Method for predicting the impact behavior of polymer composites based on molecular dynamics simulations

Abstract

The application belongs to the field of impact molecular dynamics method, and particularly relates to a method for simulating impact resistance of a polymer composite material based on molecular dynamics, which comprises the following steps: establishing a projectile model and a polymer composite material target model by using a molecular modeling software; performing compression simulation on the polymer composite material target model to make the surface of the polymer composite material target model denser and smoother; dividing the polymer composite material target model into a boundary zone, a constant temperature zone and a Newton zone, regarding the projectile as a rigid body, and impacting the target model at a certain linear velocity and angular velocity; calculating the changes of the projectile velocity, displacement, kinetic energy and resistance force with time during the impact process; and importing the simulation results into a visualization software to perform visual analysis on the damage behavior of the target model. The method can be used to study the microstructure changes and damage mechanism of the target model during the process of the projectile impacting the polymer composite material target model, and can provide a preliminary theoretical prediction and scientific basis for screening, designing and optimizing protective materials.

Description

Technical Field

[0001] This invention belongs to the field of impact molecular dynamics research, specifically a method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics. Background Technology

[0002] In daily production and activities, various equipment is often subjected to various forms of impact and wear during production, use, and maintenance, resulting in varying degrees of damage and destruction. Therefore, research on protective materials with high penetration resistance is essential for many extreme engineering applications, such as protecting soldiers from high-speed bullets, protecting space structures from micrometeorites, and protecting jet engine turbine blades from supersonic particle impacts. [3] When objects collide, complex physical phenomena occur, such as elastoplastic deformation, wave propagation, damage, fragmentation, and heat release (due to flow and friction). This involves multiple applied technology fields, including materials science and engineering, automotive, aerospace, and defense. Because impact damage is instantaneous, it is difficult to observe the entire impact damage process and its evolution in experiments. Therefore, researchers use computational simulations to study the deformation and failure mechanisms of materials during impact, predicting the response behavior of materials under different impact conditions. This provides theoretical guidance for the design and optimization of protective material structures and improves the impact protection performance of materials. Impact simulations of materials can be divided into two main categories based on scale: microscopic and macroscopic simulations. Extensive research has been conducted on macroscopic simulations both domestically and internationally. Although macroscopic simulation results can be directly compared with experimental results, their accuracy depends on the material model and parameters, which are often difficult to obtain accurately. Microscopic simulations can establish impact models at the atomic or molecular level, observe impact behavior at the atomic scale, and precisely describe changes in microstructure during impact, avoiding the drawbacks of experimental observation. They offer unique advantages in the study of microscopic mechanisms, providing new perspectives and insights for designing superior protective materials. Currently, most research focuses on using molecular dynamics simulations to study the impact resistance of metallic materials. However, non-metallic materials such as polymer composites, with their high specific strength and high specific energy absorption, are common key protective materials with important applications in the field of protection. Yet, research on molecular dynamics simulations of the impact resistance behavior of polymer composites has not yet been reported. Summary of the Invention

[0003] To address the current lack of molecular dynamics simulations of the impact resistance behavior of polymer composites, this invention provides a method for simulating the impact resistance behavior of polymer composites based on molecular dynamics.

[0004] This invention is achieved through the following technical solution: a method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics, comprising the following steps: 1) Use molecular modeling software to create projectile models and target models of polymer composite materials; 2) Perform compression simulation on the target model of polymer composite material under a certain pressure, and control the length of compression simulation time by judging the change in height of the target model of polymer composite material before and after compression; 3) Under reactive force field conditions, perform energy minimization and structural relaxation on the target model of polymer composite materials; 4) The relaxed polymer composite target model is divided into three regions: boundary region, isothermal region, and Newton region. During the impact, the atoms in the boundary region remain fixed. Molecular dynamics simulation of the NVT ensemble is performed in the isothermal region, and molecular dynamics simulation of the NVE ensemble is performed in the Newton region. 5) Treat the projectile model as a steel body and place it directly above the polymer composite target model. Impact the polymer composite target model with different angular velocities and linear velocities to obtain the atomic coordinate information, energy and temperature changes of the projectile and the polymer composite target model during the impact process. 6) Based on the output file, obtain the motion trajectory of all atoms and the changes in projectile velocity, displacement, kinetic energy, and resistance over time, as well as the temperature and energy changes during the impact process and the bond breaking information of the polymer composite target model; 7) Import the output file containing atomic coordinate information into the visualization software to perform visual analysis of the target model's damage behavior.

