JP4706244B2 - FRP hollow structure molding method - Google Patents

Description

  The present invention relates to a method for forming an FRP (fiber reinforced resin) hollow structure, and more particularly to a method for forming an FRP hollow structure using a hollow core that can be expanded and contracted.

  Conventionally, injection molding methods such as a resin transfer molding method (hereinafter referred to as RTM method) are known as a method for forming an FRP structure excellent in productivity (for example, Patent Document 1 and Non-patent document 1). In such an RTM method, a (dry) reinforcing fiber base not pre-impregnated with a matrix resin is placed in a cavity of a mold, and a liquid (low viscosity) matrix resin is injected into the reinforcing fiber base. Is impregnated with a matrix resin and molded. In such a method, when molding an FRP hollow structure having a hollow structure, generally, a reinforcing fiber base material is coated on the entire outer periphery of the core, placed in the cavity of the molding die, and then one side thereof. Alternatively, the resin is injected under pressure from one point.

However, in such a conventional technique, the injected resin does not flow evenly, and flow spots may occur in each direction. There is a possibility that a gas pool is formed at a place where the resin flow is slow, resulting in poor filling (impregnation) of the resin, that is, a void. The reason is considered as follows. (1) When a reinforcing fiber base material is arranged around the entire circumference of the core, the base material overlaps or wrinkles occur at the end of the core having a three-dimensional shape, and the base material is filled compared to other parts. The density may be different, or a minute gap without a substrate may occur.
(2) When the base material density is different, a difference in resin flow resistance occurs, and thus a difference occurs in the resin flow rate. Of course, the low-density part has a high flow rate, and the high-density part has a low flow rate and may not flow in some cases.
(3) Further, if a gap is generated even as small as described in (1), the flow resistance of the gap becomes extremely lower than that of the surroundings, so that the resin injected under pressure is selectively transferred to that part. The resin flow and resin impregnation may cause large spots.

The possibility of occurrence of such a defect hinders the formation of a stable FRP structure, and when such a problem occurs, a large burden is imposed on finishing processing such as repair of a void-generated part or a part where resin impregnation is insufficient. As a result, not only the molding yield is reduced, but the molding cycle is lengthened, and the productivity is lowered.
Japanese Patent Laid-Open No. 7-60765 "Easy-to-understand practical FRP molding" (issued February 20, 1998, Industrial Research Co., Ltd.)

  Therefore, the object of the present invention is to stably form an FRP hollow structure using a hollow core that can be expanded and contracted, to improve the molding yield by voidless molding, and to eliminate the need for finishing processing such as repair or reduce the burden. An object of the present invention is to provide a method for forming an FRP hollow structure.

In order to solve the above-mentioned problem, a method for molding an FRP hollow structure according to the present invention includes a hollow core having a reinforcing fiber base disposed on the outer periphery thereof in a cavity of a molding die composed of a plurality of dies. In the molding method of the FRP hollow structure in which a resin is injected into a molding die while pressurizing the inside of the core after the mold is clamped, a fluid for pressurizing the end with a fluid as the hollow core In the cavity, a reinforcing fiber substrate non-arranged portion is provided in the cavity with respect to the end of the hollow core, and the reinforcing fiber substrate non-arranged portion of the hollow core is disposed in the core. It consists of a method characterized by pressing against the cavity surface of the mold by pressurization .

  In addition, the molding method according to the present invention can be more easily carried out when the hollow core is made of a blow molded product and has a fluid injection port at the end.

  Moreover, what has the independent structure only as the outermost layer can be used as said reinforced fiber base material, and the designability of the surface of the FRP hollow structure shape | molded by it can be aimed at. . Although it does not specifically limit as a reinforced fiber base material, A high intensity | strength FRP hollow structure can be obtained when the reinforced fiber base material which consists of carbon fiber fabrics is used. It is also possible to employ a configuration in which a glass fiber mat having a lower basis weight than the reinforcing fiber substrate is disposed between the outermost reinforcing fiber substrate and the inner reinforcing fiber substrate. By using the glass fiber mat to reduce irregularities on the inner layer side and using a glass fiber mat having a lower basis weight than the reinforcing fiber base material, the gas remaining in the outermost layer can easily escape to the mat side, and the reinforcing fiber base of the outermost layer The surface formed by the FRP surface layer of the material and the resin can improve the design by improving the smoothness and suppressing the generation of pinholes.

