Honeycomb structure with negative poisson's ratio effect

Abstract

The application relates to a honeycomb structure with a negative Poisson's ratio effect, comprising: a central axis unit comprising a first unit cell structure arranged along a bearing direction of the honeycomb structure, the first unit cell structure being a concave hexagonal structure; a mirror image unit comprising a column of second unit cell structures or a plurality of columns of second unit cell structures arranged along a cross-section extension direction of the honeycomb structure, the second unit cell structure being a concave hexagonal structure same as the first unit cell structure, and the second unit cell structure being provided with a chiral structure; wherein the central axis unit and the mirror image unit are alternately arranged along the cross-section extension direction of the honeycomb structure, the plurality of columns of second unit cell structures and the first unit cell structure are arranged to form a honeycomb structure with the same cell size, the chiral structures in adjacent mirror image units are opposite in rotation direction, and the adjacent mirror image units are mirror symmetric about the central axis unit, so that the technical defects that the concave negative Poisson's ratio structure is prone to macroscopic shear band instability under large deformation and further causes serious degradation of the negative Poisson's ratio effect are solved.

Description

Technical Field

[0001] This invention relates to the field of mechanical metamaterials technology, and in particular to a honeycomb structure with a negative Poisson's ratio effect. Background Technology

[0002] In recent years, with the diversification of engineering application needs, the development of lightweight, high-strength novel energy-absorbing structures has become a research hotspot in academic and engineering fields. Metamaterials, as structural arrays composed of artificially designed microstructures, possess extraordinary physical and mechanical properties. Traditional concave hexagonal honeycombs, as a classic negative Poisson's ratio configuration, are widely used. However, existing traditional concave hexagonal honeycombs have significant drawbacks in practical applications: First, due to their high porosity, the structure has low load-bearing strength and insufficient stiffness; second, under in-plane large strain axial compression, the traditional structure is prone to local buckling, falling into an unstable "outward bulge" deformation mode or forming macroscopic shear bands, resulting in severe degradation of the negative Poisson's ratio effect and greatly limiting its overall energy absorption efficiency.

[0003] A foam-filled sinusoidal negative Poisson's ratio structure is disclosed in CN 120969397 A. This scheme replaces the two concave straight plates on both sides with sinusoidal curved plates on the basis of the traditional concave hexagonal structure, and fills the gaps with polyurethane foam to improve the overall load-bearing capacity. However, filling polyurethane foam with liquid foaming method will significantly increase the weight of the overall structure and reduce the specific energy absorption efficiency. Moreover, it requires multiple processes such as foaming, static curing, grinding and cutting, which greatly increases the complexity of the manufacturing process. Furthermore, simply replacing the straight plates with sinusoidal curved plates does not fundamentally change the mechanical transmission path of disordered lateral displacement caused by nodal forces. The structure still lacks a mechanism for actively and collaboratively controlling the inward contraction deformation of the overall structure.

[0004] Currently, existing concave negative Poisson's ratio structures lack coordinated motion constraints between nodes when resisting axial compression. Under large deformations, they are prone to uncontrollable macroscopic shear band instability, leading to severe degradation of the negative Poisson's ratio effect. Therefore, it is necessary to develop a new type of honeycomb structure with a negative Poisson's ratio effect. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the applicant provides a honeycomb structure with a negative Poisson's ratio effect, thereby solving the technical defect that the concave negative Poisson's ratio structure is prone to macroscopic shear band instability under large deformation, which leads to serious degradation of the negative Poisson's ratio effect.

[0006] The technical solution adopted in this invention is as follows: A honeycomb structure exhibiting a negative Poisson's ratio effect, comprising: The central axis unit includes a first unit cell structure arranged along the bearing direction of the honeycomb structure, wherein the first unit cell structure is a concave hexagonal structure. The mirror unit includes a column of second unit cell structures or multiple columns of second unit cell structures arranged along the cross-sectional extension direction of the honeycomb structure. The second unit cell structure is a concave hexagonal structure with the same concave hexagonal structure as the first unit cell structure. The second unit cell structure is provided with a chiral structure. The second unit cell structures in each column of second unit cell structures are arranged along the bearing direction of the honeycomb structure. In this arrangement, the central axis unit and the mirror unit are alternately arranged along the cross-sectional extension direction of the honeycomb structure. Multiple rows of second unit cell structures and first unit cell structures are arranged to form a honeycomb structure with the same pore size. The chiral structures in adjacent mirror units have opposite rotation directions, and adjacent mirror units are mirror symmetrical about the central axis unit.

[0007] As a further improvement to the above technical solution: The second unit cell structure includes parallel horizontal ligaments, each of which is connected to an oblique bracing ligament at its end. After the oblique bracing ligaments connected to the ends of the two horizontal ligaments on the same side are connected, a V-shaped structure is formed that is concave towards the center of the second unit cell structure. The lengths of the oblique bracing ligaments are equal, the lengths of the horizontal ligaments are equal, and the angle between the horizontal ligaments and the oblique bracing ligaments is θ1. The chiral structure includes a central ring and two inclined ligaments. The two inclined ligaments are symmetrical about the center of the central ring. One end of each inclined ligament is connected to and tangent to the outer peripheral surface of the central ring, and the other end of each inclined ligament is connected to an inclined bracing ligament. The intersection of the two axes of symmetry of the second unit cell structure coincides with the center of the central ring body, and the angle between the inclined ligament and the horizontal ligament connected to the same inclined bracing ligament is θ2, and 0 < θ2 < θ1.

