A design method of isotropic negative poisson's ratio material

Abstract

The application belongs to the technical field of metamaterial design and manufacturing, and relates to a design method of isotropic negative Poisson's ratio material, wherein the isotropic negative Poisson's ratio structure is constructed by repeated basic units, and the specific construction method comprises the following steps: designing a basic unit model, assembling and constructing an isotropic three-dimensional negative Poisson's ratio cubic structure for 3D printing, the cubic structure is constructed by transformation of the basic unit through arrangement, assembly and stacking, and the basic unit is a solid determined by the spatial coordinates of eighteen points on the surface. When subjected to complex external loads possibly from different directions, the isotropic negative Poisson's ratio material does not need to be specially oriented according to the loading direction, and the mechanical properties in different directions do not have obvious differences, thereby solving the problem that the directional limitation of negative Poisson's ratio material is serious in actual application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metamaterial design and manufacturing, and relates to a design method of an isotropic negative Poisson's ratio material. BACKGROUND

[0002] The negative Poisson's ratio material is a typical mechanical metamaterial, and has the advantages that cannot be matched by other materials in many aspects due to the unique properties different from ordinary materials, and the physical and mechanical properties of the material are greatly improved, such as excellent shear resistance, indentation resistance, fracture resistance and energy absorption performance. Thus, the negative Poisson's ratio material is expected to be used in the fields of aerospace, medicine, intelligent sensing, human engineering and the like. However, the existing negative Poisson's ratio materials are mostly designed based on the periodic arrangement of basic units to form an array structure, and can only exhibit the negative Poisson's ratio effect in two directions, i.e. in a two-dimensional plane. Even some three-dimensional negative Poisson's ratio materials are still difficult to cope with the complex situation in the actual application process.

[0003] Therefore, it is necessary to design an isotropic negative Poisson's ratio material, which has a high isotropic property under the premise of ensuring good negative Poisson's ratio effect, so as to cope with the complex actual loading conditions possibly from different directions, eliminate the directional restriction of the application of the negative Poisson's ratio material, and greatly expand the application scenarios of the negative Poisson's ratio material. SUMMARY

[0004] Therefore, the application provides a design method of an isotropic negative Poisson's ratio material to solve the problems that the existing negative Poisson's ratio material has a directional restriction in application, is difficult to cope with the complex actual working conditions in the actual application process, and leads to the limited application scenarios.

[0005] To achieve the above-mentioned purpose, the application provides the following technical scheme: a design method of an isotropic negative Poisson's ratio material, and the whole isotropic negative Poisson's ratio structure is constructed by repeated basic units, and the specific construction method comprises the following steps:

[0006] A, designing a basic unit model: each basic unit is composed of eight surface crease lines and eight outer boundary lines, and the plane parameters of each basic unit are as follows: A(-a, b, 0); B(0, b, -c); C(a, b, 0); D(-a, 0, -c); E(a, 0, -c); F(-a, -b, 0); G(0, -b, -c); H(a, -b, 0); O(0, 0, 0); wherein the ratio of a:b:c is 100:141.422:20-70; the thickness of the basic unit is defined in the z-axis direction, and the z-coordinate value is obtained by increasing or decreasing a / 10 of the coordinates of the corresponding points to form a two-dimensional basic unit entity with different thicknesses;

[0007] B, the two-dimensional base unit entity constructed by the standard software in step A is periodically arranged in the space along the x and y directions to form a two-dimensional plate with a thickness, and the number of two-dimensional base unit entities in the x and y directions is the same and is N; the same two two-dimensional plates are crossed to form a 90 ° angle, and the two crossed products are assembled around the center to form an isotropic three-dimensional negative Poisson's ratio cubic structure;

[0008] C, selecting different 3D printing raw materials; inputting a suitable file format into the printing software, setting the printing process according to the viscous flow characteristics of different printing raw materials, and not adding any support material in the printing process; slicing the model, forming a printing path, establishing a model, and uploading the model to a 3D printer; the whole is formed by support-free 3D printing, and a printed product of an isotropic negative Poisson's ratio structure is obtained.

[0009] Further, in step A, the value of a is 100, the value of b is 141.422, and the value of c is 60; the z coordinate value of the base unit is obtained by subtracting 10 from the coordinates of each corresponding point to form a two-dimensional base unit entity with different thicknesses.

[0010] Further, in step B, N is any number greater than or equal to 3.

[0011] Further, in step C, the 3D printing raw material is one of thermoplastic polyurethane elastomer rubber (TPU) and photocurable resin.

[0012] Further, in step C, when the three-dimensional negative Poisson's ratio structure is manufactured by 3D printing technology, all support options are removed, and a good printing shape is maintained during the process of layer-by-layer accumulation.

