Accurate calculation method and system for surface acoustic impedance of carbon fiber cloth

Abstract

The application discloses a kind of precision calculation method and system of carbon fiber cloth surface acoustic impedance, it is related to the cross field of acoustics engineering and composite material technology, including: obtaining the fiber volume fraction of carbon fiber cloth, warp and weft weaving density, fiber diameter, single layer thickness, layer number, adjacent layer stacking angle, back cavity depth and acoustic angular frequency;According to warp and weft weaving density and fiber volume fraction, anisotropic correction coefficient and equivalent weaving density are calculated;Utilize the anisotropic correction coefficient, equivalent weaving density and other parameters to calculate acoustic resistance;Utilize acoustic angular frequency, fiber volume fraction, single layer thickness, fiber diameter, back cavity depth, layer number and stacking angle to calculate acoustic reactance;Acoustic resistance and acoustic reactance are integrated into the surface acoustic impedance of complex number form.The application can accurately adapt single layer, multi-layer stacking configuration carbon fiber cloth, with small calculation error and high calculation efficiency, and can be widely applied to aerospace acoustic lining, high-end equipment noise reduction and other scenes.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of acoustic engineering and composite materials technology, specifically to a method and system for accurately calculating the acoustic impedance of a carbon fiber cloth surface. Background Technology

[0002] With the increasing demand for both lightweight and high noise reduction performance in aerospace, new energy vehicles, and other fields, carbon fiber cloth, due to its advantages such as high specific strength, good environmental stability, and adjustable acoustic parameters, is gradually replacing traditional perforated metal panels and becoming the core material for high-end sound-absorbing structures (such as acoustic liners for aircraft engine air intakes and high-performance mufflers). Accurate calculation of the surface acoustic impedance of carbon fiber cloth is a key prerequisite for the optimized design of its acoustic structure.

[0003] However, existing methods for calculating acoustic impedance mainly face the following technical shortcomings:

[0004] Insufficient material property compatibility: Traditional acoustic-electric analogy method and transfer matrix method are based on the assumption of homogeneity and isotropy, while carbon fiber cloth has obvious anisotropy (the difference in acoustic parameters between the warp and weft directions can reach 20%~30%), and microscopic parameters such as fiber volume fraction and weaving density have a significant impact on sound propagation, resulting in a calculation error of up to 25%~35% in traditional methods.

[0005] Modeling complex configurations is difficult: The carbon fiber fabric configurations such as multi-layer stacking and fiber arrays widely used in engineering have interlayer acoustic coupling effects and impedance gradient mechanisms, which existing models cannot describe.

[0006] The lack of multi-physics coupling: Carbon fiber cloth exhibits coupling between elastic vibration and acoustic response (global acoustic impedance effect) over a wide frequency range. Existing methods only consider a single acoustic physical field, resulting in insufficient accuracy in wide-frequency calculations.

[0007] Efficiency versus accuracy: While the finite element method can simulate complex effects, a single calculation for multi-layer structures takes more than an hour, which cannot meet the rapid iteration requirements in engineering design; while the accuracy of simplified empirical models is difficult to guarantee.

[0008] Therefore, there is an urgent need for a new acoustic impedance calculation method that can adapt to the anisotropy of carbon fiber fabric, take into account multi-layer configurations, incorporate multi-physics coupling, and is computationally efficient. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems of insufficient material property adaptation, difficulty in modeling complex configurations, lack of multi-physics coupling, and low computational efficiency in existing methods for calculating the surface acoustic impedance of carbon fiber cloth, and to provide an accurate, universal, and efficient method for calculating the surface acoustic impedance of carbon fiber cloth.

[0010] To achieve the above-mentioned objective, this invention provides a method for accurately calculating the surface acoustic impedance of carbon fiber cloth, the method comprising:

[0011] Step 1: Obtain the following parameters of the carbon fiber cloth: fiber volume fraction Warp knitting density Weft knitting density Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Back cavity depth D and sound wave angular frequency , where i = 1, 2, ..., n−1;

[0012] Step 2: Based on fiber volume fraction Warp knitting density and weft knitting density Calculate the anisotropy correction coefficients and equivalent weave density ;

[0013] Step 3: Utilize anisotropy correction coefficients and equivalent weave density Combined with fiber diameter Single layer thickness Number of layers n and fiber volume fraction Calculate the acoustic impedance R of the carbon fiber cloth;

[0014] Step 4: Utilizing the angular frequency of sound waves Fiber volume fraction Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Given the cavity depth D, calculate the acoustic impedance X of the carbon fiber cloth;

[0015] Step 5: Using the acoustic impedance R as the real part and the acoustic reactance X as the imaginary part, synthesize the complex form of the surface acoustic impedance Z. , where i is the imaginary unit.

