Aramid honeycomb based on magnetic wave-absorbing pre-preg and preparation method thereof

Abstract

This invention relates to the field of composite material technology, specifically to an aramid honeycomb based on magnetic microwave absorbing prepreg and its preparation method. The aramid honeycomb includes an aramid honeycomb core and a magnetic microwave absorbing prepreg layer covering the surface of the honeycomb core. The magnetic microwave absorbing prepreg, by mass percentage, contains 25%-30% magnetic microwave absorbing component, 40%-45% resin matrix, 20%-25% reinforcing fiber, 5%-8% dispersant (based on the magnetic microwave absorbing component), and a curing agent with a mass ratio of 1:1.2 to the resin matrix. The magnetic microwave absorbing component is selected from one or more of coated Fe3O4@SiO2 nanoparticles, nickel-doped MXene (Ni-Ti3C2), and ultrafine Fe-Si-Cr alloy powder, mixed in any proportion. The resin matrix is ​​E-51 modified epoxy resin with a glass transition temperature Tg ≥ 120℃; the reinforcing fiber is para-aramid fiber cloth (Kevlar49) with a length of 0.15 micrometers to 0.5 millimeters; the dispersant is polyetherimide (PEI); and the curing agent is methyltetrahydrophthalic anhydride (MeTHPA).

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to an aramid honeycomb based on magnetic microwave absorbing prepreg and its preparation method. Background Technology

[0002] Aramid paper is a special material made of high-performance aramid fibers, combining lightweight flexibility with excellent physicochemical properties. Its core characteristics include high temperature resistance, high strength, flame retardancy, electrical insulation, and chemical corrosion resistance, while also being lightweight, flexible, and easy to process. Aramid paper is widely used in aerospace, electrical insulation, electronic communications, protective equipment, and transportation, and is an indispensable high-performance basic material in high-end industries.

[0003] Meta-aramid honeycomb is a honeycomb structure material widely used in the aerospace industry. Compared with metal honeycomb, it has superior performance, especially in terms of lightweight, damping performance, and corrosion resistance. Aramid honeycomb core material has high strength and stiffness, as well as better corrosion resistance and insulation performance.

[0004] Currently, the main methods for preparing microwave-absorbing honeycomb composites include impregnation and spraying. However, these methods have some limitations, such as poor adhesion stability of the absorbing agent, easy detachment, limitations on the type and content of the absorbing agent, and poor process controllability. Furthermore, the uniformity and stability of the microwave-absorbing honeycomb composites prepared by these methods are uncontrollable, limiting their application in the field of integrated structural stealth composites. The specific shortcomings of current methods for preparing microwave-absorbing honeycomb composites are as follows: 1. Poor adhesion stability of the absorbing agent: Traditional impregnation and spraying methods result in weak interfacial bonding between the absorbing agent and the aramid honeycomb matrix, making it prone to detachment under vibration or humid and hot environments, affecting the durability and reliability of the microwave absorption performance. 2. Limited type and content of absorbing agents: Existing processes have stringent requirements on the particle size, density, and chemical compatibility of the absorbing agent, making it difficult to flexibly select diverse microwave-absorbing functional components, thus limiting the controllable range of the electromagnetic properties of the composite material. 3. Insufficient process uniformity and controllability: Existing methods struggle to achieve uniform distribution of the absorbing agent in complex porous honeycomb structures, leading to unstable overall absorbing performance of the composite material and the existence of localized weak areas, thus affecting its application in stealth structure integration. 4. Difficulty in achieving structural-functional integration: While composite materials prepared by conventional methods possess absorbing properties, they often sacrifice original mechanical properties or environmental resistance, making it difficult to simultaneously meet the high comprehensive performance requirements of integrating load-bearing structures and stealth functions.

