A three-dimensional lattice array structure with controllable poisson's ratio in z direction

Abstract

The application discloses a three-dimensional lattice array structure with a controllable z-direction Poisson's ratio, and a basic unit comprises a lower bottom layer, an upper bottom layer, an intra-unit connecting rod and an inter-unit connecting rod, and the intra-unit connecting rod and the inter-unit connecting rod are symmetrical about the lower bottom layer or the upper bottom layer; a surface formed after arraying the lower bottom layer and the upper bottom layer is a novel negative Poisson's ratio plane structure, which comprises a central concave-arc-side hexagonal structure composed of concave-arc-sides and a chiral structure composed of plane connecting rods, and the plane connecting rods of the lower bottom layer and the upper bottom layer are opposite to each other around the direction of the central concave-arc-side hexagonal structure. The structure proposed by the application couples a chiral structure and a concave-arc-side polygonal structure on the upper bottom layer and the lower bottom layer, has a negative Poisson's ratio characteristic, and simultaneously improves the deformation capacity and the energy absorption and vibration reduction characteristics of the structure; the three-dimensional lattice array structure proposed can change the inclination direction of the connecting rods according to actual requirements, so as to realize a variable Poisson's ratio characteristic, and thus the application range of the structure is expanded.

Description

Technical Field

[0001] This invention belongs to the field of metamaterials technology, specifically relating to a three-dimensional lattice array structure with controllable z-axis Poisson's ratio. Background Technology

[0002] As human industrial capabilities continue to improve, people are placing increasingly broader demands on the performance of material structures. Currently, the vast majority of materials still possess traditional mechanical properties. However, for applications where traditional materials are difficult to use, it is necessary to design material structures with non-traditional mechanical properties. Currently, novel mechanical property material structures include adjustable stiffness structures, negative Poisson's ratio mechanisms, and programmable structures.

[0003] Poisson's ratio is the ratio of the transverse strain to the longitudinal strain of a material when it is subjected to tension or compression, expressed as: Traditional materials typically exhibit a positive Poisson's ratio, meaning they expand laterally under longitudinal compression and contract laterally under longitudinal tension. Currently, many novel structural materials possess a negative Poisson's ratio, meaning they contract laterally under longitudinal compression and expand laterally under longitudinal tension. These materials exhibit novel deformation characteristics and excellent energy absorption and vibration reduction effects.

[0004] However, most current negative Poisson's ratio structures are concave polygonal structures or chiral structures, and most are two-dimensional negative Poisson's ratio structures, meaning that the third-axis deformation is not affected by the first and second-axis deformations, and the third-axis Poisson's ratio value cannot be changed. Meanwhile, concave polygonal structures easily form close-packed structures, thus easily improving the overall deformation rate and structural utilization rate, but their stress-bearing plateau region is narrow, causing them to enter the compaction stage prematurely, resulting in poor deformation capacity. Chiral structures have strong deformation capacity and good energy absorption and vibration reduction effects, but the central ring of a chiral structure hardly participates in the overall deformation, leading to a lower overall deformation rate and structural utilization rate. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a three-dimensional lattice array structure with controllable z-axis Poisson ratio, which addresses the shortcomings of the prior art and solves the technical problems of low overall deformation rate and difficulty in controlling z-axis Poisson ratio in current three-dimensional lattice array structures.

[0006] The present invention adopts the following technical solution:

[0007] A three-dimensional lattice array structure with controllable Z-axis Poisson's ratio includes periodic units. Multiple periodic units are arrayed and connected in the horizontal and vertical directions to form a three-dimensional lattice array structure with controllable Z-axis Poisson's ratio. Each periodic unit has an upper bottom layer and a lower bottom layer. The upper bottom layer or the lower bottom layer is connected by an array to form a continuous and unified structure. The upper bottom layers are connected by unit inner layer connecting rods with the same tilt angle to form a three-dimensional structure. In the vertical direction, adjacent periodic units are connected by inter-unit layer connecting rods. The tilt angles of the unit inner layer connecting rods and the inter-unit layer connecting rods are the same, and they are symmetrically arranged about the upper bottom layer or the lower bottom layer.

