CN118825634A - Ultra-wideband wave-absorbing honeycomb sandwich structure and preparation method thereof - Google Patents

Abstract

The present invention discloses an ultra-wideband absorbing honeycomb sandwich structure and a preparation method thereof. The structure comprises an upper panel, an absorbing honeycomb and a lower panel arranged in sequence from top to bottom. The upper panel is a metamaterial panel, the absorbing honeycomb is formed by impregnating a honeycomb structure with a high-scattering dielectric conductive slurry, and the lower panel is a low-dielectric-loss and high-magnetic-loss composite material panel. The preparation method comprises preparing a high-frequency-dispersion-effect absorbing resin, a metasurface, a metamaterial panel, a high-scattering dielectric conductive slurry, an absorbing honeycomb, and a low-dielectric-loss and high-magnetic-loss composite material panel, and gluing the metamaterial panel, the absorbing honeycomb, and the low-dielectric-loss and high-magnetic-loss composite material panel to obtain a product. The present invention realizes the design and preparation of an ultra-wideband absorbing honeycomb sandwich structure for the first time, and has the characteristics of being insensitive to both the incident angle and the polarization direction, effectively meeting the urgent need for stealth of aircraft omnidirectional ultra-wideband radars.

Description

Ultra-wideband wave-absorbing honeycomb sandwich structure and preparation method thereof

Technical Field

The present invention belongs to the field of aviation equipment design and manufacturing, and relates to an ultra-wideband absorbing honeycomb sandwich structure and a preparation method thereof, and specifically to an ultra-wideband absorbing honeycomb sandwich structure that is insensitive to polarization and incident angle and a preparation method thereof.

Background Art

As a widely used structural form in new aviation equipment, the wave-absorbing honeycomb sandwich structure plays an important role in integrating load-bearing and wave-absorbing. That is, the structure is not only a part of the fuselage and plays a role in load-bearing, but also can absorb electromagnetic waves incident on its surface and play a role in stealth. At present, radar detection technology is developing rapidly. If radar absorbing materials/structures cannot effectively absorb radar waves, it will pose a huge threat to equipment safety. Traditional absorbing materials/structures generally have problems such as limited absorption bandwidth and sensitivity to the incident angle and polarization direction of electromagnetic waves. It is difficult to meet the all-round (0-360°) ultra-wideband (0.1-18GHz) radar stealth requirements of new aviation equipment. Therefore, how to obtain high-performance radar absorbing materials/structures through composition, structure and process design is a major issue facing the field of aviation equipment design and manufacturing.

In order to solve the above problems, people have done a lot of research work: 1. In terms of component optimization, a variety of new absorbing materials are constantly being developed, such as carbon materials, ferrite absorbing materials, ceramic absorbing materials, composite materials, etc. 2. In terms of structural design, multi-layer macroscopic absorbing structure design represented by Salisbury screen, impedance matching absorbing materials and Jaumann absorbing materials, as well as mesoscopic absorbing structure design methods represented by two-dimensional frequency selective surfaces and three-dimensional honeycomb structures have been developed.

Specifically, in terms of absorbing powders, patent document CN113249092B discloses a metal-organic framework complex composite absorbing powder and a preparation method. The method composites dielectric _SiO2 with a magnetic metal-organic framework to broaden the effective absorbing bandwidth, and its effective absorbing bandwidth is 4GHz (8-12GHz); patent document CN113214787B uses cobalt ferrite-iron-cobalt alloy to co-coat hollow glass microspheres and carbon microspheres to prepare a ternary core-shell composite material powder with an effective absorption bandwidth of 4.2GHz (8.2-12.4GHz).

In the design of two-dimensional wave absorbing structures, two-dimensional frequency selective surfaces with periodic structures are widely used in the design of wave absorbing structures. In the selection of materials for frequency selective surfaces, high conductivity shielding materials represented by metals, graphene, and ITO are usually selected in the publicly published patent documents. For example, patent document CN109638450B uses graphene frequency selective surfaces to prepare reconfigurable antenna covers, patent document CN113437531B uses metal patch units to prepare miniaturized angle-insensitive wave absorbing structures with an effective absorption bandwidth of 3.5GHz (3.5-7GHz), and patent document CN112928483B uses metal-medium-metal combinations to form frequency selective surface laminate structures with an effective absorption bandwidth of 8GHz (7-15GHz). However, frequency selective surfaces only have excellent electromagnetic wave absorption performance near the resonant frequency point, and it is difficult to achieve broadband wave absorption.

In terms of three-dimensional periodic structure design, patent document CN112519365B uses dielectric absorbers such as carbon black and graphene to prepare thermoplastic absorbing honeycomb panels with an effective absorbing bandwidth of 10 GHz (8-18 GHz). Patent document CN112143023B proposes a method for preparing an absorbing honeycomb pyramid/rigid foam composite material with an effective absorption bandwidth of 16 GHz (2-18 GHz). Patent document CN106469858B proposes a honeycomb/resistor sheet laminate structure with an effective absorbing bandwidth of 21.6 GHz (2.4-24 GHz). However, the above three representative patents do not design the absorbing performance under different incident angles and polarization directions, and the test frequency band only covers 2-18 GHz, making it difficult to achieve ultra-wideband (0.1-18 GHz) absorption.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an ultra-wideband absorbing honeycomb sandwich structure that is insensitive to polarization and incident angle and a preparation method thereof, which can effectively solve the problem that the current absorbing honeycomb sandwich structure has poor low-frequency (0.1-4GHz) absorbing performance and the absorbing performance is greatly affected by the incident angle and polarization direction, and effectively meet the urgent needs of aircraft omnidirectional ultra-wideband radar stealth.

In order to solve the above technical problems, the present invention adopts the following technical solutions.

An ultra-wideband absorbing honeycomb sandwich structure comprises an upper panel, an absorbing honeycomb and a lower panel which are sequentially arranged from top to bottom, wherein the upper panel is a metamaterial panel, the metamaterial panel is composed of a quartz fiber reinforced resin-based composite material and a polymer resin film printed with a metasurface arranged in the middle of the quartz fiber reinforced resin-based composite material, the electrical performance indicators of the metasurface are shown in Table 1, the absorbing honeycomb is formed by impregnating a honeycomb structure with a high-scattering dielectric conductive slurry, the electrical performance indicators of the high-scattering dielectric conductive slurry are shown in Table 2, the lower panel is a low dielectric loss and high magnetic loss composite material panel, the electrical performance indicators of the low dielectric loss and high magnetic loss composite material panel are shown in Table 3; the quality factor target value of the ultra-wideband absorbing honeycomb sandwich structure is shown in Table 4;

Table 1 Electrical performance index table of metasurface

Frequency band (GHz) Average value of real part of impedance (Ω) Average value of the imaginary part of impedance (Ω) Thickness(mm) P(0.1-1) 400-600 40-90 0.3-0.6 L(1-2) 350-550 30-80 0.3-0.6 S(2-4) 310-540 40-90 0.3-0.6 C(4-8) 340-570 50-100 003-0.6 X(8-12) 310-510 40-90 0.3-0.6 Ku(12-18) 300-500 50-100 0.3-0.6

Table 2 Electrical performance index table of high scattering dielectric conductive paste

Frequency band (GHz) Electrical dispersion Dielectric constant amplitude AC conductivity (S/m) Electric loss tangent P(0.1-1) 10-20 50-80 0.3-0.5 0.1-0.4 L(1-2) 10-20 40-70 0.3-0.6 0.1-0.4 S(2-4) 10-20 30-60 0.4-0.6 0.2-0.6 C(4-8) 10-20 20-40 0.4-0.7 0.8-1.2 X(8-12) 10-20 15-30 0.5-0.7 1-1.5 Ku(12-18) 5-10 10-25 0.6-0.8 1-1.5

Table 3 Electrical performance index table of low dielectric loss and high magnetic loss composite panels

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 0-0.1 3-8 10-20 8-15 0.01-0.05/0.1-0.3 L(1-2) 0-0.1 2-5 10-20 6-12 0.01-0.05/0.2-0.5 S(2-4) 0-0.1 1-3 10-20 5-10 0.01-0.05/0.3-0.5 C(4-8) 0-0.1 1-3 10-20 4-8 0.05-0.1/0.3-0.6 X(8-12) 0-0.1 1-3 10-20 3-8 0.05-0.1/0.5-0.7 Ku(12-18) 0-0.1 1-3 10-20 2-7 0.05-0.1/0.6-0.9

Table 4 Quality factor target value table of ultra-wideband absorbing honeycomb sandwich structure

Frequency band (GHz) Quality Factor P(0.1-1) 0.1-0.5 L(1-2) 0.01-0.05 S(2-4) 0.01-0.05 C(4-8) 0.01-0.05 X(8-12) 0.01-0.05 Ku(12-18) 0.01-0.05

.

