A composite structure with both stealth and anti-icing functions and preparation method thereof

Abstract

The present invention belongs to the technical field of composite materials, and discloses a composite structure with both stealth and anti-icing functions, including a wave-transmitting electric heating layer and a wave-absorbing stealth layer arranged under the wave-transmitting electric heating layer; the wave-absorbing stealth layer is a metamaterial absorber, and the metamaterial absorber includes a metal resonance layer, a dielectric layer and a metal grounding layer from top to bottom. And discloses its preparation method. The present invention adopts a resin with low dielectric constant and low dielectric loss as the matrix material for the electric heating layer, and a small amount of carbon nanotubes are dispersed in the resin as a reinforcing material, thereby overcoming the technical problem that when the traditional electric heating layer and the wave-absorbing stealth layer are superimposed, the radar microwave cannot penetrate the electric heating layer, and then enters the wave-absorbing stealth layer and is absorbed. At the same time, the present invention combines anti-deicing and stealth, and can quickly remove surface ice. Compared with traditional resonant wave-absorbing metamaterials, the metamaterial absorber proposed in the present invention has the characteristics of obtaining excellent wave-absorbing performance with a small thickness structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material technology, and in particular relates to a composite structure with both stealth and anti-icing functions and a preparation method thereof. Background Art

[0002] Ice formation on solid surfaces is a common phenomenon in nature, but ice accumulation can cause serious consequences in industrial fields such as transportation and in daily life. Surface ice formation is a dangerous phenomenon when an aircraft is flying in a high-altitude flight environment. Ice on the fuselage surface of a high-altitude aircraft can seriously damage the aerodynamics and flatness of the aircraft, thereby causing the aircraft's lift-to-drag ratio and lift coefficient to decrease, leading to serious flight accidents. At present, the commonly used anti-icing / de-icing method is electric heating anti-icing. By energizing the heating elements in the composite structure to generate heat, the surface temperature of the high-altitude aircraft is increased, and the ice layer eventually falls off the surface. This method has high thermal conductivity, low energy consumption, and can better protect the aircraft surface from damage. In order to further develop aircraft surface anti-icing technology, electric heating anti-icing technology has become a hot topic in surface anti-icing research.

[0003] In the field of high-altitude flight, the high degree of electronicization and informationization of weapons and equipment has made the electromagnetic environment of the battlefield increasingly complex. Under the close surveillance of radar, strategically important military equipment such as aircraft and missiles can be easily detected, which greatly affects their survivability and combat effectiveness. Therefore, in a complex electromagnetic environment, how to avoid the precise tracking of enemy radars and how to achieve the "stealth" of military weapons have also become difficulties faced by the design of military equipment. In order to avoid being in a passive position on the battlefield in the future, the academic community has turned its attention to the research of metamaterial absorbers.

[0004] Electric heating deicing is when the heating layer generates heat and transfers heat to the surface of the aircraft when the power is turned on, causing the temperature of the aircraft surface to rise to the point where the ice layer is destroyed and falls off. The Chinese patent application with application number 201721685432.6 discloses "an electric heating film", which includes: a wear-resistant layer, a heat-conducting insulating layer, a copper sheet heating layer, a heat-conducting layer, nano-silver particles and metal strips, wherein a flexible material of alumina epoxy resin is used as a heat-conducting layer. The electric heating film can cover the surface of the heated object with the heating film, increasing the heat transfer area and heat transfer speed. However, the metal material of the heating layer of the invention does not have wave-transmitting properties and cannot be combined with the wave-absorbing metamaterial to form an integrated composite structure with stealth / anti-icing functions; the invention uses metal materials as fillers, and the heating temperature of the heating layer is not uniform enough, resulting in low deicing efficiency of the overall material; and the structure is too complex and thick, which is limited for real-world engineering applications.

[0005] Regarding the research on the wave-transmitting performance of the heating layer, the Chinese patent application with application number 202121409086.5 discloses "a wave-transmitting heating film", which is composed of a microchannel membrane and a microchannel arranged in the microchannel membrane. A pair of interfaces that are conductive and can pass conductive liquid metal liquid are installed in the microchannel, which enables the heating film to switch between the power-on heating and wave-transmitting states, although it has the effect of making the heating film have the functions of heating and wave-transmitting at the same time. However, this invention has the disadvantages of extremely high cost and cumbersome operation and processing, and is limited in the field of engineering application. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a composite structure having both stealth and anti-icing functions and a preparation method thereof.

