JP6869857B2 - Laminated structure and its manufacturing method - Google Patents

Description

The present invention relates to a laminated structure in which composite materials applicable to a pressure resistant tank and a cryogenic tank are laminated, and a method for manufacturing the same.

Among the tanks applied to the space plane, for example, a tank containing liquid hydrogen or the like is required to have pressure resistance and heat resistance to extremely low temperatures. Currently, the main material of the tank that requires pressure resistance is metal (for example, aluminum (Al)).

In future rocket operations, reuse of single-stage tanks is being considered. Redundancy measures for landing structure and electrical system required for reuse are accompanied by weight increase. In order to compensate for this increase in weight, it is essential to reduce the weight of the tank.

To reduce the weight of the tank, a lightweight material may be used. For example, if the conventional material is Al, it is conceivable to use a metal lighter than this conventional material (for example, Al—Li alloy) or a composite material such as a fiber reinforced resin as described in Patent Document 1. Normally, when the material of the tank that requires pressure resistance is a composite material, a liner for the purpose of preventing gas leakage is applied to the inside of the tank. The liner is made of metal or resin.

As another means for reducing the weight of the tank, it is conceivable to adopt a tank without a liner. Patent Document 2 discloses a method for manufacturing a septic tank and a water storage tank of an aircraft. Patent Document 2 discloses a tank in which a fiber-reinforced plastic is wound around an outer peripheral surface of an inner layer made of a resin material or a resin composite material.

JP-A-2002-36235 JP-A-2007-268929

Table 1 shows the relationship between tank material and weight and cost. In Table 1, the numerical values of weight and cost are standard values based on a tank made of Al, which is a conventional material. The items of gas leak in Table 1 are the findings obtained from the published literature and past in-house research.

Al-Li alloys and fiber reinforced resins (eg carbon fiber reinforced plastics (CFRP)) are lightweight but generally more expensive than Al. Therefore, if a material that is lighter than the conventional one is used, the manufacturing cost becomes high.

Liners applied to composites generally have a different coefficient of thermal expansion than composites. For example, when a resin liner is applied to the inside of a tank made of carbon fiber reinforced resin, there is a concern that the carbon fiber reinforced resin and the resin liner may peel off due to a difference in thermal expansion in an extremely low temperature application.

In a tank containing liquid hydrogen or the like, strain is applied to the tank wall due to the gas pressure in the tank, or the inner wall of the tank is exposed to an extremely low temperature environment due to contact with liquid hydrogen or the like. In such a case, microcracks (fine cracks) may occur on the inner wall of the tank, and gas may leak from the inside of the tank to the outside of the tank through the microcracks.

Conventionally, a liner provided inside the tank can prevent gas leakage, but when a linerless tank is used as in Patent Document 2, there is a concern that gas leakage cannot be prevented. The septic tank and the water storage tank manufactured in Patent Document 2 are not pressure vessels and do not mention the evaluation of gas leakage. Therefore, the linerless tank described in Patent Document 2 cannot be simply adopted as a tank in which liquid hydrogen or the like is stored.

According to Table 1, gas leaks occur in CFRP (without liner). The laminated structure of CFRP in Table 1 is the same as that of the comparative example described later.

The present invention has been made in view of such circumstances, and is applicable to a tank that requires at least one of pressure resistance and heat resistance to extremely low temperatures, is lighter than the conventional one, and is lightweight. The purpose is to provide technology that can suppress gas leaks.

In order to solve the above problems, the laminated structure of the present invention and the manufacturing method thereof employ the following means.

The present invention is a laminated structure in which a composite material containing reinforcing fibers and a matrix resin is laminated, and has a lower outer layer made of a first composite material, an inner layer made of a second composite material, and a first layer. The upper outer layer composed of one composite material is provided, the inner layer is arranged so as to be sandwiched between the lower outer layer and the upper outer layer, and the second composite material is made of the first composite material. Also provides a thin laminated structure.

