A three-dimensional negative Poisson's ratio structure suitable for 3D printing

Abstract

The present invention provides a three-dimensional negative Poisson's ratio structure suitable for 3D printing, wherein the spiral unit is formed by a circular array with the inner end of a spiral arm as the center; a plurality of spiral units are arranged in sequence on a plane, and two adjacent spiral units are mirror-imaged and fixedly connected; the spiral units of two adjacent planar spiral structures correspond one to one in the vertical direction and are mirror-imaged; the outer ends of the spiral arms of two adjacent spiral units correspond one to one and are connected by an inclined rod. The beneficial effects of the technical solution proposed by the present invention are: the structure has high negative Poisson's ratio performance and is suitable for 3D printing. In compression experiments, the negative Poisson's ratio structure has typical negative Poisson's ratio deformation characteristics and a typical bending-dominated mechanical response; the negative Poisson's ratio structure has a very stable platform stress in a large compression strain range, without any sharp collapse or catastrophic damage, which reflects the rationality of the negative Poisson's ratio structure design, and provides a rare opportunity for designing high-strain or impact-resistant functional devices.

Description

Technical Field

[0001] The present invention relates to the technical field of negative Poisson's ratio structures, and in particular to a three-dimensional negative Poisson's ratio structure suitable for 3D printing. Background Art

[0002] It's generally believed that almost all materials have a positive Poisson's ratio, approximately 1 / 3. Rubber materials have a value of 1 / 2, aluminum metal has a value of 0.133, copper has a value of 0.127, and typical polymer foams have values of 0.11 to 0.14. This means that these materials contract laterally when stretched. A negative Poisson's ratio, on the other hand, means that when stretched, a material expands laterally within its elastic range; when compressed, it contracts. While this phenomenon is thermodynamically possible, it's not commonly observed in materials. Recently, materials with unique structures have been discovered that exhibit negative Poisson's ratio effects, attracting considerable attention from materials scientists and physicists due to their unique properties. These negative Poisson's ratio structures can be used as surface layers in sandwich structures, protecting the core and improving the overall mechanical properties of the structure.

[0003] In contrast to materials with a positive Poisson's ratio, materials and structures with a negative Poisson's ratio expand laterally under tension and contract laterally under pressure. These materials and structures have attracted widespread attention and research due to their unique characteristics. Experiments have demonstrated that these functional materials possess excellent mechanical properties, including shear resistance, indentation resistance, impact resistance, and good energy absorption capacity, and have broad prospects for industrial application. However, due to the limitations of 3D printing technology in structural manufacturability, many conventional negative Poisson's ratio structures cannot be formed using 3D printing. Summary of the Invention

[0004] In view of this, in order to solve the above problems, an embodiment of the present invention provides a three-dimensional negative Poisson's ratio structure suitable for 3D printing.

[0005] An embodiment of the present invention provides a three-dimensional negative Poisson's ratio structure suitable for 3D printing, comprising:

[0006] A plurality of planar spiral structures are arranged in intervals in the vertical direction, the planar spiral structures comprising a plurality of spiral units, the spiral units comprising a plurality of spiral arms, the spiral arms being arranged in the shape of a quarter arc of an ellipse, the inner ends of the spiral arms coinciding with the endpoints of the major axis of the ellipse, and the outer ends coinciding with the endpoints of the minor axis of the ellipse, the spiral units being formed by a circular array of the spiral arms with the inner ends as the center, the inner ends of the plurality of spiral arms coinciding with the center point;

[0007] The plurality of spiral units are sequentially arranged along the X-axis and the Y-axis on a plane, and two adjacent spiral units are arranged in a mirror image and fixedly connected through the outer ends; the spiral units of two adjacent planar spiral structures correspond one to one in the upper and lower directions and are arranged in a mirror image;

[0008] The inclined support structure includes a plurality of inclined rods with the same inclination angle. The outer ends of the spiral arms of two adjacent spiral units correspond to each other and are respectively connected by the inclined rods.

[0009] Furthermore, the tilt angle of the tilt rod is 30-60°.

