Electromagnetic wave absorption / transmission integrated light frequency selection metamaterial based on carbon fiber felt and simplified preparation process thereof

Abstract

The invention relates to the technical field of functional composite materials, in particular to a carbon fiber felt-based electromagnetic wave absorption / transmission integrated light frequency selection metamaterial and a simplified preparation process thereof, and the metamaterial comprises a symmetric structure which is periodically arranged and is provided with at least one unit structure; each unit structure comprises a frequency selection superstructure, a dielectric layer and a lossy frequency selection superstructure which are sequentially stacked from bottom to top; the unit structure of the frequency selection superstructure is square; the unit structure of the dielectric layer is square; the unit structure of the lossy frequency selection superstructure is in a cross shape. Through coupling cooperation of multiple layers of periodic unit arrays, the frequency selection metamaterial based on the carbon fiber felt replaces a metal pattern superstructure which is widely used at present, and the electromagnetic wave absorbing / transmitting metamaterial which has the advantages of being low in cost, easy to manufacture, easy in frequency band adjustment, light in weight and the like is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of functional composite materials, and in particular to a carbon fiber felt-based lightweight frequency-selective metamaterial capable of absorbing and transmitting electromagnetic waves and a streamlined preparation process thereof. Background Art

[0002] The ubiquitous presence of electromagnetic wave (EMW) radiation in the environment not only interferes with the normal operation of sensitive equipment such as civil aircraft radios, radars, and aerospace data transceivers, but also raises public concern about its potential harm to human health. With the advent of artificial intelligence and 5G communications, these issues are expected to become increasingly severe. Therefore, when designing and manufacturing products, it is crucial to convert most EMW into heat energy while minimizing secondary pollution, thereby dissipating any EMW that enters the medium. Materials with this capability, known as absorbers, are currently a hot research topic both domestically and internationally.

[0003] Metamaterials, as artificial electromagnetic periodic structures, can be endowed with extraordinary physical properties and unique physical effects through the design of unit patterns, thereby achieving impedance adjustment and precise control of electromagnetic fields at the structural level. This superior designability provides strong support for customized electromagnetic responses. Metamaterial absorbers, one of the application areas of metamaterials, are materials that absorb, scatter, or redirect electromagnetic waves. They can be used to reduce electromagnetic interference, enhance stealth, and improve solar cell efficiency. Research on metamaterial absorbers spans multiple disciplines, including physics, materials science, and electronic engineering, and is a challenging field with broad application prospects. To achieve precise structural design, materials with excellent and stable conductivity are required as the basis for metamaterials. Metals not only meet the required conductivity requirements but also offer excellent processability, making them widely used in the design and fabrication of traditional metamaterials. However, due to the inherent issues of metals, the core materials that directly determine their performance, such as rusting, heavy weight, and poor interface properties, the performance of these metamaterials in practical applications has fallen far short of expectations.

[0004] The rapid development of carbon fiber materials in recent years has made it possible to overcome the limitations of traditional metal-based metamaterials. Compared to metal materials, carbon fiber offers many unique advantages, including excellent corrosion resistance, lightweight, and superior interfacial properties. These characteristics can effectively address the shortcomings of traditional metal-based metamaterials in practical applications. Carbon fiber has lower electrical conductivity than metal, but it is precisely this property that gives it a certain degree of natural resistance. Therefore, compared to traditional metal-based metamaterials, new carbon fiber-based metamaterials have an additional adjustable material dimension, which provides greater flexibility in performance control and structural design.

[0005] As a new type of electromagnetic wave absorbing material, the frequency selective surface belongs to the category of metamaterials and is a class of periodic unit structures composed of patches or apertures. Through the structural regulation of the patches and apertures, the frequency selective electromagnetic protection surface can achieve transparent transmission or strong reflection in the target frequency band. On this basis, the derived frequency selective absorption surface can absorb electromagnetic waves in non-passband frequency bands. The traditional metal frequency selective surface does not meet the requirements of light weight, and has a narrow wave absorption bandwidth. The new type of frequency selective surface made of carbon-based conductive composite materials has the advantages of light weight, corrosion resistance, high temperature resistance, etc. In particular, the wave absorption bandwidth can be effectively expanded. Therefore, it has become a current research hotspot. Summary of the Invention

[0006] In order to solve the problems such as the large specific gravity and complex manufacturing process of the existing metamaterial wave absorber, the present invention provides a lightweight frequency selective metamaterial for absorbing and transmitting electromagnetic waves based on carbon fiber felt and its simplified preparation process.

