Aramid paper rolling pore closing simulation analysis method

Abstract

The invention discloses an aramid paper rolling pore closing simulation analysis method which comprises the following steps: generating a fiber random distribution structure: establishing a fiber and pore random distribution heat-force coupling model according to the stress condition in the aramid honeycomb paper rolling forming process; wherein when the volume of any hole is compressed to be 80% of the original volume, bubbles in the hole are extruded by rolling, and the porosity of the formed aramid honeycomb paper is counted through a python script. According to the method, the microstructure of the aramid honeycomb paper produced through the roll forming process under different roll forming processes can be rapidly predicted, so that regulation and control of the forming process in actual production can be guided, the consistency and reliability of products are improved, and the application range of the aramid honeycomb paper is widened.

Description

Technical Field

[0001] The invention relates to the technical field of aramid honeycomb paper preparation, and in particular to a simulation analysis method for pore closure during roller pressing of aramid paper. Background Art

[0002] Aramid honeycomb paper is a high-strength special paper made from aramid short fibers and precipitated fibers as the main raw materials. It is made through wet forming, drying and hot pressing processes. It has good mechanical properties and tear resistance and is widely used in high-tech fields such as electrical, military, aerospace and new energy.

[0003] The roll forming manufacturing process of aramid honeycomb paper has a critical influence on its internal microstructure such as arrangement and pore distribution, which directly determines the final product performance. After wet forming, the structure of aramid honeycomb paper is still relatively loose and has many pores. The roll forming process can discharge the pores by applying temperature and pressure loads to the aramid base paper, and it needs to be rolled again to obtain higher comprehensive performance.

[0004] In order to further understand the mechanism of the influence of the rolling process on the microstructure and mechanical properties of aramid honeycomb paper, and to effectively regulate the rolling forming process of aramid honeycomb paper and obtain higher quality products, a large number of experimental studies are still needed. However, the rolling forming process is complex, with many process parameters, and comprehensive experimental research requires extremely high costs. Therefore, it is urgent to develop a physics-based simulation analysis method, which is of great significance to reducing experimental costs and understanding the forming mechanism, so as to further develop the application potential of aramid honeycomb paper and provide technical support for its widespread use. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a simulation analysis method for pore closure of aramid paper by roller pressing, which can quickly predict the microstructure of aramid honeycomb paper produced by roller pressing forming process under different roller pressing processes, so as to guide the molding process control in actual production, improve the consistency and reliability of products, and broaden the application scope of aramid honeycomb paper. In order to achieve the above-mentioned purpose and other advantages according to the present invention, a simulation analysis method for pore closure of aramid paper by roller pressing is provided, comprising: Generate a structure with randomly distributed fibers: According to the stress conditions during the roll forming process of aramid honeycomb paper, a thermal-mechanical coupling model with random distribution of fibers and pores was established. Among them, when the volume of any hole is compressed to 80% of its original volume, the bubbles in this hole are squeezed out by roller pressure, and the porosity of the aramid honeycomb paper after molding is calculated using a python script.

[0006] The present invention constructs a simulation analysis model of the aramid honeycomb paper rolling process to simulate the compression and closing process of the pores in the aramid paper during the forming process, and uses a python script to extract the volume of the pores in the model to obtain the porosity of the aramid honeycomb paper after forming.

[0007] The invention is based on the Gurley formula and aims at a rolling process, and proposes a method for calculating the air permeability of aramid honeycomb paper, thereby realizing the mutual conversion between porosity and air permeability.

[0008] The present invention further realizes the control of the aramid honeycomb paper forming process by establishing a functional relationship between processing conditions and the air permeability of the aramid honeycomb paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a simplified schematic diagram of the pore model of aramid paper according to the pore closure simulation analysis method of aramid paper roller pressure of the present invention; Figure 2 A finite element model diagram of the aramid paper roll-pressed pore closure simulation analysis method according to the present invention; Figure 3 A deformation distribution diagram obtained by calculation of a finite element model of the aramid paper roller pressure pore closure simulation analysis method according to the present invention; Figure 4 1 is a graph showing the relationship between air permeability and load size when the temperature is 300° C. according to the aramid paper roller pressure pore closure simulation analysis method of the present invention. DETAILED DESCRIPTION

[0010] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0011] Reference Figure 1 A simulation and analysis method for pore closure of aramid paper by roller pressing, comprising: generating a random fiber distribution structure based on a "random number" calculation method through a Monte Carlo method, first determining the fiber radius, minimum inter-fiber distance, fiber region length and other structural parameters of the region where the fibers are generated, and then pre-generating a large number of fiber filament center point coordinates in the fiber region, entering a loop, and comparing them with previously determined fibers to avoid interference or intersection, until the porosity of the gaps between the fiber filaments reaches the expected value, stopping the loop and generating a geometric model.

