A simulation method for microwave curing of carbon fiber resin matrix composite material

Abstract

The application discloses a kind of carbon fiber resin matrix composite microwave curing simulation simulation method, it is related to microwave curing technical field.Utilize maxwell equation group, heat transfer, curing reaction kinetics and multi-field coupling theory create curing reaction to establish theoretical model, further import parameter into numerical simulation software COMSOL or Ansys software and carry out finite element analysis, obtain the electromagnetic field distribution, temperature field distribution and curing degree field distribution nephogram in each stage of curing reaction process, can provide effective theoretical support for the microwave curing mechanism research of carbon fiber resin matrix composite, and provide a large number of basic data and optimization scheme for its actual microwave curing process optimization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave curing technology, and particularly relates to a microwave curing simulation method for carbon fiber resin matrix composite materials. BACKGROUND

[0002] Traditional thermal curing is the earliest and most commonly used curing method. However, this curing method is heated by heat transfer, and the heating rate is affected by the properties of the material itself. During the curing process, there is a certain temperature gradient in the product, the curing is uneven, the internal stress is large, and especially when a large product is made, the product performance will be seriously affected. The interfacial properties of composite materials mainly depend on the interaction between the reinforcing body and the matrix. In addition, traditional thermal curing generally requires a long curing cycle, and especially in the preparation process of nanocomposites, the product performance is prone to decline due to the sedimentation or re-aggregation of nanoparticles. Therefore, some new curing methods such as photocuring, electron beam curing and microwave curing are increasingly valued.

[0003] Microwave curing is essentially a thermal curing, but it is different from traditional thermal curing. From the perspective of material molecules, the overall dipole moment of the molecule is usually zero. Due to the action of microwaves, the dipole moment of the molecule changes, and the heating rate depends on the polarity of the molecule, which has a certain selectivity. From the macroscopic perspective of the material, microwave heating is a heating method caused by the conversion of dielectric loss of the material in the microwave field into heat. In a uniform microwave field, the heating effect of each part of the material is the same, and the heating efficiency is not affected by the thermal conductivity coefficient of the material. Compared with the "from surface to inside" heat transfer mode of traditional heating, microwaves directly act on molecules, and polar molecules absorb electromagnetic energy and convert it into heat energy. The heating is more uniform, the curing rate is fast, the controllability is strong, and it is energy-saving and environmentally friendly. Therefore, in recent years, microwave curing has been increasingly valued in the field of composite materials.

[0004] Microwave (Mw) is an electromagnetic wave with a frequency bandwidth of 100MHz to 300GHz and a wavelength range of 1m to 1mm. Compared with visible waves, Mw is ordered and polarized, and obeys the law of optical physics. It can be absorbed, transmitted or reflected according to the dielectric properties of the material that collides with the wave. The absorption level is determined by dielectric loss. Mw heating is a form of radiation. Due to the interaction between the material and Mw at the molecular scale, the energy is dissipated in volume. Mw dielectric heating has been used in various applications such as vulcanization of rubber, heating of food and bonding of composite materials.

[0005] Epoxy resins can be cured by absorbing MW energy in a high-frequency field and converting it into heat energy through molecular vibration / rotation in the presence of an alternating field, such as Figure 1The main mechanism of dielectric heating is dipole loss, also known as reorientation loss mechanism. If a dielectric material with permanent dipoles is subjected to an alternating electromagnetic field (or alternating current that generates an alternating expanding and collapsing magnetic field), the dipoles will vibrate violently, but it will be found that it is difficult to adapt to the high-speed reversal of the magnetic field, that is, the molecular rotation (back and forth) response can be delayed. This phenomenon is important because it will cause a phase lag with the electric field, resulting in power consumption of the dielectric material. According to the classic Debye theory and Lambert law, the MW heating of dielectric materials (i.e. materials with molecular dipole response) is described. The MW energy absorbed by the dielectric material is given by the Lambert law as follows:

[0006]

[0007] In the formula, Q is the MW energy, σ is the effective conductivity, is the field strength of the electromagnetic field, f is the MW frequency, ε'0 is the dielectric constant of air (8.8514 x 10 -12 F / m), ε' is the actual dielectric constant of the material, which quantifies the energy stored and transmitted by the material. tanδ is the loss tangent coefficient, a parameter related to the geometry, and is the electric field strength. According to the above formula, under the condition that f and are constant, the dielectric loss of the material determines the MW heating rate.

