A finite element simulation analysis method and system for radial thermal conductivity of fibers

Abstract

The application discloses a kind of finite element simulation analysis method and system of fiber radial thermal conductivity, belong to material science and engineering technical field.The application will be obtained by testing the thermal conductivity measurement value of the matrix material of composite material and the thermal conductivity measurement value of composite material perpendicular to fiber direction as benchmark, using finite element analysis software to carry out composite material perpendicular to fiber direction heat transfer analysis, based on the corresponding relationship of fiber radial thermal conductivity and composite material thermal conductivity by inverse operation realizes the evaluation of fiber radial thermal conductivity.Adopting the method of the application can be convenient and effective to quantitatively calculate fiber radial thermal conductivity, avoid the problem that fiber radial size is very small and actual test is very difficult.The application can provide reliable fiber radial thermal conductivity parameters for composite material product design, and has wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material science and engineering, in particular to a finite element simulation analysis method and system for radial thermal conductivity of fibers. BACKGROUND

[0002] With the continuous integration and integration of electronic components and the development of high-power aviation equipment, in order to effectively dissipate heat and ensure the normal operation of the equipment, the thermal conductivity of the material is more and more concerned. Fibers have become an important reinforcing body of structural / thermal conductive composite materials due to their light weight, excellent mechanical properties and high axial thermal conductivity. The in-plane thermal conductivity of the composite material laminated structure benefits from the high thermal conductivity of the fibers, which can reach the level of aluminum alloy. However, the thermal conductivity in the thickness direction of the composite material is significantly lower than that in the in-plane direction due to the relatively poor radial thermal conductivity of the fibers, the poor thermal conductivity of the matrix resin and the lack of continuous thermal conduction path. Therefore, mastering the thermal conductivity perpendicular to the fiber axis is an important prerequisite for predicting the designed thermal conductivity of the composite material layer plate thickness and then overcoming the key problem of poor thermal conductivity in the thickness direction of the composite material.

[0003] However, due to the small size of the fiber in the radial direction, with a diameter of only about 10 μm, it is difficult to test the radial thermal conductivity by using the common test methods for axial thermal conductivity of fibers such as flash method, 3ω method and Raman spectroscopy. At present, the improved 3ω method can realize the test of the radial thermal conductivity of the fiber, but the test process is complex, and the accuracy and repeatability are difficult to guarantee. The characterization of the thermal conductivity perpendicular to the fiber still faces great challenges. SUMMARY

[0004] The purpose of the present application is to provide a finite element simulation analysis method and system for radial thermal conductivity of fibers to simplify the test process of the radial thermal conductivity of fibers and improve the accuracy and repeatability of the test of the radial thermal conductivity of fibers.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] The present application provides a finite element simulation analysis method for radial thermal conductivity of fibers, which comprises the following steps:

[0007] Obtaining the thermal conductivity measurement value of the matrix material in the composite material and the thermal conductivity measurement value of the composite material perpendicular to the fiber direction; the composite material comprises a matrix material and a fiber bundle;

[0008] Establishing a geometric model of the composite material;

[0009] performing finite element analysis on the geometric model based on the thermal conductivity measured value of the matrix material and the thermal conductivity measured value of the composite material in the direction perpendicular to the fibers to determine a simulated value of the radial thermal conductivity of the fibers when a simulated value of the thermal conductivity of the composite material in the direction perpendicular to the fibers is consistent with the thermal conductivity measured value of the composite material in the direction perpendicular to the fibers.

[0010] Optionally, the preparation process of the composite material is as follows:

[0011] removing the sizing agent on the surface of the fiber bundle;

[0012] placing the fiber bundle in a mold groove;

[0013] casting the matrix material into the mold containing the fiber bundle;

[0014] placing the mold containing the fiber bundle and the matrix material into an oven for curing and forming to form a mold containing the composite material;

[0015] taking out the mold after curing and forming and demolding to obtain the composite material, wherein the fiber volume fraction of the composite material is 25%-55%.

[0016] Optionally, the obtaining of the thermal conductivity measured value of the matrix material and the thermal conductivity measured value of the composite material in the direction perpendicular to the fibers specifically comprises:

[0017] obtaining the thermal diffusivity, the bulk density and the specific heat capacity of the matrix material measured;

[0018] obtaining the thermal diffusivity, the bulk density and the specific heat capacity of the composite material measured;

[0019] calculating the thermal conductivity measured value of the matrix material by using a thermal conductivity calculation formula according to the thermal diffusivity, the bulk density and the specific heat capacity of the matrix material;

[0020] calculating the thermal conductivity measured value of the composite material in the direction perpendicular to the fibers by using a thermal conductivity calculation formula according to the thermal diffusivity, the bulk density and the specific heat capacity of the composite material.

[0021] Optionally, the thermal conductivity calculation formula is: λ = ρ · C p · α.

[0022] wherein λ is the thermal conductivity of the sample, ρ is the bulk density of the sample, C p is the specific heat capacity of the sample, and α is the thermal diffusivity of the sample.

[0023] Optionally, the specific steps of measuring the thermal diffusivity, the bulk density and the specific heat capacity of the matrix material are as follows:

[0024] obtaining a matrix material sample;

[0025] The thermal diffusivity coefficient of the matrix material sample is measured by a flash method, as the thermal diffusivity coefficient of the matrix material;

[0026] The bulk density of the matrix material sample is measured by a drainage method, as the bulk density of the matrix material;

[0027] The specific heat capacity of the matrix material sample is measured by a DSC sapphire method, as the specific heat capacity of the matrix material.

[0028] Optionally, the process of establishing the geometric model of the composite material is as follows:

[0029] The cross section of the composite material in the vertical fiber direction is polished;

[0030] The cross section of the composite material in the vertical fiber direction is polished;

[0031] The cross section of the composite material in the vertical fiber direction is observed by an ultra-depth microscope, and a metallographic photo of the microstructure of the composite material is obtained;

[0032] The metallographic photo is processed by ImageJ software, and fiber contour information is obtained;

[0033] The fiber region boundary is automatically tracked according to the fiber contour information by Solidworks software, and the geometric model of the composite material is established.

