A double-sided wave-absorbing broadband stealth composite material and a preparation method thereof

Abstract

The application belongs to the technical field of radar wave absorbing materials, and discloses a double-sided wave absorbing broadband stealth composite material and a preparation method thereof. The double-sided wave absorbing broadband stealth composite material comprises a non-metallic base composite material body and at least five metamaterial layers arranged at intervals in the thickness direction of the non-metallic base composite material body. The number of the metamaterial layers is odd, and an intermediate metamaterial layer is arranged at the middle position in the thickness direction, and the remaining metamaterial layers are symmetrically distributed on both sides of the intermediate metamaterial layer. The metamaterial layer comprises periodically arranged conductive pattern units. The relative dielectric constant of the non-metallic base composite material body is not greater than 10. The double-sided wave absorbing broadband stealth composite material does not contain a metal reflection layer. When the material is vertically incident to electromagnetic waves with a frequency of 1-18 GHz, the transmittance is small (<-13 dB, i.e. <5%), and the reflectivity is low in a wide wave band. The preparation method is simple to operate and easy to realize large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of radar absorbing materials technology, specifically relating to a broadband structure absorbing material with double-sided absorbing properties and its preparation method. Background Technology

[0002] Aero engines typically require stealth capabilities, often employing S-shaped air intakes with radar-absorbing materials on their inner walls. These S-shaped intakes prevent radar waves from directly scattering high-scattering components like engine blades. As incident radar waves enter the S-shaped intake cavity, they undergo multiple reflections and absorptions, significantly reducing backscattered energy. However, S-shaped intakes are not suitable for all aircraft models because they require substantial space within the fuselage. In the absence of S-shaped intakes, components such as aero engine fan blades become strong radar scatterers, making the design and fabrication of radar-absorbing blades and guide vanes a pressing need.

[0003] The Chinese invention patent application with application number CN202210260490.3 discloses a wave-absorbing guide fluid at the inlet of an aero-engine. The technical solution is to use a non-metallic composite material with wave-absorbing function to manufacture the outer ring, inner ring and multiple guide fluid support plates, which are combined to form a wave-absorbing guide fluid. However, it does not provide the technical solution and performance of the non-metallic composite material with wave-absorbing function.

[0004] Chinese invention patent application CN202211611081.X discloses an adaptive wave-absorbing and fluid-guiding device for aero-engines, including a casing made of wave-absorbing composite material, a wave-absorbing inner ring concentrically arranged with the casing, multiple adjustable wave-absorbing blades distributed circumferentially along the casing, a conical fairing disposed at the leading edge of the wave-absorbing inner ring, and an actuation mechanism. The adjustable wave-absorbing blades include an adjustable wave-absorbing blade leading edge made of metal material and an adjustable wave-absorbing blade rear part made of wave-absorbing composite material, but it does not provide the technical solution and performance of the wave-absorbing composite material.

[0005] The air intake guide vanes are located in the engine cavity. Radar waves encounter various components in the cavity and undergo complex scattering, incident on the front and back of the guide vanes from multiple directions. Therefore, the guide vanes are different from conventional radar-absorbing materials and can be designed to absorb radar waves on both sides. Secondly, achieving wide-band radar absorption with limited thickness, especially the absorption of low-frequency bands such as L and S, is still a pain point in the industry. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a broadband stealth composite material with double-sided absorbing properties for products such as guide vanes and to improve the absorbing performance of L and S low-frequency bands, mainly for use in components inside cavities and in applications such as projectile wings.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A broadband stealth composite material with double-sided microwave absorption includes a non-metallic matrix composite body and at least five metamaterial layers spaced apart along the thickness direction of the non-metallic matrix composite body; the number of metamaterial layers is odd, with an intermediate metamaterial layer located at the middle position along the thickness direction, and the remaining metamaterial layers symmetrically distributed on both sides of the intermediate metamaterial layer; each metamaterial layer contains periodically arranged conductive pattern units; the relative permittivity of the non-metallic matrix composite body is not greater than 10; and the broadband stealth composite material with double-sided microwave absorption does not contain a metallic reflective layer.

