CN113547822B - Radar wave-absorbing structure and preparation method thereof - Google Patents

Radar wave-absorbing structure and preparation method thereof Download PDF

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CN113547822B
CN113547822B CN202110670601.3A CN202110670601A CN113547822B CN 113547822 B CN113547822 B CN 113547822B CN 202110670601 A CN202110670601 A CN 202110670601A CN 113547822 B CN113547822 B CN 113547822B
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wave
over
honeycomb
absorbing
skin
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CN113547822A (en
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高明
王静南
余彧
李扬帆
侯宇鹏
秦慧
庞晓彬
刘雨航
段洪强
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Wuhan Haiwei Ship And Ocean Engineering Technology Co ltd
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Wuhan Haiwei Ship And Ocean Engineering Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B29/00—Layered products comprising a layer of paper or cardboard
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B29/00—Layered products comprising a layer of paper or cardboard
    • B32B29/002—Layered products comprising a layer of paper or cardboard as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B29/005—Layered products comprising a layer of paper or cardboard as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to another layer of paper or cardboard layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B29/00—Layered products comprising a layer of paper or cardboard
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/02—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions
    • B32B3/08—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions characterised by added members at particular parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
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    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
    • B32B37/1284—Application of adhesive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/0012—Mechanical treatment, e.g. roughening, deforming, stretching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/08—Impregnating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K7/00—Use of ingredients characterised by shape
    • C08K7/22—Expanded, porous or hollow particles
    • C08K7/24—Expanded, porous or hollow particles inorganic
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    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/24—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate
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    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B2038/0052—Other operations not otherwise provided for
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    • B32—LAYERED PRODUCTS
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    • B32B2250/00—Layers arrangement
    • B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
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  • Laminated Bodies (AREA)

Abstract

The invention relates to a radar wave-absorbing structure, which comprises a sandwich structure and skin structures on two sides of the sandwich structure; the sandwich structure comprises a plurality of layers of over-stretched honeycomb structures and filling materials; the over-stretched honeycomb structure comprises an over-stretched honeycomb body and a wave absorbing agent impregnated on the over-stretched honeycomb body, and the cross section of the inner cavity of the honeycomb grid of the over-stretched honeycomb body is rectangular; the wave-absorbing dosage of each layer is reduced from the surface of the product to the outside in sequence; the filling material is filled in the honeycomb grids and used for interlayer bonding, and the filling material is made of a buoyancy material. The radar wave-absorbing structure can be prepared into a surface structure type wave-absorbing material applied to a plane, large-curvature or special-shaped part, and can also be directly formed on the surface of the plane, large-curvature or special-shaped part, so that the problems of structural bearing, radar stealth and interface bonding of a large-curvature structure product can be effectively solved, and structural and functional integration is realized.

Description

Radar wave-absorbing structure and preparation method thereof
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a radar wave-absorbing structure and a preparation method thereof.
Background
The wave-absorbing material is a functional material which can effectively absorb incident electromagnetic waves, convert electromagnetic energy into heat energy and consume or enable the interference of the electromagnetic waves to be cancelled, and therefore the echo intensity of a target is obviously weakened. The traditional wave-absorbing material is mainly a coating type or structural type wave-absorbing material, the coating is generally composed of ferrite, metal powder or carbon powder and a resin system, and is characterized by small thickness and disadvantages of large density, narrow shielding or absorbing frequency band, easy falling off and the like when in use; the traditional structural wave-absorbing material has a wide-screen absorption effect on millimeter radar waves and centimeter radar waves, but has poor conformability and high water absorption rate, so that the wave-absorbing material is aged or invalid, particularly cannot bear high-strength pressure action such as water pressure and the like, and is limited to be applied to large-curvature or special-shaped components, pressure-bearing fields and marine environments.
