A multilayer composite structure for the leading edge structure of an aircraft wing and its preparation method

Abstract

This invention belongs to the field of functional materials and structural technology, specifically relating to a multilayer composite structure for the leading edge structure of an aircraft wing and its preparation method. The multilayer composite structure, from top to bottom, includes a first metal layer, an electrically heated layer, and at least one set of composite material layers. The electrically heated layer comprises a conductive layer, a fiber prepreg layer, and electrodes. The fiber prepreg layer is located on the lower surface of the first metal layer, and the conductive layer and the electrodes are located on the lower surface of the fiber prepreg layer. The electrodes are located on both sides of the edge of the conductive layer and are connected to a power source and switch via wires to form a closed circuit. The composite material layers are composed of alternating layers of resin and second metal layers. The resin layer of the composite material layer in contact with the electrically heated layer is located on the lower surface of the electrically heated layer. Through the above steps, a highly precise and functional multilayer composite structure can be achieved, suitable for the special requirements of aircraft wing leading edge structures, and improving overall performance.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and structural technology, specifically relating to a multilayer composite structure for the leading edge structure of an aircraft wing and its preparation method. Background Technology

[0002] Modern aircraft are required to have all-weather flight capabilities, a wide flight altitude range, and complex and variable external weather conditions. During flight, aircraft inevitably encounter situations such as low-temperature icing, lightning strikes, and bird strikes. The leading edge of the wing, a crucial structure for regulating aircraft lift, is located at the very front of the wing surface and is the primary area affected by icing, bird strikes, and lightning strikes. Therefore, it must meet functional requirements for anti-icing / de-icing, lightning protection, and bird strike resistance. However, current technologies for multi-functional integration in the wing leading edge are significantly inadequate. Existing technologies, to meet the requirements for anti-icing / de-icing, lightning protection, and bird strike resistance, all employ a combination of single functions.

[0003] For example, de-icing can be achieved by wrapping a metal surface with an airbag or laying hot air pipes inside; copper mesh can be laid on the surface of composite materials to prevent ablation in the event of a lightning strike, and airbags or hot air pipes, bird strike protection barriers, and honeycomb energy-absorbing layers can be added. It can be seen that in order to achieve the above multiple functions, traditional structures inevitably suffer from drawbacks such as increased structural complexity and significantly increased weight.

[0004] If multiple functions can be highly integrated into a single structure, it will enable structural lightweighting and simplified manufacturing processes, reduce the space occupied by functional components, and improve energy efficiency. However, the challenges of multifunctional integration lie in the material selection and interface matching of each functional component, cross-scale integrated design, and conformal manufacturing.

[0005] Therefore, the research on multifunctional lightweight structures integrating anti-icing, anti-lightning, and anti-bird-strike functions is of great practical significance and presents considerable challenges.

[0006] Currently, conventional technologies cannot integrate anti-icing / de-icing, lightning protection, and bird strike resistance into typical aircraft structures, and therefore cannot meet the requirements for long-endurance safe operation and weight reduction of next-generation aircraft.

[0007] Chinese invention patent application CN202311189321.6 discloses a fiber-metal laminate structure with electric heating function for use in aircraft anti-bird strike and de-icing parts. This technology uses a carbon nanotube conductive film with a sheet resistance of 1-10Ω / sq as the electric heating layer of the laminate structure. The electric heating layer is connected to rigid electrodes at both ends. However, there is a risk of failure due to poor contact when the aircraft is subjected to long-term vibration and turbulence or is struck by birds.

[0008] Furthermore, current conventional technologies cannot achieve multi-functional integration of anti-icing, lightning protection, and bird strike resistance in typical aircraft structures. For example, Chinese invention patent application CN109436338B discloses an anti-icing device and an anti-icing control method based on the device. This technology combines electrothermal materials, piezoelectric materials, and a flexible substrate, and integrates them with an ice thickness detection unit and a control unit, which can achieve anti-icing relatively well. However, it cannot integrate multiple functions into a lightweight structure, reducing energy efficiency and failing to meet the requirements of long-endurance safe operation and weight reduction for next-generation aircraft. Summary of the Invention

