Unit structure with positive and negative Poisson ratios and metamaterial

Abstract

The invention relates to the technical field of metamaterials, and discloses a unit structure with positive and negative Poisson ratios and a metamaterial. Each unit structure comprises a main body frame and a connecting rod, the main body frame comprises a first frame body and a second frame body which are arranged at intervals in the first direction and connected, and the first frame body and the second frame body are in mirror symmetry and each comprise a first bent part and a second bent part which are connected end to end and bent towards each other. The connecting rods extend in the first direction, the first frame body and the second frame body are each provided with one connecting rod, one end of each connecting rod is detachably and movably connected with the first bent part, and the other end of each connecting rod is detachably and movably connected with the second bent part. When the two connecting rods bear a tensile load and a compressive load, the connecting rods are selected to be in contact with the first bending part or the second bending part for force transmission. No matter the main body frame bears a tensile load or a compression load, the main body frame generates expansion deformation or contraction deformation in the second direction, so that the unit structure and the metamaterial have the positive Poisson's ratio characteristic and the negative Poisson's ratio characteristic, and the application range of the metamaterial is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterials, and in particular to a unit structure and a metamaterial with positive and negative Poisson's ratios. Background Art

[0002] Poisson's ratio is a key parameter in characterizing the mechanical properties of materials. It describes the ratio of lateral strain to longitudinal strain when a material is subjected to axial force. Traditional materials typically exhibit a positive Poisson's ratio effect, meaning they contract laterally when stretched axially and expand laterally when compressed axially. However, some artificial structures or specialized materials (such as auxetic materials) can exhibit a negative Poisson's ratio, exhibiting deformation behavior opposite to that of conventional materials: they expand laterally when stretched and contract laterally when compressed.

[0003] At present, most materials only have a single positive or negative Poisson's ratio characteristic, which limits their application in multi-scenario adaptive design. Although directional design of the Poisson's ratio can be achieved through artificial structure or composite material regulation, it is still difficult to achieve that the same material has both positive and negative Poisson's ratio characteristics under different conditions.

[0004] Therefore, there is an urgent need for a unit structure and metamaterial with positive and negative Poisson's ratio to solve the above problems. Summary of the Invention

[0005] Based on the above problems, the purpose of the present invention is to provide a unit structure and metamaterial with positive and negative Poisson's ratio, which can simultaneously possess positive Poisson's ratio properties and negative Poisson's ratio properties, thereby broadening the application scope of metamaterials.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, a unit cell structure having a positive and negative Poisson's ratio is provided, comprising:

[0008] The main frame includes a first frame body and a second frame body spaced apart and connected along a first direction, wherein the first frame body and the second frame body are mirror-symmetrical and each includes a first bending portion and a second bending portion connected end to end and bent toward each other;

[0009] a connecting rod extending along the first direction, the connecting rod being provided on both the first frame body and the second frame body, one end of the connecting rod being detachably connected to the first bending portion, and the other end of the connecting rod being detachably connected to the second bending portion;

[0010] When the two connecting rods are subjected to tensile loads and compressive loads, one of the connecting rods contacts the first bending portion or the second bending portion to transmit force, so that the main frame produces expansion deformation or contraction deformation along the second direction under tensile loads and compressive loads, and the first direction is perpendicular to the second direction.

[0011] As an optional solution to the unit structure with positive and negative Poisson's ratios of the present invention, the main frame also includes a first connecting portion and a second connecting portion spaced apart along the second direction, the first connecting portion connecting the first end of the first frame body and the first end of the second frame body, and the second connecting portion connecting the second end of the first frame body and the second end of the second frame body.

[0012] As an optional solution of the unit structure with positive and negative Poisson's ratio of the present invention, a first through-hole is provided at the bending part of the first bending part, the first end of the connecting rod is movable through the first through-hole, and a first stop portion is provided on the side facing away from the second bending part; a second through-hole is provided at the bending part of the second bending part, the second end of the connecting rod is movable through the second through-hole, and a second stop portion is provided on the side facing away from the first bending part.

[0013] As an optional solution of the unit structure with positive and negative Poisson's ratios of the present invention, the distance between the first stop portion and the second stop portion is greater than the distance between the first bending portion and the second bending portion in the first direction.

[0014] As an optional solution of the unit structure with positive and negative Poisson's ratio of the present invention, the first bending portion and the second bending portion each include a first inclined section, a straight section and a second inclined section connected in sequence;

[0015] The first through-hole is provided in the straight section of the first bent portion, and the cross-sectional dimension of the first stop portion is the same as the cross-sectional dimension of the straight section of the first bent portion;

[0016] The second through hole is provided in the straight section of the second bent portion, and the cross-sectional dimension of the second stopping portion is the same as the cross-sectional dimension of the straight section of the second bent portion.

