Airfoil leading edge full-frequency omnidirectional stealth structure and preparation method thereof

Abstract

The application discloses a wing leading edge full-frequency omnidirectional stealth structure and a preparation method thereof. The stealth structure is sequentially laid with an impedance matching layer, a gradient wave absorbing layer, a multi-scale dissipation layer and a high-temperature bearing matrix layer from outside to inside, and the four layers are integrally co-solidified and formed, and the interlayer impedance is continuously transitioned, so that a conformal streamline whole structure which is adapted to the aerodynamic shape of the leading edge is formed. The four layers of materials are synchronously extended to the leading edge tip and upper and lower side edge ends and are integrally shaped, so that an edge diffraction suppression configuration is formed. Through the collaborative design of the gradient impedance gradient, the multi-scale electromagnetic loss coupling and the integrated shape shaping of the leading edge end, the stable low scattering characteristic that RCS≤-15dB in the full radar frequency band of 0.3-18GHz and the full incident angle range of ±60° is realized, and the structure bearing, high-temperature resistance, wide-band stealth, omnidirectional low scattering multiple features are combined, and the application is suitable for a new generation of stealth aircraft.

Description

Technical Field

[0001] This invention belongs to the field of aerodynamic stealth technology for aircraft, specifically relating to a conformal stealth structure for the leading edge of an airfoil with full frequency and omnidirectional conformal characteristics and its preparation method, which can be adapted for long-term service of high-speed aircraft in an environment of 400°C. Background Technology

[0002] The leading edge of an airfoil is one of the core strong scattering sources in the head-on direction of a high-speed aircraft, making it extremely easy to identify and lock onto under radar detection. Its stealth performance directly determines the overall penetration effectiveness of the aircraft. Modern radar detection systems are gradually developing towards full-band, multi-angle, and high-sensitivity, placing stringent design requirements on the leading edge of the airfoil for broadband stealth, omnidirectional low scattering, high-temperature service resistance, and the integration of structural load-bearing and stealth.

[0003] Traditional wing leading edges often employ solid metal structures or ordinary composite material skins with external radar-absorbing coatings. These solutions suffer from drawbacks such as insufficient high-frequency absorption, difficulty in effectively absorbing low frequencies, a sharp deterioration in scattering performance at large incident angles, and prominent angle effects, making it impossible to achieve stable stealth throughout the 0.3–18 GHz range. Furthermore, the aerodynamic heating of 300–400°C generated by high-speed flight causes coating cracking and peeling, substrate softening, and interlayer interface failure. Under aerodynamic heating conditions of 300–400°C, the stealth performance of conventional coating structures typically decreases by more than 20% at high temperatures.

[0004] Existing integrated stealth structures are mostly flat plate configurations, which are difficult to adapt to the aerodynamic shapes of hyperboloids and thin airfoils with high curvature at the wing leading edge, and cannot achieve a smooth and continuous transition of electromagnetic impedance. Existing technologies include stealth sandwich structures using polyimide fiber composite materials, comprising a high-transmittance polyimide skin, a radar-absorbing honeycomb core layer, and a carbon fiber reflector. However, this is a sandwich structure, with the layers bonded together. The adhesive interfaces between the layers are prone to aging and failure in high-temperature environments of 300-400°C, resulting in poor bonding reliability. Furthermore, the carbon fiber reflector it contains can cause secondary reflections, increasing the risk of radar detection. Another approach is a full-frequency stealth wing scheme that uses a metal grid to scatter low-frequency electromagnetic waves and a multi-layered radar-absorbing structure to absorb high-frequency electromagnetic waves. However, this relies on the metal grid for scattering, and the metal grid, being a conductive and rigid structure, is difficult to conformally adapt to the high-curvature leading edge surface, and it also introduces structural weight increases, which is detrimental to aircraft lightweighting.

[0005] Furthermore, the leading edge tip and side edge edges of existing wings are the main sources of strong scattering. Current solutions simply thicken the absorbing material without specifically optimizing the geometry of the tips and edges, making it difficult to effectively suppress diffraction scattering. Simultaneously, they generally suffer from insufficient structural load-bearing strength, poor high-temperature thermal stability, and a disconnect between aerodynamic design and stealth capabilities. Existing edge scattering suppression methods based on absorbing foam and gradient impedance strips are mainly for metallic targets, employing a post-loading assembly method of foam and impedance strips. This method requires secondary assembly of additional structures onto the metal substrate, leading to accumulated assembly errors and scattering at the additional interface. Moreover, the low mechanical strength of foam materials makes it difficult to meet the load-bearing requirements of the aircraft's leading edge structure.

[0006] In summary, existing technologies cannot simultaneously meet multiple requirements such as wideband absorption, omnidirectional low scattering, high-temperature resistance for long-term service, structural load-bearing capacity, and conformal adaptation to curved surfaces. This is a technological bottleneck restricting the development of leading-edge structures for next-generation high-speed stealth aircraft. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a full-frequency omnidirectional stealth structure for the leading edge of a wing and its fabrication method. Through a collaborative design that achieves active suppression of edge diffraction by gradually varying the impedance in the thickness direction, coupling electromagnetic losses of multi-scale absorbing units, integrating high-temperature load-bearing substrates, and modifying the overall shape of the leading edge, stable low-scattering characteristics are achieved across the entire radar band, all incident angles, and under high-temperature service conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a full-frequency omnidirectional stealth structure for the leading edge of a wing, which consists of four composite materials laid from the outside to the inside: an impedance matching layer, a gradient absorbing layer, a multi-scale dissipation layer, and a high-temperature load-bearing matrix layer. The four layers are integrated and co-cured, with continuous impedance transition between layers, forming a conformal streamlined integral structure that adapts to the aerodynamic shape of the leading edge. The impedance matching layer, gradient absorbing layer, multi-scale dissipation layer, and high-temperature load-bearing matrix layer completely cover the entire aerodynamic surface of the wing leading edge. The four layers extend synchronously to the tip of the leading edge and the ends of the upper and lower side edges and are integrally shaped to form an edge diffraction suppression configuration. The edge diffraction suppression configuration has no independent thickness lay-up and is formed synchronously and integrally by the ends of the four composite materials. The outer surface of the configuration is the aerodynamic surface of the impedance matching layer exposed.

