Radar-acoustic compatible absorbing superstructure and method of making same

Abstract

The application discloses a radar-sound compatible absorbing superstructure and a preparation method thereof, and belongs to the technical field of sound-absorbing and wave-absorbing materials.The superstructure is formed by fusing and depositing 3D printing of a wave-absorbing material, has three-dimensional gradient composition and a multistage pore structure, the multistage pore includes micro-pore and macro-pore structure, and the macro-pore structure is a space folding inclined pore.Micro-pores and macro-pores are simultaneously constructed in the superstructure, the composite effect of the micro-pores and the macro-pores is utilized to form resonance absorption peaks at different frequencies, the problem of excessive thickness / volume of a traditional radar-sound compatible absorbing material is solved, different direction incident electromagnetic waves can be fully contacted with the absorber, omnidirectional multistage reflection is realized, the folding multistage inclined pore can extend the propagation path of sound waves and radar waves without increasing the thickness of the structure, multiple reflections are formed in the folding channel, and thus sharp wave dissipation is caused in the channel.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sound and wave absorbing materials, and particularly relates to a radar-sound compatible absorbing superstructure and a preparation method thereof. BACKGROUND

[0002] Electromagnetic radiation and noise pollution are two of the four major environmental pollution sources listed by the World Health Organization, and both are invisible pollution that seriously harms human health. In addition, with the progress of electronic technology and the enhancement of military strength, various military reconnaissance technologies emerge in an endless stream. In some special occasions where naval vessels, shipboard weapons and amphibious equipment are used, radar detection and sonar detection are the most effective and commonly used detection technologies. Therefore, it is of great significance to develop new materials with sound absorption and microwave absorption capacity in the fields of civil use and national defense security.

[0003] Due to the great difference in energy consumption mechanisms of materials to microwaves and sound waves, few materials have both microwave and sound wave absorption capacity. It is a great challenge to design and manufacture multifunctional materials with sound absorption and wave absorption functions. If a traditional method is used to combine radar wave and sound wave absorbing layers into a double-layer structure to obtain radar-sound compatible absorption performance, the large thickness and volume of the material will greatly limit its practical application.

[0004] In the past few years, due to the rapid emergence of artificial structure super materials (MMs), the design of material parameters has become possible, allowing precise control of waves in a wide range of physics at deep subwavelength scales, while opening up doors for physical operations. By using a method of combining sound absorbing superstructures and wave absorbing materials, radar-sound compatible absorption functions can be achieved in a limited thickness. Therefore, by combining a space-folding multi-stage inclined hole structure with a wave absorbing material, radar-sound compatible absorption performance can be achieved in a thin thickness. SUMMARY

[0005] The application provides a radar-sound compatible absorbing superstructure and a preparation method thereof, which can prepare a super material with excellent sound absorption performance and wave absorption performance.

[0006] To achieve the above object, the application adopts the following technical scheme:

[0007] A radar-sound compatible absorbing superstructure, which is formed by melt deposition 3D printing of a wave absorbing material, has a three-dimensional gradient composition and a multi-stage hole structure. The three-dimensional gradient composition is that the distribution of Fe3O4 and CNTs in the Fe3O4-CNTs / PLA composite material in the PLA matrix is carried out according to a certain gradient rule. From one end of the material to the other end, the content of Fe3O4 gradually increases, and the content of CNTs gradually decreases.

[0008] The multi-level hole includes micro-holes and macro-holes, the micro-holes are uniformly distributed in the whole macro-sample, the aperture size of the micro-holes is 30-60 μm, and the macro-hole structure is a spatially folded inclined hole.

[0009] The thickness of the superstructure is 20-40 mm, the aperture of the spatially folded inclined hole is 1.4-1.8 mm, the folding angle is 40°-60°, the length of each level of hole is equal, and the folding angle is also equal, which can ensure that the sound waves / radar waves are always transmitted in perpendicular directions, increase the reflection times of the radar waves-sound waves in the cavity, effectively increase the attenuation path of the radar waves-sound waves in the air, and thus improve the absorption performance; the inner wall of the folded inclined hole is a rough structure.

[0010] The sound absorption frequency band of the superstructure material is 500-6000 Hz, and the wave absorption frequency band is 8.2-12.4 GHz.