[0008] The dielectric loss of the polar molecule is related to the content of the polar group, the strength of the molecular polarity, and the mobility of the group in the matrix. Generally, during the curing process of the polymer, the dielectric properties will first increase and then decrease with the increase of temperature. The reason is that the dielectric properties of the polymer will increase with the increase of temperature, but a large number of polar groups are consumed during the curing of the polymer, the viscosity of the system gradually increases, and the movement of the polar molecules is hindered, so the dielectric properties decrease.

[0009] The material composed of carbon fiber reinforced material and resin matrix is called carbon fiber resin composite material. The resin undergoes crosslinking and curing reaction by microwave curing, and the resin gradually reacts from small molecule monomer to high molecular network. The current problems of microwave curing of carbon fiber resin matrix composite material are:

[0010] (1) The microwave curing mechanism of carbon fiber resin matrix composite material is not completely clear. There are two theories of "thermal effect" and "non-thermal effect" today. Whether there is "non-thermal effect" in the curing process of epoxy resin is not clear. The impedance effect of carbon fiber on microwave during the curing process cannot be modeled, and whether the heat generated by carbon fiber and the heat generated by curing reaction can accelerate the crosslinking and curing reaction of epoxy resin is not clear, which lacks certain precision support.

[0011] (2) The microwave-heat transfer mechanism during the curing process of the product is complex, the numerical value of the wave absorption performance is not accurate, the multi-field coupling theory mechanism is complex, and the real-time support degree of engineering practice is not high. In the simulation process, the solving process excessively depends on the basic theory and the preset theoretical model, the pre-work consumes a large amount of work, the post-computing process is simple and rapid, but it is difficult to realize the control of multiple aspects on the basis of the real-time of the model.

[0012] Therefore, it is a technical problem to be solved at present to provide a simulation method of microwave curing of carbon fiber resin matrix composite materials by comprehensively considering multi-field coupling factors.

[0013] Therefore, the present application is provided. SUMMARY

[0014] The present application aims to provide a simulation method of microwave curing of carbon fiber resin matrix composite materials, and aims to obtain the real-time resin curing degree, the temperature of the composite material, the temperature field distribution of the microwave oven and the electromagnetic field distribution of the microwave oven of the carbon fiber resin matrix composite material in the microwave oven.

[0015] The present application is implemented as follows:

[0016] In a first aspect, the present application provides a simulation method of microwave curing of carbon fiber resin matrix composite materials, comprising:

[0017] Modeling: creating a geometric model of a microwave curing device and a geometric model of a carbon fiber resin matrix composite structure in a finite element analysis software, and performing unit grid division;

[0018] Reaction kinetics derivation: according to the DSC test data of the resin under different heating rates, the chemical reaction kinetics parameters of the carbon fiber resin matrix composite material are solved, the relationship among the curing rate, the curing degree, the curing time and the curing temperature is established, and finally the reaction kinetics equation of the carbon fiber resin matrix composite material is solved;

[0019] Definition of ordinary differential and differential algebraic equations in the software: the solved reaction kinetics basic equation is brought into the geometric model of the carbon fiber resin matrix composite structure, so as to realize the calculation of the curing degree of the carbon fiber resin matrix composite material; the reaction heat source is defined in the geometric model of the carbon fiber resin matrix composite structure, so as to introduce the influence of the internal heat effect generated by the chemical reaction of the carbon fiber resin matrix composite structure during the curing process;

[0020] Setting of microwave curing power: controlling the power of the microwave curing device to present a gradient change of power and time, so as to control the temperature change of the carbon fiber resin matrix composite structure due to the action of the microwave;

[0021] Multi-field coupling setting: electromagnetic field, temperature field and curing degree field are simulated and calculated, and multi-field coupling analysis and calculation of the carbon fiber resin matrix composite structure are realized through joint solution;

[0022] Result derivation: with the help of the software post-processing module, the electromagnetic field distribution cloud diagram, the temperature field distribution cloud diagram and the curing degree field distribution cloud diagram of the carbon fiber resin matrix composite in the microwave curing process are obtained;

[0023] The software used is selected from any one of COMSOL software and Ansys software.

[0024] In the optional implementation, in the process of establishing the model, according to the actual microwave oven size, shape and microwave emission source, the geometric model of the microwave curing device and the geometric model of the carbon fiber resin matrix composite structure are created, so as to complete the establishment of the solid model of the microwave curing; the material parameter model is given to the microwave curing device and the carbon fiber resin matrix composite structure.

[0025] The material parameter model of the microwave curing device includes air domain parameters and microwave curing inner wall parameters, the air domain parameters include relative magnetic permeability, relative permittivity, electrical conductivity, constant pressure heat capacity density and thermal conductivity, and the microwave curing inner wall parameters include relative magnetic permeability, electrical conductivity and relative permittivity.

