A honeycomb wave-absorbing composite material and a preparation method thereof

Abstract

The application provides a honeycomb wave-absorbing composite material and a preparation method thereof. The composite material comprises a skin layer, a plurality of honeycomb wave-absorbing core layers and a reflection layer arranged in sequence along the thickness direction. The honeycomb wave-absorbing core layers are formed by pouring wave-absorbing slurry into a honeycomb mold and solidifying. The electromagnetic loss of each honeycomb wave-absorbing core layer is different. In the application, the honeycomb wave-absorbing core layers are formed by pouring wave-absorbing slurry into a honeycomb mold and solidifying. In this way, the porous structure of the honeycomb wave-absorbing core layers is ensured, and a higher content of wave-absorbing material can be introduced, thereby facilitating the enhancement of the overall electromagnetic loss capacity of the composite material. Furthermore, through the design of the plurality of honeycomb wave-absorbing core layers, the impedance matching characteristics of the overall composite material are reasonably optimized, thereby coordinating the impedance matching and the attenuation capacity, and realizing the wideband and efficient electromagnetic wave attenuation of the composite material.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and in particular to a honeycomb microwave absorbing composite material and its preparation method. Background Technology

[0002] For areas with strong echoes from flying targets, such as the leading and trailing edges of the wings and the edges of the fuselage, there is ample space for absorbing structures. Sandwich-structured absorbing composite materials are suitable for achieving the low scattering characteristics control requirements of the components.

[0003] Absorbing honeycomb sandwich composite materials are generally made by using a high-strength composite material with good wave transmission as the face panel and an absorbing honeycomb impregnated or filled with a lossy medium as the core material. In related technologies, the purpose of reducing reflection and enhancing absorption is usually achieved by changing the size and height of the honeycomb cells. However, there are still some shortcomings in current absorbing honeycomb materials. On the one hand, existing material systems and absorbing structures are effective in dealing with radar threats that are mainly high-frequency, but there is a lack of mature and usable broadband absorbing materials that cover low frequencies. On the other hand, absorbing honeycombs with a substrate are limited by the manufacturing process. Although the preparation process of such absorbing materials is simple, it is difficult to further improve the absorption capability of the honeycomb from the perspective of impedance matching due to factors such as thickness and gravity.

[0004] Therefore, based on the above problems, there is an urgent need to provide a novel honeycomb absorbing composite material and its preparation method. Summary of the Invention

[0005] This invention provides a honeycomb absorbing composite material and its preparation method, solving the problem that absorbing materials in related technologies cannot cover low-frequency broadband absorption and have limited absorption performance.

[0006] In a first aspect, the present invention provides a honeycomb absorbing composite material, comprising a skin layer, multiple honeycomb absorbing core layers and a reflective layer arranged sequentially along the thickness direction; wherein, the honeycomb absorbing core layer is formed by pouring absorbing slurry into a honeycomb mold and curing it, and the electromagnetic loss of each layer of the honeycomb absorbing core layer is different.

[0007] Preferably, along the direction from the skin layer to the reflective layer, the electromagnetic loss of each honeycomb absorbing core layer gradually increases.

[0008] Preferably, the thickness of the skin layer is 1-2 mm, the thickness of each honeycomb absorbing core layer is 4-20 mm, and the thickness of the reflective layer is 0.2-0.4 mm.

[0009] Preferably, the honeycomb absorbing core layer has 2 to 5 layers.

[0010] Preferably, the microwave absorbing slurry includes a binder, a microwave absorbing agent, a solvent, additives, and a curing agent; wherein the binder is at least one of acrylic resin, phenolic resin, or epoxy resin; the microwave absorbing agent is carbon black; the solvent is ethyl acetate; the additives include dispersants, defoamers, leveling agents, and pH adjusters; and the curing agent is isocyanate, phenolic acid, or 593 epoxy curing agent.

[0011] Preferably, the mass ratio of adhesive, microwave absorber, solvent and additive is (70-85):(10-25):(10-25):(7-12);

[0012] The mass ratio of the adhesive to the curing agent is (15-120):1.

[0013] Preferably, the height of the honeycomb mold is 9-25mm, the wall thickness is 2-5mm, and the distance between the center points of adjacent honeycomb holes is 8-12mm.

[0014] In a second aspect, the present invention provides a method for preparing the honeycomb absorbing composite material according to any one of the first aspects, the method comprising the following steps:

[0015] (1) Injecting microwave absorbing slurry of different concentrations into honeycomb molds of different sizes until each honeycomb cell of the honeycomb mold is filled;

[0016] (2) The filled honeycomb mold is cured and demolded in sequence to obtain multiple honeycomb absorbing core layers; among them, the electromagnetic loss of each honeycomb absorbing core layer is different;

[0017] (3) The honeycomb absorbing core layer is sequentially composited to obtain a multi-layer honeycomb absorbing core layer, and a skin layer and a reflective layer are respectively composited on the upper and lower surfaces of the multi-layer honeycomb absorbing core layer to obtain the honeycomb absorbing composite material after molding.

