Gradient-designed rotary concave hexagonal negative Poisson's ratio sandwich panel structure and preparation method of gradient-designed rotary concave hexagonal negative Poisson's ratio sandwich panel structure

Abstract

The invention discloses a gradient-designed rotary concave hexagonal negative poisson ratio sandwich panel structure and a preparation method thereof, and relates to the technical field of honeycomb sandwich structures. By reconstructing the core layer structure, the problem that the light weight and the safety cannot be both considered in the design and production process of the vehicle protection structure is solved. The negative Poisson's ratio sandwich panel structure comprises an upper end plate, a lower end plate and a core layer arranged between the upper end plate and the lower end plate. The core layer is of a rotary concave hexagonal negative Poisson's ratio layered structure; the rotary concave hexagonal negative Poisson's ratio layered structure is formed by longitudinally arranging a plurality of single-layer bearing units in a gradient manner; the single-layer bearing unit is formed by transversely arraying a plurality of single bearing units; and each single bearing unit is prepared by performing out-of-plane stretching on rotary concave hexagonal negative Poisson's ratio cell elements. The invention also provides a preparation method of the negative Poisson's ratio sandwich panel structure.

Description

Technical Field

[0001] The present application relates to the technical field of honeycomb sandwich structures, and in particular to a gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure and a preparation method thereof. Background Art

[0002] Poisson's ratio refers to the negative ratio of lateral strain to axial strain when a material is subjected to unidirectional tension or compression. Metamaterials with negative Poisson's ratio effect usually exhibit physical properties such as light weight, high damping, sound absorption, and heat insulation. They play an important role in functional materials and are of great significance to the development of aerospace, semiconductor devices, biomedical instruments and equipment, precision instruments, and building materials.

[0003] Mechanical metamaterials with negative Poisson's ratio effect have excellent mechanical properties and a wide range of applications. However, for the rotated polygonal negative Poisson's ratio structure, previous studies have focused more on rigid and semi-rigid structures. It has research significance, but its application value needs to be studied. Since rigid and semi-rigid materials do not actually exist, previous studies are difficult to apply to actual production and life. However, non-rigid structures are different. Their manufacturability allows them to be truly put into practice.

[0004] Honeycomb materials have the characteristics of light weight, high specific stiffness and strong stability. Compared with solid plates, reasonable internal structure design makes the impact and shock absorption effect of honeycomb materials more perfect and more cost-effective. Moreover, the arrangement of different types of cells will also affect the energy absorption effect of the structure. Compared with the structure with uniform arrangement mode, the reasonable gradient arrangement structure can play a significant role in reducing the initial force peak, enhancing impact resistance and energy absorption capacity. At present, with the development of negative Poisson's ratio materials and additive technology, negative Poisson's ratio structures are widely used in honeycomb sandwich panel structures. The rotated concave hexagonal negative Poisson's ratio structure has different deformation failure modes when crushed, and exhibits excellent energy absorption characteristics.

[0005] In addition, with the increasing popularity of automobiles, it has become an indispensable means of transportation for every family, so its safety has attracted much attention. While meeting the requirements of lightweight to achieve green environmental protection and energy saving, the car must also have good anti-collision and impact resistance to ensure safety. However, existing panel designs often find it difficult to meet these two requirements at the same time: lightweight design may sacrifice safety, while overly heavy designs will affect the economy of the car. Therefore, developing a new structure that allows sandwich panels to achieve both lightweight and safety has become a key issue that needs to be solved urgently. Summary of the invention

[0006] The embodiments of the present application provide a gradient-designed rotated concave hexagonal negative Poisson's ratio sandwich panel structure and a preparation method thereof, which solves the problem of both lightweight and safety being incompatible during the design and production of vehicle protective structures by reconstructing the core layer structure.

[0007] To achieve the above-mentioned objectives, on the one hand, an embodiment of the present application provides a gradient-designed rotated concave hexagonal negative Poisson's ratio sandwich panel structure, comprising an upper end plate, a lower end plate, and a core layer arranged between the upper end plate and the lower end plate; the core layer is a rotated concave hexagonal negative Poisson's ratio layered structure; the rotated concave hexagonal negative Poisson's ratio layered structure is formed by a plurality of single-layer load-bearing units arranged in a longitudinal gradient manner; the single-layer load-bearing unit is formed by a plurality of single load-bearing units arranged in a transverse array; and the single load-bearing unit is obtained by out-of-plane stretching of a rotated concave hexagonal negative Poisson's ratio cell.