Further, the present invention is a method for manufacturing a laminated structure in which a composite material containing a reinforcing fiber and a matrix resin is laminated, wherein the lower outer layer of the pre-preg composed of the first prepreg is thinner than the first prepreg. Provided is a method for producing a laminated structure in which a pre-inner layer composed of a prepreg and a pre-upper outer layer composed of a first prepreg are laminated in order, and then heated and pressurized to cure the matrix resin to form a molded product. To do. Here, "pre" means that the matrix resin is in a state before being cured.

As a result of diligent research, the present inventors can maintain the gas barrier property of the laminated structure for a longer time than before by adopting a laminated structure in which composite materials having different thicknesses are incorporated in the center of the thickness of the laminated structure. I got the finding.

According to the above invention, an inner layer is provided between the lower outer layer and the upper outer layer, and the inner layer is composed of a second composite material thinner than the first composite material constituting the outer layer, thereby causing gas leakage as compared with the conventional case. You can increase the time it takes. As a result, an increase in the amount of gas leakage over time is suppressed.

If the thickness of the molded product is the same, the thinner the composite material, the larger the number of laminated products. It is preferable to minimize the increase in the number of laminated sheets because it leads to an increase in material cost and working cost. In the laminated structure according to the above invention, the inner layer is sandwiched between the lower outer layer and the upper outer layer which are composed of the first composite material which is thicker than the second composite material, instead of being composed entirely of the second composite material. It is composed. By combining the first composite material and the second composite material having different thicknesses, it is possible to secure the necessary gas barrier property while suppressing the total number of laminated composite materials. The first composite material of the upper outer layer and the lower outer layer may have the same thickness as the conventionally used composite material.

Oite above onset bright, the inner layer has a structure in which a plurality of the second composite material are laminated, the second composite material, unidirectional composites where the reinforcing fibers are oriented in any direction , and the at the inner layer, that have different fiber orientation between the second composite adjacent.

In the adjacent second composite material, microcracks are independently generated in each. If the fiber orientation is different, the direction in which microcracks are likely to occur also changes. If the directions of the microcracks generated in the adjacent second composite materials are different, the area where the microcracks overlap each other is reduced. As a result, the cross-sectional area of the gas leak path in the thickness direction of the inner layer becomes small, and the amount of gas leak in a certain period of time is reduced. Therefore, in order to take advantage of the advantages obtained by making the second composite material thinner than the first composite material, it is better to place the second composite materials having different fiber orientations adjacent to each other.

In one aspect of the above invention, the first composite material is a unidirectional composite material in which the reinforcing fibers are oriented in any one direction, and the first composite material in the lower outer layer and the upper outer layer. In the first composite material, the fiber orientation is preferably arranged symmetrically with respect to the inner layer.

Residual stress generated in the molded product is reduced by forming a pseudo-isotropic laminate in which the fiber orientation of the lower outer layer and the fiber orientation of the upper outer layer are symmetrical, with the inner layer in the center of the laminated structure in the thickness direction as a mirror surface. It can be suppressed.

In one aspect of the above invention, the thickness of the second composite material is preferably 1 / 2n (n is a natural number not including 0) of the thickness of the first composite material.

In conventional laminated structure designs, the thicknesses of the composites to be laminated are all equal. On the other hand, in the above invention, the laminated structure is divided into a lower outer layer / inner layer / upper outer layer in the thickness direction, and the second composite material forming the inner layer in the center of the thickness is used to form the upper and lower outer layers. Make it thinner than the composite material. In other words, in the above invention, a part of the conventional laminated structure is replaced with an inner layer. When the thickness of the second composite material is 1 / 2n (n is a natural number) of the first composite material, if the first composite material of one layer is replaced with the second composite material of 2n layer, the thickness is not changed. , The laminated structure of the above invention can be easily obtained.

In one aspect of the above invention, the thickness of the second composite material is preferably 50 μm or more and 100 μm or less.

As a result of diligent research, the present inventors have found that the second composite material has an appropriate thickness for obtaining optimum gas barrier properties. By setting the thickness of the second composite material within the above range, the amount of gas leakage can be kept low while minimizing the number of layers of the second composite material.