[0005] To meet the urgent needs in fields such as integrated structural stealth composite materials, it is necessary to develop a new preparation method. This method should have advantages such as stable and uniform process, non-detachment of the absorbing agent, and wide applicability of various materials, while also being able to prepare composite materials with integrated structural stealth functions. Summary of the Invention

[0006] To address the aforementioned technical problems in the prior art, this invention provides an aramid honeycomb based on magnetic microwave absorbing prepreg and its preparation method, as detailed below: An aramid honeycomb based on magnetic microwave absorbing prepreg includes an aramid honeycomb core and a magnetic microwave absorbing prepreg layer coated on the surface of the honeycomb core; the magnetic microwave absorbing prepreg layer is composed of magnetic microwave absorbing prepreg and a curing agent, which are stored separately; the magnetic microwave absorbing prepreg, by mass percentage, contains 25%-30% magnetic microwave absorbing component, 40%-45% resin matrix, 20%-25% reinforcing fiber, and 5%-8% dispersant; the mass ratio of curing agent to resin matrix is ​​1:1.2; the magnetic microwave absorbing component is selected from one or more of coated Fe3O4@SiO2 nanoparticles, nickel-doped MXene, and ultrafine Fe-Si-Cr alloy powder, mixed in any proportion.

[0007] Furthermore, the resin matrix is ​​E-51 modified epoxy resin with a glass transition temperature Tg ≥ 120℃; the reinforcing fiber is short-cut carbon fiber of varying lengths, ranging from 0.15 micrometers to 0.5 millimeters; the dispersant is polyetherimide; and the curing agent is methyltetrahydrophthalic anhydride.

[0008] Furthermore, the aramid honeycomb core has a regular hexagonal pore shape, with a pore side length of 1.83-5.5 mm and a height of 10-30 mm. The substrate is meta-aramid paper with a density of 0.22 g / cm³. 3 .

[0009] Furthermore, the aramid honeycomb exhibits a reflection loss ≤-10dB and a density ≤0.3g / cm³ in the 1-18GHz frequency band. 3 The compressive strength is ≥2MPa, and the interfacial bonding strength between the prepreg and the honeycomb core is ≥1.5MPa.

[0010] A method for preparing aramid honeycomb based on magnetic microwave absorbing prepreg includes the following steps: (1) Preparation of magnetic microwave absorbing slurry: Add the magnetic microwave absorbing component and dispersant to acetone (the amount is 1.5-2 times the volume of the magnetic component to ensure dispersion space) and disperse. Then mix with resin matrix and curing agent in proportion. Stir for 10-15 minutes until completely mixed and uniform, without flocculent matter or layering. Measure the viscosity to 1500-2000 mPa·s using a rotational viscometer (25℃, 60 rpm). If the viscosity is >2000 mPa·s, add a small amount of acetone, stir for 5 minutes and measure again. If the viscosity is <1500 mPa·s, add appropriate amount of resin matrix or let stand for 10 minutes (to allow acetone to evaporate slightly) until the viscosity falls within the target range.

[0011] (2) Preparation of magnetic microwave absorbing prepreg: Short carbon fibers of 0.15 micrometers to 0.5 mm are added to the magnetic microwave absorbing slurry obtained in step (1) in proportion, different slurries are prepared, and curing agents are added in proportion.

[0012] (3) Aramid honeycomb treatment: The adhesive is applied to the surface of aramid paper by anilox roller coating or screen printing. The adhesive is phenolic resin with a solid content of 50%-70% and a viscosity of 1000-3000 mPa·s. The adhesive dots are arranged in a periodic hexagonal grid with a diameter of 0.5-2 mm. The spacing is designed according to the target honeycomb cell size of 2.64 mm to ensure that the regular honeycomb structure can be formed after stretching. After coating, the paper is simply dried at 60-80℃ to thicken the adhesive. The coated aramid paper sheets are then stacked one by one, with the adhesive dots of adjacent sheets staggered (for example, the adhesive dots of one sheet are facing the blank area of ​​the other sheet). This way, the paper can be stretched to form honeycomb cells. After stacking, place the paper in a press, heat it (80-120℃) and gently apply pressure to make the adhesive dots stick together, forming a hard "paper board". Put the pressed paper board into an oven, heat it to 150-200℃, and bake it for 2-4 hours to allow the adhesive to fully cure. Cut the cured blank into thin slices perpendicular to the stacking direction (thickness direction). The thickness of the slices is the "height" of the honeycomb (currently 25mm-30mm). The cut surfaces must be flat.

