JP2017085024A - Method of manufacturing fiber-reinforced plastic sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a sheet, becoming the loss layer of a radio wave absorber, accurately.SOLUTION: A radio wave absorber 10 assumes a plate-like shape by laminating a dielectric loss layer 12, an air-like layer 14, a magnetic loss layer 16 and a conductor layer 18 in order from the incident direction of radio wave. A fiber-reinforced plastic sheet for use as at least one of the dielectric loss layer 12 or magnetic loss layer 16 is formed by impregnating a reinforcing fiber sheet F with resin R where the fine particles of a magnetic material or a resistive material are dispersed. Impregnation of the reinforcing fiber sheet F with the resin R may be performed by a coating device, a squeegee mobile device, a roller coater device, or the like.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a fiber-reinforced plastic sheet used as a loss layer of a radio wave absorber.

The radio wave absorber functions by converting incident radio wave energy into heat energy by magnetic loss and dielectric loss.
For example, in the following Patent Document 1, an air-like layer is provided between a dielectric loss layer and a magnetic loss layer, and in view of the frequency dependence of the radio wave absorption capability of the shape of the air-like layer or the magnetic loss layer in contact with the air-like layer. Thus, there has been disclosed a radio wave absorber capable of adjusting the absorption capability with respect to the absorption frequency and increasing the bandwidth while being reduced in weight and thickness.

JP2015-159228A

In the radio wave absorber of Patent Document 1, a dielectric loss layer, an air-like layer, a magnetic loss layer, and a conductor layer are laminated in order from the incident direction of radio waves. More specifically, after each layer forming the radio wave absorber is individually manufactured, the layers are bonded together with an adhesive or the like to be integrated.
Heretofore, the plastic sheet used as the dielectric loss layer and the magnetic loss layer of such a wave absorber is formed by pressing a material in which ferromagnetic fine particles or resistor fine particles are dispersed in a base material such as a resin. It is formed by spreading and curing into a sheet shape by methods such as weight processing and scraping.

FIG. 9 is an explanatory view schematically showing a method for producing a lossy layer plastic sheet according to the prior art.
FIG. 9A shows a manufacturing method by press working, in which a material 912 is placed in a spacer 910 formed to have a desired thickness and area, and the material 912 is stretched by applying pressure with a press 914 from the upper surface to form a sheet. ing.
FIG. 9B shows a manufacturing method by weight processing, in which a material 922 is disposed in the spacer 920 as in the press processing, and the material 922 is stretched by applying pressure from the weight 924 from the upper surface to form a sheet.
FIG. 9C shows a manufacturing method by scraping, in which a material 932 is placed in a spacer dam 930 formed in a desired thickness and width, and the scraping bar 934 is moved on the upper surface to stretch the material 932, thereby forming a sheet shape. I have to.

  However, in such a manufacturing method, it is difficult to manufacture a sheet having a desired thickness, in which the sheet is likely to crack, and it is difficult to manufacture a sheet having a uniform thickness. There are problems such as difficulty in manufacturing a large sheet.

  This invention is made | formed in view of such a situation, The objective is to form the sheet | seat used as the loss layer of a radio wave absorber accurately.

In order to achieve the above object, a method for producing a fiber reinforced plastic sheet according to the invention of claim 1 is a method for producing a fiber reinforced plastic sheet used as a loss layer of a radio wave absorber, and is a magnetic or resistor fine particle. The fiber-reinforced plastic sheet is formed by impregnating a resin in which the resin is dispersed in a sheet-like reinforcing fiber.
In the method for producing a fiber-reinforced plastic sheet according to the invention of claim 2, the resin is impregnated into the reinforcing fiber by using at least one of a coating device, a squeegee moving device, and a roll coater device. It carries out by apply | coating resin, It is characterized by the above-mentioned.
The method for producing a fiber-reinforced plastic sheet according to the invention of claim 3 is characterized in that the material of the reinforcing fiber is at least one of vinylon, glass, polyester, polyamide, and polypropylene.
The method for producing a fiber-reinforced plastic sheet according to the invention of claim 4 is characterized in that the porosity of the reinforcing fiber is 60% or more and 90% or less.
In the method for producing a fiber-reinforced plastic sheet according to the invention of claim 5, in the radio wave absorber, a dielectric loss layer, an air-like layer, a magnetic loss layer, and a conductor layer are laminated in order from the incident direction of the radio wave, The fiber-reinforced plastic sheet is used as at least one of the dielectric loss layer and the magnetic loss layer.

