Simulation method and system of aramid honeycomb core dipping process based on dissipative particle dynamics

Abstract

The present invention provides a simulation method and system for the aramid honeycomb core dipping process based on dissipative particle dynamics, which involves computer-aided design, design simulation, dissipative particle dynamics and force analysis, and belongs to the field of electrical digital data processing technology. The present invention introduces the concept of coarse-graining, and uses frozen dissipative particle dynamics particles to describe and model the microscale geometric structure characteristics of the aramid paper sample, and adjusts the surface geometric characteristic structure by changing the arrangement direction, number, relative exposure height, etc. of the fibers. In the process of constructing a digital model of aramid paper, the present invention constructs its porosity characteristics and simulates the behavior of the glue particles penetrating into the pores. When simulating the dipping process of aramid paper, the present invention takes into account the influence of the input characteristics of the geometric characteristic size, porosity, dipping speed and infiltration time of aramid paper on the gluing rate of aramid paper. The simulation results are highly consistent with the real experimental data and have practical application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical digital data processing, and relates to computer-aided design, design simulation, dissipative particle dynamics and force analysis, and specifically relates to a method and system for simulating an aramid honeycomb core dipping process based on dissipative particle dynamics. Background Art

[0002] Aramid paper honeycomb core material has been widely used in aerospace, rail transit, national defense and military fields due to its excellent properties such as light weight, high strength, high modulus, flame retardant, high temperature resistance, corrosion resistance, low dielectric loss, etc. Its production process can be divided into gluing, drying, fixed length cutting, lamination, hot pressing, trimming, stretching, shaping, dipping and curing. Among them, dipping is one of the key processes for preparing aramid paper honeycomb. The dipping process will determine the density and density uniformity of the aramid paper honeycomb, and further affect the mechanical properties of the honeycomb.

[0003] At present, there is a relative lack of research on the process of aramid paper honeycomb impregnation, and the research method is mainly achieved through experiments. The main factors affecting the impregnation process are the surface morphology of aramid honeycomb paper and the wetting and adhesion properties of phenolic resin. Considering the differences in honeycomb manufacturing process and experimental implementation, the current research on the key process parameters of aramid honeycomb paper impregnation has not yet established a systematic theory, and the research gap in simulation needs to be filled.

[0004] Dissipative particle dynamics is a mesoscopic-scale meshless particle simulation algorithm, which is widely used in the simulation research of complex fluid systems due to its advantages such as easy tracking of two-phase interfaces, low computational cost, and large simulation time scale. Summary of the invention

[0005] The present invention is based on the above background technology and aims to provide a method and system for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics.

[0006] The present invention provides a method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics, which has the following characteristics: it is used to simulate the process of aramid paper being impregnated with glue so as to calculate the actual gluing rate of the aramid paper during dipping, and comprises the following steps: S10, determining the length reference unit, mass reference unit, speed reference unit, time reference unit and energy reference unit during the dissipative particle dynamics simulation; S20, considering the actual precipitated fibers and short-cut fibers in the aramid paper fibers and the processing flow of the aramid paper, and referring to the microscopic surface fiber distribution characteristics shown in the SEM image of the aramid paper, constructing a digital model of the aramid paper under the DPD model framework; S30, in computer modeling, using random numbers to construct the digital model porosity characteristics of the model; S40, under the framework of the DPD model, according to the MDPD method, after setting the dimensionless droplet diameter, liquid density, multi-body dissipative particle dynamics particle number and multi-body dissipative particle dynamics parameters of the glue droplet, simulate the droplet contacting the surface of the digital model, and correspond it to each stage of the actual experimental results, so as to map the dimensionless time in the simulation process with the characteristic time of the actual physical system; S50, setting the dipping speed and dipping time of the digital model, simulating the dipping and discharging process of the digital model; S60, according to the simulation process in step S50 and the mapping relationship between the dimensionless time and the characteristic time in step S40, calculate the actual glue rate of aramid paper dipping and discharging under specific conditions.

