JPS6324446B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a structure made of a so-called resin-based composite material, which is a combination of fibers and synthetic resin.

Conventionally, the autoclave method has been used to manufacture structures using laminated sheets of resin-based composite materials, such as glass fibers, organic fibers, carbon fibers, etc., impregnated with epoxy resins, polyester resins, polyimide resins, etc. There are methods such as hot press method and hot press method. All of these methods are suitable for molding relatively thin, large-area flat molded products, but are unsuitable for molding three-dimensional structures.

To be more specific, in the conventional autoclave method and hot press method, first, a flat panel is manufactured,
Assemble these to create a structure. However, autoclave molding does not provide dimensional accuracy on one side, resulting in poor manufacturing quality during assembly. Furthermore, flat structures tend to suffer from molding distortion due to the anisotropy characteristic of composite materials. In the case of adhesive assembly,
Although it is necessary to control the adhesive thickness with an accuracy of about 0.1 mm, accurate positioning is difficult for the two reasons mentioned above. Furthermore, since composite materials are susceptible to stress concentration, if an assembly method using bolts/nuts, rivets, etc. is used throughout, the weight and processing cost will increase.

On the other hand, aircraft wings, ailerons, various propellers, fan blades, etc. are all hollow objects with complex internal structures, and their performance is determined by the accuracy of their outer circumference dimensions. It is inappropriate to mold using the above-mentioned oaklave method or hot press method.

Therefore, there is a method of molding using a closed mold that gives accurate external dimensions, a pressurized bag that can be expanded under pressure, and pressing the molded object outward from the inside, as disclosed in US Pat. No. 3,713,753. No., Japanese Patent Application Publication No. 1973-
This is proposed in Publication No. 16298, etc. However, even with this method, it was difficult to accurately mold the internal structure. This was particularly a problem when there was a web-like partition wall inside.

That is, in this method, since the pressurized bag is thin and flexible, as shown in FIG. 16 and upper mold 18
When molded by applying pressure to a pressurized bag, the web 14 does not always expand at the same rate, so as shown in FIG.
occurs.

Furthermore, as shown in FIG. 2A, in the method of laminating the web 12 in an H-shape in advance and forming it,
If the pressurizing force is initially small, the pressurizing bag 16 will not come into close contact with the corner portion 22, as shown in FIG. 2B, and as the bag 16 expands and moves as the pressurizing force increases, it will pass through the state shown in FIG. As shown in the 2D diagram, wrinkles 24 may occur in the web 14. In addition, if the pressure bag 16A shown in FIG. 2E is not in close contact with the corner of the web 14 from the beginning and there is not enough room for the pressure bag to stretch, the web will not wrinkle; Since the bag 16B is in a suspended state and the pressure is supported by the thin pressurized bag itself, an accident occurs in which the pressurized bag is torn as shown by reference numeral 26 in FIG. 2F due to the increased pressurizing force.

In order to eliminate the above-mentioned problems, it is first necessary to bring the pressurized bag into close contact with each corner portion in advance. For this purpose, a method was proposed in JP-A-54-13571 (Japanese Patent Application No. 52-78631) that made the pressure bag itself slightly more rigid so that it could maintain its shape and form the final shape from the beginning. It has been proposed. This method requires a mold to accurately shape the pressurized bag in advance. This causes the following problems. That is, in the case of high-mix low-volume production such as aircraft, it becomes expensive to prepare many types of molds. Furthermore, even slight design changes to small parts require the mold to be remade. Typically, the outer shape is determined by aerodynamic or structural requirements, and the wall thickness and placement of the composite structure are also determined by mechanical requirements, making the inner shape extremely complex. Manufacturing a mold with such a complicated shape requires a large amount of cost. If there are variations in the dimensions of each part of the inner mold to create such a complex shape, this will accumulate throughout the entire inner mold, and the dimensional accuracy of the inner mold will inevitably deteriorate. However, it could not necessarily be said that the above-mentioned problems could be solved.

Furthermore, in the method of JP-A-54-13571, since the pressurized bag itself supports the molded object from the inside so as to determine the internal shape of the composite structure, in order to prevent the bag from becoming soft, It is necessary to use a film that is somewhat thick, and even with the invention disclosed in the patent publication,
It is set to be 0.1mm or more. However, even this can be said to be heavy for the structure of a small aircraft. Further, if the shape of the pressure bag and the shape of the composite material structure do not match, the pressure bag may be crushed and the shape may be greatly distorted. Since the pressurized bag is relatively thick, the bag itself supports the pressure at corners with a small radius, and no pressure is applied to the composite structure, resulting in a product with bubbles.