[0034] Optionally, the geometric model is subjected to finite element analysis based on the measured value of the thermal conductivity of the matrix material and the measured value of the thermal conductivity of the composite material in the vertical fiber direction, so as to determine the radial thermal conductivity simulation value of the fiber when the simulated value of the thermal conductivity of the composite material in the vertical fiber direction is consistent with the measured value of the thermal conductivity of the composite material in the vertical fiber direction, and the specific process includes:

[0035] The geometric model is imported into AnsysWorkbench software;

[0036] The material parameters of the geometric model are set in the AnsysWorkbench software, specifically, the value of the thermal conductivity of the matrix material is set as the measured value of the thermal conductivity of the matrix material, and the radial thermal conductivity of the fiber is set as the radial thermal conductivity simulation value of the fiber; the material parameters include the thermal conductivity of the matrix material and the radial thermal conductivity of the fiber;

[0037] The geometric model is meshed in the AnsysWorkbench software;

[0038] Boundary conditions are set in the AnsysWorkbench software; the boundary conditions include the temperature of the high-temperature surface, the temperature of the low-temperature surface, and the temperature of the adiabatic surface high-temperature surface;

[0039] In the AnsysWorkbench software, a finite element heat transfer process model is performed on the geometric model based on the boundary conditions to obtain simulation results; the simulation results include at least the overall temperature of the geometric model, the heat flux of the cross section perpendicular to the heat transfer direction, and the heat flow rate of the cross section perpendicular to the heat transfer direction.

[0040] Based on the simulation results, the simulated value of the thermal conductivity of the composite material in the direction perpendicular to the fiber was calculated;

[0041] Determine whether the simulated value of the thermal conductivity of the composite material in the direction perpendicular to the fiber is consistent with the measured value of the thermal conductivity of the composite material in the direction perpendicular to the fiber, and obtain the determination result;

[0042] If the judgment result indicates no, adjust the simulated value of the fiber radial thermal conductivity and return to the step "Set the material parameters of the geometric model in AnsysWorkbench software";

[0043] If the judgment result indicates yes, then the simulated value of the fiber radial thermal conductivity is output.

[0044] Optionally, the formula for calculating the simulated thermal conductivity of the composite material perpendicular to the fiber direction is:

[0045]

[0046] Where Q is the heat flux of the cross section perpendicular to the heat transfer direction; A is the area of ​​the cross section perpendicular to the heat transfer direction; λ c T1 represents the simulated thermal conductivity of the composite material perpendicular to the fiber direction; T2 and T1 are the temperatures of the upper and lower surfaces of the geometric model, respectively; d is the dimension of the geometric model along the heat transfer direction.

[0047] A finite element simulation analysis system for the radial thermal conductivity of fibers, the system being applied to the method described above, the system comprising:

[0048] A thermal conductivity measurement module is used to acquire the thermal conductivity measurement values ​​of the matrix material and the thermal conductivity measurement values ​​of the composite material perpendicular to the fiber direction; the composite material includes a matrix material and fiber bundles;

[0049] A geometric model building module is used to build a geometric model of the composite material.

[0050] The finite element simulation module is used to perform finite element analysis on the geometric model based on the measured thermal conductivity of the matrix material and the measured thermal conductivity of the composite material in the direction perpendicular to the fiber, so as to determine the simulated radial thermal conductivity of the fiber when the simulated thermal conductivity of the composite material in the direction perpendicular to the fiber is consistent with the measured thermal conductivity of the composite material in the direction perpendicular to the fiber.

[0051] An electronic device includes a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the above method when executing the computer program.

[0052] According to the specific embodiments of the present application, the following technical effects are disclosed.

[0053] The present application provides a kind of fiber radial thermal conductivity finite element simulation analysis method and system, the method includes the following steps: obtaining the thermal conductivity measurement value of matrix material in composite material and the thermal conductivity measurement value of composite material perpendicular to fiber direction;Establish the geometric model of the composite material;The thermal conductivity measurement value of the matrix material and the thermal conductivity measurement value of the composite material perpendicular to fiber direction are based on the thermal conductivity measurement value of the matrix material and the thermal conductivity measurement value of the composite material perpendicular to fiber direction to the geometric model is analyzed by finite element, to determine the thermal conductivity simulation value of composite material perpendicular to fiber direction and the thermal conductivity measurement value of the composite material perpendicular to fiber direction when the fiber radial thermal conductivity simulation value is consistent.The thermal conductivity measurement value of matrix material and the thermal conductivity measurement value of composite material perpendicular to fiber direction of the composite material tested are used as reference, composite material perpendicular to fiber direction heat transfer analysis is carried out using finite element analysis software, and the fiber radial thermal conductivity is evaluated by inverse operation based on the corresponding relationship between fiber radial thermal conductivity and composite thermal conductivity.The fiber radial thermal conductivity can be conveniently and effectively calculated by the method, and the problem that the actual test is very difficult due to the small size of fiber radial direction is avoided.The present application can provide reliable fiber radial thermal conductivity parameters for composite product design, and has wide application prospect.

[0054] Moreover, the composite material prepared by the present application is different from the common composite material with a fiber volume fraction of about 55%, and the present application prepares a low-volume-fraction composite material with a fiber volume fraction of 25%-55% for analysis;The present application uses fiber boundary extraction and automatic tracking technology to realize accurate and convenient modeling of composite material, and obtains reliable fiber radial thermal conductivity results. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0056] Figure 1 A flow chart of a fiber radial thermal conductivity finite element simulation analysis method provided by the present application embodiment is provided.

[0057] Figure 2A process schematic diagram for simulating and analyzing the radial thermal conductivity of fibers is provided for the embodiment of the present application.

