Progressive impedance thin film material compatible with lightning protection and edge scattering control

Abstract

The invention relates to the field of electronic material technology and lightning protection, in particular to a progressive impedance thin film material compatible with lightning protection / edge scattering control. The passive protection method based on the Faraday cage concept is applied to lightning stroke protection of a typical edge scattering suppression structure, the surface of the typical edge scattering suppression structure is covered with the whole full-covering periodic hollow impedance film, and the original electrical performance is not negatively influenced by setting the parameter value of each hollow pattern through calculation; and the lightning protection progressive impedance film can effectively guide away lightning current injected into the target body, so that the lightning current smoothly flows into the conductor to well protect the wave-absorbing material below the conductor, thereby achieving a good lightning protection effect and achieving the lightning protection effect at the same time. The method is simple in process, high in operability, easy to implement industrially and suitable for popularization.

Description

Technical Field

[0001] The invention relates to the field of electronic material technology and lightning protection, and in particular to a progressive impedance thin film material compatible with lightning protection / edge scattering control. Background Art

[0002] Lightning strikes are a great threat to aircraft in normal flight. According to statistics, an aircraft will encounter a lightning strike every 1,000 to 10,000 hours of flight, so it is very necessary to protect the aircraft from lightning and ensure the safety of the aircraft in a lightning environment. The edge scattering suppression structure of the aircraft is the initial attachment area of ​​lightning, so the edge scattering suppression structure of the aircraft is the key area for lightning protection. In addition, most of the composite materials used in the edge scattering suppression structure of the aircraft are insulating materials, and their conductivity is much lower than that of metals. They are extremely susceptible to the impact of the lightning strike environment, which is quite fatal to aircraft in a lightning environment. Therefore, the lightning protection of the edge scattering suppression structure should be focused on.

[0003] The edge scattering suppression structure refers to a structure composed of a variety of non-conductive composite materials, which can meet the load-bearing requirements and has a significantly reduced radar cross section. It is a multifunctional integrated structure that can not only meet the requirements of appearance and structure, but also effectively reduce the reflection of electromagnetic waves. Compared with the technical method of simply designing the appearance and loading materials to reduce electrical performance, this measure will not reduce the maneuverability and agility of the aircraft due to excessive emphasis on modifying the appearance, and at the same time, it also expands the application scope of absorbing materials on the body. Since the aircraft structure has a certain structural height and structural space, by optimizing the structural geometry and the electromagnetic parameters of the material, the incident wave can be repeatedly propagated and lost in the structure, maximizing the absorption of electromagnetic waves, thereby obtaining a higher absorption rate.

[0004] At present, lightning protection for non-conductive composite materials usually involves metallization treatment on the surface and the arrangement of lightning protection shunt strips. For edge scattering suppression structures, the impact of lightning protection measures on their appearance should be avoided as much as possible due to their electrical performance requirements. The arrangement of lightning protection shunt strips will form protrusions on the surface of the structure, which will seriously affect the electrical performance of the edge structure.

[0005] As lightning protection of edge scattering suppression structures becomes an increasingly important research direction, designing and realizing a progressive impedance thin film material that is compatible with lightning protection / edge scattering control has become an urgent problem to be solved in engineering applications. Summary of the invention

[0006] In view of the above-mentioned problems or shortcomings, and to solve the problem of insufficient lightning protection of existing edge scattering suppression structures, the present invention provides a progressive impedance thin film material compatible with lightning protection / edge scattering control. By loading the film with progressive impedance at the lightning protection edge, it can effectively protect against lightning while suppressing the edge scattering of the loaded target structure within a certain frequency, polarization mode and azimuth.

[0007] A progressive impedance film material compatible with lightning protection / edge scattering control, the direction from the outermost edge of the target edge scattering suppression structure from the outside to the inside is defined as the depth direction, and its length is L, corresponding to the length direction from left to right of the impedance film; the impedance film is evenly divided into six periodic units in the length direction, and the length of the periodic unit in the width direction is also taken as P = L / 6, and each periodic unit is a square periodic unit with a side length of P = L / 6;

[0008] The six square periodic units are arranged with a hollow pattern centered and not touching the outer edge in a gradient decreasing manner in the length direction, and the last periodic unit is not hollowed out, so as to form a progressive impedance film material; the hollow pattern parameters are determined according to the following formula:

[0009]

[0010] R eq is the equivalent impedance, R s is the resistance value of the uniform impedance film, P is the unit period, and w is the side length or radius of the hollowed-out pattern; so that the hollowed-out progressive impedance film material covering the edge scattering suppression structure has no negative impact on the electrical properties of horizontal polarization and vertical polarization in the frequency range of 9GHz-11GHz.

[0011] Furthermore, 40≤L≤50mm.

