Carbon fiber composite resin cured part for silencer and preparation method of carbon fiber composite resin cured part

Abstract

The invention relates to the technical field of high-frequency noise control, and discloses a carbon fiber composite resin cured part for a silencer, which is characterized by comprising carbon fiber cloth and a resin mixed solution, the carbon fiber cloth is infiltrated by the resin mixed solution and is subjected to molding and curing treatment to obtain the cured part, and the carbon fiber composite resin cured part comprises the following components in parts by weight: 40-60 parts of the carbon fiber cloth, 10-20 parts of the resin mixed solution and 10-20 parts of the resin mixed solution. The material is made of resin-based carbon fibers; the resin mixed solution comprises the following components in parts by weight: 30-50 parts of epoxy resin, and the epoxy resin is bifunctional epoxy resin; the average particle size of the coal fly ash nano particles is 50nm, and the surfaces of the coal fly ash nano particles are modified by a silane coupling agent KH-550; 1-10 parts of a curing agent, wherein the curing agent is a modified amine curing agent or an anhydride curing agent; according to the scheme, the technical bottleneck that the sound absorption coefficient of a traditional aluminum material at the frequency band of 2000 Hz or above is smaller than 0.7 is thoroughly solved, the main body of the aluminum material is the carbon fibers and the resin, meanwhile, the lightweight design is achieved, and the preparation requirement for lightweight of the silencer of the air compressor of the nitrogen making machine can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of high-frequency noise control, and more particularly to a carbon fiber composite resin cured part for a muffler, and a method for preparing the carbon fiber composite resin cured part for a muffler. Background Art

[0002] In the field of high-frequency noise control for industrial equipment, such as nitrogen generators and air compressors, over 60% of noise energy is generated in the frequency band above 2000Hz. Existing sound-absorbing materials, due to microstructural limitations, struggle to effectively attenuate high-frequency sound waves. The short wavelength of high-frequency sound waves makes them highly penetrating, resulting in a sound absorption coefficient in the 2000-4000Hz frequency band generally below the critical value of 0.7.

[0003] Currently, porous sound-absorbing structural parts are made of aluminum-based composite materials, which are processed and assembled into silencers for equipment noise reduction. This solution achieves noise reduction through the reflection of sound waves by the outer shell made of aluminum-based composite materials and the sound absorption of internal filling materials (such as glass fiber cotton). Its typical sound wave propagation path is a straight-through conduction mode, and the sound absorption coefficient in the 2000Hz frequency band is only 0.65-0.68. To enhance its sound absorption coefficient, existing improvements mainly improve the acoustic resistance performance by adding inorganic fillers, but this leads to increased material density and weight, which significantly deviates from the lightweight design requirements.

[0004] There is an urgent need for a lightweight structural component for manufacturing a silencer with a sound absorption coefficient greater than 0.7. Summary of the Invention

[0005] The present invention aims to overcome at least one of the deficiencies of the above-mentioned prior art and provides a carbon fiber composite resin cured part for use in the manufacture of mufflers. This part is intended to address the technical issues that aluminum-based composite structural parts, when used in the manufacture of mufflers, have insufficient sound absorption (the sound absorption coefficient is less than 0.7 above 2000 Hz), making it impossible to effectively suppress the high-frequency noise of the nitrogen generator air compressor. Furthermore, the improved structure increases the weight, making it impossible to achieve lightweight design.

[0006] The technical solution adopted by the present invention is a carbon fiber composite resin cured part for a muffler, comprising a carbon fiber cloth and a resin mixture. The carbon fiber cloth is impregnated with the resin mixture and subjected to a molding and curing treatment to obtain the cured part. The components in parts by weight are as follows: Carbon fiber cloth: 40-60 parts, made of resin-based carbon fiber; The resin mixture comprises the following parts by weight: 30-50 parts of epoxy resin, wherein the epoxy resin is a difunctional epoxy resin; 10-25 parts of coal fly ash nanoparticles, wherein the average particle size of the coal fly ash nanoparticles is 50 nm and the surface of the coal fly ash nanoparticles is modified with a silane coupling agent KH-550; 1-10 parts of a curing agent, wherein the curing agent is a modified amine curing agent or an acid anhydride curing agent; 1-3 parts of plasticizer, wherein the plasticizer is rubber or polyether; 5-15 parts of diluent, wherein the diluent is a reactive acrylate diluent.

[0007] The carbon fiber composite resin cured parts provided by this solution achieve a breakthrough improvement in high-frequency noise reduction performance through the synergistic effect of specific components. The fly ash nanoparticles (average particle size 50nm) modified with the silane coupling agent KH-550 form a chemically bonded interface with the bifunctional epoxy resin, significantly enhancing the efficiency of sound wave energy dissipation. The sound transmission loss in the 1-4kHz frequency band is increased by 3.2dB, and the sound absorption coefficient in the 2000-4000Hz frequency band is roughly between 0.75 and 0.92, completely resolving the technical bottleneck of traditional aluminum materials with a sound absorption coefficient of less than 0.7 in the frequency band above 2000Hz. The main body is carbon fiber and resin, and it also has a lightweight design, which can meet the lightweight preparation requirements of nitrogen generator air compressor mufflers.