Disclosure of Invention
The invention aims to solve the technical problems that the application of a traditional structural wave-absorbing material on a large-curvature part is limited, and the traditional structural wave-absorbing material is low in bearing strength and high in water absorption rate and cannot be applied to marine environments.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a radar wave absorbing structure comprises a sandwich structure and skin structures arranged on two sides of the sandwich structure; the sandwich structure comprises N layers of over-stretched honeycomb structures and filling materials, wherein N is more than or equal to 1; each layer of the over-stretched honeycomb structure comprises an over-stretched honeycomb body and a wave absorbing agent impregnated on the over-stretched honeycomb body, wherein the over-stretched honeycomb body has bending performance along the width direction of a grid and bearing performance along the length direction; the wave absorbing agent impregnated in each layer of the over-stretched honeycomb body is designed in a gradient manner along the thickness direction, and the wave absorbing agent impregnated in the over-stretched honeycomb body is sequentially reduced from the surface of the product to the outside;
the filling material is filled in the honeycomb grids and used for interlayer bonding, the filling material is made of a buoyancy material, the compression strength is not lower than 1MPa, and the water absorption rate is less than 2%.
In the scheme, the number N of layers of the over-stretched honeycomb structure, the thickness of each layer of the over-stretched honeycomb structure and the wave-absorbing dose are determined by using the wave-absorbing dose, the honeycomb thickness and the skin structure thickness as wave-absorbing performance influencing factors according to impedance matching and a multi-layer wave-absorbing material design theory, setting material parameters in a simulation system, setting a grid structure and performing electrical performance simulation and determination.
In the scheme, the cross section of the inner cavity of the honeycomb grid of the over-stretched honeycomb body is rectangular; the honeycomb net of the over-stretched honeycomb body is formed by stacking continuous positive and negative U-shaped aramid paper, and thereby the U-shaped aramid paper layers are bonded through glue strips to form a whole honeycomb structure.
In the above scheme, the density of the over-stretched honeycomb body is 48-100 kg/m 3 The thickness of the single layer is 5-20 mm.
In the above scheme, the components of the buoyancy material used by the filling material comprise, by mass: 70-90 parts of resin, 5-15 parts of glass beads and 0.5-2 parts of curing agent.
In the scheme, the resin is epoxy modified vinyl resin.
In the scheme, the density of the buoyancy material is 200-800 kg/m 3 The shear strength is not lower than 7MPa, the interface bonding strength is not lower than 7MPa,the dielectric constant is less than 2, and the dielectric loss tangent is less than 0.011.
In the scheme, the skin structure comprises a bottom skin and a surface skin, wherein the bottom skin is arranged on the outer surface of a product to be coated; the reinforced materials of the bottom layer skin and the surface layer skin are quartz fibers, and the matrix resin is epoxy resin; the thickness is 0.5-1.0mm, the dielectric constant is less than 3.4, and the dielectric loss tangent angle is less than 0.015.
In the scheme, the bottom layer skin and the surface layer skin are manufactured into an integrated structure with the sandwich structure by adopting a hand lay-up forming process.
Correspondingly, the invention also provides a preparation method of the radar wave-absorbing structure, which comprises the following steps:
s1, structural design: according to impedance matching and a multi-layer wave-absorbing material design theory, taking wave-absorbing dose, honeycomb thickness and skin structure thickness as wave-absorbing performance influence factors, setting material parameters in a simulation system, setting a grid structure, performing electrical performance simulation, and determining the number N of layers of the over-stretched honeycomb structure, the thickness of each layer of the over-stretched honeycomb structure and the wave-absorbing dose;
s2, impregnating the overstretched honeycomb body with a wave absorbing agent: determining the dipping times according to the design weight requirement, realizing the dipping of the wave absorbing agent by alternately dipping in forward dipping, reverse dipping, forward dipping and reverse dipping, and carrying out the next dipping after each dipping and curing;
s3, preparing a filling material: uniformly mixing various raw materials according to the proportion of the filling material, and performing vacuum defoaming after the mixing is finished for later use;
s4, product surface treatment: cleaning dust and oil stains on the surface of the product, and treating the surface of the product by using a solution containing a coupling agent after the surface of the product is cleaned;