[0009] Furthermore, the impedance matching layer is a low dielectric constant transparent composite material layer with a thickness of 0.2~0.5mm, an equivalent relative permittivity εr=2.8~3.2, a magnetic permeability μr≈1.0, and an air-to-structure interface reflection coefficient <0.1. It is used to reduce the impedance abrupt change between the air and the structure surface, suppress specular reflection, and allow incident radar waves to penetrate into the internal absorbing structure.

[0010] Furthermore, the gradient absorbing layer is fully covered by the impedance matching layer, forming a continuous, integrated structure without physical layering. The overall thickness is 1.5~3.5mm, and the dielectric constant gradually changes from 3.2 to 6.5 along the thickness direction, while the loss tangent gradually changes from 0.08 to 0.25. The change in dielectric constant between adjacent 0.1mm intervals is ≤0.22, and the impedance difference between adjacent regions is always <20Ω, achieving a smooth transition of electromagnetic impedance, broadening the 0.3~18GHz absorbing bandwidth, and improving low-frequency absorbing capability.

[0011] Furthermore, the gradient absorbing layer is prepared using a dual-slurry linear flow rate controlled co-casting process, with polyimide resin as the matrix, an outer SiC filler content of 8wt%, and an inner SiC filler content of 22wt%. The filler content along the thickness direction satisfies the linear relationship C(x) = 8 + 14·x / D, where C(x) is the filler content at a distance x from the outer surface, D is the total thickness of the gradient absorbing layer, and x is the thickness coordinate from the outer surface. The dielectric constant along the thickness direction satisfies the linear relationship εr(x) = 3.2 + 3.3·x / D.

[0012] Furthermore, the multi-scale dissipation layer has a thickness of 1.0~2.0mm, completely covering the leading edge surface, and is a homogeneous composite layer; based on 100 parts by mass of polyimide resin, it contains 25 parts by mass of three types of microwave absorbing fillers, including 10 parts by mass of nano-sized ferrite magnetic powder, 8.75 parts by mass of submicron silicon carbide dielectric particles, and 6.25 parts by mass of micron-sized short-cut pitch-based carbon fiber; the three types of fillers form multiple coupling synergies through magnetic loss, dielectric loss, and interface polarization loss, respectively, to achieve electromagnetic wave energy dissipation and attenuation across the entire frequency band of 0.3~18GHz.

[0013] Furthermore, the high-temperature load-bearing matrix layer extends completely through the leading edge of the wing and is made of 400℃-grade high-temperature resistant polyimide carbon fiber composite material with a thickness of 3.0~6.5mm. The carbon fibers are laid up symmetrically in the [0° / ±45° / 90°] pattern. Under long-term service conditions at 400℃, the structural tensile strength is ≥50MPa, the flexural strength is ≥75MPa, and the elastic modulus is ≥32GPa, providing stiffness, load-bearing capacity, and high-temperature dimensional stability for the overall structure.

[0014] Furthermore, the edge diffraction suppression configuration is provided with a tapered tip bevel and a side impedance strip. The tapered tip bevel angle is 12°~18°, and the side impedance strip width is 4~6mm and the radius of curvature is 2.0~3.5mm. The configuration deflects the scattering direction through the tapered tip bevel and suppresses the creeping wave through the continuous impedance at the end, achieving stable low RCS characteristics within the ±60° full incident angle range.

[0015] Furthermore, the radius of curvature of the leading edge tip of the wing is 0.8~2.0mm, the relative thickness of the airfoil is 2%~6%, and the overall outer contour curvature is ≤0.05mm.- ¹, The overall thickness ranges from 4.7 to 12.0 mm, and the overall surface density is ≤2.8 kg / m².

[0016] Furthermore, under radar frequency bands of 0.3~18GHz, incident angles of ±60°, and service temperatures of 400℃, the overall RCS of the structure is ≤-15dB; after 100h of thermal aging at 400℃, the stealth performance decays by ≤4%, with no interlayer cracking or delamination and thermal deformation <0.02mm / m; and the RCS fluctuation within the ±60° large-angle incident range is ≤3dB.

[0017] Secondly, the present invention provides a method for preparing a full-frequency omnidirectional stealth structure at the leading edge of a wing, which includes the following steps: S1: Prepare impedance matching layer prepreg, gradient absorbing layer continuous gradient film, multi-scale dissipative layer cast film, and high-temperature load-bearing substrate layer prepreg respectively; The method for preparing the continuous gradient thin film of the gradient absorbing layer is as follows: prepare low-filler slurry A and high-filler slurry B, with SiC filler content of 8wt% in slurry A and 22wt% in slurry B. Use a dual-slurry linear flow rate control co-casting process, and linearly adjust the flow rate ratio of the two material bins to switch the slurry from 100% slurry A / 0% slurry B to 0% slurry A / 100% slurry B. After dynamic mixing in the die head, the film is cast and dried in segments to obtain a single homogeneous thin film with a continuously gradually changing dielectric constant along the thickness direction. S2: In the mold cavity, high temperature bearing substrate prepreg, multi-scale dissipative layer cast film, gradient absorbing layer continuous gradient film, and impedance matching layer prepreg are laid in sequence. Each layer completely covers the entire curved surface of the leading edge, and the end is simultaneously filled with the cavity edge diffraction suppression configuration contour area. S3: After mold closing, inert gas is introduced to replace the air in the mold cavity, and segmented temperature rise curing is performed: the temperature is increased to 170~190℃ at 1~2℃ / min and held for 40~80min, then the temperature is increased to the peak curing temperature of 300~320℃ at 0.5~1.5℃ / min, the molding pressure is applied at 1.8~2.2MPa, and the temperature and pressure are kept constant for 4~5h to complete co-curing; S4: After cooling to 60~80℃, demold and trim the edges to obtain an integrated conformal leading edge stealth structure.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention employs a four-layer functional layer to completely cover the entire aerodynamic surface of the leading edge, eliminating any stealth blind spots; the gradient absorbing layer uses a dual-material linear casting to achieve a non-layered continuous dielectric gradient, combined with a three-scale powder coupling dissipation structure, to achieve ultra-wideband stealth absorbing of 0.3~18GHz, fully covering the mainstream radar detection frequency bands of meter wave, decimeter wave, and centimeter wave.

