A method for constructing a three-dimensional braided solid model and a method for predicting wave absorption performance

Abstract

This invention relates to a method for constructing a three-dimensional woven solid model and a method for predicting microwave absorption performance, belonging to the field of microwave absorbing material weaving technology. The method includes the following steps: S1: Based on the type of weaving machine and the movement mode of the chassis moving parts of the weaving machine, an algorithm for obtaining the motion trajectory of the yarn carrier is derived; S2: Based on the algorithm for the motion trajectory of the yarn carrier obtained in step S1, a spline curve is used to fit the motion trajectory of the yarn carrier to obtain a central axis model of the yarn in the three-dimensional fabric; S3: Based on the thickness value of the microwave absorbing material, the central axis model is expanded and scanned outwards to generate a three-dimensional woven solid model. This invention, through the constructed three-dimensional woven solid model, optimizes different microwave absorbing fabric models according to microwave absorption performance requirements, thereby improving the R&D efficiency of microwave absorbing fabrics.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing material weaving technology, specifically to a method for constructing a three-dimensional woven solid model and a method for predicting microwave absorbing performance. Background Technology

[0002] With technological advancements and the widespread adoption of information technology, electromagnetic radiation in our surroundings is increasing. To avoid harm from electromagnetic radiation, microwave absorbing materials have gradually become a research focus. The performance indicators for evaluating microwave absorbing materials include two aspects: first, electromagnetic wave reflection loss, which characterizes the material's ability to absorb electromagnetic waves; and second, the range of frequencies that can be absorbed, with a wider coverage being better. These two performance indicators mainly depend on the impedance matching and loss capacity of the microwave absorbing material. Good impedance matching ensures that electromagnetic waves can penetrate the material. Once inside the material, dielectric loss, magnetic loss, and conductivity loss convert electromagnetic energy into heat.

[0003] Currently, microwave absorbing materials are mainly divided into two categories: coating-type microwave absorbing materials and structural microwave absorbing materials. Compared with coating-type microwave absorbing materials, structural microwave absorbing materials have the following advantages in use: (1) They can perform both load-bearing and microwave absorption functions without increasing weight; (2) They have a high degree of freedom in thickness design and have the advantage of wide bandwidth; (3) The integrated structure-function design helps to improve structural stability and reliability; (4) They have strong design flexibility in mechanical and microwave absorption properties and can be molded into various complex shapes. Therefore, in order to meet various special needs, the development of structural microwave absorbing materials is of great significance.

[0004] Early structural microwave absorbing materials were mainly traditional two-dimensional fabrics, widely used in the automotive, aerospace, and other industries. However, due to interlayer defects in traditional two-dimensional fabrics, there is an urgent need to develop new composite materials to replace existing materials. Three-dimensional fabrics perfectly overcome these defects, possessing high specific modulus and specific strength, impact resistance, and excellent fatigue resistance. Furthermore, compared to manually laid-out two-dimensional fabrics, three-dimensional fabrics are easier to fabricate into complex parts, allowing for one-time molding and shortening the development cycle, and have gradually become the mainstream material preparation technology in the aerospace field. However, the industrial application of three-dimensional braided structures is still largely manual, with slow molding speeds, poor product consistency, and reliance on physical testing. It is difficult to predict performance through preliminary theoretical calculations, resulting in high costs and significantly limiting the widespread application of braided structures. Therefore, this invention provides a method for constructing a three-dimensional braided solid model and a method for predicting microwave absorption performance. Summary of the Invention

[0005] This invention provides a method for constructing a three-dimensional woven solid model and a method for predicting microwave absorption performance. The aim is to solve problems such as inaccurate microwave absorption fabric models, which lead to long development cycles, unadjustable absorption, and narrow absorption bandwidth in microwave absorption fabrics.

[0006] To address the aforementioned technical problems, the first objective of this invention is to provide a method for constructing a three-dimensional woven solid model, comprising the following steps:

[0007] S1: Based on the type of braiding machine and the movement mode of the chassis moving parts of the braiding machine, an algorithm is obtained to determine the movement trajectory of the yarn carrier. The algorithm for the movement trajectory is an algorithm for determining the movement trajectory of the yarn carrier of the braiding machine based on the type of braiding machine and the movement mode of the chassis moving parts of the braiding machine.

