A twist-based origami concave negative poisson's ratio metamaterial and a preparation method thereof

Abstract

The application provides a fold paper concave negative Poisson's ratio metamaterial based on compression and torsion and a preparation method thereof, and the structure comprises a plurality of fold paper concave structure units, the fold paper concave structure unit comprises four upper inclined rods and lower inclined rods arranged in a matrix, the upper inclined rods and the lower inclined rods are provided with fold paper pre-folding marks, the upper surface of the upper inclined rod is provided with an upper rod, and the lower surface of the lower inclined rod is provided with a lower rod. The application can integrate the negative Poisson's ratio effect and the compression and torsion effect, the design greatly improves the utilization rate of the energy absorption box space, and currently, the research on the combination of the fold paper structure and the concave structure in the traditional negative Poisson's ratio structure is less.

Description

Technical Field

[0001] This invention relates to the field of negative Poisson's ratio metamaterial energy absorption technology, and in particular to a paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion and its preparation method. Background Technology

[0002] Currently, most materials used in production and daily life are positive Poisson's ratio materials. These materials exhibit lateral contraction under tension and lateral expansion under compression. However, in some specialized fields, positive Poisson's ratio materials often cannot meet the needs of production and daily life. Through continuous exploration, researchers have finally discovered a metamaterial with anomalous mechanical properties—negative Poisson's ratio materials. The mechanical properties of negative Poisson's ratio materials differ from common materials; they expand laterally under tension and contract laterally under compression. It is precisely this unique mechanical property that gives negative Poisson's ratio materials characteristics not found in ordinary materials, both macroscopically and microscopically. Negative Poisson's ratio materials possess excellent impact resistance, superior specific energy absorption, and good vibration damping. Currently, various structural models of negative Poisson's ratio materials have been developed, such as chiral or anti-chiral structures, re-entry structures, hinge structures, and embedded concave structures, among others.

[0003] Traffic safety is of paramount importance. Applying negative Poisson's ratio materials or structures to shock absorption and vibration damping devices for vehicles and protective devices in the event of traffic accidents can greatly improve vehicle safety. Negative Poisson's ratio materials or structures have excellent shock absorption and stability. Placing a lattice structure of negative Poisson's ratio materials into energy-absorbing boxes or columns can greatly enhance the rigidity and energy absorption effect of the energy-absorbing box. Energy-absorbing boxes are used in collision avoidance devices for automobiles and other vehicles. While pursuing good energy absorption effect and safety and stability, it is also necessary to make the most of space. However, most traditional concave structures only have a negative Poisson's ratio effect or only have a compression and torsion effect.

[0004] Most existing negative Poisson's ratio structures are based on traditional concave structures, while research on structures that allow concave structures to twist under pressure is relatively limited. In addition, lattice structures used inside energy-absorbing boxes are also a hot research topic. However, most traditional lattice structures are concave under pressure, while lattice structures that not only concave but also twist under pressure are rare, or occupy a large space, making them unsuitable for special applications with high requirements for lightweight structures. Therefore, there is an urgent need for a negative Poisson's ratio metamaterial that is lighter, has better energy absorption, and better stability. Summary of the Invention

[0005] The purpose of this invention is to provide a paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion and its preparation method. Compared with traditional concave structures, it has better energy absorption effect and stability while improving space utilization.

[0006] According to one objective of the present invention, the present invention provides a paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion, comprising a plurality of paper-folding concave structural units, wherein each paper-folding concave structural unit comprises four upper and lower inclined rods arranged in a matrix, wherein the upper and lower inclined rods are provided with paper-folding pre-creases, the upper surface of the upper inclined rod is provided with an upper rod, and the lower surface of the lower inclined rod is provided with a lower rod.

[0007] Furthermore, each corresponding upper and lower diagonal bar is a mirror image of the other.

[0008] Furthermore, the upper rod and the upper inclined rod have a first contact surface, and the lower inclined rod and the lower rod have a second contact surface.