[0026] The material parameters in the material parameter model of the carbon fiber resin matrix composite structure include thermal conductivity, density, constant pressure heat capacity, electrical conductivity, relative magnetic permeability and relative permittivity, wherein the relative permittivity is expressed in complex form, the equation of the permittivity is expressed in the form of real part and imaginary part combination, and the relative permittivity ε(ω) = ε'(ω)-jε"(ω);

[0027] Wherein the imaginary part ε"(ω) represents dielectric loss, and the real part ε'(ω) represents permittivity.

[0028] In the optional implementation, in the process of deriving the reaction kinetics, the finally solved reaction kinetics equation is as follows:

[0029]

[0030] In the formula, is the curing reaction rate;

[0031] E is the activation energy of the curing reaction, and the unit is J / mol;

[0032] R is the universal gas constant, and the value is 8.3144 J / (mol.k);

[0033] T is the curing temperature, and the unit is ℃;

[0034] n is the reaction order I;

[0035] m is the reaction order II;

[0036] a is the degree of cure;

[0037] A is the pre-exponential factor, unit: S -1 .

[0038] In the optional implementation, in the process of defining the reaction heat source in the model of the carbon fiber resin matrix composite structure, the calculation formula of the reaction heat source is -rho0*H_r*d(alpha,t), and the unit of the calculation result is W / m 3 ;

[0039] In the formula, rho0 is the material density, and the unit is kg / m 3 ;

[0040] H_r is the chemical reaction enthalpy, and the unit is J / kg;

[0041] d(alpha,t) is the differential of the resin and the degree of cure.

[0042] In the optional implementation, in the process of calculating the reaction heat source, the initial domain temperature is defined as a certain value in 20-30 [degC], and the overall oven outer surface is defined as a thermal insulator.

[0043] In the optional implementation, a step function is introduced to control the microwave curing power, so that it changes with time;

[0044] In the step function, the dependent variable is the power W(t), and the independent variable is the time t. The power changes with time and can be divided into n stages. The expression of the function is as follows:

[0045]

[0046] Where a1-an is the microwave curing power of the corresponding stage, and the unit is w;

[0047] t1-tn is the time of the corresponding stage, and the unit is s.

[0048] In the optional implementation, in the process of multi-field coupling, the temperature field distribution and the degree of cure field distribution inside the composite material are obtained through the Maxwell equation set, the heat conduction equation and the curing kinetics equation.

[0049] In the optional implementation, the electromagnetic field is solved first, then the temperature field and the degree of cure field are solved simultaneously, and then the electromagnetic field, the temperature field and the degree of cure field are coupled.

[0050] In an optional embodiment, in the process of solving the electromagnetic field, the solving type is selected as transient, and the solving method is selected as the direct solver.

[0051] In an optional embodiment, in the process of solving the temperature field and the curing degree field, the solving type is selected as transient, and the solving method is selected as the direct solver.

[0052] The present application has the following beneficial effects: the present application creates a theoretical model of the curing reaction by using the Maxwell equation set, heat transfer theory, curing reaction kinetics and multi-field coupling theory, further introduces parameters into numerical simulation software COMSOL or Ansys software for finite element analysis, obtains the electromagnetic field distribution, temperature field distribution and curing degree field distribution cloud diagram in the curing reaction process, provides effective theoretical support for the microwave curing mechanism research of carbon fiber resin matrix composite materials, and provides a large amount of basic data and optimization scheme for the optimization of the actual microwave curing process. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0054] Figure 1 Schematic diagram of microwave response of material with alternating electromagnetic field dipole molecule;

[0055] Figure 2 Modeling diagram of microwave curing device;

[0056] Figure 3 Modeling diagram of carbon fiber resin matrix composite material pre-cured plate;

[0057] Figure 4 Definition process diagram of ordinary differential and differential algebraic equations;

[0058] Figure 5 Schematic diagram of carbon fiber composite material plate heat source definition;

[0059] Figure 6 Segmented function diagram of microwave curing power and time;

[0060] Figure 7 Schematic diagram of microwave port value setting; in the diagram, (a) and (b) respectively represent the schematic diagram of setting of different ports;

[0061] Figure 8The figure is a process diagram of energy transmission of the temperature field of the microwave curing of the composite material; in the figure, (a) represents a heat transfer diagram of the composite material and cold air; (b) represents a curing reaction heat release diagram and a heat exchange mode diagram;