[0018] Preferably, along the direction from the skin layer to the reflective layer, the concentration of the absorbing slurry or the height of the honeycomb mold in each layer of honeycomb absorbing core material gradually increases.

[0019] Preferably, in step (2), the curing temperature is 50-130°C, the heating rate is 2-3°C / min, and the holding time is 1-3h.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] In this invention, the honeycomb absorbing composite material comprises a skin layer, a multi-layer honeycomb absorbing core layer, and a reflective layer arranged sequentially. The honeycomb absorbing core layer is formed by pouring absorbing slurry into a honeycomb mold and curing it. This ensures the porous structure of the honeycomb absorbing core layer while introducing a higher content of absorbing material, thereby enhancing the overall electromagnetic loss capability of the composite material. Furthermore, by designing the multi-layer honeycomb absorbing core layer, the impedance matching characteristics of the composite material are rationally optimized, thereby coordinating impedance matching and attenuation capability to achieve broadband and efficient electromagnetic wave attenuation of the composite material. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Embodiment 1 of the present invention;

[0024] Figure 2 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Embodiment 2 of the present invention;

[0025] Figure 3 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Embodiment 3 of the present invention;

[0026] Figure 4 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Embodiment 4 of the present invention;

[0027] Figure 5 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Embodiment 5 of the present invention;

[0028] Figure 6 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Comparative Example 1 of this invention;

[0029] Figure 7 This is a graph showing the reflectivity test results of a honeycomb absorbing composite material provided in Comparative Example 2 of this invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] To address one or more of the aforementioned problems, embodiments of the present invention provide a honeycomb absorbing composite material, which includes a skin layer, multiple honeycomb absorbing core layers, and a reflective layer arranged sequentially along the thickness direction; wherein, the honeycomb absorbing core layer is formed by pouring absorbing slurry into a honeycomb mold and curing it, and the electromagnetic loss of each layer of the honeycomb absorbing core layer is different.

[0032] In this embodiment of the invention, the honeycomb absorbing composite material comprises a skin layer, a multi-layer honeycomb absorbing core layer, and a reflective layer arranged sequentially. The honeycomb absorbing core layer is formed by pouring absorbing slurry into a honeycomb mold and curing it. This ensures the porous structure of the honeycomb absorbing core layer while introducing a higher content of absorbing material, thereby enhancing the overall electromagnetic loss capability of the composite material. Furthermore, by designing the multi-layer honeycomb absorbing core layer, the impedance matching characteristics of the composite material are rationally optimized, thereby coordinating impedance matching with attenuation capability and achieving broadband and efficient electromagnetic wave attenuation of the composite material.

[0033] It should be noted that, in the use of the honeycomb absorbing composite material in the embodiments of the present invention, the skin layer is the surface layer that is in contact with air, and the reflective layer is the bottom surface that is in contact with the target surface.

[0034] According to some preferred embodiments, the electromagnetic loss of each honeycomb absorbing core layer gradually increases along the direction from the skin layer to the reflective layer.

[0035] In this embodiment of the invention, by controlling the relevant parameters in the honeycomb absorbing core layer, the electromagnetic loss performance of each honeycomb absorbing core layer is gradually enhanced along the direction from the skin layer to the reflective layer. This is beneficial for better optimizing the impedance matching of the composite material, and the electromagnetic waves are reflected multiple times in the honeycomb absorbing core layer, thereby achieving more electromagnetic wave absorption.

[0036] According to some preferred embodiments, the thickness of the skin layer is 1 to 2 mm (e.g., 1 mm, 1.5 mm, or 2 mm), the thickness h of each honeycomb absorbing core layer is 4 to 20 mm (e.g., 4 mm, 6 mm, 7 mm, 9 mm, 12 mm, or 20 mm), and the thickness of the reflective layer is 0.2 to 0.4 mm (e.g., 0.2 mm, 0.3 mm, or 0.4 mm).

[0037] In this embodiment of the invention, the honeycomb absorbing composite material is sequentially configured as a skin layer, a honeycomb absorbing core layer, and a emitting layer along the thickness direction. The skin layer, as the outermost layer of the composite material, needs to have certain wave absorption performance, corrosion resistance, and aerodynamic load transmission performance. When electromagnetic waves are incident on the composite material, a portion of the electromagnetic waves are absorbed when passing through the skin material, most of the electromagnetic waves are continuously attenuated and absorbed in the honeycomb absorbing core layer, and a small portion of the electromagnetic waves can be re-emitted by the reflective layer to the honeycomb absorbing core layer for absorption. Thus, in this embodiment, through the reasonable design of the structure and thickness of each layer in the composite material, the layer-by-layer absorption of electromagnetic waves is achieved, ensuring the good wave absorption performance of the composite material.

