Carbon-based superstructure integrated with wave-absorbing stealth and electric heating deicing and preparation method thereof

Abstract

The application discloses a carbon-based superstructure integrated with wave-absorbing stealth and electric heating deicing and a preparation method thereof, and belongs to the field of functional composite materials and aerospace stealth technology. The carbon-based superstructure comprises a substrate layer and a periodic array structure on the top surface of the substrate layer. The periodic array structure comprises a plurality of superstructure units. Each superstructure unit comprises a cylindrical dielectric layer and a circular-truncated-cone wave-absorbing layer which are alternately stacked from bottom to top, and the two are alternately stacked to form a multi-stage impedance gradient junction. The application combines machine learning to accurately optimize the geometric parameters of each layer in the superstructure unit, so that the superstructure realizes efficient wave absorption in a super-wide frequency range of 2-40 GHz (the bandwidth of the reflection loss lower than -20 dB is significantly widened), and still maintains excellent stealth performance under large-angle incidence (greater than 45 degrees). Meanwhile, the superstructure has efficient and rapid electric heating deicing capacity, and solves the problems that the traditional aviation materials are difficult to be compatible with stealth and deicing functions, and have poor large-angle stealth performance.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials and aerospace stealth technology, specifically relating to a carbon-based superstructure that integrates wave absorption stealth and electrothermal de-icing, and its preparation method. Background Technology

[0002] With the rapid development of modern aerospace technology, the survivability of aircraft in complex environments and the safety of all-weather operation have become core research focuses. On the one hand, in order to reduce the probability of being detected by enemy radar, aircraft must possess excellent low observability, i.e., stealth performance, which usually requires minimizing the radar cross section (RCS) of the fuselage. On the other hand, during high-altitude, high-temperature, or cross-medium flight, critical components such as wings and air intakes are highly susceptible to icing, severely disrupting aerodynamic shape, increasing drag, and even causing loss of lift. Therefore, an efficient anti-icing system is a necessary condition for ensuring flight safety.

[0003] However, achieving compatibility between stealth and de-icing functions within the existing technological system faces severe physical challenges, primarily manifested in the following aspects: First, the inherent contradiction in the physical properties of the functional layer: Traditional aircraft de-icing systems often employ metal-based electrothermal components (such as metal mesh or foil) or aerodynamic de-icing boots. Metal materials possess extremely high electrical conductivity, resulting in high electrothermal conversion efficiency, but electromagnetically they act as strong reflectors of electromagnetic waves. When applied to the fuselage surface, they significantly disrupt the aircraft's impedance matching characteristics, leading to total radar reflection and drastically increasing the radar cross-section (RCS), thus rendering stealth ineffective. Conversely, traditional radar-absorbing materials typically dissipate electromagnetic waves using magnetic or dielectric loss mechanisms, exhibiting generally poor electrical and thermal conductivity, making them unsuitable for direct use as efficient heating elements. This inherent material property conflict between "conductivity" and "stealth" means that traditional "superimposed" designs (i.e., covering the de-icing layer with a radar-absorbing layer) not only significantly increase structural thickness and weight, reducing the aircraft's payload, but also fail to fundamentally solve the electromagnetic compatibility problem. Secondly, there are limitations to broadband and large-angle stealth: Existing radar-absorbing structures (such as Salisbury screens and Jaumann layers) typically only achieve resonant absorption at a single frequency or within a narrow frequency band, making it difficult to meet the demands of modern battlefields for ultra-wideband stealth (such as coverage of multiple bands including S, C, X, Ku, K, and Ka). Furthermore, traditional metamaterial designs are often highly sensitive to the incident angle of electromagnetic waves. When radar waves are incident at large angles (e.g., greater than 45°), the absorption performance deteriorates sharply due to the disruption of impedance matching conditions, making all-around stealth protection impossible. Thirdly, there are bottlenecks in traditional design and manufacturing methods: While the electromagnetic response of novel metamaterials can be controlled through artificial microstructure design, their structures are becoming increasingly complex. Traditional trial-and-error design relies on researchers' experience and numerous repeated experiments, making it difficult to quickly find the globally optimal solution that balances lightweight, broadband absorption, and mechanical properties within a multi-dimensional parameter space (such as the number of layers, shape, size, and dielectric constant). Meanwhile, traditional subtractive manufacturing or mold forming processes are difficult to prepare periodic arrays with complex three-dimensional topological structures in a low-cost and rapid manner.