[0062] Figure 9 The figure is a COMSOL analysis flowchart;

[0063] Figure 10 The figure is a cloud chart of the multi-section electromagnetic field distribution in the microwave cavity;

[0064] Figure 11 The figure is a cloud chart of the overall temperature field distribution;

[0065] Figure 12 The figure is a cloud chart of the curing degree field distribution of the carbon fiber composite material plate at different time points;

[0066] Figure 13 The figure is a diagram of the established theoretical model;

[0067] Figures 14-16 The figure is a screenshot of the setting of various material parameters, wherein, Figure 14 The figure is a material parameter of the carbon fiber composite material; Figure 15 The figure is a material parameter of the air domain; Figure 16 The figure is a material parameter of the inner wall of the microwave curing;

[0068] Figure 17 The figure is a segmented function diagram of the microwave curing power;

[0069] Figure 18 The figure is a specific numerical value diagram of the segmented function of the microwave curing;

[0070] Figure 19 The figure is a cloud chart of the electric field distribution;

[0071] Figure 20 The figure is a cloud chart of the temperature field distribution;

[0072] Figure 21 The figure is a cloud chart of the curing degree field distribution. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturer are adopted. If the reagents or instruments used are not indicated by the manufacturer, they are all conventional products that can be purchased in the market.

[0074] The embodiments of the present application provide a microwave curing simulation method for carbon fiber resin matrix composite materials, which comprises the following steps:

[0075] S1, model establishment

[0076] Create the geometric model of the microwave curing device (as shown in Figure 2 Fig. 1) and the geometric model of the carbon fiber resin matrix composite structure (as shown in Figure 3 Fig. 2) in the finite element analysis software, and perform unit meshing; the microwave curing device can be referred to as a microwave emitting device, and the structure of the microwave oven cavity thereof is as shown in Figure 2 The carbon fiber resin matrix composite structure can be, but is not limited to, a carbon fiber composite plate, and the shape thereof is not limited to Figure 3 Fig. 3, but can also be a rhombus, a pentagon, a circle, etc.

[0077] Specifically, the finite element analysis software used can be the numerical simulation software COMSOL Multiphysics software. Ansys software can also be used for simulation and simulation, and the electromagnetic simulation module of Ansys can also be used for simulation analysis of microwave curing of carbon fiber resin matrix composites.

[0078] In some embodiments, in the process of establishing the model, the geometric model of the microwave curing device and the geometric model of the carbon fiber resin matrix composite structure are created according to the actual size and shape of the microwave oven and the microwave emitting source, so as to complete the establishment of the physical model of the microwave curing. The process of establishing the model also includes: setting various material parameters for the above microwave curing device and carbon fiber composite structure, and assigning the material parameter model to the microwave curing device and the carbon fiber resin matrix composite structure.

[0079] The material parameter model of the microwave curing device includes air domain parameters and microwave curing inner wall parameters, the air domain parameters include relative magnetic permeability, relative permittivity, electrical conductivity, constant pressure heat capacity density and thermal conductivity, and the microwave curing inner wall parameters include relative magnetic permeability, electrical conductivity and relative permittivity. The above parameters are input into the COMSOL software; the inner wall of the microwave curing device adopts a material with high electrical conductivity, such as copper, iron, silver, etc., and the material parameters that need to be set include relative magnetic permeability, electrical conductivity and relative permittivity.

[0080] The material parameters in the material parameter model of the carbon fiber resin matrix composite structure include thermal conductivity, density, constant pressure heat capacity, electrical conductivity, relative magnetic permeability and relative permittivity, and the above parameters are input into the COMSOL software. Among them, the relative permittivity is expressed in a complex form, and the equation of the permittivity is expressed in a combination of real and imaginary parts, and the relative permittivity ε(ω) = ε'(ω) - jε"(ω); wherein the imaginary part ε"(ω) represents dielectric loss, and the real part ε'(ω) represents permittivity.

