radar-absorbing composite component

Abstract

Composite component (1), with the following features: a) the composite component (1) comprises at least a first prepreg layer (10), a second prepreg layer (20) and a third prepreg layer (30) which are bonded together in a material-bonded manner, b) the at least first prepreg layer (10), second prepreg layer (20) and third prepreg layer (30) each have a printed radar absorption layer (12, 22, 32) on a first surface (11, 21, 31), c) the radar absorption layers (12, 22, 32) each have a different degree of radar absorption, such that the degree of radar absorption increases from the first prepreg layer (10) to the third prepreg layer (30), characterized by the following features: d) The individual prepreg layers (10, 20, 30) each have a set degree of radar absorption, e) the first prepreg layer (10) is in the installed position of the composite component (1) facing the direction of a radar radiation to be attenuated, f) the composite component (1) is made of prepreg layers (10, 20, 30) which consist of carbon fibers pre-impregnated with epoxy resin, g) the composite component (1) consists of 8 to 16 prepreg layers (10, 20, 30).

Description

[0001] The invention relates to a radar-absorbing composite component.

[0002] Reducing a radar signature is a key component in protecting against enemy attacks.

[0003] EP 2 421 701 B1 discloses a composite component with several prepreg layers. One of the prepreg layers has a printed radar absorption layer on one of its surfaces. This type of radar absorption is generally referred to as "radar-absorbing materials (RAM)" and specifically as "circuit analog RAM (CA-RAM)."

[0004] WO 2019 / 167 009 A1 discloses a composite component of the generic type with the features of the preamble of claim 1.

[0005] US 2012 / 0188114A1 shows a radar-absorbing composite component. The composite component comprises • an outer layer, • an absorption stratification and • a boundary layering, Each layer comprises several prepreg layers. In the outer layer and the absorption layer, a layer with a constant dielectric loss material alternates with a layer with a constant magnetic loss material, whereby the dielectric and magnetic losses are higher in the absorption layer than in the outer layer. The interface layer contains electrically conductive material.

[0006] The invention is based on the objective of creating a composite component with improved radar absorption.

[0007] This problem is solved according to the invention by a composite component with the features of claim 1.

[0008] The advantages of the invention lie in the fact that the composite component has a low radar signature.

[0009] Because the degree of radar absorption of the printed radar absorption layers increases from the first prepreg layer to the third, the first printed radar absorption layer is, to put it simply, almost transparent to radar radiation, while the subsequent printed radar absorption layers become increasingly absorbent or increasingly opaque to radar radiation with each additional prepreg layer. This ensures that very little radar radiation is reflected by the composite component, thus preventing detection. The radar radiation first encounters an initial radar absorption layer, where it is initially absorbed only to a small extent. Then, the radar radiation is increasingly absorbed in the subsequent radar absorption layers.If radar radiation is reflected back within the composite component, these reflected rays are absorbed in the opposite direction by the radar absorption layers.

[0010] According to an advantageous embodiment of the composite component according to the invention, the radar absorption layers comprise electrically conductive particles and / or magnetic particles. The electrically conductive particles serve to dampen the electric field of the radar wave, and the magnetic particles to dampen the magnetic field.

[0011] According to an advantageous embodiment of the composite component according to the invention, the area-specific mass of electrically conductive particles and / or magnetic particles of the printed radar absorption layers increases from at least the first prepreg layer to the third prepreg layer. By increasing the area-specific mass of electrically conductive particles and / or magnetic particles, the degree of radar absorption is increased in order to produce prepreg layers with a desired degree of radar absorption.

[0012] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. These show: Fig. 1 a section of a composite component 1, in cross-section; Fig. 2 a prepreg set with individual prepreg layers, each with a printed radar absorption layer, for the production of the in Fig. 1 of the composite component shown, depicted in perspective; Fig. 3. A device for printing a radar absorption layer onto a single prepreg layer, as a sketch.

[0013] The Fig. Figure 1 shows a radar-absorbing composite component 1 with a first prepreg layer 10, a second prepreg layer 20, and a third prepreg layer 30, which are bonded together. The first prepreg layer 10, the second prepreg layer 20, and the third prepreg layer 30 each have a printed radar absorption layer 12, 22, 32 on a first surface 11, 21, 31. The printed radar absorption layers 12, 22, 32 each have a different degree of radar absorption, such that the degree of radar absorption increases from the first prepreg layer 10 to the third prepreg layer 30. In the installed position of the composite component, the first prepreg layer 10 faces the direction of the radar radiation to be attenuated.