[0010] Furthermore, the outer end of the spiral arm of each spiral unit is located on the side length of a regular polygon, the number of sides of the regular polygon is the same as the number of the spiral arms, and each spiral arm corresponds to each side length one by one and is perpendicular to each side length, and the ratio of the side length of the regular polygon to the length of the minor axis of the ellipse is 2.

[0011] Furthermore, the plurality of spiral arms of the spiral unit are evenly spaced apart.

[0012] Furthermore, each of the spiral units has three spiral arms.

[0013] Furthermore, each of the spiral units has four spiral arms.

[0014] Furthermore, each of the spiral units has six spiral arms.

[0015] Furthermore, the inner side of the connection between the inclined rod and the outer end of the spiral arm is rounded.

[0016] The technical solutions provided by the embodiments of the present invention provide the following beneficial effects: Taking into account the forming limitations of 3D printing technology, the present invention designs a novel three-dimensional negative Poisson's ratio structure. This structure exhibits high negative Poisson's ratio performance and is suitable for 3D printing. In compression experiments, the negative Poisson's ratio structure exhibits typical negative Poisson's ratio deformation characteristics and a typical bending-dominated mechanical response. The negative Poisson's ratio structure exhibits a very stable plateau stress over a wide compressive strain range, without any rapid collapse or catastrophic failure. This demonstrates the rationality of the negative Poisson's ratio structure design and provides a rare opportunity for the design of high-strain or impact-resistant functional devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the spiral unit in Example 2 of the three-dimensional negative Poisson's ratio structure suitable for 3D printing provided by the present invention;

[0018] Figure 21 is a partial structural diagram of Example 2 of a three-dimensional negative Poisson's ratio structure suitable for 3D printing provided by the present invention;

[0019] Figure 3 yes Figure 2 Schematic diagram of the structural deformation of a three-dimensional negative Poisson's ratio structure suitable for 3D printing under tension;

[0020] Figure 4 yes Figure 2 Schematic diagram of the structural deformation of a three-dimensional negative Poisson's ratio structure suitable for 3D printing under compression;

[0021] Figure 5 It is the finite element simulation of the deformation process of negative Poisson's ratio structure under compression load;

[0022] Figure 6 (a) is the force-displacement curve of the negative Poisson's ratio structure, (b) and (c) are the optical images of the negative Poisson's ratio structure before and after compression, and (d) the compression process of the negative Poisson's ratio structure.

[0023] Figure 7 7a-7c are, respectively, a schematic structural diagram of a spiral unit, a schematic structural diagram of a single plane spiral structure, and a schematic structural diagram of a local structure in Example 1 of a three-dimensional negative Poisson's ratio structure suitable for 3D printing provided by the present invention; 7d-7f are, respectively, a schematic structural diagram of a spiral unit, a schematic structural diagram of a single plane spiral structure, and a schematic structural diagram of a local structure in Example 2 of a three-dimensional negative Poisson's ratio structure suitable for 3D printing provided by the present invention; 7g-7i are, respectively, a schematic structural diagram of a spiral unit, a schematic structural diagram of a single plane spiral structure, and a schematic structural diagram of a local structure in Example 3 of a three-dimensional negative Poisson's ratio structure suitable for 3D printing provided by the present invention;

[0024] Figure 8 8a is Figure 7 8f is a partial structural diagram, and 8b and 8c are partial structural diagrams of a three-dimensional negative Poisson's ratio structure suitable for 3D printing (the inner side of the connection of the planar spiral structure is rounded).

[0025] In the figure: spiral unit 100, lower spiral unit 101, upper spiral unit 102, left spiral unit 103, right spiral unit 104, front spiral unit 105, rear spiral unit 106, variable space 107, spiral arm 1, inner end 11, outer end 12, center point 13, inclined rod 2, connection 3. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0027] An embodiment of the present invention provides a three-dimensional negative Poisson's ratio structure suitable for 3D printing, comprising a plurality of planar spiral structures and an inclined support structure.