[0008] The length of the horizontal ligament is L, and the initial height between the horizontal ligaments is H; the included angle between the horizontal ligament and the diagonal bracing ligament is θ1. Where L:H = 0.8~1.3, 50°≤θ1≤70°.

[0009] The oblique ligaments connected to the adjacent oblique bracing ligaments of the adjacent second unit cell structure are collinear.

[0010] The outer radius of the central ring is r, the wall thickness of the central ring is t1, the wall thickness of the inclined ligament is t2, the wall thickness of the diagonal bracing ligament is t3, and the wall thickness of the horizontal ligament is t4. t1=t2≤2×t3; t3=t4; 1.5×t1≤r≤2.5×t1.

[0011] 10°≤θ2≤30°.

[0012] The first unit cell in each central unit has 1 column, and the second unit cell in each mirror unit has a positive integer number of columns.

[0013] The relative density of the unit cell structure formed by the second unit cell structure and the chiral structure is 0.20 to 0.45.

[0014] The ratio of the number of columns in the second unit cell structure to the number of columns in the first unit cell structure is 3 to 5.

[0015] The honeycomb structure is integrally molded from an elastic material.

[0016] The beneficial effects of this invention are as follows: The present invention macroscopically configures a honeycomb structure along the cross-sectional extension direction as multiple hybrid chiral units. Each chiral hybrid unit is a geometrically axisymmetric structure, with a central axisymmetric unit composed of a first unit cell structure with a concave hexagonal structure. The unit cell structures of the mirror units on both sides of the central axis unit are a combination of a second unit cell structure with a microscopic concave hexagonal structure and a chiral structure. This improves the deformation stability and load-bearing capacity of the honeycomb structure. By setting the chiral structures in the mirror units on both sides of the central axis unit to have opposite rotation directions, each mirror unit has the same internal deformation mode, and the shear torque generated by the overall deformation mode of adjacent mirror units is equal in magnitude and opposite in direction with respect to the central axis unit. This enables the honeycomb structure to achieve ordered global centripetal cohesive deformation macroscopically under large deformation conditions, reducing the severity of the negative Poisson's ratio degradation caused by macroscopic shear band instability.

[0017] Furthermore, the present invention also has the following advantages: (1) A chiral structure is set inside the second unit cell structure with two axes of symmetry. The two inclined ligaments of the chiral structure are tangentially connected to the outer wall of the central ring body. The inclined ligaments extend from the tangent point to the horizontal ligament. The outer ends of the two inclined ligaments are fixedly connected to the inclined bracing ligaments on both sides of the second unit cell structure, thus constructing a unique "rotation-contraction" synergistic mechanism. This forms a mechanical transmission network inside the cell, which amplifies the effective lever arm at the microscopic level, making the microscopic rotation response extremely rapid. The second unit cell structure as a whole undergoes regular contraction towards the two axes of symmetry of the structure, pulling the two sides of the structure to achieve highly controlled "centripetal contraction", thereby effectively suppressing the lateral escape of the material when it is squeezed, and making the microscopic centripetal cohesive deformation controlled.

[0018] (2) This embodiment relies on multiple coordination mechanisms of "microscopic effective lever arm amplification", "microscopic centripetal cohesive deformation control" and "macroscopic torque collision cancellation". When the energy-absorbing structure of this invention is subjected to large in-plane strain compression, the probability of local premature buckling of each component wall panel in the overall structure is reduced, and the load is shared synergistically and evenly, thereby reducing the shear effect and improving the load-bearing capacity. This stable negative Poisson's ratio effect significantly prolongs the effective crushing stroke and the stable high-stress plateau period, avoiding premature compaction of the structure.

[0019] (3) The inclined ligaments connected to the adjacent inclined bracing ligaments of the adjacent second unit cell structure are collinear, so that the load in the bearing direction (axial load) can be converted into the rotational torque of the chiral structure in the most direct and uniform way. The nodes of the chiral structure in the whole cellular network can achieve highly consistent synchronous rotation, thereby maximizing the conversion of external compressive displacement into lateral contractile displacement, forming a straight force transmission path in the early stage of compression, improving the axial stiffness of the material, enabling it to withstand greater initial load, achieving global steady-state progressive deformation, and improving total energy absorption and average crushing force. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention.

[0021] Figure 2 This is the front view of the present invention.

[0022] Figure 3 This is a schematic diagram of the flat and spliced ​​structure of the hybrid chiral units of the present invention.

[0023] Figure 4 This is a schematic diagram of the second unit cell structure and the chiral structure of the present invention.

[0024] Figure 5 This is a schematic diagram showing the structural dimensions of the second unit cell structure and the chiral structure of the present invention.

[0025] Figure 6a This is a schematic diagram of the deformation of a traditional honeycomb structure.

[0026] Figure 6b This is a schematic diagram of the deformation of the second unit cell structure with a chiral structure according to the present invention.

[0027] Figure 7 This is a comparison diagram of the deformation process of the honeycomb structure of the present invention and the traditional honeycomb structure under different axial compressive strains (ε=0, 0.3, 0.5).

[0028] Figure 8 This is a comparison diagram of the displacement-crushing force curves of the honeycomb structure of the present invention and the traditional honeycomb structure.

[0029] Figure 9The strain-dynamic effective Poisson's ratio comparison curves are shown for the honeycomb structure of this invention and the traditional honeycomb structure.

