A three-dimensional gradient negative Poisson's ratio thin-walled composite material, its preparation method and applications

Abstract

This invention provides a three-dimensional gradient negative Poisson's ratio thin-walled composite material, its preparation method, and its applications, relating to the field of tensile metamaterials technology. The three-dimensional gradient negative Poisson's ratio thin-walled composite material includes a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filling material filling its pores. The external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure, which 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 composite material provided by this invention fully utilizes the stretchable deformation characteristics of the honeycomb skeleton structure and the mechanical reinforcement properties of the elastic matrix filling material, effectively avoiding the poor structural stability problems caused by high porosity and low stiffness in tensile structures. While further improving the load-bearing strength and overall mechanical properties of the composite material, it achieves continuous linear elongation deformation under tension.

Description

Technical Field

[0001] This invention relates to the field of tensile metamaterials technology, specifically to a three-dimensional gradient negative Poisson's ratio thin-walled composite material, its preparation method, and its applications. Background Technology

[0002] In recent years, tensile metamaterials have become a research hotspot in the field of materials science both domestically and internationally due to their excellent mechanical and physical properties. The negative Poisson's ratio effect in tensile metamaterials is generally achieved through an embedded concave hexagonal honeycomb structure. However, the concave hexagonal honeycomb structure is characterized by high porosity, and the supporting columns are prone to bending deformation and instability under external loads, resulting in lower stiffness and weaker load-bearing capacity compared to bulk materials. Innovative designs that integrate structure and function offer a new approach to developing composite materials with good overall performance and high reliability by fully utilizing traditional materials combined with structures possessing special mechanical properties. This involves using a negative Poisson's ratio framework material as the reinforcing phase and elastic resin and other materials as the matrix phase, filling the pores of the framework structure. This two-phase composite provides higher stiffness than a single material, enhancing the overall structural stability without sacrificing the negative Poisson's ratio effect. This advanced composite material has advantages such as being lightweight, having high specific strength and specific stiffness, large specific modulus, high temperature resistance, corrosion resistance, and strong structural adjustability. It is widely used in aerospace, construction engineering, packaging engineering, automotive engineering and other fields, and can also serve under extreme conditions, providing key support for the industrialization of countries around the world.

[0003] CN202110266310.8 discloses a method for preparing an integrated three-dimensional tensile structure of foam-filled composite material. The structure is integrally molded using the VARI process. The preparation process includes: 1) preparing internally filled foam of the required size; 2) cutting and laying fiber fabric within the concave grooves of the foam; 3) stacking the foam to form a composite material structure; 4) pressing flat plates onto the perimeter and top and bottom surfaces of the composite material, placing it in a vacuum bag and evacuating it; 5) molding and curing using VARI technology, and after demolding, obtaining the desired single-layer composite material structure; 6) stacking, gluing, and curing the multi-layer structure to obtain the aforementioned three-dimensional tensile structure of the foam-filled composite material.

[0004] CN202210121982.4 discloses a 3D multi-component composite tensile metamaterial based on additive manufacturing. This composite material comprises three components: a 3D tensile metamaterial, a polymer filler, and a square tube. The matrix material of the 3D tensile metamaterial is industrial pure aluminum, and its unit cell structure is a concave honeycomb type, obtained through additive manufacturing combined with investment casting. The polymer filler is epoxy resin and epoxy resin-montmorillonite filler. The square tube is a stainless steel square tube. Based on the structural characteristics and negative Poisson's ratio effect of the 3D tensile metamaterial, this technical solution obtains a 3D multi-component composite tensile metamaterial by internally filling it with two polymers and externally adding a stainless steel tube to form internal and external constraints, effectively improving the structural utilization rate of the tensile metamaterial.