The ultra-wideband absorbing honeycomb sandwich structure, preferably, the super surface is made of a high-frequency dispersion effect absorbing resin, the electrical performance indicators of the high-frequency dispersion effect absorbing resin are shown in Table 5, the structural unit of the super surface includes a combination of one or more of a sheet structure, an open ring structure, a closed ring structure and a cross structure; the structure of the super surface is usually an array structure composed of multiple structural units;

Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent p(01-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C(4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 25 10-15 3-8 1-3/0.1-1

.

The above-mentioned ultra-wideband absorbing honeycomb sandwich structure, preferably, the resin used in the quartz fiber reinforced resin-based composite material includes one or more of epoxy resin, phenolic resin, bismaleimide resin, polyimide resin and cyanate resin, and the polymer resin film includes one or more of polyetheretherketone resin film, epoxy resin film, bismaleimide resin film and polyimide resin film.

The ultra-wideband absorbing honeycomb sandwich structure is preferably such that the hexagonal cell side length of the honeycomb structure is 2 mm to 5 mm, the thickness of the honeycomb structure is 15 mm to 25 mm, and the volume density of the absorbing honeycomb is 90 kg/m ³ to 120 kg/m ³ ;

The high-scattering dielectric conductive paste is formed by mixing dielectric absorbing powder with epoxy resin, wherein the dielectric absorbing powder includes one or more of zero-dimensional dielectric loss-type absorbing powder, one-dimensional dielectric loss-type absorbing powder and two-dimensional dielectric loss-type absorbing powder, wherein the zero-dimensional dielectric loss-type absorbing powder includes one or more of carbon balls, carbon black and fullerenes, wherein the one-dimensional dielectric loss-type absorbing powder includes one or more of carbon nanowires, carbon nanorods, carbon nanotubes and carbon nanofibers, and wherein the two-dimensional dielectric loss-type absorbing powder includes one or more of graphene, Mxene and _MoS2 .

The above-mentioned ultra-wideband absorbing honeycomb sandwich structure, preferably, the low dielectric loss and high magnetic loss composite material panel is obtained by curing and molding short fibers, magnetic powder and epoxy resin as raw materials, the short fibers are short fibers or short fibers of silicon carbide, and the magnetic powder includes one or more of carbonyl iron powder, magnetic metal organic framework and magnetic core-shell structure.

In the ultra-wideband wave-absorbing honeycomb sandwich structure, preferably, the thickness of the upper panel is 2 mm to 4 mm, and the thickness of the lower panel is 3 mm to 5 mm.

As a general technical concept, the present invention also provides a method for preparing the ultra-wideband absorbing honeycomb sandwich structure, comprising the following steps:

(1) Preparation of high-scattering effect absorbing resin: dispersing high-scattering absorber powder in epoxy resin to obtain high-scattering effect absorbing resin, which needs to meet the electrical performance indicators shown in Table 5; wherein the high-scattering absorber powder includes one or more of metal organic framework, carbonyl iron powder, acetylene black, chopped carbon fiber, graphene and carbon nanotubes;

Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L((1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C(4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1-1

;

(2) Preparation of a metasurface (i.e., a frequency selective surface): The high-frequency dispersion absorbing resin obtained in step (1) is prepared into a metasurface according to a desired structure, so that the metasurface meets the electrical performance indicators shown in Table 1;

(3) Preparation of a metamaterial panel: printing the metasurface obtained in step (2) onto a polymer resin film, paving the polymer resin film printed with the metasurface onto an intermediate layer of a quartz fiber reinforced resin-based prepreg, and curing and molding the film using a vacuum bag-autoclave curing process to obtain a metamaterial panel;

(4) Preparation of high-scattering dielectric conductive paste: Dielectric absorbing powder is mixed with epoxy resin, wherein the dielectric absorbing powder includes one or more of zero-dimensional dielectric loss absorbing powder, one-dimensional dielectric loss absorbing powder and two-dimensional dielectric loss absorbing powder, to obtain high-scattering dielectric conductive paste, and the high-scattering dielectric conductive paste needs to meet the electrical performance indicators shown in Table 2;

(5) Preparation of absorbing honeycomb: Dip the honeycomb structure into the high scattering dielectric conductive slurry obtained in step (4) for 3 to 5 minutes, then perform pre-curing by turning over at 80°C to 120°C to coat the conductive slurry on the inner wall of the honeycomb structure, and repeat the dipping and coating until the volume density of the absorbing honeycomb reaches 90 kg/m ³ to 120 kg/m ³ ;

(6) Preparation of low dielectric loss and high magnetic loss composite panel: Magnetic absorbing powder is dispersed in epoxy resin, wherein the magnetic absorbing powder includes chopped fibers and magnetic powder, and a vacuum bag-autoclave curing process is used for curing and molding to obtain a low dielectric loss and high magnetic loss composite panel. The low dielectric loss and high magnetic loss composite panel must meet the electrical performance indicators shown in Table 3.

(7) Preparation of an ultra-wideband absorbing honeycomb sandwich structure: The metamaterial panel obtained in step (3) is used as an upper panel, the absorbing honeycomb obtained in step (5) is used as a sandwich, and the low dielectric loss and high magnetic loss composite material panel obtained in step (6) is used as a lower panel. The upper panel, the absorbing honeycomb, and the lower panel are bonded together using an adhesive film to obtain an ultra-wideband absorbing honeycomb sandwich structure.

In the preparation method of the above-mentioned ultra-wideband absorbing honeycomb sandwich structure, preferably, in step (3), the process of the vacuum bag-autoclave curing process is as follows: under the condition of a vacuum degree of not less than 0.095 MPa, the temperature is increased to 80°C to 120°C at a heating rate of 1°C/min to 3°C/min, and the pressure is increased to 0.5MPa to 0.7MPa, and the temperature is kept for 2h to 3h, and the temperature is continued to be increased to 130°C to 150°C, and the temperature is kept for 1h to 2h, and finally the temperature is increased to 180°C to 200°C and the temperature is kept for 3h to 5h, and then the temperature is cooled to 40°C to 60°C at a cooling rate of 1°C/min to 3°C/min, and the pressure is released and the tank is taken out.

In the above-mentioned method for preparing the ultra-wideband wave-absorbing honeycomb sandwich structure, preferably, in step (6), the process of the vacuum bag-autoclave curing process is as follows: under the condition of a vacuum degree of not less than 0.095 MPa, the temperature is increased to 80°C to 120°C at a heating rate of 1°C/min to 3°C/min, and kept warm for 3h to 5h, and then cooled to 40°C to 60°C at a cooling rate of 1°C/min to 3°C/min, and the pressure is released and the tank is taken out.

In the preparation method of the above-mentioned ultra-wideband absorbing honeycomb sandwich structure, preferably, in step (7), the bonding process of the adhesive film is: the vacuum degree is not less than 0.095MPa, the temperature is increased to 80℃～120℃ at a heating rate of 1℃/min～3℃/min, and it is kept warm for 2h～4h, and then cooled to 40℃～60℃ at a cooling rate of 1℃/min～3℃/min.

Compared with the prior art, the advantages of the present invention are:

(1) The present invention provides an ultra-wideband absorbing honeycomb sandwich structure that is insensitive to polarization and incident angle. Compared with the traditional frequency selective surface made of shielding materials, the present invention uses a high-frequency dispersion effect absorbing resin to prepare a super surface (frequency selective surface) and uses composite material structure integration technology to composite it with the upper panel of the honeycomb sandwich structure (quartz fiber reinforced epoxy resin). A low dielectric loss and high magnetic loss composite material is used as the lower panel of the honeycomb sandwich structure. Based on the resonance effect of the composite material, the honeycomb sandwich structure is insensitive to the incident angle of electromagnetic waves. The optimized impedance matching performance is helpful to achieve ultra-wideband omnidirectional stealth. The effective absorbing bandwidth (reflection loss <-10dB) of the ultra-wideband absorbing honeycomb sandwich structure of the present invention covers 0.1-18GHz, and the electromagnetic wave absorption performance shows insensitivity to the incident angle (0-70°) and polarization direction (horizontal and vertical polarization), which effectively meets the urgent needs of aircraft omnidirectional ultra-wideband radar stealth.

