A layered electromagnetic wave absorbing metamaterial and its preparation method and application

Abstract

The present invention provides a layered electromagnetic wave absorbing metamaterial, a preparation method thereof and an application thereof. The material includes an absorbing unit formed by connecting a plurality of structural elements with regular geometric shapes up and down; a plurality of identical and / or different absorbing units are rotationally combined and periodically arranged on the same plane, and the absorbing units are connected by a filling material; or a plurality of the absorbing units are arranged in a grid matching the size and arrangement period of the absorbing unit, and a filling material is arranged between the absorbing unit and the grid; a skin is arranged on the surface of the absorbing unit or / and between the structural elements. This material has adjustable loss ability and impedance matching ability, and can realize the tunability of electromagnetic wave absorption performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and particularly relates to a layered electromagnetic wave absorbing metamaterial and a preparation method and application thereof. Background Art

[0002] With the progress of technology, the phenomena of electromagnetic pollution and electromagnetic interference are becoming increasingly serious, which will not only have an adverse impact on human health, but also cause certain interference to the operation of electromagnetic devices. Moreover, in the field of absorption and interference of radar detection signals, the performance requirements for wave-absorbing materials are gradually increasing with the improvement of radar detection technology. Therefore, the demand and performance requirements for wave-absorbing materials are increasing day by day.

[0003] A wave-absorbing metamaterial is an array material of structured sub-wavelength elements. By designing the material at the sub-wavelength scale and arranging each structural unit as a new "molecular" structure of the material, an artificial composite structure or composite material with extraordinary physical properties not possessed by natural materials can be formed, which can be used as an optimization and improvement of existing wave-absorbing materials.

[0004] However, the current electromagnetic wave absorbing metamaterials do not have adjustable loss ability and impedance matching ability, and cannot achieve the tunability of electromagnetic wave absorption performance, and cannot meet the requirements for the tunability of electromagnetic wave absorption performance in different application environments.

[0005] Therefore, there is an urgent need for a layered electromagnetic wave absorbing metamaterial with adjustable loss ability and impedance matching ability. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a layered electromagnetic wave absorbing metamaterial with adjustable loss ability and impedance matching ability, which can realize the tunability of electromagnetic wave absorption performance, and a preparation method and application thereof.

[0007] To solve the above technical problem, the present invention provides a layered electromagnetic wave absorbing metamaterial, which includes wave-absorbing units connected up and down by multiple layers of structural elements with regular geometric shapes;

[0008] A number of the same or / and different wave-absorbing units are rotationally combined and periodically arranged on the same plane, and the wave-absorbing units are connected by a filling material; or

[0009] A number of the wave-absorbing units are arranged in a grid matching the size and arrangement period of the wave-absorbing units, and a filling material is arranged between the wave-absorbing units and the grid;

[0010] A skin is arranged on the surface of the wave-absorbing unit or / and between the structural elements.

[0011] Further, the structural element of the wave-absorbing unit is in the shape of the same or / and different axisymmetric figures, and an angle is formed between the axes of the upper and lower layer structural elements and they are stacked at intervals; or

[0012] The structural element of the wave-absorbing unit is in the shape of a radially symmetric figure, and the upper and lower layer structural elements are stacked with a dislocation and at intervals.

[0013] Further, the shape of the structural element being an axisymmetric figure includes but is not limited to semi-circular, sector-shaped, triangular, strip-shaped or square; the shape of the structural element being a radially symmetric figure includes but is not limited to circular.

[0014] Further, the thickness of the structural element is 0.1 - 30 mm, and the distance between the upper and lower layers of the structural element is not more than 20 mm.

[0015] Further, the arrangement period of the wave-absorbing units is 0.1 - 100 mm, and the distance between the wave-absorbing units is not more than 100 mm.

[0016] Further, the structural elements are connected by a viscous wave-transparent material; the wave-absorbing unit and the skin are connected by a viscous wave-transparent material.