[0017] As an optional solution of the unit structure with positive and negative Poisson's ratio of the present invention, a third through-hole is provided on the first bending portion, the first end of the connecting rod is movable through the third through-hole, and a third stop portion is provided on the side facing the second bending portion, and a fourth stop portion is provided on the second end of the connecting rod, and the fourth stop portion is detachably contacted with the side of the second bending portion facing the first bending portion.

[0018] As an optional solution of the unit structure with positive and negative Poisson's ratios of the present invention, the distance between the third stop portion and the fourth stop portion is smaller than the distance between the first bending portion and the second bending portion in the first direction.

[0019] On the other hand, a metamaterial with positive and negative Poisson's ratio is provided, comprising a plurality of unit structures with positive and negative Poisson's ratio as described above, wherein the plurality of unit structures are arranged in an array.

[0020] As an optional solution of the metamaterial with positive and negative Poisson's ratios of the present invention, the unit structures are arranged in a plurality of rows, each row including a plurality of the unit structures arranged along the second direction, and the main frames of two adjacent unit structures in the same row are fixedly connected;

[0021] The connecting rods of the adjacent rows of unit structures are fixedly connected, and the connecting rods are movably connected to the corresponding main frames.

[0022] As an optional solution of the metamaterial with positive and negative Poisson's ratio of the present invention, the metamaterial with positive and negative Poisson's ratio further includes:

[0023] a first load-bearing beam, wherein in the first row of the unit structures, first ends of the connecting rods on the first frames are all fixedly connected to the first load-bearing beam;

[0024] The second load-bearing beam, in the last row of the unit structures, the first ends of the plurality of connecting rods on the second frames are all fixedly connected to the second load-bearing beam.

[0025] The beneficial effects of the present invention are:

[0026] The unit structure and metamaterial with positive and negative Poisson's ratios provided by the present invention have a first frame and a second frame that are arranged in mirror symmetry in a first direction, and the first bent portion and the second bent portion are bent toward each other. Therefore, the second bent portion of the first frame and the second bent portion of the second frame are bent away from each other, forming a positive Poisson's ratio structure between the two first bent portions and a negative Poisson's ratio structure between the two second bent portions.

[0027] The connecting rods on the first frame and the connecting rods on the second frame both bear tensile loads. When the connecting rods separate from the first bends and come into contact with the second bends to transmit force, the two second bends bear tensile loads, causing the main frame to exhibit a negative Poisson's ratio, thereby generating expansion deformation in the second direction. Correspondingly, when the two connecting rods bear compressive loads, when the connecting rods separate from the second bends and come into contact with the first bends to transmit force, the two first bends bear compressive loads, causing the main frame to exhibit a positive Poisson's ratio, thereby generating expansion deformation in the second direction. In other words, the main frame experiences expansion deformation regardless of whether it is subjected to tensile or compressive loads, resulting in the unit structure and metamaterial exhibiting both positive and negative Poisson's ratio properties, broadening the application range of metamaterials.

[0028] When the two connecting rods are subjected to a tensile load and the connecting rods separate from the second bends and contact the first bends to transmit force, the two first bends are subjected to a tensile load, and the main frame exhibits a positive Poisson's ratio, resulting in contraction deformation in the second direction. Correspondingly, when the two connecting rods are subjected to a compressive load and the connecting rods separate from the first bends and contact the second bends to transmit force, the two second bends are subjected to a compressive load, and the main frame exhibits a negative Poisson's ratio, resulting in contraction deformation in the second direction. In other words, the main frame undergoes contraction deformation regardless of whether it is subjected to a tensile or compressive load, resulting in the unit structure and metamaterial exhibiting both positive and negative Poisson's ratio properties, which can broaden the application range of metamaterials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in describing the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without any creative work.

[0030] Figure 1 Schematic diagram of a unit structure with positive and negative Poisson's ratios provided in Example 1 of the present invention;

[0031] Figure 2 1 is a schematic diagram of a decomposition of a unit structure with positive and negative Poisson's ratios provided in Example 1 of the present invention;

[0032] Figure 3 Schematic diagram of a metamaterial with positive and negative Poisson's ratio provided by Example 1 of the present invention.