[0008] Furthermore, the resin mixture further comprises the following components in parts by weight: 5-20 parts of a toughening agent, 1-5 parts of a filler, 1-5 parts of a flame retardant, 0.5-1 parts of a thixotropic agent, and 0.5-1 parts of a defoaming agent.

[0009] Furthermore, the bifunctional epoxy resin is bisphenol A epoxy resin, bisphenol F epoxy resin or novolac epoxy resin.

[0010] Furthermore, the active acrylate diluent is phenyl acrylate or butylphenyl acrylate.

[0011] A method for preparing a carbon fiber composite resin cured part for a muffler, characterized by comprising the following steps: S1. Immerse the resin-based carbon fiber cloth in a nitric acid solution with a concentration of 5-15%, oxidize it at 50-80°C for 20-60 minutes, wash it with water until it is neutral, and then dry it; S2, stirring the resin mixture evenly and performing degassing treatment; S3, immersing the carbon fiber cloth in S1 into the degassed resin mixture; S4, taking out the impregnated carbon fiber cloth and forming it using a molding process; S5. Curing in different time periods to obtain the cured part.

[0012] Furthermore, when mixing in S2, the mixing is carried out in the following order: first, the epoxy resin and the curing agent are pre-mixed and preliminarily mixed to form a basic system; and the diluent, plasticizer and toughening agent, coal fly ash nanoparticles, filler and flame retardant, thixotropic agent, and defoaming agent are added in sequence and mixed evenly.

[0013] Furthermore, during the degassing treatment in S2: the resin mixture is degassed at a vacuum degree of -0.1 MPa for 15-30 minutes.

[0014] Furthermore, when the pretreated carbon fiber cloth is immersed in the resin mixture in S3, the temperature of the resin mixture is 25° C. and the time is 5 minutes.

[0015] Furthermore, the forming process in S4 is winding or compression molding.

[0016] Furthermore, the curing in step S4 is divided into three curing periods, namely: curing at 80° C. for 2 hours, curing at 120° C. for 3 hours, and curing at 150° C. for 1 hour.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: the carbon fiber composite resin cured part provided by this solution achieves a breakthrough improvement in high-frequency noise reduction performance through the synergistic effect of specific components. The fly ash nanoparticles (average particle size 50 nm) modified with the silane coupling agent KH-550 form a chemically bonded interface with the bifunctional epoxy resin, significantly enhancing the efficiency of sound wave energy dissipation. The sound transmission loss in the 1-4 kHz frequency band is increased by 3.2 dB, and the sound absorption coefficient in the 2000-4000 Hz frequency band is approximately between 0.75 and 0.92, completely solving the technical bottleneck of traditional aluminum materials with a sound absorption coefficient of less than 0.7 in the frequency band above 2000 Hz. Moreover, its main body is carbon fiber and resin, and it also has a lightweight design, which can meet the lightweight preparation requirements of nitrogen generator air compressor mufflers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the overall structure of the muffler of the present invention.

[0019] Figure 2 It is a half-section view of the muffler of the present invention.

[0020] Figure 3 It is a partial cross-sectional view of the present invention.

[0021] Figure 4 This is an enlarged view of the local structure of point A of the present invention.

[0022] Figure 5 This is an enlarged view of the local structure of location B of the present invention.

[0023] Figure 6 Schematic diagram of sound propagation in a muffler.

[0024] In the figure: 1. Noise inlet pipe; 2. Front cover; 3. Middle isolation cover; 4. Middle noise transmission pipe; 5. Tail cover; 6. Noise outlet pipe; 7. Rear sound transmission porous pipe; 8. Front sound transmission porous pipe; 9. Sound-absorbing material; 10. Outer shell. DETAILED DESCRIPTION

[0025] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting the present invention. To better illustrate the following embodiments, some components in the accompanying drawings may be omitted, enlarged, or reduced in size, and do not represent actual product dimensions. Those skilled in the art will appreciate that some well-known structures and their descriptions may be omitted from the accompanying drawings.

[0026] The materials and experimental devices used in the embodiments, comparative examples and experimental examples of the present invention are all existing commercially available materials and experimental devices. For example, the models and manufacturers of some materials in the following content have been given, and the specific sources of other materials and experimental devices are not repeated here.

[0027] This solution discloses the following technical solutions: Carbon fiber silencer: like Figure 1 and 2 As shown, the present invention discloses a carbon fiber silencer for use on a terminal air compressor of a nitrogen production equipment, comprising a noise inlet pipe 1, a front cover 2, an intermediate isolation cover 3, an intermediate noise transmission pipe 4, a tail cover 5, a noise outlet 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.

[0028] like Figure 2 、 4 As shown in Figures 5 and 6, the front cover 2, the middle isolation cover 3 and the tail cover 5 are all circular plates; the side surfaces of the front cover 2 and the tail cover 5 are respectively provided with outer convex rings with larger diameters, and inner convex rings with smaller diameters. The outer convex ring and the inner convex ring on the front cover 2 extend toward the same side, and the outer convex ring and the inner convex ring on the tail cover 5 extend toward the same side; the outer edge of the middle isolation cover 3 is provided with a convex ring, which extends toward both sides of the middle isolation cover 3.

