Electromagnetic coupling modified fiber wave-absorbing composite material, preparation method and application thereof

Abstract

The present application relates to a kind of electromagnetic coupling modified fiber wave-absorbing composite material and its preparation method and application, belong to wave-absorbing material technical field, comprising: modified fiber and the matrix resin filled in the gap of modified fiber;Modified fiber includes fibril and the coating modification layer coated in the periphery of fibril;Coating modification layer includes electric modified wave-absorbing agent and magnetic modified wave-absorbing agent.The present application is coated with coating modification layer in the periphery of fiber, forms regular ordered wave-absorbing area, simultaneously, regular ordered refraction, reflection area is formed in the gap between fiber, since the interface of different absorption rate is formed between wave-absorbing area and refraction, reflection area due to material difference, improve the absorption effect, improve absorption rate and absorption bandwidth;Solve the technical problems, such as poor dispersion uniformity of wave-absorbing material in the structure type wave-absorbing composite material of prior art, low production efficiency, absorption bandwidth is relatively narrow, wave-absorbing effect is not good etc.

Description

[0001] This invention patent application is based on the prior patent application filed on April 30, 2025, with application number 2025105617843 and invention title "An electromagnetic coupling modified fiber microwave absorbing composite material and its preparation method and application". Technical Field

[0002] This invention relates to the field of microwave absorbing materials technology, and in particular to an electromagnetic coupling modified fiber microwave absorbing composite material, its preparation method, and its application. Background Technology

[0003] Electromagnetic absorbing materials are functional materials that can effectively absorb incident electromagnetic wave energy and convert it into heat or other forms of energy through various loss mechanisms, thereby reducing electromagnetic interference. Carbon materials, due to their low density, large specific surface area, good stability, abundant defect sites, and excellent electrical conductivity and electrical modification properties, have become a research hotspot in the field of electromagnetic absorbing materials. However, carbon materials have a single mode of electromagnetic wave loss, high electrical modification can easily lead to impedance mismatch, and the absorption bandwidth is relatively narrow, making the achievement of broadband absorption still a challenge.

[0004] Based on their molding process and load-bearing capacity, microwave absorbing materials can be divided into two types: coating type and structural type. Microwave absorbing coatings involve dispersing conductive carbon-based materials in a polymer matrix or binder and directly coating them onto the surface of an object. While this method is simple to prepare, it suffers from drawbacks such as large overall mass, narrow effective absorption frequency band, and susceptibility to detachment. Structural microwave absorbing materials, on the other hand, are multifunctional composite materials that can simultaneously meet the requirements of microwave absorption and load-bearing capacity. They also possess excellent mechanical properties, thermal stability, and chemical stability, and offer high design flexibility, making them valuable for achieving integrated structure and function.

[0005] The common method for preparing structural microwave absorbing composite materials using existing technology involves using continuous fibers as reinforcement and incorporating microwave absorbing particles into a resin matrix. This method suffers from the problem of uneven dispersion of the microwave absorbing particles, which weakens the uniformity of the material's microwave absorption performance. Simultaneously, the increased viscosity of the polymer resin makes it difficult to apply manufacturing processes such as resin transfer molding and impregnation, ultimately resulting in low production efficiency and poor microwave absorption performance. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide an electromagnetically coupled modified fiber absorbing composite material, its preparation method and application, to solve at least one of the technical problems existing in the prior art of structural absorbing composite materials, such as poor uniformity of absorbing material dispersion, low production efficiency, narrow absorption bandwidth and poor absorbing effect.

[0007] An electromagnetic coupling modified fiber absorbing composite material, comprising:

[0008] Modified fibers and matrix resin filling the gaps between the modified fibers;

[0009] Modified fibers include original fibers and a coating modification layer covering the periphery of the original fibers;

[0010] The coating modification layer contains electrically modified microwave absorbing agents and magnetically modified microwave absorbing agents.

[0011] Preferably, the electromagnetic coupling modified fiber absorbing composite material comprises multiple electromagnetic modified fiber monolayers stacked together.

[0012] Preferably, the number of modified fiber sheets in the electromagnetic coupling modified fiber absorbing composite material is ≥6.

[0013] Preferably, the coating modification layer includes an electrically modified microwave absorbing agent, a magnetically modified microwave absorbing agent, and a necessary adhesive.

[0014] Preferably, the electromodified microwave absorber is a mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO).

[0015] Preferably, the electrocoating modified layer includes an electromodified microwave absorbing agent and a necessary adhesive; the magnetic coating modified layer includes a magnetically modified microwave absorbing agent and a necessary adhesive.

[0016] Preferably, the electromagnetically coupled modified fiber microwave absorbing composite material contains 1% to 8% by mass of electrically modified microwave absorbing agent, 20% to 50% by mass of magnetically modified microwave absorbing agent, 20% to 30% by mass of fiber, and the remainder is adhesive and matrix resin.

[0017] Preferably, the mass ratio of the electrically modified microwave absorbing agent to the magnetically modified microwave absorbing agent is 1:20-30.

