Honeycomb-like three-dimensional negative poisson ratio metamaterial and assembly method

Abstract

The invention discloses a honeycomb-like three-dimensional negative Poisson's ratio metamaterial and an assembly method.The honeycomb-like three-dimensional negative Poisson's ratio metamaterial is characterized in that a three-dimensional unit cell structure is spatially arrayed to form a honeycomb structure, and the three-dimensional unit cell structure comprises two hexagonal inwards-concave units and six quadrilateral inwards-concave units; the two hexagonal inwards-concave units are arranged in parallel and are connected through the six quadrilateral inwards-concave units; the six-side concave units of every two adjacent three-dimensional unit cell structures are connected through a first internal connecting rod, and the four-side concave units of every two adjacent three-dimensional unit cell structures are connected through a second internal connecting rod; the six-side concave units of the three-dimensional unit cell structure on the outermost layer are connected with first external connecting rods, and the four-side concave units are connected with second external connecting rods; the negative Poisson's ratio performance and the energy absorption characteristic of the three-dimensional negative Poisson's ratio metamaterial can be improved; and meanwhile, the whole assembling process is simple, manufacturing is conducted without depending on a non-additive manufacturing mode, a series of defects of additive manufacturing can be overcome, and large-batch production can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional metamaterial structures, and in particular to a honeycomb-like three-dimensional negative Poisson's ratio metamaterial and an assembly method thereof. Background Art

[0002] Negative Poisson's ratio material is a kind of mechanical metamaterial, which has the special mechanical property of expanding (contracting) in the horizontal direction under the action of longitudinal tension (compression). Multi-cell structure negative Poisson's ratio material has the characteristics of light weight, high specific strength, high energy absorption efficiency, heat insulation, sound absorption, etc., which is more advantageous than traditional materials and has broad application prospects in structural design and function optimization.

[0003] Negative Poisson's ratio cell structures can be roughly divided into: concave angle, chirality, rotational rigid body and slit-type structures according to their deformation mechanisms. The existing three-dimensional negative Poisson's ratio metamaterials have the following problems: insufficient stiffness, which affects their bearing capacity and stability; under the action of external forces, the structure will undergo unexpected deformation, which seriously hinders its application in practical engineering; stress concentration is prone to occur when subjected to force, which may cause the structure to be damaged in local areas, thereby reducing the reliability and durability of the overall structure. With the rapid development of 3D printing technology, especially the maturity of additive manufacturing technology, the preparation of three-dimensional negative Poisson's ratio metamaterials has become possible. However, due to the complex structure of negative Poisson's ratio metamaterials, the current 3D printing technology for preparing negative Poisson's ratio metamaterials still has some problems, such as spheroidization, internal pores, residual stress, etc. during the forming process of metal materials. These problems will affect the mechanical properties and stability of the material, resulting in high preparation costs and inability to mass produce negative Poisson's ratio metamaterials. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a honeycomb-like three-dimensional negative Poisson's ratio metamaterial and an assembly method, which can improve the three-dimensional negative Poisson's ratio metamaterial, negative Poisson's ratio performance and energy absorption characteristics, and can be processed and manufactured using traditional processes, which can overcome a series of defects of additive manufacturing and realize mass production.

[0005] The technical solution of the present invention is as follows:

[0006] In the first aspect of the present invention, a honeycomb-like three-dimensional negative Poisson's ratio metamaterial is provided, which forms a honeycomb structure by spatially arraying a three-dimensional unit cell structure, wherein the three-dimensional unit cell structure includes two hexagonal concave units, six four-sided concave units and twelve concave unit connectors, wherein the two hexagonal concave units are arranged in parallel and connected to the six four-sided concave units through the twelve concave unit connectors; the hexagonal concave units of two adjacent three-dimensional unit cell structures are connected by a first internal connecting rod, and the four-sided concave units are connected by a second internal connecting rod; the hexagonal concave units of the outermost three-dimensional unit cell structure are connected to a first external connecting rod, and the four-sided concave units are connected to a second external connecting rod.

[0007] In some embodiments of the present invention, three grooves are provided on the concave unit connector, which are respectively used to accommodate the side ends of a hexagonal concave unit and the side ends of two quadrangular concave units, and each of the grooves is provided with a threaded hole.