[0004] In summary, there is an urgent need to develop a novel, multifunctional, integrated material that can unify dielectric loss and Joule heating effects from a physical mechanism perspective. The structural designability achieved through additive manufacturing (3D printing) technology, combined with the efficient reverse design capabilities of machine learning, allows for the construction of carbon-based superstructures with impedance gradient characteristics. This is a key technological approach to solving the aforementioned "stealth-de-icing" compatibility problem and achieving wide-angle, broadband stealth capabilities. Summary of the Invention

[0005] To address the problems of narrow bandwidth, incompatibility between stealth and de-icing functions, and poor stealth performance at large angles of incidence in existing technologies, this invention aims to provide a carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing, along with its fabrication method. Based on the properties of nylon (PA) and chopped carbon fiber (CF), and utilizing the designability of carbon fiber composites, this invention achieves synergistic effects of large-angle broadband stealth and efficient de-icing through alternating stacking of multi-level frustums / cylinders, laser post-processing, and optimization using 3D printing and machine learning.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing comprises a substrate layer and a periodic array structure located on the top surface of the substrate layer; the periodic array structure comprises a plurality of superstructure units; wherein: The substrate layer (LI-PACF layer) is formed by high-energy beam scanning-induced treatment of a composite material base plate composed of nylon and short-cut carbon fibers, and serves as an electromagnetic wave reflection boundary and an electrothermal de-icing layer. The sheet resistance of the substrate layer is the key to balancing electrothermal efficiency and electromagnetic reflection characteristics. In this invention, the sheet resistance of the LI-PACF layer after high-energy beam treatment is controlled between 50 Ω / sq and 200 Ω / sq, more preferably between 60 Ω / sq and 100 Ω / sq. The superstructure unit comprises several alternating cylindrical dielectric layers and frustum-shaped absorbing layers, stacked from bottom to top. The diameter of the cylindrical dielectric layers decreases with increasing distance from the substrate. The bottom and top diameters of the frustum-shaped absorbing layers are the same as the diameters of their adjacent cylindrical dielectric layers. In other words, the superstructure unit exhibits a macroscopic "geometric tapered" structure, with the top layer having the smallest diameter, resulting in the lowest "effective fill factor" and its average dielectric constant being closest to the impedance of free space (air). This allows incident electromagnetic waves to penetrate the material to the maximum extent possible, rather than being reflected back at the surface. As the bottom diameter gradually increases, the effective dielectric constant and loss capability of each layer increase progressively. This smooth gradient design helps electromagnetic waves of different wavelengths to be efficiently dissipated at different depths. The cylindrical dielectric layer is made of nylon, referred to as the N-PA layer; the frustum-shaped absorbing layer is made of a composite material of nylon and chopped carbon fibers, referred to as the PACF layer. The superstructure unit provided by this invention forms a multi-level impedance gradient structure through the alternating stacking of N-PA and PACF layers. Specifically, the PACF layer acts as an electromagnetic wave loss layer, utilizing the inherent dielectric loss characteristics of carbon fibers through the doping of chopped carbon fibers to convert the electromagnetic wave energy entering the material into heat energy for dissipation. The N-PA layer acts as an impedance adjustment layer; pure nylon material has a low dielectric constant and loss, similar to the electromagnetic properties of air. By using the N-PA layer to separate the PACF layer, a stepped impedance change is constructed at the microscopic level. An electromagnetic channel is artificially constructed that smoothly transitions from "air characteristics" to "strong absorption characteristics," so that electromagnetic waves, during downward propagation, not only do not encounter abrupt reflection interfaces but are also gradually "induced" to penetrate deeper and absorbed step-by-step by the PACF layer in each alternation of layers, thus achieving extremely low reflection loss at ultra-wide bandwidths and large incident angles. Omitting the N-PA layer in the stacked structure leads to impedance mismatch and enhanced reflection. The pure PACF structure only resonates and absorbs at specific frequencies, unlike the alternating structure which can achieve continuous impedance matching across an ultra-wide frequency range of 2-40 GHz, resulting in a significant reduction in the effective absorption bandwidth (EAB). The insertion of the N-PA layer allows electromagnetic waves to penetrate deeper into the structure more smoothly, which is key to achieving "multi-level impedance gradients".