[0011] A preparation method of a radar-sound compatible absorption superstructure, comprising the following steps:

[0012] (1) first, a structure model is constructed by a three-dimensional modeling software UG, and the aperture, folding angle and thickness of the folded inclined hole in the superstructure are designed;

[0013] (2) Fe3O4-CNTs composite wave-absorbing material is prepared by a coprecipitation method; PLA powder and Fe3O4-CNTs are configured and mixed uniformly according to a mass ratio of 1:1, and a 3D printing wire material is prepared by combining thermoplastic extrusion molding.

[0014] (3) finally, according to the aperture, folding angle and thickness parameters of the folded inclined hole obtained by design, a radar wave-sound wave compatible absorption structure is prepared by using a FDM 3D printing processing method with different folding angles, apertures and thicknesses.

[0015] In the above steps, the specific process of thermoplastic extrusion in step (2) is as follows: 45 parts of Fe3O4-CNTs composite material, 45 parts of polylactic acid, 5 parts of surface modifier and 5 parts of foaming agent are weighed according to the mass fraction, mixed uniformly, dried at about 40°, then poured into the feeding port of the thermoplastic machine, heated to a molten state, then extruded into a wire material by a double-screw extruder, and then a standard 3D printing consumable with a diameter of about 1.75 mm is processed by a winding machine; wherein the heating temperature is 170℃, and the speed of the extrusion screw is 45 r / min; the mass ratio of the wave-absorbing raw powder to the toughening agent is 9:1.

[0016] The specific printing parameter settings in step (3) are as follows: printing speed 30 mm / s, filling density 100%, printing temperature 220℃, and platform temperature 60℃.

[0017] Beneficial effects: The present application provides a radar-sound compatible absorbing superstructure and a preparation method thereof, which has the following advantages compared with the prior art:

[0018] (1) The single macroscopic straight / skew hole structure will cause local material loss, resulting in that part of the incident electromagnetic wave parallel to the hole axis direction directly transmits without interacting with the absorber, which finally weakens the wave absorption performance; the micro hole and macro hole are simultaneously constructed in the superstructure of the present application, and the multi-stage hole synergistically acts to ensure that the incident electromagnetic wave in different directions can fully contact with the absorber, realize omnidirectional multi-stage reflection, and guarantee the wave absorption performance at different incident angles; moreover, the folded multi-stage skew hole can extend the propagation path of the sound wave and the radar wave without increasing the thickness of the structure, and multiple reflections are formed in the folded channel, thereby causing sharp wave dissipation in the channel; at the same time, the space folded multi-stage skew hole structure can also realize wide-frequency absorption performance; and the superstructure of the present application can extend the hole channel under the limited thickness and form resonance absorption peaks at different frequencies by using the composite effect of the micro-macro hole, thereby solving the problem of excessive thickness / volume of the traditional radar-sound compatible absorbing material;

[0019] (2) The superstructure of the present application has a three-dimensional gradient composition, and Fe3O4, CNTs and PLA synergistically act in the three-dimensional gradient distribution; PLA serves as a matrix material to provide a supporting and dispersing environment for Fe3O4 and CNTs; Fe3O4 endows the material with magnetism; and CNTs can improve the electrical conductivity and mechanical properties of the material; for the Fe3O4-CNTs / PLA composite material, Fe3O4 and CNTs are distributed in the PLA matrix according to a certain gradient rule, and the content of Fe3O4 gradually increases and the content of CNTs gradually decreases from one end of the material to the other end; the gradient change can make the material have different physical, chemical and mechanical properties at different positions, for example, one side has high electrical conductivity (due to high CNTs content), and the other side has high magnetism (due to high Fe3O4 content);

[0020] (3) The superstructure with multi-stage folded skew holes inside is processed by using the FDM 3D printing technology, and by adjusting the hole diameter, folding angle and thickness of the structure, the strength of the absorption peak and the frequency range covered can be flexibly manipulated, so as to obtain excellent wide-frequency absorption performance;

[0021] (4) The 3D printing process is used to effectively control the roughness and density of the internal folded channel in the structure, thereby improving the absorption performance;

[0022] (5) Compared with the traditional resonant absorption structure, the superstructure of the present application does not need to set an air layer in the back, but is self-contained, the processing method is simple, the production cycle is short, and large-scale application in actual scenes is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a partial sectional view of a space-folding inclined hole in an embodiment of the present application;

