A Method for Calculating Anisotropic Conductivity of Carbon Fiber Composite Materials Based on Partial Element Equivalent Circuit Method

Abstract

This invention relates to the field of numerical modeling technology and discloses a method for calculating the anisotropic conductivity of carbon fiber composites based on the partial element equivalent circuit method. The method includes: establishing resistance, capacitance, and inductance matrices under the microstructure of the carbon fiber composite using the partial element equivalent circuit method; setting fiber contact points using the concept of fiber ripple and forming PEEC mesh nodes using these contact points; establishing the PEEC mesh and electric and magnetic field decoupling method under the microstructure of the carbon fiber composite; establishing the PEEC equation based on the established parameter matrix and overlap resistance, and adding excitation sources by identifying electrode positions; and calculating the anisotropic conductivity of the carbon fiber composite by solving the PEEC equation. This invention solves the problems of the inapplicability of finite element method and finite-difference time-domain mesh, the tendency for microstructure solutions to diverge, and the inapplicability of the full-wave electric network method.

Description

Technical Field

[0001] This invention relates to the field of numerical modeling technology, and more specifically, to a method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method. Background Technology

[0002] The development of numerical modeling technology is the result of the cross-integration of mathematics, computer science and applied fields, and it plays an increasingly important role in scientific research, engineering design and decision support.

[0003] Currently, numerical simulation technology is relatively mature, but research on electrical network modeling of carbon fiber composites is lacking. It is difficult to establish meshes at the μm scale for carbon fibers and the cm scale for plates, and the solution is time-consuming.

[0004] The main limitations of existing methods, such as the finite element method and the finite difference time-domain method, in setting the overlap position quickly and automatically, and the matrix constructed using the electric network method in simulating the full-wave process, are the main aspects that restrict the research on electric network modeling of carbon fiber composite materials. Summary of the Invention

[0005] This invention provides a method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method. It solves the technical problems in related technologies, such as the limitations of traditional finite element method and finite difference time-domain method in mesh generation, the tendency of microstructure solution to diverge, and the inapplicability of traditional electrical network method to full-wave modeling, which requires manual mesh generation.

[0006] This invention provides a method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, including:

[0007] Determine the coordinate matrix of the fiber center node and the adjacent index matrix under the initial cross section;

[0008] The fiber contact point increment matrix is ​​obtained based on fiber ripple and fiber cell size;

[0009] Based on the above matrix, a partial element equivalent circuit method spatial double grid is formed, a fiber overlap resistance position matrix is ​​established, and the overlap resistance value is calculated.

[0010] The impedance element matrix of the fiber network is calculated using the Gauss-Legend quadrature formula, and the resistance matrix, inductance matrix, and capacitance matrix are established.

[0011] Current nodes are established by forming a spatial-scale semi-grid at the overlapping positions, thereby decoupling the electric and magnetic fields;

[0012] Establish the partial element equivalent circuit method equations and add excitation sources by identifying electrode positions;

[0013] Solve the partial element equivalent circuit method equations to obtain the voltage and current results in the time and frequency domains;

[0014] Calculate the anisotropic electrical conductivity of carbon fiber composites;

[0015] Furthermore, the step of determining the coordinate matrix of the fiber center node under the initial cross-section includes:

[0016] Obtain microstructure information of carbon fiber composite materials;

[0017] Determine the coordinates of the fiber center node under the initial cross section;

[0018] The coordinates of the center node of the fiber are stored as a coordinate matrix.

[0019] Furthermore, the adjacent index matrix is ​​established based on the adjacency relationship of fibers and is used to represent the connection relationship between fibers.

[0020] Furthermore, the fiber contact point increment matrix is ​​calculated based on the fiber ripple and fiber cell size, and is used to determine the contact position between fibers.

[0021] Furthermore, the step of calculating the impedance element matrix of the fiber network using the Gauss-Gande quadrature formula includes:

[0022] Apply the Gauss-Legend quadrature formula to each pair of adjacent fibers;

[0023] Calculate the impedance values ​​between elements in the fiber network;

[0024] The impedance values ​​are organized into an impedance element matrix.

[0025] Furthermore, the steps of establishing the resistance matrix, inductance matrix, and capacitance matrix include:

[0026] Establish the inductance and resistance matrices using current nodes;

[0027] A capacitance matrix is ​​established using potential nodes.