[0058] Figure 3 A heat transfer analysis flowchart for the TC-HC-800 composite material in the vertical fiber direction is provided for Embodiment 1.

[0059] Figure 4 A heat transfer analysis flowchart for the TC-HC-800 composite material in the vertical fiber direction is provided for Embodiment 2.

[0060] Figure 5 A heat transfer analysis flowchart for the TC-HC-800 composite material in the vertical fiber direction is provided for Embodiment 3.

[0061] Figure 6 A heat transfer analysis flowchart for the XN-90-60S composite material in the vertical fiber direction is provided for Embodiment 4.

[0062] Figure 7 A heat transfer analysis flowchart for the XN-90-60S composite material in the vertical fiber direction is provided for Embodiment 5. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0064] The purpose of the present application is to provide a finite element simulation analysis method and system for the radial thermal conductivity of fibers, so as to simplify the testing process of the radial thermal conductivity of fibers and improve the accuracy and repeatability of the testing of the radial thermal conductivity of fibers.

[0065] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0066] The present application provides a finite element simulation analysis method for the radial thermal conductivity of fibers, as shown in Figure 1 and Figure 2 The method comprises the following steps:

[0067] Step 101, obtaining the thermal conductivity measurement value of the matrix material in the composite material and the thermal conductivity measurement value of the composite material in the vertical fiber direction; the composite material comprises a matrix material and a fiber bundle.

[0068] The preparation method of the composite material mentioned in step 101 is as follows: the unidirectional fiber bundle is placed in a mold groove, the matrix material is poured into the mold containing the fiber, and the composite material is obtained after curing and demolding. The fiber bundle is composed of a plurality of fibers with a diameter of microns arranged in parallel.

[0069] In the embodiments of the present application, the raw materials used are all commercially available goods well known to those skilled in the art, unless otherwise specified.

[0070] In the embodiments of the present application, the unidirectional fiber bundle is used to prepare the continuous fiber reinforced composite material, the unidirectional fiber bundle is composed of a plurality of fibers with a diameter of microns arranged in parallel along the axial direction of the fiber bundle, and the axial length of the fiber bundle is preferably 5 cm matched with the mold; the fibers include various types of inorganic fibers (carbon fibers, glass fibers, ceramic fibers, etc.), and the fibers preferably include polyacrylonitrile-based carbon fibers and / or mesophase pitch-based carbon fibers, and more preferably one or more of XN-90-60S mesophase pitch-based carbon fibers and TC-HC-800 mesophase pitch-based carbon fibers; in the embodiments of the present application, the mesophase pitch-based carbon fibers used are specifically XN-90-60S and TC-HC-800 carbon fibers. The cross-sectional shape of the fibers includes circular, elliptical, cashew-shaped, fan-shaped, etc., and the fiber diameter is preferably 9-14 μm. In the embodiments of the present application, the amount of fiber used is calculated according to the fiber volume fraction of the composite material. The fiber volume fraction of the composite material is preferably ≤60%, and more preferably 25%-55%. If the fiber volume fraction is too high, the fibers in the composite material are in large contact, which is not conducive to the establishment of the geometric model and the finite element analysis. If the fiber volume fraction is too low, the fiber distribution uniformity in the composite material is poor, and the geometric model established according to the metallographic photograph is not representative enough.

[0071] In the embodiments of the present application, the sizing agent exists on the surface of the fiber, which is used to avoid the problems of abrasion and fluffing during fiber transportation, and will affect the analysis of the radial thermal conductivity of the fiber in the embodiments of the present application. Before the resin pouring, the method further includes removing the sizing agent on the surface of the fiber. The method for removing the sizing agent includes solution immersion method, high temperature treatment method, etc., and the method for removing the sizing agent is preferably the solvent immersion method; the solvent is an organic solvent in which the sizing agent can be dissolved, and is preferably one or more of acetone and dichloromethane; the solvent immersion treatment is carried out in a 50℃ water bath ultrasonic; the auxiliary ultrasonic treatment time for solvent immersion is 5h, and the treatment is ended based on the complete removal of the sizing agent on the surface of the fiber, and then the fiber is washed twice with the solvent and dried. The drying process is carried out in an oven; the temperature of the drying treatment is preferably 80℃, and the drying time is preferably 30min.

[0072] In the embodiment of the present application, the fibers in the fiber bundle are closely arranged, and a dispersion treatment is needed for the fiber bundle to prepare a composite material with a low fiber volume fraction. The fiber dispersion treatment method includes an ultrasonic treatment method, and the ultrasonic treatment is realized by an ultrasonic cleaner. The ultrasonic treatment can destroy the adhesion between the fibers, and together with the organic solvent used for removing the sizing agent, the fibers are separated from each other to form a relatively dispersed fiber bundle. The longer the ultrasonic treatment time, the better the dispersion effect. In the embodiment of the present application, the ultrasonic treatment time is 5 h, and the fibers in the fiber bundle are relatively dispersed after the treatment, which can meet the requirement of preparing a composite material with a low fiber volume fraction. A longer ultrasonic treatment time can achieve a better fiber dispersion effect. The ultrasonic treatment is performed in a water bath, and the water bath provides an environment temperature higher than room temperature, which is beneficial to the destruction of the fiber adhesion and the dissolution of the sizing agent in the organic solvent. In the embodiment of the present application, the water bath temperature is 50℃, and a higher water bath temperature is beneficial to the removal of the sizing agent and the dispersion of the fibers in the fiber bundle. However, the evaporation rate of the organic solvent is faster at a higher temperature, and therefore a suitable water bath temperature should be selected.