[0018] A method for preparing an electromagnetically coupled modified fiber microwave absorbing composite material, comprising:

[0019] S1: Weigh out appropriate amounts of electromodified microwave absorbing agent, magnetically modified microwave absorbing agent and binder according to the proportion, and mix them with solvent to form electromagnetically modified microwave absorbing slurry;

[0020] S2: Electromagnetically modified absorbing slurry is coated onto a fiber monosheet by spraying or brushing, and then dried to obtain an electromagnetically modified fiber monosheet; the fibers in the electromagnetically modified fiber monosheet have gaps that communicate with the outside of the electromagnetically modified fiber monosheet.

[0021] S3: Multiple electromagnetically modified fiber sheets are arranged, combined, and stacked, and then injected with matrix resin to form an electromagnetically coupled modified fiber microwave absorbing composite material.

[0022] An application of an electromagnetically coupled modified fiber absorbing composite material, wherein the electromagnetically coupled modified fiber absorbing composite material or the electromagnetically coupled modified fiber absorbing composite material prepared by the above method is used for electromagnetic radiation and interference protection in buildings, equipment, etc.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] (1) The modified fiber prepared by the present invention with a coating modification layer on the outer periphery of the fiber has better process matching, is less prone to delamination, has strong design flexibility, has the advantage of integral molding, and has higher mechanical strength compared with the conventional method of laying the absorbing material on the fiber surface. Compared with the conventional technology of dissolving the absorbing material into the matrix resin and reinforcing fiber to construct a relatively uniform absorbing material, the present invention forms a regular and orderly absorbing area by coating the outer periphery of the fiber with a coating modification layer, and at the same time forms a regular and orderly refraction and reflection area in the gap between the fibers. Due to the different materials, the absorbing area and the refraction and reflection area form an interface with different absorption rates, which helps to improve the absorption effect, increase the absorption rate and absorption bandwidth.

[0025] (2) This invention improves the problem of poor dispersion uniformity of the absorbing material in non-polar resin by dissolving the absorbing material in a polar solvent to prepare a slurry and coating it on the outer surface of the fiber. At the same time, it avoids the defects of the increased viscosity of the polymer resin, which makes it difficult to apply the resin transfer molding, impregnation and other manufacturing processes, thus improving production efficiency and absorbing effect.

[0026] (3) The present invention uses multiple electromagnetic modified fiber monolayers and matrix resin to fill the gaps between each electromagnetic modified fiber monolayer and the fiber gaps, which helps to form regular and orderly refraction and reflection zones and wave absorption zones. The refraction and reflection zones form interfaces with different absorption rates due to different materials, which helps to improve the absorption effect, increase the absorption rate and effective absorption bandwidth.

[0027] (4) The present invention uses both conductive and magnetic absorbing agents to synergistically reduce dielectric loss and magnetic loss, thereby enhancing the absorption of electromagnetic waves.

[0028] (5) The electromagnetic coupling modified fiber absorbing composite material of the present invention belongs to the structural absorbing material and has a certain mechanical bearing capacity.

[0029] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0030] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0031] Figure 1 This is data on reflection loss (absorption loss) and effective absorption bandwidth in an embodiment of the present invention;

[0032] Figure 2 This invention provides comparative reflection loss (absorption loss) and effective absorption bandwidth data;

[0033] Figure 3 This is a photograph of the electromagnetic coupling modified fiber absorbing composite material prepared in Example 2 of the present invention.

[0034] Figure 4 This is a physical image of the electromagnetic coupling modified fiber absorbing composite material prepared in Example 6 of the present invention. Detailed Implementation

[0035] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0036] Terminology Definition

[0037] In this invention, "up and down" refers to the direction of electromagnetic wave incident on the composite material as "up," and "stacked from top to bottom" means stacked sequentially according to the direction of electromagnetic wave incident.

[0038] Effective absorption bandwidth refers to the frequency range where reflection loss (absorption loss) is continuously ≤-10dB.

[0039] In a first aspect, the present invention provides an electromagnetic coupling modified fiber absorbing composite material, comprising:

[0040] Modified fibers and matrix resin filling the gaps between the modified fibers;

[0041] Modified fibers include original fibers and a coating modification layer covering the periphery of the original fibers;

[0042] The coating modification layer contains uniformly distributed electrically modified microwave absorbing agents and magnetically modified microwave absorbing agents.

[0043] During implementation, a modified coating layer is applied to the outer periphery of the fiber to form a regular and orderly absorbing zone. At the same time, regular and orderly refractive and reflective zones are formed in the gaps between the fibers. Due to the different materials, the absorbing zone and the refractive and reflective zone form an interface with different absorption rates, which helps to improve the absorption effect, increase the absorption rate and the effective absorption bandwidth.

[0044] Compared with existing technologies, the modified fibers prepared by this invention, with a coating modification layer on the outer periphery of the fibers, have better process matching during preparation than conventional methods of laying absorbing materials on the fiber surface. They are less prone to delamination, have strong design flexibility, and have the advantage of integral molding, as well as higher mechanical strength. Compared with conventional technologies that dissolve the absorbing material in the matrix resin and reinforcing fibers to construct a relatively uniform absorbing material, this invention forms a regular and orderly absorbing zone by coating the outer periphery of the fibers with a coating modification layer. At the same time, regular and orderly refractive and reflective zones are formed in the gaps between the fibers. Due to the different materials, the absorbing zone and the refractive and reflective zone form an interface with different absorption rates, which helps to improve the absorption effect, increase the absorption rate and absorption bandwidth, and improve the problems of poor dispersion uniformity and low production efficiency of absorbing materials.

