JP2003053853A - Method for molding fiber reinforced plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding fiber reinforced plastic enhancing the impregnation properties of a resin into reinforcing fiber bundles by a relatively simple method and without lowering the mechanical strength of a molded article even if thick reinforcing fiber bundles are used. SOLUTION: In the molding method for fiber reinforced plastic (FRP) due to a filamnent winding method, the reinforcing fiber bundles impregnated with the resin are deaerated under a vacuum environment of 100 Torr or less before curing the resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber reinforced plastic (hereinafter referred to as FR
(Referred to as P).

[0002]

2. Description of the Related Art Fiber-reinforced composite materials such as FRP have been widely used from sports and leisure-related applications to transportation applications such as aircraft and industrial applications. As one of the molding methods of this fiber reinforced composite material, a reinforcing fiber bundle is mainly impregnated with a thermosetting resin composition, the reinforcing fiber bundle impregnated with the resin is wound around a mandrel (core type), and the resin is cured. There is a filament winding (hereinafter abbreviated as FW) method in which a molded product is obtained.

The FW method has a merit that the material cost can be remarkably reduced as compared with the sheet wrap method using a prepreg, so that the total cost can be reduced, and it is very suitable for forming a roll-shaped material, a tank and the like. Is the way.
In recent years, there has been a tendency to use thicker reinforcing fiber bundles in order to further improve the productivity by the FW method. However,
As the fiber bundle becomes thicker, the impregnation of the resin into the fiber bundle becomes worse, resulting in a decrease in the mechanical properties of the molded product.

In order to improve the impregnation, the resin is usually applied to the reinforcing fiber bundle by bending the resin-attached fiber bundle with several rolls after adhering the resin to the fiber. The method of impregnating the bundle is taken. However, since tension is applied to the reinforcing fiber bundle by passing through the roll, the process speed is suppressed, or the fiber bundle is damaged, and fluff occurs, which adversely affects the strength of the reinforcing fiber bundle and eventually the strength of the FRP. There was a problem that caused it.

Further, Japanese Patent Laid-Open No. 7-80948 discloses that
As a method of improving the impregnation of the resin into the fiber bundle, the resin-impregnated reinforcing fiber bundle is wound around the mandrel by the FW method, and then the release tape and the heat shrink tape are further wound around to form a bug. , A method of depressurizing the inside of this bag and curing the depressurizing bag while pressurizing it in an autoclave. However, it takes a lot of time and effort to manufacture the vacuum bag, and since the resin is hardened by the autoclave, the shape and size of the molded product are limited.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve the impregnation property of a resin into a reinforcing fiber bundle by a relatively simple method in the FW method, and to form a molded article even if a thick reinforcing fiber bundle is used. It is an object of the present invention to provide a method for molding FRP that does not reduce the mechanical strength of

[0007]

That is, the FR of the present invention
The method for molding P is characterized in that, in the method for molding FRP by the FW method, the resin-impregnated reinforcing fiber bundle is defoamed under a reduced pressure environment of 100 torr or less, and then the resin is cured. In addition, in the FRP molding method of the present invention, after defoaming the reinforcing fiber bundle impregnated with the resin,
It is desirable to return this to normal pressure. Further, the FR of the present invention
In the molding method of P, during the defoaming of the reinforcing fiber bundle impregnated with the resin and / or during the curing of the resin, defoaming and / or curing may be performed while rotating the reinforcing fiber bundle impregnated with the resin. desirable.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The FRP molding method of the present invention is the same as the FRP molding method according to the FW method.
This is a method in which the resin is cured by placing it under a reduced pressure environment of or or less and removing air bubbles remaining between the fibers of the resin and the reinforcing fiber bundle. As a method for molding such an FRP, for example, a reinforcing fiber bundle is impregnated with a resin, the resin-impregnated reinforcing fiber bundle is wound around a mandrel, and the resin is impregnated with 100 tons.
A method of curing the resin after defoaming in a reduced pressure environment of rr or less; winding a reinforcing fiber bundle with no resin attached to a mandrel, and attaching / impregnating the resin to the reinforcing fiber bundle wound on the mandrel. , This is 100t
Examples include a method of curing the resin after defoaming in a reduced pressure environment of orr or lower.

