JP2019048400A - Laminate structure and production method thereof - Google Patents

Abstract

To provide a technique which is applicable to a tank needed to have at least one property selected from pressure resistance and ultralow temperature resistance and achieves more weight saving than conventional methods, and has suppressed gas leakage.SOLUTION: A laminate structure 1 is a laminate of composite materials containing reinforcement fibers and matrix resins, wherein the laminate structure 1 contains a downside outer layer 2 composed of a first composite material 5, an inner layer 3 composed of a second composite material 7, and an upside outer layer 4 composed of a first composite material 6, the inner layer 3 is arranged to be sandwiched between the downside outer layer 2 and the upside outer layer 4, and the second composite material 7 is thinner than the first composite materials 5,6.SELECTED DRAWING: Figure 1

Description

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

  Among the tanks applied to the spacecraft, for example, a tank containing liquid hydrogen and the like is required to have pressure resistance and heat resistance to extremely low temperatures. At present, the material of the tank required to have pressure resistance is mainly metal (for example, aluminum (Al)).

  In the future rocket operation, the reuse of single-stage tanks is considered. The redundant structure of the landing structure and the electrical system that is required along with the reuse involves weight increase. In order to compensate for this increase in weight, it is essential to reduce the weight of the tank.

  In order to reduce the weight of the tank, a lightweight material may be used. For example, if the conventional material is Al, the use of a composite material such as a metal (for example, an Al-Li alloy) lighter than the conventional material or a fiber-reinforced resin as described in Patent Document 1 can be considered. Usually, when the material of the tank required to have pressure resistance is a composite material, a liner for 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, the use of a tank without a liner is also conceivable. Patent Document 2 discloses a method of 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.

JP 2002-36235 A JP 2007-268929 A

  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 leakage in Table 1 are findings obtained from existing literature and past in-house researches and the like.

  Al-Li alloys and fiber reinforced resins (e.g. carbon fiber reinforced resin (CFRP)) are lightweight but generally more expensive than Al. Therefore, the use of a lighter material than in the past increases the manufacturing cost.

  The liner material applied to the composite generally has a different coefficient of thermal expansion than the composite. For example, when a resin liner is applied to the inside of a tank made of a carbon fiber reinforced resin, there is a concern that the carbon fiber reinforced resin and the resin liner may peel off due to the difference in thermal expansion in cryogenic applications.

  In a tank containing liquid hydrogen or the like, strain is loaded on the tank wall by the gas pressure in the tank, or the inner wall of the tank is exposed to a cryogenic environment by contact with liquid hydrogen or the like. In such a case, micro cracks (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 micro cracks.

  Conventionally, the liner provided on the inside of the tank can prevent the gas from leaking. However, in the case of a linerless tank as in Patent Document 2, there is a concern that the gas can not be prevented. The septic tank and reservoir tank manufactured in Patent Document 2 are not pressure vessels and do not mention the evaluation for gas leakage. Therefore, the linerless tank described in Patent Document 2 can not simply be adopted as a tank for containing liquid hydrogen and the like.

  According to Table 1, gas leakage occurs in CFRP (no liner). The laminated configuration of CFRP in Table 1 is the same as the comparative example described later.

  The present invention has been made in view of such circumstances, and is applicable to a tank in which at least one of pressure resistance and heat resistance to extremely low temperatures is required, and is lighter than in the prior art, and The purpose is to provide technology that can reduce gas leakage.

  In order to solve the said subject, the laminated structure of this invention and its manufacturing method employ | adopt the following means.

  The present invention is a laminated structure in which a composite material including reinforcing fibers and a matrix resin is laminated, and is provided with a lower outer layer formed of a first composite material, an inner layer formed of a second composite material, An upper outer layer formed of a composite material, wherein the inner layer is disposed 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 producing a laminated structure in which a composite material containing reinforcing fibers and a matrix resin is laminated, which is a pre-lower outer layer formed of a first prepreg, and a second thinner than the first prepreg. After laminating the pre inner layer composed of the prepreg and the upper pre outer layer composed of the first prepreg in order, heat and pressure are applied to cure the matrix resin to provide a method for producing a laminated structure as a molded article Do. Here, "pre" means that the matrix resin is in a state before being cured.

