Three-dimensional negative Poisson's ratio structure of concave rib-lacking coupling configuration

Abstract

The invention discloses a three-dimensional negative Poisson's ratio structure of a concave rib-lacking coupling configuration, which is characterized in that concave hexagonal cell elements are used as basic construction units, and the concave hexagonal cell elements are densely arranged and connected in a honeycomb shape to form a sheet-shaped assembly; the sheet-shaped assemblies are connected to form swastika-shaped structural units, and the four swastika-shaped structural units are connected in a rib-lacking mode to form the minimum structural unit of the three-dimensional negative poisson ratio structure of the inwards-concave rib-lacking coupling structure. The negative Poisson's ratio characteristic is achieved in the spatial three-dimensional direction, good environmental adaptability and energy absorption performance are achieved under the multi-axis complex stress condition, and stress concentration can be reduced; the structural weight can be reduced, the structural stability is enhanced, and the method is suitable for the field sensitive to weight; the Poisson's ratio, the rigidity and the energy absorption threshold value can be flexibly regulated and controlled by adjusting the parameters such as the inward concave angle, the unit size and the wall thickness, and the requirements of different application scenes are met; the number of basic units can be controlled according to specific application requirements, and the structural density is optimized.

Description

Technical Field

[0001] The present invention relates to the design of material structures, and specifically to a three-dimensional negative Poisson's ratio structure with an inward concave rib-deficient coupling configuration. Background Technique

[0002] With the rapid development of modern industry and advanced manufacturing technologies, the demand for structural performance has become increasingly diverse. Especially in the fields of aerospace, bridge tunnels, biomedicine, protective equipment, and automotive engineering, structures not only need to have the characteristics of lightweight and high strength, but also need to exhibit excellent energy absorption, impact resistance, and deformation adaptability under complex loading conditions. Traditional homogeneous materials usually exhibit a positive Poisson's ratio effect, that is, they contract laterally when stretched and expand laterally when compressed. This characteristic to a certain extent limits their application in specific scenarios. For example, in the case of vehicle collisions, the positive Poisson's ratio body structure lacks deformation coordination, resulting in insufficient energy absorption efficiency and seriously threatening the lives of passengers; in tunnel seismic engineering, the positive Poisson's ratio damping layer exhibits brittle damage characteristics under strong earthquake effects, being unable to ensure continuous energy dissipation capacity and difficult to maintain the overall stability of the structure; furthermore, in military protection engineering, the positive Poisson's ratio reinforced concrete structure generates a non-uniform stress field under explosion shocks, triggering local stress concentration effects and causing the protection system to collapse prematurely.

[0003] Negative Poisson's ratio metamaterials, also known as auxetic materials, have attracted widespread attention due to their unique mechanical behavior. Negative Poisson's ratio materials expand laterally when stretched axially and contract laterally when compressed. This anomalous deformation property gives them significant advantages in shear modulus, dent resistance, energy absorption, etc. At present, the realization of negative Poisson's ratio structures mainly relies on the design of macroscopic artificial structures, such as two-dimensional chiral structures, concave hexagons, star structures, etc. However, two-dimensional structures have obvious limitations in three-dimensional space applications: first, their negative Poisson's ratio effect is usually only significant in a specific direction, and it is difficult to achieve isotropic response under multi-axial loads; second, the stacking or splicing method of two-dimensional structures may introduce interface weakening problems, resulting in a decrease in overall mechanical properties; third, the adaptability to specific complex surfaces or special-shaped parts is poor, which restricts the scope of engineering applications. The triangular enhanced negative Poisson's ratio cell and the negative Poisson's ratio metamaterial structure design in the honeycomb structure disclosed in CN116733880A are still limited to the method of rotating and arranging the cells in the two-dimensional plane; the three-dimensional controllable tensile expansion structure and material based on curvature design disclosed in CN111859487A realize the cell configuration control by adjusting the curvature parameters. Although this technology can achieve the spatial negative Poisson's ratio effect, its structural design relies on dense grid arrangement, and the overly dense rib layout causes structural redundancy, insufficient material utilization, and complicated and cumbersome manufacturing process. In addition, the three-dimensional negative Poisson's ratio structure is also usually obtained by stretching the two-dimensional tensile expansion unit in a certain direction. The structure has the negative Poisson's ratio characteristics only in the original two-dimensional plane, and is still a homogeneous force-bearing structure in the stretching direction, which is prone to stress concentration, resulting in poor structural applicability and fatigue resistance, and cannot meet the needs of the complex stress environment of actual working conditions. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a three-dimensional negative Poisson's ratio structure with an inner concave rib coupling configuration that has a negative Poisson's ratio effect in all three directions of space, a lightweight structure, and improved material efficiency.