[0008] In some embodiments of the present invention, the center of the hexagonal concave unit is concave inward and a first flat head screw hole is provided at the center of the concave position, and the first flat head screw hole is connected to the first internal connecting rod or the first external connecting rod through a screw.

[0009] In some embodiments of the present invention, second flat head screw holes are provided at the ends of the six sides of the hexagonal concave unit, and the second flat head screw holes are connected to the concave unit connecting member through screws.

[0010] In some embodiments of the present invention, the center of the four-sided concave unit is concave inward and a third flat-head screw hole is provided at the center of the concave position, and the third flat-head screw hole is connected to the second internal connecting rod or the second external connecting rod through screws; fourth flat-head screw holes are provided at the four side ends of the four-sided concave unit, and the fourth flat-head screw hole is connected to the concave unit connecting piece through screws.

[0011] In some embodiments of the present invention, both ends of the first inner connecting rod and the second inner connecting rod are provided with threaded holes, and one end of the first outer connecting rod and the second outer connecting rod is provided with a threaded hole.

[0012] In some embodiments of the present invention, the length of the first inner connecting rod is greater than the length of the first outer connecting rod, and the length of the second inner connecting rod is greater than the length of the second outer connecting rod.

[0013] In some embodiments of the present invention, the hexagonal concave unit and the quadrangular concave unit are both made into an integral structure by stamping and drilling processes.

[0014] In some embodiments of the present invention, the three-dimensional unit cell structure is made of steel.

[0015] In a second aspect of the present invention, a method for assembling a honeycomb-like three-dimensional negative Poisson's ratio metamaterial is provided, comprising:

[0016] Two hexagonal concave units and six quadrilateral concave units are connected through twelve concave unit connectors to form a three-dimensional unit cell structure of a hexagonal frame;

[0017] Connecting the four-sided concave units of a plurality of three-dimensional unit cell structures through a second internal connecting rod to form a single-layer negative Poisson's ratio metamaterial;

[0018] The hexagonal concave units of the three-dimensional unit cell structure of the multi-layer negative Poisson's ratio metamaterial are connected through a first internal connecting rod to form a honeycomb-like three-dimensional negative Poisson's ratio metamaterial;

[0019] A first external connecting rod is installed on the hexagonal concave unit of the outermost layer of the honeycomb-like three-dimensional negative Poisson's ratio metamaterial, and a second external connecting rod is installed on the quadrilateral concave unit to complete the assembly.

[0020] One or more technical solutions of the present invention have the following beneficial effects:

[0021] (1) The honeycomb-like three-dimensional negative Poisson's ratio metamaterial provided by the present invention forms a honeycomb structure by spatially arraying a three-dimensional unit cell structure, which can improve the three-dimensional negative Poisson's ratio metamaterial, negative Poisson's ratio performance and energy absorption characteristics. Due to the overall honeycomb structure, it has good stability.

[0022] (2) The honeycomb-like three-dimensional negative Poisson's ratio metamaterial provided by the present invention has a three-dimensional unit cell structure using a hexagon. The hexagonal honeycomb structure is more stable and can reduce the impact between surfaces and the deformation caused by distributed pressure better than other geometric shapes, making the three-dimensional negative Poisson's ratio metamaterial more stable and more durable.

[0023] (3) The honeycomb-like three-dimensional negative Poisson's ratio metamaterial provided by the present invention divides and simplifies the unit cell of the honeycomb-like three-dimensional negative Poisson's ratio metamaterial so that each component can be manufactured in a non-additive manufacturing manner, which can overcome a series of defects of additive manufacturing and realize mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the three-dimensional unit cell structure of the present invention;

[0025] Figure 2 A schematic diagram of a single-layer structure of a honeycomb-like three-dimensional negative Poisson's ratio metamaterial of the present invention;

[0026] Figure 3 A three-dimensional diagram of a multilayer structure of a three-dimensional honeycomb-like negative Poisson's ratio metamaterial according to the present invention;

[0027] Figure 4It is a schematic structural diagram of the hexagonal concave unit of the present invention;

[0028] Figure 5 It is a schematic structural diagram of a four-sided concave unit of the present invention;

[0029] Figure 6 It is a structural schematic diagram of the concave unit connecting member of the present invention;

