Wide-angular-domain wave-absorbing structure and preparation method thereof

Abstract

The invention discloses a wide-angular-domain wave-absorbing structure and a preparation method thereof, and belongs to the field of radar wave-absorbing materials, the structure comprises a non-metal porous structure and a patterned resistive film printed on the hole wall of the non-metal porous structure; the patterned resistive film comprises at least two regions, the resistive film in the first region is located at the bottom of the hole wall, and the width of the resistive film in the first region is the same as that of the hole wall; the width of the bottom of the second area resistive film is the same as that of the hole wall, the bottom of the second area resistive film is connected with the first area resistive film, and the width of the second area resistive film is gradually reduced from the bottom to the top. According to the invention, the patterned gradient resistive film is constructed on the hole wall of the three-dimensional porous hole, so that a high-efficiency impedance transition layer from air to the surface of the conductor is formed. According to the design, a bearing structure and a functional material are integrated, strong absorption of electromagnetic waves in a wide frequency band and a large incidence angle range is effectively achieved, and meanwhile the remarkable advantage of structural light weight is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radar wave-absorbing materials, and particularly relates to a wide-angle domain wave-absorbing structure and a preparation method thereof. BACKGROUND

[0002] With the continuous progress of radar detection technology, important military targets and key equipment are more likely to be exposed to enemy radar reconnaissance and attack under multi-directional and multi-angle electromagnetic wave irradiation due to the high sensitivity, high resolution and multi-angle detection capabilities. Especially under wide-angle incidence, the effect of traditional stealth means is significantly reduced, and radar stealth technology faces more severe challenges. Therefore, the demand for wave-absorbing structures that can still maintain high absorption efficiency under wide-angle (wide-angle domain) incidence is increasingly urgent, and higher performance indicators for radar stealth effect are required.

[0003] Wave-absorbing materials can convert incident electromagnetic wave energy into heat or other forms of energy for dissipation, thereby reducing radar reflection signals and achieving stealth effect. According to the loss mechanism of electromagnetic waves, wave-absorbing materials are mainly divided into three categories: resistive loss, dielectric loss, and magnetic loss. Honeycomb structures are widely used in radar stealth structures due to their lightweight, high strength, and easy processing characteristics. Combining honeycomb structures with wave-absorbing materials is an effective way to improve stealth performance without significantly increasing the weight of the structure. Traditional wave-absorbing honeycomb structures mainly rely on dielectric loss mechanisms to absorb electromagnetic waves through impregnation of wave-absorbing paste. However, this method has problems such as difficulty in precisely controlling the electromagnetic parameters of the wave-absorbing paste and limited absorption frequency band, making it difficult to achieve strong electromagnetic wave absorption in a wide frequency band and wide angle range. Therefore, existing technologies still struggle to achieve high-efficiency, lightweight, and wide-band wave-absorbing structures when faced with wide-angle domain strong electromagnetic wave threats, and innovative structural design and material printing methods are needed to improve radar stealth performance. SUMMARY

[0004] The purpose of the present application is to provide a wide-angle domain wave-absorbing structure and a preparation method thereof, which can achieve efficient absorption of electromagnetic waves under different incidence angles through the layered design of patterned resistive films.

[0005] To achieve the above-mentioned purpose, the present application provides a wide-angle domain wave-absorbing structure, which comprises a non-metallic porous structure and a patterned resistive film printed on the pore wall of the non-metallic porous structure; the patterned resistive film comprises at least two regions, the first region resistive film is located at the bottom of the pore wall, and the width is the same as the width of the pore wall; the bottom width of the second region resistive film is the same as the width of the pore wall, and the bottom is connected with the first region resistive film, and the width of the second region resistive film gradually decreases from the bottom to the top of the pore wall.

[0006] Further, the non-metallic porous structure is a honeycomb structure, a cross section of the honeycomb structure is a polygon with 3-10 sides, a side length of the cross section is 1.83-8 mm, each side corresponds to a hole wall, a shape of each hole wall is a rectangle, and a thickness of the hole wall is 0.02-1 mm.

