Material mechanical property prediction method based on microstructure unit cell model

Abstract

The invention relates to a material mechanical property prediction method based on a microstructure unit cell model, and belongs to the technical field of aircraft thermal protection, and the method comprises the steps: obtaining the residual carbon rate of a material and the pyrolysis degree data changing along with the temperature according to a thermogravimetric test result; converting the volume fractions of the components of the material by using the pyrolysis degrees to obtain the volume fractions of the components corresponding to different pyrolysis degrees; calculating by using a parallel model to obtain the change of the elastic modulus along with the pyrolysis degree; establishing a mesoscopic unit cell model under different pyrolysis degrees on the basis of the volume fraction, mesoscopic size distribution and elastic modulus of each component changing along with the pyrolysis degrees; aiming at the established unit cell model, loading a displacement boundary condition and a periodic boundary condition, and solving an equivalent elastic modulus of the material; and material elasticity moduli corresponding to different temperatures or pyrolysis degrees are obtained by combining material pyrolysis degree change data changing along with the temperature, and the problem that in the prior art, mechanical property parameters of different stages of the pyrolysis process of the resin-based heat-proof material cannot be effectively predicted is solved.

Description

Technical Field

[0001] The invention relates to a material mechanical property prediction method based on a microstructure unit cell model, and belongs to the technical field of aircraft thermal protection. Background Art

[0002] The development of thermal protection technology for aircraft has gone through several stages. Initially, it was heat sink-type thermal protection, which used metal heat sinks to absorb heat to block heat. However, with the severity of aerodynamic heating, it could no longer meet the requirements. Later, ablative thermal protection was developed, which used the evaporation, melting, sublimation and chemical reactions of materials to absorb heat. Ablative thermal protection has been widely used in re-entry satellites, spacecraft, etc. due to its efficient thermal protection effect. Ablative thermal protection is still widely used in returning satellites, spacecraft and other aircraft due to its simple form, good heat protection effect and high reliability. In order to improve the thermal insulation effect while taking into account both heat protection efficiency and mechanical properties, the resin-based thermal protection material currently developed is a composite material of a variety of hollow microspheres, fibers and matrices, which significantly reduces the thermal conductivity and density of the material without affecting the heat protection effect and mechanical strength.

[0003] At present, the research on the mechanical properties of homogeneous materials is relatively mature. The mechanical properties of the original materials can be effectively predicted by using mechanical properties testing methods or finite element calculations. The physical properties and microstructure of materials will change significantly at different stages of the pyrolysis process. The test of mechanical parameters such as the elastic modulus of materials during the pyrolysis process is relatively complicated and cannot achieve the purpose of quickly predicting the mechanical properties of materials. In addition, most tests still focus on the physical parameters of the original materials after complete carbonization, while there is less research on the changes in the mechanical properties of materials at different stages of the pyrolysis process. Summary of the invention

[0004] The technology of the present invention solves the problem: Overcoming the shortcomings of the prior art, providing a material mechanical property prediction method based on a microstructure unit cell model, solving the problem that the prior art cannot effectively predict the mechanical property parameters of resin-based heat-resistant materials at different stages of the pyrolysis process.

[0005] The technical solution of the present invention is as follows:

[0006] A method for predicting mechanical properties of materials based on a microstructure unit cell model, comprising:

[0007] Thermogravimetric tests were conducted on resin-based heat-resistant materials to obtain the degree of pyrolysis and residual carbon rate that vary with temperature;

[0008] According to the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate obtained by the thermogravimetric test as it changes with temperature, the volume fraction of each component as it changes with the degree of pyrolysis is obtained;

[0009] For each component of the resin-based heat-resistant material, the parallel model is used to calculate the elastic modulus corresponding to different pyrolysis degrees;

[0010] According to the volume fraction of each component changing with the degree of pyrolysis, the elastic modulus corresponding to different degrees of pyrolysis, and the mesoscopic size distribution, a mesoscopic mechanical unit cell model corresponding to different degrees of pyrolysis is established based on the finite element method;

[0011] Divide the established unit cell model into volume meshes;

[0012] The displacement boundary conditions and periodic boundary conditions are applied to the finite element model after body meshing, and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different pyrolysis degrees is obtained by solving the problem.

[0013] According to the temperature-varying pyrolysis degree obtained by the thermogravimetric test and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to the different pyrolysis degrees, the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different temperatures is obtained.