[0033] Figure 4 yes Figure 3 A partial view of

[0034] Figure 5 is a schematic diagram of a unit structure with positive and negative Poisson's ratios provided by the second embodiment of the present invention;

[0035] Figure 6 1 is a schematic diagram of a decomposition of a unit structure with positive and negative Poisson's ratios provided in the second embodiment of the present invention;

[0036] Figure 7 Schematic diagram of a metamaterial with positive and negative Poisson's ratio provided by the second embodiment of the present invention.

[0037] Figure 8 yes Figure 7 A partial view of the .

[0038] In the picture:

[0039] 1. Main frame; 2. Connecting rod;

[0040] 11. First frame; 12. Second frame; 13. First connecting portion; 14. Second connecting portion;

[0041] 111. First bending portion; 112. Second bending portion;

[0042] 11101, first perforation; 11102, third perforation; 1120, second perforation;

[0043] 1111, first inclined section; 1112, straight section; 1113, second inclined section;

[0044] 21. First stopper; 22. Second stopper; 23. Third stopper; 24. Fourth stopper;

[0045] 10. Unit structure; 20. First load-bearing beam; 30. Second load-bearing beam. DETAILED DESCRIPTION

[0046] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly understood, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the described embodiments are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0047] In the description of the present invention, it should be noted that the terms "center," "up," "down," "left," "right," "vertical," "horizontal," "inside," and "outside" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0048] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed or detachable connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention.

[0049] like Figures 1 to 8 As shown, this embodiment provides a unit structure 10 with positive and negative Poisson's ratios, which can simultaneously possess positive and negative Poisson's ratio properties, thereby expanding the application range of the material. The unit structure 10 with positive and negative Poisson's ratios includes a main frame 1 and a connecting rod 2.

[0050] The main frame 1 includes a first frame body 11 and a second frame body 12 spaced apart and connected along a first direction. The first frame body 11 and the second frame body 12 are mirror-symmetrical and both include a first bending portion 111 and a second bending portion 112 connected end to end and bent toward each other. The connecting rod 2 extends along the first direction. The first frame body 11 and the second frame body 12 are both provided with a connecting rod 2. One end of the connecting rod 2 is detachably connected to the first bending portion 111, and the other end is detachably connected to the second bending portion 112. When the two connecting rods 2 are subjected to tensile loads and compressive loads, the connecting rod 2 selectively contacts the first bending portion 111 or the second bending portion 112 to transmit force, so that the main frame 1 undergoes expansion deformation or contraction deformation along the second direction under both tensile loads and compressive loads, and the first direction is perpendicular to the second direction.

[0051] In this embodiment, the first direction is the direction of the tensile load and the compressive load. Figure 1 The middle direction is the up and down direction; the second direction is the deformation direction of the main frame 1, specifically Figure 1 The middle represents the left and right directions.

[0052] The unit structure 10 with positive and negative Poisson's ratios provided in this embodiment has a first frame body 11 and a second frame body 12 arranged in mirror symmetry in the first direction, and the first bending portion 111 and the second bending portion 112 are bent toward each other. Therefore, the second bending portion 112 of the first frame body 11 and the second bending portion 112 of the second frame body 12 are bent away from each other, forming a positive Poisson's ratio structure between the two first bending portions 111 and a negative Poisson's ratio structure between the two second bending portions 112.

[0053] like Figure 1 As shown, the connecting rods 2 on the first frame 11 and the connecting rods 2 on the second frame 12 are both subjected to tensile loads. When the connecting rods 2 separate from the first bend 111 and contact the second bend 112 to transmit force, the two second bends 112 are subjected to tensile loads, and the main frame 1 has a negative Poisson's ratio characteristic, thereby generating expansion deformation in the second direction. Correspondingly, the two connecting rods 2 are subjected to compressive loads. When the connecting rods 2 separate from the second bend 112 and contact the first bend 111 to transmit force, the two first bends 111 are subjected to compressive loads, and the main frame 1 has a positive Poisson's ratio characteristic, thereby generating expansion deformation in the second direction. In other words, the main frame 1 generates expansion deformation regardless of whether it is subjected to tensile or compressive loads, so that the unit structure 10 and the metamaterial have both positive and negative Poisson's ratio characteristics, which can broaden the application range of metamaterials.

[0054] like Figure 5 As shown, when the two connecting rods 2 are subjected to a tensile load and the connecting rods 2 separate from the second bend 112 and contact the first bend 111 to transmit force, the two first bends 111 are subjected to a tensile load, and the main frame 1 has a positive Poisson's ratio characteristic, thereby generating contraction deformation in the second direction. Correspondingly, when the two connecting rods 2 are subjected to a compressive load and the connecting rods 2 separate from the first bend 111 and contact the second bend 112 to transmit force, the two second bends 112 are subjected to a compressive load, and the main frame 1 has a negative Poisson's ratio characteristic, thereby generating contraction deformation in the second direction. In other words, the main frame 1 generates contraction deformation regardless of whether it is subjected to a tensile load or a compressive load, so that the unit structure 10 and the metamaterial have both positive and negative Poisson's ratio characteristics, which can broaden the application range of metamaterials.