[0008] S2: Based on the algorithm of the motion trajectory of the yarn carrier obtained in step S1, the motion trajectory of the yarn carrier is fitted using spline curves to obtain the central axis model of the yarn in the three-dimensional fabric woven by the yarn carrier.

[0009] S3: Based on the thickness value of the absorbing material, the central axis model obtained in S2 is expanded and scanned around the central axis of the yarn to generate a three-dimensional woven solid model of the three-dimensional fabric.

[0010] In step S1, the weaving machine is a processing device for three-dimensional fabrics, and the yarn carrier is one of its core components. The main function of the yarn carrier is to return and store yarn during the weaving of three-dimensional fabrics. Typical yarn carriers include passive tension-controlled yarn carriers and active tension-controlled yarn carriers. Passive tension-controlled yarn carriers, through a series of ratchet and torsion spring mechanisms, can stabilize yarn tension to a certain extent, but cannot overcome the periodic fluctuations in yarn tension, making them unsuitable for three-dimensional woven fabrics with high yarn tension requirements. Active tension-controlled yarn carriers use infrared detection and are powered by batteries. Battery replacement significantly impacts production efficiency, and these yarn carriers are expensive. In step S3, the fineness of the absorbing material is measured using a capacitance evenness meter.

[0011] The beneficial effects of the present invention are: (1) The present invention provides a method for constructing a three-dimensional woven solid model. According to the algorithm of the motion trajectory of the yarn carrier, the motion trajectory of the yarn carrier is fitted by the spline curve. First, the central axis model of the yarn in the three-dimensional fabric woven by the yarn carrier is obtained. Then, according to the thickness value of the microwave absorbing material, the central axis model is expanded and scanned to the surrounding area of ​​the central axis of the yarn, thereby generating a three-dimensional woven solid model of the three-dimensional fabric. This realizes the real reflection of the weaving situation of the microwave absorbing material in the actual microwave absorbing fabric, thus laying a good foundation for predicting the microwave absorbing performance of the microwave absorbing fabric.

[0012] (2) The industrial application of three-dimensional woven microwave absorbing fabrics is still in a semi-manual state, with slow forming speed. The microwave absorbing performance of the fabrics is mainly tested by physical testing, and it is difficult to predict the microwave absorbing performance through theoretical calculations in the early stage, resulting in high costs. This invention solves the above problems by constructing a three-dimensional woven solid model, and accelerates the research and development process of microwave absorbing materials, avoiding the waste of microwave absorbing raw materials caused by multiple tests.

[0013] (3) The present invention, through the construction of a three-dimensional weaving entity model, truly reflects the weaving of fibers in actual fabrics, which has important guiding significance.

[0014] Based on the above technical solution, the present invention can be further improved as follows.

[0015] Furthermore, the weaving machine mentioned in step S1 includes a warp and weft weaving machine or a rotary weaving machine; the movement process of the chassis moving parts of the weaving machine mentioned in step S1 includes a three-dimensional four-step method, a three-dimensional five-step method, a three-dimensional six-step method, or a three-dimensional seven-step method.

[0016] The motion design of the chassis moving parts of a three-dimensional braiding machine is as follows: the plane of motion of the yarn carrier in the three-dimensional braiding machine is set as the xoy coordinate system, and the weaving axis can be set as oz. Along the weaving axis, it makes linear motion with a velocity v(t), forming the braided structure through the spindle motion in the xoy plane. Therefore, the design of a three-dimensional braiding machine mainly involves designing the motion path of the yarn carrier in the xoy plane, that is, designing the motion process of the chassis moving parts. The motion of the yarn carrier on the chassis is divided into linear and circular motion, hence there are three-dimensional four-step, three-dimensional five-step, three-dimensional six-step, or three-dimensional seven-step methods.