[0007] In the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention, it can also have the following characteristics: wherein step S10 includes the following sub-steps: S11, the DPD model of the glue solution is regarded as containing a series of particle particles, and the variables in the DPD model are dimensionless, with the cutoff radius of the DPD r cut As a reference unit of length, the mass of a single particle m DPD As a reference unit of mass, k B T ref As an energy reference unit, the key parameter connecting the mesoscopic scale of DPD with the real physical scale is the degree of coarse-graining. N m , then we can get formula 1: r 胶液 × r cut 3 = r DPD × m DPD = r DPD × N m ×m 胶液 ; S12, from formula 1, we get formula 2: ; S13, according to formula 1 and formula 2, the mass reference unit of the DPD model of the glue is obtained m ref = m DPD = N m × m 胶液 , speed reference unit , time reference unit , r 胶液 Indicates the density of the glue. r DPD represents the number density of dissipative particle dynamics particles per unit length square in the dissipative particle dynamics system, m DPD = N m × m 胶液 Represents a dissipative particle dynamics particle containing N m A glue molecule, N m represents the degree of coarse-graining that connects the mesoscopic scale of dissipative particle dynamics and the real physical scale, m 胶液 represents the mass of a single glue molecule, r ref Indicates the length reference unit, k B =1.381×10 -23 J / K is the Boltzmann constant, T ref represents the Kelvin reference temperature, in the dissipative particle dynamics system k B T ref =1.

[0008] In the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention, it can also have the following characteristics: wherein, in step S20, according to the material-specific microscopic roughness structure formed by the protruding fibers on the microscopic surface of the aramid paper in the SEM image, and based on the microscopic surface fiber distribution characteristics under the microscopic roughness structure, the digital model is composed of particles representing precipitated fibers and particles representing chopped fibers, and the chopped fiber particles appear irregularly scattered inside and on the surface of the digital model, and the precipitated fiber particles fill the gaps between the chopped fiber particles and serve as a flat base. In the process of constructing the digital model, the precipitated fiber particles and the chopped fiber particles are arranged in a 3DSC mode.

[0009] The aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention may also have the following characteristics: wherein, in step S20, the weight of each precipitated fiber particle and / or chopped fiber particle is determined by its local density, and after the microstructure of the digital model is formed by judging the adjacent distance and deleting excess particles, the surface geometric characteristic structure of the digital model can be adjusted by changing the arrangement direction, quantity and relative exposure height of the chopped fiber particles.

[0010] In the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention, it can also have the following characteristics: wherein, step S30 includes the following sub-steps: S31, using random numbers to determine the position and direction of punching on the digital model to simulate the random characteristics of natural holes; S32, traversing and judging the solid particles of the digital model under the DPD model framework, and deleting the solid particles whose distance from the punched holes is less than the cutoff distance of the DPD model; S33, adjusting the porosity characteristics of the digital model by adjusting the number of punching positions, and the hole size is larger than the characteristic length of the glue infiltration.

[0011] In the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention, the following features can also be provided: wherein step S40 includes the following sub-steps: S41, the glue solution during the dissipative particle dynamics simulation is regarded as containing a series of particle particles, and the particle particles collide with each other according to three forces: the conservative force derived from the potential energy , the dissipative force that reduces the tangential velocity between particles , random force in the direction of particle connection , using the MDPD method, the conservative force is defined as , local density , attraction weight function , repulsive force weight function ,in, c represents the dissipation force parameter, w D represents the weight function of the dissipative force, r ij =| r i - r j |It is a particle i and particles j The distance between v ij It is a particle i and particles j The relative speed between e ij It is a connected particle i and particlesj The unit vector of s is the random force parameter, w R is the weight function of the random force, i ij is a symmetrical Gaussian white noise. A is the attraction coefficient, w c is the attraction weight function, B is the repulsion coefficient, w d is the repulsive force weight function, w ρ ( r ij ) is the density weight function, r d is the repulsive force cutoff radius, r c is the attraction cutoff radius; S42, under the DPD model framework, set the dimensionless diameter of the droplet, liquid density, multi-body dissipative particle dynamics particle number and multi-body dissipative particle dynamics parameters of the glue. The multi-body dissipative particle dynamics parameters include the attraction coefficient A, the repulsion coefficient B, and the dissipative force parameter c , Attraction cutoff radius r c and the repulsive force cutoff radius r d ; S43, start the numerical experiment, simulate the droplet contacting the surface of the digital model, so that the droplet spontaneously infiltrates the particle on the digital model; S44, correspond the simulation process in step S43 with the various stages of the actual experimental results, so as to map the dimensionless time in the simulation process with the characteristic time of the actual physical system.

[0012] In the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention, the following features may also be provided: wherein, in step S41, when the particle spacing r ij > r c hour, w c =0; when the particle distance r ij > r d hour, w d and w ρ ( r ij ) are all 0.

[0013] The aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention may also have the following characteristics: wherein, in step S60, the specific conditions include different porosities, glue output speeds and dipping times of the digital model.

[0014] In the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics provided by the present invention, the following features may also be provided: wherein, when calculating the influence of the glue discharge speed on the actual glue rate of the aramid paper dipping and discharging, the dimensionless number Weber number is used to characterize the extraction speed of the aramid paper, which is defined as: , C D is the tensile coefficient of the glue cross section, r 胶液 is the density of the glue, L is the system scale, s 胶液 is the surface tension of the glue, v 胶液 is the speed of aramid paper glue release, v 胶液 Indicates the relative speed between the glue and the aramid paper. v 胶液 It is calculated We The only variable.