  Such a method for forming an FRP hollow structure according to the present invention has been completed based on the following technical idea. That is, the resin is allowed to flow uniformly, so that a portion where the flow is slow is not formed, that is, a portion where the flow flows ahead of other portions is not formed. For this purpose, the end of the three-dimensional core is not overlapped because there is no gap between the cavity surface of the mold where the resin can easily flow and the reinforcing fiber base or core. Avoid making substrate wrinkles that tend to occur.

In order to realize such a technical idea, in the present invention, as described above, the reinforcing fiber base is disposed on the outer periphery of the hollow core, but does not cover the entire hollow core positioned in the cavity. In addition, a reinforcing fiber substrate non-arranged part where a substrate is not arranged even in part, that is, a part that exposes the core is provided (especially in the present invention, as shown in the embodiments described later, with respect to the end of the hollow core A reinforcing fiber base non-arranged part is provided). Then, a preform having a portion where the reinforcing fiber base material is not disposed in part is placed in the cavity of the mold, and after closing the mold, fluid (pressure air etc.) is injected into the core to add the core. The core portion where the base material is not disposed is expanded and the portion is adhered to the cavity surface (preferably, pressed). As a result, the resin does not flow to the core reinforcing fiber base non-arranged portion, and the resin flows only to the portion where the base exists. Therefore, the flow resistance becomes uniform in the arrangement part of the reinforcing fiber base (there is no overlap or the like), and the core sticks to the mold cavity surface in the non-arrangement part of the reinforcing fiber base, and the resin does not flow. The resin flowing through the substrate arrangement portion is uniform and can flow uniformly. As a result, voidless molding becomes possible and uniform resin impregnation becomes possible.

  According to the FRP hollow structure molding method according to the present invention, it becomes possible to stably and quickly perform good molding of an FRP hollow structure using a hollow core, and the molding yield can be improved by voidless molding. This makes it possible to eliminate the need for finishing work such as repairs or to reduce the burden thereof, and to greatly improve productivity overall.

Preferred embodiments of the present invention will be specifically described below with reference to the drawings.
In the present invention, FRP refers to a resin reinforced with reinforcing fibers. Examples of reinforcing fibers include inorganic fibers such as carbon fibers, glass fibers, and metal fibers, or aramid fibers, polyethylene fibers, and polyamide fibers. Reinforcing fibers made of organic fibers can be mentioned. Among these, when carbon fiber is used, a hollow FRP structure having high strength and high elasticity can be formed. Examples of the FRP matrix resin include thermosetting resins such as epoxy resins, unsaturated polyester resins, vinyl ester resins, and phenol resins. Furthermore, polyamide resins, polyolefin resins, dicyclopentadiene resins, polyurethane resins, Thermoplastic resins such as polypropylene resin can also be used.

  As the resin used in the molding method according to the present invention, particularly as the resin used in the RTM molding method, RIM (Reaction Injection) which forms a thermosetting resin or a thermoplastic resin that has a low viscosity and can be easily impregnated into a reinforcing fiber. (Molding) monomer is suitable, and among them, modified epoxy resin containing vinyl ester resin, epoxy resin, thermoplastic resin, rubber component, etc. from the viewpoint of reducing thermal shrinkage of FRP molded product and suppressing the occurrence of cracks Nylon resin and dicyclopentadiene resin are more suitable.

  The reinforcing fiber substrate used in the present invention refers to a substrate made of reinforcing fibers not impregnated with resin, for example, the reinforcing fiber fabric, chopped fibers, mats, knit materials, and combinations of these with insert parts, etc. Can be used properly depending on the application. Examples of the insert parts include metal plates such as steel and aluminum, metals for joining such as metal columns, metal bolts, nuts, and hinges, aluminum honeycomb cores, polyurethane, polystyrene, polyimide, vinyl chloride, phenol, acrylic, and the like. Foam materials, rubber materials, wood materials, etc. composed of the above polymer materials are mainly used, and insert parts intended for joining such as nails and screws can be raised, with a hollow structure for the purpose of weight reduction Insert parts that are used for the purpose of damping vibration are often used.

