Lattice material that simultaneously expands or contracts under tension and compression

Abstract

The application provides a lattice material which expands or shrinks simultaneously under tension and compression, first, the structural response form is converted with the direction of external force by designing the contact mode in the structure, then the stiffness difference between the S-shaped rib plate and the straight rib plate forms two types of lattice materials which can expand or shrink in the transverse direction under uniaxial tension or compression in a specific direction, and the two types of lattice materials can also shrink or expand simultaneously in the orthogonal direction, showing the characteristics of opposite deformation. The structure and material of the application can be used as a specific functional material, and have application prospects in the fields of sensing, energy absorption and shock absorption, wave propagation and mechanical logic control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mechanical metamaterials, in particular to a lattice material that simultaneously expands or shrinks under tension and compression. BACKGROUND

[0002] Mechanical metamaterials are composite materials manufactured by artificially designing microstructures, which can achieve mechanical properties that natural materials generally do not possess, such as negative Poisson's ratio, negative thermal expansion, negative stiffness, etc. Lakes obtained a negative Poisson's ratio material with a special microstructure by using polyurethane foam, proposed the condition for the generation of negative Poisson's ratio from the micro-unit, and proved it by using an internally concave hexagonal honeycomb. Since then, negative Poisson's ratio materials or structures have experienced an explosive development, and gradually applied in the fields of intelligent sensing, impact protection, medical health, etc.

[0003] Negative Poisson's ratio specifically refers to the ratio of the change in the transverse dimension to the longitudinal dimension of some materials when subjected to axial tension or compression. In most conventional materials, when a material is stretched along an axis, its transverse dimension will shrink, which is called positive Poisson's ratio. However, negative Poisson's ratio materials will increase in transverse dimension when stretched, which is relatively rare in nature. The mathematical definition is:

[0004] ,

[0005] Among them, is the transverse strain (the ratio of the change in the transverse dimension to the original transverse dimension), is the longitudinal strain (the ratio of the change in the longitudinal dimension to the original longitudinal dimension). When is negative, it indicates that the material has a negative Poisson's ratio. However, most of the current metamaterials only exhibit a special performance of Poisson's ratio. In the face of the growing demand for advanced functions of materials, a single Poisson's ratio material may not be suitable for some scenarios, so it is of great significance to break through the limit of single Poisson's ratio and promote the functionalization of metamaterials.

[0006] Patent CN111237365A discloses a structure, a lattice material and a lattice cylindrical shell with both tensile and compressive expansion properties. The difference between the present application and this patent is:

[0007] 1. The structure is different. The structure of this patent includes a spring, and the present application provides a contact.

[0008] 2. The structure is more functional. The structure of this patent only covers the deformation of expansion under tension and compression. The present application can achieve the expansion deformation function of this patent, and also can achieve the function of shrinkage deformation under tension and compression.

[0009] 3. The present invention proposes two structural forms, and this patent only proposes one.

[0010] 4. The monomer 1 of the present invention shrinks and expands along the long axis and short axis of the structure respectively when loaded in the orthogonal direction; the monomer 2 expands and shrinks along the long axis and short axis of the structure respectively when loaded in the orthogonal direction. SUMMARY

[0011] The present invention aims to provide a lattice material that simultaneously expands or shrinks under tension-compression, which has application value in energy absorption and shock absorption and aerospace engineering. Specifically, the proposed material has an asymmetric Poisson's ratio effect, and the influence of nonlinearity on the structure Poisson's ratio is weak within a certain strain range, and the functionality of the structure is maintained within a larger strain range.

[0012] To achieve the above-mentioned purpose, the present invention provides a lattice material that simultaneously expands or shrinks under tension-compression, comprising an outer ring layer, a first support structure and a second support structure are arranged in the outer ring layer, the first support structure and the second support structure are symmetrically arranged, the first support structure comprises two monomer structures: a first monomer structure and a second monomer structure under tension and compression.