[0008] Preferably, both the upper and lower layers contain a centrally concave arc-shaped hexagon, and adjacent centrally concave arc-shaped hexagons are connected by six planar connecting rods to form a chiral structure; the chiral structure is a periodic repeating unit, and the centrally concave arc-shaped hexagon is located at the center of the periodic repeating unit.

[0009] More preferably, the ratio k of the width t of the planar connecting rod to the radius R of the circumscribed circle of the central concave arc hexagon is... t The ratio k of the height d of the planar connecting rod to the radius R of the circumcircle of the central concave arc hexagon. d And the ratio k of the length L of the planar connecting rod to the radius R of the circumcircle of the central concave arc hexagon. L The following conditions must be met:

[0010] 0 < k t <0.5

[0011] 0 < k d <0.5

[0012] 0 < k L <20

[0013] More preferably, when 0 < α < 90°, the Poisson's ratio in the z-direction is... and It is negative; when 90° < α < 180°, the Poisson's ratio in the z-direction is... and It is a positive value, where α is the angle between the inclination direction of the inner layer connecting rod or the inter-layer connecting rod of the unit and the extension direction of the planar connecting rod in the vertical direction.

[0014] More preferably, the central concave arc-shaped hexagon includes six concave arc edges, the angle β between the inner layer connecting rod of the unit and the adjacent concave arc edge, and the angle β' between the inter-layer connecting rod of the unit and the adjacent concave arc edge are symmetrical about the lower bottom layer or the upper bottom layer, and satisfy 45°≤β=β'≤90°.

[0015] More preferably, with the corresponding chord length c fixed, the central angle θ of each concave arc edge satisfies 30°≤θ≤120°.

[0016] Preferably, the inner layer connecting rods and the inter-layer connecting rods are arranged alternately in the array, and the height h between the upper and lower layers formed by planar stretching and the height h' between each periodic unit satisfy h=h' when the z-direction Poisson ratio is set to a constant value.

[0017] Preferably, the number of connecting rods within the unit and the number of connecting rods between units are the same, and are integer multiples of 3, 6, or 6.

[0018] More preferably, the cross-sectional area of ​​the connecting rods between the inner and outer layers of the unit is positively correlated with the elastic modulus of the three-dimensional array structure.

[0019] Preferably, the cross-sectional shape of the inner layer connecting rod and the inter-layer connecting rod is circular, elliptical, triangular, quadrilateral or regular polygon with ≥5 sides, including variable cross-section rods. The cross-section of the variable cross-section rod is circular, elliptical, triangular, quadrilateral or regular polygon with ≥5 sides, and the rod with gradually changing cross-sectional size and shape is formed by modeling.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] A three-dimensional lattice array structure with controllable Z-axis Poisson's ratio is constructed by arranging periodic units in both horizontal and vertical directions. The upper and lower surfaces of each unit are oriented in opposite directions around their geometric centers, and the inclination angles of the connecting rods within and between units are symmetrical about the upper or lower surface. Distinguishing between the upper and lower surfaces, and between the connecting rods within and between units, helps prevent confusion during the fabrication of the array. The use of periodic units facilitates the interconnection of units to form a periodic lattice array structure, reducing manufacturing difficulty. Furthermore, the resulting periodic array structure exhibits excellent energy absorption and vibration reduction characteristics.

[0022] Furthermore, the concave hexagonal shape with a central concave edge and the chiral structure form a novel coupled negative Poisson's ratio structure after unit arraying. This structure exhibits negative Poisson's ratio characteristics under tension or compression, and both the concave hexagonal shape with a central concave edge and the chiral structure undergo deformation, thereby improving the overall deformation rate and material utilization rate of the structure.