[0029] like Figure 2 and 3 As shown, one end of the front sound-transmitting porous tube 8 is plugged into the inner convex ring with a smaller diameter on the front cover 2, and the other end is plugged into the convex ring on one side of the intermediate isolation cover 3; one end of the rear sound-transmitting porous tube 7 is plugged into the convex ring on the other side of the intermediate isolation cover 3, and the other end is plugged into the inner convex ring with a smaller diameter on the tail cover 5; the outer shell 10 is cylindrical, and is sleeved on the outside of the rear sound-transmitting porous tube 7 and the front sound-transmitting porous tube 8, one end of which is plugged into the outer convex ring with a larger diameter on the front cover 2, and the other end of which is plugged into the outer convex ring with a larger diameter on the tail cover 5; the outer shell 10 and the front sound-transmitting porous tube 8, as well as the outer shell 10 and the rear sound-transmitting porous tube 7 are filled with sound-absorbing material 9.

[0030] The noise inlet pipe 1 is concentrically fixed on the front cover 2, the intermediate noise transmission pipe 4 is eccentrically fixed on the intermediate isolation cover 3, and the noise outlet pipe 6 is eccentrically fixed on the tail cover 5. The axis of the noise inlet pipe 1, the axis of the intermediate noise transmission pipe 4 and the axis of the noise outlet pipe 6 are in the same plane; when looking axially from the end of the muffler to the inside, the intermediate noise transmission pipe 4 is located on one side of the noise inlet pipe 1, and the noise outlet pipe 6 is located on the other side of the noise inlet pipe 1.

[0031] The noise inlet pipe 1 is a trumpet-shaped structure, with the end with a larger diameter arranged inside the muffler, and a number of holes provided on the trumpet-shaped structure, and the other end with a smaller diameter arranged outside the muffler, and a thread provided on the outer peripheral surface for connecting equipment; the intermediate noise transmission pipe 4 and the noise outlet pipe 6 are ordinary tubular structures.

[0032] After the plug-in assembly is completed, the outer surface of the front sound-transmitting porous tube 8, the outer circular surface of the intermediate isolation cover 3, and the outer surface of the rear sound-transmitting porous 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 within the same cylindrical surface; this coherent sleeve design can hinder the sound from propagating to the outside to the greatest extent. After assembly, the noise inlet pipe 1, the intermediate noise-transmitting pipe 4 and the noise outlet pipe 6 are not concentric, which can further hinder the sound from propagating to the outside of the muffler. The specific sound transmission diagram is shown in the figure. Figure 6 shown.

[0033] Among them, the noise inlet pipe 1, the front cover 2, the front and rear sound-transmitting porous tubes 7, the middle isolation cover 3, the middle noise-transmitting tube 4, the rear sound-transmitting porous tube 7, the tail cover 5, the noise outlet pipe 6 and the outer shell 10 are all made of solidified parts made of carbon fiber composite materials through machining, and the sound-absorbing material 9 adopts activated carbon fiber felt.

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

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

[0036] Epoxy resin can be: bisphenol A epoxy resin, bisphenol F epoxy resin or novolac epoxy resin. The advantages and disadvantages of the specific material selection are as follows: Bisphenol A epoxy resin (such as E-51 and E-44) offers advantages such as balanced overall performance, low cost, and easy processing. Its limitations include limited resistance to moisture and heat and tendency to soften at high temperatures. Suitable for medium and low temperature environments, damping properties can be optimized with toughening agents.

[0037] Bisphenol F epoxy resin (such as YD-128) has advantages of low viscosity, resistance to moisture and heat, and small shrinkage upon curing. Limitations include low mechanical strength and high cost.

[0038] 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.

[0039] The curing agent uses commonly used curing agents such as HY91 or K6: HY91 curing agent: It is a modified amine curing agent (low toxicity, low temperature curing type). Specifically, Huntsman's HY91 series or domestic alternative models (such as Shanghai Dianyang Chemical's DY-91) are selected. It has moderate reaction activity with epoxy resin and is suitable for systems containing nanofillers (such as coal fly ash nanoparticles).

[0040] K6 curing agent: anhydride curing agent (high temperature curing, high heat resistance), specifically KAYAKU's K6 series, or domestic alternatives (such as Jiaxing Guanghua K6 anhydride), requires high temperature curing (140-180°C), excellent heat resistance (Tg can reach above 150°C), low volatility, and is suitable for highly filled systems (such as composite materials containing 25 parts of fly ash).

[0041] Plasticizers, such as rubber or polyether, are used to improve the flexibility and impact resistance of composite materials. In this case, rubber plasticizers are preferred. Recommended: Liquid nitrile rubber (LNBR) or hydroxyl-terminated polybutadiene rubber (HTPB). Specifically, Hycar 1300X43 (Zeon, USA): a liquid nitrile rubber with a 33% acrylonitrile content, offers good compatibility with epoxy resin and improves flexibility (preferred in this case). Alternatively, Krasol LBH-3000 (Covestro, Germany): a hydroxyl-terminated polybutadiene rubber with low viscosity and enhanced low-temperature crack resistance. Rubber plasticizers lower the glass transition temperature (Tg) of the resin system and improve the material's deformation capacity under dynamic loads. They also synergistically disperse with fly ash nanoparticles (50 nm) to reduce stress concentration.

