Nested concave hexagon tensegrity metamaterial structure

Abstract

This invention relates to a nested concave hexagonal tensioned monolithic metamaterial structure, belonging to the field of mechanical metamaterial structures. The structure includes an embedded concave hexagonal unit and an outer concave hexagonal frame. The outer frame consists of first and second outer concave hexagonal units spaced parallel to each other along the thickness direction, and upper and lower connecting plates, with the embedded unit positioned between them. The embedded unit and the outer unit employ the same combination of rigid and flexible connecting sections, with corresponding rigid sections of equal length. A height difference in the free state is created by setting different concave angles. After assembly, the embedded unit is in a compressive prestressed state, while the outer frame is in a tensile prestressed state, achieving internal prestress self-balancing under the constraint of the upper and lower connecting plates. This structure combines the negative Poisson's ratio deformation characteristics of a concave hexagon with the stability of a tensioned monolithic structure, and can be used in fields such as lightweight load-bearing, mechanical property control, and energy absorption.

Description

Technical Field

[0001] This invention relates to the field of mechanical metamaterial structure design, and in particular to a nested concave hexagonal tensioned monolithic metamaterial structure, which can be used in lightweight load-bearing structures, mechanical property control structures, buffer energy absorption structures, and tensioned monolithic metamaterial systems. Background Technology

[0002] Mechanical metamaterials are novel structural materials that achieve unique mechanical responses through artificially designed structural units. Their macroscopic mechanical properties mainly depend on the geometric and topological relationships of the internal structural units and the cooperative deformation patterns among different structural units. Concave hexagons, as a typical negative Poisson's ratio metamaterial structure, exhibit excellent deformation coordination, energy absorption capacity, and potential for mechanical property control by altering the geometric configuration of traditional hexagonal cells, thus enabling the structure to produce a unique lateral deformation response under external loads.

[0003] However, existing concave hexagonal negative Poisson's ratio structures mainly rely on the geometric combination of a single cell or multiple cells. Their mechanical response mainly depends on the bending deformation of local rods or the rotation of nodes, resulting in problems such as fewer structural levels, limited buffering and energy absorption capacity, and insufficient overall control performance.

[0004] Therefore, there is an urgent need to provide a nested concave hexagonal tensioned monolithic metamaterial structure. Combining the design concept of tensioned monolithic structures, the nested combination relationship between the embedded concave hexagonal units and the outer concave hexagonal frame enables mutual constraint between different structural units. The internal prestress generated during assembly is used to achieve the self-balancing state of the structure, thereby improving the overall stability and mechanical response of the structure and solving the above-mentioned problems in the existing technology. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a nested concave hexagonal tensioned monolithic metamaterial structure to solve the problems of existing concave hexagonal negative Poisson's ratio metamaterial structures having a single form, insufficient structural stability, and limited buffering and energy absorption capacity.

[0006] To achieve the above objectives, this invention provides a nested concave hexagonal tensioned monolithic metamaterial structure, comprising an embedded concave hexagonal unit and an outer concave hexagonal frame. The outer concave hexagonal frame includes a first and a second outer concave hexagonal unit arranged parallel to and spaced apart along the thickness direction, and an upper connecting plate fixedly connected to the upper ends of the first and second outer concave hexagonal units, and a lower connecting plate connected to their lower ends. A nested space is formed between the first and second outer concave hexagonal units, and the embedded concave hexagonal unit is disposed within the nested space. The first, the embedded, and the second outer concave hexagonal units are arranged sequentially and spaced apart along the thickness direction, and the frame planes of the three structural units are parallel to each other, with their axial centerlines coinciding. The upper end of the embedded concave hexagonal unit is connected to the upper connecting plate, and the lower end is connected to the lower connecting plate. The free state height of the embedded concave hexagonal unit is H1, and the free state height of the outer concave hexagonal frame is H2, where H1 > H2. During assembly, under external constraints, the embedded concave hexagonal unit is compressed along the height direction and placed within the nested space, with its upper and lower ends connected to the upper and lower connecting plates, respectively. After the external constraints are removed, the embedded concave hexagonal unit tends to elongate and recover along the height direction, and through the upper and lower connecting plates, it drives the outer concave hexagonal frame to stretch along the height direction; the outer concave hexagonal frame correspondingly exhibits a tendency to retract and recover. The two reach equilibrium under the common constraint of the connecting plate assembly, so that the common height H after assembly satisfies H2 < H < H1. The embedded concave hexagonal unit is in a compressive prestress state, and the outer concave hexagonal frame is in a tensile prestress state, thereby forming an internal prestress self-balancing state.

