Cellular energy absorbing structures, metamaterials, and energy absorbing devices

Abstract

The application belongs to the technical field of energy-absorbing materials, and discloses a unit cell energy-absorbing structure, a metamaterial and an energy-absorbing device. The unit cell energy-absorbing structure comprises a connecting frame part and a flexible embedded part, and the connecting frame part and the flexible embedded part are both concave hexagons. The connecting frame part is made of a thermoplastic polymer, and the flexible embedded part is fixedly connected to the inside of the connecting frame part and is made of an elastic material. The Young's modulus of the connecting frame part is greater than that of the flexible embedded part. The flexible embedded part and the connecting frame part can deform cooperatively to adjust the lateral deformation response of the unit cell energy-absorbing structure under pressure, so that the unit cell energy-absorbing structure can exhibit zero Poisson's ratio characteristics, and the energy-absorbing effect, compression stability and buckling resistance of the unit cell energy-absorbing structure are improved. The unit cell energy-absorbing structure also has temperature responsiveness. The metamaterial and the energy-absorbing device realize zero Poisson's ratio characteristics and also have temperature responsiveness by applying the unit cell energy-absorbing structure.

Description

Technical Field

[0001] This invention relates to the field of energy-absorbing materials technology, and in particular to a single-cell energy-absorbing structure, metamaterial, and energy absorption device. Background Technology

[0002] Metamaterials are a class of artificial materials that achieve properties exceeding those of conventional materials (such as zero Poisson's ratio or negative Poisson's ratio) through ingenious structural design rather than relying on the inherent properties of the material itself. Most energy-absorbing structures in related technologies are made of a single material or homogeneous structures, typically exhibiting a positive Poisson's ratio (lateral expansion) or, through special structural design, a negative Poisson's ratio (lateral contraction) under compressive loads. It is difficult to achieve and maintain the near-zero lateral deformation characteristic throughout the entire compression process. Furthermore, the stiffness of energy-absorbing structures in related technologies is often fixed, placing them in a passive defensive state and lacking dynamic sensing and active response mechanisms to ambient temperature.

[0003] Therefore, there is an urgent need for a single-cell energy-absorbing structure, metamaterial, and energy absorption device to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a single-cell energy-absorbing structure, metamaterial, and energy absorption device, so as to achieve the zero Poisson's ratio characteristic of the single-cell energy-absorbing structure, and also to make the single-cell energy-absorbing structure temperature responsive and have an intelligent protection mechanism.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] Single-cell energy-absorbing structures, including:

[0007] The connecting frame portion is concave hexagonal and is made of thermoplastic polymer;

[0008] A flexible embedded part is fixedly connected to the interior of the connecting frame part. The flexible embedded part is concave hexagonal and made of elastic material. The Young's modulus of the connecting frame part is greater than that of the flexible embedded part. Furthermore, at the inwardly concave nodes on opposite sides of the connecting frame part, it is fixedly connected to the corresponding outer walls on both sides of the flexible embedded part. The flexible embedded part and the connecting frame part can deform together to adjust the lateral deformation response of the unit cell energy-absorbing structure under pressure, so that the unit cell energy-absorbing structure exhibits zero Poisson's ratio characteristics.

[0009] Alternatively, the thermoplastic polymer may be polylactic acid, acrylonitrile-butadiene-styrene copolymer, or polycarbonate;

[0010] The elastic material is thermoplastic polyurethane, silicone rubber, or natural rubber.

[0011] As an optional embodiment, the connecting frame includes a first rib, a second rib, a third rib, a fourth rib, a fifth rib, and a sixth rib connected end to end. The first rib and the fourth rib are of equal length and are arranged opposite each other at intervals and parallel to each other. The second rib, the third rib, the fifth rib, and the sixth rib are all of equal length. The interior angle formed by the second rib and the third rib is an acute angle, and the interior angle formed by the fifth rib and the sixth rib is an acute angle.

[0012] The flexible embedded part includes a first connecting strip, a second connecting strip, a third connecting strip, a fourth connecting strip, a fifth connecting strip, and a sixth connecting strip connected end to end. The third connecting strip and the sixth connecting strip are of equal length and are arranged opposite each other at intervals and parallel to each other. The lengths of the first connecting strip, the second connecting strip, the fourth connecting strip, and the fifth connecting strip are all equal. The interior angle formed by the first connecting strip and the second connecting strip is an acute angle, and the interior angle formed by the fourth connecting strip and the fifth connecting strip is an acute angle.

[0013] The connection between the second rib and the third rib is fixedly connected to the third connecting strip, and the connection between the fifth rib and the sixth rib is fixedly connected to the sixth connecting strip.

[0014] As an optional configuration, the interior angles formed by the first rib and the second rib, the third rib and the fourth rib, the fourth rib and the fifth rib, and the sixth rib and the first rib are all α, and 50°≤α≤85°.

[0015] As an optional solution, the interior angles formed by the second connecting strip and the third connecting strip, the third connecting strip and the fourth connecting strip, the fifth connecting strip and the sixth connecting strip, and the sixth connecting strip and the first connecting strip are all β, and 50°≤β≤85°.

