Visible light / infrared / radar multi-band compatible stealth material with gradient structure

Abstract

The invention relates to the technical field of multi-frequency-band compatible stealth structure control, in particular to a visible light / infrared / radar multi-frequency-band compatible stealth material of a gradient structure. According to the multi-band compatible stealth material of the multi-layer gradient system provided by the invention, by designing the middle radar wave-absorbing structure layer and the bottom radar wave-absorbing structure layer of which the resonance point impedance characteristics are gradually increased in a gradient manner, multiple reflections and refractions on electromagnetic waves are increased, and the radar compatibility of the whole multi-band compatible stealth structure is improved; the technical bottleneck that the radar compatibility performance of a traditional multi-spectrum wave-absorbing coating is deteriorated in the Ku wave band is broken through, especially under the condition that the infrared emissivity is smaller than 0.2; the intrinsic impedance of the middle radar wave-absorbing structure layer and the bottom radar wave-absorbing structure layer is adjustable, so that the material adaptability and adjustability are high; the design method provided by the invention is simple in process and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-band compatible stealth structure control, and in particular to a visible light / infrared / radar multi-band compatible stealth material with a gradient structure. Background Art

[0002] Visible light / infrared / radar multi-band compatible stealth is often a multi-structure system composed of a layer of infrared stealth coating on the surface of a radar absorbing structure. It has the characteristics of reducing radar reflection characteristics and visible light and infrared radiation, and is often used in aviation, aerospace, and consumer electronics. In order to achieve effective control of visible light and infrared radiation, it is often necessary to add a large amount of metal powder pigments such as silver powder, aluminum powder or copper powder to the infrared stealth coating. However, this type of metal material has a high dielectric constant, which will reduce the impedance matching effect with the radar absorbing coating, especially worsening the radar compatibility of the multi-spectrum stealth structure in the Ku band. Therefore, how to improve the radar compatibility of the multi-spectrum stealth structure in the Ku band under low infrared radiation is a technical bottleneck in this field.

[0003] From the perspective of the intrinsic characteristics of the material and the impedance matching of the structure, reducing the dielectric constant of the infrared stealth coating can improve the radar compatibility of the multi-spectrum stealth structure. However, due to the multi-spectrum stealth structure's demand for low infrared emissivity, it is often necessary to add a large amount of metal powder pigments to the infrared stealth coating. However, the dielectric constant of metals is often large, and they have high radar reflection characteristics for electromagnetic waves. Therefore, in order to reduce the dielectric constant of the infrared stealth coating and thus improve the radar compatibility effect, the content of metal powder pigments in the infrared stealth coating can only be reduced. However, the reduction in the content of metal powder pigments will lead to an increase in infrared emissivity, and the two present contradictory characteristics.

[0004] For example, ZL201410217815.5 proposes a method of applying an infrared stealth coating on the surface of an object coated with a radar absorbing coating. It can be seen from Table 1 that when the content of metal powder pigment in the infrared stealth coating is 95% or 100%, the infrared emissivity is less than 0.30, but the radar compatibility effect in the Ku band is deteriorated (reflectivity difference>0dB). Although patent CN201611063313.7 proposes an infrared / radar compatible stealth coating and a preparation method thereof, the dielectric properties of the infrared stealth coating are reduced by reducing the dielectric constant of the resin in the infrared stealth coating, but because the dielectric constant of the metal powder pigment is too high, this method is very limited or even ineffective in improving the radar compatibility characteristics of the Ku band, especially when the infrared emissivity is less than 0.3 or even lower. As described in Table 1 of the patent, the deterioration of the Ku-band radar compatibility performance reaches more than 0.8dB. In addition, patent ZL20170511870.9 proposes an infrared coating compatible with radar stealth and its preparation method, which achieves compatible radar stealth performance by selecting and controlling the infrared coating pigments and fillers. The patent points out that the average reflectivity of the infrared coating to radar waves at 2 to 18 GHz is less than or equal to 10%. However, when the emissivity is less than 0.3, the radar compatibility of the Ku band will inevitably deteriorate (refer to the above two patents).

[0005] Therefore, it is necessary to develop a visible light / infrared / radar multi-band compatible stealth technology. Summary of the invention

[0006] In view of the above-mentioned problems or shortcomings, and to solve the technical bottleneck problems existing in the existing visible light / infrared / radar multi-band compatible stealth, the present invention provides a gradient structure of visible light / infrared / radar multi-band compatible stealth; the multi-band stealth structure designed based on the multi-layer gradient structure of the present invention can make the electromagnetic waves reflect and refract multiple times therein, thereby increasing the absorption of electromagnetic waves by the overall multi-spectrum stealth structure, thereby breaking through the technical bottleneck of poor compatibility of traditional multi-spectrum stealth coatings in the Ku-band radar.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A visible light / infrared / radar multi-band compatible stealth material with a gradient structure comprises a surface infrared stealth structure layer, a middle radar absorbing structure layer and a bottom radar absorbing structure layer which are sequentially stacked from the outside to the inside.