[0038] It should be noted that there are no specific restrictions on the materials of the skin layer and the reflective layer in this embodiment. They can be set according to the needs of use. In order to match the honeycomb absorbing core layer, the skin layer in this embodiment is preferably aramid prepreg or glass fiber prepreg, and the reflective layer is preferably carbon fiber prepreg.

[0039] According to some preferred embodiments, the honeycomb absorbing core layer has 2 to 5 layers (for example, it can be 2, 3, 4 or 5 layers).

[0040] Considering that the honeycomb absorbing composite material has both good absorption properties and is lightweight, the number of honeycomb absorbing core layers in this embodiment is set to 2 to 5 layers. This can further improve the absorption performance of the composite material while ensuring its good absorption performance.

[0041] According to some preferred embodiments, the microwave absorbing slurry includes a binder, a microwave absorbing agent, a solvent, additives, and a curing agent; wherein the binder is at least one of acrylic resin, phenolic resin, or epoxy resin; the microwave absorbing agent is carbon black; the solvent is ethyl acetate; the additives include dispersants, defoamers, leveling agents, and pH adjusters; and the curing agent is isocyanate, phenolic acid, or 593 epoxy curing agent.

[0042] In this embodiment, the microwave absorbing agent slurry is preferably made of the above-mentioned raw materials, which can make the microwave absorbing agent uniformly dispersed in the microwave absorbing slurry, thereby facilitating the uniform dispersion of the microwave absorbing slurry in the honeycomb microwave absorbing core layer, and thus helping to ensure the uniformity of the microwave absorption performance in all directions of the honeycomb microwave absorbing core layer. It should also be noted that the microwave absorbing agent in this embodiment is preferably carbon black. Compared with other microwave absorbing agents such as graphite or carbonyl iron powder, carbon black can not only be uniformly dispersed in the microwave absorbing slurry, thereby ensuring the uniformity of the microwave absorption performance of the honeycomb microwave absorbing core layer, but also helps to ensure the lightweight nature of the honeycomb microwave absorbing core layer.

[0043] It should be noted that, in order to ensure good dispersibility of the microwave absorber, in the embodiments of the present invention, the dispersant can be sodium alginate, the defoamer can be n-octanol, the leveling agent can be DIGIC leveling agent, and the pH adjuster can be triethanolamine.

[0044] According to some preferred embodiments, the mass ratio of adhesive, microwave absorber, solvent and additive is (70-85):(10-25):(10-25):(7-12) (for example, it can be 70:10:10:7:5, 70:20:20:10, 70:25:25:12, 80:10:10:7, 80:15:20:10, 80:25:25:12, 85:10:10:7 or 85:25:25:12); the mass ratio of adhesive to curing agent is (15-120):1 (for example, it can be 15:1, 20:1, 30:1, 80:1, 90:1, 100:1 or 120:1).

[0045] In this embodiment of the invention, by controlling the raw materials in the absorbing slurry within the aforementioned range, it is not only beneficial to uniformly disperse the absorbing agent in the absorbing slurry, thereby ensuring the uniformity of the absorbing performance of the honeycomb absorbing core layer, but also to ensure good mechanical properties of the honeycomb absorbing core layer and prevent the collapse of the honeycomb structure. For example, if the content of the absorbing agent is too low, it is not conducive to improving the absorbing performance of the composite material; if the content of the absorbing agent is too high, it is not conducive to the uniform dispersion of the absorbing agent in the absorbing slurry, which is also not conducive to improving the absorbing performance of the composite material. As another example, if the content of the binder is too low, it is not conducive to ensuring good mechanical properties of the honeycomb absorbing core layer; if the content of the binder is too high, it is not only not conducive to the uniformity of the absorbing performance of the composite material in all directions, but also increases the weight of the composite material, which is not conducive to ensuring the lightweight nature of the composite material.

[0046] It should be noted that in this embodiment, the type of curing agent and the mass ratio of curing agent to resin vary depending on the resin used. For example, when the adhesive is acrylic resin, the curing agent is isocyanate, and the resin-to-curing agent ratio is (15-30):1; when the adhesive is phenolic resin, the curing agent is phenolic acid, and the resin-to-curing agent ratio is (85-100):1; when the resin is epoxy resin, the curing agent is 593 epoxy curing agent, and the resin-to-curing agent ratio is (80-120):1. Furthermore, to ensure the uniformity of the microwave absorbing slurry, it is necessary to stir the slurry at high speed for 30-40 minutes during preparation, with the preferred stirring speed being 800-1000 r / min.

[0047] It should also be noted that, in this embodiment, the preferred mass ratio of dispersant, defoamer, leveling agent and pH adjuster in the additives is (3-5):(1-2):(2-3):(1-2).

[0048] According to some preferred embodiments, the height of the honeycomb mold is 9 to 25 mm (e.g., 9 mm, 11 mm, 12 mm, 14 mm, 17 mm or 25 mm), the wall thickness is 2 to 5 mm (e.g., 2 mm, 3 mm, 4 mm or 5 mm), and the distance between the center points of adjacent honeycomb cells is 8 to 12 mm (e.g., 8 mm, 10 mm or 12 mm).