[0023] Furthermore, the ratio of the width t of the planar connecting rod to the radius R of the circumscribed circle of the central concave arc hexagon, the ratio of the height d of the planar connecting rod to the radius R of the central concave arc hexagon, and the ratio of the length L of the planar connecting rod to the radius R of the central concave arc hexagon, kL, satisfy the conditions: 0 < kt < 0.5, 0 < kd < 0.5, 0 < kL < 20. This condition ensures the structural stability of the negative Poisson's ratio characteristic. The close values ​​of kt and kd ensure that the dimensions of each part of the structure are close to facilitate processing.

[0024] Furthermore, the angle α between the inclination direction of the connecting rod within a unit or the connecting rod between units and the extension direction of the planar connecting rod in the vertical direction can be selected from two ranges: 0 < α < 90° or 90° < α < 180°, depending on actual needs. This can produce negative or positive Poisson's ratio characteristics in the z-direction. By selecting different angles α within different layers of units in the vertical direction, controllable Poisson's ratio characteristics in the z-direction of the array structure can be achieved.

[0025] Furthermore, the angle β between the inner layer connecting rod and the adjacent concave arc edge, and the angle β' between the inter-layer connecting rod and the adjacent concave arc edge are symmetrical about the lower or upper layer, which can ensure that the shape of the periodic unit is constant; satisfying 45°≤β=β'≤90° can prevent the periodic unit from being crushed.

[0026] Furthermore, with the corresponding chord length c fixed, the central angle θ of each concave arc edge satisfies 30°≤θ≤120°, ensuring that the concave arc edge will not be excessively compressed when subjected to compressive load deformation, thus preventing structural fracture.

[0027] Furthermore, when the Poisson's ratio is set to a constant value, the height h between the upper and lower layers formed by planar stretching and the height h' between each periodic unit satisfy h=h', which is beneficial for the overall processing of the structure.

[0028] Furthermore, the number of connecting rods within the unit is the same as the number of connecting rods between units. The number of rods is set to an integer multiple of 3, 6, or 6 to ensure smooth connection between layers. The number of rods can be changed according to actual needs to adjust the overall elastic modulus of the structure.

[0029] Furthermore, the cross-sectional area of ​​the connecting rods within the unit and the connecting rods between the units is positively correlated with the elastic modulus of the three-dimensional array structure. The cross-sectional area of ​​the rods can be increased or decreased according to actual needs to increase or decrease the overall elastic modulus of the structure, thereby achieving the adjustment of the elastic modulus of the structure.

[0030] Furthermore, the cross-sectional shape of the connecting rods within the unit and the connecting rods between the units is circular, elliptical, triangular, quadrilateral, or a regular polygon with ≥5 sides, including variable cross-section rods. The cross-section of the variable cross-section rod is circular, elliptical, triangular, quadrilateral, or a regular polygon with ≥5 sides. The rods with gradually changing cross-sectional dimensions and shapes formed by modeling can be selected according to actual needs.

[0031] In summary, the periodic lattice array structure of this invention has excellent energy absorption and vibration reduction characteristics. The z-axis controllability of the Poisson ratio is achieved by adjusting the angle. The novel negative Poisson ratio structure in a two-dimensional plane significantly improves the overall deformation rate and material utilization. At the same time, the elastic modulus of the overall structure can be changed by adjusting the size, angle or cross-sectional shape of each part. This invention effectively expands the applicability of lattice array structures and is of great significance for expanding the application fields of three-dimensional lattice array structures.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the three-dimensional lattice multi-row array of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of the three-dimensional lattice unit of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure of the three-dimensional lattice single-row array of the present invention;

[0036] Figure 4 This is a top view of the bottom layer of the three-dimensional lattice array of the present invention;

[0037] Figure 5 This is a top view of the bottom layer of the three-dimensional lattice array of the present invention;