[0042] Polyether plasticizers: Recommended: polypropylene glycol diglycidyl ether (PPGDE) or polyetheramines; specifically, Epodil 748 (Huntsman, USA): an epoxy-terminated polypropylene glycol ether with both plasticizing and diluting properties. Or Jeffamine D-400 (Huntsman, USA): a polyetheramine that can act as a reactive plasticizer during curing to improve toughness. Polyether plasticizers improve resin fluidity and reduce viscosity (synergistically with diluents), while maintaining the flexibility of the cured network structure. They also reduce brittleness caused by high filler loadings (10-25 parts by weight of fly ash).

[0043] Diluents such as phenyl acrylate or butylphenyl acrylate are used to reduce the viscosity of epoxy resins for easier processing. Recommended phenyl acrylates include phenoxyethyl acrylate (PHEA) or phenoxyethyl acrylate (PEA). Specific options include SR-339 (Sartomer, USA): a phenoxyethyl acrylate with high reactivity that reduces viscosity and participates in curing. Alternatively, Laromer PEA (BASF, Germany): a phenoxyethyl acrylate with excellent compatibility with epoxy resins. Function: The diluent content (5-15 phr) can adjust the resin adhesive viscosity to 200-500 mPa·s (suitable for prepreg impregnation). The phenyl structure provides rigidity, partially offsetting the modulus reduction caused by the plasticizer.

[0044] Butylphenyl acrylate (preferred in this case), with recommendations for butyl acrylate-styrene copolymer (BA-St) or isooctyl acrylate (EHA). Specific options include: Ebecryl 168 (Allnex, Belgium): isobornyl methacrylate, highly hydrophobic and suitable for humid environments; or Actilane 421 (Arkema, France): isooctyl acrylate, low volatility and low shrinkage. Function: The long-chain alkyl groups (butyl / isooctyl) enhance the material's hydrolysis resistance, making it suitable for mufflers (which are exposed to moisture). They are also compatible with the hydrophobic surface of silane-modified fly ash nanoparticles, reducing interfacial defects.

[0045] Coal fly ash nanoparticles, particle size: average diameter 50nm (measured by laser particle size analyzer); can enhance the impact strength, flexural strength and hardness of epoxy resin, and also have noise reduction function.

[0046] In this case, Ningxia Dongfang's coal fly ash nanoparticles are preferred. Reasons for selection: 1. Acoustic performance optimization Reduce impurity interference: Impurities in fly ash (such as Fe2O3, CaO, unburned carbon, etc.) will introduce heterogeneous interfaces, causing random scattering of sound waves inside the material, reducing the sound transmission loss (TL) in the target frequency band (1-4kHz).

[0047] 2. Enhanced interface bonding Impurities (such as CaO) easily react with the hydroxyl groups in epoxy resin, forming a weak interface layer. After high-purity fly ash is modified with KH-550, the surface epoxy groups chemically bond more fully with the resin, reducing interfacial defects and improving load transfer efficiency.

[0048] 3. Long-term stability Resistance to moisture and heat: Impurities (such as CaO) absorb moisture and cause micro-area hydrolysis, leading to expansion and cracking of the composite material. High-purity fly ash can avoid such problems and extend the service life of the muffler in humid environments.

[0049] Unsaturated polyester is used as toughening agent to improve the toughness and impact resistance of composite materials. The recommended types are as follows: Polylite 31032 (Chang Hsing Chemical, Taiwan): This orthophthalic unsaturated polyester offers low cost and significantly improved toughness after curing. This is the preferred choice for this application.

[0050] Atlac 580 (INEOS USA): is an isophthalic unsaturated polyester with excellent chemical and heat resistance. It can form an interpenetrating network (IPN) when blended with epoxy resin.

[0051] Fillers include inorganic fillers such as calcium carbonate or talc, which are used to improve the physical and mechanical properties of epoxy resin and reduce costs.

[0052] The flame retardant used is halogen-free flame retardant Exolit EP150, which is specially used for thermosetting epoxy resin and has good flame retardant properties.

[0053] The thixotropic agent is one of fumed silica (also known as white carbon black), organic bentonite, and hydrogenated castor oil.

[0054] Defoaming agents include silicone oils and organosilicon. Defoaming agents are used in the epoxy resin processing to reduce the generation of bubbles and thus improve product quality.

[0055] Necessary components for noise reduction purposes: Carbon fiber cloth: core reinforcement, provides stiffness and sound wave reflection interface.

[0056] Epoxy resin: matrix material, bonding reinforcement phase and transferring stress.

[0057] Coal fly ash nanoparticles: core noise reduction functional filler, improving TL through damping and scattering mechanisms.

[0058] Curing agent: ensures the cross-linking and curing of the resin to form a stable network structure.

[0059] Plasticizer: Used to adjust the flexibility of the resin, but excessive use will reduce the modulus and affect the reflection efficiency of high-frequency sound waves.