[0019] 2. The four-layer material used in this invention extends synchronously to the leading edge tip and side edge, forming an edge diffraction suppression configuration with precise geometric parameters in one piece. Through the dual mechanism of shape deflection and end impedance buffering, it suppresses tip stagnation diffraction and edge creeping waves, maintaining a low RCS (radar cross section) stable output (RCS fluctuation ≤ 3dB) under ±60° large angle incident conditions, and significantly weakening the angle scattering effect.

[0020] 3. This invention adopts a 400℃-grade high-temperature resistant polyimide carbon fiber composite matrix and a conformal integrated structure with curved surfaces (high-temperature tensile strength ≥50MPa, flexural strength ≥75MPa, elastic modulus ≥32GPa at 400℃), without external microwave absorbing coating, completely solving the problem of coating peeling off at high temperatures. It has stealth capabilities under wide temperature range cycling and extremely low mechanical performance degradation (stealth degradation ≤4% and mechanical degradation <3% after 100h of 400℃ thermal aging), and the structural thermal deformation is controllable (<0.02mm / m).

[0021] 4. The load-bearing structure and the wave-absorbing matching layer of this invention are integrated into one, possessing both high structural strength and high rigidity, as well as a smooth and continuous aerodynamic streamline shape, with an overall outer contour curvature ≤0.05mm. - ¹, with a surface density of ≤2.8kg / m²; four layers of homologous resin combined with a gradient buffer layer solve the defects of multilayer thermal expansion mismatch, with an interlayer shear strength of 75~82MPa and excellent reliability in thermal shock.

[0022] 5. The entire set of molding process parameters, gradient slurry formulation, and multi-scale powder dispersion process of this invention are all quantifiable and replicable. It features integrated segmented temperature-controlled oxygen-free molding, reliable interlayer chemical bonding interface, long service life, and strong adaptability to curved surfaces. It can effectively reduce the RCS of aircraft in key head-on directions, improve the stealth penetration capability of the entire aircraft, and is compatible with the front edge components of various new-generation high-speed stealth aircraft with strong scattering curved surfaces. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the axial cross-sectional structure of the wing leading edge full-frequency omnidirectional stealth structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the thickness distribution and impedance gradient principle of each functional layer of the stealth structure in an embodiment of the present invention. Figure 3 This is a schematic diagram comparing the RCS stealth performance characteristics of the structure of this invention and the traditional structure across the entire frequency band from 0.3 to 18 GHz.

[0024] Figure labeling: 1-Impedance matching layer, 2-Gradient absorbing layer, 3-Multi-scale dissipation layer, 4-High-temperature load-bearing substrate layer, 5-Edge diffraction suppression configuration, 6-Wing leading edge tip. Detailed Implementation

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Example 1 like Figure 1 As shown, this embodiment provides a wing leading-edge all-frequency omnidirectional stealth structure. The wing leading-edge stealth load-bearing body consists of four functional composite material layers continuously laid from the outside to the inside along the thickness: an impedance matching layer 1, a gradient absorbing layer 2, a multi-scale dissipation layer 3, and a high-temperature load-bearing matrix layer 4. These four layers are completely and continuously laid along the wing leading-edge tip 6 and the entire upper and lower wing surfaces, completely covering the entire leading-edge aerodynamic surface without any gaps or segmented cutoffs. The four layers are integrally co-cured and molded, with continuous impedance transitions between layers, forming a conformal streamlined integral structure adapted to the leading-edge aerodynamic shape. There is no obvious interface reflection, and chemically bonded interfaces are formed between the layers, eliminating the need for physical adhesive layers and completely avoiding interface debonding and impedance abrupt changes at high temperatures.

[0027] Impedance matching layer 1, gradient absorbing layer 2, multi-scale dissipation layer 3, and high-temperature load-bearing matrix layer 4 completely cover the entire aerodynamic surface of the wing leading edge. These four layers extend synchronously to the wing leading edge tip 6 and the upper and lower side edges, forming an edge diffraction suppression configuration 5. The outer surface of this configuration is the exposed aerodynamic surface of impedance matching layer 1. Edge diffraction suppression configuration 5 has no independent thickness layup; it is formed by the synchronous integral molding of the ends of the four composite materials. This composite shape and local impedance synergy structure simultaneously cover the two major strong scattering areas—the wing leading edge tip and the upper and lower side edges—with a continuous curvature throughout the entire area and no sharp edges.

[0028] The stealth structure in this embodiment is an integrated conformal stealth load-bearing structure with a thin airfoil and a large leading edge curvature. The overall thickness ranges from 4.7 to 12.0 mm, and the overall surface density is ≤2.8 kg / m², meeting aviation lightweighting requirements. Its operating conditions cover the radar frequency band of 0.3 to 18 GHz, with an incident angle of ±60° (TE / TM dual-polarized radar waves). The long-term service temperature is -50 ℃ to 400 ℃, and the short-term thermal shock temperature can reach 420 ℃.

[0029] The stealth structure in this embodiment is adapted to the thin airfoil aerodynamic shape of high-speed aircraft, with continuous curvature of the overall outer contour, ≤0.05 mm. - ¹. The leading edge tip 6 of the wing adopts a single-segment circular arc transition, with a radius of curvature of 0.8~2.0 mm. The radius of curvature of the standard tip is 0.8~1.5 mm, and the radius of curvature of the high-speed, high-temperature reinforced tip is 1.0~2.0 mm. The total physical thickness of the structure is 4.7~9.0 mm for the standard type and 5.0~12.0 mm for the high-temperature reinforced type. This structure is suitable for airfoils with a relative thickness (thickness-to-chord ratio) of 2%~6%, which is within the typical thin airfoil range for high-speed aircraft. The maximum thickness of the airfoil is located at 35%~45% of the chord length, which can effectively reduce supersonic wave drag while meeting the requirements of structural load-bearing capacity and high-temperature thermal protection.

[0030] (1) Impedance matching layer Impedance matching layer 1 is a low-dielectric-constant, wave-transparent composite material layer. It serves as the outermost layer of the stealth structure, with a thickness of 0.2–0.5 mm. It conformally covers all curved surfaces along the leading edge of the wing, forming a single-layer homogeneous structure. In this embodiment, a thickness of 0.3 mm is preferred. At room temperature, the equivalent relative permittivity εr = 2.8–3.2, and the permeability μr ≈ 1.0. Based on the generalized Brewster impedance matching theory, it connects free air (impedance ≈ 377 Ω) with the inner structure, resulting in an air-structure interface reflection coefficient < 0.1. Impedance matching layer 1 achieves impedance matching between the air and the structural surface, suppressing specular reflection across the entire frequency band (0.3–18 GHz) and within a ±60° incident angle range, allowing incident radar waves to penetrate the surface and enter the internal absorbing structure.