[0015] The present invention also provides an aramid honeycomb core dipping process simulation system based on dissipative particle dynamics, which has the following characteristics: it uses any of the aforementioned aramid honeycomb core dipping process simulation methods based on dissipative particle dynamics, including: a digital model construction unit, used to construct a digital model of aramid paper with porosity characteristics; a first simulation unit, used to simulate the contact of droplets with the surface of the digital model after the user inputs relevant parameters of the glue, and correspond it to each stage of the actual experimental results, thereby mapping the dimensionless time in the simulation process with the characteristic time of the actual physical system; a second simulation unit, connected to the digital model construction unit and the first simulation unit, used to simulate the dipping and discharging process of the digital model after the user inputs the dipping speed and dipping time of the digital model, and calculate the actual gluing rate of the aramid paper dipping and discharging under specific conditions based on the simulation process and the mapping relationship between the dimensionless time and the characteristic time.

[0016] The aramid honeycomb core dipping process simulation method and system based on dissipative particle dynamics of the present invention have the following beneficial effects:

[0017] (1) The present invention introduces the concept of coarse-graining for the first time in the simulation of aramid honeycomb dipping process and uses frozen dissipative particle dynamics particles to realize the microscopic structural visualization of aramid paper.

[0018] (2) The present invention can change the arrangement direction, quantity and relative exposure height of the fibers, thereby adjusting the geometric characteristic structure of the surface of the aramid paper digital model, avoiding a lengthy experimental process and greatly saving time and economic costs in the process of process development.

[0019] (3) The present invention takes into account the pore characteristics in the microstructure of aramid paper when constructing the digital model of aramid paper, and simulates the behavior of the glue liquid penetrating into the pores, providing a theoretical basis for the quality control and performance improvement of aramid paper honeycomb glue dipping.

[0020] (4) When simulating the aramid paper dipping process, the present invention takes into account the influence of the geometric characteristic size, porosity, dipping speed and wetting time input characteristics of the aramid paper on the gluing results. The calculation results obtained by simulation are highly consistent with the actual experimental data, which provides a reliable theoretical basis for the design of the aramid honeycomb core dipping process, helps to significantly reduce the time and economic costs in the process development process, and has important practical application value; and optimizes the process design method, providing a solid guarantee for the application of aramid honeycomb materials in the aviation industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of introducing the coarse-graining concept into the dissipative particle dynamics method in an embodiment of the present invention.

[0022] Figure 2 It is a diagram of a digital model of non-porous aramid paper constructed in a test example of the present invention.

[0023] Figure 3 It is a diagram of a digital model of aramid paper having porosity characteristics constructed in a test example of the present invention.

[0024] Figure 4 3 is a diagram showing the glue droplet infiltrating aramid paper in the test example of the present invention, wherein part (a) is a numerical simulation diagram of the infiltration digital model, and part (b) is a snapshot at time T=0.55 s in the actual infiltration experiment.

[0025] Figure 5 It is a schematic diagram of the computer simulation process of the aramid paper digital model dipping and discharging glue in the test example of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments and the accompanying drawings specifically illustrate a method and system for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics of the present invention.

[0027] <Example>

[0028] Figure 1It is a schematic diagram of introducing the coarse-graining concept into the dissipative particle dynamics method in an embodiment of the present invention.

[0029] like Figure 1 As shown in the figure, the idea of ​​introducing the coarse-graining concept into the dissipative particle dynamics method is to regard the basic unit as the momentum carrier of some discrete particles, moving in continuous space and discrete time. The particles represent the collective behavior of a large number of molecules in a small area, so that research can be carried out at the coarse-grained particle scale, thereby ignoring the structure and motion conditions at smaller scales.

[0030] The DPD model consists of a series of point particles that move in a gridless space and collide with each other according to three forces:

[0031] (1) Conservative force derived from potential energy:

[0032] .

[0033] (2) Dissipative force that reduces the tangential velocity between particles:

[0034] .

[0035] (3) Random force in the direction of particle connection:

[0036] .

[0037] in, w C represents the weight function of the conservative force, r ij =| r i - r j |It is a particle i and particles j The distance between e ij It is a connected particle i and particles j The unit vector of c represents the dissipation force parameter, w D represents the weight function of the dissipative force, v ij It is a particle i and particles j The relative speed between s is the random force parameter, w R is the weight function of the random force, i ij is a symmetrical Gaussian white noise.

