An integrated manufacturing method for frequency selective surfaces with complex curved cavity structures

Abstract

The present invention discloses an integrated method for fabricating a frequency selective surface (FSS) for a complex curved cavity structure. This method utilizes multi-process composite 3D printing as a technical approach, employing FDM technology to fabricate a water-soluble substrate. 3D direct writing technology is then used to create an inner FSS pattern on the substrate surface. The cavity structure itself is then printed on top of the substrate, and an outer FSS pattern is then created on the surface of the cavity structure. The water-soluble substrate is then dissolved, ultimately resulting in a complex curved cavity FSS structure with frequency selective patterns on both the inner and outer surfaces. Furthermore, through the practice of this invention, surface treatment measures are required for the 3D printed structure before fabricating the FSS pattern, improving the quality and precision of the FSS metallization pattern and ensuring the integrated fabrication of the complex curved cavity structure and the inner and outer FSS patterns.

Description

Technical Field

[0001] The present invention belongs to the field of aircraft aerodynamic design and relates to a method for manufacturing a frequency selective surface (FSS), in particular to a method for integrating a frequency selective surface with a complex curved cavity structure. Background Art

[0002] Frequency selective surfaces (FSSs) can be used in radar radomes, aircraft canopies, satellite antennas, and other structures. FSSs consist of one or more patterned metal layers, and the level of frequency selectivity they provide depends in part on the precision with which the patterns are fabricated.

[0003] Currently, frequency selective surfaces are mostly limited to planar surfaces or simple curved cylindrical and conical surfaces that can be formed by curling a flat surface. Fabricating frequency selective surfaces on surfaces with complex curvatures is difficult, especially for surfaces with complex cavities. Existing technologies typically fabricate the base structure and FSS pattern separately, first fabricating the base structure and then metallizing the structure's surface. Furthermore, methods for fabricating curved FSS patterns have limitations. For example, methods that first prepare a flexible planar FSS and then transfer it to a curved surface for splicing suffer from large transfer errors and loss of conductive continuity between spliced ​​areas. Methods for fabricating curved FSS based on mask lithography suffer from cumbersome photolithography processes, high costs, and limited application on non-developable surfaces. Electroplating and electroless plating combined with laser etching are susceptible to problems such as poor solution flow, uneven electric field distribution, and limited accessibility to the inner cavity. 3D printing technology is widely used in the fabrication of complex structures, and with technological advancements, 3D direct writing of surface functionalized patterns is also maturing. The rise of multi-material and multi-process 3D printing technology has made it possible to integrate the frequency selective surfaces (FSS) on the inner and outer surfaces of complex curved cavity structures. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, to provide an integrated manufacturing method for the frequency selective surface of a complex curved cavity structure, to solve the manufacturing difficulties of the frequency selective surface FSS on the inner and outer surfaces of the complex curvature cavity structure, to integrate the complex curved cavity structure with the FSS patterns on the inner and outer surfaces, and to meet the research and development needs of complex FSS components of spacecraft.

[0005] The technical solution of the present invention is:

[0006] The present invention discloses an integrated manufacturing method for a frequency selective surface with a complex curved cavity structure, comprising:

[0007] Step 1: Perform 3D modeling and 3D printing preprocessing to obtain a 3D model;

[0008] Step 2: Based on the 3D model, a water-soluble inner cavity substrate support structure is printed on the positioner base plate using FDM technology, and the surface of the inner cavity substrate support structure is mechanically processed or chemically vapor polished to improve the surface quality and smoothness;

[0009] Step 3: Aerosol spraying 3D direct writing dielectric layer 1 on the surface of the water-soluble inner cavity substrate support structure produced in step 2, aerosol spraying 3D direct writing FSS pattern array 1 on dielectric layer 1 with metal nano ink, and then aerosol spraying 3D direct writing dielectric layer 2 on the surface of FSS pattern array 1 as a protective layer;

[0010] Step 4: On the dielectric layer 2 of step 3, the cavity body structure is printed using CFF technology, and the surface of the cavity body structure is mechanically processed or chemically vapor polished;

