JP3121070B2 - Molding method of fiber reinforced composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As one of methods for forming a fiber-reinforced composite comprising a high-strength high-modulus long fiber and a thermosetting matrix resin, there is a method called resin injection (RI). This is a method in which a preform serving as a core is set in a hollow mold, resin is injected, impregnated, and cured by heating. The term "preform" as used herein generally refers to a laminated base fabric made of long fibers having a high strength and a high elastic modulus, or a stitch-integrated stitch thread, or a fibrous structure such as a three-dimensional woven fabric or a braided fabric. Means

FIG. 3 is a schematic view showing an embodiment of a general RI molding method. As shown in FIG.
After setting in the sample chamber 9, the inside of the mold is evacuated through the vent 3 and the matrix resin is injected from the inlet 2 to impregnate the preform 8 evenly. Thereafter, the injection port 2 and the vent port 3 are sealed, and the entire system is heated by a heating means such as an electric heater (not shown) under predetermined temperature and time conditions to cure the resin. At this time, wrinkles and irregularities may be generated on the surface of the molded product due to the shrinkage characteristics of the resin upon curing, or voids and bubbles may be generated inside the molded product and the surface quality of the product may be degraded, which is one of the problems of the prior art. Had become.

In the RI method, consideration is given to selecting such a resin having a small volume change during curing as much as possible. However, for example, in the case of an epoxy resin widely used in this field, for example, a volume change of about 5% before and after curing. In general, the smoothness of the surface is easily lost when the workpiece is released from the mold in the mold, and in extreme cases, wrinkles and irregularities are generated on the surface.

In order to prevent this, in the RI method, the workpiece is pressurized, and while maintaining this state, the entire system is heated to cure the resin. It has been proposed to pressurize directly through the inlet 2 via a hydraulic cylinder or the like.
However, in this method, when the curing of the resin progresses and the fluidity is lost (especially when the curing proceeds near the resin injection port), it is difficult to uniformly pressurize the entire pressurized body. There is.

[0006]

SUMMARY OF THE INVENTION The present invention solves this problem of the RI method by applying an appropriate pressure to the surface of the workpiece throughout the curing process of the resin. An object of the present invention is to provide a molding method that suppresses generation of irregularities, voids, voids, and the like and enables molding of a high-quality composite member.

[0007]

In order to solve the above-mentioned problems, a preform made of high-strength high-modulus fibers is placed in a substantially closed sample chamber in a mold.
After the thermosetting matrix resin is injected into the sample chamber and impregnated in the preform, the sample chamber is filled with an airtight film that is inserted into the sample chamber in advance so as to be in contact with the preform via a rigid spacer. A pressurized gas is introduced into an air chamber formed adjacent to the preform and the workpiece made of the matrix resin is put into a pressurized state, and the mold is heated to a predetermined temperature while maintaining this state. A method for curing the matrix resin is proposed.

[0008]

In the RI molding method, a substantially closed sample chamber 9 having a matrix resin inlet 2 and a preform 8 made of a reinforcing fiber having a high strength and a high modulus of elasticity set in the sample chamber. The matrix resin injected from 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 a sample chamber 9 of the mold 1.
The airtight film 6 inserted so as to be in contact with the preform 8 through the airbag, the air chamber 7 formed by the airtight film 6, 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 pressure in the sample chamber is reduced through the vent port 3, the matrix resin is injected from the inlet port 2, and the preform 8 is impregnated evenly. The port 3 is closed, and a pressurized gas is introduced from the pressurized inlet 4 to apply pressure to the air chamber 7, and
The workpiece formed of the preform 8 and the matrix resin is pressurized by the spacer 10 having rigidity and
While maintaining this state, the entire system is heated to cure the resin.

[0010] As described above, during the curing process of the matrix resin, by maintaining the pressurized state over a wide surface of the workpiece, surface wrinkles and irregularities caused by shrinkage deformation during curing can be reduced.
Alternatively, the formation of voids / voids inside the molded article can be suppressed. At this time, a fine uneven pattern based on the structure of the preform surface can be smoothed by the interposition of the particularly rigid spacer 10, and a molded product having a smooth surface can be obtained.

Here, the action of the airtight film 6 and the spacer 10 is such that when the volumetric shrinkage of the matrix resin impregnated in the preform 8 increases while the matrix resin becomes highly viscous during the gelation / hardening process by heat treatment, the predetermined pressure is applied. Accordingly, the surface of the workpiece is kept in close contact with the surface of the workpiece, and this state is continued until the cooling and the molding are performed, whereby the smoothness of the surface of the workpiece can be maintained.