The reinforcing fiber (reinforcing fiber) in the present invention is not particularly limited, and examples thereof include glass fiber, carbon fiber, boron fiber, aramid fiber, high-strength polyethylene fiber, steel fiber and Zylon fiber. Also, the thickness of the reinforcing fiber bundle is not particularly limited, but since the FRP molding method of the present invention is more effective for a thick fiber bundle, in other words, a fiber bundle having a large number of filaments, 20,000 or more is preferable, and 40,000 or more is more preferable.

The resin in the present invention is not particularly limited, but thermosetting resins are preferably used. As the thermosetting resin, for example, epoxy resin, phenol resin,
Examples thereof include vinyl ester resins and unsaturated polyester resins. As an epoxy resin, bisphenol A
Type, bisphenol F type, bisphenol S type and other bisphenol type epoxy resins, phenol novolac type and cresol novolak type and other novolak type epoxy resins, aminophenol type and aminocresol type 3
Examples thereof include functional epoxy resins, tetrafunctional epoxy resins such as tetraglycidyl dimethyldiphenylmethane, and other polyfunctional epoxy resins. It is also possible to use a known curing agent in combination with the epoxy resin.

The method for attaching and impregnating the resin is not particularly limited, and for example, a touch roll system in which the reinforcing fiber bundle is brought into contact with a roll to which the resin is quantitatively attached and the resin is transferred to the reinforcing fiber bundle; resin bath An example is a dipping method in which a reinforcing fiber bundle is dipped in and then excess resin is squeezed out. Further, in the FRP molding method of the present invention, since it is sufficient that the resin adheres to the reinforcing fiber bundle, the reinforcing fiber bundle is wound around the mandrel without attaching the resin at all, and then the resin is adhered. May be.

In the FRP molding method of the present invention, the resin is impregnated and impregnated into the reinforcing fiber bundle, and then the resin-impregnated reinforcing fiber bundle must be placed under a reduced pressure environment of 100 torr or less. When the pressure in the depressurized environment exceeds 100 torr, the degree of depressurization is low, defoaming is not sufficiently performed, and the mechanical strength of the molded product decreases. Since the degree of defoaming is improved, the pressure in the reduced pressure environment is 10 torr
The following is preferable, and 5 torr or less is more preferable.

On the other hand, the lower limit value of the reduced pressure is preferably 0.1 torr. When the pressure in the depressurized environment is lower than 0.1 torr, low molecular weight components in the resin may evaporate, and in the case of a thermosetting resin, it may cause insufficient curing or lower mechanical strength. There is also. Also,
The time for which the reinforcing fiber bundle impregnated with the resin is placed under a reduced pressure environment is not particularly limited, but is preferably 1 minute or more under a reduced pressure state of 100 torr or less. If the decompression time is less than 1 minute,
The reinforcing fiber bundle impregnated with the resin may not be sufficiently defoamed, and the strength after molding may decrease. Since the reinforcing fiber bundle impregnated with the resin is sufficiently defoamed, the depressurization time is more preferably 5 minutes or longer. Further, 120 minutes of decompression time is sufficient.

Such a reduced pressure environment is easily achieved by placing the reinforcing fiber bundle impregnated with the resin in a vacuum dryer or the like. In a reduced pressure environment, it is preferable that the viscosity of the resin impregnated in the reinforcing fiber bundle is low, and when the resin is a thermoplastic resin, the temperature of the atmosphere is raised above the melting point of the thermoplastic resin, and the viscosity of the thermoplastic resin is It is preferable to reduce the pressure in the lowered state. However, when a thermosetting resin is used as the resin, it should be noted that if the temperature is raised too high, curing of the resin will start and the viscosity will increase before sufficient defoaming, resulting in insufficient defoaming. is there. Specifically, the viscosity of the resin during defoaming is preferably 100 poise or less.