According to the invention of claim 1, the strength of the fiber-reinforced plastic sheet is improved by the sheet-like reinforcing fibers, the fiber-reinforced plastic sheet is prevented from being damaged in the manufacturing process, and the yield at the time of manufacturing the radio wave absorber is improved. This is advantageous. In addition, since the thickness of the fiber-reinforced plastic sheet is defined by the sheet-like reinforcing fibers, it is advantageous in efficiently and reliably controlling the thickness of the loss layer.
According to the invention of claim 2, since the resin is applied to the reinforcing fiber using the apparatus, the force when the resin is stretched becomes uniform, and the thickness of the fiber-reinforced plastic sheet can be made more uniform.
According to the invention of claim 3, it is suitable for reinforcing the lossy layer and is advantageous in reinforcing the fiber-reinforced plastic sheet with a general-purpose material.
According to the invention of claim 4, it is advantageous in securing the amount of reinforcing fibers per unit area necessary for reinforcing the fiber-reinforced plastic sheet while securing the voids necessary for containing the resin.
According to the invention of claim 5, it is advantageous to provide a radio wave absorber capable of adjusting the absorption capacity with respect to the absorption frequency and widening the band while being reduced in weight and thickness.

It is sectional drawing of the electromagnetic wave absorber 10 using the fiber reinforced plastic manufactured with the manufacturing method concerning this invention. It is explanatory drawing explaining the manufacturing method of a fiber reinforced plastic sheet. It is explanatory drawing which shows the result of having evaluated the thickness of the fiber reinforced plastic sheet of this invention. It is explanatory drawing which shows the result of having evaluated the thickness of the plastic sheet manufactured by the scraping method. It is explanatory drawing which shows the result of having evaluated the thickness of the fiber reinforced plastic sheet of this invention. It is explanatory drawing which shows the result of having evaluated the thickness of the plastic sheet manufactured by the press work method. 3 is a graph showing the reflection loss characteristics of the radio wave absorber 10. It is a graph which shows the reflection loss characteristic of the electromagnetic wave absorber which does not contain the reinforcing fiber sheet F. It is explanatory drawing which shows typically the manufacturing method of the plastic sheet for loss layers concerning a prior art.

Exemplary embodiments of a method for producing a fiber-reinforced plastic according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a radio wave absorber 10 using a fiber reinforced plastic manufactured by a manufacturing method according to the present invention.
The radio wave absorber 10 has a configuration in which a dielectric loss layer 12, an air-like layer 14, a magnetic loss layer 16, and a conductor layer 18 are laminated in this order from the incident direction of the electromagnetic wave indicated by the arrow.
The conductor layer 18 is a reflective conductor made of a plate-like conductor, such as an aluminum metal plate.

  In FIG. 1, since the electric field component of the incident electromagnetic wave is short-circuited by the conductor layer 18, the electric field component becomes zero on the surface and becomes maximum at a position away from the surface of the conductor layer 18 by λ (wavelength) / 4. On the other hand, the magnetic field component of the incident electromagnetic wave is maximized on the surface of the conductor layer 18.

In the dielectric loss layer 12 and the magnetic loss layer 16, a sheet-like reinforcing fiber (hereinafter referred to as “reinforcing fiber sheet F”) is impregnated with a dielectric material such as a resin in which fine particles of a magnetic substance or a resistor are dispersed. It is made of fiber reinforced plastic sheet.
In FIG. 1, for convenience of illustration, the ratio of the thickness of the reinforcing fiber sheet F to the thickness of the dielectric loss layer 12 and the magnetic loss layer 16 is reduced, but the thickness of the reinforcing fiber sheet F is actually the dielectric loss. The thickness is about the same as the thickness of the layer 12 and the magnetic loss layer 16.
The material of the reinforcing fiber sheet F is a fiber formed of vinylon, glass, polyester, polyamide, polypropylene, or the like, and may be a mixed fiber containing these.
The reinforcing fiber sheet F is a woven or knitted knitted fabric made of the above-described fibers, or a nonwoven fabric in which fibers are entangled with each other.
Further, the porosity of the reinforcing fiber sheet F is, for example, not less than 60% and not more than 90%. This is because if the porosity is less than 60%, the reinforcing fiber sheet F is clogged, the content of the dielectric material is low, the strength of the fiber sheet with a porosity of more than 90% is weak, and the fiber reinforced plastic sheet This is because the reinforcing strength may be insufficient.
Moreover, as a method for impregnating the reinforcing fiber sheet F with the dielectric material (resin), various conventionally known methods such as application with a spatula or spraying can be employed.
In this embodiment, both the dielectric loss layer 12 and the magnetic loss layer 16 contain the reinforcing fiber sheet F. However, only one of the dielectric loss layer 12 or the magnetic loss layer 16 has the reinforcing fiber sheet F. It may be made to contain.