s5, forming a bottom layer skin: uniformly brushing a layer of epoxy resin on the surface of the product, then paving and adhering quartz fiber cloth, brushing and pressing the quartz fiber cloth to be tightly matched, and continuously brushing the epoxy resin on the surface of the quartz fiber cloth to fully impregnate the quartz fiber cloth; when the epoxy resin is brushed, the product is brushed and rotated at the same time to ensure that no glue flow and uniform glue content are realized, the steps are repeated until the thickness required by the design is reached, the surface is coated with demolding cloth after the completion, the glue flow is not generated before the epoxy resin is cured, and the epoxy resin is cured for 8 to 16 hours at the temperature of between 60 and 80 ℃;
s6, preparing a sandwich structure: coating a layer of filling material on the outer surface of the bottom skin, tightly coating a layer of over-stretched honeycomb structure impregnated with a wave absorbing agent on the outer surface of the bottom skin, positioning, tightly filling the filling material into a honeycomb grid in a multi-time blade coating mode, primarily curing for 2-4 h at 60-80 ℃, coating a layer of filling material after the outer surface is treated, then sequentially completing positioning, filling and primarily curing of the rest layers of over-stretched honeycomb structure according to the method, and forming a compact sandwich structure after the surface treatment;
s7, forming a surface layer skin: finishing the surface skin forming on the surface of the sandwich structure according to the method in the step S5;
s8, curing and forming: after the surface skin is prepared, the product is placed for 8-16 h at room temperature, then is post-cured for 16-24 h at 60-80 ℃, the hardness of the surface of the product is checked by a hardness tester, and the Babbitt hardness of at least 2 point positions reaches more than 35, namely the curing is finished.
The invention has the beneficial effects that:
1. the invention utilizes the characteristics of small density, designable thickness and capability of curling of the over-stretched honeycomb, and can effectively solve the problem of application of the over-stretched honeycomb on products with large curvature or special-shaped structures; determining the number of layers of the over-stretched honeycomb and the surface impregnation wave-absorbing dose of each layer of the over-stretched honeycomb through impedance matching design so as to meet the radar wave-absorbing index requirement; by utilizing the characteristics of high adhesion of the special filling material and high compressive strength after curing, the special filling material can be used as an interlayer adhesion material on one hand, and a light high-strength core material structure can be formed on the other hand; the composite material skin made of quartz fiber and epoxy resin has the characteristic of good wave permeability, so that the mechanical and functional requirements of the product are met on the whole structure.
2. The buoyancy material is adopted as the interlayer adhesive and the filling material, the adhesion layer of the buoyancy material is firstly coated by scraping, then the stretched honeycomb and the filling buoyancy material are positioned, the filled buoyancy material and the adhesion layer can form a uniform structure, the interlayer adhesion performance is ensured under special environments such as ocean and the like, and meanwhile, the wave-absorbing performance of the whole structure cannot be influenced by introducing other adhesives.
3. The radar wave-absorbing structure combines the crimpability of the over-stretched honeycomb, the light high-pressure high-wave permeability of the filling material and the good wave permeability of quartz fiber and epoxy resin on the basis of a honeycomb structure, can be prepared into a surface structure type wave-absorbing material applied to a plane, large-curvature or special-shaped part, and can also be directly molded on the surface of the plane, large-curvature or special-shaped part.
4. The invention provides a preparation method of a radar wave-absorbing structure, which can be used for designing the radar wave-absorbing structure into a planar or curved surface structure and can also be directly formed on the outer surface of a product, thereby endowing the product with structural and functional characteristics.
5. The radar wave-absorbing structure is tested in the reflectivity of 8-18GHz electromagnetic waves, the reflectivity is lower than-10 dB, the compressive strength is greater than 10MPa, and the radar wave-absorbing structure can meet the application field with higher pressure-bearing requirements on structural wave-absorbing materials.
Drawings
The invention will be further described with reference to the following drawings and examples, in which:
FIG. 1 is a schematic structural diagram of a radar wave-absorbing structure on the outer surface of a cylindrical product in an embodiment of the invention;
FIG. 2 is a schematic cross-sectional structure diagram of the radar absorbing structure shown in FIG. 1;
FIG. 3 is a schematic plane structure diagram of an over-stretched honeycomb body of the radar absorbing structure of the present invention;
FIG. 4 is a partial exploded structural view of the over-stretched honeycomb body of FIG. 3;
FIG. 5 is a graph of the reflectivity of four layers of an overstretched honeycomb impregnated with a wave absorber tested in an example of the invention stacked together in order;
FIG. 6 is a reflectivity graph of the whole structure after the wave absorber-impregnated four-layer over-stretched honeycomb structure is filled with the buoyancy material and the upper and lower skins in sequence in the embodiment of the invention.