[0009] Preferably, the above-mentioned dual-sided microwave-absorbing broadband stealth composite material has five metamaterial layers, including one intermediate metamaterial layer, and two inner metamaterial layers and two outer metamaterial layers arranged symmetrically from the intermediate metamaterial layer to both sides.

[0010] Preferably, the conductive pattern unit of the intermediate metamaterial layer is a square ring structure with a central square hole, the side length of a single square ring structure is 3~30mm, and the side length of the central square hole in the square ring structure is 0.3~0.8 times the unit size; the conductive pattern unit of the inner metamaterial layer is composed of a first discontinuous small square array, the side length of a single small square is 2~20mm; the conductive pattern unit of the outer metamaterial layer is composed of a second discontinuous small square array, the side length of a single small square is 2~20mm.

[0011] Preferably, the sheet resistance of the conductive pattern unit in the intermediate metamaterial layer is no greater than 0.5 Ω / □; the sheet resistance of the conductive pattern unit in the inner metamaterial layer (31, 32) is 30~50 Ω / □; and the sheet resistance of the conductive pattern unit in the outer metamaterial layer is 120~150 Ω / □.

[0012] Preferably, the conductive pattern units of the intermediate metamaterial layer, inner metamaterial layer and outer metamaterial layer are all composed of a discontinuous array of small squares, and the side length of a single small square is 5~30mm.

[0013] Preferably, the sheet resistance of the conductive pattern unit of the intermediate metamaterial layer (2) is 20~30Ω / □; the sheet resistance of the conductive pattern unit of the inner metamaterial layer is 120~180Ω / □; and the sheet resistance of the conductive pattern unit of the outer metamaterial layer is 130~170Ω / □.

[0014] Preferably, the conductive pattern is formed on a non-conductive fiber substrate by screen printing conductive paste or resistive paste; the non-conductive fiber substrate is at least one of glass fiber fabric, basalt fiber fabric and quartz fiber fabric; the conductive paste is conductive silver paste, which can be a commercially available finished product or prepared by grinding and dispersing flake silver powder in resin; the resistive paste is conductive carbon paste, which is obtained by grinding and dispersing conductive graphite and conductive carbon black in resin.

[0015] Preferably, the non-metallic composite material body is at least one of glass fiber reinforced bismaleimide resin composite material, quartz fiber reinforced bismaleimide resin composite material, glass fiber reinforced epoxy resin composite material, basalt fiber reinforced epoxy resin composite material, glass fiber reinforced vinyl ester resin composite material, and quartz fiber reinforced epoxy resin composite material; the total thickness of the double-sided absorbing broadband stealth composite material is 5~30mm.

[0016] Traditionally, double-sided absorbing composite materials typically include a metallized reflective layer in the middle, with materials on either side interacting with electromagnetic waves to achieve absorption. This reflective layer prevents the material from fully utilizing its entire thickness for absorption. This invention eliminates the reflective layer, allowing the material to function as a single unit, thus increasing the effective thickness and improving low-frequency absorption performance. This invention reduces reflectivity while maintaining low transmittance. Based on the relationship that the sum of reflectivity, transmittance, and absorptivity is 1, the invention controls the material to have low transmittance and low reflectivity, indicating high absorptivity. Simultaneously, the low transmittance ensures that the absorption performance is minimally affected by the metal reflector on the back of the material.

[0017] This invention designs a double-sided radar-absorbing composite material while limiting the transmittance of the material. The design utilizes the overall thickness of the composite material to achieve a wide-band radar absorption effect and improves the absorption performance of lower frequency bands (such as L and S bands). This is because lower frequency electromagnetic waves have longer wavelengths, requiring a larger radar-absorbing material thickness to achieve stronger absorption.

[0018] Based on a general inventive concept, the present invention also provides a method for preparing a double-sided microwave-absorbing broadband stealth composite material, comprising the following steps:

[0019] (1) On the substrate of the metamaterial layer, conductive pattern units with different structural parameters and / or sheet resistance are printed by screen printing process to form at least five metamaterial layers, including an intermediate metamaterial layer (2).

[0020] (2) Lay up a non-metallic matrix composite preform on the mold, and arrange the metamaterial layers obtained in step (1) at preset position intervals in the thickness direction of the non-metallic matrix composite preform, so that the intermediate metamaterial layer (2) is located in the middle position in the thickness direction, and the remaining metamaterial layers are symmetrically distributed on both sides of the intermediate metamaterial layer (2) to obtain a composite preform.