[0073] In the embodiment of the present application, the matrix material is an epoxy resin to which a curing agent is added in a certain proportion, and the epoxy resin is preferably an E51 epoxy resin. The curing agent is preferably BC126, and the curing agent is added to the epoxy resin under stirring. The curing temperature of the epoxy resin system to which the curing agent is added is 120℃. The epoxy resin has a certain viscosity at room temperature, and stirring when the curing agent is added can introduce air bubbles into the resin. To avoid the air bubbles affecting the molding quality of the composite material, the resin system to which the curing agent is added further includes a vacuum extraction treatment before the composite material is prepared. Under the action of the vacuum, the air bubbles in the resin move and are discharged from the resin. The mold is a self-built square groove-shaped mold with an internal size of 5 cm x 2 cm x 1 cm. The fiber bundle is arranged parallel to the bottom of the mold along the 5 cm direction of the long side.

[0074] In the embodiment of the present application, the composite material preparation method includes fiber arrangement and resin pouring, resin impregnation, and curing molding. The fiber arrangement and resin pouring step includes arranging 2 g of the fiber bundle in the mold and slowly pouring the resin along one side of the mold cavity to make the fibers fully impregnated. The purpose of the resin impregnation process is to make the resin heat up, the viscosity decrease, and the fibers fully impregnated, so as to avoid the problem that the resin with a relatively large viscosity at room temperature is difficult to effectively flow to fill the gaps between the fibers in the fiber bundle, thereby forming pores in the composite material part. In the composite material preparation process, the fiber volume fraction is controlled by the amount of the absorbing material and the dispersion of the fibers. The fibers in the fiber bundle treated by a long-time ultrasonic treatment are relatively dispersed, which can meet the requirement of preparing a composite material with a low fiber volume fraction. The more the absorbing material fiberglass cloth is laid and the greater the absorbing amount is in the preparation process, the higher the fiber volume fraction of the obtained composite material is.

[0075] In the embodiment of the present application, for the composite material with fiber volume fraction less than 30%, the resin impregnation process comprises: placing the mold containing the fibers and the resin in an oven at 80℃, and the treatment time is 0.5h. The curing forming process comprises: increasing the oven temperature to 120℃ for pressureless curing forming, and the curing time is 3h. After the curing is completed, the heating is stopped, and the product is taken out after the oven returns to room temperature, and the composite material product is obtained. The pressureless curing forming method avoids the resin flowing out under the action of pressure, so that the fiber volume fraction of the prepared composite material is very low, and the minimum can reach about 20%.

[0076] In the embodiment of the present application, for the composite material with target fiber volume fraction of 30%-50%, the resin impregnation process comprises: placing the mold containing the fibers and the resin in an oven at 80℃, and the treatment time is 1.5h. After the treatment is completed, the epoxy resin has been preliminarily cured, and the sample is taken out. The curing forming process comprises: laying auxiliary materials on the mold containing the composite system from bottom to top in turn, the auxiliary materials are polytetrafluoroethylene cloth, glass cloth, isolation film, pressure plate and vacuum bag, and the vacuum bag forming process is used to extract vacuum curing in an oven at 120℃ for 3h. After the curing is completed, the heating is stopped, and the product is taken out after the oven returns to room temperature, and the composite material product is obtained. The resin impregnation process does not lay auxiliary materials, which avoids the resin flowing out to the glass cloth in the impregnation process, and the glue absorption amount is smaller relative to the preparation process of directly laying auxiliary materials, so that the composite material with relatively low fiber volume fraction is prepared.

[0077] In the embodiment of the present application, for the composite material with target fiber volume fraction of 50% and above, the resin impregnation process comprises: laying auxiliary materials on the mold containing the fibers and the resin from bottom to top in turn, the auxiliary materials are polytetrafluoroethylene cloth, glass cloth, isolation film, pressure plate and vacuum bag, and placing the mold containing the composite system in an oven at 80℃, and the treatment time is 0.5h. The curing forming process comprises: using the vacuum bag forming process to extract vacuum curing in an oven at 120℃ for 3h. After the curing is completed, the heating is stopped, and the product is taken out after the oven returns to room temperature, and the composite material product is obtained.

[0078] The thermal conductivity measurement value of the matrix material of the composite material in the above step 102 and the thermal conductivity measurement value of the composite material in the vertical fiber direction are measured in the following manner:

[0079] In the embodiment of the present application, the thermal conductivity of the matrix material and the thermal conductivity of the composite material in the vertical fiber direction are tested, including thermal diffusivity test, bulk density test, and specific heat capacity test. The sample is a cured matrix material epoxy resin (i.e. matrix material sample) and a cured composite material (i.e. composite material sample). The thermal diffusivity test is tested by flash method according to the standard test of ASTM E1461; the sample size is 10mm×10mm×0.5mm, and the test condition is room temperature; the test direction of the composite material sample is the vertical fiber direction. The bulk density test is tested by the drainage method. The specific heat capacity test is tested by the DSC sapphire method according to the standard test of ASTM 1269; the sample size is 4mm×4mm×1mm, and the sample mass is about 30mg. The thermal conductivity is calculated according to the formula shown in formula (1):

[0080] λ=ρ·C p ·α1

[0081] In formula (1), λ is the thermal conductivity of the sample; ρ is the bulk density of the sample; C p is the specific heat capacity of the sample; and α is the thermal diffusivity of the sample.

[0082] Step 102, establishing a geometric model of the composite material.

[0083] In the embodiment of the present application, the metallographic photo of the composite material is taken by an ultra-depth microscope, and the sample of the composite material is the sample used in the thermal diffusivity test. Before taking the metallographic photo, the composite material sample is packaged with epoxy resin, the surface of the vertical fiber direction section is polished after being polished with sandpaper, and then the vertical fiber direction section surface is polished. The packaging epoxy resin for metallographic photo is preferably E51, the curing agent is preferably triethylene tetramine, and the curing condition is preferably room temperature curing. The metallographic photo is preferably taken at a magnification of 500X. If the magnification is too high, the number of fibers in the field of view is too small, and the model representation is poor. If the magnification is too low, the fiber profile is not clear, and the modeling error is large.

[0084] In the embodiment of the present application, the metallographic photo image processing adopts ImageJ software, the image processing area is a 150μm×300μm area of the metallographic photo, and the fiber profile drawing process includes grayscale processing, binaryzation processing and boundary finding processing. The image processing further includes image edge drawing processing, and the obtained processing picture contains fiber section boundary information and area boundary information.