[0017] Further, the material of the structural element is a material with wave-absorbing performance;

[0018] The filling material is a wave-transparent material;

[0019] The materials of the skin and the grid are wave-transparent materials;

[0020] The viscous wave-transparent material is phenolic resin or epoxy resin.

[0021] The present invention also provides a preparation method of a layered electromagnetic wave-absorbing metamaterial, including the following steps:

[0022] Select a material with wave-absorbing performance and process it into a structural element in the shape of an axisymmetric figure or / and a radially symmetric figure;

[0023] Stack the structural elements in the shape of axisymmetric figures with an angle between the axes of the upper and lower layer structural elements not more than 360° and a distance not more than 100 mm, or stack the structural elements in the shape of radially symmetric figures with a dislocation and a distance not more than 100 mm between the upper and lower layer structural elements;

[0024] Bond the upper and lower layer structural elements with a viscous wave-transparent material or bond them with a viscous wave-transparent material after arranging a skin between the upper and lower layer structural elements to obtain a wave-absorbing unit;

[0025] Partially rotate and combine the wave-absorbing units with the same or / and different shapes of the structural elements and arrange them in an array periodic arrangement on the same plane at an interval not more than 100 mm;

[0026] After setting a filling material between the periodically arranged wave-absorbing units, the module is integrally formed;

[0027] Covering the top of the integrally formed wave-absorbing units with a skin results in a layered electromagnetic wave-absorbing metamaterial.

[0028] Furthermore, the wave-absorbing unit parts with the same or / and different structural element shapes are rotated and combined, and then placed in a grid matching the size and arrangement period of the wave-absorbing units at intervals not greater than 100 mm for arrayed periodic arrangement;

[0029] After setting a filling material between the wave-absorbing units and the grid, the module is integrally formed;

[0030] Covering the top of the integrally formed wave-absorbing units with a skin results in a layered electromagnetic wave-absorbing metamaterial.

[0031] A layered electromagnetic wave-absorbing metamaterial provided by the present invention can be applied to an adjustable electromagnetic wave-absorbing laminate or / and an electromagnetic protection plate.

[0032] A layered electromagnetic wave-absorbing metamaterial provided by the present invention has a special structural design of layered dislocation configuration for the structural elements in the wave-absorbing metamaterial, and the wave-absorbing units in the wave-absorbing metamaterial are rotated and combined for arrayed periodic arrangement on the same plane, which can greatly improve the overall impedance ability and loss ability of the electromagnetic wave-absorbing metamaterial, and can reduce the maximum flat plate reflectivity of the layered electromagnetic wave-absorbing metamaterial in the full frequency band of 2 - 18 GHz to below -10 dB, and even the maximum flat plate reflectivity in some frequency bands is as low as -15 dB.

[0033] Moreover, a layered electromagnetic wave-absorbing metamaterial provided by the present invention can adjust the loss ability and impedance matching ability of the layered electromagnetic wave-absorbing metamaterial by adjusting the angle between the axes of the upper and lower regular geometric structural elements in the wave-absorbing unit, adjusting the distance between the upper and lower structural elements, and adjusting the discrete distance between the wave-absorbing units, so as to realize the tunability of the electromagnetic wave absorption performance of the layered electromagnetic wave-absorbing metamaterial. Therefore, in practical applications, the electromagnetic wave absorption performance of the electromagnetic wave-absorbing metamaterial can be adjusted by adjusting the structural changes of the electromagnetic wave-absorbing metamaterial, so that it has good broadband tunable electromagnetic wave absorption performance to meet the requirements of the tunability of the electromagnetic wave absorption performance in different application environments, and can be widely applied to devices such as adjustable electromagnetic wave-absorbing laminates and electromagnetic protection plates of equipment.

