Method for preparing radar wave-absorbing composite material by using natural fibers

Abstract

The invention discloses a method for preparing a radar wave-absorbing composite material by using natural fibers, and the preparation process comprises the following steps: preparing a dielectric material solution, uniformly dispersing a dielectric material in a dissolving solution, and regulating the concentration of the dielectric material in the dissolving solution to obtain the dielectric material solution with a specific concentration; dielectric solution absorption: natural fibers are soaked in the prepared dielectric material solution, and the solution is absorbed by using the high water absorbability of the natural fibers; the natural fibers are dried, the natural fibers fully absorbing the dielectric solution are dried, the dielectric material on the surfaces of the dried natural fibers is removed, and the dielectric material is only dispersed in the natural fibers; and preparing the composite material plate, namely preparing the radar wave-absorbing composite material plate by taking the prepared natural fiber as a fiber reinforced phase. According to the method, the dielectric material can be uniformly dispersed into the fiber phase by utilizing the water absorption of the natural fiber, and the dielectric property of the material can be accurately controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar wave absorbing materials, and particularly relates to a method for preparing a radar wave absorbing composite material by using natural fibers. BACKGROUND

[0002] A radar wave absorbing material is a special material capable of absorbing electromagnetic energy, especially radar signals. Its core function is to convert electromagnetic energy into heat or other forms of energy through internal electromagnetic loss mechanisms, thereby reducing radar wave reflection. Currently, ferrite-based and carbon-based wave absorbing materials are mainly used.

[0003] Ferrite-based wave absorbing materials are one of the earliest radar wave absorbing materials widely used in stealth aircraft, and are still used on a variety of active aircraft. This type of material has ferrite as the main component, has high magnetic permeability and magnetic loss tangent, and can effectively absorb radar waves in a specific frequency band. However, it is heavy and bulky. Carbon nanotubes, graphene and other carbon-based wave absorbing materials have excellent electromagnetic properties and lightweight characteristics, and have become an important choice for modern radar wave absorbing materials. This type of material is dispersed in a resin matrix material to form a nanocomposite slurry, and then a corresponding radar wave absorbing composite material is prepared.

[0004] When dielectric materials such as ferrite, carbon nanotubes or graphene are dispersed in a resin matrix to form a nanocomposite slurry, the resin viscosity increases, making processing difficult. These dielectric materials are not easily dispersed uniformly in high-viscosity resins. Different dielectric material concentrations require different processing techniques. Agglomeration may occur, resulting in defects in the composite material.

[0005] Uniform dispersion of dielectric materials into the fiber phase can significantly improve the above problems, but traditional carbon fibers and glass fibers have a tight structure, and dielectric materials cannot enter the fiber interior. However, natural fibers have obvious water absorption, can absorb 30% of water, and also have excellent mechanical properties, making it possible to obtain a high mechanical property fiber with uniform internal dielectric material dispersion by using natural fibers. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a method for preparing a radar wave absorbing composite material by using natural fibers. This method utilizes the water absorption of natural fibers to disperse dielectric materials into the fiber phase, and by adjusting the concentration of the dielectric material solution and the volume fraction of the fiber phase, the dielectric properties of the material can be precisely controlled.

[0007] A method for preparing a radar wave absorbing composite material by using natural fibers, the specific process is as follows: Step one, dielectric material solution preparation: uniformly disperse the dielectric material in the dissolving solution, by adjusting the concentration of the dielectric material in the dissolving solution, obtain the dielectric material solution with specific concentration; Step two, dielectric solution absorption: soak the natural fiber in the dielectric material solution prepared in step one, use the high water absorption of the natural fiber to absorb the solution; Step three, natural fiber drying: dry the natural fiber which has fully absorbed the dielectric solution in step two, and remove the dielectric material on the surface of the dried natural fiber, so that the dielectric material is only dispersed in the natural fiber; Step four, composite plate preparation: use the natural fiber prepared in step three as the fiber reinforced phase to prepare the radar wave absorbing composite plate.

[0008] As a preferred embodiment of the above technical solution, in step one, the dielectric material uses one or more of ferrite wave absorbing material, carbon-based wave absorbing material, and ceramic wave absorbing material.

[0009] As a preferred embodiment of the above technical solution, in step one, the dissolving solution uses one or more of dimethylformamide, deionized water, dimethyl sulfoxide, toluene, ethyl acetate, dimethylbenzene, tetrahydrofuran, ethanol, and isopropyl alcohol.

[0010] As a preferred embodiment of the above technical solution, in step one, the concentration of the prepared dielectric material solution is 0.1-30 mg / mL.

[0011] As a preferred embodiment of the above technical solution, in step two, the natural fiber uses any one of natural fiber fabric, fiber bundle, and fiber felt.

[0012] As a preferred embodiment of the above technical solution, in step three, the dielectric material on the surface of the natural fiber can be removed by mechanical vibration or patting.

[0013] As a preferred embodiment of the above technical solution, in step three, the loading amount of the dielectric material in the natural fiber is 0.1-20 wt%.