[0007] It should be noted that the embedded concave hexagonal unit includes integrally formed upper and lower rigid sections and two concave side edges symmetrically arranged on the left and right sides. Each concave side edge includes an upper inclined rigid section and a lower inclined rigid section, which are inclined inward toward the interior of the embedded concave hexagonal unit. The upper inclined rigid section is connected to the upper rigid section through an upper flexible connecting section, the upper and lower inclined rigid sections are connected through a middle flexible connecting section, and the lower inclined rigid section is connected to the lower rigid section through a lower flexible connecting section.

[0008] It should be noted that the upper flexible connecting section, the middle flexible connecting section and the lower flexible connecting section all adopt a local thinning structure. The dimension of the local thinning structure along the thickness direction is 25% of the wall thickness of the adjacent rigid section, so that the flexible connecting section is the main deformation area during the structural deformation process.

[0009] It should be noted that the first and second peripheral concave hexagonal units have the same structure and are symmetrically arranged about the middle plane of the embedded concave hexagonal unit. Both the first and second peripheral concave hexagonal units adopt the same combination of rigid and flexible connecting segments as the embedded concave hexagonal unit.

[0010] It should be noted that the corresponding rigid segment lengths of the embedded concave hexagonal unit, the first peripheral concave hexagonal unit, and the second peripheral concave hexagonal unit are the same, and their free-state height difference is formed by the difference in concave angles. Specifically, the concave angle refers to the smaller included angle formed at the middle flexible connection section between the upper inclined rigid segment and the lower inclined rigid segment on the same concave side. The concave angle of the embedded concave hexagonal unit is θ1, and the concave angles of the first peripheral concave hexagonal unit and the second peripheral concave hexagonal unit are both θ2, and satisfy 0° < θ2 < θ1 < 180°. Under the condition that the corresponding rigid segment lengths are the same, since the concave angle θ1 is greater than the concave angle θ2, the free-state height H1 of the embedded concave hexagonal unit is greater than the free-state height H2 of the peripheral concave hexagonal frame, providing initial geometric conditions for forming an internal prestressed self-balancing state after assembly.

[0011] Beneficial Effects: This invention constructs a multi-level, monolithic tension metamaterial structure by nesting embedded concave hexagonal units with an outer concave hexagonal frame. The difference in concavity angles between the inner and outer concave hexagonal units creates a free height difference, and the shared upper and lower connecting plates constrain this, enabling the embedded units to generate compressive prestress and the outer frame to generate tensile prestress. This achieves a self-balancing state of internal prestress without the need for continuous external load application. The invention features a simple structure, clear connections, and combines the negative Poisson's ratio of a concave hexagonal structure with the stability of a monolithic tension structure. It can be applied to mechanical metamaterial structures, lightweight load-bearing structures, and energy-absorbing buffer structures. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0013] Figure 1 The image shows the overall front view of a nested concave hexagonal tensioned monolithic metamaterial structure provided by this invention.

[0014] Figure 2 The image shows an isometric side view of a nested concave hexagonal tensioned monolithic metamaterial structure provided by this invention.

[0015] Figure 3 An exploded view of a nested concave hexagonal tensioned monolithic metamaterial structure provided by the present invention.

[0016] Figure 4 The front view of the embedded concave hexagonal unit in a nested concave hexagonal tensioned monolithic metamaterial structure provided by the present invention.

[0017] Figure 5 The front view of the outer concave hexagonal frame in a nested concave hexagonal tensioned monolithic metamaterial structure provided by the present invention.

[0018] Figure 6 An isometric side view of the outer concave hexagonal frame in a nested concave hexagonal tensioned monolithic metamaterial structure provided by the present invention.

[0019] Figure 7 An isometric side view of a nested concave hexagonal tensioned monolithic metamaterial structure provided by the present invention under load.