[0055] See Figure 1 and Figure 5 The main frame 1 further includes a first connecting portion 13 and a second connecting portion 14 spaced apart along the second direction. The first connecting portion 13 connects the first end of the first frame body 11 and the first end of the second frame body 12, and the second connecting portion 14 connects the second end of the first frame body 11 and the second end of the second frame body 12. That is, the first frame body 11 and the second frame body 12 are connected as a whole via the first connecting portion 13 and the second connecting portion 14. When the main frame 1 is subjected to a tensile load or a compressive load, the first connecting portion 13 and the second connecting portion 14 expand and contract in the second direction.

[0056] In this embodiment, the first connecting portion 13 and the second connecting portion 14 both extend along the first direction. The two first bent portions 111 and the first connecting portion 13 and the second connecting portion 14 form an outwardly convex hexagonal shape, which has a positive Poisson's ratio. The two second bent portions 112 and the first connecting portion 13 and the second connecting portion 14 form an inwardly concave hexagonal shape, which has a negative Poisson's ratio.

[0057] Furthermore, the first frame body 11 , the second frame body 12 , the first connecting portion 13 and the second connecting portion 14 are integrally formed, so that the structure of the entire main frame 1 is more stable and the force transmission effect is better.

[0058] For example, the main frame 1 and the connecting rod 2 can be formed by 3D printing. In other embodiments, they can also be formed by integral injection molding.

[0059] The following describes two unit structures 10 and metamaterials with positive and negative Poisson's ratios with reference to the first and second embodiments, respectively.

[0060] Example 1

[0061] like Figure 1 and Figure 2 As shown, this embodiment provides a unit structure 10 with positive and negative Poisson's ratios, which includes a main frame 1 and two connecting rods 2.

[0062] See Figure 1 and Figure 2 The first bent portion 111 is provided with a first through-hole 11101 at its bend. The first end of the connecting rod 2 is movable through the first through-hole 11101. A first stopper 21 is provided on the side facing away from the second bent portion 112. The first stopper 21 can contact and transmit force to the first bent portion 111. The second bent portion 112 is provided with a second through-hole 1120 at its bend. The second end of the connecting rod 2 is movable through the second through-hole 1120. A second stopper 22 is provided on the side facing away from the first bent portion 111. The second stopper 22 can contact and transmit force to the second bent portion 112.

[0063] Specifically, when the connecting rod 2 of the first frame 11 and the connecting rod 2 of the second frame 12 are subjected to a tensile load at the same time, the second stop portion 22 contacts and abuts the side of the second bending portion 112 facing away from the first bending portion 111, while the first stop portion 21 is separated from the first bending portion 111, and no force is applied between the two. Therefore, the bends of the two second bending portions 112 are subjected to a tensile load, thereby causing the main frame 1 to undergo expansion deformation in the second direction. When the connecting rod 2 of the first frame 11 and the connecting rod 2 of the second frame 12 are subjected to a compressive load at the same time, the first stop portion 21 contacts and abuts the side of the first bending portion 111 facing away from the second bending portion 112, while the second stop portion 22 is separated from the second bending portion 112. Therefore, the bends of the two first bending portions 111 are subjected to a compressive load, thereby causing the main frame 1 to undergo expansion deformation in the second direction.

[0064] In this embodiment, the distance between the first stop portion 21 and the second stop portion 22 is greater than the distance between the first bend portion 111 and the second bend portion 112 in the first direction. This configuration allows the connecting rod 2 to move a certain distance in the first direction. When the connecting rod 2 is subjected to a tensile load, the second stop portion 22 is ensured to contact the bend of the second bend portion 112 while the first stop portion 21 is able to separate from the first bend portion 111. When the connecting rod 2 is subjected to a compressive load, the first stop portion 21 is ensured to contact the first bend portion 111 while the second stop portion 22 is able to separate from the second bend portion 112, thereby achieving detachable contact between the first stop portion 21 and the second stop portion 22 and the corresponding first bend portion 111 and the second bend portion 112.