[0085] In the application, the geometric model of the composite material is established by using Solidworks software, and the image processed picture is used as the input of the model establishment. The geometric model establishment process includes: sketch picture import, automatic tracking to create sketch, and stretching to establish thin plate model. The size of the geometric model is 150 μm x 300 μm x 2 μm, and the geometric model includes: fiber cross-section area and resin area. The size of the geometric model of the composite material is large enough and representative, which can ensure the accuracy of the finite element analysis result

[0086] In the application, the key of the geometric model establishment process is to effectively extract the fiber boundary information. The fiber boundary information is derived from the composite material metallographic photo taken by using the super depth microscope. The metallographic photo which is clear, non-polluted, non-scar and has a representative area of fiber distribution is conducive to accurately establishing the composite material model. The boundary information extraction process is realized by using ImageJ software. According to the characteristic that there is an obvious color difference between the fiber area and the resin area, the software can distinguish the fiber area and the resin area, so as to identify and retain the area boundary information. In the boundary information extraction process, the fibers in the composite material which contact with each other form a continuous fiber area. The software identifies it as one area according to the color, and the extracted fiber boundary is a continuous boundary formed by several contact fibers, so as to realize the automatic judgment of the contact condition of the internal fibers of the composite material.

[0087] In the application, in the geometric model establishment process, the Autotrace plug-in in the Solidworks software is used to automatically track and draw the fiber area contour sketch according to the extracted fiber boundary information. The automatic tracking process can be executed by point selection, frame selection and other operations. The Autotrace plug-in can automatically find the closed contour in the picture which meets the condition and draw the sketch, so as to draw the sketch containing all the fiber contours in the range in the Solidworks software according to the fiber boundary information extracted by the ImageJ software. In the automatic tracking process, there may be a closed resin area surrounded by fibers which contact with each other. Since the closed outside fiber contour is surrounded, the resin area boundary (i.e. the inside contour of the contact fiber area) cannot be drawn by using the frame selection automatic tracking. Further, the resin area inside position is selected by point selection to perform automatic tracking, which can effectively draw the contour.

[0088] In step 103, the finite element analysis is performed on the geometric model based on the thermal conductivity measurement value of the matrix material and the thermal conductivity measurement value of the composite material in the vertical fiber direction, so as to determine the fiber radial thermal conductivity simulation value when the thermal conductivity simulation value of the composite material in the vertical fiber direction is consistent with the thermal conductivity measurement value of the composite material in the vertical fiber direction.

[0089] In the embodiment of the present application, the finite element analysis heat transfer process adopts the Static Thermal module of Ansys Workbench software, and the geometric model is used as the input of the finite element analysis. The heat transfer analysis process includes: geometric model import, material parameter input, mesh division, boundary condition setting, and result setting. The material parameters include: resin thermal conductivity and fiber radial thermal conductivity, the resin thermal conductivity is determined according to the test results, and the fiber radial thermal conductivity is set as an input parameter to be optimized. The boundary conditions include: setting the temperature of the model close to the lower side of the composite material in the vertical fiber direction, that is, the high temperature surface, setting the temperature of the model close to the upper side of the composite material in the vertical fiber direction, that is, the low temperature surface, and setting other surfaces as adiabatic surfaces. The result setting includes: the overall temperature of the model, the overall heat flux density of the model, and the heat flow of the model perpendicular to the heat transfer direction section. The composite material thermal conductivity simulation value is used as an output parameter, and is calculated according to the formula shown in formula (2):

[0090]

[0091] In formula (2), Q is the heat flux perpendicular to the heat transfer direction section; A is the area perpendicular to the heat transfer direction section; λ c is the simulation value of the thermal conductivity of the composite material in the vertical fiber direction; T1 and T2 are the temperatures of the upper surface and the lower surface of the geometric model, respectively; and d is the size of the geometric model along the heat transfer direction, that is, 300 μm.

[0092] In the embodiment of the present application, the finite element simulation inverse operation process is realized by using the Optimization module of Ansys Workbench software, and the inverse operation method adopts the Adaptive Single-Objective (ASO) optimization method; the parameter to be optimized is the fiber radial thermal conductivity, and the optimization target is that the simulation value of the thermal conductivity of the composite material in the vertical fiber direction is consistent with the experimental test result. The simulation analysis result of the fiber radial thermal conductivity is determined as the optimization result of the Optimization module, and the method in the present application will be described below in combination with the following specific embodiments.

[0093] Embodiment 1

[0094] In embodiment 1, TC-HC-800 mesophase pitch-based carbon fiber (diameter 13.04 μm) and a resin system prepared by using E51 epoxy resin and BC126 curing agent are used to prepare unidirectional continuous fiber reinforced composite material. The steps are as follows:

[0095] The TC-HC-800 carbon fiber is cut into 5 cm long segments, and is treated by ultrasonic assisted degreasing in an acetone solvent at 50°C water bath for 5 h. After the treatment, the acetone is washed twice, and then is dried in an 80°C oven for 30 min.

[0096] 2g of TC-HC-800 carbon fibers with sizing removed were placed in the mold as evenly as possible in the direction of the 5cm long side parallel to the bottom of the mold groove, about 4g of E51 resin added with BC126 curing agent was slowly injected into the mold along one side of the mold cavity, the mold containing the composite system was immersed in an 80°C oven for 1.5h, then polytetrafluoroethylene cloth, glass cloth, release film, pressing plate, vacuum bag auxiliary material were placed in turn from bottom to top, vacuum bag process was used for molding, and the product was cured in a 120°C oven for 3h. After the curing was completed, the heating was stopped and the product was removed after the oven returned to room temperature, and the product was demolded, obtaining a composite part.