[0030] Figure 10 This is a comparison diagram of the displacement-total energy absorption curves of the honeycomb structure of the present invention and the traditional honeycomb structure.

[0031] Figure 11 This is a statistical comparison chart of the average crushing force and specific energy absorption between the honeycomb structure of the present invention and the traditional honeycomb structure.

[0032] Figure 12 This is a schematic diagram of the initial structure of the tilted ligament of the honeycomb structure of the present invention under different tilt angles (such as 10°, 20°, 30°).

[0033] Figure 13 This is a comparison of the displacement-total energy absorption curves of the tilted ligaments in the honeycomb structure of the present invention at different tilt angles.

[0034] Figure 14 This is a statistical comparison chart of the average crushing force and specific energy absorption of the inclined ligaments of the honeycomb structure of the present invention at different inclination angles.

[0035] Among them: 1. First unit cell structure; 2. Second unit cell structure; 21. Horizontal ligament; 22. Oblique supporting ligament; 3. Chiral structure; 31. Central ring body; 32. Oblique ligament; A. Central axis element; B. Mirror element; C. Hybrid chiral element. Detailed Implementation

[0036] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0037] Example 1: like Figures 1-3 As shown, the honeycomb structure with negative Poisson's ratio effect in this embodiment includes: a central axis unit A and a mirror unit B.

[0038] The central axis unit A includes a first unit cell structure 1 arranged along the bearing direction of the honeycomb structure. The first unit cell structure 1 is a concave hexagonal structure. The mirror unit B includes a column of second unit cell structure 2 or multiple columns of second unit cell structure 2 arranged along the cross-sectional extension direction of the honeycomb structure. The second unit cell structure 2 is the same concave hexagonal structure as the first unit cell structure 1. The second unit cell structure 2 is provided with a chiral structure 3. The second unit cell structure 2 in each column of second unit cell structure 2 is arranged along the bearing direction of the honeycomb structure. In this structure, the central axis unit A and the mirror unit B are arranged alternately along the cross-sectional extension direction of the honeycomb structure. Multiple rows of second unit cell structures 2 and first unit cell structures 1 are arranged to form a honeycomb structure with the same pore size. The chiral structures 3 in adjacent mirror units B have opposite rotation directions, and adjacent mirror units B are mirror symmetrical about the central axis unit A.

[0039] Specifically, such as Figure 1 The load-bearing direction of the honeycomb structure shown is the X-axis direction, the cross-sectional extension direction of the honeycomb structure is the Y-axis direction, and the Z-axis is the penetration direction of the honeycomb structure. In this embodiment, both the first unit cell structure 1 and the second unit cell structure 2 are concave hexagonal structures. The combination of the first unit cell structure 1 and the second unit cell structure 2 to form a traditional honeycomb structure also exhibits a negative Poisson's ratio effect. In traditional honeycomb structures, the concave hexagonal structures, under large deformation conditions, cause the horizontal ligaments on both sides of each cell to move laterally when the overall structure is compressed, which prevents the overall structure from contracting inward smoothly. As the compressive strain increases, the sidewalls are prone to asymmetric random buckling, lacking the ability to deform inward globally. Furthermore, this asymmetric deformation under compression will generate local stress concentration inside the structure. Under large deformation conditions, these microscopic asymmetries will rapidly accumulate and evolve into macroscopic shear band instability (the whole structure tilts and collapses to one side), resulting in a severe degradation of the negative Poisson's ratio effect, premature structural failure, and greatly limiting its overall energy absorption efficiency.

[0040] In this embodiment, the central axis unit A is an axisymmetric structure composed of a first unit cell structure 1 with a concave hexagonal structure. The first unit cell structures 1 are arranged in an array along the load-bearing direction of the honeycomb structure. The second unit cell structures 2 in the mirror unit B are arranged in an array along the load-bearing direction of the honeycomb structure, and are arranged in an alternating array along the cross-sectional extension direction of the honeycomb structure. The axis of symmetry of the central axis unit A is the axis of symmetry of two adjacent mirror units B. The first unit cell structure 1 and its adjacent parts, the second unit cell structure 2 and its adjacent parts, and the first unit cell structure 1 and its adjacent parts combine to form the honeycomb wall of the honeycomb structure, such as Figure 3 , Figure 4 As shown.

[0041] In this embodiment, the mirror unit B forms a microscopic array region. The chiral structures 3 in the second unit cell structure 2 of the mirror units B located on both sides of the central axis unit A have opposite rotation directions. The central axis unit A and the mirror units B on both sides form a hybrid chiral unit C. The spatial tiling and splicing of multiple hybrid chiral units C form a macroscopic topological structure. In each hybrid chiral unit C, the chiral structures 3 in the two mirror units B have opposite rotation directions, and the two mirror units B are symmetrical about the central axis unit A. This is reflected in the structural design of hybrid chiral partitioning and central column isolation and anchoring. The resulting comprehensive effect analysis is as follows: The central axis element A of the hybrid chiral element C is a traditional concave cell with no internal rotational degrees of freedom. A torsional central axis with no rotational degrees of freedom is constructed on the structural geometric central axis of the hybrid chiral element C. Under large deformation under compression, one side mirror element B is sheared and twisted clockwise, and the other side mirror element B is sheared and twisted counterclockwise. The torque generated by the shearing and twisting of the two mirror elements B collides and cancels each other at the central axis element A, making the macroscopic torque of the hybrid chiral element C zero. This eliminates the macroscopic shear band instability phenomenon that is very easy to occur in traditional negative Poisson's ratio structures, and transforms disordered deformation into highly controlled global centripetal cohesive deformation.

