A supersurface broadband absorbing composite material based on a new supersurface substrate material and its preparation method

Abstract

The present invention belongs to the technical field of absorbing materials, and specifically relates to a metasurface broadband absorbing composite material based on a novel metasurface substrate material and a preparation method thereof. First, a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) dispersion is weighed, superabsorbent polymer beads are added thereto to absorb part of the water, and then freeze-dried to obtain solid PEDOT:PSS. The solid PEDOT:PSS is then mixed with dimethyl sulfoxide (DMSO) and deionized water to prepare a PEDOT:PSS conductive ink. An aramid unidirectional fabric is placed in an acetone solution for vibration cleaning and then dried. A frequency selective surface (FSS) pattern is prepared on the treated aramid unidirectional fabric using the PEDOT:PSS conductive ink by screen printing, and then dried. A dielectric layer uses an aramid fiber unidirectional / epoxy resin prepreg, an aramid unidirectional fabric, and an epoxy resin film, and a reflective layer uses a carbon fiber unidirectional / epoxy resin prepreg. The absorbing composite material is prepared by a hot pressing process.

Description

Technical Field

[0001] The present invention belongs to the technical field of absorbing materials, and in particular relates to a super-surface broadband absorbing composite material based on a novel super-surface substrate material and a preparation method thereof. Background Art

[0002] With the advancement of information technology and technology, electromagnetic stealth and electromagnetic protection have been increasingly widely applied in various fields. In the military, improved stealth performance can enhance the deep strike capability and penetration power of weapons, enabling them to gain the upper hand in modern warfare and easily break the offensive and defensive situation. Therefore, the stealth of military targets such as aircraft, missiles, ships, and radars has long been a research hotspot in various countries. In the civilian sector, with the development of an information-based society, the demand for mobile data has exploded, and mobile communication systems are rapidly evolving, with an increasing number of frequency bands being used for wireless communications. Information systems are rapidly developing towards multifunctionality, high performance, and high reliability. To improve system security and reliability and reduce electromagnetic radiation from equipment, electromagnetic protection is required in many situations.

[0003] The engineering application of absorbing materials in the aerospace field requires properties such as lightweight, high-temperature resistance, and corrosion resistance, while also meeting certain mechanical performance requirements. Therefore, absorbing materials with integrated structural and functional design are key technologies for achieving practical engineering applications. Metamaterial absorbing structures can adjust their performance by adjusting the size and resistance of their two-dimensional planar patterns. Applying metamaterials to absorbing structural design can maintain absorbing performance while minimizing the impact on the structure's load-bearing capacity. Fabricating the designed metamaterials and integrating them into aerospace components to achieve specific functions are also key technical challenges in moving metamaterials from the laboratory to engineering applications. A frequency selective surface (FSS) is a single- or multi-layer planar structure composed of a large number of identical units arranged in a two-dimensional periodic pattern. The performance of a FSS is determined by factors such as the pattern structure and arrangement of the periodic units, the thickness and material of the dielectric and absorbing materials, and the polarization and oblique incidence of the incident wave. Sheet resistance, also known as square resistance, refers to the edge-to-edge resistance of a square thin-film conductive material. Sheet resistance is independent of sample size and is expressed in Ω / sq. The resistance value of the FSS patch square resistor will affect the peak position, depth and width of the resonant absorption peak of the absorbing material.

[0004] In most studies, FSS is achieved on non-stretchable substrates. Considering the manufacturing process of composite materials, it is difficult to apply these methods to complex three-dimensional structures. Therefore, in recent years, some studies have used polyimide (PI) films or fiber fabrics as substrate materials to prepare FSS patterns. However, PI films as metamaterial substrates have poor compatibility with resins when preparing composite materials. This compatibility problem will lead to a decrease in the mechanical properties and absorption performance of the composite materials. Most fabrics have relatively rough surfaces, and due to the interweaving of warp and weft yarns, the height of the FSS pattern is uneven, resulting in a random distribution of the square resistance of the prepared FSS pattern, which will seriously affect the absorption performance of the final composite material.

[0005] Aramid unidirectional fabric has a high surface flatness, which helps to improve the accuracy and quality of the pattern during FSS pattern preparation and reduce the problems of pattern diffusion and surface unevenness. Figure 1 As shown in the figure, when the FSS pattern is printed on the surface of aramid plain fabric, the conductive ink diffuses due to the capillary effect of the fiber, and the interweaving of the warp and weft yarns makes the thickness of the prepared pattern uneven, resulting in large differences in the FSS pattern. Figure 1 (a1) is a real picture of FSS pattern printed on aramid plain fabric, a2 is a schematic diagram of ink diffusion, and a3 is a schematic diagram of ink thickness. Figure 1 (b) is a physical picture of the FSS pattern printed on the aramid unidirectional cloth. Secondly, due to the directional arrangement of its fibers, the aramid unidirectional cloth usually has higher strength and modulus than woven fabrics, which enables the aramid unidirectional cloth to better maintain the integrity and accuracy of the pattern when subjected to mechanical stress. Furthermore, compared with PI film, the aramid unidirectional cloth has higher compatibility with resin. The present invention uses aramid unidirectional cloth as the printing substrate for the FSS pattern, and the prepared absorbing composite material has superior absorbing performance and mechanical properties compared with existing research. Finally, we designed a dielectric protective layer on the surface of the FSS pattern to solve the problem that in actual applications, when the FSS pattern is exposed on the outer surface of the structure and is subjected to external force loading, wear damage and local delamination lead to a decrease in the absorbing performance of the absorber. Finally, a structurally functional integrated absorbing composite material with mechanical bearing and broadband absorbing performance is realized. Summary of the Invention