[0009] Furthermore, the origami concave structural unit is arranged in three arrays along the x-axis and y-axis directions.

[0010] Furthermore, the upper and lower diagonal bars are designed with varying stiffness, transitioning from thin to thick.

[0011] Furthermore, the upper rod, the lower rod, the upper inclined rod, and the lower inclined rod are seamlessly connected.

[0012] Furthermore, the corner portions of the origami structures of the upper and lower diagonal rods are thicker.

[0013] According to another objective of the present invention, the present invention provides a method for preparing the above-mentioned origami-based concave negative Poisson's ratio metamaterial based on compression and torsion, comprising the following steps:

[0014] S1. To create the downward sloping bar, first, a square with side length a is built on the top reference plane. Then, a reference plane I is built at a distance h / 2 above the top reference plane. On reference plane I, a square with side length 1.2a is first built on the reference plane, coaxial with the square in the top reference plane. Rotate it around the axis by an angle θ, and then offset it to the left by a distance d. Connect the corresponding vertices of the two squares to form two faces. Stretch the two faces backward by a distance of 1.2a to obtain the downward sloping bar.

[0015] S2, mirror the lower inclined rod with its upper surface as the mirror plane to obtain the upper inclined rod, offset the right reference plane to the left by a distance h / 2 to obtain reference plane II, take the intersection of reference plane II and the front reference plane as the reference axis, and arrange the upper and lower inclined rods in a circular array around the reference axis four times. Take a square with a side length of a on the side of the upper inclined rod close to the reference axis, stretch it to the next plane to obtain the upper rod, and then arrange two more in a circular array around the reference axis.

[0016] S3, the lower rod of the structure is obtained by taking a rectangle with a width of n and a length of a on the side of the lower inclined rod close to the reference axis, stretching it to the next plane, and then mirroring it with the lower surface of the stretched rod as the mirror plane. The upper rod, lower rod, upper inclined rod and lower inclined rod are then linearly arrayed downward to obtain a single origami concave structure. Three of the obtained single origami concave structures are arrayed in the x-axis and y-axis directions, and seamlessly connected in the middle by the lower rod. Finally, an origami concave negative Poisson's ratio metamaterial based on compression and torsion is obtained.

[0017] Furthermore, the upper and lower diagonal braces are at the same height.

[0018] Furthermore, the side length of the square on the upper surface of the lower diagonal bar is 1.2a; the side length of the square on the upper surface of the upper diagonal bar and the lower surface of the lower diagonal bar is a.

[0019] The technical solution of this invention can combine the negative Poisson's ratio effect and the compression and torsion effect. This design greatly improves the utilization rate of the energy absorption box space. Currently, there is little research on combining the origami structure with the concave structure in the traditional negative Poisson's ratio structure. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the dot matrix structure according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram showing the dimensions of the diagonal bar in the top view according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the dimensions of the diagonal bar according to an embodiment of the present invention;

[0025] Figure 5 This is a dimensioning diagram of the upper rod according to an embodiment of the present invention;

[0026] Figure 6 This is a dimensioning diagram of the lower rod according to an embodiment of the present invention;

[0027] In the diagram, 1 is the upper rod; 2 is the first contact surface; 3 is the upper inclined rod; 4 is the lower inclined rod; 5 is the second contact surface; and 6 is the lower rod. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this 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. Therefore, they should not be construed as limiting this invention.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may 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.

[0031] Example 1

[0032] like Figures 1-6 As shown,

[0033] A paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion includes a paper-folding concave structural unit. Each concave structural unit comprises four upper inclined rods 3 and lower inclined rods 4 arranged in a matrix. Each corresponding upper and lower inclined rod is a mirror image of the others. The upper surface of the upper inclined rod 3 has an upper rod 1, and a first contact surface 2 exists between the upper rod 1 and the upper inclined rod 3. The lower surface of the lower inclined rod 4 has a lower rod 6, and a second contact surface 5 exists between the lower inclined rod 4 and the lower rod 6. Paper-folding pre-creases are provided at the upper inclined rods 3 and lower inclined rods 4.

