JPS6324445B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a girder structure made of a so-called resin-based composite material that combines 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 assembly accuracy. 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 circumferential dimensions. It is inappropriate to mold using the autoclave method or hot press method.

Therefore, there is a method of molding in which a closed mold with accurate external dimensions is used, a pressurized bag that can be expanded under pressure is placed inside, and the object to be molded is pressed 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 in the case of girder structures that had internal partition walls such as webs.

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.

Further, 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 ruptures 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 is necessary to prepare many types of molds, which increases the cost. 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 material to be formed is supported from the inside so that the internal shape of the composite material structure is determined by the force-applying bag itself, 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 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 expanded and folded like an umbrella, or it can be divided like parquet, or you can make a mold out of plaster and after the molding is completed, break the plaster by poking it with a stick through the opening. There were other methods such as removing it. However, in all of these methods, as in the case of JP-A-54-13571, it is very time-consuming to produce the mold itself. especially,
When the external 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 that holds the mold, and the heat capacity of the mold itself is large, resulting in uneven temperature distribution during hot molding. Make it bigger. Furthermore, it requires a large amount of money 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.

Furthermore, as shown in FIG. 3A, the inside is made of a web 14.
When the foamable material 28 is injected into the interior of a three-dimensional structure partitioned by partition walls and foamed after molding and hardening to fill the interior with the foamed material, the buckling strength of the conventional web is low due to its structure. Because it is low, the third
As shown in Figure B, the web 14 is bent by the pressure P when the foamable material foams and expands. If the web 14 bends in this way, it is inevitable that the outer shape will be distorted even if the web 14 is surrounded by the molds 10 and 18.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a method for manufacturing a composite girder structure at low cost and with high precision by eliminating the various drawbacks mentioned above.

Furthermore, it is an object of the present invention to provide a method for manufacturing a composite girder structure that can be molded in one step and can have a desired internal shape with high precision.

Further, the present invention aims to provide a method for manufacturing a composite material girder structure without worrying about the pressure bag bursting and which allows the pressure bag to be thin.

Another object of the present invention is to provide a method for manufacturing a composite girder structure that does not require the pressurized bag to have the same shape as the internal shape.

That is, in the method for manufacturing a composite girder structure according to the present invention, upper and lower flange member materials made of synthetic resin and reinforcing fibers, and flange members made of synthetic resin and reinforcing fibers are placed in a rigid mold giving a desired shape. A web member material joined to the flange member material to create a small space between the web member material and a corner placed in the small space between the flange member material and the web member material so that the bottom surface is in contact with the flange member material. The member and a thin pressurized bag placed between the flange member material and the web member material are enclosed, and the inside of the pressurized bag is heated and molded while pressurizing, and the corner member is attached to the molded girder. Each side surface of two imaginary circles that have a height of 20% or more of the distance between the upper and lower flanges of the structure and that touch each other with the distance between the upper and lower flange members of the molded girder structure as the diameter. It is characterized by having a nearly triangular cross section where the two touch each other.

According to the method described above, the corner members have a sufficient height of 20% or more of the distance between the upper and lower flange members of the molded girder structure, and are in contact with each other with the distance between the upper and lower flange members as a diameter. Since the corner members have a substantially triangular cross section with each side touching each of the two virtual circles, the corner members can sufficiently support the internally pressurized pressure bag in a natural shape, and The webs are not tilted so that one of the pressurized bags displaces the other, and therefore the internal shape can be shaped as desired. Furthermore, since the pressure bag is supported in a natural manner by the corner members, there are no corners where cavities are likely to form, there is no fear of the pressure bag bursting, and it can be made sufficiently thin. If the pressure bag can be made thin in this way, pressure can be transmitted anywhere, and therefore the entrance of the pressure bag can be made extremely small. Further, since the internal shape is mainly defined by the flange member and the corner member, and the pressurized bag is pressurized and expanded in a natural manner, it is not necessary to make the pressurized bag exactly according to the internal shape. Further, since there is no need for an inner mold, even if the internal design of the structure is changed, the structure can be easily manufactured without using any special jig as long as the external shape remains unchanged. Furthermore, although molding distortion is unavoidable in composite structures due to their anisotropy, it is possible to fabricate three-dimensional structures with high rigidity in one go.
It has good external precision and is particularly effective in manufacturing items that require high performance, such as aircraft wings.

