A three-dimensional gradient negative poisson's ratio honeycomb skeleton structure and its preparation method and use

Abstract

The application provides a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and a preparation method and application thereof, and relates to the technical field of mechanical metamaterials; the external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a circular truncated cone tube structure; the circular truncated cone tube structure comprises a plurality of curved surface concave hexagonal cells arranged around a central axis of the circular truncated cone tube structure and in a gradient along the circular truncated cone generatrix direction; the structure gradient can be first realized by relying on inherent characteristics of the inclined wall surface of the circular truncated cone tube structure, and further controlled by adjusting internal cell parameters; and the skeleton structure can be prepared by a 3D printing process. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure has the characteristics of light self-weight, linear deformability, synergistic effects of structure gradient effects and negative Poisson's ratio effects, and deformation characteristics of flexible linear expansion under external load, and can be used in the fields of protective engineering, artificial intelligence, wearable devices, medical devices, artificial prostheses and the like.

Description

Technical Field

[0001] This invention relates to the field of mechanical metamaterials technology, specifically to a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, its preparation method, and its applications. Background Technology

[0002] Negative Poisson's ratio materials are a type of mechanical metamaterial, possessing the unique mechanical property of expanding (contracting) laterally under longitudinal tension (compression). Multicellular negative Poisson's ratio materials exhibit advantages over traditional materials in terms of lightweight, high specific strength, high energy absorption efficiency, thermal insulation, and sound absorption, showing broad application prospects in structural design and functional optimization.

[0003] Negative Poisson's ratio cell structures, based on their deformation mechanisms, can be broadly categorized into: concave angle, chiral, rotational rigid body, and slit-type structures. Rolling up two-dimensional negative Poisson's ratio planar structures with different geometric topologies can form three-dimensional circular tube structures exhibiting a negative Poisson's ratio effect, which have been applied in various fields. In the biomedical field, CN201910233257.4 discloses a negative Poisson's ratio biodegradable vascular stent structure. This structure is characterized by a uniform cylindrical shape, with its internal topology formed by several concave hexagonal cells. Placing such a negative Poisson's ratio circular tube in an artery can open up narrowed areas and prevent blockage. However, a problem regarding structural design and deformation has not been fully considered. If there are force boundaries at both ends of the structure, when stretched at both ends, the middle of the tube expands and deforms significantly, with the size at the middle position exceeding the diameter of the tube openings at both ends, resulting in a deformed structure that approximates an "olive shape." In addition, in other tissues such as arteries or esophagus, there may be pathways of uneven size at special locations such as bifurcations. If the implanted uniform cylindrical stent does not match the intima tissue, it will increase the damage to the tissue.

[0004] Based on this, designing a three-dimensional gradient frustum tube structure would allow for more comprehensive research in this area. CN201821715259.4 discloses a nail with a negative Poisson's ratio effect, which consists of three parts: a head, a shaft, and a tail. The negative Poisson's ratio effect is achieved by designing the hole distribution on the tubular structure of the shaft. However, the conical structure of the head is still made of a single positive Poisson's ratio material. Considering the differences in the structure and deformation of the two parts when the nail is driven in and compressed, stress concentration may occur at the interface between the two parts, potentially leading to fracture.

[0005] Compared to uniform and symmetrical negative Poisson's ratio structures, gradient structures can realize physical properties, such as elastic modulus, Poisson's ratio, and density, that vary with spatial location. CN201720461026.5 discloses a variable thickness gradient negative Poisson's ratio automotive buffer energy absorption structure, which comprises three layers of negative Poisson's ratio structures from the outside to the inside. Each layer of negative Poisson's ratio structure is composed of three-dimensional concave hexagonal cells, and the thickness of the three layers exhibits a variable gradient distribution. Relying solely on three layers of thickness gradient cells to improve buffer energy absorption while ensuring the structure's crashworthiness is usually not ideal, and the thickness gradient distribution can cause significant differences in the structure's mass distribution.