[0017] Furthermore, the algorithm for the motion trajectory of the yarn carrier in step S2 satisfies a set condition, which is that after one cycle, the motion trajectory of the yarn carrier returns to the initial position of the yarn carrier.

[0018] Furthermore, the spline curve mentioned in step S2 includes a Bezier curve or a B-spline curve.

[0019] A second objective of this invention is to provide a method for predicting the microwave absorption performance of microwave-absorbing fabrics, comprising the following steps:

[0020] Step 1: Prepare the microwave absorbing material, test the relative complex permittivity of the microwave absorbing material, and obtain the intrinsic relative complex permittivity of the fiber through the formula; test the relative complex permittivity of the microwave absorbing material using the NRW method;

[0021] Step 2: Using the three-dimensional woven solid model constructed above and the intrinsic relative complex permittivity of the fiber obtained in Step 1, the microwave absorption performance of the microwave absorbing fabric is calculated through finite element simulation.

[0022] The relative complex permittivity of the microwave absorbing material was tested using the NRW method and the vector network analyzer according to the SJ20512-1995 standard "Test Method for Complex Permittivity and Complex Permeability of Microwave High-Loss Solid Materials".

[0023] Furthermore, the intrinsic relative complex permittivity ε of the fiber i It is calculated using formula (Ⅰ);

[0024]

[0025] Where, ε eff ε is the relative complex permittivity of the absorbing material. e ε is the relative complex permittivity of paraffin. i denoted as the intrinsic relative complex permittivity of the fiber, and f as the fiber volume fraction;

[0026] Step 2 specifically includes:

[0027] The three-dimensional braided solid model constructed using any of the above methods and the intrinsic relative complex permittivity ε of the fiber i The microwave absorption performance of the microwave-absorbing fabric was obtained through finite element simulation calculation.

[0028] Finite Element Analysis (FEA) uses mathematical approximations to simulate real physical systems (geometry and load conditions). It utilizes simple, interacting elements, or units, to approximate a real system with an infinite number of unknowns using a finite number of unknowns. This invention can be performed using HFSS or CST software for finite element analysis.

[0029] Electromagnetic wave absorption performance includes electromagnetic wave reflection loss and the range of electromagnetic wave frequencies absorbed; electromagnetic wave reflection loss characterizes the ability to absorb electromagnetic waves, and the wider the range of electromagnetic wave frequencies absorbed, the better.

[0030] The beneficial effects of adopting the above scheme are: (1) By constructing a three-dimensional woven solid model, different wave-absorbing fabrics can be optimized according to the wave-absorbing performance requirements, thereby improving the R&D efficiency of wave-absorbing fabrics.

[0031] (2) Compared with the woven solid absorbing fabric, the three-dimensional woven solid model constructed in this invention has a high consistency between the simulated and predicted absorbing performance data and the measured absorbing performance data of the woven solid absorbing fabric, and the absorbing bandwidth is greater than 10 GHz.

[0032] (3) The optimized microwave absorbing fabric prepared by this invention is lightweight and has a density of less than 1 g / cm³. 3 Its material density is 5 to 10 times lower than that of other microwave absorbing fabrics.

[0033] Furthermore, the preparation of the microwave absorbing material in step 1 includes the following specific steps:

[0034] Step 1-1: Select fiber materials, clean the selected fiber materials, and then keep them aged at 35℃~75℃ for 1~72h, and then cut them into small fiber segments of 1~6mm.

[0035] Steps 1-2: Mix multiple segments of fiber with melted paraffin at a weight ratio of (0.1-0.5):1, and then heat and pressurize to form a microwave absorbing material.

[0036] Furthermore, the fiber material is composed of any one or at least two of carbon fiber, silicon carbide fiber, quartz fiber, and basalt fiber.

[0037] Further, the specific process of cleaning the fiber material in step 1-1 is as follows: first, the fiber material is cleaned with deionized water, and then the fiber material cleaned with deionized water is ultrasonically cleaned with a power of 80-120W for 10-60 minutes in an ethanol solution with a mass concentration of 10-70wt%. In the process of cleaning the fiber material with deionized water, ultrasonic cleaning with a power of 80-120W is performed for 10-60 minutes.

