JPH01258496A - Radio wave absorber - Google Patents

Abstract

PURPOSE:To obtain a radio wave absorber excellent in a structural strength and a radio wave absorbing property by a method wherein the absorbent is composed of layers such as a supporting layer formed of silicon carbide fiber impregnated with resin, a radio wave absorbing layer containing carbon particles, and a radio reflective layer. CONSTITUTION:An absorbent layer 3 is provided to one side of a supporting layer 2 of a composite material composed of silicon carbide fiber impregnated with epoxy resin. The absorbing layer 3 is constituted in such a manner that the mixture of hollow or ball-shaped carbon particles and epoxy resin is made to fill a honeycomb core as it is fluidized and set. A reflective layer 4 consists of an aluminum foil or aluminum plate. By these processes, a radio wave absorber excellent in a structural strength and a radio wave absorbing property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radio wave absorber. More specifically, the present invention relates to a radio wave absorber for absorbing incident radio waves and preventing reflection in the direction of incidence.

[Prior art]

Conventionally used radio wave absorbing materials can be broadly classified into ferrite-based materials and carbon-based materials. Ferrite-based radio wave absorbing materials are used in the form of mixtures with resins, rubbers, or paints, but ferrite itself has a high specific gravity, and even in the above-mentioned mixture state, it has a specific gravity of 3 to 5. Carbon-based materials are used by impregnating powder into sponge-like rubber, but this usage method not only increases the thickness of the material, but also allows water to enter the material when used outdoors. Adversely affects radio wave absorption characteristics. Additionally, sponge-like rubber has the problem of deterioration due to ultraviolet light. Furthermore, both ferrite-based and carbon-based materials have low strength and cannot be used as structural materials.

[Problem that the invention seeks to solve]

The present invention aims to solve the problems of low structural strength and poor weather resistance in conventional radio wave absorbers.

[Means for solving problems]

In order to solve the above problems, in the radio wave absorber according to the present invention, a radio wave absorbing layer is disposed on one side of a support layer formed by impregnating silicon carbide fibers with a resin. The radio wave absorption layer is
The reflector includes spherical or hollow carbon particles, and a reflector is disposed on the opposite side of the support layer with the radio wave absorbing layer in between. The reflector can be made of aluminum foil, an aluminum plate, or the like. The carbon particles of the radio wave absorbing layer are preferably mixed with a resin material and filled into the honeycomb core.

[For production]

The radio wave absorber of the present invention uses a support layer formed by impregnating silicon carbide fibers with a resin, with the support layer facing toward the radio wave incident side.

Since silicon carbide has electrical semiconductor properties, it does not reflect incident radio waves and allows them to directly enter the radio wave absorber. This property improves the radio wave absorption properties of the radio wave absorber. The carbon particles in the absorption layer exhibit radio wave absorption properties. Using hollow particles as carbon particles increases the surface area per weight, which is effective in reducing the weight of the absorption layer, and this hollow carbon particle shape is sufficiently effective for high frequency radio waves. be. The carbon particles are preferably used in combination with a resin material such as an epoxy resin.

A reflector placed inside the absorption layer reflects the radio waves that have passed through the absorption layer. The reflected radio waves enter the absorption layer again and are absorbed by carbon particles within the absorption layer. As a reflector, aluminum or other metal materials in foil or plate form,
Carbon fiber composite material, plate material coated with radio wave reflective paint, etc. can be used.

The silicon carbide fiber used in the support layer allows radio waves to pass through without being reflected as described above, and it is known that resin reinforced with this fiber has extremely high strength. Therefore, this support layer can dramatically increase the structural strength of the radio wave absorber and also has weather resistance, so that it can sufficiently withstand outdoor use.

〔Example〕

FIG. 1 shows an embodiment of the present invention. The radio wave absorber 1 of this embodiment has a supporting layer 2 made of a composite material made of silicon carbide fibers impregnated with epoxy resin, and an absorbing layer 3 on one side of this layer 2.
is placed. The absorbent layer 3 has a structure in which a mixture of hollow or spherical carbon particles and an epoxy resin is filled in a honeycomb core in a fluid state and hardened. A reflective layer 4 is disposed on the opposite side of the support layer with the absorbing layer 3 in between. This reflective layer 4 is made of aluminum foil or an aluminum plate.

FIG. 2 shows another embodiment of the invention. This embodiment differs from the embodiment shown in FIG. 1 in that, in addition to the structure of the embodiment shown in FIG. 1, a second support layer is provided between the absorption layer 3 and the reflection layer 4. The second support layer 5 is made of a composite material made of silicon carbide fibers impregnated with epoxy resin. According to this example, it is possible to obtain a hardening that can further increase the structural strength of the radio wave absorber 1.

FIG. 3 shows that in the embodiment of FIG. 2, a second absorbent layer 6 is further arranged between the absorbent layer 3 and the second support layer 5, and a third support layer is arranged between the absorbent layer 3.6. This is a configuration in which layer 7 is arranged. The third support layer 7, like the support layer 2.5, is made of a composite material made of silicon carbide fibers impregnated with an epoxy resin. In this example, the absorption layer 3.6 is configured to have different packing densities of carbon particles and exhibit absorption characteristics for radio waves of different wavelengths.

EXAMPLES In order to confirm the absorption characteristics of the radio wave absorber according to the present invention, tests were conducted according to examples. For this purpose, the samples shown in the following table were prepared.

1 Absorption layer and ^l Low 2 Absorption layer and ^1 High 8 Support layer and Aj 0.6mm9
The test results of the radio wave absorption characteristics of these samples are shown in FIG. As is clear from the figure, the configuration of the present invention exhibits superior radio wave absorption characteristics as compared to the configuration without a support layer. Furthermore, in addition to this excellent radio wave absorption property, the support layer dramatically increases the structural strength.

〔effect〕

As described above, in the present invention, the structure is strengthened due to the layered arrangement consisting of a support layer made of silicon carbide fibers impregnated with resin, a radio wave absorbing layer containing carbon particles, and a radio wave reflector. Moreover, a radio wave absorber having excellent weather resistance and radio wave absorption properties can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a radio wave absorber showing an embodiment of the present invention;
2 and 3 are cross-sectional views showing other embodiments of the present invention, and FIG. 4 is a chart showing the results of a radio wave absorption comparison test showing the effects of the present invention. 2...Support layer, 3...Absorption layer, 4...Reflection layer. Figure 2 Figure 3 Figure 4 l-1z

Claims (4)

[Claims] (1) a support layer made of silicon carbide fibers impregnated with a resin material; an absorption layer containing spherical or hollow carbon particles disposed on one side of the first layer; is a radio wave absorber comprising a plate-like body having radio wave reflecting characteristics arranged on the opposite side. (2) The radio wave absorber according to claim 1, further comprising a layer made of silicon carbide impregnated with a resin material between the absorption layer and the plate-like body. (3) The radio wave absorber according to claim 1 or 2, wherein the absorption layer is composed of a plurality of layers having different carbon concentrations. (4) The radio wave absorber according to any one of claims 1 to 3, wherein the absorption layer is formed by filling a honeycomb core with a mixture of carbon particles and a resin material.