The magnetic loss layer 16 is obtained by impregnating a reinforcing fiber sheet with a predetermined weight% (wt%) of ferromagnetic fine particles dispersed in a dielectric material made of, for example, resin as a binder (base material). Is formed.
The magnetic loss layer 16 efficiently absorbs electromagnetic waves in a region where the magnetic field component intensity of incident electromagnetic waves is high.
By dispersing and arranging fine particles, which are ferromagnetic materials, in the magnetic loss layer 16, microwaves can penetrate into the inside as an insulator as a whole. In addition, since the surface area of the ferromagnetic material is increased by dispersing the fine particles, the incident electromagnetic wave is attenuated by the magnetic loss by increasing the volume of the skin layer that functions as a magnetic material even if the skin effect acts. be able to.
The fine particles of the ferromagnetic material are brought into a non-contact state by interposing a binder between them, and become a dielectric (insulator) as a whole.
As the ferromagnetic material, for example, iron is used, and fine particles made of a ferromagnetic material such as ferrite fine powder and amorphous alloy can be used.
As the dielectric material, for example, an epoxy resin or a silicone resin may be employed, or a material molded into a plate-like porous material using a foamable synthetic resin material such as foamed polystyrene or foamed urethane may be employed.

The dielectric loss layer 12 is formed by impregnating the reinforcing fiber sheet F with a dielectric material made of, for example, a resin, in which resistors, for example, fine particles of a carbon-based material are dispersed and arranged in a predetermined wt%.
The dielectric loss layer 12 efficiently absorbs electromagnetic waves in a region where the electric field component intensity of incident electromagnetic waves is high.
As the resistor, ketjen black (made by Lion Corporation, model name EC300J), which is a carbon material, or the like can be used.
As the dielectric material, for example, a molded body of epoxy resin or urethane resin is used.

The air-like layer 14 is flattened (that is, broadened) by suppressing the behavior of the absorption characteristic of the incident electromagnetic wave, and the loss term α (= √ (μ ”ε”) per unit thickness is used to suppress the behavior. A material or structure in which)) has a large value is preferred.
As the air-similar layer 14, a resin containing a predetermined amount of microballoon (manufactured by Nippon Ferrite Co., Ltd., model name EMC40), for example, a urethane resin molded body is used. Alternatively, a structure of an aramid honeycomb (a complex relative dielectric constant real part value of 1.14 and an imaginary part value of 0.003) formed by impregnating aramid paper with resin and forming into a honeycomb shape may be used. Moreover, you may employ | adopt a foamable synthetic resin material like a polystyrene foam, for example.

  As shown in Patent Document 1, the performance of the radio wave absorber 10 varies depending on the thickness and material of each layer of the radio wave absorber 10. Therefore, the specific thickness and material of each layer of the radio wave absorber 10 are determined according to the performance required for the radio wave absorber 10.

Next, an example of a method for producing a fiber reinforced plastic sheet for forming the dielectric loss layer 12 and the magnetic loss layer 16 will be described.
First, as shown in FIG. 2A, the reinforcing fiber sheet F is prepared and set on the release plate 200.
Next, as shown in FIG. 2B, the resin R in which fine particles of a magnetic substance or a resistor are dispersed at a predetermined concentration is arranged on the surface of the reinforcing fiber sheet F, and the reinforcing fiber sheet F is formed with a spatula 202 or the like. Apply to the whole area.
You may perform this operation | work with apparatuses, such as a coating apparatus, a squeegee moving apparatus, a roll coater apparatus. By using these apparatuses, the force for extending the resin R can be made uniform, and the thickness of the fiber-reinforced plastic sheet can be made more uniform.
Thereafter, the applied resin R is cured at room temperature to complete a fiber-reinforced plastic sheet. The thickness of the fiber-reinforced plastic sheet is almost equal to that of the reinforcing fiber sheet F. For this reason, a plurality of fiber-reinforced plastic sheets are laminated and bonded according to the thickness required for the dielectric loss layer 12 or the magnetic loss layer 16 if necessary. At this time, instead of the adhesive, a resin R in which the fine particles are dispersed and arranged may be used.
Further, when the radio wave absorber 10 is manufactured, the magnetic loss layer 16, the air-like layer 14, and the dielectric loss layer 12 are laminated on the conductor layer 18 in this order.