[0038] Further, in steps 1-2, the short fiber segments are mixed with melted paraffin at a weight ratio of (0.2-0.4):1, then heated to 60-90℃, and then pressed at 1-30Pa to form the microwave absorbing material. Attached Figure Description

[0039] Figure 1 The diagram shows the electromagnetic parameters of the absorbing material and the intrinsic electromagnetic parameters of the fiber in this invention.

[0040] Where A is the electromagnetic parameter diagram of the absorbing material, ε' represents the real part of the dielectric constant of the absorbing material, and ε” represents the imaginary part of the dielectric constant of the absorbing material; B is the intrinsic electromagnetic parameter diagram of the fiber, ε' represents the real part of the intrinsic dielectric constant of the fiber, and ε” represents the imaginary part of the intrinsic dielectric constant of the fiber.

[0041] Figure 2 This is a flowchart of the algorithm in Embodiment 1 of the present invention;

[0042] Figure 3 This is a diagram showing the initial coordinates X and Y positions (Z=1) in Embodiment 1 of the present invention;

[0043] Figure 4 This is a diagram showing the positions of coordinates X, Y, and Z (Z=25) after a complete cycle in Embodiment 1 of the present invention.

[0044] Figure 5In Embodiment 1 of the present invention, the yarn trajectory and the overall yarn trajectory diagram are obtained by connecting the coordinates of the data points of a single yarn. A is the yarn trajectory diagram obtained by connecting the coordinates of the data points of a single yarn, and B is the overall yarn trajectory diagram.

[0045] Figure 6 This is a diagram of the yarn trajectory of the woven fabric after B-spline curve fitting in Embodiment 1 of the present invention;

[0046] Figure 7 This is a three-dimensional braided solid model diagram from Embodiment 1 of the present invention;

[0047] Figure 8 This is a diagram of the wave-absorbing fabric of the present invention;

[0048] Figure 9 This is a comparison chart showing the measured microwave absorption performance of the microwave absorbing fabric prepared in this invention with that simulated by a three-dimensional woven solid model. Detailed Implementation

[0049] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0050] Example 1

[0051] This embodiment relates to a method for constructing a three-dimensional woven solid model, including the following steps:

[0052] S1: Based on the type of braiding machine and the movement mode of the chassis moving parts of the braiding machine, an algorithm is obtained to determine the movement trajectory of the yarn carrier. The algorithm for the movement trajectory is an algorithm for determining the movement trajectory of the yarn carrier of the braiding machine based on the type of braiding machine and the movement mode of the chassis moving parts of the braiding machine.

[0053] S2: Based on the algorithm of the motion trajectory of the yarn carrier obtained in step S1, the motion trajectory of the yarn carrier is fitted using spline curves to obtain the central axis model of the yarn in the three-dimensional fabric woven by the yarn carrier.

[0054] S3: Based on the thickness value of the absorbing material, the central axis model obtained in S2 is expanded and scanned around the central axis of the yarn to generate a three-dimensional woven solid model of the three-dimensional fabric.

[0055] The coarseness of the absorbing material was measured using a capacitance stripe meter.

[0056] Specifically, in this embodiment, the braiding machine is a cross braiding machine; the movement process of the chassis moving parts of the braiding machine in step S1 adopts a three-dimensional four-step method. A three-dimensional braiding solid model is constructed using MATLAB.

[0057] The algorithm flowchart is as follows: Figure 2 As shown, the specific steps are: initialization; setting the number of steps; statement judgment; motion simulation of the first, second, third and fourth steps of the four parts; smoothing curves; solid model generation; and data export.

[0058] The process includes the following steps: initialization (setting the initial steps in MATLAB software), step setting (setting the number of steps in the 3D four-step method), statement judgment (checking if the number of steps is correct and resetting if incorrect), first, second, third, and fourth step motion simulations (simulating the set steps to ensure the yarn carrier returns to its initial position after one cycle), smoothing the curve (fitting the yarn carrier's trajectory with a B-spline curve to obtain the central axis model of the yarn in the 3D fabric), solid model generation (expanding the central axis model of the real yarn in the 3D fabric outwards based on the thickness of the absorbing material to generate a 3D woven solid model), and data export (exporting the data of the generated 3D woven solid model to prepare for predicting the absorption performance of the absorbing fabric through finite element simulation).