[0028] Furthermore, the steps for solving the partial element equivalent circuit method equations include:

[0029] For frequency domain excitation, the solution is obtained using matrix inverse operations or the least squares method.

[0030] For time-domain excitation, the θ method is used to solve the partial element equivalent circuit equations.

[0031] Furthermore, the step of calculating the anisotropic conductivity of the carbon fiber composite material includes:

[0032] Conductivity is calculated based on voltage and current results in the time and frequency domains.

[0033] By changing the electrode position and excitation direction, the conductivity in three orthogonal directions is calculated to form an anisotropic conductivity tensor.

[0034] Furthermore, the anisotropic conductivity tensor includes conductivity components in three orthogonal directions, which are used to characterize the electrical conduction properties of carbon fiber composite materials in three-dimensional space.

[0035] This invention provides a system for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, used to execute the aforementioned method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, including:

[0036] The microstructure modeling module is used to determine the coordinate matrix of the fiber center node and the adjacent index matrix under the initial cross section, and to obtain the fiber contact point increment matrix based on the fiber ripple and fiber cell size.

[0037] The mesh generation module is used to form a partial element equivalent circuit method spatial double mesh based on the above matrix, establish the fiber overlap resistance position matrix and calculate the overlap resistance value.

[0038] The parameter matrix establishment module is used to calculate the impedance element matrix of the fiber network using the Gauss-Legend quadrature formula, and to establish the resistance matrix, inductance matrix and capacitance matrix.

[0039] The electromagnetic field decoupling module is used to establish current nodes in a spatial-scale semi-grid form based on the overlapping position, thereby decoupling the electric field and the magnetic field.

[0040] The equation solving module is used to establish the partial element equivalent circuit method equations. By identifying the electrode positions and adding excitation sources, the partial element equivalent circuit method equations are solved to obtain the voltage and current results in the time and frequency domains.

[0041] The conductivity calculation module is used to calculate the anisotropic conductivity of carbon fiber composite materials.

[0042] The advantages of this invention are: it can quickly determine the fiber overlap position to form a PEEC grid without the need for manual grid division; the characterization of carbon fiber composite materials accurately includes parameters such as capacitance, resistance, and inductance, and the calculation efficiency is high. Attached Figure Description

[0043] Figure 1 This is a flowchart of the method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method of the present invention.

[0044] Figure 2 This is a schematic diagram of the fiber cross-section of the present invention;

[0045] Figure 3 This is an incremental diagram of the overlap points of the present invention;

[0046] Figure 4 This is a physical model diagram of the resistor-capacitor-inductor network formed by incremental overlap points according to the present invention.

[0047] Figure 5 This is a PEEC network diagram of the present invention, which is a resistance-capacitance-inductance network formed by incremental overlap points.

[0048] Figure 6 This is a circuit diagram of the PEEC network based on the incremental formation of the lap joints of the present invention.

[0049] Figure 7 This is the xy matrix diagram of the present invention;

[0050] Figure 8 This is the fiber three-dimensional space and PEEC grid point diagram of the present invention;

[0051] Figure 9 This is a three-dimensional internal current diagram of the fiber in this invention;

[0052] Figure 10 This is a three-dimensional spatial potential distribution diagram of the fiber in this invention;

[0053] Figure 11 The anisotropic current distribution of the present invention Figure 1 ;

[0054] Figure 12 The anisotropic current distribution of the present invention Figure 2 . Detailed Implementation

[0055] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0056] Example 1

[0057] This embodiment provides a method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, including the following steps:

[0058] Step 101: Establish the resistance, capacitance, and inductance matrices under the microstructure of carbon fiber composite materials. The methods for establishing these matrices include, but are not limited to, using the Gaussler-Gande quadrature formula, the geometric mean distance method, and the fitting formula.

[0059] Based on the established PEEC mesh, inductance matrix L and resistance matrix R are established through current nodes, and capacitance matrix P is established through potential nodes.

[0060] The internal elements of the inductance matrix L are calculated by the following formula:

[0061]

[0062] and These are the weights and Gaussian points (where...) (This refers to the number of Gaussian points used). It is the first The length of the line, For the first The line segment and the first The mutual inductance between line segments, when When this occurs, the element represents the self-inductance of the root line. It is by and The angle formed by the directions of the two lines Logarithmic terms, denoted as the matrix permeability.