[0034] Meanwhile, a layered electromagnetic wave absorbing metamaterial provided by the present invention has a simple structure, is easy to prepare, and has a low density. Through various different arrangement and combination methods, it is conducive to modular assembly design. Moreover, according to the design idea of layered construction, the design idea of the wave absorbing metamaterial of the present invention can be extended to other frequency bands to achieve effective absorption in multiple frequency bands, and has good editability of wave absorbing performance. Description of the Drawings

[0035] Figure 1 It is a flowchart of the preparation method of the layered electromagnetic wave absorbing metamaterial provided by the embodiment of the present invention;

[0036] Figure 2 It is a schematic structural diagram of the wave absorbing unit prepared by the preparation method of the layered electromagnetic wave absorbing metamaterial provided by Embodiment 1 of the present invention;

[0037] Figure 3 It is a flat plate reflectivity curve graph of the layered electromagnetic wave absorbing metamaterial prepared by the preparation method provided by Embodiment 1 of the present invention;

[0038] Figure 4 It is a schematic structural diagram of the wave absorbing unit prepared by the preparation method of the layered electromagnetic wave absorbing metamaterial provided by Embodiment 2 of the present invention;

[0039] Figure 5 It is a flat plate reflectivity curve graph of the layered electromagnetic wave absorbing metamaterial prepared by the preparation method provided by Embodiment 2 of the present invention;

[0040] Figure 6 It is a schematic structural diagram of the wave absorbing unit prepared by the preparation method of the layered electromagnetic wave absorbing metamaterial provided by Embodiment 3 of the present invention;

[0041] Figure 7 It is a flat plate reflectivity curve graph of the layered electromagnetic wave absorbing metamaterial prepared by the preparation method provided by Embodiment 3 of the present invention. Detailed Embodiments

[0042] A layered electromagnetic wave absorbing metamaterial provided by an embodiment of the present invention includes a wave absorbing unit formed by connecting multiple structural elements with regular geometric shapes up and down. Among them, the shape of the structural element with a regular geometric shape can be, including but not limited to, the shape of an axisymmetric figure such as a semi-circular shape, a fan shape, a triangular shape, a strip shape, or a square shape, or can also be the shape of a radially symmetric figure including but not limited to a circular shape. Moreover, the multiple structural elements of the wave absorbing unit can be respectively connected up and down with several different geometric shapes, so that wave absorbing units with various different structural elements can be formed.

[0043] As a specific embodiment of the present invention, several absorbing units are combined after being partially rotated by 90°, and then periodically arranged on the same plane. The absorbing units are connected and fixed by the filling material filled between them. Moreover, the arrangement period of the absorbing units is 0.1 - 100 mm, and the discrete distance between adjacent two absorbing units, that is, the spacing between adjacent two absorbing units, is controlled to be no greater than 100 mm.

[0044] By controlling the spacing between the absorbing units, the loss ability and impedance matching ability of the layered electromagnetic wave absorbing metamaterial can be adjusted, so as to realize the tunability of the electromagnetic wave absorption performance of the layered electromagnetic wave absorbing metamaterial.

[0045] Among them, as various specific embodiments of the present invention, the shapes of the structural elements of several periodically arranged absorbing units can all be the same shape. Or the shapes of the structural elements of several periodically arranged absorbing units are all different shapes. Of course, the structural elements of several periodically arranged absorbing units can also be such that some have the same shape and some have different shapes.

[0046] In this way, through the permutation and combination of several absorbing units with different or the same various structural elements, it is beneficial to the modular assembly design of the electromagnetic wave absorbing metamaterial. And in accordance with the design idea of layered construction, the design idea of the wave absorbing metamaterial can be extended to other frequency bands to achieve effective absorption in multiple frequency bands, and it has good editability of wave absorption performance.

[0047] As another specific embodiment of the present invention, several absorbing units with the same or different shapes of structural elements can also be respectively and sequentially placed in grids matching the size and arrangement period of the absorbing units for fixation, and the filling material is filled between the absorbing units and the grids to connect each absorbing unit.

[0048] Moreover, a skin is covered on the surface of the absorbing units after periodic arrangement, and the absorbing units and the skin are bonded by a viscous wave-transmitting material.