[0007] The present invention is realized through the following technical solutions: A lightweight frequency selective metamaterial for absorbing and transmitting electromagnetic waves based on carbon fiber felt, including a symmetric structure with n×n unit structures arranged periodically; n is a positive integer; The unit structure includes a frequency selective superstructure, a dielectric layer, and a lossy frequency selective superstructure stacked in sequence from bottom to top; The unit structure of the frequency selective superstructure is a square frame shape, the unit size a1 = 15.23 - 23.71 mm, the inner side length a2 = 9.10 - 14.33 mm, and a2 < a1; made by laminating carbon fiber felt with a sheet resistance of 3 - 5 Ω / sq and a surface density of 40 - 80 g / m 2 and quartz fiber cloth / epoxy composite material; the middle part of the unit structure of the frequency selective superstructure has a square frame-shaped groove where the carbon fiber felt is removed, and the square frame-shaped groove exposes the inner quartz fiber cloth / epoxy composite material, forming a unit structure with carbon fiber felt on the four peripheries; The unit structure of the dielectric layer is a square, the unit size is a1, and the thickness is h = 3.20 - 9.16 mm; when h varies within the range of 3.20 - 9.16 mm, the wave absorption band position and the wave transmission band position of the lightweight frequency selective metamaterial for absorbing and transmitting electromagnetic waves based on carbon fiber felt are always near the series resonance point of the lossy frequency selective superstructure and the parallel resonance point of the frequency selective superstructure respectively; the dielectric layer is made of polystyrene foam board; The unit structure of the lossy frequency selective superstructure is a cross, the unit size is a1, the arm length b1=15.00-20.75 mm, the arm width b2=1.51-3.25 mm, and b2<b1<a1; the sheet resistance is 4-25 Ω / sq and the surface density is 5-50 g / m 2 The unit structure of the lossy frequency selective superstructure comprises a cross-shaped protrusion with the carbon fiber felt removed from the periphery, and the inner quartz fiber cloth / epoxy composite material is exposed at the periphery of the cross-shaped protrusion, thereby forming a unit structure of the cross-shaped protrusion with carbon fiber felt.

[0008] As a further improvement to the technical solution of the present invention, the thicknesses of the carbon fiber felt and the quartz fiber cloth / epoxy composite material of the unit structure of the frequency selective superstructure are 0.05-1 mm and 0.5-5 mm, respectively.

[0009] As a further improvement of the technical solution of the present invention, the thicknesses of the carbon fiber felt and the quartz fiber cloth / epoxy composite material of the unit structure of the lossy frequency selective superstructure are 0.05-1 mm and 0.5-5 mm, respectively.

[0010] As a further improvement of the technical solution of the present invention, the unit structures of the frequency selective superstructure, the dielectric layer and the lossy frequency selective superstructure correspond one to one from bottom to top.

[0011] As a further improvement of the technical solution of the present invention, the frequency selective superstructure has a reflection effect similar to that of an ideal conductor in the wave absorption band, and produces a wave transmission effect through LC parallel resonance in the wave transmission band.

[0012] As a further improvement of the technical solution of the present invention, the lossy frequency selective superstructure achieves impedance matching conditions through LC series resonance in the wave absorption band, and produces a wave transmission effect through LC parallel resonance in the wave transmission band.

[0013] As a further improvement to the technical solution of the present invention, the lossy frequency selective superstructure as the top structure and the frequency selective superstructure as the bottom structure achieve effective transmission of electromagnetic waves by jointly generating parallel resonance within the wave transmission band.