[0097] The obtained unidirectional composite laminate was cut to obtain test samples needed for testing, the thermal diffusivity test sample size was 10mmx10mmx0.5mm, and the perpendicular fiber direction size was 0.5mm; the specific heat capacity test sample size was 4mmx4mmx1mm. The thermal diffusivity of the composite material in the perpendicular fiber direction was tested by flash method, the specific heat capacity of the composite part was tested by DSC sapphire method, and the bulk density of the composite material was tested by drainage method, so as to calculate the thermal conductivity of the composite material in the perpendicular fiber direction as 0.689W·m -1 ·K -1 In addition, the thermal diffusivity, specific heat capacity and bulk density of the cured epoxy resin were tested by the same method, so as to calculate the thermal conductivity of the epoxy resin as 0.191W·m -1 ·K -1 .

[0098] An E51 epoxy resin and triethylenetetramine curing agent were used to prepare a resin system, the composite thermal diffusivity test sample was packaged for metallography, the cross section of the composite material in the perpendicular fiber direction was polished by sandpaper, the surface of the cross section of the composite material in the perpendicular fiber direction polished by sandpaper was polished, and then the metallographic photo was taken by using an ultra-depth microscope. Analysis of the metallographic photo shows that the fiber volume fraction of the prepared composite material is about 38%.

[0099] The metallographic photo taken was processed by using Image J software, a 150μm×300μm metallographic area was selected, and the size in the thermal diffusivity test direction was 300μm. The picture retaining the fiber cross section profile and the selected area boundary information was obtained by gray scale, binary, boundary finding and image outlining processing. The processed picture was imported into Solidworks software, the fiber cross section profile and the selected area boundary information in the picture were captured by automatic tracking to draw a sketch, a geometric model was established by stretching operation, the thickness was 2μm of the metallographic size, and the geometric model included fiber area and resin area information. The heat transfer analysis process of the TC-HC-800 composite material in the perpendicular fiber direction is shown in Figure 3 Figure 3 ​(a) is a metallographic photo of TC-HC-800 composite material with a fiber volume fraction of 38%, Figure 3 (b) is a fiber contour information picture obtained by processing with Image J software, Figure 3 (c) is a geometric model of TC-HC-800 composite material with a fiber volume fraction of 38% established by using Solidworks software.

[0100] Ansys Workbench software Static Thermal module was used to analyze the heat transfer characteristics of the composite material in the vertical fiber direction, the established geometric model was imported, the thermal conductivity of the resin area was set to the experimental test value 0.191 W·m -1 ·K -1 , and the thermal conductivity of the fiber area was set as the input parameter to be optimized, and the initial value was set to 10 W·m -1 ·K -1 . The end surface temperature of the model close to the upper surface of the thermal diffusivity test sample was set to 25℃, and the end surface temperature close to the lower surface of the sample was set to 26℃, and the other surfaces were set as adiabatic surfaces. The heat flow in the vertical heat transfer direction section was calculated, and the simulated value of the vertical fiber direction thermal conductivity of the composite material was calculated according to formula (2) as the output parameter. The Optimization module was used, and the optimization target was the consistency of the vertical fiber direction thermal conductivity of the composite material simulated by thermal analysis and the experimental test result 0.689 W·m -1 ·K -1 . The fiber radial thermal conductivity was obtained by inverse operation. According to the simulation analysis of the unidirectional TC-HC-800 carbon fiber reinforced composite material with a fiber volume fraction of 38%, the TC-HC-800 carbon fiber radial thermal conductivity was 9.2655 W·m -1 ·K -1 .

[0101] Example 2

[0102] The fiber radial thermal conductivity was simulated according to the method of Example 1, except that 4g of fiber was placed in the mold groove during the preparation of the composite material, and the resin with curing agent was slowly injected into the mold along one side of the mold cavity, and then polytetrafluoroethylene cloth, fiberglass cloth, isolation film, pressure plate, and vacuum bag auxiliary materials were placed on the mold containing the fiber and resin, and the mold containing the composite system was placed in an 80℃ oven for impregnation treatment for 0.5h. The vacuum bag molding process was used, and the vacuum curing was carried out in a 120℃ oven for 3h. The prepared composite material had a fiber volume fraction of about 55%, and the vertical fiber direction thermal conductivity of the composite material was 1.688 W·m -1 ·K -1 . The composite material vertical fiber direction heat transfer analysis process is shown in Figure 4 , and Figure 4Image (a) is a metallographic photograph of the TC-HC-800 composite material with a fiber volume fraction of 55%. Figure 4 Image (b) in the image is a fiber contour image obtained using ImageJ software. Figure 4 (c) shows the geometric model of the TC-HC-800 composite material with a fiber volume fraction of 55%, built using Solidworks software. The radial thermal conductivity of the TC-HC-800 carbon fiber obtained through inverse finite element analysis is 9.1861 W·m. -1 ·K -1 .

[0103] Example 3

[0104] The radial thermal conductivity of the fibers was simulated and analyzed according to the method in Example 1. The difference was that when preparing the composite material, 2g of fiber was placed in the mold cavity, and 6g of resin with added curing agent was slowly injected into the mold along one side of the mold cavity. The mold containing the fiber and resin was placed in an 80°C oven for immersion treatment for 0.5h. The oven temperature was increased to 120°C for curing for 3h. After curing, heating was stopped, and the product was removed from the mold after the oven returned to room temperature to obtain the composite material part. The fiber volume fraction of the prepared composite material was approximately 25%, and the thermal conductivity of the composite material perpendicular to the fiber direction was 1.688 W·m. -1 ·K -1 The heat transfer analysis process of the composite material perpendicular to the fiber direction is as follows: Figure 5 As shown, Figure 5 Image (a) is a metallographic photograph of the TC-HC-800 composite material with a fiber volume fraction of 25%. Figure 5 Image (b) in the image is a fiber contour image obtained using ImageJ software. Figure 5 (c) shows the geometric model of the TC-HC-800 composite material with a fiber volume fraction of 25%, built using Solidworks software. The radial thermal conductivity of the TC-HC-800 fiber obtained through inverse finite element analysis is 7.4383 W·m. -1 ·K -1 .

