KR102312947B1 - 3 dimensional structure comprising multi-layer radio wave absorber and manufacturing method of the same - Google Patents

Abstract

A 3D structure according to an embodiment of the present invention includes a multi-layer radio wave absorbing composite in which a radio wave absorbing layer made of a radio wave absorbing material that loses electromagnetic waves from the outside and a foam core layer are alternately stacked a plurality of times; and a rear laminate in which a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer, and a third glass fiber reinforced plastic layer are sequentially stacked on the back surface of the multi-layer radio wave absorbing composite.

Description

A three-dimensional structure including a multi-layered radio wave absorbing composite and a method for manufacturing the same

It relates to a three-dimensional structure including a multi-layered radio wave absorbing composite and a method for manufacturing the same. Specifically, it relates to a three-dimensional structure in which a glass fiber reinforced plastic (GFRP) layer and a radio wave absorbing layer are sequentially stacked on the back surface of a multilayered radio wave absorbing composite, and a manufacturing method thereof.

In order to reduce the possibility of being caught/hit by the platform, the exposed signal should be minimized. In particular, since electromagnetic signals have advantages such as wide range, fast detection, and high resolution, the demand for low observable platforms is increasing. The low detection platform is designed with a combination of shape using the scattering and reflection characteristics of electromagnetic waves and the application of an absorber that absorbs the signal of the threat frequency.

When the frequency of the radar signal is low, the resolution is lowered, but it can detect more distant objects. In order to reduce the possibility of detection at such a low frequency in the low detection platform, the need for an absorber having broadband absorption performance is emerging.

Meanwhile, a composite-based radio wave absorber is being studied in order for the absorber to simultaneously serve as structural load support. The existing radio wave absorbing composite structure is applied to the outer skin of the platform in the form of a laminate, and there is a limit in realizing broadband performance due to weight constraints. In the case of a laminate-type radio wave absorbing composite structure, since glass fiber or Kevlar fiber is used as a basic material, increasing the thickness to realize broadband performance entails a lot of weight increase. In addition, when a magnetic material is applied, the increase in the thickness of the laminate can be minimized and broadband performance can be realized. does not

Provided are a three-dimensional structure including a multi-layered radio wave absorbing composite and a method for manufacturing the same. Specifically, it provides a dimensional structure in which a glass fiber reinforced plastic layer and a radio wave absorbing layer are sequentially stacked on the back surface of a multi-layered radio wave absorbing composite, and a method for manufacturing the same.

A three-dimensional structure according to an embodiment of the present invention includes a multi-layered radio wave absorbing composite in which a radio wave absorbing layer and a foam core layer made of a radio wave absorbing material that loses electromagnetic waves incident from the outside are alternately stacked a plurality of times; and a rear laminate in which a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer, and a third glass fiber reinforced plastic layer are sequentially laminated on the rear surface of the multilayered radio wave absorbing composite.

It may further include a fourth glass fiber-reinforced plastic layer covering the outer surface of the multi-layered radio wave absorbing composite and the outer surface of the rear laminate, and a cover layer covering the fourth glass fiber-reinforced plastic layer.

The rear laminate may extend in a direction parallel to the rear surface of the multilayer radio wave absorbing composite, and both ends of the rear laminate may be curved in opposite directions to the rear surface of the multilayer radio wave absorbing composite.

A radio wave absorbing material may be filled in the space between the curved portion of the rear laminate and the multi-layered radio wave absorbing composite.

With respect to the cross section of the multi-layered radio wave absorbing composite, the stacking direction and the radio wave incident direction of the multi-layered radio wave absorbing composite intersect, and the laminating direction and the radio wave incident direction of the multi-layered radio wave absorbing composite are 15 to 75 ° angle (θ ₁ ) can achieve

With respect to the cross section of the multilayer radio wave absorbing composite, the multilayer radio wave absorbing composite has a plurality of lamination directions in which the radio wave absorbing layer and the foam core layer are formed by bending at least once, the plurality of lamination directions intersect each other, and 15 to 90 between lamination directions An angle (θ ₂ ) of ˚ can be achieved.

