Chiral concave octagonal superstructure with high specific energy absorption and indentation resistance

Abstract

The application discloses a chiral concave octagonal superstructure with high specific energy absorption and indentation resistance, which is a grid structure formed by repeatedly arraying and stacking a plurality of cell structures; the cell structure is obtained by twice rotating array and three times mirror imaging of a two-dimensional negative Poisson's ratio structure unit; the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit is a concave octagon, and different scale chiral concave negative Poisson's ratio grid structures can be obtained by arraying the cell structure; the structure simultaneously has chiral characteristics and a concave octagonal structure in the configuration of the cell; after the mirror imaging operation, new concave polygonal structures are formed between the cells, the overall negative Poisson's ratio effect of the grid structure is enhanced, and the rotation of the chiral structure around the node during the stress process of the grid structure further promotes the enhancement of the negative Poisson's ratio effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mechanical metamaterials, and particularly relates to a chiral concave octagonal superstructure with high specific energy absorption and indentation resistance. BACKGROUND

[0002] Mechanical metamaterials are a technical field that has been widely studied in recent years. When traditional materials cannot meet the rapid development of scientific and technological level, more and more attention is paid to the design of metamaterials. Mechanical metamaterials use traditional materials as matrix materials, but can break through the performance of traditional materials in the fields of mechanics, acoustics, optics and the like. The design concept of mechanical metamaterials is to optimize the configuration of the cell structure inside the material to achieve super mechanical performance. The performance of the mechanical metamaterials mainly depends on the artificially designed cell structure.

[0003] At present, the research on negative Poisson's ratio superstructure is mainly focused on single chiral structure, concave polygon structure and rotating rigid body structure, and most of the research is on two-dimensional grid structure, and there is little research on three-dimensional structure and combined structure. Most of the structures only have novelty in structure, and do not have sufficient performance improvement.

[0004] The existing chiral negative Poisson's ratio grid metamaterial has a complex connection between chiral units, which is easy to form small-angle hinged connection, and the connection is prone to failure during the stress process. In addition, there is little research on large deformation, and most of the research is concentrated in the linear stage of small deformation. However, the mechanical properties under large deformation are more important. The large deformation condition involves many important characteristics such as structural failure and energy absorption performance.

[0005] A high-strength chiral compression-torsion superstructure material (CN202110079584) is proposed. The cell structure belongs to a circular node chiral structure, which does not have a negative Poisson's ratio effect during the stress deformation process. In the process of converting the structure into a three-dimensional structure, the cell structure can only be arranged on the six surfaces of the cubic structure, and the internal structure is hollow. The porosity of the overall grid structure is large, and the equivalent density is small, so the equivalent elastic modulus of the overall structure is very different from that of the matrix material. In the description of the drawings Figures 1 to 3In the conversion process of each corner point, 3 rods are connected at a small angle, the manufacturability of the structure is not strong, and the connection is easy to tear and deform during the stress process of the structure, which leads to the rapid yielding of the entire grid structure. The chiral concave negative Poisson's ratio structure proposed in the application can rotate the planar chiral concave octagonal structure in XYZ three directions to form a unit with higher strength, smaller porosity, larger equivalent density, and smaller difference between the equivalent elastic modulus and the elastic modulus of the base material. At the same time, the circular node proposed above is replaced by the concave octagonal node, and the concave octagonal structure itself has a negative Poisson's ratio effect, so the negative Poisson's ratio effect of the overall grid structure is enhanced, and the strength and indentation resistance of the structure are stronger. At the same time, the connection between the cells and the cells is the connection between the parallel rod sections, the connection method is simple, the manufacturability is stronger, and the practicability is stronger. SUMMARY

[0006] In view of the above problems, the purpose of the application is to provide a chiral concave polygonal negative Poisson's ratio superstructure material with high specific energy absorption and high indentation resistance, which has good reliability and stability. The structure shows obvious negative Poisson's ratio effect during deformation, and the deformation is stable, the stress platform stage is smooth, and the time occupied by the stage in the whole deformation stage is longer, which reflects that the superstructure material has high energy absorption efficiency during impact and the surface of the superstructure material is more difficult to be crushed. It has good application prospect in the manufacture of equipment materials in the fields of military industry, automobile, aerospace, etc.

[0007] The application is realized at least by one of the following technical solutions.

[0008] A chiral concave octagonal superstructure with high specific energy absorption and indentation resistance is formed by a grid structure repeatedly arrayed and stacked by a plurality of cell structures; the cell structure is obtained by twice rotating array and three times mirror image of a two-dimensional negative Poisson's ratio structure unit.

[0009] Further, the negative Poisson's ratio structure unit is a two-dimensional chiral concave octagonal negative Poisson's ratio structure unit.