(2) The present invention provides a method for preparing an ultra-wideband absorbing honeycomb sandwich structure, which comprises a highly scattering dielectric conductive slurry and a dip-coating process to prepare the absorbing honeycomb, thereby giving full play to the honeycomb's multiple scattering absorption capability for electromagnetic wave energy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a reflection loss diagram of an ultra-wideband absorbing honeycomb sandwich structure under TE (a, c) and TM (b, d) modes in Example 1 of the present invention.

Figure 2 is a schematic diagram of the open-ring periodic metasurface structure unit in Examples 1 and 2 of the present invention.

Figure 3 is a schematic diagram of the open-ring periodic metasurface structure unit in Example 3 of the present invention.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

The method for preparing the ultra-wideband wave-absorbing honeycomb sandwich structure of the present invention comprises the following steps:

(1) Electrical performance indicators of high-frequency dispersion absorbing resin

The electrical performance indicators of the high-frequency dispersion effect absorbing resin are shown in Table 5. A mixture of one or more materials including but not limited to metal organic frameworks, carbonyl iron, acetylene black, chopped carbon fibers, graphene, carbon nanotubes, etc. can be dispersed in the epoxy resin to achieve the corresponding electrical performance indicators.

Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent p(0.1-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2--4) 20--40 5-15 50-70 20--40 1-3/0.1-1 C(4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20--40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1-1

.

(2) Metasurface preparation and electrical performance index range

In terms of the selection of metasurface structural units, a single structure or a combined structure including but not limited to a sheet, an open/closed ring structure, a cross structure, etc. can be used as a structural unit, and the metasurface can be prepared using technologies including but not limited to screen printing and 3D printing. The high-frequency dispersion effect absorbing powder in step (1) is used to complete the size design of the metasurface structural unit. The prepared metasurface should meet the electrical performance indicators shown in Table 1.

Table 1 Electrical performance index table of metasurface

Frequency band (GHz) Average value of real part of impedance (Ω) Average value of the imaginary part of impedance (Ω) Thickness(mm) P(01-1) 400-600 40-90 0.3-0.6 L(1-2) 350-550 30-80 0.3-0.6 S(2--4) 310-540 40-90 0.3-0.6 C(4-8) 340-570 50-100 0.3-0.6 X(8-12) 310-510 40-90 0.3-0.6 Ku(12-18) 300-500 50-100 0.3-0.6

(3) Preparation of metamaterial panels

The metasurface designed in step (2) is printed onto a polymer resin film, wherein the resin film is selected from one or more of bismaleimide, epoxy resin film and cyanate ester film, and the printed polymer resin film is laid on the middle layer of quartz fiber reinforced epoxy resin prepreg (prepreg is a layer structure), and the preparation of the metamaterial panel is completed by a vacuum bag-autoclave curing process.

The process of vacuum bag-autoclave curing process is as follows: under the condition of vacuum degree not less than 0.095MPa, heat up to 80℃～120℃ at a heating rate of 1℃/min～3℃/min, and pressurize to 0.5MPa～0.7MPa at the same time, keep warm for 2h～3h, continue to heat up to 130℃～150℃, keep warm for 1h～2h, and finally heat up to 180℃～200℃ and keep warm for 3h～5h, then cool to 40℃～60℃ at a cooling rate of 1℃/min～3℃/min, and release the pressure to exit the tank.

(4) Preparation of high scattering dielectric conductive paste

In terms of regulating the scattering properties of dielectric conductive paste, the sensitivity of the material scattering properties to the composition and microstructure is utilized to mix zero-dimensional, one-dimensional, and two-dimensional microstructure dielectric lossy absorbing powders, wherein the zero-dimensional dielectric lossy absorbing powder includes but is not limited to one or more of carbon balls, carbon black, and fullerenes, the one-dimensional dielectric lossy absorbing powder includes but is not limited to one or more of carbon nanowires, nanorods, nanotubes, and carbon nanofibers, and the two-dimensional dielectric lossy absorbing powder includes but is not limited to one or more of graphene, Mxene, and _MoS2 . The dielectric absorbing powder is mixed with epoxy resin in a certain mass ratio, so that the electrical properties and scattering properties of the high-scattering dielectric conductive paste obtained after mixing are shown in Table 2.

Table 2 Electrical performance index table of high scattering dielectric conductive paste

Frequency band (GHz) Electrical dispersion Dielectric constant amplitude AC conductivity (S/m) Electric loss tangent P(0.1-1) 10-20 50-80 0.3-0.5 0.1-0.4 L(1-2) 10-20 40-70 0.3-0.6 0.1-0.4 S(2-4) 10-20 30-60 0.4-0.6 0.2-0.6 C(4-8) 10-20 20-40 0.4-0.7 0.8-1.2 X(8-12) 10-20 15-30 0.5-0.7 1-1.5 Ku(12-18) 5-10 10-25 0.6-0.8 1-1.5

(5) Preparation of microwave absorbing honeycomb

A honeycomb structure (preferably a white honeycomb) is selected with a hexagonal space having a side length of 2-5 mm and a honeycomb height of 15-25 mm, and the preparation of the wave-absorbing honeycomb is completed by a dip coating process. Specifically, the honeycomb structure is immersed in the high-scattering dielectric conductive slurry prepared in step (4) for 3-5 minutes, and then turned over in an oven at 80-120°C for pre-curing to achieve the coating of the conductive slurry on the inner wall of the honeycomb structure. The expected volume density is achieved by controlling the number of dip coatings, and the expected volume density is between 90-120 kg/ ^m3 .

(6) Preparation of low dielectric loss and high magnetic loss composite panels

Select and mix dielectric loss type chopped carbon fiber or chopped silicon carbide fiber with magnetic powder to obtain magnetic absorbing powder, wherein the magnetic powder includes but is not limited to one or more of carbonyl iron powder, magnetic metal organic framework and magnetic core-shell structure. The above magnetic absorbing powder is dispersed into epoxy resin at a mass ratio of 3:7, and the vacuum bag-autoclave curing process is used to complete the curing and molding at 120°C. The electrical properties of the prepared low dielectric loss and high magnetic loss composite panel are shown in Table 3.

The process of vacuum bag-autoclave curing process is as follows: under the condition of vacuum degree not less than 0.095MPa, heat up to 80℃～120℃ at a heating rate of 1℃/min～3℃/min, keep warm for 3h～5h, then cool to 40℃～60℃ at a cooling rate of 1℃/min～3℃/min, and release the pressure out of the tank.

Table 3 Electrical performance index table of low dielectric loss and high magnetic loss composite panels

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electromagnetic loss tangent P(0.1-1) 0-0.1 3-8 10-20 8-15 0.01-0.05/0-1-0.3 L(1-2) 0-0.1 2-5 10-20 6-12 0.01-0.05/0.2-0.5 S(2-4) 0-0.1 1-3 10-20 5-10 0.01-0.05/0.3-0.5 C(4-8) 0-0.1 1-3 10-20 4-8 0.05-0.1/0.3-0.6 X(8-12) 0-0.1 1-3 10-20 3-8 0.05-0.1/0.5-0.7 Ku(12-18) 0-0.1 1-3 10-20 2-7 0.05-0.1/0.6-0.9

(7) Bonding of composite panels and microwave-absorbing honeycombs (preparation of ultra-wideband microwave-absorbing honeycomb sandwich structures)

The metamaterial panel prepared in step (3) is used as the upper panel, the absorbing honeycomb prepared in step (5) is used as the interlayer, and the low dielectric loss and high magnetic loss composite material panel prepared in step (6) is used as the lower panel, and the upper and lower panels and the absorbing honeycomb are bonded using adhesive film. The thickness of the upper panel is between 2-4 mm, the thickness of the lower panel is between 3-5 mm, and the honeycomb height is between 15-25 mm;

The bonding process of the adhesive film in step 7 is: the vacuum degree is not less than 0.095 MPa, the temperature is increased to 80-120°C at a heating rate of 1-3°C/min, kept at this temperature for 2-4 hours, and then cooled to 40-60°C at a cooling rate of 1-3°C/min.

