JPH06114862A - Molding of frp - Google Patents

Abstract

PURPOSE:To mold FRP without generating the cracking and the deficiency of a resin and considering pressure timing. CONSTITUTION:A thermosetting resin is infiltrated in a fiber structure 20 under vacuum and the impregnated fiber structure is received in a fluid impermeable bag 26. Thereafter, the bag 26 is degassed and hermetically sealed to be pressed and heated by a flowable pressure heating medium within a pressure-resistant tank 38 of a device 30.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for molding fiber reinforced plastic (FRP).

[0002]

2. Description of the Related Art FRP is molded by pressurizing and heating a fibrous structure (hereinafter referred to as a molding target) impregnated with a thermosetting resin as a matrix. As this molding method, the press molding method of FIG. 4 and the autoclave molding method of FIG. 5 are known. The former are press plates 4 and 4 with a built-in heater 2.
Thus, the molded body 8 is pressed and heated through the release films 6 and 6. In the latter case, the molded body 8 placed on the jig 10 is airtightly covered with the nylon film 12 and the annular sealant 14 and placed in a high-pressure high-temperature tank to pressurize and heat the molded body 8. The inside of the nylon film 12 is evacuated by the vacuum pump 16.

[0003]

Since the press-molding method is not hydrostatic molding, a P-shaped material other than a flat-shaped material can be formed.
A uniform pressure cannot be applied to a molded object having a different shape such as a shape or an I shape. In addition, a resin-deficient product is apt to be produced because of a crack in the object to be molded due to resin shrinkage during resin curing. In particular, when a three-dimensional woven fabric is used for a fiber structure or when a heat-resistant resin is used as a matrix, many cracks may occur, and the resin shortage may become remarkable. In order to reduce the cracks and the resin shortage, it is necessary to devise such that the resin is hardened to some extent before pressing, but the timing of pressing is delicate and very difficult.

Although the autoclave molding method is hydrostatic molding, since the uncured resin is sucked out from the surface of the resin-rich molded body by evacuation, the amount of resin impregnated on the surface and inside is balanced, The problems of cracks, resin shortage and press timing remain unsolved. Further, particularly in a thick object to be molded, a partial difference in the progress of resin curing can occur, so that a partial difference in viscosity or curing of the resin occurs and uniform pressing becomes difficult, and the pressing timing becomes more difficult.

FRP with cracks has a low mechanical strength and may cause early fatigue failure or rapid and catastrophic failure without a precursor, and is not suitable as a primary structural material.

An object of the present invention is to prevent FR and lack of resin, and to avoid the timing of pressurizing FR.
It is to provide a P molding method.

[0007]

According to the present invention, a fibrous structure is vacuum-impregnated with a thermosetting resin, the fibrous structure is housed in a fluid-impermeable bag, and then the bag is degassed and hermetically sealed. And pressurize and heat in a fluid pressure heating medium.

[0008]

The object to be molded in the bag is uniformly heated while being uniformly pressurized by the fluid pressure heating medium. At this time, the resin of the molding target is not subjected to a negative pressure by vacuum evacuation as in the conventional autoclave molding method, but a uniform positive pressure is applied to the resin by the fluid pressure heating medium. The fluidization of the resin that compensates for the decrease is promoted, and the volume of the entire body to be molded is reduced at substantially the same rate, so that the generation of internal tensile stress or cracks is completely prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In this example, a three-dimensional carbon fiber woven fabric as shown in FIG. 1 (A) was used as the fiber structure 20, and this fiber structure 20 was vacuum impregnated with an epoxy resin by a conventional method (hereinafter, referred to as Is referred to as a molded body 22) and a bag 26 made of a polyimide film in which three sides are previously sealed with a sealant tape 24 as shown in FIG.
Insert it through the opening 28. Then, after the bag body 26 is filled with the resin, the air bubbles inside the bag body 26 are degassed, as shown in FIG.
The opening 28 is completely sealed with the sealant tape 24b as shown in FIG.

Next, the bag 26 is pressurized and heated by the device 30 shown in FIG. This device 30 is an electric hydraulic pump 32.
A hydraulic cylinder 34, a storage tank 36 for storing a fluid pressure heating medium, a pressure-resistant tank 38 for FRP molding, a heating unit 40 surrounding the outer circumference of the pressure-resistant tank 38, and an air bleed valve 42 are attached. The lid 44 and the electric hydraulic pump 3
2 and the hydraulic cylinder 34, and a hose 48 that connects the storage tank 36 and the lid 44.

The pressurization / heating operation by the apparatus will be further described. First, the bag 26 containing the molded body 20 is put in the pressure resistant tank 38, and the lid 44 is attached to the pressure resistant tank 38.
On the other hand, the fluid pressure heating medium 50 is put in the storage tank 36, the electric hydraulic pump 32 is operated to push down the piston 34a of the hydraulic cylinder 34, and the fluid pressure heating medium 50 is pre-compressed into the pressure tank 38 at a low pressure. At this time, the air vent valve 42 of the lid 44 is left open, and after the air in the pressure resistant tank 38 is completely deaerated, the electric hydraulic pump 32 is temporarily stopped and the air vent valve 42 is closed.

Next, the electric hydraulic pump 32 is operated again, and the heating unit 40 is energized to bring the fluid pressure heating medium 50 in the pressure resistant tank 38 to a predetermined pressure and temperature. As a result, the body 20 to be molded in the bag body 26 is moved to the fluid pressure heating medium 5
It is pressurized under a constant pressure through 0 and is heated and hardened by the heat of the fluid pressure heating medium 50.

