Double-section gradient compression torsion mechanical metamaterial structure

Abstract

The invention provides a double-section gradient compression torsion mechanical metamaterial structure, which relates to the technical field of metamaterial structures and comprises an upper-layer cross beam structure, a lower-layer cross beam structure, four middle-layer square connecting beams, four upper-layer inclined connecting beams and four lower-layer inclined connecting beams, the lower-layer cross beam structure and the upper-layer cross beam structure are parallel to each other, have the same angle and are both formed by crossing two beams which are perpendicular to each other and have the same length at the geometric center, and four end points serve as connecting nodes; the four middle-layer square connecting beams are connected end to end to form a closed square frame body which is positioned between the upper-layer cross beam structure and the lower-layer cross beam structure; the four end points of the lower-layer cross beam structure are connected with the four corner points of the middle-layer square connecting beam through the lower-layer inclined connecting beams respectively, and the four corner points of the middle-layer square connecting beam are connected with the end points of the upper-layer cross beam structure through the upper-layer inclined connecting beams; and the middle-layer square connecting beam is provided with a rotation angle around a central shaft relative to the upper-layer cross beam structure and the lower-layer cross beam structure.

Description

Technical Field

[0001] This invention relates to the field of metamaterial structure technology, and in particular to a two-segment gradient compression torsion mechanical metamaterial structure. Background Technology

[0002] Lightweight, efficient, and comfortable human protective cushioning materials have wide applications in scenarios such as police explosion protection, daily sports, and rehabilitation medicine. For example, when people suffer various impact loads such as falls, collisions, and stabbings, high-performance cushioning materials can effectively absorb and dissipate impact energy, thereby significantly reducing the external force transmitted to vital parts of the body and improving overall safety and comfort.

[0003] Existing protective cushioning materials mainly include polyurethane foam, polymer honeycomb structures, and layered composite panels, but their performance has significant limitations. While foam materials have a certain energy absorption capacity, they are prone to localized collapse and irreversible deformation, making it difficult to maintain stable energy absorption performance under high-intensity impacts. Although honeycomb or composite panel structures have high stiffness and load-bearing capacity, they often sacrifice flexibility and comfort, making it difficult to provide adequate cushioning under low-load impacts.

[0004] Mechanical metamaterials can achieve unique mechanical properties through topological configuration control, such as negative Poisson's ratio effect, multi-level energy absorption, torsional coupling, and stiffness control, bringing new possibilities to the field of high-performance protection and buffering. Nevertheless, existing mechanical metamaterial structures still have certain limitations: the deformation mode of some structures mainly relies on axial compression buckling, which is prone to uncontrollable instability during deformation; the mechanical response lacks graded control and often only manifests as a single energy absorption platform, making it difficult to achieve a flexible-rigid transition at different load stages, or to balance compliance and comfort under low-load impact with protective strength under high-load impact; some structures are prone to local instability or abrupt stiffness changes under high loads, affecting overall stability and reusability; most are in the form of rigid periodic arrays, with fixed connection methods between units and limited geometric expandability, making it difficult to achieve overall bending and local adaptive fitting on curved surfaces (such as the human head or joints). Summary of the Invention

[0005] To address the challenges of existing metamaterial structures, which primarily rely on axial compression buckling for deformation, leading to uncontrollable instability during deformation; lack of graded control over mechanical response, often exhibiting only a single energy absorption platform, making it difficult to achieve a flexible-rigid transition at different load stages, or to balance compliance and comfort under low-load impact with protective strength under high-load impact; the tendency for some structures to experience local instability or abrupt stiffness changes under high loads, affecting overall stability and reusability; and the prevalence of rigid periodic arrays with fixed inter-unit connections and limited geometric expandability, making it difficult to achieve overall bending and local adaptive fitting on curved surfaces (such as the human head or joints), this invention provides a dual-segment gradient compression-torsion mechanical metamaterial structure.

