JP2007203468A - Molding method of square pipe made of frp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining a square pipe made of FRP having a square cross section requiring a precise degree in its outer and inner dimensions as a molded product using a prepreg by a compression molding method using an autoclave or a hot press. <P>SOLUTION: When the square pipe made of FRP is molded, the prepreg is wound around a mandrel (core) having a square cross section to be laminated and a retaining mold composed of sprite molds becoming the outer mold of the square pipe is mounted on and fixed to the surface of the prepreg and subsequently heated and pressed to mold the square pipe. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method of forming a square pipe made of FRP used as an industrial application or a structural member.

Fiber reinforced plastic (FRP) is a thermosetting resin such as unsaturated polyester resin, epoxy resin and polyimide resin, matrix resin of thermoplastic resin such as polyethylene, polypropylene, polyamide, PPS, PEEK, carbon fiber, glass fiber In recent years, it is used in a wide range of fields from the aerospace industry to the general industrial field.

Known methods for forming FRP into a tubular or hollow hollow member include centrifugal molding, pultrusion molding, filament winding molding, internal pressure molding, and the like. Among these methods, the internal pressure molding method (see, for example, Patent Document 1) is a relatively simple method, in which a cylindrical molding material is placed in a mold cavity, and pressure is applied from the inside of the cylinder. It is a method of heat-curing in a state where it is in close contact with the mold, and can be applied regardless of whether the matrix resin is thermosetting or thermoplastic, and is used to form a normal hollow tubular FRP molded product. Suitable for

In order to mold hollow tubular FRP molded products (hollow members) by the internal pressure molding method, sheet-like molding is usually performed by impregnating a fiber reinforced material with a resin and adjusting fluidity and adhesiveness to improve handling. In many cases, an prepreg which is an intermediate is used. Then, using a prepreg, an inflatable bag, tube, or the like is placed inside the prepreg disposed in a hollow tubular shape in the mold cavity. Next, the bag or tube is inflated with compressed air, etc., pressure is applied from the inside of the mold, the prepreg is pressed against the inner wall of the mold, and the prepreg is heated and cured in this state to form the pressure bag. It has been. However, in the case of the conventional pressure bag molding method as described above, the outer surface of the hollow member is molded into an accurate surface along the mold, but the inner surface cannot always be molded with sufficient accuracy. (For example, refer to Patent Document 2).
JP-A-6-155595 JP 2003-334835 A

On the other hand, as a simple molding method for obtaining a molded product in which the inner surface of the hollow member is molded into an accurate surface, a core (mandrel or inner mold) is used, and this core (for example, made of aluminum or iron) is used. A method is known in which a prepreg is wound and laminated, and the wound and laminated prepreg is placed in a cavity between an upper mold and a lower mold of a mold, clamped, and then autoclaved or hot press molded. (For example, refer to Patent Document 3). Since this method is a simple molding method, it has an advantage that a hollow member can be manufactured at low cost. However, in the case of forming a square pipe whose accuracy is required for the outer and inner dimensions, the conventional molding method has a problem that the corner of the outer surface does not appear and R is easily attached.
JP 2003-334836 A

An object of the present invention is to easily obtain an FRP square pipe having a square cross section that requires accuracy in outer and inner dimensions by using a prepreg as a molded body by a compression molding method using an autoclave or a hot press. It is to provide a method.

According to the first aspect of the present invention, when an FRP square pipe is formed, a prepreg is wound and laminated on a mandrel (core) having a square cross section, and the outer mold of the square pipe is formed on the surface of the prepreg. This is a method for forming a square pipe made of FRP, characterized in that a divided mold form is mounted and fixed, and then the mold form is heated and pressurized.

The invention described in claim 2 of the present invention is the method for forming an FRP square pipe according to claim 1, wherein the mandrel is a hollow mandrel.

Invention of Claim 3 among this invention is a shaping | molding method of the square pipe made from FRP of Claim 1 or 2 whose prepreg uses carbon fiber as a fiber reinforcement.

The invention according to claim 4 of the present invention is the FRP according to any one of claims 1 to 3, wherein the divided mold is coated with a peelable film at least on the surface in contact with the prepreg. This is a method of forming a square pipe.

ADVANTAGE OF THE INVENTION According to this invention, the square pipe which is a hollow member made from FRP with a square cross section can be shape | molded accurately and easily using the prepreg excellent in the handleability and workability | operativity.