[0063] The internal elements of the capacitance matrix P are calculated by the following formula:

[0064]

[0065] in, The first in the capacitance matrix The node and the first Mutual capacitance coefficient between nodes and The first root segment and the first The length of the line segment, The dielectric constant of the matrix, The number of Gaussian integration points. For the first The weight of each Gaussian point For the first The position of a Gaussian point For logarithmic terms.

[0066] The internal elements of the resistance matrix R are calculated by the following formula:

[0067]

[0068] in, For the first The self-resistance of a line segment, For the first The length of the line segment, The resistivity of carbon fiber is denoted as . R is the radius of the carbon fiber.

[0069] The methods for establishing PEEC meshes in the microstructure of carbon fiber composites and decoupling electric and magnetic fields include:

[0070] The establishment of the PEEC mesh in the microstructure of the carbon fiber composite material includes:

[0071] First, determine the coordinate matrix xy of the fiber center node under the initial cross section, and establish the adjacency index matrix Neigber based on the fiber adjacency relationship. Then, obtain the fiber contact point increment matrix according to the fiber ripple degree beta and the fiber cell size. Then based on the matrix xy, Neigber, A PEEC spatial dual grid is formed, and finally the fiber overlap resistance position matrix Cont is established and the overlap resistance value is calculated.

[0072] The establishment of the coordinate matrix xy of the fiber center node under the initial cross section includes:

[0073] Firstly, based on the fiber volume ratio Fiber distribution coefficient Determine fiber spacing Square arrangement When arranged in hexagons .Sure The method is obtained by solving the following formula:

[0074]

[0075] based on Establish the coordinate matrix of the central node of the fiber filament The coordinate matrix of the central node of the fiber filament The methods for establishing this include, but are not limited to, the methods described above. For example, a cross-sectional microscopic image can be obtained through a microscope, and the image can be established using image recognition methods.

[0076] The Neigber-based adjacency index matrix is ​​established by means of:

[0077] The adjacent fiber indexes of a fiber are obtained by traversing the matrix xy and determining whether the Euclidean distance between the coordinates is less than or equal to the cell side length. Neigber's claims include, but are not limited to, non-sparse index storage.

[0078] The fiber contact point increment matrix Used to store the overlap positions between fibers and adjacent fibers, and the overlap intervals between fibers. like Figure 2 As shown, it is calculated by the following formula.

[0079]

[0080] In the above formula For fiber ripple, b is the distance increment of the overlap point, and b is the fiber arc height. The first overlap point between each adjacent fiber is randomly distributed in (0, ..., b). Between ), the distance increment of subsequent overlap points is ;

[0081] when The joint setting is now complete;

[0082] in For the initial overlap, This refers to the number of overlaps.

[0083] Sort the overlap increments of each fiber and insert the initial position 0 and the end length. The fiber contact point increment matrix is ​​formed. As shown in the following formula:

[0084]

[0085] The matrix-based , , Forming a PEEC spatial dual grid refers to establishing the three-dimensional spatial node coordinates of the fiber filaments. Node association matrix The process. Among them The matrix is ​​composed of and Formed by splicing, The node association matrix is ​​constructed as follows:

[0086]

[0087] In the above formula This represents the total number of nodes.

[0088] The fiber overlap resistance position matrix pass Construct an index to store the overlap points. The necessary and sufficient condition for a fiber to be an overlap point in the matrix is ​​that there are adjacent fibers between them. The values ​​in the matrix are equal. The resistance value is calculated using the following formula:

[0089]

[0090] in, This represents the fiber overlap resistance value. The resistivity of carbon fiber Apply pressure to the process, Where is the fiber radius, For fiber spacing, For fiber ripple, This represents the elastic modulus of the fiber.

[0091] Step 102: Establish the PEEC equation based on the matrix Cont, parameter matrices L, R, P, and bridging resistance R. Add an excitation source by identifying the electrode position. For frequency domain excitation, this includes, but is not limited to, using matrix inverse operations and the least squares method to solve the problem. For time domain excitation, this includes, but is not limited to, using the θ method to solve the PEEC equation. Finally, calculate the conductivity based on the voltage and current results in the time and frequency domains.