[0042] A comparison of the deformation processes of the honeycomb structure of the present invention and the traditional honeycomb structure under different axial compressive strains (ε=0, 0.3, 0.5) is shown below. Figure 7 As shown.

[0043] At the macroscopic level, the honeycomb structure in this embodiment employs a non-uniform topological arrangement of "hybrid chiral partitioned arrangement with central column isolation and anchoring." Utilizing the central chiral isolation column as an anti-torsional axis, the opposing shear torques generated by the left and right array regions converge and completely cancel each other out, resulting in zero macroscopic net torque. This eliminates the macroscopic shear band instability that is easily generated in traditional negative Poisson's ratio structures, transforming disordered deformation into highly controlled global centripetal cohesive deformation. Based on this mechanism, the overall structure achieves uniform and coordinated load-bearing, maintaining a stable negative Poisson's ratio and effectively suppressing lateral material escape while significantly extending the high-stress plateau period and improving specific energy absorption per unit mass.

[0044] Macroscopically, the honeycomb structure is configured with multiple hybrid chiral units C along the cross-sectional extension direction. Each chiral hybrid unit C is a geometrically axisymmetric structure. The central part is a geometrically axisymmetric central axis unit A composed of a first unit cell structure 1 with a concave hexagonal structure. The unit cell structures of the mirror units B on both sides of the central axis unit A are a combination of a second unit cell structure 2 with a microscopic concave hexagonal structure and a chiral structure 3. This improves the deformation stability and load-bearing capacity of the honeycomb structure. The chiral structures 3 in the mirror units B on both sides of the central axis unit A are set to have opposite rotation directions, so that the deformation mode inside each mirror unit B is the same, and the shear torque generated by the overall deformation mode of adjacent mirror units B is equal in magnitude and opposite in direction with respect to the central axis unit A. This enables the honeycomb structure to achieve ordered global centripetal cohesive deformation macroscopically under large deformation conditions, reducing the severity of the negative Poisson's ratio degradation caused by macroscopic shear band instability.

[0045] Example 2: like Figure 3 , Figure 4As shown, the honeycomb structure with negative Poisson's ratio effect in this embodiment is based on the first embodiment. The second unit cell structure 2 includes parallel horizontal ligaments 21. Each horizontal ligament 21 is connected to an oblique bracing ligament 22 at its end. After the oblique bracing ligaments 22 connected to the ends of the two horizontal ligaments 21 on the same side are connected, a V-shaped structure is formed that is concave towards the center of the second unit cell structure 2. The lengths of the oblique bracing ligaments 22 are equal, the lengths of the horizontal ligaments 21 are equal, and the included angle between the horizontal ligaments 21 and the oblique bracing ligaments 22 is θ1. The chiral structure 3 includes a central ring body 31 and two inclined ligaments 32. The two inclined ligaments 32 are symmetrical about the center of the central ring body 31. One end of the inclined ligaments 32 is connected to and tangent to the outer peripheral surface of the central ring body 31, and the other end of the inclined ligaments 32 is connected to the inclined bracing ligament 22. The intersection of the two axes of symmetry of the second unit cell structure 2 coincides with the center of the central ring body 31. The angle between the inclined ligament 32 and the horizontal ligament 21 connected to the same inclined support ligament 22 is θ2, and 0 < θ2 < θ1.

[0046] Specifically, in this embodiment, the first unit cell structure 1 and the second unit cell structure 2 have the same structural dimensions, and the concave hexagonal structure is an axisymmetric structure with two axes of symmetry, which are perpendicular to each other; 0 < θ2 < θ1, that is, the two inclined ligaments 32 are not parallel to the horizontal ligament 21.

[0047] In existing traditional unit cell structures without chiral rings, due to the lack of internal coordinating constraints in the hollow regions of the cell, when an axial compressive load is applied along the bearing direction, the disordered bending of the diagonal bracing ligaments will transfer excessive bending moments to the connection nodes at the horizontal ligaments (such as...). Figure 6a (At the left and right circular markings). This causes disordered lateral displacement of the horizontal ligaments instead of maintaining centripetal tension, resulting in coupling instability between nodes and ultimately leading to the collapse and failure of the entire structure.

[0048] like Figure 5 As shown, in this embodiment, in the second unit cell structure 2 with chiral structure 3, the overall structure formed by the two inclined ligaments 32 and the central ring 31 is inclined relative to the horizontal ligament 21, and the vertex of the V-shaped structure in the concave hexagon of the symmetrical structure and the center of the central ring 31 are located on the same horizontal line. The load transfer path of the second unit cell structure 2 in this embodiment is illustrated below: When subjected to a load in the bearing direction (axial load), the central ring 31 in the chiral structure 3 functions as the kinematic coordination center of the entire inclined bracing ligament 22 and the horizontal ligament 21. The inclined ligament 32 is inclined relative to the horizontal ligament 21, increasing the load transmission lever arm. The axial load is transmitted through the tangentially connected inclined ligament 32 ( Figure 6b(At the red dashed circle) the destructive axial pressure that could have caused buckling of the concave hexagonal sidewalls is efficiently converted into a tangential rotational torque driving the central ring 31. As the central ring 31 rotates, the inclined ligaments 32 simultaneously and actively pull the concave nodes of the V-shaped structures on both sides toward the cell center, effectively neutralizing the inherent outward expansion tendency of traditional concave structures. Relying on this "rotation-contraction" mechanical linkage effect, the left and right sidewalls of the second unit cell structure 2 can achieve equal-amplitude and stable inward contraction.

