Fiber-reinforced resin hollow molded body and method for manufacturing the same

Abstract

The present invention provides a fiber-reinforced resin hollow molded body (30) using a resin-integrated fiber sheet, the resin-integrated fiber sheet containing unidirectional continuous fibers obtained by splitting a continuous fiber group and arranged side by side in one direction, and a thermoplastic resin present on at least the surface of the unidirectional continuous fibers. In the hollow molded body (30), the resin-integrated fiber sheet is wound in a state of being laminated in one or more sheets so as to form an overlapping portion, and the resin-integrated fiber sheet is integrated by impregnating the thermoplastic resin into the unidirectional continuous fibers.

Description

Technical Field

[0001] The present invention relates to a fiber-reinforced resin hollow molded body using a semi-impregnated material and a method for manufacturing the same. Background Art

[0002] Fiber-reinforced plastics obtained by compounding a reinforcing fiber material, i.e., carbon fiber, with various matrix resins can be widely used in various fields and applications. Moreover, in the aerospace and general industrial fields that require high mechanical properties and heat resistance, etc., unidirectional continuous fibers with a thermoplastic resin as the matrix resin are adopted. Conventionally, a prepreg in which a resin is completely impregnated into a carbon fiber matrix material has been used, suggesting the possibility of excellent impact resistance, short molding time, and reduced molding cost as a composite material. However, a prepreg with complete resin impregnation is difficult to perform circular processing due to its high hardness and lack of flexibility. Therefore, attention has been focused on a semi-impregnated material (semipreg) in which the resin is not impregnated into the reinforcing fiber matrix material. A semi-impregnated material is a matrix sheet of an unimpregnated material in a state where the matrix resin is attached and fused to the fiber matrix material or in a semi-impregnated state, and is soft and has excellent formability. In addition, it can be directly formed, and thus the forming efficiency is also excellent.

[0003] However, when forming a fiber-reinforced resin, it is necessary to impregnate a thermoplastic resin into the fiber matrix material. In the case of short fibers, it is necessary to process them into a non-woven fabric, and the efficiency is very poor. In addition, in the case of continuous fibers, the orientation may sometimes shift and become disordered, and defects such as pores and wrinkles may occur. Therefore, a more suitable semi-impregnated matrix material for direct forming has been constantly sought.

[0004] In Patent Document 1, a method for integrating a fiber-reinforced resin preform and a metal molded body by using an expandable core is proposed. In Patent Document 2, a method for manufacturing a golf shaft is proposed in which a long fiber-oriented prepreg sheet is wound around the outer periphery of a core with an internal pressure holding tube, and a short fiber two-dimensional random prepreg sheet is further wound around the vicinity of a nodal portion, and heating and pressing are performed by expanding the internal pressure holding tube in a mold. In Patent Document 3, a method for manufacturing a pipe in which a strip-shaped fiber-reinforced composite material containing a specific fluororesin and reinforcing fibers is wound around the outer periphery of a first layer is proposed. In Patent Document 4, a sheet-shaped forming matrix material is proposed as a forming matrix material for a pipe, which is obtained by overlapping a non-woven fabric formed of a thermoplastic resin on a sheet in which reinforcing fibers are bundled in one direction.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-172116

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2013 - 106782

[0009] Patent Document 3: WO2017 / 191735 Specification

[0010] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2011 - 62818 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, in the above - mentioned prior art, there are problems such as the raw material matrix material being hard or unable to be processed alone, and also difficulties in hollow forming processing.

[0013] In order to solve the above - mentioned prior problems, the present invention provides a fiber - reinforced resin hollow formed body that is thin and has excellent formability and a manufacturing method thereof by using a semi - impregnated material with good processability.

[0014] Means for Solving the Problems

[0015] The present invention relates to a fiber - reinforced resin hollow formed body using a resin - integrated fiber sheet. The resin - integrated fiber sheet contains unidirectional continuous fibers separated from a continuous fiber group and arranged side - by - side in one direction, and a thermoplastic resin existing on at least the surface of the unidirectional continuous fibers. The hollow formed body is a fiber - reinforced resin hollow formed body in which the resin - integrated fiber sheet is wound in a state of being laminated with one or more sheets to form an overlapping portion, and the resin - integrated fiber sheet is integrated by impregnating the thermoplastic resin into the unidirectional continuous fibers.

[0016] In the manufacturing method of the fiber - reinforced resin hollow formed body of the present invention, a resin - integrated fiber sheet containing unidirectional continuous fibers separated from a continuous fiber group and arranged side - by - side in one direction and a thermoplastic resin existing on at least the surface of the unidirectional continuous fibers is used. On the surface of an elastomer, the resin - integrated fiber sheet is wound in a state of being laminated with one or more sheets to form an overlapping portion. The elastomer wound with the resin - integrated fiber sheet is arranged in a heating mold having a hollow shape, and pressure fluid is supplied into the interior of the elastomer to perform pressure - assisted hollow forming, melting the thermoplastic resin, impregnating the thermoplastic resin into the unidirectional continuous fibers, and integrating the resin - integrated fiber sheet.

