JPH04296538A - Manufacture of fiber reinforced plastics - Google Patents

Abstract

PURPOSE:To simply manufacture FRP free from voids. CONSTITUTION:Fiber cloth 31 is set to a mold 11 and, at the time of the impregnation of the fiber cloth 31 with a liquid resin, the level of the liquid resin is raised at a rising speed 0.5-2.5 times the initial rising speed of the level of the liquid resin rising above the fiber cloth 31 by a capillary phenomenon.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is a fiber-reinforced plastic made by impregnating fiber cloth with resin.
The present invention relates to a manufacturing method of FRP (hereinafter simply referred to as FRP).

0002

2. Description of the Related Art FRP is manufactured by impregnating fiber cloth such as glass fiber with synthetic resin such as epoxy resin. Then, generally, the fiber cloth is set in a mold and the inside of the mold is almost evacuated.
A method has been used in which fiber cloth is impregnated with the synthetic resin. In this case, even if impregnation is performed in a nearly vacuum mold, voids (bubbles) may be mixed into the synthetic resin or between the fibers. Naturally, the inclusion of voids causes deterioration of the electrical characteristics, etc. of FRP.

0003

[Problems to be Solved by the Invention] Conventionally, therefore, measures have been taken to increase the degree of vacuum within the mold as high as possible, or it has taken time to impregnate the mold with synthetic resin. Therefore,
Conventional FRP manufacturing methods have had problems in that manufacturing equipment is complicated and manufacturing takes time.

0004

[Means for Solving the Problems] In order to achieve the above object, in the invention of claim 1, a fiber cloth is set in a molding die, and when the fiber cloth is impregnated with liquid resin, capillary action is applied. 0.5 to 0.5 of the initial rate of rise of the resin liquid level on the fiber cloth due to
The resin liquid level was raised at a rising speed of 2.5 times.

[0005]

[Operation] Therefore, in this invention, the resin liquid level rises uniformly due to capillary action, and no voids are generated. Therefore, void-free impregnation can be performed even if the degree of vacuum in the mold is not so high or without taking much time.

[0006]

[Example] Below, an example embodying this invention will be shown in Figs.
This will be explained in detail based on FIG. 6. Generally, fiber cloth is made up of 50 to 800 single fibers of 5 to 20 μm bundled together to form a yarn. The yarn is then run on a loom and processed into cloth. These fiber cloths used for impregnation are generally surface-treated in consideration of adhesion with resin and impregnability.

[0007] Therefore, the impregnability of the resin into the fiber cloth changes depending on the type of surface treatment agent, the type and viscosity of the resin to be impregnated, etc. Therefore, the inventor conducted a resin impregnation test based on capillarity, and obtained the test results shown in FIGS. 3 to 5. Therefore, this test and its results will be explained. 3(a) to 3(c), each sample 4 made of fiber cloth is held upright in a Petri dish (not shown) under atmospheric pressure, and an epoxy resin liquid 5 (viscosity: 20 cpoise) was poured to a predetermined depth and the capillary phenomenon was observed. Here, sample 4 in Fig. 3(a) is a plain weave cloth made of polyester fibers, the sample in Fig. 3(b) is a plain weave cloth made of glass fibers, and the sample in Fig. 3(c) is a plain weave cloth made of glass fibers. It is.

[0008] According to this, in each sample 4, the formation of voids 6 is not observed up to about 5 mm above the liquid surface. The reason for this is that although the speed of the resin rising due to capillary action is different between yarns and yarns, the speed difference is small near the liquid surface, so the rising speed of the resin is relatively uniform, and the resin rises due to the capillary action. This is thought to be because the air above the cloth is only pushed up and does not stay on the cloth because it rises only by the action of the phenomenon.

On the other hand, the resin is impregnated with voids formed in areas 5 mm or more from the liquid level. This is thought to be because as the yarn rises, the difference between the rising speed within the yarn and the rising speed between the yarns increases, and as a result, the resin that rises quickly surrounds the unimpregnated area, trapping air bubbles here. It will be done. In addition, Fig. 3(a)(b)
The voids in the sample shown in ) are small, and the voids in the sample shown in (c) are large. This is thought to be because the open plain weave has a larger space between the yarns than the plain weave, and in this large space, the rising speed of the resin is particularly slow, making it easier for large air bubbles to be trapped.

[0010] From the results of this test, it was confirmed that voids do not occur within 5 mm above the resin liquid level when resin is impregnated by capillary action, regardless of the type of cloth. Further, FIGS. 4 and 5 show the relationship between the rising height of the epoxy resin liquid rising due to capillary action and time after conducting a test similar to the test conditions shown in FIG. 3. Figures 4 and 5 show the rising height of the epoxy resin solution until 10 minutes have passed when a fiber cloth made of polyester and a fiber cloth made of glass are impregnated with the epoxy resin solution, as well as the initial height of each sample. This is the rate at which the liquid level rises.

Furthermore, the inventor held each sample with a length of 10 cm in a glass cylinder under atmospheric pressure, and measured the difference between the epoxy resin liquid rising due to capillary action and the liquid level of the poured epoxy resin liquid. A test was conducted in which epoxy resin was poured to ensure that no difference occurred. As a result, it was confirmed that each sample having a length of 10 cm was impregnated without generating any voids.

[0012] From the above tests, it was found that A. In impregnation only by capillary action, the
If the thickness is less than mm, voids will not occur. B: Voids will not occur if the liquid level is raised to match the impregnation rate due to capillary action. The above two findings were obtained.