[0081] S2, reaction kinetics derivation

[0082] The curing reaction kinetics is a discipline of thermodynamics, and is a discipline specially used for studying the crosslinking reaction mechanism of the polymer material. The curing reaction process of the composite material is essentially the crosslinking curing reaction process of the epoxy resin, that is, the process that the resin gradually reacts from the small molecule monomer to the high molecular net. The model fitting method of the present application analyzes the formula derivation of the curing reaction kinetics of the composite material, solves the chemical reaction kinetics parameters (reaction order, pre-exponential factor and reaction activation energy) of the carbon fiber resin matrix composite according to the DSC test data of the resin under different heating rates, establishes the relationship among the curing rate, the curing degree, the curing time and the curing temperature, and finally solves the reaction kinetics equation of the carbon fiber resin matrix composite. In the derivation process of the reaction kinetics, the finally solved reaction kinetics equation is as follows:

[0083]

[0084] In the formula, is the curing reaction rate;

[0085] E is the curing reaction activation energy, and the unit is J / mol;

[0086] R is the universal gas constant, and the value is 8.3144 J / (mol.k);

[0087] T is the curing temperature, and the unit is ℃;

[0088] n is the reaction order I;

[0089] m is the reaction order II;

[0090] alpha is the curing degree;

[0091] A is the pre-exponential factor, and the unit is S -1 .

[0092] S3, definition of domain ordinary differential and differential algebraic equation in software

[0093] In the COMSOL software, the method of domain ordinary differential and differential algebraic equation is adopted, the solved reaction kinetics basic equation is brought into the geometric model of the carbon fiber resin matrix composite structure, as shown in Figure 4 , so as to realize the calculation of the curing degree of the carbon fiber resin matrix composite. In order to meet the software language, the introduced equation expression is:

[0094] A*exp(-E_a / R_const / T)*((1-alpha)^n)*alpha^m

[0095] Wherein, alpha is the curing degree of the reaction, which is equivalent to alpha in the formula of S2.

[0096] In some embodiments, further comprising: defining a reaction heat source in the geometric model of the carbon fiber resin matrix composite structure, so as to introduce the internal heat effect generated by the chemical reaction of the carbon fiber resin matrix composite structure in the curing process. In the setting, the initial domain temperature is defined as a certain determined value in 20-30 [degC], the overall oven outer surface is defined as a thermal insulator, and in order to simulate the heat release in the chemical reaction process, as shown in Figure 5 The calculation formula of the reaction heat source in the process of defining the reaction heat source in the model of the carbon fiber resin matrix composite structure is -rho0*H_r*d(alpha,t), and the unit of the calculation result is W / m 3 ;

[0097] In the formula, rho0 is the material density, with the unit of kg / m 3 ;

[0098] H_r is the chemical reaction enthalpy, with the unit of J / kg;

[0099] d(alpha,t) is the integral of the resin and the curing degree.

[0100] S4, setting of microwave curing power

[0101] The power of the microwave curing device is controlled to present a gradient change of power and time, so as to control the temperature change of the carbon fiber resin matrix composite structure due to the microwave effect. In the process of microwave curing of the composite material, since the microwave frequency is fixed, the microwave generation power is mainly used to control the speed in the curing process. In order to set different microwave curing gradients, a step function is introduced to control the microwave curing power, so that it changes with time;

[0102] In the step function, the dependent variable is power W(t), and the independent variable is time t. The power changes with time and can be divided into n stages. The expression of the function is as follows:

[0103]

[0104] Where a1-an is the microwave curing power of the corresponding stage, with the unit of w;

[0105] t1-tn is the time of the corresponding stage, with the unit of s.

[0106] In some embodiments, it can be controlled in three stages, as shown in Figure 6 .

[0107] It should be noted that, since the air domain and the composite material domain are considered for electromagnetic wave conduction, the entire domain in COMSOL is defined, and the initial value of the electric field is defined as 0. The microwave power function pl(t[1 / s])[W] is defined for the two ports, so as to obtain the power loading operation condition varying with time, and the specific function is shown in the following formula: Figure 7 The effective setting of the microwave heating power is realized through the above method.

[0108] S5, multi-field coupling setting

[0109] As shown in the following formula: Figure 8 During the microwave curing process, the curing degree of the composite material gradually increases with the increase of the temperature, the increase of the curing degree affects the dielectric properties of the composite material, and the change of the dielectric properties affects the absorption of the microwave energy by the composite material. Therefore, the temperature, the curing degree, and the dielectric properties of the composite material interact and affect each other, and the three are in a strong coupling relationship. Therefore, the microwave curing process of the epoxy resin-based composite material is a nonlinear multi-physical field coupling process containing two internal heat sources. Numerical simulation of the process needs to simulate and calculate the electromagnetic field, the temperature field, and the curing degree field at the same time, and realize the multi-field coupling analysis and calculation of the finite element of the carbon fiber resin-based composite material structure through joint solution, as shown in the following formula: Figure 9

[0110] In some embodiments, during the multi-field coupling setting process, the temperature field distribution and the curing degree field distribution inside the composite material are obtained through the Maxwell equations, the heat conduction equation, and the curing dynamics equation.