[0049] The geometric configuration of the chiral structure 3 and the second unit cell structure 2 in this embodiment establishes a direct mechanical coupling between the motion state of the oblique bracing ligament 22 and the rotational state of the central ring 31. This constitutes a unique "rotation-contraction" synergistic deformation mechanism at the microscopic level. Combined with the synergistic constraints generated by the macroscopic symmetrical arrangement, this invention successfully transforms the disordered instability of traditional concave structures into an ordered kinematic process, namely, highly controlled global centripetal contraction deformation.

[0050] When using the honeycomb structure with negative Poisson's ratio effect in this embodiment: When an external compressive load is applied to the upper end of the honeycomb structure in this embodiment, the honeycomb structure responds to the external load through a multi-stage physical action mechanism involving microscopic unit cells and macroscopic topology. The external axial load is transmitted downward along the macroscopic lattice network to the inclined bracing ligaments 22 on both sides of the concave hexagon. The two internal inclined ligaments 32 are tangential to the outer wall of the central ring 31, and the outer edges of the inclined ligaments 32 are in a specific inclined geometric relationship with the horizontal ligaments 21. This significantly increases the effective lever arm between the load transmission path and the center of the central ring 31. This increased effective lever arm causes the destructive axial pressure that would originally directly cause disordered buckling of the external concave hexagon to be efficiently converted into a powerful tangential driving torque acting on the edge of the central ring 31 along the internal inclined ligaments 32. The rotational torque reaches the central ring 31 earlier, resulting in an extremely rapid microscopic rotational response.

[0051] As the compression stroke progresses, driven by the aforementioned tangential torque, the central ring 31 at the geometric center undergoes unidirectional rotation. In the macroscopic partitioned topology, all central rings 31 within the left mirror unit B rotate in the first direction (e.g., clockwise), while all central rings 31 within the right mirror unit B rotate in the second direction (e.g., counterclockwise). This opposing chiral rotational motion, acting as an internal motion coordination hub, drives the inclined bracing ligaments 22 on both sides. The inclined ligaments 32 then exert a symmetrical inward strong traction force on the inclined bracing ligaments 22, forcing the inclined bracing ligaments 22 to contract regularly towards the central axis of the structure. Simultaneously, the inward contraction of the inclined bracing ligaments 22 further pushes the upper and lower horizontal ligaments 21 closer together. This mechanical transmission causes the honeycomb structure to be compressed vertically while its horizontal span is simultaneously, symmetrically, and regularly reduced, exhibiting a highly significant and uniform negative Poisson's ratio (tensile) effect, effectively suppressing lateral escape of the material under compression.

[0052] Under conditions of continuously increasing external compressive load, the overall clockwise shear torque generated by the left mirror unit B and the overall counterclockwise shear torque generated by the right mirror unit B converge at the central isolation column of the structure. Since the central axis unit A, which serves as the central isolation column, does not possess chiral rotational degrees of freedom, it constitutes a robust mechanical constraint boundary on a macroscopic level. The two opposing macroscopic destructive shear torques collide and cancel each other out symmetrically at this central axis unit A, resulting in a net macroscopic torque of zero. This synergistic mechanism of "microscopic rotational response - macroscopic torque cancellation" completely eliminates the macroscopic shear band failure that is prone to occur in traditional concave structures, forcibly constraining the deformation into a highly controlled centripetal cohesive deformation.

[0053] The increased effective lever arm between the load transfer path and the center of the central ring 31 enables the structure to have a faster rotational response. Its mechanical advantage lies in its ability to rapidly activate the global centripetal contraction mechanism upon compression. This not only instantly increases the absolute value of the negative Poisson's ratio, but more importantly, it forcibly transforms the destructive axial pressure into controlled, coordinated contraction. It is this extremely rapid motion response that completely prevents the degradation of the negative Poisson's ratio under large strain, enabling the structure to enter and maintain an extremely high and stable stress plateau period more quickly, ultimately achieving an improvement in energy absorption efficiency.

[0054] A chiral structure 3 is set inside the second unit cell structure 2 with two axes of symmetry. The two inclined ligaments 32 of the chiral structure 3 are tangentially connected to the outer wall of the central ring 31. The inclined ligaments 32 extend from the tangent point to the horizontal ligament 21. The outer ends of the two inclined ligaments 32 are fixedly connected to the inclined bracing ligaments 22 on both sides of the second unit cell structure 2, thus constructing a unique "rotation-contraction" synergistic mechanism. This forms a mechanical transmission network inside the cell, which amplifies the effective lever arm at the microscopic level, making the microscopic rotation response extremely rapid. The second unit cell structure 2 as a whole undergoes regular contraction towards the two axes of symmetry of the structure, pulling the structures on both sides to achieve highly controlled "centripetal contraction", thereby effectively suppressing the lateral escape of the material when it is squeezed, and controlling the microscopic centripetal cohesive deformation.