[0045] Preferably, the electromagnetic coupling modified fiber absorbing composite material comprises multiple electromagnetic modified fiber monolayers stacked together.

[0046] It should be noted that the applicant's research found that filling the spaces between the modified fiber monolayers with matrix resin and increasing the number of electromagnetically modified fiber monolayers can improve the absolute value of the minimum reflection loss and the effective absorption bandwidth. This is because, similar to filling the gaps between fibers with matrix resin, filling the spaces between the modified fiber monolayers with matrix resin helps to form regular and ordered refractive and reflective regions, as well as absorption regions. Furthermore, the different materials between the refractive and reflective regions create interfaces with different absorption rates, which helps to improve the absorption effect, increase the absorption rate, and enhance the effective absorption bandwidth.

[0047] Compared with the prior art, the present invention, by stacking multiple electromagnetic modified fiber monolayers and filling the spaces between each electromagnetic modified fiber monolayer with matrix resin, helps to form regular and orderly refractive and reflective regions and wave-absorbing regions. Furthermore, the different materials between the refractive and reflective regions form interfaces with different absorption rates, which helps to improve the absorption effect, increase the absorption rate and the effective absorption bandwidth.

[0048] Preferably, the number of modified fiber sheets in the electromagnetic coupling modified fiber microwave absorbing composite material is ≥6.

[0049] More preferably, the number of modified fiber sheets in the electromagnetic coupling modified fiber absorbing composite material is ≥8.

[0050] Specifically, the modified fiber monolayer can be in the form of fiber cloth or fiber web:

[0051] The density of the fiber mesh tread is 0.40 g / cm³. 2 ~0.85g / cm 2 It can be 0.40 g / cm³. 2 0.42g / cm 2 0.43g / cm 2 0.46 g / cm 2 0.48g / cm2 0.50g / cm 2 0.52g / cm 2 0.55g / cm 2 0.56g / cm 2 0.58g / cm 2 0.60g / cm 2 0.64 g / cm 2 0.66 g / cm 2 0.68g / cm 2 0.70g / cm 2 0.74g / cm 2 0.76 g / cm 2 0.78g / cm 2 0.80g / cm 2 or 0.84 g / cm 2 .

[0052] The surface density of the fiber fabric is 0.9 g / cm³. 2 ~1.5g / cm 2 It can be 0.9g / cm³. 2 1.0g / cm 2 1.1g / cm 2 1.2g / cm 2 1.3g / cm 2 1.4g / cm 2 Or 1.5g / cm 2 .

[0053] Preferably, the density of the fiber web tread is 0.50 g / cm³. 2 ~0.70g / cm 2 The surface density of the fiber fabric is 0.9 g / cm³. 2 ~1.2g / cm 2 .

[0054] It should be noted that if the areal density is too high, the gaps between fibers will be reduced, which will decrease the reflection and absorption of electromagnetic waves within the material; if the areal density is too low, it will be difficult to meet the strength requirements.

[0055] Specifically, the thickness of the electromagnetically modified fiber monolayer ranges from 0.2mm to 0.5mm, and can be 0.2mm, 0.3mm, 0.4mm, or 0.5mm; the coating slurry amount of the electromagnetically modified fiber monolayer is 400g / m². 2 ~900g / m 2 It can be 400g / m 2 420g / m 2 480g / m 2 500g / m 2510g / m 2 560g / m 2 580g / m 2 600g / m 2 620g / m 2 640g / m 2 660g / m 2 680g / m 2 700g / m 2 720g / m 2 740g / m 2 790g / m 2 800g / m 2 820g / m 2 840g / m 2 860g / m 2 880g / m 2 Or 900g / m 2 .

[0056] Preferably, the individual electromagnetically modified fiber sheets are connected by knitting, with the knitting material being quartz fiber and the knitting density being 10 stitches / cm. 2 ~20 stitches / cm 2 It can provide sufficient connection strength for each fiber layer.

[0057] The diameter of the original fibers in the electromagnetically modified fiber monosheet ranges from 5μm to 10μm, and can be 5μm, 6μm, 7μm, 8μm, 9μm or 10μm.

[0058] It should be noted that when the amount of slurry coated on a single sheet of electromagnetically modified fiber is within the above range, it helps to match the fiber diameter and the density of the limiting sheet, so that after the fiber sheet is electromagnetically modified, there are still sufficient gaps between the modified fibers. This allows for the formation of appropriately sized, regular, and orderly refractive and reflective zones in the gaps between the fibers after subsequent filling with matrix resin, which helps to improve the absorption effect, absorption rate, and absorption bandwidth.

[0059] Specifically, the coating modification layer includes an electrically modified microwave absorbing agent, a magnetically modified microwave absorbing agent, and necessary adhesives.

[0060] Specifically, the electromodified microwave absorber includes one or more of the following: multi-walled carbon nanotubes (MWCNT), activated carbon (CB), highly conductive carbon black (Super P), reduced graphene oxide (RGO), or vapor-grown carbon fiber (VGCF).