Another method is to use a thin thermoplastic film as the pressurized bag, cover it with a mold that can be disassembled, and then insert it inside. However, this method also has the following drawbacks. That is, after the molding of the composite material structure is completed, it is necessary to pull out the mold from the opening, which requires a mold with a very complicated structure. For example, you can make a mold that can be unfolded and folded like an umbrella, or you can make it into parts like parquet, or you can make a mold out of plaster and after the molding is completed, poke the plaster through the opening with a stick. There were other methods such as destroying and removing it. However, all of these methods require a lot of effort to produce the mold itself. In particular, when the outer shape of an aircraft wing is determined by aerodynamics, and the structure and thickness of the parts are determined by strength, the internal dimensions and shape become extremely complex. It is difficult and expensive to make a mold with an external shape, and
The heat capacity of the mold itself is large, and the temperature distribution during hot molding becomes uneven, and the temperature unevenness increases the distortion of the molded product and the variation in strength. Furthermore, it requires a large amount of cost and time to modify the mold in response to design changes during prototype production. Additionally, because the mold is complex, it often interferes with the composite material structure, damaging the thin pressurized bag and causing it to burst, or distorting the internal structure.

SUMMARY OF THE INVENTION Therefore, the present invention aims to eliminate the various drawbacks mentioned above and provide a method for manufacturing composite structures at low cost and with high precision.

That is, according to the present invention, a molded article made of synthetic resin and reinforcing fibers and an inner mold are enclosed in a rigid mold that gives a desired shape, and the inner mold is heated and molded while pressurizing the inside of the inner mold. In the method for manufacturing a composite structure, the inner mold is a pressurized bag made by bonding a thin adhesive film, and a mold made from a thermoplastic foam material slightly smaller than the required size is inserted into the pressurized bag. The pressurized bag in the inner mold is heated and molded while applying pressure to adhesively bond the pressurized bag to the object to be molded, and after the molding is completed, the shrinked thermoplastic foam material in the pressurized bag is Remove remaining materials.

According to this method, the above-mentioned Japanese Patent Application Laid-open No.
In addition to achieving all the advantages of the method disclosed in No. 13571, the pressurized bag, supported by a mold made of thermoplastic foam material, can be very thin and light, resulting in the advantages of composite materials. In addition, the composite material structure can be made lighter.
Furthermore, thermoplastic foam molds can be easily made without the need for special jigs or equipment, and the inner mold can be made by simply inserting the mold into a pressurized bag, making the inner mold very inexpensive. High-mix, low-volume production can be done at the same price as mass production. Additionally, since thermoplastic foam materials can be molded into any shape very easily, the inner mold can be easily formed into any shape. At this time, the mold made of the foamed material allows the processing bags to be brought into close contact with each other without creating any gaps even at the corners of the web, so that wrinkles are not created in the web. Furthermore, since the processing bag is thin and the pressure is spread throughout the processing bag, the internal shape of the composite material structure can be formed into a desired shape with high precision. Furthermore, the thermoplastic foam material shrinks to several tenths to several hundredths of its original volume due to the heat generated during the molding of the composite structure, so it can be easily removed even through a small outlet. Furthermore, since the thermoplastic foam material is appropriately soft, if the uncured composite structure and the mold of the thermoplastic foam material interfere, the pressure bag may be damaged or the shape of the structure may be distorted. There are no problems.
Furthermore, since the pressurized bag is thin, wrinkles in the pressurized bag itself pose little problem for the composite structure.

Note that if the surface of the thermoplastic foam mold is not smooth, the pressure bag may be damaged.
Additionally, after heat molding, the shrinked thermoplastic foam material may adhere to the pressure bag due to the adhesive used to form the foam material. In order to prevent this, a mold made of thermoplastic foam material is wrapped with a heat-resistant film and inserted into the pressure bag, and after the molding is completed, the heat-resistant film is removed from the shrinked thermoplastic foam material. Remove with wood.
In this way, the mold for the foamed material is wrapped in a heat-resistant film, so it is easy to insert the mold into the pressure bag, and when the film is pulled out after molding, the remaining material from the contracted mold can be easily removed. It is removable and convenient.

Embodiments of the method according to the invention will now be described with reference to the accompanying drawings.