[0049] As a specific embodiment of the present invention, when the shape of the structural element of the absorbing unit is an axisymmetric graphic shape such as a semicircle, a sector, a triangle, a strip or a square, when the upper and lower layer structural elements are stacked, the angle between the axes of the upper and lower layer structural elements is no greater than 360°, and the spacing between the upper and lower layer structural elements is controlled to be no greater than 20 mm.

[0050] By controlling the angle between the axes of the upper and lower layer structural elements and the spacing between the upper and lower layer structural elements, the loss ability and impedance matching ability of the layered electromagnetic wave absorbing metamaterial can be adjusted, so as to realize the tunability of the electromagnetic wave absorption performance of the layered electromagnetic wave absorbing metamaterial.

[0051] As a specific embodiment of the present invention, when the shape of the structural element of the wave-absorbing unit is a circular or other radiation-symmetrical graphic shape, the upper and lower layer structural elements are stacked in a staggered manner, and the distance between the upper and lower layer structural elements is not greater than 20 mm.

[0052] Among them, the thickness of each layer of structural elements in the wave-absorbing unit is controlled within 0.1 - 30 mm, and the upper and lower layer structural elements are connected by a viscous wave-transmitting material.

[0053] Of course, as a specific embodiment of the present invention, a skin can also be first provided between the upper and lower layer structural elements, and then the skin and the structural elements are bonded by a viscous wave-transmitting material.

[0054] Among them, the material of the structural element is a material with wave-absorbing properties, and these materials can be materials such as framework silicon carbide, framework carbon, carbon nanotubes, chopped carbon fibers, iron silicon aluminum carbide, carboxyl iron carbide, or carbon-based ferromagnetic materials.

[0055] Among them, the filling material is a wave-transmitting material with a low dielectric constant, which can be methyl methacrylate, or polyurethane foaming agent, or a mixture of methyl methacrylate and polyurethane foaming agent.

[0056] Among them, the skin material is a wave-transmitting material such as cyanate ester quartz fiber, epoxy resin quartz fiber, glass microsphere composite material, bismaleimide, etc.

[0057] Among them, the grid material is a wave-transmitting material such as cyanate ester quartz fiber, epoxy resin quartz fiber, bismaleimide, etc.

[0058] Among them, the viscous wave-transmitting material is phenolic resin or epoxy resin.

[0059] For the layered electromagnetic wave-absorbing metamaterial provided by the present invention, wave-absorbing materials such as silicon carbide are selected as the material of the structural element of the wave-absorbing unit, which can make full use of excellent electromagnetic properties such as scattering, diffraction, and polarization enhancement caused by the frame structure. Moreover, by adopting a layered structure for the structural element of the wave-absorbing unit and designing the shape of the structural element, the impedance matching ability of the layered electromagnetic wave-absorbing metamaterial is improved. At the same time, by controlling the angle and distance between the upper and lower layer structural elements and the discrete distance of the wave-absorbing unit, the overall impedance and loss of the layered electromagnetic wave-absorbing metamaterial can be adjusted, not only improving the electromagnetic wave absorption ability of the layered electromagnetic wave-absorbing metamaterial, but also realizing the tunability of the electromagnetic wave absorption performance.

[0060] See Figure 1 , the preparation method of a layered electromagnetic wave-absorbing metamaterial provided by the present invention includes the following steps:

[0061] Step 1) Select a material with wave-absorbing properties and process it into a structural element with an axisymmetric or / and radiation-symmetrical graphic shape.

[0062] Among them, the structural element material can be materials with wave absorption properties such as framework silicon carbide, framework carbon, carbon nanotubes, chopped carbon fibers, iron silicon aluminum carbide, carboxy iron carbide, or carbon-based ferromagnetic materials.

[0063] Among them, the structural element can be processed into a shape including an axisymmetric figure such as a semi-circular shape, a sector shape, a triangular shape, a strip shape, or a square shape, or the structural element can be processed into a shape including a radially symmetric figure such as a circular shape, and the thickness of the structural element is processed to be 0.1 - 30 mm.