[0061] Preferably, the electromodified microwave absorber is a multi-walled carbon nanotube (MWCNT), reduced graphene oxide (RGO), or a mixture of multi-walled carbon nanotube (MWCNT) and vapor-grown carbon fiber (VGCF).

[0062] The specific adhesive can be an acrylic adhesive, such as methyl acrylate, and more preferably methyl methacrylate.

[0063] More preferably, the electromodified microwave absorber is a mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO).

[0064] Specifically, the mass ratio of the mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) is 0.8 to 1.2:1, and can be 0.8:1, 0.82:1, 0.84:1, 0.85:1, 0.88:1, 0.9:1, 0.92:1, 0.94:1, 0.95:1, 0.96:1, 0.98:1, 1:1, 1.04:1, 1.05:1, 1.06:1, 1.08:1, 1.10:1, 1.12:1, 1.14:1, 1.15:1, 1.18:1, or 1.20:1.

[0065] Preferably, the mass ratio of the mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) is 1:1.

[0066] Specifically, magnetically modified microwave absorbers include metal oxides composed of one or more of iron, cobalt, and nickel, or alloys composed of two or more of iron, cobalt, and nickel.

[0067] Specifically, the average particle size of the magnetically modified microwave absorbing agent is 1μm to 10μm, and can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm; the average particle size of the electrically modified microwave absorbing agent is 20nm to 100μm (irregularly shaped particles, the particle size is taken as the diameter of its circumscribed sphere).

[0068] Preferably, the average particle size of the magnetically modified microwave absorbing agent is 3μm to 5μm; the average particle size of the electrically modified microwave absorbing agent is 50nm to 50μm.

[0069] Specifically, the uniform particle size of the magnetically modified microwave absorber and the electrically modified microwave absorber is within the above-mentioned range, which makes the magnetically modified microwave absorber and the electrically modified microwave absorber uniformly dispersed and less prone to agglomeration.

[0070] Specifically, the adhesive includes one or more of polyacrylonitrile or methyl methacrylate.

[0071] The fibers include one or more of quartz fibers, silicon carbide fibers, glass fibers, or high-silica fibers.

[0072] Specifically, in the electromagnetic coupling modified fiber microwave absorbing composite material, the mass percentage of the electrically modified microwave absorbing agent is 1% to 8%, the mass percentage of the magnetically modified microwave absorbing agent is 20% to 50%, the mass percentage of the fiber is 20% to 30%, and the remainder is adhesive and matrix resin.

[0073] Preferably, the mass ratio of the electrically modified microwave absorber to the magnetically modified microwave absorber is 1:20 to 30, such as 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29 or 1:30.

[0074] More preferably, the mass ratio of the electrically modified microwave absorbing agent to the magnetically modified microwave absorbing agent is 1:23-27.

[0075] More preferably, the mass ratio of the electrically modified microwave absorbing agent to the magnetically modified microwave absorbing agent is 1:25.

[0076] Specifically, the thickness of the electromagnetic coupling modified fiber absorbing composite material is 2mm to 10mm, and the density is 0.7kg / m³. 3 ~1.5kg / m 3 .

[0077] In a preferred embodiment, the electromagnetically coupled modified fiber absorbing composite material has fibers stacked in a sequence of ≥8 electromagnetically modified quartz fiber monoliths from top to bottom, and the mass ratio of electrically modified absorbing agent to magnetically modified absorbing agent is 1:20-30; the minimum reflection loss of the absorbing composite material is ≤-20dB, and the effective absorption bandwidth is ≥8GHz.

[0078] In a more preferred embodiment, the electromagnetically coupled modified fiber absorbing composite material has fibers stacked in a sequence of ≥8 electromagnetically modified quartz fiber monoliths from top to bottom; the mass ratio of electrically modified absorbing agent to magnetically modified absorbing agent is 1:23~27; the minimum reflection loss of the absorbing composite material is ≤-30dB; and the effective absorption bandwidth is ≥10GHz.

[0079] In a more preferred embodiment, the electromagnetically coupled modified fiber absorbing composite material has fibers stacked in a sequence of ≥8 electromagnetically modified quartz fiber monoliths from top to bottom; the mass ratio of the electrically modified absorbing agent to the magnetically modified absorbing agent is 1:25; the minimum reflection loss of the absorbing composite material is ≤-36.4dB; and the effective absorption bandwidth is ≥12.4GHz.

[0080] It should be noted that this invention uses both conductive and magnetic absorbing agents, which synergistically reduce dielectric and magnetic losses and enhance the absorption of electromagnetic waves. The electromagnetic coupling modified fiber absorbing composite material of this invention is a structural absorbing material with a certain mechanical load-bearing capacity.

[0081] On the other hand, the present invention provides a method for preparing an electromagnetically coupled modified fiber absorbing composite material, comprising:

[0082] S1: Weigh out appropriate amounts of electromodified microwave absorbing agent, magnetically modified microwave absorbing agent and binder according to the proportion, and mix them with solvent to form electromagnetically modified microwave absorbing slurry;

[0083] S2: Electromagnetically modified absorbing slurry is coated onto a fiber monosheet by spraying or brushing, and then dried to obtain an electromagnetically modified fiber monosheet; the fibers in the electromagnetically modified fiber monosheet have gaps that communicate with the outside of the electromagnetically modified fiber monosheet.