[0049] In this embodiment of the invention, in order to meet the requirements of absorption performance at different scales, honeycomb molds of different sizes can be prepared by 3D printing. The honeycomb mold is made of a high-temperature and corrosion-resistant material, such as polytetrafluoroethylene. By designing the honeycomb mold size and the concentration of the absorbing agent in the absorbing slurry in a coordinated manner, it is not only beneficial to achieve multi-scale adjustability of the absorption performance and absorption frequency band of the composite material, but also beneficial to better optimize the overall impedance matching characteristics of the composite material, thereby achieving broadband and efficient electromagnetic wave attenuation.

[0050] Secondly, embodiments of the present invention also provide a method for preparing the honeycomb absorbing composite material described in any one of the above claims, the method comprising the following steps:

[0051] (1) Injecting microwave absorbing slurry of different concentrations into honeycomb molds of different sizes until each honeycomb cell of the honeycomb mold is filled;

[0052] (2) The filled honeycomb mold is cured and demolded in sequence to obtain multiple honeycomb absorbing core layers; among them, the electromagnetic loss of each honeycomb absorbing core layer is different;

[0053] (3) The honeycomb absorbing core layer is sequentially composited to obtain a multi-layer honeycomb absorbing core layer, and a skin layer and a reflective layer are respectively composited on the upper and lower surfaces of the multi-layer honeycomb absorbing core layer to obtain the honeycomb absorbing composite material after molding.

[0054] In this embodiment of the invention, when the prepared absorbing slurry is poured into the honeycomb mold, in order to further ensure the uniformity of the absorbing performance in all directions of the honeycomb absorbing core layer, it is preferable to filter the absorbing slurry with a 100-mesh filter screen. Then, the absorbing slurry is slowly poured into the honeycomb mold. During the pouring process, the bottom of the mold is slightly vibrated to make the pouring dense, until the height of the slurry in the honeycomb mold no longer decreases during the slight vibration. Then, the honeycomb mold after pouring is placed in an oven for heat curing. After curing, the absorbing slurry is slowly squeezed out of the honeycomb mold to obtain the honeycomb absorbing core layer.

[0055] In the preparation of honeycomb absorbing composite materials, a film similar to or the same as the honeycomb absorbing core layer can be selected and placed between adjacent honeycomb absorbing core layers, between the honeycomb absorbing core layer and the skin layer, or between the honeycomb absorbing core layer and the reflective layer for layup. Finally, the molding process is completed using a vacuum bag or autoclave molding process to obtain the honeycomb absorbing composite material.

[0056] According to some preferred embodiments, along the direction from the skin layer to the reflective layer, the concentration of the absorbing slurry or the height of the honeycomb mold in each layer of honeycomb absorbing core material gradually increases.

[0057] In this embodiment, by controlling the concentration of the absorbing agent in the absorbing slurry or the size of the honeycomb mold during the preparation of the honeycomb absorbing core layer, the electromagnetic loss performance of the honeycomb absorbing core layer can be adjusted. With each honeycomb absorbing core layer having the same size, by gradually increasing the concentration of the absorbing agent in the absorbing slurry, or by gradually increasing the height of each honeycomb absorbing core layer with the same absorbing agent concentration, it is beneficial to achieve a gradient increase in the electromagnetic loss performance of the honeycomb absorbing layer, thereby ensuring good absorption performance of the composite material.

[0058] According to some preferred embodiments, in step (2), the curing temperature is 50 to 130°C (for example, it can be 50°C, 80°C, 100°C, 120°C or 130°C), the heating rate is 2 to 3°C / min (for example, it can be 2°C / min, 2.5°C / min or 3°C / min), and the holding time is 1 to 3 hours (for example, it can be 1 hour, 2 hours or 3 hours).

[0059] In this embodiment, the curing process is adjusted according to the type of resin. When acrylic resin is selected, the temperature is increased to 50-80°C at a rate of 2-3°C / min, held for 1-3 hours, and then cooled down in the furnace. When phenolic resin is selected, the temperature is increased to 80-100°C at a rate of 2-3°C / min, held for 1-3 hours, and then cooled down in the furnace. When epoxy resin is selected, the temperature is increased to 100-130°C at a rate of 2°C / min, held for 1-3 hours, and then cooled down naturally to complete the curing.

[0060] To more clearly illustrate the technical solution and advantages of the present invention, the following detailed description of a honeycomb microwave absorbing composite material and its preparation method is provided through several embodiments.

[0061] In the following embodiments, the carbon black is Cabot CSX946; the honeycomb cells in the honeycomb mold are all regular hexagons, and the distance between the center points of adjacent honeycomb cells is 10mm. The dimensions of the honeycomb mold are expressed in mm as length × width × height (mold) × wall thickness × height (honeycomb absorbing core layer). Among them, 350×350×9×5×4mm is designated as Y1, 350×350×11×4×6mm as Y2, 350×350×12×3×7mm as Y3, 350×350×14×2×9mm as Y4, 350×350×17×2×12mm as Y5, and 350×350×25×3×20mm as Y6.