[0064] Step 2) Select structural elements in the shape of an axisymmetric figure such as a semi-circular shape, a sector shape, a triangular shape, a strip shape, or a square shape, stack the structural elements in the shape of an axisymmetric figure up and down, and make the axes of the upper and lower layer structural elements form an angle not greater than 360°.

[0065] As another specific embodiment of the present invention, if a structural element in the shape of a radially symmetric figure such as a circular shape is selected, then the structural elements in the shape of a radially symmetric figure are stacked in a staggered manner between the upper and lower layers.

[0066] Step 3) Use a viscous wave-transparent material to bond the multi-layer structural elements together between the upper and lower layer structural elements to obtain an electromagnetic wave absorption unit, or first set a skin between the upper and lower layer structural elements, and then use a viscous wave-transparent material to bond the structural elements together to obtain an electromagnetic wave absorption unit.

[0067] Among them, after the structural elements are bonded together with a viscous wave-transparent material, or after a skin is set between the structural elements and then bonded, the distance between the structural elements is controlled to be not greater than 20 mm.

[0068] Step 4) Rotate and combine a certain number of electromagnetic wave absorption units and arrange them in an array periodic arrangement on the same plane. That is, electromagnetic wave absorption units with the same shape of structural elements can be rotated and combined and arranged in an array periodic arrangement on the same plane. Electromagnetic wave absorption units with different shapes of structural elements can also be rotated and combined and arranged in an array periodic arrangement on the same plane. At the same time, electromagnetic wave absorption units with the same shape of some structural elements and electromagnetic wave absorption units with different shapes of some structural elements can also be rotated and combined and arranged in an array periodic arrangement on the same plane.

[0069] Moreover, when the electromagnetic wave absorption units are arranged periodically, the distance between the electromagnetic wave absorption units is controlled to be not greater than 100 mm.

[0070] By adjusting the angle between the axes of the upper and lower layer regular geometric shape structural elements in the electromagnetic wave absorption unit, adjusting the distance between the upper and lower layer structural elements, and adjusting the discrete distance between the electromagnetic wave absorption units, the loss ability and impedance matching ability of the layered electromagnetic wave absorption metamaterial can be adjusted, and the tunability of the electromagnetic wave absorption performance of the layered electromagnetic wave absorption metamaterial can be realized.

[0071] Step 5) After filling the filler material between the periodically arranged wave-absorbing units, perform module integration molding. The filler material is a wave-transmitting material with a low dielectric constant, which can be methacrylic acid, or polyurethane foaming agent, or a mixture of methacrylic acid and polyurethane foaming agent.

[0072] Step 6) Cover the top of the integrated wave-absorbing units with a skin to obtain the layered electromagnetic wave-absorbing metamaterial. The wave-absorbing units and the skin are bonded through a viscous wave-transmitting material. The skin material is a wave-transmitting material such as cyanate quartz fiber, epoxy resin quartz fiber, glass microsphere composite material, bismaleimide, etc. The viscous wave-transmitting material is phenolic resin or epoxy resin.

[0073] As another specific embodiment of the present invention, after the structural elements are used to construct the wave-absorbing units, the wave-absorbing units can also be partially rotated and combined and then placed in a grid that matches the size and arrangement period of the wave-absorbing units for array-type periodic fixed arrangement. That is, the wave-absorbing units with the same shape of the structural elements can be partially rotated and combined and then placed in a grid that matches the size and arrangement period of the wave-absorbing units for array-type periodic fixed arrangement. The wave-absorbing units with different shapes of the structural elements can also be partially rotated and combined and then placed in a grid that matches the size and arrangement period of the wave-absorbing units for array-type periodic fixed arrangement. At the same time, the wave-absorbing units with the same shape of a part of the structural elements and the wave-absorbing units with different shapes of a part of the structural elements can also be partially rotated and combined and then placed in a grid that matches the size and arrangement period of the wave-absorbing units for array-type periodic fixed arrangement.