[0006] The problems existing in the existing technology include the problem that the existing FSS substrate is not stretchable and cannot be applied to complex three-dimensional structures, the problem that the existing research uses PI film as the FSS substrate and has poor compatibility with the resin matrix, the problem that the existing research uses woven fabric as the FSS substrate, and the integrity and uniformity of the prepared pattern are reduced; the problem that the existing FSS pattern on the outer surface of the structure suffers from wear damage and local delamination under various loading conditions in actual applications, resulting in a reduction in the absorbing performance of the absorber.

[0007] The present invention provides a method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material, comprising the following steps:

[0008] S1: Add polymer beads to PEDOT:PSS dispersion, let it stand, stir, remove the beads, freeze-dry to obtain solid PEDOT:PSS, and mix the solid PEDOT:PSS with a solvent to obtain PEDOT:PSS conductive ink;

[0009] S2: The aramid unidirectional fabric is cleaned by shaking in acetone and dried; an FSS pattern is prepared by screen printing on the treated aramid unidirectional fabric using the PEDOT:PSS conductive ink obtained in S1, and then the fabric is dried in an oven to obtain an aramid unidirectional fabric printed with the FSS pattern;

[0010] S3: Apply a release agent to the mold surface, cut the aramid fiber unidirectional / epoxy resin prepreg, aramid unidirectional cloth, aramid unidirectional cloth printed with FSS pattern, epoxy resin film and carbon fiber unidirectional / epoxy resin prepreg into the size of the mold, lay the carbon fiber unidirectional / epoxy resin prepreg, aramid fiber unidirectional / epoxy resin prepreg, epoxy resin film, aramid fiber unidirectional cloth printed with FSS pattern and epoxy film from bottom to top, perform hot pressing molding, naturally cool and demold, and obtain a metasurface broadband absorbing composite based on the new metasurface substrate material.

[0011] Furthermore, the standing time described in S1 is 1 to 2 hours, the stirring interval time is 20 to 30 minutes, and the freeze-drying time is 72 hours.

[0012] Furthermore, the shaking cleaning time in S2 is 2 to 5 hours, the drying temperature is 80 to 100° C., and the time is 0.5 to 1 hour.

[0013] Furthermore, the carbon fiber unidirectional / epoxy resin prepreg described in S3 is 1 to 3 layers.

[0014] Furthermore, the size of the mold in S3 is 200 mm×200 mm.

[0015] Furthermore, the hot pressing process described in S3 is performed at a temperature of 150° C., a pressure of 8 MPa, and a time of 25 min.

[0016] A metasurface broadband absorbing composite material based on a novel metasurface substrate material comprises a layered structure comprising two layers of carbon fiber unidirectional / epoxy resin prepreg laid out in a horizontal and vertical cross-ply pattern on the lower layer, six layers of aramid fiber unidirectional / epoxy resin prepreg laid out in the middle layer, and a top layer comprising, from bottom to top, a layer of epoxy film, a layer of aramid fiber unidirectional cloth printed with an FSS pattern, and a layer of epoxy film laid out in sequence.

[0017] Beneficial effects

[0018] The present invention provides a method for preparing a metasurface broadband absorbing composite material based on a new metasurface substrate material. By using aramid unidirectional cloth as the substrate of the FSS pattern, the metasurface pattern is completely prepared, and the uniformity of the square resistance of the metasurface pattern is regulated. Combined with metamaterial electromagnetic simulation, the goal of "thin, light, wide, and strong" absorbing performance of the absorbing composite material is achieved, and the absorbing performance shows better reliability and durability in various application environments.

[0019] Through the preparation method of a metasurface broadband absorbing composite material based on a new metasurface substrate material provided by the present invention, a dielectric protective layer is designed on the surface of the FSS pattern, which solves the problem that in practical applications, when the FSS pattern is exposed on the outer surface of the structure and is subjected to external force loading, wear damage and local delamination lead to a decrease in the absorbing performance of the absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following is a brief introduction to the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other relevant drawings can be obtained based on these drawings without creative work.

[0021] In the picture:

[0022] Figure 1 Actual pictures of FSS patterns printed on different aramid substrates and schematic diagrams of ink diffusion;

[0023] Figure 2 This is the electromagnetic parameter diagram of the aramid fiber / epoxy resin composite material of the present invention;

[0024] Figure 3 The top view and side view of the wave absorber containing square ring unit geometric pattern of the present invention;

[0025] Figure 4 Schematic diagram of the FSS periodic structure verified by the experiment of the present invention;

[0026] Figure 5Schematic diagram of the ply structure of Comparative Example 1 of the present invention;

[0027] Figure 6 Schematic diagram of the ply structure of Comparative Example 2 of the present invention;

[0028] Figure 7 Schematic diagram of the ply structure of Comparative Example 3 of the present invention;

[0029] Figure 8 Schematic diagram of the ply structure of Comparative Example 4 of the present invention;

[0030] Figure 9 Schematic diagram of the ply structure of Comparative Example 5 of the present invention;