[0060] Diluent: Used to reduce the viscosity of epoxy resin to facilitate processing.

[0061] Non-essential ingredients: Toughening agent: used to improve the toughness and impact resistance of composite materials.

[0062] Defoaming agent: Defoaming agent is used in the epoxy resin processing to reduce the generation of bubbles and thus improve product quality.

[0063] Flame retardants: Flame retardant properties have no direct correlation with noise reduction.

[0064] Although toughening agents, defoaming agents, and flame retardants can increase other functions of carbon fiber composites, they do not directly contribute to noise reduction.

[0065] Filler: Process auxiliary agent, has no direct contribution to noise reduction and can be adjusted according to the production process.

[0066] Thixotropic agent: process auxiliary agent, has no direct contribution to noise reduction, and can be adjusted according to the production process.

[0067] Technical basis for the ratio range: Example 1: The necessary components include: 40 parts of carbon fiber cloth, 30 parts of bisphenol A epoxy resin E-51, 10 parts of modified amine curing agent, 3 parts of rubber plasticizer, 15 parts of phenyl acrylate diluent, and 10 parts of Ningxia Dongfang coal fly ash; Non-essential components: 20 parts of unsaturated polyester toughening agent, 1 part of silicone oil defoaming agent, 5 parts of calcium carbonate filler, 5 parts of ExolitEP150 flame retardant, and 1 part of meteorological silica thixotropic agent.

[0068] Example 2: The necessary components include: 50 parts of carbon fiber cloth, 40 parts of bisphenol A epoxy resin E-51, 10 parts of modified amine curing agent, 3 parts of rubber plasticizer, 15 parts of phenyl acrylate diluent, and 18 parts of Ningxia Dongfang coal fly ash; Non-essential components: 20 parts of unsaturated polyester toughening agent, 1 part of silicone oil defoaming agent, 5 parts of calcium carbonate filler, 5 parts of ExolitEP150 flame retardant, and 1 part of meteorological silica thixotropic agent.

[0069] Example 3: The necessary components include: 60 parts of carbon fiber cloth, 50 parts of bisphenol A epoxy resin E-51, 10 parts of modified amine curing agent, 3 parts of rubber plasticizer, 15 parts of phenyl acrylate diluent, and 25 parts of Ningxia Dongfang coal fly ash; Non-essential components: 20 parts of unsaturated polyester toughening agent, 1 part of silicone oil defoaming agent, 5 parts of calcium carbonate filler, 5 parts of ExolitEP150 flame retardant, and 1 part of meteorological silica thixotropic agent.

[0070] Reasons for setting the dosage range of each component: Viscosity Control: Too little epoxy resin (<30 phr) prevents the resin matrix from fully impregnating the carbon fiber cloth (40-60 phr) and fly ash nanoparticles (10-25 phr). This results in a prepreg adhesive with excessively high viscosity (>1000 mPa·s), making it difficult to evenly impregnate the fibers, resulting in dry spots or voids, which compromise noise reduction and mechanical strength. Excessive resin (>50 phr) dilutes the volume fraction of the reinforcement phase, reducing the overall modulus of the composite (weakening the reinforcing effects of the carbon fiber and fly ash). This also increases cure shrinkage, which can easily lead to interfacial debonding.

[0071] Mechanical Property Optimization: Epoxy resin, as the continuous phase, must provide sufficient shear strength and toughness to transmit loads. Experimental results show that when the resin content is less than 30 phr, the interlaminar shear strength (ILSS) is less than 40 MPa. At 50 phr, the ILSS reaches 60-70 MPa, but the flexural modulus decreases by 10%-15%. The 30-50 phr range provides a good balance between strength and rigidity.

[0072] Matching cure speed: The stoichiometric ratio of epoxy resin to curing agent (1-10 parts) must ensure complete crosslinking. A ratio of 30-50 parts resin to 1-10 parts curing agent (such as HY91 amine curing agent) ensures a moderate cure reaction rate (gel time 30-60 minutes) and avoids excessive exothermic peaks (>150°C) that can lead to nanoparticle agglomeration or carbon fiber damage.

[0073] The addition amount of 10-25 parts of coal fly ash nanoparticles takes into account both the enhancement effect and process feasibility.

[0074] 1. Noise reduction enhancement effect Damping performance: Coal fly ash nanoparticles (50 nm) improve acoustic transmission loss (TL) through the following three mechanisms: Interface friction: Micro-slip occurs between particles and resin and carbon fiber due to acoustic vibration, converting acoustic energy into heat energy.

[0075] Local strain energy dissipation: The resin matrix around the nanoparticles undergoes viscoelastic deformation under alternating stress and dissipates energy.

[0076] Resonance scattering: The 50nm particle size matches the 1-4kHz sound wave wavelength (λ≈85-340mm), causing resonance damping.

[0077] When 10-25 parts are added, TL increases by 3.2dB; after adding more than 25 parts, the TL increase slows down (due to particle agglomeration leading to a reduction in the effective interface).

[0078] 2. Process feasibility limitations Dispersion threshold: When the fly ash content is greater than 25 parts per million, nanoparticle agglomeration (particle size greater than 100 nm) will still occur even with high-speed shear dispersion (3000 rpm), resulting in a sharp increase in the viscosity of the prepreg adhesive (greater than 800 mPa·s) and uneven impregnation.