[0010] Further, the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit is vertically and horizontally rotated by 90 degrees to obtain a three-dimensional chiral concave node unit.

[0011] Further, the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit is a concave octagon, which includes a concave octagonal structure formed by eight concave rods and four rods vertically distributed along the corner points as a support structure for cell connection.

[0012] Further, the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit is a concave octagon, and the size parameters of the concave octagon include: support rod length L1, concave rod length L2, support rod width t1, concave rod width t, concave angle θ, support rod and concave rod interface, 1 = tsinθ, wherein 45° < θ ≤ 90°.

[0013] Further, the negative Poisson's ratio structure unit is prepared by using a 3D printing technology, and the printing material is selected from elastic and ductile materials, and the grid structure is cleaned and dried after printing.

[0014] Further, the material includes TPU and ABS.

[0015] Further, when the negative Poisson's ratio structure unit is prepared by using a light-cured 3D printing additive manufacturing, a three-dimensional modeling software is used to model according to the cell structure parameter drawing, the established model is sliced by a slicing software and then imported into equipment for printing, and the grid structure is cleaned and dried after printing.

[0016] Further, the printing material is selected from ATPU95A.

[0017] Further, the cell structure is arranged in different scales to obtain negative Poisson's ratio grid structures of different scales.

[0018] Compared with the prior art, the beneficial effects of the present application are:

[0019] The present application can obtain a chiral concave negative Poisson's ratio grid structure of different scales by arranging dry cell structures, and the structure has chiral characteristics and a concave octagonal structure at the same time, and after mirror image operation, new concave polygon structures are formed between cells, which can enhance the overall negative Poisson's ratio effect of the grid structure, and the rotation of the chiral structure around the node during the stress process of the grid structure can further promote the enhancement of the negative Poisson's ratio effect. The design of the structure parameters of the chiral concave cell can obtain a negative Poisson's ratio superstructure material with large indentation resistance, high strength and excellent energy absorption performance.

[0020] The present application is an energy absorption superstructure material, which can absorb the energy brought by impact and has high energy absorption; the parameterized model of the structure can achieve optimal energy absorption effect; the impact surface or impact point can have strong indentation resistance to prevent being crushed.

[0021] The application is an energy-absorbing superstructure material, in the structural design process, a series of array and mirror image operations are carried out on the two-dimensional chiral concave octagonal negative Poisson's ratio structural unit, these processes make the units and units can be interlocked, no rod staggered overlap phenomenon occurs, and no multi-rod hinged situation occurs, the unit and unit connection is not easy to fail in the deformation process, and the space position between the units is more compact, which shows that the overall relative density is larger, and the mechanical properties such as elastic modulus are better.

[0022] The application is an energy-absorbing superstructure material, in the transformation process from the two-dimensional chiral concave octagonal negative Poisson's ratio structural unit to the three-dimensional chiral concave octagonal negative Poisson's ratio grid structure, the connection between the units is smooth, which is the cross-section docking between the parallel rods, and the processing is easier in actual application.

[0023] The high specific energy-absorbing chiral concave octagonal negative Poisson's ratio superstructure material of the application shows obvious negative Poisson's ratio effect in the deformation process, and the deformation is relatively stable, the stress platform stage is smooth, and the stage occupies a longer time in the whole deformation stage, which reflects that the superstructure material has high energy absorption efficiency in the process of being impacted, and the surface of the superstructure material is more difficult to be crushed. It has good application prospect in the equipment manufacturing materials in the fields of military industry, automobile, aerospace and the like. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a two-dimensional chiral concave octagonal negative Poisson's ratio structural unit structure diagram of the embodiment;

[0025] Figure 2 It is a three-dimensional chiral concave octagonal negative Poisson's ratio structural unit structure diagram of the embodiment;

[0026] Figure 3 It is a front view of the chiral concave octagonal negative Poisson's ratio structural unit structure of the embodiment;

[0027] Figure 4 It is an axonometric drawing of the grid structure obtained by arraying the unit structure of the embodiment for many times;

[0028] Figure 5 It is a simulation diagram of the grid structure under stress of the embodiment;

[0029] Figure 6 It is a unit structure diagram of the grid structure of the embodiment;

[0030] Figure 7 It is a simulation diagram of the grid structure under stress of the embodiment; Figure 4 It is an equivalent stress-strain relationship curve obtained by impact simulation of the embodiment. DETAILED DESCRIPTION

[0031] For the person skilled in the art to better understand the present application, the following will be further described in detail in combination with the drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The principles and characteristics of the present application are described below in combination with the drawings. The examples are only used to explain the present application, not to limit the scope of the present application.