Inside the multi-layered radio wave absorbing composite, it may further include a reflector having a cusp on the front surface, the front surface being made of a curved surface, and the rear surface being in contact with the rear surface of the multilayer radio wave absorbing composite material.

In the method for manufacturing a three-dimensional structure according to an embodiment of the present invention, a radio wave absorbing layer and a foam core layer made of a radio wave absorbing material that loses electromagnetic waves incident from the outside are alternately laminated a plurality of times, and cured to form a multi-layered radio wave absorbing composite preparing a;

laminating a cover layer, a fourth glass fiber reinforced plastic layer, and a multi-layered radio wave absorbing composite on a metal mold having an outer mold line (OML) of a three-dimensional structure; Laminating a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer and a third glass fiber reinforced plastic layer on the back surface of the multi-layered radio wave absorbing composite; and pressing and heating the laminate.

In the step of laminating the first glass fiber reinforced plastic layer, the radio wave absorbing layer, the second glass fiber reinforced plastic layer, the reflective layer, and the third glass fiber reinforced plastic layer on the back surface of the multi-layered radio wave absorbing composite, the back surface of the multi-layered radio wave absorbing composite A back laminate comprising a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer and a third glass fiber reinforced plastic layer by filling the side with a radio wave absorbing material It extends in a parallel direction, and both ends may be curved in a direction opposite to the rear surface of the multi-layered radio wave absorbing composite.

In the step of pressurizing and heating the laminate, it may be pressurized and heated at a temperature of 20° C. to 180° C. and a pressure of 3 bar to 6 bar.

According to an embodiment of the present invention, it is possible to implement a radio wave absorption band of 8 GHz or more (based on -10 dB).

According to an embodiment of the present invention, compared to the conventional laminate-type radio wave absorption structure, since the foam core is the main material, it is possible to achieve broadband absorption performance without much increase in weight.

According to an embodiment of the present invention, since the block made of the foam core layer and the radio wave absorbing layer is processed into an applied shape, there is no restriction on the shape. Therefore, it can be widely used in a wing leading edge structure having a gentle curvature, a control surface having a sharp shape, and the like.

1 is a view schematically showing a cross-section of a three-dimensional structure according to an embodiment of the present invention.
2 is a view schematically showing a cross-section of a three-dimensional structure according to another embodiment of the present invention.
3 is a view schematically showing a cross-section of a three-dimensional structure according to another embodiment of the present invention.
FIG. 4 is an enlarged view of part A of FIG. 3 .
5 is a view schematically showing a cross-section of a three-dimensional structure according to another embodiment of the present invention.
6 is a view schematically showing a cross-section of a three-dimensional structure according to another embodiment of the present invention.
7 is a view schematically showing a cross-section of a three-dimensional structure according to another embodiment of the present invention.
8 is a 10 dB bandwidth (absorption bandwidth having 90% absorption performance) contour graph according to the dielectric constant of the radio wave absorption layer 11 in the experimental example.
9 is a 20 dB bandwidth (absorption bandwidth having 90% absorption performance) contour graph according to the dielectric constant of the radio wave absorption layer 11 in the experimental example.
10 is a 30 dB bandwidth (absorption bandwidth having 90% absorption performance) contour graph according to the dielectric constant of the radio wave absorption layer 11 in the experimental example.
11 is a graph showing the absorption performance characteristics of a three-dimensional structure.

The terms first, second, third, etc. are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes the presence or absence of another characteristic, region, integer, step, operation, element and/or component. It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part refers to being "directly above" another part, the other part is not interposed therebetween.

In the present invention, the term “layer(s)” refers to a single layer, or to an overlapping multilayer. Here, the multi-layer refers to a layer in which layers in which each layer satisfies the requirements corresponding to the layer are overlapped.