[0017] Advantages of the Invention

[0018] The fiber-reinforced resin hollow molded body of the present invention can provide a fiber-reinforced resin hollow molded body and a manufacturing method thereof that have good processability of a semi-impregnated material, are thin, and have excellent formability by using a resin-integrated fiber sheet containing unidirectional continuous fibers obtained by opening a continuous fiber group and arranged side by side in one direction and a thermoplastic resin present on at least the surface of the unidirectional continuous fibers. In addition, the manufacturing method of the hollow molded body of the present invention can obtain a high-quality hollow molded body in a short time due to a fast forming cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A is a schematic perspective view of a fiber-reinforced resin hollow molded body according to an embodiment of the present invention. Figure 1 B is a schematic cross-sectional view of the same figure.

[0020] Figure 2 It shows Figure 1 A schematic explanatory view of a method of laminating a resin-integrated carbon fiber sheet used in the formation of the fiber-reinforced resin hollow molded body.

[0021] Figure 3 A is a schematic perspective view of a core used in hollow molding. Figure 3 B is a schematic perspective view of the same figure when the resin-integrated carbon fiber sheet is wound around the core. Figure 3 C is Figure 3 A cross-sectional view of B.

[0022] Figure 4 A is a schematic top view showing a state where a core wound with a resin-integrated carbon fiber sheet is inserted into a forming die. Figure 4 B is Figure 4 A cross-sectional view taken along line I-I of A.

[0023] Figure 5 It is a schematic perspective view of a resin-integrated carbon fiber sheet used in the formation of a fiber-reinforced resin hollow molded body according to an embodiment of the present invention.

[0024] Figure 6 It is Figure 5 A schematic cross-sectional view in the width direction of the resin-integrated carbon fiber sheet shown.

[0025] Figure 7 It shows Figure 5 A schematic process diagram of a manufacturing method of the resin-integrated carbon fiber sheet shown.

[0026] Figure 8 It is a test force-displacement measurement coordinate diagram on the end portion and the central portion of the fiber-reinforced resin hollow molded body of Example 1.

[0027] Figure 9It is a test force-displacement measurement coordinate diagram on the end part and the central part of the fiber-reinforced resin hollow molded body of Example 2.

[0028] Symbol Explanation

[0029] 1 Resin-integrated carbon fiber sheet

[0030] 2 Unidirectional carbon fiber

[0031] 3, 3a, 3b Bridging fiber

[0032] 4 Resin

[0033] 5 Part where resin is not attached

[0034] 6 Fiber-opening device

[0035] 7 Supply bobbin

[0036] 8 Carbon fiber filament group (carbon fiber non-opened tow)

[0037] 9a, 9b Clamping roller

[0038] 12a - 12b Bridging roller

[0039] 13a - 13g Guide roller

[0040] 14, 17 Powder supply hopper

[0041] 15, 18 Dry powder resin

[0042] 16, 19 Heating device

[0043] 20 Winding roller

[0044] 21a - 21j Fiber-opening roller

[0045] 23 Roller fiber-opening process

[0046] 24 Bridging fiber generation process

[0047] 25 Powder resin application process

[0048] 30 Hollow molded body

[0049] 31 Fiber-reinforced resin part

[0050] 32 Overlap part of resin-integrated carbon fiber sheet

[0051] 33a, 33b Resin-integrated carbon fiber sheet

[0052] 34 Overlap part

[0053] 35 Core mold

[0054] 36 Fixture

[0055] 37 Resin-integrated carbon fiber sheet

[0056] 39 Lower mold

[0057] 40 Upper mold

[0058] 41 Air supply port Detailed implementation mode

[0059] The present invention is a fiber-reinforced resin hollow molded body using a resin-integrated fiber sheet (hereinafter, the fiber-reinforced resin hollow molded body may sometimes be simply referred to as "hollow molded body"). The resin-integrated fiber sheet contains unidirectional continuous fibers obtained by splitting a continuous fiber group and arranged side by side in one direction; and a thermoplastic resin present on at least the surface of the unidirectional continuous fibers. In the hollow molded body of the present invention, the resin-integrated fiber sheets are wound in a state of being laminated in one or more sheets so as to form an overlapping portion, and the resin-integrated fiber sheets are integrated by impregnating the thermoplastic resin into the fiber sheets. The resin-integrated fiber sheet used in the manufacture of the hollow molded body preferably contains bridging fibers in a direction intersecting with the unidirectional continuous fibers, and the thermoplastic resin integrates the unidirectional continuous fibers and the bridging fibers. The resin-integrated fiber sheet may also contain auxiliary filaments arranged in other directions on the unidirectional continuous fibers. The so-called auxiliary filaments are filaments that fixedly maintain the directionality of the fiber sheet. Examples of the auxiliary filaments include glass fibers, aromatic polyamide fibers, polyester fibers, nylon fibers, and vinylon fibers.

[0060] The main component of the fibers of the resin-integrated fiber sheet used in the present invention is unidirectional continuous fibers that have been split and arranged side by side in one direction, and are unidirectional long fibers. The auxiliary component of the fibers is preferably bridging fibers arranged in a direction intersecting with the unidirectional continuous fibers. Here, when the fibers contained in the resin-integrated fiber sheet are set to 100% by mass, the so-called main component is preferably 75 to 99% by mass, and the so-called auxiliary component is preferably 1 to 25% by mass. It is preferred that the thermoplastic resin adheres to the unidirectional continuous fibers and the bridging fibers in the form of powder, melts and fuses on at least the surface of the unidirectional continuous fibers, and integrates the unidirectional continuous fibers and the bridging fibers. Since the unidirectional continuous fibers and the bridging fibers are integrated by the thermoplastic resin that is melt-fused, the sheet has good processability and excellent operability during lamination (including lamination accompanied by winding) and forming.