[0032] As shown in Figures 1 to 4 , a chiral concave octagonal superstructure with high specific energy absorption and indentation resistance is formed by a grid structure stacked by a plurality of unit structures arranged repeatedly; the unit structure is obtained by twice rotating and three times mirroring the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit.

[0033] As a preferred embodiment, the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit is vertically and horizontally rotated by 90 degrees to obtain a three-dimensional chiral concave node unit.

[0034] As a preferred embodiment, the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit is a concave octagon, including a concave octagonal structure formed by eight concave rods and four rods vertically distributed along the corner points as the support structure for connecting the unit, the in-plane concave octagon is rotated twice and then mirrored three times to obtain the unit structure, and the unit structure is arranged in different scales to obtain negative Poisson's ratio grid structures (energy absorption superstructures) of different scales, as shown in Figure 4 , which is a 2x2 scale grid structure, and the entire energy absorption superstructure is made of plastic material.

[0035] As a preferred embodiment, the design parameters of the two-dimensional chiral concave octagonal negative Poisson's ratio structure include five design parameters, as shown in Figure 1 , in order to ensure the interference between the unit rods and control the overall size of the two-dimensional chiral concave octagonal negative Poisson's ratio structure to be 30x30mm, the support rod length L1 is in the range of 4-20mm, the concave rod length L2 is in the range of 4-20mm, the support rod width t1 is in the range of 2-6mm, the concave angle θ is in the range of 50°-90°, and the thickness b of all rods is in the range of 2-6mm.

[0036] As shown in Figure 1As shown, the size parameters of the concave octagon include: support rod length L1, concave rod length L2, support rod width t1, concave rod width t, concave angle θ, support rod and concave rod interface, 1 = tsinθ, wherein 45° < θ ≤ 90°. Under the action of external force, the concave rod will first bend and deform due to being a diagonal rod, and at the same time, under the action of the support rod, it will rotate, which will enhance the overall negative Poisson's ratio effect of the structure. The specific energy absorption and Poisson's ratio can be regulated by optimizing the design parameters of the structure.

[0037] The cell structure obtained by rotating the two-dimensional negative Poisson's ratio structure unit twice and mirroring it three times, wherein the two-dimensional negative Poisson's ratio structure unit after being rotated twice forms three two-dimensional chiral concave octagonal negative Poisson's ratio structure units, that is, constitutes a three-dimensional chiral concave octagonal negative Poisson's ratio structure unit as shown in the figure. Figure 2 The cell structure obtained by mirroring the three-dimensional chiral concave octagonal negative Poisson's ratio structure unit three times obtains eight three-dimensional chiral concave octagonal negative Poisson's ratio structure units, that is, constitutes a chiral concave octagonal negative Poisson's ratio structure cell as shown in the figure. Figure 3 、 Figure 6 The chiral concave octagonal negative Poisson's ratio structure cell.

[0038] A three-dimensional chiral concave octagonal negative Poisson's ratio structure unit is composed of 36 rods, and the connecting rods between the cell structures are a total of 288. An array of a chiral concave octagonal negative Poisson's ratio structure cell can obtain a chiral concave negative Poisson's ratio grid structure of different scales. The structure has chiral characteristics and a concave octagonal structure at the same time. After mirroring, the cells and cells will form new concave polygonal structures, which will enhance the overall negative Poisson's ratio effect of the grid structure. At the same time, the rotation of the chiral structure around the node during the stress process of the grid structure will further promote the enhancement of the negative Poisson's ratio effect. Designing the structural parameters of the chiral concave cell can obtain a negative Poisson's ratio superstructure material with large indentation resistance, high strength, and excellent energy absorption performance.

[0039] The preparation of the two-dimensional chiral concave octagonal negative Poisson's ratio structure unit adopts a 3D printing technology. In order to be practical for engineering applications, materials with good elasticity and toughness should be selected. In order to obtain better energy absorption efficiency in the environment that needs to withstand large mass impact, metal materials can be selected as the base material.

[0040] As a preferred embodiment, the material includes TPU, ABS and the like, but is not limited to plastic materials. In the research process of the patent, acetal resin material is used, which has a density of 140 kg / m 3 , a Young's modulus of 2900 MPa, a Poisson's ratio of 0.3, and a yield stress of 63 MPa. Metal materials can also be used for manufacturing in the embodiment, and materials with different properties can be flexibly selected according to the application environment.

[0041] When using photopolymer 3D printing additive manufacturing, a model is first created using 3D modeling software according to the cell structure parameter drawings. The created model is then sliced ​​using slicing software and imported into the equipment for printing. The printing material used is ATPU95A. After printing, the mesh structure is cleaned and dried.