[0014] The radar absorption layers 12, 22, and 32 each contain electrically conductive and / or magnetic particles. The electrically conductive and / or magnetic particles used influence the degree of radar absorption.

[0015] The area-related mass of electrically conductive particles and / or magnetic particles of the printed radar absorption layers 12, 22, 32 increases from the first prepreg layer 10 to the third prepreg layer 30, thereby also increasing the degree of radar absorption from the first prepreg layer 10 to the third prepreg layer 30.

[0016] The Fig. Figure 2 illustrates a prepreg set with individual prepreg layers, each with a printed radar absorption layer, for the production of the in Fig. Figure 1 of the composite component shown. The individual prepreg layers each exhibit a set degree of radar absorption. An increasing degree of radar absorption is illustrated by a honeycomb structure of the radar absorption layers 12, 22, 32, drawn with broader lines.

[0017] The general manufacturing process includes the following steps: - Printing a radar absorption layer 12, 22, 32 onto a first surface 11, 21, 31 of at least a first prepreg layer 10, a second prepreg layer 20 and a third prepreg layer 30, - such that the degree of radar absorption of the respective printed radar absorption layers 12, 22, 32 increases from the first prepreg layer 10 to the third prepreg layer 30, - material-bonded joining of at least the first prepreg layer 10, the second prepreg layer 20 and the third prepreg layer 30 in order of the degree of radar absorption to form a composite component 1.

[0018] The Fig. Figure 3 shows a device for printing the radar absorption layers 12, 22, 32 using the radar absorption layer 12 as an example.

[0019] The radar absorption layers 12, 22, 32 are each printed using at least one suspension containing electrically conductive particles and / or magnetic particles.

[0020] The radar absorption layers 12, 22, 32 are printed with the at least one suspension in such a way that an area-related mass of the electrically conductive particles and / or the magnetic particles of the printed radar absorption layers 12, 22, 32 increases from the first prepreg layer 10 to the third prepreg layer 30.

[0021] The concentration of electrically conductive particles and / or magnetic particles in the at least one suspension is adjusted depending on the degree of radar absorption of a respective radar absorption layer 12, 22, 32.

[0022] The radar absorption layers 12, 22, 32 are each printed using a first suspension with electrically conductive particles applied with a first printhead 70 and a second suspension with magnetic particles applied with a second printhead 80.

[0023] The first suspension is a colloidal suspension tuned to the frequency to be absorbed. The electrically conductive particles in the first suspension are silver particles or, alternatively, gold particles with a diameter of, for example, 40–120 µm. The solvent in the first suspension is, for example, water, or alternatively, ethanol or isopropanol.

[0024] The second suspension is also a colloidal suspension, likewise tuned to the frequency to be absorbed. The magnetic particles in the second suspension are, for example, carbonyl iron with a diameter of, say, 40–120 µm. The solvent in the second suspension is, for example, water, or alternatively ethanol or isopropanol.

[0025] To adjust the concentration of electrically conductive particles in the first suspension, a highly concentrated suspension 72 containing conductive particles is fed to the first printhead 70 via a metering device 71, and a dilution solution 77 is fed via a metering device 76. The mixture of highly concentrated suspension 72 containing conductive particles and dilution solution 77 determines the concentration level.

[0026] To adjust the concentration of the magnetic particles in the second suspension, a highly concentrated suspension 82 containing magnetic particles is fed to the second printhead 80 via a metering device 81, and a dilution solution 87 is fed to the second printhead 80 via a metering device 86. The mixture of the highly concentrated suspension 82 containing magnetic particles and the dilution solution 87 determines the concentration level.

[0027] The first printhead 70 applies the first suspension containing a set concentration of electrically conductive particles. Then, the second printhead 80 applies the second suspension containing a set concentration of magnetic particles. The solvent(s) of the first and second suspensions are then allowed to evaporate, optionally at room temperature, at a slightly elevated temperature, or under vacuum. When selecting the temperature, care must be taken to ensure that the epoxy resin has not yet cured.

