Frequency selective surface, design and manufacturing method based on continuous fiber 3D printing

Abstract

A frequency selective surface, design and manufacturing method based on continuous fiber 3D printing, wherein the unit structures of the frequency selective surface are a four-chirality unit structure and a six-chirality unit structure; the four-chirality unit structure is composed of four "C"-shaped arc rods of equal size, which are rotationally symmetrically distributed, and the array form of the four-chirality metamaterial array is formed by connecting the end to the end; the six-chirality unit structure is composed of six "C"-shaped arc rods of equal size, which are rotationally symmetrically distributed, and the array form of the six-chirality metamaterial array is formed by connecting the end to the end; the four-chirality metamaterial array or the six-chirality metamaterial array is used to construct the frequency selective surface; the design method can adjust the structural parameters according to the application frequency band to achieve frequency and bandwidth adjustment in the high reflectivity frequency band; the manufacturing method adopts 3D printing, which can complete the manufacturing at a fast speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of frequency selective surface additive manufacturing, and specifically relates to a frequency selective surface based on continuous fiber 3D printing, and a design and manufacturing method. Background Art

[0002] A frequency selective surface is a periodic array structure composed of a large number of passive resonant units. It is composed of periodically arranged conductive material patch units or periodically arranged aperture units on a conductive material. Metal is usually used as the conductive material. This surface can exhibit total reflection or total transmission characteristics near the unit resonant frequency. Frequency selective surfaces are widely used in radar, microwave communications, remote sensing and telemetry, etc. They can be used for radar antenna covers to reduce radar scattering cross sections, as well as for the reflective surface of antennas to improve antenna utilization and reduce system weight. They are also used as polarizers, absorbing materials, etc.

[0003] Common manufacturing processes for frequency selective surfaces include mask exposure, flexible film transfer technology, slice hot pressing, mechanical milling, etc. These process methods have the disadvantages of cumbersome processing flow, long cycle, low degree of freedom, and difficulty in forming complex structures. The emergence of 3D printing technology has brought new ideas to the manufacture of frequency selective surfaces. The Chinese patent "A spray mask of conductive structure, preparation method and application", application number CN202210242778.8, uses a 3D printing method to print the required conductive pattern using support materials, and then ion sputtering is performed, and the sputtered support material is dissolved to obtain the required structure; the Chinese patent "A method for making a ring unit curved surface frequency selective surface array", application number CN201711364840.6, uses non-metallic materials to 3D print the curved surface frequency selective surface structure, and then metallizes the surface to obtain the curved surface frequency selective surface shell. The current method is to plate metal conductive materials on the 3D printed mold. This method can increase the complexity of the formed structure, but the post-processing process does not simplify the manufacturing process. In order to quickly manufacture usable frequency-selective metasurfaces in special environments, a purer 3D printing method needs to be invented.

[0004] Continuous fiber composite 3D printing technology is a new 3D printing technology that mixes continuous fiber filaments with matrix materials to form composite materials and extrude them. It can have excellent mechanical properties, thermal properties, electromagnetic properties, etc., depending on the material composition. It is multifunctional and has the flexible and fast manufacturing characteristics of general 3D printing technology. It has broad application prospects in aerospace, transportation, military equipment, biomanufacturing and other fields. At present, the applications of continuous fiber composite 3D printing technology include vibration reduction, negative Poisson's ratio, thermal deformation, electromagnetic shielding, sensing, etc., but it has not been applied to the manufacture of frequency selective surfaces. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a frequency selective surface, design and manufacturing method based on continuous fiber 3D printing, so as to achieve frequency and bandwidth adjustable in the high reflectivity frequency band, maximize the frequency selection performance of the structure, and complete the manufacturing at a fast speed.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A frequency selective surface based on continuous fiber 3D printing, wherein the unit structures are a four-chirality unit structure 1 and a six-chirality unit structure 2; the four-chirality unit structure 1 is composed of four "C"-shaped arc rods 3 of equal size and rotationally symmetrically distributed, and the array is connected end to end to form a four-chirality metamaterial array 4; the six-chirality unit structure 2 is composed of six "C"-shaped arc rods 3 of equal size and rotationally symmetrically distributed, and the array is connected end to end to form a six-chirality metamaterial array 5; the four-chirality metamaterial array 4 or the six-chirality metamaterial array 5 is used to construct a frequency selective surface.