Embodiment 1:

An ultra-wideband absorbing honeycomb sandwich structure of the present invention comprises an upper panel, an absorbing honeycomb and a lower panel which are sequentially arranged from top to bottom, the upper panel being a metamaterial panel, the metamaterial panel being composed of a quartz fiber reinforced resin-based composite material and a polymer resin film printed with a metasurface arranged in the middle of the quartz fiber reinforced resin-based composite material, the electrical properties of the metasurface meeting the indicators in Table 1, the absorbing honeycomb being formed by impregnating a honeycomb structure with a high-scattering dielectric conductive slurry, the electrical properties of the high-scattering dielectric conductive slurry meeting the indicators in Table 2, the lower panel being a low dielectric loss and high magnetic loss composite material panel, the electrical properties of the low dielectric loss and high magnetic loss composite material panel meeting the indicators in Table 3; the quality factor target value of the ultra-wideband absorbing honeycomb sandwich structure meeting the indicators in Table 4.

Table 1 Electrical performance index table of metasurface

Frequency band (GHz) Average value of real part of impedance (Ω) Average value of the imaginary part of impedance (Ω) Thickness(mm) p(0.1-1) 400-600 40-90 0.3-0.6 L(1-2) 350-550 30-80 0.3-0.6 S(2-4) 310-540 40-90 0.3-0.6 C(4-8) 340-570 50-100 0.3-0.6 X(8-12) 310-510 40-90 0.3-0.6 Ku(12-18) 300-500 50-100 0.3-0.6

Table 2 Electrical performance index table of high scattering dielectric conductive paste

Frequency band (GHz) Electrical dispersion Dielectric constant amplitude AC conductivity (S/m) Electric loss tangent P(0.1-1) 10-20 50-80 0.3-0.5 0.1-0.4 L(1-2) 10-20 40-70 0.3-0.6 0.1-0.4 S(2-4) 10-20 30-60 0.4-0.6 0.2-0.6 C(4-8) 10-20 20-40 0.4-0.7 0.8-1.2 X(8-12) 10-20 15-30 0.5-0.7 1-1.5 Ku(12-18) 5-10 10-25 0.6-0.8 1-1.5

Table 3 Electrical performance index table of low dielectric loss and high magnetic loss composite panels

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 0-0.1 3-8 10-20 8-15 0.01-0.05/0.1-0.3 L(1-2) 0-0.1 2-5 10-20 6-12 0.01-0.05/0.2-0.5 S(2-4) 0-0.1 1-3 10-20 5-10 0.01-0.05/0.3-0.5 C(4-8) 0-0.1 1-3 10-20 4-8 0.05-0.1/0.3-0.6 X(8-12) 0-0.1 1-3 10-20 3-8 0.05-0.1/0.5-0.7 Ku(12-18) 0-0.1 1-3 10-20 2-7 0.05-0.1/0.6-0.9

Table 4 Quality factor target value table of ultra-wideband absorbing honeycomb sandwich structure

Frequency band (GHz) Quality Factor P(0.1-1) 0.1-0.5 L(1-2) 0.01-0.05 S(2-4) 0.01-0.05 C(4-8) 0.01-0.05 X(8-12) 0.01-0.05 Ku(12-18) 0.01-0.05

.

In this embodiment, the metasurface is made of a high-frequency dispersion effect absorbing resin, the electrical performance indicators of the high-frequency dispersion effect absorbing resin meet the indicators in Table 5, and the structural unit of the metasurface is a nested combination of two open ring structures.

Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C (4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1-1

.

In this embodiment, the resin used in the quartz fiber reinforced resin-based composite material is epoxy resin, and the polymer resin film is epoxy resin film.

In this embodiment, the side length of the hexagonal cells of the honeycomb structure is 3 mm, the height of the honeycomb structure is 17 mm, and the volume density of the wave-absorbing honeycomb is 90 kg/m ³ .

In this embodiment, the high-scattering dielectric conductive paste is prepared by mixing absorbing powder and epoxy resin, and the absorbing powder is conductive carbon black and carbon nanotubes.

In this embodiment, the low dielectric loss and high magnetic loss composite material panel is obtained by curing and molding short fibers, magnetic powder and epoxy resin as raw materials, the short fibers are short fibers of silicon carbide, and the magnetic powder is a ZIF-67 metal organic framework.

In this embodiment, the thickness of the upper panel is 2 mm, and the thickness of the lower panel is 4 mm.

A method for preparing the ultra-wideband wave-absorbing honeycomb sandwich structure of this embodiment comprises the following steps:

(1) Preparation of high-frequency dispersion effect absorbing resin: Carbonyl iron powder, chopped carbon fiber, and epoxy resin were mixed and stirred in a mass ratio of 3:1:20, wherein the average particle size of the selected carbonyl iron powder was 1000 mesh, and the length of the chopped carbon fiber was 3 mm and the diameter was 7 μm. A high-speed stirrer was used to stir for 30 minutes at room temperature at a stirring speed of 800 rpm to obtain a high-frequency dispersion effect absorbing resin, which met the electrical performance indicators shown in Table 5.

(2) Preparation of open ring periodic metasurface: Design an open ring periodic metasurface structural unit as shown in FIG2. The metasurface is an array structure composed of multiple structural units. The structural unit is composed of an outer ring 1 and an inner ring 2 (set together). The outer ring 1 is a rectangular ring structure with a notch, and the inner ring 2 is a rectangular ring structure with a notch. The width a of the outer ring 1 is 1 mm, the envelope width e of the outer ring 1 is 6 mm, the width c of the inner ring 2 is 2 mm, the envelope length d of the inner ring 2 is 3 mm, the spacing b between the outer ring 1 and the inner ring 2 is 0.5 mm, and the opening size f of the outer ring 1 and the inner ring 2 is 2 mm. The high-frequency dispersion effect absorbing resin prepared in step (1) is prepared into an open ring periodic metasurface according to the above structure. The metasurface meets the electrical performance indicators shown in Table 1.

(3) Preparation of metamaterial panel: Using epoxy resin film as a carrier, the open ring periodic metasurface prepared in step (2) is printed on the epoxy resin film by screen printing technology, and then the epoxy resin film printed with the metasurface is laid on the middle layer of the quartz fiber reinforced resin-based prepreg, and the vacuum bag-autoclave curing process is used for curing and molding to obtain the metamaterial panel. The vacuum bag-autoclave curing process is as follows: under the condition of a vacuum degree of not less than 0.095MPa, the temperature is increased to 100°C at a heating rate of 2°C/min, and the pressure is increased to 0.6MPa at the same time, and the temperature is kept for 2h, and then the temperature is further increased to 150°C, and the temperature is kept for 1h, and finally the temperature is increased to 180°C and kept for 3 hours, and then the temperature is cooled to 60°C at a cooling rate of 1.5°C/min, and the pressure is released out of the tank, and the preparation of the metamaterial panel is completed.

(4) Preparation of high-scattering dielectric conductive paste: Carbon black, carbon nanotubes, and epoxy resin are mixed in a mass ratio of 2:1:10, wherein the average particle size of the carbon black is 100 nm, and the outer diameter of the carbon nanotubes is 10 nm. A high-speed stirrer is used to stir for 30 minutes at room temperature at a stirring speed of 800 rpm to obtain a high-scattering dielectric conductive paste. The high-scattering dielectric conductive paste meets the electrical performance indicators shown in Table 2.

(5) Preparation of absorbing honeycomb: A white honeycomb with a cell side length of 3 mm and a height of 17 mm was selected and immersed in the high-scattering dielectric conductive slurry prepared in step (4) for multiple times and turned over for pre-curing, wherein the time of each immersion was controlled within 3 minutes, the pre-curing temperature was 80° C., and the pre-curing time was 5 minutes. Then, the volume density of the absorbing honeycomb was achieved to be 90 kg/m ³ by controlling the number of immersion times.