According to the present invention, by providing an inner layer between the outer layers and adopting a thin composite material for the inner layer, a laminated structure in which the amount of gas leakage can be suppressed to a low level even if it is linerless.

It is the schematic which shows the laminated structure of the laminated structure which concerns on one Embodiment. It is a figure which shows the laminated structure of the pre-specimen of Examples 1-3 and the comparative example. It is the schematic of the test apparatus used for the gas leakage amount confirmation test. It is a test flow chart of a gas leakage amount confirmation test. It is a figure which shows the result of the gas leakage amount measurement. It is a schematic diagram of the microcrack generated in an arbitrary first composite material. It is a schematic diagram of the microcrack generated in the adjacent 2nd composite material. It is a schematic diagram of the leakage path when four layers of the first composite material are laminated. It is a schematic diagram of the leakage path when 8 layers of the 2nd composite material are laminated.

The laminated structure according to this embodiment can be applied to a cryogenic tank, a pressure resistant tank, and the like. The cryogenic tank and the pressure resistant tank are, for example, a fuel tank for a space plane containing liquid hydrogen. “Ultra-low temperature” is −200 ° C. or higher and -189 ° C. or lower. The "pressure resistance" means, for example, a configuration that can withstand a gas pressure of 0.5 MPa or more and 50 MPa or less in the tank.

Hereinafter, an embodiment of the laminated structure according to the present invention will be described with reference to the drawings.
FIG. 1 shows a laminated structure of the laminated structure according to the present embodiment. The laminated structure 1 according to the present embodiment has a configuration in which the lower outer layer 2, the inner layer 3, and the upper outer layer 4 are laminated in this order. The inner layer 3 is arranged so as to be sandwiched between the lower outer layer 2 and the upper outer layer 4. Here, the "upper side" is one surface side of the inner layer 3, and the "lower side" is the other surface side of the inner layer 3.

The lower outer layer 2 is composed of one or more first composite materials 5. The upper outer layer 4 is composed of one or more first composite materials 6. The number of layers of the first composite material 5 constituting the lower outer layer 2 and the first composite material 6 forming the upper outer layer 4 are equal. In FIG. 1, the lower outer layer 2 and the upper outer layer 4 each have a three-layer structure in which three first composite materials 5 and 6 are laminated.

The first composite materials 5 and 6 are composed of reinforcing fibers and a matrix resin. Reinforcing fibers are carbon fibers. As the matrix resin, an epoxy resin or the like can be used. In the first composite materials 5 and 6, the matrix resin exists in a state after being completely or almost completely cured.

The amounts of the reinforcing fibers and the matrix resin contained in the first composite materials 5 and 6 are uniform. The content (RC) of the matrix resin in the first composite materials 5 and 6 is preferably 30% by weight or more and 40% by weight or less. By setting RC in the above range, the fiber volume content is suitable for the composite material structure. The matrix resin preferably has a uniform phase structure. The diameter and length of the reinforcing fibers are not particularly limited.

The first composite materials 5 and 6 may contain a curing agent, a curing accelerator and the like. The curing agent and curing accelerator may be any as long as they accelerate the curing of the matrix resin.

The thickness of the first composite materials 5 and 6 can be appropriately set according to the applicable product. The thickness of the first composite material suitable for the technical field of aerospace aircraft is 100 μm or more and 200 μm or less.

The first composite materials 5 and 6 are unidirectional composite materials in which reinforcing fibers are oriented in any one direction. In FIG. 1, the layer composed of the first composite material in which the reinforcing fibers are mainly oriented at 0 °, the layer composed of the first composite material in which the reinforcing fibers are mainly oriented at 45 °, and the reinforcing fibers are mainly −45 °. A layer of first composite material oriented in is shown.

As shown in FIG. 1, the first composite material 5 of the lower outer layer 2 and the first composite material 6 of the upper outer layer 4 are arranged symmetrically with each other with the center (inner layer) of the thickness of the laminated structure as a mirror surface. It is preferable that it is. By forming the laminated structure of the lower outer layer 2 and the upper outer layer 4 into a pseudo isotropic layer, it is possible to suppress the generation of residual stress in the molded product.