[0011] Step 5: Aerosol spraying a 3D direct writing dielectric layer 3 on the surface of the cavity body structure, aerosol spraying a 3D direct writing outer surface FSS pattern array 2 on the dielectric layer 3 with metal nano ink, and then aerosol spraying a 3D direct writing dielectric layer 4 on the surface of the FSS pattern array 2 as a protective layer;

[0012] Step 6: Repeat step 5 on dielectric layer 4 until FSS pattern array n and dielectric layer n are printed; n is greater than or equal to 5;

[0013] Step 7: Wash off the water-soluble inner cavity substrate support structure to obtain a complex curved cavity structure.

[0014] In the above-mentioned production method, the aerosol spray 3D direct writing process parameters are as follows: the height of the aerosol spray nozzle from the positioner substrate is 1 to 5 mm, the movement speed of the nozzle is 20 to 150 mm / s, the width of a single spray pass is 10 μm to 3 mm, the thickness of a single spray pass is 100 nm to 2 μm, and the line width forming accuracy is better than ±10 μm.

[0015] In the above manufacturing method, the dielectric layer and the FSS pattern array layer are both formed by printing a number of deposition layers layer by layer and then curing them. The deposition layers are simultaneously composite-cured by a bottom substrate thermal curing method and a surface photon sintering curing method.

[0016] In the above manufacturing method, the thickness d0 of the dielectric layer is 10 μm to 1 mm, and the thickness h0 of the FSS pattern array layer is 1 μm to 10 μm.

[0017] In the above-mentioned manufacturing method, the temperature of the positioner substrate in the bottom substrate thermal curing method is set to 100℃~140℃, and the photon irradiation intensity in the surface photon sintering curing method is 500~800mW / cm 2 The curing interval between each deposition layer is 3 to 5 seconds.

[0018] In the above-mentioned production method, the three-dimensional modeling and 3D printing preprocessing in step 1 are specifically as follows: using modeling software to perform three-dimensional modeling of the complex curved cavity structure, the water-soluble inner cavity substrate support structure, the inner surface FSS pattern, and the outer surface FSS pattern respectively, and the model is input into the 3D printer after data slicing and path planning by 3D printing process processing software.

[0019] In the above manufacturing method, in step 2, the surface quality is better than Ra1.6.

[0020] In the above manufacturing method, the forming accuracy of the complex curved cavity structure in step 4 is better than 0.1 mm.

[0021] In the above-mentioned manufacturing method, in step 4, the surface of the cavity structure is subjected to mechanical processing or chemical vapor polishing. Specifically, the steam temperature of the chemical vapor polishing is 100-120° C., the processing time is 0.5-2 hours, and the surface quality is better than Ra1.6.

[0022] In the above-mentioned manufacturing method, the material of the complex curved cavity structure in step 4 is a high-performance thermoplastic material, a short fiber reinforced thermoplastic composite material or a continuous fiber reinforced thermoplastic composite material.

[0023] The advantages of the present invention compared with the prior art are:

[0024] (1) The present invention can realize the production of FSS on the inner surface of a cavity structure with complex curvature. By producing a frequency selective metallization pattern on the outer surface of a soluble liner and transferring it to the inner surface of the cavity, the method has strong feasibility and does not have problems such as poor flow of electroplating / chemical plating solutions, uneven electric field distribution, and accessibility constraints of laser etching processing;

[0025] (2) The present invention can realize the integrated production of FSS complex cavity structure and FSS pattern by adopting the technical approach of composite 3D printing. Since both adopt 3D printing technology, the design freedom can be significantly improved. The unit shape, size, array arrangement and the interlayer spacing between multi-layer FSS units of FSS can be arbitrarily adjusted. The 3D direct writing technology using aerosol spray can miniaturize the FSS unit size to the level of tens of microns, which is conducive to expanding the applicable frequency range and reducing the influence of the incident angle and polarization direction of electromagnetic waves on the transmission characteristics of the frequency selective surface. The cavity structure body is 3D printed with continuous fiber reinforced composite materials, which has the characteristics of light weight and high strength, which is conducive to improving the structural bearing capacity and lightweight level;