  As a result of earnest research, the present inventors can maintain the gas barrier properties of the laminated structure for a longer time than in the prior art by forming a laminated structure in which composite materials having different thicknesses are incorporated in the middle of the thickness of the laminated structure. The findings of the

  According to the above invention, the inner layer is provided between the lower outer layer and the upper outer layer, and the inner layer is formed of the second composite material thinner than the first composite material constituting the outer layer, whereby gas leaks more than in the prior art. You can extend the time it takes to As a result, an increase in the amount of gas leakage with the passage of time is suppressed.

  If the thickness of the molded article is the same, the thinner the composite material, the more the number of laminations. The increase in the number of laminations is preferably minimized because it leads to an increase in material costs and operation costs. The laminated structure according to the above invention does not consist entirely of the second composite material, but is a laminate in which the lower outer layer and the upper outer layer composed of the first composite material thicker than the second composite material sandwich the inner layer. Configure By combining the first composite material and the second composite material having different thicknesses, necessary gas barrier properties can be ensured while suppressing the total number of laminated composite materials. The first composite of the upper outer layer and the lower outer layer may have the same thickness as the conventionally used composite.

  In one aspect of the above invention, the inner layer is a configuration in which a plurality of the second composites are laminated, and the second composite is a unidirectional composite in which the reinforcing fibers are oriented in any one direction. Preferably, in the inner layer, the fiber orientations of adjacent second composites are different.

  In the adjacent second composites, microcracks occur independently of one another. If the fiber orientation is different, the direction in which micro cracks are likely to occur also changes. If the directions of the micro cracks generated in the adjacent second composite materials are different, the area in which the micro cracks overlap with each other is reduced. As a result, the cross section of the gas leakage path in the thickness direction of the inner layer is reduced, and the amount of gas leakage in a fixed time is reduced. Therefore, in order to take advantage of the merit obtained by making the second composite thinner than the first composite, it is better to make the second composites of 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 of the lower outer layer and the upper composite layer of the upper outer layer Preferably, in the first composite, the fiber orientation is arranged in mirror symmetry with the inner layer as a center.

  By making the inner layer at the center in the thickness direction of the laminated structure a mirror surface, and by making it a quasi-isotropic lamination in which the fiber orientation of the lower outer layer and the fiber orientation of the upper outer layer are symmetrical, It can be suppressed.

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

  In the conventional laminated structure design, 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 the lower outer layer / inner layer / upper outer layer in the thickness direction, and the second composite material constituting the inner layer at the center of the thickness is the first 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 the inner layer. Assuming that the thickness of the second composite is 1/2 n of the first composite (n is a natural number), the thickness of the second composite can be changed without changing the thickness if the first composite of one layer is replaced with the second composite of 2n layers. The laminated structure of the above invention can be easily made.

  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 intensive studies, the present inventors have found that the second composite material has an appropriate thickness for obtaining an optimal gas barrier property. By setting the thickness of the second composite material in the above-described range, it is possible to suppress the amount of gas leakage low while minimizing the number of laminated layers of the second composite material.

  According to the present invention, by providing the 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 with no liner can be obtained.

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-test object of Examples 1-3 and a comparative example. It is the schematic of the test apparatus used for the gas leak amount confirmation test. It is a test flow figure of a gas leak check. It is a figure which shows the result of gas leak amount measurement. It is a schematic diagram of the micro crack which generate | occur | produced in arbitrary 1st composite materials. It is a schematic diagram of the micro crack which generate | occur | produced in the adjacent 2nd composite material. It is a schematic diagram of the leak path at the time of laminating | stacking four layers of 1st composite materials. It is a schematic diagram of the leakage path at the time of laminating | stacking 8 layers of 2nd composite materials.

  The laminated structure according to the present embodiment can be applied to cryogenic tanks, pressure tanks, and the like. The cryogenic tank and the pressure-resistant tank are, for example, a fuel tank for a space shuttle, which contains liquid hydrogen, and the like. "Cryogenic temperature" is -200 degreeC or more and -189 degrees C or less. 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 a 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 order. The inner layer 3 is disposed so as to be sandwiched between the lower outer layer 2 and the upper outer layer 4. Here, “upper side” is one surface side of the inner layer 3, and “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 laminated layers of the first composite material 5 constituting the lower outer layer 2 and the first composite material 6 constituting the upper outer layer 4 is equal. In FIG. 1, the lower outer layer 2 and the upper outer layer 4 each have a three-layer configuration in which three first composite materials 5 and 6 are stacked.