[0031] Impedance matching layer 1 is made of low dielectric constant quartz fiber reinforced modified epoxy resin composite material, with 3%~5% hollow glass microspheres doped into the matrix to regulate dielectric properties. The fiber areal density is 120g / m², and the fiber layup is [0° / 90°] orthogonal layup, balancing wave transmission and surface erosion resistance. This layer has a Shore hardness ≥85, providing resistance to wind and sand erosion and damp heat aging; the dielectric constant fluctuation is <5% at 400℃, and there is no significant shift in electromagnetic matching performance.

[0032] (2) Gradient absorbing layer The gradient absorbing layer 2 follows the impedance matching layer 1, covering all aerodynamic surfaces at its leading edge without any local truncation. The gradient absorbing layer 2 is a continuous, homogeneous structure without physical layering; it lacks physical layers, interfaces, and independent thin-layer splicing. The smooth, gradual change in electromagnetic parameters along the thickness direction is achieved through a continuous variable-doping casting process. Figure 2As shown in the figure, parallel diagonal lines with sparser lines at the top and denser lines at the bottom represent the continuous gradual change of the dielectric constant along the thickness direction, intuitively demonstrating the structural characteristics of the electromagnetic parameters without abrupt changes. The overall thickness is 1.5~3.5mm. The dielectric constant gradually changes from 3.2 to 6.5 along the thickness direction, and the loss tangent gradually changes from 0.08 to 0.25. The change in dielectric constant between adjacent 0.1mm intervals is ≤0.22, with no abrupt changes. The impedance difference between adjacent regions is always <20Ω, completely eliminating interlayer reflection. This structure achieves a smooth transition of electromagnetic impedance, broadens the absorption bandwidth from 0.3 to 18GHz, and improves low-frequency absorption capability.

[0033] The gradient absorbing layer 2 is prepared using a dual-slurry linear flow rate controlled co-casting process, with high-temperature resistant thermosetting polyimide resin (PI) as the matrix. The outer SiC filler content is 8 wt%, and the inner SiC filler content is 22 wt%. The filler content along the thickness direction satisfies the linear relationship C(x) = 8 + 14·x / D, where C(x) is the filler content at a distance x from the outer surface in wt%, D is the total thickness of the gradient absorbing layer, and x is the thickness coordinate from the outer surface (x=0 is the outer surface, x=D is the inner surface). The dielectric constant along the thickness direction satisfies the linear relationship εr(x) = 3.2 + 3.3·x / D; the loss tangent satisfies tanδ(x) = 0.08 + 0.17·x / D.

[0034] In the specific preparation, slurry A (outer low-dielectric side, close to the impedance matching layer) is prepared as follows: 100 parts by weight of PI resin, 8 parts by weight of SiC (silicon carbide) dielectric microparticles, and viscosity adjusted with anhydrous NMP solvent; slurry B (inner high-dielectric side, close to the multi-scale dissipation layer) is prepared as follows: 100 parts by weight of PI resin, 22 parts by weight of SiC dielectric microparticles, and viscosity adjusted with anhydrous NMP solvent. The SiC particles have a uniform particle size of 0.4~0.6 μm and a purity ≥99.2%, and are pre-modified with silane coupling agent KH-560 to improve the interfacial bonding force with PI resin. NMP is a high-boiling-point inert solvent specifically for PI, which does not participate in the resin crosslinking reaction and is completely removed at high temperature without residue. The dual silos are connected to a linear flow control system, and the flow rate ratio of the two silos is linearly adjusted by PLC. Initial stage of casting (corresponding to the outer surface of the gradient layer): Slurry A flow rate 100%, slurry B flow rate 0%, SiC content in slurry 8wt%, relative permittivity εr=3.2; Finishing stage of casting (corresponding to the inner surface of the gradient layer): slurry A flow rate 0%, slurry B flow rate 100%, slurry SiC content 22wt%, relative permittivity εr=6.5.

[0035] The flow rate changes linearly and continuously throughout the casting process, without step-by-step switching. The slurry is dynamically mixed in real time inside the die head. After molding, the filler concentration of the film transitions smoothly and continuously along the thickness direction, without any delamination interface. The total thickness of the casting die slit corresponds to the thickness of the finished gradient layer. A segmented low-temperature gradient drying process is adopted, with a drying temperature rise rate of 0.5℃ / min. The temperature is uniformly raised from 60℃ to 120℃ and held at each stage to completely remove the solvent. After drying, an integral continuous gradient film is obtained directly without the need for multi-layer hot pressing.

[0036] In the low-frequency band (0.3~2 GHz), the gradient absorbing layer 2 extends the electromagnetic wave propagation path and enhances polarization loss by relying on the medium-high dielectric region, thus compensating for the shortcomings of traditional low-frequency absorption structures. In the mid-to-high frequency band (2~18 GHz), it achieves multi-band electromagnetic wave step-matched absorption by relying on the gradually varying impedance, suppressing reflection peaks within the frequency band and broadening the effective absorption bandwidth. Under 400℃ conditions, the overall dielectric constant shift is <7%, the gradient distribution remains stable, and gradient failure will not occur due to softening of the high-temperature substrate.

[0037] (3) Multiscale dissipation layer The multi-scale dissipation layer 3, with a thickness of 1.0~2.0 mm, completely covers the leading edge curved surface along with the outer two-layer structure, forming a homogeneous composite layer. Three types of microwave absorbing functional units with different particle sizes are uniformly dispersed internally, without agglomeration. The total doping amount of the microwave absorbing units is 25% of the matrix mass, as detailed below: Based on 100 parts by weight of polyimide resin, there are 25 parts by weight of three types of microwave absorbing fillers, including 10 parts by weight of nano-sized ferrite magnetic powder, 8.75 parts by weight of submicron silicon carbide dielectric particles, and 6.25 parts by weight of micron-sized short-cut pitch-based carbon fiber.