[0030] Figure 7 Schematic diagrams of the structures of the connecting rods of the present invention; wherein (a) is a schematic diagram of the first internal connecting rod, (b) is a schematic diagram of the second internal connecting rod, (c) is a schematic diagram of the first external connecting rod, and (d) is a schematic diagram of the second external connecting rod;

[0031] Figure 8 Schematic diagrams showing design parameters required for designing the hexagonal concave unit and the four-sided concave unit of the present invention, wherein (a) is a front view of the hexagonal concave unit, (b) is a front view of the four-sided concave unit, (c) is a top view of the hexagonal concave unit, and (d) is a top view of the four-sided concave unit;

[0032] Fig. 9 This is a compression simulation effect diagram of the honeycomb-like three-dimensional negative Poisson's ratio metamaterial of the present invention;

[0033] Fig.10 Extracted load-displacement plot for a compression simulation.

[0034] In the figure: 1. Hexagonal concave unit; 101. First flat head screw hole; 102. Second flat head screw hole; 2. Four-sided concave unit; 201. Third flat head screw hole; 202. Fourth flat head screw hole; 3. Concave unit connector; 301. Groove; 4. First external connecting rod; 5. Second external connecting rod; 6. First internal connecting rod; 7. Second internal connecting rod; 8. Threaded hole. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] Example 1

[0037] In a typical embodiment of the present invention, a honeycomb-like three-dimensional negative Poisson's ratio metamaterial is proposed, such as Figure 1-Figure 3As shown, a honeycomb structure is obtained by spatially arranging a three-dimensional unit cell structure, wherein the three-dimensional unit cell structure includes two hexagonal concave units 1, six four-sided concave units 2 and twelve concave unit connectors 3, wherein the two hexagonal concave units 1 are arranged in parallel and connected to the six four-sided concave units 2 through the twelve concave unit connectors 3; the hexagonal concave units 1 of two adjacent three-dimensional unit cell structures are connected by a first internal connecting rod 6, and the four-sided concave units are connected by a second internal connecting rod 7; the hexagonal concave units of the outermost three-dimensional unit cell structure are connected to the first external connecting rod 4, and the four-sided concave units are connected to the second external connecting rod 5.

[0038] The three-dimensional unit cell structure in this embodiment is a hexagon. Compared with other shapes, the hexagonal honeycomb structure is more stable and can reduce the impact between surfaces and the deformation caused by distributed pressure better than other geometric shapes, making the honeycomb structure more stable and more durable. Therefore, the three-dimensional unit cell structure is similar to the three-dimensional negative Poisson's ratio metamaterial of the honeycomb hexagon, which has better stability.

[0039] In this embodiment, the hexagonal concave unit 1 and the quadrangular concave unit 2 are connected via a concave unit connector 3. Figure 6 As shown, three grooves 301 are provided on the concave unit connector 3, which are respectively used to accommodate the side ends of a hexagonal concave unit and the side ends of two quadrangular concave units, and a threaded hole 8 is provided in each of the grooves 301.

[0040] like Figure 4 As shown, the center of the hexagonal concave unit 1 is concave inwards and a first flat head screw hole 101 is provided at the center of the concave position, and the first flat head screw hole 101 is connected to the first internal connecting rod 6 or the first external connecting rod 4 through screws; the six side ends of the hexagonal concave unit 1 are provided with second flat head screw holes 102, and the second flat head screw holes 102 are connected to the concave unit connector 3 through screws. The use of flat head screws will not affect the mutual contact of each unit cell during compression, so that the overall metamaterial can fully shrink inwards.

[0041] like Figure 5 As shown, the center of the four-sided concave unit 2 is concave inward and a third flat-head screw hole 201 is provided at the center of the concave position, and the third flat-head screw hole 201 is connected to the second internal connecting rod 7 or the second external connecting rod 5 through screws; the four side ends of the four-sided concave unit 2 are provided with fourth flat-head screw holes 202, and the fourth flat-head screw hole 202 is connected to the concave unit connecting piece 3 through screws.

[0042] Therefore, the three-dimensional unit cell structure is composed of two hexagonal concave units 1, six quadrilateral concave units 2 and 12 concave unit connectors, and the hexagonal concave units, the quadrilateral concave units and the concave unit connectors are connected and fixed by cross-slot countersunk screws.