[0014] The present invention further provides a method for preparing a lightweight frequency selective metamaterial based on carbon fiber felt that absorbs and transmits electromagnetic waves, comprising the following steps: (1) Cut square carbon fiber felt and quartz fiber cloth according to the side length n×a1, and the required quartz fiber cloth is 2-10 layers in total; prepare epoxy resin glue, lay a layer of quartz fiber cloth, brush the resin glue once and let the glue soak into the quartz fiber cloth, and compact it after laying; soak the carbon fiber felt with epoxy resin glue and place it on the surface of the laid and compacted quartz fiber cloth, and obtain the carbon fiber felt-quartz fiber cloth / epoxy resin prepreg of frequency selective superstructure and lossy frequency selective superstructure respectively; (2) After evenly applying the release agent on the mold surface, the frequency selective superstructure and the lossy frequency selective superstructure carbon fiber felt-quartz fiber cloth / epoxy resin prepreg are placed in the mold respectively, the molds are closed and cured at 120 °C and 15 MPa. After curing, they are naturally cooled to room temperature and demolded to obtain the frequency selective superstructure and the lossy frequency selective superstructure carbon fiber felt-quartz fiber cloth / epoxy resin composite material plates respectively; (3) The frequency selective superstructure and the carbon fiber felt-quartz fiber cloth / epoxy resin composite material plate of the lossy frequency selective superstructure are respectively placed on the engraving machine table and fixed, and the carbon fiber felt of a part of the carbon fiber felt-quartz fiber cloth / epoxy resin composite material plate of the frequency selective superstructure is removed by a milling cutter to form n×n square grooves, exposing the inner quartz fiber cloth / epoxy composite material, forming a unit structure of the frequency selective superstructure with periodic distribution, and obtaining the frequency selective superstructure; the carbon fiber felt of a part of the carbon fiber felt-quartz fiber cloth / epoxy resin composite material plate of the lossy frequency selective superstructure is removed by a milling cutter to form n×n cross-shaped protrusions, and the inner quartz fiber cloth / epoxy composite material is exposed around the cross-shaped protrusions to form a unit structure of the lossy frequency selective superstructure with periodic distribution, and obtaining the lossy frequency selective superstructure; (4) The prepared frequency selective superstructure and lossy frequency selective superstructure are respectively glued to the two surfaces of the polystyrene foam board through one side of the quartz fiber cloth / epoxy composite material with glue, and after compaction, the carbon fiber felt-based electromagnetic wave absorbing / permeable integrated lightweight frequency selective metamaterial is obtained.

[0015] Compared with the prior art, the present invention has the following advantages: 1) By coupling multi-layer periodic unit arrays, a frequency-selective metamaterial based on carbon fiber mat replaces the currently widely used metal patterned metastructures, resulting in an electromagnetic wave-absorbing / transmitting metamaterial with advantages such as low cost, ease of manufacture, easily adjustable frequency bands, and low weight. This invention utilizes a frequency-selective metamaterial based on carbon fiber mat to replace the currently widely used metal patterned metastructures. Combined with an epoxy resin-reinforced quartz fiber cloth composite material, the resulting metamaterial possesses advantages such as low weight, corrosion resistance, and high temperature resistance.

[0016] 2) The present invention can adjust the parameters of the specific structure according to actual needs. By changing the electrical performance parameters of the metamaterial, the required electromagnetic wave transmission and absorption frequency bands can be obtained. In addition, the metamaterial has excellent wave transmission performance in the required operating frequency band, with the minimum insertion loss reaching -1.14 dB. At the same time, the metamaterial has excellent wave absorption performance in the required operating frequency band, with an absorption rate of more than 0.9. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 This is a schematic diagram of the unit structure of the carbon fiber felt-based electromagnetic wave absorption / transmission integrated lightweight frequency selective metamaterial of the present invention.

[0020] Figure 2 Schematic diagram of the frequency selection superstructure unit structure of the present invention.

[0021] Figure 3 Schematic diagram of the structure of the lossy frequency selection superstructure unit of the present invention.

[0022] Figure 4 This is a front view of the carbon fiber felt-based lightweight frequency-selective metamaterial that absorbs and transmits electromagnetic waves in one body, prepared in Example 1 of the present invention.

[0023] Figure 5 This is a back view of the carbon fiber felt-based lightweight frequency-selective metamaterial capable of absorbing and transmitting electromagnetic waves prepared in Example 1 of the present invention.

[0024] Figure 6 Radar wave absorptivity curves for the 2-18 GHz radar wave absorptivity of the carbon fiber felt-based lightweight frequency-selective metamaterials fabricated in Examples 1, 2, 3, and 4 of the present invention. The graphs show that all of the metastructures achieve absorptivity greater than 0.9 at various frequencies. Examples 1 and 2 primarily absorb at low frequencies below 12 GHz, while Examples 3 and 4 also exhibit high absorptivity at high frequencies above 16 GHz.