[0084] S3: Multiple electromagnetically modified fiber sheets are arranged, combined, and stacked, and then injected with matrix resin to form an electromagnetically coupled modified fiber microwave absorbing composite material.

[0085] It should be noted that by controlling the amount of slurry, fiber diameter, and fiber surface density of the electromagnetically modified fiber sheet and using a spraying or brushing process, it is possible to ensure that there are still sufficient gaps between the modified fibers after electromagnetic modification. This allows for the formation of appropriately sized, regular, and orderly refractive and reflective zones between the fibers after subsequent filling with matrix resin, which helps to improve the absorption effect, absorption rate, and absorption bandwidth.

[0086] Specifically, the modified fiber monolayer can be in the form of fiber cloth or fiber web, with the fiber web having a surface density of 0.40 g / cm³. 2 ~0.85g / cm 2 The surface density of the fiber fabric is 0.9 g / cm³. 2 ~1.5g / cm 2 The amount of slurry used to coat the electromagnetically modified fiber single sheet is 400 g / m². 2 ~900g / m 2 The diameter of the original fibers in the electromagnetically modified fiber monosheet ranges from 5μm to 10μm.

[0087] During implementation, step S3 includes:

[0088] S301: Vertical fiber monolithic sheet is sewn together with multiple fiber monolithic sheets to form a fiber preform;

[0089] S302: The fiber preform is laid in the mold, the matrix resin is injected into the mold under pressure, and the mixture is cured and dried in a high-temperature environment to obtain the electromagnetic coupling modified fiber absorbing composite material.

[0090] In implementation, in step S1, the mass ratio of the electrically modified microwave absorbing agent to the binder in the electromagnetically modified microwave absorbing slurry is (4-20):1, and the mass ratio of the magnetically modified microwave absorbing agent to the binder is (30-50):1; the amount of solvent used relative to the solid component in the electromagnetically modified microwave absorbing agent slurry is 300ml / kg to 500ml / kg.

[0091] Compared with the prior art, the present invention improves the problem of poor dispersion uniformity of microwave absorbing materials in non-polar resins by dissolving the microwave absorbing material in a polar solvent to prepare a slurry and coating it on the outer surface of the fiber. At the same time, it avoids the defects of the increased viscosity of polymer resin, which makes it difficult to apply manufacturing processes such as resin transfer molding and impregnation, thereby improving production efficiency and microwave absorption effect.

[0092] Specifically, the adhesive includes one or more of polyacrylonitrile or methyl methacrylate.

[0093] It should be noted that the mass ratio of electromagnetic modified microwave absorber to binder and the amount of solvent relative to solid component in the electromagnetic modified microwave absorber slurry within the above range help to form regularly ordered refractive and reflective zones of appropriate size in the gaps between fibers, which helps to improve the absorption effect, absorption rate and absorption bandwidth.

[0094] Specifically, the solvent includes one of N,N-dimethylformamide, N-methylpyrrolidone, or N-ethylpyrrolidone.

[0095] Furthermore, depending on the thickness and performance requirements of the composite material, the fiber preform in step S3 can be composed of 8 to 40 fibers loaded with the same or different types and contents of electrically modified / magnetically modified microwave absorbing agents.

[0096] Furthermore, in step S3, the curing temperature and time in the high-temperature environment are 60℃~100℃ and 12h~48h, respectively.

[0097] Thirdly, an application of the electromagnetic coupling modified fiber absorbing composite material as described above, which is used in the field of electromagnetic wave absorption, specifically for electromagnetic radiation and interference protection in buildings, equipment, etc.

[0098] To better illustrate the present invention, the following embodiments and comparative examples are provided:

[0099] Example 1

[0100] This embodiment discloses an electromagnetic coupling modified fiber absorbing composite material and its preparation method. The specific preparation steps are as follows:

[0101] S1: Weigh 5g of methyl methacrylate and add it to 400ml of N,N-dimethylformamide. Stir thoroughly at room temperature until dissolved. Weigh 3g of conductive carbon black and add it to the above solution in portions. Sonicate for 10-15min to disperse evenly. Weigh 60g of carbonyl iron powder and add it to the above solution. Mechanically stir until a suspension is formed to obtain the electromagnetically modified absorbing slurry. The average particle size of the magnetically modified absorbing agent is 3μm; the average particle size of the electrically modified absorbing agent is 100nm.

[0102] S2: Weigh 30g of the above slurry each time and evenly disperse it onto a single piece of silicon carbide fiber mesh using a spraying process. The surface density of the fiber mesh is 0.60g / cm³. 2 The fibers were then dried in an 80°C oven for 10 hours to obtain electromagnetically modified silicon carbide fibers. The average diameter of the original fibers in the modified fibers was 10 μm, the thickness of a single sheet of electromagnetically modified fiber was 0.25 mm, and the amount of slurry coated on a single sheet of modified fiber was 500 g / m². 2 .