[0005] As a further improvement to the technical solution of the present invention, in step 3), in order to prevent the polymer composite material from decomposing during the relaxation process, additional bond constraints are applied to the target model of the polymer composite material.

[0006] As a further improvement to the technical solution of the present invention, the specific method of the additional bond constraint is to use the bond_style harmonic command, and gradually eliminate the constraint strength until the constraint is completely eliminated by continuously reducing the energy term of bond_coeff during the relaxation process.

[0007] As a further improvement to the technical solution of the present invention, in step 4), when performing molecular dynamics simulation of the NVT ensemble in the isothermal region, the temperature is controlled by the Nose-Hoover hot bath method to keep the system temperature constant, and heat is absorbed from the Newtonian region by adjusting the atomic velocity in the isothermal region.

[0008] As a further improvement to the technical solution of the present invention, in step 5), the specific method of setting the projectile model as a steel body is to use the fix rigid command to treat all atoms in the projectile model as a whole.

[0009] As a further improvement to the technical solution of the present invention, in step 5), simulation parameters for the impact process are set, including boundary conditions, initial temperature, and time step.

[0010] As a further improvement to the technical solution of the present invention, the target model of the polymer composite material is a target model of a polymer composite material with graphene as the upper layer and cross-linked epoxy resin as the lower layer.

[0011] As a further improvement to the technical solution of the present invention, the target model of the polymer composite material can be replaced with a target model of polymer material.

[0012] The method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics, as described in this invention, has the following advantages compared with existing technologies: 1. This invention can study the impact resistance behavior and damage mechanism of polymer composite materials at the microscopic level of molecules and atoms; 2. To make the surface of the polymer composite target model in contact with the projectile more compact and flat, a compression simulation was performed on the polymer composite target model. The compression time was determined by judging the change in height of the polymer composite target model before and after compression. 3. When performing structural optimization and relaxation on the target model under reactive force field conditions, additional bond constraints were applied to the model to prevent the decomposition of the polymer composite material; 4. The target model of the polymer composite material is divided into three regions: the boundary region, the isothermal region, and the Newtonian region. During the impact, the atoms in the boundary region remain stationary. Molecular dynamics simulations are performed using the NVT ensemble in the isothermal region, and molecular dynamics simulations are performed using the NVE ensemble in the Newtonian region. 5. This method can use molecular dynamics simulation to study the microstructure changes and damage mechanisms of polymer composite target models during projectile impact, providing preliminary theoretical predictions and scientific basis for screening, designing, and optimizing protective materials. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 A flowchart provided for an embodiment of the present invention.

[0016] Figure 2 The figure shows the changes in the polymer composite target model before and after compression, as provided in an embodiment of the present invention. As can be seen from the figure, after compression, the polymer composite target model has no voids, and its surface is denser and smoother.

[0017] Figure 3 This is a model diagram of a projectile impacting a polymer composite target model provided in an embodiment of the present invention. As can be seen from the diagram, the projectile is placed directly above the polymer composite target model, which is divided into three regions: a boundary region, an isothermal region, and a Newtonian region.

[0018] Figure 4 This figure shows the variation of projectile velocity with simulation time when projectiles impact a polymer composite target model at different velocities, as provided in an embodiment of the present invention. As can be seen from the figure, the projectile velocity continuously decreases with increasing simulation time. Projectiles with initial velocities of 10 km / s, 20 km / s, and 30 km / s eventually reach 0 km / s, 0.26 km / s, and approximately 1.3 km / s, respectively. Projectiles with initial velocities of 40, 50, and 60 km / s pass through the polymer composite target model with final velocities of 5 km / s, 13.5 km / s, and 36 km / s, respectively.

