Method for simulating wave-absorbing performance of fabric composite material covering carbon nanotubes

Abstract

The application discloses a simulation method for wave-absorbing performance of fabric composite material covered with carbon nanotubes, which comprises carbon nanotube microstructure homogenization analysis, carbon nanotube-glass fiber mesostructure homogenization analysis and macrostructure homogenization analysis of the fabric composite material covered with carbon nanotubes. The carbon nanotube microstructure homogenization analysis comprises the following steps: a Monte-Carlo method is used to establish a carbon nanotube composite material microstructure model; the carbon nanotube composite material microstructure model is divided into tetrahedral grids; a self-programmed finite element program is used to calculate the conductivity of the carbon nanotube composite material under different filling densities; a numerical simulation method is used to calculate the electromagnetic shielding performance of the fabric composite material covered with carbon nanotubes under different carbon nanotube lengths, densities and weaving modes; the physical mechanism behind the wave-absorbing performance is understood in depth through the numerical simulation result, the structure design of the wave-absorbing composite material of the structure can be better guided, and the design scheme can be efficiently guided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, in particular to a simulation method for wave-absorbing performance of fabric composite material covered with carbon nanotubes. BACKGROUND

[0002] Due to the rapid development of electronic devices, electromagnetic absorbers have attracted extensive research attention to reduce interference with other devices and protect human health from potential electromagnetic radiation.

[0003] Electromagnetic wave-absorbing materials are mainly divided into two categories, one is surface coating material, and the other is structural electromagnetic wave-absorbing material, among which the latter is extremely attractive in some fields requiring lightness and strength such as aerospace.

[0004] Glass fiber is a widely used structural material, and recently some researchers have grown carbon nanotubes on the surface of glass fiber by chemical vapor deposition to realize the development of a high-performance structural wave-absorbing composite material. However, there is no in-depth research progress on the influence of the length and density of the grown carbon nanotubes and the weaving scheme of the glass fiber fabric on its electromagnetic shielding performance. In order to better guide the structural design of this kind of structural wave-absorbing composite material, we need to propose an efficient and accurate numerical model to simulate the wave-absorbing performance of this kind of material, and through the results of numerical simulation, to deeply understand the physical mechanism behind its wave-absorbing performance. SUMMARY

[0005] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0006] In view of the above and / or existing problems in the development of high-performance structural wave-absorbing composite materials, the present application is proposed.

[0007] Therefore, the purpose of the present application is to provide a simulation method for wave-absorbing performance of fabric composite material covered with carbon nanotubes, which uses numerical simulation method to calculate the electromagnetic shielding performance of fabric composite material covered with carbon nanotubes under different carbon nanotube lengths, densities and weaving methods, thereby playing an efficient guiding role in the design scheme of this kind of product.

[0008] To solve the above technical problems, according to one aspect of the present application, the present application provides the following technical scheme:

[0009] A simulation method for wave-absorbing performance of fabric composite material covered with carbon nanotubes, characterized in that it comprises:

[0010] S1, Homogenization analysis of carbon nanotube microstructure

[0011] 1) A microstructure model of carbon nanotube composite material was established using the Monte Carlo method, in which the carbon nanotubes are parallel to each other and do not cross or contact each other, and the structure satisfies periodic boundary conditions.

[0012] 2) Divide the microstructure model of carbon nanotube composite material into tetrahedral meshes, calculate the shortest distance between each endpoint of the finite element mesh and all carbon nanotube segments in the system, and use the finite element program to calculate the electrical conductivity of carbon nanotube composite material under different filling densities.

[0013] S2, Homogenization analysis of carbon nanotube-glass fiber mesostructure

[0014] 1) Establish a mesoscopic structural model of carbon nanotube-glass fiber composite material;

[0015] 2) Calculate the electrical conductivity and dielectric constant of the glass fiber structure coated with carbon fibers in the mesoscopic structure model of carbon nanotube composite material using the finite element method;

[0016] S3. Macrostructural homogenization analysis of carbon nanotube-coated fabric composites

[0017] 1) Use COMSOL to create a glass fiber braided structure model;

[0018] 2) Input the electrical conductivity and dielectric constant of the glass fiber and carbon nanotubes calculated in S2 into the AC / DC module to obtain the microwave absorption performance of the glass fiber system with carbon nanotubes grown on it.

[0019] 3) Calculate the representative volume element of the glass fiber braided structure model, where the distance and arrangement of the glass fibers can be adjusted.

[0020] In a preferred embodiment of the method for simulating the microwave absorption performance of a fabric composite material covered with carbon nanotubes as described in this invention, in step S2, the distance function of the endpoints of the finite element mesh within the system is:

[0021] ,

[0022] in, For van der Waals distance, It is the sum of the values ​​of the two smallest endpoints and the shortest distance of all CNT segments. denoted as , where is the diameter of the carbon nanotube.