[0103] S3: Take the above 8 modified silicon carbide fibers and connect them into a fiber preform using a sewing process. Lay the fiber preform in a 330mm×330mm×2mm mold, pressurize and inject silicone resin until the fiber preform is completely impregnated with the silicone resin solution, then seal the mold. Place the mold after injection in an 80℃ oven for curing for 24 hours, and then dry it in a 100℃ environment for 24 hours; the thickness of the composite material is 2.45mm.

[0104] The composite material contains 1.25% by mass of electrically modified microwave absorber, 20% by mass of fiber, 25% by mass of magnetically modified microwave absorber, and the remainder consists of adhesive and silicone resin.

[0105] The tensile and compressive properties of the electromagnetic coupling modified fiber microwave absorbing composite material prepared in this embodiment were tested according to GB / T 1447-2005 and GB / T 1448-2005. The loading speed for each experiment was 2 mm / min, and 5 samples were tested in parallel in each group. The maximum tensile stress of the composite material was 18.6 MPa and the compressive stress was 25.4 MPa, which showed good mechanical properties.

[0106] The complex conductivity constant and complex permeability of the electromagnetically coupled modified fiber absorbing composite material prepared in this embodiment were tested in the range of 2 GHz to 18 GHz using the free-space method according to GB / T 42741-2023. Based on transmission line theory, the reflection loss of the absorbing composite material at different thicknesses can be calculated using formulas (1) and (2).

[0107] Formula (1): In the formula, Z0 is the self-used space impedance, approximately 377Ω, Z in This is the input impedance.

[0108] Formula (2): In the formula ε r μ is the complex conductivity constant. r denoted as complex permeability, j represents the imaginary part, f is the frequency, d is the sample thickness, and c is the speed of light.

[0109] According to calculations, such as Figure 1As shown, the minimum reflection loss is -16.0dB and the effective absorption bandwidth is 4.9GHz when the material thickness is 2.45mm.

[0110] Example 2

[0111] This embodiment discloses an electromagnetic coupling modified fiber absorbing composite material and its preparation method. The specific preparation steps are as follows:

[0112] The difference from Example 1 is that the amounts of methyl methacrylate, conductive carbon black, and carbonyl iron powder are 6g, 4g, and 100g, respectively; the mass percentage of the prepared composite material is 1% of the electrically modified microwave absorber, 20% of the fiber, 25% of the magnetically modified microwave absorber, and the remainder is silicone resin.

[0113] After testing (using the same method as in Example 1), the maximum tensile stress of the electromagnetic coupling modified fiber absorbing composite material prepared in this example was 14.2 MPa. Figure 1 As shown, the minimum reflection loss is -36.4dB, and the effective absorption bandwidth is 12.4GHz.

[0114] Example 3

[0115] This embodiment discloses an electromagnetic coupling modified fiber absorbing composite material and its preparation method. The specific preparation steps are as follows:

[0116] The difference from Example 1 is that the amounts of methyl methacrylate, conductive carbon black, and carbonyl iron powder are 7g, 5g, and 140g, respectively; the mass percentage of the prepared composite material is 1% of the electrically modified microwave absorber, 20% of the fiber, 28% of the magnetically modified microwave absorber, and the remainder is silicone resin.

[0117] After testing (using the same testing method as in Example 1), the electromagnetic coupling modified fiber absorbing composite material (such as...) prepared in this example... Figure 3 As shown), the maximum tensile stress is 11.6 MPa. Figure 1 As shown, the minimum reflection loss is -18.1dB and the effective absorption bandwidth is 5.1GHz.

[0118] Example 4

[0119] This embodiment discloses an electromagnetically coupled modified fiber absorbing composite material and its preparation method. The difference from Example 1 is that, in S1, when preparing the electromagnetically modified absorbing slurry, a mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) in a 1:1 mass ratio is used. This mixture serves as the electrically modified absorbing agent, while the magnetically modified absorbing agent remains unchanged.

[0120] S1: Weigh 5g of methyl methacrylate and add it to 400ml of N,N-dimethylformamide. Stir thoroughly at room temperature until dissolved. Weigh 3g of a mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) in a 1:1 mass ratio and add it to the above solution in portions. Sonicate for 10-15 minutes to disperse evenly, and mechanically stir until a suspension is formed to obtain the electromagnetically modified absorbing slurry; the average particle size of the electromagnetically modified absorbing agent is 90nm.

[0121] S2: Weigh 30g of the above slurry each time and evenly disperse it onto a single piece of silicon carbide fiber cloth using a spraying process. The surface density of the fiber cloth is 1.1g / cm³. 2 The fibers were then dried in an oven at 80°C for 10 hours to obtain electromagnetically modified silicon carbide fibers. The average diameter of the original fibers in the modified fibers was 10 μm, the thickness of a single sheet of electromagnetically modified fiber was 0.2 mm, and the coating slurry amount per sheet of modified fiber was 520 g / m². 2 .

[0122] S3: Take the above 8 pieces of modified silicon carbide fibers and connect them into a fiber preform using a sewing process. Lay the fiber preform in a 330mm×330mm×2mm mold, pressurize and inject silicone resin until the fiber preform is completely impregnated with the silicone resin solution, then seal the mold. Place the mold after injection in an 80℃ oven to cure for 24 hours, and then dry it in a 100℃ environment for 24 hours; the material thickness is 2.45mm.