  The hollow core that can be expanded / contracted used for molding the FRP hollow structure of the present invention is not particularly defined, but a hollow core or film molded by blow molding or rotational molding is fused to form a bag. An air core, a hollow core having a balloon-like shape by dipping, and the like can be used, and examples of the material include polypropylene, polyethylene, nylon, and various rubbers.

  The pressure range applied to the hollow core is preferably 0.3 MPa or more as the lower limit of the pressure from the viewpoint of pressing a part of the core against the cavity surface, although it depends on the shape and material of the core. 1 MPa or less is preferable from the viewpoint of preventing deformation damage to the molded body. More preferably, the lower limit is 0.5 MPa or more, and the upper limit is 1.5 MPa or less.

  The molding die used in the present invention is composed of, for example, a molding die composed of an upper die and a lower die. For example, the upper die is attached to a die lifting device. Reinforcing fiber base and core are installed in the lower mold. This reinforcing fiber base is prepared by a shaping mold for the purpose of shaping the reinforcing fiber base into a product shape so that it can be easily accommodated in the mold in advance. Examples of the material of the mold include FRP, cast steel, structural carbon steel, aluminum alloy, zinc alloy, nickel electroforming, and copper electroforming. For mass production, structural carbon steel is suitable in terms of rigidity, heat resistance, and workability.

  Specific embodiments of the method for forming an FRP hollow structure according to the present invention will be described below with reference to the drawings. In the following embodiments, a method for forming, for example, a horizontal wing of an automobile rear spoiler or a wind turbine blade as an FRP hollow structure will be described.

  FIG. 1 shows a hollow core 1 made of resin or rubber. When the resin hollow core 1 is used, it is made of, for example, a thermoplastic resin, and resins such as polypropylene, polyethylene, nylon, and ABS can be used. The most suitable method for producing such a hollow core 1 is a blow molding method. However, when the length is relatively large, such as 2 m or more, rotational molding is good. The thickness of the core of the blow molded product is preferably 0.5 to 3 mm. Moreover, depending on the case, a bag-like thing can also be formed with a resin film of several hundred microns. When the rubber hollow core 1 is used, rubbers such as chloroprene, polyisoprene, butadiene, and silicone can be used. On one side of such a hollow core 1, a fluid inlet 2 for performing pressurization with a fluid (for example, compressed air) is provided.

  As shown in FIG. 2, the reinforcing fiber base 3 is disposed on the outer periphery of the hollow core 1. In the example shown in FIG. 2, the reinforcing fiber base 3 is wound. When the reinforcing fiber base 3 is disposed, the reinforcing fiber base non-arranged portion 11 is provided for the hollow core 1. In this example, the reinforcing fiber base 3 is disposed leaving the end of the hollow core 1.

  Next, as shown in FIG. 3, a hollow core in which a reinforcing fiber base 3 is arranged in a cavity 12 part of a lower mold 5 of an RTM mold (for example, a metal mold) composed of an upper mold 4 and a lower mold 5. 1 is set and the upper mold 4 is closed. However, the lower mold 5 is provided with a resin injection port 8 that leads to a resin injection runner 6 and a resin discharge port 9 that leads to a resin discharge runner 7 that discharges gas remaining in the mold together with excess resin. An O-ring (not shown) that surrounds them and seals resin and air is disposed. The fluid inlet 2 of the hollow core 1 protrudes from the mold and is connected to a fluid pipe or tube (not shown) for supplying pressurized air or the like. The mold is heated using an electric heater or hot water to heat and cure the resin.

  As shown in FIG. 4, a pressurized fluid is injected from the fluid inlet 2 of the hollow core 1 in a state where the upper mold 4 is closed (closed state) (C), and the core 1 is expanded. Then, the reinforcing fiber base 3 and the reinforcing fiber base non-arranged portion 11 of the hollow core 1 are pressed against the cavity surface of the mold.