[0009] (a) Technical problems to be solved

[0010] This invention addresses the above-mentioned problems by proposing a multi-layer composite structure for the leading edge of an aircraft wing and its preparation method. The purpose is to solve the problem that existing technologies cannot simultaneously achieve the requirements of multi-functionality and lightweighting, such as anti-icing / de-icing, lightning strike protection, and bird strike resistance.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, a first aspect of the present invention provides a multi-layer composite structure for the leading edge structure of an aircraft wing, wherein the multi-layer composite structure comprises, from top to bottom, a first metal layer, an electrically heated layer, and at least one set of composite material layers, wherein:

[0013] The electric heating layer includes a conductive layer, a fiber prepreg layer, and electrodes. The fiber prepreg layer is located on the lower surface of the first metal layer. The conductive layer and the electrodes are located on the lower surface of the fiber prepreg layer. The electrodes are located on both sides of the edge of the conductive layer and are connected to the power supply and switch through wires to form a closed circuit.

[0014] The composite material layer is composed of alternating layers of resin and a second metal layer, with the resin layer of the composite material layer in contact with the electric heating layer located on the lower surface of the electric heating layer.

[0015] Furthermore, the first metal layer and the second metal layer are selected from one or more of aluminum alloy, titanium alloy, titanium-aluminum alloy, and magnesium alloy.

[0016] Furthermore, the conductive layer is composed of one or more of metal nanowires, carbon materials, and oxides, and the sheet resistance of the conductive layer is 10-3000 Ω / sq, and the areal density is 100-900 g / m². 2 .

[0017] Furthermore, the metal nanowires are composed of silver nanowires, the carbon material is composed of one or more of carbon nanotubes, graphene, carbon black, and fullerene, and the oxide is composed of one or more of antimony-doped tin oxide, aluminum-doped zinc oxide, and indium tin oxide.

[0018] Furthermore, the fiber prepreg layer comprises one or more of glass fiber, carbon fiber, silicon carbide fiber, aramid fiber, nylon fiber, and quartz fiber, and their fabrics.

[0019] Furthermore, the electrode thickness is 0.01-0.2 mm, the electrode sheet resistance is 20-300 mΩ / sq, and the electrothermal conversion efficiency of the electric heating layer is 60-90%.

[0020] Furthermore, the thickness of the electric heating layer is 0.02-0.1 mm, and the thickness of the multilayer composite structure is 1-10 mm.

[0021] Furthermore, the resin layer is epoxy resin or bismaleimide resin.

[0022] To achieve the above objectives, a second aspect of the present invention provides a method for preparing a multilayer composite structure for the leading edge structure of an aircraft wing, the method comprising the following steps:

[0023] A conductive layer is prepared by depositing one or more of metal nanowires, carbon materials, or oxides on the surface of fiber prepreg.

[0024] Electrodes are added to the conductive layer using screen printing or inkjet printing methods.

[0025] The conductive layer with electrodes is assembled with the fiber prepreg layer to form an electric heating layer;

[0026] The first metal layer, the electric heating layer, and at least one set of composite material layers are bonded together through a co-curing process to form the multilayer composite structure, wherein the composite material layer is composed of alternating layers of resin and second metal layers.

[0027] The multi-layered composite structure is manufactured into the leading edge structure of an aircraft wing using conformal manufacturing technology.

[0028] Furthermore, the specific steps for adding electrodes to the conductive layer using screen printing or inkjet printing include:

[0029] Microfluidic technology was used to generate electrode patterns with multiple branched structures.

[0030] A photosensitive material is coated on the surface of the conductive layer, and the desired electrode pattern is formed on the conductive layer using photolithography.

[0031] By selectively activating the photolithographically lithographically oriented area, inkjet printing technology is used to spray electrode material onto the selectively activated photolithographically oriented area, so that the electrode material is deposited only within the predetermined pattern area;

[0032] The sprayed electrode material is cured using ultraviolet light or thermal curing technology.

[0033] (III) Beneficial Effects

[0034] Compared with existing technologies, the present invention provides a multi-layer composite structure and its preparation method for the leading edge structure of an aircraft wing. By utilizing a conductive layer to achieve anti-icing / de-icing function, utilizing the high conductivity of the outermost first metal layer to achieve lightning strike protection function, and utilizing the energy absorption effect of multiple sets of composite material layers to improve bird strike resistance, it can achieve multi-functional integration of anti-icing / de-icing, lightning strike protection, and bird strike resistance. Furthermore, by adopting a multi-layer composite structure, the weight reduction effect is significant compared with traditional structures, and the high-adhesion flexible electrode significantly improves the working durability and stability of the overall structure, which can meet the multi-functional and lightweight requirements of typical aircraft structures. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a multi-layer composite structure for the leading edge structure of an aircraft wing disclosed in this application.