[0031] Figure 10 Schematic diagram of the ply structure of Comparative Example 6 of the present invention;

[0032] Figure 11 Schematic diagram of the ply structure of Example 1 of the present invention;

[0033] Figure 12 Schematic diagram of the ply structure of Comparative Example 7 of the present invention;

[0034] Figure 13 Surface and cross-sectional views of the structural and functional integrated absorbing composite material of the present invention;

[0035] Figure 14 This is a test curve of the wave absorption performance of Example 1 of the present invention;

[0036] Figure 15 The top view and side view of the absorber containing square unit geometric patterns of the present invention;

[0037] Figure 16 Schematic diagram of the FSS periodic structure of the present invention;

[0038] Figure 17 Schematic diagram of the ply structure of Comparative Example 8 of the present invention;

[0039] Figure 18 Schematic diagram of the ply structure of Comparative Example 9 of the present invention;

[0040] Figure 19 Schematic diagram of the ply structure of comparative example 10 of the present invention. DETAILED DESCRIPTION

[0041] The following is a summary of the invention's embodiment 1 and comparative examples 1 to 10 and the accompanying drawings. Figures 1 to 19The present invention clearly and completely describes the technical solution of the present invention. It is obvious that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0042] The present invention provides a method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material, comprising the following steps:

[0043] S1: First, weigh a PEDOT:PSS dispersion, add superabsorbent polymer beads to it, let it stand at room temperature with occasional stirring, then remove the beads and pre-freeze it in a refrigerator; freeze-dry it in a freeze dryer to obtain solid PEDOT:PSS; weigh the solid PEDOT:PSS, DMSO, and deionized water, and manually mix them by pushing back and forth between two syringes to ensure that the PEDOT:PSS and the solvent are completely mixed to prepare PEDOT:PSS conductive ink;

[0044] S2: The aramid unidirectional fabric is placed in an ultrasonic cleaner in an acetone solution for vibration cleaning, and then placed in an oven for drying to ensure that impurities and colloids on the fiber surface are completely removed; the desired FSS pattern is prepared on the treated aramid unidirectional fabric using PEDOT:PSS conductive ink by screen printing, and the fabric is placed in an oven to obtain an aramid unidirectional fabric printed with the FSS pattern;

[0045] S3: Use aramid fiber unidirectional / epoxy resin prepreg, aramid unidirectional cloth, and epoxy resin film as the dielectric layer, and carbon fiber unidirectional / epoxy resin prepreg as the reflective layer. First, apply a release agent to the mold surface, then cut the aramid fiber unidirectional / epoxy resin prepreg, aramid unidirectional cloth, aramid unidirectional cloth printed with an FSS pattern, epoxy resin film, and carbon fiber unidirectional / epoxy resin prepreg into the mold size. Lay several layers of carbon fiber unidirectional / epoxy resin prepreg on the bottom layer, and lay several layers of aramid fiber unidirectional / epoxy resin prepreg in the middle layer according to the thickness requirements. The top layer is laid out in order from bottom to top: a layer of epoxy film, a layer of aramid unidirectional cloth printed with an FSS pattern, and a layer of epoxy film. After smoothing, place the layers into the mold. The unidirectional prepreg layers are laid in a cross-wise manner to prevent deformation caused by excessive stress concentration during the hot pressing process. The mold is placed in a hot press and formed through a hot pressing process. After natural cooling, the mold is removed from the mold to obtain a metasurface broadband absorbing composite based on the new metasurface substrate material. The composite material in the absorbing composite refers to a composite material.

[0046] Example 1

[0047] S1: Weigh 100 mL of PEDOT:PSS (PHV500) dispersion, add 2 g of superabsorbent polymer beads, let stand at room temperature for 1 h with occasional stirring, and then remove the beads; prefreeze in a refrigerator for 3 h, and freeze-dry in a freeze dryer for 72 h to obtain solid PEDOT:PSS; take 1.5 g of solid PEDOT:PSS, 2 ml of DMSO, and 18 ml of deionized water, and manually mix them by pushing two syringes back and forth for more than 5 minutes to completely mix the PEDOT:PSS and the solvent to prepare PEDOT:PSS conductive ink;

[0048] S2: The aramid fiber unidirectional fabric was placed in an acetone solution in an ultrasonic cleaner for 2 hours, and then placed in an 80°C oven for 1 hour to dry for later use, ensuring that impurities and colloids on the surface of the aramid fiber unidirectional fabric were completely removed; the desired FSS pattern was prepared on the treated aramid fiber unidirectional fabric using PEDOT:PSS conductive ink by screen printing;

[0049] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of aramid fiber unidirectional / epoxy resin prepreg on the middle layer, and lay a layer of epoxy film, a layer of aramid fiber unidirectional cloth printed with FSS pattern and a layer of epoxy film on the top layer from bottom to top. After leveling, put it into the mold. The layout diagram is shown as follows: Figure 11 As shown; the mold is placed in a hot press, vacuumed, heated and pressurized, kept warm and pressurized, and finally cooled. It is hot pressed at 150°C and 8MPa for 25 minutes, naturally cooled to below 50°C, demolded and taken out to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0050] In S1, the volume ratio of DMSO should not exceed 50% of the total volume, and the viscosity of the conductive ink prepared by controlling the solid content of PEDOT:PSS at 5% to 9% is more suitable; the ratio of solid PEDOT:PSS to DMSO and deionized water can be adjusted within a certain range according to the required square resistance of the FSS pattern.