[0024] Figure 2 is a schematic diagram of a micro-macro hole in an embodiment of the present application;

[0025] Figure 3 is a schematic diagram of a simulation model as a whole in an embodiment of the present application;

[0026] Figure 4 is a schematic diagram of finite element meshing in an embodiment of the present application;

[0027] Figure 5 is a curve showing the relationship between the sound absorption performance of the superstructure in Example 1 and the space-folding inclined hole aperture in the range of 500-6000Hz;

[0028] Figure 6 is a curve showing the relationship between the sound absorption performance of the superstructure in Example 2 and the space-folding inclined hole folding angle in the range of 500-6000Hz;

[0029] Figure 7 is a curve showing the relationship between the sound absorption performance of the superstructure in Example 3 and the overall thickness of the structure in the range of 500-6000Hz;

[0030] Figure 8 is a curve showing the relationship between the wave absorption performance of the superstructure in Example 4 and the content of doped carbon nanotubes in the range of 2-18GHz;

[0031] Figure 9 is a curve showing the relationship between the wave absorption performance of the superstructure in Example 5 and the calcination temperature in the range of 2-18GHz;

[0032] Figure 10 is a curve showing the relationship between the wave absorption performance of the superstructure in Example 6 and the space-folding inclined hole angle in the range of 8.2-12.4GHz;

[0033] Figure 11 is a curve showing the relationship between the wave absorption performance of the superstructure in Example 7 and the space-folding inclined hole aperture in the range of 8.2-12.4GHz;

[0034] Figure 12 is the sound absorption performance of the sound absorption structure with optimal geometric parameters printed by 3%CNTs-600°C wave-absorbing wire material with the best wave-absorbing performance in Example 8. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be described in detail below in combination with the drawings and examples.

[0036] As shown in Figure 1 and Figure 2 A radar-acoustic compatible absorption superstructure formed by a wave-absorbing material through fused deposition 3D printing, having a three-dimensional gradient composition and a multi-stage pore structure.

[0037] The three-dimensional gradient composition is a synergistic effect of Fe3O4, CNTs and PLA in a three-dimensional gradient distribution, PLA as a matrix material provides a supporting and dispersing environment for Fe3O4 and CNTs; Fe3O4 imparts magnetic properties to the material; CNTs can improve the electrical conductivity and mechanical properties of the material; for Fe3O4-CNTs / PLA composite material, Fe3O4 and CNTs are distributed in the PLA matrix according to a certain gradient rule, from one end of the material to the other end, the content of Fe3O4 gradually increases, and the content of CNTs gradually decreases.

[0038] As shown in Figure 2 The multi-stage pore includes micro-pores and macro-pore structures, the micro-pores are uniformly distributed inside the entire macro-sample, the pore size is 30-60 μm, and the macro-pore structure is a multi-stage folded inclined pore.

[0039] The thickness of the superstructure is 20-40 mm; the pore size of the multi-stage folded inclined pore is 1.4-1.8 mm, the folding angle is 40°-60°, the length of each stage of the pore is equal, and the folding angle is also equal, which can ensure that the acoustic wave / radar wave always transmits in a perpendicular direction, increase the reflection times of the radar wave-acoustic wave inside the cavity, effectively improve the attenuation path of the radar wave-acoustic wave in the air, and thus improve the absorption performance; the inner wall of the folded inclined pore is a rough structure.

[0040] The preparation method of the above-mentioned radar-acoustic compatible absorption superstructure material comprises the following steps:

[0041] (1) First, construct a structure model through a three-dimensional modeling software UG, and design the pore size, folding angle and thickness of the folded inclined pore inside the superstructure, the specific process is as follows:

[0042] Since the solid material used in the structure designed in the present application is a hard material, its density is much greater than the density of air, that is, the acoustic impedance of the solid material is much greater than the acoustic impedance of air, therefore, the contact surface between the structure and air can be set as an acoustic hard boundary condition, avoiding the coupling of multiple physical fields, thereby simplifying the calculation process and saving calculation time;

[0043] The settings of physical field, material, region division, solver configuration, etc. used in simulation are as follows:

[0044] (a) Model region setting

[0045] A three-dimensional model is established in the model wizard, a pressure-acoustic interface is selected, the sound absorption structure established in UG is imported into COMSOL software, and a duct region same as the structure region is constructed as a sound wave incidence area; through Boolean operation, all geometric elements are set union, the structure solid domain is deleted, and only the air domain is retained; a virtual domain is added at the top of the incident sound field, the region is set as a perfect matched layer (PML) to separate the sound wave propagation free domain to simulate an infinite region, and to absorb reflected waves to avoid the influence of secondary reflected waves on the calculation of the structure sound absorption coefficient Figure 3 ;

[0046] (b) Material definition

[0047] The solid material of the multi-stage inclined hole space folding structure acoustic superstructure is defined as PLA, and the fluid inside the multi-stage inclined hole folding cavity inside the structure is defined as air. The specific structure parameters of the material are shown in Table 1.

[0048] Table 1 Material parameter table of acoustic superstructure

[0049]

[0050] (c) Pressure-acoustic setting

[0051] The physical field conditions of all domains are defined as pressure-acoustic, and the external boundary conditions of the structure and sound radiation domain are defined as acoustic hard boundary; the incidence condition is set as a background pressure field in the sound radiation region, and the type is plane wave radiation; the sound pressure amplitude p0 of the incident pressure field is defined as 1 Pa, and the sound propagation direction is perpendicular to the structure surface incidence; the multi-stage inclined hole folding cavity part of the structure is set as a narrow region acoustic

[0052] (d) Mesh division

[0053] When dividing the mesh, the size and type of the mesh determine the quality of the mesh, and the quality of the mesh division directly determines the time cost and accuracy of the calculation results. The smaller the mesh division, the more the number of meshes, and the calculation cost and time will increase linearly. Generally, the principle of mesh division is to use large meshes as much as possible under the premise of ensuring accurate calculation results, so as to reduce the calculation time cost. However, in acoustic finite element simulation, at least six second-order units should be used to analyze the wavelength, so when dividing the mesh, the size of the largest mesh should be at least smaller than 1 / 6 of the smallest wavelength, that is, the following formula should be met to completely analyze the sound waves of all wavelengths in the frequency domain range

[0054] ,

[0055] wherein C0 represents the speed of sound, i.e. the propagation speed of a sound wave in a medium; f max represents the maximum frequency, i.e. the highest frequency at which a sound wave can propagate in a medium;

[0056] The structural region is divided using a tetrahedral mesh, and the maximum size of the mesh is limited to satisfy the above condition. The mesh is divided in a sweeping manner for the plane wave incidence region and the virtual PML layer. The number of units swept in the axial direction of the PML layer is defined to ensure that the reflected sound wave is fully absorbed by the PML layer. As shown in FIG. 3, the finite element mesh division is shown in the schematic diagram. After the mesh division, 83658 domain units, 15730 boundary units and 4801 edge units are included. Figure 4

[0057] The non-local coupling condition is defined for the air contact surface of the environmental medium on the surface of the structure, and the variables incident sound pressure p inc and reflected sound pressure p scat are defined. The reflection coefficient is R = p scat / p inc , and the sound absorption coefficient expression is defined according to the sound absorption coefficient calculation formula as a = 1 - abs(R)^2.

[0058] (e) Simulation model solver configuration

[0059] In the direct solver of COMSOL, the two solvers MUMPS and PARDISO have relatively high calculation efficiency. The main difference between different solvers is their relative speed. MUMPS and PARDISO can store solutions outside the core, and the MUMPS solver also supports cluster computing. Through comparison and verification, the results obtained by using the two solvers for calculation are not different, but from the aspect of calculation efficiency, the PARDISO solver is obviously higher than the MUMPS solver. Therefore, from the aspect of improving the calculation speed, the PARDISO solver is selected for the finite element solution of the sound absorption structure;

[0060] (2) Fe3O4-CNTs composite wave-absorbing material is prepared by co-precipitation method; PLA powder and Fe3O4-CNTs are configured and mixed uniformly according to a mass ratio of 1:1, and 3D printing wire is prepared by combining thermoplastic extrusion molding, and different folding angles, pore diameters and thicknesses of the superstructure are prepared by using FDM 3D printing processing method to test the wave-absorbing performance, and a radar wave-sound wave compatible absorbing structure part is designed by selecting appropriate folding inclined hole diameters, folding angles and thickness parameters.