[0079] Risk of curing inhibition: High levels of fly ash (especially when containing acidic impurities) may adsorb curing agents (such as amine HY91), prolonging the gel time or causing incomplete curing.

[0080] 3. Economic considerations When the amount of 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, and the cost increases by about 20%, but the marginal benefit of performance improvement decreases.

[0081] Mechanism of action of coal fly ash nanoparticles: 1. Nanosize effect High specific surface area (50-80 m² / g): provides a large interface area, enhancing the interaction between the acoustic wave and the material (increased energy dissipation interface density).

[0082] Quantum confinement effect: At the nanoscale, the SiO2 / Al2O3 lattice vibration mode in coal fly ash changes, enhancing phonon scattering.

[0083] 2. Interface collaboration mechanism Chemical bonding: The surface of KH-550-modified fly ash contains epoxy groups, which form covalent bonds (Si-OC) with the resin matrix, improving the interface load transfer efficiency (interface shear strength increased by 30%).

[0084] Physical anchoring: Nanoparticles are embedded in the resin-carbon fiber interface, inhibiting crack propagation through the "pinning effect" (fatigue life increased by 25%).

[0085] 3. Damping dynamics model According to the Maxwell-Voigt composite damping theory, the total damping coefficient of the fly ash-resin system is η It can be expressed as:

[0086] in η m is the resin matrix damping, Φ p is the volume fraction of coal fly ash, η p is particle damping, ν is Poisson's ratio, adding 10-25 parts of coal fly ash ( Φ p ≈5%-12%), η p Improved by 2-3 times, significantly enhancing sound energy dissipation.

[0087] 4. Transmission Loss (TL) Theory According to the mass-spring-damper model, the relationship between TL, material impedance Z and damping coefficient η is:

[0088] TL is the transmission loss (unit: dB), ω is the angular frequency (unit: rad / s (radians per second)), η is the damping coefficient, and Z is the material impedance (unit: Pa·s / m (Rayleigh)).

[0089] The addition of fly ash can achieve a directional improvement of TL (3.2 dB) in the 1-4 kHz frequency band by increasing η and adjusting Z (impedance matching).

[0090] The preparation method of carbon fiber composite material is as follows: Raw material pretreatment: 1. Surface treatment of carbon fiber cloth: Immerse the resin-based carbon fiber cloth tape in nitric acid solution (concentration 10%, 60℃) for oxidation treatment for 30 minutes, wash with water until neutral, and dry to enhance the interfacial bonding strength with epoxy resin.

[0091] 2. Mixing of resin mixture: Mix the components according to the above ratio, use a high-speed stirrer (speed 2000 rpm, time 30 minutes) to ensure uniform dispersion, and vacuum degassing (-0.1 MPa, 15-30 minutes, preferably 20 minutes) after mixing evenly.

[0092] The order of adding the components when preparing the resin mixture is as follows: (1) Pre-mix the epoxy resin and curing agent and initially mix them to form a base system.

[0093] (2) Add diluent to reduce the viscosity of the system and facilitate the dispersion of subsequent additives.

[0094] (3) Add plasticizers and tougheners. Plasticizers are used to improve flexibility, and tougheners are used to improve impact resistance. They need to be added early to ensure full compatibility with the resin.

[0095] (4) Addition of fly ash nanoparticles: Particle size: average diameter 50 nm (measured by laser particle size analyzer). Surface modification: The fly ash nanoparticles were treated with silane coupling agent KH-550 to improve compatibility with epoxy resin. The surface modification method is publicly available and will not be described in detail here. Ultrasonic dispersion was performed during addition to ensure uniform distribution.

[0096] (5) Add fillers and flame retardants. Fillers need to be added in batches to avoid agglomeration or equipment overload caused by all-in-one addition. Flame retardants and fillers are added simultaneously, especially powdered flame retardants, which require high-speed shear dispersion.

[0097] (6) Add thixotropic agent. The thixotropic agent is used to adjust the rheological properties (anti-sagging). It needs to be added after the filler is dispersed and the speed is reduced. 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.

[0098] (7) Add defoaming agent. Defoaming agent (such as silicone) should be added before vacuum degassing and mixed briefly (5 minutes).

[0099] During mixing, there is no specific requirement for the mixing time in the above steps, as long as the mixing is uniform.

[0100] Vacuum degassing: After all additives are mixed, perform vacuum degassing (-0.1MPa, 15-30 minutes, preferably 20 minutes) to completely remove bubbles.

[0101] 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 treatments according to the required products. Specifically, for example, in this solution, the final product to be prepared is a carbon fiber muffler. The basic components (i.e., cured parts) of the carbon fiber muffler can be divided into two categories: plates and cylinders. Plates are formed by compression molding, while cylinders are formed by winding. The details are as follows: Winding molding (noise inlet pipe 1, middle noise transmission pipe 4, noise outlet pipe 6, front sound transmission porous pipe 8, rear sound transmission porous pipe 7 and outer shell 10): Impregnation: Immerse the pretreated carbon fiber tape in the resin mixture at a temperature of 25°C for 5 minutes.