[0061] The resin integrated fiber sheet is preferably a semi-impregnated material formed by attaching and heat-fusing a thermoplastic powder resin serving as a matrix on the surface of unidirectional continuous fibers. This semi-impregnated material is shaped so that the thermoplastic resin on the surface penetrates and diffuses equally within and between the resin integrated fiber sheets. Thereby, a hollow molded body with excellent formability (moldability) and no pores can be obtained.

[0062] When the total of the unidirectional continuous fibers and the bridging fibers is set to 100% by mass, the unidirectional continuous fibers are preferably 75 to 99% by mass, more preferably 80 to 97% by mass, and further preferably 85 to 97% by mass. In addition, the bridging fibers are preferably 1 to 25% by mass, more preferably 3 to 20% by mass, and further preferably 3 to 15% by mass. As long as the mass ratio is within the above range, a resin integrated fiber sheet with high integrity of unidirectional continuous fibers and high tensile strength in the width direction can be formed.

[0063] Preferably, the fiber volume (Vf) of the resin integrated fiber sheet is 20 to 65% by volume, and the thermoplastic resin is 35 to 80% by volume. More preferably, the fiber is 25 to 60% by volume, and the resin is 40 to 75% by volume. Thereby, the resin component of the resin integrated fiber sheet can directly become the matrix resin component of the hollow molded body. That is, when manufacturing a hollow molded body, it is not necessary to add a new resin. The mass per unit area of the resin integrated fiber sheet is preferably 10 to 3000 g / m 2 , more preferably 20 to 2000 g / m 2 , and further preferably 30 to 1000 g / m 2 .

[0064] The above fibers are preferably at least one selected from carbon fibers, glass fibers, and high elastic modulus fibers with an elastic modulus of 380 cN / dtex or more. As the above high elastic modulus fibers, for example, there are aromatic polyamide fibers, especially para-aramid fibers (elastic modulus: 380 to 980 cN / dtex), polyacrylate fibers (elastic modulus: 600 to 741 cN / dtex), heterocyclic polymer (PBO, elastic modulus: 1060 to 2200 cN / dtex) fibers, high molecular weight polyethylene fibers (elastic modulus: 883 to 1413 cN / dtex), polyvinyl alcohol fibers (PVA, strength: 14 to 18 cN / dtex), etc. (Fiber Encyclopedia Dictionary, page 522, March 25, 2002, Maruzen). These fibers are useful as resin reinforcing fibers. Carbon fibers are particularly useful.

[0065] The thickness of one piece of the above resin-integrated fiber sheet is preferably 0.01 to 5.0 mm. The resin-integrated fiber sheet having a thickness within this range is easily formed. When forming a hollow molded body, one or two or more pieces of the resin-integrated fiber sheet are laminated and wound. The preferred number of laminated sheets is 2 to 20, and more preferably 3 to 15.

[0066] As the above thermoplastic resin, polyamide resins, polycarbonate resins, polypropylene resins, polyester resins, polyethylene resins, acrylate resins, phenoxy resins, polystyrene resins, polyimide resins, polyetheretherketone resins, etc. can be used, but it is not limited to these resins.

[0067] Regarding the attachment state of the resin of the resin-integrated fiber sheet of the present invention, it is preferred that the resin is attached near the surface of the fibrillated fiber sheet by melting and curing, and it is preferred that the resin does not infiltrate or partially infiltrate into the interior of the fibrillated fiber sheet. If it is in the above state, it is preferred to form a plurality of laminated resin-integrated fiber sheets.

[0068] Regarding the width of the fibrillated fiber sheet (hereinafter also referred to as "fibrillated sheet"), in the case of carbon fiber, it is preferably 0.1 to 5.0 mm per 1000 constituent fiber filaments. Specifically, regarding the width of the fibrillated sheet, in the case of a thick tow such as 50K or 60K, it is in the range of 0.1 to 1.5 mm per 1000 constituent fiber filaments, and in the case of a normal tow such as 12K or 15K, it is in the range of 0.5 to 5.0 mm per 1000 constituent fiber filaments. Here, K represents 1000 constituent fiber filaments. The more the number of constituent fiber filaments per single tow increases, the greater the twist of the fiber and the more difficult it is to fibrillate, so the width of the fibrillated sheet becomes narrower. By unwinding the unfibrillated tow sold by the carbon fiber manufacturer in this way to form an easily usable fibrillated sheet, it can be supplied for use in various hollow molded bodies. The carbon fiber bundle (tow) supplied for manufacturing the resin-integrated fiber sheet is preferably 5000 to 50000 fibers / bundle, and preferably 10 to 280 fibers of the carbon fiber bundle (tow) are supplied to the fibrillating device. If the carbon fiber bundle (tow) is fibrillated by supplying multiple fibers in this way to form one sheet, it is easy for cracks to occur between the carbon fiber bundles (tows), but if bridging fibers having multiple directions are bonded and anchored to the sheet by resin, cracking between the tows can be prevented.