[0034] The present invention relates to a paper-fold concave negative Poisson's ratio metamaterial based on compression and torsion, which is formed by combining multiple paper-fold concave structural units. In this embodiment, three paper-fold concave structural units are arrayed in the x-axis and y-axis directions, and are seamlessly connected in the middle by the lower rod 6 and the upper rod 1, thus obtaining a paper-fold concave negative Poisson's ratio metamaterial based on compression and torsion.

[0035] In this embodiment, the upper diagonal rod 3 and the lower diagonal rod 4 are designed with varying stiffness from thin to thick. The upper diagonal rod 3 and the lower diagonal rod 4 employ a paper-folding pre-crease design, which causes the diagonal rods to twist laterally under axial compression. The upper rod 1, lower rod 6, upper diagonal rod 3, and lower diagonal rod 4 are all seamlessly connected. The corner portions of the paper-folding structure of the upper diagonal rod 3 and the lower diagonal rod 4 are relatively thick.

[0036] According to another objective of the present invention, the present invention provides a method for preparing the above-mentioned origami-based concave negative Poisson's ratio metamaterial based on compression and torsion, comprising the following steps:

[0037] S1. The lower diagonal bar 4 in this structure is first constructed by building a square with a side length of a (mm) on the upper reference plane. Then, a reference plane I is built at a distance of h / 2 (mm), or h0 (mm), above the upper reference plane. On the reference plane I, a square with a side length of 1.2a (mm) coaxial with the square in the upper reference plane is first built. This square is then rotated around the axis by an angle θ and then offset to the left by a distance d (mm). The corresponding vertices of the two squares are connected to form two faces. The two faces are then stretched backward by a distance of 1.2a (mm) to obtain the lower diagonal bar 4.

[0038] S2, mirror the lower inclined rod 4 with its upper surface as the mirror plane to obtain the upper inclined rod 3. Offset the right reference plane to the left by a distance of h / 2 (mm), which is h0 (mm), to obtain the reference plane II. Using the intersection of the reference plane II and the front reference plane as the reference axis, arrange the upper inclined rod 3 and the lower inclined rod 4 in a circular array around the reference axis. Take a square with a side length of a (mm) on the side of the upper inclined rod 3 that is close to the reference axis, stretch it to the next plane to obtain the upper rod 1, and then arrange two more in a circular array around the reference axis.

[0039] S3, the lower rod 6 of the structure is obtained by taking a rectangle with a width of n (mm) and a length of a (mm) on the side of the lower inclined rod 4 close to the reference axis, stretching it to the next plane, and then mirroring it with the lower surface of the stretched rod as the mirror plane. The upper rod 1, lower rod 6, upper inclined rod 3, and lower inclined rod 4 are then linearly arrayed downwards to obtain a single origami concave structure. Three of the obtained single origami concave structures are arrayed in the x-axis and y-axis directions, and seamlessly connected in the middle by the lower rod 6. Finally, an origami concave negative Poisson's ratio metamaterial based on compression and torsion is obtained.

[0040] like Figure 2As shown, the overall height of the origami concave negative Poisson's ratio metamaterial based on compression and twisting is H (mm), and the overall side length is L (mm); the combined height of a single upper diagonal bar 3 and lower diagonal bar 4 is h (mm), and the side length is l (mm).

