A design method for impact-resistant bionic materials based on molecular dynamics

Abstract

The present invention provides a design method for impact-resistant bionic materials based on molecular dynamics, comprising the following steps: preliminarily determining the range of the number of plies of the Brigan film; determining the design criteria of the helical angle of the Brigan film to select a suitable Brigan structural material and potential function; constructing a target model of projectile impacting the Brigan film, energy minimization and relaxation target model until the model reaches an equilibrium state; setting the projectile as a rigid body under the NVE ensemble, giving the projectile impact velocity ballistic impact to the Brigan film; evaluating the impact resistance of the Brigan film according to the ballistic limit velocity and the penetration energy index, visually analyzing the trajectory file, and selecting a suitable helical angle parameter range; changing the number of plies of the Brigan film to obtain the final Brigan configuration. The present invention uses molecular dynamics to reveal the microscopic mechanism of dynamic impact of Brigan bionic materials, improves the design level of nano-scale impact protection materials, shortens the development cycle of new materials and reduces costs.

Description

Technical Field

[0001] The invention belongs to the field of bionic impact protection, and in particular relates to a design method of impact-resistant bionic materials based on molecular dynamics. Background Art

[0002] In nature, after a long period of natural selection, existing biomaterials have evolved various sophisticated multi-level and multi-scale structures to adapt to the harsh living environment, thus having extraordinary mechanical properties. Brigan structures are widely found in biological tissues such as mantis shrimp maxillofacials, crab exoskeletons, and scorpion claws. Brigan structures are composed of spiral fiber layered microstructures, and their special structural characteristics give them high strength, high impact resistance, and high damage resistance. Therefore, impact-resistant bionic materials developed based on Brigan structures have broad application prospects in advanced fields such as automobiles, bulletproof vests, and aerospace.

[0003] On a macroscopic scale, traditional composite materials can reduce the interlaminar shear stress of layered composite materials by introducing spiral ply through the bionic Brigan structure, increase the damage area within the layer to diffuse cracks, thereby improving the fracture toughness and impact resistance of the laminate, and reducing the degree of catastrophic damage caused by brittle fracture. However, traditional Brigan bionic composite materials are limited to macroscopic scale research and parameter design, and they cannot achieve nanoscale enhanced mechanical properties similar to natural biomaterials. Therefore, it is crucial to understand the relationship between Brigan microstructure and impact resistance on a microscopic scale, so as to design a new type of nanoscale impact-resistant bionic material film.

[0004] At present, experimental and continuum calculation methods are insufficient in revealing the relationship between the microstructure and performance of Brigans. It is urgent to use molecular dynamics (MD) to simulate the dynamic impact of nanoscale bionic materials and conduct research on the impact resistance and mechanism of Brigans structural configuration parameter regulation, so as to provide new perspectives and insights for the design of superior protective materials. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for designing impact-resistant bionic materials based on molecular dynamics.

[0006] The present invention is implemented in this way: a method for designing impact-resistant bionic materials based on molecular dynamics, comprising the following steps:

[0007] S1, based on the actual use and performance requirements of the Brigan nanofilm, preliminarily determine the range of the number of layers of the Brigan film;

[0008] S2, determining a design criterion for the helical angle of the Brigan film, wherein the design criterion for the helical angle of the Brigan film adopts an incremental helical angle configuration and / or an exponential helical angle configuration;

[0009] S3, select appropriate Brigan structure materials and potential functions;

[0010] S4, using molecular dynamics modeling software to build a target model of projectile impacting Brigan film, energy minimization and relaxation of the target model until the model reaches equilibrium;

[0011] S5, under the NVE ensemble, the projectile is set as a rigid body, and the projectile is given a ballistic impact velocity to impact the Brigan membrane;

[0012] S6, evaluate the impact resistance of the Brigan film according to the ballistic limit velocity and penetration energy index, use visualization software to visualize the trajectory file, and select the appropriate range of helix angle parameters; change the number of Brigan film layers, return to continue executing S2~S6, and finally determine the number of layers and helix angle parameters that meet both the actual process thickness requirements and the ballistic limit velocity and penetration energy requirements to obtain the final Brigan configuration.

