Novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure

Abstract

The invention discloses a novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure. A unit cell structure of the novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure is composed of a double-folding bent plate, a trapezoidal bridge, a type I bearing column and a type II bearing column. The thickness of the double-folded bent plate is t, and the length of a middle folded corner is 2t; the included angle between the inner concave plate surface and the adjacent horizontal plane and the included angle between the trapezoidal bridge and the horizontal plane are a; the distance between the starting point of the longitudinal concave part and the I-shaped bearing column and the distance between the starting point of the transverse concave part and the center are both L; the I-shaped bearing column is a cuboid with a square section, and the side length of the bottom surface is d; and the width of the peripheral bent plate is l. The novel three-dimensional snowflake-plate-shaped negative poisson ratio unit cells are of a complete structure formed through transverse rotation and longitudinal array combination, the adjacent unit cells along the diagonal oblique lines share 1 / 2 bent plates, and the unit cell bearing columns and the bent plates adjacent in the vertical direction intersect. The novel three-dimensional snowflake-plate-shaped negative Poisson's ratio structure has an obvious negative Poisson's ratio effect and good energy absorption capacity in the vertical direction.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterials / metastructures, and in particular to a novel three-dimensional snowflake-shaped negative Poisson's ratio structure. Background Art

[0002] Since the 21st century, the concept of "metamaterial" has been proposed, which refers to a class of artificial composite structures or materials with extraordinary physical properties that natural materials do not have. The research on metamaterials covers many fields such as acoustics, optics, thermal, mechanics and electromagnetism, and has shown broad application prospects in high-tech fields such as aerospace, defense industry, and biomedicine.

[0003] In the field of mechanics, negative Poisson's ratio materials / structures are a kind of mechanical metamaterials / metastructures. Different from most positive Poisson's ratio materials in nature, their special geometric structure makes them show the characteristics of lateral expansion (under tension) or lateral contraction (under compression) when subjected to force and deformation. Compared with traditional materials, negative Poisson's ratio structures have significant advantages in shear resistance, fracture resistance, energy absorption, etc., and also have excellent physical properties such as lightweight, high damping, sound absorption and energy absorption, vibration reduction and heat insulation.

[0004] Negative Poisson's ratio metamaterials / metastructures have important application value in many engineering fields. In the field of aerospace, their special mechanical properties make spacecraft more stable under extreme conditions such as landing, vibration, and high-speed flight. At the same time, they can improve structural stiffness and reduce material usage, thereby reducing overall mass and improving fuel efficiency. In the biomedical field, negative Poisson's ratio structures can be used for high-performance implantable medical devices, such as cardiovascular stents, artificial intervertebral discs, and orthopedic implants. Their special mechanical properties can provide more uniform support when subjected to force, reduce stress concentration, and thus improve the stability and durability of implants. In the field of civil engineering, negative Poisson's ratio structures can be used for seismic support and vibration isolation devices. Through their lateral contraction characteristics when under pressure, they can effectively disperse stress, absorb seismic wave energy, and improve the seismic resistance of building structures.

[0005] At present, researchers have developed a variety of negative Poisson's ratio structures, each with different geometric characteristics and mechanical properties to meet specific application requirements. Common negative Poisson's ratio structures include: concave hexagonal structure, double arrow structure, star structure, chiral structure and rotating rigid body structure.

[0006] Among them, the star-shaped negative Poisson's ratio structure is outstanding in terms of energy absorption and deformation stability due to its strong structural symmetry, and is suitable for applications such as impact protection and high-damping energy-absorbing materials. However, traditional two-dimensional or single-star structures still have certain limitations. For example, the stress plateau region is relatively short, resulting in the structure entering the densification stage earlier, limiting the energy absorption capacity. At the same time, traditional structures may exhibit local instability or buckling under large deformations, and coupled with the already insufficient compressive strength, their reliability in high-load environments is reduced.

[0007] The proposed three-dimensional negative Poisson's ratio structure provides a new solution to the above problems. Compared with traditional two-dimensional negative Poisson's ratio structures, the three-dimensional concave star structure achieves a more uniform stress distribution, a greater energy absorption capacity, and more excellent mechanical stability through spatial topology optimization, thus expanding the application range of negative Poisson's ratio materials. This new structure can maintain a stable negative Poisson's ratio effect under multi-axial loading conditions, further improving the impact resistance and fatigue resistance, and is suitable for fields such as high-performance buffer structures, intelligent deformable materials, and aerospace equipment.