[0005] Technical solution: The present invention describes a three-dimensional negative Poisson's ratio structure with an inward-concave rib-missing coupling configuration, which uses inward-concave hexagonal cells as basic structural units, and the inward-concave hexagonal cells are closely connected in a honeycomb pattern to form a sheet-like component; the sheet-like components are connected to form a "卐"-shaped structural unit, and four "卐"-shaped structural units are connected with missing ribs to form the minimum structural unit of the three-dimensional negative Poisson's ratio structure with an inward-concave rib-missing coupling configuration.

[0006] Furthermore, the inwardly concave hexagonal cell is a symmetrical structure, including parallel transverse ribs, oblique rods respectively connecting the upper and lower transverse ribs and connected in pairs, and intermediate ribs located at the connection of the oblique rods and parallel to the transverse ribs; the angle between the transverse ribs and the oblique rods is an acute angle.

[0007] Furthermore, the size of the included angle is 20°≤α≤80°.

[0008] Furthermore, the length relationship between the transverse ribs, the oblique rods and the intermediate ribs satisfies: L1>2L2sinα, L3≥0.5L1, where L1 is the length of the transverse ribs, L2 is the length of the oblique rods, L3 is the length of the intermediate ribs, and α is the angle between the transverse ribs and the oblique rods. Within this length range, the concave hexagonal cell structure has a negative Poisson's ratio characteristic, and the deformation is more uniform.

[0009] Furthermore, the thickness relationship between the transverse ribs, the oblique rods and the intermediate ribs satisfies: 0.5≤T1 / T3≤2, 1≤T2 / T1≤1.5, where T1 is the thickness of the transverse ribs, T2 is the thickness of the oblique rods, and T3 is the thickness of the intermediate ribs. This thickness range is consistent with the stress characteristics of the concave hexagonal cell when it is deformed, and is not prone to cause local stress concentration.

[0010] Furthermore, the sheet-like component is composed of upper and lower concave hexagonal cells which are stacked and connected by transverse ribs, and the left and right concave hexagonal cells are connected by two ends of the intermediate ribs.

[0011] Furthermore, the connection angle formed by connecting the sheet-like components in the "卐"-shaped structural unit is 20°≤β≤90°.

[0012] Furthermore, the sheet component is connected by concave hexagonal cells in a honeycomb pattern of n*n, and the sheet component formed includes n 2 +(n-1) 2 Concave hexagonal cell, where n≥2.

[0013] Furthermore, the inwardly concave hexagonal cells are made of metal materials, high molecular polymer materials or high-toughness cement-based materials.

[0014] Furthermore, the “卐”-shaped structural unit can be replaced by a “卍”-shaped structural unit.