[0051] In S3, one to three layers of carbon fiber unidirectional / epoxy resin prepreg are sufficient for the reflective layer to achieve full electromagnetic wave reflection. The aramid fiber unidirectional / epoxy resin prepreg in the middle layer can also be replaced by alternating layers of aramid unidirectional cloth and epoxy resin film. There are no strict requirements for the areal density of the aramid fiber unidirectional / epoxy resin prepreg, carbon fiber unidirectional / epoxy resin prepreg, aramid unidirectional cloth, and epoxy resin film. However, the epoxy resin used in both prepregs and the epoxy resin film should be the same, which improves the overall mechanical properties of the absorbing composite. The hot pressing process parameters should be determined based on the selected epoxy resin prepreg. The hot pressing temperature should not exceed 200°C, otherwise it may negatively affect the conductivity of the PEDOT:PSS film. The hot pressing pressure should not exceed 15 MPa, otherwise it may cause extrusion deformation during processing, which may damage the integrity of the metasurface pattern. The demolding temperature should not exceed 60°C, otherwise it will affect the overall mechanical properties of the absorbing composite.

[0052] For the extraction of electromagnetic parameters of dielectric layer composite materials, a surface density of 700g / m 2 Aramid fiber plain weave / epoxy resin prepreg, wherein the aramid plain weave fabric surface density is 410g / m 2 Through the lamination and hot pressing process (hot pressing at 150℃ and 8MPa for 25min, naturally cooling to below 50℃ and demolding), an aramid fiber / epoxy resin composite material with a thickness of 5.35mm was prepared. Then a cutting machine was used to cut out the waveguide dimensions corresponding to each band within 2 to 18GHz. Finally, the dielectric properties of the aramid / epoxy resin composite material were measured by the waveguide method, and the corresponding electromagnetic parameters were extracted. The specific test results are as follows. Figure 2 shown. Figure 2 It includes the real part (ε') and imaginary part (ε") of the dielectric constant, the real part (μ') and imaginary part (μ") of the magnetic permeability

[0053] For the measurement of absorption performance data, the square ring patch used in this patent has a strong design, including five parameters: periodic unit side length P, square ring outer side length a, square ring inner side length b, square ring patch square resistance cond and dielectric layer thickness h. The top view and side view of the absorber with unit geometry are as follows: Figure 3 The designed metamaterial absorbers were simulated using the frequency domain solver of the electromagnetic simulation software CST Microwave Studio. The absorbers were placed in a periodic distribution on the xy plane, with an open (add space) boundary in the z direction. The simulation frequency ranged from 2 to 18 GHz.

[0054] In order to verify the accuracy of the model, a composite material containing FSS film was prepared with the corresponding parameters of the optimal absorbing performance. The periodic unit side length P = 8mm, the patch side length a = 6mm, b = 4mm, the patch square resistance cond = 30Ω / sq, and the dielectric layer thickness h = 3mm. The accuracy of the simulation was verified by comparing the experiment with the simulation. The square resistance of the FSS film was tested by the four-probe method, and the absorbing performance of the structural and functional integrated absorbing composite material containing the FSS film was tested by the bow method. Figure 4 shown.

[0055] In the test results of Example 1, the density of the absorbing composite material is 1.138 g / cm 3 , thickness 3.2mm, FSS film square resistance cond = 30±8Ω / sq, reflection loss less than -10dB in the frequency range of 2~18GHz, effective absorption bandwidth (EAB) is 10.52GHz (7.28~17.80GHz), and tensile strength is 572.6MPa.

[0056] Figure 13 The microscopic morphology of the surface and side of the structural and functional integrated absorbing composite material of Example 1 is shown in FIG. Figure 13 (a) It can be seen that the surface of the aramid fiber / epoxy resin prepreg composite material is smooth after hot pressing and curing, and the epoxy resin has good coating on the aramid fiber. Figure 13 (b) It can be seen that the interface performance of carbon fiber unidirectional / epoxy resin prepreg and aramid fiber / epoxy resin prepreg is good after hot pressing and curing, and no obvious delamination phenomenon occurs.

[0057] Figure 14 The test results of the absorbing performance of the absorbing composite material of Example 1 show that the prepared structural and functional integrated composite material based on metamaterials achieves a reflection loss of less than -10dB in the frequency range of 7.28 to 17.80GHz, and the EAB is as high as 10.52GHz.

