Lightweight broadband metamaterial absorber based on c-shaped sandwich structure

Abstract

The application provides a light-weight broadband metamaterial wave-absorbing structure based on a C-shaped sandwich structure, which comprises a first composite layer, a second composite layer and a reflecting layer arranged in sequence along the electromagnetic wave propagation direction; the first composite layer comprises a sandwich structure composed of multiple wave-transparent layers and skin layers arranged alternately; the second composite layer comprises a resistance film layer and a wave-transparent dielectric layer arranged alternately; and the lowermost wave-transparent dielectric layer is provided with the reflecting layer on the lower surface. The C-shaped sandwich structure can greatly improve the wave-absorbing performance of the wave-absorbing sandwich structure in the high-frequency (Ku) band, and overcomes the shortcoming that when the skin is thicker than 0.5 mm, the wave-absorbing sandwich structure is difficult to obtain satisfactory wave-absorbing effect in the high-frequency (Ku) band.

Description

Technical Field

[0001] This invention relates to the field of visibility meters, and in particular to a lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich. Background Technology

[0002] With the development of radar detection and guidance technology, the main detection bands of detection radars are constantly expanding to higher frequency bands, creating an urgent need for stealth structures with high-frequency (Ku) band electromagnetic wave absorption capabilities in weaponry. Furthermore, with increasing practical demands, stealth structures not only need wide effective bandwidth, strong absorption peaks, and low weight, but also require certain strength, stiffness, and toughness to improve their mechanical load-bearing performance.

[0003] Lightweight sandwich absorbing structures have a wide range of applications in equipment requiring stealth capabilities, exhibiting excellent broadband absorption performance. Some equipment demands high mechanical properties from its skin, inevitably requiring thicker skins. However, when the skin of a sandwich structure is thick (greater than 0.5 mm), regardless of adjustments to the composite material's absorbing structure, satisfactory absorption performance in the high-frequency (Ku) band becomes difficult to achieve. Therefore, improving the high-frequency absorption performance of sandwich structures becomes a pressing problem to be solved.

[0004] CN108274879A discloses a method for manufacturing a high-frequency transparent sandwich composite material 5G radome. The radome consists of inner and outer skins and a core material. The skin material is a glass fiber reinforced cyanate ester modified epoxy resin composite material, and the core material is an aramid honeycomb core. This radome has a panel transmittance of over 90% at a working frequency of 28 GHz, meaning it exhibits excellent transmittance only at a single frequency. However, current radomes do not only receive signals at a single frequency but also need to simultaneously receive signals from multiple frequency bands with high bandwidth.

[0005] CN104103898A discloses a high-transmittance, low-RCS radome, comprising thin-layer units of a transmissive sandwich structure. Each thin-layer unit is fixed to a metallized flange frame area made of carbon fiber, forming a transmissive window. The radome is stacked layer by layer. The transmissive area of ​​the radome has a rhomboid or almond-shaped streamlined shape. Simulation or testing is performed on a low-RCS carrier platform. Direct simulation or testing of the radome cannot accurately reflect its RCS level. The thin-layer unit of the transmissive sandwich structure is a three-layer structure, consisting of quartz fiber glass cloth, PMI foam, and another layer of quartz fiber glass cloth from top to bottom. This radome only meets the requirement of high transmittance; its transmittance in multiple frequency bands and high bandwidths is not ideal. Summary of the Invention

[0006] The main objective of this invention is to provide a lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich, which solves the problem that no matter how the absorbing structure of the composite material is adjusted, it is difficult to obtain a satisfactory absorbing effect in the high-frequency (Ku) band.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a lightweight broadband metamaterial wave-absorbing structure based on a C-shaped sandwich, wherein a first composite layer, a second composite layer and a reflective layer are sequentially provided along the electromagnetic wave propagation direction;

[0008] The first composite layer comprises a sandwich structure consisting of multiple layers of wave-transparent layers and skin layers arranged in an alternating manner;

[0009] The second composite layer includes an alternating resistive film layer and a wave-transparent dielectric layer;

[0010] The bottom layer of the wave-transparent medium has a reflective layer on its lower surface.