  The first composites 5 and 6 are composed of reinforcing fibers and a matrix resin. Reinforcing fibers are carbon fibers. An epoxy resin etc. can be used for matrix resin. In the first composites 5 and 6, the matrix resin is present after being completely or almost completely cured.

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

  The first composites 5 and 6 may contain a curing agent, a curing accelerator, and the like. The curing agent and the curing accelerator may be any one that accelerates the curing of the matrix resin.

  The thickness of the first composites 5 and 6 may be appropriately set according to the applied product. The thickness of the first composite material suitable for the technical field of aerospace vehicles is 100 μm or more and 200 μm or less.

  The first composites 5 and 6 are unidirectional composites in which reinforcing fibers are oriented in any direction. In FIG. 1, a layer comprising the first composite material in which the reinforcing fibers are mainly oriented at 0 °, a layer comprising the first composite material in which the reinforcing fibers are mainly oriented at 45 °, and the reinforcing fibers are mainly -45 ° A layer of the first composite material oriented in.

  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 with symmetrical fiber orientations with the thickness center (inner layer) of the laminated structure as a mirror surface. Is preferred. By making the laminated structure of the lower outer layer 2 and the upper outer layer 4 pseudo-isotropic lamination, it is possible to suppress the generation of residual stress in a molded article.

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

  The second composite 7 is composed of reinforcing fibers and a matrix resin. The second composite 7 is similar to the first composites 5 and 6 with respect to elements other than thickness. The thickness of the second composite 7 is preferably 1/2 n (n is a natural number not including 0) of the thickness of the first composites 5 and 6. The thickness of the second composite material 7 is 25 μm to 100 μm, preferably 50 μm to 100 μm.

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

  In the inner layer 3, the second composite material 7 is stacked in a number of layers capable of maintaining dynamic symmetry with respect to the center m of the plate thickness of the laminated structure. The number of laminated layers of the second composite material 7 may be an even unit. In that case, the minimum number of laminated layers of the second composite material 7 is four.

  “The 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 7 contained in each section is between two sections Mean equal or nearly equal.

  For example, when the inner layer 3 having a laminated configuration of 90 ° / 45 ° / 0 ° / -45 ° / 45 ° / 0 ° / -45 ° / 90 ° is divided into two at the center m of the plate thickness, each section “90 ° / 45 ° / 0 ° / −45 °” and “45 ° / 0 ° / −45 ° / 90 °”. The two sections contain the second composite 7 at 0 °, ± 45 °, and 90 °. The 0 ° and 90 ° second composites 7 are arranged with mirror orientation of fiber orientation at the center m of the plate thickness. The layers (45 ° and -45 °) that are in symmetrical positions but do not match the fiber orientation between the two compartments are in a 90 ° different fiber orientation relationship. In the case where the fiber orientations of the layers whose fiber orientations do not match differ between the two sections by 90 °, in the present embodiment, the total fiber orientation balance is substantially equal. When the layers having the same fiber direction are adjacent to each other, the effect of making the second composite 7 thinner than the first composites 5 and 6 is lost. In the laminated configuration, the fiber directions of adjacent layers are arranged to be different.

  For example, in the case where the inner layer 3 having the laminated configuration of the second composite 7 of 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 the two compartments, the total fiber orientation contained in each compartment is not completely coincident, but the layers (45 ° and -45 °) which are not coincident between the two compartments have a 90 ° difference in fiber orientation. . The 90 ° second composite material 7 has the fiber orientation mirror-symmetrically arranged at the center m of the plate thickness. Therefore, in the laminated configuration, the total fiber orientation balance becomes substantially even.

  Below, the manufacturing method of the laminated structure 1 which concerns on this embodiment is demonstrated.

  In the manufacturing method according to the present embodiment, the pre-lower outer layer formed of the first prepreg, the pre-inner layer formed of the second prepreg thinner than the first prepreg, and the pre-upper outer layer formed of the first prepreg are sequentially laminated After heating, pressure is applied to cure the matrix resin to form a molded article (laminated structure 1).

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

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

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

  The pre-lower outer layer / pre inner layer / pre upper outer layer are heat-pressed to cure the matrix resin. Thereby, the laminated structure 1 provided with lower side outer layer 2 / inner layer 3 / upper side outer layer 4 is obtained.