[0006] The technical solutions provided by the embodiments of the present invention are as follows: The present invention provides a dual-segment gradient compression torsion mechanical metamaterial structure, comprising: an upper cross beam structure, a lower cross beam structure, four middle-layer square connecting beams, four upper-layer oblique connecting beams, and four lower-layer oblique connecting beams; The lower cross beam structure and the upper cross beam structure are parallel to each other and at the same angle. They are both formed by two mutually perpendicular beams of equal length intersecting at the geometric center, and the four ends are all used as connection nodes. The four middle-layer square connecting beams are connected end to end to form a closed square frame, located between the upper-layer cross beam structure and the lower-layer cross beam structure; The four endpoints of the lower cross beam structure are connected to the four corners of the middle square connecting beam through the lower oblique connecting beam, and the four corners of the middle square connecting beam are connected to the endpoints of the upper cross beam structure through the upper oblique connecting beam, thereby forming a two-segment gradient spatial frame. The middle-layer square connecting beam has a rotation angle about the central axis relative to the upper-layer cross beam structure and the lower-layer cross beam structure, so that the upper-layer cross beam structure and the lower-layer cross beam structure form a spatial torsional connection through the middle-layer square connecting beam; By adjusting the rotation angle and side length ratio of the middle-layer square connecting beam, a two-segment gradient geometric layout with a wider top and narrower bottom is achieved, so as to obtain graded energy absorption and stable load-bearing performance during compression loading.

[0007] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: (1) In this embodiment of the invention, a two-stage gradient spatial frame is formed by the upper and lower cross beams and the middle square connecting beam. With the rotation and torsion angle of the middle layer, a two-stage energy absorption response of first soft and then hard is achieved. In the initial stage of loading, the oblique connecting beams in the lower and middle layers first bend and twist at a small angle to form a low-load flexible platform, achieve comfortable buffering, and improve the compliant comfort under low-load impact. As the deformation deepens, the upper structure participates in bearing, the system stiffness is improved, and a high-load rigid platform is formed, thereby achieving stable energy absorption and graded response throughout the entire compression process, and improving the protection strength under high-load impact.

[0008] (2) In the embodiments of the present invention, the spatial arrangement of the oblique connecting beams guides the force path, avoids the early local buckling and asymmetric instability in traditional beam or lattice structures, makes the deformation mode more directional and repeatable, and ensures that it can maintain stable mechanical response and recoverable performance under multiple loading.

[0009] (3) In the embodiments of the present invention, the unit structure can be arranged into an array in a modular manner, and adjacent units are connected by ring buckles. It can be continuously bent in a single direction to conform to the unfolded surface of a cylinder or cone, thereby realizing flexible fitting and partition protection functions under the curved surface. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the external structure of a two-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0012] Figure 2 This is a schematic diagram of a single-cell three-dimensional structure of a two-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0013] Figure 3 This is a unit cell front view of a two-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0014] Figure 4 This is a top-cell view of a two-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0015] Figure 5 This is a unit cell bottom view of a two-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0016] Figure 6 This is a schematic diagram of the unit cell deformation process of a two-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0017] Figure 7 The force-displacement response curve of a unit cell of a two-segment gradient compression-torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0018] Figure 8 This is a schematic side view of a curved array assembly structure of a dual-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0019] Figure 9 This is a schematic front view of a curved array assembly structure of a dual-segment gradient compression torsion mechanical metamaterial structure provided in an embodiment of the present invention.

[0020] Reference numerals: 1. Lower layer cross beam structure; 2. Middle layer square connecting beam; 3. Upper layer cross beam structure; 4. Lower layer diagonal connecting beam; 5. Upper layer diagonal connecting beam.

[0021] As shown in the figure, specific structures and devices are marked in the figure to clearly illustrate the structure of the embodiments of the present invention. However, this is only for illustrative purposes and is not intended to limit the present invention to this specific structure, device and environment. Those skilled in the art can adjust or modify these devices and environments according to specific needs. Detailed Implementation

[0022] The technical solutions of the present invention will now be described with reference to the accompanying drawings. It should also be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. Those skilled in the art can also use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0023] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0024] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0025] It is understood that the meanings of “on”, “above”, and “above” in this invention should be interpreted in the broadest manner, such that “on” means not only “directly on” something, but also includes the meaning of being “on” something with an intervening feature or layer, and that “above” or “above” means not only “on” something, but also includes the meaning of being “on” something without an intervening feature or layer.