[0005] However, existing negative Poisson's ratio concave hexagonal honeycomb structures are often uniformly sized cylinders or cuboids, which are not suitable for scenarios requiring non-uniform shapes. Similarly, composite tensile metamaterials, constrained by the external configuration of the negative Poisson's ratio concave hexagonal honeycomb structure, are also unsuitable for scenarios with specific requirements for non-uniform shapes. Therefore, there is a need to develop a three-dimensional gradient negative Poisson's ratio thin-walled composite material, its preparation method, and its applications. Summary of the Invention

[0006] In view of the problems existing in the prior art, a three-dimensional gradient negative Poisson's ratio thin-walled composite material, its preparation method and application are provided. The three-dimensional gradient negative Poisson's ratio thin-walled composite material includes a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filling material filling the pores. The external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure, which belongs to a deformable skeleton structure composed of gradient concave hexagonal multi-cell units. The elastic matrix filling material belongs to a flexible reinforcing material. The composite material of the present invention can further improve the strength of the material based on the flexible deformable metastructure system. The thin-walled composite material of the present invention is prepared by 3D printing combined with high temperature hot molding and can be used as a tensile metastructure material in aerospace, construction engineering, packaging engineering and automotive engineering fields.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] One of the objectives of this invention is to provide a three-dimensional gradient negative Poisson's ratio thin-walled composite material, which includes a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filling material that fills the pores therein;

[0009] 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.

[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. iThe 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 thin-walled composite material as described in the first objective. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is prepared by 3D printing, and the elastic matrix filling material is filled into the pores of the honeycomb skeleton structure by high-temperature hot molding.

[0020] Preferably, the base material used in the preparation of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure includes polylactic acid, polyurethane thermoplastic materials, composite materials combining continuous fibers / short fibers and thermoplastic materials, or composite materials combining continuous fibers / short fibers and thermosetting materials.

[0021] Preferably, the base material used in the preparation of the elastic matrix filler includes any one or a combination of at least two of chloroprene rubber, natural rubber, EPDM or nitrile rubber.

[0022] The third objective of this invention is to provide an application for a three-dimensional gradient negative Poisson's ratio thin-walled composite material, wherein the three-dimensional gradient negative Poisson's ratio thin-walled composite material described in the first objective, or the three-dimensional gradient negative Poisson's ratio thin-walled composite material obtained by the preparation method described in the second objective, is used as an aerospace, construction engineering, packaging engineering, and automotive engineering fields as a tensile metamaterial.

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

[0024] (1) The three-dimensional gradient negative Poisson's ratio thin-walled composite material of the present invention uses a flexible deformable skeleton structure as a reinforcing phase to support the overall deformation behavior of the load-bearing components, and the matrix material as a reinforcing phase to play a strength-enhancing role. Structurally, it integrates the synergistic effect of negative Poisson's ratio and gradient mechanisms in three-dimensional space. In terms of composition, the skeleton structure and the filling matrix are allocated different materials to give full play to the complementary properties of different components of the materials, which are related and synergistic with each other, thereby developing superior performance compared to single materials and avoiding the problem of low strength and stiffness caused by the porous characteristics of a single superstructure skeleton structure.

[0025] (2) 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;

[0026] (3) The three-dimensional gradient negative Poisson's ratio thin-walled composite material of the present invention can maintain the initial expansion angle when subjected to tension, while achieving deformation along the tube wall. It maximizes the potential and efficiency of the material and structure, provides a theoretical basis for the performance optimization of tensile metamaterials, and has a very broad prospect for practical application;

[0027] (4) The three-dimensional gradient negative Poisson's ratio thin-walled composite material of the present invention is prepared by 3D printing combined with high temperature hot molding. The structure has the characteristics of good integrity, short processing cycle, low cost and high reliability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the composition of a certain gradient composite material in the three-dimensional gradient negative Poisson's ratio thin-walled composite material described in the embodiments of the present invention;

[0029] Figure 2 This is a three-dimensional structural schematic diagram of the three-dimensional gradient negative Poisson's ratio thin-walled composite material described in an embodiment of the present invention;

[0030] Figure 3 This is a three-dimensional structural diagram of a concave hexagonal cell in the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention.

[0031] Figure 4 This is a schematic diagram of the two-dimensional concave hexagonal planar structure corresponding to a certain curved concave hexagonal cell in the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] 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:

[0034] This invention provides a three-dimensional gradient negative Poisson's ratio thin-walled composite material, which includes a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filling material filling the pores therein;

[0035] 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.

[0036] The three-dimensional gradient negative Poisson's ratio thin-walled composite material of this invention comprises a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filler material filling its pores. The external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure, which 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 composite material provided by this invention uses the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure as a flexible deformable body and the elastic matrix filler material filling its pores as a reinforcement, fully utilizing the tensile deformation characteristics of the honeycomb skeleton structure and the mechanical reinforcement properties of the elastic matrix filler material. This effectively avoids the poor structural stability problem caused by high porosity and low stiffness in tensile structures, further improving the load-bearing strength and overall mechanical properties of the composite material while achieving continuous linear elongation deformation under tension.