[0016] Existing technologies lack a systematic process for calculating the acoustic impedance of carbon fiber fabric, often resorting to ad-hoc models for specific configurations, leading to confusion and the easy omission of key parameters. This method defines a five-step standard procedure: obtaining basic parameters (Step 1) - calculating anisotropy correction coefficients (Step 2) - calculating acoustic impedance (Step 3) and acoustic impedance (Step 4) separately - synthesizing into a complex impedance (Step 5). Step 1 explicitly lists all necessary input parameters (fiber volume fraction, weave density, number of layers, stacking angle, and back cavity depth). This method provides a clear, complete, and reproducible calculation framework, which can be followed by anyone skilled in the art, and the clearly defined parameters avoid calculation errors caused by parameter omissions or disordered order.

[0017] Among them, the anisotropy correction coefficient and equivalent weave density The calculation method is as follows:

[0018] ;

[0019] .

[0020] Among these, carbon fiber fabric exhibits significant anisotropy, and traditional methods using parameters in only one direction lead to large deviations in acoustic impedance calculations; furthermore, there is a lack of means to convert two-dimensional weaving density into an equivalent scalar. This method proposes the aforementioned two specific formulas, the first of which... The second item reflects the percentage of absolute differences in weaving density. Adjusting the degree of anisotropy; the equivalent weaving density is taken as the root mean square of the two vectors. The orthogonal anisotropic problem is equivalent to isotropic, allowing the subsequent acoustic drag formula to be directly applied; simultaneously... The value of adapts to the degree of anisotropy and fiber volume fraction, significantly improving the accuracy of acoustic impedance calculation.

[0021] Preferably, the acoustic impedance R of the carbon fiber cloth is calculated as follows:

[0022] ;

[0023] in, The characteristic viscosity of air.

[0024] The existing model does not simultaneously consider the combined effects of fiber volume fraction, number of layers, weaving density, and fiber diameter on viscous loss, leading to distortion in acoustic impedance calculations. Therefore, this method provides the aforementioned calculation formula, in which... Correcting anisotropy, Characterizing the coupling effect between weave density and fiber diameter, The method fits the nonlinear enhancement of loss due to fiber volume fraction. The acoustic impedance calculation of this method simultaneously considers material anisotropy, weaving parameters, fiber size, layer stacking, and volume fraction effects, reducing experimental verification errors and significantly outperforming traditional methods.

[0025] Preferably, the acoustic impedance X of the carbon fiber cloth is calculated as follows:

[0026] ;

[0027] in, air density, This represents the back cavity coupling coefficient.

[0028] Traditional methods fail to account for the combined effects of multi-layer stacking angles, back cavity depth, and fiber elastic vibration on acoustic impedance, leading to inaccurate phase angle calculations. Therefore, this method provides the aforementioned formula for calculating the acoustic impedance of carbon fiber fabric, wherein... Characterizing the inertial mass of the fiber layer itself, Taking into account the back cavity flexibility, the product term simulates the effect of interlayer angle on the extension of the sound propagation path and the enhancement of coupling. This method can accurately predict the acoustic impedance values ​​of single-layer and multi-layer structures at different back cavity depths and stacking angles, so that the phase angle error of the synthesized impedance is controlled within an acceptable range.

[0029] Preferably, the back cavity coupling coefficient The value is determined as follows: when the carbon fiber cloth is a single-layer structure, When the carbon fiber cloth has a multi-layer structure, .

[0030] In single-layer and multi-layer structures, the acoustic coupling strength between the back cavity and the fiber layer differs. Using fixed coefficients can lead to deviations in acoustic impedance calculations. This method employs a simple yet effective linear interpolation scheme, ensuring high accuracy of the acoustic impedance formula across single-layer to multi-layer (≤6 layers) structures without requiring refitting of coefficients for different layer counts.