[0026] Furthermore, spatially related terms such as “below,” “under,” “lower,” “above,” and “upper” are used herein for convenience to describe the relationship of one element or feature to one or more other elements or features, as illustrated in the accompanying drawings. Spatially related terms are intended to cover different orientations in the use or operation of the device other than those depicted in the accompanying drawings. The device may be oriented in other ways, and the spatially related descriptive terms used herein can be interpreted similarly.

[0027] like Figures 1 to 2 As shown, an embodiment of the present invention provides a dual-segment gradient compression torsion mechanical metamaterial structure, comprising: an upper cross beam structure 3, a lower cross beam structure 1, four middle-layer square connecting beams 2, four upper-layer oblique connecting beams 5, and four lower-layer oblique connecting beams 4. The lower cross beam structure 1 and the upper cross beam structure 3 are parallel to each other and have the same angle. They are both formed by two mutually perpendicular beams of equal length intersecting at the geometric center, and the four ends are all used as connection nodes. The four middle-layer square connecting beams 2 are connected end to end to form a closed square frame, located between the upper-layer cross beam structure 3 and the lower-layer cross beam structure 1; The four endpoints of the lower cross beam structure 1 are connected to the four corners of the middle square connecting beam 2 through the lower oblique connecting beam 4, and the four corners of the middle square connecting beam 2 are connected to the endpoints of the upper cross beam structure 3 through the upper oblique connecting beam 5, thereby forming a double-segment gradient spatial frame. The middle-layer square connecting beam 2 has a rotation angle about the central axis relative to the upper-layer cross beam structure 3 and the lower-layer cross beam structure 1, so that the upper-layer cross beam structure 3 and the lower-layer cross beam structure 1 form a spatial torsional connection through the middle-layer square connecting beam 2; In this embodiment of the invention, a two-stage gradient spatial frame is formed by upper and lower cross beams and a middle square connecting beam. With the rotation and torsion angle of the middle layer, a two-stage energy absorption response of first being flexible and then rigid is achieved. In the initial stage of loading, the oblique connecting beams in the lower and middle layers first bend and twist at a small angle, forming a low-load flexible platform to achieve comfortable buffering and improve the compliance and comfort under low-load impact. As the deformation deepens, the upper structure participates in bearing the load, the system stiffness increases, and a high-load rigid platform is formed, thereby achieving stable energy absorption and graded response throughout the entire compression process and improving the protection strength under high-load impact.

[0028] Furthermore, the spatial arrangement of the oblique connecting beams guides the force path, avoiding early local buckling and asymmetric instability in traditional beam or lattice structures, making the deformation mode more directional and repeatable, and ensuring stable mechanical response and recoverable performance under multiple loading.

[0029] Furthermore, by adjusting the rotation angle and side length ratio of the middle-layer square connecting beam 2, a two-segment gradient geometric layout with a wider top and narrower bottom is achieved to obtain graded energy absorption and stable load-bearing performance during compression loading.

[0030] It should be noted that the rotation angle and side length ratio of the middle square connecting beam 2 can be parametrically designed according to the target force-displacement curve, and the starting point, platform length and energy absorption ratio of the flexible platform and the rigid platform can be adjusted to achieve customizable performance adjustment.

[0031] In one possible implementation, the lower end of the lower inclined connecting beam 4 is fixedly connected to the end point of the lower cross beam structure 1, and the upper end is fixedly connected to the corner point of the middle square connecting beam 2.

[0032] In one possible implementation, the lower end of the upper inclined connecting beam 5 is fixedly connected to the corner of the middle square connecting beam 2, and the upper end is fixedly connected to the end point of the upper cross beam structure 3.

[0033] In one possible implementation, the side length of the middle-layer square connecting beam 2 is smaller than the diagonal distance of the lower-layer cross beam structure 1, so as to form an upward-converging spatial shape.