[0062] Example 1:

[0063] Y1, Y1, and Y5 were selected as the honeycomb molds;

[0064] (1) Add 350g of adhesive (acrylic resin), 125g of microwave absorber (carbon black), 50g of solvent (ethyl acetate), 35g of additives (15g of sodium alginate dispersant, 5g of n-octanol defoamer, 10g of DIGIC leveling agent and 5g of triethanolamine pH adjuster), and 20g of curing agent (isocyanate curing agent) to a mixing tank. After stirring at 1000r / min for 30min, transfer the mixture to microwave absorbing slurry X. 25 ;

[0065] Add 375g of adhesive (acrylic resin), 100g of microwave absorber (carbon black), 60g of solvent (ethyl acetate), 35g of additives (15g sodium alginate dispersant, 5g n-octanol defoamer, 10g DIG leveling agent, and 5g triethanolamine pH adjuster), and 25g of curing agent (isocyanate curing agent) to a mixing tank. After stirring at 1000 rpm for 30 minutes, transfer the mixture to microwave absorbing slurry X. 20 ;

[0066] Add 850g of adhesive (acrylic resin), 100g of microwave absorber (carbon black), 250g of solvent (ethyl acetate), 116g of additives (50g sodium alginate dispersant, 20g n-octanol defoamer, 30g of DIGIC leveling agent, and 16g of triethanolamine pH adjuster), and 56g of curing agent (isocyanate curing agent) to a mixing tank. After stirring at 1000 rpm for 30 minutes, pour the mixture into microwave absorbing slurry X. 10 ;

[0067] The above-mentioned microwave absorbing slurry X was applied separately. 25 X 20 and X 10After filtering with a 100-mesh filter, the slurry is slowly poured into the Y1, Y2, and Y5 honeycomb molds until each honeycomb cell of the mold is filled. During the pouring process, the bottom of the mold is gently vibrated to ensure that the slurry is poured densely until the height of the slurry does not drop during the gentle vibration.

[0068] (2) Place the filled honeycomb mold in an oven and heat it to 50°C at a heating rate of 2°C / min. Keep it at that temperature for 2 hours and then cool it down in the oven to complete the curing. After curing, apply force evenly to the demolding mold along the direction of the positioning pins and slowly squeeze until the honeycomb absorbing core layer is completely demolded. The honeycomb absorbing core layers are named Y1-X respectively. 25 Y1-X 20 Y5-X 10 The shrinkage tolerance of the absorbing cell is ±0.1mm;

[0069] (3) Lay up the layers on the mold, in the following order from bottom to top: release fabric, reflective layer (2 sheets of carbon fiber acrylic prepreg), adhesive film (acrylic resin), Y1-X 25 Honeycomb absorbing core layer, adhesive film (acrylic resin), Y1-X 20 Honeycomb absorbing core layer, adhesive film (acrylic resin), Y5-X 10 The microwave absorbing core layer, adhesive film (acrylic resin), skin layer (3 sheets of glass fiber acrylic prepreg), and release cloth are laid out and placed in a vacuum bag to be vacuumed. The mixture is then placed in an oven and heated to 50°C at a heating rate of 2°C / min to cure. After being kept at this temperature for 2 hours, the mixture is cooled down in the oven. Once it reaches room temperature, the vacuum pressure is removed to obtain the honeycomb microwave absorbing composite material.

[0070] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 1 As shown.

[0071] Example 2:

[0072] Y1, Y3, and Y4 were selected as the honeycomb mold.

[0073] (1) Add 350g of adhesive (phenolic resin), 125g of microwave absorber (carbon black), 50g of solvent (ethyl acetate), 35g of additives (15g of sodium alginate dispersant, 5g of n-octanol defoamer, 10g of DIGIC leveling agent and 5g of triethanolamine pH adjuster), and 5g of curing agent (phenolic acid curing agent) to a mixing tank. After stirring at 1000r / min for 30min, pour the mixture into microwave absorbing slurry X. 25 ;

[0074] Add 800g of adhesive (phenolic resin), 150g of microwave absorber (carbon black), 200g of solvent (ethyl acetate), 110g of additives (50g sodium alginate dispersant, 20g n-octanol defoamer, 25g of DIGIC leveling agent, and 15g of triethanolamine pH adjuster), and 10g of curing agent (phenolic acid curing agent) to a mixing tank. After stirring at 1000r / min for 30min, pour the mixture into microwave absorbing slurry X. 15 ;

[0075] The above-mentioned microwave absorbing slurry X was applied separately. 25 and X 20 After filtering with a 100-mesh filter, the slurry is slowly poured into the Y1, Y3, and Y4 honeycomb molds until each honeycomb cell of the mold is filled. During the pouring process, the bottom of the mold is gently vibrated to ensure that the slurry is poured densely until the height of the slurry does not drop during the gentle vibration.