[0055] This embodiment relies on a multi-coordination mechanism of "microscopic effective lever arm amplification," "microscopic centripetal cohesive deformation control," and "macroscopic torque collision cancellation." When subjected to large in-plane strain compression, the energy-absorbing structure of this invention reduces the probability of premature local buckling among its constituent wall panels, collaboratively and evenly distributing the load, thus reducing shear effects and improving load-bearing capacity. This stable negative Poisson's ratio effect significantly prolongs the effective crushing stroke and the stable high-stress plateau period, preventing premature compaction of the structure.

[0056] Example 3: Based on Example 2, this embodiment provides a detailed structural design for a honeycomb structure with a negative Poisson's ratio effect.

[0057] The length of the horizontal ligament 21 is L, and the initial height between the horizontal ligaments 21 is H; the angle between the horizontal ligament 21 and the oblique bracing ligament 22 is θ1. Where L:H = 0.8~1.3, 50°≤θ1≤70°.

[0058] The preferred value for θ1 is 60°.

[0059] Furthermore, such as Figure 3 As shown, the inclined ligament 32 is collinear with the adjacent inclined bracing ligament 22 of the adjacent second unit cell structure 2.

[0060] like Figure 3 , Figure 4 As shown, specifically, the oblique bracing ligament 22 at the upper part of one second unit cell structure 2 and the oblique bracing ligament 22 at the lower part of another second unit cell structure 2 merge into a local honeycomb wall, that is, the adjacent oblique bracing ligaments 22. The connection points of the oblique ligaments 32 of different chiral structures 3 with the local honeycomb wall coincide.

[0061] like Figure 12As shown, for a concave hexagon with θ1 of 60°, the initial structural schematic diagram of the inclined ligament 32 of the honeycomb structure of the present invention is displayed under different inclination angles (e.g., θ2 of 10°, 20°, and 30°), and the displacement-total energy absorption curves under different θ2 conditions are compared (e.g., ...). Figure 13 And a statistical comparison of mean crushing force and specific energy absorption (e.g.) Figure 14 When θ2 is 20°, the inclined ligament 32 connected to the adjacent inclined bracing ligament 22 of the adjacent second unit cell structure 2 is collinear; when θ2 is 10° and 30°, the inclined ligament 32 connected to the adjacent inclined bracing ligament 22 of the adjacent second unit cell structure 2 is not collinear.

[0062] The negative Poisson's ratio effect relies on the inward contraction of the structure under compression. In this example, the contraction of the honeycomb structure is mainly achieved by the rotation of the chiral structure 3, which drives the inward pulling of the surrounding diagonal bracing ligaments 22. When the diagonal bracing ligaments 32 are collinear, the load in the bearing direction (axial load) can be converted into the rotational torque of the chiral structure 3 most directly and uniformly. The nodes of the chiral structure 3 in the entire honeycomb network can achieve highly consistent synchronous rotation, thereby maximizing the conversion of external compressive displacement into lateral contraction displacement. In the non-collinear state of the diagonal bracing ligaments 32: there is an eccentricity between the stress points of the diagonal bracing ligaments 22. In the initial stage of compression, the force will preferentially cause the diagonal bracing ligaments 22 to undergo local bending deformation, rather than the rotation of the chiral structure 3. This local deformation not only consumes the displacement originally used to drive the rotation, but also destroys the synergy of the overall structural deformation, resulting in a weakening of the negative Poisson's ratio effect. Therefore, the total energy absorption point of the collinear diagonal bracing ligaments 32 is the highest and the displacement (effective displacement) is the longest, the compression distance for energy absorption of the overall structure is the longest, and the total energy absorbed is greater.

[0063] Mean crush force depends on the structure's ability to resist deformation throughout the compressive failure process. When the tilted ligaments 32 are collinear, they form a straight force transmission path in the initial stage of compression. At this time, these tilted ligaments 32 mainly bear axial compressive force. The axial stiffness and strength of the material are much greater than its bending stiffness. Therefore, the structure can withstand a larger initial load and maintain higher resistance during crushing. The non-collinear state of the tilted ligaments 32 is equivalent to artificially introducing an initial defect or eccentric moment. Under compression, the eccentric position will immediately generate a huge bending moment, causing the structure to buckle locally or form plastic hinges under lower loads. Therefore, the collinear design of the tilted ligaments 32 delays the occurrence of this buckling, thereby significantly improving the mean crush force.

[0064] Specific energy absorption is the ratio of the total energy absorbed by a structure to its mass. Energy absorption mainly relies on the evolution of the material's plastic hinges and the steady-state folding of the overall structure. Because of its optimal force transmission path, the collinear structure with inclined ligaments (32) often exhibits a globally steady-state, progressive deformation mode, unlike non-collinear structures which are prone to localized random collapse.

[0065] The inclined ligaments 32, which are collinear with the adjacent inclined bracing ligaments 22 of the adjacent second unit cell structure 2, enable the load in the bearing direction (axial load) to be converted into the rotational torque of the chiral structure 3 most directly and uniformly. The nodes of the chiral structure 3 in the entire cellular network can achieve highly consistent synchronous rotation, thereby maximizing the conversion of external compressive displacement into lateral contractile displacement. In the initial stage of compression, a straight force transmission path is formed, which improves the axial stiffness of the material, enables it to withstand greater initial loads, achieves global steady-state progressive deformation, and improves total energy absorption and average crushing force.

[0066] Furthermore, such as Figure 5 As shown, the outer radius of the central ring 31 is r, the wall thickness of the central ring 31 is t1, the wall thickness of the inclined ligament 32 is t2, the wall thickness of the inclined bracing ligament 22 is t3, and the wall thickness of the horizontal ligament 21 is t4. t1=t2≤2×t3; t3=t4; 1.5×t1≤r≤2.5×t1.