[0105] Example 4

[0106] The radial thermal conductivity of the fibers was simulated and analyzed according to the method in Example 1, except that XN-90-60S mesophase pitch-based carbon fibers (10.42 μm in diameter) were used. The resulting composite material had a fiber volume fraction of approximately 35%, and the thermal conductivity perpendicular to the fiber direction was 0.412 W·m. -1 ·K -1 The heat transfer analysis process of the composite material perpendicular to the fiber direction is as follows: Figure 6 As shown, Figure 6(a) is a metallographic photo of XN-90-60S composite material with a fiber volume fraction of 35%, Figure 6 (b) is a fiber profile information picture obtained by processing with ImageJ software, Figure 6 (c) is a geometric model of XN-90-60S composite material with a fiber volume fraction of 35% established by Solidworks software. The radial thermal conductivity of XN-90-60S carbon fiber obtained by finite element analysis inverse operation is 2.8692 W·m -1 ·K -1 .

[0107] Example 5

[0108] The fiber radial thermal conductivity was simulated and analyzed according to the method of Example 2, except that the carbon fiber used was XN-90-60S mesophase pitch-based carbon fiber (diameter 10.42 μm). The fiber volume fraction of the prepared composite material was about 50%, and the thermal conductivity of the composite material perpendicular to the fiber direction was 0.642 W·m -1 ·K -1 . The composite material perpendicular to the fiber direction heat transfer analysis process is shown in Figure 7 Figure 7 (a) is a metallographic photo of XN-90-60S composite material with a fiber volume fraction of 50%, Figure 7 (b) is a fiber profile information picture obtained by processing with ImageJ software, Figure 7 (c) is a geometric model of XN-90-60S composite material with a fiber volume fraction of 50% established by Solidworks software. The radial thermal conductivity of XN-90-60S carbon fiber obtained by finite element analysis inverse operation is 3.4239 W·m -1 ·K -1 .

[0109] Table 1 results of simulated analysis of fiber radial thermal conductivity

[0110]

[0111] The TC-HC-800 mesophase pitch-based carbon fiber used in Examples 1-4 above was provided by Shaanxi Tengce New Material Technology Co., Ltd.

[0112] The XN-90-60S mesophase pitch-based carbon fiber was purchased from Japan Graphite Co., Ltd.

[0113] The E51 epoxy resin was purchased from Nantong Xingchen Synthetic Material Co., Ltd.

[0114] The BC126 curing agent was purchased from Dasen (Tianjin) Material Technology Co., Ltd.

[0115] ​Triethylenetetramine curing agent was purchased from Macrolin Biochemical Technology Co., Ltd.

[0116] Auxiliary material sealing tape, polytetrafluoroethylene cloth, air-permeable felt, glass cloth, release film and vacuum bag were purchased from Airtech Company.

[0117] Organic solvents acetone and dichloromethane were purchased from Beijing Chemical Plant.

[0118] The embodiment of the present application also provides a finite element simulation analysis system for radial thermal conductivity of fibers, which is applied to the above method, and comprises:

[0119] A thermal conductivity measurement value acquisition module is configured to acquire a thermal conductivity measurement value of a matrix material in a composite material and a thermal conductivity measurement value of the composite material in a direction perpendicular to fibers; the composite material comprises the matrix material and a fiber bundle.

[0120] A geometric model establishment module is configured to establish a geometric model of the composite material.

[0121] A finite element simulation module is configured to perform finite element analysis on the geometric model based on the thermal conductivity measurement value of the matrix material and the thermal conductivity measurement value of the composite material in the direction perpendicular to fibers, so as to determine a fiber radial thermal conductivity simulation value when a thermal conductivity simulation value of the composite material in the direction perpendicular to fibers is consistent with the thermal conductivity measurement value of the composite material in the direction perpendicular to fibers.

[0122] The embodiment of the present application also provides an electronic device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the above method when executing the computer program.

[0123] The embodiment of the present application also provides a computer readable storage medium, which stores a computer program, and the computer program is executed to implement the above method.

[0124] The technical scheme of the embodiment of the present application has the beneficial effects as follows:

[0125] The present application adopts the researched fiber and epoxy resin to prepare unidirectional continuous fiber reinforced composite material, respectively tests the thermal conductivity of the matrix resin and the composite material as the simulated input, the test method is simple and the precision is higher. The present application models according to the metallographic photos of the composite material cross section perpendicular to the fiber direction, then uses the finite element analysis software to analyze the heat transfer of the composite material perpendicular to the fiber direction, and realizes the evaluation of the radial thermal conductivity of the heat conducting fiber based on the corresponding relationship between the radial thermal conductivity of the fiber and the thermal conductivity of the composite material through the inverse operation. The present application can quantitatively calculate the radial thermal conductivity of the fiber conveniently and effectively, and avoids the problem that the actual test is very difficult due to the small radial size of the fiber. The present application can provide reliable radial thermal conductivity parameters of the fiber for the composite material product design, and has a wide application prospect.

[0126] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the system disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0127] The principles and implementation manners of the present application are described by applying specific examples in the present application, and the above embodiment description is only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manner and application range can be changed. In conclusion, the content of the specification should not be understood as the limitation of the present application.