[0009] The surface infrared stealth structure layer realizes visible light and infrared stealth.

[0010] The intermediate radar absorbing structure layer and the bottom radar absorbing structure layer realize radar stealth, and the impedance characteristics of the two at the resonance point are gradually increased; by involving the intermediate radar absorbing structure layer and the bottom radar absorbing structure layer at the resonance point, the impedance characteristics are gradually changed, so as to reflect and refract the incident electromagnetic waves multiple times, thereby increasing the absorption of electromagnetic waves by the bottom radar absorbing structure layer, thereby improving the radar compatibility performance of the Ku band.

[0011] Furthermore, the thickness of the surface infrared stealth structure layer is t3 = 50 μm, the thickness of the middle radar absorbing structure layer is t2 = 0.05 mm to 0.2 mm, and the thickness of the bottom radar absorbing structure layer is t1 = 0.2 mm to 0.4 mm.

[0012] Furthermore, the infrared emissivity of the surface infrared stealth structure layer is ≤0.2. Because the smaller the infrared emissivity, the worse the corresponding radar stealth of the traditional multi-spectrum absorbing coating, and the worse the overall compatibility; but the intermediate radar absorbing structure layer and the bottom radar absorbing structure layer of the present invention, whose impedance characteristics at the resonance point increase gradually, are not afraid of this point, and can still achieve both radar stealth.

[0013] Furthermore, the impedance difference between the middle radar absorbing structure layer and the bottom radar absorbing structure layer is 28Ohm to 46Ohm.

[0014] Furthermore, the intermediate radar absorbing structure layer and the bottom radar absorbing structure layer are additionally provided with at least one radar absorbing structure layer, and the impedance characteristics of all radar absorbing structure layers at the resonance point still increase gradually, so that the intrinsic impedance of the overall radar absorbing structure layer can be adjusted higher, and the material adaptability and adjustability are strong.

[0015] Furthermore, the additional radar absorbing structure layer is located between the middle radar absorbing structure layer and the bottom radar absorbing structure layer.

[0016] Furthermore, the additional radar absorbing structural layer is located on both sides of the middle radar absorbing structural layer and the bottom radar absorbing structural layer.

[0017] In summary, the multi-band compatible stealth structure provided by the present invention is a multi-layer gradient system. By designing an intermediate radar absorbing structure layer and a bottom radar absorbing structure layer with gradient impedance characteristics at the resonance point, multiple reflections of electromagnetic waves are increased, thereby improving the radar compatibility of the overall multi-band stealth structure. The technical bottleneck of the deterioration of the Ku-band radar compatibility of traditional multi-spectrum absorbing coatings has been broken through, especially when the infrared emissivity is less than 0.2. The intrinsic impedance of the overall radar absorbing structure layer is adjustable, so that its material adaptability and adjustability are strong. In addition, the design method and process involved in the present invention are simple and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 It is a schematic diagram of the structure of the comparative example of structure 1;

[0020] Figure 3 It is a schematic diagram of the structure of the comparative example of structure 2;

[0021] Figure 4 It is a schematic diagram of the structure of the comparative example of structure 3 (the thickness of the radar absorbing structure is t1+t2);

[0022] Figure 5 The comparison diagram of the real and imaginary impedance parts of Example 1, Structure 1, Structure 2, and Structure 3;

[0023] Figure 6 is the radar reflectivity curve of Example 1;

[0024] Figure 7 The comparison diagram of the real and imaginary impedance parts of Example 2, Structure 1, Structure 2, and Structure 3;

[0025] Figure 8 is the radar reflectivity curve of Example 2;

[0026] Fig. 9 The comparison diagram of the real and imaginary impedance parts of Example 3 and Structure 1, Structure 2, and Structure 3;

[0027] Fig.10 is the radar reflectivity curve of Example 3;

[0028] Fig.11 The comparison diagram of the real and imaginary impedance parts of Example 4, Structure 1, Structure 2, and Structure 3;

[0029] Fig.12 This is the radar reflectivity curve of Example 4. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below in conjunction with the embodiments and drawings.

[0031] In order to more clearly understand the technical features of the present invention, Figure 1 , Figure 2 , Figure 3 , Figure 4 Provide explanation.