[0011] In the preferred embodiment, the thickness of the skin layer is 0.3 mm to 1 mm.

[0012] In the preferred embodiment, the material of the skin layer is one or more of the following composite materials: glass fiber cloth reinforced resin composite material, quartz fiber cloth reinforced resin composite material, or aramid fiber cloth reinforced resin composite material.

[0013] The relative permittivity of the skin layer is between 2 and 5.

[0014] In the preferred embodiment, the wave-transparent layer is a honeycomb structure layer or a foam structure layer, and the thickness of the wave-transparent layer is 0.5mm to 3mm.

[0015] In the preferred embodiment, the wave-transparent layer material is one or more of the following: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam, or polymethacrylamide foam.

[0016] The relative permittivity of the wave-transparent layer is between 1 and 1.5.

[0017] In the preferred embodiment, the material of the wave-transmitting dielectric layer is one or more of the following composite materials: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam or polymethacrylamide foam, quartz fiber cloth reinforced ceramic, alumina fiber reinforced ceramic, boron nitride fiber reinforced ceramic, silicon nitride fiber reinforced ceramic, glass fiber cloth reinforced resin composite, quartz fiber cloth reinforced resin composite, aramid fiber cloth reinforced resin composite, and ultra-high molecular weight polyethylene.

[0018] The relative permittivity of the wave-transparent dielectric layer is between 1 and 10.

[0019] In the preferred embodiment, the base material of the resistive film layer is a polyimide film or a PET film;

[0020] A resistive film is fabricated on the surface of a base material using screen printing or laser etching processes.

[0021] In the preferred embodiment, the sheet resistance R of the resistive film layer S 100–1000 Ω / sq;

[0022] Along the direction of electromagnetic propagation, the sheet resistance of the multilayer resistive film decreases sequentially.

[0023] In the preferred embodiment, the reflective layer is a carbon fiber fabric reinforced resin composite material.

[0024] In the preferred embodiment, the skin layer includes a first skin layer, a second skin layer and a third skin layer, the first wave-transparent layer is disposed between the first skin layer and the second skin layer, and the second wave-transparent layer is disposed between the second skin layer and the third skin layer.

[0025] The first skin layer, the second skin layer, and the third skin layer, together with the first and second wave-transparent layers, form a C-shaped sandwich structure.

[0026] The C-shaped sandwich structure, together with the cross-stacked wave-transmitting dielectric layer and the single-layer resistive film layer, forms a broadband wave-absorbing structure, with the reflective layer located at the bottom of the broadband wave-absorbing structure.

[0027] This invention provides a lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich. The structure, designed along the electromagnetic wave propagation direction, is composed of a first skin layer, a first transparent layer, a second skin layer, a second transparent layer, a third skin layer, a first resistive film layer, a first transparent dielectric layer, a second resistive film layer, a second transparent dielectric layer, an Nth resistive film layer, an Nth transparent dielectric layer, and a reflective layer stacked on top of each other. This three-layer skin structure ensures structural strength. Furthermore, by positioning the three skin layers on either side of the transparent layer and limiting their thickness, the incident electromagnetic wave undergoes multiple reflections between the three skin layers. Ultimately, all reflected waves interfere destructively, significantly reducing direct reflection of electromagnetic waves at the skin portion of the absorbing structure. This allows the electromagnetic wave to be introduced into the absorbing material, where it is absorbed, greatly improving the radar wave transmittance in the high-frequency (Ku) band. In summary, the present invention significantly improves the high-frequency wave absorption performance of the structure while ensuring the strength of the sandwich structure. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0029] Figure 1 This is a schematic diagram of the broadband metamaterial absorbing structure of the present invention;

[0030] Figure 2 This is a comparative example of the sandwich-type microwave absorbing structure of the present invention;

[0031] Figure 3 This is the simulation result of the reflectivity of the broadband metamaterial absorbing structure based on a C-shaped sandwich provided in Embodiment 1 of the present invention;

[0032] Figure 4 This is the simulation result of the reflectivity of the single-layer skin absorbing sandwich structure provided in Comparative Example 1 of this invention;

[0033] Figure 5 This is the simulation result of the reflectivity of the broadband metamaterial absorbing structure based on a C-shaped sandwich provided in Embodiment 2 of the present invention;

[0034] Figure 6 The results are simulation results of the reflectivity of the single-layer skin absorbing sandwich structure provided in Comparative Example 2.