[0058] Comparative Example 1

[0059] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0060] S2: The PI film is placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that all impurities on the surface of the PI film are completely removed; the desired FSS pattern is prepared on the treated PI film using PEDOT:PSS conductive ink by screen printing;

[0061] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes between each application. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of aramid fiber unidirectional / epoxy resin prepreg in the middle layer, and lay a layer of epoxy resin film and a layer of PI film printed with FSS pattern on the top layer from bottom to top. The schematic diagram of the layer laying is shown in the figure. Figure 5 As shown, after being leveled, it is placed in a mold; the mold is placed in a hot press, vacuumed, heated and pressurized, kept warm and pressurized, and finally cooled, hot pressed at 150°C and 8MPa for 25 minutes, naturally cooled to below 50°C and demolded to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0062] In Comparative Example 1, the FSS pattern substrate is PI film + aramid fiber unidirectional / epoxy resin prepreg, and the top layer has no epoxy resin protective layer. Through testing, the density of the absorbing composite material is 1.008g / cm 3 , thickness 3.2mm, FSS film square resistance cond = 30±5Ω / sq, EAB with reflection loss less than -10dB in the frequency range of 2 to 18GHz is 10.13GHz (7.28 to 17.41GHz), and tensile strength is 521.5MPa. However, since there is no protective layer on the upper layer of the FSS film, the film will fall off if placed in an outdoor environment for a long time, and the PI film has poor compatibility with epoxy resin, and delamination occurs between the two, which leads to the collapse of the overall structure of the absorbing composite material in the later stage and a sharp decline in the absorbing performance.

[0063] Comparative Example 2

[0064] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0065] S2: The PI film is placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that all impurities on the surface of the PI film are completely removed; the desired FSS pattern is prepared on the treated PI film using PEDOT:PSS conductive ink by screen printing;

[0066] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of aramid fiber unidirectional / epoxy resin prepreg in the middle layer, and lay a layer of epoxy film, a layer of PI film printed with FSS pattern and a layer of epoxy resin film on the top layer from bottom to top. The layup diagram is shown in the figure. Figure 6As shown, after being leveled, it is placed in a mold; the mold is placed in a hot press, vacuumed, heated and pressurized, kept warm and pressurized, and finally cooled, hot pressed at 150°C and 8MPa for 25 minutes, naturally cooled to below 50°C and demolded to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0067] In Comparative Example 2, the FSS pattern substrate is a PI film, the dielectric layer is an aramid fiber unidirectional / epoxy resin prepreg, and the top layer has an epoxy resin protective layer. Through testing, the density of the absorbing composite material is 1.098g / cm 3 , thickness 3.2mm, FSS film square resistance cond=30±5Ω / sq, EAB with reflection loss less than -10dB in the frequency range of 2~18GHz is 10.07GHz (7.06~17.13GHz), and tensile strength is 510.8MPa. However, due to the poor compatibility between PI film and epoxy resin, delamination occurs between the two, resulting in the collapse of the overall structure of the absorbing composite material and a sharp decline in the absorbing performance.

[0068] Comparative Example 3

[0069] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0070] S2: The PI film is placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that all impurities on the surface of the PI film are completely removed; the desired FSS pattern is prepared on the treated PI film using PEDOT:PSS conductive ink by screen printing;

[0071] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes between each application. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of aramid fiber plain weave / epoxy resin prepreg on the middle layer, and lay a layer of epoxy resin film, a layer of PI film printed with FSS pattern, and a layer of epoxy resin film on the top layer from bottom to top. The layup diagram is shown in the figure below. Figure 7 As shown, after being leveled, it is placed in a mold; the mold is placed in a hot press, vacuumed, heated and pressurized, kept warm and pressurized, and finally cooled, hot pressed at 150°C and 8MPa for 25 minutes, naturally cooled to below 50°C and demolded to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0072] In Comparative Example 3, the FSS pattern substrate is a PI film, the dielectric layer is an aramid fiber plain weave / epoxy resin prepreg, and the top layer has an epoxy resin protective layer. Through testing, the density of the absorbing composite material is 1.102g / cm 3The thickness is 3.2mm, the FSS film square resistance cond = 30±5Ω / sq, the EAB with reflection loss less than -10dB in the frequency range of 2 to 18GHz is 9.45GHz (7.68 to 17.13GHz), and the tensile strength is 432.7MPa. However, due to the poor compatibility between the PI film and the epoxy resin, delamination occurs between the two, resulting in the collapse of the overall structure of the absorbing composite material and a sharp decline in absorbing performance. Secondly, because the surface of the aramid fiber plain weave is not smooth enough, the surface of the PI film printed with the FSS pattern after hot pressing is printed with fabric texture, which affects the accuracy of the FSS pattern and causes a slight decrease in absorbing performance.

[0073] Comparative Example 4

[0074] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0075] S2: The glass fiber plain fabric was placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that all impurities and colloids on the surface of the glass fiber plain fabric were removed. The desired FSS pattern was prepared on the treated glass fiber plain fabric using PEDOT:PSS conductive ink by screen printing.

[0076] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes between each application. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of glass fiber plain weave / epoxy resin prepreg on the middle layer, and lay a layer of epoxy film, a layer of glass fiber plain weave fabric printed with FSS pattern, and a layer of epoxy film on the top layer from bottom to top. The layup diagram is shown in the figure below. Figure 8 As shown, after being leveled, it is placed in a mold; the mold is placed in a hot press, vacuumed, heated and pressurized, kept warm and pressurized, and finally cooled, hot pressed at 150°C and 8MPa for 25 minutes, naturally cooled to below 50°C and demolded to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0077] In Comparative Example 4, the FSS pattern substrate is glass fiber plain weave fabric, the dielectric layer is glass fiber plain weave / epoxy resin prepreg, and the top layer has an epoxy resin protective layer. Through testing, the density of the absorbing composite material is 1.733g / cm 3The FSS film has a thickness of 3.2 mm, a square resistance of 30 ± 40 Ω / sq, an EAB with a reflection loss less than -10 dB in the 2-18 GHz frequency range at 7.26 GHz (10.06-17.32 GHz), and a tensile strength of 325.0 MPa. Due to the capillary effect of the glass fiber, the conductive ink diffuses, and the interweaving of the warp and weft yarns results in uneven thickness of the prepared pattern, resulting in significant variations in the FSS pattern. This poorly uniform pattern square resistance results in reduced absorption performance.