[0074] Moreover, when the wave-absorbing units are arranged periodically, the distance between the wave-absorbing units is controlled to be no more than 100 mm.

[0075] Then, fill the filler material between the wave-absorbing units and the grid and perform module integration molding.

[0076] Finally, cover the top of the integrated wave-absorbing units with a skin to obtain the layered electromagnetic wave-absorbing metamaterial.

[0077] The grid material is a wave-transmitting material such as cyanate quartz fiber, epoxy resin quartz fiber, bismaleimide, etc.

[0078] In practical applications, the electromagnetic wave absorption performance of the electromagnetic wave-absorbing metamaterial can be adjusted by adjusting the structural changes of the electromagnetic wave-absorbing metamaterial, so that it has good broadband tunable electromagnetic wave absorption performance to meet the requirements of tunable electromagnetic wave absorption performance in different application environments. Therefore, the prepared layered electromagnetic wave-absorbing metamaterial of the present invention can be widely applied to devices such as adjustable electromagnetic wave-absorbing laminates and electromagnetic protection shields of equipment.

[0079] The following specifically describes the preparation method of the layered electromagnetic wave-absorbing metamaterial provided by the present invention through several embodiments.

[0080] Example 1

[0081] Refer to Figure 2 , select framework silicon carbide as the material of structural element 11, and process it into a triangular sheet-shaped structural element 11 with a side length of 20 mm and a thickness of 4 mm. Stack two triangular sheet-shaped structural elements 11 up and down with an included angle of 61° between their axes. The connection part of the upper and lower two structural elements 11 is bonded with epoxy resin with a thickness of 0.1 mm. The two connected triangular sheet-shaped structural elements form an absorbing unit 1. According to the direct periodic rotation symmetry distribution arrangement method, a certain number of absorbing units 1 are bonded to a 300 mm * 300 mm bottom plate with epoxy resin, and the distance between the absorbing units 1 is 10 mm. Then, after placing the periodically arranged absorbing units 1 into a mold, use polymethacrylimide foam as the filling material 12 to fill between the absorbing units 1. After the curing is completed, process the material into a 300 mm * 300 mm flat material, and cover a 0.5 mm thick cyanate quartz fiber on the top of the material as the skin 13. The skin 13 and the flat material are bonded with thin epoxy resin with a thickness of 0.1 mm. In this way, a layered electromagnetic wave absorbing metamaterial is obtained.

[0082] Adopt the bow method to test the flat reflectivity of the layered electromagnetic wave absorbing metamaterial prepared in this example on a vector network analyzer. The flat reflectivity of the layered electromagnetic wave absorbing metamaterial in the 2 - 18 GHz frequency band is as Figure 3 shown. It can be seen from Figure 3 that the flat reflectivity of the layered electromagnetic wave absorbing metamaterial prepared in this example is lower than -10 dB in the 2 - 18 GHz frequency band, and less than -15 dB in some frequency bands. Therefore, the layered electromagnetic wave absorbing metamaterial prepared in this example has excellent electromagnetic wave absorption performance.

[0083] Example 2

[0084] Refer to Figure 4, a carbon framework plate composed of carbon nanotubes with a thickness of 4 mm is selected as the material of the structural element 21, and processed into a sheet-shaped structural element 21 with a triangular side length of 30 mm and a thickness of 6 mm. Two sheet-shaped structural elements 21 are stacked up and down with an included angle of 105° between their axes. The connection between the upper and lower two structural elements 21 is bonded with a thin epoxy resin with a thickness of 0.15 mm. The two connected triangular sheet-shaped structural elements 21 form an absorbing unit 2. According to the method of direct periodic arrangement and a 90° rotation periodic arrangement with adjacent two absorbing units 2, the absorbing units 2 are respectively bonded to a 300 mm * 300 mm bottom plate with epoxy resin. The distance between the absorbing units 2 is 6 mm. Then, a bismaleimide grid 22 with a period of 30 mm * 30 mm and a wall thickness of 2 mm is used to isolate the absorbing units 2. After being placed in a mold, polymethacrylimide foam is used as the filling material 23 to fill between the absorbing units 2 and the grid 22 material. After the curing is completed, the material is processed into a 300 mm * 300 mm flat plate material, and then a 1 mm thick epoxy quartz fiber is covered on the top of the material as the skin 24. The skin 24 and the flat plate material are bonded with a thin epoxy resin with a thickness of 0.5 mm. In this way, a layered electromagnetic wave absorbing metamaterial is obtained.