[0035] In the figure: First skin layer 1; First wave-transparent layer 2; Second skin layer 3; Second wave-transparent layer 4; Third skin layer 5; Resistive film layer 6; Wave-transparent dielectric layer 7; Reflective layer 8. Detailed Implementation

[0036] like Figures 1-6 As shown, a lightweight broadband metamaterial wave-absorbing structure based on a C-shaped sandwich is provided with a first composite layer, a second composite layer and a reflective layer 8 in sequence along the electromagnetic wave propagation direction;

[0037] The first composite layer comprises a sandwich structure consisting of multiple layers of wave-transparent layers and skin layers arranged in an alternating manner;

[0038] The second composite layer includes an alternating resistive film layer 6 and a wave-transparent dielectric layer 7.

[0039] A reflective layer 8 is provided on the lower surface of the bottommost wave-transparent dielectric layer.

[0040] In the preferred embodiment, the thickness of the skin layer is 0.3 mm to 1 mm.

[0041] In the preferred embodiment, the material of the skin layer is one or more of the following composite materials: glass fiber cloth reinforced resin composite material, quartz fiber cloth reinforced resin composite material, or aramid fiber cloth reinforced resin composite material.

[0042] The relative permittivity of the skin layer is between 2 and 5.

[0043] In the preferred embodiment, the wave-transparent layer is a honeycomb structure layer or a foam structure layer, and the thickness of the wave-transparent layer is 0.5mm to 3mm.

[0044] In the preferred embodiment, the wave-transparent layer material is one or more of the following: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam, or polymethacrylamide foam.

[0045] The relative permittivity of the wave-transparent layer is between 1 and 1.5.

[0046] In the preferred embodiment, the material of the wave-transparent dielectric layer 7 is one or more of the following composite materials: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam or polymethacrylamide foam, quartz fiber cloth reinforced ceramic, alumina fiber reinforced ceramic, boron nitride fiber reinforced ceramic, silicon nitride fiber reinforced ceramic, glass fiber cloth reinforced resin composite, quartz fiber cloth reinforced resin composite, aramid fiber cloth reinforced resin composite, and ultra-high molecular weight polyethylene.

[0047] The relative permittivity of the wave-transparent dielectric layer 7 is between 1 and 10.

[0048] In the preferred embodiment, the base material of the resistive film layer 6 is a polyimide film or a PET film;

[0049] A resistive film is fabricated on the surface of a base material using screen printing or laser etching processes.

[0050] In the preferred embodiment, the sheet resistance R of the resistive film layer is 6. S 100–1000 Ω / sq;

[0051] Along the direction of electromagnetic propagation, the sheet resistance of the multilayer resistive film decreases sequentially.

[0052] In the preferred embodiment, the reflective layer 8 is a carbon fiber fabric reinforced resin composite material.

[0053] In the preferred embodiment, the skin layer includes a first skin layer 1, a second skin layer 3 and a third skin layer 5, a first wave-transparent layer 2 is disposed between the first skin layer 1 and the second skin layer 3, and a second wave-transparent layer 4 is disposed between the second skin layer 3 and the third skin layer 5.

[0054] The first skin layer 1, the second skin layer 3 and the third skin layer 5 together with the first wave-transparent layer 2 and the second wave-transparent layer 4 form a C-shaped sandwich structure;

[0055] The C-shaped sandwich structure, together with the cross-layered wave-transmitting dielectric layer 7 and the single-layer resistive film layer 6, forms a broadband absorbing structure, with the reflective layer 8 disposed at the bottom of the broadband absorbing structure. The first, second, and third skin layers, together with the first and second wave-transmitting layers, constitute the C-shaped sandwich structure. The C-shaped sandwich structure, together with the second resistive film layer, the second wave-transmitting dielectric layer, the Nth resistive film layer, the Nth wave-transmitting dielectric layer, and the reflective layer, forms a broadband absorbing structure.