[0038] In the DPD model, mass and momentum are naturally conserved, considering the conserved mass density r ( r , t )= mn ( r , t ) and momentum density r ( r , t ) u ( r , t ), defined in the following form:

[0039] .

[0040] in, r is the spatial position vector, t It's time. m is the mass of a single particle, n is the number of particles per unit volume, u is the average velocity per unit volume.

[0041] The distribution function of a single particle and the distribution function of a pair of particles are defined as:

[0042] .

[0043] Then we can get the macroscopic conservation law:

[0044] .

[0045] Among them, ▽ = ∂ / ∂r is the local pressure tensor, and ∏ is the momentum flow rate density.

[0046] The above derivation proves that the fluid dynamics equations of the discrete dissipative particle dynamics system have a form consistent with the Navier-Stokes equations, laying a theoretical foundation for dissipative particle dynamics as a simulation method that is more flexible at the mesoscopic scale and easy to track the two-phase interface.

[0047] This embodiment provides a simulation method for the aramid honeycomb core dipping process based on dissipative particle dynamics, which is used to simulate the process of aramid paper being infiltrated with glue to calculate the actual gluing rate of the aramid paper, including the following steps:

[0048] S10, the variables in the dissipative particle dynamics simulation are dimensionless. In order to establish the mapping relationship between the dimensionless parameters and the real physical quantities, it is first necessary to obtain the reference units (length reference unit, mass reference unit, speed reference unit, time reference unit and energy reference unit), including the following sub-steps S11~S13:

[0049] S11, the DPD model of the colloid is considered to contain a series of particles, with the cutoff radius of DPD r cut As a reference unit of length, the mass of a single particle m DPD As a reference unit of mass, k B T ref As an energy reference unit, the key parameter connecting the mesoscopic scale of DPD with the real physical scale is the degree of coarse-graining. N m , then we can get formula 1:

[0050] r 胶液 × r cut 3 = r DPD × m DPD = r DPD × N m × m 胶液 .

[0051] in, r 胶液 Indicates the density of the glue. r DPD represents the number density of dissipative particle dynamics particles per unit length square in the dissipative particle dynamics system, m DPD = N m × m 胶液 Represents a dissipative particle dynamics particle containing N m A glue molecule, N m represents the degree of coarse-graining that connects the mesoscopic scale of dissipative particle dynamics and the real physical scale, m 胶液 represents the mass of a single glue molecule, k B =1.381×10 -23J / K is the Boltzmann constant, T ref represents the Kelvin reference temperature, in the dissipative particle dynamics system k B T ref =1.

[0052] S12, from formula 1, we get formula 2:

[0053] .

[0054] in, r ref Indicates the length reference unit.

[0055] From the above formula 2, we can see that N m and r cut Both can be used as input variables to start the calculation of the mapping relationship.

[0056] S13, according to equations 1 and 2, the following reference units of the DPD model of the glue are obtained:

[0057] The mass reference unit is the mass of a single DPD particle: m ref = m DPD = N m × m 胶液 .

[0058] The speed reference unit is thermal speed: .

[0059] Time reference unit .

[0060] S20, constructing a digital model of aramid paper, including the following sub-steps S21 to S23:

[0061] S21, consider the actual fibrils and chopped fibers in aramid paper fibers and the processing flow of aramid paper.

[0062] Short-cut fibers are linear structures of varying lengths that appear randomly inside and on the surface of aramid paper. The precipitated fiber material fills the gaps between the short-cut fibers and serves as a relatively flat base.

[0063] S22, based on step S21, with reference to the SEM image of the aramid paper, according to the material-specific microscopic roughness structure formed by the protruding fibers on the microscopic surface of the aramid paper in the SEM image, and based on the microscopic surface fiber distribution characteristics under the microscopic roughness structure, modeling is performed under the DPD model framework, the simulation box size is a dimensionless length rectangular area, periodic boundary conditions are used, and the substrate thickness and the reference frame density of the solid particles are set at the same time.

[0064] The constructed digital model is composed of particles representing fibrillation and particles representing chopped fibers. The chopped fiber particles appear randomly inside and on the surface of the digital model, and the fibrillation particles fill the gaps between the chopped fiber particles and serve as a flat base.

[0065] In the process of constructing the digital model, the arrangement of the precipitated fiber particles and the chopped fiber particles is the 3DSC mode. The significance of the 3DSC feature space is to establish a representation of the point distribution in the local area. In the vicinity of each point, the point density and the corresponding distribution geometric characteristics need to be clearly represented. P 0 is the center of the sphere, R 0 is a sphere with a radius of 0. The north pole of the sphere is estimated by the reconstructed normal. There are concentric spheres of different sizes in 3DSC. The radius calculation formula is as follows:

[0066] .