[0078] Comparative Example 5

[0079] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0080] S2: The glass fiber unidirectional cloth was placed in an acetone solution in an ultrasonic cleaner for 2 hours, and then placed in an 80°C oven for 1 hour to dry for later use, ensuring that impurities and colloids on the surface of the glass fiber unidirectional cloth were completely removed; the desired FSS pattern was prepared on the treated glass fiber unidirectional cloth using PEDOT:PSS conductive ink by screen printing;

[0081] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of glass fiber unidirectional / epoxy resin prepreg in the middle layer, and lay a layer of epoxy film, a layer of glass fiber unidirectional cloth printed with FSS pattern, and a layer of epoxy film on the top layer from bottom to top. The layup diagram is shown in the figure below. Figure 9 As shown; after being leveled, put it into a mold; place the mold in a hot press, perform vacuuming, heating and pressurizing, heat preservation and pressure maintenance, and finally cool it; hot press it at 150°C and 8MPa for 25min, cool it naturally to below 50°C, demould it and take it out to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0082] In Comparative Example 5, the FSS pattern substrate is glass fiber unidirectional cloth, the dielectric layer is glass fiber unidirectional / epoxy resin prepreg, and the top layer has an epoxy resin protective layer. Through testing, the density of the absorbing composite material is 1.825g / cm 3 , thickness 3.2mm, FSS film square resistance cond = 30±8Ω / sq, EAB with reflection loss less than -10dB in the frequency range of 2 to 18GHz is 9.94GHz (8.06 to 18.00GHz), and tensile strength is 380.6MPa.

[0083] Comparative Example 6

[0084] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0085] S2: The aramid fiber plain weave fabric was placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that all impurities and colloids on the surface of the aramid fiber plain weave fabric were removed. The desired FSS pattern was prepared on the treated aramid fiber plain weave fabric using PEDOT:PSS conductive ink by screen printing.

[0086] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes between each application. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay six layers of aramid fiber plain weave / epoxy resin prepreg on the middle layer, and lay a layer of epoxy film, a layer of aramid fiber plain weave fabric printed with FSS pattern, and a layer of epoxy film on the top layer from bottom to top. The layup diagram is shown in the figure below. Figure 10 As shown; after being leveled, put it into a mold; place the mold in a hot press, perform vacuuming, heating and pressurizing, heat preservation and pressure maintenance, and finally cool it; hot press it at 150°C and 8MPa for 25min, cool it naturally to below 50°C, demould it and take it out to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0087] In Comparative Example 6, the FSS pattern substrate is aramid fiber plain weave fabric, the dielectric layer is aramid fiber plain weave / epoxy resin prepreg, and the top layer has an epoxy resin protective layer. According to the test, the density of the absorbing composite material is 1.182g / cm 3 The FSS film has a thickness of 3.2 mm, a square resistance of 30 ± 40 Ω / sq, an EAB with a reflection loss less than -10 dB in the 2-18 GHz frequency range at 6.68 GHz (9.24-15.92 GHz), and a tensile strength of 455.3 MPa. Due to the capillary effect of the aramid fibers, the conductive ink diffuses, and the interweaving of the warp and weft yarns results in uneven thickness of the prepared pattern, resulting in significant variations in the FSS pattern. This results in poor uniformity in the final pattern square resistance, leading to reduced absorption performance.

[0088] Comparative Example 7

[0089] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0090] S2: The aramid fiber unidirectional fabric was placed in an acetone solution in an ultrasonic cleaner for 2 hours, and then placed in an 80°C oven for 1 hour to dry for later use, ensuring that impurities and colloids on the surface of the aramid fiber unidirectional fabric were completely removed; the desired FSS pattern was prepared on the treated aramid fiber unidirectional fabric using PEDOT:PSS conductive ink by screen printing;

[0091] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, lay five layers of aramid fiber plain weave / epoxy resin prepreg on the middle layer, and lay a layer of epoxy resin film, a layer of aramid fiber unidirectional cloth, a layer of epoxy resin film, a layer of aramid fiber unidirectional cloth printed with FSS pattern and a layer of epoxy resin film on the top layer from bottom to top. The layup diagram is shown in the figure below. Figure 12 As shown; after being leveled, put it into a mold; place the mold in a hot press, perform vacuuming, heating and pressurizing, heat preservation and pressure maintenance, and finally cool it; hot press it at 150°C and 8MPa for 25min, cool it naturally to below 50°C, demould it and take it out to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0092] In comparative example 7, the FSS pattern substrate is aramid fiber unidirectional cloth, the dielectric layer is aramid fiber plain weave / epoxy resin prepreg, and the top layer has an epoxy resin protective layer. Through testing, the density of the absorbing composite material is 1.114g / cm 3 , thickness 3.2mm, FSS film square resistance cond = 30±8Ω / sq, EAB with reflection loss less than -10dB in the frequency range of 2 to 18GHz is 10.24GHz (7.76 to 18.00GHz), and tensile strength is 482.9MPa.