[0032] The embodiment structure of the present invention (such as Figure 1As shown in FIG. 1 , the following are stacked outward on the metal substrate: a bottom radar absorbing structure layer (radar absorbing structure C), an intermediate radar absorbing structure layer (radar absorbing structure B), and a surface infrared stealth structure layer (infrared stealth structure A). The thickness of the infrared stealth structure A is t3, the thickness of the radar absorbing structure B is t2, and the thickness of the radar absorbing structure C is t1.

[0033] Structure 1 (such as Figure 2 ) is an embodiment structure that does not include the radar absorbing structure C. The radar absorbing layer in the structure is a homogeneous material and only includes the radar absorbing structure B, as a comparative example.

[0034] Structure 2 (such as Figure 3 ) is an embodiment structure that does not include the radar absorbing structure B. The radar absorbing layer in the structure is a homogeneous material and only includes the radar absorbing structure C, as a comparative example.

[0035] Structure 3 (such as Figure 4 (shown) is a traditional visible light / infrared / radar multi-band compatible stealth coating system. The radar absorbing layer in this structure is a homogeneous material, but its thickness is t2+t1, as a comparative example.

[0036] Example 1

[0037] In this embodiment, the gradient structure of the visible light / infrared / radar multi-band compatible stealth material is realized on the basis of t1=0.2mm, t2=0.05mm, t3=50μm, wherein the infrared emissivity of the infrared stealth structure in the 8-14μm band is controlled at 0.20. Structures 1, 2, and 3 with corresponding thickness parameters are used as the control group of this embodiment. Figure 5 : The impedance change curves of Structure 1, Structure 2, Structure 3 and the present embodiment; wherein, the frequency point corresponding to the imaginary part being zero is the resonance point, the real impedance values ​​of Structure 1, Structure 2, Structure 3 and the present embodiment are 90.1Ohm, 136.1Ohm, 161Ohm and 185Ohm respectively, and the impedance difference between Structure 2 and Structure 1 is 46Ohm.

[0038] Figure 6 The reflectivity test results of 2 to 18 GHz obtained from the experiment are shown in Table 1. The average radar compatibility data of each frequency band in Case 1 are shown in Table 1. Figure 6 As can be seen from Table 1, the radar compatibility performance of the multi-band compatible stealth material designed by the present invention is improved in the entire band, and the Ku band reaches -0.46dB.

[0039] Table 1: Average values ​​of radar compatibility data for Case 1

[0040] Frequency band 2~4GHz 4~8GHz 8~12GHz 12~18GHz Case 1 -0.24dB -0.57dB -0.91dB -0.46dB

[0041] Example 2

[0042] In this embodiment, the gradient structure of the visible light / infrared / radar multi-band compatible stealth material is realized on the basis of t1=0.3mm, t2=0.1mm, t3=50μm, wherein the infrared emissivity of the infrared stealth structure in the 8-14μm band is controlled at 0.15. Structures 1, 2, and 3 with corresponding thickness parameters are used as the control group of this embodiment. Figure 7 : are impedance change curves of structure 1, structure 2, structure 3 and the present embodiment; wherein, the real part values ​​of the impedance of structure 1, structure 2, structure 3 and the present embodiment are 122.1Ohm, 161.6Ohm, 210.4Ohm and 242.8Ohm respectively, and the impedance difference between structure 2 and structure 1 is 39.5Ohm.

[0043] Figure 8 The reflectivity test results of 2 to 18 GHz obtained from the experiment are shown in Table 2. The average values ​​of radar compatibility data of each frequency band in Case 2 are shown in Table 2. Figure 8 As can be seen from Table 2, the radar compatibility performance of the multi-band compatible stealth gradient structure designed by the present invention is improved in the entire band, reaching -0.84dB in the Ku band.

[0044] Table 2: Average values ​​of radar compatibility data for Case 2

[0045] parameter 2~4GHz 4~8GHz 8~12GHz 12~18GHz Case 2 -0.35dB -0.67dB -0.86dB -0.84dB

[0046] Example 3

[0047] In this embodiment, the gradient structure of the visible light / infrared / radar multi-band compatible stealth material is realized on the basis of t1=0.4mm, t2=0.05mm, t3=50μm, wherein the infrared emissivity of the infrared stealth structure in the 8-14μm band is controlled at 0.15. Structures 1, 2, and 3 with corresponding thickness parameters are used as the control group of this embodiment. Fig. 9 : The impedance change curves of Structure 1, Structure 2, Structure 3 and the present embodiment; wherein, the real impedance values ​​of Structure 1, Structure 2, Structure 3 and the present embodiment are 121.5Ohm, 166.5Ohm, 198.4Ohm and 228.7Ohm respectively, and the impedance difference between Structure 2 and Structure 1 is 39.5Ohm.