[0059] Figure 3 Part A and Part B in the text Figure 4 Sections A to C of the diagram provide the initial yarn coordinate values ​​of the yarn carrier in the knitting machine and the yarn coordinate values ​​after a complete cycle (25 steps), respectively. By comparison... Figure 3 Parts A and B in the text, and Figure 4 In section A to C, the yarn label values ​​of the yarn carrier in the X and Y directions are consistent with the initial label values, while the Z direction increases from 1 to 25. This indicates that after one complete cycle, the yarn label values ​​of the yarn carrier are consistent with the initial label values, proving the correctness of the algorithm. After all motion steps are completed, the spatial coordinates of the yarn movement of the yarn carrier can be obtained. By connecting the matrix data points sequentially, the motion trajectory of the yarn carrier can be obtained, as shown below. Figure 5 Parts A and B are shown in the figure, where Figure 5 Part A in the diagram represents the movement trajectory of the yarn after one complete cycle of the yarn carrier. Figure 5 Part B in the diagram represents the motion trajectory of the three-dimensional fabric woven by the yarn carrier, which is the model of the central axis of the yarn in the three-dimensional fabric woven by the yarn carrier.

[0060] This can be achieved by writing a B-spline curve simulation program. Figure 5Part B in the diagram corresponds to the spline curve of the control points, which is a model of the central axis of the yarn in the three-dimensional fabric woven by the yarn carrier, such as... Figure 6 As shown. The B-spline is defined as shown in equation (II).

[0061]

[0062] Where Pi (i = 0, 1, ..., n) is a k-th (k+1 order) B-spline basis function. Let node ti be a node, satisfying 0 ≤ t0 ≤ … ≤ tn + k ≤ 1, and by convention 0 / 0 = 0. Then the basis function can be expressed by formulas (Ⅲ) and (Ⅳ).

[0063]

[0064]

[0065] However, this fitted curve only represents the movement trajectory of the yarn, that is, the central axis model of the yarn in the three-dimensional fabric woven by the yarn carrier, but it cannot form a "yarn body" and cannot show the real state of the yarns interweaving and contacting each other. Therefore, based on the thickness value of the absorbing material, the surface function in MATLAB is used to expand the central axis model to the surrounding area of ​​the central axis of the yarn, realizing the generation from the yarn trajectory curve of the yarn carrier to the yarn surface mesh, that is, the three-dimensional woven solid model of the three-dimensional fabric, such as... Figure 7 As shown. Figure 7 It intuitively displays the interweaving structure of yarns in a three-dimensional fabric. It can be seen that the spatial trajectory of the yarn simulated by the program is completely consistent with the spatial trajectory of the yarn in the actual weaving process, and it accurately simulates the yarn morphology in the actual fabric.

[0066] In summary, the industrial application of three-dimensional woven microwave absorbing fabrics is currently still in a semi-manual state, with slow forming speeds. The microwave absorption performance is mainly tested through physical samples, making it difficult to predict its absorption performance through preliminary theoretical calculations, resulting in high costs. This invention addresses these problems by constructing a three-dimensional woven entity model, accelerating the research and development process of microwave absorbing materials and avoiding the waste of raw materials caused by multiple experiments. This invention provides a method for constructing a three-dimensional woven entity model, realistically reflecting the weaving of microwave absorbing materials (collectively referred to as yarns) in actual microwave absorbing fabrics, thus laying a foundation for predicting the microwave absorption performance of these fabrics. The three-dimensional woven entity model constructed in this invention realistically reflects the weaving of fibers in actual fabrics, and has significant guiding significance.