According to an embodiment of the manufacturing method of the present invention, the corner member may have an isosceles triangular cross-sectional shape with a right angle apex, and each side surface of the corner member has a smooth concave curved surface. Alternatively, it may have two planes that touch each other at an obtuse angle so as to be concave. Furthermore, the corner members may be made of a material made of hollow spheres hardened with resin. In this case, the hollow sphere may be made of glass, for example. And also, the corner members may be made of thermosetting foam.

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

Figures 4A to 4F illustrate the process of making a fixed wing for an aircraft according to the method of the present invention. First, as shown in FIG. 4A, a skin material 32 is placed on a lower die 30 of a mold giving an outer shape so that the fibers are oriented at 45 degrees. This outer skin material is, for example, a synthetic resin sheet containing reinforcing fibers. On top of that, an uncured main girder member material 34 made of a unidirectional material layer made of continuous fibers and synthetic resin and strong only in the fiber direction, and a flange member material made of a honeycomb material 36 are layered, and further, as shown in FIG. 4B. As shown in
Layer the inner skin material 38. A corner member 40 having a substantially triangular cross section is placed on top of the main girder member material 34.
Then, the web member material 42 is placed as shown in FIG. 4C. After that, a pressure bag 44 made of a thin film is placed between the web member materials 42 in the fourth D.
Insert as shown. Lower mold 3 prepared as such
An upper mold 46, in which each material except the web member material is laminated in the same way as the lower mold, is placed on top of the mold 46 as shown in FIG. 4E, and the upper mold 46 is closed. Then, the pressure inside the molds 30 and 46 is reduced to force the uncured main spar member material 34, honeycomb material 36, etc. into the molds and allow them to settle at predetermined positions. Thereafter, the molds 30 and 46 are heated and molded while applying pressure to the pressure bag 44. Then, when the mold is removed, a wing having a cross section as shown in the partial cross-sectional view of FIG. 4F is completed.

The corner members used in the above method have a height that is 20% or more of the distance H between the upper and lower flange members, and have, for example, an isosceles right triangular cross section. That is, referring to FIGS. 6A and 6B, flange members 48 and 50 of distance H
If the pressure bags 44A and 44B are inflated under pressure between the two ends, the ends of the pressure bags initially draw a circle with a diameter H. Since the pressurized bags 44A and 44B do not necessarily have the same internal volume, their inflation speeds are not the same. Therefore, if the corner member 40 is small, as shown in FIG. 6B,
One pressure bag 44A enters the other pressure bag 44B beyond the line A connecting the corner members, and the two pressure bags come into contact. If further pressure is applied in this state, the pressurized bag presses the web member material as shown by reference numerals 42A and 42B, and the web member is in a position deviated from the line connecting the corner members and the cavity 52. You can also do it. On the other hand, by increasing the size of the corner members,
When both sides thereof touch an imaginary circle with a diameter H, the corner member will touch the end of the pressurized bag that is inflated in a natural shape, that is, the end of the pressurized bag that draws a circle with a diameter H, as shown in FIG. 6A. Restrain it to keep its shape. Therefore, even if the inflation speeds of the pressure bags are different, the pressure bag 44A that expands faster is restrained by the corner member 40 as shown in FIG. 6A. Therefore, even if the other pressure bag 44B is not fully inflated at that time, as it is pressurized, the pressure bag 44B will also expand to the line A connecting the corner members, as shown by reference numeral 44b. Therefore, the web member can always be positioned on the line A connecting the corner members and will not be tilted. As a result of various experiments, it was found that the height of this corner member needs to be 0.2H or more.

Furthermore, this corner member also exhibits the following effects.