In the present invention, the FRP square pipe is obtained by winding a prepreg around a mandrel having a square cross section a plurality of times. The mandrel itself may have, for example, not only accurate triangular, quadrangular, pentagonal, and hexagonal corners, but also rounded corners, that is, an R shape. However, in the outer wall cross section of the square pipe having the hollow portion corresponding to the mandrel, at least one of the corner portions of the outer wall must have an accurate corner (not R-shaped). When it is going to shape | mold such a square pipe using a prepreg, since the fiber reinforcement which forms a prepreg has considerable rigidity, it is difficult to take out an exact outer wall angle.

This state will be described with reference to the drawings. FIG. 1 is an explanatory view (cross-sectional view) in the case where a square pipe having a square outer surface is molded by a conventional method. In FIG. 1, reference numeral 1 denotes an upper die of an upper and lower split mold having a shape corresponding to the outer surface shape of the square pipe, and 2 denotes a lower die. 3 is a mandrel having a square cross section, 4 is a prepreg wound around the mandrel a plurality of times, and 5 is a portion corresponding to the corner of the lower mold. In the conventional method shown in FIG. 1 in which a prepreg is used to mold with a mold, the prepreg is stretched in the vicinity of the corner of the lower mold cavity, and an angle is accurately measured at the portion 5 corresponding to the corner of the lower mold. There is a problem that it is not formed and becomes R-shaped.

The molding method of the present invention solves the above-mentioned problems. When molding a square pipe made of FRP, a prepreg is wound and laminated on a mandrel (core) having a square cross section. The mold is characterized in that a split mold that is an outer mold of the square pipe is mounted and fixed on the surface of the mold, and then the mold is heated and pressurized. The present invention will be described with reference to FIG.

FIG. 2 is a diagram (sectional view) for explaining the present invention. FIG. 2 shows a cross-sectional state of the wall of the square pipe, 3 is a mandrel (hollow), 4 is a prepreg wound several times, that is, a cross-section of the wall of the square pipe. Reference numerals 6a, 6b, 6c, and 6d denote divided molds, that is, frame plates, that are the outer molds of the square pipes, and are the molds that form the upper, lower, left, and right outer surfaces of the square pipes. 7a, 7b, 7c, and 7d are peelable films, and each mold is covered with the film.

In FIG. 2, the mandrel 3 is shown as being hollow, but it may be a solid one with a solid inside. The material of the mandrel is not particularly limited, and for example, aluminum, iron, or FRP can be used. FIG. 2 shows a state where the split mold is covered with a peelable film at least on the surface in contact with the prepreg. Use of such a film is convenient in removing the molded product, and is preferable in the present invention. Although there is no restriction | limiting in particular as a peelable film, For example, a silicon resin film and a fluororesin film can be used. As the fluororesin film, for example, a Tedlar (DuPont registered trademark) film is preferable.

In the present invention, a prepreg is wound and laminated on a mandrel (core) having a square cross section, and a split formwork serving as an outer mold of the square pipe is mounted and fixed on the surface of the prepreg. The split mold is a frame plate having a thickness of about 5 mmT, which can form a shape corresponding to the outer surface shape of a target square pipe, for example, a triangle, a quadrangle, a pentagon, or a hexagon. In the case of a square pipe having a square cross section, four frame plates may be used as shown in FIG. The cross section of the mandrel must also be square (including those having R) corresponding to the outer surface of the square pipe. However, the formwork and mandrel are not particularly limited in material and others.

In the present invention, the method / means (not shown in FIG. 2) for fixing the divided mold mounted on the surface of the prepreg is not particularly limited. For example, it is possible to employ a method / means for fixing the molds to each other by screwing them or winding them with a tape or the like. A simple and convenient method is to fix the mold with a heat-resistant resin tape.

In the present invention, a split mold that is an outer mold of the square pipe is mounted and fixed, and then the mold is heated and pressurized. In the present invention, since the mold frame is a divided frame plate, for example, pressure is applied from the upper and lower surfaces, and the square shape of the square pipe is accurately formed. As a method and means for heating and pressurizing the mold, it may be performed by a method such as normal autoclave molding, hot press molding, or vacuum molding. The molding conditions are suitably a pressure of 0.05 to 4 MPa, a temperature of 80 to 200 ° C., and a time of 1 to 3 hours. After the prepreg is cured by heating, the mold or the whole is cooled, and the molded product is removed from the mold. In vacuum forming, compression molding is carried out as a result by enclosing and sealing the entire form including a mold with a bagging film, and making the inside in a reduced pressure state and heating in a curing furnace or the like.