In the figure: 10. a sandwich structure; 11. over-stretching the honeycomb structure; 111. overstretching the honeycomb body; 112. a wave absorbing agent; 12. a filler material; 121. a cellular network filling section; 122. an interlayer bonding portion;
20. a skin structure; 201. a bottom skin; 202. and covering the surface layer.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
As shown in fig. 1-2, the radar wave absorbing structure provided in the embodiment of the present invention is disposed on an outer surface of a cylindrical product, and includes a sandwich structure 10 and skin structures 20 disposed on two sides of the sandwich structure 10.
The sandwich structure 10 includes one or more layers of an over-stretched honeycomb 11 and a filler material 12, and the over-stretched honeycomb 11 includes an over-stretched honeycomb body 111 and a wave-absorbing agent 112 impregnated thereon. As shown in fig. 3, the cross section of the inner cavity of the honeycomb grid of the over-stretched honeycomb body 111 is rectangular, and has good bending performance and covering performance along the width direction (i.e. transverse direction) of the grid, and the original mechanical and bearing performance is maintained in the length direction (i.e. longitudinal direction). The amount of the wave absorbing agent 112 impregnated in each layer of the overstretched honeycomb body 111 is designed in a gradient manner along the thickness direction, and the amount of the wave absorbing agent 112 decreases from the surface of the product to the outside. The filling material 12 includes a honeycomb-cell filling portion 121 and an interlayer bonding portion 122, the honeycomb-cell filling portion 121 is filled in the honeycomb cells, and the interlayer bonding portion 122 is used for interlayer bonding. The filling material 12 completes honeycomb grid filling and interlayer bonding in a multi-time blade coating mode, and finally the compact sandwich structure 10 is formed. The filling material 12 is a buoyancy material with low density, high compression strength after curing and low dielectric constant, and the density is 200-800 kg/m 3 The compressive strength is not lower than 1MPa, the shear strength is not lower than 7MPa, the interfacial adhesion strength is not lower than 7MPa, the water absorption is less than 2 percent, the dielectric constant is less than 2, and the dielectric loss factor is smallAt 0.011.
Skin structure 20 includes a bottom skin 201 and a face skin 202, where bottom skin 201 is provided on the outer surface of the cylindrical product. The reinforcing materials of the bottom layer skin 201 and the surface layer skin 202 are high-strength quartz fibers with excellent dielectric property, and the matrix resin is epoxy resin with excellent property and is formed by a hand lay-up forming process. The thicknesses of the bottom layer skin 201 and the surface layer skin 202 are both 0.5-1.0mm, the dielectric constant is less than 3.4, and the dielectric loss tangent angle is less than 0.015.
The number N of layers of the over-stretched honeycomb structure 11, the thickness of each layer of the over-stretched honeycomb structure 11 and the amount of the wave absorbing agent 112 are determined according to impedance matching and a multi-layer wave absorbing material design theory, the amount of the wave absorbing agent 112, the thickness of the honeycomb and the thickness of the skin structure 20 are used as wave absorbing performance influencing factors, material parameters are set in a simulation system, a grid structure is set, and electrical performance simulation determination is carried out. In the embodiment, simulation results show that four layers of over-stretched honeycomb structures 11 with the same pore diameter and the same thickness of 5mm are adopted, gradient design is carried out on wave absorbing agents 112 impregnated in each layer in the thickness direction (the weight ratio of the content of each layer of wave absorbing agent 112 in the layer is 60-90 percent of the first layer, 40-70 percent of the second layer, 30-50 percent of the third layer and 20-40 percent of the fourth layer, wherein the first layer is a bottom layer, and the fourth layer is a surface layer), a composite material with a low dielectric constant of 0.5mm and a low dielectric loss tangent angle is matched and used as a wave-transmitting skin, and the reflectivity of the designed honeycomb wave absorbing material with the total thickness of 21mm is lower than-10 dB for a normal incidence flat plate of 8 GHz-18 GHz.