[0076] (2) Place the filled honeycomb mold in an oven and heat it to 80°C at a heating rate of 2°C / min. Keep it at this temperature for 2 hours and then cool it down in the oven to complete the curing process. After curing, apply force evenly to the demolding mold along the direction of the positioning pins and slowly press until the honeycomb absorbing core layer is completely demolded. The honeycomb absorbing core layers are named Y1-X respectively. 25 Y3-X 15 Y4-X 15 The shrinkage tolerance of the absorbing cell is ±0.1mm;

[0077] (3) Lay up the layers on the mold, in the following order from bottom to top: release fabric, reflective layer (2 sheets of carbon fiber phenolic resin prepreg), adhesive film (phenolic resin), Y1-X 25 Honeycomb absorbing core layer, adhesive film (phenolic resin), Y3-X 15 Honeycomb absorbing core layer, adhesive film (phenolic resin), Y4-X 15 The microwave absorbing core layer, adhesive film (phenolic resin), skin layer (3 sheets of glass fiber phenolic resin prepreg), and release cloth are laid out and placed in a vacuum bag for vacuuming. The bag is then placed in an oven and heated to 80°C at a heating rate of 2°C / min for curing. After holding at this temperature for 2 hours, the bag is cooled down with the oven. Once the bag reaches room temperature, the vacuum pressure is removed to obtain the honeycomb microwave absorbing composite material.

[0078] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 2 As shown.

[0079] Example 3:

[0080] Y2, Y3, and Y3 were selected as the honeycomb mold.

[0081] (1) Add 375g of adhesive (epoxy resin), 100g of microwave absorber (carbon black), 60g of solvent (ethyl acetate), 46g of additives (18g of sodium alginate dispersant, 7g of n-octanol defoamer, 13g of DIGIC leveling agent and 8g of triethanolamine pH adjuster) and 3.125g of curing agent (593 epoxy resin curing agent) to a mixing tank, stir at high speed of 1000r / min for 30min, and then pour into microwave absorbing slurry X. 20 ;

[0082] Add 400g of adhesive (epoxy resin), 75g of microwave absorber (carbon black), 100g of solvent (ethyl acetate), 53g of additives (20g sodium alginate dispersant, 10g n-octanol defoamer, 15g of DIGIC leveling agent, and 8g of triethanolamine pH adjuster) and 3.6g of curing agent (593 epoxy resin curing agent) to a mixing tank. After stirring at 1000 rpm for 30 minutes, pour the mixture into microwave absorbing slurry X. 15 ;

[0083] Add 425g of adhesive (epoxy resin), 50g of microwave absorber (carbon black), 125g of solvent (ethyl acetate), 58g of additives (25g sodium alginate dispersant, 10g n-octanol defoamer, 15g DIGIC leveling agent, and 8g triethanolamine pH adjuster), and 4g of curing agent (593 epoxy resin curing agent) to a mixing tank. After stirring at 1000 rpm for 30 minutes, pour the mixture into microwave absorbing slurry X. 10 ;

[0084] The above-mentioned microwave absorbing slurry X was applied separately. 20 X 15 and X 10 After filtering with a 100-mesh filter, the slurry is slowly poured into the Y2, Y3, and Y3 honeycomb molds until each honeycomb cell of the mold is filled. During the pouring process, the bottom of the mold is gently vibrated to ensure that the slurry is poured densely until the height of the slurry does not drop during the gentle vibration.

[0085] (2) Place the filled honeycomb mold in an oven and heat it to 130℃ at a heating rate of 2℃ / min for curing. Keep it at this temperature for 2 hours and then cool it down in the oven to complete the curing. After curing, apply force evenly to the demolding mold along the direction of the positioning pins and slowly squeeze until the honeycomb absorbing core layer is completely demolded. The honeycomb absorbing core layers are named Y2-X. 20 Y3-X 15 Y3-X 10 The shrinkage tolerance of the absorbing cell is ±0.1mm;

[0086] (3) Lay up the layers on the mold, in the following order from bottom to top: release fabric, reflective layer (2 sheets of carbon fiber epoxy resin prepreg), adhesive film (epoxy resin), Y2-X 20Honeycomb absorbing core layer, adhesive film (epoxy resin), Y3-X 15 Honeycomb absorbing core layer, adhesive film (epoxy resin), Y3-X 10 The microwave absorbing core layer, adhesive film (epoxy resin), skin layer (3 sheets of glass fiber epoxy resin prepreg), and release cloth are laid out and placed in a vacuum bag to be vacuumed. The bag is then placed in an oven and heated to 130°C at a heating rate of 2°C / min for curing. After being kept at this temperature for 2 hours, the bag is cooled down with the oven. Once the bag has cooled to room temperature, the vacuum pressure is removed to obtain the honeycomb microwave absorbing composite material.

[0087] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 3 As shown.