[0038] Figure 6 This is an overall diagram of the upper or lower two-dimensional structure of the present invention;

[0039] Figure 7 This is a simulation diagram of the upper or lower two-dimensional structure of the present invention before deformation;

[0040] Figure 8 This is a simulation diagram of the upper or lower two-dimensional structure of the present invention after deformation;

[0041] Figure 9 A schematic diagram of simulated deformation of a three-dimensional lattice structure with negative Poisson's ratio in the z-direction;

[0042] Figure 10 This is a schematic diagram of the simulated deformation of a three-dimensional lattice structure with positive Poisson's ratio in the z-direction.

[0043] Among them: 1. Periodic unit; 2. Lower bottom layer; 21. Hexagon with concave arc edge at the center; 211. Concave arc edge; 22. Chiral structure; 221. Planar connecting rod; 3. Upper bottom layer; 41. Inner layer connecting rod of the unit; 42. Interlayer connecting rod of the unit. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0046] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0048] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0049] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0050] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0051] This invention provides a three-dimensional lattice array structure with controllable Z-axis Poisson ratio. Each plane layer is a novel negative Poisson ratio structure that combines good deformation effect with high structural application rate. Furthermore, the Z-axis direction can be set to different sizes of Poisson ratio structures according to actual needs.

[0052] Please see Figure 1 The present invention discloses a three-dimensional lattice array structure with controllable z-direction Poisson ratio, comprising multiple periodic units 1, which are arranged in a horizontal and vertical array to form a three-dimensional lattice array structure with controllable z-direction Poisson ratio.

[0053] Please see Figure 2 and Figure 3 The periodic unit 1 includes an upper bottom layer 3 and a lower bottom layer 2 formed by planar stretching, an inner layer connecting rod 41 and an inter-layer connecting rod 42. The upper bottom layer 3 and the lower bottom layer 2 are connected by the inner layer connecting rod 41, and the periodic units 1 are connected by the inter-layer connecting rod 42. Multiple periodic units 1 form a three-dimensional lattice array structure in three-dimensional space through planar connecting rod 221, inner layer connecting rod 41 and inter-layer connecting rod 42. The z-direction is the normal direction of the plane stretched into the upper bottom layer 3 and the lower bottom layer 2, and the xy plane is the plane where the plane stretched into the upper bottom layer 3 and the lower bottom layer 2 is located.

[0054] Please see Figure 4 In the upper layer 3 and lower layer 2 formed by planar stretching, each layer includes a central concave arc-edge hexagon 21 and six planar connecting rods 221. Adjacent central concave arc-edge hexagons 21 are connected by the six planar connecting rods 221 to form a chiral structure 22. The chiral structure formed by the central concave arc-edge hexagon 21 and the planar connecting rods 221 is coupled to form a novel two-dimensional negative Poisson's ratio structure.

[0055] The chiral structure formed by the central concave arc-shaped hexagon 21 of the periodic unit 1 and the planar connecting rod 221 can deform under tensile or compressive stress, and has a negative Poisson's ratio characteristic in the xy plane. It is a negative value.

[0056] When the central concave arc-shaped hexagon 21 is subjected to tension from the planar connecting rod, the tension generates a torque relative to the geometric center of the central concave arc-shaped hexagon 21. This torque causes the central concave arc-shaped hexagon 21 to rotate and expand in all directions.

[0057] In the chiral structure 22, each planar connecting rod 221 has a length of L, a width of t, and a height of d; the ratio of width t to R is k. t The ratio of d to R is k. d The ratio of L to R is k L , where k t k d k L Each satisfies 0 < k t <0.5, 0<k d <0.5, 0<k L <20; ratio k t The condition must be met when k t When >0.5, the absolute value of the negative Poisson's ratio in the xy-plane Significant decrease.