[0019] Figure 5 The graph shows the displacement of a projectile impacting a polymer composite target model at different velocities, as provided in this embodiment of the invention, as a function of simulation time. As can be seen from the graph, the distances traveled by projectiles with initial velocities of 10 km / s, 20 km / s, 30 km / s, 40 km / s, 50 km / s, and 60 km / s in the polymer composite target model are 6.8 Å, 36.0 Å, 54.6 Å, 100 Å, 113 Å, and 110 Å, respectively.

[0020] Figure 6The graph shows the variation of kinetic energy of a projectile impacting a polymer composite target model at different velocities, as provided in this embodiment of the invention, over simulation time. As can be seen from the graph, the kinetic energy of projectiles with initial velocities of 10 km / s, 20 km / s, 30 km / s, 40 km / s, 50 km / s, and 60 km / s eventually decreases to 0 Kal / mol, 8 Kal / mol, 245 Kal / mol, 3547 Kal / mol, 24628 Kal / mol, and 182206 Kal / mol, respectively.

[0021] Figure 7 This figure shows the variation of drag force experienced by a projectile impacting a polymer composite target model at different velocities, as provided in this embodiment of the invention, over simulation time. As can be seen from the figure, the drag force experienced by the projectile impacting the polymer composite target model is not the same for projectiles with different initial velocities.

[0022] Figure 8 The figures show the process changes of a projectile impacting a polymer composite target model at speeds of 10 km / s (a) and 20 km / s (b) according to embodiments of the present invention. As can be seen from the figures, the changes are not the same when projectiles with different initial speeds impact the polymer composite target model; projectiles at speeds of 10 km / s and 20 km / s remain within the polymer composite target model.

[0023] Figure 9 The figures show the process changes of a projectile impacting a polymer composite target model at speeds of 30 km / s (c) and 40 km / s (d) according to an embodiment of the present invention. As can be seen from the figures, a projectile traveling at 30 km / s will remain inside the polymer composite target model, while a projectile traveling at 40 km / s will pass through it.

[0024] Figure 10 The figures show the process changes of a projectile impacting a polymer composite target model at speeds of 50 km / s (e) and 60 km / s (f) according to embodiments of the present invention. As can be seen from the figures, projectiles traveling at 50 km / s and 60 km / s will pass through the polymer composite target model.

[0025] Figure 11 The figures show the damage to a localized polymer composite material target model when impacted by projectiles at different velocities, as provided in this embodiment of the invention. As can be seen from the figures, the higher the projectile velocity, the greater the damage to the target model. Detailed Implementation

[0026] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0028] This invention provides a specific embodiment of a method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics, comprising the following steps: 1) Use molecular modeling software to establish a projectile model and a polymer composite material target model; In this invention, the projectile model can be spherical, cylindrical or a combination of both, the projectile material can be diamond, metal or other materials, and the polymer composite material target model can be any shape such as a disc or a cube.

[0029] 2) Perform compression simulation on the target model of polymer composite material under a certain pressure, and control the length of compression simulation time by judging the change in height of the target model of polymer composite material before and after compression.

[0030] 3) Under reactive force field conditions, the target model of polymer composite material is subjected to energy minimization and structural relaxation.

[0031] 4) The relaxed polymer composite target model is divided into three regions: the boundary region, the isothermal region, and the Newton region. During the impact, the atoms in the boundary region remain fixed. Molecular dynamics simulation of the NVT ensemble is performed in the isothermal region, and molecular dynamics simulation of the NVE ensemble is performed in the Newton region.

[0032] 5) Treat the projectile model as a steel body and place it directly above the polymer composite target model. Impact the polymer composite target model with different angular velocities and linear velocities to obtain the atomic coordinate information, energy and temperature changes of the projectile and the polymer composite target model during the impact process.

[0033] 6) Based on the output file, obtain the motion trajectory of all atoms (projectile model and polymer composite target model), as well as the changes in projectile velocity, displacement, kinetic energy, and resistance over time, the temperature and energy changes during the impact, and the bond breaking information of the polymer composite target model.