[0025] Figure 7These are the S-parameter curves for the 2-18 GHz range of the lightweight, frequency-selective metamaterials based on carbon fiber felt that absorb and transmit electromagnetic waves, manufactured in Examples 1, 2, 3, and 4 of the present invention. The figures show that all of the metastructures in these examples achieve an insertion loss (IL) of less than -3 dB at various frequencies. Examples 1 and 2 primarily transmit high frequencies above 13 GHz, while Examples 3 and 4 primarily transmit mid-range frequencies between 8 and 10 GHz. DETAILED DESCRIPTION

[0026] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0028] The specific embodiments of the present invention are described in detail below.

[0029] The polystyrene foam board used in the following examples was purchased from Shanxi Sihai Youcheng Building Materials Technology Co., Ltd. Example 1

[0030] A lightweight frequency selective metamaterial based on carbon fiber felt that absorbs and transmits electromagnetic waves, which consists of 10×10 periodically arranged Figure 1 The symmetrical structure of the unit cell structure shown; The unit structure of the frequency selective superstructure is a square shape, with a unit size a1 = 18 mm and an inner side length a2 = 11.48 mm; the square resistance is 4 Ω / sq and the surface density is 50 g / m 2 The carbon fiber felt is 1 mm thick and the quartz fiber cloth / epoxy resin composite material is 2 mm thick.

[0031] The thickness of the dielectric layer is h = 7.9 mm.

[0032] The unit structure of the lossy frequency selective superstructure is a cross-shaped unit with a unit size a1=18 mm, an arm length b1=17.16 mm, and an arm width b2=2.16 mm; the sheet resistance is 25 Ω / sq and the surface density is 5 g / m 2 The carbon fiber felt is 0.05 mm thick and the quartz fiber cloth / epoxy resin composite material is 3 mm thick.

[0033] Its manufacturing process is: (1) Preparation of E-51 epoxy resin glue First, the curing agent, cis-hexahydrophthalic anhydride (HHPA), was preheated in a 70°C oven until liquid. Next, E-51 epoxy resin and HHPA were weighed in a mass ratio of 1:0.8 and thoroughly mixed in a 60°C water bath using mechanical stirring at 500 rpm and ultrasonic dispersion at 100 W. During this process, 0.1 wt% of the accelerator 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) and 0.3 wt% of a silicone oil defoamer were added to the resin system. Finally, the mixture was defoamed in a 70°C vacuum oven for 30 minutes to obtain the prepared epoxy resin adhesive.

[0034] (2) Preparation of carbon fiber felt-quartz fiber cloth / epoxy resin prepreg First, four layers of 180 × 180 mm quartz fiber cloth and a frequency-selective superstructure carbon fiber felt (SCFV) of the same size were cut. The quartz fiber cloth was then weighed and E-51 resin adhesive was weighed to a 40% volume fraction. A layer of quartz fiber cloth was laid, and the resin adhesive was applied once, allowing the adhesive to penetrate the quartz fiber cloth. After laying, the cloth was compacted. Next, the SCFV of the frequency-selective superstructure was soaked with epoxy resin adhesive and placed on top of the laid and compacted quartz fiber cloth, resulting in a frequency-selective superstructure SCFV-quartz fiber cloth / epoxy resin prepreg.

[0035] Six layers of 180 × 180 mm quartz fiber cloth and a lossy frequency selective superstructure (SCFV) of the same size were cut. The quartz fiber cloth was then weighed and E-51 resin adhesive was weighed to a 40% volume fraction. A layer of quartz fiber cloth was laid and the resin adhesive was applied once, allowing the adhesive to saturate the cloth. After laying, the cloth was compacted. Next, epoxy resin adhesive was soaked in the SCFV and placed on top of the laid and compacted quartz fiber cloth, resulting in a SCFV-quartz fiber cloth / epoxy resin prepreg.

[0036] (3) Fabrication of frequency selective superstructures and lossy frequency selective superstructures by hot pressing-machining After evenly applying mold release agent to the surface of a 250×250 mm steel mold, the mold was preheated in a 100°C oven. The SCFV-quartz fiber cloth / epoxy resin prepreg, a frequency-selective superstructure or lossy frequency-selective superstructure, was placed on the mold's lower plate and prepolymerized in a 100°C hot press for 30 minutes. After prepolymerization, the mold was closed and a pressure of 15 MPa was applied. The hot press temperature was raised to 120°C and cured for 2 hours. Finally, after maintaining the pressure and cooling naturally to room temperature, the mold was removed, resulting in a SCFV-quartz fiber cloth / epoxy resin composite plate, a frequency-selective superstructure or lossy frequency-selective superstructure.