[0028] Multiple planar spiral structures are spaced apart in the vertical direction, see Figure 1 and Figure 2 The planar spiral structure includes multiple spiral units 100, each of which includes multiple spiral arms 1. The spiral arms 1 are arranged in the shape of a quarter arc of an ellipse, with the inner end 11 of the spiral arm 1 coinciding with the endpoint of the major axis of the ellipse, and the outer end 12 coinciding with the endpoint of the minor axis of the ellipse. The spiral unit 100 is formed by a circular array of spiral arms 1 centered around the inner end 11. The multiple spiral arms 1 of the spiral unit 100 are evenly spaced, and the inner ends 11 of the multiple spiral arms 1 coincide to form a center point 13. See [referring to] Figure 7 The number of spiral arms 1 in the spiral unit 100 is n. The outer end of the spiral arm 1 of each spiral unit 100 can be located on the side length of the regular polygon. The number of sides of the regular polygon is the same as the number of spiral arms 1, and each spiral arm 1 corresponds to and is perpendicular to each side length. To facilitate compression and stretching of the model, in this embodiment, the ratio of the length of the side of the regular polygon to the length of the minor axis of the ellipse is 2. The negative Poisson's ratio performance of the structure is good during both stretching and compression. When the length of the side of the regular polygon is greater than 2 compared to the length of the minor axis of the ellipse, the negative Poisson's ratio performance of the structure is good during compression. When the length of the side of the regular polygon is less than 2 compared to the length of the minor axis of the ellipse, the negative Poisson's ratio performance of the structure is good during stretching.

[0029] See Figure 3 and Figure 4 , multiple spiral units 100 are arranged in sequence along the X-axis and the Y-axis on the plane, two adjacent spiral units 100 are mirror-imaged and fixedly connected through the outer end 12, and four spiral units 100 in the circumferential direction are connected in sequence through the outer end 12 to form a variable space 107; in the upper and lower directions, the spiral units 100 of the two adjacent planar spiral structures correspond one to one in the upper and lower directions and are mirror-imaged.

[0030] The tilt support structure includes multiple tilt rods 2 with the same tilt angle. The outer ends 12 of the spiral arms 1 of two adjacent spiral units 100 correspond to each other and are connected by the tilt rods 2. To meet the manufacturing requirements of 3D printing, the tilt angle of the tilt rods 2 (the initial angle between the tilt rods 2 and the XY plane) is 30-60°.

[0031] Example 1, see Figure 7 a- Figure 7c. Each spiral unit 100 has three spiral arms 1. The planar spiral structure rotates with the inner end 11 of the spiral arm 1 as the center of rotation. The spiral arms 1 are arranged in a circular array three times with a step size of 120° to obtain the spiral unit 100. The two adjacent spiral units 100 on the X-axis, Y-axis and Z-axis (up and down) are mirrored. The upper and lower adjacent spiral units 100 are connected by three inclined rods 2, and the upper and lower ends of the inclined rods 2 are respectively connected to the outer end 12 of the spiral unit 100.

[0032] Example 2, see Figure 7 d- Figure 7 f. Each of the spiral units 100 has four spiral arms 1. The planar spiral structure rotates with the inner end 11 of the spiral arm 1 as the center of rotation. The spiral arms 1 are arranged in a circular array four times with a step size of 90° to obtain the spiral unit 100. The two adjacent spiral units 100 on the X-axis, Y-axis and Z-axis (up and down) are mirror-imaged. The upper and lower adjacent spiral units 100 are connected by four inclined rods 2, and the upper and lower ends of the inclined rods 2 are respectively connected to the outer end 12 of the spiral unit 100.

[0033] Example 3, see Figure 7 g- Figure 7 i. Each spiral unit 100 has six spiral arms 1. The planar spiral structure rotates with the inner end 11 of the spiral arm 1 as the center of rotation. The spiral arms 1 are arranged in a circular array six times with a step size of 60° to obtain the spiral unit 100. The two adjacent spiral units 100 on the X-axis, Y-axis and Z-axis (up and down) are mirrored. The upper and lower adjacent spiral units 100 are connected by six inclined rods 2, and the upper and lower ends of the inclined rods 2 are respectively connected to the outer end 12 of the spiral unit 100.