According to the mechanics of materials, the membrane stress σ in the circumferential direction acting on a cylindrical internal pressure vessel is given by σ=pR/t, where p is the internal pressure and t is the membrane thickness, and R is the radius. The force F that causes the thin film to expand per unit width is F=σt=pR.

Therefore, when the radius of the pressure bag 44 is large as shown in FIG.
The force F that tends to expand along the .

On the other hand, as shown in Fig. 7B, when the membrane is sufficiently stretched so that a portion with a small radius remains on the even side, the membrane force F' of this portion is only pr, where r is the radius of curvature of the even side. Once the adhesive force and the tension force acting on the membrane are balanced, it will not expand any further, even if the pressure bag has sufficient dimensions. This is because as the pressure increases, the pressurized bag is pressed more and more strongly against the composite material, and the sheer force (adhesive force) acting on the bag also increases to balance the membrane force F'.

That is, assuming that the massing coefficient is μ and the contact length between the pressure bag and the composite material is L, the massing force F _F is F _F =μpL. On the other hand, as mentioned earlier, the membrane force is F=pR. In order for the membrane to expand, it is necessary that F> _FF , but F-F _F = pR-μpL=p(R-μL)>0, so R = μL regardless of the pressure p. Stop at. If you think about it further, the mass coefficient μ is not a constant value as is generally said in the case of uncured resins, but changes depending on the temperature (ie, the viscosity of the resin). Note that at room temperature, the minimum radius of the pressurized bag does not change much even when the pressure reaches several atmospheres. That is, at room temperature, the thermoplastic film that is the material of the pressurized bag has considerable strength, and the resin of the composite material also has high adhesive strength, and is balanced with a relatively large radius r.

When this is placed in an autoclave, the pressure is increased, and the thermoplastic is heated, the thermoplastic softens and the membrane begins to expand again little by little. On the other hand, as the temperature rises, the viscosity of the resins in the composite material also decreases, causing them to shift relative to each other. Since the heating is not rapid, the process develops at a slow rate. At this time, the above-mentioned problems appear in various forms in the conventional case. However, in the present invention, the corner members keep the radius of the pressure bag large so that when the pressure bag is pressurized at room temperature and low pressure, it takes on a shape that is almost close to the final shape. will not occur and the internal structure will be stable.

In order for the corner members to fully exhibit the above functions, the corner members must be able to withstand the pressure and temperature during molding, and
Additionally, it must be able to support the web and prevent buckling. For this purpose, a certain degree of compressive stiffness is required. Therefore, the corner member is made of, for example, a molded product made of a minute glass hollow sphere (glass microballoon) hardened with resin. This is a preferred material because it has very strong hydrostatic pressure properties and is lightweight. Furthermore, this material
Since it can be easily processed, it can be cut out from a block by cutting, or it can be cast into a mold with the desired shape. The micro balloon is
It is not limited to glass, and may be made of materials such as phenol and shirasu. Further, the corner members may be made by cutting out a foamed material of a thermosetting resin having a relatively high foaming density, such as urethane foam, or by pouring it into a mold. Furthermore, for example, it is possible to form the composite material itself into a desired shape and use it as a corner member.Furthermore, if a unidirectional material is used and the fiber direction is the load direction, it can be used to handle large tensile loads. Effective for structures.

According to the method of the present invention using the corner members as described above, not only the external shape but also the internal structure of the composite material structure can be determined accurately. Therefore, high quality products with less variation in structure can be produced. Furthermore, because the pressurized bag is maintained in its natural inflated configuration, problems such as bursting of the pressurized bag are eliminated. If the pressure bag ruptures,
No matter how small the hole is, the pressing force will be drastically reduced and the structure will no longer be able to take its shape. especially,
Composite materials often use thermosetting resins, which cannot be softened once they harden, so a rupture means that all parts of the structure are scrapped, causing no damage. is enormous.