As shown in fig. 4, the honeycomb mesh of the over-stretched honeycomb body 111 is formed by stacking continuous positive and negative U-shaped aramid paper, and the U-shaped aramid paper layers are bonded by glue strips to form an integral honeycomb structure. When more complicated curved surface takes shape, traditional regular hexagon honeycomb can receive the influence of cell shape in the aspect of crooked, and the inboard receives the extrusion, and the outside receives tensile to destroy original cell shape, reduce and bear and the mechanical properties of material, simultaneously and curved surface product between the laminating nature poor. The over-stretched honeycomb adopted by the invention is a honeycomb structure with a rectangular cross section of an inner cavity formed by enclosing aramid paper and glue strips, has better laying performance in the aspect of transverse bending, and longitudinally keeps the original mechanical and bearing performance.
Further optimized, the density of the over-stretched honeycomb body 111 is 48-100 kg/m 3 The thickness of the single layer is 5-20 mm.
Further optimized, the buoyancy material used for the filling material 12 comprises the following components in parts by mass: 70-90 parts of resin, 5-15 parts of glass beads and 0.5-2 parts of curing agent. The adopted resin has the characteristics of low viscosity, controllable curing and forming temperature and small curing shrinkage rate, and has excellent bonding and wettability, so that the bonding strength is provided, such as epoxy modified vinyl resin and the like. The glass beads have high compressive strength and low water absorption and thermal shrinkage coefficients, the density of the material can be effectively reduced without excessively reducing the compressive strength of the material, and the resin and the glass beads play a role in mutual support. Through the curing action of the curing agent, the over-stretched honeycomb with the impregnated wave absorbing agent and the buoyancy material (namely, resin and glass beads) are co-cured to form an integral structure, no obvious cavity is formed inside the wave absorbing structure, the compact structure filled with the buoyancy material protects the inside of the wave absorbing material from being corroded by water, meanwhile, the upper surface skin structure and the lower surface skin structure greatly eliminate the water seepage passage of the whole wave absorbing structure, and the service life of the wave absorbing structure is greatly prolonged.
Further optimizing, the buoyancy material further comprises the following components in parts by mass: 0.1-4 parts of accelerator, 0.5-3 parts of coupling agent, 0.1-1 part of diluent and 0.1-2 parts of defoaming agent.
Correspondingly, the invention also provides a preparation method of the radar wave-absorbing structure, which comprises the following steps:
s1, structural design of a radar wave absorbing structure: according to impedance matching and a multi-layer wave-absorbing material design theory, the wave-absorbing agent 112 amount, the honeycomb thickness and the skin structure 20 thickness are used as wave-absorbing performance influence factors, the wave-absorbing agent amount soaked by each layer of the stretched honeycomb body 111 is subjected to gradient design along the thickness direction, material parameters are set in a simulation system, a grid structure is set, electrical performance simulation is carried out, and the number N of layers of the over-stretched honeycomb structure 11, the thickness of each layer of the over-stretched honeycomb structure 11 and the wave-absorbing agent 112 amount are determined.
S2, impregnating the overstretched honeycomb body 111 with a wave absorbing agent 112: the dipping times are determined according to the design weight requirement, the dipping of the wave absorbing agent 112 is realized by alternately carrying out the dipping through forward dipping, reverse dipping, forward dipping and reverse dipping, and the next dipping is carried out after each dipping and curing.
S3, preparing a filling material 12: according to the proportion of the light high-pressure high-wave-transparent buoyancy material, various raw materials are sequentially put into a kneader and are uniformly mixed for 1-2 h, and after the mixing is finished, the mixed materials are subjected to vacuum defoaming for 0.5-1 h for standby.
S4, product surface treatment: and cleaning dust and oil stains on the surface of the product by using a cleaning agent, and treating the surface of the product by using a solution containing a coupling agent after the surface of the product is cleaned.
