The method of receiving radio-absorbing material

 

(57) Abstract:

The invention relates to the absorbers of electromagnetic waves, in particular to methods of producing a multilayer nonwoven materials. The method of receiving radio-absorbing material allows you to extend the range of the lengths of the absorbed electromagnetic waves, to simplify and intensify the process by pre-molding canvases of synthetic fibers, dispersion of carbon fibers in a liquid or gaseous medium, filtering the dispersion through the canvas, synthetic fibers or styling ribbon electrically conductive materials on the canvas, of synthetic fibres Assembly of a multilayer stack of at least two non-woven synthetic canvases, one of which put a layer of carbon fibers or ribbons of conductive material so that the layer of carbon fibers or tapes electrically conductive materials alternated with a layer of canvas, of synthetic fibers, with subsequent perforation of the assembled multilayer stack of needles. 6 C.p. f-crystals, 7 ill., table 1.

The invention relates to the absorbers of electromagnetic waves and means of masking, and more specifically to methods for mn is awewsome properties in a wide range of electromagnetic radiation (EMR). The invention can be used in the manufacture of protection from the adverse effects of EMP.

Known absorber of electromagnetic waves and method of its manufacture, which allows to reduce the prominence when the radar in a wide range of frequencies [1] . A method of producing an absorber EMP includes mating hollow crests on dvukhfotonnoi machine parallel to each other, and stitch rows of hollow ridges knit from a dielectric filament needles of one needle cases and hollow comb injected conductive thread with tension. Each hollow ridge additionally fill conductive threads with variable density altitude attainable by a change in the proportions between the dielectric and conductive fibers in the mixture. A method of obtaining a blend dielectric and conductive yarns and the filling ridges in the patent does not describe the characteristics of radar absorbing properties of the material are not shown. The disadvantage of this method is the complexity of technology and the high cost of conducting filaments.

The closest to the technical nature of the claimed is a method of receiving radio-absorbing material, comprising obtaining a blend dielektricheskoi thickness of 1-2 mm contains 6,8 about. % randomly arranged filaments "plan" length 2-5 mm, which is introduced perpendicular to the plane of the layer of dielectric thread length 20 mm and strands of fiber "plan" length 15-18 mm in fiber content "plan" layer 6,8 - 8,5% vol. Dielectric filaments embedded in a flat layer, protrude above the ends of the carbon fibers at 5-2 mm [2]. The method of preparation of the blend of fibers and the implementation of the threads perpendicular to the flat layer in the description of the invention is not disclosed. There is a method allows to obtain materials with a minimum reflectance of ELECTROMAGNETIC radiation at a frequency of 10 GHz -19,2 dB.

The disadvantage of this method is the complexity of technology and the narrow range of lengths absorbed electromagnetic waves.

The technical problem on which this invention is directed, is the expansion of the range of the lengths of the absorbed electromagnetic waves, simplification and intensification of the process.

The problem is solved in that in the method of receiving radio-absorbing material, comprising forming a multilayer non-woven fabric of synthetic and carbon fibers, a blend of synthetic and carbon fibers do not produce pre-formed into a canvas of synthetic fibers, Donskih fibers for drawing on the canvas specified number of carbon fiber or put tape electrically conductive materials, then collect layered package of at least two non-woven canvases, at least one of which put a layer of carbon fibers or ribbons of conductive material, the assembled package is covered with a canvas made of synthetic fibers and needles pierce. Filtering the dispersion of carbon fibers through the canvas of synthetic fiber produced by drawing it on the canvas, laid on a perforated substrate for separating the dispersion medium.

Preliminary molding of the canvas, of synthetic fibers carried by wind or mechanical application of polyester fibers or a blend of polypropylene and polyester fibers onto the conveyor with the subsequent binding hypoproteinemia and/or heat treatment to thermostat.

Filtering the gas dispersion on the surface of the canvas of dielectric fibers are produced by feeding carbon fibres carding machines, air jet onto the conveyor.

