outer shell 10, and the rear sound transmission porous tube 7.

[0158] The sound propagation path inside the silencer is as follows: Figure 6As shown, the noise from the air compressor at the end of the nitrogen generator is transmitted to the front cavity through the horn-shaped noise inlet pipe 1. After entering the front cavity, the sound is dispersed once. The remaining sound enters the rear cavity through the middle noise transmission pipe 4. After multiple sound reflections and sound absorption by the sound-absorbing material 9, the noise is finally transmitted out through the noise outlet pipe 6. The sound passes through the two chambers in the silencer. Under the excellent noise reduction effect of the carbon fiber material, the noise produced by the air compressor can be greatly reduced.

[0159] Tests showed that, compared to the carbon fiber composite material without added fly ash, the cured parts exhibited the following noise reduction performance: a 3.2 dB improvement in sound transmission loss (STL) in the 1-4 kHz frequency band (verified by COMSOL simulation); a 52% increase in impact strength (up to 18.5 kJ / m²); and an increase in flexural modulus to 4.3 GPa. Mechanical properties included a 20% increase in flexural strength (ASTM D790) and a Shore D hardness of 85.

[0160] The test data for noise reduction performance and specific impact resistance are as follows:

[0161]

[0162] Comparative Example 1

[0163] The difference between Comparative Example 1 and Example 1 is that no coal fly ash nanoparticles were added when preparing the epoxy resin.

[0164] The components and dosages of the epoxy resin are as follows: 40 parts resin-based carbon fiber cloth, 30 parts bisphenol A type epoxy resin E-51, 10 parts modified amine curing agent, 3 parts rubber plasticizer, 15 parts phenyl acrylate diluent, 20 parts unsaturated polyester toughening agent, 1 part silicone oil defoamer, 5 parts calcium carbonate filler, 5 parts Exolit EP150 flame retardant, 1 part atmospheric silica thixotropic agent, and 1 part defoamer.

[0165] Comparative Example 2

[0166] The difference between Comparative Example 2 and Comparative Example 1 is that an equal amount of phenolic resin (such as DEN431) is used instead of the bisphenol A type epoxy resin E-51 in Example 1.

[0167] Comparative Example 3

[0168] The difference between Comparative Example 3 and Comparative Example 1 is that the resin used is an unsaturated resin.

[0169] As can be seen from the above embodiments and comparative embodiments, the carbon fiber composite material obtained by adding coal fly ash has excellent noise reduction performance and impact resistance.

[0170] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the technical solution of this utility model, and are not intended to limit the specific implementation of this utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A carbon fiber sound damper, characterized by, include: Noise inlet tube (1), front cover (2), middle isolation cover (3), middle noise transmission tube (4), tail cover (5), noise outlet tube (6), rear sound transmission multi-hole tube (7), front sound transmission multi-hole tube (8), sound-absorbing material (9) and outer shell (10). One end of the front sound transmission porous tube (8) is inserted into the inner convex ring on the front cover (2), and the other end is inserted into the convex ring on one side of the middle isolation cover (3); one end of the rear sound transmission porous tube (7) is inserted into the convex ring on the other side of the middle isolation cover (3), and the other end of the rear sound transmission porous tube (7) is inserted into the inner convex ring on the tail cover (5); the outer shell (10) is cylindrical, one end is inserted into the outer convex ring on the front cover (2), and the other end is inserted into the outer convex ring on the tail cover (5); the sound-absorbing material (9) fills the gap between the outer shell (10) and the front sound transmission porous tube (8), and the gap between the outer shell (10) and the rear sound transmission porous tube (7); the noise inlet tube (1) is fixed on the front cover (2), the middle noise transmission tube (4) is fixed on the middle isolation cover (3), and the noise outlet tube (6) is fixed on the tail cover (5).

2. The carbon fiber silencer of claim 1, wherein, The noise inlet tube (1), front cover (2), middle isolation cover (3), middle noise transmission tube (4), tail cover (5), noise outlet tube (6), rear sound transmission porous tube (7), front sound transmission porous tube (8) and outer shell (10) are all made of carbon fiber composite material.

3. The carbon fiber silencer of claim 1, wherein, The sound-absorbing material (9) is an activated carbon fiber felt.

4. The carbon fiber sound damper of claim 1, wherein, The axis of the noise inlet tube (1), the axis of the intermediate noise transmission tube (4) and the axis of the noise outlet tube (6) are located in the same plane. The intermediate noise transmission tube (4) is located on one side of the axis of the noise inlet tube (1), and the noise outlet tube (6) is located on the other side of the axis of the noise inlet tube (1).

5. The carbon fiber silencer of claim 1, wherein, The noise inlet tube (1) has a horn-shaped structure. The end with a larger diameter is located inside the muffler and has several holes, while the other end with a smaller diameter is located outside the muffler. The outer circumference is provided with connecting threads.

6. The carbon fiber sound damper of claim 1, wherein, Both the front acoustic porous tube (8) and the rear acoustic porous tube (7) are provided with holes, the hole diameter is 2-5mm, and the hole spacing is 10-20mm.

7. The carbon fiber silencer of any one of claims 1-6, wherein, The diameter of the larger end of the noise inlet tube (1) is smaller than the diameter of the intermediate noise transmission tube (4) and the diameter of the noise outlet tube (6), respectively.

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