[0006] To address the aforementioned issues, and considering applications in specific locations and scenarios with special requirements for non-uniform shapes, the design of three-dimensional gradient negative Poisson's ratio structures urgently needs improvement. Furthermore, three-dimensional multi-cell negative Poisson's ratio materials are structurally complex and difficult to process, thus limiting their applications. The emergence of 3D printing technology has effectively solved this problem. This invention addresses the shortcomings of existing three-dimensional negative Poisson's ratio structure designs by proposing a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, its fabrication method, and its applications. Specifically, it is a three-dimensional gradient negative Poisson's ratio multi-cell structure with a frustum-shaped tube as its outer form, and by adjusting the structural geometric parameters, configurations with different gradient degrees and internal topological configurations can be achieved. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, its preparation method and applications. The external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure. The frustum tube structure includes a plurality of curved concave hexagonal cells arranged in a gradient around the central axis of the frustum tube structure and along the generatrix direction of the frustum tube. The structural gradient can first be achieved by relying on the inherent characteristics of the inclined wall of the frustum tube structure, and further controlled by adjusting the internal cell parameters. The skeleton structure can be prepared by 3D printing. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure provided by the present invention has the characteristics of light weight, linear deformability, and synergistic effect of structural gradient effect and negative Poisson's ratio effect. Under the action of external load, it has the deformation characteristics of flexible linear expansion and can be used in protective engineering, artificial intelligence, wearable devices, medical devices, artificial prostheses and other fields.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] One objective of this invention is to provide a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, wherein the external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure; the sidewall of the frustum tube structure is composed of a plurality of gradient-arranged concave hexagonal cells; the stacking method of the gradient arrangement includes: concave hexagonal cells of the same size are arranged along the circumference of the frustum tube, and concave hexagonal cells of varying size gradients are arranged along the generatrix direction of the frustum tube.

[0010] As a preferred technical solution of the present invention, the topological configuration of the concave hexagonal cells of the frustum tube structure includes: defining a spatial rectangular coordinate system XYZ, with the upper bottom surface of the frustum tube structure located in the XY plane, the central axis of the frustum tube structure parallel to the Z-axis, and the positive direction of the Z-axis pointing from the upper bottom surface to the lower bottom surface of the frustum tube structure; a plurality of concave hexagonal cells with gradually varying sizes are arranged along the generatrix direction of the frustum tube to form a lattice, and the plurality of lattices are arrayed around the central axis of the frustum tube structure to form a complete closed-loop structure.

[0011] As a preferred embodiment of the present invention, any of the concave hexagonal cells has a curvature, wherein the curvature is... Wherein, N is the number of lattice arrays around the central axis of the frustum tube structure, and N satisfies 2≤N≤360 and N is divisible by 360.

[0012] As a preferred technical solution of the present invention, the cell structure corresponding to any of the curved concave hexagonal cells is a two-dimensional concave hexagonal planar structure; the two-dimensional concave hexagonal planar structure includes a horizontal support column, which is parallel to the bottom surface of the frustum tube structure; the curved concave hexagonal cell also includes two upwardly inclined support columns located above the horizontal support column, and two downwardly inclined support columns located below the horizontal support column.

[0013] As a preferred technical solution of the present invention, the two-dimensional concave hexagonal planar structure is trapezoidal, the thickness of the horizontal support column is t, the upper concave angle of the unit cell is θ1, the lower concave angle of the unit cell is θ2, the length of the upper inclined support column of the unit cell is l1, the length of the lower inclined support column of the unit cell is l2, and the height of the unit cell is h.

[0014] The geometric parameter relationships within a unit cell include: l1×sinθ1+l2×sinθ2=h;

[0015] The upper concave angle θ1 of the unit cell ranges from 30° to 80°; the lower concave angle θ2 of the unit cell ranges from 30° to 80°, and θ1 and θ2 may be equal or unequal.