[0012] The roll-forming process of aramid honeycomb paper is carried out under high temperature conditions. The microstructure of aramid honeycomb paper conducts heat under the action of external heat load, which in turn generates a temperature gradient, causing the material or structure to deform. Based on this, a thermal-mechanical coupling model of the roll-forming process of aramid honeycomb paper is established, including using free grids to mesh the geometric model of aramid honeycomb paper with randomly distributed fibers and pores, and applying mechanical and temperature boundary conditions to the calculation model based on the roll-forming process of aramid honeycomb paper.

[0013] The pore distribution of aramid honeycomb paper during the roller forming process was calculated based on the above model. When the volume of any hole was compressed to 80% of the original volume, the bubble in this hole was considered to be squeezed out by roller pressing. Finally, a python script was used to calculate the porosity of the aramid honeycomb paper after forming.

[0014] In order to further convert the porosity into air permeability, the present invention converts Figure 1 The pore distribution model of aramid paper shown in (a) is simplified as follows: Figure 1 In the single hole model shown in (b), it is assumed that the cross-sectional area of ​​the air column is The total cross-sectional area of ​​the model is , then the porosity can be expressed as: (1) Assume that the velocity of the air column when it is discharged through the other end is , then at time In a very short time, according to the Gurley air permeability formula: (2) in For air permeability, It's time The volume of gas passing through. According to the momentum theorem: (3) Combining formula (2) we can get: (4) in is the pressure difference, is the air density. Combining equations (1) and (4), the air permeability can be expressed as: (5) On this basis, the cftool tool of Matlab was used to perform polynomial fitting on the air permeability under different pressures (Equation (6)), and the functional relationship between the process conditions and the air permeability of aramid honeycomb paper was further established to achieve a rapid prediction of the air permeability of aramid honeycomb paper after forming under specified process conditions: (6) in , , , , , are the polynomial coefficients, Roller pressure.

[0015] The initial porosity of the aramid honeycomb base paper is 4%, and the fiber ratio is 16%. Figure 2 The finite element model shown in (a) is subjected to lateral compression loads ( Figure 2 In (b), a tensile load is applied transversely ( Figure 2 In (c), the boundary temperature is 300 °C.

[0016] The stress distribution results calculated by the finite element model are as follows: Figure 3 As shown in the figure, the fiber area shows a higher stress distribution, while the stress level in the matrix area is lower; in addition, its thickness is significantly reduced compared to before molding. The porosity in the model is extracted using a python script and converted into permeability according to the formula.

[0017] The fifth-order polynomial was used to fit the air permeability under different loads. The results are as follows: Figure 4 As shown, the relationship between the air permeability and the rolling load under this rolling process is obtained. It can be seen that the air permeability of the aramid honeycomb paper gradually decreases during the rolling process.

[0018] The number of devices and processing scales described here are used to simplify the description of the present invention, and the application, modification and variation of the present invention will be obvious to those skilled in the art.

[0019] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A simulation analysis method for pore closure of aramid paper by roller pressing, characterized in that: include: Generate a structure with randomly distributed fibers: According to the stress conditions during the roll forming process of aramid honeycomb paper, a thermal-mechanical coupling model with random distribution of fibers and pores was established. Among them, when the volume of any hole is compressed to 80% of its original volume, the bubbles in this hole are squeezed out by roller pressure, and the porosity of the aramid honeycomb paper after molding is calculated using a python script.

2. The aramid paper roll-pressed pore closure simulation analysis method according to claim 1, characterized in that: The random distribution structure of fibers is generated by the Monte Carlo method based on the "random number" calculation method, as follows: Determine the structural parameters of the region where the fibers are generated; A large number of fiber single filament center point coordinates are generated in advance in the fiber area, enter a loop, and are compared with previously determined fibers; The cycle is stopped and the geometric model is generated until the porosity of the space between the fiber filaments reaches the expected value.

3. The aramid paper roll-pressed pore closure simulation analysis method according to claim 1, characterized in that: The porosity is converted into air permeability, and then the expression of air permeability is solved by the Gurley air permeability formula.

4. A simulation analysis method for pore closure of aramid paper by roller pressing as claimed in claim 3, characterized in that: According to the air permeability, a functional relationship between the process conditions and the air permeability of the aramid honeycomb paper is established to achieve a rapid prediction of the air permeability of the aramid honeycomb paper after forming under the specified process conditions.

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