FIG. 3 is an explanatory view showing the results of evaluating the thickness of the fiber-reinforced plastic sheet produced by the method of FIG. 2 (the present invention), and FIG. 4 is a method of scraping without the reinforcing fiber sheet F as a comparative example (FIG. 9C). It is explanatory drawing which shows the result of having evaluated the thickness of the plastic sheet manufactured by reference.
In FIGS. 3 and 4, four fiber reinforced plastic sheets or plastic sheets are manufactured with a thickness target value of 0.3 mm, and the thickness of each of the sheets is measured to evaluate the variation. Yes.
In FIG. 3, the reinforcing fiber sheet F is one vinylon fiber sheet having a thickness of 0.3 mm. From the top, the entire weight, the amount of impregnation of the resin R, the measured thickness (8 places), and the average of the measured thickness Values and standard deviations are shown.
Further, in FIG. 4, the entire weight (resin amount), measured thickness (8 places), average value and standard deviation of the measured thickness are shown in order from the top.
As shown in FIG. 3, the standard deviation of the thickness of the fiber reinforced plastic sheet manufactured by the method of the present invention is in the range of 0.002 to 0.012, and the standard deviation of the comparative example shown in FIG. ~ 0.038), the thickness variation can be greatly reduced.

Further, a case where the reinforcing fiber sheet F is laminated to increase the thickness will be considered.
FIG. 5 is an explanatory view showing the result of evaluating the thickness of the fiber-reinforced plastic sheet produced by the method of FIG. 2 (the present invention), and FIG. 6 is a press-pressing method (FIG. 9A) without the reinforcing fiber sheet F as a comparative example. It is explanatory drawing which shows the result of having evaluated the thickness of the plastic sheet manufactured by reference.
In FIGS. 5 and 6, four fiber reinforced plastic sheets or plastic sheets are manufactured with a thickness target value of 1 mm, and the thickness of each of the sheets is measured to evaluate the variation.
In FIG. 5, the reinforcing fiber sheets F are three vinylon fiber sheets having a thickness of 0.3 mm. The three reinforcing fiber sheets F were impregnated with resin R and cured, and then these three sheets were bonded.
The items in the tables of FIGS. 5 and 6 are the same as those of FIGS. 3 and 4, respectively.
As shown in FIG. 5, the thickness of the fiber-reinforced plastic sheet produced by the method of the present invention has a standard deviation in the range of 0.029 to 0.039, and the standard deviation (0.053 of the comparative example shown in FIG. 6). ~ 0.084), the thickness variation can be greatly reduced.

FIG. 7 is a graph showing the reflection loss characteristics of the radio wave absorber 10. As a comparative example, FIG. 8 shows a graph of the reflection loss characteristics of a radio wave absorber that does not include the reinforcing fiber sheet F in the dielectric loss layer 12 and the magnetic loss layer 16.
In the graphs of FIGS. 7 and 8, the vertical axis represents reflection loss (dB), and the horizontal axis represents radio wave frequency (GHz).
7 and FIG. 8 show the results of measuring how much the amount of radio wave reflection in the radio wave absorber is attenuated compared to metal by calibrating a metal flat plate of the same size as that of the radio wave absorber at 0 dB. . The position of 0 dB in the graph is the metal reflection level.

As a specific configuration of the radio wave absorber, an epoxy resin molded body containing 3.5 wt% ketjen black is used as the dielectric loss layer 12, and a vinyl chloride resin foam molded body having a density of 60 kg / m ³ is used as the air-like layer 14. And an epoxy resin molded body containing 80 wt% of the magnetic powder content in the resin molded body was used as the magnetic loss layer 16.
The thicknesses of the dielectric loss layer 12, the air-like layer 14, and the magnetic loss layer 16 are 0.38 mm, 2.87 mm, 1.02 mm, and the weight of the absorber per 1 m ² , respectively.
For the measurement, Narda S.H. T.A. S. Using a transmission / reception antenna 640 made by Anritsu Corporation and a vector network analyzer 37369C made by Anritsu Corporation, reflection loss (radio wave absorption ability) in a frequency band of 1.0 GHz to 18 GHz was evaluated by a free space method.
The measurement uses a time domain gating method, and the gate span is 500 picoseconds.

