JPH05124118A - Method of molding fiber-reinforced composite body - Google Patents

Abstract

PURPOSE:To provide a molding method, in which the formation of creases, irregularities, voids, vacuoles and surface crimps is inhibited and a composite body member having an excellent grade can be molded, by applying proper pressure to the surface of a body to be worked for the entire time of the curing process of a resin when a fiber-reinforced composite body is molded. CONSTITUTION:A preform 8 composed of high-strength high-elastic-modulus fibers is positioned in a substantially sealed sample chamber 9 in a molding die 1, and a thermosetting matrix resin is injected into the sample chamber 9 and the preform 8 is impregnated with the resin. A pressurized gas is introduced into a gas chamber 7 formed adjoined to the sample chamber 9 by an airtight film 6 previously inserted into the sample chamber so as to be brought into contact with the preform 8 through a spacer 10 having rigidity, the preform 8 and a body to be worked consisting of the matrix resin are brought to a pressed state, and the molding die 1 is heated at a fixed temperature while holding the state and the matrix resin is cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a fiber-reinforced composite used for structural members such as aircraft, ships and vehicles.

[0002]

2. Description of the Related Art A method called resin injection (RI) is one of the methods for forming a fiber-reinforced composite body composed of long fibers having high strength and high elastic modulus and a thermosetting matrix resin. This is a method in which a preform to be a core is set in a hollow molding die, a resin is injected and impregnated, and the resin is cured by heating. Here, the "preform" is usually a laminate of woven fabrics made of long fibers of high strength and high elastic modulus, or a product obtained by stitching and integrating these with a stitch thread, or a fiber structure such as a three-dimensional fabric or braid. Means

FIG. 3 is a schematic view showing an embodiment of a general RI molding method. Preform 8 as shown in figure 1
After being set in the sample chamber 9, the inside of the mold is depressurized through the vent port 3, and the matrix resin is injected through the injection port 2 to uniformly impregnate the preform 8. After that, the injection port 2 and the vent port 3 are sealed, and the entire system is heated by a heating means (not shown) such as an electric heater under predetermined temperature and time conditions to cure the resin. At this time, the shrinkage characteristics of the resin during curing may cause wrinkles and irregularities on the surface of the molded product, or voids and bubbles inside the molded product, which may lower the surface quality of the product. Was becoming.

In the RI method, consideration is given to selecting a resin whose volume change is as small as possible at the time of curing. For example, an epoxy resin often used in this field has a volume change of about 5% before and after curing. However, the smoothness of the surface is likely to be lost when the work piece is separated from the mold in the molding die, and wrinkles and irregularities are generated on the surface when the work is not smooth.

In order to prevent this, in the RI method, the object to be processed is pressed, and while maintaining this state, the entire system is heat treated to cure the resin. It has been proposed to directly pressurize through the inlet 2 via a hydraulic cylinder or the like.
However, in this method, when the resin is hardened and the fluidity is lost (particularly when the resin is hardened in the vicinity of the resin injection port), it is difficult to apply uniform pressure to the entire body to be pressed. There is.

[0006]

SUMMARY OF THE INVENTION In order to improve such a problem of the RI method, the present invention provides a wrinkle by applying an appropriate pressure to the surface of the work piece throughout the curing process of the resin. It is intended to provide a molding method that suppresses the generation of irregularities, voids, air bubbles, and the like and enables molding of a composite member with good quality.

[0007]

In order to solve the above problems, a preform made of high-strength and high-modulus fibers is placed in a substantially sealed sample chamber in a mold.
After the thermosetting matrix resin is injected into the sample chamber to impregnate the preform, the sample chamber is sealed by the airtight membrane that is inserted inside the sample chamber so as to come into contact with the preform through the spacer having rigidity. A pressurized gas is introduced into the air chamber formed adjacent to the preform and the matrix resin to be in a pressurized state, and the mold is heated to a predetermined temperature while maintaining this state. A method of curing the matrix resin is proposed.