[0069] The average length of the bridging fiber is preferably 1 mm or more, and more preferably 5 mm or more. As long as the average length of the bridging fiber is within the above range, a carbon fiber sheet having high strength in the width direction and excellent processability can be formed.

[0070] The manufacturing method of the resin integrated fiber sheet used in the manufacture of the hollow molded body of the present invention includes, for example, the following steps. Taking a carbon fiber sheet as an example, the fiber sheet will be described.

[0071] (1) By at least one means selected from opening the carbon fiber filament group by a plurality of rollers, by an opening fiber rod, and by air opening, when the carbon fiber filament group is arranged side by side in one direction, bridging fibers are generated from the carbon fiber filament group during or after opening, or the bridging fibers fall on the carbon fiber sheet during or after opening. The above-mentioned bridging fibers are set to be 1 or more per 10 mm 2 of the area of the carbon fiber sheet. When opening the carbon fiber filament group by a roller or an opening fiber rod, by applying tension to the carbon fiber filament group, bridging fibers can be generated from the carbon fiber filament group during opening. The tension of the carbon fiber filament group can be set, for example, in the range of 2.5 to 30 N per 15,000 filaments. When using air opening, it is preferable to generate bridging fibers by a roller or an opening fiber rod thereafter. When generating bridging fibers from the carbon fiber filament group, the bridging fibers are formed in a state of intersecting with the carbon fibers constituting the carbon fiber sheet. Here, the so-called intersection includes being wound together. For example, part or all of the bridging fibers are present in the carbon fiber sheet and intersect three-dimensionally with the carbon fibers arranged in one direction.

[0072] (2) Powder resin is imparted to the opened carbon fiber sheet.

[0073] (3) The powder resin is heated and melted in a pressureless (unpressurized) state and then cooled, so that the resin is locally present in at least a part of the surface of the carbon fiber sheet. At this time, the bridging fibers are bonded and anchored to the carbon fiber sheet by the resin on the surface.

[0074] The hollow molded body of the present invention is formed by winding and molding one or more layers of the above-mentioned resin-integrated fiber sheets on the surface of an elastomer in a manner that produces an overlapping portion. It is preferable to wind the above-mentioned resin-integrated fiber sheets at least two turns or more in a state of being laminated in one or more sheets. The width of the above-mentioned overlapping portion is preferably 3 mm or more, more preferably 10 mm or more. Furthermore, in the present invention, when winding two turns, an overlapping portion having a width corresponding to the circumference is regarded as being generated, and when winding three turns, an overlapping portion having a width twice that of the circumference is regarded as being generated. When laminating two or more sheets of the resin-integrated fiber sheets, they can also be laminated in such a way that the directionality of the unidirectional continuous fibers (the length direction of the fibers of the unidirectional continuous fibers) is different. In addition, the elastomer can also be a core type. For example, when laminating two sheets, it can be set to 0° / 90°. Thus, a hollow molded body having the mechanical properties required for a hollow molded body can be obtained. When using one sheet of the resin-integrated fiber sheet, for example, a long-sized molded body wound obliquely with respect to the length direction of the core type or a hollow molded body wound multiple times in the 90° direction with respect to the length direction of the core type can be obtained. As the hollow molded body, it can be a tube, a shaft, a frame, etc., and can be a hollow body having a circular hollow cross-section, a square hollow cross-section, or various other shapes.

[0075] The hollow molded body of the present invention is preferably formed by a fluid that expands outward from the hollow portion. As the fluid, for example, pressure fluids such as compressed air can be cited.

[0076] In one embodiment, the manufacturing method of the hollow molded body of the present invention has the following steps.

[0077] (a) A step of winding the above-mentioned resin-integrated fiber sheets on the surface of an elastomer in one or more sheets in a manner that produces an overlapping portion.

[0078] (b) A step of disposing the elastomer wound with the above-mentioned resin-integrated fiber sheets in a heating mold having a hollow shape, and performing pressure-air forming by supplying a pressure fluid into the interior of the elastomer (for example, making the above-mentioned resin-integrated fiber sheets adhere to the above-mentioned heating mold by compressed air to obtain the desired shape).

[0079] (c) A step of melting a thermoplastic resin, infiltrating it into the unidirectional continuous fibers, and integrating the wound above-mentioned resin-integrated fiber sheets.

[0080] In other embodiments, the manufacturing method of the hollow molded body of the present invention includes the following steps.

[0081] (a′) A step of winding one or more sheets of the resin-integrated fiber sheets on the surface of an elastomer.

[0082] (b′) The step of disposing the elastomer wrapped with the resin-integrated fiber sheet in a heating mold having a hollow cavity.

[0083] (c′) The step of supplying a pressure fluid to the inside of the elastomer, performing hollow forming by expanding the resin-integrated fiber sheet outward from the elastomer, and simultaneously melting and infiltrating the thermoplastic resin into the entire laminated portion (the entire wound resin-integrated fiber sheet).

[0084] (d′) Then, the step of cooling is performed.

