Composite porous structure with almost zero Poisson's ratio

Abstract

The invention provides a composite porous structure with a Poisson's ratio close to zero, and belongs to the technical field of metamaterials. The composite porous structure comprises a plurality of simple cubic unit cells and regular octahedral unit cells, and the simple cubic unit cells and the regular octahedral unit cells are alternately arranged in the X-axis direction, the Y-axis direction and the Z-axis direction which are perpendicular to one another, so that each simple cubic unit cell is connected with one regular octahedral unit cell in the six directions; wherein the centers of six surfaces of the simple cubic unit cells and the regular octahedron unit cells are all provided with rod end points, so that the simple cubic unit cells and the regular octahedron unit cells are connected through the rod end points. Simple cubic unit cells and regular octahedral unit cells are alternately arranged to form a composite porous structure, the unit cells are connected in the three-axis direction in the mode that plane centers share rod end points, the continuity and stability of the structure are ensured, and the effect that the Poisson's ratio is approximate to zero is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metamaterials, and more specifically, relates to a composite porous structure with a Poisson's ratio close to zero. Background Art

[0002] Poisson's ratio is the negative value of the ratio of transverse strain to longitudinal strain, and is used to describe the relationship between transverse deformation and longitudinal deformation of a material when it is stretched or compressed. For most common materials, when the transverse deformation is positive, the longitudinal deformation is negative, and vice versa. For example, metals and plastics, their Poisson's ratio is usually between 0 and 0.5. The higher the Poisson's ratio of a material, the more obvious the transverse deformation; the lower the Poisson's ratio of a material, the smaller the transverse deformation.

[0003] Materials with a Poisson's ratio of 0 do not deform laterally when stretched or compressed. This property makes them valuable in certain special application scenarios, such as precision mechanical parts and flexible electronic devices. However, in reality, the Poisson's ratio of natural materials is rarely close to 0, because almost all materials will produce a certain degree of lateral deformation when subjected to force. In addition, artificial materials or structures designed with a Poisson's ratio of 0 in the prior art often have problems such as high manufacturing complexity, high cost or insufficient mechanical properties. Summary of the invention

[0004] The main purpose of the present application is to provide a composite porous structure with a Poisson's ratio close to zero, which can ensure the continuity and functionality of the internal structure through an alternating arrangement of unit cells.

[0005] In order to achieve the above-mentioned purpose, the present application proposes a composite porous structure with a Poisson's ratio of almost zero, including a plurality of simple cubic unit cells and regular octahedral unit cells, wherein the simple cubic unit cells and the regular octahedral unit cells are alternately arranged in mutually perpendicular X-axis, Y-axis and Z-axis directions, so that each of the six directions of the simple cubic unit cell is connected to a regular octahedral unit cell respectively; wherein the six surface centers of the simple cubic unit cell and the regular octahedral unit cell are provided with rod end points, so that the simple cubic unit cell and the regular octahedral unit cell are connected to the regular octahedral unit cell through the rod end points.

[0006] Furthermore, the six surfaces of the simple cubic unit cell are all provided with a first connecting rod extending from the center of the unit cell to the center of the surface, and a rod end point is formed at the end of the first connecting rod to connect the regular octahedral unit cell.

[0007] Furthermore, the six surfaces of the regular octahedral unit cell are each provided with a second connecting rod extending from the center of each adjacent surface to the center of the surface, and a rod end point is formed at the end of the second connecting rod to connect the simple cubic unit cell.

[0008] Furthermore, each of the second connecting rods has a smooth transition structure at the connection points of the rod end points.

[0009] Furthermore, the simple cubic unit cell and the regular octahedral unit cell have a smooth transition structure at the connection between the rod end points.

[0010] Furthermore, the material of the composite porous structure includes thermoplastic polyurethane.

[0011] Furthermore, the composite porous structure is printed using selective laser sintering 3D printing technology.

[0012] Compared with the prior art, the composite porous structure of the present invention has the following advantages: the composite porous structure is formed by alternating simple cubic unit cells with regular octahedral unit cells, and the unit cells are connected in three-axis directions by sharing the rod end points at the face centers, thereby ensuring the continuity and stability of the structure and achieving a Poisson's ratio of approximately 0; compared with traditional materials, the present structure can significantly reduce lateral deformation during stretching or compression, and meet application scenarios requiring high precision and special mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of the structure of a composite porous structure with a Poisson's ratio close to zero provided in an embodiment of the present invention; Figure 2 A front view of a composite porous structure with a Poisson's ratio close to zero provided by an embodiment of the present invention; Figure 3 A simplified plan view of a composite porous structure with a Poisson's ratio close to zero provided in an embodiment of the present invention; Figure 4 A schematic diagram of the structure of a regular octahedral unit cell provided in an embodiment of the present invention; Figure 5 A schematic diagram of the structure of a simple cubic unit cell provided in an embodiment of the present invention; Figure 6 A composite structure parameter information table provided by an embodiment of the present invention; Figure 7 A composite structure simulation test diagram provided by an embodiment of the present invention; Figure 8 A compression test diagram of a composite structure provided by an embodiment of the present invention.