[0008]

In the RI molding method, a substantially sealed sample chamber 9 having a matrix resin injection port 2, and a preform 8 made of reinforcing fibers having a high strength and a high elastic modulus, which are usually set in the sample chamber, And the matrix resin injected through the injection port 2 is a basic element.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. A spacer 10 having rigidity is provided in the sample chamber 9 of the mold 1.
The airtight film 6 inserted so as to be in contact with the preform 8 via the air chamber 7, the air chamber 7 formed thereby, and the pressure introducing port 4 communicating with the air chamber 7 constitute the features of the present invention. That is, as shown in the figure, the preform 8 is set, the sample chamber is depressurized through the vent port 3, the matrix resin is injected through the injection port 2, and the preform 8 is uniformly impregnated. The mouth 3 is closed, and pressurized gas is introduced from the pressure introducing port 4 to apply pressure to the air chamber 7, thereby forming the airtight film 6
And a spacer 10 having rigidity puts a preform 8 and a matrix resin into a work piece under pressure,
While maintaining this state, the entire system is heat treated to cure the resin.

As described above, during the curing process of the matrix resin, by maintaining a pressure state over a wide surface of the object to be processed, surface wrinkles and irregularities caused by shrinkage deformation during curing,
Alternatively, formation of voids / air bubbles inside the molded product can be suppressed. At this time, by interposing the spacer 10 having rigidity, the fine concavo-convex pattern based on the structure of the preform surface can be smoothed to obtain a molded product having a smooth surface.

Here, the action of the airtight film 6 and the spacer 10 is that the matrix resin impregnated in the preform 8 is highly viscous in the process of gelation / curing by heat treatment and volumetric shrinkage is performed at a predetermined pressure. By doing so, the surface of the work piece is kept in close contact with the surface of the work piece, and the state is continued until the material is gradually cooled and die-formed, which makes it possible to maintain the smoothness of the surface of the work piece.

[0012]

[Example] Carbon fiber woven fabric (Toray Industries, Inc. Trading Card (registered trademark) Cloth # C06644B) cut into a length of 350 mm and a width of 120 mm, 13 pieces were stacked and the periphery was lock stitched with KEVLAR (registered trademark) aramid spun yarn. A laminated body having a thickness of about 5.5 mm was prepared and used as a preform test piece 8.

A mold 1 having the structure shown in FIG. 1 was made of SS41 steel. The internal dimensions of the sample chamber 9 are 355 mm long, 125 mm wide, and 5 mm wide. The inner surface has a 3 ° opening taper and is chrome-plated and has a smooth finish. O-ring 5 is used to seal the mold 1.
And a total of 16 M12 bolts and nuts (not shown) that engage the body 1a and body 1b. The inside of the mold was treated with a fluorocarbon mold release material, and then the above-mentioned preform 8 was set.

A stainless steel plate having the same size and a thickness of 0.4 mm is placed as a spacer 10 on the uppermost layer of the preform 8 and then a pressure bag film (AI
RTECH INTERNATIONAL INC., WRITRON (registered trademark) # 7400
) A 2 mil-thick piece cut into 400 mm x 170 mm was inserted into the upper surface of the sample chamber 9 so as to cover the above preform 8, and the mold 1 was sealed in this state. The mold 1 was placed in a temperature-controlled room where the temperature could be adjusted, and the vent port 3 was connected to the vacuum pump decompression system, and the pressurized air introduction port 4 was connected to the compressor pneumatic system.