[0013] Preferably, the first monomer structure is provided with a third connecting plate, one end of the third connecting plate is provided with a fourth connecting plate and a fifth connecting plate, one end of the fourth connecting plate and the fifth connecting plate is directly connected, the connection between the fourth connecting plate and the fifth connecting plate is in contact with one end of the third connecting plate, the fourth connecting plate and the fifth connecting plate are directly connected with the outer ring layer;

[0014] The second monomer structure is provided with a third connecting plate, one end of the third connecting plate is provided with a fourth connecting plate and a fifth connecting plate, one end of the fourth connecting plate and the fifth connecting plate is directly connected with the third connecting plate, one end of the fourth connecting plate and the fifth connecting plate is respectively in contact with the outer ring layer, one side of the position where the fourth connecting plate and the fifth connecting plate are in contact with the outer ring layer is provided with a protrusion on the outer ring layer.

[0015] Preferably, the outer ring layer is provided with a first rib plate, a second rib plate, a third rib plate and a fourth rib plate, the first rib plate, the second rib plate, the third rib plate and the fourth rib plate are located at the four corners of the outer ring layer, a first connecting plate is arranged between the first rib plate and the third rib plate, the first connecting plate is directly connected with the first rib plate and the second rib plate respectively, a second connecting plate is arranged between the second rib plate and the fourth rib plate, the second connecting plate is directly connected with the second rib plate and the fourth rib plate respectively.

[0016] Preferably, one end of the first rib plate and the second rib plate is directly connected, and one end of the third rib plate and the fourth rib plate is directly connected.

[0017] Preferably, the third connecting plate is directly connected with the first rib plate and the second rib plate at the connecting position of the first rib plate and the second rib plate.

[0018] Preferably, the first rib plate and the second rib plate are S-shaped rib plates with the same structure, the circular arc angle θ2 of the first rib plate is greater than 85°, and the included angle between the fourth connecting plate and the third connecting plate is θ1, and θ1 is not too large, and the range is 55°-65°.

[0019] Preferably, the cross-sectional dimension of the first rib plate and the first connecting plate, the second connecting plate, the third connecting plate, the fourth connecting plate and the fifth connecting plate is not too small, and the width is required to be greater than 2mm, which can prevent the rod from buckling when subjected to axial compression.

[0020] Preferably, the first monomer structure is subjected to axial stretching or compression along the long axis of the structure (the direction of the third connecting plate), and the third connecting plate is in contact with the fourth connecting plate and the fifth connecting plate at the connecting position, and the contact is designed to be mirror-symmetric in the first support structure and the second support structure, and the number is 2.

[0021] The second monomer structure is subjected to axial stretching or compression along the long axis of the structure, and the side of the connecting position of the first connecting plate and the first rib plate is in contact with the fourth connecting plate, and the contact is designed to be mirror-symmetric in the first support structure and the second support structure, and the number is 2; the side of the connecting position of the second connecting plate and the second rib plate is in contact with the fifth connecting plate, and the contact is designed to be mirror-symmetric in the first support structure and the second support structure, and the number is 2.

[0022] Preferably, the contact gap is designed to be zero, and the contact form is a plane. In the actual manufacturing process, cutting or setting the contact surface distance to be less than <1mm can be adopted for manufacturing.

[0023] Preferably, the first monomer structure is subjected to axial stretching or compression along the direction perpendicular to the third connecting plate, and the second monomer structure is subjected to axial stretching or compression along the direction perpendicular to the third connecting plate.

[0024] Preferably, the first monomer structure and the second monomer structure are subjected to expansion or shrinkage deformation under the action of stretching and compression, and the structures are periodically arrayed in the plane where they are located to form a planar lattice material; the first monomer structure and the second monomer structure are subjected to expansion or shrinkage deformation under the action of stretching and compression, and the structures are first orthogonally combined, and then periodically arrayed along the three-dimensional coordinate axis direction to form a three-dimensional lattice material.