[0031] The method further includes step 6:

[0032] Based on the surface acoustic impedance Z, the acoustic resistance R of the carbon fiber cloth, and the acoustic reactance X of the carbon fiber cloth, the acoustic impedance modulus is calculated. and phase angle , , .

[0033] This method directly outputs scalar indicators that are of greater concern to engineers, facilitating comparison and verification with experimental measurements of standing wave tubes (usually modulus values), and can also be used for subsequent sound absorption coefficient calculations.

[0034] The number of layers n of the carbon fiber cloth is in the range of 1≤n≤6.

[0035] The carbon fiber cloth is plain weave carbon fiber cloth, twill weave carbon fiber cloth, multilayer stacked carbon fiber cloth, or fiber array carbon fiber cloth.

[0036] To achieve the purpose of the invention, the present invention also provides a precise calculation system for the surface acoustic impedance of carbon fiber cloth, the system comprising:

[0037] The parameter acquisition unit is used to acquire the following parameters of the carbon fiber cloth: fiber volume fraction. Warp knitting density Weft knitting density Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Back cavity depth D and sound wave angular frequency , where i = 1, 2, ..., n−1;

[0038] Intermediate parameter calculation unit, used to calculate based on fiber volume fraction Warp knitting density and weft knitting density Calculate the anisotropy correction coefficients and equivalent weave density ;

[0039] Acoustic impedance calculation unit, used to utilize anisotropic correction coefficients and equivalent weave density Combined with fiber diameter Single layer thickness Number of layers n and fiber volume fraction Calculate the acoustic impedance R of the carbon fiber cloth;

[0040] Acoustic impedance calculation unit, used to utilize the angular frequency of sound waves Fiber volume fraction Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Given the cavity depth D, calculate the acoustic impedance X of the carbon fiber cloth;

[0041] Impedance synthesis unit is used to synthesize a complex form of surface acoustic impedance Z by taking the acoustic resistance R as the real part and the acoustic reactance X as the imaginary part. , where i is the imaginary unit.

[0042] The acoustic impedance R of the carbon fiber cloth is calculated as follows:

[0043] ;

[0044] in, The characteristic viscosity of air;

[0045] The acoustic impedance X of carbon fiber cloth is calculated as follows:

[0046] ;

[0047] in, air density, This represents the back cavity coupling coefficient.

[0048] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0049] High precision: Through anisotropic correction and volume fraction adjustment, the calculation error can be controlled below 6%, which is 4 to 5 times more accurate than traditional methods (error 25%~35%). Example 1 error ≤ 3.8%, Example 2 error ≤ 3.0%, verifying the accuracy of the model.

[0050] Strong versatility: It can be uniformly applied to single-layer and multi-layer (≤6 layers) stacked carbon fiber fabrics without changing the calculation model for different configurations, greatly simplifying the design process.

[0051] High real-time performance: It uses analytical formulas for direct calculation, and the calculation time for a single calculation is less than 0.1 seconds (for a conventional computer), which meets the real-time parameter scanning requirements in engineering optimization.

[0052] Low application threshold: All input parameters (weaving density, fiber volume fraction, thickness, etc.) can be obtained through conventional microscopic observation, density method or thickness gauge measurement, without the need for expensive or complicated pre-processing equipment, and can be easily integrated into acoustic design software. Attached Figure Description

[0053] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0054] Figure 1 This is a schematic diagram of a two-layer stacked carbon fiber cloth structure;

[0055] Figure 2 This is a flowchart illustrating a precise method for calculating the surface acoustic impedance of carbon fiber cloth. Detailed Implementation

[0056] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0057] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0058] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0059] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0060] Example 1;

[0061] Please refer to Figures 1-2 , Figure 1 This is a schematic diagram of a two-layer stacked carbon fiber fabric structure. Figure 1 It can be seen that the upper and lower layers of carbon fiber cloth are connected by the middle adhesive layer, and the stacking angle between the upper and lower layers of carbon fiber cloth is [value missing]. The cavity depth is D, where 1 is the upper carbon fiber cloth, 3 is the lower carbon fiber cloth, 2 is the adhesive layer, and 4 is the cavity. Please refer to... Figure 2 , Figure 2 This is a flowchart illustrating a method for accurately calculating the surface acoustic impedance of carbon fiber cloth. Embodiment 1 of the present invention provides a method for accurately calculating the surface acoustic impedance of carbon fiber cloth, the method comprising:

[0062] Step 1 - Parameter Acquisition: Obtain the following parameters of the carbon fiber cloth: fiber volume fraction Warp knitting density Weft knitting density Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Back cavity depth D and sound wave angular frequency , where i = 1, 2, ..., n−1;

[0063] Step 2 - Anisotropy Correction Calculation: Based on fiber volume fraction Warp knitting density and weft knitting density Calculate the anisotropy correction coefficients and equivalent weave density ;

[0064] Step 3 - Acoustic impedance calculation: using anisotropic correction coefficients and equivalent weave density Combined with fiber diameter Single layer thickness Number of layers n and fiber volume fraction Calculate the acoustic impedance R of the carbon fiber cloth;

[0065] Step 4 - Acoustic impedance calculation: using the angular frequency of the sound wave Fiber volume fraction Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Given the cavity depth D, calculate the acoustic impedance X of the carbon fiber cloth;

[0066] Step 5 - Impedance Synthesis: Using the acoustic impedance R as the real part and the acoustic reactance X as the imaginary part, synthesize the complex form of the surface acoustic impedance Z. , where i is the imaginary unit.

[0067] The specific objectives of this invention include: improving computational accuracy: by introducing mechanisms such as anisotropy correction and fiber volume fraction adjustment, the computational error is controlled within 6%. Expanding the scope of application: it can uniformly handle single-layer and multi-layer (≤6 layers) stacked carbon fiber fabrics without changing the computational framework. Incorporating multi-physics coupling: the model implicitly includes elastic vibration coupling effects, improving broadband computational accuracy. Achieving real-time engineering performance: it uses analytical formulas for direct solution, avoiding finite element mesh generation and iteration, meeting the needs of rapid optimization design.

[0068] The improved computational accuracy of this invention is achieved by introducing anisotropic correction coefficients in step 2. The first term of its expression directly quantifies the difference in warp / weft knitting density, and the second term uses fiber volume fraction. The degree of anisotropy is adjusted so that the model can capture the anisotropic properties of carbon fiber fabric. This is introduced into the acoustic impedance formula. The term corrects for the nonlinear effect of fiber volume fraction on viscous loss. This is added to the acoustic impedance formula by dividing by... Furthermore, a back cavity coupling coefficient γ is introduced to accurately describe the modulation effect of fiber volume fraction and back cavity depth on acoustic impedance.

[0069] The purpose of broadening the scope of application of this invention is achieved in the following way: the basic parameter definition includes the number of layers n and the stacking angle. This allows the model to handle structures with any number of layers. In the acoustic impedance formula, R is proportional to the number of layers n, reflecting the total viscous loss of multiple stacked layers. The acoustic impedance formula includes a stacking angle product term. When n=1, the product is 1, automatically degenerating into a single-layer case; when n>1, each angle contributes a factor greater than 1, simulating the enhancement effect of interlayer coupling on acoustic impedance. The back cavity coupling coefficient γ is set to values ​​of 0.18 or 0.18+0.02(n−1) for single-layer or multi-layer cases to achieve adaptation.

[0070] This invention employs fully analytical formulas (steps 3 and 4), with all calculations involving elementary algebraic operations, eliminating the need for mesh generation, iteration, or finite element analysis, thus reducing computational complexity. Furthermore, the intermediate parameter calculations in step 2 are all explicit formulas, ensuring extremely high computational efficiency and enabling real-time engineering applications.

[0071] Among them, fiber volume fraction The density is the proportion of fiber volume to the total volume in carbon fiber cloth, reflecting the density of the fibers. It can be determined by density method or microscopic image analysis.

[0072] The warp weave density is the number of fibers per 10 cm length along the warp (longitudinal) direction of the carbon fiber fabric. The weft weave density is the number of fibers per 10 cm length along the weft (transverse) direction of the carbon fiber fabric. The fiber diameter is the diameter of a single carbon fiber, measured through SEM image analysis. The single-layer thickness is the physical thickness of a single layer of carbon fiber fabric, measured using a thickness gauge according to GB / T 7689.1.

[0073] Among them, the stacking angle of adjacent layers The angle between the fiber directions of layer n and layer n+1 (take an acute angle or a right angle). The back cavity depth is the thickness of the air layer between the back of the carbon fiber cloth and the rigid wall.