[0037] (4) The prepared frequency selective superstructure SCFV-quartz fiber cloth / epoxy resin composite material plate is placed on the table of the engraving machine and fixed, and a milling cutter is used to process it into a U-shaped unit structure of 10×10 frequency selective superstructures, wherein the middle part of the U-shaped unit structure has a U-shaped groove with the carbon fiber felt removed, and the U-shaped groove exposes the quartz fiber cloth / epoxy composite material on the inside, forming a unit structure with carbon fiber felt on the edges, thereby obtaining a frequency selective superstructure; A lossy frequency selective superstructure SCFV-quartz fiber cloth / epoxy resin composite material plate is placed on the table of an engraving machine and fixed. A milling cutter is used to process it into a 10×10 cross-shaped unit structure of the lossy frequency selective superstructure. The middle part of the cross-shaped unit structure has a cross-shaped protrusion with the carbon fiber felt removed from the periphery. The periphery of the cross-shaped protrusion exposes the inner quartz fiber cloth / epoxy composite material, forming a unit structure with the cross-shaped protrusion and carbon fiber felt, thereby obtaining a lossy frequency selective superstructure.

[0038] (5) Assembling and preparing a lightweight frequency-selective metamaterial based on carbon fiber felt that absorbs and transmits electromagnetic waves The prepared frequency-selective superstructure and the loss-frequency-selective superstructure were glued to the two surfaces of a polystyrene foam board with a thickness of h=7.9 mm through one side of a quartz fiber cloth / epoxy resin composite material. After compaction, a lightweight frequency-selective metamaterial based on carbon fiber felt that absorbs / transmits electromagnetic waves was obtained.

[0039] Depend on Figure 6 (a) It can be seen that the strongest absorption of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 5.38 GHz, with an absorption rate of 0.93; the effective absorption bandwidth (S 11 ≤-10 dB and S 21 ≤-10 dB) is 4.60-10.08 GHz, reaching 5.48 GHz.

[0040] Depend on Figure 7(a) It can be seen that the minimum IL of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 15.12 GHz, as low as -1.14 dB, and the transmittance can reach more than 70%; effective transmission is achieved at 12.54-16.88 GHz (S 11 ≤-10 dB and S 21 ≥-3 dB). Example 2

[0041] The manufacturing process is the same as that of Example 1, except that the surface density of the carbon fiber felt of the frequency selective superstructure is 40 g / m 2 , the square resistance is 5Ω / sq; the surface density of the carbon fiber felt of the lossy frequency selective superstructure is 10 g / m 2 The square resistance is 20Ω / sq. The thickness of the carbon fiber felt of the frequency selective superstructure is 0.05 mm, and the thickness of the quartz fiber cloth / epoxy resin composite material is 0.5 mm. The thickness of the carbon fiber felt of the lossy frequency selective superstructure is 1 mm, and the thickness of the quartz fiber cloth / epoxy resin composite material is 5 mm. In addition, the structural parameters are: a1=15.23 mm, a2=9.10 mm, b1=15.00 mm, b2=1.51 mm, h=3.20 mm.

[0042] Depend on Figure 6 (b) It can be seen that the strongest absorption of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 4.98 GHz, with an absorption rate of 0.94; the effective absorption bandwidth (S 11 ≤-10 dB and S 21 ≤-10 dB) is 4.09-10.04 GHz, reaching 5.95 GHz.

[0043] Depend on Figure 7 (b) It can be seen that the minimum IL of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 14.43 GHz, as low as -1.95 dB, and the transmittance can reach more than 60%; effective transmission is achieved at 12.80-15 GHz (S 11 ≤-10 dB and S 21 ≥-3 dB). Example 3

[0044] The manufacturing process is the same as that of Example 1, except that the surface density of the carbon fiber felt of the frequency selective superstructure is 70 g / m 2 , the square resistance is 3.5 Ω / sq; the surface density of the carbon fiber felt of the lossy frequency selective superstructure is 20 g / m 2The sheet resistance is 15 Ω / sq. The thickness of the carbon fiber felt of the frequency selective superstructure is 1 mm, and the thickness of the quartz fiber cloth / epoxy resin composite material is 0.5 mm. The thickness of the carbon fiber felt of the lossy frequency selective superstructure is 1 mm, and the thickness of the quartz fiber cloth / epoxy resin composite material is 0.5 mm. In addition, the structural parameters are: a1=20.45 mm, a2=11.74 mm, b1=19 mm, b2=3.00 mm, and h=8.30 mm.