[0034] Taking Example 2 as an example, when a reverse load is applied to the spiral unit 100 in the Z-axis direction (pulling the upper spiral unit 102 upward and pulling the lower spiral unit 101 downward), for example, see Figure 3, the lower spiral unit 101 below the tilting rod 2 rotates clockwise, and the upper spiral unit 102 above the tilting rod 2 rotates counterclockwise, so that the tilting rod 2 rotates toward a vertical state under the action of tension. The upper spiral unit 102 is adjacent to the left spiral unit 103 and the right spiral unit 104 on the X-axis, and the upper spiral unit 102 is adjacent to the front spiral unit 105 and the rear spiral unit 106 on the Y-axis. The upper spiral unit 102 rotates counterclockwise, driving the front spiral unit 105, the rear spiral unit 106, the left spiral unit 103, and the right spiral unit 104 to rotate clockwise, thereby increasing the area of the variable space 107 between the spiral units 100. The spiral unit 100 below the tilting rod 2 rotates in the same direction. When the structure is stretched longitudinally, the multiple inclined rods 2 tend to be vertical, pulling the upper and lower adjacent spiral units 100 in the XY plane direction to rotate, and the rotation directions are opposite (clockwise / counterclockwise). When the inclined rods 2 are completely vertical, the spiral units 100 tend to be straight after rotation and the size of the planar spiral structure increases.

[0035] When a load in the same direction is applied to the spiral unit 100 in the Z-axis direction (compressing the upper spiral unit 102 downward and compressing the lower spiral unit 101 upward), for example, see Figure 4 , the lower spiral unit 101 below the tilt rod 2 rotates counterclockwise, and the upper spiral unit 102 above the tilt rod 2 rotates clockwise, so that the tilt rod 2 rotates toward the horizontal state under the action of compression. The upper spiral unit 102 is adjacent to the left spiral unit 103 and the right spiral unit 104 on the X-axis, and the upper spiral unit 102 is adjacent to the front spiral unit 105 and the rear spiral unit 106 on the Y-axis. The upper spiral unit 102 rotates clockwise, driving the front spiral unit 105, the rear spiral unit 106, the left spiral unit 103, and the right spiral unit 104 to rotate counterclockwise, thereby reducing the area of the variable space 107 between the spiral units 100. The rotation direction of the spiral unit 100 below the tilt rod 2 is the same. When the structure is longitudinally compressed, the multiple tilted rods 2 tend to be horizontal, pushing the upper and lower adjacent spiral units 100 in the XY plane direction to rotate, and the rotation directions are opposite (clockwise / counterclockwise). When the tilted rods 2 are completely horizontal, the spiral structure tends to a semicircular arc after rotation and the unit structure size is reduced.

[0036] See Figure 8 b and 8c, the inner side of the connection 3 between the tilt rod 2 and the outer end 12 of the spiral arm 1 is rounded. The rounded corner treatment at the node can improve the manufacturability of 3D printing and is also used to avoid fracture caused by stress concentration at the node.

[0037] See Figure 5By establishing a three-dimensional array of negative Poisson's ratio structural models for mechanical finite element simulation, the three-dimensional negative Poisson's ratio structure of the present invention has significant typical deformation characteristics of negative Poisson's ratio. The tilted rods 2 of the mirror array are in the shape of multiple broken lines. During the compression process, the tilted rods 2 fold close to each other with the inflection point as the axis, and the long axis direction of the tilted rods 2 is closer to the horizontal. At the same time, the tilted rods 2 push the spiral structure in the XY plane direction to rotate, causing the negative Poisson's ratio structure to shrink in the horizontal direction. When the negative Poisson's ratio structure is compressed in the Z-axis direction, it also shrinks in the horizontal direction (X / Y axis). Similarly, conversely, when the negative Poisson's ratio structure is stretched in the Z-axis direction, it also expands in the horizontal direction (X / Y axis).