In the present invention, the term “front” refers to a surface on which radio waves are incident to a three-dimensional structure. "Back" means the opposite side of "front".

In the present invention, the term "cross-section" of the three-dimensional structure refers to a surface cut vertically from the rear surface of the three-dimensional structure.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, they are not interpreted in an ideal or very formal meaning.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

1 schematically shows a cross-section of a three-dimensional structure 100 according to an embodiment of the present invention. The three-dimensional structure 100 of FIG. 1 is only for illustrating the present invention, and the present invention is not limited thereto. Accordingly, the three-dimensional structure 100 of FIG. 1 may be deformed into various shapes.

As shown in FIG. 1, the three-dimensional structure 100 according to an embodiment of the present invention has a plurality of radio wave absorbing layers 11 and foam core layers 12 made of a radio wave absorbing material that loses electromagnetic waves incident from the outside. A multi-layered radio wave absorbing composite 10 stacked in gray; and a first glass fiber reinforced plastic layer 21, a radio wave absorption layer 22, a second glass fiber reinforced plastic layer 23, a reflective layer 24 and a third glass fiber reinforced plastic layer on the back surface of the multi-layered radio wave absorbing composite 10. It includes a back laminate 20 in which plastic layers 25 are sequentially stacked.

Hereinafter, each configuration will be described in detail.

The multi-layered radio wave absorbing composite 10 includes a radio wave absorbing layer 11 and a foam core layer 12 that are alternately stacked a plurality of times.

The radio wave absorbing layer 11 is a layer made of a radio wave absorbing material that loses electromagnetic waves incident from the outside. The electromagnetic wave incident from the outside may be, for example, an optical signal, an electromagnetic signal, an infrared signal, a vibration signal, etc. irradiated by an enemy detection asset, but is not limited thereto. In addition, the radio wave absorbing material may correspond to a material made of a dielectric material, a magnetic material, or a conductor.

The foam core layer 12 serves to fill the gaps between the plurality of radio wave absorption layers 11 . Foam core layer 12 may include a material having a dielectric constant similar to that of air or a conductive material having electromagnetic performance.

The thickness of the foam core layer 12 may be 5.0 to 10.0 mm.

1, the radio wave absorption layer 11 and the foam core layer 12 may be alternately laminated a plurality of times. More specifically, it may be laminated 3 to 100 times. More specifically, it may be laminated 10 to 30 times.

If the number of laminations is too small, the electromagnetic wave absorption performance may be insufficient. Even if the number of laminations is further increased, the electromagnetic wave absorbing performance does not increase, but rather the overall thickness of the multilayered radio wave absorbing composite 10 may increase to increase the weight of the three-dimensional structure 100 .

The thickness ratio of the radio wave absorbing layer 11 and the foam core layer 12 (foam core layer / radio wave absorbing layer) may be 1 to 200. More specifically, it may be 10 to 50. It is possible to efficiently lose electromagnetic waves in the above-mentioned range.

The total thickness of the multilayer radio wave absorbing composite 10 may be 50 to 200 mm.

The rear laminate 20 includes a first glass fiber reinforced plastic layer 21 , a radio wave absorbing layer 22 , a second glass fiber reinforced plastic layer 23 , a reflective layer 24 and a third glass fiber reinforced plastic layer 25 . This multi-layered radio wave absorbing composite 10 is sequentially laminated from the back surface.

The first glass fiber reinforced plastic layer 21 is made of a glass fiber reinforced plastic material. Here, the glass fiber reinforced plastic is a material that combines aromatic nylon fibers such as glass fiber, carbon fiber, and Kevlar with a thermosetting resin such as unsaturated polyester and epoxy resin. have The first glass fiber reinforced plastic layer 21 serves to protect the multi-layered radio wave absorbing composite 10 from external environmental factors (humidity, external impact, etc.).