[0056] In existing foam sandwich structures, composite material skins with a single skin thickness greater than 0.5 mm generally exhibit strong direct reflection of high-frequency electromagnetic waves (Ku band), which is detrimental to the design of wave-absorbing structures. To address this issue, such as... Figure 1As shown, a lightweight broadband absorbing structure based on a C-shaped sandwich structure provided according to an embodiment of the present invention comprises, along the electromagnetic propagation direction, a first skin layer M1, a first wave-transparent layer T1, a second skin layer M2, a second wave-transparent layer T2, a third skin layer M3, a first resistive film layer X1, a first wave-transparent dielectric layer J1, a second resistive film layer X2, a second wave-transparent dielectric layer J2, and an Nth resistive film layer X... N The Nth wave-transparent dielectric layer J N And the reflective layer F in the order of M1-T1-M2-T2-M3-X1-J1-X2-J2……X N -J N The structure is composed of layers in the form of -F, with the first skin layer M1, the second skin layer M2, and the third skin layer M3 having thicknesses of 0.5mm to 1mm respectively. The wave-transparent layer T is an aramid honeycomb or foam structure layer with a thickness of 0.5mm to 3mm. Any one of the wave-transparent media layers is an aramid honeycomb, rigid foam, resin-based composite material layer, or ceramic material.

[0057] This invention presents a lightweight, broadband radar-absorbing structure based on a C-shaped sandwich structure. Along the electromagnetic wave propagation direction, it is constructed by sequentially stacking a first skin layer, a first transparent layer, a second skin layer, a second transparent layer, a third skin layer, a first resistive film layer, a first transparent dielectric layer, a second resistive film layer, a second transparent dielectric layer, an Nth resistive film layer, an Nth transparent dielectric layer, and a reflective layer. The C-shaped sandwich structure formed by the skin layer and the transparent layer ensures structural strength. Furthermore, the three skin layers are positioned on either side of the two transparent layers. By limiting the thickness of the skin and transparent layers, the incident electromagnetic wave can undergo multiple reflections between the two skin layers. Ultimately, all reflected waves interfere destructively, significantly reducing direct reflection of electromagnetic waves at the skin portion of the radar-absorbing structure. This allows the electromagnetic wave to be introduced into the radar-absorbing material, where it is absorbed, greatly improving the radar wave transmittance in the high-frequency (Ku) band.

[0058] In this embodiment of the invention, the thicknesses of the first skin layer M1 and the second skin layer M2 are designed to be 0.5mm to 1mm, respectively. It can be seen that even if the skin layer used in this embodiment of the invention is greater than 0.5mm, the performance of the wave-absorbing structure can still be guaranteed. The reason is that this embodiment of the invention adopts a three-layer skin design and sets the three layers of skin on both sides of the wave-transparent layer of a specific thickness. In this way, even if the skin layer has the above-mentioned thickness, through this structural design, the incident electromagnetic wave can be reflected multiple times between the two skin layers. In the end, all the reflected waves interfere and cancel each other out, which can greatly reduce the direct reflection of electromagnetic waves at the skin part of the wave-absorbing structure, thereby introducing electromagnetic waves into the interior of the wave-absorbing material.

[0059] In addition, to ensure better structural strength, the skin thickness in this embodiment of the invention cannot be less than 0.5 mm and cannot be greater than 1 mm. The reason is that if the skin thickness is greater than 1 mm, even if a three-layer skin scheme is used, the wave absorption structure will hardly achieve a good wave absorption effect.