[0038] The negative Poisson's ratio structure of the present invention has been successfully manufactured by 3D printing ( Figure 6 b), showing the manufacturability of this structure for 3D printing and the significant negative Poisson's ratio structural deformation characteristics ( Figure 6 b, d). In the process of vertical compression of conventional materials, the sample will expand in the horizontal direction at the same time. However, in the process of vertical compression of negative Poisson's ratio structure, the sample will shrink ( Figure 6 d). In the compression test, it can be clearly observed that with the increase of vertical compressive strain, the sample shrinks inward in the horizontal direction, forming an inward concave arc on both sides ( Figure 6 c, d).

[0039] By analyzing the force-displacement curve of the negative Poisson's ratio structure, it is shown that ( Figure 6 a), the negative Poisson's ratio structure has a bending-dominated mechanical response. The force-displacement curve characteristics show that the negative Poisson's ratio structure goes through an elastic stage, a plastic stage, and a densification stage during the deformation process. And in the densification stage, the material is concentrated to the center of the compression area to the maximum extent, which is conducive to maximizing the stiffness and strength of the material in the compression area during the compression process, thereby having the potential to achieve impact resistance or buffering functions. The negative Poisson's ratio structure has a very stable platform stress in a large compressive strain range, without any sharp collapse or catastrophic damage. This reflects the rationality of the design of the negative Poisson's ratio structure, which provides a rare opportunity for the design of high-strain or impact-resistant functional devices.

[0040] In this document, directional terms such as front, back, top, and bottom are defined based on the positions of components in the drawings and relative to each other, and are intended for clarity and convenience in describing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application.

[0041] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A three-dimensional negative Poisson's ratio structure suitable for 3D printing, characterized in that: include: A plurality of planar spiral structures are arranged in intervals in the vertical direction, the planar spiral structures comprising a plurality of spiral units, the spiral units comprising a plurality of spiral arms, the spiral arms being arranged in the shape of a quarter arc of an ellipse, the inner ends of the spiral arms coinciding with the endpoints of the major axis of the ellipse, and the outer ends coinciding with the endpoints of the minor axis of the ellipse, the spiral units being formed by a circular array of the spiral arms with the inner ends as the center, the inner ends of the plurality of spiral arms coinciding with the center point; The plurality of spiral units are sequentially arranged along the X-axis and the Y-axis on a plane, and two adjacent spiral units are arranged in a mirror image and fixedly connected through the outer ends; the spiral units of two adjacent planar spiral structures correspond one to one in the upper and lower directions and are arranged in a mirror image; An inclined support structure comprising a plurality of inclined rods with the same inclination angle, wherein the outer ends of the spiral arms of two adjacent spiral units correspond to each other and are respectively connected by the inclined rods; The tilt angle of the tilt rod is 30-60°; The outer end of the spiral arm of each spiral unit is located on the side length of a regular polygon, the number of sides of the regular polygon is the same as the number of spiral arms, and each spiral arm corresponds to each side length one by one and is perpendicular to each side length, and the ratio of the side length of the regular polygon to the length of the minor axis of the ellipse is 2.

2. The three-dimensional negative Poisson's ratio structure suitable for 3D printing according to claim 1, characterized in that: The plurality of spiral arms of the spiral unit are evenly spaced apart.

3. The three-dimensional negative Poisson's ratio structure suitable for 3D printing according to claim 1, characterized in that: Each of the spiral units has three spiral arms.

4. The three-dimensional negative Poisson's ratio structure suitable for 3D printing according to claim 1, characterized in that: Each of the spiral units has four spiral arms.

5. The three-dimensional negative Poisson's ratio structure suitable for 3D printing according to claim 1, characterized in that: The number of spiral arms of each of the spiral units is six.

6. The three-dimensional negative Poisson's ratio structure suitable for 3D printing according to claim 1, characterized in that: The inner side of the connection between the inclined rod and the outer end of the spiral arm is rounded.

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