Metamaterial honeycomb and preparation method thereof

Abstract

The invention discloses a metamaterial honeycomb and a preparation method thereof, and relates to the technical field of aramid paper honeycombs. The preparation method of the metamaterial honeycomb comprises the following steps: carrying out electromagnetic modification, gluing, overlapping, pressing, stretching and shaping, and pre-curing on aramid paper to obtain the metamaterial honeycomb after the target density is reached. By means of the method, the metamaterial honeycomb with the excellent wave-absorbing performance in the broadband range can be prepared, the density of the wave-absorbing honeycomb can be greatly reduced while the excellent wave-absorbing performance is achieved, meanwhile, the compression strength under the same density is increased, the weight of functional structural parts of an aircraft can be greatly reduced, and the service life of the aircraft is prolonged. And the cost-effectiveness ratio of the aircraft is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aramid paper honeycombs, and in particular to a metamaterial honeycomb and a preparation method thereof. Background Art

[0002] Aramid paper honeycombs, with their excellent mechanical properties, high-temperature and corrosion resistance, and lightweight construction, are widely used in aerospace, rail transit, and defense industries. The recent emergence of stealth technology has significantly altered the dynamics of future warfare. To evade radar detection, the development of novel structurally absorbing honeycombs is crucial. While aramid paper honeycombs are ideally transparent, they lack excellent electromagnetic response, making them ineffective for achieving stealth in aircraft.

[0003] To create an ideal structurally functional honeycomb, the traditional method involves first preparing a honeycomb core material through a honeycomb fabrication process. This core material is then impregnated with an absorbent to create an absorbing honeycomb, effectively absorbing electromagnetic waves. While this method is relatively simple, it is difficult to precisely design the electromagnetic parameters of the gradient honeycomb due to factors such as thickness and gravity.

[0004] Therefore, how to achieve excellent absorbing performance while significantly reducing the density of the absorbing honeycomb and increasing the compressive strength at the same density has always been a goal that the industry urgently needs to improve. Summary of the Invention

[0005] The main purpose of the present invention is to provide a metamaterial honeycomb and a preparation method thereof, so as to solve the technical problem in the prior art that it is impossible to significantly reduce the density of the absorbing honeycomb while ensuring excellent absorbing performance.

[0006] To achieve the above object, according to a first aspect of the present invention, a method for preparing a metamaterial honeycomb is provided, comprising the following steps:

[0007] S1, compounding aramid paper with an electromagnetic metamaterial microstructure film to obtain electromagnetically modified aramid paper;

[0008] S2, applying glue on the electromagnetically modified aramid paper;

[0009] S3, stacking the electromagnetically modified aramid paper after gluing in a staggered stacking manner according to the required size in the width direction;

[0010] S4, pressing the stacked aramid paper blocks;

[0011] S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb;

[0012] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing;

[0013] S7, repeating S6 until the honeycomb density reaches a preset target density, thereby obtaining the metamaterial honeycomb.

[0014] Furthermore, the electromagnetic metamaterial microstructure film includes a PI film and a metal metamaterial microstructure attached to the surface of the PI film.

[0015] Furthermore, in step S2, after adjusting the mixing ratio of the node glue and ethyl acetate and the viscosity of the mixed glue solution, setting the number of core glue strips, the length of paper cutting and the gluing rate, the electromagnetically modified aramid paper is glued.

[0016] Furthermore, in the step S4, pressing is performed at a temperature of 150° C. to 250° C. and a pressure of 0.4 MPa to 1 MPa for 3 to 6 hours.

[0017] Furthermore, in step S5, the pressed aramid paper block is stretched to a preset theoretical length using a honeycomb stretching machine at a stretching rate of 80-120 mm / min.

[0018] Furthermore, in the step S5, after stretching, the film is placed in a shaping oven and cured at a temperature of 200-300° C. for 2-3 hours for shaping.

[0019] Furthermore, in step S6, the resin is phenolic resin, the pre-curing temperature is 120° C. to 150° C., and the pre-curing time is 0.5 h to 2 h.

[0020] Furthermore, in step S7, the target density is 30 kg / m 3 ~150kg / m 3 .

[0021] Furthermore, in step S1, the honeycomb cells of the aramid paper are hexagonal or rectangular.

[0022] According to a second aspect of the present invention, a metamaterial honeycomb is provided, which is prepared by the above-mentioned preparation method.