[0058] Please see Figure 2 and Figure 3 The angle between the inner layer connecting rod 41 and the planar connecting rod 221 is α. When 0 < α < 90°, the Poisson's ratio in the z-direction is... and It is negative; when 90° < α < 180°, the Poisson's ratio in the z-direction is... and It is a positive value. In different elements, the angle α is set to different values. When the angle α is set to different values ​​in different directions, it exhibits anisotropic Poisson's ratio characteristics.

[0059] The inner layer connecting rod 41 and the inter-layer connecting rod 42 are arranged alternately in the array. The height h between the upper layer 3 and the lower layer 2 formed by planar stretching and the height h' between each periodic unit 1 satisfy h=h'. When the height h and h' increase, the density of the lattice array structure will decrease.

[0060] The angle between the inner layer connecting rod 41 and the adjacent concave arc edge 211 is β, and the angle between the inter-layer connecting rod 42 and the adjacent concave arc edge 211 is β'; β and β' are symmetrical about the lower bottom layer 2 or the upper bottom layer 3, and satisfy 45°≤β=β'≤90°.

[0061] The cross-sectional shape of the inner layer connecting rod 41 and the inter-layer connecting rod 42 is circular, elliptical, triangular, quadrilateral or regular polygon with ≥5 sides, including variable cross-section rods.

[0062] A variable cross-section bar is a bar whose cross-section is a circle, ellipse, triangle, quadrilateral, or a regular polygon with ≥5 sides. The cross-sectional dimensions and shape of the bar gradually change through modeling methods such as lofting and scanning.

[0063] The number of inner-layer connecting rods 41 is the same as the number of inter-layer connecting rods 42, which is a multiple of 3, 6, or 6; the cross-sectional area of ​​the inner-layer connecting rods 41 and the inter-layer connecting rods 42 is positively correlated with the elastic modulus of the three-dimensional array structure.

[0064] Please see Figure 2 and Figure 4 Periodic unit 1 is formed Figure 1 After the array structure shown, the top view of the lower layer 2 or the bottom view of the upper layer 3 is... Figure 4 , Figure 4 The structure shown includes a centrally concave arc-shaped hexagon 21 and a chiral structure 22. The centrally concave arc-shaped hexagon 21 is composed of concave arc edges 211, and the chiral structure 22 is connected by a planar connecting rod 221 and is composed of adjacent concave arc edges 211.

[0065] The six planar connecting rods 221 in the upper layer 3 and the lower layer 2 have a clear clockwise or counterclockwise circling direction with respect to the central concave arc-shaped hexagon 21, and the circling direction of the upper layer 3 is opposite to that of the lower layer 2. That is, when the planar connecting rods of the upper layer 3 circulate clockwise around the central concave arc-shaped hexagon 21, the lower layer 2 needs to circulate counterclockwise around the central concave arc-shaped hexagon 21; the six arc sides of the central concave arc-shaped hexagon 21 have the same size with respect to the central angle θ.

[0066] In the centrally concave arc-side hexagon 21, the central angle of each concave arc-side 211 is θ, and the chord length corresponding to each concave arc-side 211 is c; when c remains unchanged, θ satisfies 30°≤θ≤120°; the radius of the circumcircle of the centrally concave arc-side hexagon 21 is R.

[0067] The corresponding chord of the concave arc edge 211 has an angle γ with the planar connecting rod 221. The distance between the geometric centers of two adjacent central concave arc edge hexagons 21 is A. That is, the line connecting the geometric centers of any three adjacent concave arc edge hexagons 21 forms an equilateral triangle. The angle γ is determined by the center spacing A of two adjacent central concave arc edge hexagons 21. When the center spacing A increases, the density of the lattice array structure will decrease.

[0068] Preferably, the connection between the central concave arc-shaped hexagon 21 and the planar connecting rod 221 is rounded, and the connection within the ring of the central concave arc-shaped hexagon 21 is also rounded.