[0061] Example 1

[0062] ​(1) Construct four cylinders with a diameter of 29 mm and a height of 40 mm by using three-dimensional modeling software UG, and then design spatially folded multi-stage inclined holes and micro-holes inside the cylinder, wherein the hole diameters of the inclined holes are set to 1.4 mm, 1.6 mm, 1.8 mm, respectively;

[0063] (2) Manufacture polylactic acid (PLA) 3D printing wire with a diameter of 1.75 mm by using a thermoplastic extruder; mix 45 parts of Fe3O4-CNTs composite material, 45 parts of polylactic acid, 5 parts of surface modifier, and 5 parts of foaming agent according to the mass fraction; after the above mixed raw materials are dried at 40° for 3 h, pour them into the feeding port of the extruder, heat the raw materials to a molten state, extrude the wire through a double-screw extruder, and then use a wire winding machine to prepare 3D printing wire with a diameter of 1.75 mm and uniform distribution. The heating temperature is 170°C, and the rotation speed of the screw is 45 r / min.

[0064] (3) Process and form by using 3D printing, and set the 3D printing parameters: printing speed is 30 mm / s, filling density is 100%, printing temperature is 190°C, platform temperature is 60°C, and finally process a broadband sound absorption structure.

[0065] The sound absorption frequency band of the superstructure prepared in this embodiment is 500-6000 Hz, and the sound absorption coefficient is tested by using an AWA6290T type transfer function sound absorption coefficient measurement system.

[0066] As shown in Figure 5 The sound absorption coefficient of the superstructure in this embodiment under different hole diameters d is shown in the comparison chart. Compared with the structure with a hole diameter of 1.6-1.8 mm, the structure with a hole diameter of 1.4 mm has a wider effective sound absorption range and exhibits more resonance absorption peaks, especially at 1100 Hz, 3300 Hz, and 5600 Hz, which exhibit near-perfect sound absorption performance. This indicates that selecting an appropriate hole diameter plays a key role in sound absorption performance. A too small hole diameter will increase the acoustic resistance and affect the absorption of mid-low frequency sound waves. In addition, a too small hole diameter will reduce the air permeability and increase the reflection of sound waves on the surface, reducing the contact opportunities between the sound absorption structure and the sound waves, thereby reducing the sound absorption effect. A too large hole diameter will cause the resonance frequency to continuously move to high frequencies and reduce the effective resonance absorption peak, thereby shortening the effective sound absorption range of the sound absorption structure. This is mainly because the increase in the hole diameter will cause the acoustic mass and the acoustic resistance to decrease, resulting in an increase in the resonance frequency, and the absorption monomer will go through the process of impedance mismatch to impedance matching and then impedance mismatch again.

[0067] Example 2

[0068] (1) Using three-dimensional modeling software UG to construct four cylinders with a diameter of 29 mm and a height of 40 mm, and then designing a spatially folded multi-stage inclined hole inside the cylinder, wherein the folding angle of the inclined hole is set to 40°, 50°, and 60°, respectively;

[0069] (2) A polylactic acid (PLA) 3D printing filament with a diameter of 1.75 mm is manufactured by a thermoplastic extruder, and the specific preparation process is the same as that of Example 1;

[0070] (3) 3D printing is used for molding, and the 3D printing parameters are set as follows: printing speed is 30 mm / s, filling density is 100%, printing temperature is 200°C, platform temperature is 60°C, and finally a broadband sound absorption structure part is processed.

[0071] The sound absorption frequency band of the superstructure prepared in this example is 500-6000 Hz, and the sound absorption coefficient is tested by using an AWA6290T type transfer function sound absorption coefficient measurement system.

[0072] As shown in Figure 6 , as the spatial folding angle decreases, the peak value of the sound absorption coefficient of the superstructure gradually moves to low frequency, and the effective sound absorption range in the range of 500-6000 Hz is wider, especially in the frequency band of 3000-6000 Hz, the sound absorption coefficient reaches more than 0.8, which greatly improves the sound absorption performance. When the folding angle is small, the number of reflections of sound waves in the structure increases, which increases the contact opportunity of sound waves with the structure, thereby improving the sound absorption coefficient. However, when the folding angle exceeds a certain critical value, the propagation path of sound waves in the structure will be shortened, resulting in a decrease in the sound absorption coefficient.