[0065] Furthermore, the dimensions of the first through-hole 11101 and the second through-hole 1120 are both larger than the cross-sectional dimensions of the connecting rod 2, ensuring that the connecting rod 2 can move freely in the first direction. The cross-sectional dimensions of the first stopper 21 are larger than the dimensions of the first through-hole 11101, and the cross-sectional dimensions of the second stopper 22 are larger than the dimensions of the second through-hole 1120, preventing the connecting rod 2 from detaching from the first frame 11 (second frame 12).

[0066] Optionally, see Figure 1 and Figure 2 The first bend 111 and the second bend 112 each include a first inclined section 1111, a straight section 1112, and a second inclined section 1113, which are connected in sequence. The first inclined section 1111 and the second inclined section 1113 are inclined toward each other. The first through-hole 11101 is provided in the straight section 1112 of the first bend 111. The cross-sectional dimensions of the first stopper 21 are the same as those of the straight section 1112 of the first bend 111. The second through-hole 1120 is provided in the straight section 1112 of the second bend 112. The cross-sectional dimensions of the second stopper 22 are the same as those of the straight section 1112 of the second bend 112. This arrangement ensures that the contact between the first stopper 21 and the first bend 111 is planar, and the contact between the second stopper 22 and the second bend 112 is planar, resulting in more uniform and stable force transmission.

[0067] Exemplarily, the first stop portion 21 and the second stop portion 22 are both rectangular blocks, and the length and width of the rectangular blocks are equal to the length and width of the straight section 1112 .

[0068] Of course, in other embodiments, the cross-sectional area of ​​the straight section 1112 may also be designed to be slightly larger than the cross-sectional area of ​​the first stop portion 21 (the second stop portion 22 ).

[0069] like Figure 3 As shown, this embodiment also provides a metamaterial with positive and negative Poisson's ratios, including a plurality of unit structures 10 with positive and negative Poisson's ratios as described above, and the plurality of unit structures 10 are arranged in an array. When the metamaterial is subjected to a tensile load along a first direction, the connecting rods 2 of all the unit structures 10 are separated from the first bending portion 111 and contact the second bending portion 112 to transmit force. The metamaterial as a whole has a negative Poisson's ratio characteristic and can produce expansion deformation in the second direction. When the metamaterial is subjected to a compressive load along the first direction, the connecting rods 2 of all the unit structures 10 are separated from the second bending portion 112 and contact the first bending portion 111 to transmit force. The metamaterial as a whole has a positive Poisson's ratio characteristic and can produce expansion deformation in the second direction. That is, regardless of whether it is subjected to a tensile load or a compressive load, the metamaterial produces expansion deformation, and has both positive Poisson's ratio characteristics and negative Poisson's ratio characteristics.

[0070] See Figure 3The unit structures 10 are arranged in a plurality of rows, each row comprising a plurality of unit structures 10 arranged along the second direction. The main frames 1 of two adjacent unit structures 10 in the same row are fixedly connected, so that the multiple unit structures 10 in the same row can expand and deform synchronously when subjected to tensile or compressive loads. Specifically, in this embodiment, the first connecting portion 13 and the second connecting portion 14 of the main frames 1 of two adjacent unit structures 10 are combined, that is, the two main frames 1 share a single connecting portion, making the structure more compact and reasonable.

[0071] Furthermore, the connecting rods 2 of adjacent rows of unit structures 10 are fixedly connected and movably connected to the corresponding main frames 1. When the metamaterial is subjected to tensile and compressive loads, the main frames 1 of adjacent rows of unit structures 10 transmit force through the two fixedly connected connecting rods 2, allowing multiple rows of unit structures 10 to simultaneously withstand tensile or compressive loads.

[0072] See Figure 3 and Figure 4 In two adjacent rows of unit structures 10, the connecting rod 2 on the second frame body 12 of the main frame 1 of the upper row is fixedly connected to the connecting rod 2 on the first frame body 11 of the main frame 1 of the lower row. Specifically, in this embodiment, the first stopper 21 of the two connecting rods 2 is combined, that is, the two connecting rods 2 share a first stopper 21, making the structure more compact and reasonable.

[0073] See Figure 3 The metamaterial with positive and negative Poisson's ratios also includes a first load-bearing beam 20 and a second load-bearing beam 30. In the first row of unit structures 10, the first ends of the connecting rods 2 on the first frame 11 are fixedly connected to the first load-bearing beam 20; in the last row of unit structures 10, the first ends of the connecting rods 2 on the second frame 12 are fixedly connected to the second load-bearing beam 30. The arrangement of the first and second load-bearing beams 20 and 30 enables the multiple unit structures 10 in the first row to simultaneously withstand tensile or compressive loads. Similarly, the multiple unit structures 10 in the last row can also simultaneously withstand tensile or compressive loads, thereby ensuring uniform force distribution across the entire metamaterial.