[0012] Furthermore, the hollowed-out figure is an even-numbered regular polygon with the number of sides being greater than or equal to 4, and one side of the hollowed-out figure is parallel to one side of the periodic unit square to which it belongs.

[0013] Furthermore, the hollow pattern is a square or a regular hexagon.

[0014] Furthermore, the hollowed-out figure is a circle.

[0015] Furthermore, when in use, the largest periodic unit (with the largest impedance) in the hollowed-out pattern is on the left, and the length direction of the periodic unit is adapted to the depth direction of the edge scattering suppression structure. The impedance of the square periodic unit decreases from left to right, and the size of the hollowed-out pattern gradually decreases; the wide sides of the periodic unit are successively spread along the edge direction of the edge scattering suppression structure, and then fully cover the upper and lower exposed surfaces of the entire edge scattering suppression structure.

[0016] In order to realize the lightning protection of edge scattering suppression structure, the passive protection method based on the concept of Faraday cage is applied to the lightning protection of edge scattering suppression structure. The main goal of lightning protection is to ensure that most of the current stays only on the surface and can be quickly conducted away without causing serious damage by providing a safe current conduction path for the external structure. In order to achieve the purpose of lightning protection, a progressive impedance film material compatible with lightning protection / edge scattering control is designed, and the impedance film is prepared with good conductivity; and in order to be compatible with the electrical properties of the edge scattering suppression structure, the equivalent surface impedance is gradually changed through a graphical periodic gradient design, and the impedance change is large, which effectively suppresses edge scattering and does not deteriorate the electrical performance.

[0017] In summary, the present invention uses a fully covered periodic hollow impedance film to cover the surface of the edge scattering suppression structure, and the parameter values ​​of each hollow pattern are calculated and set to have no negative impact on the original electrical performance, while the lightning protection progressive impedance film can effectively guide the lightning current to achieve a good lightning protection effect, so that the lightning protection effect can be achieved at the same time. In addition, the present invention has a simple process, strong operability, and is easy to implement industrially, and is suitable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the periodic structure of the progressive impedance film in the length direction of the embodiment;

[0019] Figure 2 A schematic diagram and coordinate description of the structure of the target body of the embodiment loaded with absorbing material and progressive impedance film;

[0020] Figure 3 The radar cross section of the target before and after loading is shown in the following figure: (a) horizontal polarization; (b) vertical polarization;

[0021] Figure 4 A schematic diagram of a target body loaded with absorbing materials and a lightning protection progressive impedance film in an embodiment;

[0022] Figure 5 Schematic diagram of target current density distribution in the embodiment;

[0023] Figure 6 This is a diagram of the target body of the lightning direct effect test in the embodiment. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] The invention provides a progressive impedance film material compatible with lightning protection / edge scattering control, which introduces a progressive periodic hollow impedance film structure on an impedance film.

[0026] In this embodiment, the impedance of the impedance film Rs =30Ω, the periodic structure adopts square hole form, L = 45mm, P = 7.5mm, such as Figure 1 As shown. From left to right, the side length of the square hollow pattern of the first-level periodic unit is a = 5.250mm, the side length of the hollow pattern of the second-level periodic unit is b = 4.637mm, the side length of the hollow pattern of the third-level periodic unit is c = 3.858mm, the side length of the hollow pattern of the fourth-level periodic unit is d = 2.866mm, the side length of the hollow pattern of the fifth-level periodic unit is e = 1.604mm, and the sixth-level periodic unit structure is not hollowed out. The corresponding impedances are R eq1 =100Ω、R eq2 =78.6Ω, R eq3 =61.8Ω, R eq4 =48.55Ω, R eq5 =38.16Ω, R eq6 =30Ω.

[0027] A metal body with a length of 600mm and a width of 400mm is loaded with absorbing materials and a progressive impedance film for lightning protection. At 40mm from the front edge of the metal target body in the x-axis direction, the metal target body is cut off along the direction with an angle of 45° with the z-axis, and the absorbing material is loaded, and the upper and lower surfaces of the absorbing material are completely covered with a progressive impedance film for lightning protection. The impedance at the contact position between the absorbing material and the target metal body is the smallest, and the structure is as follows: Figure 2 shown.

[0028] Set the incident wave frequency to 10 GHz. The incident wave is at 10 GHz. θ=90°, the average RCS value of pure metal at single station under horizontal polarization is -30.879dBsm, and the average RCS value after loading is -31.254dBsm. The average RCS value of pure metal at single station under vertical polarization is -37.096dBsm, and the average RCS value after loading is -43.877dBsm. Figure 3 shown.