(6) Preparation of low dielectric loss and high magnetic loss composite panel: Short-cut silicon carbide fiber, ZIF-67 metal organic framework, and epoxy resin were mixed and stirred in a mass ratio of 1:3:10, wherein the short-cut silicon carbide fiber was selected to have a length of 3 mm and a diameter of 14 μm. A high-speed stirrer was used to stir at room temperature for 30 minutes at a stirring speed of 800 rpm. A vacuum bag-autoclave curing process was used under a vacuum degree of not less than 0.095 MPa, and the temperature was raised to 100°C at a heating rate of 1.5°C/min, and the temperature was kept for 4 hours. Then, the temperature was cooled to 60°C at a cooling rate of 1.5°C/min, and the pressure was released from the can to obtain a low dielectric loss and high magnetic loss composite panel. The low dielectric loss and high magnetic loss composite panel met the electrical performance indicators shown in Table 3.

(7) Preparation of an ultra-wideband absorbing honeycomb sandwich structure: The metamaterial panel prepared in step (3) is used as the upper panel, the absorbing honeycomb prepared in step (5) is used as the sandwich, and the low dielectric loss and high magnetic loss composite material panel prepared in step (6) is used as the lower panel. The upper panel, the absorbing honeycomb, and the lower panel are bonded together by adhesive film to obtain an ultra-wideband absorbing honeycomb sandwich structure. The thickness of the upper panel is 2 mm, the thickness of the lower panel is 4 mm, and the bonding process is as follows: the vacuum degree is not less than 0.095 MPa, the temperature is raised to 80°C at a heating rate of 1.5°C/min, and the temperature is kept for 2 hours, and then the temperature is cooled to 40°C to 60°C at a cooling rate of 1.5°C/min to complete the bonding.

The electrical performance of the ultra-wideband absorbing honeycomb sandwich structure of this embodiment is characterized as follows:

FIG1 shows the reflection loss of the absorbing honeycomb sandwich structure at different electromagnetic wave incident angles in the 0.1-18 GHz frequency band in the TE mode (FIG1a, FIG1c) and TM mode (FIG1b, FIG1d). It can be seen from FIG1 that the absorbing honeycomb sandwich structure of the present invention can achieve a reflection loss of <-10 dB under different polarization directions and incident angles, that is, the effective absorbing bandwidth covers 0.1-18 GHz. The ultra-wideband absorbing honeycomb sandwich structure of the present invention generates resonance loss at the 0.5 GHz frequency point, and the reflection loss in other frequency bands except the resonance frequency point shows insensitivity to the incident angle and polarization direction. FIG1(c) is a partial enlarged view of FIG1(a) at 0.1-1 GHz, and FIG1(d) is a partial enlarged view of FIG1(b) at 0.1-1 GHz. FIG1(c) and FIG1(d) show that by constructing resonance in the 0.1-1 GHz frequency band, the absorbing performance outside the resonance-affected frequency band is insensitive to the incident angle (as shown by the close proximity of the curves).

In order to better illustrate the characteristics of insensitivity to the incident angle and polarization direction, the quality factor Q is used to characterize the resonance characteristics at the resonant frequency point, and the quality factor can be calculated by the ratio of the resonant frequency to the resonance half-width. Table 4 gives the target value of the quality factor of the absorbing honeycomb sandwich structure with insensitivity to the incident angle and polarization direction in the 0.1-18GHz frequency band, indicating that the present invention constructs resonance in the P band (0.1-1GHz) and quantifies and constrains the resonance behavior through the quality factor, and finally realizes that the effective absorbing bandwidth covers the 0.1-18GHz frequency band, realizes ultra-wideband absorption, and is insensitive to the incident angle and polarization direction of electromagnetic waves.

Table 4 Quality factor target value table of ultra-wideband absorbing honeycomb sandwich structure

Frequency band (GHz) Quality Factor P(0.1-1) 0.1-0.5 L(1-2) 0.01-0.05 S(2-4) 0.01-0.05 C(4-8) 0.01-0.05 X(8-12) 0.01-0.05 Ku(12-18) 0.01-0.05

.

Example 2

An ultra-wideband absorbing honeycomb sandwich structure of the present invention comprises an upper panel, an absorbing honeycomb and a lower panel which are sequentially arranged from top to bottom, the upper panel being a metamaterial panel, the metamaterial panel being composed of a quartz fiber reinforced resin-based composite material and a polymer resin film printed with a metasurface arranged in the middle of the quartz fiber reinforced resin-based composite material, the electrical properties of the metasurface meeting the indicators in Table 1, the absorbing honeycomb being formed by impregnating a honeycomb structure with a high-scattering dielectric conductive slurry, the electrical properties of the high-scattering dielectric conductive slurry meeting the indicators in Table 2, the lower panel being a low dielectric loss and high magnetic loss composite material panel, the electrical properties of the low dielectric loss and high magnetic loss composite material panel meeting the indicators in Table 3; the quality factor target value of the ultra-wideband absorbing honeycomb sandwich structure meeting the indicators in Table 4.

Table 1 Electrical performance index table of metasurface

Frequency band (GHz) Average value of real part of impedance (Ω) Average value of the imaginary part of impedance (Ω) Thickness(mm) P(0.1-1) 400-600 40-90 0.3-0.6 L(1-2) 350-550 30-80 0.3-0.6 S(2-4) 310-540 40-90 0.3-0.6 C(4-8) 340-570 50-100 0.3-0.6 X(8-12) 310-510 40-90 0.3-0.6 Ku(12-18) 300-500 50-100 0.3-0.6

Table 2 Electrical performance index table of high scattering dielectric conductive paste

Frequency band (GHz) Electrical dispersion Dielectric constant amplitude AC conductivity (S/m) Electric loss tangent P(0.1-1) 10-20 50-80 0.3-0-5 0.1-0.4 L(1-2) 10-20 40-70 0.3-0.6 0.1-0.4 S(24) 10-20 30-60 0.4-0.6 0.2-0.6 C(4-8) 10-20 20-40 0.4-0.7 0.8-1.2 X(8-12) 10-20 15-30 0.5-0.7 l-1.5 Ku(12-18) 5-10 10-25 0.6-0.8 1-1.5

Table 3 Electrical performance index table of low dielectric loss and high magnetic loss composite panels

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 0-0.1 3-8 10-20 8-15 0.01-0.05/0.1-0.3 L(1-2) 0-0.1 2-5 10-20 6-12 0.01-0.05/0.2-0.5 S(2-4) 0-0.1 1-3 10-20 5-10 0.01-0.05/0.3-0.5 C(4-8) 0-0.1 1-3 10-20 4-8 0.05-0.1/0.3-0.6 X(8-12) 0-0.1 1-3 10-20 3-8 0.05-0.1/0.5-0.7 Ku(12-18) 0-0.1 1-3 10-20 2-7 0.05-0.1/0.6-0.9

Table 4 Quality factor target value table of ultra-wideband absorbing honeycomb sandwich structure

Frequency band (GHz) Quality Factor P(0.1-1) 0.1-0.5 L(1-2) 0.01-0.05 S(2-4) 0.01-0.05 C(4-8) 0.01-0.05 X(8-12) 0.01-0.05 Ku(12-18) 0.01-0.05

.

In this embodiment, the metasurface is made of a high-frequency dispersion effect absorbing resin, the electrical performance indicators of the high-frequency dispersion effect absorbing resin meet the indicators in Table 5, and the structural unit of the metasurface is a nested combination of two open ring structures.

Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C (4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1-1

.

In this embodiment, the resin used in the quartz fiber reinforced resin-based composite material is epoxy resin, and the polymer resin film is polyetheretherketone resin film.

In this embodiment, the side length of the hexagonal cells of the honeycomb structure is 4 mm, the height of the honeycomb structure is 20 mm, and the volume density of the wave-absorbing honeycomb is 110 kg/m ³ .

In this embodiment, the high-scattering dielectric conductive paste is prepared by mixing absorbing powder and epoxy resin, and the absorbing powder is MXene and carbon nanotubes.

In this embodiment, the low dielectric loss and high magnetic loss composite material panel is obtained by curing and molding short fibers, magnetic powder and epoxy resin as raw materials, the short fibers are short chopped carbon fibers, and the magnetic powder is carbonyl iron powder.

In this embodiment, the thickness of the upper panel is 3 mm, and the thickness of the lower panel is 3 mm.