[0020] Labeling Explanation: 100, Embedded concave hexagonal unit; 110, Rigid sections at both ends; 111, Upper rigid section; 112, Lower rigid section; 120, Concave side; 121, Upper inclined rigid section; 122, Lower inclined rigid section; 130, Flexible connection section; 131, Upper flexible connection section; 132, Middle flexible connection section; 133, Lower flexible connection section; 200, Peripheral concave hexagonal frame; 210, Connecting plate assembly; 211, Upper connecting plate; 212, Lower connecting plate; 220, Peripheral concave hexagonal unit; 221, First peripheral concave hexagonal unit; 222, Second peripheral concave hexagonal unit; 230, Nested space. Detailed Implementation

[0021] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar parts, or parts having the same or similar functions. The embodiments described below in conjunction with the accompanying drawings are only for explaining the present invention and should not be construed as limiting the scope of protection of the present invention.

[0022] In the description of this invention, it should be noted that the terms "upper", "lower", "inner", "outer", "middle", "both sides", "thickness direction", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only used to facilitate the description of this invention and simplify the text, and do not indicate or imply that the structure or component referred to must have a specific orientation, be constructed or used in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed connection," "nested arrangement," "parallel arrangement," "spaced arrangement," "compression," and "tension," etc., should be interpreted broadly. For example, "fixed connection" can be a direct connection or an indirect connection through connectors; "nested arrangement" refers to a structure being housed within the space formed by another structure along its thickness direction; "prestressed self-balancing state" refers to a stable state achieved by multiple structural units generating mutually canceling internal elastic forces under assembly constraints.

[0024] Existing concave hexagonal negative Poisson's ratio structures typically rely on single-cell geometric deformation to achieve the negative Poisson's ratio effect. However, during structural expansion and multi-layer assembly, they are prone to problems such as insufficient overall stability, poor deformation coordination, and weak buffering and energy absorption capacity. Therefore, this invention provides a nested concave hexagonal tensioned monolithic metamaterial structure. This structure combines nested concave hexagonal units with larger concave angles with a double-layered outer concave hexagonal frame with smaller concave angles, and uses upper and lower connecting plates for fixed connection. This creates an internal prestressed self-balancing state between different structural units, thereby improving the overall structural stability and mechanical response.

[0025] See Figures 1 to 7 This embodiment provides a nested concave hexagonal tensioned monolithic metamaterial structure, including an embedded concave hexagonal unit 100 and an outer concave hexagonal frame 200. The embedded concave hexagonal unit 100 includes rigid sections 110 at both ends, concave sides 120, and flexible connecting sections 130. The outer concave hexagonal frame 200 includes a connecting plate assembly 210, an outer concave hexagonal unit 220, and the resulting nested space 230.

[0026] See Figures 1 to 6The first outer concave hexagonal unit 221 and the second outer concave hexagonal unit 222 are spaced apart along the thickness direction. Their upper ends are fixedly connected to the upper connecting plate 211, and their lower ends are fixedly connected to the lower connecting plate 212. A nested space 230 extending along the thickness direction is formed between the two outer concave hexagonal units. The embedded concave hexagonal unit 100 is disposed within the nested space 230 along the thickness direction, and the frame planes of the embedded concave hexagonal unit 100 and the two outer concave hexagonal units 220 are parallel to each other, with their axial center lines coinciding. The upper and lower ends of the embedded concave hexagonal unit 100 are connected to the upper and lower parts of the connecting plate assembly 210, respectively, so that the embedded concave hexagonal unit and the outer concave hexagonal frame together constitute a nested tensioned integral structure.