[0037] The three-dimensional gradient negative Poisson's ratio thin-walled composite material of the present invention includes a deformable skeleton structure composed of gradient concave hexagonal multi-cell units and a flexible reinforcing material filling the voids. The flexible reinforcing material, as the filling matrix, fills the voids of the concave hexagonal cells and matches the size of the skeleton void structure. It can improve the strength of the material and achieve the effect of mechanical reinforcement on the basis of a flexible deformable metastructure system.

[0038] 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.

[0039] For the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure described in this invention, the gradient meta-skeleton cell is a gradient curved concave hexagon with a gradient change in cell size, and is arranged periodically to form a porous skeleton structure with a frustum thin wall as the overall structure; the skeleton structure is composed of a multi-cell structure composed of several concave hexagons, and has a frustum thin wall structure with a certain thickness. The cell is a gradient concave hexagon with a gradually changing size, that is, distributed along the axial direction of the frustum thin wall, and the size of the cells in each layer is different.

[0040] The composite material of the present invention has a negative Poisson's ratio effect, and the negative Poisson's ratio effect increases approximately linearly from top to bottom with the height position of the axis. The three-dimensional gradient negative Poisson's ratio composite material of the present invention has a fixed upper boundary and a tensile load applied to the lower boundary. Within the elastic deformation range, the frustum tube maintains the initial expansion angle unchanged, that is, the frustum tube maintains the size of its apex angle V unchanged, and the deformation mode is a linear elongation mode along the tube wall.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The geometric parameter relationships within a unit cell include: l1×sinθ1+l2×sinθ2=h;

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] This invention provides a method for preparing a three-dimensional gradient negative Poisson's ratio thin-walled composite material. The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is prepared by 3D printing, and the elastic matrix filling material is filled into the pores of the honeycomb skeleton structure by high-temperature hot molding.

[0055] Preferably, the base material used in the preparation of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure includes polylactic acid, polyurethane thermoplastic materials, composite materials combining continuous fibers / short fibers and thermoplastic materials, or composite materials combining continuous fibers / short fibers and thermosetting materials.

[0056] Preferably, the base material used in the preparation of the elastic matrix filler includes any one or a combination of at least two of chloroprene rubber, natural rubber, EPDM, or nitrile rubber. This invention provides an application for a three-dimensional gradient negative Poisson's ratio thin-walled composite material, which, or the three-dimensional gradient negative Poisson's ratio thin-walled composite material obtained by the aforementioned preparation method, is used as an aerospace, construction, packaging, and automotive engineering field tensile metamaterial.

[0057] See Figures 1 to 4 This embodiment provides a three-dimensional gradient negative Poisson's ratio thin-walled composite material, comprising two parts: a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filling material filling the pores therein. The construction steps include:

[0058] (1) Construct a gradient composite material of a certain column in a three-dimensional gradient negative Poisson's ratio thin-walled composite material.

[0059] Step a: Determine the macroscopic structural parameters of the frustum tube structure according to requirements and uses, including the total structural height H, apex angle V, thin wall thickness d, and thickness T of the upper (lower) annular boundary;

[0060] Step b: Based on the macroscopic structural parameters determined in step a, further determine the mesoscopic structural parameters, including the number of cell layers L and the number of circumferential cells N; wherein, the number of circumferential cells is the number of gradient lattice columns; the height of the i-th cell layer is h. i Then the gradient lattice height, which is the total structural height H = (h1 + h2 + ... + hL) + 2T, and since the ratio of the heights of two adjacent cells is q, q is defined as... but

[0061] Step c: Based on the macroscopic structural parameters determined in step a and the mesoscopic structural parameters determined in step b, further optimize the microscopic geometric parameters, including the tilt angle γ of the gradient cell, the thickness t of the horizontal support column, the upper concave angle θ1 of the unit cell, and the lower concave angle θ2 of the unit cell; complete the drawing of the structural model through modeling software, and further process the error of the structure.