[0013] Further, in S4, the target model of the projectile impacting the Brigan film is constructed using molecular dynamics modeling software, and the energy is minimized and the Brigan model is relaxed until the model reaches an equilibrium state, specifically:

[0014] S41, the target model of the Brigan film constructed using molecular dynamics modeling software, and the conjugate gradient method was used to energy minimize the Brigan film and relax the Brigan film to reach equilibrium;

[0015] S42, dividing the Brigan film into two parts: a circular central region and a boundary region, and setting the velocity and force of the atoms in the boundary region to zero to simulate the fixed support boundary condition;

[0016] S43, long-term relaxation of the film with fixed boundary regions until equilibrium;

[0017] S44, after combining the projectile and the Brigan membrane, the projectile is fixed just above the membrane, the atoms in the fixed area continue to be fixed, and the entire combined model is relaxed until it reaches equilibrium.

[0018] Furthermore, when constructing the target model, the projectile of the target model is located directly above the film and is regarded as a rigid body. The non-bonded interaction between the projectile and the cellulose nanocrystal Brigan film is described as the Lennard-Jones potential function:

[0019]

[0020] Where: r is the distance between coarse particles, r c is the cutoff radius, the interatomic distance at which the potential energy is zero Potential well depth ε LJ =20kcal / mol.

[0021] Further, in S5, under the NVE ensemble, the projectile is set as a rigid body, and the projectile is given a ballistic impact velocity to impact the Brigan membrane, specifically:

[0022] S51, under the NVE ensemble, the projectile is set as a rigid body, and the NVE ensemble is used to simulate the adiabatic process of the projectile impact, the projectile impact direction adopts non-periodic boundary conditions, and the other two sides adopt periodic boundaries;

[0023] S52, assigning multiple groups of impact velocities of the projectile to impact the Brigan film;

[0024] S53, record the changes of each group of projectile velocity, kinetic energy, temperature field and stress field of the film during the impact process to evaluate the ballistic performance of the Brigan film.

[0025] Furthermore, in S2, the design criteria for the helix angle of the Brigan film adopt an increasing helix angle configuration and an exponential helix angle configuration respectively; the design method may also include: in S6, according to the specific ballistic limit velocity and specific penetration energy indicators, comparing the impact resistance of the Brigan film constructed according to the increasing helix angle configuration and the Brigan film constructed according to the exponential helix angle configuration, and screening out the Brigan configuration with better impact resistance.

[0026] Beneficial effects:

[0027] The present invention provides a method for designing impact-resistant bionic materials based on molecular dynamics. Molecular dynamics is used to reveal the microscopic mechanism of dynamic impact of Brigon bionic materials, which makes up for the shortcomings of experimental and continuum calculation methods in revealing the relationship between Brigon microstructure and performance, so as to improve the design level of nano-scale impact protection materials, significantly shorten the development cycle of new materials and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a flow chart of a method for designing impact-resistant bionic materials based on molecular dynamics according to the present invention;

[0030] Figure 2 Schematic diagram of the Brigan unit cell structure of the present invention, wherein α represents the helical angle, D represents the pitch, and N represents the total number of layers;

[0031] Figure 3The mapping scheme of the coarse-grained model of cellulose nanocrystals shows the mapping relationship between the all-atom model of cellulose nanocrystals (left) and the corresponding coarse-grained model (right);

[0032] Figure 4 Schematic diagram of the ballistic impact simulation of the coarse-grained model of the incremental Brigan configuration, where 1 represents the projectile, V represents the impact velocity, and α represents the helix angle. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] To facilitate understanding of the present invention, the following first describes the relevant concepts involved in the present invention:

[0035] Brigan is a general term for spatial spiral stacked layered structures. The high impact resistance of the microscopic tissue characteristics of mantis shrimp maxillopods and other biological materials is directly related to the Brigan periodic structure inside them. The Brigan structure is mainly a spatial spiral configuration composed of orderly arranged chitin. The specific characteristics of the Brigan configuration are: 1) In a plane, all chitin fibers are parallel to each other. In the thickness direction outside the plane, all layers of film layers are stacked on each other, and there is a spiral angle between adjacent layers; 2) Because the periodic region configuration has periodic symmetry, the last film layer completes a 180° rotation relative to the first film layer, and this group of film layers can be regarded as a group of Brigan unit cell structures. The schematic diagram of the Brigan unit cell structure is shown in the figure. Figure 2 As shown in the figure, α represents the helix angle, D represents the pitch, and N represents the total number of layers in the unit cell structure. On this basis, the Brigan film configuration can be described by two typical characteristic parameters: the number of layers and the helix angle.