[0013] (4) Honeycomb impregnation and shaping: The treated aramid honeycomb paper is impregnated in the magnetic absorbing slurry obtained in step (3) for 5-10 minutes. After impregnation, it is taken out of the slurry and left to stand for 5 minutes on each side. A horizontal tension is applied to the slice at a stretching rate of 5-10 mm / min to ensure that the pores are uniform and there is no tearing or glue drop. Using the rigidity of the interlayer adhesive and the toughness of the paper, the stacked paper is spread out along the glue dots to form a regular hexagonal honeycomb pore. After stretching to the design size, it is fixed. The stretched honeycomb structure is cured for 1-2 hours in an oven at 120-180℃ to further enhance the adhesive strength and eliminate tensile stress, so that the honeycomb shape is stable (pore size deviation ≤ ±0.1 mm).

[0014] Furthermore, in step (1), after the magnetic absorbing component and the dispersant are added to acetone for dispersion, ultrasonic dispersion is performed with an ultrasonic dispersion power of 300W, a frequency of 20kHz, and a dispersion time of 30-40min; the high-speed stirring speed is 3000r / min, and the stirring time is 20min; the solid content of the slurry is 60%-65%.

[0015] Furthermore, in step (2), the short-cut carbon fibers are first mixed evenly with the dispersant and then ground. A high-speed mixer is used during grinding, with a rotation speed of 3000 rpm and a grinding time of 30 min, to prevent the carbon fibers from agglomerating and the slurry particles from being too large after the magnetic slurry is added.

[0016] Furthermore, in step (3), after the honeycomb is cured, the honeycomb cell size, honeycomb height, and apparent density (currently ≤90kg / m³) are adjusted. 3 The honeycomb blocks are tested for indicators such as compressive strength, and cut according to the design dimensions, removing edge burrs to ensure that the end face is flat.

[0017] Furthermore, in step (3), aramid paper, which is usually a nonwoven fabric woven from aramid short fibers and aramid pulp, has a thickness of 0.05-0.2 mm and has high tensile strength, temperature resistance (long-term use temperature -196~200℃) and insulation. It needs to be pretreated, and the surface of the aramid paper is cleaned (removing oil or dust). If necessary, plasma or chemical treatment (such as coating with a coupling agent) is used to improve its interfacial bonding with the adhesive.

[0018] The application of the aramid honeycomb in the manufacture of secondary load-bearing structures for aerospace, housings of electronic devices, or protective components for communication base stations.

[0019] Compared with the prior art, the technical effects of this invention are reflected in: (1) Good performance synergy: This application integrates magnetic wave absorbing components into the prepreg for the first time, and combines them with aramid honeycomb in situ to achieve the integration of "structural bearing-electromagnetic wave absorption", avoiding the weight increase and interface problems caused by additional coatings; (2) Wide absorption band: This application covers the entire frequency band from 1 to 18 GHz by selecting and compounding magnetic materials, especially improving the absorption performance in the low frequency band, and solving the defect of narrow absorption band of existing materials; (3) High structural stability: The aramid honeycomb based on magnetic microwave absorbing prepreg obtained in this application has a honeycomb density of ≤80kg / m³. 3 With a compressive strength ≥1.9 MPa, it exhibits minimal performance degradation under high and low temperatures and humid heat, meeting the requirements of demanding working conditions. (4) The process is industrializable: This application adopts the traditional prepreg impregnation and hot-press curing process, which does not require special equipment, the raw material cost is controllable, and it is suitable for mass production. Attached Figure Description

[0020] Figure 1 This is a diagram showing the product test results of Example 1.

[0021] Figure 2 This is a graph showing the product test results for Example 2.

[0022] Figure 3 This is a graph showing the product test results for Example 3.

[0023] Figure 4 This is a diagram showing the product test results for Example 4.

[0024] Figure 5 This is a photo of the white aramid honeycomb core material used (before impregnation with coating).

[0025] Figure 6 This is a photo of the final product. Detailed Implementation

[0026] The technical solution of the present invention will be further defined below with reference to specific embodiments, but the scope of protection is not limited to the description made.