[0042] like Figure 4 , Figure 5 As shown, the energy-absorbing superstructure with negative Poisson's ratio effect includes a grid structure formed by arrays of different sizes. The three-dimensional chiral concave node units are connected by support rods extending from the cell, and will deform under the action of external forces from above and below.

[0043] This example is a three-dimensional negative Poisson's ratio energy-absorbing superstructure, and its energy absorption and deformation working principle is as follows:

[0044] like Figure 5 As shown, a uniformly distributed load is applied to the top and bottom of a three-dimensional chiral concave octagonal negative Poisson's ratio mesh structure. Under the action of external force, the concave rods first undergo bending deformation, causing the rods on both sides to bend inward. At the same time, the pressure of the supporting rods causes the chiral structure to rotate clockwise, further enhancing the inward displacement of the rods on both sides. During this deformation process, because the material does not diffuse under stress but accumulates at the stress location, the energy absorption capacity and indentation resistance of the material are further enhanced. The overall mesh structure becomes very difficult to crush, and the energy at the stress location is quickly absorbed.

[0045] In this example, during the loading and deformation process, under conditions of large deformation, the equivalent stress-equivalent strain relationship curve is as follows: Figure 7 As shown, unlike traditional material stress-strain curves, the chiral concave octagonal negative Poisson's ratio grid structure proposed in this paper undergoes four stages during deformation: the linear region, the stress plateau region, the plateau stress enhancement region, and the densification region. During large deformations where the strain exceeds 70%, the plateau stress region occupies a significant portion, and the energy absorption effect of the structure is very pronounced in this region. The specific energy absorption of the structure in this stage is the area enclosed by the curve and the horizontal axis. The entire energy absorption process is stable and efficient.

[0046] This energy-absorbing superstructure can absorb energy from impacts. By adjusting the cell structure parameters, different energy absorption effects can be achieved, and the optimal solution can be sought through structural parameter optimization, resulting in more efficient energy absorption and resistance to indentation drag. The structure can be optimized using Poisson's ratio and specific energy absorption as optimization targets, and the structure can be designed using a mathematical model established based on the design parameters to achieve the optimal dimensional parameters. Furthermore, the energy absorption efficiency and other performance characteristics of the structure can be quantified throughout the entire deformation and aging process.

[0047] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to best explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and get the best results from the application. The application is only limited by the claims and their full scope and equivalents.

Claims

1. A chiral concave octagonal superstructure with high specific energy absorption and dent resistance, characterized in that, A grid structure stacked by repeating arrays of cell structures; the cell structure is obtained by twice rotating arrays and three times mirroring of a two-dimensional negative Poisson's ratio structure unit; The negative Poisson's ratio structure unit is a two-dimensional chiral concave octagon negative Poisson's ratio structure unit, which is a concave octagon including a concave octagon structure formed by eight concave rods and four rods vertically distributed along the corner points as support structures for cell connection; the two-dimensional chiral concave octagon negative Poisson's ratio structure unit is vertically and horizontally rotated by 90 degrees around its central axis to obtain a three-dimensional chiral concave node unit, and then three times mirroring is performed to obtain the cell structure, wherein the three times mirroring is mirroring in the XY plane, YZ plane and XZ plane of the XYZ coordinate system, respectively, and the origin of the XYZ coordinate system is located at the center of the cell structure.

2. A chiral concave octagonal superstructure with high specific energy absorption and dent resistance according to claim 1, characterized in that, The two-dimensional chiral concave octagon negative Poisson's ratio structure unit is a concave octagon, and the size parameters of the concave octagon include: support rod length , concave rod length , support rod width , concave rod width t , concave angle , support rod and concave rod interface, , wherein .

3. A chiral concave octagonal superstructure with high specific energy absorption and dent resistance according to claim 1, characterized in that, The negative Poisson's ratio structure unit is prepared by using 3D printing technology, and the printing material is selected from elastic and ductile materials, and the grid structure is cleaned and dried after printing.

4. A chiral concave octagonal superstructure with high specific energy absorption and dent resistance according to claim 3, characterized in that, The material includes TPU and ABS.

5. A chiral concave octagonal superstructure with high specific energy absorption and dent resistance according to claim 1, characterized in that, When the negative Poisson's ratio structure unit is prepared by using light-cured 3D printing additive manufacturing, a three-dimensional modeling software is used to model according to the cell structure parameter drawing, the established model is sliced by a slicing software and then imported into the equipment for printing, and the grid structure is cleaned and dried after printing.

6. A chiral concave octagonal superstructure with high specific energy of adsorption and indentation resistance according to any one of claims 1-5, characterized in that, The cell structure is arrayed in different scales to obtain negative Poisson's ratio grid structures of different scales.

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