[0007] Further, a height from a bottom to a top of the hole wall is 5-50 mm, and a height of the first area resistance film is 5-80% of the height of the hole wall.

[0008] Further, a width of the second area resistance film decreases to 0 when the second area resistance film reaches the top of the hole wall, and a top of the second area resistance film is located at a center of the top of the hole wall, and a shape of the second area resistance film is preferably an isosceles triangle.

[0009] Further, a sheet resistance value of the second area resistance film ranges from 100 to 2000 Ω, and a sheet resistance value of the first area resistance film ranges from 50 to 1000 Ω, the sheet resistance value of the first area resistance film is less than or equal to the sheet resistance value of the second area resistance film, and the patterned resistance film is printed on two opposite surfaces of the hole wall.

[0010] Further, a density of the non-metallic porous structure is 30-80 kg / m 3 , and a plane compressive strength is 0.6-4.2 MPa, and a material of the non-metallic porous structure is para-aramid or meta-aramid.

[0011] Further, the non-metallic porous structure is further provided with a metal back plate at a bottom of the non-metallic porous structure, and the metal back plate is perpendicular to the hole wall and the patterned resistance film of the non-metallic porous structure.

[0012] The application further provides a preparation method of the wide-angle domain wave-absorbing structure, and the preparation method comprises the following steps: S1, cutting a non-metallic sheet into a plurality of pieces according to a hole wall size of a non-metallic porous structure; S2, printing a patterned resistance film on a surface of each of the cut non-metallic sheets; S3, printing an adhesive line on each of the non-metallic sheets, and then stacking the plurality of non-metallic sheets in an interlaced manner and heat pressing and curing to obtain a bonding body; S4, stretching the bonding body, unfolding an area not bonded by the adhesive line to form a porous structure, and obtaining a wide-angle domain wave-absorbing structure.

[0013] Further, in step S3, the heat pressing and curing is performed at a temperature of 160-200 ℃ and a pressure of 0.5-2 MPa.

[0014] Further, in step S4, the porous structure after stretching is heat cured at 150-170 ℃ for 10-40 minutes.

[0015] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages: (1) A wide-angle domain wave-absorbing structure based on a honeycomb hole wall printed patterned resistive film is provided, the patterned resistive film is printed on the hole wall of the porous structure, and strong absorption of incident electromagnetic waves is realized under the premise of not significantly increasing the mass. The structure takes low-density, high-mechanical-strength materials as the substrate, has an absorption efficiency of more than 90% in a wide frequency range of 4-18 GHz, an absorption efficiency of more than 97% in a range of 5-18 GHz, and excellent angle stability in a wide angle range of 0°-45°, with a reflection coefficient basically kept below -15 dB, which is suitable for the absorption requirements of multi-angle radar waves.

[0016] (2) The patterned resistive film design realizes stable absorption of large-angle range incident electromagnetic waves, compared with the traditional impregnated honeycomb wave-absorbing material, overcomes the problems of difficult precise control of electromagnetic parameter distribution and uneven angle response, and significantly improves the direction independence and stealth effect of the structure.

[0017] (3) The present application provides a patterned gradient resistive film honeycomb wave-absorbing structure preparation method with reasonable structure design and strong expandability, which can be directly adapted to the honeycomb expansion process. Through flexible design of the resistive film pattern and gradient, three-dimensional distribution absorption loss is realized, which overcomes the limitations of traditional impregnation process in material selection and process stability, and has good engineering applicability and broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A perspective view of a wide-angle domain wave-absorbing structure based on a honeycomb hole wall printed patterned resistive film is provided for the present application embodiment 1; Figure 2 A different structure schematic diagram of the patterned resistive film is provided; Figure 3 A preparation process flow chart of the honeycomb hole wall printed patterned resistive film structure is provided for the present application embodiment 1; Figure 4 A wave-absorbing performance simulation result graph of the present application embodiment 1 is provided; Figure 5 A wave-absorbing performance simulation result graph of the present application embodiment 2 is provided.