[0014] Reference numerals in the figure: 10, simple cubic unit cell; 11, first connecting rod; 20, regular octahedral unit cell; 21, second connecting rod. DETAILED DESCRIPTION

[0015] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0016] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0017] Poisson's ratio is the negative value of the ratio of transverse strain to longitudinal strain, and is used to describe the relationship between transverse deformation and longitudinal deformation of a material when it is stretched or compressed. For most common materials, when the transverse deformation is positive, the longitudinal deformation is negative, and vice versa. For example, metals and plastics, their Poisson's ratio is usually between 0 and 0.5. The higher the Poisson's ratio of a material, the more obvious the transverse deformation; the lower the Poisson's ratio of a material, the smaller the transverse deformation.

[0018] Materials with a Poisson's ratio of 0 do not deform laterally when stretched or compressed. This property makes them valuable in certain special application scenarios, such as precision mechanical parts and flexible electronic devices. However, in reality, the Poisson's ratio of natural materials is rarely close to 0, because almost all materials will produce a certain degree of lateral deformation when subjected to force. In addition, artificial materials or structures designed with a Poisson's ratio of 0 in the prior art often have problems such as high manufacturing complexity, high cost or insufficient mechanical properties.

[0019] To address this problem, this embodiment provides a composite porous structure with a Poisson's ratio of nearly zero.

[0020] like Figure 1-Figure 5 As shown, the composite porous structure of this embodiment includes a plurality of simple cubic unit cells and regular octahedron unit cells, and the simple cubic unit cells and the regular octahedron unit cells are alternately arranged in the mutually perpendicular X-axis, Y-axis and Z-axis directions, so that each simple cubic unit cell is connected to a regular octahedron unit cell in six directions. That is, in the x-axis direction, for every simple cubic unit cell arranged, a regular octahedron unit cell is placed in its adjacent position; similarly, the arrangement mode in the y-axis and z-axis directions is also the same, ensuring that the same type of unit cells are not adjacent to each other in space.

[0021] Furthermore, the six surface centers of the simple cubic unit cell and the regular octahedron unit cell are provided with rod endpoints, so that the simple cubic unit cell and the regular octahedron unit cell are connected through the rod endpoints. The simple cubic unit cell and the regular octahedron unit cell both constitute a cubic structure within the unit range, and at the center of the face of each cubic unit, there are rod endpoints extending from the two types of unit cells, so that the two types of unit cells can be connected through shared rod endpoints in any direction. Except for the external surface, the entire composite structure does not have independent, unconnected rod endpoints, thereby ensuring the continuity and integrity of the overall structure, achieving the effect of Poisson's ratio being approximately 0, and enabling the structure to significantly reduce lateral deformation during stretching or compression, meeting application scenarios requiring high precision and special mechanical properties.

[0022] Since the composite porous structure of this embodiment is formed by arranging two types of unit cells alternately in the three-axis direction, the six surfaces of each simple cubic unit cell are connected to one surface of a regular octahedral unit cell, and the six surfaces of the two unit cells are the same, the rod end points are also the same, and the six surfaces of the simple cube all have a first connecting rod extending from the center of the unit cell to the center of the surface (such as Figure 5 As shown), and a rod end point is formed at the end of the first connecting rod to connect the regular octahedron unit cell; the six surfaces of the regular octahedron each have a second connecting rod extending from the center of each adjacent face to the center of the surface (as shown Figure 4 As shown in FIG. 1 ), and at the end of the second link a rod endpoint is formed to the simple cubic unit cell so that they can be connected at the center of the surface of the contact surface of the two unit cells.

[0023] Furthermore, the rod end points of each contact surface of the two unit cells can be connected. Compared with the Boolean operation of two unit cells with non-zero rod diameters, the rods of the composite porous structure of this embodiment can be integrally formed according to the set rod diameter, and smooth transition structures are formed at the connection between the second connecting rods at the rod end points and at the first connecting rod and the second connecting rod at the rod end points, so that the structure has continuity. At the same time, powder accumulation is avoided at the turning points of the rods during printing, thereby ensuring the beauty of the structure and enhancing printability.

[0024] Except for the outer surface of the porous structure, or except for the outermost unit cell which has no contact surface, there are no independent, unconnected rod end points inside the porous structure, so as to avoid the random movement of the rod connected at only one end inside during testing and actual use, which is not affected by the overall structure, resulting in waste of manufacturing materials, reduced lightweight efficiency, unpredictable structural activities affecting mechanical properties, and destroying stability.

[0025] In a possible embodiment, the selective laser sintering (SLS) printing method in 3D printing can accurately manufacture the composite porous structure in this embodiment, and can realize the alternating arrangement of unit cells without supporting materials, ensuring the continuity and functionality of the internal structure. Thermoplastic polyurethane (TPU) has excellent elasticity, flexibility and durability, can effectively absorb impact energy and avoid brittle failure, and its unique mechanical properties make the relationship between lateral and longitudinal deformation more intuitive, which helps to optimize the performance of Poisson's ratio. Therefore, we use SLS technology to print this TPU composite porous structure, and perform mechanical tests on the structure in subsequent simulation tests and compression tests to determine whether the Poisson's ratio meets the expected requirements.