[0036] like Figure 1 As shown, an embodiment of the present invention provides a method for designing impact-resistant bionic materials based on molecular dynamics, comprising the following steps:

[0037] S1, according to the actual use and performance requirements of the Burigang nanofilm, determine the range of the number of ply layers of the Burigang film. For example, according to the actual use and performance requirements of the Burigang nanofilm, the film thickness range is 30 nanometers to 100 nanometers, the thickness of each layer is 4 nanometers, and the number of ply layers ranges from N=8 to 25. Therefore, the number of ply layers of the Burigang film can be tentatively determined to be N=8.

[0038] S2, determining a design criterion for the helix angle of the Brigan film, wherein the design criterion for the helix angle of the Brigan film adopts an increasing helix angle configuration and / or an exponential helix angle configuration.

[0039] Among them, the incremental helix angle change satisfies [θ1 / θ2 / ... / θ i=θ i-1 +α(i-1)] rule, the first layer laying angle θ1 = 0°, the i-th layer laying angle relative to the (i-1)th layer increment is a fixed helix angle α. The exponential helix angle change satisfies [θ1 / θ2 / ... / θ i =β i ] rule, the first layer laying angle θ1 = 0°, the second layer laying angle θ2 = β°, the i-th layer laying angle is β times the (i-1)-th layer, and the helix angle changes with an exponential β growth. In this embodiment, the required helix angle configuration can be selected according to actual needs.

[0040] S3, select appropriate Brigan structure materials and potential functions.

[0041] Brigan structural materials mainly select many biologically derived nanomaterials, which self-assemble into spiral films with adjustable spiral angles. For example, cellulose nanocrystal materials can be selected, and the mapping scheme of the coarse-grained model of cellulose nanocrystals, such as Figure 3 As shown in Figure 1, each coarse-grained model represents three repeating units on the surface of the 36-chain structure (110) of the all-atom model. At the same time, the potential function form and parameters of the coarse-grained model of cellulose nanocrystals are shown in Table 1. The potential function of the coarse-grained model contains three parts: bond length interaction, bond angle interaction and non-bond interaction, which are used to describe the interaction between coarse particles.

[0042] Table 1 Potential function form and parameters of cellulose nanocrystal coarse-grained model

[0043]

[0044] At the same time, the non-bonded interaction between the projectile and the cellulose nanocrystal Brigan film is described as the Lennard-Jones potential function:

[0045]

[0046] Where: r is the distance between coarse particles, r c is the cutoff radius, the interatomic distance at which the potential energy is zero Potential well depth ε LJ =20kcal / mol.

[0047] S4, using molecular dynamics modeling software to build a target model of projectile impacting Brigan film, energy minimization and relaxation of the target model until the model reaches equilibrium.

[0048] For step S4, the following steps may be specifically adopted:

[0049] S41, the target model of the Brigan film was constructed using molecular dynamics modeling software, and the conjugate gradient method was used to energy minimize the Brigan film and relax the Brigan film to reach equilibrium.

[0050] In this embodiment, when constructing the target model, Figure 4 As shown in the figure, the projectile of the target model is located directly above the film and is regarded as a rigid body. The projectile adopts a diamond cubic lattice structure and its density is 3.48g / cm 3 In this step, the molecular structure is optimized by conjugate gradient energy minimization, and long relaxation is used to release the internal stress of the model and allow the Brigon film to reach equilibrium.

[0051] S42, divide the Brigan film into two parts: a circular central area and a boundary area. The central area is the impacted part, and the velocity and force of the atoms in the boundary area are set to zero to simulate the fixed boundary condition.

[0052] S43, long-term relaxation of the film with fixed boundary regions until equilibrium.

[0053] S44, after combining the projectile and the Brigan membrane, the projectile is fixed just above the membrane, the atoms in the fixed area continue to be fixed, and the entire combined model is relaxed until it reaches equilibrium.