[0038] The specific specifications of the three types of fillers are as follows: Nanoscale ferrite magnetic powder with a particle size of 30-80 nm, accounting for 40% of the total filler, relies on magnetic moment reversal to generate magnetic loss, primarily targeting 1-10 GHz mid-frequency radar waves; the powder is modified with aluminate high-temperature anti-oxidation coating, exhibiting no oxidation or demagnetization at 400℃; submicron silicon carbide dielectric particles with a particle size of 0.3-0.8 μm, accounting for 35% of the total filler, rely on electric dipole polarization to generate dielectric loss, primarily targeting 10-18 GHz high-frequency radar waves; and micron-sized short-cut pitch-based carbon fibers with a length of 10-30 μm, accounting for 25% of the total filler, rely on microscopic interface-induced interfacial polarization loss, primarily targeting 0.3-1 GHz low-frequency radar waves. These three types of fillers achieve multi-coupling synergy through magnetic loss, dielectric loss, and interfacial polarization loss, respectively, to achieve energy dissipation and attenuation of electromagnetic waves across the entire 0.3-18 GHz frequency band.

[0039] Three types of fillers were dispersed and molded into a homogeneous, non-agglomerated film through stepwise high-speed dispersion. The specific dispersion process was as follows: the powders were ultrasonically cleaned for 30 min and dried at 110℃ for 2 h; the ferrite powder was coated with a 5wt% aluminate anti-oxidation layer; all powders were surface activated with KH-550 aminosilane coupling agent; SiC particles were first added to the PI resin solvent solution and stirred at 1800 r / min for 40 min in a high-speed disperser; then nano-ferrite was added and stirred at 2200 r / min for 60 min; finally, short-cut carbon fibers were added at 800 r / min and stirred for 25 min to prevent fiber breakage; the slurry viscosity was adjusted to 3200±200 mPa·s using NMP solvent, and the mixture was allowed to stand for 3 h to defoam without powder sedimentation or agglomeration, resulting in a uniform distribution of fillers within the molded layer.

[0040] The coating and molding process of the three types of fillers is as follows: the mixed multi-scale dissipative slurry is uniformly cast into a complete film with a single die head and an overall thickness of 1.0~2.0 mm. After casting and drying, it is directly bonded to the inner side of the gradient absorbing layer without any breaks or missing material areas. During the co-curing stage, the resin melts and interpenetrates with the gradient absorbing layer, and there are no air gaps at the interface.

[0041] The three types of fillers form a multi-loss coupling system and simultaneously construct a microscopic conductive network to extend the electromagnetic wave dissipation path, achieving electromagnetic wave energy dissipation and attenuation across the entire frequency band from 0.3 to 18 GHz. All absorbing units undergo high-temperature oxidation-resistant modification, exhibiting no oxidation failure or magnetic attenuation at 400℃; with incident at large angles of ±60°, the absorption efficiency fluctuation is <3%, and the angle effect is extremely weak.

[0042] (4) High-temperature load-bearing substrate layer The high-temperature load-bearing substrate layer 4 serves as the main load-bearing base for the stealth structure, completely penetrating and covering the entire leading edge of the wing. It is made of 400℃-grade high-temperature resistant polyimide (PI) carbon fiber composite material, with a thickness of 3.0~6.5mm. The carbon fibers are symmetrically laid up at [0° / ±45° / 90°], allowing for long-term service at 400℃ without softening or creep. Its mechanical properties are as follows: at room temperature, tensile strength ≥60 MPa, flexural strength ≥90 MPa, and elastic modulus ≥32 GPa; under long-term service conditions at 400℃, structural tensile strength ≥50 MPa, flexural strength ≥75 MPa, and mechanical property retention rate >83%. After 100 hours of heat aging at 400℃, the mechanical strength decreases by <3%, and the structural dimensional deformation is <0.02 mm / m, meeting the aerodynamic shape accuracy requirements of the aircraft.

[0043] The high-temperature load-bearing substrate layer 4 is designed with electromagnetic compatibility optimization, eliminating the need for additional absorbing coating. The three-layer absorbing structure between the layers and the outer layer is co-cured and bonded together, with no air gaps, eliminating interface scattering, and achieving integrated load-bearing, high-temperature resistance and stealth functions, providing stiffness, load-bearing capacity and high-temperature dimensional stability for the entire stealth structure.

[0044] (5) Edge diffraction suppression configuration The edge diffraction suppression configuration 5 is formed by the simultaneous integral molding of four fully covered functional layers at the tip and side edges, without independent thickness layers or separate additional components. It features a tapered bevel at the tip and impedance strips at the side edges. The tapered bevel angle is 12°~18°, and the width of the impedance strips is 4~6mm with a radius of curvature of 2.0~3.5mm. This configuration achieves stable low RCS characteristics across a ±60° full incident angle range by deflecting the scattering direction through the tapered bevel and suppressing creeping waves through continuous impedance buffering at the ends. The outer surface of the edge diffraction suppression configuration 5 is the exposed aerodynamic curved surface of the outermost impedance matching layer. Radar waves directly incident on this modified curved surface achieve scattering suppression, eliminating the logical contradiction of an inner structure acting solely on the outer radar illumination surface.

[0045] In this embodiment, the leading edge of the wing features a gradual chamfer transition of 12° to 18° at six points, while the side edges are fitted with arc-shaped strakes with a width of 4 to 6 mm and a radius of curvature of 2.0 to 3.5 mm. When illuminated by radar waves, the chamfered tip deflects the diffraction energy to a non-threatening direction, and the arc-shaped strakes on the side edges suppress the propagation of creeping waves through continuous curvature changes.

[0046] In this embodiment, the stealth structure adopts an integrated co-curing and co-forming process, strictly adhering to the entire set of process parameters including segmented temperature rise, constant pressure, and nitrogen-oxygen-free curing. The overall performance test results are as follows: under radar frequency bands of 0.3~18GHz, incident angles of ±60°, and service temperatures of 400℃, the RCS is ≤-15dB across all frequencies and directions. Figure 3 As shown. From Figure 3 As can be seen, the RCS value of the structure of this invention is consistently lower than that of the structure in the 0.3~18GHz full frequency range. The 15dB reflection with no reflection spikes across the entire frequency band indicates that this invention achieves a stable and consistent stealth effect across the entire frequency band; while traditional metal leading-edge structures exhibit strong specular reflection characteristics across the entire frequency band, showing no stealth effect whatsoever. Within a ±60° wide-angle incidence range, the RCS fluctuation is ≤3dB; after 100 hours of constant-temperature thermal aging at 400℃, the RCS stealth performance decays by ≤4%, and ultrasonic C-scan detection shows no interlayer cracking, delamination, or separation defects; the structural tensile strength at room temperature and 400℃ is ≥55MPa, exceeding the 50MPa design threshold, meeting the wing leading-edge structure load-bearing design requirements; the measured average interlayer shear strength is 78MPa, exceeding the 68MPa design threshold.