[0014] As a preferred embodiment of the above technical solution, in step four, the thickness of the prepared composite plate is 0-50 mm.

[0015] Compared with the prior art, the present application has the following advantages: 1. The process is simple, by using the high water absorption of the natural fiber, directly absorbing the solution containing the dielectric material, and then drying to obtain the fiber phase loaded with the dielectric material, for subsequent composite material preparation; 2. The porous structure and high water absorption of the natural fiber can uniformly absorb the low viscosity dielectric material solution, so that the dielectric material is uniformly distributed; 3. Controllable dielectric properties: By controlling the concentration of dielectric materials and the volume fraction of fiber in the load, the dielectric properties of the composite plate can be accurately controlled to meet the needs of different application scenarios. 4. Lightweight: Natural fibers are lightweight, and the prepared composite material plate has low density and is lightweight, suitable for lightweight electronic devices and military equipment. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The preparation flowchart of the invention is shown. DETAILED DESCRIPTION

[0017] To make the purpose, technical scheme and advantages of the embodiments of the invention clearer, the technical scheme in the embodiments of the invention will be described clearly and completely below with reference to the drawings of the embodiments of the invention. Obviously, the described embodiments are part of the embodiments of the invention, not all embodiments. Based on the embodiments in the invention, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the invention.

[0018] The invention will be described in further detail below with reference to the drawings: As Figure 1 described above, the method for preparing a radar wave-absorbing composite material using natural fibers has the following specific process: Step 1: Preparation of dielectric material solution: uniformly disperse the dielectric material in the dissolving solution, and by adjusting the concentration of the dielectric material in the dissolving solution, obtain a dielectric material solution with a specific concentration. Step 2: Absorption of dielectric solution: soak the natural fibers in the dielectric material solution prepared in step 1, and use the high water absorption of the natural fibers to absorb the solution. Specifically, the natural fibers are in the form of continuous fibers, non-woven fabric, fabric, etc.

[0019] Step 3: Drying of natural fibers: dry the natural fibers that have fully absorbed the dielectric solution in step 2, and remove the dielectric material on the surface of the dried natural fibers, so that the dielectric material is only dispersed in the interior of the natural fibers. Step 4: Preparation of composite material plate: use the natural fibers prepared in step 3 as the fiber reinforcement phase to prepare a radar wave-absorbing composite material plate.

[0020] In this embodiment, in step 1, the dielectric material uses one or more of ferrite wave-absorbing material, carbon-based wave-absorbing material, and ceramic wave-absorbing material.

[0021] In this embodiment, in step 1, the dissolving solution uses one or more of dimethylformamide, deionized water, dimethyl sulfoxide, toluene, ethyl acetate, dimethylbenzene, tetrahydrofuran, ethanol, and isopropyl alcohol.

[0022] In this embodiment, in step one, the concentration of the prepared dielectric material solution is 0.1-30 mg / mL.

[0023] In this embodiment, in step two, the natural fiber is any one of natural fiber fabric, fiber bundle, and fiber felt.

[0024] In this embodiment, in step three, the dielectric material on the surface of the natural fiber can be removed by mechanical vibration or patting.

[0025] In this embodiment, in step three, the loading amount of the dielectric material in the natural fiber is 0.1-20 wt%.

[0026] In this embodiment, in step four, the thickness of the prepared composite material plate is 0-50 mm.

[0027] The specific implementation is as follows: Example 1

[0028] (1) 500 mL of dimethylformamide was taken into a 1000 mL beaker, 2.5 g of graphene oxide was weighed and slowly added into the solvent, and ultrasonic dispersion was performed for 30 min by using an ultrasonic cleaner, and then it was transferred into a magnetic stirrer for continuous stirring for 1 h, to prepare a graphene oxide solution with a concentration of 5 mg / mL; (2) The silk fabric was cut into a sample with a size of 100 mm x 100 mm, and was completely soaked in the above graphene oxide solution, and was placed at room temperature (25°C) for 24 h, and during the period, ultrasonic dispersion was performed for 30 min every 2 h by using an ultrasonic cleaner; (3) The fabric was taken out, and the excess solution on the surface was absorbed by filter paper, and was placed in a 50°C vacuum drying oven for drying for 12 h, to obtain a graphene oxide-loaded silk fabric; (4) The above “soaking-drying” operation was repeated once (totally twice), and finally the fabric was placed on a low-frequency vibration table for vibration for 30 min, to remove the unbound graphene oxide on the surface; (5) The epoxy resin matrix (epoxy resin E-51, polyamide 650 curing agent, with a mass ratio of 10:3) was weighed according to a mass ratio of 4:6 of the silk fabric:epoxy resin matrix, the graphene oxide-loaded silk fabric was laid flat in a mold, the prepared epoxy resin matrix was poured in, and hot pressing was performed to form and complete curing, to obtain a graphene oxide-loaded radar wave-absorbing silk fiber composite material plate. Example 2