[0021] (3) The double-sided microwave-absorbing broadband stealth composite material preform obtained after step (2) is cured to impregnate and cure the resin to form an integrated composite material.

[0022] (4) Demold the composite material obtained after curing in step (3) and perform surface treatment to obtain the broadband stealth composite material with double-sided wave absorption.

[0023] In the above preparation method, preferably, the curing treatment is performed by vacuum resin injection molding or compression molding;

[0024] When the vacuum resin injection molding method is used, the non-metallic matrix composite preform in step (2) is a dry fiber fabric. In step (3), liquid resin is introduced into the mold under negative pressure and the dry fiber fabric and metamaterial layer are impregnated, and then vacuum pressure curing is performed.

[0025] When the molding and curing method is adopted, the non-metallic composite material preform in step (2) is a resin prepreg of fiber fabric, and in step (3), the resin in the resin prepreg of the fiber fabric is melted, impregnated and cured by heating and pressurizing the mold.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The broadband stealth composite material with double-sided wave absorption of the present invention eliminates the metallized reflective layer in the traditional design. By setting several layers of metamaterial layers with periodic patterns in the non-metallic matrix composite material, and by optimizing the design of the pattern, sheet resistance and position of the metamaterial layers in the composite material, double-sided absorption of electromagnetic waves incident from the front and back is achieved. It also has low reflectivity and low transmittance in a wide frequency band (especially in the low frequency band), ensuring high absorption rate.

[0028] 2. The broadband stealth composite material with double-sided wave absorption of the present invention has a low transmittance (<-13dB, i.e., <5%) when electromagnetic waves of frequency 1~18GHz are vertically incident, and at the same time has a low reflectivity (less than -10dB) in a wide band (6GHz-18GHz).

[0029] 3. The broadband stealth composite material with double-sided wave absorption of the present invention has both structural load-bearing and stealth functions, and can be directly used to manufacture structural components such as guide vanes, realizing the integrated design of stealth and structure; and the low transmittance means that the metal or high reflective components on the back of the material have little impact on the wave absorption performance of the front of the material, thus improving the performance stability in actual complex cavity environments.

[0030] 4. The preparation method of the present invention adopts screen printing and composite material molding process (such as vacuum introduction and molding), which is simple to operate and easy to achieve large-scale production. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the broadband stealth composite material structure with double-sided wave absorption according to the present invention;

[0033] Figure 2 This is a schematic diagram of the periodic pattern of the intermediate metamaterial layer in Embodiment 1 of the present invention;

[0034] Figure 3 This is a schematic diagram of the periodic pattern of the inner metamaterial layer in Embodiment 1 of the present invention;

[0035] Figure 4 This is a reflectance curve of the broadband stealth composite material with double-sided wave absorption according to Embodiment 1 of the present invention;

[0036] Figure 5 This is a transmittance curve of the broadband stealth composite material with double-sided wave absorption according to Embodiment 1 of the present invention.

[0037] Figure 6 This is a comparison diagram of the reflectivity of the double-sided absorbing broadband stealth composite material of Embodiment 1 of the present invention with and without a metal backing.

[0038] Figure 7 This is a schematic diagram of the periodic pattern of the intermediate metamaterial layer in Embodiment 2 of the present invention;

[0039] Figure 8 This is a reflectance curve of the broadband stealth composite material with double-sided wave absorption in Embodiment 2 of the present invention;

[0040] Figure 9 This is a transmittance curve of the broadband stealth composite material with double-sided wave absorption in Embodiment 2 of the present invention;

[0041] Figure 10 This is a comparison diagram of the reflectivity of the double-sided absorbing broadband stealth composite material of Embodiment 2 of the present invention with and without a metal backing.