[0043] like Figure 7 As shown, both ends of the first internal connecting rod 6 and the second internal connecting rod 7 are provided with threaded holes 8, and one end of the first external connecting rod 4 and the second external connecting rod 5 is provided with a threaded hole 8.

[0044] In this embodiment, the length of the first internal connecting rod 6 is greater than that of the first external connecting rod 4 , and the length of the second internal connecting rod 7 is greater than that of the second external connecting rod 5 .

[0045] Among them, the first internal connecting rod 6 is used for connecting the internal three-dimensional unit cell structure in the vertical direction (two hexagonal concave units are connected); the second internal connecting rod 7 is used for connecting the three-dimensional unit cell structure on six sides (two four-sided concave units are connected); the first external connecting rod 4 installs the external internal three-dimensional unit cell structure, which plays a role in supporting the entire three-dimensional structure and contacting the external force (installed on the hexagonal concave unit); the second external connecting rod 5 installs the external honeycomb-like three-dimensional negative Poisson's ratio metamaterial unit cell, which plays a role in supporting the entire three-dimensional structure and contacting the external force (installed on the four-sided concave unit).

[0046] In this embodiment, the connection rod and the unit cell are also connected and fixed by cross recessed countersunk screws.

[0047] When designing the concave unit, the main design parameters are as follows: Figure 8 As shown, the design parameters for the hexagonal concave unit include: L1: the distance from the center to the bending point of the concave plate; θ1: the concave angle; B1: the width of the concave plate; T1: the thickness of the concave plate.

[0048] The design parameters for the four-sided concave unit include: L2: the distance from the center to the bending point of the concave plate; θ2: the concave angle; B2: the width of the concave plate; T2: the thickness of the concave plate.

[0049] The concave unit connectors and four types of connecting rods are designed according to the parameters of the two concave units.

[0050] The production process of each component in this embodiment is shown in Table 1. Each component can be prepared by a non-additive manufacturing method, which can overcome the defects of the additive manufacturing method (such as surface roughness, step effect, etc.) and the limited printing size, and at the same time solve the problems of high preparation cost and inability to mass produce in practical applications.

[0051] Table 1 Production process of each component

[0052]

[0053] Finite element simulation is performed on the honeycomb-like three-dimensional negative Poisson's ratio metamaterial. The design parameters of the honeycomb-like three-dimensional negative Poisson's ratio metamaterial are as follows:

[0054] Hexagonal concave unit: L1: 18mm; θ1: 20°; B1: 4mm; T1: 1mm.

[0055] Four-sided concave unit: L2: 12mm; θ2: 30°; B2: 2.85mm; T2: 1mm.

[0056] First internal connecting rod: length: 15mm; diameter: 6mm.

[0057] Second internal connecting rod: length: 15mm; diameter: 4mm.

[0058] First external connecting rod: length: 8mm; diameter: 6mm.

[0059] Second external connecting rod: length: 8mm; diameter: 4mm.

[0060] Material: Steel; Density: 7.82g / cm 3 ; Young's modulus: 210Gpa; Poisson's ratio: 0.3.

[0061] The simulation results are as follows Fig. 9 As shown, from the structural deformation diagram under quasi-static compression, it can be seen that during the compression process, the structure exhibits a good shrinkage phenomenon, which proves that the structure designed by the present invention can exhibit a good negative Poisson's ratio phenomenon. Fig.10 It is the load-displacement curve extracted from the compression simulation, which can be roughly divided into two stages. The AB stage is the stage before the contact between the unit cells. Mainly, with the progress of compression in the Z direction (vertical direction), the first internal connecting rod drives the hexagonal concave unit to shrink, and the unit cells begin to contact in the Z direction. At this time, the negative Poisson's ratio of the structure is not obvious, and the line segments in this stage are relatively smooth; in the BC stage, the unit cells begin to contact and squeeze. As the internal four-sided concave unit shrinks into the unit cell, the second connecting rod drives the unit cells to shrink into the structure, and the structure shows a significant negative Poisson's ratio phenomenon. It can be seen that the line segments in this stage show an upward trend. Such mechanical performance can make the structure perform better in energy absorption characteristics.