[0036] Figure 2 This is a schematic diagram of a multi-layer composite structure disclosed in this application applied to a typical leading edge structure of an aircraft.

[0037] Figure 3 This is an infrared thermal image of a multilayer composite structure sample with carbon nanotube-quartz fiber as the electric heating layer under energized conditions.

[0038] Figure 4 The figures show the temperature rise-fall curves of multiple regions on the surface of a multilayer composite structure sample with carbon nanotube-quartz fiber as the electric heating layer under a voltage of 110V.

[0039] Figure 5 The figures show the temperature rise-fall curves of multiple regions on the surface of a multilayer composite structure sample with carbon nanotube-quartz fiber as the electric heating layer under a voltage of 155V.

[0040] The reference numerals in the figure are as follows: 1. Typical leading edge structure of an aircraft; 2. Multi-layer composite structure; 110. Electrically heated layer; 111. Conductive layer; 112. Electrode; 113. Power supply; 114. Switch; 120. First metal layer; 130. Resin layer. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings, and the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figures 1-5As shown in the figure, this embodiment provides a multi-layer composite structure for the leading edge structure of an aircraft wing. Figure 1 , Figure 2 In the illustrated embodiment, the multilayer composite structure 2 comprises, from top to bottom, a first metal layer 120, an electric heating layer 110, and at least one set of composite material layers. The electric heating layer 110 includes a conductive layer 110, a fiber prepreg layer (not shown), and an electrode 112. The fiber prepreg layer is located on the lower surface of the first metal layer 120, the conductive layer 111 and the electrode 112 are located on the lower surface of the fiber prepreg layer, and the electrode 112 is located on both sides of the edge of the conductive layer 111. It is connected to the power supply 113 and the switch 114 through wires to form a closed circuit. The composite material layer 2 is composed of alternating layers of resin layer 130 and a second metal layer (not shown). The resin layer 130 of the composite material layer in contact with the electric heating layer 110 is located on the lower surface of the electric heating layer 110. The electric heating layer 110 has an anti-icing / de-icing function, the first metal layer 120 has a lightning protection function, the multilayer composite structure 2 has a bird strike resistance function, and the multilayer composite structure 2 is lightweight.

[0043] In a preferred embodiment, the first metal layer 120 and the second metal layer are composed of one or more of aluminum alloy, titanium alloy, titanium-aluminum alloy, and magnesium alloy, and have a thickness of 0.3-3 mm.

[0044] In a preferred embodiment, the composite method of the conductive layer 111 and the substrate and the insulation treatment method of the conductive layer surface include impregnation, spraying, roller coating, spin coating, filtration, vapor deposition, induced self-assembly, layer-by-layer self-assembly, etc., and the thickness of the electric heating layer 110 is 0.02-0.1 mm.

[0045] In a preferred embodiment, the conductive layer 111 is composed of one or more of metal nanowires, carbon materials, and oxides, and has a sheet resistance of 10-3000 Ω / sq and an areal density of 100-900 g / m². 2 The metal nanowires are composed of silver nanowires, the carbon materials are composed of one or more of carbon nanotubes, graphene, carbon black, and fullerenes, and the oxides are composed of one or more of antimony-doped tin oxide, aluminum-doped zinc oxide, and indium tin oxide, with carbon nanofilms being preferred.

[0046] In a preferred embodiment, the fiber prepreg is composed of one or more of glass fiber, carbon fiber, silicon carbide fiber, aramid fiber, nylon fiber, and quartz fiber, and their fabrics, with quartz fiber and carbon fiber being preferred.

[0047] The in-plane shear strength of the multi-layer composite structure is 100-2000 MPa, and the tensile ultimate strength is 500-3000 MPa.

[0048] Electrode 112 is fabricated on a conductive layer using screen printing and inkjet printing. In a preferred embodiment, electrode 112 is a flexible electrode, forming a dense top contact with the conductive layer 111 with a width of 10-20 mm. The flexible electrode is composed of one or more of copper, gold, silver, chromium, and aluminum, with a thickness of 0.01-0.2 mm, a sheet resistance of 20-300 mΩ / sq, a minimum bending radius of 6-10 mm, and a bonding strength between the flexible electrode and the conductive layer of 15-25 MPa. The electrothermal conversion efficiency of the fabricated electric heating layer is 60-90%.