[0067] Furthermore, such as Figure 3 As shown, the number of columns of the first unit cell structure 1 in each central axis unit A is 1, and the number of columns of the second unit cell structure 2 in each mirror unit B is a positive integer, ensuring the relative structural stability of the central axis unit A.

[0068] The preferred number of columns in the first unit cell structure 1 is one.

[0069] Furthermore, the relative density of the honeycomb structure unit formed by the central axis unit A and the two adjacent mirror units B is 0.20 to 0.45. The relative density of the honeycomb structure in this embodiment is relatively small, achieving a balance between quantification and structural stiffness.

[0070] Specifically, the ratio of the number of columns in the second unit cell structure 2 to the number of columns in the first unit cell structure 1 is 3 to 5. The optimal ratio of different structures in the mixed chiral unit C is then determined.

[0071] Furthermore, the honeycomb structure is integrally molded using elastic materials.

[0072] The material can be a highly elastic thermoplastic polyurethane polymer (TPU 95A), and more preferably, it can be prepared by 3D printing technology in one piece.

[0073] Example 4: In a specific embodiment, the specific geometric parameters of the honeycomb structure with negative Poisson's ratio effect are configured as follows: The horizontal ligament 21 has a length L = 18 mm; the unit cell height H = 16 mm; the wall thickness of the horizontal ligament 22 is t4, the wall thickness of the oblique bracing ligament 22 is t3, t3 = t4 = 0.75 mm, θ1 = 60°; r = 2.0 mm, the wall thickness of the central ring body 31 is t1, the wall thickness of the oblique ligament 32 is t2, t1 = t2 = 1.25 mm; and θ2 is set to 20°.

[0074] The first unit cell structure 1 in each central axis unit A has 1 column, and the second unit cell structure 2 in each mirror unit B has 3 columns.

[0075] To further reveal the mechanical response characteristics of the metamaterial of this invention, finite element analysis was performed using ABAQUS software, and its properties were compared with those of a traditional concave hexagonal structure. Figure 7 As shown, the deformation processes of the honeycomb structure of this invention and the traditional concave hexagonal structure under different axial compressive strains (ε=0, 0.3, 0.5) are compared. The results clearly demonstrate that this invention, through the rotational coordination mechanism of the central chiral component, successfully transforms the disordered "outward bulging" instability mode that is prone to occur in traditional structures under compression into highly controlled centripetal cohesive deformation, fundamentally improving the shear resistance and instability resistance of the structure.

[0076] like Figure 8 The figure shows a comparison of displacement-crushing force curves. These curves demonstrate that, under the same compressive displacement conditions, the crushing force that the structure of this invention can withstand is significantly greater than that of a traditional honeycomb structure. Furthermore, the structure of this invention exhibits a longer and more stable stress plateau period, completely overcoming the problem of drastic load fluctuations caused by severe local buckling and the formation of macroscopic shear bands in the later stages of compression in traditional structures.

[0077] like Figure 9 The curve shown is a comparison of strain and dynamic effective Poisson's ratio. It shows that the present invention maintains a highly linear, stable, and larger negative Poisson's ratio response over a large strain range, effectively eliminating the inherent drawback of the negative Poisson's ratio effect in traditional concave structures degrading rapidly with increasing strain.

[0078] like Figure 10 and Figure 11The figures show a comparison of displacement-total energy absorption curves and a statistical comparison of average crushing force and specific energy absorption, respectively. The unique structure of this invention successfully decouples the inherent contradiction between "enhanced stiffness" and "maintaining a negative Poisson's ratio" in traditional structures. Compared to traditional concave hexagonal (REH) honeycomb structures, the optimized honeycomb structure of this invention increases specific energy absorption (SEA) by 183.9% to 244.8%, and the average crushing force (Pm) increases by up to 259.6%. This verifies that this invention has a longer energy absorption displacement and higher energy dissipation efficiency. Data demonstrates that this invention, through unique topological geometry optimization, significantly improves the energy absorption value per unit mass, successfully decoupling the contradiction between increasing structural stiffness and lightweight energy absorption. Simultaneously, by adjusting local geometric variables such as the radius and wall thickness of the central ring 31 and the angle of the inclined ligaments 32, the macroscopic mechanical response can be flexibly customized, providing an ideal paradigm for developing lightweight, high-performance safety protection structures.

[0079] Experimental and high-fidelity simulation data demonstrate that the optimized configuration of this invention exhibits excellent energy dissipation performance when subjected to in-plane quasi-static compression and even dynamic impact loads. In practical engineering applications, chiral hybrid units C are arranged in a two-dimensional periodic array in a plane, ultimately spliced ​​together to form a macroscopic impact-resistant composite metamaterial plate or protective filling layer. The assembled structure can be widely applied in aerospace, automotive engineering, and advanced collision protection fields, effectively meeting the collision energy absorption requirements of occupants and equipment. In the application of vibration isolation platforms for precision equipment, its excellent negative Poisson's ratio characteristics show extremely broad prospects for industrial application.