[0093] The present invention is applicable to the preparation of any metasurface absorbing composite material requiring a relatively fine FSS pattern, and can greatly improve the accuracy and uniformity of the FSS pattern. The square patch used in this study has a strong design, including five parameters: the periodic unit side length P, the square side length a, the square patch square resistance cond, and the dielectric layer thickness h1 and h. The top view and side view of the absorber containing the unit geometry are shown in the figure. Figure 15 The designed metamaterial absorbers were simulated using the frequency domain solver of the electromagnetic simulation software CST Microwave Studio. The absorbers were placed in a periodic distribution on the xy plane, with an open (add space) boundary in the z direction. The simulation frequency ranged from 2 to 18 GHz.

[0094] In order to verify the accuracy of the model, a composite material containing FSS film with the corresponding parameters of the optimal absorbing performance was prepared, with the periodic unit side length P = 10mm, the patch side length a = 6mm, the patch square resistance cond = 50Ω / sq, the dielectric layer thickness h1 = 2.0mm, h = 3.4mm. The accuracy of the simulation was verified by comparing the experiment with the simulation. The square resistance of the FSS film was tested by the four-probe method, and the absorbing performance of the structural and functional integrated absorbing composite material containing the FSS film was tested by the bow method. Figure 16 The schematic diagram of the FSS periodic structure can be obtained.

[0095] Comparative Example 8

[0096] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0097] S2: The PI film is placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that all impurities on the surface of the PI film are completely removed; the desired FSS pattern is prepared on the treated PI film using PEDOT:PSS conductive ink by screen printing;

[0098] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, and lay five layers of aramid fiber plain weave / epoxy resin prepreg in the middle layer. Then, lay a layer of epoxy film, a layer of PI film printed with FSS pattern, and a layer of epoxy film from bottom to top. Lay three layers of aramid fiber plain weave / epoxy resin prepreg on the top layer. The layup diagram is shown in the figure. Figure 17 As shown, after being leveled, it is placed in a mold; the mold is placed in a hot press, vacuumed, heated and pressurized, kept warm and pressurized, and finally cooled, hot pressed at 150°C and 8MPa for 25 minutes, naturally cooled to below 50°C and demolded to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0099] In Comparative Example 8, the FSS square pattern substrate is a PI film, and the dielectric layer is an aramid fiber plain weave / epoxy resin prepreg. Through testing, the density of the absorbing composite material is 1.201g / cm 3The thickness is 3.6mm, the FSS film square resistance cond = 50±5Ω / sq, the EAB with reflection loss less than -10dB in the frequency range of 2 to 18GHz is 8.12GHz (8.21 to 16.33GHz), and the tensile strength is 408.5MPa. However, due to the poor compatibility between the PI film and the epoxy resin, delamination occurs between the two, resulting in the collapse of the overall structure of the absorbing composite material and a sharp decline in absorbing performance. Secondly, because the surface of the aramid fiber plain weave is not smooth enough, the surface of the PI film printed with the FSS pattern after hot pressing is printed with fabric texture, which affects the accuracy of the FSS pattern and causes a slight decrease in absorbing performance.

[0100] Comparative Example 9

[0101] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0102] S2: The aramid fiber plain weave fabric was placed in an acetone solution and ultrasonically cleaned for 2 hours, then placed in an 80°C oven for 1 hour and dried for later use to ensure that the colloid and impurities on the surface of the aramid fiber plain weave fabric were completely removed; the desired FSS pattern was prepared on the treated aramid fiber plain weave fabric using PEDOT:PSS conductive ink by screen printing;

[0103] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay two layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, and lay five layers of aramid fiber plain weave / epoxy resin prepreg in the middle layer. Then, lay a layer of epoxy film, a layer of aramid fiber plain weave fabric printed with FSS pattern, and a layer of epoxy film from bottom to top. Lay three layers of aramid fiber plain weave / epoxy resin prepreg on the top layer. The layup diagram is shown in the figure. Figure 18 As shown; after being leveled, put it into a mold; place the mold in a hot press, perform vacuuming, heating and pressurizing, heat preservation and pressure maintenance, and finally cool it; hot press it at 150°C and 8MPa for 25min, cool it naturally to below 50°C, demould it and take it out to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0104] In Comparative Example 9, the FSS square pattern substrate is aramid plain weave fabric, and the dielectric layer is aramid fiber plain weave / epoxy resin prepreg. According to the test, the density of the absorbing composite material is 1.244g / cm 3The FSS film has a thickness of 3.6mm, a square resistance of 50±40Ω / sq, an EAB with a reflection loss less than -10dB in the 2-18GHz frequency range at 6.14GHz (8.12-14.26GHz), and a tensile strength of 448.7MPa. Due to the capillary effect of the aramid fibers, the conductive ink diffuses, and the interweaving of the warp and weft yarns results in uneven thickness of the prepared pattern, resulting in significant variations in the FSS pattern. This results in poor uniformity in the final pattern square resistance, leading to reduced absorption performance.