[0042] Figure 1 Legend of the diagram:

[0043] 1. Non-metallic matrix composite body; 2. Intermediate metamaterial layer; 31, 32. Inner metamaterial layer; 41, 42. Outer metamaterial layer. Detailed Implementation

[0044] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0045] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0046] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0047] Example 1:

[0048] A broadband stealth composite material with double-sided wave absorption, such as Figure 1 Five metamaterial layers are arranged at intervals in the non-metallic composite material body 1 (glass fiber reinforced epoxy resin composite material), with a total material thickness of 10 mm. An intermediate metamaterial layer 2 is positioned at the midpoint of the thickness direction. Two inner metamaterial layers 31 and 32 and two outer metamaterial layers 41 and 42 are symmetrically arranged on both sides of the intermediate metamaterial layer 2. Each metamaterial layer contains periodically arranged conductive pattern units. These conductive pattern units are obtained by screen printing conductive silver paste onto the glass fiber fabric. Specifically:

[0049] The periodically arranged conductive pattern units in the intermediate metamaterial layer 2 have a side length of 20mm and are squares with a central square hole (i.e., a square ring structure). The side length of the central square hole is 9.3mm. Figure 2 As shown; the sheet resistance of the pattern is no greater than 0.5Ω / □;

[0050] The conductive pattern units periodically arranged in the inner metamaterial layers 31 and 32 also have a side length of 20mm, such as... Figure 3 The image shows a periodic pattern composed of discontinuous small squares, with the sheet resistance of the small squares ranging from 20 to 30 Ω / □.

[0051] The conductive pattern units arranged periodically in the outer metamaterial layers 41 and 42 also have a side length of 20mm and are periodic patterns composed of small squares; the sheet resistance of the small squares is between 120 and 150Ω / □.

[0052] The preparation method of the broadband stealth composite material with double-sided wave absorption in this embodiment includes the following steps:

[0053] (1) Printing metamaterial layers: Using screen printing technology, periodic patterns with different structural parameters and different sheet resistances are printed on glass fiber satin cloth with commercially available conductive silver paste to obtain intermediate metamaterial layer 2, inner metamaterial layers 31 and 32, and outer metamaterial layers 41 and 42.

[0054] (2) Laying up: On a flat mold coated with release agent, glass fiber fabric is laid up according to the designed thickness. The middle metamaterial layer 2 is placed in the middle position so that the pattern is located at the center of the thickness. The inner metamaterial layers 31 and 32 and the outer metamaterial layers 41 and 42 are placed symmetrically on both sides of the middle metamaterial layer 2 to obtain the composite material preform.

[0055] (3) Vacuum introduction: The composite preform is molded using the vacuum introduction process. The release cloth, guide net, vacuum tube, and injection tube are laid, the sealing strip is attached, the vacuum bag film is covered, the vacuum is drawn, the resin pipeline is opened, and the liquid epoxy resin is introduced under negative pressure. The glass fiber fabric of the composite preform is impregnated along the guide net, and the vacuum pressure is maintained to cure it.

[0056] (4) Demolding and post-processing: After curing, demold, grind the surface and cut the edges to obtain a broadband stealth composite material with double-sided wave absorption.

[0057] The reflectance curve of this embodiment is as follows: Figure 4 As shown, the transmittance curve is as follows Figure 5 As shown. Figure 4 The figure shows the reflectivity of the intermediate metamaterial layer 2 without holes for comparison. As can be seen from the figure, the periodically arranged square holes in the intermediate metamaterial layer 2 give it a certain degree of wave transmission, improving its low-frequency absorption performance. The average reflectivity in the L-band (frequency 1GHz~2GHz) decreases from -0.6dB (when the intermediate layer has total internal reflection) to -1.5dB. Figure 5 It can be seen that the transmittance of the material is less than -13dB in the range of 1GHz to 18GHz.

[0058] The reflectivity of the material with and without a metal backing was compared, such as Figure 6 As shown, thanks to the low transmittance, the material reflectivity is less affected by the metal backing, meaning that when electromagnetic waves are incident on the surface, its absorption performance is not affected by the backscattering component.

[0059] Example 2:

[0060] A broadband stealth composite material with double-sided wave absorption, such as Figure 1 Five metamaterial layers are arranged at intervals in a non-metallic composite material body 1 (quartz fiber reinforced bismaleimide resin composite material), with a total material thickness of 12 mm. An intermediate metamaterial layer 2 is positioned at the midpoint of the thickness direction. Two inner metamaterial layers 31 and 32 and two outer metamaterial layers 41 and 42 are symmetrically arranged on both sides of the intermediate metamaterial layer 2. Each metamaterial layer contains periodically arranged conductive pattern units. These conductive pattern units are obtained by screen printing resistive paste onto quartz fiber fabric. The conductive pattern units in each metamaterial layer have the same structural parameters but different sheet resistances. Specifically:

[0061] The conductive pattern units arranged periodically in the intermediate metamaterial layer 2 have a side length of 24.15 mm, such as... Figure 7 The image shows a periodic pattern composed of discontinuous small squares; the sheet resistance of the small squares is between 20 and 30 Ω / □.