[0029] (1) 500 mL of deionized water was taken into a 1000 mL beaker, 10 g of Fe3O4 particles was weighed and slowly added into the solvent, and ultrasonic dispersion was performed for 30 min by using an ultrasonic cleaner, and then it was transferred into a magnetic stirrer for continuous stirring for 1 h, to prepare a Fe3O4 solution with a concentration of 20 mg / mL; (2) Cut the linen fabric into a sample of 100 mm x 100 mm, completely immerse it in the Fe3O4 solution, and stand still at room temperature (25°C) for 24 h, during which the ultrasonic dispersion instrument is used to ultrasonically disperse for 30 min every 2 h; (3) Take out the fabric, use filter paper to absorb the excess solution on the surface, and place it in a vacuum drying oven at 50°C to dry for 12 h, to obtain the Fe3O4-loaded linen fabric; (4) Place the fabric on a low-frequency vibration table to vibrate for 30 min, to remove the unbound Fe3O4 on the surface.

[0030] (5) According to the mass ratio of the linen fabric: epoxy resin matrix (epoxy resin E-51, polyamide 650 curing agent, the mass ratio of the two is 10:3) is 3:7, weigh the epoxy resin matrix, lay the Fe3O4-loaded linen fabric in a mold, pour the prepared epoxy resin matrix, hot-press to form, complete curing, and obtain the Fe3O4-loaded radar wave-absorbing linen fiber composite plate. Example 3

[0031] (1) Take 500 mL of ethanol into a 1000 mL beaker, weigh 1 g of carbon nanotubes, and slowly add them into the solvent, and use an ultrasonic cleaning instrument to ultrasonically disperse for 30 min, and then transfer into a magnetic stirrer to continuously stir for 1 h, to prepare a carbon nanotube solution with a concentration of 2 mg / mL; (2) Cut the sisal fiber felt into a sample of 100 mm x 100 mm, completely immerse it in the carbon nanotube solution, and stand still at room temperature (25°C) for 24 h, during which the ultrasonic dispersion instrument is used to ultrasonically disperse for 30 min every 2 h; (3) Take out the fiber felt, use filter paper to absorb the excess solution on the surface, and place it in a vacuum drying oven at 50°C to dry for 12 h, to obtain the carbon nanotube-loaded sisal fiber felt; (4) Repeat the above “immersion-drying” operation for another 4 times (a total of 5 times), and finally place the fabric on a low-frequency vibration table to vibrate for 30 min, to remove the unbound carbon nanotubes on the surface; (5) According to the mass ratio of the sisal fiber felt: epoxy resin matrix (epoxy resin E-51, polyamide 650 curing agent, the mass ratio of the two is 10:3) is 2:8, weigh the epoxy resin matrix, lay the carbon nanotube-loaded sisal fiber felt in a mold, pour the prepared epoxy resin matrix, hot-press to form, complete curing, and obtain the carbon nanotube-loaded radar wave-absorbing sisal fiber composite plate.

[0032] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing radar absorbing composites with natural fibers, characterized in that: The specific process is as follows: Step one, preparation of dielectric material solution: uniformly disperse the dielectric material in the dissolving solution, by adjusting the concentration of the dielectric material in the dissolving solution, get the specific concentration of dielectric material solution; Step two, dielectric solution absorption: soak the natural fiber in the dielectric material solution prepared in step one, use the high water absorption of natural fiber to absorb the solution; Step three, natural fiber drying: dry the natural fiber fully absorbed in step two, and remove the dielectric material on the surface of the dried natural fiber, so that the dielectric material is only dispersed in the natural fiber; Step four, preparation of composite material plate: use the natural fiber prepared in step three as the fiber reinforced phase, and prepare the radar absorbing composite material plate.

2. The method for preparing radar absorbing composite materials with natural fibers according to claim 1, characterized in that: In step one, the dielectric material uses one or more of ferrite wave absorbing material, carbon-based wave absorbing material, and ceramic wave absorbing material.

3. The method for preparing radar absorbing composite materials with natural fibers according to claim 1, characterized in that: In step one, the dissolving solution uses one or more of dimethylformamide, deionized water, dimethyl sulfoxide, toluene, ethyl acetate, dimethylbenzene, tetrahydrofuran, ethanol, and isopropyl alcohol.

4. The method for preparing radar-absorbing composite materials with natural fibers according to claim 1, characterized in that: In step one, the concentration of the prepared dielectric material solution is 0.1-30mg / mL.

5. The method for preparing radar absorbing composite materials with natural fibers according to claim 1, characterized in that: In step two, the natural fiber uses any one of natural fiber fabric, fiber bundle, and fiber felt.

6. The method for preparing radar-absorbing composite materials with natural fibers according to claim 1, characterized in that: In step three, the dielectric material on the surface of the natural fiber can be removed by mechanical vibration or patting.

7. The method for preparing radar absorbing composite materials with natural fibers according to claim 1, characterized in that: In step three, the loading amount of the dielectric material in the natural fiber is 0.1-20wt%.

8. The method of claim 1, wherein the natural fibers are selected from the group consisting of hemp, jute, flax, ramie, sisal, and combinations thereof. In step four, the thickness of the prepared composite material plate is 0-50mm.

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