[0062] Example 2

[0063] In a typical embodiment of the present invention, a method for assembling a honeycomb-like three-dimensional negative Poisson's ratio metamaterial is provided, comprising:

[0064] Two hexagonal concave units and six quadrilateral concave units are connected through twelve concave unit connectors to form a three-dimensional unit cell structure of a hexagonal frame;

[0065] Connecting the four-sided concave units of a plurality of three-dimensional unit cell structures through a second internal connecting rod to form a single-layer negative Poisson's ratio metamaterial;

[0066] The hexagonal concave units of the three-dimensional unit cell structure of the multi-layer negative Poisson's ratio metamaterial are connected through a first internal connecting rod to form a honeycomb-like three-dimensional negative Poisson's ratio metamaterial;

[0067] A first external connecting rod is installed on the hexagonal concave unit of the outermost layer of the honeycomb-like three-dimensional negative Poisson's ratio metamaterial, and a second external connecting rod is installed on the quadrilateral concave unit to complete the assembly.

[0068] This honeycomb-like three-dimensional negative Poisson's ratio metamaterial can be directly assembled by screws after the various components are processed using traditional techniques. The entire assembly process is simple and does not rely on additive manufacturing technology. It can overcome a series of defects of additive manufacturing and can also achieve mass production.

[0069] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A honeycomb-like three-dimensional negative Poisson's ratio metamaterial, characterized in that: A honeycomb structure is formed by spatially arraying a three-dimensional unit cell structure, wherein the three-dimensional unit cell structure includes two hexagonal concave units, six four-sided concave units and twelve concave unit connectors, wherein the two hexagonal concave units are arranged in parallel and connected to the six four-sided concave units through the twelve concave unit connectors; the hexagonal concave units of two adjacent three-dimensional unit cell structures are connected by a first internal connecting rod, and the four-sided concave units are connected by a second internal connecting rod; the hexagonal concave units of the outermost three-dimensional unit cell structure are connected to a first external connecting rod, and the four-sided concave units are connected to a second external connecting rod.

2. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 1, characterized in that: The concave unit connecting piece is provided with three grooves, which are respectively used to accommodate the side ends of a hexagonal concave unit and the side ends of two quadrangular concave units, and each of the grooves is provided with a threaded hole.

3. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 2, characterized in that: The center of the hexagonal concave unit is concave inwards, and a first flat head screw hole is arranged at the center of the concave position. The first flat head screw hole is connected to the first internal connecting rod or the first external connecting rod through a screw.

4. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 2, characterized in that: The six side ends of the hexagonal concave unit are provided with second flat head screw holes, and the second flat head screw holes are connected to the concave unit connecting piece through screws.

5. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 2, characterized in that: The center of the four-sided concave unit is concave inward and a third flat-head screw hole is arranged at the center of the concave position, and the third flat-head screw hole is connected to the second internal connecting rod or the second external connecting rod through screws; fourth flat-head screw holes are arranged at the four side ends of the four-sided concave unit, and the fourth flat-head screw hole is connected to the concave unit connecting piece through screws.

6. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 1, characterized in that: Both ends of the first inner connecting rod and the second inner connecting rod are provided with threaded holes, and one end of the first outer connecting rod and the second outer connecting rod is provided with a threaded hole.

7. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 1, characterized in that: The length of the first inner connecting rod is greater than that of the first outer connecting rod, and the length of the second inner connecting rod is greater than that of the second outer connecting rod.

8. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 1, characterized in that: The hexagonal concave unit and the quadrilateral concave unit are both made into an integral structure by stamping and drilling processes.

9. The honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to claim 1, characterized in that: The three-dimensional unit cell structure is made of steel.

10. A method for assembling the honeycomb-like three-dimensional negative Poisson's ratio metamaterial according to any one of claims 1 to 9, characterized in that: include: Two hexagonal concave units and six quadrilateral concave units are connected through twelve concave unit connectors to form a three-dimensional unit cell structure of a hexagonal frame; Connecting the four-sided concave units of a plurality of three-dimensional unit cell structures through a second internal connecting rod to form a single-layer negative Poisson's ratio metamaterial; The hexagonal concave units of the three-dimensional unit cell structure of the multi-layer negative Poisson's ratio metamaterial are connected through a first internal connecting rod to form a honeycomb-like three-dimensional negative Poisson's ratio metamaterial; A first external connecting rod is installed on the hexagonal concave unit of the outermost layer of the honeycomb-like three-dimensional negative Poisson's ratio metamaterial, and a second external connecting rod is installed on the quadrilateral concave unit to complete the assembly.

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