[0023] By applying the preparation method disclosed in the present invention, a metamaterial honeycomb with excellent wave-absorbing performance in a wide frequency range can be prepared. While achieving excellent wave-absorbing performance, the density of the wave-absorbing honeycomb can be significantly reduced, and the compressive strength at the same density can be increased. This can significantly reduce the weight of the functional structural parts of the aircraft and improve the cost-effectiveness of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1Flow chart of the preparation of metamaterial honeycomb in an embodiment of the present invention.

[0025] Figure 2 Schematic diagram of the structure of paper stacking in an embodiment of the present invention.

[0026] Figure 3 Schematic diagram of the metamaterial honeycomb prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0028] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0029] As described in the background of the present invention, the prior art has the technical problem of being unable to significantly reduce the density of absorbing honeycombs while ensuring excellent absorbing performance. In order to solve the above technical problem, in a typical embodiment of the present invention, a method for preparing a metamaterial honeycomb is provided, and its flow chart is as follows: Figure 1 As shown, the following steps are included:

[0030] S1, compounding aramid paper with an electromagnetic metamaterial microstructure film to obtain electromagnetically modified aramid paper;

[0031] S2, applying glue on the electromagnetically modified aramid paper;

[0032] S3, stacking the electromagnetically modified aramid paper after gluing in a staggered stacking manner according to the required size in the width direction (such as Figure 2 shown);

[0033] S4, pressing the stacked aramid paper blocks;

[0034] S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb;

[0035] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing;

[0036] S7, repeating S6 until the honeycomb density reaches a preset target density, thereby obtaining the metamaterial honeycomb.

[0037] The aramid paper honeycomb is empowered from the source of the aramid paper, that is, an electromagnetic metamaterial microstructure film is bonded to the surface of the aramid paper to obtain electromagnetically modified aramid paper. After the improvement, the density of the absorbing honeycomb can be greatly reduced while achieving excellent absorbing performance.

[0038] The method of the present invention can flexibly control the density of the metamaterial honeycomb by the number of impregnation and pre-curing times to meet the specific needs of different application scenarios.

[0039] Through steps such as pressing, stretching, shaping, and curing, the stability of the metamaterial honeycomb structure can be ensured, avoiding structural deformation or damage during the process or subsequent use, thereby ensuring the consistency and stability of its absorbing performance.

[0040] In some embodiments, in S1, the electromagnetic metamaterial microstructure film includes a PI film and a metal metamaterial microstructure attached to the surface of the PI film. Metamaterials are composite materials with artificially designed structures and exhibit extraordinary physical properties that natural materials do not possess. By changing the unit size of the metal resonator, it is possible to achieve near-perfect absorption of electromagnetic waves. By compounding the metal metamaterial microstructure on the surface of aramid paper, broadband absorption can be achieved, and the absorption performance can be designed over a large range through the metal metamaterial microstructure, and the comprehensive performance is better than the conventional absorbing honeycomb in the prior art. Among them, the metal metamaterial microstructure on the electromagnetic metamaterial microstructure film can be customized according to the actual function required, for example, it can be designed into a cross-shaped structure, such as Figure 3 As shown in the actual picture, the electromagnetic metamaterial microstructure film serves as the electromagnetic functional layer of the metamaterial honeycomb, which is used to realize the modulation of electromagnetic waves. The absorbing performance of the metamaterial honeycomb can be designed in a super-large range through the metal metamaterial microstructure. The comprehensive performance is better than the existing conventional absorbing honeycomb and can achieve broadband absorbing.

[0041] In some embodiments, in step S2, after adjusting the mixing ratio of node glue and ethyl acetate and the viscosity of the mixed glue solution, setting the number of core glue strips, the length of paper cutting and the gluing rate, the electromagnetically modified aramid paper is glued.

[0042] In some embodiments, in step S4, pressing is performed at a temperature of 150°C to 250°C and a pressure of 0.4 MPa to 1 MPa for 3 to 6 hours. Pressing under these conditions can improve the curing effect of the core adhesive, enhance the bonding strength between the aramid composite paper and the core adhesive, and thereby improve the structural stability of the metamaterial honeycomb.

[0043] In some embodiments, in step S5, the laminated aramid paper block is stretched to a predetermined theoretical length using a honeycomb stretching machine at a stretching rate of 80-120 mm / min. During the stretching process of the composite paper block into a honeycomb structure, residual stress is generated within the material. After the tensile force is removed, the uncured honeycomb may shrink or deform due to the residual stress, resulting in dimensional instability and affecting its performance as a structural material. Stretching under these conditions can improve the stability of the structural material.

[0044] In some embodiments, in step S5, after stretching, the material is placed in a shaping oven and cured for 2-3 hours at a temperature of 200-300° C. Under the above conditions, curing and shaping after stretching can also improve the stability of the structural material.