[0067] in, H represents the number of concentric spheres, r min and r max denote the minimum and maximum radii of the concentric spheres, respectively. h Indicates h radially concentric spheres.

[0068] The weight of each fibrid particle and / or chopped fiber particle is determined by its local density and the weight formula is:

[0069] .

[0070] in, r i is the local density, V ( h , k , l ) is the h Radial, k Azimuth and l The volume corresponding to the elevation angle area.

[0071] S23, after the microstructure of the digital model is formed by judging the adjacent distance and deleting the redundant particles, the surface geometric characteristic structure of the digital model can be adjusted by changing the arrangement direction, quantity and relative exposure height of the chopped fiber particles.

[0072] S30, pores are naturally formed cavity structures between different fibers, some of which are connected to form a network, and some form blind holes. In computer modeling, the digital model constructed above is punched to obtain holes, so as to construct the porosity characteristics of the digital model, including the following sub-steps S31~S33:

[0073] S31, using random numbers to determine the location and direction of punching holes on the digital model to simulate the random characteristics of natural holes.

[0074] S32, after determining the position and direction of the hole, perform traversal judgment on all solid particles, and delete solid particles whose distance from the hole is less than the cutoff distance of the DPD model, so as to ensure the formation of holes in the lattice particle model. Because of the lattice distribution characteristics of solid particles, the holes finally formed often do not present circular geometric characteristics. These random holes will also form a network in space, and the holes in the structure with higher porosity are more intertwined, which is similar to natural voids.

[0075] S33, the size of the hole is larger than the characteristic length of the glue infiltration, ensuring that the glue particles can enter these pores driven by capillary force. The porosity characteristics of the digital model can be adjusted by adjusting the number of punching positions.

[0076] S40, simulating that a droplet of glue contacts the surface of the digital model, thereby mapping the dimensionless time in the simulation process with the characteristic time of the actual physical system, including the following sub-steps S41 to S44:

[0077] S41, in the DPD model framework, according to the MDPD method, the conservative force Redefine as:

[0078] .

[0079] in, A is the attraction coefficient, w c is the attraction weight function, B is the repulsion coefficient, w d is the repulsion weight function.

[0080] Local Density .

[0081] in, w ρ (r ij ) is the density weight function, r d is the repulsive force cutoff radius.

[0082] Attraction Weight Function .

[0083] in, r c Cutoff radius for attraction.

[0084] When the particle distance r ij > r c hour, w c =0; when the particle distance r ij > r d hour, w d and w ρ ( r ij ) are all 0.

[0085] S42, under the framework of DPD model, set the dimensionless diameter of the droplet, liquid density, number of multi-body dissipative particle dynamics particles and multi-body dissipative particle dynamics parameters of the glue. The multi-body dissipative particle dynamics parameters include the attraction coefficient A, the repulsion coefficient B, and the dissipative force parameter c , Attraction cutoff radius r c and the repulsive force cutoff radius r d ;

[0086] S43, start the numerical experiment, apply z The initial velocity in the direction makes it contact the surface of the digital model, and then due to the interaction between the glue particles and the particles in the digital model, the glue will spontaneously infiltrate and spread.

[0087] S44, the simulation process in step S43 is made to correspond to each stage of the actual experimental results, so as to map the dimensionless time in the simulation process with the characteristic time of the actual physical system.

[0088] S50, setting the dipping speed and dipping time of the digital model, simulating the dipping and discharging process of the digital model.

[0089] S60, according to the simulation process in step S50 and the mapping relationship between the dimensionless time and the characteristic time in step S40, calculate the actual glue rate of aramid paper dipping and glue discharge under specific conditions, specifically including the following sub-steps:

[0090] S61, simulation of the effect of different porosities on the actual gluing rate of aramid paper.

[0091] The glue rate is defined as the volume of glue adsorbed per unit volume of the digital model. Considering the different porosities of the simulated digital models, the volume of the digital model is defined as the total number of digital model particles divided by the grid density of the digital model particles, that is, the volume of the digital model excluding the porosity.

[0092] The volume of adsorbed glue is obtained by subtracting the number of particles remaining at the bottom after immersion from the number of liquid particles in the initial glue pool, and then dividing it by the equilibrium particle number density of the glue.

[0093] In this step, the glue applied includes not only the glue that penetrates into the pores inside the porous medium through the capillary phenomenon, but also a layer of liquid film hanging on the surface of the digital model.

[0094] After the simulation is completed, the actual glue rate of aramid paper dipping and glue discharge in the corresponding case is calculated according to the simulation process and the mapping relationship between dimensionless time and characteristic time.