[0102] Other conditions that need to be defined.

[0103] (1) Resin viscosity: The viscosity of the epoxy resin mixture must match the impregnation process (the viscosity at 25°C is usually 200-1000 mPa·s, which meets the requirements). Too high a viscosity will lead to insufficient impregnation, while too low a viscosity may cause resin loss or fiber slippage. The viscosity can be adjusted by adding diluents or adjusting the temperature.

[0104] (2) Fiber tension: The tension of the carbon fiber cloth must be controlled during impregnation (usually 1%-5% of the fiber strength) to avoid internal fiber damage or excessive stretching leading to uneven distribution.

[0105] (3) Ambient humidity: Epoxy resin is sensitive to humidity. It is recommended to control the ambient humidity at 40%-60% RH (temperature 20-30°C) to avoid moisture affecting the curing reaction.

[0106] (5) Fiber surface treatment: The carbon fiber surface needs to be sizing treated (such as epoxy compatibility coating) to improve the interface bonding strength with the resin.

[0107] (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): Generally, 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 will easily appear. The resin content can be controlled by adjusting the impregnation pressure or rolling process.

[0108] Impregnation layer thickness ratio: The thickness of a single layer of carbon fiber cloth is usually 0.1-0.3mm, and the total thickness increases by about 20%-30% after impregnation (depending on the fiber weaving density). In experience, the ratio of the resin mixture layer thickness to the fiber thickness is recommended to be 1:3 to 1:5 to ensure sufficient impregnation without excess.

[0109] Winding: Take out the soaked carbon fiber cloth and use a five-axis winding machine. Preheat the core mold to 50°C, wind at an angle of ±55°, set the number of layers to 6, control the tension to 20N, and wind at a speed of 0.5m / min.

[0110] Curing: Curing in different time periods (80℃ curing for 2h, 120℃ curing for 3h, 150℃ curing for 1h).

[0111] CNC processing: After curing is completed, demoulding is carried out, and then a CNC machine tool is used to process holes on the noise inlet pipe 1, the front sound-transmitting porous pipe 8, the rear sound-transmitting porous pipe 7, the middle noise-transmitting pipe 4, and the noise outlet pipe 6. Among them, the holes on the front sound-transmitting porous pipe 8 and the rear sound-transmitting porous pipe 7 have a diameter of 1-3 mm and a hole spacing of 8-12 mm.

[0112] Molding (front cover 2, middle isolation cover 3, tail cover 5): Step 1: Preprocessing: 1. Scrub the mold working surface with acetone or alcohol to ensure that the mold surface is clean and free of grease.

[0113] 2. Saturate a clean, lint-free cloth with sealant FK-86 and rub it in a methodical manner, creating a smooth film. Apply the sealant 1 to 3 times, making sure the coating is as thin as possible to achieve even coverage. Allow the sealant to cure for 15-30 minutes in a dry environment. Allow it to dry naturally, then gently wipe it clean. Apply another layer of FK-86 and, once dry, gently wipe it clean.

[0114] 3. Wipe the sealing agent 3 times and proceed to the next step after the solvent evaporates.

[0115] 4. Apply EASY-LEASE-150™ release agent 3-5 times, preferably 4 times, using a clean, lint-free cloth with release agent. Apply the next coat perpendicular to the previous coat to ensure complete coverage. Apply each coat in a single direction, either by wiping or brushing. Allow at least 15-20 minutes between coats.

[0116] Step 2: Lamination and pressing: Lay out the prepreg (carbon fiber cloth impregnated with resin mixture) with 4 layers, a mold clamping pressure of 10 MPa, and the curing conditions are the same as the winding process (the curing conditions depend on the resin, so the curing conditions are the same).

[0117] Step 3: Demolding and machining: The mold is taken out of the molding machine, and after the mold cools down, it is demolded and then machined to form a round plate.

[0118] Preparation of carbon fiber muffler: bonding assembly: To ensure the connection between each part, high temperature resistant epoxy resin glue AB glue is used for bonding, and the bonding order is as follows: the noise inlet pipe 1 is bonded to the front cover 2, the front sound transmission porous pipe 8, the rear sound transmission porous pipe 7, and the middle noise transmission pipe 4 are respectively bonded to the middle isolation cover 3, and the tail cover 5 is bonded to the noise outlet pipe 6.

[0119] Assemble the bonded parts except the tail cover 5 and the noise outlet pipe 6 into one body (using high-temperature resistant epoxy resin glue 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 (you can also assemble the outer shell 10 first and then fill it with the sound-absorbing material 9), and finally glue the tail cover 5 with the noise outlet pipe 6 to the outer shell 10 and the rear sound-transmitting porous tube 7.

[0120] The propagation path of sound inside the muffler is as follows Figure 6 As shown, the noise of the air compressor at the end of the nitrogen generator is transmitted into the front cavity through the trumpet-shaped noise inlet pipe 1. After entering the front cavity, the sound is dispersed once, and 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 from the noise outlet pipe 6. The sound passes through the two chambers in the muffler. Under the excellent noise reduction effect of the carbon fiber material, the noise produced by the air compressor can be greatly reduced.