FIG. 3A is a perspective view of a hollow rotor blade of a helicopter, and FIG. 3B is a perspective view of a hollow rotor blade of a helicopter; FIG.
- It is a sectional view at A. This rotor blade 30
has a hollow portion 32, a hole 34 and an opening 36 for the root mounting bolt.

In order to make such a rotor blade, according to the present invention, adhesive thermoplastic plastic films are first pasted together to form a pressurized bag 40 having approximately the same size as the hollow portion 32, as shown in FIG. 4A.
to make. However, it is not necessarily necessary to have the same shape as the hollow part 32. A mold 42 as shown in FIG. 4B, which is slightly smaller than the dimensions of the hollow portion 32, is then made of a thermoplastic foam material such as styrofoam.

This mold 42 can also be made all at once by forming upper and lower molds 44 as shown in FIG. 5 and foaming the styrene therein. This method allows a large number of molds 42 to be made in a short time and is inexpensive. Furthermore, the surface can be made smooth.

Moreover, the mold 42 has portions 42A, 42B, 42
Since it can be divided into C and 42D, it can be made in four parts and then joined together with adhesive. In this case, as shown in FIG. 6A, a Styrofoam material 50 is placed on a plate 48 provided with templates 46 on both sides, and a heating wire 52 is moved along the template to cut off the top of the material. Then, by cutting the material 50 along the template 54 as shown in FIG. 6B with a heating wire 52, a portion 42 as shown in FIG. 6C is obtained.
You can also make B.

The mold 42 made as described above is inserted into the pressurized bag 40 as shown in FIG. 4C, and then a rigid metal lower mold 60 with an uncured composite material sheet 58 laminated thereon is placed as shown in FIG. 4D. A rigid metal upper mold 64 on which a similarly uncured composite material sheet 62 is laminated is placed on top of the mold and closed. A vacuum is then applied inside the molds 60 and 64 to force the uncured composite sheets 58 and 62 against the inside surfaces of the molds and allow them to settle into their predetermined positions. Thereafter, while applying pressure to the pressure bag 40, the upper and lower molds 60 and 64 are heated and molded. As a result, the pressure bladder 40 adheres to the molded composite structure or rotor blade 30 of FIG. 3A due to its adhesive properties. On the other hand, the shrunk remaining material of the expanded polystyrene is removed from the opening 36.

In the method described above, by inserting an inner mold made of polystyrene foam, the pressurized bag is brought into close contact with the inner mold in advance, so the above-mentioned problems are eliminated and a stable internal shape can always be obtained. Furthermore, since Styrofoam is very soft, even if the uncured composite structure and the Styrofoam mold interfere, there will be no problem such as damage to the pressure bag or distortion of the shape of the structure. Furthermore, the inner mold made of styrofoam does not require special jigs or equipment to manufacture it. That is, as mentioned above, polystyrene foam molds can be easily manufactured in large quantities using two templates and heating wires, and are very inexpensive, and design changes can be easily made by changing the template. . Also,
If a mold as shown in FIG. 5 is used, mass production is also possible.

Furthermore, the styrofoam shrinks to several tenths to several hundredths of its original volume due to the heat generated during molding of the composite structure, so it can be easily taken out even through a small outlet.

For example, aircraft wing structures and helicopter rotor blades have thin and long tips, and the mounting parts usually have large metal fittings, so no matter which direction you insert the pressurized bag, the openings will not fit. is narrow;
Although it is difficult to pull out the mold for pressurized bag molding inserted inside, the remaining material can be easily taken out even through such a small opening, and the present method is convenient for manufacturing such items.

Furthermore, the pressurized bag can be made very thin, thus reducing the weight of the pressurized bag and taking advantage of the lightweight advantages of composite materials.

Note that the thermoplastic foam material is not limited to foamed polystyrene, and may be any foamed material of thermoplastic resin such as PVC. These have a tendency to shrink when heated, and can also be cut with a heating wire.

If each part of the Styrofoam mold is made separately and then joined together with adhesive, the adhesive will ooze out after heating and shrink, and the shrunken Styrofoam residue will adhere to the inside of the molded composite structure. Sometimes I put it away. In this case, as shown in FIG. 7A, the styrofoam mold 42 is once wrapped in a heat-resistant plastic film 68 and fixed with heat-resistant tape 70, for example.
Next, it is inserted into the pressurized bag 40 as shown in FIG. 7B. In this way, after the molding, the remaining foamed polystyrene material 70 scattered and adhered inside can be easily removed at the same time through the small opening when the heat-resistant plastic film 68 is pulled out from the composite material structure 72 as shown in FIG. 7C. This is very convenient.