[0026] (3) The present invention has great comprehensive advantages in terms of quality, cost, and efficiency: compared with photolithography mask technology, it does not require molds, has low cost, fewer processes, and is more suitable for complex curved surfaces; compared with electroplating / chemical plating combined with laser etching technology, it has better quality in FSS pattern processing on the inner cavity surface, is more green and friendly, and has no restrictions on molding; compared with flexible plane FSS transfer and splicing technology, it has high manufacturing accuracy and continuous graphics;

[0027] (4) The manufacturing method of the present invention can be used to manufacture both open-hole unit arrays and patch unit arrays; it can be used to manufacture FSS with complex curvature outer surfaces and FSS with complex inner cavity surfaces, and it can also realize the integrated manufacturing of structure and FSS functional pattern. The number of FSS layers is not limited. The present invention is also applicable to the production of metallized patterns on other three-dimensional functional structure conformal surfaces, and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The complex curved cavity structure and the inner cavity substrate support structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the FDM printing of the inner cavity substrate support structure of the present invention;

[0030] Figure 3 3D direct writing FSS pattern on the surface of the structure of the present invention;

[0031] Figure 4 This is a schematic diagram of the CFF printing of the complex curved cavity structure body of the present invention;

[0032] Figure 5 This is a schematic cross-sectional view of the FSS structure of the complex curved cavity of the present invention. DETAILED DESCRIPTION

[0033] The working principle and working process of the present invention will be further explained and illustrated below with reference to the accompanying drawings.

[0034] Using multi-process composite 3D printing as a technical approach, FDM technology is used to create a water-soluble substrate. 3D direct writing technology is used to create an inner FSS pattern on the substrate surface. The cavity structure is then printed on top of the substrate. The outer FSS pattern is then created on the surface of the cavity structure. The water-soluble substrate is then dissolved away, ultimately resulting in a complex curved cavity FSS structure with frequency-selective patterns on both the inner and outer surfaces. Furthermore, through the practice of this invention, surface treatment measures are required for the 3D printed structure before the FSS pattern is created, improving the quality and precision of the FSS metallization pattern and ensuring the integrated production of the complex curved cavity structure and the inner and outer FSS patterns.

[0035] The present invention discloses an integrated manufacturing method for a frequency selective surface with a complex curved cavity structure, comprising the following steps:

[0036] Step 1: 3D modeling and 3D printing pre-processing of the complex curved cavity structure ①, mainly including the cavity body structure ②, water-soluble inner cavity substrate support structure ③, inner surface FSS pattern ⑨, outer surface FSS pattern , the model is input into the 3D printer after data slicing and path planning by 3D printing process processing software; Figure 1 shown.

[0037] Step 2: Based on the 3D model, FDM technology ⑤ is used to print the water-soluble inner cavity substrate support structure ② on the positioner base plate ④, and the surface of the inner cavity substrate support structure ③ is mechanically processed or chemically (such as acetone) vapor polished to improve the surface quality and finish. The surface quality is better than Ra1.6; Figure 2 shown.

[0038] Step 3: Aerosol spray 3D direct writing ⑥ dielectric layer 1⑧ on the surface of water-soluble inner cavity substrate support structure ③, and aerosol spray 3D direct writing inner surface FSS unit array 1⑨ on it with metal nano ink, including but not limited to Y-shaped, circular, square, and cross-shaped arrays, and then aerosol spray 3D direct writing dielectric layer 2 on the surface of FSS pattern 1⑨ As a protective layer, the specific requirements are as follows:

[0039] In this embodiment, the aerosol spray 3D direct writing process parameters are: the height of the nozzle from the substrate is 1 to 5 mm, the nozzle movement speed is 20 to 150 mm / s, the single pass width is 10 μm to 3 mm, the single pass layer thickness is between 100 nm and 2 μm, and the line width forming accuracy is better than ±10 μm.