[0073] Example 3

[0074] (1) Using three-dimensional modeling software UG to construct three spatially folded multi-stage inclined hole sound absorption parts with different heights, wherein the diameter of the fixed structure is 29 mm, the hole diameter is 1.4 mm, and the folding angle is 40° unchanged, and then the height of the structure is set to 20 mm, 30 mm, and 40 mm, respectively;

[0075] (2) A polylactic acid (PLA) 3D printing filament with a diameter of 1.75 mm is manufactured by a thermoplastic extruder; 45 parts of Fe3O4-CNTs composite material, 45 parts of polylactic acid, 5 parts of surface modifier, and 5 parts of foaming agent are weighed according to the mass fraction and mixed uniformly; after the above mixed raw materials are dried at 40° for 3 h, they are poured into the feeding port of the extruder, and the raw materials are heated to a molten state to extrude a filament through a double screw extruder, and then a wire winding machine is used to prepare a 3D printing filament with a diameter of 1.75 mm and uniform distribution. The heating temperature is 170°C, and the rotation speed of the screw is 45 r / min;

[0076] (3) 3D printing processing forming, setting 3D printing parameters: printing speed is 30 mm / s, filling density is 100%, printing temperature is 210 DEG C, platform temperature is 60 DEG C, finally process wideband sound absorption structure piece.

[0077] As shown in Figure 7 When the thickness of the sound absorption piece is 40 mm, the effective sound absorption range covered is the widest, in the 2400-6000 Hz frequency band, the sound absorption coefficient is all above 0.6, realizing near perfect sound absorption effect, 3200-5400 Hz, the sound absorption coefficient is all above 0.9, realizing perfect sound absorption effect; Moderate increase in thickness can widen the resonance frequency range and improve the sound absorption performance of medium and low frequencies, but too high thickness will lead to the decline of high frequency sound absorption performance, and violate the design principle of lightweight, therefore, the thickness of the present application is designed to be 10-40 mm.

[0078] Example 4

[0079] (1) Fe3O4-CNTs composite material is prepared by co-precipitation method, first, different mass of CNTs powder and Fe3O4 powder are mixed to form mixed powder with mass fraction of 0%, 1%, 3%, 5%, 7% and 9% respectively.

[0080] (2) After the composite powder is dissolved in 100 mL of ethanol, it is sealed and stirred for 30 min.

[0081] (3) Then the precipitate is taken out after drying in an oven at 80 DEG C.

[0082] (4) After grinding, 1g of composite powder is mixed with paraffin in a mass ratio of 1:1, then stirred under constant temperature heating, and pressed into a coaxial ring with an inner diameter of 3.04 mm and an outer diameter of 7 mm.

[0083] The electromagnetic parameters of the coaxial ring are tested by a vector network analyzer, as shown in Figure 8 When the doping ratio of CNTs is 3%, the wave absorption performance of the material is the best, under the thickness of 2.55 mm, the effective absorption bandwidth is 4.1 GHz, and the strongest absorption peak can reach-59 dB.

[0084] Example 5

[0085] (1) In order to further improve the wave absorption performance of the material, the composite material with 3% mass fraction is calcined at 400 DEG C, 600 DEG C and 800 DEG C respectively;

[0086] (2) After grinding, 1g of composite powder is mixed with paraffin in a mass ratio of 1:1, then stirred under constant temperature heating, and pressed into a coaxial ring with an inner diameter of 3.04 mm and an outer diameter of 7 mm.

[0087] The electromagnetic parameters of the coaxial ring are tested by a vector network analyzer, as shown in FIG. Figure 9 When the calcination temperature is 600℃, the material has the best wave absorption performance, and the effective absorption bandwidth is 4.6GHz at a thickness of 1.65mm, further reducing the optimal matching thickness of the material.

[0088] Example 6

[0089] (1) Three cuboids with a length of 22.86mm, a width of 10.16mm, and a height of 5mm are constructed by using a three-dimensional modeling software UG, and then a space folding structure with a folding angle of 40°, 50°, and 60° is respectively set on the three cuboids.