[0016] As an optional solution, the volume of the flexible embedded part accounts for 10% to 40% of the volume of the connecting frame part.

[0017] Metamaterial, the metamaterial comprising multiple unit cell energy-absorbing structures as described above, the multiple unit cell energy-absorbing structures being arranged in an array and interconnected to form a whole.

[0018] As an optional embodiment, multiple unit cell energy-absorbing structures are arranged in an array in a first plane to form a first monolayer plate, and multiple unit cell energy-absorbing structures are arranged in an array in a second plane to form a second monolayer plate. The metamaterial includes multiple first monolayer plates and multiple second monolayer plates. The multiple first monolayer plates are arranged parallel to each other and spaced apart, and the multiple second monolayer plates are arranged parallel to each other and spaced apart. Each first monolayer plate and multiple second monolayer plates are stacked orthogonally to each other, and the centers of two orthogonal unit cell energy-absorbing structures coincide. The first plane and the second plane are perpendicular to each other.

[0019] As an optional solution, in the first single-layer plate and the second single-layer plate, the connecting frame portions of the unit cell energy-absorbing structures arranged in any adjacent manner are fixedly connected to each other.

[0020] Furthermore, the connecting frame portions of the two mutually orthogonal unit cell energy-absorbing structures are fixedly connected to each other.

[0021] An energy absorption device, comprising an energy-absorbing element made of a metamaterial as described above.

[0022] The beneficial effects of this invention are:

[0023] The single-cell energy-absorbing structure provided by the present invention has a connecting frame and a flexible embedded part that are both concave hexagonal. The nodes of the connecting frame on both sides that are concave inward are fixedly connected to the outer walls of the corresponding sides of the flexible embedded part. The connecting frame is made of thermoplastic polymer and the flexible embedded part is made of elastic material. The present invention utilizes the nonlinear mechanical coupling effect of structural topology and bimodal material.

[0024] When the unit cell energy-absorbing structure is subjected to axial compressive load, the inward tensile deformation generated by the flexible inlay can precisely offset the outward lateral deformation of the connecting frame. This internal static self-balancing mechanism enables the unit cell energy-absorbing structure to achieve and maintain ideal zero Poisson's ratio characteristics throughout the entire compression process.

[0025] In confined high-end engineering assembly spaces (such as the interior of compact new energy battery packs or the base of precision instruments), the negative Poisson's ratio energy-absorbing structure in related technologies tends to contract violently inward under pressure. This inward contraction creates physical gaps between the negative Poisson's ratio energy-absorbing structure and the protected device, causing the protected device to lose lateral support and trigger a secondary collision. Simultaneously, the inward contraction deformation of the negative Poisson's ratio energy-absorbing structure easily leads to a "densification" phenomenon, significantly reducing the effective energy absorption stroke. The single-cell energy-absorbing structure provided by this invention effectively overcomes the above defects by achieving zero Poisson's ratio characteristics. This ensures that the sidewalls of the single-cell energy-absorbing structure remain straight throughout the entire process of subjected to severe axial compression, achieving true "zero expansion and zero contraction" laterally. This unidirectional piston-like deformation mode neither squeezes surrounding components outward nor contracts inward to create space, maintaining 100% tight fit and continuous support for adjacent components, eliminating the risk of interface tearing, and providing an extremely stable and long-lasting high-efficiency energy absorption plateau.

[0026] Furthermore, the single-cell energy-absorbing structure provided by this invention utilizes a thermoplastic polymer for the connecting frame portion. Thermoplastic polymers are temperature-responsive, allowing the ratio of the Young's modulus of the connecting frame portion to the flexible embedded portion to change under the same compressive load at different ambient temperatures. This achieves dynamic adjustment of the Poisson's ratio of the single-cell energy-absorbing structure, overcoming the physical limitations of fixed stiffness and passive defense in related technologies. This gives the single-cell energy-absorbing structure a smart protection mechanism. Taking new energy power battery pack applications as an example: under normal operating temperatures, the connecting frame portion maintains a high modulus, and the single-cell energy-absorbing structure exhibits high compressive stiffness, providing reliable mechanical support and anti-vibration positioning for the dense cell array. However, in the early stages of catastrophic thermal runaway in a battery, there is usually a localized abnormal temperature rise (such as exceeding 50°C to 60°C) and severe volume expansion caused by internal cell vaporization. If the stiffness of the isolation structure remains constant, the expanding battery cells will generate enormous mechanical compressive stress on each other, easily puncturing the internal separator and accelerating the instantaneous short-circuit explosion. However, when the single-cell energy-absorbing structure of this invention senses an abnormal temperature rise threshold, the thermoplastic polymer (i.e., the connecting frame portion) undergoes thermal softening, and the overall stiffness of the entire single-cell energy-absorbing structure dynamically decreases, seamlessly switching from rigid support to a highly flexible unloading state. This adaptive softening mechanism acts as a "thermal-mechanical stress relief valve" within the battery pack, actively absorbing the thermal expansion deformation of the battery cells and cutting off the mechanical cycle of "chain thermal runaway induced by compression" from its physical source, significantly improving the safety boundary of energy storage equipment.

