High pressure tank and its manufacturing method

Abstract

To provide a technology which enables an inner FRP layer and an outer FRP layer to be joined securely.SOLUTION: A technology disclosed by the specification is realized by a high pressure tank having a shape in which both ends of a cylindrical part for storing high pressure fluid have dome parts. The high pressure tank includes: an inner FRP layer formed of a fiber reinforcement material; an outer FRP layer located at an outer side of the inner FRP layer and formed of a fiber reinforcement material; and an adhesion layer provided between the inner FRP layer and the outer FRP layer in at least the cylindrical part. The adhesion layer has: an inner adhesion layer which contacts with the inner FRP layer; an outer adhesion layer which contacts with the outer FRP layer; and a barrier layer located between the inner adhesion layer and the outer adhesion layer and having a barrier property higher than those of the inner FRP layer and the outer FRP layer.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a high-pressure tank for storing a high-pressure fluid and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses a high-pressure tank having a cylindrical portion with dome portions on both ends. The high-pressure tank includes an inner FRP layer (referred to as a reinforcing body in Patent Document 1) made of fiber reinforced resin, and an outer FRP layer (referred to as a further reinforcing layer in Patent Document 1) made of fiber reinforced resin and positioned outside the inner FRP layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-119034 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a high-pressure fluid is filled in a high-pressure tank or when a high-pressure fluid is discharged from the high-pressure tank, the internal pressure of the high-pressure tank changes significantly. When the internal pressure of the high-pressure tank changes significantly, the high-pressure tank is deformed. In particular, the cylindrical part of the high-pressure tank having a planar shape is more likely to deform when the high-pressure fluid is filled or discharged than the dome part that is curved in a dome shape. In the high-pressure tank of Patent Document 1, the movement of the fibers of the outer FRP layer is restrained by the adhesive force of the resin of the inner FRP layer. In a high-pressure tank having such a configuration, if the high-pressure tank is deformed when the high-pressure fluid is filled or discharged, the inner FRP layer and the outer FRP layer may be displaced in the cylindrical part. This specification discloses a technology that can firmly bond the inner FRP layer and the outer FRP layer in the cylindrical part. [Means for solving the problem]

[0005] The technology disclosed in this specification is embodied in a high-pressure tank having a shape with dome portions at both ends of a cylindrical portion for storing a high-pressure fluid. The high-pressure tank includes an inner FRP layer made of a fiber-reinforced material, an outer FRP layer located outside the inner FRP layer and made of a fiber-reinforced material, and an adhesive layer provided between the inner FRP layer and the outer FRP layer at least in the cylindrical portion. The adhesive layer includes an inner adhesive layer in contact with the inner FRP layer, an outer adhesive layer in contact with the outer FRP layer, and a barrier layer located between the inner adhesive layer and the outer adhesive layer and having a higher barrier property than the inner FRP layer and the outer FRP layer.

[0006] According to the above-mentioned high pressure tank, at least in the cylindrical portion, the adhesive layer provided between the inner FRP layer and the outer FRP layer firmly bonds the inner FRP layer and the outer FRP layer. This makes it possible to prevent the inner FRP layer and the outer FRP layer from being displaced when the cylindrical portion is deformed due to a change in the internal pressure of the high pressure tank. Furthermore, the adhesive layer is located between the inner adhesive layer in contact with the inner FRP layer and the outer adhesive layer in contact with the outer FRP layer, and has a barrier layer with higher barrier properties than the inner FRP layer and the outer FRP layer. Therefore, for example, there is no need to provide a barrier layer other than the adhesive layer inside the inner FRP layer. The high pressure tank disclosed in this specification can simplify its manufacturing process.