[0034] In one possible implementation, the side length of the middle-layer square connecting beam 2 is greater than the diagonal distance of the upper-layer cross beam structure 3, so as to form an upward-converging spatial shape.

[0035] It should be noted that forming an upward-converging spatial shape helps to achieve gradual structural contraction and graded energy absorption response during compression. Specifically, it enables the structure to exhibit flexible energy absorption characteristics under low loads, while under high loads, the different gradient layouts of the upper and lower layers enhance rigidity and compressive strength, thereby achieving a smooth transition between flexibility and rigidity, and improving overall energy absorption efficiency and structural stability.

[0036] In one possible implementation, the rotation angle θ is between 5° and 85°.

[0037] In one possible implementation, the cross sections of the upper cross beam structure 3, the lower cross beam structure 1, the middle square connecting beam 2, the upper oblique connecting beam 5, and the lower oblique connecting beam 4 are circular, elliptical, or polygonal.

[0038] Preferably, the cross-section is circular to reduce stress concentration.

[0039] like Figures 3 to 5 As shown, in one possible implementation, the height of the dual-segment gradient compression torsion mechanical metamaterial structure is h, where h is between 8 and 15 mm; the diameter of the circular cross-section beam is d; the length of the upper cross beam structure 3 is l2; the length of the lower cross beam structure 1 is l1; the length of the middle square connecting beam 2 is l3; and the ratios of l1 to d, l2 to d, and l3 to d are all between 6 and 20.

[0040] Furthermore, by controlling the combination of the length l3 of the middle-layer square connecting beam 2 and the rotation angle θ, the energy absorption curve can be customized and controlled.

[0041] In one possible implementation, the material of the bi-segment gradient compression torsion mechanical metamaterial structure is a thermoplastic elastomer, polyurethane elastomer, or high-toughness polymer material used for 3D printing.

[0042] like Figures 8 to 9 As shown, in one possible implementation, multiple dual-segment gradient compression torsion mechanical metamaterial structures are arranged in a matrix manner, with adjacent structural units connected by interlocking rings, so that the array can be continuously bent in a single-axis direction to conform to the unfolded surface of a cylinder.

[0043] In this embodiment of the invention, the unit structure can be arranged into an array in a modular manner, and adjacent units are connected by rings. It can be continuously bent in a single direction to conform to the unfolded surface of a cylinder or cone, so as to realize the flexible fitting and partition protection function under the curved surface.

[0044] During the quasi-static compression loading process, the deformation and energy absorption process of this structure can be divided into two stages.

[0045] like Figures 6 to 7 As shown, during the quasi-static compressive loading process, the deformation and energy absorption process of this structure can be divided into two stages. Among them, Figure 6 'a' represents the initial state of the structure when it is not deformed. Figure 6 b represents the first stage of compression. Figure 6 c represents the second stage of compression.

[0046] The working process of the metamaterial of this invention is as follows: (1) Stage I Flexible Platform: In the initial stage of compression loading, the lower inclined connecting beam 4 first enters the stress state. Due to the spatial angle and rotational misalignment between the lower cross beam structure 1 and the middle square connecting beam 2, the lower inclined connecting beam 4 undergoes controllable bending and small-angle torsion under compression. The frame formed by the middle square connecting beam 2 then undergoes slight rotation and lateral contraction, gradually forming a stable flexible deformation zone. During this stage, the load increases slowly, and the force-displacement curve shows a clear plateau segment. The energy absorption of the structure mainly comes from the bending buckling and geometric torsional deformation of the beams, rather than the plastic energy dissipation of the material, thus achieving efficient and recoverable buffer energy absorption under low load conditions.

[0047] The main function of this stage is to reduce the peak value of the initial impact load and provide a compliant deformation response, which is suitable for human contact areas or low-intensity impact scenarios.

[0048] (2) Stage II Rigid Platform: As the compressive displacement further increases, the upper inclined connecting beam 5 begins to participate in deformation and gradually bears the main load, forming a spatial staggered support between the upper cross beam structure 3 and the middle square connecting beam 2. At this time, the rotation angle θ of the middle layer induces the upper and lower inclined beams to continue to undergo torsional-compression coordinated deformation during the compression process. Furthermore, since the geometric parameters of the upper structure are smaller than those of the lower structure, and it has an upward-retracting gradient layout, the support radius and bending arm length of the upper beam are reduced, which restricts the overall deformation, makes the force transmission path more compact, and significantly improves the equivalent stiffness of the structure.