[0045] In some embodiments, in step S6, the resin is a phenolic resin, and the pre-curing temperature is 120°C to 150°C for 0.5 to 2 hours. The purpose of resin impregnation and pre-curing in step S6 is to improve the mechanical properties of the metamaterial honeycomb, such as compressive strength, tensile strength, and impact resistance. Resin impregnation makes the metamaterial honeycomb structure more compact and able to withstand greater external forces, thereby improving its overall mechanical properties. Furthermore, resin impregnation can improve the processing, molding, and chemical stability of the aramid honeycomb, thereby enhancing its durability and service life.

[0046] The purpose of controlling pre-curing and curing conditions is to ensure that the resin fully penetrates every tiny void in the aramid paper by controlling the temperature and time during the pre-curing stage, forming a more uniform composite structure and preventing the resin from curing too quickly at high temperatures, which could restrict its flow. By controlling the curing temperature and time within the above ranges, the resin can be fully cured, forming a stable three-dimensional cross-linked network, improving the mechanical strength and stiffness of the metamaterial honeycomb and enhancing the stability and durability of the overall structure.

[0047] In some embodiments, the resin is a phenolic resin (e.g., F01-30, 2124, etc.), or the resin can also be a polyimide resin (e.g., GI001, etc.). At least one of the phenolic resin and the polyimide resin is selected as the resin matrix of the metamaterial honeycomb mainly because these resins have excellent thermal stability, good dielectric properties, high strength and stiffness, chemical stability, low hygroscopicity, environmental adaptability, good processing performance, and environmental protection characteristics. These advantages work together to enable the metamaterial honeycomb to maintain a stable structure and efficient wave absorbing performance when facing complex environmental conditions, and is suitable for multiple fields such as aerospace, national defense, and military industry. The basic structure of the honeycomb wall of the metamaterial honeycomb made in this way is: phenolic resin-electromagnetic metamaterial microstructure membrane-aramid paper-phenolic resin, or phenolic resin-electromagnetic metamaterial microstructure membrane-aramid paper-electromagnetic metamaterial microstructure membrane-phenolic resin, polyimide resin-electromagnetic metamaterial microstructure membrane-aramid paper-polyimide resin, or polyimide resin-electromagnetic metamaterial microstructure membrane-aramid paper-electromagnetic metamaterial microstructure membrane-polyimide resin.

[0048] In some embodiments, in step S7, the target density is 30 kg / m 3 ~150kg / m 3 Controlling the target density opens up a wider range of applications for metamaterial honeycombs. Lower density (e.g. close to 30kg / m 3 ) means lighter weight, which is particularly important in the aerospace field because it can directly affect the load capacity and fuel efficiency of the aircraft. Higher density (such as close to 150kg / m 3 ) may provide better mechanical strength and rigidity, making it more suitable for structural components bearing higher loads. This density flexibility enables the metamaterial honeycomb to adapt to the needs of different application scenarios, enhancing its applicability and innovation in multiple industries. The metamaterial honeycomb produced by this invention has a low density, comparable to that of ordinary white honeycombs, and only less than 50% of the density of existing conventional absorbing honeycombs. Furthermore, density control through the number of impregnations ensures that the metamaterial honeycomb has both good structural integrity and good absorbing performance.

[0049] In some embodiments, in step S1, the honeycomb cells of the aramid paper are hexagonal or rectangular. This structural design can increase the compressive strength at the same density, significantly reduce the weight of the functional structural components of the aircraft, improve the cost-effectiveness of the aircraft, and enhance the structural stability of the metamaterial honeycomb.

[0050] In another typical embodiment of the present invention, a metamaterial honeycomb prepared by the preparation method in the above embodiment is provided, and the prepared physical object is shown in FIG. Figure 3As shown, the metamaterial honeycomb has excellent wave-absorbing performance over a wide frequency range. While achieving excellent wave-absorbing performance, the density of the wave-absorbing honeycomb can be significantly reduced, while at the same time increasing the compressive strength at the same density. This can significantly reduce the weight of the functional structural components of the aircraft, improve the cost-effectiveness of the aircraft, and help enhance the structural stability of the metamaterial honeycomb and broaden its application areas. Due to the lightweight, structurally stable, and wide-frequency absorption performance of the metamaterial honeycomb of the present invention, it is suitable for application in the aerospace and defense military fields.