[0025] Therefore, the present application adopts the above-mentioned lattice material which is subjected to expansion or shrinkage deformation under the action of stretching and compression, and the technical effects are as follows:

[0026] (1) The invention associates the directionality of external force with the positive and negative of the Poisson's ratio of the structure, and the direction information of external force can be reflected by the sign of Poisson's ratio, thereby establishing the logical relationship between load working condition and material response.

[0027] (2) The material in the invention expands or shrinks under axial tension or compression, and we can manufacture a self-locking or unlocking mechanism by using this function, which can be self-tightened or self-loosened under external vibration.

[0028] (3) The Poisson's ratio of the structure or material proposed in the invention has the characteristics of adjustability and programmability. The size parameters of the structure can be adjusted to adjust the size of the Poisson's ratio, and the distance of contact and the way of applying pre-strain can be adjusted to control the time of the step change of the Poisson's ratio, so that the sign of the Poisson's ratio can be changed in the tension or compression stage. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a structural design diagram of two monomers that both expand or shrink under axial tension or compression; Figure 1 (a) is a first monomer structure; Figure 1 (b) is a second monomer structure;

[0030] Figure 2 is a deformation state diagram of two monomers along the x and y directions when tensioned and compressed; Figure 2 (a) is a deformation state diagram of a first monomer structure along the x and y directions when tensioned and compressed; Figure 2 (b) is a deformation state diagram of a second monomer structure along the x and y directions when tensioned and compressed;

[0031] Figure 3 is a Poisson's ratio diagram of two monomers that both expand or shrink under tension and compression; Figure 3 (a) is a Poisson's ratio diagram of a first monomer structure that both expands or shrinks under tension and compression; Figure 3 (b) is a Poisson's ratio diagram of a first monomer structure that both expands or shrinks under tension and compression; Figure 3 (c) is a Poisson's ratio diagram of a second monomer structure that both expands or shrinks under tension and compression; Figure 3 (d) is a Poisson's ratio diagram of a second monomer structure that both expands or shrinks under tension and compression;

[0032] Figure 4 is a deformation state diagram of a two-dimensional lattice material composed of two monomers; Figure 4 (a) is a deformation state diagram of a two-dimensional lattice material composed of a first monomer structure; Figure 4(b) a deformation state diagram of a two-dimensional lattice material composed of the first monomer structure; Figure 4 (c) a deformation state diagram of a two-dimensional lattice material composed of the second monomer structure; Figure 4 (d) a deformation state diagram of a two-dimensional lattice material composed of the second monomer structure;

[0033] Figure 5 a design schematic of two monomer three-dimensional lattice materials; Figure 5 (a) a design schematic of a first monomer three-dimensional lattice material; Figure 5 (b) a design schematic of a second monomer three-dimensional lattice material;

[0034] Figure 6 a design schematic of a second monomer structure.

[0035] Reference numerals

[0036] 11, first rib plate; 12, second rib plate; 13, third rib plate; 14, fourth rib plate; 15, first connecting plate; 16, second connecting plate; 21, third connecting plate; 22, fourth connecting plate; 23, fifth connecting plate; 24, protrusion; 3, second support structure. DETAILED DESCRIPTION

[0037] The technical solutions of the present application are further described below by means of the accompanying drawings and examples.

[0038] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those with ordinary skills in the art to which the present application pertains. The terms "monomer 1", "monomer 2" and similar terms used in the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. The terms "comprise", "include" and similar terms mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "upper", "lower", "left", "right" and the like only indicate relative positional relationships, which may change accordingly when the absolute positions of the described objects change.

[0039] The principles and features of the present application are described below in conjunction with the accompanying drawings, and the examples are only used to explain the present application and not to limit the scope of the present application.

[0040] Example 1

[0041] As Figure 6As shown, the lattice material which expands or shrinks simultaneously under tension and compression includes an outer ring layer, the outer ring layer is provided with a first support structure and a second support structure 3, the first support structure and the second support structure 3 are symmetrically arranged, the first support structure includes two single structures under tension and compression: a first single structure and a second single structure.