[0049] On the force-displacement curve, this is characterized by the formation of a second high-load plateau, where the load level is high and stable, and the structure can continuously absorb a large amount of energy during this stage. The energy absorption mechanisms at this stage mainly include: further bending buckling and secondary contact compaction of the beams; torsional coupling caused by mid-level rotational constraints; and load diffusion due to the space truss effect.

[0050] The structural energy absorption efficiency per unit mass can reach 0.18–0.25 J / g. The platform stability coefficient CFE (mean load to peak load ratio) is ≥70%, indicating a smooth deformation process without sudden instability. Furthermore, the stiffness transition between the two platforms is smooth and controllable, without significant peak-to-valley fluctuations, ensuring comfort and structural safety during impact energy absorption.

[0051] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the preferred embodiments, while those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A two-stage gradient compression torsal mechanical metamaterial structure, characterized by, The application relates to a double-section gradient compression-torsion mechanical metamaterial structure. The upper cross beam structure and the lower cross beam structure are parallel to each other and have the same angle, and are formed by intersecting two mutually perpendicular and equal-length beams at the geometric center, and four end points are used as connecting nodes. The four middle square connecting beams are connected in a closed square frame and are located between the upper cross beam structure and the lower cross beam structure. The four end points of the lower cross beam structure are connected with the four corner points of the middle square connecting beam through the lower inclined connecting beam, and the four corner points of the middle square connecting beam are connected with the end points of the upper cross beam structure through the upper inclined connecting beam, so that a double-section gradient space frame is formed. The middle square connecting beam is provided with a rotation angle around a central axis relative to the upper cross beam structure and the lower cross beam structure, so that the upper cross beam structure and the lower cross beam structure are connected in space through the middle square connecting beam. The rotation angle and the length ratio of the middle square connecting beam are adjusted to realize a double-section gradient geometric layout of wide at the top and narrow at the bottom, so that the performance of graded energy absorption and stable load bearing is obtained in the compression loading process. The lower end of the lower inclined connecting beam is fixedly connected with the end point of the lower cross beam structure, and the upper end is fixedly connected with the corner point of the middle square connecting beam.

2. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, The lower end of the upper inclined connecting beam is fixedly connected with the corner point of the middle square connecting beam, and the upper end is fixedly connected with the end point of the upper cross beam structure.

3. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, The length of the middle square connecting beam is smaller than the diagonal distance of the lower cross beam structure, so that an upper-receiving space convergence form is formed.

4. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, The length of the middle square connecting beam is greater than the diagonal distance of the upper cross beam structure, so that an upper-receiving space convergence form is formed.

5. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, The rotation angle is 5-85 degrees.

6. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, The cross section of the upper cross beam structure, the lower cross beam structure, the middle square connecting beam, the upper inclined connecting beam and the lower inclined connecting beam is circular, elliptical or polygonal.

7. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, The height of the double-section gradient compression-torsion mechanical metamaterial structure is h, the value of h is 8-15 mm, the diameter of the circular cross section beam is d, the length of the upper cross beam structure is l2, the length of the lower cross beam structure is l1, and the length of the middle square connecting beam is l3, the ratio of l1 to d, the ratio of l2 to d and the ratio of l3 to d are all between 6 and 20.

8. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 7, wherein, The material of the double-section gradient compression-torsion mechanical metamaterial structure is a thermoplastic elastomer, a polyurethane elastomer or a high-toughness polymer material for 3D printing.

9. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, A plurality of the double-section gradient compression-torsion mechanical metamaterial structures are arranged in a matrix mode, and adjacent structure units are connected through a ring buckle, so that the array can be continuously bent in a single-axis direction to conform to a cylindrical developed curved surface.

10. The two-stage gradient-compressed torsal mechanical metamaterial structure of claim 1, wherein, ​

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