[0051] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0052] Some of the materials used in the examples are as follows:

[0053] Resin: phenolic resin, model F01-30;

[0054] Aramid paper: thickness 0.03mm-0.08mm, model YT-836;

[0055] Core strip glue: Model is J-80B;

[0056] Node glue: Model J-80B Nomex;

[0057] Example 1

[0058] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0059] S1, using J-159 adhesive film to bond aramid paper with a thickness of 0.08 mm and an electromagnetic metamaterial microstructure film to obtain an electromagnetically modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.8 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0060] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0061] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0062] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 180° C. and a pressure of 0.5 MPa for 3 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0063] S5, stretching and shaping the laminated aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the laminated aramid paper block to a preset theoretical length at a stretching rate of 100 mm / min, and after stretching, placing the laminated aramid paper block in a shaping oven and curing it at a temperature of 260° C. for 2 hours to shape it;

[0064] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 130°C, and the time is 1 hour. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0065] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0066] Example 2

[0067] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0068] S1, using J-159 adhesive film to bond aramid paper with a thickness of 0.05 mm and an electromagnetic metamaterial microstructure film to obtain an electromagnetically modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.4 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0069] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0070] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0071] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 210° C. and a pressure of 0.6 MPa for 3 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0072] S5, stretching and shaping the laminated aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the laminated aramid paper block to a preset theoretical length at a stretching rate of 100 mm / min, and after stretching, placing the laminated aramid paper block in a shaping oven and curing it at a temperature of 250° C. for 2 hours to shape it;

[0073] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 140°C, and the time is 1 hour. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0074] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0075] Example 3

[0076] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0077] S1, using J-159 adhesive film to bond aramid paper with a thickness of 0.04 mm and an electromagnetic metamaterial microstructure film to obtain an electromagnetically modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.1 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0078] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0079] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0080] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 160° C. and a pressure of 0.7 MPa for 3 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0081] S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the pressed aramid paper block to a preset theoretical length at a stretching rate of 90 mm / min, and after stretching, placing the pressed aramid paper block in a shaping oven and curing it at a temperature of 210° C. for 3 hours to shape it;

[0082] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 140°C, and the time is 2 hours. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0083] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0084] Example 4

[0085] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0086] S1, using J-159 adhesive film to bond aramid paper with a thickness of 0.03 mm and an electromagnetic metamaterial microstructure film to obtain an electromagnetically modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.2 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0087] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0088] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0089] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 150° C. and a pressure of 0.4 MPa for 3 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0090] S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the pressed aramid paper block to a preset theoretical length at a stretching rate of 80 mm / min, and after stretching, placing the pressed aramid paper block in a shaping oven and curing it at a temperature of 200° C. for 2 hours to shape it;

[0091] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 120°C, and the time is 0.5h. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0092] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0093] Example 5

[0094] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0095] S1, using J-159 adhesive film to bond aramid paper with a thickness of 0.08 mm and an electromagnetic metamaterial microstructure film to obtain an electromagnetically modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.4 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0096] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0097] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0098] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 250° C. and a pressure of 1 MPa for 6 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0099] S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the pressed aramid paper block to a preset theoretical length at a stretching rate of 1200 mm / min, and after stretching, placing the pressed aramid paper block in a shaping oven and curing it at a temperature of 300° C. for 3 hours to shape it;

[0100] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 150°C, and the time is 2 hours. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0101] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0102] Example 6

[0103] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0104] S1, using J-159 adhesive film to bond 0.06 mm thick aramid paper and electromagnetic metamaterial microstructure film to obtain electromagnetic modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.3 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0105] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0106] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0107] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 230° C. and a pressure of 0.9 MPa for 5 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0108] S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the pressed aramid paper block to a preset theoretical length at a stretching rate of 110 mm / min, and after stretching, placing the pressed aramid paper block in a shaping oven and curing it at a temperature of 280° C. for 2.5 hours to shape it;

[0109] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 130°C, and the time is 1.5 hours. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0110] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0111] Example 7

[0112] An embodiment of the metamaterial honeycomb of the present invention, and a method for preparing the metamaterial honeycomb of this embodiment are as follows:

[0113] S1, using J-159 adhesive film to bond aramid paper with a thickness of 0.07 mm and an electromagnetic metamaterial microstructure film to obtain an electromagnetically modified aramid paper, forming a structure of electromagnetic metamaterial microstructure film + aramid paper, or forming a structure of electromagnetic metamaterial microstructure film + aramid paper + electromagnetic metamaterial microstructure film, to form a composite thin layer, wherein the S21 of the aramid paper is controlled within the range of -0.2 dB to 0, and the honeycomb cells of the aramid paper are hexagonal or rectangular;