[0027] Furthermore, the single-cell energy-absorbing structure provided by the present invention can be simplified by fixing the flexible embedded part to the inside of the connecting frame part, thereby reducing the manufacturing cost.

[0028] The present invention also provides a metamaterial that, by applying the above-mentioned unit cell energy-absorbing structure, exhibits zero Poisson's ratio characteristics, and also makes the metamaterial temperature responsive, has an intelligent protection mechanism, and takes into account both structural simplicity and manufacturing feasibility.

[0029] The present invention also provides an energy absorption device, which uses the above-mentioned metamaterial to make an energy-absorbing element, enabling the energy-absorbing element to exhibit zero Poisson's ratio characteristics, and also enabling the energy-absorbing element to have temperature responsiveness and intelligent protection mechanism, while taking into account structural simplicity and manufacturing feasibility. Attached Figure Description

[0030] Figure 1 This is a front view of the single-cell energy-absorbing structure provided in an embodiment of the present invention;

[0031] Figure 2 This is an isometric view of the single-cell energy-absorbing structure provided in the embodiments of the present invention;

[0032] Figure 3 This is a front view of the first single-layer plate provided in an embodiment of the present invention;

[0033] Figure 4 This is a front view of the second single-layer plate provided in an embodiment of the present invention;

[0034] Figure 5 This is an isometric view of the metamaterial provided in an embodiment of the present invention;

[0035] Figure 6 This is a deformation diagram of the metamaterial provided in the embodiments of the present invention under compressive load;

[0036] Figure 7 This is a graph showing the relationship between the major axis strain and the transverse strain of the metamaterial provided in this embodiment of the invention under a compressive load at a specific temperature (55°C).

[0037] Figure 8 This is a deformation diagram of the metamaterial provided in Comparative Example 1 of the present invention under compressive load;

[0038] Figure 9 This is a comparison curve of the Poisson's ratio as a function of the long axis strain under a specific temperature (55°C) when subjected to compressive load, according to the embodiments of the present invention and related comparative examples 2 and 4.

[0039] In the picture:

[0040] 10. Unit cell energy-absorbing structure; 200. First monolayer plate; 300. Second monolayer plate;

[0041] 1. Connecting frame part; 11. First rib; 12. Second rib; 13. Third rib; 14. Fourth rib; 15. Fifth rib; 16. Sixth rib; 2. Flexible embedded part; 21. First connecting strip; 22. Second connecting strip; 23. Third connecting strip; 24. Fourth connecting strip; 25. Fifth connecting strip; 26. Sixth connecting strip. Detailed Implementation

[0042] 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 components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0045] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0046] Example

[0047] Most energy-absorbing structures in related technologies are made of a single material or are homogeneous. When subjected to compressive loads, they typically exhibit a positive Poisson's ratio (lateral expansion) or, through special structural design, a negative Poisson's ratio (lateral contraction). It is difficult to achieve and maintain the "zero Poisson's ratio" characteristic, where lateral deformation approaches zero, throughout the entire compression process. Furthermore, the stiffness of energy-absorbing structures in related technologies is often fixed, placing them in a passive defensive state and lacking a dynamic sensing and active response mechanism for ambient temperature.

[0048] To solve the above problems, such as Figure 1 and Figure 2 As shown, this embodiment provides a single-cell energy-absorbing structure 10, which includes a connecting frame portion 1 and a flexible embedded portion 2. The connecting frame portion 1 is a concave hexagon and is made of a thermoplastic polymer. The flexible embedded portion 2 is fixedly connected to the interior of the connecting frame portion 1. The flexible embedded portion 2 is also a concave hexagon and is made of an elastic material. The Young's modulus of the connecting frame portion 1 is greater than that of the flexible embedded portion 2. Furthermore, at the inwardly concave nodes on opposite sides of the connecting frame portion 1, the corresponding outer walls on both sides of the flexible embedded portion 2 are fixedly connected. The flexible embedded portion 2 and the connecting frame portion 1 can deform collaboratively to adjust the lateral deformation response of the single-cell energy-absorbing structure 10 under pressure, so that the single-cell energy-absorbing structure 10 exhibits zero Poisson's ratio characteristics.

[0049] The unit cell energy-absorbing structure 10 provided in this embodiment has a connecting frame portion 1 and a flexible embedded portion 2, both of which are concave hexagons. The nodes of the connecting frame portion 1 that are concave on opposite sides are fixedly connected to the corresponding outer walls of the flexible embedded portion 2. The connecting frame portion 1 is made of thermoplastic polymer and the flexible embedded portion 2 is made of elastic material. This embodiment utilizes the nonlinear mechanical coupling effect of structural topology and bimodal material.

[0050] When the unit cell energy-absorbing structure 10 is subjected to axial compressive load, the inward tensile deformation generated by the flexible insert 2 can precisely offset the outward lateral deformation of the connecting frame 1. This internal static self-balancing mechanism enables the unit cell energy-absorbing structure 10 to achieve and maintain ideal zero Poisson's ratio characteristics throughout the entire compression process.