[0069] If the concave hexagonal ring 21 with a central concave arc edge is replaced with a traditional geometric ring such as a circular ring, triangular ring, square ring, or hexagonal ring, the ability of the central part to expand outward will be significantly reduced, thus reducing the deformation capacity.

[0070] The centrally concave arc-shaped hexagon 21 can be replaced by a structure composed of concave dodecagons or hexagonal stars, etc. The replaceable geometric structures must satisfy the following:

[0071] 1. The number of sides is 3, 6, or a multiple of 6;

[0072] 2. It has a negative Poisson's ratio characteristic.

[0073] The cross-sectional shape of the planar connecting rod 221 perpendicular to the central concave arc-shaped hexagon 21 is T-shaped, I-shaped, channel-shaped, box-shaped, circular, elliptical, triangular, quadrilateral, or a regular polygon with ≥5 sides.

[0074] The three-dimensional lattice array structure was fabricated using 3D printing technology.

[0075] The materials used are metals or polymers.

[0076] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0077] Please see Figure 4 and Figure 5 The planar connecting rod 221 of the array of the lower layer 2 and the array of the upper layer 3 is equivalent to the surrounding direction of the central concave arc-shaped hexagon 21 being opposite.

[0078] The number of inner-layer connecting rods 41 and inter-layer connecting rods 42 is 6.

[0079] h=h'=1.6mm, β=β'=58°, α=66.66°.

[0080] R=1mm, c=1mm, θ=60°, A=3.15mm, γ=25.35°, L=2.57mm, t=0.2mm, d=0.2mm.

[0081] Simulation experiments were conducted using ABAQUS software. In the two-dimensional and three-dimensional structural simulations, the material properties assigned were based on titanium alloy properties, with an elastic modulus of 110,000 MPa and a Poisson's ratio of 0.3; the mesh was divided into tetrahedral meshes with a size of 0.12 mm. The simulations of the two-dimensional and three-dimensional structures are as follows: Figure 6 , Figure 7 , Figure 8 and Figure 9 As shown.

[0082] Please see Figures 6 to 8 This is a simulation experiment of a two-dimensional structure forming an array of lower layer 2 or upper layer 3. In the two-dimensional structure simulation, the boundary condition is that one end of the structure is completely fixed, and the load is a tensile load of 200N theoretically applied to the other end. According to the simulation results, when a tensile load is applied in the x-direction, expansion occurs in the y-direction, and both the centrally concave arc-edge hexagonal structure 21 and the chiral structure 22 expand. Therefore, the xy-plane has obvious negative Poisson's ratio characteristics.

[0083] Please see Figures 9-10 This is a simulation experiment of two three-dimensional lattice array structures. In the three-dimensional structure simulation, the boundary condition is that the bottom of the two structures is completely fixed, and the load is a pressure load with a theoretical value of 1000N applied to the top of the two structures in the z direction. Figure 9 The structure shown contracts in the x and y directions after being subjected to pressure in the z direction, exhibiting a negative Poisson's ratio characteristic. Figure 10 The structure shown expands in the x and y directions after being subjected to pressure in the z direction, exhibiting a positive Poisson's ratio characteristic. Figure 9 , Figure 10 The difference in the structure shown is that, Figure 9 The α angle of the structure shown is 66.66°. Figure 10 The α angle of the structure shown is 113.34°. When the α angle changes, the magnitude and sign of the Poisson's ratio in the z-direction can also change. Therefore, this structure can adjust the α angle according to actual needs, setting up structural units with different Poisson's ratios in different parts of specific practical components, and connecting them to the inter-unit layer connecting rods 42 through the planar connecting rod 221, thereby meeting actual usage requirements.