The resin impregnated into the molded body 20 shrinks along with the curing reaction and its volume decreases. At this time, the volume of the entire molded body 20 also decreases to the same extent due to the pressure of the fluid pressure heating medium 50. Therefore, internal tensile stress or cracks do not occur in the molded body 20. In this respect, it is considered that in the conventional molding method, uniform pressure is not applied to the entire body to be molded and the amount of shrinkage of the resin is large, so that cracks are generated.

The three-dimensional woven fabric is excellent in retaining the original shape, and although the woven structure is slightly deformed due to resin shrinkage, FR
There is no significant deformation that affects the strength of P. Therefore, if a three-dimensional fabric is used, a high-strength FRP can be obtained.

The present inventors conducted an evaluation test on 10 examples and 3 comparative examples for confirming the effect of the present invention, and confirmed that good results shown in Table 1 were obtained.

In Table 1, A to E in the evaluation column indicate the degree of cracking in five stages, and the FRP cross section corresponding to FIGS. 3A to 3E is shown. As shown in the figure, (A) has no cracks 52 at all, and (E) has the most cracks 52.

[0017]

[Table 1]

The details of the test are as follows.

(1) Fiber structure used in the test Type: three-dimensional fabric Orientation ratio (x: y: z) = 21: 26: 53 Volume ratio (vf) = 30% Name “Toray Trading Card T300 12K (trade name) ) ”(Manufactured by Toray Industries, Inc.) (2) Resin for matrix used in the test Resin: Name“ Araldite LY556 (trade name) ”100 parts by weight Curing agent: Name“ Hardener HT976 (trade name) ”35 parts by weight Also manufactured by Nippon Ciba-Geigy Co., Ltd.) Examples 1 to 9 in Table 1 are different in the type, pressure, and curing temperature of the fluid pressure medium 50.

In Example 10, a high-pressure high-temperature tank of an autoclave molding method was used, but without vacuum evacuation, nitrogen was used as a fluid pressure-heating medium and isobaric pressurization and heat curing were performed.

In Comparative Example 1, the object to be molded was placed in a stainless steel container and cured by heating in a dryer.

In Comparative Example 2, an object to be molded is pressed and heated and cured by a press molding method.

In Comparative Example 3, a body to be molded is pressed and heated and cured by an autoclave molding method.

The embodiment of the present invention has been described above.
The present invention is not limited to the above embodiment, but various modifications can be made. For example, the fiber structure may be a conventional woven fabric, a braid, a knitted fabric, or the like, as well as a three-dimensional woven fabric.

The thermosetting resin may be an epoxy resin, a bismaleimide triazine resin, an unsaturated polyester resin, a polyimide resin or the like. The point is not particularly limited as long as it does not generate a byproduct gas in the resin curing reaction. No need.

In addition to silicone oil, the fluid pressure heating medium may be polyethylene glycol, epoxy resin, water, oxygen, nitrogen, air, etc. In short, if it does not decompose at each operating temperature, it is a liquid. There is no particular limitation on the gas.

In addition to the polyimide film, various resin bags can be used as the bag 26, and it is not particularly limited as long as it is a fluid impermeable bag.

[0028]

EFFECTS OF THE INVENTION The present invention is different from the conventional press molding method and autoclave molding method, in that the uncured resin is heated and cured while applying a positive pressure to the molded body by the fluid pressure heating medium. Even if it is a deformed object that does not flow out, uniform positive pressure and temperature from the fluid pressure heating medium can be continuously applied to the entire object from the start of molding to the end of molding. The generation of internal tensile stress and cracks can be greatly reduced.

Further, unlike the conventional press molding method and autoclave molding method, there is no need to be caught at the timing of pressurization, so that molding is easy and variations in product quality can be reduced.

[Brief description of drawings]

1A is a perspective view of a fibrous structure, FIG. 1B is a perspective view of a molded body and a bag body before sealing, and FIG. 1C is a perspective view of a molded body and bag body after sealing.

FIG. 2 is a front view of a device that pressurizes and heats a bag containing a molding target.

FIG. 3A to FIG. 3E are cross-sectional views showing cracked states of FRP under different molding conditions.

FIG. 4 is a schematic cross-sectional view of an apparatus used in a conventional press molding method.

FIG. 5 is a schematic cross-sectional view of an apparatus used for a conventional autoclave molding method.

[Explanation of symbols]

 20 Fiber Structure 22 Object to be Molded 24a, 24b Sealant Tape 26 Bag Body 30 Device for Pressurizing and Heating Bag Body 34 Hydraulic Cylinder 38 Pressure Tank 40 Heating Unit 42 Air Venting Valve 50 Fluid Pressure Heat Medium

Claims (4)

[Claims] 1. A fibrous structure is vacuum-impregnated with a thermosetting resin, the fibrous structure is housed in a fluid-impermeable bag, and then the bag is deaerated and sealed in a fluid pressure heating medium. Pressurize with
A method for molding an FRP, which comprises heating. 2. The FRP molding method according to claim 1, wherein the fluid pressure heating medium is a liquid. 3. The FRP molding method according to claim 1, wherein the fluid pressure heating medium is a gas. 4. The three-dimensional woven fabric as a fiber structure.
The method for molding the FRP described.