[0008] As a preferred technical solution, the mass fraction of chopped carbon fibers in the composite material composed of nylon and chopped carbon fibers is between 5 wt% and 30 wt%. The minimum value of 5 wt% ensures that the carbon fibers reach the electroosmotic threshold within the nylon matrix, forming an effective conductive path. Below this value, the material's conductivity is insufficient, failing to generate enough Joule heat for de-icing, and its dielectric loss is too low to effectively absorb electromagnetic waves. The maximum value of 30 wt% avoids excessive conductivity leading to total internal reflection (metallic properties) on the material surface, disrupting impedance matching and thus losing its stealth function. Simultaneously, limiting the filler content ensures the melt flow of the composite filament during FDM printing, preventing nozzle clogging and embrittlement of the printed parts.

[0009] As a preferred technical solution, the nylon is at least one of polyamide 6 (PA6), polyamide 66 (PA66), polyamide 11 (PA11), and polyamide 12 (PA12).

[0010] As a preferred technical solution, the high-energy beam is a laser beam, an electron beam, or an ion beam. Further, the high-energy beam is preferably a CO2 laser; the processing parameters of the CO2 laser are: wavelength of 10.6 μm or 9.3 μm, power of 10-30 W, pulse frequency of 5-20 kHz, focal length of 1-50 cm, and laser scanning speed of 100-400 mm / s.

[0011] As a preferred technical solution, based on finding a critical balance between the contradictory goals of 'wideband absorption' and 'lightweight / low thickness', this invention designs the total number of cylindrical dielectric layers and frustum-shaped absorbing layers in the superstructure unit to be four to ten layers. If the number of layers is too small, the interlayer impedance gradient will be too large, leading to enhanced low-frequency reflection and the bandwidth will not be able to cover 2-40GHz; if the number of layers is too large, the structural thickness and weight will exceed the optimal threshold for aerospace applications. More preferably, the total number of cylindrical dielectric layers and frustum-shaped absorbing layers in the superstructure unit is six layers, defined from bottom to top as layer one, layer two, layer three, layer four, layer five, and layer six. The diameter of layer one is 15 mm, the diameter of layer three is 9 mm to 13 mm, the diameter of layer five is 5 mm to 9 mm, and the diameter of the top surface of layer six is ​​2 mm to 4 mm. The height of each cylindrical dielectric layer in the superstructure unit is 1 mm; the height of each frustum-shaped absorbing layer is 2 mm to 6 mm.

[0012] As a preferred technical solution, both the cylindrical dielectric layer and the frustum-shaped microwave absorbing layer in the superstructure unit are 3D printed using a fused deposition modeling (FDM) process. Preferably, the specific parameters of the 3D printing process are: a printing nozzle diameter of 0.2 mm to 0.8 mm; a layer height of 0.1 mm to 0.5 mm; a printing speed of 10 mm / s to 100 mm / s; a hot-end nozzle temperature of 250 ℃ to 300 ℃ during printing; and a printer heated bed temperature of 50 ℃ to 80 ℃.

[0013] This invention also provides a method for preparing the aforementioned carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing, comprising the following steps: We offer pure nylon materials, as well as composite materials made of nylon and chopped carbon fibers; Using fused deposition modeling 3D printing technology, a composite material base plate was printed using a composite material composed of nylon and chopped carbon fiber as raw material. On the top surface of the composite material base plate, cylindrical dielectric layers and frustum-shaped wave-absorbing layers are alternately printed using fused deposition modeling 3D printing technology to form a superstructure unit, and finally a periodic array structure is obtained. The composite material substrate is scanned using a high-energy beam to induce carbonization / graphitization on its surface, forming a three-dimensional conductive network composed of amorphous carbon and short-cut carbon fibers stacked and interconnected. This significantly improves its conductivity to achieve Joule heating de-icing function and electromagnetic wave lossy reflection function, forming a base layer.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention achieves the structural integration of electromagnetic stealth and electrothermal de-icing functions, solving the problem of incompatibility between traditional discrete systems. In the prior art, the high reflectivity of metal electrothermal de-icing components can compromise the stealth effect, while traditional radar-absorbing materials typically lack de-icing capabilities. This invention utilizes the multiple physical properties of carbon fiber, on the one hand, using its dielectric loss characteristics to dissipate radar waves, and on the other hand, using the conductive network formed after laser-induced treatment to generate Joule heating. This design eliminates the dependence on metal heating elements and avoids additional electromagnetic reflection.