[0054] S5, under the NVE ensemble, the projectile is set as a rigid body and the projectile is given a ballistic impact velocity to impact the Brigan membrane.

[0055] In this embodiment, step S5 may specifically adopt the following steps:

[0056] S51, under the NVE ensemble, the projectile is set as a rigid body, and the NVE ensemble is used to simulate the adiabatic process of the projectile impact, the projectile impact direction adopts non-periodic boundary conditions, and the other two sides adopt periodic boundaries;

[0057] S52, assigning multiple groups of impact velocities of the projectile to impact the Brigan film;

[0058] S53, record the changes of each group of projectile velocity, kinetic energy, temperature field and stress field of the film during the impact process to evaluate the ballistic performance of the Brigan film.

[0059] By calculating the projectile velocity and kinetic energy, the corresponding parameters are provided for the subsequent calculation of the ballistic limit velocity and specific penetration energy. The changes in the temperature field and stress field of the film during the projectile impact are monitored to qualitatively analyze its stress propagation process and perforation behavior.

[0060] S6, evaluate the impact resistance of the Brigan film according to the ballistic limit velocity and penetration energy index, use visualization software to visualize the trajectory file, and select the appropriate range of helix angle parameters; change the number of Brigan film layers, return to execute S2~S6, and finally determine the minimum number of layers and helix angle parameters that meet both the actual process thickness requirements and the ballistic limit velocity and penetration energy requirements to obtain the final Brigan configuration.

[0061] In this embodiment, the ballistic limit velocity (V 50 ) and penetration energy (ΔE k ) are two key indicators for evaluating the impact resistance of films. Ballistic limit velocity (V 50 ) represents the incident velocity when the probability of the projectile penetrating the film is 50%, and the penetration energy (ΔE k ) refers to the kinetic energy lost in the process of projectile penetrating the film. For the Brigan film configuration with different densities, the ballistic limit velocity (V 50 / ρ, ρ is the density of the Brigan film) and specific penetration energy (ΔE k / ρ, ρ is the Brigan film density) to quantify the impact resistance.

[0062] Assume that the film needs to satisfy the ballistic limit velocity V 50 / ρ≥200(m·cm 3 / g·s), specific penetration energy ΔE k / ρ≥260(fJ·cm 3 / g) performance requirements, firstly, the helix angle parameter analysis is performed on the Brigan film with the number of plies N = 8. If the requirements of the specific ballistic limit velocity and the specific penetration energy are met, the design variable parameter range of the helix angle α is determined; if the requirements of the indicators are not met, within the value range of the number of plies N = 8 to 25 determined in S1, the number of plies is appropriately increased and adjusted, and the helix angle parameter analysis is performed, and the process returns to execute S2 to S6 until the minimum number of plies that meet the actual process thickness requirements and the impact resistance requirements and the corresponding helix angle design variable parameters are selected.

[0063] In this embodiment, the helical angle design criteria of the Brigan film in S2 respectively adopt an incremental helical angle configuration and an exponential helical angle configuration; the design method may also include: in S6, according to the ballistic limit velocity and the specific penetration energy index, the impact resistance of the Brigan film constructed according to the incremental helical angle configuration and the Brigan film constructed according to the exponential helical angle configuration are compared, and the Brigan configuration with better impact resistance is selected. For example, when it is determined that the minimum number of plies that meet the impact resistance requirements is N=12, the incremental helical angle configuration is first used to construct the target model of the Brigan film, and the helical angle parameter range I that meets the ballistic limit velocity and the penetration energy index is 18°~45°, wherein the ballistic limit velocity V50 / ρ≥200(m·cm 3 / g·s), specific penetration energy ΔE k / ρ≥260(fJ·cm 3 / g), it can be determined that the impact resistance of the Burigang film is relatively good within the range of the helix angle parameter, so the helix angle parameter is selected within this range. Subsequently, under the premise that the number of layers of the incremental and exponential helix angle configurations is the same, the exponential helix angle configuration is selected to construct the target model of the Burigang film, and the exponential helix angle β is selected to obtain the corresponding helix angle parameter range II. On this basis, the impact resistance of the Burigang film constructed according to the incremental helix angle configuration and the Burigang film constructed according to the exponential helix angle configuration are compared, and the helix angle configuration with the best impact resistance is screened out.