[0095] S62, simulate the effect of different glue discharge speeds on the actual glue rate of aramid paper.

[0096] In this step, the dimensionless Weber number is used to characterize the glue discharge speed of the digital model. The Weber number is a dimensionless number commonly used in fluid mechanics research. It contains information such as fluid density, velocity, characteristic length, and surface tension. It can be understood as the strength comparison of the drag force and adhesion force received by the droplet. It can also be used as a dimensionless characteristic form of velocity when the fluid properties remain unchanged.

[0097] The Weber number is defined as:

[0098] ,

[0099] C D is the tensile coefficient of the glue cross section, r 胶液 is the density of the glue, L is the system scale, s 胶液 is the surface tension of the glue, v 胶液 is the speed of aramid paper glue release, v 胶液 Indicates the relative speed between the glue and the aramid paper.

[0100] r 胶液 , L, s 胶液 are all invariants, only v胶液 is the only variable used to calculate We.

[0101] After the simulation is finished, the actual glue rate of the aramid paper in the corresponding case is calculated in the same manner as step S61.

[0102] S63, simulate the effect of different soaking time on the actual gluing rate of aramid paper.

[0103] The soaking time refers to the time it takes to completely immerse the digital model in the glue. Since the size of the dissipative particle dynamics system is different from that of the actual system, by matching the various stages of the numerical simulation experiment with the actual experimental results, the dimensionless time of the dissipative particle dynamics system can be obtained to map the characteristic time of the physical system. Finally, the actual glue rate of aramid paper dipping and dispensing under the corresponding conditions is calculated.

[0104] This embodiment also provides an aramid honeycomb core dipping process simulation system based on dissipative particle dynamics, which uses the aramid honeycomb core dipping process simulation method based on dissipative particle dynamics in this embodiment, including a digital model construction part, a first simulation part and a second simulation part.

[0105] The digital model building part is used to build a digital model of aramid paper with porosity characteristics.

[0106] The first simulation unit is connected to the digital model building unit, and is used to simulate the contact of the droplet with the digital model surface after the user inputs the relevant parameters of the glue, and corresponds it to each stage of the actual experimental results, thereby mapping the dimensionless time in the simulation process with the characteristic time of the actual physical system.

[0107] The second simulation unit is connected to the digital model construction unit and the first simulation unit, and is used to simulate the process of dipping and discharging the digital model after the user inputs the dipping speed and dipping time of the digital model, and calculates the actual gluing rate of aramid paper dipping and discharging under specific conditions based on the simulation process and the mapping relationship between dimensionless time and characteristic time.

[0108] <Test example>

[0109] This test example uses an aramid honeycomb core dipping process simulation system based on dissipative particle dynamics in the embodiment, and according to an aramid honeycomb core dipping process simulation method based on dissipative particle dynamics in the embodiment, the process of aramid paper being impregnated with glue is simulated to calculate the actual gluing rate of the aramid paper.

[0110] First, a digital model of aramid paper is constructed according to the method of steps S10 to S20 in the embodiment. The obtained digital model is as follows: Figure 2 shown.

[0111] Figure 2 is a diagram of a digital model of a non-porous aramid paper constructed in a test example of the present invention. Figure 2 As shown, the digital model of aramid paper is composed of particles of two materials, yellow represents the particle type of chopped fiber material, and gray represents the particle type of precipitated fiber material.

[0112] Then, the porosity characteristics of the digital model are constructed according to the method of step S30 to obtain a digital model with porosity characteristics such as Figure 3 shown.

[0113] Figure 3 is a diagram of a digital model of aramid paper with porosity characteristics constructed in the test example of the present invention. Figure 3 As shown, porosity is the cavity structure naturally formed between different fibers. In computer modeling, the aramid paper digital model structure formed above is punched to form holes. The position and direction of the punching are determined by random numbers, simulating the random characteristics of natural holes.

[0114] Next, according to the method of step S40, the wetting process of the droplet on the surface of the aramid paper digital model is simulated. Under the DPD model framework of the aramid paper digital model, the simulation box size is a dimensionless length of 100×100×100, and periodic boundary conditions are used. The diameter of the glue droplet is 28, which contains 79507 multi-body dissipative particle dynamics particles, and the liquid density is 6.92. The key multi-body dissipative particle dynamics (MDPD) parameters are: A =-40, B =3, c =8, r c =1.0, r d = 0.75. Initially, the colloid droplet undergoes thermal equilibrium and has a standard spherical shape.