[0028] In detail regarding radar absorption layers, the radar-absorbing properties, such as the degree of radar absorption and the preferred absorption frequency, are adjusted by varying the material properties of the particles and the shape of the printed structures. The printed structure can be a honeycomb structure. A single honeycomb acts as an electrical resonant circuit. Other resonant circuit shapes are also possible and conceivable. By selecting a resonant circuit shape and varying its size, capacitive, and inductive properties, the resonant frequency can be adjusted to achieve a desired degree of radar absorption for a specific frequency to be attenuated. Printed coils and capacitors can also be used to adjust the frequency.By selecting the magnetic and / or electrically conductive particles used, with regard to the particle material, coating thickness, mass, and spatial distribution within the printed pattern, the radar-absorbing properties can be precisely controlled. It is also possible to attenuate low frequencies below 2 GHz using the printed structure, which are difficult to attenuate with conventional radar-absorbing materials.

[0029] The degree of radar absorption of the respective printed radar absorption layers 12, 22, 32 should increase from the first prepreg layer 10 to the third prepreg layer 30 in such a way that the attenuation of the radar radiation is at its maximum.

[0030] To manufacture the composite component, the individual prepreg layers are stacked on top of each other in order of increasing radar absorption. The resulting prepreg stack is then cured in an autoclave at a vacuum typically up to 6 bar and a temperature of approximately 170°C.

[0031] The composite component cures at higher temperatures. This leads to the sintering of the electrically conductive particles, resulting in increased electrical conductivity. In contrast, sintering of the magnetic particles is neither necessary nor desirable, as their interaction is governed by the magnetic exchange integral. The nature of the magnetic interaction can be influenced by the spacing of the magnetic particles. This spacing, in turn, can be influenced by a coating.

[0032] The in Fig. 1 The composite component shown is made of prepregs, which consist of carbon fibers pre-impregnated with epoxy resin.

[0033] The in Fig. The composite component shown was cured in an autoclave. Alternatively, cold-curing systems can also be used.

[0034] The in Fig. The composite component shown in Figure 1 has only three prepreg layers, 10, 20, and 30, for the sake of clarity. The typical thickness of a prepreg is 0.125 mm or 0.25 mm. Composite components typically have a thickness of 20 mm. Therefore, a typical composite component, unlike the one shown in Figure 1, consists of only three layers. Fig. 1. Composite component shown, consisting of 8 to 16 prepreg layers.

[0035] The in Fig. The composite component shown in Figure 1 is a raw component that can be further processed. For example, the raw component can receive a surface coating.

[0036] In Fig.3. A first printhead 70 and a second printhead 80 are used. A single printhead would also suffice. However, the printhead would have to be cleaned if, after printing a suspension with conductive particles, one wanted to print a suspension with magnetic particles using the same printhead, and vice versa. Reference symbol list 1 composite component 10 first prepreg layer 10 11 first surface 12 Radar absorption layer 20 second prepreg layer 21 first surface 22 Radar absorption layer 30 third prepreg layer 31 first surface 32 Radar absorption layer 70 first push button 71 Dosing unit 72 highly concentrated suspension with conductive particles 76 Dosing unit 77 Dilution solution 80 second push button 81 Dosing device 82 highly concentrated suspension with magnetic particles 86 Dosing device 87 Dilution solution

Claims

[1] Composite component (1), having the following features: a) the composite component (1) comprises at least a first prepreg layer (10), a second prepreg layer (20) and a third prepreg layer (30) which are bonded together in a material-bonded manner, b) the at least first prepreg layer (10), second prepreg layer (20) and third prepreg layer (30) each have a printed radar absorption layer (12, 22, 32) on a first surface (11, 21, 31), c) the radar absorption layers (12, 22, 32) each have a different degree of radar absorption, such that the degree of radar absorption increases from the first prepreg layer (10) to the third prepreg layer (30), characterized by the following characteristics: d) The individual prepreg layers (10, 20, 30) each have a set degree of radar absorption, e) the first prepreg layer (10) is in the installed position of the composite component (1) facing the direction of a radar radiation to be attenuated, f) the composite component (1) is made of prepreg layers (10, 20, 30) which consist of carbon fibers pre-impregnated with epoxy resin, g) the composite component (1) consists of 8 to 16 prepreg layers (10, 20, 30). [2] Composite material (1) according to claim 1, wherein the radar absorption layers (12, 22, 32) each comprise electrically conductive particles and / or magnetic particles. [3] Composite component (1) according to the preceding claim, wherein an area-related mass of electrically conductive particles and / or magnetic particles of the respective radar absorption layers (12, 22, 32) increases from at least the first prepreg layer (10) to the third prepreg layer (30).

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