[0114] S2, adjusting the mixing ratio of J-80B Nomex node glue and ethyl acetate and the viscosity of the mixed glue solution, setting parameters such as the number of core glue strips, paper cutting length, and glue coating rate, and then coating the glue on the electromagnetically modified aramid paper;

[0115] S3, stacking the glued electromagnetically modified aramid paper in a staggered stacking manner according to the required size in the width direction (i.e., W direction);

[0116] S4, pressing the stacked aramid paper blocks; specifically, pressing at a temperature of 190° C. and a pressure of 0.8 MPa for 4 hours according to the curing parameters of the node glue, and then cooling and releasing the pressure;

[0117] S5, stretching and shaping the laminated aramid paper block to obtain a semi-finished honeycomb; specifically, using a honeycomb stretching machine to stretch the laminated aramid paper block to a preset theoretical length at a stretching rate of 100 mm / min, and after stretching, placing the laminated aramid paper block in a shaping oven and curing it at a temperature of 250° C. for 2 hours to shape it;

[0118] S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; specifically, the semi-finished honeycomb after stretching and shaping is impregnated with phenolic resin according to the target density, the pre-curing temperature is 130°C, and the time is 1 hour. If the target density is not reached, the impregnation is repeated until the target density is reached.

[0119] S7, repeating S6 until the honeycomb density reaches a preset target density to obtain the metamaterial honeycomb, the target density being 30 kg / m 3 ~150kg / m 3 .

[0120] Performance Testing

[0121] Reflectivity test: Tested according to the national military standard "GJB 2038A-2011 Radar Absorbing Material Reflectivity Test Method." The results are shown in Table 1.

[0122] Table 1

[0123]

[0124] The above test results show that the reflectivity of the metamaterial honeycomb in the embodiment of the present application is relatively low at 10 GHz. This result shows that the metamaterial honeycomb in the embodiment of the present application has excellent wave absorbing performance in a wide frequency range, and while achieving excellent wave absorbing performance, the density of the wave absorbing honeycomb can be greatly reduced, while increasing the compressive strength at the same density, which can significantly reduce the weight of the functional structural parts of the aircraft, improve the cost-effectiveness of the aircraft, and is conducive to improving the structural stability of the metamaterial honeycomb and broadening its application field. Since the metamaterial honeycomb of the present invention has lightweight, structural stability and wave absorbing performance in a wide frequency range, it is suitable for application in the aerospace field and the defense and military industry.

[0125] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a metamaterial honeycomb, characterized in that: The steps include: S1, compounding aramid paper with an electromagnetic metamaterial microstructure film to obtain electromagnetically modified aramid paper; S2, applying glue on the electromagnetically modified aramid paper; S3, stacking the electromagnetically modified aramid paper after gluing in a staggered stacking manner according to the required size in the width direction; S4, pressing the stacked aramid paper blocks; S5, stretching and shaping the pressed aramid paper block to obtain a semi-finished honeycomb; S6, placing the semi-finished honeycomb in a resin for impregnation and pre-curing; S7, repeating S6 until the honeycomb density reaches a preset target density, thereby obtaining the metamaterial honeycomb.

2. The preparation method according to claim 1, characterized in that The electromagnetic metamaterial microstructure film includes a PI film and a metal metamaterial microstructure attached to the surface of the PI film.

3. The preparation method according to claim 1, characterized in that In step S2, after adjusting the mixing ratio of the node glue and ethyl acetate and the viscosity of the mixed glue solution, setting the number of core glue strips, the length of paper cutting and the gluing rate, the electromagnetically modified aramid paper is glued.

4. The preparation method according to claim 1, characterized in that In the step S4, pressing is performed at a temperature of 150° C. to 250° C. and a pressure of 0.4 MPa to 1 MPa for 3 to 6 hours.

5. The preparation method according to claim 1, characterized in that In step S5, the pressed aramid paper block is stretched to a preset theoretical length using a honeycomb stretching machine at a stretching rate of 80-120 mm / min.

6. The preparation method according to claim 5, characterized in that In step S5, after stretching, the film is placed in a shaping oven and cured at a temperature of 200-300° C. for 2-3 hours to shape it.

7. The preparation method according to claim 1, characterized in that In step S6, the resin is phenolic resin, the pre-curing temperature is 120° C. to 150° C., and the pre-curing time is 0.5 h to 2 h.

8. The preparation method according to claim 1, characterized in that In step S7, the target density is 30 kg / m 3 ~150kg / m 3 .

9. The preparation method according to claim 1, characterized in that In the step S1, the honeycomb cells of the aramid paper are hexagonal or rectangular.

10. A metamaterial honeycomb, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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