[0051] In confined high-end engineering assembly spaces (such as the interior of compact new energy battery packs or the base of precision instruments), the negative Poisson's ratio energy-absorbing structure in related technologies will contract violently inward under pressure. This "inward contraction" will cause physical gaps between the negative Poisson's ratio energy-absorbing structure and the protected device, causing the protected device to lose lateral support and trigger a secondary collision. At the same time, the inward contraction deformation of the negative Poisson's ratio energy-absorbing structure is prone to "densification," significantly reducing the effective energy absorption stroke. The unit cell energy-absorbing structure 10 provided in this embodiment effectively overcomes the above defects by achieving zero Poisson's ratio characteristics. During the entire process of subjected to severe axial compression, the sidewall of the unit cell energy-absorbing structure 10 remains flat, achieving true "zero expansion and zero contraction" in the lateral direction. This unidirectional piston-like deformation mode neither squeezes the surrounding components outward nor contracts inward to leave space, always maintaining 100% tight fit and continuous support for adjacent components, eliminating the risk of interface tearing, and providing an extremely stable and long-lasting high-efficiency energy absorption plateau period.

[0052] Furthermore, the unit cell energy-absorbing structure 10 provided in this embodiment uses a thermoplastic polymer for the connecting frame portion 1. The thermoplastic polymer is temperature-responsive, causing the ratio of the Young's modulus of the connecting frame portion 1 to the flexible embedded portion 2 to change when subjected to the same compressive load at different ambient temperatures. This achieves dynamic adjustment of the Poisson's ratio of the unit cell energy-absorbing structure 10, thus overcoming the physical limitations of fixed stiffness and passive defense in related technologies. This gives the unit cell energy-absorbing structure 10 provided in this embodiment an intelligent protection mechanism. Taking the application of new energy power battery packs as an example: under normal operating temperatures, the connecting frame portion 1 maintains a high modulus, and the unit cell energy-absorbing structure 10 exhibits high compressive stiffness, providing reliable mechanical support and anti-vibration positioning for the dense cell array. However, in the early stages of catastrophic thermal runaway in the battery, it is usually accompanied by localized abnormal temperature rise (such as exceeding 50°C to 60°C) and severe volume expansion caused by internal vaporization of the cells. If the stiffness of the isolation structure remains constant, the expanding battery cells will generate enormous mechanical compressive stress on each other, easily puncturing the internal separator and accelerating the instantaneous short-circuit explosion. However, when the unit cell energy-absorbing structure 10 provided in this embodiment senses the critical point of abnormal temperature rise, the thermoplastic polymer (i.e., the connecting frame part 1) undergoes thermal softening, and the overall stiffness of the entire unit cell energy-absorbing structure 10 dynamically decreases, instantly and seamlessly switching from a rigid support to a highly flexible unloading state. This adaptive softening mechanism acts as a "thermal-mechanical stress relief valve" within the battery pack, actively absorbing the thermal expansion deformation of the battery cells and cutting off the mechanical cycle of "chain thermal runaway induced by compression" from the physical source, significantly improving the safety boundary of the energy storage equipment.

[0053] Furthermore, the single-cell energy-absorbing structure 10 provided in this embodiment can be simplified by fixing the flexible embedded part 2 to the inside of the connecting frame part 1, thereby reducing the manufacturing cost.

[0054] It should be noted that the unit cell energy-absorbing structure 10 provided in this embodiment has a zero Poisson's ratio characteristic, which originates from the nonlinear mechanical coupling mechanism of the two materials of the connecting frame part 1 and the flexible embedded part 2 under specific topological constraints. According to the microscopic static model, when the unit cell energy-absorbing structure 10 is subjected to macroscopic axial compressive load, its internal inclined ribs mainly undergo compression-bending combined deformation and generate bending moments at the ends. In this embodiment, the connecting frame part 1 with a higher external modulus and the flexible embedded part 2 with a lower internal modulus are rigidly physically anchored at the recessed nodes on both sides. Based on the mechanical "deformation coordination condition", due to the difference in bending stiffness and geometric parameters of the materials of the connecting frame part 1 and the flexible embedded part 2, they have different lateral deformation tendencies when under compression; the relative difference of this lateral deformation tendency is transformed into mutually restrictive lateral internal forces at the constraint nodes. By accurately matching the modulus ratio and geometric topological relationship between the two, the lateral deformation driving force of the connecting frame part 1 and the lateral elastic constraint reaction force of the flexible embedded part 2 achieve "static self-equilibrium" at the nodes. The work done by the externally applied compressive load is efficiently converted into micro-bending strain energy within each level of the member, while the lateral macroscopic displacement at the node is suppressed, thus achieving ideal zero Poisson's ratio deformation and constant section support on a macroscopic scale.