[0111] In some embodiments, the electromagnetic field is solved first, and then the temperature field and the curing degree field are solved at the same time, and the electromagnetic field, the temperature field, and the curing degree field are coupled, as shown in the following formula: Figure 9 First, the electromagnetic field is solved according to the model (curvilinear coordinates, local coordinate system) established in the above steps, and then the temperature field and the curing degree field are solved at the same time according to the general form of the partial differential equation of the solid heat conduction coupling, and finally the temperature-curing degree coupling field is obtained.

[0112] In some embodiments, during the process of solving the electromagnetic field, the solving type is selected as transient, and the solving method is selected as direct solver. During the process of solving the temperature field and the curing degree field, the solving type is selected as transient, and the solving method is selected as direct solver. The research methods and solvers involved in the COMSOL software are shown in the following table 1:

[0113] Table 1 Different physical fields and corresponding research methods and solver selection

[0114]

[0115] ​S6, result derivation

[0116] With the help of the post-processing module of COMSOL software, the electromagnetic field distribution cloud chart of the carbon fiber resin matrix composite material in the microwave curing process (as shown in Figure 10 ), the temperature field distribution cloud chart (as shown in Figure 11 ) and the curing degree field distribution cloud chart (as shown in Figure 12 ) are obtained.

[0117] It should be noted that the electromagnetic field distribution cloud chart can describe the effect of electromagnetic field on the carbon fiber resin matrix composite material, which is used to analyze the electromagnetic field distribution on the surface and inside of the carbon fiber resin matrix composite material, so as to provide a basis for subsequent theoretical analysis. The obtained temperature field distribution cloud chart can describe the temperature change of the carbon fiber resin matrix composite material, the temperature change of the air domain inside the curing furnace and the heat transfer effect of the carbon fiber resin matrix composite material and air in the microwave curing process, which can provide a theoretical model of temperature field and basic research data in the microwave curing process. The obtained curing degree field distribution cloud chart can describe the change of the curing degree of the carbon fiber resin matrix composite material in the microwave heating process with temperature and microwave power, so as to provide a key theoretical model and parameters for studying the microwave curing mechanism of the carbon fiber resin matrix composite material.

[0118] The features and properties of the present application are further described in detail in combination with the following examples.

[0119] Example 1

[0120] The present embodiment provides a microwave curing simulation method for carbon fiber resin matrix composite material, comprising the following steps:

[0121] (1) Model establishment

[0122] According to the actual size and shape of the microwave oven and the microwave emission source, the geometric model of the microwave curing device and the geometric model of the carbon fiber resin matrix composite material structure (as shown in Figure 13 ) are created in the software.

[0123] The composition of the carbon fiber resin matrix composite material is T700 carbon fiber / epoxy resin composite material, in which the carbon fiber in the composite material is unidirectional 0 degree direction, the shape is cuboid, and the size is 120mm*30mm*1.4mm (length*width*height).

[0124] The size of the microwave oven is 375mm*375mm*375mm, and the shape is a cube. The microwave emission source is two mutually perpendicular cuboids, and the size is 80mm*35mm*30mm (length*width*height).

[0125] The material parameter model is assigned to the microwave curing device and the carbon fiber resin-based composite structural member based on the above microwave curing device and the carbon fiber composite material plate.

[0126] The material parameter model of the microwave curing device includes air domain parameters and microwave curing inner wall parameters. The air domain parameters include relative magnetic permeability, relative dielectric constant, electrical conductivity, constant pressure heat capacity density, and thermal conductivity, which are input into the COMSOL software. The microwave curing inner wall is made of a material with high electrical conductivity, specifically copper, and the material parameters that need to be set include relative magnetic permeability, electrical conductivity, and relative dielectric constant ε(ω) = 2 - j * 0.2. The material parameters in the material parameter model of the carbon fiber resin-based composite structural member include thermal conductivity, density, constant pressure heat capacity, electrical conductivity, relative magnetic permeability, and relative dielectric constant, which are input into the COMSOL software. Specifically as shown in Figure 14 (material parameters of carbon fiber composite material), Figure 15 (material parameters of air domain), and Figure 16 (material parameters of microwave curing inner wall).

[0127] (2) Reaction kinetics derivation

[0128] The model fitting method is used to study the curing kinetics of the resin system, which mainly solves the kinetic parameters (reaction order, pre-exponential factor, and reaction activation energy) in the fitting model, thereby establishing the relationship between curing rate, curing degree, and time, temperature. Finally, the following reaction kinetics equation is solved:

[0129]

[0130] The specific meanings of each parameter are referred to other parts of the specification.