Examples based on this knowledge are shown in FIG.
This will be explained with reference to FIG. Figure 1 shows a molding die 11 and a core material 12.
The F formed by this molding die 11 and core material 12
RP13 is shown. The molding die 11 includes a cylindrical portion 14, and a lower cap 15 and an upper cap 16 screwed to the lower and upper portions of the cylindrical portion 14. This molding die 11 is installed upright in a heating device (not shown). An injection pipe 17 for injecting resin is connected to the lower cap 15, and an exhaust pipe 18 for discharging air is connected to the lower cap. Recesses 19 and 20 for accommodating the ends of the core material 18 are formed at the centers of the inner sides of both caps 15 and 16, respectively.

A resin tank 21 for delivering resin is connected to the injection pipe 17, and a suction side of a vacuum pump 22 is connected to the exhaust pipe 18. Resin tank 21
A resin made of liquid thermosetting epoxy resin is stored inside. Further, the resin tank 21 is provided with a vacuum pump 23 for discharging air mixed in the resin, and a resin stirring device 24. A tube pump 25 is disposed in the middle of the injection pipe 17, and is capable of supplying a constant amount of resin into the molding die 11. Further, a reservoir 26 is arranged in the middle of the exhaust pipe 18 to collect resin overflowing from the molding die 11. 32-36
is a valve.

Next, a method for manufacturing FRP using the apparatus configured as described above will be explained. First, a long cross 31 with a narrower width is attached to the outer periphery of the cylindrical core material 12.
Wrap it around the specified number of times. As this cloth 31, polyester fiber cloth or glass fiber cloth is used. This cloth 31 is made of plain-woven glass fiber with a thickness of 0.21 mm and a mass of 206 grams square centimeter, and its surface is subjected to silane coupling treatment.

Next, the core 41 formed in this way is
As shown in FIG. 1, the recesses 1 of the upper and lower caps 15 and 16
Both upper and lower ends of the core material 12 are fitted into the upper and lower ends of the core material 12, respectively, so that the core material 12 is erected and set within the molding die 11. After doing the above, the vacuum pump 22 is driven with the valve 35 closed to exhaust the air inside the mold, and a heating device (not shown) is used to remove the mold from the mold.
is heated. In addition, with the liquid resin stored in the resin tank 21, the stirring device 24 and the vacuum pump 23
is driven to vacuum agitate and defoam the resin. After the vacuum stirring and defoaming is completed, the valve 32 is closed, the stirring device 24 and the vacuum pump 23 are stopped, and the valves 34 and 36 are opened.

Next, the tube pump 25 is driven to supply a predetermined amount of liquid resin into the molding die 11. After the liquid resin is filled into the molding die 11, the tube pump 25 is stopped and the valves 34 and 36 are closed. Then, the vacuum pump 22 is stopped, the valve 35 is opened,
In this state, the liquid resin is cured. After sufficient heat curing, the upper cap 16 was removed, the core 41 was taken out from the mold 11, and the presence or absence of voids was examined.

An impregnation test was conducted on Samples 1 to 3 using the method described above. Each sample is as shown in FIG. Here, the supplied resin was a mixture of epoxy resins of diglycidyl ether type resins having different molecular weights to adjust the viscosity, and an acid anhydride curing agent was added thereto to form an impregnated resin. In addition, the initial capillary rise speed was determined from the relationship between the capillary rise height and the elapsed time for each sample in the same manner as when the data in FIG. 5 was obtained.

[0019] Also, each impregnated sample 1 to 3 was observed,
We investigated the existence of voids. As a result, the liquid level rise rate (B
) and the initial capillary rising speed (A), the ratio B/A is 3.0
In Samples 1 and 9, cylindrical voids were generated. In addition, spherical voids were generated in samples 5 and 13 in which the ratio B/A was less than 0.5. On the other hand, no voids were observed in samples 2 to 4, 6 to 8, and 10 to 12 in which the ratio B/A was in the range of 0.5 to less than 3.0.

From now on, samples 2 to 4, in which the resin liquid level rose at a rising rate within the range of 0.5 to 3.0 of the rising rate of the capillary liquid level rising in the cloth due to capillary action,
It was found that samples Nos. 6 to 8 and 10 to 12 could be impregnated without generating voids. Although this embodiment shows an example in which the inside of the molding die 11 is evacuated during resin impregnation, it is not necessarily necessary to evacuate the interior, and an air vent may be provided at the top of the upper cap 14.

[0021]

[Effects of the Invention] As is clear from the above explanation, the present invention does not require the provision of a complicated means for evacuating the inside of the mold as much as possible, or the need to spend a long time on impregnation. Also, it is possible to impregnate the synthetic resin into the cloth without creating voids.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a molding die with a cloth attached thereto.

FIG. 2 is a pipeline diagram of the manufacturing device.

FIG. 3 is an explanatory diagram showing a state of resin impregnation.

FIG. 4 is a table showing the relationship between the resin liquid level rising due to capillary action and time.

FIG. 5 is a graph showing the relationship between the resin liquid level rising due to capillary action and time.

FIG. 6 is a table showing a sample impregnation test.

[Explanation of symbols]

11 Molding mold 13 FRP 31 Cross

Claims (1)

[Claims] Claim 1: When a fiber cloth is set in a mold and the fiber cloth is impregnated with liquid resin, the initial rate of rise of the resin liquid level rising above the fiber cloth due to capillary action is 0.5. A method for producing fiber-reinforced plastics, characterized in that the resin liquid level is raised at a rising speed of ~2.5 times.