[0015] The principle of the present invention is: using concave hexagonal cells as basic structural units, forming sheet components through honeycomb close arrangement, and connecting multiple groups of sheet components through central symmetric rotation connection to form a "卐"-shaped structural unit. The "卐"-shaped structural unit is obtained by functionally removing some ribs from the "田"-shaped grid structure. The "卐"-shaped structural unit is connected in three-dimensional space with missing ribs, that is, the "卐"-shaped structural unit is connected at the ends of the diagonal sides, and the whole is arranged in a linear array to form a three-dimensional negative Poisson's ratio structure with a concave missing rib coupling configuration. By utilizing the three-dimensional negative Poisson's ratio characteristics of the structure, by adjusting the concave angle, unit size, wall thickness and other parameters, the Poisson's ratio, stiffness, and energy absorption threshold can be flexibly controlled. Under tensile or compressive loads in any direction, the structure undergoes corresponding expansion or contraction strain in the transverse direction. The three-dimensional negative Poisson's ratio structure of the concave rib-less coupling configuration is not obtained by a dense array of single cells in space, but by forming a rib-less configuration through the basic units of the concave structure, effectively combining the deformation advantages of the two configurations to improve the compression and expansion potential and material efficiency ratio of the structure.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0017] 1. The structure has negative Poisson's ratio characteristics in all three-dimensional directions of space, has better environmental adaptability under multi-axial complex stress conditions, and can reduce stress concentration;

[0018] 2. The concave rib-missing coupling configuration effectively combines the deformation advantages of a single concave hexagonal cell and a "卐"-shaped structural unit, thereby improving the compression and expansion potential of the structure;

[0019] 3. The hollow and thin-walled features of the structure and the "卐"-shaped construction can achieve lightweight structure, while enhancing structural stability with the help of negative Poisson's ratio effect, making it suitable for weight-sensitive fields;

[0020] 4. By adjusting the concave angle, unit size, wall thickness and other parameters, the Poisson's ratio, stiffness and energy absorption threshold can be flexibly adjusted to meet the needs of different application scenarios. The number of basic units can be controlled according to specific application requirements to optimize the structural density;

[0021] 5. The structure is combined with additive manufacturing 3D printing technology to break through processing limitations, and the integrated molding technology reduces assembly steps and improves the integrity of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the present invention;

[0023] Figure 2 is a front view of the present invention;

[0024] Figure 3 is a top view of the present invention;

[0025] Figure 4 is a schematic structural diagram of a concave hexagonal cell 1 of the present invention;

[0026] Figure 5 It is a schematic structural diagram of a sheet component 2 of the present invention;

[0027] Figure 6 It is a 3D printed physical picture of the sheet component 2 of the present invention;

[0028] Figure 7 It is a schematic diagram of the static compression deformation process of the structures of Example 1, Example 2 and Comparative Example 1 of the present invention along the direction of the rib-less plane;

[0029] Figure 8 It is a schematic diagram of the static compression deformation process along the concave plane of the present invention;

[0030] Figure 9It is a curve diagram of the Poisson's ratio of the structures of Example 1, Example 2 and Comparative Example 1 of the present invention changing with the longitudinal strain. DETAILED DESCRIPTION

[0031] In the following examples, the materials and reagents used are all commercially available unless otherwise specified. Experimental methods without specific conditions in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0032] Example 1

[0033] like Figure 4 As shown, the four angles 104 formed between the transverse ribs 101 and the oblique rods 102 of the concave hexagonal cell 1 of the basic structural unit of the three-dimensional negative Poisson's ratio structure of the concave rib-missing coupling configuration all satisfy α=60°, because the inter-ribs 103 are parallel to the transverse ribs 101, and the angles between the oblique rods 102 and the inter-ribs 103 are both 60°, that is, the oblique rod-inter-rib angle is consistent with the transverse rib-oblique rod angle, and the length relationship between the transverse ribs 101, the oblique rods 102 and the inter-ribs 103 satisfies: L1=1.5L2=2L3, and the thickness relationship satisfies: T1=T2=T3. Figure 5 , Figure 6 As shown, 9 concave hexagonal cells 1 are closely connected in a 3*3 honeycomb pattern to form a sheet component 2, and the transverse ribs 101 of the upper and lower concave hexagonal cells 1 are superimposed and connected. After connection, the two concave hexagonal cells 1 share the transverse rib 101, and the left and right concave hexagonal cells 1 are connected through the cross-sections at both ends of the intermediate rib 103. After the four concave hexagonal cells 1 are combined in pairs, the middle part reconstructs the concave hexagonal cell 1, so that 13 concave hexagonal cells 1 are finally formed; the connection angle 301 formed by connecting the sheet components 2 in pairs is β=90°, and the sheet components 2 are formed into a structural unit with a top view shape of "卐" by a rotation connection method symmetrical to the central axis, as shown in FIG. Figures 1 to 3 As shown, four "卐"-shaped structural units, including 32 sheet components 2, are connected by missing ribs in three-dimensional space to form the minimum structural unit of a three-dimensional negative Poisson's ratio structure with an inner concave missing rib coupling configuration.