[0131] E is the curing reaction activation energy, with a value of 33.87 [kJ / mol];

[0132] R is the universal gas constant, with a value of 8.3144 J / (mol.k);

[0133] T is the curing temperature, with a unit of ℃;

[0134] n is the reaction order, with a value of 1.37;

[0135] m is the reaction order, with a value of 0.54;

[0136] A is the pre-exponential factor, with a value of 185.79 [1 / s].

[0137] (3) Definition of ordinary differential and differential algebraic equations in software domains

[0138] The solved reaction kinetics basic equation is brought into the model of carbon fiber resin-based composite structural parts, as shown in Figure 4 , so as to realize the calculation of the curing degree of carbon fiber resin-based composite. In order to conform to the software language, the equation expression introduced is:

[0139] A*exp(-E_a / R_const / T)*((1-alpha)^n)*alpha^m

[0140] Wherein, alpha is the curing degree of the reaction, which is equivalent to a in the S2 formula.

[0141] In the setting, the initial domain temperature is defined as 20 [degC], the overall oven outer surface is defined as thermal insulation, and in order to simulate the heat release in the chemical reaction process, as shown in Figure 5 , a reaction heat source is defined in the composite plate, and the calculation formula of the reaction heat source is -rho0*H_r*d(alpha,t), and the unit of the calculation result is W / m 3 ;

[0142] In the formula, rho0 is the material density, which is 1650 [kg / m^3];

[0143] H_r is the chemical reaction enthalpy, which is 500 [kJ / kg];

[0144] d(alpha,t) is the calculus of resin and curing degree.

[0145] (4) Setting of microwave curing power

[0146] In order to set different microwave curing gradients, a piecewise function is set as shown in Figure 17 , to establish the function relationship between power and time in the curing process.

[0147] The overall domain in COMSOL is defined, in which the initial value of the electric field is defined as 0. The microwave power function pl(t[1 / s])[W] is defined for its two ports, so as to obtain the loading operation condition of the power changing with time, and the specific parameters are shown in Figure 18 .

[0148] (5) Multi-field coupling setting

[0149] First, the electromagnetic field is solved, then the temperature field and the curing degree field are solved, and then the temperature field and the curing degree field are coupled, as shown in Figure 9 . First, the model (curvilinear coordinates, local coordinate system) established according to the above steps is solved to solve the electromagnetic field, then the general form of partial differential equation of solid heat conduction coupling is solved according to the temperature field analysis model, and the temperature field and the curing degree field are solved, and finally the temperature-curing degree coupling field is obtained. The solving mode is referred to Table 1.

[0150] (6) Result derivation

[0151] With the help of the post-processing module of COMSOL software, the electromagnetic field distribution cloud chart (as shown in Figure 19 ), the temperature field distribution cloud chart (as shown in Figure 20 ) and the degree of curing field distribution cloud chart (as shown in Figure 21 ) of the carbon fiber resin matrix composite material in the microwave curing process are obtained.

[0152] In summary, the present application provides a kind of carbon fiber resin matrix composite material microwave curing simulation method, through the modeling module of COMSOL software, the model of 1:1 microwave oven and carbon fiber resin matrix composite sample can be established;By introducing the reaction kinetics of microwave curing resin, define domain ordinary differential and differential algebraic equation in COMSOL software, and give the corresponding simulation material parameters and set the segmented heating power of microwave by function, the simulation of carbon fiber resin matrix composite material curing heat, curing degree and temperature under the condition of electromagnetic wave can be realized;Finally, through the multi-field coupling mode of COMSOL, the multi-field coupling of electromagnetic wave (frequency domain) + solid heat (transient) + reaction heat (transient) can be realized, and the simulation of microwave curing carbon fiber composite material is realized. Thus, the real-time resin curing degree of carbon fiber resin matrix composite material in microwave oven, composite material temperature, temperature field distribution of microwave oven and electromagnetic field distribution of microwave oven are obtained, which provides a theoretical basis for the curing process optimization of microwave curing carbon fiber composite material, and can be used to guide subsequent process optimization, avoid a large number of test verification, greatly avoid the waste of resources.