[0016] As a preferred embodiment of the present invention, along the positive direction of the Z-axis, the cell height of the i-th layer of the concave hexagonal cells is h. i The height ratio of two adjacent cells is q, and q is defined as... Let the total height of the frustum-shaped tube structure be H, then Where L is the number of concave hexagonal cells arranged along the generatrix of the frustum tube, T1 is the thickness of the upper annular boundary of the frustum tube structure, and T2 is the thickness of the lower annular boundary of the frustum tube structure.

[0017] In a preferred embodiment of the present invention, the thicknesses of the upper and lower annular boundaries of the frustum-shaped tube structure are equal, i.e., T1 = T2 = T.

[0018] As a preferred technical solution of the present invention, the apex angle V of the frustum tube structure is in the range of 10° to 90°, and the wall thickness d of the frustum tube structure is in the range of 2 to 20 mm.

[0019] The second objective of this invention is to provide a method for preparing the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in the first objective, which is prepared by additive manufacturing and uses a base material including a single-component material or a multi-component material.

[0020] Preferably, the single-component material includes any one of metal, polylactic acid, thermoplastic polyurethane, high-elasticity material, or shape memory alloy.

[0021] Preferably, the multi-component material includes a composite material consisting of a combination of continuous fiber / short fiber and thermoplastic material, or a composite material consisting of a combination of continuous fiber / short fiber and thermosetting material.

[0022] The third objective of this invention is to provide an application for a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, which can be used in protective engineering, artificial intelligence, wearable devices, medical devices, and artificial prostheses, either as described in the first objective or as prepared by the second objective.

[0023] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0024] (1) The gradient negative Poisson's ratio multi-cell structure design of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure of the present invention is no longer limited to two-dimensional plane and uniform symmetrical design, but extends to three-dimensional space and non-uniform curved surface design, giving full play to the expansion effect of negative Poisson's ratio cells; compared with other uniform and perfectly symmetrical three-dimensional circular tube negative Poisson's ratio structures, the gradient negative Poisson's ratio circular tube provides a linear progressive expansion deformation mode, which can be used in non-uniform external environment or special location; further, by adjusting the internal structural parameters, the negative Poisson's ratio effect of the structure can be changed;

[0025] (2) The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure of the present invention is based on a porous and lightweight structure, and combines the synergistic effect of negative Poisson's ratio and gradient in three-dimensional space. It has the characteristic of adjustable deformation state and has a very broad prospect for practical application. Attached Figure Description

[0026] Figure 1 This is a three-dimensional structural schematic diagram of one of the concave hexagonal cells of the present invention;

[0027] Figure 2 This is a schematic diagram of a two-dimensional concave hexagonal planar structure corresponding to a certain concave hexagonal cell of the present invention;

[0028] Figure 3 This is a three-dimensional structural diagram of a three-dimensional gradient concave hexagonal honeycomb skeleton structure described in this invention. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0031] This invention provides a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, wherein the external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure; the sidewall of the frustum tube structure is composed of a plurality of gradient-arranged curved concave hexagonal cells; the stacking method of the gradient arrangement includes: curved concave hexagonal cells of the same size are arranged along the circumference of the frustum tube, and curved concave hexagonal cells of varying size gradients are arranged along the generatrix direction of the frustum tube.

[0032] The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention has the characteristics of light weight, linear deformability, and synergistic effect of structural gradient effect and negative Poisson's ratio effect, and has the deformation characteristic of flexible linear expansion under external load.

[0033] The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure topology described in this invention is a multi-cell structure formed by several curved concave hexagonal cells arranged in space, thus exhibiting a negative Poisson's ratio effect; the basic cell is a curved, gradient concave hexagonal structure, and the cell structure is formed by a two-dimensional gradient concave hexagonal planar structure; the flexible deformation distribution of the skeleton structure can be adjusted by adjusting the geometric parameters of the basic cell structure.