[0007] Furthermore, this specification also discloses a method for manufacturing a high-pressure tank having a shape with dome portions at both ends of a cylindrical portion for storing a high-pressure fluid. The high-pressure tank includes an inner FRP layer made of a fiber-reinforced material, an outer FRP layer located outside the inner FRP layer and made of the fiber-reinforced material, and an adhesive layer provided between the inner FRP layer and the outer FRP layer at least in the cylindrical portion. The adhesive layer includes an inner adhesive layer in contact with the inner FRP layer, an outer adhesive layer in contact with the outer FRP layer, and a barrier layer located between the inner adhesive layer and the outer adhesive layer and having a higher barrier property than the inner FRP layer and the outer FRP layer. The inner FRP layer includes a first inner FRP layer located in the cylindrical portion and a second inner FRP layer located in the dome portion. The fiber material of the fiber-reinforced material is not continuous between the first inner FRP layer and the second inner FRP layer. The manufacturing method includes a first forming step of forming the first inner FRP layer from the fiber reinforced material, a second forming step of forming the second inner FRP layer from the fiber reinforced material, a joining step of joining the formed first inner FRP layer and the second inner FRP layer, an adhesive layer forming step of providing the adhesive layer on at least the outside of the first inner FRP layer before or after the joining step, and a third forming step of forming the outer FRP layer from the fiber reinforced material on the outside of the joined first inner FRP layer and second inner FRP layer.

[0008] According to the above-mentioned manufacturing method, in the adhesive layer forming step performed before or after the joining step, an adhesive layer is provided on the outside of at least the first inner FRP layer. The adhesive layer has a barrier layer. Therefore, compared to a configuration in which, for example, an inner FRP layer is provided on the outer peripheral surface of a barrier layer separate from the adhesive layer, and an adhesive layer is provided on the outside of the inner FRP layer, the barrier layer can be provided in the same step as the inner and outer adhesive layers, thereby simplifying the process.

[0009] Details and further improvements of the technology disclosed in this specification are described in the following "Forms for Carrying Out the Invention". [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view of a high-pressure tank 2 according to an embodiment of the present invention. [Diagram 2] 2 shows a cross-sectional view taken along line II-II in FIG. [Diagram 3] 3 shows a first forming step in the manufacturing method of the embodiment. [Figure 4] 4 shows a second forming step in the manufacturing method of the embodiment. [Diagram 5] 4 shows a bonding step in the manufacturing method according to the embodiment. [Figure 6] 4 shows an adhesive layer forming step and a third forming step in the manufacturing method of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In one embodiment of the present technology, the inner FRP layer may have a first inner FRP layer located in the cylindrical portion and a second inner FRP layer located in the dome portion. In that case, the fiber material of the fiber reinforced material may not be continuous between the first inner FRP layer and the second inner FRP layer. According to such a configuration, the first inner FRP layer and the second inner FRP layer can be formed separately. Therefore, for example, a different amount of fiber reinforced material can be arranged for each FRP layer so that the fiber reinforced material of the second inner FRP layer is more than that of the first inner FRP layer. This allows an appropriate amount of fiber reinforced material to be arranged for each of the cylindrical portion and the dome portion. Furthermore, the first inner FRP layer and the second inner FRP layer of the inner FRP layer can be firmly connected by the outer FRP layer located outside the inner FRP layer.

[0012] In one embodiment of the present technology, a part of the adhesive layer may extend to the dome portion and be located between the second inner FRP layer and the outer FRP layer. With this configuration, the first inner FRP layer and the second inner FRP layer of the inner FRP layer can be firmly connected by the adhesive layer.

[0013] In one embodiment of the present technology, a part of the adhesive layer may extend to the dome portion and be located between the first inner FRP layer and the second inner FRP layer that overlap each other at the boundary between the cylindrical portion and the dome portion. With this configuration, the first inner FRP layer and the second inner FRP layer of the inner FRP layer can be firmly connected by the adhesive layer.

[0014] (Example) FIG. 1 shows a perspective view of a high-pressure tank 2 of an embodiment. The high-pressure tank 2 is mounted on, for example, a fuel cell vehicle (not shown). The high-pressure tank 2 stores high-pressure hydrogen gas used by the fuel cell vehicle to generate power. In other words, the high-pressure tank 2 is a tank that stores high-pressure fluid. Note that the high-pressure fluid stored in the high-pressure tank 2 is not limited to hydrogen gas, and may be, for example, a high-pressure liquid.

[0015] The high-pressure tank 2 has a cylindrical portion 21 having a cylindrical shape extending along a central axis CL, and dome portions 22, 26 provided on both ends of the cylindrical portion 21. Hereinafter, the direction parallel to the central axis CL of the cylindrical portion 21 (i.e., the positive and negative directions of the Z axis in the coordinate system in the figure) will be referred to as the axial direction.