In the radio wave absorber not including the reinforcing fiber sheet F shown in FIG. 8, there is a peak of reflection loss at about 8 GHz to 10 GHz, and the reflection loss at the peak is about −18 dB to −25 dB. On the other hand, in the radio wave absorber 10 including the reinforcing fiber sheet F shown in FIG. 7, there is a reflection loss peak at about 8.5 GHz to 10 GHz, and the reflection loss at the peak is about −20 dB to −35 dB.
Thus, even if the reinforcing fiber sheet F is added to the radio wave absorber, there is almost no influence on the radio wave performance, and higher radio wave absorption performance may be obtained depending on the specifications.

As described above, the fiber-reinforced plastic manufacturing method according to the embodiment improves the strength of the fiber-reinforced plastic sheet by the reinforcing fiber sheet F, prevents the fiber-reinforced plastic sheet from being damaged in the manufacturing process, and absorbs radio waves. This is advantageous in improving the yield when the body 10 is manufactured.
Further, since the thickness of the fiber-reinforced plastic sheet is defined by the reinforcing fiber sheet F, it is advantageous in efficiently and reliably controlling the thickness of the loss layer.
Further, in the method for manufacturing a fiber reinforced plastic according to the embodiment, if the resin R is applied to the reinforcing fiber sheet F using an apparatus, the force when the resin R is stretched becomes uniform, and the fiber reinforced plastic sheet The thickness can be made more uniform.
Further, since the material of the reinforcing fiber sheet F includes at least one of vinylon, glass, polyester, polyamide, and polypropylene, it is suitable for reinforcing the loss layer and reinforces the fiber reinforced plastic sheet with a general-purpose material. be able to.
Further, since the porosity of the reinforcing fiber sheet F is 60% or more and 90% or less, the amount of reinforcing fibers per unit area required for the fiber-reinforced plastic sheet is ensured while ensuring the voids necessary to contain the resin R. It is advantageous in securing.
The radio wave absorber 10 has a dielectric loss layer 12, an air-like layer 14, a magnetic loss layer 16 and a conductor layer 18 laminated in order from the incident direction of the radio wave, so that the absorption frequency can be reduced while being reduced in weight and thickness. This is advantageous in providing a radio wave absorber capable of adjusting absorption capacity and broadening the bandwidth.

  DESCRIPTION OF SYMBOLS 10 ... Wave absorber, 12 ... Dielectric loss layer, 14 ... Air-like layer, 16 ... Magnetic loss layer, 18 ... Conductor layer, F ... Reinforcement fiber sheet, R ... Resin.

Claims (5)

A method for producing a fiber-reinforced plastic sheet used as a loss layer of a radio wave absorber,
The fiber-reinforced plastic sheet is formed by impregnating a resin in which fine particles of a magnetic substance or a resistor are dispersedly arranged into a sheet-like reinforcing fiber.
A method for producing a fiber-reinforced plastic sheet. The impregnation of the resin into the reinforcing fiber is performed by applying the resin to the reinforcing fiber using at least one of a coating device, a squeegee moving device, and a roll coater device.
The method for producing a fiber-reinforced plastic sheet according to claim 1. The material of the reinforcing fiber is at least one of vinylon, glass, polyester, polyamide, and polypropylene.
The method for producing a fiber-reinforced plastic sheet according to claim 1 or 2. The porosity of the reinforcing fiber is 60% or more and 90% or less,
The method for producing a fiber-reinforced plastic sheet according to any one of claims 1 to 3. The radio wave absorber has a dielectric loss layer, an air-like layer, a magnetic loss layer, and a conductor layer laminated in order from the incident direction of the radio wave,
The fiber reinforced plastic sheet is used as at least one of the dielectric loss layer or the magnetic loss layer.
The manufacturing method of the fiber reinforced plastic sheet of any one of Claim 1 to 4 characterized by the above-mentioned.

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