[0042] The first single structure is provided with a third connecting plate 21, one end of the third connecting plate 21 is provided with a fourth connecting plate 22 and a fifth connecting plate 23, one end of the fourth connecting plate 22 and the fifth connecting plate 23 is directly connected, the connection of the fourth connecting plate 22 and the fifth connecting plate 23 is in contact with one end of the third connecting plate 21, the fourth connecting plate 22 and the fifth connecting plate 23 are directly connected with the outer ring layer;

[0043] The second single structure is provided with a third connecting plate 21, one end of the third connecting plate 21 is provided with a fourth connecting plate 22 and a fifth connecting plate 23, one end of the fourth connecting plate 22 and the fifth connecting plate 23 is directly connected with one end of the third connecting plate 21, one end of the fourth connecting plate 22 and the fifth connecting plate 23 is respectively in contact with the outer ring layer, one side of the position where the fourth connecting plate 22 and the fifth connecting plate 23 are in contact with the outer ring layer is provided with a protrusion 24 on the outer ring layer.

[0044] The outer ring layer is provided with a first rib plate 11, a second rib plate 12, a third rib plate 13 and a fourth rib plate 14, the first rib plate 11, the second rib plate 12, the third rib plate 13 and the fourth rib plate 14 are located at the four corners of the outer ring layer, the first rib plate 11 and the third rib plate 13 are provided with a first connecting plate 15, the first connecting plate 15 is directly connected with the first rib plate 11 and the second rib plate 12 respectively, the second rib plate 12 and the fourth rib plate 14 are provided with a second connecting plate 16, the second connecting plate 16 is directly connected with the second rib plate 12 and the fourth rib plate 14 respectively.

[0045] One end of the first rib plate 11 and the second rib plate 12 is directly connected, one end of the third rib plate 13 and the fourth rib plate 14 is directly connected.

[0046] The third connecting plate 21 is directly connected with the first rib plate 11 and the second rib plate 12 at the connection of the first rib plate 11 and the second rib plate 12.

[0047] The first rib plate 11, the second rib plate 12, the third rib plate 13 and the fourth rib plate 14 are S-shaped rib plates with the same structure, the circular arc angle θ2 of the first rib plate 11 is greater than 85°, the included angle between the fourth connecting plate 22 and the third connecting plate 21 is θ1.

[0048] The cross-sectional dimension of the first rib plate 11 and the first connecting plate 15, the second connecting plate 16, the third connecting plate 21, the fourth connecting plate 22 and the fifth connecting plate 23 should not be too small, which can prevent the rod from buckling when subjected to axial compression.

[0049] When the first single structure is stretched or compressed along the long axis of the structure (direction of the third connecting plate 21), it will expand and deform. The third connecting plate 21 is in contact with the fourth connecting plate 22 and the fifth connecting plate 23. This contact is designed in a mirror symmetric manner in the first support structure and the second support structure 3, and the number is 2.

[0050] When the second single structure is stretched or compressed along the long axis of the structure, it undergoes shrinkage deformation. One side of the connection between the first connecting plate 15 and the first rib 11 is in contact with the fourth connecting plate 22. This contact is designed in a mirror symmetric manner in the first support structure and the second support structure 3, and the number of such contacts is 2. One side of the connection between the second connecting plate 16 and the second rib 12 is in contact with the fifth connecting plate 23. This contact is designed in a mirror symmetric manner in the first support structure and the second support structure 3, and the number of such contacts is 2.

[0051] The thickness of the first rib 11 and the second rib 12 is preferably 0.4 mm, and the thickness T1 of the fourth connecting plate 22 and the fifth connecting plate 23 is preferably 1 mm.

[0052] The structure undergoes shrinkage deformation when stretched or compressed axially along its minor axis (perpendicular to the direction of the third connecting plate 21); the structure undergoes shrinkage deformation when stretched or compressed axially along its major axis.

[0053] Expansion deformation occurs when the structure is stretched or compressed axially along its minor axis in its orthogonal direction.