[0045] Depend on Figure 6 (c) It can be seen that the strongest absorption of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 17.75 GHz, producing a strong absorption rate of 0.98; the effective absorption bandwidth (S 11 ≤-10 dB and S 21 ≤-10dB) are 2.98-4.55, 6.15-8, 16.72-18 GHz, totaling to 4.7 GHz.

[0046] Depend on Figure 7 (c) It can be seen that the minimum IL of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 10.79 GHz, as low as -2.39 dB, and the transmittance can reach more than 50%; effective transmission is achieved at 10.06-11.41 GHz (S 11 ≤-10 dB and S 21 ≥-3 dB). Example 4

[0047] The manufacturing process is the same as that of Example 1, except that the surface density of the carbon fiber felt of the frequency selective superstructure is 80 g / m 2 , the square resistance is 3 Ω / sq; the surface density of the carbon fiber felt of the lossy frequency selective superstructure is 5 g / m 2 The square resistance is 25 Ω / sq. The thickness of the carbon fiber felt of the frequency selective superstructure is 1 mm, and the thickness of the quartz fiber cloth / epoxy resin composite is 5 mm. The thickness of the carbon fiber felt of the lossy frequency selective superstructure is 0.05 mm, and the thickness of the quartz fiber cloth / epoxy resin composite is 0.5 mm. In addition, the structural parameters are: a1=23.71 mm, a2=14.33 mm, b1=20.75 mm, b2=3.25 mm, h=9.16 mm.

[0048] Depend on Figure 6 (d) It can be seen that the strongest absorption of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 17.02 GHz, producing a strong absorption rate of 0.99; the effective absorption bandwidth (S 11≤-10 dB and S 21 ≤-10dB) is 3.17-6.88, 15.84-18 GHz, reaching 5.87 GHz.

[0049] Depend on Figure 7 (d) It can be seen that the minimum IL of the electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial based on carbon fiber felt appears at 9.48 GHz, as low as -2.20 dB, and the transmittance can reach more than 50%; effective transmission is achieved at 8.64-10.15 GHz (S 11 ≤-10 dB and S 21 ≥-3 dB).

[0050] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. A lightweight frequency selective metamaterial based on carbon fiber felt that absorbs and transmits electromagnetic waves, characterized by: A symmetrical structure comprising periodically arranged n×n unit structures, wherein n is a positive integer; the unit structure comprises a frequency selective superstructure, a dielectric layer, and a lossy frequency selective superstructure stacked in sequence from bottom to top; The unit structure of the frequency selective superstructure is in the shape of a square frame. The unit size a1 = 15.23 - 23.71 mm, the inner side length a2 = 9.10 - 14.33 mm, and a2 < a1; it is made by laminating a carbon fiber felt with a sheet resistance of 3 - 5 Ω / sq and a surface density of 2 2 40 - 80 g / m and a quartz fiber cloth / epoxy composite material; there is a square frame-shaped groove in the middle of the unit structure of the frequency selective superstructure, and the square frame-shaped groove exposes the inner quartz fiber cloth / epoxy composite material, forming a unit structure with carbon fiber felt on the four peripheries; The dielectric layer has a square unit structure, a unit size a1, and a thickness h = 3.20-9.16 mm. When h varies within the range of 3.20-9.16 mm, the absorption band position and the transmission band position of the carbon fiber felt-based electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial are always located near the series resonance point of the lossy frequency selective superstructure and the parallel resonance point of the frequency selective superstructure, respectively. The dielectric layer is made of polystyrene foam board. The unit structure of the lossy frequency selective superstructure is a cross-shaped unit with a unit size of a1, an arm length b1=15.00-20.75mm, an arm width b2=1.51-3.25mm, and b2<b1<a1; the sheet resistance is 4-25Ω / sq and the surface density is 5-50g / m 2 The unit structure of the lossy frequency selective superstructure comprises a cross-shaped protrusion with the carbon fiber felt removed from the periphery, and the inner quartz fiber cloth / epoxy composite material is exposed at the periphery of the cross-shaped protrusion, thereby forming a unit structure of the cross-shaped protrusion with carbon fiber felt.