[0016] The high-pressure tank 2 includes an inner FRP (Fiber Reinforced Plastics) layer 4, an outer FRP layer 6, and a cap 8. Each of the FRP layers 4, 6 is formed by impregnating long carbon fiber filaments with a thermosetting resin (e.g., epoxy resin). That is, each of the FRP layers 4, 6 is formed of a fiber-reinforced resin. The outer FRP layer 6 is located outside the inner FRP layer 4 and covers the outer surface of the inner FRP layer 4. In a modified example, instead of the thermosetting resin, the long carbon fiber filaments may be impregnated with a thermoplastic resin.

[0017] The nozzle 8 is a boss made of metal, and is provided at one axial end of the dome portion 22 (i.e., the right end in FIG. 1). The nozzle 8 has a through hole that communicates between the inside and outside of the high-pressure tank 2. Through the through hole of the nozzle 8, hydrogen gas in the high-pressure tank 2 is released to the outside, and hydrogen gas is supplied from the outside into the high-pressure tank 2.

[0018] The detailed structure of the high-pressure tank 2 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. The inner FRP layer 4 has a first inner FRP layer 41 and a second inner FRP layer 42. The first inner FRP layer 41 is located in the cylindrical portion 21 (see Fig. 1) of the high-pressure tank 2. The second inner FRP layer 42 is located in the dome portion 22 (see Fig. 1) of the high-pressure tank 2. As will be described in detail later, the inner FRP layers 41, 42 are formed in separate filament winding processes. Therefore, the filaments (i.e., fiber materials) of the inner FRP layers 41, 42 are not continuous.

[0019] An axial end of the first inner FRP layer 41 is located inside (i.e., on the central axis CL side) of the second inner FRP layer 42. That is, in the axial direction, the first inner FRP layer 41 extends to the dome portion 22. In other words, at the boundary B1 between the cylindrical portion 21 and the dome portion 22 of the high-pressure tank 2, the inner FRP layers 41, 42 overlap each other.

[0020] The adhesive layer 10 is provided between the inner FRP layer 4 and the outer FRP layer 6 in the cylindrical portion 21 and part of the dome portion 22. The adhesive layer 10 bonds the inner FRP layer 4 and the outer FRP layer 6. The adhesive layer 10 is formed of a flat sheet.

[0021] As shown in the enlarged view of FIG. 2, the adhesive layer 10 has an inner adhesive layer 14, an outer adhesive layer 16, and a first barrier layer 15. The layers 14, 15, and 16 are laminated to form a sheet-like adhesive layer 10. In this embodiment, the inner adhesive layer 14 and the outer adhesive layer 16 are made of PP (polypropylene). The first barrier layer 15 in this embodiment is made of EVOH (ethylene-vinylalcohol copolymer). The first barrier layer 15 has higher gas barrier properties than the FRP layers 4 and 6. Therefore, the first barrier layer 15 prevents hydrogen gas in the high-pressure tank 2 from leaking to the outside.

[0022] In this way, in the high-pressure tank 2 of this embodiment, the adhesive layer 10 firmly bonds the inner FRP layer 4 and the outer FRP layer 6 in a part of the cylindrical portion 21 and the dome portion 22. This makes it possible to prevent the inner FRP layer 4 and the outer FRP layer 6 from shifting from each other when the cylindrical portion 21 is deformed due to a change in the internal pressure of the high-pressure tank 2. Furthermore, as described above, the adhesive layer 10 includes the first barrier layer 15. Therefore, the high-pressure tank 2 does not need to include another barrier layer located inside the inner FRP layer 4, such as a conventional liner. Therefore, the high-pressure tank 2 of this embodiment can simplify the manufacturing process compared to the conventional process of forming another barrier layer such as a liner and wrapping the inner FRP layer 4 around the outer periphery of the liner.