[0027] Aramid honeycomb based on magnetic microwave absorbing prepreg was prepared in the following manner: (1) Preparation of magnetic microwave absorbing slurry: Add the magnetic microwave absorbing component and dispersant to acetone (the amount is 1.5-2 times the volume of the magnetic component to ensure dispersion space) and disperse. Then mix with resin matrix and curing agent in proportion. Stir for 10-15 minutes until completely mixed and uniform, without flocculent matter or layering. Measure the viscosity to 1500-2000 mPa·s using a rotational viscometer (25℃, 60rpm). If the viscosity is >2000 mPa·s, add a small amount of acetone, stir for 5 minutes and measure again. If the viscosity is <1500 mPa·s, add appropriate amount of resin matrix or let stand for 10 minutes (to allow acetone to evaporate slightly) until the viscosity falls within the target range.

[0028] (2) Preparation of magnetic microwave absorbing prepreg: Short carbon fibers of 0.15 micrometers to 0.5 mm are added to the magnetic microwave absorbing slurry obtained in step (1) in proportion, different slurries are prepared, and curing agents are added in proportion.

[0029] (3) Aramid honeycomb treatment: The adhesive is applied to the surface of aramid paper by anilox roller coating or screen printing. The adhesive is phenolic resin with a solid content of 50%-70% and a viscosity of 1000-3000 mPa·s. The adhesive dots are arranged in a periodic hexagonal grid with a diameter of 0.5-2mm. The spacing is designed according to the target honeycomb cell size of 2.64mm to ensure that the stretching after stacking can form a regular honeycomb structure. After coating, the paper is simply dried at 60-80℃ to thicken the adhesive. The coated aramid paper sheets are then stacked one by one, with the adhesive dots of adjacent sheets staggered (for example, the adhesive dots of one sheet are facing the blank area of ​​the other sheet). This way, the paper can be stretched to form honeycomb cells. After stacking, place the paper in a press, heat it (80-120℃) and gently apply pressure to bond the adhesive dots firmly, forming a hard "paper board". Place the pressed paper board in an oven, heat it to 150-200℃, and bake for 2-4 hours to allow the adhesive to fully cure. Cut the cured blank into thin slices perpendicular to the stacking direction (thickness direction). The slice thickness is the "height" of the honeycomb (currently 25mm-30mm), and the cut surfaces must be flat.

[0030] (4) Honeycomb impregnation and shaping: The treated aramid honeycomb paper is impregnated in the magnetic absorbing slurry obtained in step (3) for 5-10 minutes. After impregnation, it is taken out of the slurry and left to stand for 5 minutes on each side. A horizontal tension is applied to the slice at a stretching rate of 5-10 mm / min to ensure that the pores are uniform and there is no tearing or adhesive drop. Using the rigidity of the interlayer adhesive and the toughness of the paper, the stacked paper is spread out along the adhesive dots to form a regular hexagonal honeycomb pore. After stretching to the design size, it is fixed. The stretched honeycomb structure is cured for 1-2 hours in an oven at 120-180℃ to further enhance the adhesive strength and eliminate tensile stress, so that the honeycomb shape is stable (pore size deviation ≤ ±0.1 mm).

[0031] Example 1: Magnetic aramid honeycomb based on Fe3O4@SiO2 nanoparticles 1. Raw material preparation • Magnetic absorbing component: Coated Fe3O4@SiO2 nanoparticles (particle size 50-80 nm, saturation magnetization 85 emu / g), accounting for 28% of the prepreg mass; • Resin matrix: E-51 modified epoxy resin, accounting for 42% of the prepreg mass; • Reinforcing fiber: Finely ground 0.15-micron carbon fiber, accounting for 22% of the prepreg mass; • Dispersant: PEI, accounting for 6% of the magnetic component mass; • Curing agent: MeTHPA, with a mass ratio of 1:1.2 to epoxy resin; • Aramid honeycomb core: pore side length 2.75 mm, height 25 mm, density 0.22 g / cm³ 3 .

[0032] 2. Preparation process Prepare according to the steps described above. After adding carbon fiber, the stirring time is 15 min. After stretching, the honeycomb hot-press curing parameters are 120℃ for 1 h.