[0012]

Example: 13 pieces of carbon fiber fabric (Toray Industries, Inc., Torayca (registered trademark) cloth # C06644B) cut to a length of 350 mm and a width of 120 mm are overlapped, and the periphery is rock-stitched with KEVLAR (registered trademark) aramid spun yarn. A laminate having a thickness of about 5.5 mm was prepared and used as a preform specimen 8.

A mold 1 having the structure shown in FIG. 1 was made from 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 ° open taper and chrome-plated smooth finish. The mold 1 is sealed with an O-ring 5
And a total of 16 M12 bolts and nuts (not shown) engaged with the main body 1a and the main body 1b. After the inside of the mold was treated with a CFC-based release material, the preform 8 was set.

A stainless steel plate having the same dimensions 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 for autoclave (AI)
RTECHINTERNATIONAL INC., WRITRON (registered trademark) # 7400
) A 2 mil piece cut to 400 mm x 170 mm was inserted into the upper surface of the sample chamber 9 so as to cover the 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 controlled.

The epoxy resin was blended according to the formulation shown in Table 1, and the mixture was stirred for 25 minutes under reduced pressure of a vacuum pump, sufficiently degassed, and then injected from the resin inlet 2 into the sample chamber. The injection was performed using a reduced pressure (-50 to -100 mmHg) at the vent 3 and a static pressure difference due to the liquid level of the resin tank, and the injection rate was adjusted to 10 cc / min or less to avoid bubbles remaining inside. After confirming that the inside of the sample chamber 9 was filled with the resin due to the resin overflow from the vent port 3, the inlet port 2 and the vent port 3 were checked.
Is sealed again, and pressurized air is introduced from the pressurized air inlet 4 to apply a pressure of 5 kg / cm ² to the air chamber 7 formed by the bag film 6 (airtight film) and the mold 1. The resin was cured by changing the temperature of the thermostatic chamber according to the program in Table 2 while keeping the condition. After the completion of the curing treatment, the mold was slowly cooled at -30 ° C / hr, the mold was opened, and the molded product was taken out as Sample 1.

[0016]

[Table 1]

[0017]

[Table 2] In the above (1), a molded product obtained by performing exactly the same operation except that the mounting of the spacer 10 was omitted was designated as Sample 2.

In the above (1), except that a) the autoclave bag film is not inserted into the molding die 1, b) the compressed air is not introduced after the resin is injected, and c) the mounting of the spacer 10 is omitted. A molded product obtained by performing exactly the same operation was designated as Sample 3. For samples 1, 2 and 3 respectively
After performing n = 5 molding trials, the obtained molded product was visually evaluated for surface quality by gloss, sink, void, and surface texture (irregularities corresponding to the structure of the preform). I got it.

That is, Sample 1 molded by the apparatus and method of the present invention had no defect in the above evaluation items and was of good quality. Sample 2 also has few defects and has no problem in practical use. However, a concave / convex pattern corresponding to the structure of the preform (generated by pressing the airtight film against the preform surface) remains. Sample 3 had defects in gloss, sink marks, and voids.

[0020]

[Table 3] * Gloss ◎ mirror ○ turbidity surface located △ Note the tissue corresponding to the unevenness of the turbidity surface often ** *** surface textured preform was defined as sink the concave portion of the irregularly shaped not void was defined as grain, the present invention The present invention is not limited to the above-described example, but 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 has been formed in advance in a shape similar to the inner surface of a substantially semi-circular molding die 1a. In this case, it is preferable to set a clearance d in consideration of the resin shrinkage rate for the gap between the mold 1a and the preform 8.

Further, 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 blending of the resin, and changing 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 the workpiece in close contact with the rigid spacer via a rigid spacer. The separation can be prevented, and a fiber-reinforced composite having high gloss and free from voids, sink marks, and surface irregularities can be produced.

[Brief description of the 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, 5 O-ring, 6 airtight membrane, 7 air chamber, 8 preform, 9 sample chamber, 1
0,11 spacer.

Claims (1)

(57) [Claims] A preform comprising high strength, high modulus fibers is placed in a substantially sealed sample chamber within a mold.
After the thermosetting matrix resin is injected into the sample chamber and impregnated in the preform, the sample chamber is filled with an airtight film that is inserted into the sample chamber in advance so as to be in contact with the preform via a rigid spacer. A pressurized gas is introduced into an air chamber formed adjacent to the preform and the workpiece made of the matrix resin is put into a pressurized state, and the mold is heated to a predetermined temperature while maintaining this state. A method for molding a fiber-reinforced composite, comprising curing a matrix resin.