[0019] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein: 1-aramid paper honeycomb, 2-second printing area, 3-first printing area, 4-metal base plate, a-hole diameter length of the honeycomb structure. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0021] In the present application, the terms "first", "second", etc. (if any) in the present application and the drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0022] The present application provides a wide-angle domain wave-absorbing structure, comprising: a non-metallic porous structure and a patterned resistive film printed on the hole wall of the non-metallic porous structure; the patterned resistive film comprises at least two regions, the first region resistive film is located at the bottom of the hole wall, and the width is the same as the width of the hole wall; the bottom width of the second region resistive film is the same as the width of the hole wall, and the bottom is connected with the first region resistive film, and the width of the second region resistive film gradually decreases from the bottom to the top.

[0023] The bottom of the non-metallic porous structure is also provided with a metal back plate, which is perpendicular to the hole wall of the non-metallic porous structure and the patterned resistive film. The metal back plate is used to provide an approximately ideal electrical boundary. In actual application, the wide-angle domain wave-absorbing structure also has a packaging structure at the top, and preferably can also be filled with foam material in the porous structure.

[0024] Through the synergistic effect of the two regions, high-efficiency wave-absorbing in a wide incident angle range is realized, the reflection coefficient is lower than -15dB in the electromagnetic wave incident angle range of 0° to 45°, the absorption rate is greater than 90% in the frequency band of 4-18GHz, and the absorption rate is greater than 97% in the frequency band of 5-18GHz.

[0025] The non-metallic porous structure is composed of a plurality of hole walls connected to each other to form a through porous structure, and the through direction of each hole grid is the same, i.e. the height direction of each hole wall is the same. The non-metallic porous structure is preferably a honeycomb structure, and the cross section of the honeycomb structure is a polygon with 3-10 sides; the side length of the cross section is 1.83-8mm. Each side corresponds to a hole wall, and the shape of each hole wall is preferably rectangular.

[0026] The height of the hole wall from the bottom to the top is 5-50mm, and the height of the first region resistive film is 5-80% of the height of the hole wall. For example, the height of the first region resistive film is 1-40mm, preferably 5-20mm; the height of the second region resistive film is 2-45mm, preferably 10-40mm.

[0027] Preferably, the width of the second area resistance film decreases to 0 when reaching the top of the hole wall, and the top of the second area resistance film is located at the center of the top of the hole wall; the structure of the second area resistance film is shown in Figure 2 The width gradually decreases to 0 from the hole wall width a, and the area of the second area resistance film accounts for 50%-80% of the area of the hole wall where it is located, preferably an isosceles triangle. The first area resistance film is rectangular or square.

[0028] The sheet resistance value of the first area resistance film ranges from 100 to 2000 Ω, such as 100 Ω, 200 Ω, 300 Ω, 400 Ω, 500 Ω, etc., and the sheet resistance value of the second area resistance film ranges from 100 to 1000 Ω; the sheet resistance value of the first area resistance film is preferably less than or equal to the sheet resistance value of the second area resistance film. The first area resistance film can also be further divided into several areas in the height direction, and each area is provided with a resistance film with a different sheet resistance value. The resistance carbon paste is used for screen printing on the surface of the printing material, and the sheet resistance value of the patterned resistance film is controlled by the pattern area and thickness to achieve gradient distribution.

[0029] The patterned resistance film is printed on the two opposite surfaces of the hole wall, and the patterns on the two sides are preferably the same.

[0030] Further, the density of the non-metallic porous structure is 30-80 kg / m 3 , and the plane compressive strength is 0.6-4.2 MPa; the material of the non-metallic porous structure is para-aramid or meta-aramid.

[0031] The preparation method of the wide-angle domain wave absorption structure specifically includes the following steps: Material preparation and pretreatment: a heat-curable non-metallic sheet material such as aramid paper is selected as the honeycomb core material base, and cutting, surface dust removal and drying treatment are performed in advance. Preferably, the sheet is pre-impregnated with phenolic resin to improve the mechanical strength and stability after hot pressing.