[0014] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, the resin-based heat-resistant material was subjected to a thermogravimetric test, and the pyrolysis degree and residual carbon rate that varied with temperature were obtained as follows:

[0015]

[0016] Among them, α(T) is the degree of pyrolysis that changes with temperature, A is the residual carbon rate, m 0 is the initial mass, m ∞ is the mass after pyrolysis, and m(T) is the change of mass with temperature during pyrolysis.

[0017] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, based on the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate obtained by the thermogravimetric test, the volume fraction of each component changing with the pyrolysis degree is obtained, including the volume fraction of the resin matrix and pores changing with the pyrolysis degree;

[0018] Volume fraction of resin matrix changes with pyrolysis degree It is expressed as follows:

[0019]

[0020] Where: B is the volume ratio, α is the degree of pyrolysis, m 1 is the resin mass, ρ 1 is the density, V 1 is the volume, m 2 is the mass after carbonization, m 2 =Am 1 , A is the residual carbon rate, ρ 2 is the density, V 2is the volume;

[0021] Volume fraction of pores changing with pyrolysis degree It is expressed as follows:

[0022]

[0023] in, is the volume fraction of hollow resin microspheres, is the fiber volume fraction, is the volume fraction of glass microspheres.

[0024] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, a parallel model is used to calculate the elastic modulus corresponding to different pyrolysis degrees for each component of the resin-based heat-resistant material, including the elastic modulus of the hollow resin microsphere wall and the elastic modulus of the resin matrix:

[0025] Hollow resin microspheres will have pores in the carbonization process, and the physical parameters of the base will change. The residual carbon after carbonization of the resin matrix of the hollow resin microsphere wall is connected in parallel with the small pores formed, and its elastic modulus E ms It is expressed as:

[0026] E ms =E 0 (1-α)+BαE c +(1-B)αE g

[0027] Among them, E 0 is the thermal conductivity of the resin matrix, E c Thermal conductivity after complete carbonization; E g is the elastic modulus of air, B is the volume ratio, and α is the degree of thermal decomposition;

[0028] Elastic modulus E of the resin matrix m The change with the degree of pyrolysis is expressed as:

[0029] E m =E 0 (1-α)+E c α.

[0030] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, the micromechanical unit cell model corresponding to different pyrolysis degrees is established based on the finite element method, including: establishing a unit cell model according to the size distribution law of hollow resin microspheres, the size distribution law of hollow glass microspheres, the size distribution law of fibers, and the volume fraction of each component that changes with the pyrolysis degree and the elastic modulus corresponding to different pyrolysis degrees.

[0031] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, the established unit cell model is divided into a body grid, and the grid size of the microstructure component is equal to 1 / 50 to 1 / 30 times the diameter of the microsphere; the control body is a cube, and the side length of the cube is more than twenty times the average diameter of the microsphere.

[0032] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, displacement boundary conditions and periodic boundary conditions are applied to the finite element model after body meshing to obtain the equivalent elastic modulus corresponding to different thermal decomposition degrees, including:

[0033] Apply periodic boundary conditions to the sides:

[0034]

[0035] Loading displacement boundary conditions on upper and lower surfaces:

[0036]

[0037] Among them, u 1 、u 2 、u 4 、u 5 They represent the displacement of the corresponding vertices of the control body along the x direction, v 1 、v 4 、v 2 、v 5 They represent the displacement of the corresponding vertices of the control body along the y direction, w 1 、w 2 、w 4 、w 5 They represent the displacement of the corresponding vertices of the control body along the z direction, u x1 、v x1 、w x1 They represent the displacement of each point on the plane with x=0 along the x, y, and z directions, respectively. x2 、v x2 、w x2 They represent the displacement of each point on the plane x=L along the x, y, and z directions, respectively. y1 、v y1 、w y1 They represent the displacement of each point on the plane of y=0 along the x, y, and z directions, respectively. y2 、v y2 、w y2 They represent the displacement of each point on the plane y=L along the x, y, and z directions, respectively. z1 、v z1 、w z1 They represent the displacement of each point on the plane z=0 along the x, y, and z directions, respectively. z2 、v z2 、wz2 They represent the displacement of each point on the plane z=L along the x, y, and z directions respectively;

[0038] The equivalent elastic modulus E corresponding to different pyrolysis degrees is expressed as follows:

[0039]

[0040] Among them, F is the cross-sectional normal force, S is the cross-sectional area of ​​the control body, L is the side length of the control body, and Δl is the axial deformation.