[0023] Here, the required shape rigidity may differ between the cylindrical portion 21 and the dome portion 22 of the high-pressure tank 2. For example, compared to the cylindrical portion 21, the dome portion 22 located around the nozzle 8 is more likely to be subjected to a large axial load when releasing and filling hydrogen gas. In addition, since the cylindrical portion 21 is formed with a flat surface, it is easy to wind filaments evenly around the entire outer circumferential surface of the cylindrical portion 21 without the filaments overlapping each other. In contrast, since the dome portion 22 is formed with a curved surface, the filaments are more likely to overlap each other when wound around the entire surface of the dome portion 22.

[0024] Here, for example, a comparative example is assumed in which the first inner FRP layer 41 and the second inner FRP layer 42 are integrally formed by filament winding. In this comparative example, when a necessary amount of filaments is wound around the entire surface of the second inner FRP layer 42 forming the dome portion 22 while overlapping the filaments, the filaments wound around the first inner FRP layer 41 forming the cylindrical portion 21 also overlap. As a result, in this comparative example, the amount of filaments arranged in the first inner FRP layer 41 may increase more than necessary. In the high pressure tank 2 of this embodiment, as described above, each of the inner FRP layers 41, 42 is formed by a separate filament winding process. Therefore, the amount of carbon fiber filaments in each of the inner FRP layers 41, 42 can be set separately. As in the comparative example, the amount of filaments in the first inner FRP layer 41 forming the cylindrical portion 21 does not increase due to the filaments being wound around the entire surface of the second inner FRP layer 42 forming the dome portion 22. An appropriate amount of filaments can be wound around each of the inner FRP layers 41, 42.

[0025] Furthermore, the outer FRP layer 6 has carbon fiber filaments wound around the cylindrical portion 21 and the dome portion 22. Therefore, in the high-pressure tank 2, the outer FRP layer 6 can firmly connect the first inner FRP layer 41 and the second inner FRP layer 42, which are formed separately.

[0026] A second barrier layer 44 is provided on the inner side of the second inner FRP layer 42. The second barrier layer 44 is also made of an EVOH sheet, similar to the first barrier layer 15. In a modified example, the second barrier layer 44 may be formed by applying polyethylene to the inner side of the second inner FRP layer 42, for example.

[0027] An axial end of the adhesive layer 10 extends beyond the boundary B1 and is located on the outer surface of the second inner FRP layer 42. That is, a portion of the adhesive layer 10 extends to the dome portion 22 of the high-pressure tank 2. As a result, the adhesive layer 10 bonds the first inner FRP layer 41 and the second inner FRP layer 42. This makes it possible to firmly connect the first inner FRP layer 41 and the second inner FRP layer 42, which are separate bodies.

[0028] Next, a method for manufacturing the high-pressure tank 2 will be described with reference to Figs. 3 to 6. First, a first forming step will be described with reference to Fig. 3. In the first forming step, a filament F1 is wound around an outer peripheral surface of a cylindrical first mandrel M1 by so-called hoop winding of a filament winding method. As shown in the left diagram of Fig. 3, in the first forming step, the nozzle N1 moves back and forth along a direction G1 parallel to the axial direction while the first mandrel M1 is rotated in a rotation direction R1 about a central axis CL. As a result, the filament F1 is wound around the outer peripheral surface of the first mandrel M1. The nozzle N1 repeatedly moves back and forth in the direction G1, so that the filament F1 is laminated in multiple layers around the outer peripheral surface of the first mandrel M1.

[0029] After being wound around the outer circumferential surface of the first mandrel M1, the filament F1 is heated. The heat causes the thermosetting resin impregnated in the filament F1 to harden. The first mandrel M1 is then removed from the hardened filament F1. As a result, the first inner FRP layer 41 is formed, as shown in the right diagram of FIG.

[0030] The second forming step will be described with reference to FIG. 4. In the second forming step, the filament F2 is wound around the outer peripheral surface of the second mandrel M2 by so-called helical winding of the filament winding method. The second mandrel M2 has an elliptical shape in a side view. Both axial ends of the second mandrel M2 are curved into a dome shape. A nozzle 8 is fixed to one axial end of the second mandrel M2.