The Assembly of a multilayer stack of several non-woven canvas with a layer of carbon fiber or foil is produced so that the layer of carbon fibers or tapes electrically conductive materials (foil) Cherepovetskaya permeability layers) increased from layer to layer from top to bottom.

Prokalyvanie package needles is at a depth of 4-8 mm in the downward direction or toward each other with a density of 100 to 500 punctures on 1 cm2.

The invention is illustrated in the schemes and examples.

Fig. 1. Assembly diagram of the multilayer stack in the manufacture of radar absorbing material.

1, 3, 5, 7 - canvas synthetic (dielectric) fibers, 2, 4, 6 - layer carbon(conductive) fibers or ribbons of electrically conductive materials.

Fig. 2. Assembly diagram of the multilayer stack in the manufacture of radar absorbing material.

1, 3, 4, 6 - canvas synthetic (dielectric) fibers, 2, 5 - layer carbon(conductive) fibers.

Fig.3. Radio-absorbing properties of the material of example 1.

Fig.4. Radio-absorbing properties of the material according to example 4.

Fig.5. Radio-absorbing properties of the material according to example 5.

Fig.6. Radio-absorbing properties of the material according to example 6.

The technical proposal. A positive effect is achieved by introducing in the non-woven fabric, which in this case, the dielectric matrix with electrophysical properties close to the characteristics of the nation two types of input in the non-woven fabric, conductive components provides a wider range of absorption of electromagnetic radiation, penetrating into the material and create interference effects, providing a minimum reflectivity at the desired frequency AMY.

In the non-woven fabric is set in a certain way by descending order of concentration from the boundary between "material is securable to the external surface of the material is divided conductive particles of the absorber consisting of a carbon fiber.

Electromagnetic wave incident on such material penetrates into it without reflection, due to the proximity of the dielectric characteristics of free space and the dielectric matrix in the upper layers which low concentration of absorbing particles that affect these characteristics.

As the distribution in depth of the material wave interacts with the absorbent particles, and they heat up due to the loss of their energy.

Due to the gradual increase of the concentration of the absorber, the lack of sharp boundaries between layers of the electromagnetic wave is virtually no reflection in the material and there is damped with corresponding changes in the amplitude and length.

Example 1. Get a radar absorbing material Assembly chetyrehkolka formed in accordance with table four canvas surface density (weight) of 100-200 g/m2of synthetic fibres mechanically and fasten by hypoproteinemia with a density of 180 cm-2. The formation of the canvas And In the produce of polyester staple fibers, canvas D - from a blend of polyester and polypropylene fibers. Canvas D from a blend of polyester and polypropylene fibers additionally thermoablative at 170oC for 3 minutes to seal. Carbon fiber length of 20 mm was dispersed in 5% aqueous solution of surface-active substances OS-20. Dispersion with a content of carbon fiber, 2 g/l filtered through the canvas of synthetic fibers in amounts corresponding data table. For this purpose, each canvas is placed on a perforated substrate and pour the appropriate amount of water dispersion of carbon fiber. Then the canvas is dried and collected in a four-layer package so that the layer of carbon fibers alternated with a layer of synthetic fibers and the content of carbon fibers (dielectric constant) increased from layer to layer from the top down (in the direction opposite to the direction of propagation of the electromagnetic wave). Four-layer package fasten by hypoproteinemia to a depth of 6 mm with a density of 300 cm-2.

Example 2. Get a radar absorbing material of example 1, but the preliminary molding of the canvas provide an aerodynamic way. The dependence of the coefficient of reflection of radio waves from the frequency of the ELECTROMAGNETIC radiation similar to that shown in Fig.3.

Example 3. Receive radio-absorbing material according to example 1 or 2, but after filtering the dispersion of carbon fiber through pre-molded cloth made of synthetic fibers on it is placed next canvas made of synthetic fibers and again carry out the filtration of a dispersion of carbon fiber for the application already fewer of the latter in accordance with the table. The dependence of the coefficient of reflection of radio waves from the frequency of the ELECTROMAGNETIC radiation similar to that shown in Fig.3.