[0062] Step d: Draw the corresponding base structure components according to the gap dimensions of the skeleton structure;

[0063] Step e: Combine the above-mentioned column of skeleton structure and column of matrix structure components to form a column of gradient composite material, such as... Figure 1 As shown;

[0064] (2) Figure 2As shown, the above-mentioned gradient composite material is taken as an integral structural unit and rotated around the central axis of the frustum tube structure for one revolution. The number of arrays is N, which can form a complete three-dimensional gradient negative Poisson's ratio thin-walled composite material with a thin-wall thickness of d and a total structural height of H.

[0065] (3) The adjustable geometric parameters of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure include the apex angle V of the frustum tube structure, the total structural height H of the frustum tube structure, and the base radius R of the frustum tube structure. d The number of circumferential arrays N, the number of axial cell layers L, and the height h of the i-th layer cell i The thickness t of the horizontal support column, the upper concave angle θ1 of the unit cell, and the lower concave angle θ2 of the unit cell;

[0066] (4) The size of the filling material in the three-dimensional gradient negative Poisson's ratio thin-walled composite material is matched with the size of the voids in the skeleton structure. Therefore, the size of the composite material is controlled by the skeleton structure. By adjusting the geometric parameters mentioned in (3), multiple three-dimensional gradient negative Poisson's ratio thin-walled composite materials with different topologies can be formed.

[0067] (5) The skeleton structure of the three-dimensional gradient negative Poisson's ratio thin-walled composite material of the present invention is prepared by 3D printing, and the elastic matrix filling material is filled into the pores of the skeleton structure by high-temperature hot molding. The skeleton structure is composed of polylactic acid, polyurethane thermoplastic materials or continuous fiber and polymer composite materials; the elastic matrix material can be composed of elastic rubber materials such as chloroprene rubber, natural rubber, EPDM, and nitrile rubber.

[0068] Through dynamic simulation analysis, uniaxial tensile simulations were applied to a single three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and its corresponding three-dimensional gradient negative Poisson's ratio thin-walled composite material, with the load direction downward along the tube wall. Statistical analysis revealed that the deformed structure maintained the same expansion angle as the original structure; that is, the frustum tube maintained the same apex angle V, and the tube wall did not exhibit indentation or deformation, thus exhibiting linear elongation along the tube wall.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 thin-walled composite material, characterized in that, The three-dimensional gradient negative Poisson's ratio thin-walled composite material includes a three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure and an elastic matrix filling material that fills the pores therein. The external configuration of the three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure is a frustum tube structure; the sidewalls of the frustum tube structure are composed of several gradient-arranged concave hexagonal cells; the gradient arrangement includes: concave hexagonal cells of the same size are arranged along the circumference of the frustum tube, several concave hexagonal cells of varying sizes are arranged along the generatrix of the frustum tube to form a lattice, and several lattices are arrayed around the central axis of the frustum tube structure to form a complete closed-loop structure.

2. The three-dimensional gradient negative Poisson's ratio thin-walled composite material according to claim 1, characterized in that, The topological configuration of the concave hexagonal cell 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 of the frustum tube structure to the lower bottom surface.

3. The three-dimensional gradient negative Poisson's ratio thin-walled composite material 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 thin-walled composite material 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 thin-walled composite material 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 thin-walled composite material 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 thin-walled composite material 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 thin-walled composite material 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 thin-walled composite material according to any one of claims 1-8, characterized in that, The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure was prepared by 3D printing, and the elastic matrix filling material was filled into the pores of the honeycomb skeleton structure by high temperature hot molding.

10. The preparation method according to claim 9, characterized in that, The three-dimensional gradient negative Poisson's ratio honeycomb skeleton structure uses polylactic acid, polyurethane thermoplastic materials, composite materials combining continuous fibers / short fibers and thermoplastic materials, or composite materials combining continuous fibers / short fibers and thermosetting materials as the base materials in the preparation process.

11. The preparation method according to claim 9, characterized in that, The base material used in the preparation of the elastic matrix filler includes any one or a combination of at least two of chloroprene rubber, natural rubber, EPDM or nitrile rubber.

12. An application of a three-dimensional gradient negative Poisson's ratio thin-walled composite material, characterized in that, The three-dimensional gradient negative Poisson's ratio thin-walled composite material according to any one of claims 1-8, or the three-dimensional gradient negative Poisson's ratio thin-walled composite material obtained by the preparation method according to any one of claims 9-11, can be used as a dilatational metamaterial in the fields of aerospace, construction engineering, packaging engineering, and automotive engineering.

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