[0041] In the above-mentioned material mechanical property prediction method based on the microstructure unit cell model, the equivalent elastic modulus E(T) of the corresponding resin-based heat-resistant material at different temperatures is obtained according to the temperature-varying thermal decomposition degree α(T) obtained from the thermogravimetric test and the equivalent elastic modulus E(α) of the resin-based heat-resistant material corresponding to the different thermal decomposition degrees.

[0042] A material mechanical property prediction system based on a microstructure unit cell model, comprising:

[0043] The module for obtaining the degree of pyrolysis and residual carbon rate is used to conduct thermogravimetric tests on resin-based heat-resistant materials to obtain the degree of pyrolysis and residual carbon rate that vary with temperature.

[0044] A volume fraction acquisition module, which obtains the volume fraction of each component as the degree of pyrolysis changes according to the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate as the temperature changes obtained by the thermogravimetric test;

[0045] The elastic modulus acquisition module uses a parallel model to calculate the elastic modulus corresponding to different pyrolysis degrees for each component of the resin-based heat-resistant material;

[0046] A unit cell model acquisition module, which establishes a mesoscopic mechanical unit cell model corresponding to different pyrolysis degrees based on the finite element method according to the volume fraction of each component that changes with the pyrolysis degree, the elastic modulus corresponding to different pyrolysis degrees, and the mesoscopic size distribution;

[0047] The meshing module is used to divide the volume mesh of the established unit cell model;

[0048] The first equivalent elastic modulus acquisition module applies displacement boundary conditions and periodic boundary conditions to the finite element model after body meshing, and solves to obtain the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different pyrolysis degrees;

[0049] The second equivalent elastic modulus acquisition module obtains the equivalent elastic modulus of the resin-based heat-resistant material at different temperatures according to the temperature-varying thermal decomposition degree obtained by the thermogravimetric test and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to the different thermal decomposition degrees.

[0050] A computer program product comprises a computer program, which implements the steps of the above method when executed by a processor.

[0051] Compared with the prior art, the present invention has at least the following beneficial effects:

[0052] (1) The embodiment of the present invention provides a material mechanical property prediction method based on a microstructure unit cell model, wherein the residual carbon rate of the material and the pyrolysis degree data varying with temperature are obtained from the results of thermogravimetric tests; the volume fractions of the components of the material corresponding to different pyrolysis degrees are converted using the pyrolysis degree; the elastic modulus of the phenolic hollow microspheres and the resin matrix varying with the pyrolysis degree is calculated using a parallel model; based on the volume fractions of the components varying with the pyrolysis degree, the mesoscopic size distribution and the elastic modulus, a mesoscopic unit cell model is established at different pyrolysis degrees; for the established unit cell model, displacement boundary conditions and periodic boundary conditions are loaded to obtain the equivalent elastic modulus of the material; combined with the test data of the pyrolysis degree of the material varying with temperature, the elastic modulus of the material corresponding to different temperatures or pyrolysis degrees is obtained, thereby solving the problem that the mechanical property parameters of the resin-based heat-resistant material at different stages of the pyrolysis process cannot be effectively predicted in the prior art.

[0053] (2) In the current mechanical property calculation model of resin-based heat-resistant materials, the mechanical properties at different stages of pyrolysis are obtained by heating the material to a certain temperature, cooling it, and then testing the mechanical properties. However, it is impossible to obtain the mechanical property parameters at different stages of pyrolysis. Based on this, the present invention combines thermogravimetric testing, micro-parameter analysis and finite element modeling to predict the elastic modulus of the resin-based heat-resistant materials at different stages of the pyrolysis process, thereby solving the problem that the prior art cannot effectively predict the mechanical parameters of the resin-based heat-resistant materials at different stages of the pyrolysis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A flowchart of the steps of a method for predicting mechanical properties of materials based on a microstructure unit cell model in an embodiment of the present invention;

[0055] Figure 2 is a finite element model diagram in an embodiment of the present invention;

[0056] Figure 3 A schematic diagram of a mechanical unit cell boundary condition in an embodiment of the present invention;

[0057] Figure 4 It is a deformation cloud diagram at a temperature of 573K in an embodiment of the present invention;

[0058] Figure 5 is a stress cloud diagram at a temperature of 573K in an embodiment of the present invention;

[0059] Figure 6Graph showing the change in elastic modulus of the material with temperature in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0061] like Figure 1 As shown, the material mechanical property prediction method based on the microstructure unit cell model in the embodiment of the present invention includes the following steps:

[0062] Step 1: Perform a thermogravimetric test on the resin-based heat-resistant material to obtain the degree of pyrolysis and the residual carbon rate that vary with temperature. For example, phenolic resin is used as an example in this embodiment.