[0008] A design method for a frequency selective surface based on continuous fiber 3D printing, comprising:

[0009] 1) When the frequency selective surface needs to reflect high-frequency electromagnetic waves, the arc length of the "C"-shaped arc of the chiral metamaterial array structure needs to be reduced to move the peak of the electromagnetic reflectivity toward the high frequency; when the frequency selective surface needs to reflect low-frequency electromagnetic waves, the arc length of the "C"-shaped arc of the chiral metamaterial array structure needs to be increased to move the peak of the electromagnetic reflectivity toward the low frequency;

[0010] The method of increasing the length of the "C"-shaped arc is to increase the radius r of the "C"-shaped arc, or to increase the radian a of the "C"-shaped arc; the method of reducing the length of the "C"-shaped arc is the opposite;

[0011] 2) When the frequency selective surface needs to reflect broadband electromagnetic waves, the surface density of the chiral metamaterial array structure, that is, the proportion of the area occupied by the metamaterial per unit square area, needs to be increased to widen the electromagnetic reflectivity-frequency curve in the bandwidth of the specified reflectivity; when the frequency selective surface needs to reflect narrowband electromagnetic waves, the surface density of the chiral metamaterial array structure needs to be reduced to narrow the electromagnetic reflectivity-frequency curve in the bandwidth of the specified reflectivity;

[0012] The method to increase the surface density of the chiral metamaterial array structure is to increase the curvature a of the "C"-shaped arc and simultaneously reduce the radius r of the "C"-shaped arc, changing the four-chiral unit structure 1 into a six-chiral unit structure 2; the method to reduce the surface density of the chiral metamaterial array structure is the opposite.

[0013] The width t of the "C"-shaped arc is determined by the printing material and the nozzle diameter of the 3D printer, and is 0.2 to 1.5 mm;

[0014] The arc a of the "C"-shaped arc is limited to a maximum angle of 0.6π to 1.2π by geometrical relationship;

[0015] The radius r and width t of the “C”-shaped arc are in proportional relationship, reflecting the contour density of the structure, and the ratio r / t does not exceed 10.

[0016] A method for manufacturing a frequency selective surface based on continuous fiber 3D printing, comprising the following steps:

[0017] 1) For the four-chiral metamaterial array 4, printing is started from the edge of the structure, and continuous arc lines in the first direction are first printed back and forth in sequence; after all continuous arc lines distributed in the first direction are completed, continuous arc lines in the second direction are then printed back and forth in sequence from the adjacent edge;

[0018] For the six-chiral metamaterial array 5, after completing all the continuous arc lines distributed in the second direction, the continuous arc lines in the third direction are printed back and forth in sequence from the adjacent edge;

[0019] The first direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the first time, the second direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the second time, and the third direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the third time; the four-chirality metamaterial array 4 has only the first direction and the second direction, and the angle between the two is 90°, and the six-chirality metamaterial array 5 has the first direction, the second direction and the third direction, and the angles between the three are 60° to each other;

[0020] 2) The above steps complete the printing of the first layer. Repeat the above steps for the second and subsequent layers at the corresponding layer height positions.

[0021] During the manufacturing process of the manufacturing method, auxiliary cooling measures should be applied to allow the molten extruded material to be quickly cooled and shaped to avoid deformation of the structure due to the tension of the fibers.

[0022] The speed of printing the first layer is 100-400 mm / min, and the speed of printing other layers is 0.5-0.8 times that of printing the first layer.

[0023] The 3D printer used in the manufacturing method is generally a continuous fiber composite material 3D printer with a fiber cutting function. If a printer without a cutting function is used, the printed parts need to be post-processed to remove the parts printed due to nozzle jump.

[0024] The material used in the manufacturing method is a composite material of continuous fiber and resin, the continuous fiber includes materials with good conductive properties such as metal wire and carbon fiber wire, and the resin includes PLA, ABS, PA, PC, PPS, PEI, PEEK, etc.

[0025] The beneficial effects of the present invention are:

[0026] The electromagnetic frequency selective surface, design and manufacturing method based on continuous fiber 3D printing of the present invention is adopted. The frequency selective surface structure design method can adjust the structural parameters according to the application frequency band to achieve frequency and bandwidth adjustment in the high reflectivity frequency band; the 3D printing method of the frequency selective surface conforms to the characteristics of the chiral metamaterial structure, can manufacture a structure with a better fiber orientation, maximize the frequency selection performance of the structure, and can complete the manufacturing at a faster speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the chiral unit structure.

[0028] Figure 2 Schematic diagram of the “C” shaped arc rod structure and its parameters.

[0029] Figure 3 Schematic diagram of a chiral metamaterial array.