  A "prepreg" is an intermediate material of a composite material. The “prepreg” is a sheet obtained by impregnating a reinforcing material composed of long fibers (continuous fibers) such as reinforcing fibers with a matrix resin. In "prepreg", the matrix resin is in a semi-cured state. A composite material is obtained by further curing the matrix resin of "prepreg". What completely or almost completely cured the matrix resin of the first prepreg and the second prepreg becomes the first composites 5 and 6 and the second composite 7. In the present specification, “hardening” means that the matrix resin is brought into a state of being further cured from the semi-cured state of the prepreg.

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

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

  The heating and pressing can be performed by the existing method.

<Gas leakage check test>
The confirmation test of the amount of gas leakage was implemented using the laminated structure (Examples 1-3) of a structure which concerns on the said embodiment, and the laminated structure (comparative example) of the conventional structure.

(Production of the specimen)
The prepreg used was manufactured by Fukui Industrial Technology Center S セ ン タ ー ren. The reinforcing fiber was carbon fiber (T800SC-24000-10E). The matrix resin was a general epoxy resin (jER 828 + jER 1001 / hardening agent: DICY15, hardening accelerator: DCMU 99).

An outline of the used prepreg is shown in Table 2.

In Table 3, the outline of the laminated constitution of the pre-test object of Examples 1-3 and a comparative example is shown. The total thickness of each pre-specimen was assumed to be the same.

  FIG. 2 shows the laminated structure of the pre-samples in which the fiber orientation is displayed. In Examples 1 to 3, prepregs of different fiber orientations were adjacent to one another so that the stacking angles do not overlap. In the comparative example, in accordance with the conventional design, the prepreg is pseudo-isotropically laminated so that the fiber orientation is mirror-symmetrical at the center of the thickness of the pre-test specimen.

  As shown in Table 3 and FIG. 2, the prepregs were laminated by hand lay-up method to prepare a pre-test specimen. The pre-test specimen was heated and pressurized (130 ° C., 0.5 MPa, 2 Hrs) with an autoclave, and the matrix resin was cured to prepare a specimen.

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

(S1) He leakage measurement -1
First, the sealing jig 12 provided with the air supply pipe 10 and the intake pipe 11 was installed at the central portion of the sample 13. The He leak detector 15 (stock, which is pressurized (0.49 MPa) with He gas from the air supply pipe 10 connected to the He gas cylinder 14 at normal temperature (25 ° C.) and no distortion applied, and has a suction function The amount of He (He leaked amount) which was aspirated by an intake pipe 11 connected to the company ULVAC, Inc., and passed through the specimen 13 was measured.

(S2) He leakage measurement-2
Next, both ends of the specimen 13 were held by the chuck 16 and the amount of He (He leakage) transmitted through the specimen was measured in a state (room temperature: 25 ° C.) to which strain of 4500 μ was applied by a tensile load.

(S3) Cryogenic strain load Subsequently, the specimen was immersed in liquid nitrogen (LN ₂ ) and held for 30 minutes in a state of being given a strain of 4500 μ.

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

The results of the above tests are described below.
In the above (S1) and (S2), the amount of gas leakage from the specimen was below the detection limit (background noise level: 1 × 10 ⁻⁹ Ncm ³ / cm ² / s). This confirmed that the specimen had no initial failure.

FIG. 5 shows the result of (S4) He leakage measurement-3. In the figure, the vertical axis is the amount of gas leakage (cc / cm ² / sec). In the same figure, the measurement result of the amount of gas leakage 10 minutes and 60 minutes after the pressurization start with He gas is shown about Example 1-3 and a comparative example.

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

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

  The reason why the amount of gas leakage can be reduced will be described with reference to FIGS.

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

  FIG. 8 is a schematic view of a leak path when four layers of the first composite material 25 are stacked. 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 the first composite material 25 are stacked. The arrows in FIGS. 8 and 9 are leak paths, and it is assumed that micro cracks (arrows in the thickness direction) occur in all the composites.

