All-metal progressive impedance edge scattering control material compatible with lightning protection

Abstract

The invention relates to the field of electronic material technology and lightning protection, in particular to an all-metal progressive impedance edge scattering control material compatible with lightning protection. 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 edge scattering suppression structure is covered with the whole full-covering periodic hollow full-metal membrane, and the gradual hollow metal sheet is formed by carving a gradual change hole unit structure on the metal sheet. Therefore, the propagation characteristic of the electromagnetic wave on the metal surface is changed, and the electromagnetic wave adjusting effect is achieved. According to the invention, no negative influence is generated on the original electrical performance, strong lightning protection is compatible, and lightning current injected into a target body can be efficiently guided away, so that the lightning current smoothly flows into a conductor to well protect a wave-absorbing material below the conductor, and a good lightning protection effect is achieved. 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 an all-metal progressive impedance edge scattering control material compatible with lightning protection. Background Art

[0002] Lightning strikes pose a significant threat to aircraft in normal flight. According to statistics, an aircraft may be struck by lightning once every 1,000 to 10,000 hours of flight. Therefore, it is particularly necessary to ensure the safety of aircraft in lightning environments. The leading edge structure of the aircraft's wing is in the first lightning zone, which is the area where lightning first attaches and is extremely vulnerable to the threat of lightning strikes. Therefore, lightning protection at the leading edge of the aircraft wing is particularly important. At present, due to the need for weight reduction or low detectability, all or part of the aircraft's wings (including the leading edge) are made of composite materials. Most of these materials are of low conductivity or even insulating nature, and their conductivity is much lower than that of metals. Once struck by lightning, they may cause serious safety hazards. In order to meet this challenge, lightning protection at the leading edge of the aircraft wing has become the core and key.

[0003] Strong scattering sources such as cockpits, radar cabins and air intakes of low-observable aircraft have been effectively controlled, and the electromagnetic scattering problem of surface electromagnetic defects such as edges has become prominent. The edge scattering suppression structure is the main technical means for electromagnetic repair of edge-type surface electromagnetic defects. It is generally composed of a variety of non-conductive composite materials, which not only meets the structural strength requirements of the aircraft, but also effectively reduces the radar scattering cross section. This structure has multiple functions of shape optimization and electromagnetic wave reflection reduction. Compared with the traditional method of radar absorbing coating, the edge scattering suppression structure has obvious advantages in low-frequency ultra-wideband electromagnetic scattering control capabilities, and has become the main technical solution for edge scattering control.

[0004] At present, lightning protection for composite materials or composite structures usually adopts methods such as surface metallization or the arrangement of lightning protection shunt strips. However, for edge scattering suppression structures, surface metallization will seriously damage the impedance characteristics of the interface, causing impedance mismatch, thereby generating strong electromagnetic scattering; lightning protection shunt strips are similar to dipole antennas, becoming strong radiation sources, and also generating strong electromagnetic scattering. Therefore, how to achieve lightning protection compatible edge scattering suppression materials has become an urgent problem to be solved in current academic research and engineering applications.

[0005] Patent CN202411345484.3 designs a gradient impedance thin film material based on lightning protection and edge scattering control. This patent applies the passive protection method of the Faraday cage concept to the lightning protection of the edge scattering suppression structure. It provides a safe current conduction path for the external structure to ensure that most of the current stays only on the surface and can be quickly conducted without causing serious damage, and meets certain electrical performance requirements within a certain frequency, polarization mode and azimuth. However, it has the defect of being unable to withstand the impact of lightning current with a large peak value. Summary of the invention

[0006] In view of the above problems or shortcomings, in order to solve the problem that the existing impedance edge scattering control materials compatible with lightning protection cannot effectively withstand large peak lightning currents, the present invention provides an all-metal progressive impedance edge scattering control material compatible with lightning protection, which has better lightning protection performance under the premise of ensuring the performance requirements of the impedance edge scattering control material (effectively suppressing edge scattering).

[0007] A full-metal progressive impedance edge scattering control material compatible with lightning protection, wherein the direction from the outside to the inside of the outermost edge of the target edge scattering suppression structure is defined as a depth direction, and its length is L, corresponding to the length direction from left to right of the full-metal film; the full-metal 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 to form a progressive impedance full metal diaphragm material. After determining the operating frequency, the S parameter inversion method is used to determine the relative impedance of the hollow pattern according to the following formula:

[0009]

[0010] Where S 11 , S 21 is the scattering parameter, S 11 represents the reflection coefficient, S 21 represents the transmission coefficient and z represents the relative impedance.