[0049] The multi-layer composite structure 2 is bonded with self-adhesive resin, and the thickness after bonding is 1-10mm. The mechanical properties of the splice are an in-plane shear strength of 100-800MPa and a tensile ultimate strength of 700-3000MPa.

[0050] The multi-layer composite structure 2 is processed into typical aircraft structures such as spherical, conical, and arc surfaces using conformal manufacturing technology, for example, the typical leading edge structure 1 of an aircraft.

[0051] The typical leading-edge structure 1 of the aircraft has a water content of 0-0.35 g / m³ in the cloud. 3 The average water droplet diameter is 5-25 μm, and the ambient temperature is -10 to 0℃. It will not freeze from the ground to an altitude of 300-500m. The typical leading edge structure 1 of an aircraft can prevent dangerous consequences caused by lightning, and has lightning protection function. In addition, the typical leading edge structure 1 of an aircraft can ensure that the aircraft can continue to fly and land safely after colliding with a bird weighing 0.5-5 kg.

[0052] This embodiment also provides a method for preparing a multilayer composite structure for the leading edge structure of an aircraft wing, the method comprising the following steps:

[0053] S100, deposit one or more of metal nanowires, carbon materials or oxides on the surface of fiber prepreg to obtain a conductive layer 111.

[0054] The deposition process can employ physical or chemical methods, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and wet chemical deposition, to create a conductive layer 111 for subsequent electrothermal functions to achieve de-icing.

[0055] S200, The preparation method using screen printing or inkjet printing is to add electrode 112 to conductive layer 111;

[0056] S300, The conductive layer 111 with electrode 112 is assembled with the fiber prepreg layer to form an electric heating layer 110;

[0057] S400, the first metal layer 120, the electric heating layer 110, and at least one set of composite material layers are bonded together in a top-to-bottom order through a co-curing process to form the multilayer composite structure 2, wherein the composite material layer is composed of an alternating stack of resin layer 130 and second metal layer;

[0058] The first metal layer 120, the electrically heated layer 110, and at least one set of composite material layers are sequentially bonded together and co-cured to form a stable multilayer composite structure 2. Co-curing refers to the process under certain conditions (temperature, pressure, etc.) to allow the resins between different material layers to penetrate and cure each other, forming a whole.

[0059] S500, the multi-layer composite structure 2 is processed into a typical leading edge structure 1 of an aircraft using conformal manufacturing technology.

[0060] Overall, this preparation method efficiently integrates anti-icing / de-icing, lightning strike protection, and bird strike resistance functions through the above steps, while also achieving lightweight structure and performance optimization.

[0061] In current technology, the ends of the conductive layer 111 are connected to the corresponding electrodes 112. This connection method may lead to poor contact after prolonged use. For example, when using a carbon nanotube conductive film with a sheet resistance of 1-10 Ω / sq as the laminated electrothermal layer 110, and connecting both ends of the electrothermal layer 110 to rigid electrodes, there is a risk of failure due to poor contact during prolonged vibration and turbulence in the aircraft or when subjected to bird strikes. To avoid the above problems, in step S200, the specific steps for adding electrodes to the conductive layer using screen printing or inkjet printing include:

[0062] S201. Using microfluidics technology to generate electrode patterns with multiple branched structures.

[0063] Microfluidics is a technology that manipulates the flow of liquids within microscale channels. Using microfluidic chips, the flow of conductive materials (such as silver paste) can be precisely controlled, thereby forming intricate and complex multi-branched electrode patterns on the surface of a conductive layer. This method greatly improves the flexibility and precision of electrode design, helping to enhance the contact area and electrical performance between the electrode and the conductive layer.

[0064] S202. Coat the surface of the conductive layer with a photosensitive material, and form the desired electrode pattern on the conductive layer using photolithography.

[0065] A photosensitive material is applied to the surface of the conductive layer. This material changes its chemical properties in response to light of a specific wavelength, making certain areas conductive or insulating. Photolithography (a technique that uses light to transfer tiny patterns onto a material surface) is used to precisely define the electrode pattern, thereby directly forming the desired multi-branched pattern on the conductive layer.