[0013] The beneficial effects of the present application are:

[0014] 1. The cubic structure of the isotropic negative Poisson's ratio material disclosed in the present application is constructed by arranging, assembling and stacking the base units, and the base unit is a solid determined by the spatial coordinates of the eighteen points on the surface. Such isotropic negative Poisson's ratio material does not need to be specially oriented according to the loading direction when subjected to complex external loads that may come from different directions, and there is no obvious difference in mechanical properties in different directions, which gives it a highly isotropic negative Poisson's ratio property, and it exhibits almost the same negative Poisson's ratio effect under different direction loading conditions, solving the problem of serious directional limitation of negative Poisson's ratio materials in practical application, and being able to cope with complex actual loading conditions that may come from different directions.

[0015] 2. The design method of the isotropic negative Poisson's ratio material, the isotropic negative Poisson's ratio structure supports manufacturing by various 3D printing technologies due to the cubic structure characteristics of the orthogonal assembly, that is, the design and manufacturing method of the isotropic negative Poisson's ratio material can endow various 3D printing raw materials with isotropic negative Poisson's ratio properties and enhance the mechanical properties, and the material has strong applicability. Combined with the compatible advantages of various materials, the application scenarios of the negative Poisson's ratio material are greatly expanded.

[0016] Other advantages, objects, and features of the present application will be apparent to those skilled in the art from the following specification, and will be learned from the practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to make the objects, technical solutions and advantages of the present application clearer, the preferred detailed description of the present application will be combined with the drawings, in which:

[0018] Figure 1 The schematic diagram of the isotropic negative Poisson's ratio cubic structure of the present application;

[0019] Figure 2 The definition diagram of two-dimensional basic unit parameters in the isotropic negative Poisson's ratio cubic structure of the present application;

[0020] Figure 3 The flow chart of constructing the isotropic negative Poisson's ratio cubic structure of the present application;

[0021] Figure 4 The physical diagram of the isotropic negative Poisson's ratio cubic TPU material of the present application;

[0022] Figure 5 The physical diagram of the isotropic negative Poisson's ratio cubic light-cured resin material of the present application;

[0023] Figure 6 The isotropic negative Poisson's ratio data diagram of the isotropic negative Poisson's ratio cubic structure material of the present application;

[0024] Figure 7 The comparison diagram of the isotropic negative Poisson's ratio cubic structure TPU and light-cured resin materials of the present application.

[0025] The drawings show that the two-dimensional plate 1 and the isotropic three-dimensional negative Poisson's ratio cubic structure 2. DETAILED DESCRIPTION

[0026] Following, the advantages and effects of the present application can be easily understood by those skilled in the art from the description. The present application can also be implemented or applied by different specific embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0027] The drawings shown in the drawings are only schematic diagrams, not real diagrams, and cannot be understood as a limitation of the present application; in order to better illustrate the embodiments of the present application, some components in the drawings can be omitted, enlarged or reduced, and do not represent the actual size of the product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings can be omitted.

[0028] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore the terms describing the positional relationship in the drawings are only used for illustrative purposes, and cannot be understood as a limitation of the present application, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0029] As Figure 1 and Figure 3 The design method of an isotropic negative Poisson's ratio material is shown in the drawings, the isotropic three-dimensional negative Poisson's ratio cubic structure 2 is built by repeating two-dimensional plates 1, the two-dimensional plates 1 are two-dimensional basic unit entities with different thicknesses. The two-dimensional basic units are periodically arranged in the X and Y directions with the same number and the same thickness to form two-dimensional plates, and the two two-dimensional plates are crossed at a 90° angle, and the two groups of crossed products are assembled vertically around the center to build the isotropic three-dimensional negative Poisson's ratio structure.

[0030] The isotropic negative Poisson's ratio material is prepared by using existing 3D printing technology (fused deposition modeling, stereolithography, selective laser sintering, etc.). The structure has a cubic structure feature of orthogonal assembly, and the 3D printing process can not add additional support. Therefore, according to different conditions, the appropriate 3D printing technology is selected, the corresponding printing material is selected according to the actual application requirement, and the printing process suitable for the selected material is matched. The printing parameters such as printing temperature, printing speed, layer height are focused on, so as to complete the manufacturing of the isotropic negative Poisson's ratio material, and bring the effect of mechanical property enhancement.

[0031] Embodiment 1

[0032] As Figure 2 shown, the design method of the isotropic negative Poisson's ratio material includes the following steps:

[0033] A, design a basic unit model: each two-dimensional basic unit is composed of sixteen surface crease lines and sixteen outer boundary lines, and the parameters of each two-dimensional basic unit are: A (-100, 141.422, 0); B (0, 141.422, -60); C (100, 141.422, 0); D (-100, 0, -60); E (100, 0, -60); F (-100, -141.422, 0); G (0, -141.422, -60); H (100, -141.422, 0); O (0, 0, 0); A' (-100, 141.422, -60); B' (0, 141.422, -120); C' (100, 141.422, -60); D' (-100, 0, -120); E' (100, 0, -120); F' (-100, -141.422, -60); G' (0, -141.422, -120); H' (100, -141.422, -60); O (0, 0, -60);

[0034] B, the two-dimensional basic unit entity constructed by the standard software in step A is periodically arranged in space along the x and y directions to form a two-dimensional plate with a thickness, and the number of two-dimensional basic units in the x and y directions is the same, which is 6; the same two two-dimensional plates are crossed in a way of forming a 90 ° angle, and the two groups of cross products are assembled vertically around the center to form an isotropic three-dimensional negative Poisson's ratio cubic structure;

[0035] C. 3D printing raw material selection thermoplastic polyurethane (TPU) wire; 3D printer adopts fused deposition modeling 3D printer (Raise 3D), input suitable file format into printing software, set printing process according to different printing raw material viscosity characteristics, printing process does not need to add any support material; slice the model, form the printing path, establish the model, upload the model to the 3D printer; support-free 3D printing integral molding, get isotropic negative Poisson's ratio structure printing finished product.