[0034] The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure of this invention corresponds to a three-dimensional gradient cell that evolves from a classic concave hexagonal cell to a concave hexagonal cell with a trapezoidal outer boundary. Further, through structural optimization design, a gradient concave hexagonal cell entity with a certain curvature and thickness is formed. The three-dimensional gradient cell structure can change the negative Poisson's ratio effect and deformation distribution by adjusting the micro-geometric parameters. The number of gradient cell structures arranged circumferentially is greater than two. When the cell size is fixed, this number affects the cross-sectional size of the three-dimensional gradient negative Poisson's ratio structure; the fewer the number, the smaller the cross-sectional radius corresponding to the frustum tube position. The number of gradient cell structures arranged along the tube wall is greater than two. The number of gradient cell structures determines the axial length of the overall structure, and the specific number can be determined by actual needs and structural strength.

[0035] The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure of this invention exhibits a negative Poisson's ratio effect. When a tensile load is applied, within the elastic deformation range, the overall shape of the structure remains stable while the tube wall undergoes linear elongation deformation. When an external tensile load is applied, the frustum tube structure maintains its external configuration while achieving linear elongation deformation along the tube wall without radial contraction or other deformations. The frustum tube structure is characterized by its light weight and linear deformability. The flexible deformation distribution of the skeleton structure can be adjusted by adjusting the geometric parameters of the basic cell structure.

[0036] As a preferred technical solution of the present invention, the topological configuration of the concave hexagonal cells of the frustum tube structure includes: defining a spatial rectangular coordinate system XYZ, with the upper bottom surface of the frustum tube structure located in the XY plane, the central axis of the frustum tube structure parallel to the Z-axis, and the positive direction of the Z-axis pointing from the upper bottom surface to the lower bottom surface of the frustum tube structure; a plurality of concave hexagonal cells with gradually varying sizes are arranged along the generatrix direction of the frustum tube to form a lattice, and the plurality of lattices are arrayed around the central axis of the frustum tube structure to form a complete closed-loop structure.

[0037] As a preferred embodiment of the present invention, any of the concave hexagonal cells has a curvature, wherein the curvature is... Where N is the number of lattice cells arranged around the central axis of the frustum tube structure, and N satisfies 2 ≤ N ≤ 360 and N is divisible by 360, that is, it guarantees... It is an integer.

[0038] As a preferred technical solution of the present invention, the cell structure corresponding to any of the curved concave hexagonal cells is a two-dimensional concave hexagonal planar structure; the two-dimensional concave hexagonal planar structure includes a horizontal support column, which is parallel to the bottom surface of the frustum tube structure; the curved concave hexagonal cell also includes two upwardly inclined support columns located above the horizontal support column, and two downwardly inclined support columns located below the horizontal support column.

[0039] It is worth noting that the horizontal support column of the present invention mainly provides a connecting function, while the upper and lower inclined support columns mainly provide axial support and lateral expansion deformation.

[0040] As a preferred technical solution of the present invention, the two-dimensional concave hexagonal planar structure is trapezoidal, the thickness of the horizontal support column is t, the upper concave angle of the unit cell is θ1, the lower concave angle of the unit cell is θ2, the length of the upper inclined support column of the unit cell is l1, the length of the lower inclined support column of the unit cell is l2, and the height of the unit cell is h.

[0041] The geometric parameter relationships within a unit cell include: l1×sinθ1+l2×sinθ2=h;

[0042] The upper concave angle θ1 of the unit cell ranges from 30° to 80°; the lower concave angle θ2 of the unit cell ranges from 30° to 80°, and θ1 and θ2 may be equal or unequal.

[0043] It is worth noting that the thickness of the horizontal support column corresponding to the i-th layer concave hexagonal cell is set to t. i Then the thickness ratio t of the horizontal support column corresponding to two adjacent cells i-1 / t i The value is fixed and can be equal to 1, greater than 1, or less than 1; that is, the thickness t of the horizontal support column. i The size of t can be the same, or increase, or decrease; i The size of the t will change the density of the frustum tube structure, thus affecting its stiffness, but will not affect the deformation effect. i The stiffness increases from top to bottom to ensure that the stiffness of the large end and the small end of the cone are consistent.