[0066] S203. By selectively activating the photolithographically lithographically oriented area, an electrode material is sprayed onto the selectively activated photolithographically oriented area using inkjet printing technology, so that the electrode material is deposited only within the predetermined pattern area.

[0067] After photolithography, selected areas on the conductive layer will be able to adhere conductive materials. Using inkjet printing technology, conductive materials (such as silver paste) can be precisely sprayed onto these specific areas. Inkjet printing technology allows for the spraying of material in very precise locations and in very precise amounts, ensuring that the electrode material covers only the pre-defined pattern.

[0068] S204. Use ultraviolet light or thermal curing technology to cure the sprayed electrode material.

[0069] After the electrode material is coated, it needs to be cured (using ultraviolet light or heat treatment) to stabilize its physical and chemical properties and ensure the conductivity and mechanical stability of the electrode. During the curing process, the particle structure inside the conductive material is locked, thus forming a stable electrode.

[0070] Finally, the conductive layer with the newly formed electrodes is integrated with other layers (such as metal layers, resin layers, etc.) using 3D printing or hot pressing techniques. These techniques ensure close adhesion between layers and structural integrity, enhancing the mechanical strength and functionality of the multilayer composite structure.

[0071] Through the above steps, a highly precise and functional multi-layered composite structure can be achieved, which is suitable for the special requirements of the leading edge structure of aircraft wings and improves overall performance.

[0072] In the above embodiments, microfluidic technology is used to precisely control the flow of conductive material to form complex multi-branched electrode patterns. The microfluidic chip can precisely control the deposition of material on the surface of the conductive layer, thereby achieving precise pattern design. This step establishes the basic structure and layout of the electrodes, providing patterning and placement guidance for subsequent steps.

[0073] After forming the initial electrode pattern using microfluidic technology, the next step is to apply photosensitive materials to the conductive layer and further refine the electrode pattern using photolithography. This step, based on the initially designed electrode pattern, uses selective exposure and development processes to form a photolithographic template with a fine pattern. This ensures the accuracy and quality of the final conductive layer pattern.

[0074] After the photolithography process forms an accurate electrode pattern, the next step is to precisely spray a conductive material (such as silver paste) onto the defined pattern. Inkjet printing technology is used here to precisely position the conductive material to specific areas of the conductive layer, ensuring accurate deposition of the electrode material.

[0075] To provide a more thorough explanation of the solution in this embodiment, the following will be explained using specific embodiments:

[0076] Example 1

[0077] Graphene films were prepared on 500 mm wide glass fibers via chemical vapor deposition (CVD). The deposition temperature was 1050 °C, the pressure was atmospheric pressure, and methane was used as the carbon source. The flow rates of argon, hydrogen, and methane were 800 sccm, 500 sccm, and 60 sccm, respectively. The deposition time was 4 hours. After deposition, the furnace was cooled to room temperature to obtain graphene-glass fiber films. Graphene was uniformly distributed on the surface of the glass fibers, with an areal density of 220 g / m³. 2 Electrical performance tests showed that the resistance difference at various points was less than 10%.

[0078] Using the graphene-glass fiber as the conductive film in Example 1, a flexible electrode with a thickness of 0.1 mm was fabricated by screen printing. The sheet resistance of the flexible electrode was 100 mΩ / sq. The electrothermal conversion efficiency of this heating layer was measured to be 83% at room temperature and pressure and a rated voltage of 36V. The heating uniformity was good, with temperature differences across the heating surface less than 5°C. Using self-adhesive ACTECH1302 epoxy resin and bismaleimide resin, and by adjusting the prepreg composite parameters, a multi-layer composite structure was formed by splicing the aluminum alloy plate, the heating layer, and the resin layer.

[0079] The multi-layer composite structure was tested by mechanical testing and found to have a tensile strength of 1000 MPa at 0°, an elongation at 0° break of 4.5%, a bending strength of 700 MPa at 0°, an in-plane shear strength of 200 MPa at 0°, and a floating roll peel strength of 3.5 kN / m.