Epoxy resin was blended according to the formulation shown in Table 1, stirred for 25 minutes under a vacuum pump under reduced pressure, sufficiently deaerated, and then injected into the sample chamber through the resin injection port 2. The injection was performed using the depressurization (-50 to -100 mmHg) by the vent port 3 and the static pressure difference due to the height of the liquid surface of the resin tank, and the injection speed was adjusted to 10 cc / min or less in order to avoid residual air bubbles inside. After confirming that the sample chamber 9 was filled with resin due to resin overflow from the vent port 3, the injection port 2 and the vent port 3
The air chamber 7 formed by the bag film 6 (airtight film) and the mold 1 is closed by re-sealing, and pressurized air is introduced from the pressurized air introduction port 4 to apply a gauge pressure of 5 kg / cm ^2. The resin was cured by changing the temperature of the temperature-controlled room according to the program of Table 2 while maintaining the state. After completion of the curing treatment, it was slowly cooled at -30 ° C / hr, the molding die was opened, and a molded product was taken out to obtain Sample 1.

[0016]

[Table 1]

[0017]

[Table 2] A molded product obtained by performing exactly the same operation except that the spacer 10 was omitted in the above (1) was designated as Sample 2.

Further, in the above (1), except that a) the autoclave bag film is not inserted into the mold 1, b) compressed air is not introduced after resin injection, and c) the spacer 10 is omitted. A molded product obtained by performing exactly the same operation was designated as Sample 3. Samples 1, 2 and 3 respectively
Molding trials were performed n = 5 times, and the resulting molded products were visually evaluated for surface quality by gloss, sink marks, voids, and surface textures (irregularities corresponding to the microstructure of the preform). I got it.

That is, the sample 1 molded by the apparatus and method of the present invention had no defects regarding the above-mentioned evaluation items and was of good quality. Sample 2 also has few defects and can be said to have no problem in practical use, but an uneven pattern corresponding to the structure of the preform (generated by the airtight film being pressed against the preform surface) remains. In sample 3, defects such as gloss, sink marks, and voids occurred.

[0020]

[Table 3] * Gloss ◎ Mirror surface ○ Has cloudy surface △ Has many cloudy surface ** Irregular non-void recesses are defined as sink marks *** Surface unevenness Corresponding to the texture of the preform is defined as wrinkle The present invention is not limited to the above-mentioned embodiments, and can be implemented in various embodiments. For example, as shown in FIG. 2, a semi-circular molded product can be produced by using a spacer 11 that is pre-molded in a shape similar to the inner surface of the molding die 1a having a substantially semi-circular shape. In this case, it is preferable to set the clearance d for the gap between the mold 1a and the preform 8 in consideration of the shrinkage ratio of the resin.

In addition, according to the shape of the preform 8,
Various embodiments are possible, such as using a mold and a spacer having a shape other than a semicircle, changing the resin composition, and the curing program.

[0022]

As described above, in the method of the present invention,
When the matrix resin is heated and cured, the airtight film follows closely with the object to be processed through the spacer having rigidity, so even if the volume of the matrix resin changes, the mold of the mold and the object of processing It is possible to prevent separation, and it is possible to produce a fiber-reinforced composite having high gloss and free of voids, sink marks and surface wrinkles.

[Brief description of drawings]

FIG. 1 is a schematic diagram of the present invention.

FIG. 2 is a schematic diagram of another embodiment.

FIG. 3 is a schematic diagram of the prior art.

[Explanation of symbols]

1 Mold, 1a body, 1b body, 2 inlet, 3
Vent port, 4 pressure inlet port, 5 O-ring, 6 airtight membrane, 7 air chamber, 8 preform, 9 sample chamber, 1
0,11 Spacer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29K 105: 24

Claims (1)

[Claims] 1. A preform comprising high strength, high modulus fibers is placed in a substantially sealed sample chamber in a mold.
After the thermosetting matrix resin is injected into the sample chamber to impregnate the preform, the sample chamber is sealed by the airtight membrane that is inserted inside the sample chamber so as to come into contact with the preform through the spacer having rigidity. A pressurized gas is introduced into the air chamber formed adjacent to the preform and the matrix resin to be in a pressurized state, and the mold is heated to a predetermined temperature while maintaining this state. A method for molding a fiber-reinforced composite, which comprises curing a matrix resin.