[0047] This embodiment also provides a method for preparing a full-frequency omnidirectional stealth structure at the leading edge of a wing, which includes the following steps: Step S1: Prepare the impedance matching layer prepreg, the gradient absorbing layer continuous gradient film, the multi-scale dissipative layer cast film, and the high-temperature bearing substrate layer prepreg respectively.

[0048] (1) Preparation of impedance matching layer prepreg: Modified epoxy resin is doped with 4wt% hollow glass microspheres and stirred to disperse evenly. 120g / m² quartz fiber cloth is made by orthogonal layup at [0° / 90°], impregnated with the above resin system, with a prepreg resin content of 38~42wt%, and pre-dried in a low-temperature oven before being rolled up for use.

[0049] (2) Preparation of continuous gradient thin films for gradient absorbing layers: Prepare low-filler slurry A and high-filler slurry B. Slurry A: 100 parts PI resin + 8 parts SiC microparticles (particle size 0.4~0.6μm, KH-560 modified), adjust viscosity to 2500~3000 mPa·s with NMP. Slurry B: 100 parts PI resin + 22 parts SiC microparticles (particle size 0.4~0.6μm, KH-560 modified), adjust viscosity to 2500~3000 mPa·s with NMP.

[0050] A dual-slurry linear flow rate controlled co-casting process is employed. By linearly adjusting the flow rate ratio of the two silos, the filler is linearly switched from 100% slurry A / 0% slurry B to 0% slurry A / 100% slurry B. After dynamic mixing within the die, the film is cast. The total thickness of the slit in the casting die corresponds to the thickness of the gradient layer in the finished product. Segmented low-temperature gradient drying is used: the temperature is uniformly increased from 60℃ to 120℃ at a rate of 0.5℃ / min, with segmented temperature holding to completely remove the solvent. After drying, a single homogeneous film with a continuously gradually changing dielectric constant along the thickness direction is directly obtained.

[0051] (3) Preparation of multi-scale dissipative laminar cast films: 100 parts of PI resin were mixed with 25 parts of modified microwave absorbing filler (10 parts of nano-modified ferrite, particle size 30~80nm, aluminate coated + KH-550 activated; 8.75 parts of SiC particles, particle size 0.3~0.8μm, KH-550 activated; 6.25 parts of short-cut pitched carbon fiber, length 10~30μm, KH-550 activated). The mixture was dispersed in steps at high and low speeds: first, SiC particles were added and stirred at 1800 rpm for 40 min; then, nano-ferrite was added and stirred at 2200 rpm for 60 min; finally, short-cut carbon fiber was added at 800 rpm and stirred for 25 min. The viscosity was adjusted to 3200±200 mPa·s with NMP, and the mixture was allowed to stand for 3 hours to defoam. A single die was used to uniformly cast a complete film with an overall thickness of 1.0~2.0 mm.

[0052] (4) Preparation of high-temperature load-bearing matrix layer prepreg: T700 grade aerospace carbon fiber is laid up symmetrically at [0° / ±45° / 90°], impregnated with the same grade of PI resin (homogeneous with the gradient layer and dissipative layer matrix), with a prepreg resin content of 35~40wt%, and is wound up for use after low-temperature pre-drying.

[0053] Step S2: In the mold cavity, the high-temperature load-bearing substrate prepreg, the multi-scale dissipative layer cast film, the gradient absorbing layer continuous gradient film, and the impedance matching layer prepreg are laid in sequence.

[0054] The mold interior is coated with a high-temperature release agent, and the mold cavity is pre-processed with edge diffraction suppression to maintain the complete outline of the configuration (tip arc curvature 0.8~1.5mm, 12°~18° chamfer, side edge strip width 4~6mm, curvature radius 2.0~3.5mm).

[0055] Following the order from the inside out (corresponding to the final structure being laid in reverse order from the outside in): high-temperature load-bearing substrate prepreg, multi-scale dissipative laminar flow film, gradient absorbing continuous gradient film, and outer impedance matching fabric are laid sequentially. Each layer completely covers the entire curved surface of the leading edge, including the leading edge tip and the entire area of ​​the upper and lower flanges. The four layers are simultaneously filled at the ends to fill the cavity arcs, chamfers, and edge diffraction suppression configuration contour areas of the edge strips. After curing, the end-shaping structure is integrally formed without secondary assembly or splicing.

[0056] Step S3: After mold closing, inert gas is introduced to replace the air in the mold cavity, and segmented heating and curing are performed.

[0057] After the mold is closed and locked, high-purity nitrogen is introduced to replace the air in the mold cavity, stabilizing the oxygen content to <100ppm and providing continuous nitrogen protection. A segmented heating curve is executed: the temperature is increased at 1~2℃ / min to 170~190℃ and held for 40~80min (in this embodiment, the temperature is increased at 1.5℃ / min to 180℃ and held for 60min to remove small molecule volatiles); then the temperature is increased at 0.5~1.5℃ / min to the peak curing temperature of 300~320℃ (in this embodiment, the temperature is increased at 1℃ / min to the peak temperature of 310℃), and a molding pressure of 1.8~2.2MPa is applied (in this embodiment, the overall molding pressure is 2.0MPa, with local pressure applied to the leading edge tip to 2.1MPa), and the temperature and pressure are maintained for 4~5h (in this embodiment, the temperature and pressure are maintained at 310℃ for 4.5h) to complete co-curing.

[0058] Step S4: After cooling to 60~80℃, demold and trim the edges to obtain an integrated conformal leading edge stealth structure.