[0062] The conductive pattern units arranged periodically in the inner metamaterial layers 31 and 32 also have a length and width of 24.15mm, and are periodic patterns composed of discontinuous small squares; the sheet resistance of the small squares is between 120 and 180Ω / □.

[0063] The conductive pattern units arranged periodically in the outer metamaterial layers 41 and 42 also have a length and width of 24.15mm, and are also periodic patterns composed of small squares; the sheet resistance of the small squares is between 130 and 170Ω / □.

[0064] The preparation method of the broadband stealth composite material with double-sided wave absorption in this embodiment includes the following steps:

[0065] (1) Printing metamaterial layers: Using screen printing technology, periodic patterns with different sheet resistances are printed on a quartz fiber reinforced bismaleimide resin composite thin plate using commercially available conductive carbon paste and other resistive pastes to obtain intermediate metamaterial layer 2, inner metamaterial layers 31 and 32, and outer metamaterial layers 41 and 42.

[0066] (2) Laying up: On a flat mold coated with release agent, quartz fiber / bismaleimide prepreg is laid up, and an intermediate metamaterial layer 2 is placed in the middle position so that the pattern is located at the center of the thickness. Inner metamaterial layers 31 and 32 and outer metamaterial layers 41 and 42 are placed symmetrically on both sides of the intermediate metamaterial layer 2 to obtain a composite material preform.

[0067] (3) Molding and curing: According to the curing requirements of quartz fiber / bismaleimide prepreg, the mold is heated and pressurized to cure it. The specific process conditions are as follows: heat to 125℃ within 45min, then pressurize to 0.4MPa and keep warm for 60min; pressurize to 0.6MPa, then keep pressure and heat to 190℃ and keep for 120min, then keep pressure and heat to 230℃ and keep for 120min, then keep pressure and heat to 250℃ and keep for 240min;

[0068] (4) Cooling and demolding: After curing, turn off the heating and cool to room temperature to release pressure and demold;

[0069] (5) Post-processing: After curing, demold, grind the surface and cut the edges to obtain a broadband stealth composite material with double-sided wave absorption.

[0070] The reflectance curve of this embodiment is as follows: Figure 8 As shown, the transmittance curve is as follows Figure 9 As shown. Figure 8 The comparison is shown when the intermediate metamaterial layer 2 is replaced with a complete metallic total internal reflection film. The intermediate metamaterial layer 2 is a resistive layer, and its periodic array of small squares gives it a certain degree of wave transmittance, improving both low-frequency and broadband absorption performance. The average reflectivity in the 1GHz~4GHz frequency band decreased from -1.3dB (with the intermediate layer undergoing total internal reflection) to -2.3dB. In this embodiment, the reflectivity is less than -10dB in the 6GHz~18GHz range, with a bandwidth of 12GHz; with the intermediate layer undergoing total internal reflection, the reflectivity is less than -10dB in the 5.5GHz~11GHz and 16GHz~18GHz ranges, with a bandwidth of 7.5GHz. The strong absorption bandwidth of this embodiment with a reflectivity of less than -10dB is significantly higher than the comparative design. Figure 9 It can be seen that the transmittance of the material is less than -13dB in the range of 3GHz to 18GHz.

[0071] The reflectivity of the material with and without a metal backing was compared, such as Figure 10 As shown, thanks to the low transmittance, the material reflectivity is less affected by the metal backing when the frequency is greater than 3GHz. That is, when electromagnetic waves are incident on the surface, its absorption performance is not affected by the backscattering component.