[0034] 7) Import the output file containing atomic coordinate information into the visualization software to perform visual analysis of the target model's damage behavior.

[0035] In one embodiment of the present invention, in step 3), in order to prevent the polymer composite material from decomposing during the relaxation process, additional bond constraints are applied to the target model of the polymer composite material.

[0036] In another embodiment of the present invention, the specific method of the additional bond constraint is to use the bond_style harmonic command, which gradually eliminates the constraint strength until the constraint is completely eliminated by continuously reducing the energy term of bond_coeff during the relaxation process.

[0037] In one embodiment of the present invention, in step 4), when performing molecular dynamics simulation of the NVT ensemble in the isothermal region, the temperature is controlled by the Nose-Hoover hot bath method to keep the system temperature constant, and heat is absorbed from the Newtonian region by adjusting the atomic velocity in the isothermal region.

[0038] In another embodiment of the present invention, in step 5), the specific method of setting the projectile model as a steel body is to use the fix rigid command to treat all atoms in the projectile model as a whole.

[0039] In one embodiment of the present invention, in step 5), simulation parameters for the impact process are set, including boundary conditions, initial temperature, and time step. In this invention, the boundary conditions are periodic, the initial temperature is preferably 300K, and the time step is preferably 0.1fs. Then, the projectile impacts the polymer composite target model with linear velocities of 10 km / s, 20 km / s, 30 km / s, 40 km / s, 50 km / s, and 60 km / s and an angular velocity of 0°.

[0040] In another embodiment of the present invention, the polymer composite material target model is a polymer composite material target model with graphene as the upper layer and cross-linked epoxy resin (polymer material) as the lower layer. In the present invention, the polymer composite material target model can be replaced with a polymer material target model, that is, the target model contains only cross-linked epoxy resin. Of course, in the present invention, the graphene in the upper layer of the polymer composite material target model can be disposed inside the cross-linked epoxy resin or in the lower layer. Moreover, the graphene described in the present invention can be replaced with other three-dimensional molecular models, and the cross-linked epoxy resin can also be replaced with other polymer materials. Furthermore, the polymer composite material target model described in the present invention can not only be a two-layer structure, but also a three-layer or multi-layer structure of other structures.

[0041] The specific embodiments of the present invention will be described in detail below. Example

[0042] like Figure 1 As shown, a method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics includes the following steps: Step 1) Use Materials Studio, a molecular modeling software, to create a projectile model and a target model of the polymer composite material. First, use the modeling module in Materials Studio to construct three-dimensional molecular models of the projectile, cross-linked epoxy resin, and graphene, respectively. Then, use the Build Layer module to construct a target model of the polymer composite material with graphene as the upper layer and cross-linked epoxy resin as the lower layer. Use the msi2lmp program to export the target model as a data format file recognizable by LAMMPS software. The projectile is a sphere with a diameter of 10 Å, and the target model is 47 Å × 47 Å × 68 Å in size. To eliminate boundary effects, the side length of the target model must be greater than four times the diameter of the projectile.

[0043] Step 2) To make the surface of the polymer composite target model denser and smoother, LAMMPS software was used to perform a compression simulation of the polymer composite target model under a pressure of 120 MPa. By judging the change in height of the polymer composite target model before and after compression, the duration of the compression simulation was controlled. The structural changes of the target model before and after compression are as follows: Figure 2 As shown.

[0044] Step 3) In order to eliminate unreasonable structures in the target model of polymer composite materials, the model is subjected to energy minimization and structural relaxation under the reaction force field. In order to prevent the polymer composite material from decomposing during the relaxation process, the bond_style harmonic command is used to apply additional bond constraints to the model. By continuously reducing the energy term of bond_coeff during the relaxation process, the bond constraint strength is gradually eliminated until the constraints are completely eliminated.

[0045] Step 4) Divide the relaxed polymer composite target model into three regions: the boundary region, the isothermal region, and the Newtonian region. In the boundary region, atoms remain fixed at their equilibrium positions to simulate the boundary and reduce boundary effects. In the isothermal region, molecular dynamics simulations of the NVT ensemble are performed. The temperature is controlled using the Nose-Hoover thermobath method to maintain a constant system temperature, and heat is absorbed from the Newtonian region by adjusting the atomic velocities in the isothermal region. Molecular dynamics simulations of the NVE ensemble are performed in the Newtonian region.