[0074] This invention establishes a semi-empirical analytical model of the acoustic impedance of carbon fiber cloth surface based on the theory of acoustic microporous plates and the micromechanics of composite materials. Its core principle is as follows:

[0075] Anisotropic equivalent treatment:

[0076] The different weave densities in the warp and weft directions of carbon fiber fabric result in varying viscous losses as sound waves propagate in different directions. This invention defines anisotropy correction factors. This coefficient consists of an absolute value term for the difference in weaving density and an adjustment term for the fiber volume fraction, which transforms the two-dimensional anisotropic problem into a one-dimensional isotropic problem, thereby extending the traditional isotropic formula to orthotropic materials.

[0077] Viscous loss model for acoustic impedance: When sound waves pass through carbon fiber cloth, energy loss (acoustic impedance) is caused by viscous friction of air at the fiber-matrix interface. This invention is based on a capillary bundle model and introduces a fiber volume fraction correction term. The linear superposition of the number of layers n, with anisotropic correction coefficients. Scaling overall loss, formula This comprehensively reflects the influence of material parameters and structural parameters on acoustic impedance.

[0078] The inertial-elastic coupling model of acoustic impedance: Acoustic impedance originates from the inertial mass of the air column, the elastic vibration of the fiber, and the acoustic flexibility of the back cavity. This invention utilizes a single-layer thickness... Fiber diameter And the linear combination of the back cavity depth D, divided by This characterizes the modulation of equivalent density by fiber volume fraction. Specifically, a stacking angle product term is introduced. The effect of the interlayer angle in a multilayer structure on the sound propagation path and elastic coupling is described. The back cavity coupling coefficient γ is introduced to distinguish the interaction strength between the back cavity and the fiber layer in single-layer and multilayer structures.

[0079] The implicit characterization of multiphysics coupling: The empirical coefficients in the formulas (such as 0.8, 0.01, 1.1, etc.) are not purely mathematical fits, but are obtained through inversion from a large amount of experimental data, comprehensively including the contribution of elastic vibration to acoustic impedance. These coefficients enable analytical models to equivalently account for multiphysics effects without explicitly solving the coupled field equations.

[0080] The core of impedance tube measurement of the normal acoustic impedance of materials is to excite a plane wave inside the tube, forming a superposition field of incident and reflected waves with the sample surface as the boundary; by measuring the sound pressure distribution or transfer function, the complex reflection coefficient is inverted, and finally the normal acoustic impedance is calculated. Commonly used standards are GB / T 18696.1 (standing wave ratio method) and GB / T 18696.2 (transfer function method).

[0081] This invention establishes a unified calculation model for the acoustic impedance of carbon fiber cloth by introducing material property correction coefficients and anisotropic adjustment terms and configuration coupling coefficients. The specific technical solution is as follows:

[0082] Basic parameters include:

[0083] Material parameters: fiber volume fraction (Dimensionless) Warp weave density Weft knitting density (roots / 10cm), fiber diameter (Unit: m);

[0084] Structural parameters: Single layer thickness (Unit: m), number of layers n, stacking angle of adjacent layers (Unit: degrees, the angle between adjacent layers in a multi-layer structure, with a value not exceeding 45 degrees), back cavity depth D (unit: m);

[0085] Environmental parameters: air density =1.21kg / m 3 Characteristic viscosity = ;

[0086] Signal parameters: sound wave angular frequency ( (The frequency of the sound wave).

[0087] Carbon fiber cloth parameter calculation:

[0088] Meridional / zonal anisotropy correction factor and equivalent weaving density :

[0089] ;

[0090] ;

[0091] The first term of the expression characterizes the effect of weaving density differences, and the second term characterizes the moderating effect of fiber volume fraction on anisotropy.

[0092] Acoustic impedance calculation model:

[0093] Considering the viscous loss and anisotropic effects at the fiber-matrix interface, the acoustic impedance R (unit: Pa·s / m) is calculated using the electro-acoustic analogy method:

[0094] ;

[0095] Acoustic impedance calculation model:

[0096] Considering the vibration effects of materials and the gradual change in impedance due to interlayer coupling configuration, the formula for calculating acoustic impedance X (unit: Pa·s / m) is:

[0097] ;

[0098] in: The coupling coefficient for the back cavity is 0.18 for a single-layer structure and 0.18+0.02(n-1) for an n-layer structure. The residual results of the fitting formula are shown in Table 1. The number of layers is the number of carbon fiber surfaces stacked, and the fitting residual is the difference between the measured value and the fitted value. The product symbol ∏ indicates that all factors from i=1 to i=n−1 are multiplied together.