  The change in the state is shown in FIG. 5 which is a cross-sectional view of the mold cut at the longitudinal center. That is, in the state where it is only disposed in the mold cavity 12 part, as shown in the state diagram of FIG. 5 (1), the reinforcing fiber substrate non-arranged portion 11 of the hollow core 1 and the surface of the cavity 12 are interposed. The gap 10 corresponding to the thickness of the reinforcing fiber base 3 substantially occurs. The result of injecting a pressurized fluid such as compressed air into the hollow core 1 from the fluid injection port 2 in this state is the state diagram of FIG. That is, the reinforcing fiber base non-arranged portion 11 of the hollow core 1 is pressed against the surface of the cavity 12, and the resin flow can be completely suppressed. In this state, FRP matrix resin such as thermosetting resin is injected under pressure from the resin injection port 8 (A in FIG. 4). After the resin is filled in the resin injection runner 6 shown in FIG. 3, the resin flows uniformly from the runner 6 toward the resin discharge runner 7 in the width direction. In the meantime, the reinforcing fiber base 3 is impregnated with resin. The resin is once filled in the resin discharge runner 7 together with the residual gas in the mold, but is eventually discharged out of the mold through the resin discharge port 9 (B in FIG. 4). The mold is heated at a predetermined temperature so that the filling resin is cured in a predetermined curing time, and a predetermined FRP hollow structure is formed by resin curing.

  Then, after the resin is cured, as shown in FIG. 6, the upper die 4 is opened, and the fluid is discharged from the fluid inlet 2 of the hollow core 1 and decompressed before the upper die 4 is opened (D). Since the hollow core 1 (for example, resin) is heated by the mold, it is in a softened state and easily contracts (becomes indented) due to reduced pressure.

  As shown in FIG. 7, after the FRP hollow structure 20 as a molded product is removed from the mold, the hollow core 1 contracted (reduced) by decompression is extracted from the molded product 20. The molded product 20 that has been extracted becomes an FRP hollow structure having a predetermined shape as shown in FIG. The extracted hollow core 1 can be reused in some cases. In particular, in the case of rubber, there is a high possibility that it can be reused.

  An example in which a horizontal wing having a length of 1 m, a chord length of 250 mm, a blade height (maximum part) of 30 mm, and an average thickness of 1.5 mm will be described. As the mold, both the upper mold 4 and the lower mold 5 were 200 mm thick, 1400 mm long and 400 mm wide. In this mold, warm water flow paths (diameter 10 mm) are formed at a pitch of 100 mm in the width direction for temperature control. The hollow core 1 was made of polypropylene and had a length of 1100 mm, a chord length of 247 mm, a blade height (maximum part) of 27 mm, and an average thickness of 2.0 mm.

The hollow core 1 was wound with a reinforcing fiber base, that is, “Torayca” T300 plain woven fabric (weight per unit: 200 g / m ² ) manufactured by Toray Industries, Inc. at 6 ply and an average tension of 8 kg / m. A hollow core 1 in which a reinforcing fiber base material was wound around the lower mold 5 was set, and the upper mold 4 was closed. The upper and lower molds are heated to about 95 ° C. by warm water. In this state, compressed air of about 0.6 MPa was injected from the fluid inlet 2 of the hollow core 1. Thereafter, an epoxy resin [main agent; “Epicoat” 828 (epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.), a curing agent; blend TR-C35H (imidazole derivative) manufactured by Toray Industries, Inc.] is applied at a resin pressure of 0.5 MPa from the resin injection port 8. Injected. About 3 minutes later, the epoxy resin containing gas was discharged from the resin discharge port 9 through the resin discharge runner 7. Thereafter, the resin was continuously discharged for about 1 minute, and after confirming that the gas in the discharged resin was exhausted, the valve of the resin discharge port 9 was closed. Thereafter, the resin from the resin inlet 8 side was held while being pressurized for 30 seconds, and then the valves on the resin inlet 8 side were also closed (however, the valves are not shown). After all the valves were closed, the resin had a curing time in the mold for about 15 minutes.