[0007] To achieve the above objectives, the present invention relates to a composite structure with both stealth and anti-icing functions, which adopts the following technical solutions:

[0008] A composite structure with both stealth and anti-icing functions, comprising a wave-transmitting electric heating layer and a wave-absorbing stealth layer arranged under the wave-transmitting electric heating layer;

[0009] The wave-absorbing stealth layer is a metamaterial wave absorber, which includes a metal resonance layer, a dielectric layer and a metal grounding layer from top to bottom. The metal resonance layer includes a metal array structure composed of multiple identical metal units arranged in a periodic manner.

[0010] Preferably, the method for preparing the wave-transmitting electric heating layer comprises the following steps:

[0011] Step 1, mixing a polar solution, a resin, a carbon nanotube and a thermoplastic polyurethane in a mass ratio of 7:1:0.25 to 0.4:0.2 to obtain a liquid mixture;

[0012] Step 2, magnetically stirring the liquid mixture and subjecting it to ultrasonic treatment;

[0013] Step 3, after the solute is evenly dispersed, a scraper is used to scrape the film, and then the wet film is dried to obtain an electric heating film, that is, the material of the wave-transmitting electric heating layer.

[0014] Preferably, in step 1, the resin is any one of bismaleimide resin, polyimide resin, polytetrafluoroethylene resin and silicone resin, or a mixture of several of them; and the polar solution is N,N-dimethylformamide.

[0015] Preferably, in step 2, the magnetic stirring temperature is 60°C and the time is 1.5 hours; the ultrasonic treatment time is 0.5 hours; in step 3, the wet film is placed in an oven for drying, the oven setting temperature is 80°C, and the drying treatment time is 2 hours.

[0016] Preferably, the metal unit structure includes a metal open ring, a metal closed ring and a "cross" shaped metal film, the "cross" shaped metal film is located at the center of the resonant structure unit, the metal closed ring and the annular metal opening are arranged from the inside to the outside with the geometric center of the "cross" shaped metal film as the center, the metal open ring includes two pairs of symmetrical openings that divide the metal open ring into four parts, and resistor patches are provided at the openings.

[0017] Preferably, the material of the metal resonance layer and the metal grounding layer is copper with a thickness of 0.02-0.03 mm and a conductivity of 5.8×10 7 S / m.

[0018] Preferably, the diameter of the metal open ring is 8.0-9.0 mm, the diameter of the metal closed ring is 6.0-7.0 mm, the single side length of the "cross" shaped metal film is 4.0-4.5 mm, the single side width is 0.5-0.7 mm, and the distance between adjacent metal array structures is 10.0-12.0 mm.

[0019] Preferably, the resistance of the resistor patch is 80Ω.

[0020] Preferably, the dielectric layer material is FR-4, with a dielectric constant of 3.8 to 4.2 and a thickness of 1.0 to 2.2 mm.

[0021] Preferably, the method for preparing the composite structure having both stealth and anti-icing functions comprises the following steps:

[0022] Press the copper plate, fiberglass plate, and copper plate together in order. After pressing, polish the copper plate with fine sandpaper and then clean it.

[0023] The copper foil surface of the copper plate placed on the glass fiber board is processed by chemical etching process to obtain metal open rings, metal closed rings and "cross" shaped metal films with designed specifications, and four resistor patches are welded to the opening positions of the annular metal foil to obtain the wave absorbing stealth layer.

[0024] Adhesive is used to connect the wave-transmitting electric heating layer and the wave-absorbing stealth layer, ultimately obtaining a composite structure with both stealth and anti-icing functions.

[0025] The method involved in the present invention realizes the integrated forming of electric thermal deicing and stealth, and has the characteristics of simple operation and good structural formability.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention adopts a resin with low dielectric constant and low dielectric loss as the matrix material for the electric heating layer, and disperses a small amount of carbon nanotubes in the resin as the reinforcing material, thereby overcoming the technical problem that when the traditional electric heating layer is superimposed with the wave-absorbing stealth layer, radar microwaves cannot penetrate the electric heating layer and then enter the wave-absorbing stealth layer and are absorbed.

[0028] (2) The absorbing stealth layer described in the present invention has a high absorbing ability, and the electromagnetic resonant coupling can efficiently absorb the energy of the incident electromagnetic wave. When the radar microwave is incident, an induced current will be generated on the annular metal resonant pattern of the metamaterial absorber. The current passes through the resistor patch connecting the pattern, and the current is dissipated in the resistor patch, thereby completing the absorption of electromagnetic microwaves. Compared with the traditional resonant absorbing metamaterial, which can usually only achieve strong absorption in a narrow frequency band, the absorbing metamaterial structure proposed in the present invention has obvious advantages in broadband absorption; compared with the multi-layer absorbing metamaterial with broadband absorbing performance, the metamaterial absorber structure proposed in the present invention has the advantages of small structural thickness and simple processing.