[0074] For example, when there is only one row of unit structures 10, the first load-bearing beam 20 is fixedly connected to the connecting rods 2 of the first frames 11 of the multiple unit structures 10, and the second load-bearing beam 30 is fixedly connected to the connecting rods 2 of the second frames 12 of the multiple unit structures 10. When two rows of unit structures 10 are provided, the first load-bearing beam 20 is fixedly connected to the connecting rods 2 on the first frames 11 of the multiple unit structures 10 in the first row, and the second load-bearing beam 30 is fixedly connected to the connecting rods 2 on the second frames 12 of the multiple unit structures 10 in the second row, and so on.

[0075] In this embodiment, the metamaterial can be formed by 3D printing, that is, the main frame 1 and the connecting rod 2 are printed at the same time, and a gap is provided at the contact interface between the connecting rod 2 and the first bending portion 111 and the second bending portion 112 of the main frame 1.

[0076] In some other embodiments, the main frame 1 and the connecting rod 2 can also be manufactured separately, and then the connecting rod 2 is assembled to the first frame 11 (second frame 12) through the first through-hole 11101 and the second through-hole 1120. At this time, the first stop portion 21 and / or the second stop portion 22 on the connecting rod 2 can be designed to be detachable for easy assembly.

[0077] The unit structure 10 and metamaterial with positive and negative Poisson's ratios of this embodiment are of great significance for expanding the application of materials in flexible devices, intelligent protection, biomedicine and other fields.

[0078] Example 2

[0079] This embodiment provides a unit structure 10 with positive and negative Poisson's ratios, which differs from the first embodiment in that:

[0080] See Figure 5 and Figure 6 The first bent portion 111 is provided with a third through-hole 11102. The first end of the connecting rod 2 is movable through the third through-hole 11102. A third stopper 23 is provided on the side facing the second bent portion 112. The third stopper 23 can contact and transmit force to the first bent portion 111. A fourth stopper 24 is provided on the second end of the connecting rod 2. The fourth stopper 24 is in detachable contact with the side of the second bent portion 112 facing the first bent portion 111. The fourth stopper 24 can contact and transmit force to the second bent portion 112.

[0081] Specifically, when the connecting rod 2 of the first frame 11 and the connecting rod 2 of the second frame 12 are simultaneously subjected to a tensile load, the third stopper 23 contacts and abuts the side of the first bend 111 toward the second bend 112, while the fourth stopper 24 is separated from the second bend 112, and no force is applied between the two. Therefore, the bends of the two first bends 111 are subjected to a tensile load, thereby causing the main frame 1 to produce a contraction deformation in the second direction. When the connecting rod 2 of the first frame 11 and the connecting rod 2 of the second frame 12 are simultaneously subjected to a compressive load, the fourth stopper 24 contacts and abuts the side of the second bend 112 toward the first bend 111, while the third stopper 23 is separated from the first bend 111. Therefore, the bends of the two second bends 112 are subjected to a compressive load, thereby causing the main frame 1 to produce a contraction deformation in the second direction.

[0082] In this embodiment, the distance between the third stopper 23 and the fourth stopper 24 is smaller than the distance in the first direction between the first bend 111 and the second bend 112. This arrangement allows the connecting rod 2 to move a certain distance in the first direction. When the connecting rod 2 is subjected to a tensile load, the third stopper 23 is ensured to be in contact with the bend of the first bend 111 while the fourth stopper 24 is able to separate from the second bend 112. When the connecting rod 2 is subjected to a compressive load, the fourth stopper 24 is ensured to be in contact with the bend of the second bend 112 while the third stopper 23 is able to separate from the first bend 111, thereby achieving detachable contact between the third and fourth stopper 23 and the corresponding first and second bends 111 and 112.

[0083] Furthermore, the size of the third through hole 11102 is larger than the cross-sectional size of the connecting rod 2, ensuring that the connecting rod 2 can move freely in the first direction. The cross-sectional size of the third stopper 23 is larger than the size of the third through hole 11102, preventing the connecting rod 2 from detaching from the first frame 11 (second frame 12).