[0036] The printing process is set as follows:

[0037]

[0038] Example 2

[0039] The difference between example 2 and example 1 is that the 3D printing raw material in step C is selected as light curing resin (Formlabs Flexible); the 3D printer adopts stereolithography 3D printer (Form 2), the suitable file format is input into the printing software, the printing process is set according to the viscosity characteristics of different printing raw materials, and the printing process does not need to add any support material; slice the model, form the printing path, establish the model, upload the model to the 3D printer; support-free 3D printing integral molding, get isotropic negative Poisson's ratio structure printing finished product.

[0040] The printing process is set as follows:

[0041]

[0042] The printing finished product of the isotropic negative Poisson's ratio structure of example 1 TPU material is shown in Figure 4 The printing finished product of the isotropic negative Poisson's ratio structure of example 2 is shown in Figure 5 The isotropic three-dimensional negative Poisson's ratio structure is applied to TPU and light curing resin materials, and the sample manufactured by 3D printing presents good details such as concave-convex of the basic unit, smooth surface, and the precision meets the actual demand.

[0043] According to the national standard GB / T 1041-2008 test of plastic compression performance, uniaxial compression test is carried out on the model. The isotropic negative Poisson's ratio material has almost the same shrinkage deformation behavior in the other two directions perpendicular to the compression direction when it is uniaxially compressed, and the negative Poisson's ratio data is shown in Figure 6 Due to the overall height symmetrical cubic structure characteristics, the material has the property of highly isotropic negative Poisson's ratio.

[0044] As shown in Figure 7As shown, the specific modulus of the isotropic negative Poisson's ratio TPU material and the photocured resin material both have good reinforcing effect. Similarly, the present application is applicable to other printable materials to impart isotropic negative Poisson's ratio properties and enhance the mechanical properties thereof.

[0045] When the isotropic negative Poisson's ratio material is subjected to external load, it does not exhibit differences in mechanical properties due to different load directions, and the highly isotropic negative Poisson's ratio property eliminates the directional property of the negative Poisson's ratio material when applied to complex working conditions from different directions, so that it can cope with complex loading conditions and maximize the bearing efficiency.

[0046] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A design method for an isotropic negative Poisson's ratio material, characterized in that, The isotropic negative Poisson's ratio structure is constructed from repeating basic units. The specific construction method includes the following steps: A. Design of the basic unit model: Each basic unit consists of eight surface crease lines and eight outer boundary lines. The planar parameters of each basic unit are: A(-a, b, 0); B(0, b, -c); C(a, b, 0); D(-a, 0, -c); E(a, 0, -c); F(-a, -b, 0); G(0, -b, -c); H(a, -b, 0); O(0, 0, 0); where the ratio of a:b:c is 100:141.422:20~70; the thickness of the basic unit is defined as... z The axial direction is obtained by adding or subtracting a / 10 from the coordinates of the corresponding points. z The coordinate values ​​are used to form two-dimensional basic unit entities of different thicknesses, where a is 100, b is 141.422, and c is 60. The basic unit is obtained by subtracting 10 from the coordinates of each corresponding point. z Coordinate values ​​are used to form two-dimensional basic unit entities of different thicknesses; B. The two-dimensional basic unit entities constructed in step A using standard software are respectively placed in space along... x , y The directional periodic arrangement forms a two-dimensional plate with thickness. x , y The number of directional two-dimensional basic unit entities is the same, N, where N is any number ≥ 3; two identical two-dimensional plates can form a 90° angle. ° The products of the intersection are then vertically assembled around the center to construct an isotropic three-dimensional negative Poisson's ratio cube structure. C. Select different 3D printing raw materials; import the appropriate file format into the printing software, set the printing process according to the viscosity and flow characteristics of different printing materials, and no support material needs to be added during the printing process; slice the model to form the printing path, build the model, and upload the model to the 3D printer; unsupported 3D printing integrally forms an isotropic negative Poisson's ratio structure printed product.

2. The design method for isotropic negative Poisson's ratio materials as described in claim 1, characterized in that, In step C, the 3D printing raw material is one of thermoplastic polyurethane elastomer rubber (TPU) and photocurable resin.

3. The design method for isotropic negative Poisson's ratio materials as described in claim 1, characterized in that, In step C, when manufacturing the three-dimensional negative Poisson's ratio structure using 3D printing technology, all support option settings are cleared to maintain a good printed shape during the layer-by-layer stacking process.

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