[0031] As shown in the left diagram of FIG. 4, in the second forming step, the nozzle N1 moves in a direction G2 inclined at an angle θ2 with respect to the central axis CL while rotating the second mandrel M2 in a rotation direction R2 about the central axis CL. As a result, the filament F2 is wound around the outer peripheral surface of the second mandrel M2, which is curved into a dome shape. Here, the angle θ2 is set according to the shape of the curved surface of the second mandrel M2, the diameter of the filament F2, and the like. As the nozzle N2 repeatedly moves back and forth in the direction G2, the filament F2 is laminated in multiple layers on the outer peripheral surface of the second mandrel M2.

[0032] After the filament F2 is wound around the outer circumferential surface of the second mandrel M2, the filament F2 is heated to harden the thermosetting resin impregnated in the filament F2. The hardened filament F2 is then cut along the cut line C1. The cut filament F2 is removed from the second mandrel M2. At this time, the nozzle 8 is also removed from the second mandrel M2 together with the filament F2. As a result, the second inner FRP layers 42, 46 curved in a dome shape are formed, as shown in the right diagram of FIG. 4. Then, sheet-like second barrier layers 44, 48 are attached to the inner circumferential surfaces of the formed second inner FRP layers 42, 46, respectively.

[0033] The joining step will be described with reference to Fig. 5. In the joining step, the second inner FRP layers 42, 46 are assembled to both ends of the first inner FRP layer 41 in the direction J1. At this time, as shown in the enlarged view at the top of Fig. 5, the second inner FRP layer 42 is disposed so as to cover the outer peripheral surface of the first inner FRP layer 41. In other words, in the joining step, the first inner FRP layer 41 is inserted into the second inner FRP layer 42. As a result, the first inner FRP layer 41 overlaps the second inner FRP layer 42 at the ends of the first inner FRP layer 41.

[0034] The adhesive layer forming step and the third forming step will be described with reference to Fig. 6. In the adhesive layer forming step, a sheet-like adhesive layer 10 is wrapped around the outer peripheral surfaces of the first inner FRP layer 41 and the second inner FRP layer 42, 46 assembled in the joining step. As described with reference to Fig. 2, the adhesive layer 10 has an inner adhesive layer 14, an outer adhesive layer 16, and a first barrier layer 15.

[0035] Next, in the third forming step, the filament F3 is wound around the outer circumferential surfaces of the first inner FRP layer 41, the second inner FRP layer 42, 46, and the adhesive layer 10 (hereinafter referred to as the bonded body) by hoop winding and helical winding of the filament winding method. In the helical winding of the third forming step, the nozzle N3 moves in a direction G3 inclined by a predetermined angle θ3 with respect to the central axis CL while rotating the bonded body in a rotation direction R3 about the central axis CL. Here, the angle θ3 is set according to the shape of the bonded body, the diameter of the filament F3, and the like. In a modified example, the filament F3 may be wound around the outer circumferential surface of the bonded body by only helical winding in the third forming step.

[0036] After being wound around the outer circumferential surface of the joined body in the third forming process, the filament F3 is heated. The heating hardens the thermosetting resin impregnated in the filament F3. In this way, the high-pressure tank 2 (see FIG. 1) is manufactured.

[0037] Furthermore, since the adhesive layer 10 is provided between the inner FRP layer 4 and the outer FRP layer 6 in the cylindrical portion 21 and in parts of the dome portions 22, 26, the FRP layers 4, 6 are firmly fixed, particularly in the cylindrical portion 21. Although the adhesive layer 10 is only partially provided in the dome portions 22, 26, the dome portions 22, 26 have a curved shape and are more rigid than the cylindrical portion 21. Therefore, even if the internal pressure of the high-pressure tank 2 changes, the dome portions 22, 26 are less likely to deform than the cylindrical portion 21. Therefore, the range of the adhesive layer 10 can be made smaller in the dome portions 22, 26 than in the cylindrical portion 21. This allows the size of the adhesive layer 10 to be made smaller.

[0038] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Modifications of the above embodiments are listed below.

[0039] (Variation 1) The adhesive layer forming step may be performed before the joining step. In this case, a part of the adhesive layer 10 may be located between the first inner FRP layer 41 and the second inner FRP layer 42 that overlap each other at the boundary B1 between the cylindrical portion 21 and the dome portion 22. With this configuration, the second barrier layer 44 is fixed to the outer adhesive layer 16, so that the first inner FRP layer 41 and the second inner FRP layer 42 can be firmly connected to each other.