The inner layer 3 has a structure in which a plurality of second composite materials 7 are laminated.

The second composite material 7 is composed of reinforcing fibers and a matrix resin. The second composite material 7 is the same as the first composite materials 5 and 6 in terms of elements other than the thickness. The thickness of the second composite material 7 is preferably 1 / 2n (n is a natural number not including 0) of the thickness of the first composite materials 5 and 6. The thickness of the second composite material 7 is 25 μm or more and 100 μm, preferably 50 μm or more and 100 μm or less.

In the inner layer 3, the second composite material 7 is laminated so that layers having different fiber orientations are adjacent to each other. It is preferable that the second composite material 7 is arranged so that the fiber orientation approaches mirror symmetry at the center m of the plate thickness of the laminated structure to the extent possible. The two central layers sandwiching the center m of the thickness of the laminated structure give priority to the fact that the fiber stacking angles do not overlap.

In the inner layer 3, the second composite material 7 is laminated with a number of layers capable of maintaining mechanical symmetry with respect to the center m of the plate thickness of the laminated structure. It is preferable that the number of layers of the second composite material 7 can be an even number unit. In that case, the minimum number of layers of the second composite material 7 is 4.

"Mechanical symmetry can be maintained" means that when the inner layer 3 is divided into two at the center m of the plate thickness, the total fiber orientation balance of the second composite material 7 included in each compartment is between the two compartments. Means even or substantially equal.

For example, when the inner layer 3 having a laminated structure of 90 ° / 45 ° / 0 ° / −45 ° / 45 ° / 0 ° / −45 ° / 90 ° is divided into two at the center m of the plate thickness, each compartment is divided into two. It becomes "90 ° / 45 ° / 0 ° / -45 °" and "45 ° / 0 ° / -45 ° / 90 °". The two compartments both contain a second composite of 0 °, ± 45 °, 90 °. In the 0 ° and 90 ° second composite materials 7, the fiber orientations are mirror-symmetrically arranged at the center m of the plate thickness. Layers (45 ° and −45 °) that are symmetrically located between the two compartments but whose fiber orientations do not match are 90 ° different in fiber orientation. When the fiber orientations of the layers in which the fiber orientations do not match between the two compartments are different by 90 °, the total fiber orientation balance is assumed to be substantially equal in the present embodiment. Adjacent layers having the same fiber direction impair the effect of making the second composite 7 thinner than the first composites 5 and 6. In the laminated structure, the adjacent layers are arranged so that the fiber directions are different.

For example, when the inner layer 3 in which the laminated structure of the second composite material 7 is 90 ° / 45 ° / −45 ° / 90 ° is divided into two at the center m of the plate thickness, each section is “90 ° / 45 °”. And "-45 ° / 90 °". In these two compartments, the total fiber orientation contained in each compartment does not completely match, but the layers (45 ° and −45 °) that do not match between the two compartments have a relationship in which their fiber orientations differ by 90 °. .. In the 90 ° second composite material 7, the fiber orientation is mirror-symmetrically arranged at the center m of the plate thickness. Therefore, in the laminated structure, the total fiber orientation balance becomes substantially uniform.

Hereinafter, a method for manufacturing the laminated structure 1 according to the present embodiment will be described.

In the manufacturing method according to the present embodiment, the pre-lower outer layer composed of the first prepreg, the pre-inner layer composed of the second prepreg thinner than the first prepreg, and the pre-upper outer layer composed of the first prepreg are laminated in this order. After that, it is heated and pressurized to cure the matrix resin to obtain a molded product (laminated structure 1).

Specifically, first, the first prepreg in which the reinforcing fibers are oriented in the 45 ° direction, the first prepreg in which the reinforcing fibers are oriented in the 0 ° direction, and the first prepreg in which the reinforcing fibers are oriented in the −45 ° direction are first. They are laminated in order to form a pre-lower outer layer.