[0033] 3. Performance test results • Absorption performance: Reflection loss (RL) ≤ -10 dB in the 1-18 GHz band, RL ≤ -18 dB in the 8-12 GHz band (absorption rate ≥ 98%). • Structural properties: Density 68kg / m³ 3 The compressive strength is 1.9 MPa, and the interfacial bond strength between the prepreg and the honeycomb core is 1.8 MPa. • Environmental stability: After 10 cycles at -55℃ / 120℃, the microwave absorption performance changed by 8%, and the compressive strength changed by 3%; after 1000 hours of humid heat at 40℃ and 95% RH, the mass change rate was 0.8%.

[0034] Test results as follows Figure 1 As shown, the reflectivity of the obtained absorbing cell was tested using the bow-shaped method. The absorption performance met the following requirements: reflection loss (RL) ≤ -10 dB in the 1-18 GHz band and RL ≤ -18 dB in the 8-12 GHz band (absorption rate ≥ 98%). The average density of the produced products was 67-69 kg / m³. 3 It meets its structural requirements. The compressive strength, tested with a universal testing machine, is ≥1.9MPa. After testing its environmental adaptability (such as salt spray resistance, corrosion resistance, etc.), its reflectivity and compressive strength were measured using the bow method, and they still meet the performance requirements.

[0035] Example 2: Magnetic Absorbing Aramid Honeycomb Based on Ni-Ti3C2 1. Raw material preparation • Magnetic absorbing component: Nickel-doped MXene (Ni-Ti3C2, sheet thickness 1-3 nm, μ'=9 at 1 GHz), accounting for 25% of the prepreg mass; • Resin matrix: E-51 modified epoxy resin, accounting for 45% of the prepreg mass; • Reinforcing fibers: The ratio of milled 0.15-micron and 0.5-mm carbon fibers is 5:1, accounting for 23% of the prepreg mass; • Dispersant: PEI, accounting for 8% of the magnetic component mass; • Curing agent: MeTHPA, with a mass ratio of 1:1.2 to epoxy resin; • Aramid honeycomb core: pore side length 2.75 mm, height 30 mm, density 0.22 g / cm³ 3 .

[0036] 2. Preparation process Prepare according to the steps described above. After adding carbon fiber, stir for 30 minutes. After stretching, the honeycomb hot-press curing parameters are 150℃ for 1 hour.

[0037] 3. Performance test results • Absorption performance: RL≤-10 dB in the 1-18 GHz band, RL≤-15 dB in the 4-16 GHz band; • Structural properties: Density 72kg / m³ 3 The compressive strength is 2.2 MPa, and the interfacial bond strength is 2.0 MPa. • Environmental stability: Performance change rate after high and low temperature cycling ≤7%, mass change rate after damp heat 0.7%.

[0038] Test results as follows Figure 2As shown, the reflectivity of the obtained absorbing cell was tested using the bow-shaped method. The absorption performance met the requirements of RL≤-10 dB in the 1-18 GHz band and RL≤-15 dB in the 4-16 GHz band. The average density of the produced product was 71-73 kg / m³. 3 It meets its structural requirements. The compressive strength, tested with a universal testing machine, is ≥2.2MPa. After testing its environmental adaptability (such as salt spray resistance, corrosion resistance, etc.), its reflectivity and compressive strength were measured using the bow method, and they still meet the performance requirements.

[0039] Example 3: Magnetic Absorbing Aramid Honeycomb Based on Fe-Si-Cr Alloy Powder 1. Raw material preparation • Magnetic absorbing component: Ultrafine Fe-Si-Cr alloy powder (particle size 1-3 μm, coercivity 45 Oe), accounting for 30% of the prepreg mass; • Resin matrix: E-51 modified epoxy resin, accounting for 40% of the prepreg mass; • Reinforcing fibers: The ratio of milled 0.15-micron and 0.5-mm carbon fibers is 1:3, accounting for 20% of the prepreg mass; • Dispersant: PEI, accounting for 5% of the magnetic component mass; • Curing agent: MeTHPA, with a mass ratio of 1:1.2 to epoxy resin; • Aramid honeycomb core: pore side length 2.75 mm, height 30 mm, density 0.22 g / cm³ 3 .

[0040] 2. Preparation process Prepare according to the steps described above. After adding carbon fiber, stir for 30 minutes. After stretching, the honeycomb hot-press curing parameters are 180℃ for 1 hour.