[0059] The temperature is slowly reduced to 60-80℃ at a rate of 0.5-1.0℃ / min (75℃ in this embodiment at a rate of 0.8℃ / min), and ventilation is stopped. The mold is then opened and the complete leading edge component is removed. The forming flash is removed by grinding to obtain an integrated conformal leading edge stealth structure.

[0060] Step S5: Post-processing and performance testing After grinding to remove the forming flash, a full set of tests were carried out in sequence: ultrasonic C-scan was used for interlayer non-destructive testing, and there were no delamination interfaces inside the gradient absorbing layer and no voids or delamination defects in the whole component; the dielectric constant of the gradient layer was tested at multiple points along the thickness, and the value was linearly smooth from 3.2 to 6.5; the average value of the interlayer shear strength (ILSS) was 78 MPa, which meets the design threshold of ≥68 MPa; after completing 50 cycles of thermal shock from -50 ℃ to 400 ℃, a re-inspection was carried out, and there was no filler segregation or interface cracking and delamination in the gradient layer and dissipation layer; finally, the RCS of the entire frequency band from 0.3 to 18 GHz and the high temperature mechanical properties at 400 ℃ were tested, and all indicators met the design requirements of the standard leading edge.

[0061] Example 2 (High-speed, high-temperature enhanced type) Based on Example 1, the design was optimized as follows: the proportion of high-temperature resistant matrix resin was increased, the thickness of the gradient absorbing layer was increased to 2.5~3.5mm, the curvature of the leading edge and the chamfered configuration were optimized to enhance the diffraction suppression effect, and the ratio of multi-scale absorbing units was fine-tuned to improve high-temperature electromagnetic stability; the radius of curvature of the leading edge tip was optimized to 1.0~2.0 mm, and the radius of curvature of the side edge strips was 2.0~3.5mm, further improving the high-temperature structural stiffness and thermal stress adaptability; the four functional layers still completely cover the entire curved surface of the leading edge. The molding process and testing conditions are completely consistent with those of Example 1.

[0062] Performance test results: Under long-term hot service at 400℃, the structural dimensions, interlayer bonding and stealth performance remain stable; the critical frontal view RCS of the aircraft is ≤-18dB; the scattering consistency at ±60° angles is good, with no local strong scattering peaks; after 50 cycles of thermal shock, there are no defects at the interface; the mechanical properties under high-temperature conditions remain stable, meeting the long-term and stringent service requirements of high-speed aircraft.

[0063] Comparative Example 1 (Conventional solid metal leading edge) This comparative example uses a conventional aerospace aluminum alloy integral machined solid leading edge structure, without the four-layer composite stealth functional layer with full coverage (no impedance matching layer, gradient absorbing layer, multi-scale dissipation layer), and without an integrated end diffraction suppression configuration. The test conditions are completely consistent with those of Example 1.

[0064] Performance test results: The overall RCS is not reduced, and the strong specular reflection characteristics are significant; there is no broadband absorption loss capability, and the scattering level rises sharply when incident at a large angle, and it does not have broadband omnidirectional stealth capability; the metal thermal deformation is obvious at 400℃, and the aerodynamic shape accuracy is greatly reduced.

[0065] Comparative Example 2 (Front edge of conventional surface absorbing coating) This comparative example uses a common glass fiber composite matrix, with only a commercial conventional microwave absorbing coating (nominal temperature resistance upper limit 200℃) applied locally on the outer surface. It cannot achieve full coverage, and has no continuous gradient microwave absorbing layer, no multi-scale synergistic dissipation layer, and no tip + side edge integrated geometric suppression configuration. The test conditions are the same as those in Example 1.

[0066] Performance test results: The effective absorption bandwidth is narrow, and the absorption effect in the low frequency band of 0.3~2GHz is extremely poor; the coating cannot completely cover the curved surface, resulting in multiple stealth blind spots. Under large-angle incident light, the RCS rises rapidly, and the angle effect is prominent; under a 400℃ aerodynamic heating environment, the coating cracks, blisteres, peels off, and fails at the interface, with the overall stealth performance decreasing by more than 20%; the bonding force between the coating and the substrate is weak, with an interlayer shear strength of only about 45MPa. It is prone to local delamination after thermal shock, resulting in a short service life.

[0067] The performance testing methods of this invention mainly include the following: Radar Cross Section (RCS) Test: A microwave anechoic chamber compact field test system was used, with a test frequency band of 0.3~18GHz and an incident angle coverage of ±60°. The test was conducted in accordance with the relevant RCS test specifications for military aircraft. Each test condition was repeated 5 times and the average value was taken. The data error was <0.5dB.

[0068] High-temperature thermal stability test: The sample was thermally aged at a constant temperature of 400℃ for 100h. The RCS attenuation amplitude and electromagnetic performance stability of the whole frequency band before and after aging were compared. The presence of cracks and delamination between layers was detected, and the amount of thermal deformation was measured.

[0069] Mechanical performance testing: Based on the mechanical testing standards for aerospace composite material structures, key mechanical indicators such as tensile strength, flexural strength, elastic modulus, and interlaminar shear strength of the structure are tested.

[0070] Angular scattering consistency test: RCS values ​​were tested at typical incident angles of 0°, ±30°, and ±60°, and the RCS fluctuation amplitude was statistically analyzed across the entire angular range.

[0071] Interlayer interface reliability testing: After a high-temperature thermal shock cycle test of 50℃~400℃ (50 cycles), visual inspection and ultrasonic C-scan non-destructive testing were used to observe the integrity of the bonding between functional layers and whether there were any cracks or delamination defects on the surface.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wing leading edge all-frequency omnidirectional stealth structure, characterized in that: The composite material consists of four layers: an impedance matching layer, a gradient absorbing layer, a multi-scale dissipation layer, and a high-temperature load-bearing matrix layer, laid sequentially from the outside to the inside. The four layers are integrated and co-cured, with continuous impedance transition between layers, forming a conformal streamlined overall structure that adapts to the aerodynamic shape of the leading edge. The impedance matching layer, gradient absorbing layer, multi-scale dissipation layer, and high-temperature load-bearing matrix layer completely cover the entire aerodynamic surface of the wing leading edge. The four layers extend synchronously to the leading edge tip and the upper and lower side edges and are integrally shaped to form an edge diffraction suppression configuration. The edge diffraction suppression configuration has no independent thickness lay-up and is formed synchronously and integrally by the ends of the four composite materials. The outer surface of the configuration is the aerodynamic surface of the impedance matching layer exposed. The impedance matching layer is a low dielectric constant wave-transparent composite material layer with a thickness of 0.2~0.5mm and an equivalent relative permittivity εr=2.8~3.