[0027] See Figures 3 to 4 The embedded concave hexagonal unit 100 includes rigid sections 110 at both ends, concave side edges 120, and flexible connecting sections 130. The rigid sections 110 at both ends include an upper rigid section 111 and a lower rigid section 112. The concave side edges 120 are symmetrically arranged on the left and right sides of the embedded concave hexagonal unit 100, and each concave side edge 120 includes an upwardly inclined rigid section 121 and a downwardly inclined rigid section 122. The upwardly inclined rigid section 121 and the downwardly inclined rigid section 122 are inclined towards the interior of the embedded concave hexagonal unit 100, forming an inwardly concave hexagonal side structure. The flexible connecting section 130 includes an upper flexible connecting section 131, a middle flexible connecting section 132, and a lower flexible connecting section 133. The upper inclined rigid segment 121 is connected to the upper rigid segment 111 via the upper flexible connecting segment 131. The upper inclined rigid segment 121 and the lower inclined rigid segment 122 are connected via the middle flexible connecting segment 132. The lower inclined rigid segment 122 is connected to the lower rigid segment 112 via the lower flexible connecting segment 133. The upper flexible connecting segment 131, the middle flexible connecting segment 132, and the lower flexible connecting segment 133 all adopt a locally thinned structure. The dimension of the thinned structure along the thickness direction is 25% of the wall thickness of the adjacent rigid segment. This allows the embedded concave hexagonal unit 100 to generate axial elastic deformation through the bending deformation of the flexible connecting segment when subjected to axial load, thereby achieving the compliant deformation capability of the overall structure.

[0028] See Figures 5 to 6The outer concave hexagonal unit 220 includes a first outer concave hexagonal unit 221 and a second outer concave hexagonal unit 222 with identical structures, symmetrically arranged about the mid-plane of the embedded concave hexagonal unit 100. The first outer concave hexagonal unit 221 and the second outer concave hexagonal unit 222 adopt the same combination of rigid and flexible connecting segments as the embedded concave hexagonal unit 100, but their initial concave angle is smaller than that of the embedded concave hexagonal unit 100, resulting in elastic constraints in different directions between the outer and inner structures during assembly. The concave angle θ1 of the embedded concave hexagonal unit 100 and the concave angle θ2 of the outer concave hexagonal unit 220 satisfy: 0° < θ2 < θ1 < 180°.

[0029] See Figures 1 to 3 The height of the embedded concave hexagonal unit 100 in its free state is H1, and the height of the outer concave hexagonal frame 200 in its free state is H2, where H1 > H2. During assembly, under external constraints, the embedded concave hexagonal unit 100 is compressed along its height direction to match the free state height H2 of the outer concave hexagonal frame 200, and then inserted into the nesting space 230, so that the upper end of the embedded concave hexagonal unit 100 is connected to the upper connecting plate 211 and the lower end is connected to the lower connecting plate 212. After the connection is completed and the external constraints are removed, the embedded concave hexagonal unit 100, being in a compressed state relative to its free state, exhibits a tendency to elongate along the height direction. This elongation is then caused by the upper connecting plate 211 and the lower connecting plate 212, which in turn stretch the first peripheral concave hexagonal unit 221 and the second peripheral concave hexagonal unit 222 along the height direction. Conversely, the first peripheral concave hexagonal unit 221 and the second peripheral concave hexagonal unit 222, being in a stretched state relative to their free state, exhibit a tendency to retract along the height direction. Under the combined constraints of the upper connecting plate 211 and the lower connecting plate 212, the embedded concave hexagonal unit 100 and the peripheral concave hexagonal frame 200 achieve mechanical equilibrium. Their combined height H after assembly satisfies H2 < H < H1, placing the embedded concave hexagonal unit 100 in a compressive prestress state and the peripheral concave hexagonal frame 200 in a tensile prestress state, thus forming an internal prestress self-balancing state.

[0030] See Figure 7When the structure is subjected to an external axial load, the flexible connecting sections in the embedded concave hexagonal unit 100 and the outer concave hexagonal frame 200 undergo bending deformation, and each concave hexagonal unit produces coordinated deformation along the height direction. Due to the prestress constraint relationship between the embedded structure and the outer structure, the overall structure can maintain a stable deformation process and exhibit negative Poisson's ratio deformation characteristics. After the external load is removed, the elastic energy stored inside the structure drives each flexible connecting section to return to its initial state, allowing the structure to restore its original geometric configuration. This invention, by nesting and combining the large-angle embedded concave hexagonal unit 100 with the double-layer small-angle outer concave hexagonal frame 200, forms a stable prestressed self-balancing state inside the structure. This not only preserves the negative Poisson's ratio deformation characteristics of the concave hexagonal structure but also improves the overall stability and deformation coordination ability of the structure, and can be applied in fields such as mechanical metamaterials, buffer energy-absorbing structures, and flexible support structures.