S5, molding of a bottom layer skin 201: uniformly brushing a layer of prepared epoxy resin on the surface of a product by using a brush, then paving and sticking high-strength quartz fiber cloth, brushing and pressing the high-strength quartz fiber cloth by using the brush or a scraper to enable the high-strength quartz fiber cloth to be tightly matched, and continuously brushing the epoxy resin on the surface of the quartz fiber cloth to fully impregnate the quartz fiber cloth; when the epoxy resin is brushed, the product is brushed and rotated at the same time to ensure that no glue flow and uniform glue content are realized, the steps are repeated until the thickness required by the design is reached, the surface is coated with demolding cloth after the completion, the glue flow is not generated before the epoxy resin is cured, and the epoxy resin is cured for 8 to 16 hours at the temperature of between 60 and 80 ℃; and finally, polishing the surface of the bottom skin 201.
S6, preparing a sandwich structure 10: coating a layer of filling material 12 on the outer surface of the bottom-layer skin 201, tightly coating a layer of over-stretched honeycomb structure 11 impregnated with the wave absorbing agent 112 on the outer surface of the bottom-layer skin 201, positioning, tightly filling the filling material 12 in honeycomb grids in a blade coating mode for many times, performing primary curing for 2-4 h at 60-80 ℃, coating a layer of filling material 12 on the outer surface after the treatment, then sequentially completing the positioning, filling and primary curing of the second, third and fourth layers of over-stretched honeycomb structures 11 according to the method, and forming the compact sandwich structure 10 after the surface treatment.
S7, forming a surface layer skin 202: finishing the forming of the surface skin 202 on the surface of the sandwich structure 10 according to the method of the step S5;
s8, curing and forming: after the surface skin 202 is prepared, the product is placed at room temperature for 8-16 h, then is post-cured at 60-80 ℃ for 16-24 h, the hardness of the surface of the product is checked by a hardness tester, and the Babbitt hardness of at least 2 points reaches more than 35, namely the curing is completed.
And finally, polishing the surface of the product to obtain the structural wave-absorbing material on the outer surface of the product.
FIG. 5 shows the reflectivity of the over-stretched honeycomb impregnated with the wave absorbing agent, which is measured by sequentially overlapping four layers after the wave absorbing agent is impregnated in the over-stretched honeycomb by adopting a national military standard GJB 2038A-2011 bow-shaped frame method for the reflectivity of the electromagnetic wave absorbing material, and the test result shows that the reflectivity is lower than-15 dB in the range of 8-18 GHz.
FIG. 6 shows that the reflectivity of the electromagnetic wave of 8-18GHz of the prepared buoyancy-filled honeycomb sandwich structure composite material plate is tested by adopting a GJB 2038A-2011 electromagnetic wave absorbing material reflectivity bow-shaped frame method, and the reflection loss is lower than-10 dB.
In addition, the compression strength of the prepared buoyancy-filled honeycomb sandwich structure composite material plate is measured by adopting a GB/T1453-2005 sandwich structure or core flat compression performance test method, and the compression strength is more than 10MPa.
The performance test of marine environment resistance shows that the surface soaked in the seawater has no cracking, no bubble, no softening and no color change.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (8)

1. A radar wave absorbing structure comprises a sandwich structure and skin structures arranged on two sides of the sandwich structure; the sandwich structure is characterized by comprising N layers of over-stretched honeycomb structures and filling materials, wherein N is more than or equal to 1; each layer of over-stretched honeycomb structure comprises an over-stretched honeycomb body and a wave absorbing agent impregnated on the over-stretched honeycomb body, wherein the over-stretched honeycomb body has bending performance along the width direction of a grid and has bearing performance along the length direction; the wave absorbing agent impregnated in each layer of the over-stretched honeycomb body is designed in a gradient manner along the thickness direction, and the wave absorbing agent impregnated in the over-stretched honeycomb body is sequentially reduced from the surface of the product to the outside;
the filling material is filled in the honeycomb grids and used for interlayer bonding, adopts a buoyancy material, and comprises the following components in parts by mass: 70-90 parts of resin, 5-15 parts of glass beads and 0.5-2 parts of curing agent, wherein the compression strength of the buoyancy material is not lower than 1MPa, the water absorption rate is less than 2%, and the density is 200-800 kg/m 3 The shear strength is not lower than 7MPa, the interface bonding strength is not lower than 7MPa, the dielectric constant is less than 2, and the dielectric loss factor is less than 0.011.