[0030] Figure 4 Schematic diagram of the nozzle movement trajectory for 3D printing frequency-selective surfaces.

[0031] Figure 5 Schematic diagram of the S11 parameter curve that reflects the effect of changing the arc radius on the reflection performance of the quadrilateral frequency selective surface.

[0032] Figure 6 Schematic diagram of the S11 parameter curve that reflects the effect of changing the arc angle on the reflection performance of the quadrilateral frequency selective surface.

[0033] Figure 7 Schematic diagram of the S11 parameter curve reflecting the effect of changing the surface density of the quadrilateral frequency selective surface on the reflection performance.

[0034] Figure 8 Schematic diagram of the S11 parameter curve that reflects the effect of changing the structural type of the frequency selective surface on the reflection performance.

[0035] Fig. 9 Schematic diagram of the S11 parameter curve reflecting the influence of different structures of the four-chiral frequency selective surface with the same surface density on the reflection performance. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with embodiments and drawings.

[0037] Reference Figure 1 , Figure 2 and Figure 3A frequency selective surface based on continuous fiber 3D printing, combining the technical characteristics of continuous fiber 3D printing, according to the principle of process matching, the unit structures of the frequency selective surface are determined to be a four-chiral unit structure 1 and a six-chiral unit structure 2; the four-chiral unit structure 1 is composed of four "C"-shaped arc rods 3 of equal size and rotationally symmetrically distributed, and the array form of end-to-end connection constitutes a four-chiral metamaterial array 4; the six-chiral unit structure 2 is composed of six "C"-shaped arc rods 3 of equal size and rotationally symmetrically distributed, and the array form of end-to-end connection constitutes a six-chiral metamaterial array 5, any kind of chiral metamaterial array can be used to construct the frequency selective surface.

[0038] According to the finite element electromagnetic wave transmission analysis, the S parameter curve of the four-chirality metamaterial array 4 or the six-chirality metamaterial array 5 structure shows an obvious resonance peak. In the frequency band where the resonance peak appears, the chiral metamaterial array structure produces a near total reflection performance for electromagnetic waves, and as the structural parameters change, the frequency selection performance also changes accordingly, thereby obtaining a frequency selective surface design method for a target frequency; a design method for a frequency selective surface based on continuous fiber 3D printing, comprising:

[0039] 1) When the frequency selective surface needs to reflect high-frequency electromagnetic waves, the arc length of the "C"-shaped arc of the chiral metamaterial array structure needs to be reduced to move the peak of the electromagnetic reflectivity toward the high frequency; when the frequency selective surface needs to reflect low-frequency electromagnetic waves, the arc length of the "C"-shaped arc of the chiral metamaterial array structure needs to be increased to move the peak of the electromagnetic reflectivity toward the low frequency;

[0040] Reference Figure 2 , the method of increasing the arc length of the "C"-shaped arc is to increase the radius r of the "C"-shaped arc, or to increase the arc angle a of the "C"-shaped arc; the method of reducing the arc length of the "C"-shaped arc is the opposite;

[0041] 2) When the frequency selective surface needs to reflect broadband electromagnetic waves, the surface density of the chiral metamaterial array structure, that is, the proportion of the area occupied by the metamaterial per unit square area, needs to be increased to widen the electromagnetic reflectivity-frequency curve in the bandwidth of the specified reflectivity; when the frequency selective surface needs to reflect narrowband electromagnetic waves, the surface density of the chiral metamaterial array structure needs to be reduced to narrow the electromagnetic reflectivity-frequency curve in the bandwidth of the specified reflectivity;

[0042] Reference Figure 2 The method to increase the surface density of the chiral metamaterial array structure is to increase the curvature a of the "C"-shaped arc and simultaneously reduce the radius r of the "C"-shaped arc, changing the four-chiral unit structure 1 into a six-chiral unit structure 2; the method to reduce the surface density of the chiral metamaterial array structure is the opposite.

[0043] Reference Figure 2The width t of the “C”-shaped arc is determined by the printing material and the nozzle diameter of the 3D printer, and is generally 0.2 to 1.5 mm;

[0044] Reference Figure 2 The arc a of the "C"-shaped arc is limited by the geometric relationship to a maximum angle, and the frequency selection characteristics of the structure with a smaller angle are not obvious, so it is generally 0.6π~1.2π;

[0045] Reference Figure 2 The radius r and width t of the "C"-shaped arc are proportional to each other, reflecting the contour density of the structure. The ratio of r / t generally does not exceed 10, otherwise the resonance peak will be reduced and the frequency selection function cannot be well met.