[0040] The dielectric layer and FSS pattern array layer are formed by printing several deposition layers layer by layer and then curing them. The deposition layers are cured synchronously by using the bottom substrate thermal curing method and the surface photon sintering curing method. The thickness d0 of the metal FSS pattern layer 1⑨ is 10μm to 1mm, and the thickness can be adjusted as needed. The thickness h0 of the metal FSS pattern layer 1⑨ is 1μm to 10μm, and should not exceed 10μm. The deposition layers d1, d2, ..., d n ;h1,h2,…,h n The accumulated thickness of the dielectric layer or metal layer reaches the set value (d0 = d1 + d2 + ... d n ; h0=h1+h2+…h n ); sedimentary layer (d1, d2, ..., d n ;h1,h2,…,h n) Synchronous curing is achieved by using a composite curing technology of thermal curing of the bottom substrate and photon sintering of the surface. This can promote the spreading and leveling of the liquid material, inhibit the coffee ring effect, and avoid bubbling during the curing of the deposited layer. The substrate temperature is 100°C to 140°C, and the photon irradiation intensity is 500 to 800mW / cm 2 The curing interval between the previous deposition layer and the next deposition layer is 4s to avoid deformation or quality defects caused by excessive heat accumulation.

[0041] Step 4: On the dielectric layer 2 of step 3, the cavity body structure ② is printed using CFF technology ⑩, with a forming accuracy better than 0.1 mm. Materials include high-performance thermoplastic materials (such as PEEK, PEI, PPSU, etc.), short fiber reinforced thermoplastic composites (such as PEEK-CF (short carbon fiber), PEEK-GF (short glass fiber), etc.), or continuous fiber reinforced thermoplastic composites (such as carbon fiber, glass fiber, Kevlar reinforced ULTEM9085 resin, Onyx, etc.). The surface of the cavity body structure is mechanically processed or chemically (such as acetone) steam polished (steam temperature 110°C, processing time 0.5-2 hours) to achieve a surface quality better than Ra1.6;

[0042] Step 5: Aerosol spray 3D direct writing medium layer 3 on the surface of the curved cavity body structure , on which the outer surface FSS pattern array 2 is directly written by metal nano-ink aerosol jet 3D , including but not limited to Y ring, circular ring, square ring, and cross ring arrays, and then a 3D direct writing medium layer 4 is sprayed on the surface of the FSS pattern array 2 by aerosol spraying. As a protective layer, the deposited layer is cured simultaneously using a composite curing technology that combines thermal curing of the bottom substrate with photonic sintering of the surface. Specific parameters and requirements are the same as those described in step 3.

[0043] There are two ways to obtain a multilayer FSS structure (>2 layers): one is to obtain a multilayer FSS structure by repeating steps 4 and 5. At this time, the interlayer spacing between the multilayer FSS patterns mainly depends on the thickness of the cavity formed in step 4; the other is to repeatedly print FSS pattern layer-dielectric layer...FSS pattern layer n-dielectric layer n in step 3 or step 5. At this time, the interlayer spacing between the FSS pattern layers depends on the thickness of the dielectric layer n. The interlayer coupling effect of the multilayer FSS structure obtained in this way is stronger.

[0044] Step 6: Wash off the water-soluble inner cavity substrate support structure to obtain the final structure.

[0045] like Figure 1 As shown in the figure, the complex curved surface cavity structure model ① is mainly composed of the cavity body structure model ② and the inner cavity substrate support structure model ③. Figure 2 and Figure 4The process of 3D printing the inner cavity substrate support structure ③ and the cavity body structure ② on the positioner base plate ④ is shown. Figure 3 Shown is the 3D direct writing of FSS patterns on the structure surface⑨. Figure 5 Shows the frequency selection pattern ⑨ and pattern with inner and outer surfaces AA cross-section of a complex curved cavity FSS structure. The main innovation is the precise fabrication of FSS patterns on the inner and outer surfaces of a complex cavity structure in a simple and easy way.