A method for preparing the ultra-wideband wave-absorbing honeycomb sandwich structure of this embodiment comprises the following steps:

(1) Preparation of high-frequency dispersion effect absorbing resin: ZIF-67 metal organic framework, acetylene carbon black and epoxy resin were mixed in a mass ratio of 2:3:10, wherein the average particle size of the selected acetylene carbon black was 80 nm. The mixture was stirred at room temperature for 30 minutes with a high-speed stirrer at a stirring speed of 800 rpm to obtain a high-frequency dispersion effect absorbing resin. The high-frequency dispersion effect absorbing resin met the electrical performance indicators shown in Table 5.

(2) Preparation of the supersurface: The preparation method of the supersurface in this step is basically the same as step (2) in Example 1, with the only difference being that the opening size f of the outer ring 1 and the inner ring 2 is increased from 2 mm to 4 mm.

(3) Preparation of metamaterial panel: Using epoxy resin film as a carrier, the open ring periodic metasurface prepared in step (2) is printed on the epoxy resin film by screen printing technology, and then the epoxy resin film printed with the metasurface is laid on the middle layer of the quartz fiber reinforced resin-based prepreg, and the vacuum bag-autoclave curing process is used for curing and molding to obtain the metamaterial panel. The vacuum bag-autoclave curing process is as follows: under the condition of a vacuum degree of not less than 0.095MPa, the temperature is increased to 100°C at a heating rate of 2°C/min, and the pressure is increased to 0.6MPa at the same time, and the temperature is kept for 2h, and then the temperature is further increased to 150°C, and the temperature is kept for 1h, and finally the temperature is increased to 180°C and kept for 3 hours, and then the temperature is cooled to 60°C at a cooling rate of 1.5°C/min, and the pressure is released and the metamaterial panel is prepared.

(4) Preparation of high-scattering dielectric conductive paste: MXene, carbon nanotubes, and epoxy resin were mixed in a mass ratio of 1:3:10, wherein the selected MXene had an accordion-shaped microstructure and a single-layer size of 200-1000 nm, and the outer diameter of the carbon nanotubes was 10 nm. The mixture was stirred at room temperature for 30 minutes using a high-speed stirrer at a stirring speed of 800 rpm to obtain a high-scattering dielectric conductive paste. The high-scattering dielectric conductive paste met the electrical performance indicators shown in Table 2.

(5) Preparation of absorbing honeycomb: A white honeycomb with a cell side length of 4 mm and a height of 20 mm was selected and immersed in the high-scattering dielectric conductive slurry prepared in step (4) for multiple times and turned over for pre-curing. The immersion time for each time was controlled within 4 minutes, the pre-curing temperature was 100° C., and the pre-curing time was 3 minutes. By controlling the number of immersion times, the absorbing honeycomb volume density was 110 kg/m ³ .

(6) Preparation of low dielectric loss and high magnetic loss composite panel: Short-cut carbon fiber, carbonyl iron powder and epoxy resin were mixed and stirred in a mass ratio of 1:4:10, wherein the short-cut carbon fiber length was 3 mm and the diameter was 7 μm. The average particle size of carbonyl iron powder was 1000 mesh, and a high-speed stirrer was used to stir at room temperature for 30 minutes at a stirring speed of 800 rpm. The vacuum bag-autoclave curing process was used under a vacuum degree of not less than 0.095 MPa, and the temperature was raised to 100°C at a heating rate of 1.5°C/min, and the temperature was kept for 4 hours, and then the temperature was cooled to 60°C at a cooling rate of 1.5°C/min, and the pressure was released from the can to obtain a low dielectric loss and high magnetic loss composite panel. The low dielectric loss and high magnetic loss composite panel met the electrical performance indicators shown in Table 3.

(7) Preparation of an ultra-wideband absorbing honeycomb sandwich structure: The metamaterial panel prepared in step (3) is used as the upper panel, the absorbing honeycomb prepared in step (5) is used as the sandwich, and the low dielectric loss and high magnetic loss composite material panel prepared in step (6) is used as the lower panel. The upper panel, the absorbing honeycomb, and the lower panel are bonded together by adhesive film, thereby achieving the preparation of an ultra-wideband absorbing honeycomb sandwich structure that is insensitive to polarization and incident angle. The thickness of the upper panel is 3 mm, the thickness of the lower panel is 3 mm, and the bonding process is as follows: the vacuum degree is not less than 0.095 MPa, the temperature is raised to 80°C at a heating rate of 1.5°C/min, and the temperature is kept for 2 hours, and then the temperature is cooled to 40-60°C at a cooling rate of 1.5°C/min to complete the bonding.

Example 3

An ultra-wideband absorbing honeycomb sandwich structure of the present invention comprises an upper panel, an absorbing honeycomb and a lower panel which are sequentially arranged from top to bottom, the upper panel being a metamaterial panel, the metamaterial panel being composed of a quartz fiber reinforced resin-based composite material and a polymer resin film printed with a metasurface arranged in the middle of the quartz fiber reinforced resin-based composite material, the electrical properties of the metasurface meeting the indicators in Table 1, the absorbing honeycomb being formed by impregnating a honeycomb structure with a high-scattering dielectric conductive slurry, the electrical properties of the high-scattering dielectric conductive slurry meeting the indicators in Table 2, the lower panel being a low dielectric loss and high magnetic loss composite material panel, the electrical properties of the low dielectric loss and high magnetic loss composite material panel meeting the indicators in Table 3; the quality factor target value of the ultra-wideband absorbing honeycomb sandwich structure meeting the indicators in Table 4.

Table 1 Electrical performance index table of metasurface

Frequency band (GHz) Average value of real part of impedance (Ω) Average value of the imaginary part of impedance (Ω) Thickness(mm) P(0.1-1) 400-600 40-90 0.3-0.6 L(1-2) 550-550 30-80 0.3-0.6 S(2-4) 310-540 40-90 0.5-0.6 C(4-8) 340-570 50-100 0.3-0.6 X(8-12) 310-510 40-90 0.3-0.6 Ku(12-18) 300-500 50-100 0.3-0.6

Table 2 Electrical performance index table of high scattering dielectric conductive paste

Frequency band (GHz) Electrical dispersion Dielectric constant amplitude AC conductivity (S/m) Electric loss tangent P(0.1-1) 10-20 50-80 0.3-0.5 0.1-0.4 L(1-2) 10-20 40-70 0.3-0.6 0.1-0.4 S(2-4) 10-20 30-60 0.4-0.6 0.2-0.6 C(4-8) 10-20 20-40 0.4-0.7 0.8-1.2 X(8-12) 10-20 15-30 0.5-0.7 1-1.5 Ku(12-18) 5-10 10-25 0.6-0.8 1-1.5

Table 3 Electrical performance index table of low dielectric loss and high magnetic loss composite panels

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent P(0.1-1) 0-0.1 3-8 10-20 8-15 0.01-0.05/0.1-0.3 L(1-2) 0-0.1 2-5 10-20 6-12 0.01-0.05/0.2-0.5 S(2-4) 0-0.1 1-3 10-20 5-10 0.01-0.05/0.3-0.5 C(4-8) 0-0.1 1-3 10-20 4-8 0.05-0.1/0.3-0.6 X(8-12) 0-0.1 1-3 10-20 3-8 0.05-0.1/0.5-0.7 Ku(12-18) 0-0.1 1-3 10-20 2-7 0.05-0.1/0.6-0.9

Table 4 Quality factor target value table of ultra-wideband absorbing honeycomb sandwich structure

Frequency band (GHz) Quality Factor P(0.1-1) 0.1-0.5 L(1-2) 0.01-0.05 S(2-4) 0.01-0.05 C(4-8) 0.01-0.05 X(8-12) 0.01-0.05 Ku(12-18) 0.01-0.05

.

In this embodiment, the metasurface is made of a high-frequency dispersion effect absorbing resin, the electrical performance indicators of the high-frequency dispersion effect absorbing resin meet the indicators in Table 5, and the structural unit of the metasurface is a nested combination of two open ring structures.

Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin

Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electric/Magnetic Loss Tangent p(0.1-1) 300-400 50-100 400-600 150-500 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C(4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1-1

.

In this embodiment, the resin used in the quartz fiber reinforced resin-based composite material is epoxy resin, and the polymer resin film is epoxy resin film.

In this embodiment, the side length of the hexagonal cells of the honeycomb structure is 4 mm, the height of the honeycomb structure is 20 mm, and the volume density of the wave-absorbing honeycomb is 90 kg/m ³ .