[0080] Example 2

[0081] A single-layer graphene film was prepared on a copper foil with a thickness of 0.025 mm using chemical vapor deposition. The graphene on the copper was then transferred to a carbon fiber with a width of 500 mm using a roll-to-roll transfer method. The graphene and carbon fiber were bonded together with a UV-curable adhesive. The transfer was repeated three times to obtain an electrothermal layer with three layers of graphene as the conductive film and carbon fiber as the substrate.

[0082] Flexible electrodes with a thickness of 0.1 mm were fabricated using screen printing on a conductive thin film. The sheet resistance of the flexible electrodes was 100 mΩ / sq. The electrothermal conversion efficiency of this heating layer was measured to be 88% at room temperature and pressure and a rated voltage of 110 V. The heating uniformity was good, with temperature differences across the heating surface less than 3℃. A self-adhesive bismaleimide resin was used to join the titanium alloy plate, the heating layer, and the resin layer into a multi-layered composite structure.

[0083] The multi-layer composite structure was tested by mechanical testing and found to have a tensile strength of 1300 MPa at 0°, an elongation at 0° of break of 5.0%, a bending strength of 1000 MPa at 0°, an in-plane shear strength of 240 MPa at 0°, and a floating roll peel strength of 3.0 kN / m.

[0084] Example 3

[0085] Carbon nanotubes were uniformly dispersed in deionized water containing a surfactant to prepare a solution with a concentration of 1 mg / mL. -1 The conductive paste is uniformly coated on the surface of the quartz fiber prepreg by electrostatic spraying. After drying, copper electrodes are added to the carbon nanotube-quartz fiber electric heating layer by screen printing. The aluminum alloy plate, electric heating layer and resin layer are co-cured with epoxy resin to obtain a multi-layer composite structure.

[0086] The multi-layered composite structure test specimen was clamped and placed directly in front of an infrared thermal imager. A DC voltage of 110-155V was set, and electric heating tests were conducted on the specimen at different voltages. After the power was switched on, the temperature of the test specimen increased, and the temperature distribution was uniform within the infrared camera's field of view. Figure 3 Different regions of the electrically heated sample were selected, and temperature rise curves under different voltages were plotted, such as... Figure 4 and Figure 5 As shown in the figure. The experimental results show that the multilayer composite structure sample with carbon nanotube-quartz fiber as the electric heating layer has good electric heating performance.

[0087] Example 4

[0088] The multi-layer composite structure was conformally manufactured to form a test specimen of a typical wing leading edge structure. The anti-icing / de-icing performance of the leading edge structure was tested through component performance testing, assembly function testing, typical specimen ground testing, and full-size specimen demonstration verification. The lightning protection performance of the leading edge structure was tested through material-level and component-level tests. High-intensity RF (High-Intensity RF) environmental testing was conducted on the flat plate and typical structural components of the leading edge structure, with direct lightning current injection into the leading edge of the multi-layer composite wing. The bird strike resistance performance of the leading edge structure was tested through typical and full-size specimens. The detection accuracy of the bird strike impact force test was 2%.

[0089] The typical structure of the aircraft has a water content of 0.35 g / m³ in clouds. 3 With an average water droplet diameter of 20 μm and an ambient temperature of -9°C, it will not freeze from the ground to a height of 457 m, meeting the icing cloud envelope requirements of CCAR-25-R4 Appendix C. Furthermore, the leading-edge structure, made using the aforementioned lightweight multi-layer composite structure, reduces the weight of its anti-icing and de-icing system by 30% compared to the current model, and the overall multi-functional wing leading-edge structure reduces the weight by 15% compared to the current model.

[0090] The aircraft's typical structure is designed to prevent dangerous consequences caused by lightning strikes and is equipped with lightning protection capabilities, meeting the requirements of CCAR-25-R4§25.581 (Lightning Protection).

[0091] Using this structure as the wing leading edge, at the sea-level cruising speed V selected in §25.335(a) C The structure was subjected to flight and a 1.8 kg (4 lb) bird strike; it was not penetrated, and the deformation was acceptable. Using this structure as the leading edge of the tail fin, it was cruised at sea level at the speed V selected in §25.335(a). C The aircraft underwent flight and a 3.6 kg (8 lb) bird strike, with no penetration of the leading edge or front spar, and the degree of deformation was acceptable. The bird strike resistance of the wing leading edge meets the bird strike resistance requirements of CCAR-25-R4 §25.631, and the aircraft was able to continue safe flight and landing after a bird strike.