Claims

1. A broadband stealth composite material with double-sided wave absorption, characterized in that, The material comprises a non-metallic composite material body and at least five metamaterial layers spaced apart along the thickness direction of the non-metallic composite material body; the number of metamaterial layers is odd, and an intermediate metamaterial layer (2) is provided at the middle position along the thickness direction, and at least two inner metamaterial layers (31, 32) and at least two outer metamaterial layers (41, 42) are arranged symmetrically from the intermediate metamaterial layer (2) to both sides; the relative permittivity of the non-metallic composite material body is not greater than 10; the double-sided absorbing broadband stealth composite material does not contain a metal reflective layer; The conductive pattern unit of the intermediate metamaterial layer (2) is a square ring structure with a central square hole. The side length of a single square ring structure is 3~30mm. The side length of the central square hole in the square ring structure is 0.3~0.8 times the unit size. The conductive pattern unit of the inner metamaterial layer (31, 32) is composed of a first discontinuous small square array. The side length of a single small square is 2~20mm. The conductive pattern unit of the outer metamaterial layer (41, 42) is composed of a second discontinuous small square array. The side length of a single small square is 2~20mm.

2. The broadband stealth composite material with double-sided wave absorption according to claim 1, characterized in that, The number of metamaterial layers is five, including one intermediate metamaterial layer (2), and two inner metamaterial layers (31, 32) and two outer metamaterial layers (41, 42) arranged symmetrically from the intermediate metamaterial layer (2) to both sides.

3. The broadband stealth composite material with double-sided wave absorption according to claim 2, characterized in that, The sheet resistance of the conductive pattern unit of the intermediate metamaterial layer (2) is no greater than 0.5Ω / □; the sheet resistance of the conductive pattern unit of the inner metamaterial layer (31, 32) is 30~50Ω / □; and the sheet resistance of the conductive pattern unit of the outer metamaterial layer (41, 42) is 120~150Ω / □.

4. The broadband stealth composite material with double-sided wave absorption according to claim 1, characterized in that, The conductive pattern is formed on a non-conductive fiber substrate by screen printing conductive paste or resistive paste; the non-conductive fiber substrate is at least one of glass fiber fabric, basalt fiber fabric and quartz fiber fabric; the conductive paste is conductive silver paste; the resistive paste is conductive carbon paste.

5. The broadband stealth composite material with double-sided wave absorption according to any one of claims 1-4, characterized in that, The non-metallic composite material body is at least one of glass fiber reinforced bismaleimide resin composite material, quartz fiber reinforced bismaleimide resin composite material, glass fiber reinforced epoxy resin composite material, basalt fiber reinforced epoxy resin composite material, glass fiber reinforced vinyl ester resin composite material, and quartz fiber reinforced epoxy resin composite material; the total thickness of the double-sided microwave absorbing broadband stealth composite material is 5~30mm.

6. A method for preparing a broadband stealth composite material with double-sided wave absorption as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) On the substrate of the metamaterial layer, conductive pattern units with different structural parameters and / or sheet resistance are printed by screen printing process to form at least five metamaterial layers, including an intermediate metamaterial layer (2). (2) Lay up a non-metallic matrix composite preform on the mold, and arrange the metamaterial layers obtained in step (1) at preset position intervals in the thickness direction of the non-metallic matrix composite preform, so that the intermediate metamaterial layer (2) is located in the middle position in the thickness direction, and the remaining metamaterial layers are symmetrically distributed on both sides of the intermediate metamaterial layer (2) to obtain a composite preform. (3) The double-sided microwave-absorbing broadband stealth composite material preform obtained after step (2) is cured to impregnate and cure the resin to form an integrated composite material. (4) Demold the composite material obtained after curing in step (3) and perform surface treatment to obtain the broadband stealth composite material with double-sided wave absorption.

7. The method for preparing the double-sided absorbing broadband stealth composite material according to claim 6, characterized in that, The curing process is performed by vacuum resin injection molding or compression molding. When the vacuum resin injection molding method is used, the non-metallic matrix composite preform in step (2) is a dry fiber fabric. In step (3), liquid resin is introduced into the mold under negative pressure and the dry fiber fabric and metamaterial layer are impregnated, and then vacuum pressure curing is performed. When the molding and curing method is adopted, the non-metallic composite material preform in step (2) is a resin prepreg of fiber fabric, and in step (3), the resin in the resin prepreg of the fiber fabric is melted, impregnated and cured by heating and pressurizing the mold.

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