Next, on the lower outer layer of the pre, the second prepreg in which the reinforcing fibers were oriented in the 90 ° direction, the second prepreg in which the reinforcing fibers were oriented in the 45 ° direction, and the reinforcing fibers were oriented in the −45 ° direction. The second prepreg and the second prepreg in which the reinforcing fibers are oriented in the 90 ° direction are laminated in this order to form a pre-inner layer.

Next, on the pre-inner layer, the first prepreg in which the reinforcing fibers are oriented in the −45 ° direction, the first prepreg in which the reinforcing fibers are oriented in the 0 ° direction, and the first prepreg in which the reinforcing fibers are oriented in the 45 ° direction. 1 The prepregs are laminated in order to form the pre-upper outer layer.

The pre-lower outer layer / pre-inner layer / pre-upper outer layer is heat-press molded to cure the matrix resin. As a result, the laminated structure 1 including the lower outer layer 2 / inner layer 3 / upper outer layer 4 can be obtained.

"Prepreg" is an intermediate material for composite materials. "Prepreg" is a sheet in which a reinforcing material made of long fibers (continuous fibers) such as reinforcing fibers is impregnated with a matrix resin. In the "prepreg", the matrix resin is in a semi-cured state. A composite material is obtained by further curing the matrix resin of "prepreg". The first prepreg and the matrix resin of the second prepreg are completely or substantially completely cured to obtain the first composite materials 5 and 6 and the second composite material 7. As used herein, "curing" means changing the matrix resin from a semi-cured state of the prepreg to a further cured state.

In the present embodiment, the thickness of the first prepreg is preferably 100 μm or more and 200 μm or less. With such a prepreg, it is easy to adjust the thickness of the molded product.

The second prepreg is thinner than the first prepreg. The thickness of the second prepreg is 1 / 2n (n is a natural number not including 0) of the thickness of the first prepreg. The thickness of the second prepreg may be, for example, 25 μm or more and 100 μm, preferably 50 μm or more and 100 μm or less.

Heat / pressure molding can be performed by existing methods.

<Gas leak confirmation test>
A confirmation test of the amount of gas leakage was carried out using the laminated structure having the configuration according to the above embodiment (Examples 1 to 3) and the laminated structure having the conventional configuration (comparative example).

(Preparation of specimen)
For the prepreg, the one manufactured by Fukui Prefectural Industrial Technology Center Seiren Co., Ltd. was used. The reinforcing fiber was carbon fiber (T800SC-24000-10E). The matrix resin was a general epoxy resin (jER828 + jER1001 / curing agent: DICY15, curing accelerator: DCMU99).

Table 2 shows an outline of the prepreg used.

Table 3 shows an outline of the laminated structure of the pre-specimens of Examples 1 to 3 and Comparative Examples. The total thickness of each pre-specimen was the same.

FIG. 2 shows the laminated structure of the pre-specimen whose fiber orientation is displayed. In Examples 1 to 3, prepregs having different fiber orientations were adjacent to each other so that the stacking angles did not overlap. In the comparative example, the prepregs were quasi-isotropically laminated so that the fiber orientation was mirror-symmetrical at the center of the plate thickness of the pre-specimen according to the conventional design.

The prepregs were laminated by the hand lay-up method to form a pre-specimen so as to have the configurations shown in Table 3 and FIG. The pre-specimen was heated and pressurized (130 ° C., 0.5 MPa, 2 Hrs) by an autoclave to cure the matrix resin, and used as the specimen.

The outline of the test will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic view of the test apparatus. FIG. 4 is an operation flow diagram.

(S1) He leakage amount measurement-1
First, a sealing jig 12 provided with an air supply pipe 10 and an intake pipe 11 was installed in the central portion of the specimen 13. He leak detector 15 (stock) that has a suction function while being pressurized (0.49 MPa) with He gas from the air supply pipe 10 connected to the He gas cylinder 14 at room temperature (25 ° C) and without distortion. The amount of He (He leakage amount) that was sucked by the intake pipe 11 connected to (manufactured by ULVAC, Inc.) and passed through the specimen 13 was measured.