2. It is used to achieve impedance matching between the air and the surface of the structure so that the incident radar wave can penetrate into the internal wave-absorbing structure. The gradient absorbing layer is fully covered by the impedance matching layer, forming a continuous, integrated structure without physical layering. The overall thickness is 1.5~3.5mm, and the dielectric constant gradually changes from 3.2 to 6.5 along the thickness direction. The loss tangent gradually changes from 0.08 to 0.

25. The change in dielectric constant between adjacent 0.1mm intervals is ≤0.22, and the impedance difference between adjacent regions is always <20Ω. The multi-scale dissipation layer has a thickness of 1.0~2.0mm and completely covers the leading edge curved surface, forming a homogeneous composite layer. Based on 100 parts by weight of polyimide resin, it contains 25 parts by weight of three types of microwave absorbing fillers, including 10 parts by weight of nano-sized ferrite magnetic powder, 8.75 parts by weight of submicron silicon carbide dielectric particles, and 6.25 parts by weight of micron-sized short-cut pitch-based carbon fiber. The high-temperature load-bearing matrix layer runs through the entire leading edge of the wing. It is made of 400℃-grade high-temperature resistant polyimide carbon fiber composite material with a thickness of 3.0~6.5mm. The carbon fibers are laid up symmetrically in the pattern of [0° / ±45° / 90°].

2. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: The impedance matching layer is made of low dielectric constant quartz fiber reinforced modified epoxy resin composite material, with 3%~5% hollow glass microspheres doped in the matrix, fiber surface density of 120g / m², and fiber layup in [0° / 90°] orthogonal layup; the magnetic permeability of the impedance matching layer is μr≈1.0, and the air-structure interface reflection coefficient is <0.

1.

3. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: The gradient absorbing layer is prepared using a dual-slurry linear flow rate controlled co-casting process. Polyimide resin is used as the matrix, with 8wt% SiC filler on the outer side and 22wt% SiC filler on the inner side. The filler content along the thickness direction satisfies the linear relationship C(x) = 8 + 14·x / D, where C(x) is the filler content at a distance x from the outer surface, D is the total thickness of the gradient absorbing layer, and x is the thickness coordinate from the outer surface. The dielectric constant along the thickness direction satisfies the linear relationship εr(x) = 3.2 + 3.3·x / D.

4. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: In the multi-scale dissipation layer, the nanoscale ferrite magnetic powder has a particle size of 30~80nm and is modified by high-temperature anti-oxidation coating with aluminate; the submicron silicon carbide dielectric particles have a particle size of 0.3~0.8μm; and the micron-sized short-cut pitch-based carbon fibers have a length of 10~30μm. The three types of fillers form multiple coupling synergies through magnetic loss, dielectric loss and interface polarization loss, respectively, to achieve electromagnetic wave energy dissipation and attenuation across the entire frequency band of 0.3~18GHz.

5. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: The high-temperature load-bearing matrix layer has a tensile strength ≥50MPa, a flexural strength ≥75MPa, and an elastic modulus ≥32GPa under long-term service conditions at 400℃, providing stiffness, load-bearing capacity, and high-temperature dimensional stability for the overall structure.

6. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: The edge diffraction suppression configuration has a tapered tip bevel and a side impedance strip. The tapered tip bevel angle is 12°~18°, and the side impedance strip width is 4~6mm and the radius of curvature is 2.0~3.5mm. The configuration deflects the scattering direction through the tapered tip bevel and suppresses the creeping wave through the continuous impedance at the end, achieving stable low RCS characteristics within the ±60° full incident angle range.

7. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: The leading edge tip curvature radius of the wing is 0.8~2.0mm, the relative thickness of the airfoil is 2%~6%, and the overall outer contour curvature is ≤0.05mm. - ¹, The overall thickness ranges from 4.7 to 12.0 mm, and the overall surface density is ≤2.8 kg / m².

8. The wing leading edge all-frequency omnidirectional stealth structure according to claim 1, characterized in that: Under radar frequency bands of 0.3~18GHz, incident angles of ±60°, and service temperatures of 400℃, the overall RCS of the structure is ≤-15dB; after 100h of thermal aging at 400℃, the stealth performance decreases by ≤4%, with no interlayer cracking or delamination and thermal deformation <0.02mm / m; and the RCS fluctuation within the ±60° large-angle incident range is ≤3dB.

9. A method for fabricating a wing leading-edge all-frequency omnidirectional stealth structure, used to fabricate the structure described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Prepare impedance matching layer prepreg, gradient absorbing layer continuous gradient film, multi-scale dissipative layer cast film, and high-temperature load-bearing substrate layer prepreg respectively; The method for preparing the continuous gradient thin film of the gradient absorbing layer is as follows: prepare low-filler slurry A and high-filler slurry B, with SiC filler content of 8wt% in slurry A and 22wt% in slurry B. Use a dual-slurry linear flow rate control co-casting process, and linearly adjust the flow rate ratio of the two material bins to switch the slurry from 100% slurry A / 0% slurry B to 0% slurry A / 100% slurry B. After dynamic mixing in the die head, the film is cast and dried in segments to obtain a single homogeneous thin film with a continuously gradually changing dielectric constant along the thickness direction. S2: In the mold cavity, high temperature bearing substrate prepreg, multi-scale dissipative layer cast film, gradient absorbing layer continuous gradient film, and impedance matching layer prepreg are laid in sequence. Each layer completely covers the entire curved surface of the leading edge, and the end is simultaneously filled with the cavity edge diffraction suppression configuration contour area. S3: After mold closing, inert gas is introduced to replace the air in the mold cavity, and segmented temperature rise curing is performed: the temperature is increased to 170~190℃ at 1~2℃ / min and held for 40~80min, then the temperature is increased to the peak curing temperature of 300~320℃ at 0.5~1.5℃ / min, the molding pressure is applied at 1.8~2.2MPa, and the temperature and pressure are kept constant for 4~5h to complete co-curing; S4: After cooling to 60~80℃, demold and trim the edges to obtain an integrated conformal leading edge stealth structure.

Images