[0046] Step 5) Treat the projectile model as a rigid body and place it directly above the polymer composite target model to establish a model of the projectile impacting the polymer composite material, such as... Figure 3As shown, the `fix rigid` command is used to treat all atoms in the projectile model as a whole for impact simulation. Simulation parameters during the impact process are set, including boundary conditions, initial temperature, and time step. The boundary conditions are periodic, the initial temperature is 300K, and the time step is 0.1fs. Then, the projectile impacts the polymer composite target model at linear velocities of 10 km / s, 20 km / s, 30 km / s, 40 km / s, 50 km / s, and 60 km / s, and an angular velocity of 0°. Output files are obtained showing the atomic coordinates, energy, and temperature changes of the projectile and the polymer composite target model at different impact velocities.

[0047] Step 6) Obtain the trajectory of all atoms and the velocity of the projectile during the impact process from the output file (e.g., Figure 4 As shown), displacement (as shown) Figure 5 As shown), kinetic energy (such as) Figure 6 As shown), the resistance (such as) Figure 7 As shown in the figure, the changes in temperature and energy over time.

[0048] Step 7) Import the output file containing atomic coordinate information into the visualization software Ovito to analyze the process changes of the polymer composite target model under different velocities, such as... Figure 8-10 As shown; information on broken bonds in localized polymer composite materials, such as... Figure 11 As shown.

[0049] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics, characterized in that, Includes the following steps: 1) Use molecular modeling software to create projectile models and target models of polymer composite materials; 2) Perform compression simulation on the target model of polymer composite material under a certain pressure, and control the length of compression simulation time by judging the change in height of the target model of polymer composite material before and after compression; 3) Under the reaction force field conditions, the target model of the polymer composite material is subjected to energy minimization and structural relaxation; in step 3), in order to prevent the polymer composite material from decomposing during the relaxation process, the target model of the polymer composite material is subjected to additional bond constraints; the specific method of the additional bond constraints is to use the bond_style harmonic command, and gradually eliminate the constraint strength until the constraint is completely eliminated by continuously reducing the energy term of bond_coeff during the relaxation process. 4) The relaxed polymer composite target model is divided into three regions: boundary region, isothermal region, and Newton region. During the impact, the atoms in the boundary region remain fixed. Molecular dynamics simulation of the NVT ensemble is performed in the isothermal region, and molecular dynamics simulation of the NVE ensemble is performed in the Newton region. 5) Treat the projectile model as a rigid body and place it directly above the polymer composite target model. Impact the polymer composite target model with different angular velocities and linear velocities to obtain the atomic coordinate information, energy and temperature changes of the projectile and the polymer composite target model during the impact process. 6) Based on the output file, obtain the motion trajectory of all atoms and the changes in projectile velocity, displacement, kinetic energy, and resistance over time, as well as the temperature and energy changes during the impact process and the bond breaking information of the polymer composite target model; 7) Import the output file containing atomic coordinate information into the visualization software to perform visual analysis of the target model's damage behavior.

2. The method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics according to claim 1, characterized in that, In step 4), when performing molecular dynamics simulations of the NVT ensemble in the isothermal region, the temperature is controlled using the Nose-Hoover hot bath method to maintain a constant system temperature, and heat is absorbed from the Newtonian region by adjusting the atomic velocities in the isothermal region.

3. The method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics according to claim 1, characterized in that, In step 5), the specific method for treating the projectile model as a rigid body is to use the fix rigid command to treat all atoms in the projectile model as a whole.

4. The method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics according to claim 1, characterized in that, In step 5), simulation parameters for the impact process are set, including boundary conditions, initial temperature, and time step.

5. The method for simulating the impact resistance behavior of polymer composite materials based on molecular dynamics according to claim 1, characterized in that, The target model of the polymer composite material can be replaced with a target model of polymer materials.

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