[0032] Patterned resistance film printing: the surface of the treated sheet is printed with a patterned resistance film using screen printing technology. The bottom edge of each layer of pattern is aligned with the bottom of the sheet to achieve vertical patterns and gradient distribution. The resistance film uses resistance carbon paste material, and after printing, it is dried and cured in an environment of 120-200°C for 10-30 minutes.

[0033] Adhesive line printing: print a line of thermosetting adhesive on the surface of the sheet according to the position of the predetermined honeycomb structure unit cell. The area without printing adhesive will form the opening of the honeycomb wall in the subsequent stretching process, and the printed area is used for local bonding between the sheets.

[0034] Stacking and hot-pressing curing: stack the multi-layer printed finished sheet according to the set order, place it in the hot-pressing mold, and hot-press it at 180 °C and 1 MPa pressure to form a solid block with a compact structure.

[0035] Cutting: using high-precision cutting equipment, cut the cured block into pieces with a thickness of 5-50 mm (i.e. the height of the hole wall) along the direction perpendicular to the sheet, and the inside of the cut piece has printed resistance film patterns and bonding nodes.

[0036] Stretch forming and curing: clamp and uniformly stretch both ends of the cut piece, and the areas not bonded by the adhesive will expand to form a hexagonal honeycomb structure, and the patterned resistance film will be distributed on the inner wall of the honeycomb. For aramid honeycomb structures, further place them in a shaping mold and heat cure at 160 °C for 30 minutes to ensure the honeycomb geometry and structural strength.

[0037] Through the above expansion process, the three-dimensional patterned resistance film can be efficiently printed on the honeycomb wall, achieving wideband, wide-angle, and high-efficiency absorption of electromagnetic waves, especially in the 0°-45° incident angle range, the reflection coefficient is stably below -15 dB, significantly improving the full-angle performance consistency of the wave-absorbing structure.

[0038] Example One A wide-angle wave-absorbing structure based on printing patterned resistance film on honeycomb hole walls, as shown in Figure 1 , includes aramid paper honeycomb 1, first printing area 3, second printing area 2, and metal base plate 4. The aperture length (side length) of the honeycomb structure is 5.5 mm, and the hole wall height is 24 mm. The first printing area 3 is rectangular, with a width of 5.5 mm and a length of 6 mm, and the square resistance value is 100 Ω; the second printing area 2 is an isosceles triangle, with a height of 18 mm, and the base is aligned with the wide side of the first printing area 3, and the upper vertex is located at the center of the top side of the hole wall, and the square resistance value is 240 Ω. Preferably, the honeycomb structure uses aligned aramid honeycomb.

[0039] This example uses an expansion process to prepare the honeycomb wave-absorbing structure. The core idea of this process is to first bond multiple layers of composite sheets into a solid block, and then form a honeycomb structure through a stretching process. In this process, the patterned resistance film is pre-printed on the surface of the sheet, so that it is uniformly distributed on the honeycomb hole wall after stretching, achieving wide-angle absorption of electromagnetic waves.

[0040] The process includes steps as shown in Figure 3 , and the specific process details are as follows: Step one: material preparation and processing. Non-metallic materials with heat- setting properties, such as aramid paper, are selected as the base material for the honeycomb core. The material can be pretreated before use, including cutting (cutting according to the width of the hole wall), surface dust removal, drying, etc. The material is pre-impregnated with phenolic resin to facilitate subsequent heat setting and shaping.

[0041] Step two: patterned resistive film is prepared on the surface of the treated aramid paper using screen printing. The printed pattern combines geometric design to achieve resistance gradient control and improve wide-angle wave absorption performance.

[0042] First, the honeycomb wall surface is divided into two functional areas from bottom to top according to height: First printing area: height h1 is 6mm, rectangular pattern is used for screen printing, rectangular covers the bottom of honeycomb wall to the position of height 6mm, forming a continuous and uniform low resistance area. The material used is resistive carbon paste with a square resistance value of 100 Ω. After printing, it is dried and cured at 160°C for 10 minutes to ensure the stability and adhesion of the pattern.