In the present invention, the prepreg wound around and laminated on the mandrel may be anything and is not particularly limited. A prepreg is a molded intermediate material in which a fiber reinforcing material is impregnated with a matrix resin such as a thermosetting resin or a thermoplastic resin, and the flowability and adhesiveness are adjusted to improve the handleability. In this invention, there is no restriction | limiting in particular about the form of the fiber reinforcement which forms the prepreg wound and laminated | stacked on a mandrel. The fiber reinforcement is usually composed of warp and weft such as plain weave, twill weave, satin weave, etc., and the fiber bundle is aligned in one direction into a sheet shape, and this is uniaxially stitched with stitch threads in the perpendicular direction It is used in the form of a woven fabric, a multi-axis woven fabric in which a plurality of sheet-like materials arranged in one direction are stacked at different angles and stitched with a stitch thread in a perpendicular direction.
Alternatively, the fiber bundles (strands) are aligned in one direction in parallel to form a sheet and impregnated with resin, or the fiber bundles are arranged at ± 45 degrees and impregnated with resin. There may be.

The fiber reinforcing material is not particularly limited, and examples thereof include carbon fiber, glass fiber, aramid fiber, boron fiber, and metal fiber. Preferred is carbon fiber.

Examples of the thermosetting resin include epoxy resins, unsaturated polyester resins, phenol resins, vinyl ester resins, cyanate ester resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, maleimide resins and cyanate ester resins. There are resins selected from prepolymerized resins. These can also be used as one type or a mixture of two or more types. Examples of thermoplastic resins include polypropylene, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, aromatic polyamide, aromatic polyester, aromatic polycarbonate, polyetherimide, polyarylene oxide, thermoplastic polyimide, and polyamideimide. is there. Two or more of these resins may be used in combination.

Hereinafter, the present invention will be described by way of examples. An example of forming an FRP square pipe having a square cross section as shown in FIG. 2 will be described. First, a prepreg 4 of carbon fiber was wound around a hollow core (made of aluminum) as shown by 3 in FIG. As a carbon fiber prepreg, an epoxy resin was impregnated into a plain fabric (Toho Tenax Co., Ltd., W-3101) having warp weft using carbon fiber HTA3K (Toho Tenax Co., Ltd., general-purpose grade carbon fiber, 3000 filaments). What was used (resin content: 40%). Five prepregs were stacked so that the laminated pattern was (0/90), (± 45), (30/120), (± 45), (0/90) and wound around the core.

Then, as shown in FIG. 2, the upper and lower, front and rear, and left and right sides of the core around which the prepreg is wound and laminated are pressed by a stainless steel frame plate having a thickness of 5 mmT. Fixed with tape (installed and fixed with a split formwork). A Tedlar (DuPont registered trademark) film was disposed between the prepreg and the frame plate. After that, the mold is put in an autoclave and cured by heating at a pressure of 4 kgf / cm ² and a temperature of 130 ° C. for 2 hours, and then cooled and shaped to obtain a square pipe having a square shape as shown in FIG. It was. The four corners of the obtained square pipe were precisely formed at right angles.

It is explanatory drawing of the conventional shaping | molding method. It is explanatory drawing of the shaping | molding method of this invention.

Explanation of symbols

1 Upper mold 2 Lower mold 3 Mandrel (core)
4 Prepreg wound around the mandrel 5 Lower mold corner (the part where the prepreg is not laid)
6a, 6b, 6c, 6d Split molds 7a, 7b, 7c, 7d Release films

Claims (4)

When forming a square pipe made of FRP, a prepreg is wound and laminated on a mandrel (core) having a square cross section, and a split formwork, which is the outer mold of the square pipe, is mounted and fixed on the surface of the prepreg. Then, a method for forming a square pipe made of FRP, wherein the mold is heated and pressurized. The method for forming an FRP square pipe according to claim 1, wherein the mandrel is a hollow mandrel. The method for forming an FRP square pipe according to claim 1 or 2, wherein the prepreg comprises carbon fiber as a fiber reinforcement. The method for forming an FRP square pipe according to any one of claims 1 to 3, wherein the split mold is at least a surface in contact with the prepreg is covered with a peelable film.

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