[0088] Example 4:

[0089] Example 4 is basically the same as Example 1, except that in step (1), the absorbing slurry filled in the honeycomb molds of Y1, Y2, and Y5 is the same, which is absorbing slurry X. 25 The honeycomb absorbing core layers are named Y1-X respectively. 25 Y1-X 25 Y5-X 25 The shrinkage tolerance of the absorbing cell is ±0.1mm.

[0090] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 4 As shown.

[0091] Example 5:

[0092] Example 5 is basically the same as Example 1, except that in step (3), layers are laid on the mold, and the layup order from bottom to top is: release cloth, reflective layer (2 sheets of carbon fiber acrylic prepreg), adhesive film (acrylic resin), Y1-X 10 Honeycomb absorbing core layer, adhesive film (acrylic resin), Y1-X 20 Honeycomb absorbing core layer, adhesive film (acrylic resin), Y5-X 25 The microwave absorbing core layer, adhesive film (acrylic resin), skin layer (3 sheets of glass fiber acrylic prepreg), and release cloth are laid out and placed in a vacuum bag to be vacuumed. The mixture is then placed in an oven and heated to 50°C at a heating rate of 2°C / min to cure. After being kept at this temperature for 2 hours, the mixture is cooled down in the oven. Once it reaches room temperature, the vacuum pressure is removed to obtain the honeycomb microwave absorbing composite material.

[0093] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 5 As shown.

[0094] Comparative Example 1:

[0095] Y6 was selected as the honeycomb mold;

[0096] (1) Add 800g of adhesive (epoxy resin), 150g of microwave absorber (carbon black), 200g of solvent (ethyl acetate), 95g of additives (50g of sodium alginate dispersant, 15g of n-octanol defoamer, 20g of DIGIC leveling agent, and 10g of triethanolamine pH adjuster) and 7g of curing agent (593 epoxy resin curing agent) to a mixing tank. After stirring at high speed of 1000r / min for 30min, pour the mixture into microwave absorbing slurry X. 15 ;

[0097] The above-mentioned microwave absorbing paste X 15 After filtering with a 100-mesh filter, the slurry is slowly poured into the Y6 honeycomb mold until each honeycomb cell of the mold is filled. During the pouring process, the bottom of the mold is gently shaken to ensure that the slurry is poured densely until the height of the slurry does not drop during the gentle shaking.

[0098] (2) Place the filled honeycomb mold in an oven and heat it to 130℃ at a heating rate of 2℃ / min for curing. Keep it at this temperature for 2 hours and then cool it down in the oven to complete the curing. After curing, apply force evenly to the demolding mold along the direction of the positioning pins and slowly squeeze until the honeycomb absorbing core layer is completely demolded. The honeycomb absorbing core layers are named Y6-X. 15 The shrinkage tolerance of the absorbing cell is ±0.1mm;

[0099] (3) Lay up the layers on the mold, in the following order from bottom to top: release fabric, reflective layer (2 sheets of carbon fiber epoxy resin prepreg), adhesive film (epoxy resin), Y6-X 15 The honeycomb absorbing core layer, adhesive film (epoxy resin), skin layer (3 sheets of glass fiber epoxy resin prepreg), and release cloth are laid out and placed in a vacuum bag to be vacuumed. The mixture is then placed in an oven and heated to 130°C at a heating rate of 2°C / min for curing. After being kept at this temperature for 2 hours, the mixture is cooled down in the oven. Once it reaches room temperature, the vacuum pressure is removed to obtain the honeycomb absorbing composite material.

[0100] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 6 As shown.

[0101] Comparative Example 2:

[0102] Select aramid honeycomb core materials with the same length, width, thickness and center-to-center distance between adjacent honeycomb cells as Y1, Y1, and Y5, and denote them as Y1', Y1', and Y5'.

[0103] (1) Add 350g of adhesive (phenolic resin), 125g of microwave absorber (carbon black), 50g of solvent (ethyl acetate), 35g of additives (15g of sodium alginate dispersant, 5g of n-octanol defoamer, 10g of DIGIC leveling agent and 5g of triethanolamine pH adjuster), and 5g of curing agent (phenolic acid curing agent) to a mixing tank. After stirring at 1000r / min for 30min, pour the mixture into microwave absorbing slurry X. 25 ;

[0104] Add 375g of adhesive (phenolic resin), 100g of microwave absorber (carbon black), 60g of solvent (ethyl acetate), 35g of additives (15g sodium alginate dispersant, 5g n-octanol defoamer, 10g DIG leveling agent, and 5g triethanolamine pH adjuster), and 5g of curing agent (phenolic acid curing agent) to a mixing tank. After stirring at 1000 rpm for 30 minutes, pour the mixture into microwave absorbing slurry X. 20 ;

[0105] Add 850g of adhesive (phenolic resin), 100g of microwave absorber (carbon black), 250g of solvent (ethyl acetate), 116g of additives (50g sodium alginate dispersant, 20g n-octanol defoamer, 30g of DIGIC leveling agent, and 16g of triethanolamine pH adjuster), and 10g of curing agent (phenolic acid curing agent) to a mixing tank. After stirring at 1000r / min for 30min, pour the mixture into microwave absorbing slurry X. 10 ;