[0026] Among them, the selected material is 95A TPU, and the main performance parameters are: print density 0.00115g / mm³, tensile strength 21MPa, tensile modulus 61MPa, elongation at break 310%, flexural strength 3.3MPa, flexural modulus 74MPa, and tear strength 101N / mm.

[0027] Among them, the SLS process parameters are: laser power 20W, laser scanning speed 2500mm / s, laser scanning spacing 0.1mm, powder deposition thickness 0.15mm, and powder bed temperature 125℃.

[0028] The test results can be referred to Figure 6 , Figure 7 and Figure 8 .

[0029] Figure 7 The stress distribution information of the composite porous structure simulation experiment with different volume fractions is shown, including the stress distribution diagram, the deformation diagram of the longitudinal compression of 10 mm, and the deformation diagram of the longitudinal compression of 15 mm. Figure 6 The simulation test structure of ① is 29.91%, the simulation test structure of ② is 40.12%, and the simulation test structure of ③ is 49.90%. According to the pictures, the composite porous structures with different volume fractions have no significant deformation in the lateral direction except for the longitudinal deformation under the condition of longitudinal compression of 10mm and 15mm, and the lateral dimensions after deformation are basically the same as before deformation, which meets the basic performance of zero Poisson's ratio structure.

[0030] Figure 8The following is a compression test diagram of a composite structure with a volume fraction of 40.00% (±0.10%). In the test, the loading rate was set to 5mm / min, and the loading continued until the height of the sample was compressed to 10mm (the sample basically reached the yield stage) and 18mm (the sample basically reached the compaction stage). According to the picture, the composite porous structures with different volume fractions did not undergo significant deformation in the lateral direction except for the longitudinal deformation under the conditions of longitudinal compression of 10mm and 15mm, which is consistent with the basic performance of a structure with a near-zero Poisson's ratio.

[0031] It can be seen that the composite porous structure of this embodiment achieves the effect of Poisson's ratio being approximately zero through unit cell design and arrangement optimization, making the lateral deformation extremely small, meeting the requirements of high-precision measurement, structural stability and simplified engineering design; since the lateral deformation is extremely small, the composite porous structure can be used to manufacture high-precision measuring tools or reference parts. In these occasions, the structure needs to maintain dimensional stability when subjected to force to ensure the accuracy of measurement and operation; in architectural or engineering design, the use of this structure can ignore the deformation caused by the Poisson effect to a certain extent, thereby simplifying structural design and calculation, improving design efficiency and reducing complexity.

[0032] In the description of the present invention, it is necessary to understand that the terms "middle", "length", "up", "down", "front", "back", "vertical", "horizontal", "inside", "outside", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention 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, and therefore cannot be understood as a limitation on the present invention.

[0033] In the present invention, unless otherwise clearly specified and limited, the first feature "on" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. "Multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically limited.

[0034] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] The above is only for explaining the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention without creative work should be included in the protection scope of the present invention.

Claims

1. A composite porous structure with a Poisson's ratio close to zero, characterized in that: It comprises a plurality of simple cubic unit cells and regular octahedron unit cells, wherein the simple cubic unit cells and the regular octahedron unit cells are alternately arranged in mutually perpendicular X-axis, Y-axis and Z-axis directions, so that each of the simple cubic unit cells is connected to a regular octahedron unit cell in six directions; wherein the six surface centers of the simple cubic unit cells and the regular octahedron unit cells are provided with rod end points, so that the simple cubic unit cells and the regular octahedron unit cells are connected through the rod end points.

2. The composite porous structure with a Poisson's ratio close to zero according to claim 1, characterized in that: The six surfaces of the simple cubic unit cell are all provided with a first connecting rod extending from the center of the unit cell to the center of the surface, and a rod end point is formed at the end of the first connecting rod to connect the regular octahedral unit cell.

3. The composite porous structure with a Poisson's ratio close to zero according to claim 1, characterized in that: The six surfaces of the regular octahedral unit cell are all provided with a second connecting rod extending from the center of each adjacent surface to the center of the surface, and a rod end point is formed at the end of the second connecting rod to connect the simple cubic unit cell.

4. The composite porous structure with a Poisson's ratio close to zero according to claim 3, characterized in that: The second connecting rods have a smooth transition structure at the connection points of the rod end points.

5. The composite porous structure with a Poisson's ratio close to zero according to claim 1, characterized in that: The simple cubic unit cell and the regular octahedral unit cell have a smooth transition structure at the connection point of the rod end points.

6. The composite porous structure with a Poisson's ratio close to zero according to claim 1, characterized in that: The material of the composite porous structure includes thermoplastic polyurethane.

7. The composite porous structure with a Poisson's ratio close to zero according to claim 1, characterized in that: The composite porous structure is printed using selective laser sintering 3D printing technology.

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