[0115] After the numerical experiment begins, an initial velocity of -0.05 in the z direction is applied to the droplet to make it contact the surface of the aramid paper digital model. Subsequently, due to the interaction between the glue particles and the aramid paper digital model particles, the glue will spontaneously infiltrate and spread. The process is as follows: Figure 4 As shown. Since the size of the dissipative particle dynamics system is different from that of the actual system, by matching the various stages of the numerical simulation experiment with the actual experimental results, the dimensionless time of the dissipative particle dynamics system can be obtained to map the characteristic time of the physical system.

[0116] Finally, according to the method of step S50 to step S60, the process of aramid paper being immersed in glue is simulated. Figure 5 As shown, the sample is placed vertically above the liquid pool, and the z-direction depth of the liquid pool is 110 to ensure that the aramid paper can be completely immersed.x The width in the direction is the same as that of aramid paper. Considering the periodic boundary conditions, it is equivalent to an infinitely wide aramid paper sheet immersed in an infinitely wide liquid pool. y The thickness in the direction is 30. There are frozen particles with a thickness of 2 at the bottom of the liquid pool as the pool bottom to prevent penetration. All glue particles are subjected to a dimensionless gravitational acceleration of 0.002, in a downward direction. The speed of aramid paper entering the glue is 0.1, and it takes 200,000 steps from the initial state to complete immersion. The system time integration step is 0.005 dimensionless time units. After being immersed in the glue, it remains stationary for 200,000 steps. After that, it moves upward at a uniform speed of 0.1 for 300,000 steps until it completely leaves the liquid pool.

[0117] Based on the above method, the effects of different porosity, glue discharge speed and impregnation time on the gluing rate of aramid paper were simulated by adjusting the corresponding parameters.

[0118] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A simulation method for aramid honeycomb core dipping process based on dissipative particle dynamics, characterized in that: The method is used to simulate the process of aramid paper being impregnated with glue so as to calculate the actual gluing rate of aramid paper, including the following steps: S10, determining a length reference unit, a mass reference unit, a velocity reference unit, a time reference unit, and an energy reference unit during a dissipative particle dynamics simulation; S20, considering the actual fibrillation and short-cut fibers in aramid paper fibers and the processing flow of aramid paper, and referring to the microscopic surface fiber distribution characteristics shown in the SEM image of aramid paper, a digital model of aramid paper is constructed under the framework of the DPD model; S30, in computer modeling, using random numbers to construct porosity characteristics of the digital model; S40, in the framework of the DPD model, according to the MDPD method, after setting the dimensionless droplet diameter, liquid density, multi-body dissipative particle dynamics particle number and multi-body dissipative particle dynamics parameters of the droplet of the glue, simulate the droplet contacting the surface of the digital model, and correspond it to each stage of the actual experimental results, so as to map the dimensionless time in the simulation process with the characteristic time of the actual physical system; S50, setting the dipping speed and dipping time of the digital model to simulate the dipping and discharging process of the digital model; S60, according to the simulation process in step S50 and the mapping relationship between the dimensionless time and the characteristic time in step S40, calculating the actual glue rate of the aramid paper during the gluing and gluing under specific conditions, Wherein, in step S20, according to the material-specific microscopic roughness structure formed by the protruding fibers on the microscopic surface of the aramid paper in the SEM image, and based on the microscopic surface fiber distribution characteristics under the microscopic roughness structure, the digital model is composed of particles representing the fibrids and particles representing the chopped fibers, the chopped fiber particles appear irregularly scattered inside and on the surface of the digital model, the fibrid particles fill the gaps between the chopped fiber particles and serve as a flat base, in the process of constructing the digital model, the fibrid particles and the chopped fiber particles are arranged in a 3DSC mode, the weight of each of the fibrid particles and / or the chopped fiber particles is determined by its local density, after the microscopic structure of the digital model is formed by judging the adjacent distance and deleting the redundant particles, the surface geometric characteristic structure of the digital model can be adjusted by changing the arrangement direction, quantity and relative exposure height of the chopped fiber particles, Step S40 includes the following sub-steps: S41, the colloid in the dissipative particle dynamics simulation is regarded as comprising a series of mass particles, and the mass particles collide with each other according to three forces: Conservative force derived from potential energy Dissipative forces that reduce the tangential velocity between particles Random force in the direction of particle connection Using the MDPD method, the conservative force is defined as Local Density Attraction Weight Function Repulsive force weight function Among them, γ represents the dissipation force parameter, w D Represents the weight function of the dissipative force, r ij =|r i -r j | is the distance between particles i and j, v ij is the relative velocity between particles i and j, e ij is the unit vector connecting particle i and particle j, σ is the random force parameter, and w R is the weight function of the random force, θ ij is a symmetrical Gaussian white noise, A is the attraction coefficient, w c is the attraction weight function, B is the repulsion coefficient, w d is the repulsive force weight function, w ρ (r ij ) is the density weight function, r d is the repulsive force cutoff radius, r c is the attraction cutoff radius, S42, under the framework of the DPD model, setting the dimensionless diameter of the droplet of the glue, the liquid density, the number of multi-body dissipative particle dynamics particles and the multi-body dissipative particle dynamics parameters, wherein the multi-body dissipative particle dynamics parameters include the attraction coefficient A, the repulsion coefficient B, the dissipative force parameter γ, the attraction cutoff radius r c and the repulsive force cutoff radius r d , S43, starting a numerical experiment to simulate the liquid droplet contacting the surface of the digital model so that the liquid droplet spontaneously infiltrates the mass particles on the digital model. S44, the simulation process in step S43 is made to correspond to each stage of the actual experimental results, so as to map the dimensionless time in the simulation process with the characteristic time of the actual physical system.