[0067] Example 2

[0068] This embodiment relates to a method for predicting the microwave absorption performance of microwave absorbing fabric, including the following steps:

[0069] Step 1: Prepare the microwave absorbing material, obtain the relative complex permittivity of the microwave absorbing material, and obtain the intrinsic relative complex permittivity of the fiber using the formula;

[0070] Step 2: Using the three-dimensional woven solid model constructed above and the fiber intrinsic relative complex permittivity obtained in Step 1, the microwave absorption performance of the microwave absorbing fabric is calculated through finite element simulation.

[0071] Among them, the relative complex permittivity ε of the absorbing material eff The results were obtained through NRW testing using a vector network analyzer, in accordance with the SJ20512-1995 standard "Test Method for Complex Permittivity and Complex Permeability of Microwave High-Loss Solid Materials". Figure 1 As shown in Figure A, the intrinsic relative complex permittivity (ε) of the fiber i The result is obtained by formula (Ⅰ), and the result is as follows: Figure 1 As shown in B;

[0072]

[0073] Where, ε eff ε is the relative complex permittivity of the absorbing material. e ε is the relative complex permittivity of paraffin. i denoted as the intrinsic relative complex permittivity of the fiber, and f is the volume fraction of a small fiber segment.

[0074] Finite Element Analysis (FEA) is a method of simulating real physical systems (geometry and load conditions) using mathematical approximations. It utilizes simple, interacting elements, or units, to approximate a real system with an infinite number of unknowns using a finite number of unknowns. This invention can employ HFSS or CST software for finite element analysis.

[0075] Electromagnetic wave absorption performance includes electromagnetic wave reflection loss and the range of electromagnetic wave frequencies absorbed; electromagnetic wave reflection loss characterizes the ability to absorb electromagnetic waves, and the wider the range of electromagnetic wave frequencies absorbed, the better.

[0076] In summary, by constructing a three-dimensional woven solid model, different microwave absorbing fabrics can be optimized according to the microwave absorption performance requirements, thereby improving the R&D efficiency of microwave absorbing fabrics.

[0077] Example 3: Verification of the wave absorption performance predicted by the three-dimensional woven solid model constructed in this invention

[0078] This embodiment uses the optimized three-dimensional woven solid model that meets performance requirements from Embodiment 2 to prepare a solid microwave absorbing fabric by weaving a microwave absorbing material. Figure 8 As shown, the solid microwave absorbing fabric prepared has the advantages of being lightweight with a density of less than 1 g / cm³. 3Its material density is 5 to 10 times lower than that of other microwave absorbing fabrics.

[0079] The preparation of the microwave absorbing material includes the following specific steps:

[0080] Step 1-1: Select fiber materials, clean the selected fiber materials, and then keep them aged at 35℃~75℃ for 48 hours. After that, cut them into small fiber segments of 1~6mm.

[0081] Steps 1-2: Mix multiple segments of fiber with melted paraffin at a weight ratio of 0.4:1, and then heat and pressurize to form a microwave absorbing material.

[0082] The fiber material is carbon fiber. The specific cleaning process for the fiber material in step 1-1 is as follows: first, it is cleaned with deionized water; then, it is ultrasonically cleaned for 60 minutes in a 50wt% ethanol solution using 80W power; finally, it is ultrasonically cleaned for 60 minutes in deionized water using 80W power. In step 1-2, the material is heated to 75℃ and then pressurized to 2Pa for molding to obtain the microwave absorbing material.

[0083] For the fabricated solid radar-absorbing material, the radar absorption performance was tested using a vector network analyzer according to the military standard GJB2038A-2001 "Test Method for Reflectivity of Radar Absorbing Materials". The results are as follows: Figure 9 As shown. By Figure 9 It can be seen that as the radiation frequency increases, the trend of the reflection loss change of the woven solid absorbing fabric and the three-dimensional woven solid model is consistent, and the specific reflection loss values ​​are similar. This indicates that the absorption performance data simulated and predicted by the three-dimensional woven solid model constructed in this invention is highly consistent with the absorption performance data of the woven solid absorbing fabric measured in reality, and the absorption bandwidth is greater than 10GHz.