[0015] (2) Traditional absorbing materials (such as single-layer coatings or Salisbury screens) typically rely on the quarter-wavelength resonance effect, producing destructive interference only at specific frequencies (or harmonics), resulting in a narrow absorption bandwidth. This invention overcomes this problem by designing an alternating stacked structure of cylindrical dielectric layers and frustum-shaped absorbing layers (hereinafter referred to as the "frustum / cylindrical" structure) to construct a gradient impedance gradient frequency response system. Specifically: First, based on the equivalent dielectric theory, the top layer of the structure adopts a frustum design with the smallest diameter, resulting in the lowest effective volume fill rate at that location, and its equivalent wave impedance is highly matched with free space (air). This design effectively constructs a broadband impedance matching interface, maximally suppressing the direct reflection (i.e., specular reflection) of high-frequency short-wavelength electromagnetic waves on the material surface, ensuring that electromagnetic energy can be smoothly coupled into the interior of the structure. Second, along the thickness direction, a fine stepped impedance gradient structure is constructed by alternating stacks of low-dielectric-loss pure nylon (N-PA) layers and high-dielectric-loss carbon fiber composite (PACF) layers. In this structure, the N-PA layer acts as an impedance modulation medium, smoothing out abrupt impedance changes between layers and preventing secondary reflections of electromagnetic waves at the internal interfaces. This design creates a frequency-graded response mechanism: high-frequency electromagnetic waves with shallow penetration depth are rapidly dissipated in the shallow PACF layer of the structure, while low-frequency electromagnetic waves with stronger penetration are guided to the deeper layers and bottom of the structure for cumulative absorption. The synergistic effect of these mechanisms ultimately achieves continuous strong absorption in the ultra-wide frequency range of 2-40 GHz.

[0016] (3) Traditional metamaterials (such as open resonant rings and polygonal steps) often have specific directions. When the incident angle increases (>30°) or the polarization direction changes, the equivalent electromagnetic parameters will change drastically, leading to impedance mismatch. The "frustum / cylinder" structure selected in this invention has infinite rotational symmetry. No matter how the electric field vector (E field) of the electromagnetic wave rotates (TE mode or TM mode), the geometric cross section of the structure remains unchanged. This makes the structure insensitive to the polarization direction of the electromagnetic wave, ensuring performance stability in complex electromagnetic environments. At the same time, the side slope of the frustum itself constitutes a geometric surface that is friendly to obliquely incident waves, reducing lateral scattering. Therefore, even when the incident angle is large, the internal impedance matching conditions of the structure can still be maintained. This invention breaks through the bottleneck of narrow bandwidth and failure at large angles of traditional absorbing structures, and realizes strong absorption with ultra-wide bandwidth and wide angle. Thanks to the unique frustum / cylinder structure and the fine impedance gradient design, the superstructure optimized in this invention exhibits excellent absorption performance in the ultra-wide frequency range of 2-40 GHz. In particular, this structure effectively extends the strong absorption bandwidth to below -20 dB (i.e., absorption rate >99%), significantly outperforming the conventional -10 dB standard. Furthermore, under large-angle oblique incidence conditions with an incident angle greater than 45°, this structure still maintains a wide effective absorption bandwidth and stable stealth performance.

[0017] (4) This invention introduces a multi-model competition mechanism and machine learning optimization to achieve efficient optimization of complex superstructure designs. This invention abandons the traditional trial-and-error method and innovatively introduces four models—Random Forest (RF), XGBoost, CatBoost, and Multilayer Perceptron (MLP)—for game-based selection. By comprehensively comparing the structural parameters optimized by different models, while ensuring "lightweight (low thickness, low mass)," a globally optimal balance between absorption bandwidth (especially EAB < -20 dB) and large-angle stability is achieved, significantly shortening the material development cycle.