[0046] The printing trajectory generated by the existing 3D printing slicing software for the structure cannot guarantee the continuity of the fiber to the greatest extent, which will directly affect the performance of the frequency selective surface. Therefore, a printing nozzle movement trajectory scheme suitable for rapid manufacturing of the structure is designed; a method for manufacturing a frequency selective surface based on continuous fiber 3D printing, comprising the following steps:

[0047] 1)Reference Figure 4 For the four-chiral metamaterial array 4, printing starts from the edge of the structure, and firstly, continuous arc lines in the first direction are printed back and forth in sequence; after all continuous arc lines distributed in the first direction are completed, continuous arc lines in the second direction are printed back and forth in sequence from the adjacent edge;

[0048] For the six-chiral metamaterial array 5, after completing all the continuous arc lines distributed in the second direction, the continuous arc lines in the third direction are printed back and forth in sequence from the adjacent edge;

[0049] The first direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the first time, the second direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the second time, and the third direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the third time; the four-chirality metamaterial array 4 has only the first direction and the second direction, and the angle between the two is 90°, and the six-chirality metamaterial array 5 has the first direction, the second direction and the third direction, and the angles between the three are 60° to each other;

[0050] 2) The above steps complete the printing of the first layer. Repeat the above steps for the second and subsequent layers at the corresponding layer height positions.

[0051] During the manufacturing process of the manufacturing method, auxiliary cooling measures, such as air blowing, should be applied to enable the molten extruded material to be quickly cooled and shaped to avoid deformation of the structure due to the tension of the fibers.

[0052] The speed of printing the first layer is generally 100-400 mm / min, and the speed of printing other layers is generally 0.5-0.8 times that of printing the first layer.

[0053] The 3D printer used in the manufacturing method is generally a continuous fiber composite material 3D printer with a fiber cutting function. If a printer without a cutting function is used, the printed parts need to be post-processed to remove the parts printed due to nozzle jump.

[0054] The material used in the manufacturing method is a composite material of continuous fiber and resin, the continuous fiber includes materials with good conductive properties such as metal wire and carbon fiber wire, and the resin includes PLA, ABS, PA, PC, PPS, PEI, PEEK, etc.

[0055] Reference Figure 5 , Figure 5 This is a schematic diagram of the S11 parameter curve that reflects the effect of changing the arc radius on the reflection performance of the quadrilateral frequency selective surface. By changing the arc radius by 3 to 7 mm, the frequency corresponding to the peak of S11 can be adjusted from 7.4 to 16.2 GHz.

[0056] Reference Figure 6 , Figure 6 Schematic diagram of the S11 parameter curve to reflect the effect of changing the arc angle on the reflection performance of the quadrilateral frequency selective surface. By changing the arc angle from 0.83π to 1.17π, the frequency corresponding to the peak value of S11 can be adjusted from 10 to 12.4 GHz.

[0057] Reference Figure 7 , Figure 7 Schematic diagram of the S11 parameter curve to reflect the effect of changing the surface density of the quadrilateral frequency selective surface on the reflection performance. By changing the arc radius from 4.5 to 5.625 mm and the arc angle from 0.89π to 1.11π, the arc length remains unchanged but the surface density changes. The half-power bandwidth of S11 can be further adjusted from 2 to 4.3 GHz, but the frequency corresponding to the peak value is maintained at 10.3±0.3 GHz.

[0058] Reference Figure 8 , Figure 8 Schematic diagram of the S11 parameter curve to reflect the effect of changing the structural type of the frequency selective surface on the reflection performance. By changing the type of unit structure and achieving a change in surface density, the half-power bandwidth of S11 can be further made variable between 3 GHz and 6.3 GHz.

[0059] Reference Fig. 9 , Fig. 9A schematic diagram of the S11 parameter curve is provided to reflect the influence of different structures of the four-chiral frequency selective surface with the same surface density on the reflection performance. By changing the arc radius from 4.47 to 6.25 mm and the arc length from 0.83π to 1.17π, the surface density remains unchanged but the arc length changes. The half-power bandwidth of S11 can be further maintained at 3.4±0.2 GHz, but the frequency corresponding to the peak value is adjustable from 7.8 to 14.3 GHz.