[0029] (3) Compared with the single-function anti-icing and stealth absorbing technologies, the present invention overcomes the problem that when the traditional electric heating layer and the absorbing stealth layer are superimposed, the radar microwave cannot pass through the electric heating layer, and then enters the absorbing stealth layer and is absorbed, thereby creating a wave-transmissive electric heating layer and combining the anti-icing and stealth absorbing properties. The electric heating layer heats the surface of the aircraft by electric heating to remove the adhered ice layer, solving the problem of low efficiency and high energy consumption caused by traditional passive electric heating deicing. It has the characteristics of simple steps and easy preparation and processing. The absorbing stealth layer can reduce the target echo intensity by virtue of its excellent absorbing performance, and is an important technical approach to radar wave stealth for weapons, equipment and special devices. The combination of electric heating and absorbing functions can provide technical guarantees for improving the combat survivability and flight safety of future aviation aircraft in icy environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 This is a schematic diagram of a finished product of a composite structure having both stealth and anti-icing functions according to the present invention;

[0032] Figure 2 This is a schematic diagram of the metal array structure in the metal resonance layer of the wave-absorbing stealth layer of the present invention;

[0033] Markings in the figure: 1 is the wave-transmitting electric heating layer, 2 is the metal resonance layer, 3 is the dielectric layer, and 4 is the metal grounding layer;

[0034] 21-metal open ring, 22-metal closed ring, 23-"cross" shaped metal film, 24-resistance patch. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0036] Example 1

[0037] like Figure 1 A composite structure with both stealth and anti-icing functions is shown, comprising a wave-transmitting electric heating layer 1 and a wave-absorbing stealth layer arranged under the wave-transmitting electric heating layer 1;

[0038] The wave-absorbing stealth layer is a metamaterial absorber with a periodic array structure, and the metamaterial absorber includes a metal resonance layer (loss layer) 2, a dielectric layer 3 and a metal grounding layer 4 in order from top to bottom.

[0039] The method for preparing the wave-transmitting electric heating layer comprises the following steps:

[0040] Step 1, mixing a polar solution, a resin, carbon nanotubes and thermoplastic polyurethane in a mass ratio of 7:1:0.25 to 0.4:0.2 to obtain a liquid mixture; the resin is a silicone resin; the polar solution is N,N-dimethylformamide; the silicone resin is used to prepare a wave-transmitting electric heating layer, thereby increasing the overall high and low temperature resistance and thermal shock resistance of the composite material, making it more suitable for service environments under high temperature and humidity.

[0041] Step 2, placing the beaker containing the liquid mixture in a magnetic stirrer, stirring, and performing ultrasonic treatment; the magnetic stirring temperature is 60° C., the time is 1.5 h; the ultrasonic treatment time is 0.5 h;

[0042] Step 3, after the solute is evenly dispersed, a scraper is used to scrape the film, and then the wet film is placed in an oven at 80° C. for drying for 2 hours to obtain an electric heating film, that is, the material of the wave-transmitting electric heating layer.

[0043] The wave-transmitting electric heating layer can heat the ice layer on the surface of the aircraft through its electrothermal characteristics, so that it cannot remain on the surface of the aircraft for a long time and falls off. Experiments show that under a voltage of 28V, the surface of the electric heating layer rises to the saturation temperature within 20s, and the maximum temperature reaches 121°C. When the ambient temperature is -20°C, the loading power density is 0.5W / cm 21 cm thick (14 g) of ice can be removed from the surface of a static helicopter rotor blade; at the same time, the wave-transmitting heating layer involved has a high wave-transmitting performance, so that microwaves can pass through the wave-transmitting heating layer and enter the wave-absorbing stealth layer for wave absorption. The bow method is used to test the dielectric constant and dielectric loss of the composite material in the range of 2-18 GHz. The results show that the dielectric constant of the composite material can be as low as 2.3, and the dielectric loss can be as low as 0.008-0.009, which has excellent wave-transmitting performance.