[0008] In recent years, the rapid development of 3D printing and additive manufacturing technologies has made the manufacturing of complex topological structures a reality, providing broad space for the design and application of three-dimensional negative Poisson's ratio structures. This progress further promotes the research of multifunctional metamaterials, endowing them with greater development potential in future engineering applications. Summary of the Invention

[0009] Aiming at the above problems, the purpose of the present invention is to propose a new three-dimensional snowflake plate-shaped negative Poisson's ratio structure, which is formed by rotating a unit cell around a fixed axis in the horizontal direction and arraying it in the vertical direction. Each of the periodic unit cells consists of four double-folded curved plates, two trapezoidal bridges and ΙΙ-shaped supporting columns embedded in the middle of the curved plates, Ι-shaped supporting columns on the upper and lower top surfaces, and trapezoidal bridges formed between the ends of the curved plates and the supporting columns. This new rotating star-shaped negative Poisson's ratio structure has a good negative Poisson's ratio effect and the ability to resist external impacts, and the change of the structural geometric parameters has an important influence on the mechanical properties of the overall structure.

[0010] To achieve the purpose of the present invention, the present invention is realized through the following technical solutions:

[0011] A further improvement lies in that: the manufacturing material of the three-dimensional concave star-shaped negative Poisson's ratio structure is one of metals, shape memory alloys (nickel-titanium alloy, copper-zinc-aluminum alloy, iron-titanium alloy), polylactic acid (PLA), or thermoplastic polyurethane (TPU) superelastic materials.

[0012] A further improvement lies in that: the three-dimensional concave part of the structure consists of four curved plates arranged vertically and eight trapezoidal bridges. The bending angle of the curved plate (the angle with the vertical direction) and the inclination angle of the trapezoidal bridge (the angle with the horizontal direction) are the same, both being a. The thickness of both the curved plate and the trapezoidal bridge is t, and the width of the curved plate is l. (2) The upper and lower sides of the structure are respectively connected by four trapezoidal bridges, converging to one end and connected to one end of the Ι-shaped receiving column; the Ι-shaped receiving column is a cuboid with a square cross-section, the side length of the cross-section is d, and the length is represented by L×cosa; the middle turning part of the curved plate is connected to two trapezoidal bridges, and the middle of the trapezoidal bridge is connected to the ΙΙ-shaped receiving column; the cross-section of the ΙΙ-shaped receiving column is an isosceles right triangle with a bottom length of d, and the length is twice that of the Ι-shaped receiving column; the ΙΙ-shaped receiving column can be rotated along the axis of the right-angle vertex to obtain the Ι-shaped receiving column.

[0013] A further improvement lies in that: the novel three-dimensional snowflake-shaped negative Poisson's ratio structure is obtained by rotating horizontally along the right-angle edge of the ΙΙ-shaped receiving column and longitudinally arraying with the cell height as the unit length. When rotating horizontally, due to the cross-section being an isosceles right triangle, the side surfaces of the ΙΙ-shaped receiving column are mutually attached after rotation to obtain an Ι-shaped receiving column with twice the length. When longitudinally arraying, the array length unit is the height of a single cell, that is, 2L + 2t; after the array is completed, the Ι-shaped receiving columns of adjacent cells in the longitudinal direction are connected and attached, and the curved plates around are also respectively connected and attached end to end. The structure after rotation and arraying shares 1 / 2 of a curved plate, 1 trapezoidal bridge, and 1 / 2 of an ΙΙ-shaped receiving column for two cells along the diagonal direction.

[0014] A further improvement lies in that: in the preprocessing module of the ABAQUS software, first set the material parameters of the structure, divide the finite element mesh of the structure, set the analysis steps, set the boundary conditions and load conditions, and set the contact properties, so as to conduct a quasi-static compression simulation on the structure.

[0015] A further improvement lies in that: using the finite element ABAQUS simulation software to conduct a quasi-static compression simulation on the novel three-dimensional snowflake-shaped negative Poisson's ratio structure, and obtaining the deformation process cloud diagram, stress-strain curve, Poisson's ratio-strain curve, and specific energy absorption-strain curve of the novel three-dimensional snowflake-shaped negative Poisson's ratio structure under the action of in-plane quasi-static compression load.

[0016] A further improvement lies in that: the mechanical properties and energy absorption efficiency of the novel three-dimensional snowflake-shaped negative Poisson's ratio structure under the action of quasi-static compression load can be determined by adjusting the concave angle a, wall thickness t, and cell size.