[0084] Optionally, see Figure 5 and Figure 6 The first bend 111 and the second bend 112 each include a first inclined section 1111, a straight section 1112, and a second inclined section 1113 connected in sequence, with the first inclined section 1111 and the second inclined section 1113 being inclined toward each other. The third through-hole 11102 is provided in the straight section 1112 of the first bend 111. The cross-sectional dimensions of the third stopper 23 are the same as those of the straight section 1112 of the first bend 111. The cross-sectional dimensions of the fourth stopper 24 are the same as those of the straight section 1112 of the second bend 112. This arrangement enables the third stopper 23 to contact the first bend 111 in a planar manner, and the fourth stopper 24 to contact the second bend 112 in a planar manner, making force transmission more uniform and stable.

[0085] For example, the third stopper 23 and the fourth stopper 24 are both rectangular blocks, and the length and width of the rectangular blocks are equal to the length and width of the straight section 1112. Of course, in other embodiments, the cross-sectional area of ​​the straight section 1112 can also be designed to be slightly larger than the cross-sectional area of ​​the third stopper 23 (fourth stopper 24).

[0086] like Figure 7As shown, this embodiment also provides a metamaterial with positive and negative Poisson's ratios, including a plurality of unit structures 10 with positive and negative Poisson's ratios as described above, and the plurality of unit structures 10 are arranged in an array. When the metamaterial is subjected to a tensile load along a first direction, the connecting rods 2 of all the unit structures 10 are separated from the second bending portion 112 and are in contact with the first bending portion 111 to transmit force. The metamaterial as a whole has a positive Poisson's ratio characteristic and can produce a contraction deformation in the second direction. When the metamaterial is subjected to a compressive load along the first direction, the connecting rods 2 of all the unit structures 10 are separated from the first bending portion 111 and are in contact with the second bending portion 112 to transmit force. The metamaterial as a whole has a negative Poisson's ratio characteristic and can produce a contraction deformation in the second direction. That is, regardless of whether it is subjected to a tensile load or a compressive load, the metamaterial produces a contraction deformation, and has both positive Poisson's ratio characteristics and negative Poisson's ratio characteristics.

[0087] like Figure 7 As shown, the unit structures 10 are arranged in several rows, each row including multiple unit structures 10 arranged along the second direction. The main frames 1 of two adjacent unit structures 10 in the same row are fixedly connected, so that the multiple unit structures 10 in the same row can shrink and deform synchronously when subjected to tensile or compressive loads. Specifically, in this embodiment, the first connecting portion 13 and the second connecting portion 14 of the main frames 1 of two adjacent unit structures 10 are combined, that is, the two main frames 1 share a single connecting portion, making the structure more compact and reasonable.

[0088] Furthermore, the connecting rods 2 of adjacent rows of unit structures 10 are fixedly connected and movably connected to the corresponding main frames 1. When the metamaterial is subjected to tensile and compressive loads, the main frames 1 of adjacent rows of unit structures 10 transmit force through the two fixedly connected connecting rods 2, allowing multiple rows of unit structures 10 to simultaneously withstand tensile or compressive loads.

[0089] like Figure 8 As shown, in two adjacent rows of unit structures 10, the connecting rod 2 on the second frame body 12 of the main frame 1 of the upper row is fixedly connected to the connecting rod 2 on the first frame body 11 of the main frame 1 of the lower row. Specifically in this embodiment, the portions of the two connecting rods 2 extending out of the third through-holes 11102 are merged, making the structure more compact and the force transmission more stable.

[0090] like Figure 7 and Figure 8As shown, the metamaterial with positive and negative Poisson's ratios also includes a first load-bearing beam 20 and a second load-bearing beam 30. In the first row of unit structures 10, the first ends of the connecting rods 2 on the multiple first frames 11 (one end of the telescopic third through-hole 11102) are all fixedly connected to the first load-bearing beam 20; in the last row of unit structures 10, the first ends of the connecting rods 2 on the multiple second frames 12 are all fixedly connected to the second load-bearing beam 30. This allows the multiple unit structures 10 in the first row to simultaneously withstand tensile or compressive loads. Correspondingly, the multiple unit structures 10 in the last row can also simultaneously withstand tensile or compressive loads, thereby ensuring uniform force distribution across the entire metamaterial.

[0091] In this embodiment, the metamaterial can be formed by 3D printing, that is, the main frame 1 and the connecting rod 2 are printed at the same time, and a gap is provided at the contact interface between the connecting rod 2 and the first bending portion 111 and the second bending portion 112 of the main frame 1.

[0092] In some other embodiments, the main frame 1 and the connecting rod 2 can also be manufactured separately, and then the connecting rod 2 can be assembled to the first frame 11 (second frame 12) through the third through hole 11102. At this time, the third stop portion 23 and / or the fourth stop portion 24 on the connecting rod 2 can be designed to be detachable for easy assembly.