[0018] (5) The present invention adopts the manufacturing process of "3D printing + high-energy beam processing", which is simple, low-cost and highly controllable. The present invention utilizes fused deposition modeling (FDM) technology to quickly and cost-effectively manufacture periodic arrays with complex three-dimensional topological structures; and the composite material system of nylon and chopped carbon fiber has good processing adaptability. Among them, the PA matrix provides a continuous rheological basis for the high-filling composite system due to its excellent melt flowability and polar wetting ability; while the chopped carbon fiber not only meets the passability requirements of the FDM micro nozzle, but also solves the problem of easy warping and poor precision of pure nylon printing by improving the thermal conductivity of the system and inhibiting crystallization shrinkage; the synergistic effect of PA and chopped carbon fiber gives the PACF composite material excellent FDM process adaptability, enabling it to stably prepare high-precision complex three-dimensional superstructures. Meanwhile, by utilizing the in-situ induction technology of high-energy beam (CO2 laser), there is no need to coat additional conductive coatings or embed resistance wires. The sheet resistance and heating power of the underlying layer can be precisely controlled simply by adjusting the laser parameters, thus achieving precise customization of material surface functionalization, which is suitable for large-scale industrial preparation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing in Example 1; Figure 2 This is a structural diagram of a superstructure unit; Figure 3 This is a schematic diagram of the overall preparation process of the carbon-based superstructure in Example 1; Figure 4 This is a comparison of the reflection loss curves of the optimal structure predicted by the four machine learning models (RF, XGBoost, CatBoost, MLP) used in Example 2 and Comparative Example 1 of this invention when electromagnetic waves are incident vertically from directly above.

[0020] Figure 5 This is a physical image of the optimal structure from Example 2, prepared by 3D printing.

[0021] Figure 6 The reflection loss in Example 2 (the optimal structure after MLP optimization) in the 2-40 GHz range under two polarization modes with different incident angles (0-75°) is shown.

[0022] Figure 7 The images show the electrothermal heating curves of the LI-PACF base plate under different voltage conditions and the optical and infrared thermal images of the de-icing process under 25 V voltage in Example 2 (the optimal structure after MLP optimization).

[0023] Figure 8This is a comparison of the microstructure of the substrate surface before and after laser-induced treatment in Example 2 (the optimal structure after MLP optimization).

[0024] Figure 9 The reflection loss of the product prepared for Comparative Example 2 when electromagnetic waves are incident at an angle of 0° (directly above).

[0025] Figure 10 This is a performance comparison chart between the product prepared in Comparative Example 3 and the product prepared in Example 2.

[0026] Reference numerals: 100-substrate layer, 200-superstructure unit, 21-cylindrical dielectric layer, 22-frustum-shaped absorbing layer, 201-first layer, 202-second layer, 203-third layer, 204-fourth layer, 205-fifth layer, 206-sixth layer. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the following embodiments will help those skilled in the art to further understand the embodiments of this invention, but do not limit the embodiments of this invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the embodiments of this invention. These all fall within the protection scope of the embodiments of this invention.

[0028] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail.

[0029] Example 1 refer to Figure 1 A carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing is disclosed, comprising a substrate 100 and a periodic array structure on the top surface of the substrate 100; the periodic array structure comprises several superstructure units 200; the substrate 100 is a composite material base plate composed of nylon and chopped carbon fibers, formed by high-energy beam scanning induction treatment; the superstructure unit 200 comprises several cylindrical dielectric layers 21 and frustum-shaped microwave absorbing layers 22 alternately stacked from bottom to top, the diameter of the cylindrical dielectric layers 21 decreasing with increasing distance from the substrate; the diameter of the lower and upper surfaces of the frustum-shaped microwave absorbing layers 22 are the same as the diameter of their adjacent cylindrical dielectric layers; the cylindrical dielectric layers are made of nylon; the frustum-shaped microwave absorbing layers are made of a composite material composed of nylon and chopped carbon fibers.

[0030] In a preferred embodiment, the mass fraction of chopped carbon fibers in the composite material composed of nylon and chopped carbon fibers is 5 wt% to 30 wt%. Specifically, the mass fraction of chopped carbon fibers can be 5 wt%, 10 wt%, 20 wt%, or 30 wt%, etc., and those skilled in the art can make appropriate selections as needed.

[0031] refer to Figure 2 In this embodiment 1, the total number of cylindrical dielectric layers and frustum-shaped absorbing layers in the superstructure unit is designed to be six layers, defined from bottom to top as layer 201, layer 202, layer 203, layer 204, layer 205, and layer 206; wherein: the base layer 100 is square, with dimensions of 16 mm × 16 mm and a thickness of 1 mm; the diameter of layer 201 is 15 mm and the height is 1 mm; the diameter of layer 202 is 15 mm at the bottom, with a top diameter ranging from 9 mm to 13 mm and a height ranging from 2 mm to 6 mm; the diameter of layer 203 is 9 mm to 13 mm and the height is 1 mm; the bottom diameter of layer 4 is 9 mm to 13 mm, with a top diameter ranging from 5 mm to 9 mm and a height ranging from 2 mm to 6 mm; the diameter of layer 5 is 5 mm to 9 mm and the height is 1 mm; the bottom diameter of layer 6 is 5 mm to 9 mm and the top diameter ranges from 2 mm to 6 mm. The values ​​for the height range from 2 mm to 6 mm.