[0044] like Figure 2 As shown, the metal resonance layer includes a periodically arranged metal unit structure, and the metal unit structure includes a metal open ring 21, a metal closed ring 22 and a "cross" shaped metal film 23. The "cross" shaped metal film is located at the center of the resonance structure unit, and the metal closed ring and the annular metal opening are arranged from the inside to the outside with the geometric center of the "cross" shaped metal film as the center. The metal open ring includes two pairs of symmetrical openings that divide the metal open ring into four parts, and the openings are each provided with a resistor patch 24.

[0045] The metal resonant layer (loss layer) and the metal grounding layer are made of copper with a thickness of 0.02 to 0.03 mm and a conductivity of 5.8×10 7 S / m; the diameter of the annular metal open ring is 8.0-9.0mm, the diameter of the annular metal closed ring is 6.0-7.0mm, the length of the single side of the "cross" metal film is 4.0-4.5mm, and the width of the single side is 0.5-0.7mm. The unit structure period size is 10.0-12.0mm; the resistance of the resistor patch is 80Ω. The metal resonance layer pattern is processed by chemical etching process.

[0046] The dielectric layer is made of FR-4, has a dielectric constant of 3.8 to 4.2, and a thickness of 1.0 to 2.2 mm.

[0047] Example 2

[0048] A composite structure with both stealth and anti-icing functions, comprising, from top to bottom, a wave-transmitting electric heating layer 1, a metal resonance layer 2, a dielectric layer 3 and a metal grounding layer 4;

[0049] in,

[0050] The metal resonance layer 2 is a metal array structure composed of a plurality of identical metal units in different shapes such as rings and crosses arranged in a periodic manner. In this embodiment, the metal units are arranged in sequence and in rows at the same intervals.

[0051] The dielectric layer 3 is FR-4.

[0052] The method for preparing the wave-transmitting electric heating layer comprises the following steps:

[0053] Step 1: Mix the polar solution, bismaleimide resin, carbon nanotubes and thermoplastic polyurethane in a mass ratio of 7:1:0.25:0.2 to obtain a liquid mixture. The bismaleimide resin is used as a matrix to prepare a wave-transmitting electric heating layer to improve the mechanical properties and heat resistance of the composite material;

[0054] Step 2: Place the beaker containing the blended liquid in a magnetic stirrer at 60° C., stir for 1.5 hours, and perform ultrasonic treatment for 0.5 hour.

[0055] Step 3: After the solute is evenly dispersed, a scraper is used to scrape the film, and then the wet film is placed in an oven at 80° C. for 2 hours for drying to obtain an electric heating film.

[0056] The preparation process of the composite structure having both stealth and anti-icing functions is as follows:

[0057] Place the glass fiber board (FR-4) in an organic impregnation solution with a vacuum pressure of 0.05 MPa, take it out and dry it in a preheated infrared dryer for 30 to 60 minutes. Use a kraft paper cutter and a copper foil cutter to cut out a glass fiber board with a size of 200 mm × 200 mm and two copper plates with a size of 200 mm × 200 mm respectively;

[0058] Use a hot press to press the copper plate and the fiberglass plate together in the order of copper plate, fiberglass plate, and copper plate. The hot press time is 40 minutes at a temperature of 250°C. After pressing, polish the copper plate with fine sandpaper and then clean it.

[0059] Use carbon paper to copy the designed open ring, ring and "cross" copper foil patterns onto the copper foil surface of the copper plate placed on the fiberglass board. Then use transparent tape to cover the copper foil surface, and use a knife to remove the tape outside the metal pattern;

[0060] Use 30% to 40% ferric chloride aqueous solution as the etching solution to corrode the exposed copper foil. After the etching is completed, rinse with clean water, peel off the tape, and wipe off the protective paint on the surface with a cotton ball dipped in a dilute acetone solution.

[0061] Four resistor patches are respectively welded to the opening positions of the annular metal foil to obtain a wave-absorbing stealth layer.

[0062] Adhesive is used to connect the wave-transmitting electric heating layer and the wave-absorbing stealth layer, ultimately obtaining a composite structure with both stealth and anti-icing functions.

[0063] The method involved in the present invention realizes the integrated forming of electric thermal deicing and stealth, and has the characteristics of simple operation and good structural formability.