[0034] Example 2

[0035] The difference from the first embodiment is that the connection angle 301 formed by connecting two of the sheet-like components 2 is β=85°.

[0036] Comparative Example

[0037] like Figure 4 As shown, the basic structural unit is also a concave hexagonal cell 1, and the four angles 104 formed between the transverse ribs 101 and the oblique rods 102 are all α=60°. Since the intermediate ribs 103 are parallel to the transverse ribs 101, the angles between the oblique rods 102 and the intermediate ribs 103 are all 60°, that is, the oblique rod-intermediate rib angle is consistent with the transverse rib-oblique rod angle.Figure 5 , Figure 6 As shown in Figure 6 , nine concave hexagonal cells 1 are connected in a 3×3 honeycomb close-packed manner to form a sheet-like component 2. The transverse ribs 101 of the upper and lower concave hexagonal cells 1 are superposed and connected. After connection, two concave hexagonal cells 1 share the transverse rib 101. The left and right concave hexagonal cells 1 are connected by the cross-sections at both ends of the intermediate rib 103. After four concave hexagonal cells 1 are combined in pairs, a concave hexagonal cell 1 is re-formed in the middle. Therefore, a total of 13 concave hexagonal cells 1 are finally formed. The connection angles 301 formed by connecting the sheet-like components 2 in pairs, i.e., β = 90°. Different from Embodiment 1, 32 sheet-like components 2 are assembled in a square grid configuration, i.e., a non-rib-deficient type, and two groups of sheet-like components 2 are connected to form the sides of the grid. The overall grid structure includes four groups of grids.

[0038] ABAQU software is used to perform parametric simulation on the three-dimensional negative Poisson's ratio material with a concave rib-deficient coupling configuration. The high-tough thermoplastic polyurethane elastomer material (TPU) is used as the analysis material, and the material parameters are set as follows: elastic modulus E = 10 MPa; Poisson's ratio 0.38; mass density 1.22 g / cm 3 . The rib-deficient plane of the structure is defined as the X-Y plane, and the direction along the concave hexagonal cell is the Z direction. Compressive loads in the X / Y / Z three directions are applied to the structure respectively to obtain the lateral displacement change of the structure, and verify the negative Poisson's ratio effect of the above-mentioned Embodiment 1, Embodiment 2 and the comparative example structure.

[0039] As Figure 7 , Figure 8 shown in Figure 8 , in Embodiment 1 and Embodiment 2, both contract laterally under the longitudinal displacement in the X-Y plane, showing a significant negative Poisson's ratio effect. Their sheet-like structures also have a compressive negative Poisson's ratio effect in the Z direction, indicating that both Embodiment 1 and 2 have negative Poisson's ratio characteristics in three-dimensional space. While in the comparative example 1, the honeycomb structure expands laterally under the longitudinal displacement, showing a significant positive Poisson's ratio effect.

[0040] As Figure 9 shown in Figure 9 , for the structure of Embodiment 1, the Poisson's ratio ranges from -0.36 to -0.74 in the Z direction and from -0.17 to -0.35 on the X-Y plane. For the structure of Embodiment 2, the Poisson's ratio ranges from -0.36 to -0.75 in the Z direction and from -0.20 to -0.29 on the X-Y plane, both having three-dimensional negative Poisson's ratio characteristics in space. For the structure of Comparative Example 1, the Poisson's ratio ranges from -0.36 to -0.75 in the Z direction and from 0.26 to 0.48 on the X-Y plane.