[0032] It should be noted that six layers in the superstructure unit in Embodiment 1 is preferred. Similar purposes can be achieved when the total number of layers is other. Those skilled in the art can select and set the number of layers from four to ten as needed.

[0033] Example 2 The fabrication method of the carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing as described in Example 1 is illustrated in the flowchart below. Figure 3 This includes the following steps: (1) Preparation of 3D printing filament: 400 g of dried nylon 6 (PA6) granules and 100 g of chopped carbon fibers (average length 500 μm, average diameter 10 μm) were mixed evenly in a high-speed mixer, wherein the mass fraction of chopped carbon fibers was 20 wt%. The mixture was added to a twin-screw extruder and vacuum melt-blended for 30 min at a temperature range of 230-250 ℃, and then pelletized. Subsequently, the composite masterbatch was melt-extruded again through a single-screw extruder and drawn into nylon / short carbon fiber composite filaments (PACF) with a diameter of 1.75 mm ± 0.05 mm. The extrusion temperature of the single-screw extruder was set as follows: zone 1 temperature 135 ℃, zone 2 temperature 285 ℃, zone 3 temperature 275 ℃, zone 4 temperature 245 ℃, the inner diameter of the extrusion die of the single-screw extruder was 2.0 mm, and the screw speed was 30 rpm / min. The tracked traction device has a traction speed of 3 m / min, and the temperature of the controllable constant-temperature cooling water bath is 30 ℃. (No short-cut carbon fiber is needed in the pure nylon 6 (N-PA) printing filament preparation process; all other steps are the same.) (2) Design and derivation of the structural model: Based on the six-layer superstructure unit model proposed in Example 1, a dataset of geometric parameters (diameter, height) and electromagnetic performance (effective absorption bandwidth EAB) was established using CST2022 simulation software. The multilayer perceptron (MLP) algorithm was used for training and optimization to maximize the bandwidth with reflection loss less than -20dB and the stability at large angles of incidence. The optimal geometric parameters of the superstructure unit were obtained as follows: Base layer (LI-PACF): length 16 mm × width 16 mm × thickness 1 mm; First layer 201: diameter = 15 mm, height = 1 mm; Second layer 202: bottom diameter = 15 mm, top diameter = 9 mm, height = 3.5 mm; Third layer 203: diameter = 9 mm, height = 1 mm; Fourth layer 204: bottom diameter = 9 mm, top diameter = 5 mm, height = 3.65 mm; Fifth layer 205: diameter = 5 mm, height = 1 mm; Sixth layer 206: bottom diameter = 5 mm, top diameter = 3 mm, height = 2 mm.

[0034] (3) Integrated 3D Printing: A dual-nozzle fused deposition modeling (FDM) 3D printer was used, with PACF filament and N-PA filament loaded separately. The above-mentioned optimal model was imported, and the printing process parameters were set as follows: nozzle diameter 0.4 mm, layer height 0.2 mm, printing speed 30 mm / s, hot-end nozzle temperature for PACF filament 280 ℃, hot-end nozzle temperature for N-PA filament 250 ℃, and heated bed temperature 60 ℃. A periodic array structure was printed in an integrated manner from bottom to top.

[0035] (4) High-energy beam-induced functionalization: The printed structure was placed on the worktable of a CO2 laser marking machine, and the focal length was adjusted to 20 cm. The laser process parameters were set as follows: wavelength 10.6 μm, power 25 W, pulse frequency 20 kHz, and scanning speed 200 mm / s. The surface of the bottom PACF board was scanned by a raster to induce the formation of a LI-PACF conductive layer in situ, forming the substrate layer and obtaining the final integrated superstructure sample.

[0036] Comparative Example 1: The preparation method of this comparative example is the same as that of Example 2. The only difference between this example and Example 2 is that the Random Forest (RF) algorithm, XGBoost algorithm, and CatBoost algorithm are used for training and optimization, respectively.