[0064] The present invention provides a method for designing impact-resistant bionic materials based on molecular dynamics. Molecular dynamics is used to reveal the microscopic mechanism of dynamic impact of Brigon bionic materials, which makes up for the shortcomings of experimental and continuum calculation methods in revealing the relationship between Brigon microstructure and performance, so as to improve the design level of nano-scale impact protection materials, significantly shorten the development cycle of new materials and reduce costs.

[0065] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment that includes a series of elements is inherent to the elements, or also includes elements inherent to these processes, methods, articles or equipment. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the existence of other identical elements in the process, method, article or equipment that includes the elements.

[0066] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for designing impact-resistant bionic materials based on molecular dynamics, characterized in that: The following steps are involved: S1, based on the actual use and performance requirements of the Brigan nanofilm, preliminarily determine the range of the number of layers of the Brigan film; S2, determining a design criterion for the helical angle of the Brigan film, wherein the design criterion for the helical angle of the Brigan film adopts an incremental helical angle configuration and / or an exponential helical angle configuration; S3, select appropriate Brigan structure materials and potential functions; S4, using molecular dynamics modeling software to build a target model of projectile impacting Brigan film, energy minimization and relaxation of the target model until the model reaches equilibrium; S5, under the NVE ensemble, the projectile is set as a rigid body, and the projectile is given a ballistic impact velocity to impact the Brigan membrane; S6, evaluate the impact resistance of the Brigan film according to the ballistic limit velocity and penetration energy indicators, use visualization software to visualize the trajectory file and select the appropriate helix angle parameter range; Change the number of Brigan film layers, return to continue to execute S2~S6, and finally determine the number of layers and helix angle parameters that meet both the actual process thickness requirements and the requirements of the ballistic limit velocity and the specific penetration energy index, so as to obtain the final Brigan configuration; In S4, the target model of the projectile impacting the Brigan film is constructed using molecular dynamics modeling software, and the energy is minimized and the Brigan model is relaxed until the model reaches an equilibrium state, specifically: S41, the target model of the Brigan film constructed using molecular dynamics modeling software, and the conjugate gradient method was used to energy minimize the Brigan film and relax the Brigan film to reach equilibrium; S42, dividing the Brigan film into two parts: a circular central area and a boundary area, and setting the velocity and force of the atoms in the boundary area to zero to simulate the fixed support boundary condition; S43, long-term relaxation of the film with fixed boundary regions until equilibrium; S44, after combining the projectile and the Brigan film, the projectile is fixed just above the film, the atoms in the fixed area continue to be fixed, and the entire combined model is relaxed until the equilibrium state; When constructing the target model, the projectile of the target model is located directly above the film and is regarded as a rigid body. The non-bonded interaction between the projectile and the cellulose nanocrystal Brigan film is described as the Lennard-Jones potential function: , where: r is the distance between coarse particles, is the cutoff radius, the interatomic distance at which the potential energy is zero , potential well depth .

2. The method for designing impact-resistant bionic materials based on molecular dynamics according to claim 1, characterized in that: In S5, under the NVE ensemble, the projectile is set as a rigid body, and the projectile is given a ballistic impact velocity to impact the Brigan membrane, specifically: S51, under the NVE ensemble, the projectile is set as a rigid body, and the NVE ensemble is used to simulate the adiabatic process of the projectile impact, the projectile impact direction adopts non-periodic boundary conditions, and the other two sides adopt periodic boundaries; S52, assigning multiple groups of impact velocities of the projectile to impact the Brigan film; S53, record the changes of each group of projectile velocity, kinetic energy, temperature field and stress field of the film during the impact process to evaluate the ballistic performance of the Brigan film.

3. The method for designing impact-resistant bionic materials based on molecular dynamics according to claim 1, characterized in that: In S2, the helix angle design criteria of the Burigang film adopt an incremental helix angle configuration and an exponential helix angle configuration respectively; the design method may also include: in S6, according to the specific ballistic limit velocity and specific penetration energy indicators, comparing the impact resistance of the Burigang film constructed according to the incremental helix angle configuration and the Burigang film constructed according to the exponential helix angle configuration, and screening out the Burigang configuration with better impact resistance.

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