[0060] In this embodiment of the invention, when the skin thickness is 0.5mm to 1mm and the electromagnetic wave frequency is in the Ku band, the thickness of the wave-transmitting layer is selected within the range of 0.5mm to 3mm, which can maximize the transmittance of electromagnetic waves in the skin portion of the absorbing structure. Moreover, within the above thickness range, the selection of the thickness of the first wave-transmitting layer T1 and the second wave-transmitting layer T2 is also related to the thickness of the three skin layers and the frequency of the electromagnetic wave. The thickness of the wave-transmitting layer generally needs to be selected based on the thickness of the skin layers.

[0061] As one embodiment of the present invention, the materials of the first, second and third skin layers can be one of glass fiber cloth reinforced resin composite material, quartz fiber cloth reinforced resin composite material or aramid fiber cloth reinforced resin composite material, but are not limited thereto.

[0062] In this embodiment of the invention, the wave-transparent layer is selected from honeycomb or foam structures, and can be any one of aramid honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam, or polymethacrylimide foam. The aforementioned honeycomb / foam structures possess good compression resistance and excellent wave-transparent properties.

[0063] In this embodiment of the invention, the wave-transmitting dielectric layer is selected from any one of the following: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam or polymethacrylamide foam, quartz fiber reinforced ceramic, alumina fiber reinforced ceramic, boron nitride fiber reinforced ceramic, silicon nitride fiber reinforced ceramic, glass fiber reinforced resin composite material, quartz fiber reinforced resin composite material, aramid fiber reinforced resin composite material, and ultra-high molecular weight polyethylene. The above materials possess good compressive strength and excellent wave-transmitting properties.

[0064] In this embodiment of the invention, the resistive film is attached to the surface of a polyimide film or a PET film and processed using screen printing or laser etching.

[0065] In this embodiment of the invention, for any one of the several resistive film layers, the sheet resistance RS is between 100 and 1000 Ω / sq.

[0066] In this embodiment of the invention, the sheet resistance of the multilayer resistive film decreases sequentially along the electromagnetic propagation direction.

[0067] In this embodiment of the invention, when the sheet resistance RS of the resistive film is greater than 1000Ω / sq, the absorption effect on electromagnetic waves is weak; when the sheet resistance RS of the resistive film is less than 100Ω / sq, the reflection of electromagnetic waves is large. Both of these situations are not conducive to the design of the impedance matching structure.

[0068] In this embodiment of the invention, the resistive film layer is preferably multi-layered, i.e., at least two layers, wherein the sheet resistance of the multi-layered resistive film decreases sequentially along the electromagnetic propagation direction. This design creates a gradient impedance structure, which effectively introduces and absorbs electromagnetic waves into the absorbing material, improving its stealth performance.

[0069] In this embodiment of the invention, the reflective layer can be a carbon fiber fabric-reinforced resin composite material. The carbon fiber fabric has good electrical conductivity and can be co-cured with the composite material.

[0070] The features and performance of the present invention will be further described in detail below with reference to the accompanying drawings, specific embodiments and comparative examples.

[0071] like Figure 1 As shown, the lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich provided in this embodiment of the invention is composed of a first skin layer M1, a first wave-transparent layer T1, a second skin layer M2, a second wave-transparent layer T2, a third skin layer M3, a first resistive film layer X1, a first wave-transparent dielectric layer J1, a second resistive film layer X2, a second wave-transparent dielectric layer J2, an Nth resistive film layer XN, an Nth wave-transparent dielectric layer JN, and a reflective layer F in the form of M1-T1-M2-T2-M3-X1-J1-X2-J2……XN-JN-F.

[0072] like Figure 2 As shown, the single-layer skin absorbing sandwich structure provided in the comparative example of the present invention is composed of a skin layer M1, a first resistive film layer X1, a first wave-transparent medium layer J1, a second resistive film layer X2, a second wave-transparent medium layer J2, an Nth resistive film layer XN, an Nth wave-transparent medium layer JN, and a reflective layer F stacked in the form of M1-X1-J1-X2-J2……XN-JN-F along the electromagnetic propagation direction.