The radio wave absorbing layer 22 is a layer made of a radio wave absorbing material that loses electromagnetic waves incident from the outside. It may be made of the same material as the radio wave absorbing layer 11 in the multi-layered radio wave absorbing composite 10 or a different material. The radio wave absorbing layer 22 serves to continuously impart the radio wave absorbing ability of the entire three-dimensional structure in addition to the radio wave absorbing layer 11 in the radio wave absorbing composite 10 without being interrupted.

The second glass fiber reinforced plastic layer 23 may be made of the same or a different material from the first glass fiber reinforced plastic layer 21 . The second glass fiber reinforced plastic layer 23 serves to protect the radio wave absorbing layer 22 from external environmental factors (humidity, external impact, etc.).

The reflective layer 24 plays a role of shielding to prevent further propagation of radio waves passing through the interior. The reflective layer 24 may include a metal film such as Al, Cu, Fe, or Ni, and may also include a carbon fiber-reinforced composite material.

The third glass fiber reinforced plastic layer 25 may be made of the same or different material from the first glass fiber reinforced plastic layer 21 and the second glass fiber reinforced plastic layer 23 . The third glass fiber reinforced plastic layer 25 serves to protect the reflective layer 24 from galvanic corrosion from external environmental factors (humidity, external impact, etc.).

2 schematically shows a cross-section of a three-dimensional structure 100 according to another embodiment of the present invention.

As shown in FIG. 2 , the three-dimensional structure 100 includes a fourth glass fiber reinforced plastic layer 31 and a fourth glass fiber covering the outer surface of the multi-layered radio wave absorbing composite 10 and the outer surface of the rear laminate 20 . A cover layer 32 covering the reinforced plastic layer 31 may be further included. That is, the three-dimensional structure 100 may be covered by the cover layer 32 and the fourth glass fiber reinforced plastic layer 31 .

The cover layer 32 serves to protect the 3D structure 100 and maintain the shape of the 3D structure 100 . The fourth glass fiber reinforced plastic layer 31 is made of the same or different material from the first glass fiber reinforced plastic layer 21 , the second glass fiber reinforced plastic layer 23 and the third glass fiber reinforced plastic layer 25 . can be done The fourth glass fiber reinforced plastic layer 31 serves as a transparent window from the viewpoint of electromagnetic waves incident from the unit, and serves to protect the three-dimensional structure 100 from external environmental factors (humidity, external impact, etc.) do When changing to the multilayer radio wave absorbing composite 10 and the rear laminate 20, in order to minimize the impedance mismatch, the fourth glass fiber reinforced plastic layer 31 may remain the same.

When the back laminate 20 is curved as in FIG. 3 , the fourth glass fiber reinforced plastic layer 31 and the cover layer 32 may cover the outer surface of the curved back laminate 20 .

3 schematically shows a cross-section of a three-dimensional structure 100 according to another embodiment of the present invention.

As shown in FIG. 3 , the three-dimensional structure 100 may implement an outermost shape (OML, Outer Mold Line) according to an applied part. 3 is an example of implementing an outermost shape (OML, Outer Mold Line) for an aircraft part.

As shown in FIG. 3 , the rear laminate 20 extends in a direction parallel to the rear surface of the multi-layered radio wave absorbing composite 10 , and both ends of the rear laminate 20 are of the multi-layered radio wave absorbing composite 10 . It can be curved in the opposite direction to the back side. That is, the rear laminate 20 may have a 'C'-shaped cross-section. The rear laminate 20 may be in contact with the 'C'-shaped left flat portion and the rear surface of the multi-layered radio wave absorbing composite 10 . Since the rear laminate 20 has a 'C'-shaped cross-section, it can be continuously laminated.

In Fig. 4, the curved portion (part A) is shown in an enlarged manner. As shown in FIG. 4 , the radio wave absorbing material 33 may be filled in the space between the curved portion and the multi-layered radio wave absorbing composite 10 . When the rear laminate 20 is curved, a space due to the curvature of the material is inevitably generated. By filling the radio wave absorbing material 33 in this space, structural stability can be expected by eliminating defects, and scattering of electromagnetic signals can be minimized on the discontinuous surface.