[0044] It is worth noting that the range of the upper concave angle θ1 or the lower concave angle θ2 of the unit cell described in this invention is 30° to 80°, such as 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75° or 80°, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] As a preferred embodiment of the present invention, along the positive direction of the Z-axis, the cell height of the i-th layer of the concave hexagonal cells is h. i The height ratio of two adjacent cells is q, and q is defined as... Let the total height of the frustum-shaped tube structure be H, then Where L is the number of concave hexagonal cells arranged along the generatrix of the frustum tube, T1 is the thickness of the upper annular boundary of the frustum tube structure, and T2 is the thickness of the lower annular boundary of the frustum tube structure.

[0046] It is worth noting that when q is 1, the cell height of each layer of concave hexagonal cells is equal; when q < 1, along the positive direction of the Z-axis, that is, the direction from the top surface of the frustum tube structure to the bottom surface, the cell height of the concave hexagonal cells increases layer by layer; when q > 1, along the positive direction of the Z-axis, that is, the direction from the top surface of the frustum tube structure to the bottom surface, the cell height of the concave hexagonal cells decreases layer by layer.

[0047] In a preferred embodiment of the present invention, the thicknesses of the upper and lower annular boundaries of the frustum-shaped tube structure are equal, i.e., T1 = T2 = T.

[0048] As a preferred technical solution of the present invention, the apex angle V of the frustum tube structure is in the range of 10° to 90°, such as 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° or 90°, etc., and the wall thickness d of the frustum tube structure is in the range of 2 to 20 mm, such as 2 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm or 20 mm, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0049] It is worth noting that the external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention is a frustum tube structure, and the size of the apex angle V can be adjusted to form a three-dimensional gradient concave hexagonal honeycomb skeleton structure with different macroscopic gradient degrees; similarly, for other macroscopic parameters, such as the total height H of the frustum tube structure, the frustum tube structure can be adjusted into different macroscopic gradient structures according to specific requirements and applications.

[0050] This invention provides a method for preparing a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, which is prepared by additive manufacturing and uses a base material including single-component materials or multi-component materials.

[0051] Preferably, the single-component material includes any one of a single metal, polylactic acid (PLA), thermoplastic polyurethane (TPU), a high-elasticity material, or a shape memory alloy; the high-elasticity material is, for example, styrene-acrylonitrile-butadiene terblock copolymer (ABS).

[0052] Preferably, the multi-component material includes a composite material combining continuous fibers / short fibers and thermoplastic materials, or a composite material combining continuous fibers / short fibers and thermosetting materials. The composite material obtained by combining continuous fibers and short fibers together with thermoplastic (solid) materials can effectively ensure the strength of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure.

[0053] This invention provides an application of a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, or the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure obtained by the preparation method, can be used in the fields of protective engineering, artificial intelligence, wearable devices, medical devices, and artificial prostheses. Specifically, it can be used in protective devices such as safety seats, safety helmets, and helmets, as well as in the fields of flexible and stretchable materials such as vascular stents and radar.

[0054] See Figure 1 , Figure 2 and Figure 3 This invention provides a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure. Its external configuration is a hollow structure in the shape of a frustum tube. The three-dimensional gradient structure is constrained by the shape of the frustum tube. The tube wall is composed of several gradient-sized curved concave hexagonal cells. The structure has periodicity and is obtained by cell array.

[0055] The structure is formed as follows:

[0056] (1) Define a spatial rectangular coordinate system XYZ. The upper bottom surface of the frustum tube structure is located in the XY plane. The central axis of the frustum tube structure is parallel to the Z axis, and the positive direction of the Z axis is from the upper bottom surface of the frustum tube structure to the lower bottom surface.