[0055] Optionally, in this embodiment, the thermoplastic polymer is polylactic acid (PLA). The glass transition temperature of PLA falls precisely in the range of 55°C to 60°C. At normal temperatures, PLA is in a glassy state, exhibiting extremely high stiffness and modulus. However, when the ambient temperature (such as the localized abnormal temperature rise during the precursor period of battery thermal runaway) reaches this critical range, the macromolecular chains of PLA begin to move, and the material transitions from a glassy state to a highly elastic state, resulting in a precipitous drop in its Young's modulus. This embodiment utilizes this inherent physical phase transition critical point of the material to precisely align it with the danger warning temperature of the energy storage equipment, endowing the structure with purely physical intelligent sensing capabilities.

[0056] In other embodiments, the thermoplastic polymer may also be an acrylonitrile-butadiene-styrene copolymer or polycarbonate, as long as the thermoplastic polymer is responsive to temperature.

[0057] Optionally, in this embodiment, the elastic material is thermoplastic polyurethane, silicone rubber, or natural rubber. This embodiment does not limit the specific material of the elastic material.

[0058] In this embodiment, as Figure 1 and Figure 2As shown, the connecting frame 1 includes a first rib 11, a second rib 12, a third rib 13, a fourth rib 14, a fifth rib 15, and a sixth rib 16 connected end-to-end. The first rib 11 and the fourth rib 14 are of equal length, arranged opposite each other at intervals and parallel to each other. The second rib 12, the third rib 13, the fifth rib 15, and the sixth rib 16 are all of equal length. The interior angle formed by the second rib 12 and the third rib 13 is an abscissa, and the interior angle formed by the fifth rib 15 and the sixth rib 16 is also an abscissa. The flexible embedded part 2 includes a first connecting strip 21, a second connecting strip 22, and a third connecting strip 23 connected end-to-end. The fourth connecting strip 24, the fifth connecting strip 25, and the sixth connecting strip 26 are provided. The third connecting strip 23 and the sixth connecting strip 26 are of equal length, arranged opposite each other at intervals and parallel to each other. The first connecting strip 21, the second connecting strip 22, the fourth connecting strip 24, and the fifth connecting strip 25 are all of equal length. The interior angle formed by the first connecting strip 21 and the second connecting strip 22 is an anomalous angle, and the interior angle formed by the fourth connecting strip 24 and the fifth connecting strip 25 is an anomalous angle. The connection between the second rib 12 and the third rib 13 is fixedly connected to the third connecting strip 23, and the connection between the fifth rib 15 and the sixth rib 16 is fixedly connected to the sixth connecting strip 26. This arrangement effectively improves the load-bearing capacity of the entire unit cell energy-absorbing structure 10. Optionally, in this embodiment, the flexible embedded part 2 is located in the middle region of the connecting frame part 1, allowing the load to be uniformly transmitted throughout the entire unit cell energy-absorbing structure 10.

[0059] Optionally, in this embodiment, as Figure 1 As shown, the interior angles formed by the first rib 11 and the second rib 12, the third rib 13 and the fourth rib 14, the fourth rib 14 and the fifth rib 15, and the sixth rib 16 and the first rib 11 are all α, and 50°≤α≤85°. Specifically, α can be 50°, 55°, 60°, 65°, 70°, 75°, 80°, or 85°. This arrangement not only ensures the structural stability of the connecting frame portion 1 but also guarantees the uniformity of load distribution on the connecting frame portion 1.

[0060] Optionally, in this embodiment, as Figure 1As shown, the interior angles formed by the second connecting strip 22 and the third connecting strip 23, the third connecting strip 23 and the fourth connecting strip 24, the fifth connecting strip 25 and the sixth connecting strip 26, and the sixth connecting strip 26 and the first connecting strip 21 are all β, and 50°≤β≤85°. Specifically, β can be 50°, 55°, 60°, 65°, 70°, 75°, 80°, or 85°. This configuration not only ensures the structural stability of the flexible embedded part 2 but also guarantees the uniformity of load distribution on the flexible embedded part 2. Optionally, in this embodiment, α and β are equal.

[0061] Optionally, in this embodiment, the volume of the flexible embedded part 2 accounts for 10% to 40% of the volume of the connecting frame part 1. Specifically, the volume of the flexible embedded part 2 accounts for 10%, 15%, 20%, 25%, 30%, 35%, or 40% of the volume of the connecting frame part 1. The above arrangement not only ensures the load-bearing capacity of the entire unit cell energy-absorbing structure 10, but also ensures the reliability of the flexible embedded part 2 in counteracting the lateral deformation of the connecting frame part 1.

[0062] It should be noted that the angle limits for α and β, and the volume limit for the flexible embedded part 2 relative to the volume of the connecting frame part 1, in this embodiment are optimal ranges derived from the static self-balancing mechanism and the spatial interference limit. When the angle is less than 50° or the volume ratio is greater than 40%, the internal space of the unit cell energy-absorbing structure 10 is excessively crowded. When subjected to large strain compression, physical interference and collisions are very likely to occur between the rods of the connecting frame part 1 and the flexible embedded part 2, causing the structure to enter the "densification" stage prematurely and lose the stable energy absorption stroke. Conversely, when the angle is greater than 85° or the volume ratio is less than 10%, the pull-back effect (negative stiffness effect) of the flexible embedded part 2 is greatly weakened. The inward pulling force generated after the flexible embedded part 2 is compressed and folded is insufficient to completely offset the radial expansion force of the connecting frame part 1, resulting in the static balance being broken and the structure being difficult to maintain a stable zero Poisson's ratio state.