[0123] The composite material contains 1.5% by mass of electrically modified microwave absorber, 20% by mass of fiber, and the remainder is silicone resin.

[0124] The maximum tensile stress of the electromagnetic coupling modified fiber absorbing composite material prepared in this example was 14.8 MPa, as tested (using the same method as in Example 1). Figure 1 As shown, the minimum reflection loss is -22.4dB and the effective absorption bandwidth is 7.8GHz.

[0125] Example 5

[0126] This embodiment discloses an electromagnetically coupled modified fiber absorbing composite material and its preparation method. The difference from Embodiment 1 is that, in S1, when preparing the electromagnetically modified absorbing slurry, iron-cobalt alloy powder is used as the magnetically modified absorbing agent, while the electrically modified absorbing agent remains unchanged.

[0127] The maximum tensile stress of the electromagnetic coupling modified fiber absorbing composite material prepared in this example was 13.4 MPa, as tested (using the same method as in Example 1). Figure 1 As shown, the minimum reflection loss is -18.2dB and the effective absorption bandwidth is 8.8GHz.

[0128] Example 6

[0129] This embodiment discloses an electromagnetically coupled modified fiber microwave absorbing composite material and its preparation method. The difference from Embodiment 2 is that when preparing the electromagnetically modified microwave absorbing slurry in S1, the mass ratio of the mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) is 1:1. The mixture is used as the electrically modified microwave absorbing agent, while the magnetically modified microwave absorbing agent remains unchanged.

[0130] After testing (using the same testing method as in Example 1), the electromagnetic coupling modified fiber absorbing composite material (such as...) prepared in this example... Figure 4 As shown in the figure, the maximum tensile stress is 14.2 MPa, the minimum reflection loss is -38.2 dB, and the effective absorption bandwidth is 12.8 GHz.

[0131] Comparative Example 1

[0132] This comparative example discloses an unmodified fiber-reinforced resin matrix composite material and its preparation method. The specific preparation steps are as follows:

[0133] In steps S1 and S2, the silicon carbide fibers were not modified in any way.

[0134] S3: Take the above 8 silicon carbide fiber sheets and stack them sequentially, then connect them into a fiber preform using a stitching process. Lay the fiber preform in a 330mm×330mm×2mm mold and prepare an electrically modified microwave absorbing composite material using the same process;

[0135] The remaining conditions are the same as in Example 1.

[0136] The electromagnetic parameters were tested according to the test method of Example 1, and the results are shown in Table 1 below.

[0137] The maximum tensile stress of the electromagnetic coupling modified fiber absorbing composite material prepared in this example was 8.7 MPa, as tested (using the same method as in Example 1). Figure 2 As shown, the minimum reflection loss is -12.0dB and the effective absorption bandwidth is 3.7GHz.

[0138] Comparative Example 2

[0139] This comparative example discloses a C2 electrically modified microwave absorbing composite material and its preparation method. The specific preparation steps are as follows:

[0140] S1: Prepare only the electrically modified microwave absorbing slurry according to step S1 of Example 1, without adding carbonyl iron powder;

[0141] S2: Prepare electro-modified silicon carbide fibers only according to step S2 of Example 1;

[0142] S3: Take the above 8 electro-modified silicon carbide fiber sheets and stack them sequentially, then connect them into a fiber preform by stitching. Lay the fiber preform in a 330mm×330mm×2mm mold and prepare the electro-modified microwave absorbing composite material under the same process;

[0143] The remaining conditions are the same as in Example 1.

[0144] The electromagnetic parameters were tested according to the test method of Example 1, and the results are shown in Table 1 below.

[0145] After testing (using the same method as in Example 1), the maximum tensile stress of the electromagnetic coupling modified fiber absorbing composite material prepared in this example was 9.2 MPa; Figure 2 As shown, the minimum reflection loss is -21.1dB and the effective absorption bandwidth is 2.8GHz.

[0146] Comparative Example 3

[0147] This comparative example discloses an Fe magnetically modified microwave absorbing composite material and its preparation method. The specific preparation steps are as follows:

[0148] S1: Prepare magnetically modified microwave absorbing slurry according to step S1 of Example 1, without adding conductive carbon black;

[0149] S2: Prepare magnetically modified silicon carbide fibers only according to step S2 of Example 1;

[0150] S3: Take the above 8 magnetically modified silicon carbide fiber sheets and stack them sequentially, then connect them into a fiber preform using a stitching process. Lay the fiber preform in a 330mm×330mm×2mm mold and prepare the magnetically modified microwave absorbing composite material using the same process;

[0151] The remaining conditions are the same as in Example 1.

[0152] The electromagnetic parameters were tested according to the test method of Example 1, and the results are shown in Table 1 below.

[0153] The maximum tensile stress of the electromagnetic coupling modified fiber absorbing composite material prepared in this example was 12.9 MPa, as tested (using the same method as in Example 1). Figure 2 As shown, the minimum reflection loss is -14.5dB, and the effective absorption bandwidth is 4.8GHz.