[0092] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. For the embodiments of the method, relevant parts can be referred to the description of the device embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0093] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A multi-layer composite structure for an aircraft airfoil leading edge structure, characterized by, The multilayer composite structure, from top to bottom, includes a first metal layer, an electrically heated layer, and at least one set of composite material layers, wherein: The electric heating layer includes a conductive layer, a fiber prepreg layer, and electrodes. The fiber prepreg layer is located on the lower surface of the first metal layer. The conductive layer and the electrodes are located on the lower surface of the fiber prepreg layer. The electrodes are located on both sides of the edge of the conductive layer and are connected to the power supply and switch through wires to form a closed circuit. The composite material layer is composed of alternating layers of resin and a second metal layer. The resin layer of the composite material layer that is in contact with the electric heating layer is located on the lower surface of the electric heating layer. The electrode is a flexible electrode. The flexible electrode forms a dense top contact with the conductive layer with a width of 10-20 mm. The bonding strength between the flexible electrode and the conductive layer is 15-25 MPa, and the minimum bending radius of the flexible electrode is 6-10 mm.

2. A multi-layer composite structure for an aircraft airfoil leading edge structure according to claim 1, wherein, The first metal layer and the second metal layer are selected from one or more of aluminum alloy, titanium alloy, titanium-aluminum alloy, and magnesium alloy.

3. A multi-layer composite structure for an aircraft airfoil leading edge structure according to claim 1, wherein, The conductive layer is composed of one or more of metal nanowires, carbon materials, oxides, the sheet resistance of the conductive layer is 10-3000 Ω / sq, and the areal density is 100-900 g / m 2 .

4. A multi-layer composite structure for an aircraft airfoil leading edge structure according to claim 3, wherein, The metal nanowires are composed of silver nanowires, the carbon material is composed of one or more of carbon nanotubes, graphene, carbon black, and fullerene, and the oxide is composed of one or more of antimony-doped tin oxide, aluminum-doped zinc oxide, and indium tin oxide.

5. A multi-layer composite structure for the leading edge structure of an aircraft wing according to claim 1, characterized in that, The fiber prepreg layer comprises one or more of glass fiber, carbon fiber, silicon carbide fiber, aramid fiber, nylon fiber, and quartz fiber, as well as their fabrics.

6. A multi-layer composite structure for the leading edge structure of an aircraft wing according to claim 1, characterized in that, The electrode thickness is 0.01-0.2 mm, the electrode sheet resistance is 20-300 mΩ / sq, and the electrothermal conversion efficiency of the electric heating layer is 60-90%.

7. A multi-layer composite structure for the leading edge structure of an aircraft wing according to claim 1, characterized in that, The thickness of the electric heating layer is 0.02-0.1 mm, and the thickness of the multilayer composite structure is 1-10 mm.

8. A multi-layer composite structure for the leading edge structure of an aircraft wing according to claim 1, characterized in that, The resin layer is epoxy resin or bismaleimide resin.

9. A method for preparing a multilayer composite structure for the leading edge structure of an aircraft wing as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: A conductive layer is prepared by depositing one or more of metal nanowires, carbon materials, or oxides on the surface of fiber prepreg. Electrodes are added to the conductive layer using screen printing or inkjet printing methods. The conductive layer with electrodes is assembled with the fiber prepreg layer to form an electric heating layer; The first metal layer, the electric heating layer, and at least one set of composite material layers are bonded together in a top-to-bottom order through a co-curing process to form the multilayer composite structure, wherein the composite material layer is composed of an alternating layer of resin and a second metal layer. The multi-layered composite structure is manufactured into the leading edge structure of an aircraft wing using conformal manufacturing technology.

10. A method for preparing a multilayer composite structure for the leading edge structure of an aircraft wing according to claim 9, characterized in that, The specific steps for adding electrodes to the conductive layer using screen printing or inkjet printing methods include: Microfluidic technology was used to generate electrode patterns with multiple branched structures. A photosensitive material is coated on the surface of the conductive layer, and the desired electrode pattern is formed on the conductive layer using photolithography. By selectively activating the photolithographically lithographically oriented area, inkjet printing technology is used to spray electrode material onto the selectively activated photolithographically oriented area, so that the electrode material is deposited only within the predetermined pattern area; The sprayed electrode material is cured using ultraviolet light or thermal curing technology.

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