[0073] Compared with the comparative examples, the present invention only removes the first wave-transparent layer T1, the second skin layer M2, and the third skin layer M3; all other parts are the same.

[0074] Example 1

[0075] The microwave absorbing honeycomb sandwich structure based on C-shaped sandwich provided in this embodiment is made of glass fiber fabric reinforced resin composite material for the first, second, and third skin layers. The thickness of the first and third skin layers is 0.5 mm, and the thickness of the second skin layer is 0.4 mm. The material used for the first and second wave-transmitting layers is aramid honeycomb, and the thickness of each layer is 2.3 mm. There are three layers in total: a resistive film layer and a wave-transmitting dielectric layer. The thickness of the first wave-transmitting dielectric layer is 7.5 mm, the thickness of the second wave-transmitting dielectric layer is 7.3 mm, and the thickness of the third wave-transmitting dielectric layer is 6.5 mm. The sheet resistance of the resistive film along the electromagnetic wave propagation direction is 320 Ω / sq, 640 Ω / sq, and 790 Ω / sq, respectively. The material used for the reflective layer is carbon fiber fabric reinforced resin composite material.

[0076] Comparative Example 1

[0077] The single-layer skin absorbing honeycomb sandwich structure provided in this comparative example has a skin layer made of glass fiber fabric reinforced resin composite material with a thickness of 0.5 mm; a resistive film layer and a wave-transmitting dielectric layer, totaling 3 layers, with the first wave-transmitting dielectric layer having a thickness of 7.5 mm, the second wave-transmitting dielectric layer having a thickness of 7.3 mm, and the third wave-transmitting dielectric layer having a thickness of 6.5 mm, and the sheet resistance of the resistive film along the electromagnetic wave propagation direction being 320 Ω / sq, 640 Ω / sq, and 790 Ω / sq, respectively; and a reflective layer made of carbon fiber fabric reinforced resin composite material.

[0078] The reflectivity of the metamaterial absorbing honeycomb sandwich structure based on C-type sandwich fabrication in Example 1 and the single-layer skin absorbing honeycomb sandwich structure in Comparative Example 1 were tested across the entire frequency band. The results are as follows: Figure 3 and 4 As shown. By Figure 3 It can be seen that the average reflectivity of the material obtained in Example 1 is -21.1 dB at frequencies of 12–18 GHz. Figure 4 It can be seen that the average reflectivity of the material obtained in Comparative Example 1 is -14.9 dB at frequencies of 12–18 GHz. Therefore, it is evident that the performance of the material obtained in Example 1 is significantly improved compared to that in Comparative Example 1.

[0079] Example 2

[0080] The microwave absorbing foam sandwich structure based on C-shaped sandwich provided in this embodiment is as follows: the first, second, and third skin layers are all made of quartz fiber fabric reinforced resin composite material, the thickness of the first and third skin layers is 0.5 mm, and the thickness of the second skin layer is 0.4 mm; the first and second wave-transmitting layers are made of PMI foam, and the thickness of each layer is 2.3 mm; there are three layers in total, including a resistive film layer and a wave-transmitting medium layer, with the thickness of the first wave-transmitting medium layer being 7.5 mm, the second wave-transmitting medium layer being 7.3 mm, and the third wave-transmitting medium layer being 5.5 mm. The sheet resistance of the resistive film along the electromagnetic wave propagation direction is 395 Ω / sq, 680 Ω / sq, and 730 Ω / sq, respectively; the reflective layer is made of carbon fiber fabric reinforced resin composite material.

[0081] Comparative Example 2

[0082] The single-layer skin-reinforced microwave absorbing foam sandwich structure provided in this comparative example includes a skin layer made of quartz fiber fabric reinforced resin composite material with a thickness of 0.5 mm; three layers in total, including a resistive film layer and a microwave-transparent medium layer, with the first microwave-transparent medium layer having a thickness of 7.5 mm, the second microwave-transparent medium layer having a thickness of 7.3 mm, and the third microwave-transparent medium layer having a thickness of 5.5 mm, and the sheet resistances of the resistive film along the electromagnetic wave propagation direction being 395 Ω / sq, 680 Ω / sq, and 730 Ω / sq, respectively; and a reflective layer made of carbon fiber fabric reinforced resin composite material.