[0017] The beneficial effects of the present invention are: the novel rotating star-shaped negative Poisson's ratio structure of the present invention has the advantages of light weight, high specific strength, high resistance to external impact, and good negative Poisson's ratio performance, and the change of the geometric parameters of its structure has an important impact on the overall mechanical properties of the structure. Description of the Drawings

[0018] Figure 1 This is the geometric cell configuration of the novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure in Embodiment 1 of the present invention;

[0019] Figure 2 This is the novel three-dimensional concave novel negative Poisson's ratio 2×2×3 structure in Embodiment 1 of the present invention;

[0020] Figure 3 This is the deformation nephogram of the novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure in Embodiment 2 of the present invention under quasi-static compression load;

[0021] Figure 4 This is the load-displacement curve of the novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure in Embodiment 2 of the present invention under quasi-static compression load;

[0022] Figure 5 This is the Poisson's ratio-strain curve of the novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure in Embodiment 2 of the present invention under quasi-static compression load;

[0023] Figure 6 This is the specific energy absorption-strain curve of the novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure in Embodiment 2 of the present invention under quasi-static compression load. Detailed implementation manners

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0025] Embodiment 1:

[0026] According to Figure 1 As shown, this embodiment provides a novel three-dimensional snowflake plate-shaped negative Poisson's ratio structure. Its unit cell structure consists of four double-folded curved plates, two trapezoidal bridges and II-shaped supporting columns embedded in the middle of the curved plates, I-shaped supporting columns on the upper and lower top surfaces, and trapezoidal bridges formed between the ends of the curved plates and the supporting columns. The three-dimensional concave part consists of four curved plates arranged vertically and eight trapezoidal bridges. The bending angle (the angle with the vertical direction) of the curved plates and the inclination angle (the angle with the horizontal direction) of the trapezoidal bridges are the same, both being a. The thicknesses of the curved plates and the trapezoidal bridges are both t, and the width of the curved plates is l. (2) The upper and lower sides of the structure are respectively connected by four trapezoidal bridges, converging to one end and connected to one end of the I-shaped supporting column; the I-shaped supporting column is a cuboid with a square cross-section, the side length of the cross-section is d, and the length can be expressed as L×cosa; the middle turning part of the curved plate is connected to two trapezoidal bridges, and the middle of the trapezoidal bridge is connected to the II-shaped supporting column; the cross-section of the II-shaped supporting column is an isosceles right triangle with a bottom length of d, and the length is twice that of the I-shaped supporting column; the II-shaped supporting column can be rotated along the right-angle edge to obtain the I-shaped supporting column.

[0027] According to Figure 2 As shown, this embodiment provides a novel three-dimensional snowflake-shaped negative Poisson's ratio structure. The novel three-dimensional snowflake-shaped negative Poisson's ratio unit cell is obtained by rotating horizontally along the right-angle edge of the Type-II supporting column and arraying longitudinally in units of the cell height. During horizontal rotation, since the cross-section is an isosceles right triangle, the sides of the Type-II supporting column are mutually attached after rotation to obtain a Type-I supporting column with twice the length. During longitudinal arraying, the array length unit is the height of the unit cell, i.e., 2L + 2t; after arraying, the Type-I supporting columns of adjacent cells in the longitudinal direction are connected and attached, and the curved plates around are also respectively connected and attached at the ends. The structure after rotation and arraying shares 1 / 2 of a curved plate, 1 trapezoidal bridge, and 1 / 2 of a Type-II supporting column for two cells in the diagonal direction.

[0028] The manufacturing material of the three-dimensional concave star-shaped negative Poisson's ratio structure is one of metal, shape memory alloy (nickel-titanium alloy, copper-zinc-aluminum alloy, iron-titanium alloy), polylactic acid (PLA), or thermoplastic polyurethane (TPU) superelastic material.

[0029] Example 2:

[0030] In the preprocessing module of the ABAQUS finite element software, first set the material parameters of the structure, divide the finite element mesh of the structure, set the analysis step, set the boundary conditions and load conditions, and set the contact properties, so as to perform a quasi-static compression simulation calculation on the structure.

[0031] Set the material parameters in the ABAQUS finite element simulation software, select PLA-CF as the research object, with the material elastic modulus E = 1.8 GPa, the material Poisson's ratio μ = 0.3, and the yield stress σ = 40 MPa.

[0032] According to Figure 3 As shown, this embodiment provides a deformation nephogram of a novel three-dimensional snowflake-shaped negative Poisson's ratio structure under quasi-static compression load. Figure (a) shows the strain ε = 0.05, Figure (b) shows the strain ε = 0.1, Figure (c) shows the strain ε = 0.2, Figure (d) shows the strain ε = 0.4, and Figure (e) shows the strain ε = 0.6. It can be seen from the figure that when ε is in the range of 0.05 to 0.4, the star-shaped angles of the structure gradually merge, and a step-by-step contraction phenomenon from the middle to the upper and lower sides appears, showing obvious negative Poisson's ratio performance and good stability without instability. As the strain increases, the middle star-shaped structure becomes denser and the cavity gradually shrinks. When the strain ε = 0.54, the structure shows densification and the negative Poisson's ratio effect disappears.