[0063] It should be noted that, according to the mechanical model of Timoshenko Beam theory, the modulus ratio, moment of inertia, and geometric dimensions of the connecting frame part 1 and the flexible embedded part 2 jointly affect the lateral deformation response of the unit cell energy-absorbing structure 10. When the relevant parameters are matched, the lateral deformation under compression can be reduced, and the unit cell energy-absorbing structure 10 can exhibit zero Poisson's ratio characteristics.

[0064] like Figures 3-5As shown, this embodiment also provides a metamaterial comprising multiple unit cell energy-absorbing structures 10 as described above. These unit cell energy-absorbing structures 10 are arranged in an array and interconnected to form a whole. By applying the aforementioned unit cell energy-absorbing structures 10, the metamaterial provided in this embodiment exhibits zero Poisson's ratio characteristics, temperature responsiveness, and an intelligent protection mechanism, while also maintaining structural simplicity and manufacturing feasibility.

[0065] Optionally, such as Figures 3-5 As shown, multiple unit-cell energy-absorbing structures 10 are arrayed in a first plane to form a first monolayer plate 200, and multiple unit-cell energy-absorbing structures 10 are arrayed in a second plane to form a second monolayer plate 300. The metamaterial includes multiple first monolayer plates 200 and multiple second monolayer plates 300. The multiple first monolayer plates 200 are parallel to each other and spaced apart, and the multiple second monolayer plates 300 are parallel to each other and spaced apart. Each first monolayer plate 200 and multiple second monolayer plates 300 are stacked orthogonally to each other, and the centers of two orthogonal unit-cell energy-absorbing structures 10 coincide. The first plane and the second plane are perpendicular to each other. The above configuration enables the metamaterial to form a three-dimensional structure, allowing the metamaterial to form a more stable load transfer path in three-dimensional space. This not only helps to adjust the Poisson's ratio of the overall structure, but also facilitates a more uniform stress distribution and progressive collapse deformation of the metamaterial under compressive loads, thereby improving the compressive stability, buckling resistance, and energy absorption effect of the metamaterial.

[0066] It should be noted that in this embodiment, the structures of the first single-layer plate 200 and the second single-layer plate 300 are basically the same. In this embodiment, both the first single-layer plate 200 and the second single-layer plate 300 include nine unit cell energy-absorbing structures 10 arranged in a matrix. In other embodiments, the specific number of unit cell energy-absorbing structures 10 in the first single-layer plate 200 and the second single-layer plate 300 can be set according to requirements.

[0067] Optionally, in the first single-layer plate 200 and the second single-layer plate 300, the connecting frame portions 1 of any adjacent arrangement of unit cell energy-absorbing structures 10 are fixedly connected to each other, and the connecting frame portions 1 of two mutually orthogonal unit cell energy-absorbing structures 10 are fixedly connected to each other. This configuration further ensures the structural stability of the metamaterial and guarantees that the metamaterial can form a more stable load transfer path in three-dimensional space. Optionally, the entire metamaterial is a monolithic molded part. It should be noted that the metamaterial can be manufactured using multi-material 3D printing technology. In other embodiments, the connecting frame portions 1 can also be fixedly connected by adhesive bonding, thermal fusion connection, or mechanical interlocking; this application does not limit the specific connection method. This configuration allows the metamaterial to form synergistic stress and coordinated deformation in multiple directions of space when subjected to compressive loads. On the one hand, it retains the characteristic of the unit cell energy-absorbing structure 10 controlling lateral deformation through the flexible embedded portion 2; on the other hand, it forms spatial support through orthogonal stacking, improving the overall structural compressive stability and energy absorption capacity.

[0068] This embodiment also provides an energy absorption device, which includes an energy-absorbing element made of the aforementioned metamaterial. The energy absorption device provided in this embodiment, by using the aforementioned metamaterial as the energy-absorbing element, enables the energy-absorbing element to exhibit zero Poisson's ratio characteristics, and also makes the energy-absorbing element temperature-responsive, possessing an intelligent protection mechanism, while simultaneously ensuring structural simplicity and manufacturing feasibility.

[0069] Optionally, in this embodiment, the energy absorption device can be specifically applied to automotive anti-collision energy absorption boxes, aerospace vehicle landing shock absorbers, rail transit buffer pads, or vibration damping bases for precision machinery equipment, etc.

[0070] To verify the mechanical properties and energy absorption characteristics of the metamaterial provided in this embodiment, a finite element method (FEM) simulation analysis was performed on the metamaterial. The FEM model is the metamaterial provided in this embodiment. During the FEM simulation analysis, an upper pressure plate was set at the upper end of the FEM model, and a lower pressure plate was set at the lower end of the FEM model. The lower pressure plate was fixed on the base surface, and the upper pressure plate applied a displacement load to the FEM model in the vertical direction to simulate a quasi-static compression process. The metamaterial and the upper and lower pressure plates were subjected to surface-to-surface contact, and the contact properties could be set to hard contact. The tangential friction coefficient could be set according to the material and experimental conditions. During mesh generation, the connection area between the connecting frame part 1 and the flexible embedded part 2, as well as the cross-connection area of ​​the two orthogonal unit cell energy-absorbing structures 10, could be locally refined to improve the calculation accuracy.