[0023] As a preferred embodiment of the simulation method for the microwave absorption performance of a fabric composite material covered with carbon nanotubes as described in this invention, the finite element program is written in MATLAB.

[0024] As a preferred embodiment of the simulation method for the microwave absorption performance of a fabric composite material covered with carbon nanotubes according to the present invention, the weak form derivation process of the finite element program is as follows:

[0025] The sum of the potential energy density in the matrix resin and the potential energy density in the carbon nanotubes

[0026]

[0027] Among them, the potential energy density of the matrix CNT potential energy density ;

[0028] Minimizing the total energy of the system along the direction of the electric field yields the finite element weak form as follows:

[0029] .

[0030] As a preferred embodiment of the method for simulating the microwave absorption performance of a fabric composite material covered with carbon nanotubes as described in this invention, the potential energy inside the matrix is...

[0031]

[0032] The cutoff distance for tunneling current is given by the distance function at a point within the system. If it is less than 1, it is a normal resin part with no tunneling current; if it is less than 1, it is a normal resin part with no tunneling current. If so, the existence of tunneling current needs to be considered at that point.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses numerical simulation to calculate the electromagnetic shielding performance of fabric composite materials covered with carbon nanotubes under different carbon nanotube lengths, densities and weaving methods. Through the results of numerical simulation, we can gain a deeper understanding of the physical mechanism behind its wave absorption performance, which can better guide the structural design of this type of wave absorption composite material, thus playing an efficient guiding role in the design scheme of this product. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0035] Figure 1 This is a schematic diagram of the microstructure model of the carbon nanotube composite material of the present invention;

[0036] Figure 2 This is a schematic diagram of the mesoscopic structure model of the carbon nanotube-glass fiber composite material of the present invention;

[0037] Figure 3 This is a schematic diagram of the glass fiber braided structure model of the present invention;

[0038] Figure 4 This is a schematic diagram of a representative volume unit of the glass fiber braided structure model of the present invention. Detailed Implementation

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0042] This invention provides a method for simulating the electromagnetic shielding performance of a fabric composite material covered with carbon nanotubes. The method uses numerical simulation to calculate the electromagnetic shielding performance of the fabric composite material covered with carbon nanotubes under different carbon nanotube lengths, densities, and weaving methods, thereby providing efficient guidance for the design of such products.

[0043] This invention provides a method for simulating the microwave absorption performance of a fabric composite material covered with carbon nanotubes, the specific steps of which are as follows:

[0044] S1, Homogenization analysis of carbon nanotube microstructure

[0045] 1) Establishing a model using the Monte Carlo method, such as Figure 1 The microstructure model of the carbon nanotube composite material shown is in which the carbon nanotubes are parallel to each other and do not cross or contact each other, and the structure satisfies the periodic boundary conditions.

[0046] 2) Divide the microstructure model of the carbon nanotube composite material into tetrahedral meshes, calculate the shortest distance between each endpoint of the finite element mesh and all carbon nanotube segments, and use a finite element program written in MATLAB to calculate the electrical conductivity of the carbon nanotube composite material under different filling densities. For each endpoint of the finite element mesh, first calculate the shortest distance between that point and all carbon nanotube segments. Considering the diameter of the carbon nanotubes, the final distance function for that point is... ,in, For van der Waals distance, It is the sum of the values ​​of the two smallest endpoints and the shortest distance of all CNT segments. denoted as , where is the diameter of the carbon nanotube.

[0047] The weak form derivation process of the finite element method is as follows:

[0048] The sum of the potential energy density in the matrix resin and the potential energy density in the carbon nanotubes

[0049]

[0050] Among them, the potential energy density of the matrix CNT potential energy density ;

[0051] Minimizing the total energy of the system along the direction of the electric field yields the finite element weak form as follows:

[0052] .

[0053] Considering the tunneling effect, the potential energy inside the matrix is ​​divided into the following two parts.

[0054]

[0055] The cutoff distance for tunneling current is given by the distance function at a point within the system. If it is less than 1, it is a normal resin part with no tunneling current; if it is less than 1, it is a normal resin part with no tunneling current. If a tunneling current is present at that point, it needs to be considered. Applying potential differences along the principal directions of representative volume elements, the average current and average electric field intensity within the system are calculated using the finite element method described above. Their ratio is the effective conductivity of the system. Similarly, by introducing a dielectric constant in the weak form, the effective dielectric constant of the system can be simulated using the finite element method.