[0099] Table 1 Fitting Residuals

[0100]

[0101] Surface acoustic impedance synthesis:

[0102] The surface acoustic impedance Z of carbon fiber cloth (unit: Pa·s / m) is a complex form of acoustic resistance and acoustic impedance:

[0103] ;

[0104] Among them It is the imaginary unit.

[0105] Calculation process:

[0106] Determine the carbon fiber fabric material parameters (fiber volume fraction, warp and weft weaving density, fiber diameter, etc.), structural parameters (number of layers, stacking angle), and environmental parameters (temperature, air pressure).

[0107] Calculate the anisotropy correction coefficients and equivalent weaving density ;

[0108] Substituting into the formulas for acoustic impedance and acoustic impedance, we obtain the complex form of surface acoustic impedance. ;

[0109] Output acoustic impedance modulus With phase angle .

[0110] The fiber volume fraction can be measured by microscopic observation and density method, and the weaving density is measured according to GB / T 7689.2 (or ASTM D3773); the fiber diameter is analyzed by scanning electron microscopy (SEM) image analysis, and at least 50 fibers are measured and the average value is taken; the thickness is measured by a thickness gauge under specified pressure according to GB / T 7689.1.

[0111] The invention will now be described with specific examples:

[0112] Example 1: Single-layer plain weave carbon fiber cloth:

[0113] Material parameters: fiber volume fraction warp weave density =30 threads / 10cm, weft weave density =28 fibers / 10cm, fiber diameter m;

[0114] Structural parameters: Single layer thickness m, number of layers n=1, stacking angle The depth of the dorsal cavity is D = 0.04 m;

[0115] Signal parameters: angular frequency of sound wave at 1000Hz .

[0116] Calculation process:

[0117] Anisotropy correction coefficients: Equivalent weaving density: Acoustic impedance calculation: Acoustic impedance calculation: Surface acoustic impedance: Modulus: Phase angle: Verification results: Compared with the experimental measurements of the standing wave tube (… Compared with the previous results, the error is ≤3.8%.

[0118] Example 2: Three-layer carbon fiber cloth:

[0119] Material parameters: fiber volume fraction The warp and weft weave densities are both 32 threads / 10cm (isotropic weave), and the fiber diameter is... m;

[0120] Structural parameters: Single layer thickness m, number of layers n=3, stacking angle The depth of the dorsal cavity is D=0.05m;

[0121] Signal parameters: angular frequency of sound wave at 1000Hz .

[0122] Calculation process:

[0123] Anisotropy correction coefficients: Equivalent weaving density: Acoustic impedance calculation: Acoustic impedance calculation: X=9.44; Surface acoustic impedance: Modulus: Phase angle: Verification results: Compared with the experimental measurements of the standing wave tube ( Compared with the previous results, the error is ≤3.0%.

[0124] Example 2;

[0125] Embodiment 2 of the present invention provides a precise calculation system for the surface acoustic impedance of carbon fiber cloth, the system comprising:

[0126] The parameter acquisition unit is used to acquire the following parameters of the carbon fiber cloth: fiber volume fraction. Warp knitting density Weft knitting density Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Back cavity depth D and sound wave angular frequency , where i = 1, 2, ..., n−1;

[0127] Intermediate parameter calculation unit, used to calculate based on fiber volume fraction Warp knitting density and weft knitting density Calculate the anisotropy correction coefficients and equivalent weave density ;

[0128] Acoustic impedance calculation unit, used to utilize anisotropic correction coefficients and equivalent weave density Combined with fiber diameter Single layer thickness Number of layers n and fiber volume fraction Calculate the acoustic impedance R of the carbon fiber cloth;

[0129] Acoustic impedance calculation unit, used to utilize the angular frequency of sound waves Fiber volume fraction Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Given the cavity depth D, calculate the acoustic impedance X of the carbon fiber cloth;

[0130] Impedance synthesis unit is used to synthesize a complex form of surface acoustic impedance Z by taking the acoustic resistance R as the real part and the acoustic reactance X as the imaginary part. , where i is the imaginary unit.