[0011] By changing the side length of each periodic structure's hollow figure, S 11 , S 21 The value of changes, thereby achieving the purpose of changing the relative impedance and realizing the effect of gradual impedance. This ensures that the hollowed-out gradual 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 10 GHz frequency range.

[0012] Furthermore, the material of the all-metal film is copper.

[0013] Furthermore, 40≤L≤50mm.

[0014] 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.

[0015] Furthermore, the hollowed-out figure is a circle.

[0016] Furthermore, the hollow pattern is a square or a regular hexagon.

[0017] 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.

[0018] In order to realize strong lightning protection of edge scattering suppression structure, the present invention applies the passive protection method based on the concept of Faraday cage 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 strong lightning protection, an all-metal progressive impedance edge scattering control material with good conductivity is designed; and in order to be compatible with the electrical properties of the edge scattering suppression structure, the equivalent surface impedance is gradually changed by an all-metal hollow periodic diaphragm with gradually changing impedance, and the impedance change is large. This gradual impedance can help achieve specific electromagnetic wave transmission effects, reduce reflection losses, achieve impedance matching, etc., and will not deteriorate electrical performance.

[0019] In summary, the present invention uses a full-coverage periodic hollow full metal film to cover the surface of the edge scattering suppression structure. By calculating and setting the parameter values ​​of each hollow pattern, it does not have a negative impact on the original electrical performance, and the lightning protection progressive full metal film can very effectively guide the lightning current to achieve a good lightning protection effect, so that the lightning protection effect can be stronger and at the same time have edge scattering suppression. 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

[0020] Figure 1 Schematic diagram of the periodic structure of the all-metal progressive impedance edge scattering control material in the length direction of the embodiment;

[0021] Figure 2 A schematic diagram and coordinate description of the structure of the target body loaded with absorbing material and all-metal progressive impedance edge scattering control material in the embodiment;

[0022] 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;

[0023] Figure 4 A schematic diagram of a target body loaded with absorbing materials and all-metal progressive impedance edge scattering control materials in an embodiment;

[0024] Figure 5 This is a schematic diagram of current density distribution after the target body is loaded with international A wave lightning current injection in the embodiment;

[0025] Figure 6 This is a schematic diagram of the temperature distribution of the target body of the embodiment after the international A wave lightning current is injected. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0027] The present invention provides a full-metal progressive impedance edge scattering control material compatible with lightning protection, which introduces a progressive periodic structure on a full-metal (copper) diaphragm. The periodic structure adopts a square hole form. Figure 1 shown.

[0028] In this embodiment, a target body with a length of 600 mm and a width of 400 mm is loaded with absorbing materials and all-metal progressive impedance edge scattering control materials compatible with lightning protection. At 40 mm 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 all-metal progressive impedance edge scattering control materials compatible with lightning protection. The impedance of the absorbing material at the contact position with the target metal body is the smallest, and its basic structure is as follows: Figure 2 As shown: with the largest periodic unit (with the largest impedance) in 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 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.

[0029] In this embodiment, the hollow pattern is a square, L = 45mm, and from left to right, the side length of the hollow pattern of the first-level periodic unit is a = 7.25mm, the side length of the hollow pattern of the second-level periodic unit is b = 3.63mm, the side length of the hollow pattern of the third-level periodic unit is c = 2.5mm, the side length of the hollow pattern of the fourth-level periodic unit is d = 1.83mm, the side length of the hollow pattern of the fifth-level periodic unit is e = 1.38mm, and the side length of the hollow pattern of the sixth-level periodic unit is f = 0.01mm.

[0030] Set the incident wave frequency to 10 GHz. The incident wave is at 10 GHz. θ=90°, the average single-station RCS of the target before loading under horizontal polarization is -30.88dBsm, and the average RCS of the target after loading is -29.70dBsm. The average single-station RCS of the target before loading under vertical polarization is -37.10dBsm, and the average RCS of the target after loading is -43.34dBsm.

[0031] Through the above loading design method, the RCS under horizontal polarization remains basically unchanged, but the RCS reduction value under vertical polarization is 6.24dB. Figure 3 As shown in the figure, the scattering of the target under vertical polarization is effectively reduced without increasing the horizontal polarization scattering.