[0037] Figure 4 This is a comparison of the reflection loss curves under full-wave simulation between the optimal structure optimized by the MLP model in Example 2 and the optimal structures predicted by the other three machine learning models (RF, XGBoost, CatBoost) in Comparative Example 1. Calculations and statistics show: The optimal structure optimized by the MLP model has an effective absorption bandwidth of less than -10 dB (EAB < -10 dB) in the 2-40 GHz frequency range, accounting for 88.38% of the total, and an effective absorption bandwidth of less than -20 dB (EAB < -20 dB) in the remaining 56.20% of the total. The optimized RF model, after optimization, shows that 84.01% of the structures have an effective absorption bandwidth of less than -10 dB (EAB < -10 dB) in the 2-40 GHz frequency range, and 38.13% have an effective absorption bandwidth of less than -20 dB (EAB < -20 dB). The optimal structure after XGBoost model optimization was calculated to have an effective absorption bandwidth of less than -10 dB (EAB < -10 dB) in the 2-40 GHz frequency range, accounting for 89.30% and 50.87% of the effective absorption bandwidth of less than -20 dB (EAB < -20 dB).

[0038] The optimal CatBoost model, after optimization, shows that 84.17% of the structures have an effective absorption bandwidth of less than -10 dB (EAB < -10 dB) in the 2-40 GHz frequency range, and 35.84% have an effective absorption bandwidth of less than -20 dB (EAB < -20 dB).

[0039] The results above demonstrate that the optimal structure optimized by the MLP model has excellent broadband strong absorption performance, and its overall performance is superior to the optimal structures of the other three machine learning models in Comparative Example 1. Figure 5The image shows the physical product of the optimal structure of Example 2 prepared by 3D printing. It can be seen that there are several superstructure units arranged periodically on the base layer.

[0040] Figure 6 Figure (a) shows the reflection loss of the product prepared in Example 2 in the 2-40 GHz range under different incident angles (Theta=0-75°) and TE polarization mode. Figure (b) shows the reflection loss in the 2-40 GHz range under different incident angles (0-75°) and TM polarization mode. It can be seen that the designed superstructure can still maintain a wide effective absorption bandwidth and stable stealth performance under large incident angles. When the incident angle is 75°, the proportion of effective absorption bandwidth less than -10 dB (EAB<-10 dB) in the 2-40 GHz range under TE and TM polarization modes still exceeds 72%.

[0041] Figure 7 Figure (a) shows the electrothermal heating curves of the LI-PACF substrate under different voltage conditions in Example 2, and Figure (b) shows the optical and infrared thermal images of the de-icing process (de-icing times of 0s, 30s, and 60s) under a voltage of 25 V. It can be seen that the LI-PACF substrate exhibits excellent electrothermal conversion characteristics. Under different DC bias driving conditions, the surface exhibits a rapid thermal response rate and good thermal equilibrium stability. Thanks to the highly conductive network constructed by laser processing, rapid thermal removal of the iced surface can be achieved within a safe voltage range without the need for a high-voltage power supply.

[0042] Figure 8 The images show a comparison of the microstructure of the substrate surface before and after high-energy beam-induced treatment in Example 2, where (a) shows the surface before high-energy beam-induced treatment and (b) shows the surface after treatment. As can be seen from the images, high-energy beam-induced treatment using a laser induces a rapid photothermal ablation process. Due to the significant difference in thermodynamic properties between the nylon matrix and the carbon fiber, the PA6 matrix decomposes and vaporizes. This process effectively removes the surface insulating layer, exposing the underlying chopped carbon fibers and forming a tightly packed and interconnected three-dimensional conductive network. Furthermore, the localized high temperature promotes the in-situ carbonization of residual polyamide into amorphous carbon. These carbonization products act as conductive bridges connecting adjacent fibers, enabling efficient electrothermal conversion and electromagnetic wave reflection.

[0043] Comparative Example 2: Compared with Example 2, the difference in this comparative example is that the composition of the substrate layer is pure short-cut carbon fiber, that is, it does not contain nylon 6, and it does not undergo high-energy beam-induced functionalization treatment. All other processes are the same as in Example 2.

[0044] Figure 9The reflection loss of the product prepared for Comparative Example 2 when the electromagnetic wave is incident at a 0° angle (directly above). (The curves for TE mode and TM mode are the same when incident at a 0° angle). Figure 9 It can be seen that, according to calculations, the proportion of effective absorption bandwidth less than -10 dB (EAB < -10 dB) in the 2-40 GHz frequency range is 77.16%, which is a decrease of 11.22% compared to Example 2. The proportion of effective absorption bandwidth less than -20 dB (EAB < -20 dB) is 31.97%, which is a decrease of 24.23% compared to Example 2.