[0057] The basic unit of the frustum tube structure described in this invention is a curved concave hexagonal cell, formed by a two-dimensional concave hexagonal planar structure; a three-dimensional structural diagram of the curved concave hexagonal cell is shown below. Figure 1 As shown; a schematic diagram of the two-dimensional concave hexagonal planar structure is shown below. Figure 2 As shown, the two-dimensional concave hexagonal planar structure is located on the XZ plane, and multiple gradient concave hexagonal cells with varying sizes are constructed along the Z-axis direction;

[0058] Specifically, taking any cell in the i-th layer as an example, the size variation rule means that the base angle γ of the trapezoidal outer contour of the cell remains unchanged, the upper base of any cell in the i-th layer is equal in length to the lower base of any cell in the (i-1)-th layer, and the lower base of any cell in the i-th layer is equal in length to the upper base of any cell in the (i+1)-th layer; where, for a certain cell in the i-th layer, the height of the single cell is h. i The concave angle of the unit cell is θ1, the concave angle of the unit cell is θ2, the base angle of the trapezoidal outer contour of the unit cell is γ, and the thickness of the horizontal support column is t; L is the number of concave hexagonal units arranged along the generatrix of the frustum tube, and L is also the number of layers of concave hexagonal units along the positive Z-axis; T1 is the thickness of the upper annular boundary of the frustum tube structure, and T2 is the thickness of the lower annular boundary of the frustum tube structure. Here, T1 = T2 = T, so the total height H of the frustum tube structure is the sum of the total height of the L layers of units and the reserved annular boundary thickness 2T;

[0059] (2) The aforementioned series of two-dimensional concave hexagonal planar structures with varying dimensions are subjected to structural bending and thickening to form a series of curved concave hexagonal cells with varying dimensions, i.e., forming a series of curved three-dimensional gradient concave hexagonal structures; the aforementioned curved series of three-dimensional gradient concave hexagonal structures are cyclically arrayed around the Z-axis, with the number of arrays being N, to form a complete three-dimensional gradient concave hexagonal honeycomb skeleton structure (e.g. Figure 3 As shown), its external configuration is a frustum tube structure with a tube wall thickness of d, that is, the thickness of any concave hexagonal cell on any curved surface is d, and the total height of the frustum tube structure is H.

[0060] Specifically, any of the aforementioned concave hexagonal cells has a curvature, wherein the curvature is... The apex angle of the frustum-shaped tube structure is V, and the radius of the upper base of the frustum-shaped tube structure is r. u The radius of the lower base is r d Let 'a' be the upper base edge length of the first cell at the very top of the frustum tube structure, and 'b' be the lower base edge length of the Lth cell at the very bottom of the frustum tube structure. Then, the two-dimensional gradient lattice parameters and the three-dimensional frustum tube must satisfy certain geometric relationships:

[0061]

[0062]

[0063]

[0064] The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention is a three-dimensional gradient concave hexagonal skeleton structure. Therefore, the gradient factor includes three aspects: first, a macroscopic gradient factor, specifically the apex angle and height-to-diameter ratio of the frustum tube structure; second, a mesoscopic gradient factor, including the number of circumferential array cells and the number of axial layers; and third, a three-dimensional microscopic gradient factor, including parameters such as cell height ratio, concave angle size, and support column thickness. By adjusting the gradient factors in these three aspects, three-dimensional gradient concave hexagonal honeycomb skeleton structures with different topological configurations can be formed.

[0065] The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention can be fabricated using 3D printing technology. The parent material can be a single metal, polylactic acid (PLA), thermoplastic polyurethane (TPU), styrene-acrylonitrile-butadiene terpolymer (ABS), or a composite material composed of continuous fibers and thermoplastic (solid) materials. Through kinetic simulation analysis, applying a uniaxial tension downwards along the tube wall to the structure described in this invention yields a deformed structure. Compared to the original structure, this deformed structure exhibits linear elongation along the tube wall while maintaining the initial configuration of the frustum tube.