[0054] The first and second monomer structures, which simultaneously expand or contract under tension and compression, are periodically arrayed in their respective planes to form a planar lattice material; the first and second monomer structures, which simultaneously expand or contract under tension and compression, are first orthogonally combined and then periodically arrayed along the three-dimensional coordinate axes to form a three-dimensional lattice material.

[0055] like Figure 1 Table 1 provides a structural design scheme and dimensional references for each part of the structure that can simultaneously expand or contract under tension and compression. Specifically, unit 1 undergoes contraction deformation under both tension and compression in the x-direction (along the long axis of the structure). It undergoes expansion deformation under both tension and compression in the y-direction; the deformation state is detailed in Table 1. Figure 2 The four images on the left illustrate this. When the structure is compressed along its long axis, the contact closes. Because the S-shaped ribs are very weak, the deformation of the entire structure is mainly "concave structure" deformation, exhibiting a negative Poisson's ratio effect. When stretched along the long axis, the contact opens, and the entire structure deforms mainly "honeycomb structure," exhibiting a positive Poisson's ratio effect. Figure 3(a) shown, the structure can shrink when stretched or compressed along the long axis direction. Similarly, when stretched or compressed in the y direction, the opening or closing of the contact controls the deformation mode of the structure, the Poisson's ratio is like Figure 3 (b) shown, the structure can expand when stretched or compressed along the y axis direction.

[0056] Table 1 Size design reference of each part

[0057]

[0058] Figure 1 The design of monomer 2 in (b) is mainly different from monomer 1 in the position of the contact. The contact is arranged on the upper and lower left and right of the structure, and a small protrusion is specially designed to prevent the sliding of the contact surface when stretched in the x direction. Unlike monomer 1, when the structure is compressed along the x axis direction, the contact is opened, and the entire structure is mainly deformed as a "honeycomb structure", with a positive Poisson's ratio. When stretched, the contact is closed, and the entire structure is mainly deformed as a "concave structure", with a negative Poisson's ratio (β = -0.5) Figure 3 (c), so the structure can expand when stretched or compressed along the long axis direction. Similarly, when stretched and compressed in the y direction, Figure 2 The right two images show the deformation state diagram of monomer 2 structure, and it can be seen that the opening or closing of the contact is related to the direction of the force, and the Poisson's ratio is like Figure 3 (d) shown, the structure can shrink when stretched or compressed along the short axis y axis direction.

[0059] In addition, the contact design contained in monomer 1 and monomer 2 is shown in the enlarged view, and a certain distance is drawn for clear expression. In fact, the distance between the contact surfaces is as small as possible, generally not more than 1mm. The width of the rib plate is between 10-20mm, in order to prevent out-of-plane buckling. Figure 1 Although the structure shown in (c) is a three-dimensional schematic diagram, the study of the deformation mode is limited to the xy plane.

[0060] For two structures that can simultaneously expand or shrink under the action of stretching and compression, a periodic array is carried out in the plane where they are located, to form a planar lattice material. The deformation state of the two lattice materials when stretched and compressed along their long and short axes is shown in Figure 4 .

[0061] In addition to the design of two-dimensional planar lattice materials, two structures can also be orthogonally combined, and then periodically arrayed along the spatial coordinate axis direction to design a three-dimensional lattice material, as shown in Figure 5 . This three-dimensional lattice material can realize the functions of expansion or shrinkage when stretched or compressed in the axial direction.

[0062] The structure and lattice material manufacturing method capable of swelling or shrinking deformation under axial stretching and compression can be manufactured by using 3D printing technology, and comprises the following manufacturing steps:

[0063] (1) The lattice structure and material are modeled by using software, wherein the modeling parameters refer to Table 1.

[0064] (2) PA11 (nylon) is selected as the printing material, and the material has high mechanical strength and toughness characteristics.

[0065] (3) The printing equipment comprises a high-precision nozzle and an adjustable light source, the printing head can accurately spray the melting agent and the refining agent to control the melting and solidification of the powder layer. The solidification process adopts a light source with a specific wavelength to ensure uniform solidification of the powder layer.