[0008] Furthermore, the rotated concave hexagonal negative Poisson's ratio cell includes four concave hexagons; the inclination directions and angles of two adjacent concave hexagons are different, and the two are connected by a connecting rod; the connecting rod is made of the same material as the concave hexagons.

[0009] Furthermore, the single carrying unit is a strip structure.

[0010] Furthermore, the number of the connecting rods is four; two of the connecting rods are respectively arranged on two horizontal sides of the concave hexagon, and the other two connecting rods are respectively arranged at the vertices formed by two oblique sides of the concave hexagon.

[0011] Furthermore, the angle between the two connected connecting rods is adjustable.

[0012] Furthermore, the size and rotation angle of the concave hexagon are adjustable.

[0013] Furthermore, the longitudinal gradient includes a positive gradient, a negative gradient, a symmetric positive gradient or a symmetric negative gradient.

[0014] Furthermore, the concave hexagon close to the upper end plate or the lower end plate is connected to the upper end plate or the lower end plate through a connecting rod.

[0015] Furthermore, the single carrying unit is prepared by 3D printing or wire cutting technology.

[0016] On the other hand, an embodiment of the present application also provides a method for preparing the above-mentioned gradient-designed rotated concave hexagonal negative Poisson's ratio sandwich panel structure, comprising the following steps: S1, selecting an initial negative Poisson's ratio unit cell, and adjusting its size parameters to obtain a rotated concave hexagonal negative Poisson's ratio unit cell with different structural properties; S2, stretching the rotated concave hexagonal negative Poisson's ratio unit cell out-of-plane to obtain a single load-bearing unit; S3, arranging the single load-bearing units laterally to form a single-layer load-bearing unit; S4, arranging each single-layer load-bearing unit longitudinally with a gradient according to preset gradient patterns to form a core layer; S5, fixing the core layer between the upper end plate and the lower end plate.

[0017] Compared with the prior art, this application has the following beneficial effects:

[0018] 1. The gradient-designed rotated inward-concave hexagonal negative Poisson's ratio sandwich panel structure of the embodiment of the present application includes an upper end plate, a lower end plate, and a core layer arranged between the upper end plate and the lower end plate. The core layer is a rotated inward-concave hexagonal negative Poisson's ratio layered structure. The layered structure has a rotated inward-concave hexagonal structure as a cell and has a negative Poisson's ratio effect. When the end plate is subjected to an impact load, the effects of buffering, shock absorption, and energy absorption are stronger than those of a traditional layered sandwich.

[0019] 2. The gradient-designed rotated concave hexagonal negative Poisson's ratio sandwich panel structure of the embodiment of the present application is applied to protective structures such as automobile bodies or energy absorption boxes. While ensuring the lightweight of the automobile, it can absorb more energy when it is impacted, thereby ensuring its safety.

[0020] 3. The rotated concave hexagonal negative Poisson's ratio sandwich panel structure with a gradient design in the embodiment of the present application takes into account the concave hexagonal structure, the rotated structure and the structural gradient design at the same time, and reconstructs the internal structure of the panel layer, thereby solving the problem of being unable to take both lightness and safety into consideration during the automobile design and production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A schematic diagram of the three-dimensional structure of a gradient-designed rotating inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application;

[0023] Figure 2 A front view of a rotated concave hexagonal negative Poisson's ratio sandwich panel structure designed for gradient according to an embodiment of the present application;

[0024] Figure 3A schematic structural diagram of a rotating inward-concave hexagonal negative Poisson's ratio cell in a rotating inward-concave hexagonal negative Poisson's ratio sandwich panel structure with a gradient design according to an embodiment of the present application;

[0025] Figure 4 A schematic diagram of the deformation mechanism of a rotating inward-concave hexagonal negative Poisson's ratio cell in a gradient-designed rotating inward-concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application;

[0026] Figure 5 A trend diagram of the equivalent Poisson's ratio of a rotating concave hexagonal negative Poisson's ratio cell in a gradient-designed rotating concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application as a function of the rotating structure cell angle φ parameter;

[0027] Figure 6 A graph showing a trend of the equivalent Poisson's ratio of a rotating concave hexagonal negative Poisson's ratio cell in a gradient-designed rotating concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application as a function of the cell angle θ parameter of the concave hexagonal structure;

[0028] Figure 7 A graph showing a trend of the equivalent Poisson's ratio of a rotating concave hexagonal negative Poisson's ratio cell in a gradient-designed rotating concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application, as a function of the length-to-height ratio (L / H) of the concave hexagonal structure;