[0153] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A simulation method for microwave curing of carbon fiber resin-based composite materials, characterized in that, include: Model creation: Create geometric models of the microwave curing device and carbon fiber resin matrix composite structural components in finite element analysis software, and perform element mesh generation; Reaction kinetics derivation: Based on the DSC test data of the resin at different heating rates, the chemical reaction kinetic parameters of the fitted carbon fiber resin matrix composite were solved, the relationship between curing rate, degree of curing, curing time and curing temperature was established, and finally the reaction kinetic equation of the carbon fiber resin matrix composite was solved. Definition of domain ordinary differential equations and differential algebraic equations in the software: The solved basic equations of reaction kinetics are substituted into the geometric model of the carbon fiber resin matrix composite structure to calculate the degree of curing of the carbon fiber resin matrix composite; a reaction heat source is defined in the geometric model of the carbon fiber resin matrix composite structure to introduce the influence of the internal heat effect generated by the chemical reaction of the carbon fiber resin matrix composite structure during the curing process. Microwave curing power setting: Controlling the power of the microwave curing device to present a gradient change in power and time, so as to control the temperature change of carbon fiber resin matrix composite structural parts caused by microwave action; Multi-field coupling setting: Simulate and calculate electromagnetic field, temperature field and curing degree field, and realize finite element multi-field coupling analysis and calculation of carbon fiber resin matrix composite structural parts through joint solution; Results Export: With the help of the software post-processing module, electromagnetic field distribution cloud map, temperature field distribution cloud map and curing degree field distribution cloud map of carbon fiber resin matrix composite material during microwave curing were obtained. The software used is selected from either COMSOL or Ansys.

2. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 1, characterized in that, During the model building process, based on the actual size and shape of the microwave oven and the microwave emission source, a geometric model of the microwave curing device and a geometric model of the carbon fiber resin-based composite material structural component are created, thereby completing the establishment of the solid model of microwave curing; material parameter models are then assigned to the microwave curing device and the carbon fiber resin-based composite material structural component. The material parameter model of the microwave curing device includes air domain parameters and microwave curing inner wall parameters. The air domain parameters include relative permeability, relative permittivity, electrical conductivity, constant pressure heat density, and thermal conductivity. The microwave curing inner wall parameters include relative permeability, electrical conductivity, and relative permittivity. The material parameters in the material parameter model of the carbon fiber resin matrix composite material structure include thermal conductivity, density, constant pressure heat capacity, electrical conductivity, relative magnetic permeability and relative permittivity. The relative permittivity is expressed in complex form, and the equation of the permittivity is expressed by combining the real part and the imaginary part. The relative permittivity ε(ω)=ε′(ω)-jε″(ω) The imaginary part ε″(ω) represents the dielectric loss, and the real part ε′(ω) represents the dielectric constant.

3. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 1, characterized in that, In the process of deriving the reaction kinetics, the final reaction kinetic equations obtained are as follows: In the formula, This represents the curing reaction rate; E is the activation energy of the curing reaction, in J / mol; R is the universal gas constant, with a value of 8.3144 J / (mol·K); T represents the curing temperature, measured in °C. n is the reaction order I; m is the reaction order II; α represents the degree of curing; A is the pre-exponential factor, with units of S. -1 .

4. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 1, characterized in that, In defining the reaction heat source in the model of carbon fiber resin matrix composite structural components, the calculation formula for the reaction heat source is -rho0*H_r*d(alpha,t), and the unit of the calculation result is W / m³. 3 ; In the formula, rho0 is the material density, with units of kg / m³. 3 ; H_r is the enthalpy of chemical reaction, with units of J / kg; d(alpha,t) is the calculus of the resin and the degree of curing.

5. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 4, characterized in that, In the calculation of the reaction heat source, the initial domain temperature is defined as a certain value between 20 and 30 [degC], and the outer surface of the overall oven is defined as a thermal insulator.

6. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 1, characterized in that, A step function is introduced to control the microwave curing power, causing it to change over time; In the step function, the dependent variable is power W(t), and the independent variable is time t. The change of power with time can be divided into n stages, and the expression of the function is as follows: in: a1~an represent the microwave curing power of the corresponding stage, in watts (W). t1 to tn represent the time of the corresponding stage, in seconds.

7. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 1, characterized in that, During the multi-field coupling process, the temperature field distribution and curing degree field distribution inside the composite material are obtained through Maxwell's equations, heat conduction equations, and curing kinetic equations.

8. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 7, characterized in that, First, solve for the electromagnetic field, then simultaneously solve for the temperature field and the curing degree field, and finally couple the electromagnetic field, temperature field and curing degree field.

9. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 8, characterized in that, In solving the electromagnetic field, the solution type is selected as transient, and the solution method is selected as direct solver.

10. The microwave curing simulation method for carbon fiber resin matrix composites according to claim 1, characterized in that, In solving the temperature field and the degree of solidification field, the solution type is selected as transient, and the solution method is selected as direct solver.

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