[0085] In the above steps (a) and (a′), when winding multiple resin-integrated fiber sheets, it is preferable to laminate and wind multiple resin-integrated resin sheets in such a manner that the directions of the unidirectional continuous fibers are different. Thus, a hollow molded body having the mechanical properties required for the hollow molded body can be obtained. In addition, the resin-integrated fiber sheet can be directly wound on the surface of the elastomer, or after forming a preform by winding the resin-integrated fiber sheet, it can be disposed on the surface of the elastomer.

[0086] The following will be described with reference to the drawings. In the following drawings, the same reference numerals denote the same components. Figure 1 A is a schematic perspective view of a hollow molded body 30 according to an embodiment of the present invention. Figure 1 B is a schematic cross-sectional view of the same figure. The inside of the hollow molded body 30 is hollow in the longitudinal direction. In the fiber-reinforced resin portion 31, multiple resin-integrated carbon fiber sheets are laminated and integrated. 32 is an overlapping portion of the resin-integrated carbon fiber sheets. The preferred diameter (outer diameter) of the hollow molded body 30 is 10 to 200 mm, the preferred length is 50 to 5000 mm, the preferred thickness is 0.03 to 5 mm, and the more preferred thickness is 0.04 to 5 mm.

[0087] Figure 2 is a schematic explanatory view showing Figure 1 the lamination method of the resin-integrated carbon fiber sheets used in the formation of the fiber-reinforced resin hollow molded body. The unidirectional continuous fibers of the resin-integrated carbon fiber sheet 33a are 0°, and the unidirectional continuous fibers of the resin-integrated carbon fiber sheet 33b are 90°. A portion 34 where the resin-integrated carbon fiber sheets 33a and 33b overlap is cut out and wound around a mandrel. The number of winding times can be once or multiple times. When winding once, a part is made to overlap.

[0088] Figure 3 A is a schematic perspective view of a mandrel 35 used in hollow forming. Figure 3 B is a schematic perspective view of the same figure when the resin-integrated carbon fiber sheet 37 is wound around the mandrel 35. Figure 3 C is Figure 3Cross-sectional view of B. A jig 36 is installed at the front end of the core 35 to seal the pressure fluid inside the core. The core is, for example, a tube made of fluororubber (heat-resistant limit temperature: 230°C) or silicone rubber (heat-resistant limit temperature: 230°C). For example, a tube with an outer diameter of 19 mm, an inner diameter of 15 mm, and a length of 500 mm can be used. Figure 3 In C, when the resin-integrated carbon fiber sheet is wound n times, the width of the overlapping portion is the sum of the length of the circumference corresponding to n - 1 turns and the length of the portion indicated by 38 in the figure.

[0089] Figure 4 A is a schematic plan view showing a state where the core 35 wound with the resin-integrated carbon fiber sheet 37 is inserted into the forming die. Figure 4 B is Figure 4 A sectional view taken along line I-I of A. The forming die is composed of a lower die 39 and an upper die 40. The forming die is preheated, and the core 35 wound with the resin-integrated carbon fiber sheet 37 is placed inside the die. Compressed air is supplied from the air supply port 41 fixed to one end of the core 35 to expand the core. As a result, the resin-integrated carbon fiber sheet 37 wound around the core 35 expands all the way to the die, and by receiving heat from the die, the thermoplastic resin on the surface of the resin-integrated carbon fiber sheet 37 melts and infiltrates into the entire laminated portion (the entire resin-integrated carbon fiber sheet 37 wound). Then, the die is cooled by water cooling. Thus, a fiber-reinforced resin hollow molded body can be obtained.

[0090] Figure 5 is a schematic perspective view of the resin-integrated carbon fiber sheet 1 used in the manufacture of the hollow molded body according to an embodiment of the present invention. Figure 6 is a schematic cross-sectional view in the width direction of the resin-integrated carbon fiber sheet 1 in the same figure. Bridging fibers 3 are arranged in various directions on the surface of the opened unidirectional carbon fiber 2. In addition, the resin 4 adheres thereto by melting and solidifying near the surface of the unidirectional carbon fiber 2, and the resin 4 is in a state where it does not infiltrate or only partially infiltrates into the unidirectional carbon fiber 2. The resin 4 bonds and fixes the bridging fibers 3 to the surface of the unidirectional carbon fiber 2. As Figure 6As shown, bridging fibers 3a and 3b exist on the surface of the unidirectional carbon fiber 2. All of the bridging fibers 3a are located on the surface of the unidirectional carbon fiber 2. A part of the bridging fiber 3b is located on the surface of the unidirectional carbon fiber 2, and a part thereof enters the interior and is in a state of being interleaved with the carbon fibers. The resin 4 bonds and fixes the bridging fibers 3 to the surface of the unidirectional carbon fiber 2. In addition, the surface of the unidirectional carbon fiber 2 has a portion where the resin 4 is attached and a resin-unattached portion 5. When the resin-integrated carbon fiber sheet 1 is heated in a state of being laminated in multiple layers to form a fiber-reinforced resin molded product, the resin-unattached portion 5 becomes a passage for discharging the air inside the fiber sheet from this portion, and it is easy to infiltrate the resin on the surface into the entire fiber sheet by pressing. Thus, the resin 4 becomes the matrix resin of the fiber-reinforced resin hollow molded body.