[0031] In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. The illustrative expressions of the above terms in this specification do not necessarily correspond to the same embodiment; the specific features, structures, materials, or characteristics described may be used in any reasonable combination of one or more embodiments or examples.

[0032] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications, substitutions, or variations to the above embodiments without departing from the technical concept and protection scope of the present invention.

Claims

1. A nested concave hexagonal tensioned monolithic metamaterial structure, characterized in that, The system includes an embedded concave hexagonal unit (100) and an outer concave hexagonal frame (200). The outer concave hexagonal frame includes a connecting plate assembly (210) and an outer concave hexagonal unit (220). The connecting plate assembly (210) includes an upper connecting plate (211) and a lower connecting plate (212). The outer concave hexagonal unit (220) includes a first outer concave hexagonal unit (221) and a second outer concave hexagonal unit (222) that are parallel and spaced apart along the thickness direction. The upper ends of the two units are fixedly connected to the upper connecting plate (211) and the lower ends are fixedly connected to the lower connecting plate (212), forming a nested space for accommodating the embedded concave hexagonal unit (100). (230); The embedded concave hexagonal unit (100) is disposed in the nested space (230), and its upper end is connected to the upper connecting plate (211), and its lower end is connected to the lower connecting plate (212); The free state height H1 of the embedded concave hexagonal unit (100) is greater than the free state height H2 of the outer concave hexagonal frame (200). After assembly, the common height H satisfies H2 < H < H1, so that the embedded concave hexagonal unit (100) is in a compressive prestress state, and the outer concave hexagonal frame (200) is in a tensile prestress state. They are mutually constrained by the upper connecting plate (211) and the lower connecting plate (212), forming an internal prestress self-balancing state.

2. The nested concave hexagonal tensioned monolithic metamaterial structure according to claim 1, characterized in that, The embedded concave hexagonal unit (100) includes integrally formed rigid sections at both ends (110), concave side edges (120), and flexible connecting sections (130); the rigid sections at both ends (110) include an upper rigid section (111) and a lower rigid section (112); the concave side edges (120) are two symmetrically arranged, each of the concave side edges (120) including an upper inclined rigid section (121) and a lower inclined rigid section (122), the upper inclined rigid section (121) and the lower inclined rigid section (122) are... The downwardly inclined rigid segment (122) is inclined toward the interior of the embedded concave hexagonal unit (100); the upwardly inclined rigid segment (121) is connected to the upper rigid segment (111) through the upper flexible connecting segment (131); the upwardly inclined rigid segment (121) and the downwardly inclined rigid segment (122) are connected through the middle flexible connecting segment (132); the downwardly inclined rigid segment (122) is connected to the lower rigid segment (112) through the lower flexible connecting segment (133).

3. The nested concave hexagonal tensioned monolithic metamaterial structure according to claim 2, characterized in that, The upper flexible connecting section (131), the middle flexible connecting section (132) and the lower flexible connecting section (133) are all locally thinned structures, and the dimension of the locally thinned structure along the thickness direction is 25% of the wall thickness of the adjacent rigid section.

4. The nested concave hexagonal tensioned monolithic metamaterial structure according to claim 2, characterized in that, The first peripheral concave hexagonal unit (221) and the second peripheral concave hexagonal unit (222) have the same structure, and both include rigid sections at both ends, concave sides arranged symmetrically on the left and right, and flexible connecting sections connecting the rigid sections and concave sides. Their structural form is the same as that of the embedded concave hexagonal unit (100).

5. The nested concave hexagonal tensioned monolithic metamaterial structure according to claim 1, characterized in that, The corresponding rigid segment lengths of the embedded concave hexagonal unit (100) and the peripheral concave hexagonal unit (220) are the same; the concave angle θ1 of the embedded concave hexagonal unit (100) is greater than the concave angle θ2 of the peripheral concave hexagonal unit (220), and satisfies 0°<θ2<θ1<180°; under the condition that the corresponding rigid segment lengths are the same, the difference between the concave angle θ1 and the concave angle θ2 makes the free state height H1 of the embedded concave hexagonal unit (100) greater than the free state height H2 of the peripheral concave hexagonal frame (200).

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