[0092] The time-domain equation and the frequency-domain equation are shown below:

[0093]

[0094]

[0095] in: For the node association matrix, This is the transpose of the node incidence matrix. It is a resistance matrix. For the inductor matrix, For the capacitance matrix, For the inductor admittance matrix, The imaginary unit, Angular frequency, For node voltage vectors, The branch current vector, For voltage source vectors, For current source vectors, Let be the derivative of the node voltage with respect to time. This is the derivative of the branch current with respect to time.

[0096] The Solving the PEEC equations using this method requires rewriting the frequency domain equations in general form:

[0097]

[0098] in: For the system matrix, The coefficient matrix of the time derivative term. For the state variable vector, Let be the derivative of the state variable with respect to time. This is the source term vector.

[0099] The solution is an iterative process:

[0100]

[0101] in: This is the time integration parameter, with a value range of [0,1]. For the system matrix, The coefficient matrix of the time derivative term. For time step, Let the state variable vector be the state variable vector at the current moment. Let this be the state variable vector for the next time step. Let the source term vector be the vector at the current time. This is the source term vector for the next time step.

[0102] Used to store the solution of PEEC, the vector is read by identifying the electrode position. The voltage and current of the internal electrodes are used to calculate the resistivity and conductivity based on the dimensional parameters of the composite material plate.

[0103] In this embodiment, the transverse resistivity is calculated using 9 fibers with a diameter of 7μm, a plate length of 10cm, VF=0.43, and a square distribution at equal intervals.

[0104] like Figure 2-12 As shown, the implementation process is as follows:

[0105] Step 100: Generate the xy matrix based on the fiber volume fraction, as shown below. Figure 7 As shown;

[0106] Step 200: Generate an incremental matrix of fiber overlap points based on fiber waviness and fiber adjacency, and form a three-dimensional space for the fibers, such as... Figure 8 As shown;

[0107] Step 300: After adding additional nodes, including overlapping resistance additional nodes, current excitation additional nodes, and electrode additional nodes, assemble the PEEC equations and solve them in the time domain. The 2000Hz fiber internal potential and current contour plot is shown below. Figure 9 and 10 As shown.

[0108] Example 2

[0109] This embodiment provides a method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, including the following steps:

[0110] Step 2100: Establish stress-damage mapping relationship

[0111] The stress-damage mapping algorithm is used to analyze the mechanical stress field distribution of carbon fiber composites and generate a damage parameter field. Specifically, this includes:

[0112] Step 2101: Obtain the mechanical stress field distribution of the carbon fiber composite material. ,in Three-dimensional spatial coordinates;

[0113] Step 2102: Determine the stress-damage mapping function based on material properties. The function can be expressed as:

[0114]

[0115] in, The damage threshold stress, The critical failure stress, and These are material-related parameters, obtained through experimental calibration.

[0116] Step 2103, apply the mechanical stress field Substitute into the mapping function The spatially distributed damage parameter field was calculated. .

[0117] Step 2200: Design a two-way coupled equation system

[0118] A two-way coupling equation set is constructed for a damage-conductivity coupled multiphysics model to establish the interaction mechanism between the mechanical and electric fields. Specifically, this includes:

[0119] Step 2201, establish the correction function The parameter matrix in the PEEC equation is used to adjust the parameters according to the damage parameters and can be expressed as:

[0120]

[0121]

[0122]

[0123] in, , , For correction factor, , , The damage sensitivity index is determined based on the material properties.

[0124] Step 2202: Modify the parameter matrix in the PEEC equations based on the correction function:

[0125]

[0126]

[0127]

[0128] in, , and These are the corrected resistance, inductance, and capacitance matrices;

[0129] Step 2203: Establish the equation for the reverse influence of the electric field on the mechanical field, considering the stress change caused by the thermoelectric effect:

[0130]

[0131] in, The additional stress caused by the electric field For electric field strength, The thermoelectric coupling coefficient reflects the ability of a material to convert electric field energy into heat energy, thereby generating thermal stress.

[0132] Step 2300: Introduce the fiber breakage probability distribution function.

[0133] The fiber breakage probability distribution function is applied to process the fracture behavior of carbon fiber composites under stress, generating fiber breakage distribution results. Specifically, this includes:

[0134] Step 2301: Establish the fiber breakage probability distribution function Used to describe stress state Lower spatial position The probability of carbon fiber fracture at a given point can be expressed as:

[0135]

[0136] in, For characteristic stress parameters, For the Weibull modulus, Effective volume factor;

[0137] Step 2302, combining fiber geometric distribution information, based on the node coordinate matrix Fiber overlap position matrix Calculate the breakage probability of each fiber;

[0138] Step 2303: Determine the fiber breakage location using the Monte Carlo method, compare the fiber breakage probability value with a random number, and generate a fiber breakage distribution matrix. Its elements are defined as:

[0139]

[0140] Step 2304, based on the fiber breakage distribution matrix Modify the PEEC mesh node association matrix This reflects the changes in mesh connectivity caused by fiber breakage:

[0141]

[0142] in, This represents the Hadamard product (the product of corresponding elements).