[0066] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0067] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0069] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, characterized in that, The external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure; the sidewall of the frustum tube structure is composed of several gradient-arranged concave hexagonal cells; the stacking method of the gradient arrangement includes: concave hexagonal cells of the same size are arranged along the circumference of the frustum tube, and concave hexagonal cells of varying size gradients are arranged along the generatrix direction of the frustum tube.

2. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 1, characterized in that, The topological configuration of the concave hexagonal cells of the frustum tube structure includes: defining a spatial rectangular coordinate system XYZ, with the upper base of the frustum tube structure located in the XY plane, the central axis of the frustum tube structure parallel to the Z-axis, and the positive direction of the Z-axis pointing from the upper base to the lower base of the frustum tube structure; a number of concave hexagonal cells with gradually varying sizes are arranged along the generatrix of the frustum tube to form a lattice, and the number of lattices are arrayed around the central axis of the frustum tube structure to form a complete closed-loop structure.

3. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 2, characterized in that, Any of the aforementioned concave hexagonal cells has a curvature, wherein the curvature is... Where N is the number of lattice arrays around the central axis of the frustum tube structure, and N satisfies 2≤N≤360 and N is divisible by 360.

4. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 1, characterized in that, The cell structure corresponding to any of the curved concave hexagonal cells is a two-dimensional concave hexagonal planar structure; the two-dimensional concave hexagonal planar structure includes a horizontal support column, which is parallel to the bottom surface of the frustum tube structure; the curved concave hexagonal cell also includes two upwardly inclined support columns located above the horizontal support column, and two downwardly inclined support columns located below the horizontal support column.

5. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 4, characterized in that, The two-dimensional concave hexagonal planar structure is trapezoidal, the thickness of the horizontal support column is t, the upper concave angle of the unit cell is θ1, the lower concave angle of the unit cell is θ2, the length of the upper inclined support column of the unit cell is l1, the length of the lower inclined support column of the unit cell is l2, and the height of the unit cell is h. The relationships between geometric parameters within a unit cell include: ; The upper concave angle θ1 of the unit cell ranges from 30° to 80°; the lower concave angle θ2 of the unit cell ranges from 30° to 80°, and θ1 and θ2 may be equal or unequal.

6. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 2, characterized in that, Along the positive Z-axis, the cell height of the i-th layer's concave hexagonal cell is h. i The height ratio of two adjacent cells is q, and q is defined as... Let the total height of the frustum-shaped tube structure be H, then Where L is the number of concave hexagonal cells arranged along the generatrix of the frustum tube, T1 is the thickness of the upper annular boundary of the frustum tube structure, and T2 is the thickness of the lower annular boundary of the frustum tube structure.

7. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 6, characterized in that, The upper and lower annular boundaries of the frustum-shaped tube structure have equal thicknesses, i.e., T1=T2=T. .

8. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 1, characterized in that, The apex angle V of the frustum tube structure ranges from 10° to 90°, and the wall thickness d of the frustum tube structure ranges from 2 to 20 mm.

9. A method for preparing a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to any one of claims 1-8, characterized in that, The additive manufacturing process uses a base material that can be a single-component material or a multi-component material.

10. The method for preparing the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 9, characterized in that, The single-component material includes any one of metal, polylactic acid, thermoplastic polyurethane, high-elasticity material, or shape memory alloy.

11. The method for preparing the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to claim 9, characterized in that, The multi-component material includes a composite material consisting of a combination of continuous fiber / short fiber and thermoplastic material, or a composite material consisting of a combination of continuous fiber / short fiber and thermosetting material.

12. An application of a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure, characterized in that, The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure according to any one of claims 1-8, or the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure obtained by the preparation method according to claim 9, can be used in the fields of protective engineering, artificial intelligence, wearable devices, medical devices, and artificial prostheses.

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