[0029] Through the loading design method, the RCS reduction value under horizontal polarization is 0.375dBsm, and the RCS reduction value under vertical polarization is 6.781dBsm. Without increasing the horizontal polarization scattering, the scattering of the target under vertical polarization is effectively reduced.

[0030] For target bodies loaded with absorbing materials and lightning protection progressive impedance films, such as Figure 4 As shown in the figure, the direct effect of lightning current is simulated. A peak value of 100k A wave lightning current is applied to the center of the target body, and the bottom of the target body is grounded. From the simulation results, it can be seen that the current density of the progressive impedance loading thin mold can reach up to 133.9kA / mm 2, while the maximum current density of the absorbing material under the progressive impedance loading film is only 0.188A / mm 2 ,like Figure 5 The sample was then tested for direct lightning effects. After the test, visual inspection showed that the overall structure of the target remained intact, the injected paint layer and the loaded lightning protection progressive impedance film fell off, and there was stratification at the bottom. Figure 6 shown.

[0031] It can be seen from the above embodiments that the passive protection method based on the concept of Faraday cage of the present invention is applied to the lightning protection of edge scattering suppression structure, and the entire fully covered periodic hollow impedance film is used to cover the surface of the edge scattering suppression structure. The parameter values ​​of each hollow figure are calculated and set to have no negative impact on the original electrical performance, and the lightning protection progressive impedance film can effectively guide the lightning current injected into the target body, so that the lightning current flows smoothly into the conductor and well protects the absorbing material below it, achieving a good lightning protection effect, so that the lightning protection effect can be achieved at the same time. The present invention has simple process, strong operability, easy industrial implementation, and is suitable for promotion.

Claims

1. Progressive impedance film material compatible with lightning protection / edge scattering control, characterized by: The direction from the outermost edge of the target edge scattering suppression structure from the outside to the inside is defined as the depth direction, and its length is L, which corresponds to the length direction from left to right of the impedance film; the impedance film is evenly divided into six periodic units in the length direction, and the length of the periodic unit in the width direction is also taken as P = L / 6, and each periodic unit is a square periodic unit with a side length of P = L / 6; The six square periodic units are arranged with a hollow pattern centered and not touching the outer edge in a gradient decreasing manner in the length direction, and the last periodic unit is not hollowed out, so as to form a progressive impedance film material; the hollow pattern parameters are determined according to the following formula: R eq is the equivalent impedance, R s is the resistance value of the uniform impedance film, P is the unit period, and w is the side length or radius of the hollowed-out pattern; so that the hollowed-out progressive impedance film material covering the edge scattering suppression structure has no negative impact on the electrical properties of horizontal polarization and vertical polarization in the frequency range of 9GHz-11GHz.

2. The progressive impedance thin film material compatible with lightning protection / edge scattering control as claimed in claim 1, characterized in that: 40≤L≤50mm.

3. The progressive impedance thin film material compatible with lightning protection / edge scattering control as claimed in claim 1, characterized in that: The hollowed-out figure is an even-numbered regular polygon with the number of sides being greater than or equal to 4, and one side of the hollowed-out figure is parallel to one side of the periodic unit square to which it belongs.

4. The progressive impedance thin film material compatible with lightning protection / edge scattering control as claimed in claim 3, characterized in that: The hollowed-out pattern is a square or a regular hexagon.

5. The progressive impedance thin film material compatible with lightning protection / edge scattering control as claimed in claim 4, characterized in that: The hollow pattern is a square, L = 45 mm, R s =30Ω, P=7.5mm; from left to right, the side length of the hollow pattern of the first-level periodic unit is a=5.250mm, the side length of the hollow pattern of the second-level periodic unit is b=4.637mm, the side length of the hollow pattern of the third-level periodic unit is c=3.858mm, the side length of the hollow pattern of the fourth-level periodic unit is d=2.866mm, the side length of the hollow pattern of the fifth-level periodic unit is e=1.604mm, and the sixth-level periodic unit structure is not hollowed out; the impedance corresponding to each level of periodic unit is R eq1 =100Ω、R eq2 =78.6Ω, R eq3 =61.8Ω, R eq4 =48.55Ω, R eq5 =38.16Ω, R eq6 =30Ω.

6. The progressive impedance thin film material compatible with lightning protection / edge scattering control as claimed in claim 1, characterized in that: The hollowed-out figure is a circle.

7. The progressive impedance thin film material compatible with lightning protection / edge scattering control as claimed in claim 1, characterized in that: When in use: take the largest periodic unit of the hollowed-out pattern on the left, the length direction of the periodic unit is adapted to the depth direction of the edge scattering suppression structure, the wide sides of the periodic unit are sequentially distributed along the edge direction of the edge scattering suppression structure, and then the upper and lower exposed surfaces of the entire edge scattering suppression structure are fully covered.

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