[0143] Step 2400: Develop a hierarchical iterative solution algorithm

[0144] Design and implement a hierarchical iterative solution algorithm to alternately solve for mechanical and electric fields, outputting the field distribution under equilibrium conditions. Specifically, this includes:

[0145] Step 2401, Initialize the mechanical field distribution and electric field distribution ;

[0146] Step 2402, establish the iterative update equation:

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] in, This represents the number of iteration steps. The function represents the additional stress induced by the electric field, and its specific implementation is: multiplying the square of the electric field strength by the thermoelectric coupling coefficient, i.e.:

[0153]

[0154] in Thermoelectric coupling coefficient, which reflects the ability of an electric field energy in a material to be converted into heat energy and thus generate thermal stress; It is the stress-damage mapping function defined in step 2102, which is used to convert the updated stress field into the corresponding damage parameter field;

[0155] Step 2403: Based on the corrected parameter matrix, solve the PEEC equation to obtain the new electric field distribution. The PEEC equation can be expressed in the frequency domain as:

[0156]

[0157] in, , , These are the admittance matrices for inductors, capacitors, and resistors, respectively. The electric potential vector, For the current source vectors; these admittance matrices can be calculated from the modified parameter matrix as follows:

[0158]

[0159]

[0160]

[0161] in, This is the corrected grid node correlation matrix. The potential correlation matrix, The imaginary unit, The angular frequency is obtained; the potential vector is solved. Then, the new electric field distribution can be calculated using the following formula:

[0162]

[0163] in, It is based on the nodal potential vector The spatial potential scalar field obtained by interpolation. Represents the gradient operator;

[0164] Step 2404: Calculate the convergence criterion :

[0165]

[0166] in, The L2 norm (Euclidean norm) measures the magnitude of changes in a field distribution. For a discretized field distribution, it is calculated as the square root of the sum of the squares of the corresponding physical quantities at each grid node, i.e., for a vector... Its L2 norm is defined as The convergence criterion takes into account the relative changes in the mechanical and electric fields, and the iterative process converges when both tend to be stable.

[0167] Step 2405, if (in If a preset convergence threshold is set, the iteration ends, and the mechanical field distribution in equilibrium is output. and electric field distribution Otherwise, return to step 2402 and continue iterating.

[0168] Step 2500: Calculate the anisotropic conductivity.

[0169] The anisotropic electrical conductivity of carbon fiber composites under damage conditions was calculated based on the equilibrium state PEEC solution. Specifically, this includes:

[0170] Step 2501: Under equilibrium conditions, extract the solution of the PEEC equation to obtain the potential distribution. and current distribution ;

[0171] Step 2502: Identify the set of electrode location nodes where voltage is applied. Calculate the voltage difference between the electrodes :

[0172]

[0173] Step 2503: Calculate the total current through the electrodes. :

[0174]

[0175] Step 2504, based on the sample size parameter (length) Cross-sectional area ), calculate along a specific direction conductivity :

[0176]

[0177] in, The sample size is in the direction of the current. The cross-sectional area is perpendicular to the direction of the current.

[0178] Step 2505: By changing the electrode position and excitation direction, calculate the three orthogonal directions respectively. , , conductivity on , and This constitutes the anisotropic conductivity tensor. :

[0179]

[0180] Step 2506: For samples with more complex anisotropic properties, this can be expanded to a complete anisotropic conductivity tensor:

[0181]

[0182] By applying electric fields in different directional combinations and measuring the response current, the individual components of the anisotropic conductivity tensor are determined.

[0183] It is understood that data preprocessing methods known to those skilled in the art include data cleaning, data transformation, and data reduction. Data transformation includes type conversion and normalization and standardization. Although the dimensions and types of data were omitted in the description of the preceding embodiments, data preprocessing is a technical knowledge known to those skilled in the art and a prerequisite step for data processing. Therefore, the known data preprocessing steps were not described independently in the preceding content.