[0091] Figure 7 It is a schematic process diagram showing a method for manufacturing a resin-integrated carbon fiber sheet used in the manufacture of a hollow molded body according to an embodiment of the present invention. Carbon fiber filament groups (tow) 8 are drawn out from a plurality of supply bobbins 7 ( Figure 7 only one is shown in the figure, and the others are omitted), and the carbon fiber filament groups 8 are opened by passing between the splitting rollers 21a - 21j (roller splitting process 23). Air splitting may be specified instead of roller splitting. The splitting rollers may be fixed or rotated, and may also vibrate in the width direction.

[0092] After the splitting process, the split tow is clamped between the clamping rollers 9a and 9, and passed between a plurality of bridging rollers 12a - 12b provided therebetween. By applying a tow tension in the range of, for example, 2.5 to 30 N per 15,000 filaments (equivalent to the carbon fiber filament group supplied from one supply bobbin), bridging fibers are generated (bridging fiber generation process 24). The bridging rollers may be rotated, and may also vibrate in the width direction. The bridging rollers are, for example, a plurality of rollers having wrinkles, irregularities or a mirror surface on the surface, and the bridging rollers are arranged in a bent state with respect to the carbon fiber filament group, and bridging fibers are generated by fixing, rotating, vibrating in the width direction or a combination thereof of the bridging rollers. 13a - 13g are guide rollers.

[0093] Then, dry powder resin 15 is sprayed onto the surface of the fibrillated sheet from the powder supply hopper 14, and is supplied into the heating device 16 in a pressureless state for heating to melt the dry powder resin 15, and is cooled between the guide rollers 13e - 13g. Then, dry powder resin 18 is also sprayed onto the back surface of the fibrillated sheet from the powder supply hopper 17, and is supplied into the heating device 19 in a pressureless state for heating to melt the dry powder resin 18, and then is cooled and wound around the winding roller 20 (powder resin application step 25). The dry powder resins 15 and 18 are, for example, set as polypropylene resins (melting point: 150 - 165°C), the respective temperatures in the heating devices 16 and 19 are, for example, set as +5 - 60°C of the melting point, softening point or fluidization point of the dry powder resin, and the residence time is, for example, set as 4 seconds each. Thereby, the strength in the width direction of the carbon fiber fibrillated sheet is improved, the constituent carbon fibers do not become scattered, and it can be processed as a sheet.

[0094] The application of the powder resin can adopt methods such as powder coating method, electrostatic coating method, spraying method or flow impregnation method, etc. The powder coating method of scattering the powder resin on the surface of the carbon fiber sheet is preferably adopted. For example, dry powder resin in powder form is sprayed onto the fibrillated carbon fiber sheet.

[0095] The advantages of the present invention are summarized as follows.

[0096] (1) Different from the prepreg material, the resin integrated carbon fiber sheet can be directly formed because it is a semi - impregnated material. Therefore, even without softening before forming and moving the softened material into the forming die, the forming of a hollow formed body can be carried out. In addition, the shaping of the resin integrated carbon fiber sheet and the impregnation of the thermoplastic resin into the entire fiber matrix material can be carried out substantially simultaneously.

[0097] (2) Different from the prepreg material, the resin integrated carbon fiber sheet can be formed with high cycle due to being a semi - impregnated material, and has excellent formability and formability.

[0098] (3) Since the thermoplastic resin is heat - fused in powder form, the impregnation property into the fibers is good. That is, different from the resin in film form, the gas exhaust property is excellent during the forming of the hollow formed body, and pores are difficult to generate.

[0099] (4) The main component of the fibers in the fiber integrated resin sheet is a continuous fiber (not a short fiber) such as carbon fiber, for example. Therefore, a thin and high - strength hollow formed body can be obtained.

[0100] (5) Through the following comparison, it can be known that in the present invention, since a semi - impregnated material is adopted, the thermal history relative to the resin can be reduced. Thereby, the deterioration of the resin can be prevented.

[0101] · Prepreg material: Long time when the sheet is made + Pre - heating time (softening of the prepreg material) + Forming time + Thermal curing time

[0102] · Semi - impregnated material: Short time when the sheet is made + only heated during forming

[0103] As described above, the semi - impregnated material can make the forming time high - speed.

[0104] (6) Since the pre - impregnated material cools when moving towards the forming die after softening, the smoothness (die replication) of the surface of the formed product is poor. In the present invention, since it is directly formed, the smoothness of the surface of the formed product is good.

[0105] (7) Since the pre - impregnated material cools when moving towards the forming die after softening, the formed product requires a certain thickness (it is not possible to form a thin formed product). In the present invention, since it can be directly formed, there is no need to replace the movement of the base material (pre - impregnated material) towards the forming die before forming after pre - heating. Therefore, it is also possible to manufacture a thin hollow formed body.

[0106] Examples

[0107] Hereinafter, the present invention will be specifically described by way of examples. Furthermore, the present invention is not limited to the following examples.