  Thereafter, the pressurization of the hollow core 1 was stopped, a vacuum suction hose was connected to the fluid injection port 2, and the interior of the hollow core 1 was decompressed by suction for about 10 seconds. The upper mold 4 was opened, and the hollow core 1 and the molded product 20 were removed from the mold. Thereafter, the hollow core 1 was pulled out from the molded product 20. The hollow core 1 was in a depressed state due to the reduced pressure, so that it could be pulled out relatively easily. As a CFRP (carbon fiber reinforced resin) molded product from which the hollow core 1 was pulled out, a good product of horizontal wing having a wing shape with no voids or distortion anywhere on the entire circumference was obtained.

The same reinforcing fiber base material and resin as in Example 1 above were used, and the molding conditions (temperature and various pressures) were exactly the same, but after winding the reinforcing fiber base material 5ply around the hollow core 1, glass was placed on it. A fiber mat (weight per unit area: 70 g / m ² ) was wound 1 ply, and a reinforcing fiber substrate was further wound 1 ply thereon. However, up to 5 ply, the average tension is the same 8 kg / m, the mat is almost tensionless and has no wrinkles, and the outermost reinforcing fiber substrate 1ply has a tension of about 2 kg / m. Wound so that the weaving pattern is not disturbed.

  As a result of arranging the preform in a mold and performing RTM molding similar to that of Example 1, the outer surface (design surface) is smoother than the molded product of Example 1, and has high quality with almost no pinholes. A horizontal wing made of CFRP was obtained.

  The molding method according to the present invention can be applied to molding of any FRP structure having a hollow structure. Among them, FRP hollow structures that are mass-produced such as automobile members, and relatively large FRP hollow structures such as wind turbine blades. It is suitable for molding.

It is a perspective view of the hollow core which shows a mode that the shaping | molding method of the FRP hollow structure which concerns on one embodiment of this invention is implemented. It is a perspective view of a hollow core and a reinforced fiber base material which shows a mode that a reinforced fiber base material is arrange | positioned on the outer periphery of the hollow core of FIG. It is a disassembled perspective view of a shaping | molding die which shows a mode that the hollow core in which the reinforced fiber base material of FIG. 2 is arrange | positioned is set to a shaping | molding die. It is a perspective view of the shaping | molding die which shows a mode that the shaping | molding die of FIG. 3 was closed. It is a fragmentary longitudinal cross-sectional view of the shaping | molding die which shows the state before pressurization (1) in a hollow core in the state shown in FIG. 4, and the state after pressurization (2). It is a disassembled perspective view of the shaping | molding die which shows the mode of the mold opening of the shaping | molding die after resin hardening. It is a perspective view of the hollow core and FRP hollow structure which show a mode that a hollow core is extracted from the demolded FRP hollow structure. It is a perspective view of the shape | molded FRP hollow structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow core 2 Fluid injection port 3 Reinforcement fiber base material 4 Upper mold | type 5 Lower mold | type 6 Resin injection runner 7 Resin discharge runner 8 Resin injection port 9 Resin discharge port 10 Crevice 11 Reinforcement fiber base material non-arrangement part 12 Cavity 20 Molded article (FRP hollow structure)

Claims (5)

A hollow core having a reinforcing fiber base disposed on the outer periphery is disposed in a cavity of a mold composed of a plurality of molds, and after clamping, a resin is injected into the mold while pressurizing the core. In the molding method of the FRP hollow structure to be molded, the hollow core having a fluid inlet for pressurization with a fluid at the end is used, and the end of the hollow core is formed in the cavity. A reinforcing fiber base non-arranged part is provided , and the reinforcing fiber base non-arranged part of the hollow core is pressed against the cavity surface of the molding die by pressurization in the core. Molding method. Wherein in Kuchuko is ing from blow-molded article, the molding method of the FRP hollow structure according to claim 1. The method for forming an FRP hollow structure according to claim 1 or 2 , wherein the reinforcing fiber base has an independent structure only in the outermost layer. The method for forming an FRP hollow structure according to any one of claims 1 to 3 , wherein the reinforcing fiber base is made of a carbon fiber fabric. 4. The method for forming an FRP hollow structure according to claim 3 , wherein a glass fiber mat having a lower basis weight than the reinforcing fiber base is disposed between the outermost reinforcing fiber base and the inner reinforcing fiber base.

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