2. The carbon fiber felt-based lightweight frequency selective metamaterial capable of absorbing and transmitting electromagnetic waves according to claim 1, characterized in that: The thicknesses of the carbon fiber felt and the quartz fiber cloth / epoxy composite material of the unit structure of the frequency selective superstructure are 0.05-1 mm and 0.5-5 mm respectively.

3. The carbon fiber felt-based electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial according to claim 1, characterized in that: The thicknesses of the carbon fiber felt and the quartz fiber cloth / epoxy composite material of the unit structure of the lossy frequency selective superstructure are 0.05-1 mm and 0.5-5 mm respectively.

4. The carbon fiber felt-based lightweight frequency selective metamaterial capable of absorbing and transmitting electromagnetic waves according to claim 1, characterized in that: The unit structures of the frequency selective superstructure, the dielectric layer and the lossy frequency selective superstructure correspond one to one from bottom to top.

5. The carbon fiber felt-based electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial according to claim 1, characterized in that: The frequency selective superstructure has a reflection effect similar to that of an ideal conductor in the wave absorption band, and produces a wave transmission effect through LC parallel resonance in the wave transmission band.

6. The carbon fiber felt-based electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial according to claim 1, characterized in that: The lossy frequency selective superstructure achieves impedance matching conditions through LC series resonance in the wave absorbing band, and produces a wave transmitting effect through LC parallel resonance in the wave transmitting band.

7. The carbon fiber felt-based electromagnetic wave absorbing / transmitting integrated lightweight frequency selective metamaterial according to claim 1, characterized in that: The lossy frequency selective superstructure as the top structure and the frequency selective superstructure as the bottom structure achieve effective transmission of electromagnetic waves by jointly generating parallel resonance within the wave transmission band.

8. The method for preparing a lightweight frequency selective metamaterial based on carbon fiber felt that absorbs and transmits electromagnetic waves according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Cut square carbon fiber felt and quartz fiber cloth according to the side length n×a1, and the required quartz fiber cloth is 2-10 layers in total; prepare epoxy resin glue, lay a layer of quartz fiber cloth, brush the resin glue once and let the glue soak into the quartz fiber cloth, and compact it after laying; soak the carbon fiber felt with epoxy resin glue and place it on the surface of the laid and compacted quartz fiber cloth, and obtain the carbon fiber felt-quartz fiber cloth / epoxy resin prepreg of frequency selective superstructure and lossy frequency selective superstructure respectively; (2) After evenly applying the release agent on the mold surface, the frequency selective superstructure and the lossy frequency selective superstructure carbon fiber felt-quartz fiber cloth / epoxy resin prepreg are placed in the mold respectively, the molds are closed and cured at 120 °C and 15 MPa. After curing, they are naturally cooled to room temperature and demolded to obtain the frequency selective superstructure and the lossy frequency selective superstructure carbon fiber felt-quartz fiber cloth / epoxy resin composite material plates respectively; (3) The frequency selective superstructure and the carbon fiber felt-quartz fiber cloth / epoxy resin composite material plate of the lossy frequency selective superstructure are respectively placed on the engraving machine table and fixed, and the carbon fiber felt of a part of the carbon fiber felt-quartz fiber cloth / epoxy resin composite material plate of the frequency selective superstructure is removed by a milling cutter to form n×n square grooves, exposing the inner quartz fiber cloth / epoxy composite material, forming a unit structure of the frequency selective superstructure with periodic distribution, and obtaining the frequency selective superstructure; the carbon fiber felt of a part of the carbon fiber felt-quartz fiber cloth / epoxy resin composite material plate of the lossy frequency selective superstructure is removed by a milling cutter to form n×n cross-shaped protrusions, and the inner quartz fiber cloth / epoxy composite material is exposed around the cross-shaped protrusions to form a unit structure of the lossy frequency selective superstructure with periodic distribution, and obtaining the lossy frequency selective superstructure; (4) The prepared frequency selective superstructure and lossy frequency selective superstructure are respectively glued to the two surfaces of the polystyrene foam board through one side of the quartz fiber cloth / epoxy composite material with glue, and after compaction, the carbon fiber felt-based electromagnetic wave absorbing / permeable integrated lightweight frequency selective metamaterial is obtained.

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