[0041] like Figure 4 As shown, the heights of the upper inclined rod 3 and the lower inclined rod 4, based on the compressive twisting concave negative Poisson's ratio metamaterial, are the same, h0 (mm); the side length of the square on the upper surface of the lower inclined rod 4 is 1.2a (mm); the side lengths of the squares on the upper surface of the upper inclined rod 3 and the lower surface of the lower inclined rod 4 are a (mm); the angle between the plane of the upper inclined rod 3 near the reference axis and the upper reference plane is δ; the angle between the projection of one side AC of the lower inclined rod 4 and the front reference plane is γ; the angle between AC and AB of the triangular plane ABC in the lower inclined rod 4 is α, the angle between AB and BC is β, the angle between AC and CB is η, the length of AC is b (mm), the length of AB is c (mm), and the length of BC is a (mm).

[0042] like Figure 5 As shown, the single-sided contact surface of the lower rod 6 with the upper inclined rod 3 and the lower inclined rod 4, based on the twisted origami concave negative Poisson's ratio metamaterial, has a length of a, a width of n, and a vertical height of a; the length of the upper surface of the lower rod 6 is p, and one of the included angles between the single-sided contact surfaces of the lower rod 6 with the upper inclined rod 3 and the lower inclined rod 4 is ω. In this embodiment, the origami dimensions in the structure can be determined by a, h0, and θ to design the geometry.

[0043] The construction parameters for this case are as follows: H = 60 (mm); h = 20 (mm); L = 65.25 (mm);

[0044] I=15.91(mm); h0=h / 2=10(mm); α=12.05°; β=61.41°; eta=106.54°; θ=45°;

[0045]

[0046]

[0047] This invention provides a pressure-torsion negative Poisson's ratio energy absorption structure, specifically relating to the design and energy absorption characteristics of a pressure-torsion origami concave negative Poisson's ratio metamaterial. The thicknesses of the upper inclined rod 3 and the lower inclined rod 4 are different in the axial direction. This design makes the overall negative Poisson's ratio structure lighter, which is beneficial for applications in various fields, such as vehicles, ships, aerospace, and medical devices where lightweighting is a high priority.

[0048] In this invention, the upper and lower inclined rods 3 and 4 of the concave structure adopt a paper-folding pre-crease design, which enables the structure to achieve concave-torsion coupling when under pressure, thereby improving the specific energy absorption of the structure. At the same time, the inclined rods adopt a variable stiffness design, and the corner part of the paper-folding structure on the inclined rods is thickened, which improves the overall stiffness of the structure and further improves the specific energy absorption of the overall structure.

[0049] The paper-folding structure established in this invention at the upper inclined rod 3 and lower inclined rod 4 has been thickened at its corners, which improves the stiffness of the negative Poisson's ratio structure while it is compressed downwards under the guidance of the paper-folding pre-crease.

[0050] The negative Poisson's ratio structure of this invention allows for stiffness adjustment of the inclined bar structure. By changing the values ​​of a, h0, and θ of the inclined bar, the stiffness of the inclined bar structure can be adjusted to achieve the effect of variable stiffness, thereby further adapting to the needs of various locations.

[0051] Compared to traditional negative Poisson's ratio concave structures, this invention achieves concave-torsional coupling under compression, significantly reducing space occupation and improving space utilization efficiency. The concave-torsional coupling characteristic under compression makes the structure less prone to tilting and instability under sudden loads, resulting in a safer and more stable compressive characteristic compared to traditional concave structures.

[0052] Compared to traditional negative Poisson's ratio concave structures, the structure designed in this invention achieves concave-torsional coupling under compression, significantly reducing space occupation and improving space utilization efficiency. The concave-torsional coupling characteristic under compression in this design makes the structure less prone to tilting and instability under sudden loads, resulting in a safer and more stable compressive characteristic compared to traditional concave structures.

[0053] The present invention proposes a design of a paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion, which can combine the negative Poisson's ratio effect and the compression and torsion effect. This design greatly improves the utilization rate of the energy absorption box space. At present, there are few studies on combining paper-folding structure with concave structure in traditional negative Poisson's ratio structure.