[0063] In the embodiment of the present invention, a thermogravimetric test is performed on the resin-based heat-resistant material to obtain the pyrolysis degree and residual carbon rate that vary with temperature, including the initial mass m 0 , mass after pyrolysis m ∞ , the change of mass with temperature during pyrolysis is m(T), so the change of pyrolysis degree with temperature is:

[0064]

[0065] Residual carbon rate:

[0066]

[0067] Among them, α(T) is the degree of pyrolysis that changes with temperature, and A is the residual carbon rate.

[0068] Step 2: Based on the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate of the resin component that changes with temperature obtained by thermogravimetric test, the volume fraction of each component that changes with the degree of pyrolysis is obtained, including the volume fraction of the resin matrix and pores that changes with the degree of pyrolysis. For example, phenolic resin is taken as an example in this embodiment.

[0069] In the embodiment of the present invention, the mass of the resin is m 1 , the density is ρ 1 , the volume is V 1 , the mass after carbonization is m 2 , the density is ρ 2 , the volume is V 2 , and m is obtained from the residual carbon rate 2 =A·m 1 , the volume ratio is:

[0070]

[0071] Volume fraction of resin matrix changes with pyrolysis degree It is expressed as:

[0072]

[0073] Volume fraction of pores changing with pyrolysis degree It is expressed as:

[0074] in, is the volume fraction of the resin matrix, is the volume fraction of hollow resin microspheres, is the fiber volume fraction, is the volume fraction of glass microspheres.

[0075] Step 3: For each component of the resin-based heat-resistant material, a parallel model is used to calculate the elastic modulus corresponding to different pyrolysis degrees, including the elastic modulus of the hollow resin microsphere wall and the elastic modulus of the resin matrix. For example, phenolic resin is used as an example in this embodiment.

[0076] In the embodiment of the present invention, after carbonization, the volume of the hollow glass microspheres and glass fibers remains unchanged, and the volume fraction of the hollow phenolic microspheres remains unchanged, but the microsphere wall will have small pores during the carbonization process, so the matrix physical parameters will change. The microsphere wall is a phenolic resin matrix, and the residual carbon after the carbonization of the resin matrix of the microsphere wall is in parallel with the formed small pores, and its elastic modulus E ms for:

[0077] E ms =E 0 (1-α)+BαE c +(1-B)αE g

[0078] Among them, E 0 is the thermal conductivity of the resin matrix, E c Thermal conductivity after complete carbonization, E g is the elastic modulus of air, B is the volume ratio, and α is the degree of thermal decomposition;

[0079] For the resin matrix, its elastic modulus E m The change with the degree of pyrolysis α is expressed as:

[0080] E m =E 0 (1-α)+E c α

[0081] Step 4: According to the volume fraction of each component that changes with the degree of pyrolysis, the elastic modulus corresponding to different degrees of pyrolysis, and the mesoscopic size distribution, a mesoscopic mechanical unit cell model corresponding to different degrees of pyrolysis is established based on the finite element method. For example, phenolic resin is taken as an example in this embodiment.

[0082] In the embodiment of the present invention, a unit cell model is established according to the size distribution law of hollow phenolic microspheres, the size distribution law of hollow glass microspheres, the size distribution law of fibers, the volume fraction of each component varying with the degree of pyrolysis and the elastic modulus corresponding to different degrees of pyrolysis, as given by the material process. Figure 2 shown.

[0083] Step 5: Divide the established unit cell model into volume meshes, for example, phenolic resin is taken as an example in this embodiment.

[0084] In the embodiment of the present invention, the control body is used to simulate the resin-based heat-resistant material. The control body is a cube, the side length of the cube is more than twenty times the pore diameter, and the grid size of the microstructure component is equal to 1 / 50 to 1 / 30 times the diameter of the microsphere.