[0040] (Modification 2) The inner adhesive layer 14 and the outer adhesive layer 16 may be made of an epoxy resin instead of PP. In a further modification, the inner adhesive layer 14 and the outer adhesive layer 16 may be made of polyimide or thermoplastic polyester.

[0041] (Modification 3) Each of the barrier layers 15, 44, 48 may be made of a nylon sheet instead of an EVOH sheet. In a further modification, each of the barrier layers 15, 44, 48 may be made of a PET (PolyEthylene Terephthalate) sheet. Also, the second barrier layer 44 may be made of a sheet similar to the adhesive layer 10. That is, the second barrier layers 44, 48 may include an inner adhesive layer 14 and an outer adhesive layer 16. With this configuration, the adhesive layers 14, 16 of the second barrier layers 44, 48 can further firmly connect the first inner FRP layer 41 and the second inner FRP layer 42.

[0042] The technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0043] 2: High pressure tank 4: Inner FRP layer 6: Outer FRP layer 8: Cap 10: Adhesive layer 14: Inner adhesive layer 15: First barrier layer 16:Outer adhesive layer 21: Cylindrical part 22, 26: Dome section 41: First inner FRP layer 42: Second inner FRP layer 44, 48: Second barrier layer B1: Boundary C1: Cut line CL: Central axis F1~F3: Filament M1: First mandrel M2: Second mandrel N1~N3: Nozzle

Claims

1. A high-pressure tank having a cylindrical portion for storing a high-pressure fluid and a dome portion at each end thereof, An inner FRP layer made of a fiber reinforced material; an outer FRP layer located outside the inner FRP layer and made of the fiber reinforced material; an adhesive layer provided between the inner FRP layer and the outer FRP layer at least in the cylindrical portion; Equipped with The adhesive layer is an inner adhesive layer in contact with the inner FRP layer; an outer adhesive layer in contact with the outer FRP layer; a barrier layer located between the inner adhesive layer and the outer adhesive layer and having a higher barrier property than the inner FRP layer and the outer FRP layer; High pressure tank.

2. the inner FRP layer includes a first inner FRP layer located in the cylindrical portion and a second inner FRP layer located in the dome portion, 2. The high pressure tank according to claim 1, wherein the fiber material of the fiber reinforced material is not continuous between the first inner FRP layer and the second inner FRP layer.

3. 3. The high pressure tank according to claim 2, wherein a portion of the adhesive layer extends to the dome portion and is located between the second inner FRP layer and the outer FRP layer.

4. 3. The high-pressure tank according to claim 2, wherein a portion of the adhesive layer extends to the dome portion and is located between the first inner FRP layer and the second inner FRP layer that overlap each other at the boundary between the cylindrical portion and the dome portion.

5. A method for manufacturing a high-pressure tank having a cylindrical portion for storing a high-pressure fluid and a dome portion at each end thereof, comprising the steps of: The high pressure tank comprises: An inner FRP layer made of a fiber reinforced material; an outer FRP layer located outside the inner FRP layer and made of the fiber reinforced material; an adhesive layer provided between the inner FRP layer and the outer FRP layer at least in the cylindrical portion; Equipped with The adhesive layer is an inner adhesive layer in contact with the inner FRP layer; an outer adhesive layer in contact with the outer FRP layer; a barrier layer located between the inner adhesive layer and the outer adhesive layer and having a higher barrier property than the inner FRP layer and the outer FRP layer; the inner FRP layer includes a first inner FRP layer located in the cylindrical portion and a second inner FRP layer located in the dome portion, The fiber material of the fiber reinforced material is not continuous between the first inner FRP layer and the second inner FRP layer, The manufacturing method includes: a first forming step of forming the first inner FRP layer from the fiber reinforced material; a second forming step of forming the second inner FRP layer from the fiber reinforced material; a joining step of joining the formed first inner FRP layer and the formed second inner FRP layer; an adhesive layer forming step of providing the adhesive layer on at least the outer side of the first inner FRP layer before or after the joining step; a third forming step of forming the outer FRP layer out of the fiber reinforced material on an outer side of the joined first inner FRP layer and the second inner FRP layer; Equipped with Manufacturing method.

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