In the FRP molding method of the present invention, when the resin is cured after defoaming under reduced pressure, it is preferable to return the pressure to normal pressure before curing. The bubbles remaining without being degassed in the depressurized state have a large volume due to the depressurization, but the volume of the bubbles becomes small by returning the pressure to normal pressure. Even if the resin is cured with the bubbles remaining, if the bubbles are small, the mechanical strength of the obtained molded product is slightly reduced. Further, it is more preferable to apply pressure when curing the resin. Examples of the pressurizing method include a method of applying pressure in an autoclave and the like, a method of wrapping a shrink tape and the like, and applying a pressure by the shrink force.

Further, in the FRP molding method of the present invention, since the resin may be biased downward due to gravity, the resin may be removed during defoaming of the resin-impregnated reinforcing fiber bundle and / or during curing of the resin. It is preferable to perform defoaming and / or curing while rotating the impregnated reinforcing fiber bundle. The direction of rotation is not particularly limited, but it is meaningless unless the resin is rotated in a direction in which the resin is not biased. For example, when the mandrel is positioned horizontally, it is preferable to rotate it about the mandrel axis.

As described above, in the FRP molding method of the present invention, the reinforcing fiber bundle impregnated with the resin is 100 to
Since defoaming is performed under a reduced pressure environment of rr or less, bubbles remaining in the resin-impregnated reinforcing fiber bundle can be sufficiently reduced, and the impregnation property of the resin into the reinforcing fiber bundle can be improved. Further, since the resin is cured after being sufficiently defoamed, the mechanical strength of the molded product does not decrease even if a thick reinforcing fiber bundle is used.

If the reinforcing fiber bundle impregnated with the resin is degassed and then returned to normal pressure, the volume of the slight air bubbles remaining without being degassed can be reduced. Therefore, even if bubbles remain, it is possible to minimize the decrease in mechanical strength of the molded product. Further, during defoaming of the resin and / or curing of the resin, if defoaming and / or curing is performed while rotating the reinforcing and reinforcing bundle impregnated with the resin, the resin is not biased and uniform and mechanical strength is improved. A high molded product can be obtained.

[0019]

EXAMPLES The FRP molding method of the present invention will be described below based on examples while comparing it with comparative examples. [Example 1] Carbon fiber TR50S-24L (filament number: 24,000) manufactured by Mitsubishi Rayon Co., Ltd. as a reinforcing fiber
This), and as a resin, Japan Epoxy Resin Co., Ltd., Epicoat 828 (liquid bisphenol A type epoxy resin) 100 parts by mass, Nippon Kayaku Co., Ltd., Kayahard MCD (methyl nadic acid anhydride) 90 parts by mass, An epoxy resin composition containing 2 parts by mass of benzyldimethylamine was used.

2. The epoxy resin composition is attached to the carbon fiber, and a mandrel having a diameter of 500 mm is prepared by the FW method.
A 300 mm long cylinder in which 6 plies were stacked and reciprocated 3 times at a pitch of 6 mm was wound. The carbon fiber impregnated with the resin and wound on the mandrel was placed in a vacuum dryer and kept at 30 ° C. for 10 minutes for 1 minute.
Degassing was performed by placing under a reduced pressure of torr. After defoaming, the atmospheric pressure is returned to normal pressure, the resin-impregnated carbon fiber wound on the mandrel is heated at a rate of 2 ° C./min, 130 ° C. × 2 hours, 1
The resin was cured by heating under conditions of 50 ° C. × 1 hour and 170 ° C. × 2 hours. After curing the resin, the mandrel was pulled out to obtain a cylindrical molded product. The Vf (volume content of carbon fiber) of the obtained molded product was 65%.

The formed cylinder was cut into a ring shape having a width of 25 mm, and a burst test was conducted in the following manner. The burst pressure was 26.3 MPa, which was a very high value. (Burst test) There is a wall thickness of 1 inside the ring which is a molded product.
A ring made of silicone rubber having a diameter of 0 mm and an outer circumference of 500 mm was installed, and pressure was uniformly applied from the inside of the silicone rubber by hydraulic pressure. Pressure was evenly applied to the molded part ring through the silicone rubber, and the molded part ring burst. The pressure (hydraulic pressure) at which the ring burst was recorded as the burst pressure.