[0105] Comparative Example 10

[0106] S1: The preparation process of PEDOT:PSS conductive ink is the same as that of Example 1;

[0107] S2: The aramid fiber unidirectional fabric was placed in an acetone solution in an ultrasonic cleaner for 2 hours, and then placed in an 80°C oven for 1 hour to dry for later use, ensuring that the colloid and impurities on the surface of the aramid fiber unidirectional fabric were completely removed; the desired FSS pattern was prepared on the treated aramid fiber unidirectional fabric using PEDOT:PSS conductive ink by screen printing;

[0108] S3: Apply mold release agent to the mold surface 2 to 3 times, with an interval of 5 minutes each time. Then cut the required materials into a mold size of 200mm×200mm. Lay 2 layers of carbon fiber unidirectional / epoxy resin prepreg in a horizontal and vertical cross-laying manner on the lower layer, and lay 5 layers of aramid fiber unidirectional / epoxy resin prepreg in the middle layer. Then, lay a layer of epoxy film, a layer of aramid fiber unidirectional cloth printed with FSS pattern and a layer of epoxy film from bottom to top. Lay 3 layers of aramid fiber unidirectional / epoxy resin prepreg on the top layer. The layup diagram is shown as follows: Figure 19 As shown; after being leveled, put it into a mold; place the mold in a hot press, perform vacuuming, heating and pressurizing, heat preservation and pressure maintenance, and finally cool it; hot press it at 150°C and 8MPa for 25min, cool it naturally to below 50°C, demould it and take it out to obtain a super-surface broadband absorbing composite material based on the new super-surface substrate material.

[0109] In Comparative Example 10, the FSS square pattern substrate is aramid unidirectional cloth, and the dielectric layer is aramid fiber unidirectional / epoxy resin prepreg. According to the test, the density of the absorbing composite material is 1.208g / cm 3 , thickness 3.6mm, FSS film square resistance cond = 50±8Ω / sq, EAB with reflection loss less than -10dB in the frequency range of 2 to 18GHz is 8.97GHz (8.55 to 17.52GHz), and tensile strength is 554.3MPa.

[0110] By using aramid unidirectional cloth as the substrate of the FSS pattern, the present invention successfully solves the problem that the traditional FSS substrate is non-stretchable and cannot be applied to complex three-dimensional structures, while improving the preparation integrity of the FSS pattern and the control of the uniformity of the pattern square resistance. Compared with the PI film or woven fabric used in existing research, this solution greatly improves the compatibility of the FSS substrate and the resin matrix, ensuring the uniformity and integrity of the pattern. In addition, by designing a dielectric protective layer on the surface of the FSS pattern, the problem of reduced absorption performance caused by wear damage or local delamination when the pattern is exposed to external conditions is effectively avoided. Combined with the electromagnetic simulation design of metamaterials, the absorbing composite material is finally significantly optimized in terms of "thin, light, wide, and strong" performance, showing higher reliability and durability in various application environments.

Claims

1. A method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material, characterized in that: The following steps are involved: S1: Add polymer beads to PEDOT:PSS dispersion, let it stand, stir, remove the beads, freeze-dry to obtain solid PEDOT:PSS, and mix the solid PEDOT:PSS with a solvent to obtain PEDOT:PSS conductive ink; S2: The aramid unidirectional fabric is cleaned by shaking in acetone and dried; an FSS pattern is prepared by screen printing on the treated aramid unidirectional fabric using the PEDOT:PSS conductive ink obtained in S1, and then the fabric is dried in an oven to obtain an aramid unidirectional fabric printed with the FSS pattern; S3: Apply a release agent to the mold surface, cut the carbon fiber unidirectional / epoxy resin prepreg, aramid fiber unidirectional / epoxy resin prepreg, aramid unidirectional cloth printed with FSS pattern, and epoxy resin film into the size of the mold, lay the carbon fiber unidirectional / epoxy resin prepreg, aramid fiber unidirectional / epoxy resin prepreg, epoxy resin film, aramid fiber unidirectional cloth printed with FSS pattern, and epoxy resin film from bottom to top, perform hot pressing molding, and naturally cool and demold to obtain a metasurface broadband absorbing composite based on the new metasurface substrate material.

2. The method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material according to claim 1, characterized in that: The standing time in S1 is 1 to 2 hours, the stirring interval is 20 to 30 minutes, and the freeze-drying time is 72 hours.

3. The method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material according to claim 1, characterized in that: The shaking cleaning time in S2 is 2 to 5 hours, the drying temperature is 80 to 100°C, and the time is 0.5 to 1 hour.

4. The method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material according to claim 1, characterized in that: The carbon fiber unidirectional / epoxy resin prepreg described in S3 is 1 to 3 layers.

5. The method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material according to claim 1, characterized in that: The size of the mold in S3 is 200 mm×200 mm.

6. The method for preparing a supersurface broadband absorbing composite material based on a novel supersurface substrate material according to claim 1, characterized in that: The hot pressing process described in S3 is performed at a temperature of 150° C., a pressure of 8 MPa, and a time of 25 min.

7. A supersurface broadband absorbing composite material based on a novel supersurface substrate material obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The metasurface broadband absorbing composite material based on the new metasurface substrate material has a layered structure in which two layers of carbon fiber unidirectional / epoxy resin prepreg are laid in a horizontal and vertical cross-ply manner on the lower layer, six layers of aramid fiber unidirectional / epoxy resin prepreg are laid in the middle layer, and a layer of epoxy resin film, a layer of aramid fiber unidirectional cloth printed with an FSS pattern, and a layer of epoxy resin film are laid in sequence on the top layer from bottom to top.

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