Furthermore, the pressurized bag is easy and inexpensive to manufacture. According to the method of the invention, there is no need to give the pressurized bag a special shape in advance. Simply make a bag that roughly matches the inner circumference or is larger, and even if the bag is too large and wrinkles form inside, the weight loss is extremely small because the film is thin. Therefore,
The only jig required for molding is a mold that gives the outer shape, and it is inexpensive. In particular, structures such as aircraft wings not only have a complex curved outer shape, but also have extremely strict dimensional accuracy, so manufacturing a mold requires a huge amount of cost. Furthermore, the thickness and internal structure of the structure may undergo extremely complex changes because weight reduction is the top priority.
Therefore, since the internal dimensions of the structure are very complex, methods that impose manufacturing constraints on the pressurized bag will result in increased weight and cost. Therefore, this feature of the invention is particularly suitable for manufacturing aircraft wings and the like.

This feature is not just limited to the processing cost of the pressurized bag itself. For example, even if the structure has a complicated internal shape, the pressurized bag may have a linear shape. That is,
The method of the present invention not only facilitates the manufacture of the girder structure, but also solves the problem of molding the girder structure, which was a problem with the conventional integral molding method using an irregularly shaped pressurized bag. As a result, the integral molding method became truly practical, and many of its effects were put to use.

Further, according to the present invention, even if the design of a structure is changed, if the external shape is not changed, there are no jigs or tools required to make the change, and it is possible to easily produce prototypes and provide excellent products in a short time and at low cost. . For example, even if the number of webs increases, pressurized bags can be easily made without increasing the number of jigs and tools. As mentioned above, jigs and tools are not only expensive, but also have the problem of durability. As the number of jigs and tools increases, the problem of their durability increases rapidly.

And also, when an adhesive thermoplastic film is used in the pressure bag, it is glued inside and does not need to be removed. This is a desirable feature because if the structure is deep and complex, the pressurized bag cannot be easily removed, even with sufficient demolding treatment. Furthermore, if the pressure bag is adhered to the inside of the structure after molding, not only will there be no problems associated with removal, but it will also be possible to prevent moisture from entering from the inside and improve weather resistance. Since the pressurized bag can be a thin film, pressure can be transmitted no matter how narrow the space, and it does not matter even if the entrance of the pressurized bag is extremely small. Since the size of the opening is usually limited to a small size, the method of the present invention can provide a wide range of flexibility in the design of composite structures in this respect. However, in a relatively shallow structure where the pressure bag can be easily removed, non-adhesive heat-resistant plastic film or heat-resistant rubber sheet can also be used as the material for the pressure bag.

In addition, according to the method of the present invention, although molding distortion cannot be avoided due to the anisotropy of the composite material structure, it is possible to fabricate a three-dimensional structure with high rigidity in one step, so the external shape can be reduced. It has good accuracy and exhibits high performance on aircraft wings.

Additionally, the method of the invention increases the buckling strength of the web.

That is, in Fig. 9A, the shear buckling strength τ _CR of the web is given by τ _CR = KE (t/h) ² E: Young's modulus of the material K: a constant given by the buckling condition, and the web height As the height h increases, the buckling strength decreases rapidly. Metal materials are designed to withstand higher stress even if the web buckles and wrinkles, but this is not possible with composite materials, so the web is designed to have a corrugated shape to increase its buckling strength, or As shown in the figure, a honeycomb sandwich structure 56 may be used. However, according to the present invention, as shown in Fig. 4F, the web height h is 3/5 or less of the distance between the flange members due to the corner members, so the buckling strength τ _CR increases by at least 4 times. .
Therefore, even a simple flat plate structure can be used without a corrugated plate structure or a honeycomb sandwich structure, simplifying the structure and making molding easier.

That is, if a web with a complicated shape is used, the integral molding manufacturing method cannot be applied, but with the method of the present invention, there are no restrictions on strength, and the integral molding method, which has excellent advantages, can be applied.

Furthermore, as shown in FIG. 4G, even if the foam material is injected and foamed into the cavity between the outer skin 32 and the web 42 after molding without using the honeycomb material, the height of the web is low and the overall height is low. Since the shape is designed to withstand pressure, there is no problem of the web bending or distorting the overall shape.