[0043] Second printing area: located above the first printing area, height h2 is 18 mm, screen printing is carried out using isosceles triangle pattern. The base of each triangle pattern is aligned with the top edge of the first printing area, with a length equal to the width of the honeycomb wall, and the vertex is located at the midpoint of the top edge of the honeycomb wall. This area uses resistive carbon paste with a square resistance value of 240 Ω. After printing, it is also dried and cured at 160°C for 10 minutes. This structure helps to achieve a gradual resistance distribution and gradient control of incident waves.

[0044] Step three: printing adhesive lines. High-precision screen printing equipment is used to print heat- setting adhesive lines on the sheet. The printing position and direction of the adhesive determine the future geometric structure of the honeycomb unit. The area without printed adhesive will form the opening part of the honeycomb wall.

[0045] Step four: stacking and heat pressing and curing. The multiple layers of printed patterned resistive film and adhesive sheet are stacked alternately and aligned, then placed in a heat pressing device under the conditions of set temperature and pressure (e.g. 180°C, 1 MPa) for heat pressing and curing, forming a solid block with a compact structure.

[0046] Step five: cutting. The above block is cut into thin slices with a predetermined thickness of 24 mm using high-precision cutting equipment, and the cutting slice already contains complete resistive film pattern structure and adhesive nodes.

[0047] Step six: stretch forming and shaping and curing The slices are clamped at both ends and stretched evenly, unfolding the areas not bonded by adhesive to form a hexagonal honeycomb structure. During the stretching process, the patterned resistive film is simultaneously stretched to the honeycomb pore walls, forming a continuously distributed patterned resistive film. For honeycomb structures made of non-metallic materials such as aramid paper, they need to be placed in a shaping mold and subjected to high-temperature thermosetting treatment (e.g., 160°C, 30 minutes) to ensure the stability of the honeycomb geometry.

[0048] The simulation results of this embodiment are as follows: Figure 4 As shown, Figure 4 This indicates that the composite structure has a reflection coefficient of less than -10 dB for TE and TM polarization in the 4-18 GHz frequency band within the electromagnetic wave incident angle range of 0° to 45°, and a reflectivity of less than -15 dB in the 5-18 GHz frequency band.

[0049] The honeycomb absorbing structure prepared by the above steps not only has good structural strength and lightweight properties, but also, due to the ordered patterned distribution and gradient design of the resistive film, can achieve electromagnetic wave absorption with wide bandwidth, high efficiency and a large incident angle range, thus having excellent radar stealth performance and broad engineering application prospects.

[0050] Example 2 A wide-angle absorption structure based on a patterned resistive film printed on the walls of a honeycomb hole is proposed. The difference between this embodiment and Embodiment 1 is that step two is different. Step two of this embodiment is as follows.

[0051] Step two: Divide the honeycomb wall surface into two areas from bottom to top, designated as Area 1 and Area 2. Area 1 has a height of 6 mm, and Area 2 has a height of 18 mm. Simultaneously print resistive carbon paste onto both areas using screen printing. Area 1 uses resistive carbon paste with a sheet resistance of 240 Ω and is printed as a rectangular pattern. The base of the rectangle extends along the bottom edge of the honeycomb wall, with a length equal to the width of the honeycomb wall. Area 2 is located above Area 1, forming an isosceles triangle with its base coinciding with the top of Area 1. Its top vertex is located at the center of the cell wall width, and it is also entirely covered with resistive carbon paste with a sheet resistance of 240 Ω. After printing, the entire structure is dried and cured at 160℃ for 10 minutes.

[0052] The three-dimensional image of the resistive film solid structure based on honeycomb hole wall printed patterning prepared in this embodiment is shown below. Figure 2 The experimental steps are shown, and the simulation results of this embodiment are as follows: Figure 5 As shown, Figure 5 This indicates that the composite structure has a reflection coefficient of less than -10 dB for TE and TM polarization in the 6-18 GHz frequency band within the electromagnetic wave incident angle range of 0° to 45°, and a reflectivity of less than -15 dB in the 8-18 GHz frequency band.