Example 4. Receive radio-absorbing material according to example 1 or 2, but after molding canvases from synthetic fibers and filtering water dispersion of carbon fibers collect multilayer package (Fig.2), in which the layer 1 and 5 is formed of synthetic (polyester) fibers, and layers 3 and 6 is formed from a synthetic (polyester) fibers, which filtered air disperse the CSOs fiber length of 5 mm at a rate of 13 g/m2.

The dependence of the coefficient of reflection of radio waves from the frequency of the ELECTROMAGNETIC radiation shown in Fig. 4. Radio-absorbing material according to example 4 has a reflection coefficient AMY less than -10 dB in the frequency range from 5 to 30 GHz, which is considerably wider frequency range radiopalmwine materials obtained by known methods [1, 2].

Example 5. Receive radio-absorbing material according to example 1 or 2, but of the two canvases of synthetic (polyester) fibers, one of which is applied by filtering water dispersions put a layer of shredded carbon fiber length of 200 μm in the amount of 7,010-3g/cm2. The dependence of the coefficient of reflection of radio waves from the frequency of the ELECTROMAGNETIC radiation shown in Fig.5. Radio-absorbing material according to example 5 has a reflectance AMY about 20 dB at a frequency of 15 GHz, which corresponds to the level of radiopalmwine material obtained by a known method [2] , when obviously the simpler the technology of its production.

Example 6. Receive radio-absorbing material according to example 1 or 2, but instead of carbon fiber on the pre-molded cloth made of synthetic fibers are placed tape conductive material is aluminum foil or metalized p is cake 10x10 mm with decreasing cell size in the direction opposite to the direction of propagation of the incident electromagnetic wave. The dependence of the coefficient of reflection of radio waves from the frequency of the ELECTROMAGNETIC radiation shown in Fig.6.

Literary sources

1. The absorber of electromagnetic waves and method of its manufacture. Pat. RF 2119216, CL H 01 Q 17/00, 1998

2. The method of receiving radio-absorbing material. Pat. The USSR 1790795, CL H 01 Q 17/00, 1990

1. The method of receiving radio-absorbing material comprising an Assembly of a multilayer non-woven fabric of synthetic and carbon fibers, wherein the pre-formed into a canvas of synthetic fibers, dispersed carbon fiber in a liquid or gaseous medium, filtering the dispersion through the canvas, synthetic fibers or put tape electrically conductive materials on the canvas of synthetic fibers, collecting the multilayer package, at least two non-woven canvases, of synthetic fibres, one of which is coated with the layer of carbon fibers or tapes electrically conductive materials, thus, to the layer of carbon fibers or ribbons of conductive material interspersed with canvas made of synthetic fibers and assembled multilayer package was covered Holst receiving radar absorbing material p. 1, wherein the preliminary forming of the canvas, of synthetic fibers carried by wind or mechanical application of polyester fibers or a mixture of polypropylene and polyester fibers onto the conveyor with the subsequent binding hypoproteinemia and/or heat treated.

3. The method of receiving radio-absorbing material under item 1, characterized in that the filtering liquid dispersion of carbon fibers through the canvas of synthetic fibers produced by irrigation on a perforated substrate for separating liquid.

4. The method of receiving radio-absorbing material under item 1, characterized in that the dispersing carbon fibers in a gaseous environment carried out by the flow of air in the process of scratching on the carding machine.

5. The method of receiving radio-absorbing material under item 1, characterized in that the Assembly of a multilayer stack of several non-woven canvas made of synthetic fibers coated with a layer of carbon fibre or film of electrically conductive material is produced so that the layer of carbon fibers or ribbons of conductive material interspersed with canvas made of synthetic fibers and the content of the>/P>6. The method of receiving radio-absorbing material under item 1, characterized in that as the strips of conductive material using a foil or metallized polymeric film.

7. The method of receiving radio-absorbing material under item 1, characterized in that the assembled multilayer package puncture needle with one or two sides, with a density of punctures 100500 cm-2.

 

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