[0080] Furthermore, 10°≤θ2≤30°. When the tilt angle θ2 is within the range of 10° to 30°, due to the aforementioned setting of the outer radius r=2.0mm of the central ring body 31 and the ring wall thickness t1=t2=1.25mm, ample space is reserved for the coordinated movement of the internal components, and each cell can induce efficient centripetal contraction and expansion energy absorption effects. When θ1 is 60° and θ2 is 20°, the conversion rate of micro-torque, the rolling path of the ligaments inside the cell, and the overall structural instability resistance reach the optimal physical balance, exhibiting the most outstanding energy dissipation and specific energy absorption performance.

[0081] This invention significantly increases the effective lever arm between the load transfer path and the center of the central ring 31 by introducing internal ligaments with a specific tilt angle (10°≤θ2≤30°) into the microscopic unit cell. This efficiently converts the axial load in the initial stage of compression into a tangential driving torque, rapidly activating and driving the centripetal contraction of the external frame. In the initial stage of axial loading, the destructive axial pressure that would otherwise cause disordered buckling of the frame is converted into a tangential torque driving the rotation of the central ring 31 with extremely high efficiency. This rapidly activates the mechanical dissipation mechanism in the initial stage of compression and provides a powerful driving force for subsequent efficient centripetal contraction from the microscopic source. It also significantly increases the eccentricity during loading, improving the conversion efficiency of axial load into rotational torque.

[0082] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A honeycomb structure with a negative Poisson's ratio effect, characterized in that: include: The central axis unit (A) includes a first unit cell structure (1) arranged along the bearing direction of the honeycomb structure, wherein the first unit cell structure (1) is a concave hexagonal structure; The mirror unit (B) includes a column of second unit cell structures (2) or multiple columns of second unit cell structures (2) arranged along the cross-sectional extension direction of the honeycomb structure. The second unit cell structure (2) is the same concave hexagonal structure as the first unit cell structure (1). The second unit cell structure (2) is provided with a chiral structure (3). The second unit cell structures (2) in each column of second unit cell structures (2) are arranged along the bearing direction of the honeycomb structure. The central axis unit (A) and the mirror unit (B) are arranged alternately along the cross-sectional extension direction of the honeycomb structure. Multiple rows of second unit cell structures (2) and first unit cell structures (1) are arranged to form a honeycomb structure with the same pore size. The chiral structures (3) in adjacent mirror units (B) have opposite rotation directions, and adjacent mirror units (B) are mirror symmetrical about the central axis unit (A).

2. The honeycomb structure with negative Poisson's ratio effect as described in claim 1, characterized in that: The structure of the second unit cell structure (2) includes parallel horizontal ligaments (21), and each horizontal ligament (21) is connected to an oblique bracing ligament (22) at its end. After the oblique bracing ligament (22) connected to the ends of the two horizontal ligaments (21) on the same side is connected, a V-shaped structure is formed that is concave towards the center of the second unit cell structure (2). The lengths of the oblique bracing ligaments (22) are equal, the lengths of the horizontal ligaments (21) are equal, and the included angle between the horizontal ligaments (21) and the oblique bracing ligaments (22) is θ1. The chiral structure (3) includes a central ring body (31) and two inclined ligaments (32). The two inclined ligaments (32) are symmetrical about the center of the central ring body (31). One end of the inclined ligament (32) is connected to and tangent to the outer peripheral surface of the central ring body (31), and the other end of the inclined ligament (32) is connected to the inclined bracing ligament (22). The intersection of the two axes of symmetry of the second unit cell structure (2) coincides with the center of the central ring body (31). The angle between the inclined ligament (32) and the horizontal ligament (21) connected to the same inclined bracing ligament (22) is θ2, and 0 < θ2 < θ1.

3. The honeycomb structure with negative Poisson's ratio effect as described in claim 2, characterized in that: The length of the horizontal ligament (21) is L, and the initial height between the horizontal ligaments (21) is H; the included angle between the horizontal ligament (21) and the oblique bracing ligament (22) is θ1; Where L:H = 0.8~1.3, 50°≤θ1≤70°.

4. The honeycomb structure with negative Poisson's ratio effect as described in claim 2, characterized in that: The oblique ligament (32) connected to the adjacent oblique bracing ligament (22) of the adjacent second unit cell structure (2) is collinear.

5. The honeycomb structure with negative Poisson's ratio effect as described in claim 2, characterized in that: The outer radius of the central ring (31) is r, the wall thickness of the central ring (31) is t1, the wall thickness of the inclined ligament (32) is t2, the wall thickness of the inclined bracing ligament (22) is t3, and the wall thickness of the horizontal ligament (21) is t4. t1=t2≤2×t3; t3=t4; 1.5×t1≤r≤2.5×t1.

6. The honeycomb structure with negative Poisson's ratio effect as described in claim 2, characterized in that: 10°≤θ2≤30°.

7. The honeycomb structure with negative Poisson's ratio effect as described in claim 1, characterized in that: The number of columns in the first unit cell structure (1) of each central unit (A) is 1, and the number of columns in the second unit cell structure (2) of each mirror unit (B) is a positive integer.

8. The honeycomb structure with negative Poisson's ratio effect as described in claim 7, characterized in that: The relative density of the unit cell structure formed by the second unit cell structure (2) and the chiral structure (3) is 0.20 to 0.

45.

9. The honeycomb structure with negative Poisson's ratio effect as described in claim 1, characterized in that: The ratio of the number of columns in the second unit cell structure (2) to the number of columns in the first unit cell structure (1) is 3 to 5.

10. The honeycomb structure with negative Poisson's ratio effect as described in claim 1, characterized in that: The honeycomb structure is integrally molded from an elastic material.

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