[0053] In summary, the application provides a wide-angle wave-absorbing structure based on a honeycomb wall printing patterned resistive film. The structure combines a light and high-strength honeycomb material with a patterned resistive film with resistive loss characteristics, obtaining a light and strong-absorbing wave-absorbing structure with good wide-angle reflection performance. The reflection coefficient is stably better than -15 dB in the range of 0° to 45° incident angle, has excellent angle insensitivity characteristics, good electromagnetic compatibility and engineering realizability.

[0054] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A wide-angle domain wave-absorbing structure, characterized in that, The application relates to a wide-angle wave-absorbing structure, which comprises the following parts: a nonmetallic porous structure and a patterned resistive film printed on the hole wall of the nonmetallic porous structure; the patterned resistive film comprises at least two areas, a first area of the resistive film is located at the bottom of the hole wall and has the same width as the hole wall, and a second area of the resistive film has the same width as the hole wall at the bottom and is connected with the first area of the resistive film, and the width of the second area of the resistive film gradually decreases from the bottom to the top of the hole wall.

2. The wide-angle wave-absorbing structure according to claim 1, characterized in that, The nonmetallic porous structure is a honeycomb structure, the side length of the cross section of the honeycomb structure is 1.83-8 mm, each side corresponds to a hole wall, and the thickness of the hole wall is 0.02-1 mm.

3. The wide-angle wave-absorbing structure according to claim 1, wherein, The height of the hole wall from the bottom to the top is 5-50 mm, and the height of the first area of the resistive film is 5-80% of the height of the hole wall.

4. The wide-angle wave-absorbing structure according to claim 1, wherein, When the second area of the resistive film reaches the top of the hole wall, the width of the second area of the resistive film is reduced to 0, and the top of the second area of the resistive film is located at the center of the top of the hole wall, and the shape of the second area of the resistive film is preferably an isosceles triangle.

5. The wide-angle wave-absorbing structure according to claim 1, wherein, The sheet resistance of the second area of the resistive film ranges from 100 to 2000 ohms, and the sheet resistance of the first area of the resistive film ranges from 50 to 1000 ohms; the sheet resistance of the first area of the resistive film is less than or equal to the sheet resistance of the second area of the resistive film; and the patterned resistive film is printed on the two opposite surfaces of the hole wall.

6. The wide-angle wave-absorbing structure according to claim 1, wherein, The density of the non-metallic porous structure is 30-80 kg / m 3 The plane compressive strength is 0.6-4.2 MPa; and the material of the non-metallic porous structure is para-aramid or meta-aramid.

7. The wide-angle wave-absorbing structure according to any one of claims 1-6, characterized in that, The bottom of the nonmetallic porous structure is further provided with a metal back plate which is perpendicular to the hole wall of the nonmetallic porous structure and the patterned resistive film.

8. A method for preparing the wide-angle area wave-absorbing structure according to any one of claims 1-6, characterized in that, The application further relates to a preparation method of the wide-angle wave-absorbing structure, which comprises the following steps: S1, cutting a nonmetallic sheet into several pieces according to the size of the hole wall of the nonmetallic porous structure; S2, printing a patterned resistive film on the surface of each cut nonmetallic sheet; S3, printing an adhesive line on each nonmetallic sheet, then stacking the several nonmetallic sheets in an interlaced mode and heat pressing and curing to obtain a bonding body; S4, stretching the bonding body, unfolding the areas not bonded by the adhesive line to form a porous structure, and obtaining the wide-angle wave-absorbing structure.

9. The method of claim 8, wherein the method further comprises: In step S3, the temperature of the heat pressing and curing is 160-200 DEG C, and the pressure is 0.5-2 MPa.

10. The method of claim 8, wherein the method further comprises: In step S4, the porous structure after stretching is heat cured at 150-170 DEG C for 10-40 minutes.

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