[0041] 3. Performance test results • Absorption performance: RL≤-12 dB in the low-frequency band of 1-3 GHz, and RL≤-10 dB across the entire frequency band; • Structural properties: Density 75kg / m³ 3 The compressive strength is 2.5 MPa, and the interfacial bond strength is 1.6 MPa. • Environmental stability: Performance change rate after high and low temperature cycling is 9%, and mass change rate after damp heat is 0.9%.

[0042] Test results as follows Figure 3 As shown, the reflectivity of the obtained absorbing cell was tested using the bow-shaped method. The absorption performance met the requirements of RL≤-12 dB in the low-frequency band of 1-3 GHz and RL≤-10 dB across the entire frequency band. The average density of the produced product was 73-76 kg / m³.3 It meets its structural requirements. The compressive strength, tested with a universal testing machine, is ≥2.5MPa. After testing its environmental adaptability (such as salt spray resistance, corrosion resistance, etc.), its reflectivity and compressive strength were measured using the bow method, and they still meet the performance requirements.

[0043] Example 4: Magnetic Wave-Absorbing Aramid Honeycomb Based on Composite Magnetic Components 1. Raw material preparation • Magnetic absorbing component: Fe3O4@SiO2 nanoparticles and Ni-Ti3C2 are compounded in a mass ratio of 1:1, accounting for 27% of the prepreg mass; • The remaining raw materials are the same as in Example 1.

[0044] 2. Preparation process Same as step 3.2.2.

[0045] 3. Performance test results • Absorption performance: RL≤-12 dB across the entire 1-18 GHz frequency band, with no obvious absorption blind zone; • Structural properties: Density 68kg / m³ 3 Compressive strength 2 MPa; • Environmental stability: Performance degradation after high and low temperature and damp heat tests is ≤6%.

[0046] Test results as follows Figure 4 As shown, the reflectivity of the obtained absorbing cell was tested using the bow-shaped method. The absorption performance met the requirement of RL≤-12 dB across the entire 1-18 GHz frequency band, with no obvious absorption blind zone. The average density of the produced products was 66-69 kg / m³. 3 It meets its structural requirements. The compressive strength was tested with a universal testing machine and found to be ≥2MPa. After testing its environmental adaptability (such as salt spray resistance, corrosion resistance, etc.), its reflectivity and compressive strength were measured using the bow method, and it still met the performance requirements.

[0047] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should be considered within the scope of protection of this invention.

Claims

1. An aramid honeycomb based on magnetic microwave absorbing prepreg, characterized in that, The device includes an aramid honeycomb core and a magnetic microwave absorbing prepreg layer coated on the surface of the honeycomb core. The magnetic microwave absorbing prepreg layer consists of a magnetic microwave absorbing prepreg and a curing agent, which are stored separately. The magnetic microwave absorbing prepreg contains, by mass percentage, 25%-30% magnetic microwave absorbing components, 40%-45% resin matrix, 20%-25% reinforcing fibers, and 5%-8% dispersant. The mass ratio of curing agent to resin matrix is ​​1:1.

2. The magnetic microwave absorbing components are selected from one or more of coated Fe3O4@SiO2 nanoparticles, nickel-doped MXene, and ultrafine Fe-Si-Cr alloy powder, mixed in any proportion.

2. The aramid honeycomb according to claim 1, characterized in that, The resin matrix is ​​E-51 modified epoxy resin with a glass transition temperature (Tg) ≥ 120℃; the reinforcing fiber is short-cut carbon fiber of varying lengths, ranging from 0.15 micrometers to 0.5 millimeters; the dispersant is polyetherimide; and the curing agent is methyltetrahydrophthalic anhydride.

3. The aramid honeycomb according to claim 1, characterized in that, The aramid honeycomb core has a regular hexagonal pore shape, with a pore side length of 1.83-5.5 mm and a height of 10-30 mm. The substrate is meta-aramid paper with a density of 0.22 g / cm³. 3 .

4. The aramid honeycomb according to claim 1, characterized in that, Reflection loss ≤ -10dB and density ≤ 0.3g / cm³ in the 1-18GHz frequency band. 3 The compressive strength is ≥2MPa, and the interfacial bonding strength between the prepreg and the honeycomb core is ≥1.5MPa.