(S2) He leakage amount measurement-2
Next, the amount of He (He leakage amount) that passed through the specimen was measured in a state where both ends of the specimen 13 were sandwiched between chucks 16 and a strain of 4500 μm was applied by a tensile load (room temperature: 25 ° C.).

(S3) Cryogenic strain load Next, the specimen _{was immersed in liquid nitrogen (LN 2} ) and held for 30 minutes with a strain of 4500 μm.

(S4) He leakage amount measurement-3
Then, the specimen was returned to room temperature, and the amount of He leakage was measured in the same manner as in (S2) above in a state where a strain of 4500 μm was applied (room temperature: 25 ° C.).

The results of the above tests will be described below.
In the above (S1) and (S2), the amount of gas leaked from the specimen was below the detection limit (background noise level: 1 × 10 ^-9 Ncm ³ / cm ² / s). From this, it was confirmed that there was no initial defect in the specimen.

FIG. 5 shows the result of the above (S4) He leakage amount measurement-3. In the figure, the vertical axis is the amount of gas leak (cc / cm ² / sec). In the figure, the measurement results of the gas leakage amount 10 minutes and 60 minutes after the start of pressurization with He gas are shown for Examples 1 to 3 and Comparative Examples.

The amount of gas leak after 10 minutes was almost the same between Comparative Examples and Examples 1 to 3. In the comparative example, the amount of gas leak after 60 minutes increased significantly. On the other hand, in Examples 1 to 3, the amount of gas leak after 60 minutes was suppressed, which was considerably smaller than that in Comparative Example.

From this result, it was confirmed that by applying the second prepreg (Thin or Ultra-Thin) to the layer (inner layer) in the center of the thickness of the laminated structure, the increase in the amount of gas leakage with the passage of time can be suppressed. It was.

The reason why the gas leakage amount can be suppressed will be described with reference to FIGS. 6 to 9.

FIG. 6 is a schematic view of microcracks X generated in an arbitrary first composite material 25 (first prepreg after curing the matrix resin). FIG. 7 is a schematic view of microcracks Y and Z generated in the second composite material 27 (second prepreg after curing the matrix resin) of any two adjacent layers.

FIG. 8 is a schematic view of a leakage path when the first composite material 25 is laminated in four layers. FIG. 9 is a schematic view of a leakage path when eight layers of the second composite material 27 having a thickness of 1/2 of that of the first composite material 25 are laminated. The arrows in FIGS. 8 and 9 are leakage paths, and it is assumed that microcracks (arrows in the thickness direction) have occurred in all the composite materials.

Generally, in a composite material composed of reinforcing fibers and a matrix resin, microcracks are likely to occur in parallel with the fiber direction. Therefore, in the one-layer first composite material 25, as shown in FIG. 6, microcracks X are generated so as to penetrate in the thickness direction.

On the other hand, when two layers of the second composite material 27, which is thinner than the first composite material 25, are laminated, microcracks Y and Z are generated separately in each layer as shown in FIG. 7. Since the fiber orientations of the two adjacent layers of the second composite material 27 do not overlap, the microcracks Y and Z face different directions. As shown in FIG. 7, the microcracks Y and the microcracks Z are connected only at the intersection of the two. That is, since only the connecting portion S between the microcrack Y and the microcrack Z becomes the leakage path P, the leakage path cross-sectional area becomes small.

When the combined thickness of the two layers of the second composite material 27 is the same as the thickness of the first composite material 25, the crack area (leakage path cross-sectional area) penetrating per fixed thickness is larger in FIG. It becomes smaller. If the crack area that penetrates becomes smaller, the amount of gas that passes through it is limited. As a result, the time required for gas leakage becomes longer than that in FIG.

Further, in the portion where the microcracks Y and Z are not directly connected, it is considered that the gas moves along the boundary between the adjacent composite materials (see the arrows in the plane direction in FIGS. 8 and 9). As can be seen by comparing FIGS. 8 and 9, when the total thickness of the laminated structure is constant, the leakage path P becomes longer as the number of laminated composite materials increases.