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

  On the other hand, when the second composite material 27 thinner than the first composite material 25 is laminated in two layers, micro cracks Y and Z are generated separately in each layer as shown in FIG. Since the adjacent two layers of the second composite material 27 do not have overlapping fiber orientations, the micro cracks Y and Z face in different directions. As shown in FIG. 7, the micro cracks Y and the micro cracks Z are communicated only at the intersection of the two. That is, since only the connection portion S between the micro crack Y and the micro crack Z is the leak path P, the leak path cross-sectional area is reduced.

  When the combined thickness of the second composite material 27 of the two layers is the same as the thickness of the first composite material 25, the crack area (leakage cross-sectional area) per unit thickness in FIG. It becomes smaller. If the crack area penetrated is reduced, the amount of gas passing therethrough is limited. As a result, the time required for gas leakage becomes longer than that in FIG.

  Further, it is considered that the gas moves along the boundary between the adjacent composites in the portion where the micro cracks Y and Z are not in direct communication (see the arrow in the plane direction of 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 layers of the composite material increases.

  As described above, in Examples 1 to 3, by disposing Thin or Ultra-Thin between Nominal, the amount of flowing gas is restricted more than in Comparative Example, and the leakage path becomes longer, and as a result, it is accompanied by the passage of time. It is considered that the increase in the amount of gas leakage can be suppressed. If the fiber orientations of adjacent composites are the same, the direction of the microcracks will be the same between adjacent composites. In order to reduce the crack area at a certain thickness and to develop the gas barrier property, it is preferable that adjacent composite materials be configured so that the same lamination angle does not overlap.

  Next, Examples 1 and 2 to which Thin is applied are compared with Example 3 to which Ultra-Thin is applied. Although the number of laminated layers of the composite material in Example 3 is larger than that in Examples 1 and 2, the gas leakage amount in 60 minutes was higher than that in Examples 1 and 2.

  The matrix resin in the composite has gas barrier properties, but can not completely block the permeation of gas. The Ultra-Thin of Example 3 is considered to have reduced gas barrier properties because the layer of the matrix resin contributing to the gas barrier properties is thinner than Thin.

  From this result, it was suggested that there is a suitable second composite (second prepreg) thickness for obtaining the optimum gas barrier properties. 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 4 layers of Thin are laminated and Example 2 in which 8 layers of Thin are laminated are compared. Although the number of laminated layers of the composite material in Example 1 was smaller than that in Example 2, the gas leakage amount in 60 minutes was lower than that in Example 2. From these results, it was suggested that sufficient gas barrier properties can be obtained even when thin is applied by the minimum number of laminations capable of maintaining mechanical symmetry.

1 laminated structure 2 lower outer layer 3 inner layer 4 upper outer layer 5, 6, 25 first composite material (first prepreg after curing of matrix resin)
7, 27 Second composite material (second prepreg after curing of matrix resin)
DESCRIPTION OF SYMBOLS 10 Air supply pipe 11 Intake pipe 12 Sealing jig 13 Test object 14 He gas cylinder 15 He detector measurement apparatus 16 Chuck

Claims (6)

A laminated structure in which a composite containing reinforcing fibers and a matrix resin is laminated,
A lower outer layer formed of the first composite material, an inner layer formed of the second composite material, and an upper outer layer formed of the first composite material,
The inner layer is disposed to be sandwiched between the lower outer layer and the upper outer layer,
The second composite material is a laminated structure thinner than the first composite material. The inner layer has a configuration in which a plurality of the second composite materials are stacked,
The second composite material is a unidirectional composite material in which the reinforcing fibers are oriented in any direction,
The laminated structure according to claim 1, wherein in the inner layer, the fiber orientations of adjacent second composites are different. The first composite material is a unidirectional composite material in which the reinforcing fibers are oriented in any direction,
The laminated structure according to claim 1 or 2, wherein fiber orientations of the first composite of the lower outer layer and the first composite of the upper outer layer are arranged in mirror symmetry with respect to the inner layer. .   The laminated structure according to any one of claims 1 to 3, wherein the thickness of the second composite material is 1/2 n (n is a natural number not including 0) of the thickness of the first composite material.   The thickness of the said 2nd composite material is 50 micrometers or more and 100 micrometers or less, The laminated structure in any one of the Claims 1-4. A method for producing a laminated structure in which a composite material containing reinforcing fibers and a matrix resin is laminated,
Heat and pressure are applied after sequentially laminating 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. A method for producing a laminated structure, wherein the matrix resin is cured to form a molded article.

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