[0108] (Example 1)

[0109] (1) Unopened carbon fiber tow

[0110] The unopened carbon fiber tow used is of the model: PYROFILE TR50S15L manufactured by Mitsubishi Chemical Corporation of Japan, shape: standard tow filament 15K (15,000 filaments), and the single - fiber diameter is 7 μm. On the carbon fibers of this unopened carbon fiber tow, an epoxy - based compound is attached as a sizing agent.

[0111] (2) Means for opening the unopened tow

[0112] The following Figure 7 opening means is used for opening (opening process). In the opening process, the tension of the carbon fiber filament group (tow) is set to 15 N per 15,000 filaments. Thus, an opened sheet having 15K carbon fiber filaments, an opening width of 500 mm, and a thickness of 0.08 mm is formed. The bridging fibers are 3.3% by mass.

[0113] (3) Semi - impregnated material

[0114] Polypropylene (melting point: 150 - 165 °C (manufactured by Prime Polymer Co., Ltd.)) is used as the dry powder resin. The average particle diameter of the dry powder resin is 80 μm. This resin is relative to 1 m of carbon fiber 2The average weight per single side is 28.2 g, and 56.4 g for both sides. The temperatures in the heating devices 16 and 19 are each set to 220 °C, and the residence time is each set to 8 seconds (powder resin application process). The mass of the obtained resin-integrated fiber sheet is 132.4 g / m 2 , the thickness is 0.2 mm, the fiber volume (Vf) is 40 vol%, and the thermoplastic resin is 60 vol%.

[0115] (4) Lamination conditions

[0116] · Number of laminated sheets of the resin-integrated fiber sheet: 2 sheets (the overlapping part is about 4 sheets, and the width of the overlapping part is 53.9 mm)

[0117] · Fiber direction of the resin-integrated fiber sheet: Two directions (laminated in the straight direction), 0° / 90° (the outside is 90°)

[0118] (5) Hollow forming

[0119] Through Figure 4 the device shown, the hollow forming was carried out under the following conditions.

[0120] · Mold temperature 200 °C

[0121] · Air pressure 0.6 MPa

[0122] · Heating and forming time 3 minutes

[0123] · Water cooling time 5 minutes

[0124] After cooling, the air duct was cut off to demold the hollow formed body.

[0125] (Example 2)

[0126] Except that the lamination conditions were specified as follows and the heating and forming time was set to 5 minutes, the experiment was carried out in the same manner as in Example 1.

[0127] · Number of laminated sheets of the resin-integrated fiber sheet: 4 sheets (the overlapping part is about 8 sheets, and the width of the overlapping part is 53.1 mm)

[0128] · Fiber direction of the resin-integrated fiber sheet: Two directions (laminated in the straight direction), 0° / 90° / 0° / 90° (the outside is 90°)

[0129] (Evaluation)

[0130] The dimensions of the hollow formed bodies (tubes) of Examples 1 and 2 were measured. The diameter (outer diameter) and length were measured with a caliper, and the thickness was measured with a micrometer. Regarding the thickness, it was measured at 5 points and the average value was taken. The results are shown in Table 1.

[0131] Table 1

[0132]

[0133] In addition, compression tests were performed on the hollow molded articles of Example 1 and Example 2 in the diameter direction. The compression tests were carried out using an autograph (model: AG-50kNXplus manufactured by Shimadzu Corporation, Japan), by bringing a φ50 mm disk into contact with the hollow molded article (end portion or central portion). Compression with strokes of 2.5 mm and 5.0 mm was carried out in Example 1, and compression with a stroke of 2.5 mm was carried out in Example 2. However, the hollow molded articles of Example 1 and Example 2 did not break or deform. Tables 2 and Figures 8 - 9 show the results of the compression tests. Figure 8 is a test force-displacement measurement coordinate diagram on the end portion and the central portion of the hollow molded article of Example 1, Figure 9 is a test force-displacement measurement coordinate diagram on the end portion and the central portion of the hollow molded article of Example 2. Figures 8 - 9 In the figure, a represents the measurement result of the end portion of the hollow molded article, and b represents the measurement result of the central portion of the hollow molded article.

[0134] Table 2

[0135]

[0136] As described above, it was found that the hollow molded articles of Example 1 and Example 2 have sufficient practical performance.

[0137] Industrial availability

[0138] The hollow molded article of the present invention is a tube, a shaft, a frame, etc., and can be a hollow body having a circular hollow cross section, a square hollow cross section, or various other shapes. The present invention can be widely applied to general industrial uses such as building members, sporting goods, windmills, bicycles, automobiles, railways, ships, aviation, space, etc.

Claims

1. A fiber-reinforced resin hollow molded body, characterized in that: A fiber-reinforced resin hollow molded body using a resin-integrated carbon fiber sheet, The resin-integrated carbon fiber sheet used in the manufacture of the fiber-reinforced resin hollow molded body contains unidirectional continuous carbon fibers obtained by splitting a continuous carbon fiber group and arranged side by side in one direction; And a thermoplastic resin present on at least a part of the surface of the unidirectional continuous carbon fibers, The resin-integrated carbon fiber sheet is a semi-impregnated material formed by attaching and heat-fusing a thermoplastic powder resin that becomes the matrix of the fiber-reinforced resin hollow molded body on the surface of the unidirectional continuous carbon fibers, In the hollow molded body, the resin-integrated carbon fiber sheets are wound in a state of being laminated in one or more layers so as to produce overlapping portions, and the resin-integrated carbon fiber sheets are integrated by impregnating the thermoplastic resin throughout the unidirectional continuous carbon fibers, The resin-integrated carbon fiber sheet contains bridging fibers having multiple directions, the bridging fibers include bridging fibers located on the surface of the unidirectional continuous carbon fibers and bridging fibers in a state of being staggered with the unidirectional continuous carbon fibers, the bridging fibers are carbon fibers, and the thermoplastic resin integrates the unidirectional continuous carbon fibers and the bridging fibers.