[0054] In this invention, by adding pre-folded creases to the concave structure, the concave structure twists in the direction of the pre-folds when under pressure, which improves the stability of the structure and avoids the large tilting of the car when it is subjected to a collision impact, which would cause the energy-absorbing structure to fail. Therefore, the design of the origami concave negative Poisson's ratio metamaterial based on pressure and torsion proposed in this invention has better energy absorption effect and stability than the traditional concave structure, while also improving the space utilization rate.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion, characterized in that, The structure comprises multiple origami-inspired concave structural units, each including four upper and lower diagonal braces arranged in a matrix. The upper and lower diagonal braces have pre-folded creases. The upper surface of the upper diagonal brace has an upper rod, and the lower surface of the lower diagonal brace has a lower rod. The upper and lower diagonal braces feature a variable stiffness design, transitioning from thin to thick. The corner portions of the origami structure of the upper and lower diagonal braces are thicker. The pre-folded crease design of the upper and lower diagonal braces enables a concave-torsional coupling effect under pressure. This effect causes the structure to contract laterally and twist synchronously under pressure, improving space utilization and impact resistance.

2. The origami-concave negative Poisson's ratio metamaterial based on compression and torsion according to claim 1, characterized in that, Each corresponding upper and lower diagonal bar is a mirror image of the other.

3. The origami-concave negative Poisson's ratio metamaterial based on compression and torsion according to claim 1, characterized in that, The upper rod and the upper inclined rod have a first contact surface, and the lower inclined rod and the lower rod have a second contact surface.

4. The origami-concave negative Poisson's ratio metamaterial based on compression and torsion according to claim 1, characterized in that, The origami concave structural unit is arranged in three arrays along the x-axis and y-axis directions.

5. The origami-concave negative Poisson's ratio metamaterial based on compression and torsion according to claim 1, characterized in that, The upper rod, the lower rod, the upper diagonal rod, and the lower diagonal rod are seamlessly connected.

6. A method for preparing a paper-folding concave negative Poisson's ratio metamaterial based on compression and torsion, characterized in that, Includes the following steps: S1. To create the downward sloping bar, first, a square with side length a is built on the top reference plane. Then, a reference plane I is built at a distance h / 2 above the top reference plane. On reference plane I, a square with side length 1.2a is first built on the reference plane, coaxial with the square in the top reference plane. Rotate it around the axis by an angle θ, and then offset it to the left by a distance d. Connect the corresponding vertices of the two squares to form two faces. Stretch the two faces backward by a distance of 1.2a to obtain the downward sloping bar. S2, mirror the lower inclined rod with its upper surface as the mirror plane to obtain the upper inclined rod, offset the right reference plane to the left by a distance h / 2 to obtain reference plane II, take the intersection of reference plane II and the front reference plane as the reference axis, and arrange the upper and lower inclined rods in a circular array around the reference axis four times. Take a square with a side length of a on the side of the upper inclined rod close to the reference axis, stretch it to the next plane to obtain the upper rod, and then arrange two more in a circular array around the reference axis. S3, the lower rod of the structure is obtained by taking a rectangle with a width of n and a length of a on the side of the lower inclined rod close to the reference axis, stretching it to the next plane, and then mirroring it with the lower surface of the stretched rod as the mirror plane. The upper rod, lower rod, upper inclined rod and lower inclined rod are then linearly arrayed downward to obtain a single origami concave structure. Three of the obtained single origami concave structures are arrayed in the x-axis and y-axis directions, and seamlessly connected in the middle by the lower rod. Finally, an origami concave negative Poisson's ratio metamaterial based on compression and torsion is obtained.

7. The method for preparing the origami concave negative Poisson's ratio metamaterial based on compression and torsion according to claim 6, characterized in that, The upper and lower diagonal braces are at the same height.

8. The method for preparing the origami concave negative Poisson's ratio metamaterial based on compression and torsion according to claim 6, characterized in that, The side length of the square on the upper surface of the lower diagonal bar is 1.2a; the side length of the square on the upper surface of the upper diagonal bar and the lower surface of the lower diagonal bar is a.

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