Claims

1. A method for manufacturing a frequency selective surface based on continuous fiber 3D printing, characterized in that: A frequency selective surface based on continuous fiber 3D printing, wherein the unit structures are a four-chirality unit structure (1) and a six-chirality unit structure (2); the four-chirality unit structure (1) is composed of four "C"-shaped arc rods (3) of equal size, which are rotationally symmetrically distributed, and are connected end to end in an array to form a four-chirality metamaterial array (4); the six-chirality unit structure (2) is composed of six "C"-shaped arc rods (3) of equal size, which are rotationally symmetrically distributed, and are connected end to end in an array to form a six-chirality metamaterial array (5); the four-chirality metamaterial array (4) or the six-chirality metamaterial array (5) is used to construct a frequency selective surface; The manufacturing method comprises the following steps: 1) For the four-chiral metamaterial array (4), printing is started from the edge of the structure, and continuous arc lines in a first direction are first printed back and forth in sequence; after all continuous arc lines distributed in the first direction are completed, continuous arc lines in a second direction are then printed back and forth in sequence from the adjacent edge; For the six-chiral metamaterial array (5), after completing all the continuous arc lines distributed in the second direction, the continuous arc lines in the third direction are printed back and forth in sequence starting from the adjacent edge; The first direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the first time, the second direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the second time, and the third direction is the two directions of the line connecting the start and end points of the continuous arc line selected for the third time; the four-chirality metamaterial array (4) has only the first direction and the second direction, and the angle between the two directions is 90°; the six-chirality metamaterial array (5) has the first direction, the second direction and the third direction, and the angles between the three directions are 60° to each other; 2) The above steps complete the printing of the first layer, and the second and subsequent layers are printed at the corresponding layer height positions, and the above steps are repeated; Auxiliary cooling measures should be applied during the manufacturing process to allow the molten extruded material to cool and set quickly to avoid deformation of the structure due to the tension of the fibers; A method for designing a frequency selective surface based on continuous fiber 3D printing in a manufacturing method, comprising: 1) When the frequency selective surface needs to reflect high-frequency electromagnetic waves, the arc length of the "C"-shaped arc of the chiral metamaterial array structure needs to be reduced to move the peak of the electromagnetic reflectivity toward high frequency; when the frequency selective surface needs to reflect low-frequency electromagnetic waves, the arc length of the "C"-shaped arc of the chiral metamaterial array structure needs to be increased to move the peak of the electromagnetic reflectivity toward low frequency; The method to increase the length of the "C" shaped arc is to increase the radius r of the "C" shaped arc, or to increase the radian a of the "C" shaped arc; the method to decrease the length of the "C" shaped arc is the opposite; 2) When the frequency selective surface needs to reflect broadband electromagnetic waves, the surface density of the chiral metamaterial array structure, that is, the proportion of the area occupied by the metamaterial per unit square area, needs to be increased to make the electromagnetic reflectivity-frequency curve wider in the bandwidth of the specified reflectivity; when the frequency selective surface needs to reflect narrowband electromagnetic waves, the surface density of the chiral metamaterial array structure needs to be reduced to make the electromagnetic reflectivity-frequency curve narrower in the bandwidth of the specified reflectivity; The method for increasing the surface density of the chiral metamaterial array structure is to increase the curvature a of the "C"-shaped arc and simultaneously reduce the radius r of the "C"-shaped arc, thereby changing the four-chiral unit structure (1) into a six-chiral unit structure (2); the method for reducing the surface density of the chiral metamaterial array structure is the opposite.

2. The method according to claim 1, characterized in that: The width t of the "C"-shaped arc is determined by the printing material and the nozzle diameter of the 3D printer, and is 0.2~1.5 mm.

3. The method according to claim 1, characterized in that: The radian a of the "C"-shaped arc is limited to a maximum angle of 0.6π~1.2π by geometric relationships.

4. The method according to claim 1, characterized in that: The radius r and width t of the "C"-shaped arc are proportional to each other, reflecting the contour density of the structure, and the ratio r / t does not exceed 10.

5. The method according to claim 1, characterized in that: The speed of printing the first layer is 100~400 mm / min, and the speed of printing other layers is 0.5~0.8 times that of printing the first layer.

6. The method according to claim 1, characterized in that: The 3D printer used is a continuous fiber composite material 3D printer with the function of cutting fiber filaments. If a printer without the cutting function is used, the printed parts need to be post-processed to remove the parts that were printed due to nozzle jumping.

7. The method according to claim 1, characterized in that: The material used is a composite material of continuous fiber and resin. The continuous fiber includes metal wire and carbon fiber wire with good conductive properties. The resin includes PLA, ABS, PA, PC, PPS, PEI and PEEK.

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