[0033] According to Figure 4As shown, this embodiment provides a stress-strain curve of a novel three-dimensional snowflake-shaped negative Poisson's ratio structure under quasi-static compressive load. As can be seen from the figure, the stress-strain response of the novel three-dimensional snowflake-shaped negative Poisson's ratio structure can be divided into five stages. First, at a relatively small compressive strain, the stress increases linearly with the strain. This region is called the linear elastic region, and no plastic deformation occurs in the structure in this stage until the peak stress is reached. Subsequently, it enters a relatively long plateau region. When the compressive strain ε is about 0.27, a second linear elastic region appears, and at this time the load rapidly rises to the second peak, entering the second yield stage. When the compressive strain ε is about 0.54, the stress rises rapidly, reaching the densification region. The novel three-dimensional snowflake-shaped negative Poisson's ratio structure has a relatively long stress plateau period, which can effectively increase the energy absorption of the structure.

[0034] According to Figure 5 As shown, this embodiment provides a Poisson's ratio-strain curve of a novel three-dimensional snowflake-shaped negative Poisson's ratio structure under quasi-static compressive load. As can be seen from the figure, the novel three-dimensional snowflake-shaped negative Poisson's ratio structure exhibits a good negative Poisson's ratio effect in the linear elastic stage. Starting from the plateau period, the Poisson's ratio of the structure increases with the increase of the strain, and the negative Poisson's ratio phenomenon disappears when the strain ε is about 0.6.

[0035] According to Figure 6 As shown, this embodiment provides a specific energy absorption (SEA)-strain curve of a novel three-dimensional snowflake-shaped negative Poisson's ratio structure under quasi-static compressive load. As can be seen from the figure, the specific energy absorption of the novel three-dimensional snowflake-shaped negative Poisson's ratio structure increases with the increase of the strain, and the structure exhibits a good energy absorption effect.

[0036] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A novel three-dimensional snowflake-shaped negative Poisson's ratio structure, characterized by: The structure is composed of unit cells rotated horizontally around a fixed axis and arrayed in a vertical direction; each of the periodic unit cells is composed of four double-folded curved plates, two trapezoidal bridges and II-type receiving columns embedded in the middle of the curved plates, I-type receiving columns on the upper and lower top surfaces, and a trapezoidal bridge formed between the ends of the curved plates and the receiving columns.

2. A novel three-dimensional snowflake-shaped negative Poisson's ratio structure according to claim 1, characterized in that: The three-dimensional concave part is composed of four curved plates and eight trapezoidal bridges arranged in the vertical direction. The bending angle of the curved plate is the same as the inclination angle of the trapezoidal bridge, both of which are a; the thickness of the curved plate and the trapezoidal bridge is t, and the width of the curved plate is l; the upper and lower sides of the structure are respectively connected by four trapezoidal bridges, converging at one end and connected to one end of the I-type supporting column; the I-type supporting column is a rectangular parallelepiped with a square cross-section and a side length of d, and the length can be expressed as L×cosa; the middle turning part of the curved plate is connected to two trapezoidal bridges, and the middle of the trapezoidal bridge is connected to the II-type supporting column; the cross-section of the II-type supporting column is an isosceles right triangle with a base length of d, and the length is twice the length of the I-type supporting column; the II-type supporting column can be obtained by rotating the II-type supporting column along the right-angle vertex axis.

3. The novel three-dimensional snowflake-shaped negative Poisson's ratio structure according to claim 1, characterized in that: A novel three-dimensional snowflake-shaped negative Poisson's ratio unit cell is obtained by rotating laterally along the right-angled edges of the II-type receiving column and arraying it in the vertical direction with the cell height as the unit; when rotating laterally, since the cross-section is an isosceles right triangle, the side surfaces of the II-type receiving column fit together after rotation to obtain an II-type receiving column of twice the length; when arrayed vertically, the array length unit is the height of the unit cell, that is, 2L+2t; after the array is completed, the I-type receiving columns of adjacent cells in the vertical direction are connected and fitted, and the curved plates on all sides are also terminated, connected and fitted; after the rotation and array are completed, the two cells along the diagonal direction of the structure share 1 / 2 curved plate, 1 trapezoidal bridge and 1 / 2 II-type receiving column.

4. The novel three-dimensional snowflake-shaped negative Poisson's ratio structure according to claim 1 is characterized in that: Prepared using 3D printing technology.

5. The novel three-dimensional snowflake-shaped negative Poisson's ratio structure according to claim 1 is characterized in that: The three-dimensional concave star-shaped negative Poisson's ratio structure is made of a material selected from metal, shape memory alloy, polylactic acid or thermoplastic polyurethane superelastic material.

Images