5 schematically shows a cross-section of a three-dimensional structure 100 according to another embodiment of the present invention.

As shown in FIG. 5 , the stacking direction and the radio wave incidence direction of the multi-layered radio wave absorbing composite 10 intersect, and the stacking direction and the radio wave incident direction of the multi-layered radio wave absorbing composite 10 are 15 to 75 degrees angle (θ ₁₎ ) can be achieved. The lamination direction of the multilayered radio wave absorbing composite 10 means a direction normal to the plane of the radio wave absorbing layer 11 and the foam core layer 12 constituting the multilayered radio wave absorbing composite 10 . The stacking direction and the radio wave incident direction of the multi-layered radio wave absorbing composite 10 are not parallel, and the angle θ ₁ is properly formed, so that the direction of partially reflected waves from the radio wave absorbing layer 11 is set to a non-hazardous area Because it can scatter to the scattering, mono-static RCS (Radar Cross Section) can be further reduced. More specifically, the stacking direction and the radio wave incident direction of the multi-layered radio wave absorbing composite 10 may form _{an angle (θ 1 ) of 30 to 60°.}

6 schematically shows a cross-section of a three-dimensional structure 100 according to another embodiment of the present invention.

As shown in FIG. 6 , the multilayered radio wave absorbing composite 10 has a plurality of lamination directions in which the radio wave absorbing layer 11 and the foam core layer 12 are bent at least once, and the plurality of lamination directions intersect each other, _{An angle (θ 2} ) of 15 to 90° between directions may be formed.

There are a plurality of stacking directions of the multi-layered radio wave absorbing composite 10, and the angle θ ₂ is properly formed, so that the direction of the reflected wave partially reflected by the radio wave absorbing layer 11 can be scattered to a non-hazardous area. Therefore, mono-static RCS (Radar Cross Section) can be further reduced. _{More specifically, an angle (θ 2} ) of 45 to 90° between the stacking directions may be formed.

7 schematically shows a cross-section of a three-dimensional structure 100 according to another embodiment of the present invention.

As shown in FIG. 7 , inside the multilayered radio wave absorbing composite 10 , it has a cusp on the front surface and the front surface is made of a curved surface, and the rear surface is a reflector 13 in contact with the rear surface of the multilayer radio wave absorption composite 10 . may further include. This shape is a structure that can effectively scatter and reflect incident electromagnetic waves to non-hazardous areas. In addition, it is possible to further reduce the signal returned by realizing the electromagnetic wave absorption effect and the shape scattering effect at the same time.

In order to cope with anti-stealth technology including the broadening radar detection frequency band, wide-band stealth performance is essential. In addition, since the characteristics of stealth weapon systems generally have sharp appearances in most cases, the performance of the designed radio wave absorber may not be reflected in the RCS of the structure as it is with the existing radio wave absorber application method. However, the radio wave absorber in which the radio wave absorption material patterned according to the present embodiment is laminated in multiple layers hardly deteriorates the radio wave absorption performance and may have broadband radio wave absorption performance. Therefore, broadband radio wave absorption performance can be more effectively implemented in terms of space, material, and weight to which the radio wave absorber is to be applied to the structure.

In one embodiment of the present invention, the manufacturing method of the three-dimensional structure 100 may be used without limitation as long as it is a method capable of implementing the above-described structure. As an example, the three-dimensional structure 100 may be manufactured by the following method.