From the above, in Examples 1 to 3, by arranging Thin or Ultra-Thin between Nominal, the gas flow amount is limited and the leakage path becomes longer than in Comparative Example, and as a result, it accompanies the passage of time. It is probable that the increase in gas leakage amount could be suppressed. If the fiber orientations of adjacent composites are the same, the orientation of the microcracks will be the same between the adjacent composites. In order to reduce the crack area at a constant thickness and develop gas barrier properties, it is preferable that adjacent composite materials have a configuration in which the same stacking angles do not overlap.

Next, Examples 1 and 2 to which Thin is applied are compared with Example 3 to which Ultra-Thin is applied. In Example 3, the number of laminated composite materials was larger than in Examples 1 and 2, but the amount of gas leaked in 60 minutes was higher than in Examples 1 and 2.

The matrix resin in the composite material has a gas barrier property, but cannot completely block the permeation of gas. It is considered that Ultra-Thin of Example 3 has a reduced gas barrier property because the layer of the matrix resin that contributes to the gas barrier property is thinner than that of Thin.

From this result, it was suggested that there is an appropriate second composite material (second prepreg) thickness for obtaining the optimum gas barrier property. According to the above results, the appropriate thickness of the second composite material (second prepreg) was 50 μm or more and 100 μm or less.

Next, Example 1 in which four layers of Thin are laminated and Example 2 in which eight layers of Thin are laminated are compared. In Example 1, the number of laminated composite materials was smaller than that in Example 2, but the amount of gas leaked in 60 minutes was lower than that in Example 2. From this result, it was suggested that sufficient gas barrier property can be obtained even when Thin is applied to the minimum number of layers capable of maintaining mechanical symmetry.

1 Laminated structure 2 Lower outer layer 3 Inner layer 4 Upper outer layer 5, 6, 25 1st composite material (1st prepreg after curing matrix resin)
7,27 Second composite material (second prepreg after curing the matrix resin)
10 Air supply pipe 11 Intake pipe 12 Sealing jig 13 Specimen 14 He gas cylinder 15 He detector measuring device 16 Chuck

Claims (5)

It is a laminated structure in which a composite material containing reinforcing fibers and a matrix resin is laminated.
The lower outer layer made of the first composite material, the inner layer made of the second composite material, and the upper outer layer made of the first composite material are provided.
The inner layer is arranged so as to be sandwiched between the lower outer layer and the upper outer layer.
The second composite material, rather thin than the first composite,
The inner layer has a structure in which a plurality of the second composite materials are laminated.
The second composite material is a unidirectional composite material in which the reinforcing fibers are oriented in any one direction.
A laminated structure in which the fiber orientations of adjacent second composite materials are different in the inner layer. The first composite material is a unidirectional composite material in which the reinforcing fibers are oriented in any one direction.
The laminated structure according to claim 1, wherein the first composite material of the lower outer layer and the first composite material of the upper outer layer are arranged with fiber orientations mirror-symmetrical about the inner layer. The laminated structure according to claim 1 or 2 , wherein the thickness of the second composite material is 1 / 2n (n is a natural number not including 0) of the thickness of the first composite material. The laminated structure according to any one of claims 1 to 3 , wherein the thickness of the second composite material is 50 μm or more and 100 μm or less. A method for manufacturing a laminated structure in which a composite material containing reinforcing fibers and a matrix resin is laminated.
The lower outer layer of the pre-preg composed of the first prepreg, the inner layer of the pre-preg composed of the second prepreg thinner than the first prepreg, and the upper outer layer of the pre-preg composed of the first prepreg are laminated in this order, and then heated and pressurized. , The matrix resin is cured to obtain a molded product .
As the second prepreg, an intermediate material of a composite material in which the reinforcing fibers are oriented in any one direction is used.
A method for producing a laminated structure in which a plurality of the second prepregs are laminated to form the pre-inner layer so that the fiber orientations of adjacent second prepregs are different.

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