[0048] Fig.10 Table 3 is the experimental reflectivity test result of 2-18 GHz, and Table 4 is the average value of radar compatibility data of each frequency band in Case 3. Fig.10 As can be seen from Table 3, the radar compatibility performance of the multi-layer gradient structure designed in the present invention is improved in the entire band, especially in the 12-18 GHz band, reaching -0.93 dB.

[0049] Table 3: Average values ​​of radar compatibility data for Case 3

[0050] parameter 2~4GHz 4~8GHz 8~12GHz 12~18GHz Case 3 -0.22dB -0.31dB -0.85dB -0.93dB

[0051] Example 4

[0052] In this embodiment, the gradient structure of the visible light / infrared / radar multi-band compatible stealth material is realized on the basis of t1=0.4mm, t2=0.2mm, t3=50μm, wherein the infrared emissivity of the infrared stealth structure in the 8-14μm band is controlled at 0.10. Structures 1, 2, and 3 with corresponding thickness parameters are used as the control group of this embodiment. Fig.11 : The impedance change curves of Structure 1, Structure 2, Structure 3 and the present embodiment; wherein, the real part values ​​of the impedances of Structure 1, Structure 2, Structure 3 and the present embodiment are 130.9Ohm, 158.9Ohm, 186.6Ohm and 202.5Ohm respectively, and the impedance difference between Structure 2 and Structure 1 is 28.0Ohm.

[0053] Fig.12 Table 4 is the average value of radar compatibility data in each frequency band of Case 4. Fig.12 As can be seen from Table 4, the radar compatibility performance of the multi-band compatible stealth structure designed by the present invention is improved in the entire band, especially when the emissivity is as low as 0.10, the Ku band still reaches -0.55dB.

[0054] Table 4: Average values ​​of radar compatibility data for Case 3

[0055] parameter 2~4GHz 4~8GHz 8~12GHz 12~18GHz Case 4 -0.43dB -0.63dB -0.73dB -0.55dB

[0056] It can be seen from the experimental data of the above embodiments and the control group that the multi-band compatible stealth material of the multi-layer gradient system provided by the present invention increases multiple reflections and refractions of electromagnetic waves and improves the radar compatibility of the overall multi-band stealth structure by designing the intermediate radar absorbing structure layer and the bottom radar absorbing structure layer whose impedance characteristics at the resonance point are gradually changed (increased) by gradient, and breaks through the technical bottleneck of the deterioration of the Ku-band radar compatibility of the traditional multi-spectrum absorbing coating, especially when the infrared emissivity is less than 0.2; the intrinsic impedance of the intermediate radar absorbing structure layer and the bottom radar absorbing structure layer is adjustable, so that the material adaptability and adjustability are strong; and the design method and process involved in the present invention are simple and suitable for large-scale production.

Claims

1. A gradient structured visible light / infrared / radar multi-band compatible stealth material, characterized by: It includes a surface infrared stealth structure layer, a middle radar absorbing structure layer and a bottom radar absorbing structure layer which are sequentially stacked from the outside to the inside; The surface infrared stealth structure layer realizes visible light and infrared stealth; The middle radar absorbing structure layer and the bottom radar absorbing structure layer realize radar stealth, and the impedance characteristics of the two at the resonance point increase gradually.

2. The visible light / infrared / radar multi-band compatible stealth material with gradient structure as claimed in claim 1, characterized in that: The thickness of the surface infrared stealth structure layer is t3 = 50 μm, the thickness of the middle radar absorbing structure layer is t2 = 0.05 mm to 0.2 mm, and the thickness of the bottom radar absorbing structure layer is t1 = 0.2 mm to 0.4 mm.

3. The visible light / infrared / radar multi-band compatible stealth material with gradient structure as claimed in claim 1, characterized in that: The infrared emissivity of the surface infrared stealth structure layer is ≤0.

2.

4. The visible light / infrared / radar multi-band compatible stealth material with gradient structure as claimed in claim 1, characterized in that: The impedance difference between the middle radar absorbing structure layer and the bottom radar absorbing structure layer is 28Ohm to 46Ohm.

5. The visible light / infrared / radar multi-band compatible stealth material with gradient structure as claimed in claim 1, characterized in that: The middle radar absorbing structural layer and the bottom radar absorbing structural layer are additionally provided with at least one radar absorbing structural layer, and the impedance characteristics of all the radar absorbing structural layers at the resonance point still increase gradually.

6. The visible light / infrared / radar multi-band compatible stealth material with gradient structure as claimed in claim 5, characterized in that: The additional radar absorbing structure layer is located between the middle radar absorbing structure layer and the bottom radar absorbing structure layer.

7. The visible light / infrared / radar multi-band compatible stealth material with gradient structure as claimed in claim 5, characterized in that: The additional radar absorbing structural layer is located on both sides of the middle radar absorbing structural layer and the bottom radar absorbing structural layer.

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