[0083] The reflectivity of the C-shaped sandwich-based metamaterial absorbing foam sandwich structure prepared in Example 2 and the single-layer skin absorbing foam sandwich structure prepared in Comparative Example 2 were tested across the entire frequency band. The results are as follows: Figure 5 and 6 As shown. By Figure 5 It can be seen that the average reflectivity of the material obtained in Example 1 is -20.6 dB at frequencies of 12–18 GHz. Figure 6 It can be seen that the average reflectivity of the material obtained in Comparative Example 2 is -14.1 dB at frequencies of 12–18 GHz. Therefore, it is evident that the performance of the material obtained in Example 2 is significantly improved compared to that of Comparative Example 2.

[0084] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich, characterized by: A first composite layer, a second composite layer, and a reflective layer are sequentially provided along the direction of electromagnetic wave propagation (8); The first composite layer comprises a sandwich structure consisting of multiple layers of wave-transparent layers and skin layers arranged in an alternating manner; The second composite layer includes an alternating resistive film layer (6) and a wave-transparent dielectric layer (7). A reflective layer (8) is provided on the lower surface of the bottom wave-transparent medium layer. The skin layer includes a first skin layer (1), a second skin layer (3) and a third skin layer (5), a first wave-transparent layer (2) is disposed between the first skin layer (1) and the second skin layer (3), and a second wave-transparent layer (4) is disposed between the second skin layer (3) and the third skin layer (5); The first skin layer (1), the second skin layer (3) and the third skin layer (5) together with the first wave-transparent layer (2) and the second wave-transparent layer (4) form a C-shaped sandwich structure; The C-type sandwich structure, together with the cross-stacked wave-transmitting dielectric layer (7) and the single-layer resistive film layer (6), forms a broadband wave-absorbing structure, and the reflective layer (8) is set at the bottom of the broadband wave-absorbing structure. Shear resistance of resistive film layer (6) R S 100–1000 Ω / sq; Along the direction of electromagnetic propagation, the sheet resistance of the multilayer resistive film decreases sequentially.

2. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 1, characterized in that: The thickness of the skin layer is 0.3mm to 1mm.

3. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 2, characterized in that: The material of the skin layer is one or more of the following: glass fiber cloth reinforced resin composite material, quartz fiber cloth reinforced resin composite material, or aramid fiber cloth reinforced resin composite material; The relative permittivity of the skin layer is between 2 and 5.

4. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 1, characterized in that: The wave-transparent layer is a honeycomb structure layer or a foam structure layer, and the thickness of the wave-transparent layer is 0.5mm to 3mm.

5. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 4, characterized in that: The wave-transparent layer material is one or more of the following: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam, or polymethacrylamide foam; The relative permittivity of the wave-transparent layer is between 1 and 1.

5.

6. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 1, characterized in that: The material of the wave-transparent dielectric layer (7) is one or more of the following composite materials: aramid paper honeycomb, polyvinyl chloride foam, polyurethane foam, epoxy foam or polymethacrylamide foam, quartz fiber cloth reinforced ceramic, alumina fiber reinforced ceramic, boron nitride fiber reinforced ceramic, silicon nitride fiber reinforced ceramic material, glass fiber cloth reinforced resin composite material, quartz fiber cloth reinforced resin composite material, aramid fiber cloth reinforced resin composite material, and ultra-high molecular weight polyethylene material. The relative permittivity of the wave-transparent dielectric layer (7) is between 1 and 10.

7. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 1, characterized in that: The base material of the resistive film layer (6) is a polyimide film or a PET film; A resistive film is fabricated on the surface of a base material using screen printing or laser etching processes.

8. The lightweight broadband metamaterial absorbing structure based on a C-shaped sandwich as described in claim 1, characterized in that: The reflective layer (8) is a carbon fiber fabric reinforced resin composite material.

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