[0084] In summary, this invention presents a three-dimensional lattice array structure with controllable Poisson's ratio in the z-direction. In the xy-plane, it is a novel negative Poisson's ratio structure, and its Poisson's ratio in the z-direction can be adjusted according to actual needs, allowing it to be set as an anisotropic Poisson's ratio structure. Each plane layer of this structure is a novel negative Poisson's ratio structure that combines good deformation performance with high structural applicability. It couples a concave arc-edge hexagonal negative Poisson's ratio structure and a chiral structure, resulting in numerous deformable structural locations and a high overall deformation rate. Furthermore, this three-dimensional lattice array structure exhibits excellent energy absorption, vibration reduction, and buffering effects, demonstrating good mechanical properties under various loads. Its practical applications include, but are not limited to, shock absorbers such as seat belts and medical assistive devices such as interbody fusion devices.

[0085] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A three-dimensional lattice array structure with controllable z-direction Poisson's ratio, characterized in that, The structure includes a periodic unit 1, and multiple periodic units 1 are arranged in a horizontal and vertical array to form a three-dimensional lattice array structure with controllable z-direction Poisson ratio. Each periodic unit (1) has an upper bottom layer (3) and a lower bottom layer (2). The upper bottom layer (3) or the lower bottom layer (2) is connected by an array to form a continuous and unified structure. The upper bottom layer (3) and the lower bottom layer (2) are connected by unit inner layer connecting rods (41) with the same tilt angle to form a three-dimensional structure. Both the upper bottom layer (3) and the lower bottom layer (2) contain a central concave arc-edge hexagon (21). Adjacent central concave arc-edge hexagons (21) are connected by six planar connecting rods (221) to form a chiral structure (22). The chiral structure (22) is a periodic repeating unit. The central concave arc-edge hexagon (21) is located at the center of the periodic repeating unit. When 0 < α < 90°, the z-direction Poisson ratio is 1. and It is negative; when 90° < α < 180°, the Poisson's ratio in the z-direction is... and The value is positive, where α is the angle between the inclination direction of the inner layer connecting rod (41) or the inter-layer connecting rod (42) and the extension direction of the planar connecting rod (221) in the vertical direction; in the vertical direction, adjacent periodic units (1) are connected by the inter-layer connecting rod (42); the inclination angle of the inner layer connecting rod (41) and the inter-layer connecting rod (42) is the same, and they are symmetrically arranged about the upper bottom layer (3) or the lower bottom layer (2).

2. The z-Poisson-ratio-controllable three-dimensional lattice array structure of claim 1, wherein, The ratio k of the width t of the flat connecting rod (221) to the radius R of the circumscribed circle of the central concave arc-edged hexagon (21) t The ratio k of the height d of the flat connecting rod (221) to the radius R of the circumscribed circle of the central concave arc-edged hexagon (21) d The ratio k of the length L of the flat connecting rod (221) to the radius R of the circumscribed circle of the central concave arc-edged hexagon (21) L The following conditions are met: 0＜k t ＜0.5 0＜k d ＜0.5 0＜k L ＜20。 3. The z-Poisson-ratio-controllable three-dimensional lattice array structure of claim 1, wherein, The center concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°.

4. The z-Poisson-ratio-controllable three-dimensional lattice array structure of claim 3, wherein, The central concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°.

5. The z-Poisson-ratio-controllable three-dimensional lattice array structure of claim 1, wherein The central concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°.

6. The z-directed Poisson's ratio controllable three-dimensional lattice array structure of claim 1, wherein, The central concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°.

7. The z-Poisson-ratio-controllable three-dimensional lattice array structure of claim 6, wherein, The central concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°.

8. The z-directed Poisson's ratio controllable three-dimensional lattice array structure of claim 1, wherein, The central concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°. The central concave arc edge hexagon (21) comprises six concave arc edges (211), the included angle β between the unit inner layer connecting rod (41) and the adjacent concave arc edge (211), and the included angle β' between the unit interlayer connecting rod (42) and the adjacent concave arc edge (211) are symmetrical about the lower bottom layer (2) or the upper bottom layer (3), and satisfy 45°≤β=β'≤90°.

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