Claims

1. A three-dimensional negative Poisson's ratio structure of an inward-concave rib-missing coupling configuration, wherein the structure uses an inward-concave hexagonal cell (1) as a basic structural unit, and the inward-concave hexagonal cell (1) is closely connected in a honeycomb shape to form a sheet component (2); characterized in that: The sheet-like components (2) are connected to form a "卐”-shaped structural unit (3), and four of the "卐”-shaped structural units (3) are connected with ribs missing to form the minimum structural unit of a three-dimensional negative Poisson's ratio structure with a concave rib-missing coupling configuration.

2. The three-dimensional negative Poisson's ratio structure of the inner concave rib coupling configuration according to claim 1, characterized in that: The concave hexagonal cell (1) is a symmetric structure, including parallel transverse ribs (101), diagonal rods (102) that connect the upper and lower transverse ribs (101) and are pairwise connected, and intermediate ribs (103) located at the connection of the diagonal rods (102) and parallel to the transverse ribs (101); the angle (104) between the transverse rib (101) and the diagonal rod (102) is an acute angle.

3. The three-dimensional negative Poisson's ratio structure of the inner concave rib coupling configuration according to claim 2, characterized in that: The size of the angle (104) is 20° ≤ α ≤ 80°.

4. The three-dimensional negative Poisson's ratio structure of the inner concave rib coupling configuration according to claim 2, characterized in that: The length relationship among the transverse rib (101), the diagonal rod (102), and the intermediate rib (103) satisfies: L1 > 2L2sinα, L3 ≥ 0.5L1, where L1 is the length of the transverse rib (101), L2 is the length of the diagonal rod (102), L3 is the length of the intermediate rib (103), and α is the angle between the transverse rib (101) and the diagonal rod (102).

5. The three-dimensional negative Poisson's ratio structure of the inner concave-rib coupling configuration according to claim 2, characterized in that: The thickness relationship among the transverse rib (101), the diagonal rod (102), and the intermediate rib (103) satisfies: 0.5 ≤ T1 / T3 ≤ 2, 1 ≤ T2 / T1 ≤ 1.5, where T1 is the thickness of the transverse rib (101), T2 is the thickness of the diagonal rod (102), and T3 is the thickness of the intermediate rib (103).

6. The three-dimensional negative Poisson's ratio structure of the inner concave rib coupling configuration according to claim 1, characterized in that: The sheet-like components (2) are stacked and connected by the transverse ribs (101) between the upper and lower concave hexagonal cells (1), and the two ends of the intermediate ribs (103) are connected between the left and right concave hexagonal cells (1).

7. The three-dimensional negative Poisson's ratio structure of the inner concave rib coupling configuration according to claim 1, characterized in that: The size of the connection angle (301) formed by the connection of the sheet-like components (2) in the "卐”-shaped structural unit (3) is 20° ≤ β ≤ 90°.

8. The three-dimensional negative Poisson's ratio structure of inner concave-rib coupling configuration according to claim 1, characterized in that: The sheet-like component (2) is composed of inwardly concave hexagonal cells (1) connected in a honeycomb pattern in a close arrangement of n*n. The sheet-like component (2) comprises n 2 +(n-1) 2 concave hexagonal cells (1), where n≥2.

9. The three-dimensional negative Poisson's ratio structure of the inner concave-rib coupling configuration according to claim 1, characterized in that: The concave hexagonal cell (1) is made of a metal material, a polymer material, or a high-toughness cement-based material.

10. The three-dimensional negative Poisson's ratio structure of inner concave-rib coupling configuration according to claim 1, characterized in that: The "卐”-shaped structural unit (3) can be replaced by a "卍”-shaped structural unit.

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