2. The fiber-reinforced resin hollow molded body according to claim 1, wherein, The multi-layered resin-integrated carbon fiber sheets are laminated in such a way that the directions of the unidirectional continuous carbon fibers are different.

3. The fiber-reinforced resin hollow molded body according to claim 1 or 2, wherein, The resin-integrated carbon fiber sheet is wound at least two turns or more in a state of being laminated in one or more layers.

4. The fiber-reinforced resin hollow molded body according to claim 1 or 2, wherein, The hollow molded body is formed by a fluid that expands from the hollow portion to the outside.

5. The fiber-reinforced resin hollow molded body according to claim 1 or 2, wherein, In the semi-impregnated material, the thermoplastic resin is not impregnated or partially impregnated into the unidirectional continuous carbon fibers.

6. The fiber-reinforced resin hollow molded body according to claim 1, wherein, When the total of the unidirectional continuous carbon fibers and the bridging fibers is set to 100% by mass, the unidirectional continuous carbon fibers are 75 to 99% by mass, and the bridging fibers are 1 to 25% by mass.

7. The fiber-reinforced resin hollow molded body according to claim 1 or 2, wherein, The thickness of the resin-integrated carbon fiber sheet is 0.01 to 5.0 mm.

8. The fiber-reinforced resin hollow molded body according to claim 1 or 2, wherein, The mass per unit area of the resin-integrated carbon fiber sheet is 10 to 3000 g / m 2 .

9. The fiber-reinforced resin hollow molded body according to claim 1 or 2, wherein, The fiber volume (Vf) in the resin-integrated carbon fiber sheet is 20 to 65% by volume, and the volume percentage of the thermoplastic resin is 35 to 80% by volume.

10. A method for manufacturing a fiber-reinforced resin hollow molded body, wherein, A resin-integrated carbon fiber sheet containing unidirectional continuous carbon fibers obtained by splitting a continuous carbon fiber group and arranged side by side in one direction, a thermoplastic resin present on at least a part of the surface of the unidirectional continuous carbon fibers, and bridging fibers having multiple directions is used; the resin-integrated carbon fiber sheet is a semi-impregnated material formed by attaching and heat-fusing a thermoplastic powder resin that becomes the matrix of the fiber-reinforced resin hollow molded body on the surface of the unidirectional continuous carbon fibers, The bridging fibers include bridging fibers located on the surface of the unidirectional continuous carbon fibers and bridging fibers in a state of being staggered with the unidirectional continuous carbon fibers, the bridging fibers are carbon fibers, and the thermoplastic resin integrates the unidirectional continuous carbon fibers and the bridging fibers, On the surface of the elastomer, the resin-integrated carbon fiber sheets are wound in a state of being laminated in one or more layers so as to produce overlapping portions; The elastomer that has wrapped the resin-integrated carbon fiber sheet is disposed within a heating mold having a hollow shape; By supplying a pressure fluid to the interior of the elastomer, pressure-air forming is performed to melt the thermoplastic resin, impregnate the entire unidirectional continuous carbon fiber with the thermoplastic resin, and integrate the resin-integrated carbon fiber sheet.

11. The method for manufacturing a fiber-reinforced resin hollow molded body according to claim 10, wherein, There are multiple resin-integrated carbon fiber sheets, and the multiple resin-integrated carbon fiber sheets are laminated and wound in a manner such that the directionality of the unidirectional continuous carbon fibers is different.

12. The method for manufacturing a fiber-reinforced resin hollow molded body according to claim 10 or 11, wherein, In the semi-impregnated material, the thermoplastic resin is not impregnated or partially impregnated into the unidirectional continuous carbon fiber.

13. The manufacturing method of the fiber-reinforced resin hollow molded body according to claim 10, wherein, When the total of the unidirectional continuous carbon fiber and the bridging fiber is set to 100% by mass, the unidirectional continuous carbon fiber is 75 to 99% by mass, and the bridging fiber is 1 to 25% by mass.

14. The method for manufacturing a fiber-reinforced resin hollow molded body according to claim 10 or 11, wherein, The thickness of the resin-integrated carbon fiber sheet is 0.01 to 5.0 mm.

15. The method for manufacturing a fiber-reinforced resin hollow molded body according to claim 10 or 11, wherein, In the resin-integrated carbon fiber sheet, the fiber volume (Vf) is 20 to 65% by volume, and the volume percentage of the thermoplastic resin is 35 to 80% by volume.

16. According to the method for manufacturing a fiber-reinforced resin hollow molded body according to claim 10 or 11, wherein, Overlap multiple resin-integrated carbon fiber sheets, Cut out the overlapped portion, Wind it in a manner that generates an overlapping portion.

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