[0084] In summary, this invention improves the R&D efficiency of microwave absorbing fabrics by constructing a three-dimensional woven solid model and optimizing different microwave absorbing fabric models according to microwave absorption performance requirements.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0086] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for predicting the microwave absorption performance of a microwave absorbing fabric, characterized in that, Includes the following steps: Step 1: Prepare the microwave absorbing material, test the relative complex permittivity of the microwave absorbing material, and obtain the intrinsic relative complex permittivity of the fiber through the formula; Step 2: Using the constructed three-dimensional woven solid model and the intrinsic relative complex permittivity of the fiber obtained in Step 1, the microwave absorption performance of the microwave absorbing fabric is calculated through finite element simulation. The method for constructing the three-dimensional woven solid model includes the following steps: S1: Based on the type of braiding machine and the movement mode of the chassis moving parts of the braiding machine, an algorithm is obtained to determine the movement trajectory of the yarn carrier. The algorithm for the movement trajectory is an algorithm for determining the movement trajectory of the yarn carrier of the braiding machine based on the type of braiding machine and the movement mode of the chassis moving parts of the braiding machine. S2: Based on the algorithm of the motion trajectory of the yarn carrier obtained in step S1, the motion trajectory of the yarn carrier is fitted using spline curves to obtain the central axis model of the yarn in the three-dimensional fabric woven by the yarn carrier. S3: Based on the thickness value of the absorbing material, the central axis model obtained in S2 is expanded and scanned around the central axis of the yarn to generate a three-dimensional woven solid model of the three-dimensional fabric. The intrinsic relative complex permittivity of the fiber ε i The result is obtained by formula (Ⅰ): ， in, ε eff The relative complex permittivity of the absorbing material is . ε e The relative complex permittivity of paraffin is... ε i denoted as the intrinsic relative complex permittivity of the fiber, and f as the fiber volume fraction; Step 2 specifically includes: Using the three-dimensional braided solid model and the intrinsic relative complex permittivity of the fiber ε i The microwave absorption performance of the microwave-absorbing fabric was obtained through finite element simulation calculation.

2. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 1, characterized in that, The knitting machine mentioned in step S1 includes a cross-weaving machine or a rotary knitting machine; the movement mode of the chassis moving parts of the knitting machine mentioned in step S1 includes a three-dimensional four-step method, a three-dimensional five-step method, a three-dimensional six-step method, or a three-dimensional seven-step method.

3. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 1, characterized in that, The algorithm for the motion trajectory of the yarn carrier in step S2 satisfies the set condition that the motion trajectory of the yarn carrier returns to the initial position of the yarn carrier after one cycle.

4. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 1, characterized in that, The spline curve mentioned in step S2 includes a Bezier curve or a B-spline curve.

5. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 1, characterized in that, Step 1, the preparation of the microwave absorbing material, includes the following specific steps: Step 1-1: Select fiber materials, clean the selected fiber materials, and age them at 35℃~75℃ for 1~72 hours. After aging, cut them into small fiber segments of 1~6mm. Steps 1-2: Mix multiple segments of fiber with melted paraffin at a weight ratio of (0.1-0.5):1, and then heat and pressurize to form a microwave absorbing material.

6. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 5, characterized in that, The fiber material is composed of any one or at least two of carbon fiber, silicon carbide fiber, quartz fiber, and basalt fiber.

7. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 5, characterized in that, The specific process of cleaning the selected fiber material described in step 1-1 is as follows: First, the fiber material is cleaned with deionized water. Then, the fiber material cleaned with deionized water is ultrasonically cleaned for 10-60 minutes in an ethanol solution with a mass concentration of 10-70 wt%. During the process of cleaning the fiber material with deionized water, ultrasonic cleaning with a power of 80-120 W is performed for 10-60 minutes.

8. The method for predicting the microwave absorption performance of a microwave absorbing fabric according to claim 5, characterized in that, In steps 1-2, short fiber segments are mixed with melted paraffin at a weight ratio of (0.2-0.4):1, then heated to 60-90℃, and then pressed at 1-30 Pa to form a microwave absorbing material.

Images