[0056] S2, Homogenization analysis of carbon nanotube-glass fiber mesostructure

[0057] 1) Establish such Figure 2 The model shown is a mesoscopic structure model of carbon nanotube-glass fiber composite material;

[0058] 2) The electrical conductivity and dielectric constant of the carbon nanotube-glass fiber structure described above were calculated using the finite element method. A representative volume element was a double-layered cylinder, with an inner layer of glass fiber and an outer layer of the same thickness as the grown carbon nanotubes. The dielectric properties and conductivity of the outer layer were calculated in step S1. Note that the radial and axial values ​​are anisotropic. This model yields the electrical conductivity and dielectric constant of a single glass fiber with grown carbon nanotubes. These electrical properties are influenced by the length and density of the outer carbon nanotube layer, with the density adjusted in step S1 and the length adjusted by the layer thickness.

[0059] S3, Homogenization analysis of macroscopic structure of carbon nanotubes

[0060] 1) Use COMSOL to create such Figure 4 The glass fiber braided structure model shown is a representative volume element. Figure 3 This is a detailed diagram of the fabric structure.

[0061] 2) Input the conductivity and dielectric constant of the carbon nanotube-glass fiber structure calculated in S2 into the AC / DC module to obtain the microwave absorption performance of the glass fiber fabric composite material with carbon nanotubes growing on it.

[0062] The distance and arrangement of the glass fibers are adjustable. The entire system incorporates wave equation conditions, with the upper and lower surfaces being perfect electrical conductors and periodic boundary conditions in the X and Y directions.

[0063] This invention utilizes numerical simulation to calculate the electromagnetic shielding performance of fabric composites covered with carbon nanotubes under different carbon nanotube lengths, densities, and weaving methods. By using the results of numerical simulation to gain a deeper understanding of the physical mechanism behind its wave absorption performance, it can better guide the structural design of this type of wave-absorbing composite material, thus providing efficient guidance for the design of such products.

[0064] Although the present invention has been described above with reference to embodiments, various modifications and substitutions of components with equivalents are possible without departing from the scope of the invention. In particular, features in the disclosed embodiments can be combined in any manner as long as there is no structural conflict; the lack of an exhaustive description of these combinations in this specification is merely for brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for simulating the microwave absorption performance of a fabric composite material covered with carbon nanotubes, characterized in that, include: S1, Homogenization analysis of carbon nanotube microstructure 1) A microstructure model of carbon nanotube composite material was established using the Monte Carlo method, in which the carbon nanotubes are parallel to each other and do not cross or contact each other, and the structure satisfies periodic boundary conditions. 2) Divide the microstructure model of carbon nanotube composite material into tetrahedral meshes, calculate the shortest distance between each endpoint of the finite element mesh and all carbon nanotube segments in the system, and use the finite element program to calculate the electrical conductivity of carbon nanotube composite material under different filling densities. The weak form derivation process of the finite element program described in step S1 is as follows: The sum of the potential energy density in the matrix resin and the potential energy density in the carbon nanotubes ； Among them, the potential energy density of the matrix CNT potential energy density ; Minimizing the total energy of the system along the direction of the electric field yields the finite element weak form as follows: ； The electrical potential energy inside the matrix ； The cutoff distance for tunneling current is given by the distance function at a point within the system. If it is less than 1, it is a normal resin part with no tunneling current; if it is less than 1, it is a normal resin part with no tunneling current. Then the existence of tunneling current needs to be considered at that point; If a potential difference is applied in the principal direction of a representative volume element, the average current and average electric field intensity in the system can be calculated using the finite element method described above. The ratio of the average current to the average electric field intensity is the effective conductivity of the system. S2, Homogenization analysis of carbon nanotube-glass fiber mesostructure 1) Establish a mesoscopic structure model of carbon nanotube composite material-glass fiber. The mesoscopic structure model of carbon nanotube composite material-glass fiber is a glass fiber structure uniformly coated with carbon nanotubes. 2) Calculate the electrical conductivity and dielectric constant of the mesoscopic structure model of the carbon nanotube composite material using the finite element method; S3. Macrostructural homogenization analysis of carbon nanotube-coated fabric composites 1) A representative volume element of the glass fiber braided structure model is established using COMSOL. The representative volume element is a double-layer cylinder with an inner layer of glass fiber and an outer layer with a thickness consistent with the length of the grown carbon nanotubes. The dielectric properties and conductivity of the outer layer are the values ​​obtained in S1. 2) Input the conductivity and dielectric constant of the glass fiber structure coated with carbon nanotubes calculated in S2 into the AC / DC module to calculate the wave absorption performance of the glass fiber braided system with grown carbon nanotubes. The distance and arrangement of the glass fibers can be adjusted.

2. The method for simulating the microwave absorption performance of a fabric composite material covered with carbon nanotubes according to claim 1, characterized in that, In step S1, the distance function of the endpoints of the finite element mesh within the system is: ， in, For van der Waals distance, It is the sum of the values ​​of the two smallest endpoints and the shortest distance of all CNT segments. denoted as the diameter of the carbon nanotube.

3. The method for simulating the microwave absorption performance of a fabric composite material covered with carbon nanotubes according to claim 1, characterized in that, The finite element program described in step S1 was written using MATLAB.

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