Also, when polystyrene is processed with heating wire, the surface is melted by the heat and becomes jagged.
If a pressurized bag is placed over the bag in this condition, the bag may be damaged. In this case as well, these problems can be eliminated by wrapping the styrene mold with a heat-resistant plastic film.

FIG. 8 is a horizontal stabilizer for a fixed wing aircraft having an angle of attack modification bearing mounting 80 and an opening 82 therethrough. The wings of such fixed wing aircraft have one or more internal webs. Therefore, when making such a composite material structure, a Styrofoam mold is made for each internal space partitioned by the web and placed in a pressurized bag. Then, as shown in FIG. 9, pressurized bags 86A and 86B containing styrofoam molds 84A and 84B made for each space partitioned by a web.
are placed on both sides of a web 92 on a rigid metal lower mold 90 in which an uncured composite material sheet 88A and a honeycomb core 88B are laminated, and an uncured composite material sheet 94A and a honeycomb core 94B are stacked on top of the rigid metal lower die 90. A metal upper mold 96 is placed over and closed. and,
A vacuum is applied inside the molds 90 and 96 to force the uncured composite sheet and honeycomb core against the mold interior surface and settle into position. After that, while applying pressure to 84A and 84B, the upper and lower molds 9
0 and 96 are heated and molded. As a result, the pressure bags 84A and 84B adhere to the molded composite structure, honeycomb core, and web due to their adhesive properties. On the other hand, the shrunken remaining material of Styrofoam is removed from the opening 82.

According to the present invention, as described above, it has become possible to manufacture a structure requiring high external precision in its internal structure at a small cost without using expensive jigs. Furthermore, the method of the present invention can be modified in various ways without departing from its spirit.
Its structure is simple, molding is easy, and it can be provided at low cost, making it highly practical.

[Brief explanation of the drawing]

Figures 1A and 1B and Figures 2A to 2
Figure F is a diagram illustrating a conventional method of manufacturing hollow composite structures; Figures 3A and 3B are perspective and longitudinal cross-sectional views of a helicopter rotor blade; Figures 4A to 4D; FIG. 5 is a perspective view of a mold for forming the Styrofoam mold shown in FIG. 4B, and FIG. 6A is a diagram showing each step of the method according to the present invention.
6C to 6C are diagrams showing each step of the method of making each part of the Styrofoam mold of FIG. 4B using a template and heating wire, and FIGS. 7A to 7C are diagrams showing another method according to the present invention. FIG. 8 is a perspective view of a horizontal stabilizer of a fixed-wing aircraft, and FIG. 9 is a diagram illustrating one step in making a composite structure with a web by the method of the present invention. It is a diagram. 10, 18... Mold, 12... Composite material, 14
... Web, 16 ... Pressure bag, 20 ... Hollow, 2
2...Corner, 24...Wrinkle in the web, 26...
...Rear, 30...Rotor blade, 32...Hollow part, 34...Mounting bolt hole, 36...Opening, 40...Pressure bag, 42...Styrofoam mold, 44...For Styrofoam mold mold,
46, 54... Template, 50... Styrofoam material, 58, 62... Composite material, 60, 62...
Mold, 68...Heat-resistant plastic film, 8
4A, 84B... Styrofoam mold, 86A,
86B...Pressure bag, 92...Web, 90,96
……Mold.

Claims (1)

[Claims] 1. A molded article made of synthetic resin and reinforcing fibers and an inner mold are sealed in a rigid mold that gives a desired shape, and the mold is heated and molded while pressurizing the inside of the inner mold. In the method for manufacturing a composite structure, the inner mold is formed by inserting a mold slightly smaller than the required size from a thermoplastic foam material into a pressurized bag made by bonding thin adhesive films. The pressurized bag of the inner mold is heated and molded while applying pressure, and the pressurized bag is adhesively bonded to the object to be molded. A method for manufacturing a composite material structure, characterized by removing material. 2. The mold made of the thermoplastic foam material is wrapped with a heat-resistant film and inserted into the pressure bag, and after the molding is completed, the heat-resistant film is removed together with the shrunken thermoplastic foam material. A method for manufacturing a composite material structure according to claim 1, characterized in that: 3. The method for manufacturing a composite material structure according to claim 1 or 2, wherein the thermoplastic foam material is expanded polystyrene.