[0046] The above embodiments are merely explanations of the present invention and are not intended to limit the present invention. Therefore, any implementation methods similar to the present invention or implementation methods used in other similar structures but with similar concepts to the present invention are within the scope of protection of the present invention.

[0047] The above description is only the best specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

[0048] The contents not described in detail in the specification of the present invention belong to the common knowledge of professionals in this field.

Claims

1. An integrated manufacturing method for a frequency selective surface with a complex curved cavity structure, characterized in that: include: Step 1: Perform 3D modeling and 3D printing preprocessing to obtain a 3D model; Step 2: Based on the 3D model, a water-soluble inner cavity substrate support structure is printed on the positioner base plate using FDM technology, and the surface of the inner cavity substrate support structure is mechanically processed or chemically vapor polished to improve the surface quality and smoothness; Step 3: Aerosol spraying 3D direct writing dielectric layer 1 on the surface of the water-soluble inner cavity substrate support structure produced in step 2, aerosol spraying 3D direct writing FSS pattern array 1 on dielectric layer 1 with metal nano ink, and then aerosol spraying 3D direct writing dielectric layer 2 on the surface of FSS pattern array 1 as a protective layer; Step 4: On the dielectric layer 2 of step 3, the cavity body structure is printed using CFF technology, and the surface of the cavity body structure is mechanically processed or chemically vapor polished; Step 5: Aerosol spraying a 3D direct writing dielectric layer 3 on the surface of the cavity body structure, aerosol spraying a 3D direct writing outer surface FSS pattern array 2 on the dielectric layer 3 with metal nano ink, and then aerosol spraying a 3D direct writing dielectric layer 4 on the surface of the FSS pattern array 2 as a protective layer; Step 6: Repeat step 5 on dielectric layer 4 until FSS pattern array n and dielectric layer n are printed; n is greater than or equal to 5; Step 7: Wash off the water-soluble inner cavity substrate support structure to obtain a complex curved cavity structure.

2. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: The process parameters of the aerosol spray 3D direct writing are as follows: the height of the aerosol spray nozzle from the positioner substrate is 1 to 5 mm, the movement speed of the nozzle is 20 to 150 mm / s, the width of a single spray pass is 10 μm to 3 mm, the thickness of a single spray pass is 100 nm to 2 μm, and the line width forming accuracy is better than ±10 μm.

3. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: The dielectric layer and the FSS pattern array layer are both formed by printing a number of deposition layers layer by layer and then curing them. The deposition layers are cured synchronously by using a bottom substrate thermal curing method and a surface photon sintering curing method.

4. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: The thickness d0 of the dielectric layer is 10 μm to 1 mm, and the thickness h0 of the FSS pattern array layer is 1 μm to 10 μm.

5. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 3, characterized in that: The temperature of the positioner substrate in the bottom substrate thermal curing method of the deposited layer is set to 100°C to 140°C, and the photon irradiation intensity in the surface photon sintering curing method is 500 to 800 mW / cm 2 The curing interval between each deposition layer is 3 to 5 seconds.

6. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: The three-dimensional modeling and 3D printing preprocessing in step 1 are specifically as follows: using modeling software to perform three-dimensional modeling on the complex curved cavity structure, the water-soluble inner cavity substrate support structure, the inner surface FSS pattern, and the outer surface FSS pattern respectively, and the model is input into the 3D printer after data slicing and path planning by 3D printing process processing software.

7. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: In step 2, the surface quality is better than Ra1.

6.

8. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: The forming accuracy of the complex curved cavity structure in step 4 is better than 0.1 mm.

9. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: In step 4, the surface of the cavity structure is subjected to mechanical processing or chemical vapor polishing. Specifically, the steam temperature of the chemical vapor polishing is 100-120° C., the processing time is 0.5-2 hours, and the surface quality is better than Ra1.

6.

10. The integrated manufacturing method of a frequency selective surface with a complex curved cavity structure according to claim 1, characterized in that: The material of the complex curved cavity structure in step 4 is a high-performance thermoplastic material, a short fiber reinforced thermoplastic composite material or a continuous fiber reinforced thermoplastic composite material.

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