In this embodiment, the high-scattering dielectric conductive paste is prepared by mixing absorbing powder and epoxy resin, and the absorbing powder is MXene and carbon black.

In this embodiment, the low dielectric loss and high magnetic loss composite material panel is obtained by curing and molding short fibers, magnetic powder and epoxy resin as raw materials, the short fibers are short fibers of silicon carbide, and the magnetic powder is a ZIF-67 metal organic framework.

In this embodiment, the thickness of the upper panel is 3 mm, and the thickness of the lower panel is 3 mm.

A method for preparing the ultra-wideband wave-absorbing honeycomb sandwich structure of this embodiment comprises the following steps:

(1) Preparation of high-frequency dispersion effect absorbing resin: ZIF-67 metal organic framework, short-cut carbon fiber and epoxy resin were mixed and stirred in a mass ratio of 4:1:10, wherein the short-cut carbon fiber was selected to have a length of 3 mm and a diameter of 7 μm. A high-speed stirrer was used to stir at room temperature for 30 minutes at a stirring speed of 800 rpm to obtain a high-frequency dispersion effect absorbing resin, which met the electrical performance indicators shown in Table 5.

(2) Preparation of metasurface: An open ring periodic metasurface structural unit as shown in FIG3 is designed. The metasurface is an array structure composed of multiple structural units. The structural unit is composed of an outer ring 1 and an inner ring 2 (set together). The outer ring 1 is a circular ring structure with a gap, and the inner ring 2 is a circular ring structure with a gap. The width a of the outer ring 1 is 2 mm, the radius R of the outer ring 1 is 10 mm, the width b of the inner ring 2 is 2 mm, the radius r of the inner ring 2 is 6 mm, the opening size c of the outer ring 1 is 5 mm, and the opening size of the inner ring 2 is 5 mm. The high-frequency dispersion effect absorbing resin prepared in step (1) is prepared into an open ring periodic metasurface according to the above structure. The metasurface meets the electrical performance indicators shown in Table 1.

(3) Preparation of metamaterial panel: Using epoxy resin film as carrier, the open ring periodic metasurface prepared in step (2) is printed on the epoxy resin film by screen printing technology, and then the epoxy resin film printed with the metasurface is laid on the middle layer of quartz fiber reinforced resin-based prepreg, and the vacuum bag-autoclave curing process is used for curing and molding to obtain the metamaterial panel. The vacuum bag-autoclave curing process is as follows: under the condition of vacuum degree not less than 0.095MPa, the temperature is increased to 100°C at a heating rate of 2°C/min, and the pressure is increased to 0.6MPa at the same time, and the temperature is kept for 2h, and then the temperature is further increased to 150°C, and the temperature is kept for 1h, and finally the temperature is increased to 180°C and kept for 3 hours, and then the temperature is cooled to 60°C at a cooling rate of 1.5°C/min, and the pressure is released out of the tank, and the preparation of the metamaterial panel is completed.

(4) Preparation of high-scattering dielectric conductive paste: MXene, carbon black and epoxy resin were mixed in a mass ratio of 4:2:10, wherein the selected MXene had an accordion-shaped microstructure with a single layer size of 200-1000 nm, and the average particle size of carbon black was 100 nm. The mixture was stirred at room temperature for 30 minutes with a high-speed stirrer at a stirring speed of 800 rpm to obtain a high-scattering dielectric conductive paste. The high-scattering dielectric conductive paste met the electrical performance indicators shown in Table 2.

(5) Preparation of absorbing honeycomb: A white honeycomb with a cell side length of 4 mm and a height of 20 mm was selected and immersed in the high-scattering dielectric conductive slurry prepared in step (4) for multiple times and turned over for pre-curing. The immersion time for each time was controlled within 3 minutes, the pre-curing temperature was 90° C., and the pre-curing time was 4 minutes. By controlling the number of immersion times, the volume density of the absorbing honeycomb was 90 kg/m ³ .

(6) Preparation of low dielectric loss and high magnetic loss composite panel: Short-cut carbon fiber, carbonyl iron powder and epoxy resin were mixed and stirred in a mass ratio of 1:3:10, wherein the short-cut carbon fiber was selected to have a length of 3 mm and a diameter of 7 μm. The average particle size of the carbonyl iron powder was selected to be 1000 mesh, and a high-speed stirrer was used to stir for 30 minutes at room temperature, and the stirring speed was 800 rpm. The vacuum bag-autoclave curing process was used under a vacuum degree of not less than 0.095 MPa, and the temperature was raised to 100°C at a heating rate of 1.5°C/min, and the temperature was kept for 4 hours, and then the temperature was cooled to 60°C at a cooling rate of 1.5°C/min, and the pressure was released from the can to obtain a low dielectric loss and high magnetic loss composite panel. The low dielectric loss and high magnetic loss composite panel met the electrical performance indicators shown in Table 3.

(7) Preparation of an ultra-wideband absorbing honeycomb sandwich structure: The metamaterial panel prepared in step (3) is used as the upper panel, the absorbing honeycomb prepared in step (5) is used as the sandwich, and the low dielectric loss and high magnetic loss composite material panel prepared in step (6) is used as the lower panel. The upper panel, the absorbing honeycomb, and the lower panel are bonded together by adhesive film to obtain an ultra-wideband absorbing honeycomb sandwich structure. The thickness of the upper panel is 3 mm, the thickness of the lower panel is 3 mm, and the bonding process is as follows: the vacuum degree is not less than 0.095 MPa, the temperature is raised to 80°C at a heating rate of 1.5°C/min, and the temperature is kept for 2 hours, and then the temperature is cooled to 40-60°C at a cooling rate of 1.5°C/min.

The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims (10)