[Example 2] The same procedure as in Example 1 except that the mandrel shaft was set horizontally during curing and rotated about the shaft at a speed of 10 seconds / cycle, and the length was 300 mm and 50 mm.
A 0 mmφ cylinder was molded. Example 1 from the obtained cylinder
A ring was cut out and a burst test was performed in the same manner as in. The burst pressure was as high as 26.8 MPa.

[Comparative Example 1] A cylinder having a length of 300 mm and a diameter of 500 mm was molded in the same manner as in Example 1 except that the vacuum degassing treatment was not carried out and the cylinder was wound and then immediately cured. The Vf of the molded product was 65%. A ring was cut out from the obtained cylinder in the same manner as in Example 1 and a burst test was performed. The burst pressure was as low as 19.2 MPa.

[Comparative Example 2] A 300 mm length was prepared in the same manner as in Example 1, except that the vacuum defoaming treatment was not carried out, and after the cylinder was wound, a molding shrink tape made of polyethylene terephthalate was wound and cured. A 500 mmφ cylinder was molded.
The Vf of the molded product was 65%. A ring was cut out from the obtained cylinder in the same manner as in Example 1 and a burst test was performed. The burst pressure was as low as 22.5 MPa.

[Embodiment 3] Three TR50S-24L yarns are combined and a resin is attached to the mandrel.
A cylinder having a length of 300 mm and a diameter of 500 mm was molded in the same manner as in Example 2 except that the two-ply winding was performed once at a pitch of 2 mm. During curing, the mandrel shaft was set horizontally as in Example 2, and the mandrel was rotated about the shaft at a speed of 10 seconds / cycle. The Vf of the molded product was 65%. A ring was cut out from the obtained cylinder in the same manner as in Example 1 and a burst test was performed. Burst pressure is 27.
It showed a high value of 5 MPa.

[Comparative Example 3] A 300 mm long sheet was prepared in the same manner as in Example 3, except that the vacuum degassing treatment was not carried out, and after the cylinder was wound, a molding shrink tape made of polyethylene terephthalate was wound and cured. A 500 mmφ cylinder was molded.
The Vf of the molded product was 65%. A ring was cut out from the obtained cylinder in the same manner as in Example 1 and a burst test was performed. The burst pressure was as low as 20.8 MPa.

[0027]

As described above, the method for molding FRP of the present invention is the same as the method for molding FRP according to the FW method, in which the resin-impregnated reinforcing fiber bundle is defoamed under a reduced pressure environment of 100 torr or less. Since this is a method of curing the resin, the impregnation property of the resin into the reinforcing fiber bundle is improved, and the mechanical strength of the molded product is not reduced even if a thick reinforcing fiber bundle is used.

If the reinforcing fiber bundle impregnated with the resin is defoamed and then returned to normal pressure, the decrease in mechanical strength of the molded product can be minimized even if air bubbles remain. You can Further, during defoaming of the reinforcing fiber bundle impregnated with the resin and / or during curing of the resin, if defoaming and / or curing is performed while rotating the reinforcing fiber bundle impregnated with the resin, uniform mechanical strength is obtained. It is possible to obtain a molded product of high quality.

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Claims (3)

[Claims] 1. A method for molding a fiber-reinforced plastic by a filament winding method, wherein a resin-impregnated reinforcing fiber bundle is defoamed under a reduced pressure environment of 100 torr or less, and then the resin is cured. Plastic molding method. 2. The method for molding a fiber-reinforced plastic according to claim 1, wherein the reinforcing fiber bundle impregnated with the resin is defoamed and then returned to normal pressure. 3. Defoaming and / or curing is performed while rotating the reinforcing fiber bundle impregnated with resin during defoaming and / or curing of the reinforcing fiber bundle impregnated with resin. The method for molding the fiber-reinforced plastic according to claim 1 or 2.