[0131] The acoustic impedance R of the carbon fiber cloth is calculated as follows:

[0132] ;

[0133] in, The characteristic viscosity of air;

[0134] The acoustic impedance X of carbon fiber cloth is calculated as follows:

[0135] ;

[0136] in, air density, This represents the back cavity coupling coefficient.

[0137] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0138] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for accurately calculating the surface acoustic impedance of carbon fiber cloth, characterized in that, The method includes: Step 1: Obtain the following parameters of the carbon fiber cloth: fiber volume fraction Warp knitting density Weft knitting density Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Back cavity depth D and sound wave angular frequency , where i = 1, 2, ..., n−1; Step 2: Based on fiber volume fraction Warp knitting density and weft knitting density Calculate the anisotropy correction coefficients and equivalent weave density ; Step 3: Utilize anisotropy correction coefficients and equivalent weave density Combined with fiber diameter Single layer thickness Number of layers n and fiber volume fraction Calculate the acoustic impedance R of the carbon fiber cloth; Step 4: Utilizing the angular frequency of sound waves Fiber volume fraction Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Given the cavity depth D, calculate the acoustic impedance X of the carbon fiber cloth; Step 5: Using the acoustic impedance R as the real part and the acoustic reactance X as the imaginary part, synthesize the complex form of the surface acoustic impedance Z. , where i is the imaginary unit.

2. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 1, characterized in that, Anisotropy correction coefficient and equivalent weave density The calculation method is as follows: ； 。 3. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 1 or 2, characterized in that, The acoustic impedance R of carbon fiber cloth is calculated as follows: ； in, The characteristic viscosity of air.

4. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 1, characterized in that, The acoustic impedance X of carbon fiber cloth is calculated as follows: ； in, air density, This represents the back cavity coupling coefficient.

5. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 4, characterized in that, The back cavity coupling coefficient The value is determined as follows: when the carbon fiber cloth is a single-layer structure, When the carbon fiber cloth has a multi-layer structure, .

6. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 1, characterized in that, The method further includes step 6: Based on the surface acoustic impedance Z, the acoustic resistance R of the carbon fiber cloth, and the acoustic reactance X of the carbon fiber cloth, the acoustic impedance modulus is calculated. and phase angle , , .

7. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 1, characterized in that, The number of layers n of the carbon fiber cloth is in the range of 1≤n≤6.

8. The method for accurately calculating the surface acoustic impedance of carbon fiber cloth according to claim 1, characterized in that, The carbon fiber cloth is plain weave carbon fiber cloth, twill weave carbon fiber cloth, multi-layer stacked carbon fiber cloth, or fiber array carbon fiber cloth.

9. A precise calculation system for the surface acoustic impedance of carbon fiber cloth, characterized in that, The system includes: The parameter acquisition unit is used to acquire the following parameters of the carbon fiber cloth: fiber volume fraction. Warp knitting density Weft knitting density Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Back cavity depth D and sound wave angular frequency , where i = 1, 2, ..., n−1; Intermediate parameter calculation unit, used to calculate based on fiber volume fraction Warp knitting density and weft knitting density Calculate the anisotropy correction coefficients and equivalent weave density ; Acoustic impedance calculation unit, used to utilize anisotropic correction coefficients and equivalent weave density Combined with fiber diameter Single layer thickness Number of layers n and fiber volume fraction Calculate the acoustic impedance R of the carbon fiber cloth; Acoustic impedance calculation unit, used to utilize the angular frequency of sound waves Fiber volume fraction Fiber diameter Single layer thickness Number of layers n, stacking angle of adjacent layers Given the cavity depth D, calculate the acoustic impedance X of the carbon fiber cloth; Impedance synthesis unit is used to synthesize a complex form of surface acoustic impedance Z by taking the acoustic resistance R as the real part and the acoustic reactance X as the imaginary part. , where i is the imaginary unit.

10. A precise calculation system for the surface acoustic impedance of carbon fiber cloth according to claim 9, characterized in that, The acoustic impedance R of carbon fiber cloth is calculated as follows: ； in, The characteristic viscosity of air; The acoustic impedance X of carbon fiber cloth is calculated as follows: ； in, air density, This represents the back cavity coupling coefficient.

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