[0066] (4) After printing, the part is subjected to powder removal, surface cleaning and post-solidification treatment to improve the performance of the part.

[0067] Therefore, the lattice material capable of swelling or shrinking deformation under the stretching and compression is applied to the energy absorption and shock absorption and the aerospace engineering field. The material has an asymmetric Poisson's ratio effect, and the influence of the nonlinear factor on the structure Poisson's ratio is weak within a certain strain range, and the functionality of the structure is maintained within a larger strain range.

[0068] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, 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 still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A lattice material that simultaneously expands or contracts under tension and compression, characterized in that, It includes an outer ring layer, within which a first support structure and a second support structure are provided. The first support structure and the second support structure are symmetrically arranged. Under tension and compression, the first support structure includes two types of single-unit structures: a first single-unit structure and a second single-unit structure. The first single-unit structure is provided with a third connecting plate, and a fourth connecting plate and a fifth connecting plate are provided at one end of the third connecting plate. The ends of the fourth connecting plate and the fifth connecting plate are directly connected. The connection point of the fourth connecting plate and the fifth connecting plate is in contact with one end of the third connecting plate. The fourth connecting plate and the fifth connecting plate are directly connected to the outer ring layer. The second single-unit structure is provided with a third connecting plate, and a fourth connecting plate and a fifth connecting plate are provided at one end of the third connecting plate. The fourth connecting plate, the fifth connecting plate and one end of the third connecting plate are directly connected. One end of the fourth connecting plate and the fifth connecting plate are in contact with the outer ring layer. A protrusion is provided on the outer ring layer on one side of the position where the fourth connecting plate and the fifth connecting plate are in contact with the outer ring layer. The outer ring layer is provided with a first rib, a second rib, a third rib, and a fourth rib. The first rib, the second rib, the third rib, and the fourth rib are located at the four corners of the outer ring layer. A first connecting plate is provided between the first rib and the third rib, and the first connecting plate is directly connected to the first rib and the second rib respectively. A second connecting plate is provided between the second rib and the fourth rib, and the second connecting plate is directly connected to the second rib and the fourth rib respectively.

2. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, One end of the first rib and the second rib are directly connected, and one end of the third rib and the fourth rib are directly connected.

3. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, The third connecting plate is directly connected to the first rib and the second rib at the connection point.

4. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, The first rib, the second rib, the third rib, and the fourth rib are S-shaped ribs with the same structure. The arc angle θ2 of the first rib is greater than 85°, and the included angle formed between the fourth connecting plate and the third connecting plate is θ1.

5. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, When the first single structure is stretched or compressed axially along the direction of the third connecting plate, it undergoes shrinkage deformation. The third connecting plate is in contact with the fourth and fifth connecting plates at the connection point. This contact is designed in a mirror symmetric manner in the first and second support structures, and the number of such contacts is 2. When the second single structure is stretched or compressed axially along the direction of the third connecting plate, it expands and deforms. One side of the connection between the first connecting plate and the first rib is in contact with the fourth connecting plate. This contact is designed in a mirror symmetric manner in the first support structure and the second support structure, and the number of such contacts is 2. One side of the connection between the second connecting plate and the second rib is in contact with the fifth connecting plate. This contact is designed in a mirror symmetric manner in the first support structure and the second support structure, and the number of such contacts is 2.

6. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, The first single-unit structure expands when stretched or compressed along the axial direction perpendicular to the third connecting plate; the second single-unit structure contracts when stretched or compressed along the axial direction perpendicular to the third connecting plate.

7. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, The first and second monomer structures, which simultaneously expand or contract under tension and compression, are periodically arrayed in their respective planes to form a planar lattice material.

8. The lattice material that simultaneously expands or contracts under tension and compression according to claim 1, characterized in that, The first and second monomer structures, which simultaneously expand or contract under tension and compression, are orthogonally combined and then periodically arrayed along the three-dimensional coordinate axis to form a three-dimensional lattice material.

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