[0085] Step 6: Apply displacement boundary conditions and periodic boundary conditions to the finite element model after volume meshing in step 5, and perform post-processing to obtain the equivalent elastic modulus corresponding to different thermal decomposition degrees.

[0086] like Figure 3 As shown, in the embodiment of the present invention, since the air in the pores does not transmit mechanical loads, its stiffness effect is ignored. Loading periodic boundary conditions on the side:

[0087]

[0088] Loading displacement boundary conditions on upper and lower surfaces:

[0089]

[0090] Among them, u 1 、u 2 、u 4 、u 5 Respectively indicate attachment Figure 2 The displacement of the corresponding vertex of the control body along the x direction, v 1 、v 4 、v 2 、v 5 Respectively indicate attachment Figure 2 The displacement w of the corresponding vertex of the control volume along the y direction 1 、w 2 、w 4 、w 5 Respectively indicate attachment Figure 2 The displacement of the corresponding vertex of the control body along the z direction, u x1 、v x1 、w x1 They represent the displacement of each point on the plane with x=0 along the x, y, and z directions, respectively. x2 、v x2 、w x2They represent the displacement of each point on the plane x=L along the x, y, and z directions, respectively. y1 、v y1 、w y1 They represent the displacement of each point on the plane of y=0 along the x, y, and z directions, respectively. y2 、v y2 、w y2 They represent the displacement of each point on the plane y=L along the x, y, and z directions, respectively. z1 、v z1 、w z1 They represent the displacement of each point on the plane z=0 along the x, y, and z directions, respectively. z2 、v z2 、w z2 They represent the displacement of each point on the plane z=L along the x, y, and z directions respectively.

[0091] like Figure 4 , Figure 5 Shown are the deformation cloud diagram and stress cloud diagram at a certain temperature of 573K in an embodiment of the present invention.

[0092] The equivalent elastic modulus E corresponding to different pyrolysis degrees is expressed as follows:

[0093]

[0094] In the formula, F is the cross-sectional normal force, S is the cross-sectional area, L is the side length, and Δl is the axial deformation. This formula is used to calculate the equivalent elastic modulus of the material at different pyrolysis degrees. Combined with the relationship between the pyrolysis degree and temperature in step one, the equivalent elastic modulus at different temperatures is obtained.

[0095] Step 7: According to the temperature-dependent pyrolysis degree α(T) obtained by thermogravimetric test and the equivalent elastic modulus E(α) of the resin-based heat-resistant material corresponding to different pyrolysis degrees, the equivalent elastic modulus E(T) of the resin-based heat-resistant material corresponding to different temperatures is obtained, such as Figure 6 shown.

[0096] The present invention also provides a material mechanical property prediction system based on a microstructure unit cell model, comprising:

[0097] The module for obtaining the degree of pyrolysis and residual carbon rate is used to conduct thermogravimetric tests on resin-based heat-resistant materials to obtain the degree of pyrolysis and residual carbon rate that vary with temperature.

[0098] A volume fraction acquisition module, which obtains the volume fraction of each component as the degree of pyrolysis changes according to the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate as the temperature changes obtained by the thermogravimetric test;

[0099] The elastic modulus acquisition module uses a parallel model to calculate the elastic modulus corresponding to different pyrolysis degrees for each component of the resin-based heat-resistant material;

[0100] A unit cell model acquisition module is used to establish a mesoscopic mechanical unit cell model corresponding to different pyrolysis degrees based on the finite element method according to the volume fraction of each component that changes with the pyrolysis degree, the elastic modulus corresponding to different pyrolysis degrees, and the mesoscopic size distribution;

[0101] The meshing module is used to divide the volume mesh of the established unit cell model;

[0102] The first equivalent elastic modulus acquisition module applies displacement boundary conditions and periodic boundary conditions to the finite element model after body meshing, and solves to obtain the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different pyrolysis degrees;

[0103] The second equivalent elastic modulus acquisition module obtains the equivalent elastic modulus of the resin-based heat-resistant material at different temperatures according to the temperature-varying thermal decomposition degree obtained by the thermogravimetric test and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to the different thermal decomposition degrees.

[0104] The present invention also provides a computer program product, comprising a computer program, which implements the steps of the above method when executed by a processor.