[0090] (2) Fe3O4 / CNTs-600℃ / PLA composite 3D printing wire with a diameter of 1.75mm is manufactured by a thermoplastic extruder; 45 parts of Fe3O4-CNTs composite material, 45 parts of polylactic acid, 5 parts of surface modifier, and 5 parts of foaming agent are mixed according to the mass fraction; after the above mixed raw materials are dried at 50° for 3h, they are poured into the feeding port of the extruder, and the raw materials are heated to a molten state to extrude the wire through a double screw, and then the wire is prepared into 3D printing wire with a diameter of 1.75mm and uniform distribution by using a winding machine, wherein the heating temperature is 190℃, and the rotation speed of the screw is 45r / min.

[0091] (3) The 3D printing parameter is set as follows: printing speed is 30mm / s, filling density is 100%, printing temperature is 200℃, and platform temperature is 60℃, and finally a broadband wave absorbing structural member is processed.

[0092] The electromagnetic parameters of the wave absorbing structural member are tested by a vector network analyzer, as shown in FIG. Figure 10 When the folding angle is 50°, the wave absorbing performance of the structural member is the best, the effective absorption bandwidth is 3.22GHz, and almost covers the entire X-band, and the strongest absorption peak can reach-43dB.

[0093] Example 7

[0094] (1) Three cuboids with a length of 22.86mm, a width of 10.16mm, and a height of 5mm are constructed by using a three-dimensional modeling software UG, and then a space folding structure with a pore size of 1.4mm, 1.6mm, and 1.8mm is respectively set on the three cuboids.

[0095] (2) Fe3O4-CNTs / PLA composite 3D printing wire with a diameter of 1.75mm is manufactured by a thermoplastic extruder, and the specific preparation process is the same as that of Example 6.

[0096] (3) 3D printing is used to process the shape. The 3D printing parameters are set as follows: printing speed is 30mm / s, filling density is 100%, printing temperature is 210℃, platform temperature is 60℃, and a broadband absorbing structure is finally processed.

[0097] Electromagnetic parameters of the absorbing structure were tested using a vector network analyzer. (See [link to relevant documentation]). Figure 11 When the diameter of the oblique hole is 1.4mm, the structural component has the best wave absorption performance, with an effective absorption bandwidth of 3.05GHz and the strongest absorption peak reaching -23dB.

[0098] Example 8

[0099] (1) Based on the above test results, a spatial folding sound-absorbing structure with a height of 40mm, a folding angle of 40°, and an aperture of 1.4mm was constructed using the 3D modeling software UG.

[0100] (2) Then, a Fe3O4-CNTs-600℃ / PLA composite 3D printing filament with a diameter of 1.75 mm was manufactured using a thermoplastic extruder; 45 parts of Fe3O4-CNTs composite material, 45 parts of polylactic acid, 5 parts of surface modifier, and 5 parts of foaming agent were weighed according to the mass fraction and mixed evenly; after the above mixed raw materials were dried at 40° for 3 hours, they were poured into the feed port of the extruder, and the raw materials were heated to a molten state and extruded into filaments through a twin-screw extruder, and then the filaments were prepared into a 3D printing filament with a diameter of 1.75 mm and uniform distribution using a winding machine. The heating temperature was 190°, and the screw rotation speed was 45 r / min;

[0101] (3) Use 3D printing to process and shape the product. Set the 3D printing parameters: printing speed is 30mm / s, filling density is 100%, printing temperature is 220℃, platform temperature is 60℃, and finally process the broadband sound-absorbing structure.

[0102] like Figure 12 As shown, the sound-absorbing structural component prepared in this embodiment has excellent sound absorption performance in low, medium and high frequencies.

[0103] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A radar-acoustic compatible absorbing superstructure, characterized in that, The superstructure is formed by melt deposition 3D printing of wave-absorbing material, has three-dimensional gradient composition and multi-stage pore structure, the multi-stage pore includes micro-pore and macro-pore structure; the micro-pore is uniformly distributed in the whole superstructure, and the macro-pore structure is a folded inclined pore arranged in the superstructure; the pore diameter of the micro-pore is 30-60 μm; the pore diameter of the folded inclined pore is 1.4-1.8 mm, and the folding angle is 40°-60°; the three-dimensional gradient composition is that the distribution of Fe3O4 and CNTs in the Fe3O4-CNTs / PLA superstructure composite material in the PLA matrix is carried out according to a certain gradient rule, and from one end of the material to the other end, the content of Fe3O4 gradually increases, and the content of CNTs gradually decreases.