[0106] (2) The prepared microwave absorbing slurry X was prepared separately. 25 Microwave Absorbing Paste X 20 And microwave absorbing paste X 10 As for the impregnation tank, the microwave absorbing slurry was thoroughly stirred for 20 minutes before impregnation. Then, the aramid paper honeycomb core materials of the above-mentioned dimensions were immersed in the impregnation tank for 10 minutes. During the impregnation process, the honeycomb core materials needed to be gently moved left and right with clamps. After removal, they were allowed to air dry until no liquid flowed down the walls of the honeycomb core materials. The impregnation process was repeated twice. Finally, the impregnated honeycomb microwave absorbing core materials were placed in an oven and heated to 50°C at a heating rate of 2°C / min for curing. After holding at that temperature for 1 hour, the temperature was lowered to room temperature with the oven to obtain honeycomb microwave absorbing core materials with microwave absorbing slurry on the surface. The honeycomb microwave absorbing core layers were named Y1'-X. 25 Y1'-X 20 Y5'-X 10 ;

[0107] (3) Lay up the layers on the mold, in the following order from bottom to top: release fabric, reflective layer (2 sheets of carbon fiber phenolic resin prepreg), adhesive film (phenolic resin), Y1'-X 25 Honeycomb absorbing core layer, adhesive film (phenolic resin), Y1'-X 20Honeycomb absorbing core layer, adhesive film (phenolic resin), Y5'-X 10 The microwave absorbing core layer, the adhesive film (phenolic resin), the skin layer (3 sheets of glass fiber phenolic resin prepreg), and the release cloth are laid out and placed in a vacuum bag to be vacuumed. The bag is then placed in an oven and heated to 50°C at a heating rate of 2°C / min to cure. After being kept at this temperature for 2 hours, the bag is cooled down with the oven. Once the bag has cooled to room temperature, the vacuum pressure is removed to obtain the honeycomb microwave absorbing composite material.

[0108] The reflectivity was tested according to GJB2038A-2011 to verify the electromagnetic wave absorption performance of the honeycomb absorbing composite material. The reflectivity results are as follows: Figure 7 As shown.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A honeycomb microwave absorbing composite material, characterized in that, The device comprises a skin layer, multiple honeycomb absorbing core layers, and a reflective layer arranged sequentially along its thickness direction. The honeycomb absorbing core layers are formed by pouring absorbing slurry into a honeycomb mold and then curing it. Each honeycomb absorbing core layer has a different electromagnetic loss. The honeycomb mold has a height of 9-25 mm, a wall thickness of 2-5 mm, and a spacing of 8-12 mm between the center points of adjacent honeycomb cells. The absorbing slurry includes an adhesive, an absorbing agent, a solvent, additives, and a curing agent. The adhesive is acrylic resin. The adhesive is selected from at least one of phenolic resin or epoxy resin; the microwave absorber is carbon black; the solvent is ethyl acetate; the additives include dispersant, defoamer, leveling agent and pH adjuster; the curing agent is isocyanate, phenolic acid, 593 epoxy curing agent; the mass ratio of adhesive, microwave absorber, solvent and additives is (70~85):(10~25):(10~25):(7~12); the mass ratio of adhesive to curing agent is (15~120):

1.

2. The composite material according to claim 1, characterized in that, Along the direction from the skin layer to the reflective layer, the electromagnetic loss of each honeycomb absorbing core layer gradually increases.

3. The composite material according to claim 1, characterized in that, The thickness of the skin layer is 1~2mm, the thickness of each honeycomb absorbing core layer is 4~20mm, and the thickness of the reflective layer is 0.2~0.4mm.

4. The composite material according to claim 1, characterized in that, The honeycomb absorbing core layer consists of 2 to 5 layers.

5. A method for preparing a honeycomb absorbing composite material according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: (1) Different concentrations of microwave absorbing slurry are injected into honeycomb molds of different sizes until each honeycomb cell of the honeycomb mold is filled; (2) The filled honeycomb mold is cured and demolded in sequence to obtain multiple honeycomb absorbing core layers; among them, the electromagnetic loss of each honeycomb absorbing core layer is different; (3) The honeycomb absorbing core layer is sequentially composited to obtain a multi-layer honeycomb absorbing core layer, and a skin layer and a reflective layer are respectively composited on the upper and lower surfaces of the multi-layer honeycomb absorbing core layer to obtain the honeycomb absorbing composite material after molding.

6. The preparation method according to claim 5, characterized in that, Along the direction from the skin layer to the reflective layer, the concentration of the absorbing slurry or the height of the honeycomb mold in each layer of honeycomb absorbing core material gradually increases.

7. The preparation method according to claim 5, characterized in that, In step (2), the curing temperature is 50~130℃, the heating rate is 2~3℃ / min, and the holding time is 1~3h.

Images