In an embodiment of the present invention, the method of manufacturing the three-dimensional structure 100 alternately stacks the radio wave absorbing layer 11 and the foam core layer 12 made of a radio wave absorbing material that loses electromagnetic waves incident from the outside, a plurality of times, Curing to prepare a multi-layered radio wave absorbing composite 10 (S10); Laminating a cover layer 32, a fourth glass fiber reinforced plastic layer 31 and a multi-layered radio wave absorbing composite 10 on a metal mold having an outer mold line (OML) of the three-dimensional structure 100 step (S20); A first glass fiber reinforced plastic layer 21, a radio wave absorbing layer 22, a second glass fiber reinforced plastic layer 23, a reflective layer 24, and a third glass fiber reinforced plastic layer on the back surface of the multi-layered radio wave absorbing composite 10 Laminating the layer 25 (S30); and pressing and heating the laminate (S40).

Hereinafter, each step will be described in detail.

First, in step S10, the radio wave absorbing layer 11 and the foam core layer 12 made of a radio wave absorbing material that loses electromagnetic waves incident from the outside are alternately laminated a plurality of times and cured to form a multi-layered radio wave absorbing composite 10 ) is manufactured. Curing can be performed at high temperature and high pressure in the autoclave process. For example, the curing process may be performed at a temperature of 120° C. to 180° C. and a pressure of 3 bar to 6 bar.

After manufacturing the multi-layered radio wave absorbing composite 10, processing may be performed to fit the shape of a desired part.

Next, in step S20, the cover layer 32, the fourth glass fiber-reinforced plastic layer 31, and the multi-layer propagation are performed on the metal mold having an outer mold line (OML) of the three-dimensional structure 100. An absorbent composite (10) is laminated. At this time, the fourth glass fiber reinforced plastic layer 31 is in the form of a sheet in a prepreg state.

Next, in step S30, the first glass fiber reinforced plastic layer 21, the radio wave absorbing layer 22, the second glass fiber reinforced plastic layer 23, and the reflective layer 24 on the back surface of the multi-layered radio wave absorbing composite 10. ) and a third glass fiber reinforced plastic layer 25 are laminated.

At this time, the first glass fiber reinforced plastic layer 21, the radio wave absorption layer 22, the second glass fiber reinforced plastic layer 23, A rear laminate 20 including a reflective layer 24 and a third glass fiber reinforced plastic layer 25 extends in a direction parallel to the rear surface of the multi-layered radio wave absorbing composite 10, and both ends have the multi-layered radio wave absorbing composite 10 It may be curved in a direction opposite to the back surface of the absorbent composite 10 .

Next, in step S40, the laminate is pressed and heated. At this time, the three-dimensional structure 100 may be finally manufactured through a vacuum condition and a high-temperature and high-pressure autoclave process. In this process, the multi-layered radio wave absorbing composite 10 and the rear laminate 20 are integrated. For example, the pressurization and heating process may be performed at a temperature of 120° C. to 180° C. and a pressure of 3 bar to 6 bar.

Hereinafter, the present invention will be described in more detail through experimental examples. However, these experimental examples are only for illustrating the present invention, and the present invention is not limited thereto.

Experimental example

The three-dimensional structure 100 illustrated in FIG. 3 was manufactured. At this time, the radio wave absorption band was measured by varying the dielectric constant of the radio wave absorption layer 11 and shown in FIGS. 8 to 10 . As shown in FIG. 8, if the material of the radio wave absorption layer 11 between the real part 10 to 15 and the imaginary part 8 to 12 of the permittivity is applied, it is possible to realize absorption performance of 8 GHz or more in the radio wave absorption bandwidth (based on -10 dB) can confirm.

In addition, in order to verify the present invention with reference to the results of FIGS. 8 to 10 , performance verification was performed after specimen production and is shown in FIG. 11 . It can be seen that the analysis graph and the measurement graph of the manufactured specimen agree well. In addition, it can be seen that the radio wave absorption band (based on -10 dB) can be implemented at 8 GHz or higher.