[0071] Through the above finite element simulation analysis, the following can be obtained: Figure 6 The displacement cloud diagram of the metamaterial under compressive load shown in the figure intuitively demonstrates that the metamaterial's sidewalls remain straight when subjected to extreme axial compression, and there is no significant lateral contraction or expansion.

[0072] To further verify the mechanical response and energy absorption properties of the metamaterial provided in this embodiment, a compression test was conducted on the prepared metamaterial sample. In this test embodiment, the thermoplastic polymer of the sample was specifically polylactic acid (PLA), and the elastic material was specifically thermoplastic polyurethane (TPU). The sample was prepared as a single unit using 3D printing technology. The compression test was conducted at a specific temperature of 55°C. The sample was placed between the upper and lower plates of a universal testing machine. The lower plate was fixed to the base surface, and the upper plate applied a compressive load to the sample in the vertical direction at a preset loading rate. The relationship between the long axis strain and the transverse strain during the compression process was recorded, as shown below. Figure 7 The curves shown are from experimental data precisely extracted through pixel displacement. The results demonstrate a high degree of consistency between the experimental verification and the aforementioned finite element simulation analysis: within a broad compression range where the long-axis strain exceeds 20%, the metamaterial's transverse strain stably adheres to the 0% horizontal baseline. This quantitative evidence rigorously confirms that the metamaterial maintains its ideal zero Poisson's ratio characteristic throughout the entire compression process.

[0073] Comparative Example 1

[0074] In this comparative example, the connecting frame and flexible embedded part have the same structure as in the above embodiment. However, both the connecting frame and flexible embedded part in this comparative example are made of metal; the connecting frame is made of aluminum, and the flexible embedded part is made of copper. Finite element buckling behavior analysis was performed on them. Figure 8 As shown, although the structure did not undergo significant lateral deformation in the early stages of compression, due to the poor ductility of the metallic material and its inability to provide elastic restraint under large strain, irreversible out-of-plane buckling instability rapidly occurred once the axial deformation exceeded 10% due to high local stress concentration. This result demonstrates the absolute advantage of the "thermoplastic polymer + elastic element" in the above embodiment in maintaining stable energy absorption under large deformation and long stroke.

[0075] Comparative Example 2

[0076] In this comparative example, the connecting frame and flexible insert have the same structure as in the above embodiments, but both the connecting frame and flexible insert in this comparative example are made of thermoplastic polymers; in this comparative example, it is polylactic acid (PLA). Figure 9 The curve indicated by the "□" shows that when the connecting frame and the flexible insert are made of a single polylactic acid (PLA) material, the flexible insert cannot effectively exert elastic tension on the connecting frame due to the lack of modulus difference. When the structure is subjected to axial loading, its Poisson's ratio slowly decreases from the initial 0.12 to 0.085, exhibiting a clear positive Poisson's ratio characteristic, meaning that the structure undergoes lateral expansion and cannot achieve a zero Poisson's ratio effect.

[0077] Comparative Example 3

[0078] In this comparative example, the connecting frame and flexible embedded part have the same structure as in the above embodiment. However, both the connecting frame and flexible embedded part in this comparative example are made of elastic material, specifically thermoplastic polyurethane (TPU). Due to the lack of sufficient compressive and bending stiffness in the connecting frame, the structure is prone to overall inward collapse and disordered instability deformation in the initial stage of compression. At this time, the connecting frame cannot provide a stable anchor point for the flexible embedded part, the static self-balancing mechanism fails, and thus the effective stable energy absorption plateau period is lost.

[0079] Comparative Example 4

[0080] In this comparative example, the connecting frame is made of polylactic acid (PLA), and the flexible insert is made of thermoplastic polyurethane (TPU). The connecting frame remains a concave hexagon, but when the concave angle β of the flexible insert changes to 90° (i.e., the flexible insert becomes rectangular), as... Figure 9 The curve indicated by the "△" shows that when the structure is under pressure, its Poisson's ratio curve decreases, turning directly from positive to negative, due to the significant disruption of the mechanical properties of the concave structure of the flexible embedded part. A negative Poisson's ratio means that the structure contracts towards the center under pressure, completely losing its self-stabilizing ability to maintain a zero Poisson's ratio. As described earlier, this uncontrolled inward contraction leads to physical gaps between the energy-absorbing component and the protected device, weakening lateral support and easily triggering interface tearing and premature densification. This analysis further confirms the necessity for both the connecting frame and the flexible embedded part to maintain a concave hexagonal topology.

[0081] It should be noted that, Figure 9 The curve indicated by "○" in the figure is the Poisson's ratio curve of the metamaterial structure in the above embodiment, which rigorously confirms that the metamaterial can maintain the ideal zero Poisson's ratio characteristic throughout the entire process of being subjected to pressure.