2. The radar-acoustic compatible absorbing metasurface of claim 1, wherein, The length of each stage of the pore channel of the folded inclined pore is equal, and the folding angle is equal.

3. The radar-acoustic compatible absorbing metasurface of claim 1, wherein, The thickness of the superstructure is 20-40 mm.

4. The radar-acoustic compatible absorptive metasurface of claim 1, wherein, The inner wall of the folded inclined pore is a rough structure.

5. Process for the preparation of a radar-acoustic compatible absorbing superstructure according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) constructing a model of the superstructure by a three-dimensional modeling software UG, and designing the pore diameter, folding angle and thickness of the folded inclined pore in the superstructure; (2) preparing Fe3O4-CNTs composite wave-absorbing material by a coprecipitation method; mixing Fe3O4-CNTs composite material, polylactic acid, surface modifier and foaming agent uniformly, and combining with thermoplastic extrusion molding to prepare 3D printing wire material; (3) finally, according to the pore diameter, folding angle and thickness parameters of the folded inclined pore obtained by design, a radar wave-sound wave compatible absorption superstructure is prepared by using an FDM 3D printing processing method.

6. The method of claim 5, wherein the radar-acoustic compatible absorptive metastructure is prepared by, The process of thermoplastic extrusion is as follows: 45 parts of Fe3O4-CNTs composite material, 45 parts of polylactic acid, 5 parts of surface modifier and 5 parts of foaming agent are weighed according to the mass fraction, mixed uniformly, dried at 40℃, then poured into the feeding port of the thermoplastic machine, heated to a molten state, then extruded into a wire material through a double-screw extruder, and then combined with a winding machine to process a standard 3D printing consumable with a diameter of about 1.75 mm; wherein the heating temperature is 170℃, and the speed of the extrusion screw is 45 r / min; the mass ratio of the wave-absorbing raw material powder to the toughening agent is 9:

1.

7. The method of claim 5, wherein the radar-acoustic compatible absorptive superstructure is prepared by, The parameter setting of 3D printing is as follows: printing speed 30 mm / s, filling density 100%, printing temperature 220℃, and platform temperature 60℃.

8. The method of claim 5, wherein the radar-acoustic compatible absorptive metastructure is prepared by, Step (1) specifically comprises the following steps: a three-dimensional model is established in the model wizard, a pressure acoustic interface is selected, the sound-absorbing structure established in UG is imported into COMSOL software, and a duct region same as the structure region is constructed as a sound wave incidence area; all geometric elements are handled by set operation, the structure solid domain is deleted, and only the air domain is reserved; a virtual domain is added at the top of the incident sound field, the region is set as a perfect matched layer to separate the sound wave propagation free domain to simulate an infinite region, and the reflected wave is absorbed to avoid the influence of secondary reflected wave on the calculation of the structure sound absorption coefficient; The solid material of the multi-stage inclined hole space folding structure acoustic superstructure is defined as PLA, the fluid inside the multi-stage inclined hole folding cavity inside the structure is defined as air, the physical field conditions of all domains are defined as pressure acoustics, the structure and the external boundary conditions of the sound radiation domain are defined as acoustic hard boundary; The incident conditions in the sound radiation area are set as background pressure field, the type is plane wave radiation, the sound pressure amplitude p0 of the incident pressure field is defined as 1Pa, and the sound propagation direction is perpendicular to the structure surface incident; The multi-stage inclined hole folding cavity part of the structure is set as narrow area acoustics; The structure area is divided by tetrahedral mesh, and the size of the largest mesh is at least smaller than 1 / 6 of the smallest wavelength, that is, the following formula is met to completely analyze the sound waves of all wavelengths in the frequency domain range; ， where Co represents the speed of sound, i.e. the propagation speed of a sound wave in a medium; f max represents the maximum frequency, i.e. the highest frequency at which a sound wave can propagate in a medium; In the structural surface definition environment medium air contact surface set non-local coupling conditions, define variable incident sound pressure p inc and p scat , the reflection coefficient is R=p scat / p inc , according to the sound absorption coefficient formula definition sound absorption coefficient expression is α=1-abs(R)^2; The PARDISO solver is selected for finite element solving of the sound absorption structure.

Images