[0093] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments, and substitutions are possible for those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A unit structure with positive and negative Poisson's ratio, characterized in that: include: A main frame (1) comprises a first frame body (11) and a second frame body (12) spaced apart and connected along a first direction, wherein the first frame body (11) and the second frame body (12) are mirror-symmetrical and each comprises a first bending portion (111) and a second bending portion (112) connected end to end and bent toward each other; a connecting rod (2) extending along the first direction, the connecting rod (2) being provided on both the first frame (11) and the second frame (12), one end of the connecting rod (2) being detachably connected to the first bending portion (111), and the other end being detachably connected to the second bending portion (112); When the two connecting rods (2) are subjected to a tensile load and a compressive load, the connecting rod (2) selectively contacts the first bending portion (111) or the second bending portion (112) to transmit force, so that the main frame (1) generates expansion deformation or contraction deformation along a second direction under both the tensile load and the compressive load, and the first direction is perpendicular to the second direction.

2. The unit structure with positive and negative Poisson's ratio according to claim 1, characterized in that: The main frame (1) further comprises a first connecting portion (13) and a second connecting portion (14) spaced apart along the second direction, wherein the first connecting portion (13) connects the first end of the first frame (11) and the first end of the second frame (12), and the second connecting portion (14) connects the second end of the first frame (11) and the second end of the second frame (12).

3. The unit structure with positive and negative Poisson's ratio according to claim 1, characterized in that: A first through-hole (11101) is provided at the bending portion of the first bending portion (111), the first end of the connecting rod (2) is movable through the first through-hole (11101), and a first stopper (21) is provided on the side facing away from the second bending portion (112); a second through-hole (1120) is provided at the bending portion of the second bending portion (112), the second end of the connecting rod (2) is movable through the second through-hole (1120), and a second stopper (22) is provided on the side facing away from the first bending portion (111).

4. The unit structure with positive and negative Poisson's ratio according to claim 3, characterized in that: The distance between the first stop portion (21) and the second stop portion (22) is greater than the distance between the first bending portion (111) and the second bending portion (112) in the first direction.

5. The unit structure with positive and negative Poisson's ratio according to claim 3, characterized in that: The first bending portion (111) and the second bending portion (112) each comprise a first inclined section (1111), a straight section (1112), and a second inclined section (1113) connected in sequence; The first through hole (11101) is provided in the straight section (1112) of the first bending portion (111), and the cross-sectional dimension of the first stop portion (21) is the same as the cross-sectional dimension of the straight section (1112) of the first bending portion (111); The second through hole (1120) is provided in the straight section (1112) of the second bending portion (112), and the cross-sectional dimension of the second stop portion (22) is the same as the cross-sectional dimension of the straight section (1112) of the second bending portion (112).

6. The unit structure with positive and negative Poisson's ratio according to claim 1, characterized in that: A third through-hole (11102) is provided on the first bending portion (111), the first end of the connecting rod (2) is movable through the third through-hole (11102), and a third stopper (23) is provided on the side facing the second bending portion (112), and a fourth stopper (24) is provided on the second end of the connecting rod (2), and the fourth stopper (24) is in detachable contact with the side of the second bending portion (112) facing the first bending portion (111).

7. The unit structure with positive and negative Poisson's ratio according to claim 6, characterized in that: The distance between the third stop portion (23) and the fourth stop portion (24) is smaller than the distance between the first bending portion (111) and the second bending portion (112) in the first direction.

8. A metamaterial with positive and negative Poisson's ratio, characterized in that It comprises a plurality of unit structures with positive and negative Poisson's ratios as described in any one of claims 1 to 7, wherein the plurality of unit structures are arranged in an array.

9. The metamaterial having positive and negative Poisson's ratio according to claim 8, characterized in that: The unit structures are arranged in a plurality of rows, each row comprising a plurality of the unit structures arranged along the second direction, and the main frames (1) of two adjacent unit structures in the same row are fixedly connected; The connecting rods (2) of the adjacent rows of unit structures are fixedly connected, and the connecting rods (2) are movably connected to the corresponding main frames (1).

10. The metamaterial with positive and negative Poisson's ratio according to claim 9, characterized in that: The metamaterial having positive and negative Poisson's ratios further includes: a first load-bearing beam (20), wherein in the first row of the unit structures, the first ends of the connecting rods (2) on the first frames (11) are all fixedly connected to the first load-bearing beam (20); The second load-bearing beam (30) is configured such that in the last row of the unit structures, the first ends of the connecting rods (2) on the plurality of second frames (12) are fixedly connected to the second load-bearing beam (30).

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