[0032] like Figure 4 As shown in the figure, a lightning current thermoelectric coupling simulation is performed on a target body loaded with absorbing materials and all-metal progressive impedance edge scattering control materials compatible with lightning protection, and the metal sheet material is set to copper. A peak value of 100k A wave lightning current is applied to the center position above the target body, and the bottom of the target body is grounded. Figure 5 As shown, (a) is the current density distribution of the patterned metal copper sheet, and (b) is the current density distribution of the absorbing material. From the simulation results, it can be seen that the current density of the all-metal progressive impedance edge scattering control material compatible with lightning protection can reach up to 1.40e06A / mm 2 , while the absorbing material located below the all-metal progressive impedance edge scattering control material compatible with lightning protection has almost no current density passing through it. And since the melting point of copper is 1083.4℃, based on this standard, the area with a temperature exceeding the melting point of copper is defined as the lightning current ablation area.

[0033] like Figure 6 As shown, (a) is the temperature distribution of the patterned metal copper sheet, and (b) is the temperature distribution of the absorbing material. On the all-metal progressive impedance edge scattering control material compatible with lightning protection, only the ablation area of ​​the all-metal progressive impedance edge scattering control material compatible with lightning protection near the lightning strike attachment point is higher, and the ablation area in other places is smaller, while the highest temperature of the absorbing material below is only 72°C.

[0034] It can be seen from the above embodiments that, through the above loading method, the all-metal progressive impedance edge scattering control material compatible with lightning protection can effectively guide away the lightning current injected into the target body, so that the lightning current can flow smoothly into the conductor and well protect the absorbing material below it. 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 a full-coverage periodic hollow full metal film is used to cover the surface of the edge scattering suppression structure. The parameter values ​​of each hollow figure are calculated and set without negatively affecting the original electrical performance. The all-metal film with progressive lightning protection can efficiently guide away the lightning current injected into the target body, so that the lightning current can flow smoothly into the conductor and well protect the absorbing material below it, achieving a good lightning protection effect, so as to achieve a strong lightning protection effect, and at the same time have edge scattering suppression. In addition, the present invention has a simple process, strong operability, and is easy to implement industrially, and is suitable for promotion.

Claims

1. A full-metal progressive impedance edge scattering control material compatible with lightning protection, 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 full metal film; the full metal 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 to form a progressive impedance full metal diaphragm material; after determining the operating frequency, the S parameter inversion method is used to determine the relative impedance of the hollow pattern according to the following formula: Where S 11 , S 21 is the scattering parameter, S 11 represents the reflection coefficient, S 21 represents the transmission coefficient, and z represents the relative impedance; By changing the side length of each periodic structure's hollow figure, S 11 , S 21 The value of changes, thereby achieving the purpose of changing the relative impedance and realizing the effect of gradual impedance; the hollowed-out gradual impedance thin film material covering the edge scattering suppression structure has no negative impact on the electrical properties of horizontal polarization and vertical polarization in the 10GHz frequency range.

2. The all-metal progressive impedance edge scattering control material compatible with lightning protection as claimed in claim 1, characterized in that: The material of the all-metal film is copper.

3. The all-metal progressive impedance edge scattering control material compatible with lightning protection as claimed in claim 1, characterized in that: 40≤L≤50mm.

4. The all-metal progressive impedance edge scattering control material compatible with lightning protection 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.

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

6. The all-metal progressive impedance edge scattering control material compatible with lightning protection as claimed in claim 1, characterized in that: The hollowed-out pattern is a square or a regular hexagon.

7. The all-metal progressive impedance edge scattering control material compatible with lightning protection as claimed in claim 1, characterized in that: The hollowed-out pattern is a square, L=45mm, and from left to right, the side length of the hollowed-out pattern of the first-level periodic unit is a=7.25mm, the side length of the hollowed-out pattern of the second-level periodic unit is b=3.63mm, the side length of the hollowed-out pattern of the third-level periodic unit is c=2.5mm, the side length of the hollowed-out pattern of the fourth-level periodic unit is d=1.83mm, the side length of the hollowed-out pattern of the fifth-level periodic unit is e=1.38mm, and the side length of the hollowed-out pattern of the sixth-level periodic unit is f=0.01mm.

8. The all-metal progressive impedance edge scattering control material compatible with lightning protection as claimed in claim 1, characterized in that: When in use, the largest periodic unit 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, thereby fully covering the upper and lower exposed surfaces of the entire edge scattering suppression structure.

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