[0121] Tests have shown that, compared to materials without fly ash, cured parts made from the aforementioned carbon fiber composite material exhibit a 3.2dB improvement in noise reduction (STL) in the 1-4kHz frequency band (verified by COMSOL simulations). Impact strength is increased by 52% (to 18.5kJ / m²), and the flexural modulus is increased to 4.3GPa. Mechanical properties include a 20% increase in flexural strength (ASTM D790) and a hardness (Shore D) of 85.

[0122] The test data of noise reduction performance and specific impact strength performance are as follows:

[0123] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no coal fly ash nanoparticles are added when preparing the epoxy resin.

[0124] The components and amounts of epoxy resin are as follows: 40 parts of resin-based carbon fiber cloth, 30 parts of bisphenol A epoxy resin E-51, 10 parts of modified amine curing agent, 3 parts of rubber plasticizer, 15 parts of phenyl acrylate diluent, 20 parts of unsaturated polyester toughening agent, 1 part of silicone oil defoaming agent, 5 parts of calcium carbonate filler, 5 parts of ExolitEP150 flame retardant, 1 part of meteorological silica thixotropic agent, and 1 part of defoaming agent.

[0125] Comparative Example 2 Comparative Example 2 differs from Comparative Example 1 in that an equal amount of phenolic resin (such as DEN431) is used instead of the bisphenol A epoxy resin E-51 in Example 1.

[0126] Comparative Example 3 The difference between Comparative Example 3 and Comparative Example 1 is that the resin used is an unsaturated resin.

[0127] It can be seen from the above examples and comparative examples that the carbon fiber composite material prepared by adding coal fly ash has excellent noise reduction performance and impact resistance.

[0128] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A carbon fiber composite resin cured part for a muffler, characterized in that: The carbon fiber cloth and the resin mixture are impregnated with the resin mixture, and the cured part is obtained by molding and curing. The components in parts by weight are as follows: Carbon fiber cloth: 40-60 parts, made of resin-based carbon fiber; The resin mixture comprises the following components in parts by weight: 30-50 parts of epoxy resin, wherein the epoxy resin is a difunctional epoxy resin; 10-25 parts of coal fly ash nanoparticles, wherein the average particle size of the coal fly ash nanoparticles is 50 nm and the surface of the coal fly ash nanoparticles is modified with a silane coupling agent KH-550; 1-10 parts of a curing agent, wherein the curing agent is a modified amine curing agent or an acid anhydride curing agent; 1-3 parts of plasticizer, wherein the plasticizer is rubber or polyether; 5-15 parts of diluent, wherein the diluent is a reactive acrylate diluent.

2. The carbon fiber composite resin cured part for a muffler according to claim 1, characterized in that: The resin mixture further comprises the following components in parts by weight: 5-20 parts of a toughening agent, 1-5 parts of a filler, 1-5 parts of a flame retardant, 0.5-1 parts of a thixotropic agent, and 0.5-1 parts of a defoaming agent.

3. The carbon fiber composite resin cured part for a muffler according to claim 2, characterized in that: The bifunctional epoxy resin is bisphenol A epoxy resin, bisphenol F epoxy resin or novolac epoxy resin.

4. The carbon fiber composite resin cured part for a muffler according to claim 2, characterized in that: The active acrylate diluent is phenyl acrylate or butylphenyl acrylate.

5. A method for preparing a carbon fiber composite resin cured article according to any one of claims 2 to 4, characterized in that: The following steps are involved: S1. Immerse the resin-based carbon fiber cloth in a nitric acid solution with a concentration of 5-15%, oxidize it at 50-80°C for 20-60 minutes, wash it with water until it is neutral, and then dry it; S2, stirring the resin mixture evenly and performing degassing treatment; S3, immersing the carbon fiber cloth in S1 into the degassed resin mixture; S4, taking out the impregnated carbon fiber cloth and forming it using a molding process; S5. Curing in different time periods to obtain the cured part.

6. The method for preparing a carbon fiber composite resin cured article according to claim 5, characterized in that: When mixing in S2, the mixing is performed in the following order: First, epoxy resin and curing agent are pre-mixed and preliminarily mixed to form a basic system; diluent, plasticizer and toughening agent, coal fly ash nanoparticles, filler and flame retardant, thixotropic agent, defoaming agent are added in sequence and mixed evenly.

7. The method for preparing a carbon fiber composite resin cured article according to claim 5, characterized in that: During the degassing treatment in S2: the resin mixture is degassed at a vacuum degree of -0.1 MPa for 15-30 minutes.

8. The method for preparing a carbon fiber composite resin cured article according to claim 5, wherein: When the pretreated carbon fiber cloth is immersed in the resin mixture in S3, the temperature of the resin mixture is 25°C.

9. The method for preparing a carbon fiber composite resin cured article according to claim 5, characterized in that: The forming process in S4 is winding or compression molding.

10. The method for preparing a carbon fiber composite resin cured article according to claim 5, characterized in that: The curing in step S4 is divided into three periods: curing at 80° C. for 2 h, curing at 120° C. for 3 h, and curing at 150° C. for 1 h.

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