[0154] Table 1 Comparison of Absorption Performance Test Results

[0155]

[0156]

[0157] Note: Matching thickness refers to the thickness of the composite material sample being measured.

[0158] As can be seen from the above, when the mass ratio of the electrically modified absorbing agent to the magnetically modified absorbing agent is 1:20-30, and the thickness of the absorbing composite material prepared in the embodiments of the present invention is 2.37mm-3.01mm, the minimum reflection loss is between -16.0dB and -36.4dB, the effective absorption bandwidth is between 4.9GHz and 12.4GHz, and the maximum tensile stress is ≥11.6MPa; preferably, the minimum reflection loss of the absorbing composite material is ≤-30dB, and the effective absorption bandwidth is ≥10GHz; when the mass ratio of the electrically modified absorbing agent to the magnetically modified absorbing agent is 1:23-27, the minimum reflection loss of the absorbing composite material is ≤-36.4dB, the effective absorption bandwidth is ≥12.4GHz, and the maximum tensile stress is ≥14.2MPa.

[0159] Comparing Examples 1, 2, and 5, it can be seen that when the mass ratio of the electrically modified absorbing agent to the magnetically modified absorbing agent is 1:20-30, selecting a mixture of multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) as the electrically modified absorbing agent can significantly improve the effective absorption bandwidth and reduce the minimum reflection loss.

[0160] Comparative Examples 1 and 1-3 show that electromagnetically modified absorbing composite materials can improve the effective absorption bandwidth and / or reduce the minimum reflection loss compared to electrically modified and magnetically modified absorbing composite materials.

[0161] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic coupling modified fiber absorbing composite material, characterized in that, include: Modified fibers and matrix resin filling the gaps between the modified fibers; The modified fiber includes the original fiber and the coating modification layer covering the outer periphery of the original fiber; the outer periphery of the original fiber is coated with the coating modification layer, and the gaps between the fibers form refractive and reflective regions; a regular and orderly absorption region and refractive and reflective regions are formed, and different materials form interfaces with different absorption rates; The coating modification layer includes electrically modified microwave absorbing agents and magnetically modified microwave absorbing agents; The mass ratio of electrically modified microwave absorbing agent to magnetically modified microwave absorbing agent is 1:20-30; The electromodified microwave absorber is a mixture of multi-walled carbon nanotubes and reduced graphene oxide; The minimum reflection loss of the absorbing composite material is ≤-30dB, and the effective absorption bandwidth is ≥10GHz; The electromagnetic coupling modified fiber absorbing composite material comprises multiple electromagnetic modified fiber monoliths stacked together, with the number of monoliths being ≥6. The modified fiber monosheet is in the form of fiber cloth or fiber web; the areal density of the fiber web is 0.40 g / cm³. 2 ~0.85g / cm 2 The areal density of the fiber cloth is 0.9 g / cm³. 2 ~1.5g / cm 2 ; The preparation method of the electromagnetic coupling modified fiber absorbing composite material includes: S1: Weigh out appropriate amounts of electromodified microwave absorbing agent, magnetically modified microwave absorbing agent and binder according to the proportion, and mix them with solvent to form electromagnetically modified microwave absorbing slurry; S2: Electromagnetically modified absorbing slurry is coated onto a fiber monosheet by spraying or brushing, and then dried to obtain an electromagnetically modified fiber monosheet; the fibers in the electromagnetically modified fiber monosheet have gaps that communicate with the outside of the electromagnetically modified fiber monosheet. S3: Multiple electromagnetically modified fiber sheets are arranged, combined, and stacked, and then injected with matrix resin to form an electromagnetically coupled modified fiber microwave absorbing composite material.

2. The electromagnetic coupling modified fiber absorbing composite material according to claim 1, characterized in that, The electromagnetic coupling modified fiber microwave absorbing composite material contains 1% to 8% by mass of electrically modified microwave absorbing agent, 20% to 50% by mass of magnetically modified microwave absorbing agent, 20% to 30% by mass of fiber, and the remainder is adhesive and matrix resin.

3. A method for preparing an electromagnetically coupled modified fiber-absorbing composite material, characterized in that, For preparing the electromagnetic coupling modified fiber absorbing composite material according to claim 1 or 2, comprising: S1: Weigh out appropriate amounts of electromodified microwave absorbing agent, magnetically modified microwave absorbing agent and binder according to the proportion, and mix them with solvent to form electromagnetically modified microwave absorbing slurry; S2: Electromagnetically modified absorbing slurry is coated onto a fiber monosheet by spraying or brushing, and then dried to obtain an electromagnetically modified fiber monosheet; the fibers in the electromagnetically modified fiber monosheet have gaps that communicate with the outside of the electromagnetically modified fiber monosheet. S3: Multiple electromagnetically modified fiber sheets are arranged, combined, and stacked, and then injected with matrix resin to form an electromagnetically coupled modified fiber microwave absorbing composite material.

4. An application of an electromagnetically coupled modified fiber-absorbing composite material, characterized in that, The electromagnetic coupling modified fiber absorbing composite material according to claim 1 or 2, or the electromagnetic coupling modified fiber absorbing composite material prepared according to claim 3, is used for electromagnetic radiation and interference protection in buildings and equipment.

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