[0029] Figure 8 A schematic structural diagram of a single load-bearing unit in a gradient-designed rotating inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application;

[0030] Fig. 9 A schematic structural diagram of a single-layer load-bearing unit in a gradient-designed rotating inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to an embodiment of the present application;

[0031] Fig.10 Schematic diagram of the core layer with different gradient patterns in the rotated concave hexagonal negative Poisson's ratio sandwich panel structure with gradient design for an embodiment of the present application, wherein (a) is a positive gradient; (b) is a negative gradient; (c) is a symmetric positive gradient; and (d) is a symmetric negative gradient. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0034] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, they can understand the specific meanings of the above terms in this application according to specific circumstances.

[0035] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" can explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0036] Reference Figures 1 to 10 The embodiment of the present application provides a gradient-designed rotated inward-concave hexagonal negative Poisson's ratio sandwich panel structure, comprising an upper end plate 1, a lower end plate 2, and a core layer 3 fixed between the upper end plate 1 and the lower end plate 2. The upper end plate 1 and the lower end plate 2 are metal plates. The core layer 3 is a rotated inward-concave hexagonal negative Poisson's ratio layered structure, which is composed of a single-layer load-bearing unit 4 arranged in a longitudinal gradient. The single-layer load-bearing unit 4 is composed of a plurality of single load-bearing units 5 arranged in a transverse array, and the single load-bearing unit 5 is obtained by out-of-plane stretching of a rotated inward-concave hexagonal negative Poisson's ratio cell 6.

[0037] The rotated inwardly concave hexagonal negative Poisson's ratio cell 6 can form different single load-bearing units 5 by adjusting the cell size and rotation angle, and then stretched outward. The single load-bearing unit 5 is a strip structure. The single load-bearing unit 5 can be prepared by 3D printing or wire cutting technology. Different single load-bearing units 5 can be arranged in different horizontal arrays to form different single-layer load-bearing units 4. The single-layer load-bearing units 4 are connected by connecting rods 8 to form the whole sandwich layer 2. Different arrangement patterns form different gradients. Fig.10 (a) to (d), the gradient modes include positive gradient, negative gradient, symmetric positive gradient or symmetric negative gradient, etc. Different gradient modes form different core layers 3 .

[0038] The rotated concave hexagonal negative Poisson's ratio cell 6 can be a concave hexagonal cell with any parameters. Specifically, the rotated concave hexagonal negative Poisson's ratio cell 6 includes four concave hexagons 7. The concave hexagons 7 of the same cell or adjacent cells are connected by connecting rods 8. The number of connecting rods 8 is four. Two connecting rods 8 are respectively arranged on the two horizontal sides of the concave hexagon 7, and the other two connecting rods 8 are respectively arranged at the vertices formed by the two hypotenuses of the concave hexagon 7. The two connecting rods 8 of two adjacent concave hexagons 7 are connected to each other, and the angle between the two can be any angle. The concave hexagon 7 close to the upper end plate 1 or the lower end plate 2 is also connected to the upper end plate 1 or the lower end plate 2 through the connecting rod 8. That is, the concave hexagon 7 and the concave hexagons 7 or the upper end plate 1 and the lower end plate 2 in front, behind, left and right are connected by connecting rods 8. The length of the connecting rod 8 can be determined according to actual conditions. The rotation angle of the concave hexagon 7 can be any angle.

[0039] Reference Figure 3 , the rotated concave hexagonal negative Poisson's ratio cell 6 uses the same material as a whole, for example, a lightweight material. The in-plane thickness is t, the out-of-plane thickness is b, the concave hexagonal cell angle is θ, the length and height of the concave hexagon are L and H respectively, and the rotated structure cell angle is φ. Because its equivalent Poisson's ratio expression is too complicated, it is not shown here.

[0040] In summary, the gradient-designed rotated concave hexagonal negative Poisson's ratio sandwich panel structure of the present application reconstructs the internal structure of the layers of the new sandwich panel, and can obtain a lightweight and energy-absorbing mechanical metamaterial structure for use in protective structures.

[0041] On the other hand, an embodiment of the present application further provides a method for preparing the above-mentioned gradient-designed rotated concave hexagonal negative Poisson's ratio sandwich panel structure, comprising the following steps:

[0042] S1. Select an initial negative Poisson's ratio unit cell and adjust its geometric parameters to obtain a rotated concave hexagonal negative Poisson's ratio unit cell 6 with different structural properties.