[0082] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A single-cell energy-absorbing structure, characterized in that, include: The connecting frame part (1) is in the shape of a concave hexagon and is made of thermoplastic polymer; The flexible embedded part (2) is fixedly connected to the interior of the connecting frame part (1). The flexible embedded part (2) is a concave hexagon. The flexible embedded part (2) is made of elastic material. The Young's modulus of the connecting frame part (1) is greater than that of the flexible embedded part (2). Furthermore, the nodes of the connecting frame part (1) that are concave on opposite sides are fixedly connected to the outer walls of the corresponding sides of the flexible embedded part (2). The flexible embedded part (2) and the connecting frame part (1) can deform together to adjust the lateral deformation response of the unit cell energy-absorbing structure under pressure, so that the unit cell energy-absorbing structure exhibits zero Poisson's ratio characteristics.

2. The single-cell energy-absorbing structure according to claim 1, characterized in that, The thermoplastic polymer is polylactic acid, acrylonitrile-butadiene-styrene copolymer, or polycarbonate; The elastic material is thermoplastic polyurethane, silicone rubber, or natural rubber.

3. The single-cell energy-absorbing structure according to claim 1 or 2, characterized in that, The connecting frame part (1) includes a first rib (11), a second rib (12), a third rib (13), a fourth rib (14), a fifth rib (15), and a sixth rib (16) connected end to end. The first rib (11) and the fourth rib (14) are of equal length. The first rib (11) and the fourth rib (14) are arranged opposite each other at intervals and are parallel to each other. The second rib (12), the third rib (13), the fifth rib (15), and the sixth rib (16) are all of equal length. The interior angle formed by the second rib (12) and the third rib (13) is an anomalous angle. The interior angle formed by the fifth rib (15) and the sixth rib (16) is an anomalous angle. The flexible embedded part (2) includes a first connecting strip (21), a second connecting strip (22), a third connecting strip (23), a fourth connecting strip (24), a fifth connecting strip (25), and a sixth connecting strip (26) connected end to end. The third connecting strip (23) and the sixth connecting strip (26) are of equal length. The third connecting strip (23) and the sixth connecting strip (26) are arranged opposite each other at intervals and are parallel to each other. The lengths of the first connecting strip (21), the second connecting strip (22), the fourth connecting strip (24), and the fifth connecting strip (25) are all equal. The interior angle formed by the first connecting strip (21) and the second connecting strip (22) is an anomalous angle. The interior angle formed by the fourth connecting strip (24) and the fifth connecting strip (25) is an anomalous angle. The connection between the second rib (12) and the third rib (13) is fixedly connected to the third connecting strip (23), and the connection between the fifth rib (15) and the sixth rib (16) is fixedly connected to the sixth connecting strip (26).

4. The single-cell energy-absorbing structure according to claim 3, characterized in that, The interior angles formed by the first rib (11) and the second rib (12), the third rib (13) and the fourth rib (14), the fourth rib (14) and the fifth rib (15), and the sixth rib (16) and the first rib (11) are all α, and 50°≤α≤85°.

5. The single-cell energy-absorbing structure according to claim 4, characterized in that, The interior angles formed by the second connecting strip (22) and the third connecting strip (23), the third connecting strip (23) and the fourth connecting strip (24), the fifth connecting strip (25) and the sixth connecting strip (26), and the sixth connecting strip (26) and the first connecting strip (21) are all β, and 50°≤β≤85°.

6. The single-cell energy-absorbing structure according to claim 1 or 2, characterized in that, The volume of the flexible embedded part (2) accounts for 10% to 40% of the volume of the connecting frame part (1).

7. Metamaterials, characterized in that, The metamaterial includes a plurality of single-cell energy-absorbing structures as described in any one of claims 1 to 6, wherein the plurality of single-cell energy-absorbing structures are arranged in an array and interconnected to form a whole.

8. The metamaterial according to claim 7, characterized in that, Multiple unit cell energy-absorbing structures are arranged in an array in a first plane to form a first monolayer plate (200), and multiple unit cell energy-absorbing structures are arranged in an array in a second plane to form a second monolayer plate (300). The metamaterial includes multiple first monolayer plates (200) and multiple second monolayer plates (300). The multiple first monolayer plates (200) are arranged parallel to each other and spaced apart, and the multiple second monolayer plates (300) are arranged parallel to each other and spaced apart. Each first monolayer plate (200) and multiple second monolayer plates (300) are stacked orthogonally to each other, and the centers of two orthogonal unit cell energy-absorbing structures coincide. The first plane and the second plane are perpendicular to each other.

9. The metamaterial according to claim 8, characterized in that, In the first single-layer plate (200) and the second single-layer plate (300), the connecting frame portions (1) of the unit cell energy-absorbing structures arranged in any adjacent manner are fixedly connected to each other; Furthermore, the connecting frame portions (1) of the two mutually orthogonal unit cell energy-absorbing structures are fixedly connected to each other.

10. An energy absorption device, characterized in that, The energy absorption device includes an energy-absorbing element, which is made of any one of the metamaterials described in claims 7 to 9.

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