2. The radar absorbing structure according to claim 1, wherein the number of layers N of the over-stretched honeycomb structure, the thickness of each over-stretched honeycomb structure and the amount of the wave-absorbing agent are determined by performing simulation and determination of electrical properties by setting material parameters and a grid structure in a simulation system, taking the amount of the wave-absorbing agent, the thickness of the honeycomb and the thickness of a skin structure as the influence factors of the wave-absorbing properties according to impedance matching and a multi-layer wave-absorbing material design theory.
3. The radar absorbing structure of claim 1, wherein the cross-section of the honeycomb mesh cavity of the overstretched honeycomb body is rectangular; the honeycomb net of overstretch honeycomb body forms through continuous positive and negative U type aramid paper pile, thereby bonds through the glue strip between each layer U type aramid paper and forms holistic honeycomb.
4. The radar absorbing structure of claim 1, wherein the density of the over-stretched honeycomb body is 48 to 100kg/m 3 The thickness of the single layer is 5-20 mm.
5. The radar absorbing structure of claim 1, wherein the resin is an epoxy modified vinyl resin.
6. The radar absorbing structure of claim 1, wherein the skin structure comprises a bottom skin and a top skin, wherein the bottom skin is disposed on an outer surface of the product to be coated; the reinforcing materials of the bottom layer skin and the surface layer skin are both quartz fibers, and the matrix resin is both epoxy resin; the thickness is 0.5-1.0mm, the dielectric constant is less than 3.4, and the dielectric loss tangent angle is less than 0.015.
7. The radar absorbing structure of claim 6, wherein the bottom skin and the surface skin are formed into an integrated structure with the sandwich structure by hand lay-up molding.
8. The method for preparing the radar absorbing structure according to claim 1, comprising the following steps:
s1, structural design: according to impedance matching and a multi-layer wave-absorbing material design theory, taking wave-absorbing dose, honeycomb thickness and skin structure thickness as wave-absorbing performance influence factors, setting material parameters in a simulation system, setting a grid structure, performing electrical performance simulation, and determining the number N of layers of the over-stretched honeycomb structure, the thickness of each layer of the over-stretched honeycomb structure and the wave-absorbing dose;
s2, soaking the over-stretched honeycomb body with a wave absorbing agent: determining the dipping times according to the design weight requirement, realizing the dipping of the wave absorbing agent by alternately carrying out the dipping through forward dipping, reverse dipping, forward dipping and reverse dipping, and carrying out the next dipping after each dipping and curing;
s3, preparing a filling material: uniformly mixing various raw materials according to the proportion of the filling material, and performing vacuum defoaming after the mixing is finished for later use;
s4, product surface treatment: cleaning dust and oil stains on the surface of the product, and treating the surface of the product by using a solution containing a coupling agent after the surface of the product is cleaned;
s5, forming a bottom layer skin: uniformly brushing a layer of epoxy resin on the surface of the product, then paving and adhering quartz fiber cloth, brushing and pressing the quartz fiber cloth to be tightly matched, and continuously brushing the epoxy resin on the surface of the quartz fiber cloth to fully impregnate the quartz fiber cloth; when the epoxy resin is brushed, the product is brushed and rotated at the same time, the glue flowing is prevented, the glue content is uniform, the process is repeated until the thickness required by the design is reached, the surface is coated with demolding cloth after the process is finished, the glue flowing is prevented from being generated before the epoxy resin is cured, and finally the epoxy resin is cured;
s6, preparing a sandwich structure: coating a layer of filling material on the outer surface of the bottom skin, closely coating a layer of over-stretched honeycomb structure impregnated with a wave absorbing agent on the outer surface of the bottom skin, positioning, closely filling the filling material into a honeycomb grid in a multi-time blade coating mode, then carrying out primary curing, coating a layer of filling material after the outer surface is treated, then sequentially completing positioning, filling and primary curing of the rest layers of over-stretched honeycomb structures according to the method, and forming a compact sandwich structure after the surface is treated;
s7, forming a surface layer skin: finishing the surface skin forming on the surface of the sandwich structure according to the method in the step S5;
s8, curing and forming: after the surface skin is prepared, the product is placed at room temperature for a period of time and then cured.
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