[0043] S2. The determined cells are stretched out of the plane to form a single load-bearing unit, that is, the rotated concave hexagonal negative Poisson's ratio cell 6 is stretched out of the plane to obtain a single load-bearing unit 5.

[0044] S3, the single load-bearing units 5 are arranged in a horizontal array to form a single-layer load-bearing unit 4. The single load-bearing units 5 after the array are connected by connecting rods 8.

[0045] S4, according to each preset gradient mode, the corresponding single-layer bearing units 4 are arranged longitudinally in a gradient manner to form a core layer 3. The gradient mode includes positive gradient, negative gradient, symmetric positive gradient or symmetric negative gradient, etc.

[0046] S5. Fix the core layer 3 between the upper end plate 1 and the lower end plate 2 through the connecting rod 8.

[0047] As an important part of the vehicle's passive safety system, the main function of the automobile energy absorption box is to quickly absorb and dissipate the kinetic energy generated by external impact loads through the plastic deformation mechanism. The rotating concave hexagonal negative Poisson's ratio sandwich panel structure with a gradient design in the embodiment of the present application is applied to the design of the automobile energy absorption box. By optimizing the number of layers of the rotating concave hexagonal negative Poisson's ratio layered structure sandwich layer, the structural assembly requirements of the crash box can be effectively met.

[0048] Reference Figures 5 to 7 The impact dynamics simulation analysis results of the gradient-designed rotating inward-concave hexagonal negative Poisson's ratio sandwich panel structure in the embodiment of the present application show that the rotating inward-concave hexagonal negative Poisson's ratio layered structure sandwich layer has significantly improved the unit mass energy absorption performance index compared with the traditional structure, and the use of a multi-layer sandwich layer configuration can maximize the energy absorption efficiency of the energy absorption box. This structural design not only achieves the goal of lightweighting, but also significantly improves the passive safety performance of the vehicle, thereby providing better safety protection for the occupants.

[0049] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A gradient-designed rotating concave hexagonal negative Poisson's ratio sandwich panel structure, characterized in that: It includes an upper end plate, a lower end plate, and a core layer arranged between the upper end plate and the lower end plate; the core layer is a rotating concave hexagonal negative Poisson's ratio layered structure; the rotating concave hexagonal negative Poisson's ratio layered structure is formed by a plurality of single-layer bearing units arranged in a longitudinal gradient; the single-layer bearing unit is formed by a plurality of single bearing units arranged in a transverse array; A single load-bearing unit is made by out-of-plane stretching of a rotated concave hexagonal negative Poisson's ratio cell.

2. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 1, characterized in that: The rotated concave hexagonal negative Poisson's ratio cell includes four concave hexagons; the inclination directions and angles of two adjacent concave hexagons are different, and the two are connected by a connecting rod; the connecting rod is made of the same material as the concave hexagons.

3. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 1, characterized in that: The single carrying unit is a strip structure.

4. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 2, characterized in that: The number of the connecting rods is four; two of the connecting rods are respectively arranged on two horizontal sides of the concave hexagon, and the other two connecting rods are respectively arranged at the vertices formed by two oblique sides of the concave hexagon.

5. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 1, characterized in that: The angle between the two connected connecting rods is adjustable.

6. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 2, characterized in that: The size and rotation angle of the concave hexagon are adjustable.

7. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 1, characterized in that: The longitudinal gradient includes a positive gradient, a negative gradient, a symmetric positive gradient or a symmetric negative gradient.

8. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 2, characterized in that: The concave hexagon close to the upper end plate or the lower end plate is connected to the upper end plate or the lower end plate through a connecting rod.

9. The gradient-designed rotated inwardly concave hexagonal negative Poisson's ratio sandwich panel structure according to claim 1, characterized in that: The single carrying unit is prepared by 3D printing or wire cutting technology.

10. A method for preparing a gradient-designed rotating inward-concave hexagonal negative Poisson's ratio sandwich panel structure based on any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Select the initial negative Poisson's ratio unit cell and adjust its size parameters to obtain a rotated concave hexagonal negative Poisson's ratio unit cell with different structural properties; S2, stretching the rotated inwardly concave hexagonal negative Poisson's ratio cell out of the plane to obtain a single load-bearing unit; S3, arranging the single load-bearing units in a horizontal array to form a single-layer load-bearing unit; S4, arranging each single-layer load in a longitudinal gradient manner according to each preset gradient mode to form a core layer; S5. Fix the core layer between the upper end plate and the lower end plate.

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