2. The method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics according to claim 1, characterized in that: in, Step S10 includes the following sub-steps: S11, the DPD model of the colloid is regarded as comprising a series of mass particles, and the variables in the DPD model are dimensionless. cut As a reference unit of length, the mass of a single particle m DPD As a reference unit of mass, k B T ref As an energy reference unit, the key parameter connecting the mesoscopic scale of DPD and the real physical scale is the coarse-graining degree N. m , then we can get formula 1: r 胶液 ×r cut 3 =ρ DPD ×m DPD =ρ DPD ×N m ×m 胶液 ; S12, from formula 1, we get formula 2: S13, according to formula 1 and formula 2, the mass reference unit m of the DPD model of the glue is obtained. ref =m DPD =N m ×m 胶液 , speed reference unit Time reference unit ρ 胶液 represents the density of the glue, ρ DPD represents the number density of dissipative particle dynamics particles per unit length square in the dissipative particle dynamics system, m DPD =N m ×m 胶液 Represents a dissipative particle dynamics particle containing N m Glue molecules, N m represents the degree of coarse-graining that connects the mesoscopic scale of dissipative particle dynamics and the real physical scale, m 胶液 represents the mass of a single glue molecule, r ref Indicates the length reference unit, k B =1.381×10 -23 J / K is the Boltzmann constant, T ref represents the Kelvin reference temperature, k in the dissipative particle dynamics system B T ref =1.

3. The method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics according to claim 1, characterized in that: in, Step S30 includes the following sub-steps: S31, using random numbers to determine the position and direction of punching holes on the digital model to simulate the random characteristics of natural holes; S32, performing traversal judgment on the solid particles of the digital model under the DPD model framework, and deleting the solid particles whose distance from the punched hole is less than the cutoff distance of the DPD model; S33, adjusting the porosity characteristics of the digital model by adjusting the number of punching positions, The hole size is larger than the characteristic length of glue infiltration.

4. The method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics according to claim 1, characterized in that: in, In step S41, when the particle distance r ij >r c When c =0; when the particle distance r ij >r d When d and w ρ (r ij ) are all 0.

5. The method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics according to claim 1, characterized in that: in, In step S60, the specific conditions include different porosities, glue output speeds and glue dipping times of the digital model.

6. The method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics according to claim 5, characterized in that: in, When calculating the effect of the glue extraction speed on the actual glue rate of the aramid paper during the dipping and extraction, the dimensionless number Weber number is used to characterize the extraction speed of the aramid paper, which is defined as: C D is the tensile coefficient of the glue cross section, ρ 胶液 is the density of the glue, L is the system scale, σ 胶液 is the surface tension of the glue, v 胶液 is the glue-out speed of aramid paper, v 胶液 Indicates the relative speed between the glue and the aramid paper, v 胶液 is the only variable used to calculate We.

7. A simulation system for aramid honeycomb core dipping process based on dissipative particle dynamics, characterized in that: The method for simulating the aramid honeycomb core dipping process based on dissipative particle dynamics as described in any one of claims 1 to 6 comprises: A digital model building unit, used for building a digital model of aramid paper with porosity characteristics; The first simulation unit is used to simulate the contact of the droplet with the surface of the digital model after the user inputs the relevant parameters of the glue, and corresponds it to each stage of the actual experimental results, so as to map the dimensionless time in the simulation process with the characteristic time of the actual physical system; The second simulation unit is connected to the digital model construction unit and the first simulation unit, and is used for simulating the process of dipping and discharging the digital model after the user inputs the dipping speed and dipping time of the digital model, and calculates the actual gluing rate of the aramid paper dipping and discharging under specific conditions according to the simulation process and the mapping relationship between the dimensionless time and the characteristic time.

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