The present invention is not limited to the above embodiments, but can be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

100: three-dimensional structure,
10: multi-layered radio wave absorbing composite,
11: the second wave absorption layer,
12: foam core layer,
20: back laminate,
21: a first glass fiber reinforced plastic layer,
22: radio wave absorption layer,
23: a second glass fiber reinforced plastic layer,
24: reflective layer,
25: a third glass fiber reinforced plastic layer,
31: a fourth glass fiber reinforced plastic layer,
32: cover layer,
33: radio wave absorbing material

Claims (10)

a multi-layered radio wave absorbing composite in which a radio wave absorbing layer made of a radio wave absorbing material and a foam core layer are alternately stacked a plurality of times to lose electromagnetic waves incident from the outside; and
A first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer, and a third glass fiber reinforced plastic layer are sequentially stacked on the rear surface of the multi-layered radio wave absorbing composite. structure. According to claim 1,
A three-dimensional structure further comprising a fourth glass fiber-reinforced plastic layer covering the outer surface of the multi-layered radio wave absorbing composite and the outer surface of the rear laminate, and a cover layer covering the fourth glass fiber-reinforced plastic layer. According to claim 1,
The rear laminated body extends in a direction parallel to the rear surface of the multilayered radio wave absorbing composite, and both ends of the rear laminated body are curved in the opposite direction to the rear of the multilayered radio wave absorbing composite. A three-dimensional structure. 4. The method of claim 3,
A three-dimensional structure in which a radio wave absorbing material is filled in the space between the curved portion of the rear laminate and the multi-layered radio wave absorbing composite. According to claim 1,
With respect to the cross section of the multi-layered radio wave absorbing composite, the stacking direction and the radio incident direction of the multi-layered radio wave absorbing composite intersect, and the laminating direction and the radio wave incident direction of the multi-layered radio wave absorbing composite are 15 to 75 degrees angle (θ) ₁ ) forming a three-dimensional structure. According to claim 1,
With respect to the cross section of the multi-layered radio wave absorbing composite, the multi-layered radio wave absorbing composite has a plurality of lamination directions in which the radio wave absorbing layer and the foam core layer are bent at least once, and the plurality of lamination directions intersect each other, and the lamination direction A three-dimensional structure that forms an angle (θ _{2 ) between 15 and 90˚.} According to claim 1,
A three-dimensional structure further comprising a reflector having a cusp on the front surface and a curved surface, the rear surface of which is in contact with the rear surface of the multilayer radio wave absorption composite, inside the multi-layered radio wave absorbing composite. manufacturing a multi-layered radio wave absorbing composite by alternately stacking a radio wave absorbing layer and a foam core layer made of a radio wave absorbing material that loses electromagnetic waves incident from the outside, a plurality of times, and curing;
laminating a cover layer, a fourth glass fiber reinforced plastic layer, and the multi-layered radio wave absorbing composite on a metal mold having an outer mold line (OML) of a three-dimensional structure;
laminating a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer and a third glass fiber reinforced plastic layer on the rear surface of the multi-layered radio wave absorbing composite; and
A method of manufacturing a three-dimensional structure comprising the step of pressing and heating the laminate. 9. The method of claim 8,
In the step of laminating a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer and a third glass fiber reinforced plastic layer on the back surface of the multi-layered radio wave absorbing composite,
A back laminate comprising a first glass fiber reinforced plastic layer, a radio wave absorbing layer, a second glass fiber reinforced plastic layer, a reflective layer, and a third glass fiber reinforced plastic layer by filling the side of the back side of the multi-layered radio wave absorbing composite with a radio wave absorbing material A method of manufacturing a three-dimensional structure in which a sieve extends in a direction parallel to the rear surface of the multi-layered radio wave absorbing composite, and both ends of the rear laminate are curved in opposite directions to the rear of the multi-layered radio wave absorbing composite. 9. The method of claim 8,
A method of manufacturing a three-dimensional structure for pressurizing and heating the laminate at a temperature of 20° C. to 180° C. and a pressure of 3 bar to 6 bar in the step of pressing and heating the laminate.

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