[0184] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, characterized in that, Includes the following steps: Determine the coordinate matrix of the fiber center node and the adjacent index matrix under the initial cross section; The adjacent index matrix is ​​established based on the adjacency relationship of fibers and is used to represent the connection relationship between fibers; The fiber contact point increment matrix is ​​obtained based on fiber ripple and fiber cell size; The fiber contact point increment matrix is ​​calculated based on the fiber ripple and fiber cell size, and is used to determine the contact position between fibers. Based on the above matrix, a partial element equivalent circuit method spatial double grid is formed, a fiber overlap resistance position matrix is ​​established, and the overlap resistance value is calculated. The impedance element matrix of the fiber network is calculated using the Gauss-Legend quadrature formula, and the resistance matrix, inductance matrix, and capacitance matrix are established. The steps for calculating the impedance element matrix of the fiber network using the Gauss-Legend quadrature formula include: Apply the Gauss-Legend quadrature formula to each pair of adjacent fibers; Calculate the impedance values ​​between elements in the fiber network; Organize the impedance values ​​into an impedance element matrix; Current nodes are established by forming a spatial-scale semi-grid at the overlapping positions, thereby decoupling the electric and magnetic fields; Establish the partial element equivalent circuit method equations and add excitation sources by identifying electrode positions; Solve the partial element equivalent circuit method equations to obtain the voltage and current results in the time and frequency domains; Calculate the anisotropic electrical conductivity of carbon fiber composites; The partial element equivalent circuit method spatial double grid is achieved by adding additional nodes to the partial element equivalent circuit method equations through fiber overlap points and establishing potential nodes. Current nodes are established by forming a spatial scale half-grid using the overlap positions, thereby decoupling the electric field and magnetic field.

2. The method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method according to claim 1, characterized in that, The steps for determining the coordinate matrix of the fiber center node under the initial cross section include: Obtain microstructure information of carbon fiber composite materials; Determine the coordinates of the fiber center node under the initial cross section; The coordinates of the center node of the fiber are stored as a coordinate matrix.

3. The method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method according to claim 1, characterized in that, The steps for establishing the resistance matrix, inductance matrix, and capacitance matrix include: Establish the inductance and resistance matrices using current nodes; A capacitance matrix is ​​established using potential nodes.

4. The method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method according to claim 1, characterized in that, The steps for solving the partial element equivalent circuit method equations include: For frequency domain excitation, the solution is obtained using matrix inverse operations or the least squares method. For time-domain excitation, the θ method is used to solve the partial element equivalent circuit equations.

5. The method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method according to claim 1, characterized in that, The step of calculating the anisotropic electrical conductivity of the carbon fiber composite material includes: Conductivity is calculated based on voltage and current results in the time and frequency domains. By changing the electrode position and excitation direction, the conductivity in three orthogonal directions is calculated to form an anisotropic conductivity tensor.

6. The method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method according to claim 5, characterized in that, The anisotropic conductivity tensor includes conductivity components in three orthogonal directions, which are used to characterize the electrical conduction properties of carbon fiber composites in three-dimensional space.

7. A system for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method, used to execute the method for calculating the anisotropic conductivity of carbon fiber composite materials based on the partial element equivalent circuit method as described in any one of claims 1-6, characterized in that, include: The microstructure modeling module is used to determine the coordinate matrix of the fiber center node and the adjacent index matrix under the initial cross section, and to obtain the fiber contact point increment matrix based on the fiber ripple and fiber cell size. The mesh generation module is used to form a partial element equivalent circuit method spatial double mesh based on the above matrix, establish the fiber overlap resistance position matrix and calculate the overlap resistance value. The parameter matrix establishment module is used to calculate the impedance element matrix of the fiber network using the Gauss-Legend quadrature formula, and to establish the resistance matrix, inductance matrix and capacitance matrix. The electromagnetic field decoupling module is used to establish current nodes in a spatial-scale semi-grid form based on the overlapping position, thereby decoupling the electric field and the magnetic field. The equation solving module is used to establish the partial element equivalent circuit method equations. By identifying the electrode positions and adding excitation sources, the partial element equivalent circuit method equations are solved to obtain the voltage and current results in the time and frequency domains. The conductivity calculation module is used to calculate the anisotropic conductivity of carbon fiber composite materials.

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