[0045] Comparative Example 3: Compared with Example 2, the difference in this comparative example is that the prepared superstructure does not contain an N-PA layer, but consists only of a three-layer PACF frustum structure, while the other processes are the same as in Example 2.

[0046] Figure 10 The figures show a performance comparison between the product prepared in Comparative Example 3 and the product prepared in Example 2. Figures (a) and (b) are Smith charts of the products from Comparative Example 3 and Example 2, respectively. It can be seen that the superstructure without the N-PA layer exhibits significant impedance mismatch in the low-to-mid-frequency band. Figure (c) compares the reflection loss with and without the N-PA layer superstructure. Calculations show that the percentage of products with an effective absorption bandwidth less than -10 dB (EAB < -10 dB) in the 2-40 GHz frequency range is 54.15%, a decrease of 34.23% compared to Example 2. The percentage of products with an effective absorption bandwidth less than -20 dB (EAB < -20 dB) is 5.33%, a decrease of 50.87% compared to Example 2.

[0047] The preferred embodiments of the present invention have been described in detail above, outlining the basic principles, main features, and advantages of the invention. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the above-described embodiments. The embodiments and descriptions in the specification are merely preferred examples of the present invention and are not intended to limit the invention. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the embodiments of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. However, obvious changes or modifications derived therefrom are still within the protection scope of the embodiments of the present invention.

Claims

1. A carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing, characterized in that, It includes a base layer and a periodic array structure located on the top surface of the base layer; the periodic array structure includes several superstructure units; wherein: The base layer is a composite material plate made of nylon and short-cut carbon fiber, which is formed by high-energy beam scanning induction treatment. The superstructure unit comprises several cylindrical dielectric layers and frustum-shaped absorbing layers stacked alternately from bottom to top. The diameter of the cylindrical dielectric layers decreases as the distance from the substrate increases. The diameter of the bottom surface and the diameter of the top surface of the frustum-shaped absorbing layer are the same as the diameter of the adjacent cylindrical dielectric layer. The cylindrical dielectric layer is made of nylon; The frustum-shaped absorbing layer is made of a composite material of nylon and short-cut carbon fiber.

2. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 1, characterized in that, The mass fraction of chopped carbon fibers in the composite material composed of nylon and chopped carbon fibers is 5 wt% to 30 wt%.

3. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 1, characterized in that, The nylon is at least one of polyamide 6, polyamide 66, polyamide 11, and polyamide 12.

4. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 1, characterized in that, The high-energy beam is a laser beam, an electron beam, or an ion beam.

5. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 1, characterized in that, The total number of cylindrical dielectric layers and frustum-shaped absorbing layers in the superstructure unit is four to ten.

6. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 5, characterized in that, The superstructure unit has a total of six layers, including cylindrical dielectric layers and frustum-shaped absorbing layers.

7. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 6, characterized in that, The cylindrical dielectric layer and the frustum-shaped absorbing layer in the superstructure unit are defined from bottom to top as the first layer, the second layer, the third layer, the fourth layer, the fifth layer, and the sixth layer, respectively. The diameter of the first layer is 15 mm, the diameter of the third layer is 9 mm to 13 mm, the diameter of the fifth layer is 5 mm to 9 mm, and the diameter of the top surface of the sixth layer is 2 mm to 4 mm.

8. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 7, characterized in that, The height of each cylindrical dielectric layer in the superstructure unit is 1 mm; the height of each frustum-shaped absorbing layer is 2 mm to 6 mm.

9. The carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing according to claim 1, characterized in that, The cylindrical dielectric layer and the frustum-shaped absorbing layer in the superstructure unit are both fabricated using 3D printing.

10. The method for preparing the carbon-based superstructure integrating microwave absorption stealth and electrothermal de-icing as described in any one of claims 1 to 9, characterized in that, Includes the following steps: We offer nylon materials, as well as composites made of nylon and chopped carbon fibers; Using fused deposition modeling 3D printing technology, a composite material base plate was printed using a composite material composed of nylon and chopped carbon fiber as raw material. On the top surface of the composite material base plate, cylindrical dielectric layers and frustum-shaped wave-absorbing layers are alternately printed using fused deposition modeling 3D printing technology to form a superstructure unit, and finally a periodic array structure is obtained. The composite material substrate is scanned using a high-energy beam, causing the nylon in the substrate to be carbonized in situ into amorphous carbon, forming a three-dimensional conductive network composed of amorphous carbon and short-cut carbon fibers stacked together and interconnected, thus forming the substrate layer.

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