[0085] Using the bow method, the flat reflectivity of the layered electromagnetic wave absorbing metamaterial prepared in this embodiment is measured on a vector network analyzer. The flat reflectivity of the obtained layered electromagnetic wave absorbing metamaterial in the 2 - 18 GHz frequency band is as Figure 5 shown. From Figure 5 it can be seen that the flat reflectivity of the layered electromagnetic wave absorbing metamaterial prepared in this embodiment in the 2 - 18 GHz frequency band is lower than -10 dB. Therefore, the layered electromagnetic wave absorbing metamaterial prepared in this embodiment has excellent electromagnetic wave absorption performance.

[0086] Example 3

[0087] See Figure 6, a frame silicon carbide plate is selected as the material of the first structural element 31, and processed into a square structural element 31 with a size of 31*31*4 mm as the top-layer wave-absorbing material; then a frame silicon carbide plate is selected as the material of the second structural element 31, and processed into a strip-shaped structural element 31 with a size of 27*27*3 mm as the second-layer wave-absorbing material; then a frame silicon carbide plate is selected as the material of the third structural element 31, and processed into a square structural element 31 with a size of 26*26*6 mm as the bottom-layer wave-absorbing material. The bottom-layer wave-absorbing material is bonded to the skin material 32 made of a layer of epoxy fiberglass at a period of 50 mm with 0.1 mm thick epoxy resin. Then, epoxy fiberglass with a period of 50 and a wall thickness of 2 mm is selected as the grid 33 to isolate the wave-absorbing units 3. The top is covered with a skin 32 made of a second layer of epoxy fiberglass. The second-layer wave-absorbing material, the top-layer wave-absorbing material and the grid 33 are assembled in this way in turn, with a period of 50 mm. The top-layer wave-absorbing material and the second-layer wave-absorbing material are placed crosswise, with an included angle of 89°. A 0.2 mm thick epoxy glass is covered between layers and on the top as the skin 32, and the joints are bonded and fixed with 0.1 mm thick epoxy resin. In this way, the wave-absorbing unit 3 is formed. After the wave-absorbing unit 3 is placed in the mold, polyurethane foam is used as the filling material 34 to fill the space between the wave-absorbing unit 3 and the grid 33. After curing, the wave-absorbing unit 3 is processed into a flat plate material with a size of 300 mm*300 mm. A 0.6 mm thick epoxy fiberglass is covered on the top of the flat plate material as the skin 32, and the skin 32 and the flat plate material are bonded with 0.3 mm thick thin epoxy resin. In this way, the layered electromagnetic wave-absorbing metamaterial is obtained.

[0088] Using the bow method, the flat reflectivity of the layered electromagnetic wave-absorbing metamaterial prepared in this embodiment is tested on a vector network analyzer. The flat reflectivity of the obtained layered electromagnetic wave-absorbing metamaterial in the 2-18 GHz frequency band is as Figure 7 shown. From Figure 7 it can be seen that the flat reflectivity of the wave-absorbing material of the layered electromagnetic wave-absorbing metamaterial prepared in this embodiment is lower than -10 dB in the 2-18 GHz frequency band, and less than -15 dB in some frequency bands. Therefore, the layered electromagnetic wave-absorbing metamaterial prepared in the embodiment of the present invention has excellent electromagnetic wave absorption performance.