1. An ultra-wideband absorbing honeycomb sandwich structure, characterized in that it comprises an upper panel, an absorbing honeycomb and a lower panel arranged in sequence from top to bottom, wherein the upper panel is a metamaterial panel, the metamaterial panel is composed of a quartz fiber reinforced resin-based composite material and a polymer resin film printed with a metasurface arranged in the middle of the quartz fiber reinforced resin-based polymer composite material, the electrical performance indicators of the metasurface are shown in Table 1, the absorbing honeycomb is formed by impregnating a honeycomb structure with a high-scattering dielectric conductive slurry, the electrical performance indicators of the high-scattering dielectric conductive slurry are shown in Table 2, the lower panel is a low dielectric loss and high magnetic loss composite material panel, the electrical performance indicators of the low dielectric loss and high magnetic loss composite material panel are shown in Table 3; the quality factor target value of the ultra-wideband absorbing honeycomb sandwich structure is shown in Table 4; Table 1 Electrical performance index table of metasurface Frequency band (GHz) Average value of real part of impedance (Ω) Average value of the imaginary part of impedance (Ω) Thickness(mm) p(0.1-1) 400-600 40-90 0.3-0.6 L(1-2) 350-550 30-80 0.3-0.6 S(2-4) 310-540 40-90 0.3-0.6 C(4-8) 340-570 50-100 0.3-0.6 X(8-12) 310-510 40-90 0.3-0.6 Ku(12-18) 300-500 50-100 0.3-0.6 Table 2 Electrical performance index table of high scattering dielectric conductive paste Frequency band (GHz) Electrical dispersion Dielectric constant amplitude AC conductivity (S/m) Electric loss tangent P(0.1-1) 10-20 50-80 0.3-0.5 0.1-0.4 L(1-2) 10-20 40-70 0.3-0.6 0.1-0.4 S(2-4) 10-20 30-60 0.4-0.6 0.2-0.6 C(4-8) 10-20 20-40 0.4-0.7 0.8-1.2 X(8-12) 10-20 15-30 0.5-0.7 1-1.5 Ku(12-18) 5-10 10-25 0.6-0.8 1-1.5 Table 3 Electrical performance index table of low dielectric loss and high magnetic loss composite material panels Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electromagnetic loss tangent P(0.1-1) 0-0.1 3-8 10-20 8-15 0.01-0.05/0.1-0.3 L(1-2) 0-0.1 2-5 10-20 6-12 0.01-0.05/0.2-0.5 S(2-4) 0-0.1 1-3 10-20 5-10 0.01-0.05/0.3-0.5 C(4-8) 0-0.1 1-3 10-20 4-8 0.05-0.1/0.3-0.6 X(8-12) 0-0.1 1-3 10-20 3-8 0.05-0.1/0.5-0.7 Ku(12-18) 0-0.1 1-3 10-20 2-7 0.05-0.1/0.6-0.9 Table 4 Quality factor target value table of ultra-wideband absorbing honeycomb sandwich structure Frequency band (GHz) Quality Factor P(0.1-1) 0.1-0.5 L(1-2) 0.01-0.05 S(2-4) 0.01-0.05 C(4-8) 0.01-0.05 X(8-12) 0.01-0.05 Ku(12-18) 0.01-0.05 . 2. The ultra-wideband absorbing honeycomb sandwich structure according to claim 1, characterized in that the super surface is made of a high-frequency dispersion effect absorbing resin, the electrical performance indicators of the high-frequency dispersion effect absorbing resin are shown in Table 5, and the structural unit of the super surface includes a combination of one or more of a sheet structure, an open ring structure, a closed ring structure and a cross structure; Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electromagnetic loss tangent P(0.1-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C(4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1.1 . 3. The ultra-wideband absorbing honeycomb sandwich structure according to claim 1 is characterized in that the resin used in the quartz fiber reinforced resin-based composite material includes one or more of epoxy resin, phenolic resin, bismaleimide, polyimide resin and cyanate resin, and the polymer resin film includes one or more of polyetheretherketone resin film, epoxy resin film, bismaleimide resin film and polyimide resin film. 4. The ultra-wideband absorbing honeycomb sandwich structure according to claim 1, characterized in that the hexagonal cell side length of the honeycomb structure is 2 mm to 5 mm, the height of the honeycomb structure is 15 mm to 25 mm, and the volume density of the absorbing honeycomb is 90 kg/m ³ to 120 kg/m ³ ; The high-scattering dielectric conductive paste is formed by mixing dielectric absorbing powder with epoxy resin, wherein the dielectric absorbing powder includes one or more of zero-dimensional dielectric loss-type absorbing powder, one-dimensional dielectric loss-type absorbing powder and two-dimensional dielectric loss-type absorbing powder, wherein the zero-dimensional dielectric loss-type absorbing powder includes one or more of carbon balls, carbon black and fullerenes, wherein the one-dimensional dielectric loss-type absorbing powder includes one or more of carbon nanowires, carbon nanorods, carbon nanotubes and carbon nanofibers, and wherein the two-dimensional dielectric loss-type absorbing powder includes one or more of graphene, Mxene and _MoS2 . 5. The ultra-wideband absorbing honeycomb sandwich structure according to claim 1 is characterized in that the low dielectric loss and high magnetic loss composite material panel is obtained by curing and molding short fibers, magnetic powder and epoxy resin as raw materials, the short fibers are short fibers or short fibers of silicon carbide, and the magnetic powder includes one or more of carbonyl iron powder, magnetic metal organic framework and magnetic core-shell structure. 6 . The ultra-wideband wave-absorbing honeycomb sandwich structure according to claim 1 , wherein the thickness of the upper panel is 2 mm to 4 mm, and the thickness of the lower panel is 3 mm to 5 mm. 7. A method for preparing an ultra-wideband absorbing honeycomb sandwich structure according to any one of claims 1 to 6, characterized in that it comprises the following steps: (1) Preparation of high-scattering effect absorbing resin: dispersing high-scattering absorber powder in epoxy resin to obtain high-scattering effect absorbing resin, which needs to meet the electrical performance indicators shown in Table 5; wherein the high-scattering absorber powder includes one or more of metal organic framework, carbonyl iron powder, acetylene black, chopped carbon fiber, graphene and carbon nanotubes; Table 5 Electrical performance index table of high frequency dispersion effect absorbing resin Frequency band (GHz) Electrical dispersion Magnetic dispersion Dielectric constant amplitude Magnetic permeability amplitude Electromagnetic loss tangent P(0.1-1) 300-400 50-100 400-600 150-300 0.5-1.5/0.2-1 L(1-2) 40-50 10-30 80-150 50-80 1-3/0.1-1 S(2-4) 20-40 5-15 50-70 20-40 1-3/0.1-1 C(4-8) 10-20 5-10 30-50 10-20 1-2/0.1-1 X(8-12) 5-10 2-5 20-40 5-15 1-3/0.1-1 Ku(12-18) 5-10 2-5 10-15 3-8 1-3/0.1-1 ; (2) Preparation of metasurface: The high-frequency dispersion effect absorbing resin obtained in step (1) is prepared into a metasurface according to the required structure, so that the metasurface meets the electrical performance indicators shown in Table 1; (3) Preparation of a metamaterial panel: printing the metasurface obtained in step (2) onto a polymer resin film, paving the polymer resin film printed with the metasurface onto an intermediate layer of a quartz fiber reinforced resin-based prepreg, and curing and molding the film using a vacuum bag-autoclave curing process to obtain a metamaterial panel; (4) Preparation of high-scattering dielectric conductive paste: Dielectric absorbing powder is mixed with epoxy resin, wherein the dielectric absorbing powder includes one or more of zero-dimensional dielectric loss absorbing powder, one-dimensional dielectric loss absorbing powder and two-dimensional dielectric loss absorbing powder, to obtain high-scattering dielectric conductive paste, and the high-scattering dielectric conductive paste needs to meet the electrical performance indicators shown in Table 2; (5) Preparation of absorbing honeycomb: Dip the honeycomb structure into the high scattering dielectric conductive slurry obtained in step (4) for 3 to 5 minutes, then perform pre-curing by turning over at 80°C to 120°C to coat the conductive slurry on the inner wall of the honeycomb structure, and repeat the dipping and coating until the volume density of the absorbing honeycomb reaches 90 kg/m ³ to 120 kg/m ³ ; (6) Preparation of low dielectric loss and high magnetic loss composite panel: Magnetic absorbing powder is dispersed in epoxy resin, wherein the magnetic absorbing powder includes chopped fibers and magnetic powder, and a vacuum bag-autoclave curing process is used for curing and molding to obtain a low dielectric loss and high magnetic loss composite panel. The low dielectric loss and high magnetic loss composite panel must meet the electrical performance indicators shown in Table 3. (7) Preparation of an ultra-wideband absorbing honeycomb sandwich structure: The metamaterial panel obtained in step (3) is used as an upper panel, the absorbing honeycomb obtained in step (5) is used as a sandwich, and the low dielectric loss and high magnetic loss composite material panel obtained in step (6) is used as a lower panel. The upper panel, the absorbing honeycomb, and the lower panel are bonded together using an adhesive film to obtain an ultra-wideband absorbing honeycomb sandwich structure. 8. The method for preparing an ultra-wideband wave-absorbing honeycomb sandwich structure according to claim 7 is characterized in that in step (3), the process of the vacuum bag-autoclave curing process is as follows: under the condition of a vacuum degree of not less than 0.095 MPa, the temperature is increased to 80°C to 120°C at a heating rate of 1°C/min to 3°C/min, and the pressure is increased to 0.5MPa to 0.7MPa, and the temperature is kept for 2h to 3h, and the temperature is further increased to 130°C to 150°C, and the temperature is kept for 1h to 2h, and finally the temperature is increased to 180°C to 200°C and the temperature is kept for 3h to 5h, and then the temperature is cooled to 40°C to 60°C at a cooling rate of 1°C/min to 3°C/min, and the pressure is released and the tank is taken out. 9. The method for preparing an ultra-wideband wave-absorbing honeycomb sandwich structure according to claim 7 is characterized in that in step (6), the process of the vacuum bag-autoclave curing process is as follows: under a vacuum degree of not less than 0.095 MPa, the temperature is increased to 80°C to 120°C at a heating rate of 1°C/min to 3°C/min, and the temperature is kept for 3h to 5h, and then the temperature is cooled to 40°C to 60°C at a cooling rate of 1°C/min to 3°C/min, and the pressure is released and the product is taken out of the autoclave. 10. The method for preparing an ultra-wideband absorbing honeycomb sandwich structure according to any one of claims 7 to 9, characterized in that in step (7), the bonding process of the adhesive film is as follows: the vacuum degree is not less than 0.095 MPa, the temperature is increased to 80°C to 120°C at a heating rate of 1°C/min to 3°C/min, and the temperature is kept for 2h to 4h, and then cooled to 40°C to 60°C at a cooling rate of 1°C/min to 3°C/min.