5. A method for preparing aramid honeycomb based on magnetic absorbing prepreg as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of magnetic microwave absorbing slurry: Add the magnetic microwave absorbing components and dispersant to acetone for dispersion, then mix with resin matrix and curing agent in proportion, stir for 10-15 minutes until completely mixed and uniform, without flocculent matter or layering, and measure the viscosity to 1500-2000 mPa·s using a rotational viscometer; if the viscosity is >2000 mPa·s, add a small amount of acetone, stir for 5 minutes and measure again; if the viscosity is <1500 mPa·s, add appropriate amount of resin matrix or let stand for 10 minutes until the viscosity falls within the target range; (2) Preparation of magnetic microwave absorbing prepreg: Short carbon fibers of 0.15 micrometers to 0.5 mm are added to the magnetic microwave absorbing slurry obtained in step (1) in proportion, and different slurries are prepared and curing agents are added in proportion; (3) Aramid honeycomb treatment: The adhesive is applied to the surface of aramid paper by anilox roller coating or screen printing. The adhesive is phenolic resin with a solid content of 50%-70% and a viscosity of 1000-3000 mPa·s. The adhesive dots are arranged in a periodic hexagonal grid with a diameter of 0.5-2 mm. The spacing is designed according to the target honeycomb cell size of 2.75 mm to ensure that a regular honeycomb structure can be formed after stacking and stretching. After coating, the paper is simply dried at 60-80℃ to thicken the adhesive. Stack the coated aramid paper sheets one by one, making sure the glue dots on adjacent sheets are staggered so that they can be stretched to form honeycomb cells. After stacking, place them in a press, heat and gently press to make the glue dots stick together, forming a hard "paper board". Put the pressed paper board into an oven, heat it to 150-200℃, and bake for 2-4 hours to allow the glue to fully cure. Cut the cured blank into thin slices perpendicular to the stacking direction. The thickness of the slices is the "height" of the honeycomb, and the cut surfaces must be flat. (4) Honeycomb impregnation and shaping: The treated aramid honeycomb paper is impregnated in the magnetic absorbing slurry obtained in step (3) for 5-10 minutes. After impregnation, it is taken out from the slurry and left to stand for 5 minutes on each side. A horizontal tension is applied to the slice at a stretching rate of 5-10 mm / min to ensure that the pores are uniform and there is no tearing or glue drop. The rigidity of the interlayer adhesive and the toughness of the paper are used to unfold the stacked paper along the glue dots to form a regular hexagonal honeycomb pore. The paper is stretched to the design size and then fixed. The stretched honeycomb structure is cured for 1-2 hours in an oven at 120-180℃ to further enhance the adhesive strength and eliminate tensile stress, so that the honeycomb shape is stable.

6. The preparation method according to claim 5, characterized in that, In step (1), after the magnetic absorbing component and dispersant are added to acetone for dispersion, ultrasonic dispersion is used. The ultrasonic dispersion power is 300W, the frequency is 20kHz, and the dispersion time is 30-40min. The high-speed stirring speed is 3000r / min, and the stirring time is 20min. The solid content of the slurry is 60%-65%.

7. The preparation method according to claim 5, characterized in that, In step (2), the short-cut carbon fibers are first mixed evenly with the dispersant and then ground. A high-speed mixer is used during grinding at a speed of 3000 rpm for 30 minutes to prevent carbon fiber agglomeration and large particle size of the slurry after the magnetic slurry is added.

8. The preparation method according to claim 5, characterized in that, In step (3), after the honeycomb is cured, the honeycomb cell size, honeycomb height, apparent density, compressive strength and other indicators are tested, and the honeycomb blocks are cut according to the design size, the edge burrs are removed and the end face is flat.

9. The preparation method according to claim 5, characterized in that, In step (3), aramid paper is a nonwoven fabric made of aramid short fibers and aramid pulp, with a thickness of 0.05-0.2mm, and has high tensile strength, temperature resistance and insulation.

10. The application of the aramid honeycomb according to claim 1 in the preparation of secondary load-bearing structures for aerospace, housings of electronic devices, or protective components for communication base stations.

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