[0089] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A layered electromagnetic absorbing metamaterial, characterized in that: It includes a wave absorbing unit formed by connecting multiple layers of structural primitives of regular geometric shapes up and down; When the structural primitives of the absorbing unit are the same or / and different axisymmetric figures, the axes of the upper and lower structural primitives form an angle of no more than 360° and are stacked at intervals; when the structural primitives of the absorbing unit are radially symmetrical figures, the upper and lower structural primitives are staggered and stacked at intervals; The material of the structural unit is a material with wave absorbing performance; The shape of the structural element being an axisymmetric figure includes, but is not limited to, a semicircle, a fan, a triangle, a bar or a square; the shape of the structural element being a radially symmetrical figure includes, but is not limited to, a circle; The spacing between the upper and lower layers of the structural element is not greater than 20 mm; A plurality of identical or / and different absorbing units are rotated and combined to be periodically arranged on the same plane, and the absorbing units are connected by filling materials, or a plurality of identical or / and different absorbing units are arranged in a grid matching the size and arrangement period of the absorbing units, and filling materials are arranged between the absorbing units and the grid; The spacing between the absorbing units is no more than 100 mm; A skin is arranged on the surface of the absorbing unit and / or between the structural elements.

2. The layered electromagnetic absorbing metamaterial according to claim 1, characterized in that: The thickness of the structural element is 0.1-30 mm.

3. The layered electromagnetic absorbing metamaterial according to claim 2, characterized in that: The arrangement period of the wave absorbing units is 0.1-100 mm.

4. The layered electromagnetic absorbing metamaterial according to claim 3, characterized in that: The structural elements are connected to each other through a viscous wave-transmitting material; the wave-absorbing unit and the skin are connected to each other through a viscous wave-transmitting material.

5. The layered electromagnetic absorbing metamaterial according to claim 4, characterized in that: The filling material is a wave-transmitting material; The material of the skin and the grid is a wave-transmitting material; The viscous wave-transmitting material is phenolic resin or epoxy resin.

6. A method for preparing the layered electromagnetic absorbing metamaterial according to any one of claims 1 to 5, characterized in that: The steps include: Select materials with wave-absorbing properties and process them into structural elements in the shape of axisymmetric patterns or / and radially symmetrical patterns; The structural primitives of the axially symmetrical shape are stacked with the axis angle of the upper and lower structural primitives being no greater than 360° and the spacing being no greater than 100 mm, or the structural primitives of the upper and lower layers of the radially symmetrical shape are stacked with the offset and spacing being no greater than 100 mm; The upper and lower structural elements are bonded with a viscous wave-transmitting material or a skin is provided between the upper and lower structural elements and then bonded with a viscous wave-transmitting material to obtain a wave-absorbing unit; The wave absorbing units of the same or / and different structural unit shapes are rotated and combined and periodically arranged in an array on the same plane at intervals of no more than 100 mm; After the filling material is arranged between the periodically arranged absorbing units, the module is integrated into a single unit; A layered electromagnetic absorbing metamaterial is obtained by providing a skin on the top of the integrated absorbing unit.

7. The method for preparing the layered electromagnetic absorbing metamaterial according to claim 6, characterized in that: The wave absorbing units of the same or / and different structural unit shapes are rotated and combined, and then placed in a grid matching the size and arrangement period of the wave absorbing units at a spacing of no more than 100 mm and arranged in an array-like periodic manner; After the filling material is arranged between the absorbing unit and the grid, the module is integrated into one piece; A layered electromagnetic absorbing metamaterial is obtained by providing a skin on the top of the integrated absorbing unit.

8. An application of a layered electromagnetic absorbing metamaterial, characterized in that: The layered electromagnetic absorbing metamaterial according to any one of claims 1 to 5 is applied to an adjustable electromagnetic absorbing layer plate and / or an electromagnetic protection plate.

Images