Although the embodiments of the present invention have been described above, the corner member 4
For example, as shown in FIG. 8A, the two sides of the right-angled isosceles triangle can be a smooth concave curved surface in the shape of an arc, which is close to the natural shape of the pressure bag. In addition, the corner member is divided into two parts, an upper part 40a and a lower part 40b, as shown in FIG. 8B, and the lower part 40a is divided into two parts.
For 0b, a configuration in which a honeycomb core is used to reduce the weight is also considered. In this case, the side surfaces of the portions 40a and 40b form an obtuse angle to each other so as to be concave.

In addition, in the above embodiment of the present invention, all the wing structural parts were molded in one step, but for example, if an opening is required for inspecting the inside of the wing, as shown in FIGS. 5A and 5B, It is conceivable to create the opening 58 by cutting out a portion of the portion that does not affect the bending strength. By arranging it in this way, the rigidity of the wing structure is almost ensured, and the high precision external shape achieved by integral molding is sufficiently maintained.

As described above, according to the present invention, 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, has a simple structure, is easy to mold, and 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 a hollow composite structure; Figures 3A and 3B are diagrams illustrating an example of filling a conventional structure with foam material; Figure 4A; 4F to 4F illustrate the steps of the method according to the invention, FIG. 4G is a cross-sectional view of a structure made according to the invention filled with foam material, and FIGS. 5A and 5B show the steps of the method according to the invention. A perspective view and a cross-sectional view of another girder structure made by FIGS. 6A and 6B are
Diagrams illustrating the function of corner members, Figures 7A and 7B
The figure is a diagram illustrating the extension of the pressurized bag, FIGS. 8A and 8B are diagrams showing a modified example of the corner member, and
9A and 9B are cross-sectional views of conventional web structures. 10, 18... Mold, 12... Composite material, 14
... Web, 16 ... Pressure bag, 20 ... Hollow, 2
2...Corner, 24...Wrinkle in the web, 26...
...Tear, 28...Foamable material, 30...Lower mold, 3
2... Outer skin, 34... Main girder member material, 36... Honeycomb material, 38... Inner outer skin, 40... Corner member, 42... Web member material, 44... Pressure bag,
46... Upper mold, 48, 50... Flange member, 5
2...Cavity portion, 54...Wrinkle, 56...Honeycomb member, 58...Opening.

Claims (1)

[Scope of Claims] 1. A small space is provided between upper and lower flange member materials made of synthetic resin and reinforcing fibers and the flange member material made of synthetic resin and reinforcing fibers in a rigid mold that provides a desired shape. a corner member placed in the small space between the flange member material and the web member material so that its bottom surface contacts the flange member material; A thin pressurized bag placed between the flange member material and the web member material is enclosed, and the inside of the pressurized bag is heated and molded while pressurizing, and the corner member is formed into a molded girder structure. The height is 20% or more of the distance between the upper and lower flanges of the molded girder structure, and each side surface touches each of two imaginary circles that touch each other with the diameter being the distance between the upper and lower flange members of the molded girder structure. A method for manufacturing a composite girder structure, characterized in that the cross section is approximately triangular. 2. The method for manufacturing a composite material girder structure according to claim 1, wherein the corner member has an isosceles triangular cross-sectional shape with a right angle apex. 3. The method for manufacturing a composite girder structure according to claim 1, wherein each side surface of the corner member has a smooth concave curved surface. 4. The method for manufacturing a composite girder structure according to claim 1, wherein each side surface of the corner member has two planes that touch each other at an obtuse angle so as to be concave. 5. The method for manufacturing a composite girder structure according to any one of claims 1 to 4, wherein the corner members are made of a material made of hollow spheres hardened with resin. 6. The method of manufacturing a composite girder structure according to claim 5, wherein the hollow sphere is made of glass. 7. The method for manufacturing a composite girder structure according to any one of claims 1 to 4, wherein the corner members are made of a thermosetting foam material.