Claims

1. A finite element simulation analysis method of radial thermal conductivity of fibers, characterized by, The method comprises the following steps: Obtaining the thermal conductivity measurement value of the matrix material in the composite material and the thermal conductivity measurement value of the composite material perpendicular to the fiber direction; the composite material comprises a matrix material and a fiber bundle; Establishing a geometric model of the composite material; Based on the thermal conductivity measurement value of the matrix material and the thermal conductivity measurement value of the composite material perpendicular to the fiber direction, the finite element analysis is performed on the geometric model to determine the fiber radial thermal conductivity simulation value when the thermal conductivity simulation value of the composite material perpendicular to the fiber direction is consistent with the thermal conductivity measurement value of the composite material perpendicular to the fiber direction, and the fiber radial thermal conductivity simulation value is determined. Importing the geometric model into the Ansys Workbench software; Setting the material parameters of the geometric model in the Ansys Workbench software, specifically: setting the thermal conductivity value of the matrix material as the thermal conductivity measurement value of the matrix material, and setting the fiber radial thermal conductivity as the fiber radial thermal conductivity simulation value; the material parameters include the thermal conductivity of the matrix material and the fiber radial thermal conductivity; Grid division is performed on the geometric model in the Ansys Workbench software; Setting boundary conditions in the Ansys Workbench software; the boundary conditions include the temperature of the high-temperature surface, the temperature of the low-temperature surface, and the temperature of the adiabatic surface; Based on the boundary conditions, the finite element heat transfer process model of the geometric model is obtained in the Ansys Workbench software, and the simulation result is obtained; the simulation result at least includes the overall temperature of the geometric model, the heat flux of the cross section perpendicular to the heat transfer direction, and the heat flow of the cross section perpendicular to the heat transfer direction; According to the simulation result, the thermal conductivity simulation value of the composite material perpendicular to the fiber direction is calculated; Judging whether the thermal conductivity simulation value of the composite material perpendicular to the fiber direction is consistent with the thermal conductivity measurement value of the composite material perpendicular to the fiber direction, and obtaining a judgment result; If the judgment result is no, the fiber radial thermal conductivity simulation value is adjusted, and the step of setting the material parameters of the geometric model in the Ansys Workbench software is returned; If the judgment result is yes, the fiber radial thermal conductivity simulation value is outputted; The formula for calculating the thermal conductivity simulation value of the composite material perpendicular to the fiber direction is: ； wherein, Q is the heat flux through a cross section perpendicular to the heat transfer direction; A is the area of a cross section perpendicular to the heat transfer direction; The preparation process of the composite material is as follows: c is the simulated value of the thermal conductivity of the composite material perpendicular to the fiber direction; T 1 and T 2 are the temperatures of the upper and lower surfaces of the geometric model, respectively; d is the dimension of the geometric model in the direction of heat transfer.

2. The finite element modeling analysis method of fiber radial thermal conductivity according to claim 1, characterized in that, Removing the sizing agent on the surface of the fiber bundle; Dispersing the fiber bundle; Setting the fiber bundle in the mold groove; Pouring the matrix material into the mold containing the fiber bundle; Placing the mold containing the fiber bundle and the matrix material in the oven for curing and forming to form a mold containing the composite material; Taking out the cured and formed mold and demolding to obtain the composite material, and the fiber volume fraction of the composite material is 25%-55%. Obtaining the thermal conductivity measurement value of the matrix material in the composite material and the thermal conductivity measurement value of the composite material perpendicular to the fiber direction, specifically comprising:

3. The finite element modeling analysis method of radial thermal conductivity of fiber according to claim 1, characterized in that, Obtaining the thermal diffusivity, bulk density and specific heat capacity of the matrix material measured; Obtaining the thermal diffusivity, bulk density and specific heat capacity of the composite material measured; ​ According to the thermal diffusivity, the bulk density and the specific heat capacity of the matrix material, a thermal conductivity calculation formula is used to obtain a thermal conductivity measurement value of the matrix material; According to the thermal diffusivity, the bulk density and the specific heat capacity of the composite material, a thermal conductivity calculation formula is used to obtain a thermal conductivity measurement value of the composite material in the vertical fiber direction.

4. The finite element modeling analysis method of radial thermal conductivity of fiber according to claim 3, characterized in that, The thermal conductivity calculation formula is: ; wherein, is the thermal conductivity of the sample, is the bulk density of the sample, is the specific heat capacity of the sample, is the thermal diffusivity of the sample.

5. The finite element modeling analysis method of radial thermal conductivity of fiber according to claim 3, characterized in that, The specific steps for measuring the thermal diffusivity, the bulk density and the specific heat capacity of the matrix material are as follows: Obtain a matrix material sample; Use a flash method to measure the thermal diffusivity of the matrix material sample as the thermal diffusivity of the matrix material; Use a drainage method to measure the bulk density of the matrix material sample as the bulk density of the matrix material; Use a DSC sapphire method to measure the specific heat capacity of the matrix material sample as the specific heat capacity of the matrix material.

6. The finite element modeling analysis method of radial thermal conductivity of fiber according to claim 1, characterized in that, The process of establishing a geometric model of the composite material is as follows: Use sandpaper to polish the cross section of the composite material in the vertical fiber direction; Polish the cross section of the composite material in the vertical fiber direction; Use an ultra-depth microscope to observe the cross section of the composite material in the vertical fiber direction to obtain a metallographic photo of the microstructure of the composite material; Use Image J software to process the metallographic photo to obtain fiber contour information; Use Solidworks software to automatically track the fiber region boundary according to the fiber contour information to establish a geometric model of the composite material.

7. A finite element modeling system for radial thermal conductivity of fibers, comprising: The system is applied to the method of any one of claims 1 to 6, and the system comprises: A thermal conductivity measurement value acquisition module for acquiring a thermal conductivity measurement value of a matrix material in a composite material and a thermal conductivity measurement value of the composite material in the vertical fiber direction; the composite material comprises the matrix material and a fiber bundle; A geometric model establishment module for establishing a geometric model of the composite material; A finite element simulation module for performing finite element analysis on the geometric model based on the thermal conductivity measurement value of the matrix material and the thermal conductivity measurement value of the composite material in the vertical fiber direction to determine a fiber radial thermal conductivity simulation value when a thermal conductivity simulation value of the composite material in the vertical fiber direction is consistent with the thermal conductivity measurement value of the composite material in the vertical fiber direction.

8. An electronic device, comprising: A computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method of any one of claims 1 to 6. A computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method of any one of claims 1 to 6.

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