[0105] According to the application demand and current status of resin-based heat-proof materials, the present invention aims at the deficiencies in the calculation of mechanical properties of current resin-based heat-proof materials at different stages of pyrolysis, and combines the microscopic microstructural characteristics of heat-proof materials. The present invention proposes a prediction method for the mechanical properties of resin-based materials based on a microstructural unit cell model. The object of analysis of the present invention is a resin-based heat-proof material, the inner surface of which is fixedly mounted on the aircraft skin, the outer surface is in contact with the atmosphere, the inner surface and the outer surface are resin materials, and the resin material contains pores, fibers, hollow phenolic microspheres and hollow glass microspheres. Firstly, thermogravimetric tests were carried out on resin-based heat-resistant materials to obtain the relationship between the degree of pyrolysis and temperature and the residual carbon rate of the resin. Then, the volume percentage of each component in the pyrolysis process was calculated based on the residual carbon rate of pyrolysis and the volume percentage of each component of the material. For the resin components, the elastic modulus of different degrees of pyrolysis was calculated using a parallel model. Finally, based on the volume fraction of components corresponding to different degrees of pyrolysis, the elastic modulus and the mesoscopic size distribution law, a finite element unit cell model was established, the body mesh was divided, the displacement boundary conditions and periodic boundary conditions were loaded, and the equivalent elastic modulus was obtained by solving.

[0106] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0107] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for predicting mechanical properties of materials based on a microstructure unit cell model, characterized in that: include: Thermogravimetric tests were conducted on resin-based heat-resistant materials to obtain the degree of pyrolysis and residual carbon rate that vary with temperature; According to the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate obtained by the thermogravimetric test as it changes with temperature, the volume fraction of each component as it changes with the degree of pyrolysis is obtained; For each component of the resin-based heat-resistant material, the parallel model is used to calculate the elastic modulus corresponding to different degrees of pyrolysis; According to the volume fraction of each component changing with the degree of pyrolysis, the elastic modulus corresponding to different degrees of pyrolysis, and the mesoscopic size distribution, a mesoscopic mechanical unit cell model corresponding to different degrees of pyrolysis is established based on the finite element method; Divide the established unit cell model into volume meshes; The displacement boundary conditions and periodic boundary conditions are applied to the finite element model after volume meshing, and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different pyrolysis degrees is obtained by solving the problem. According to the temperature-varying pyrolysis degree obtained by the thermogravimetric test and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to the different pyrolysis degrees, the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different temperatures is obtained.

2. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: Thermogravimetric tests were conducted on resin-based heat-resistant materials, and the pyrolysis degree and residual carbon rate that varied with temperature were obtained as follows: Among them, α(T) is the degree of pyrolysis that changes with temperature, A is the residual carbon rate, m0 is the initial mass, and m ∞ is the mass after pyrolysis, and m(T) is the change of mass with temperature during pyrolysis.

3. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: Based on the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate obtained by thermogravimetric test, the volume fraction of each component changing with the degree of pyrolysis is obtained, including the volume fraction of the resin matrix and pores changing with the degree of pyrolysis; Volume fraction of resin matrix changes with pyrolysis degree It is expressed as follows: Where: B is the volume ratio, α is the degree of pyrolysis, m1 is the resin mass, ρ1 is the density, V1 is the volume, m2 is the mass after carbonization, m2=A·m1, A is the residual carbon rate, ρ2 is the density, V2 is the volume; Volume fraction of pores changing with pyrolysis degree It is expressed as follows: in, is the volume fraction of hollow resin microspheres, is the fiber volume fraction, is the volume fraction of glass microspheres.

4. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: For each component of the resin-based heat-resistant material, a parallel model is used to calculate the elastic modulus corresponding to different pyrolysis degrees, including the elastic modulus of the hollow resin microsphere wall and the elastic modulus of the resin matrix: Hollow resin microspheres will have pores in the carbonization process, and the physical parameters of the base will change. The residual carbon after carbonization of the resin matrix of the hollow resin microsphere wall is connected in parallel with the small pores formed, and its elastic modulus E ms It is expressed as: E ms =E0(1-α)+BαE c +(1-B)αE g Where E0 is the thermal conductivity of the resin matrix, E c Thermal conductivity after complete carbonization; E g is the elastic modulus of air, B is the volume ratio, and α is the degree of thermal decomposition; Elastic modulus E of the resin matrix m The change with the degree of pyrolysis is expressed as: E m =E0(1-α)+E c a.

5. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: The micromechanical unit cell model corresponding to different pyrolysis degrees is established based on the finite element method, including: establishing a unit cell model according to the size distribution law of hollow resin microspheres, the size distribution law of hollow glass microspheres, the size distribution law of fibers, and the volume fraction of each component that changes with the pyrolysis degree and the elastic modulus corresponding to different pyrolysis degrees.

6. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: The established unit cell model is divided into body grids, and the grid size of the microstructure component is equal to 1 / 50 to 1 / 30 times the diameter of the microsphere; the control body is a cube, and the side length of the cube is more than twenty times the average diameter of the microsphere.

7. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: The finite element model after volume meshing is subjected to displacement boundary conditions and periodic boundary conditions, and the equivalent elastic modulus corresponding to different thermal decomposition degrees is obtained by solving the problem, including: Apply periodic boundary conditions to the sides: Loading displacement boundary conditions on upper and lower surfaces: Among them, u1, u2, u4, and u5 represent the displacement of the corresponding vertex of the control body along the x direction, v1, v4, v2, and v5 represent the displacement of the corresponding vertex of the control body along the y direction, w1, w2, w4, and w5 represent the displacement of the corresponding vertex of the control body along the z direction, and u x1 、v x1 、w x1 They represent the displacement of each point on the plane with x=0 along the x, y, and z directions, respectively. x2 、v x2 、w x2 They represent the displacement of each point on the plane x=L along the x, y, and z directions, respectively. y1 、v y1 、w y1 They represent the displacement of each point on the plane of y=0 along the x, y, and z directions, respectively. y2 、v y2 、w y2 They represent the displacement of each point on the plane y=L along the x, y, and z directions, respectively. z1 、v z1 、w z1 They represent the displacement of each point on the plane z=0 along the x, y, and z directions, respectively. z2 、v z2 、w z2 They represent the displacement of each point on the plane z=L along the x, y, and z directions respectively; The equivalent elastic modulus E corresponding to different pyrolysis degrees is expressed as follows: Among them, F is the cross-sectional normal force, S is the cross-sectional area of ​​the control body, L is the side length of the control body, and Δl is the axial deformation.

8. The material mechanical property prediction method based on the microstructure unit cell model according to claim 1 is characterized in that: According to the temperature-varying thermal decomposition degree α(T) obtained by the thermogravimetric test and the equivalent elastic modulus E(α) of the resin-based heat-resistant material corresponding to the different thermal decomposition degrees, the equivalent elastic modulus E(T) of the resin-based heat-resistant material corresponding to different temperatures is obtained.

9. A material mechanical properties prediction system based on a microstructure unit cell model, characterized in that: include: The module for obtaining the degree of pyrolysis and residual carbon rate is used to conduct thermogravimetric tests on resin-based heat-resistant materials to obtain the degree of pyrolysis and residual carbon rate that vary with temperature. A volume fraction acquisition module, which obtains the volume fraction of each component as the degree of pyrolysis changes according to the volume fraction of each component of the resin-based heat-resistant material and the residual carbon rate as the temperature changes obtained by the thermogravimetric test; The elastic modulus acquisition module uses a parallel model to calculate the elastic modulus corresponding to different pyrolysis degrees for each component of the resin-based heat-resistant material; A unit cell model acquisition module, which establishes a mesoscopic mechanical unit cell model corresponding to different pyrolysis degrees based on the finite element method according to the volume fraction of each component that changes with the pyrolysis degree, the elastic modulus corresponding to different pyrolysis degrees, and the mesoscopic size distribution; The meshing module is used to divide the volume mesh of the established unit cell model; The first equivalent elastic modulus acquisition module applies displacement boundary conditions and periodic boundary conditions to the finite element model after body meshing, and solves to obtain the equivalent elastic modulus of the resin-based heat-resistant material corresponding to different pyrolysis degrees; The second equivalent elastic modulus acquisition module obtains the equivalent elastic modulus of the resin-based heat-resistant material at different temperatures according to the temperature-varying thermal decomposition degree obtained by the thermogravimetric test and the equivalent elastic modulus of the resin-based heat-resistant material corresponding to the different thermal decomposition degrees.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to claim 1 are implemented.

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