[0064] Compared with the single-function anti-icing and stealth absorbing technology, the present invention overcomes the problem that when the traditional electric heating layer and the absorbing stealth layer are superimposed, the radar microwave cannot penetrate the electric heating layer, and then enters the absorbing stealth layer and is absorbed, creating a wave-permeable electric heating layer, and combining the anti-icing and stealth absorbing performance. The electric heating layer heats the surface of the aircraft by electric heating to make the adhered ice layer fall off, solving the problem of low efficiency and high energy consumption brought by traditional passive electric heating deicing. The absorbing stealth layer can reduce the target echo intensity with its excellent absorbing performance, and is an important technical approach for radar wave stealth of weapons, equipment and special devices. The test results show that the absorption rate of the composite structure in the frequency band of 4.23 to 18.31 GHz reaches more than 90%, and the relative thickness is 0.075λ, which verifies that the composite structure has excellent ultra-wideband absorbing performance. The combination of electric heating and absorbing functions can provide technical guarantee for improving the combat survivability and flight safety of future aviation aircraft in frost environment.

[0065] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A composite structure with both stealth and anti-icing functions, characterized in that: It includes a wave-transmitting electric heating layer and a wave-absorbing stealth layer arranged under the wave-transmitting electric heating layer; The wave absorbing stealth layer is a metamaterial wave absorber, which includes a metal resonance layer, a dielectric layer and a metal grounding layer from top to bottom, and the metal resonance layer includes a metal array structure composed of a plurality of identical metal units arranged in a periodic manner; The metal unit includes a metal open ring, a metal closed ring and a "cross"-shaped metal film. The "cross"-shaped metal film is located at the center of the resonant structure unit. The metal closed ring and the annular metal opening are arranged from the inside to the outside with the geometric center of the "cross"-shaped metal film as the center. The metal open ring includes two pairs of symmetrical openings that divide the metal open ring into four parts on average. Resistor patches are arranged at the openings.

2. The composite structure with both stealth and anti-icing functions according to claim 1, characterized in that: The method for preparing the wave-transmitting electric heating layer comprises the following steps: Step 1, mixing a polar solution, a resin, a carbon nanotube and a thermoplastic polyurethane in a mass ratio of 7:1:0.25 to 0.4:0.2 to obtain a liquid mixture; Step 2, magnetically stirring the liquid mixture and subjecting it to ultrasonic treatment; Step 3, after the solute is evenly dispersed, a scraper is used to scrape the film, and then the wet film is dried to obtain an electric heating film, that is, the material of the wave-transmitting electric heating layer.

3. The composite structure with both stealth and anti-icing functions according to claim 2, characterized in that: In step 1, the resin is any one of bismaleimide resin, polyimide resin, polytetrafluoroethylene resin and silicone resin, or a mixture of several of them; and the polar solution is N,N-dimethylformamide.

4. The composite structure with both stealth and anti-icing functions according to claim 2, characterized in that: In step 2, the magnetic stirring temperature is 60° C. and the time is 1.5 h; the ultrasonic treatment time is 0.5 h; in step 3, the wet film is placed in an oven for drying, the oven setting temperature is 80° C., and the drying treatment time is 2 h.

5. The composite structure with both stealth and anti-icing functions according to claim 1, characterized in that: The metal resonance layer and the metal grounding layer are made of copper with a thickness of 0.02-0.03 mm and a conductivity of 5.8×10 7 S / m.

6. The composite structure with both stealth and anti-icing functions according to claim 1, characterized in that: The diameter of the metal open ring is 8.0-9.0 mm, the diameter of the metal closed ring is 6.0-7.0 mm, the single side length of the "cross" shaped metal film is 4.0-4.5 mm, the single side width is 0.5-0.7 mm, and the distance between adjacent metal array structures is 10.0-12.0 mm.

7. The composite structure with both stealth and anti-icing functions according to claim 1, characterized in that: The resistance of the resistor patch is 80Ω.

8. The composite structure with both stealth and anti-icing functions according to claim 1, characterized in that: The dielectric layer is made of FR-4, has a dielectric constant of 3.8 to 4.2, and a thickness of 1.0 to 2.2 mm.

9. The composite structure with both stealth and anti-icing functions according to any one of claims 1 to 8, characterized in that: The method for preparing the composite structure having both stealth and anti-icing functions is as follows: Press the copper plate, fiberglass plate, and copper plate together in order. After pressing, polish the copper plate with fine sandpaper and then clean it. The copper foil surface of the copper plate placed on the glass fiber board is processed by chemical etching process to obtain metal open rings, metal closed rings and "cross" shaped metal films with designed specifications, and four resistor patches are welded to the opening positions of the annular metal foil to obtain the wave absorbing stealth layer. Adhesive is used to connect the wave-transmitting electric heating layer and the wave-absorbing stealth layer, ultimately obtaining a composite structure with both stealth and anti-icing functions.

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