JP2007076202A - Molding method of frp-made square pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining a square pipe, or a FRP-made hollow member having a square shape in the cross section, easily and as a molded body having an accurate angle by using a prepreg. <P>SOLUTION: The molding method of the FRP-made square pipe using a split type die separable into upper and lower parts, or a form block and a bagging film, comprises the steps of arranging a prepreg comprising a reinforcing material of a one-direction-arrayed fiber in the parts that correspond to the edge parts of the lower die or the form block, that are inside of the outermost layer of the prepreg wound in a plurality of times around the mandrel having a square cross section, so that the fiber axial direction of the prepreg agrees with the axial direction of the mandrel, then clamping the die or sealing the form block and the bagging film, and executing the compression molding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for 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. Centrifugal molding is a method in which fibers are wound around the inner surface of a rotating cylindrical body from a roller disposed concentrically within the cylindrical body, and the resin is sprayed and impregnated with a matrix resin, followed by curing. It is suitable for manufacturing a product having a relatively large diameter and a simple shape. The pultrusion molding method is a method in which a reinforcing fiber base material is impregnated with a resin and then drawn using a mold, and the resin is solidified or cured to obtain a molded product. A straight pipe having a uniform cross section is obtained. Used for manufacturing. The filament winding molding method is a method in which a fiber impregnated with resin is wound around a mandrel, and the mandrel is pulled out after the resin is solidified or cured. Used to manufacture the body. The internal pressure molding method is a method in which a cylindrical molding material is placed in the mold cavity, and this is heat-cured in a state where pressure is applied from the inside of the cylinder and in close contact with the mold. It is applicable to both normal and thermoplastic, and is suitable for molding a normal hollow tubular FRP product.
JP-A-6-155595

On the other hand, when molding an FRP product, a prepreg, which is a sheet-shaped molding intermediate in which a fiber reinforcing material is impregnated with a resin and has good handling properties except for fluidity and adhesiveness, is often used. As a method for forming a hollow member using a prepreg, an autoclave molding method, a hot press molding method, a vacuum bag molding method, an elastomeric molding method, and the like are known (for example, see Patent Document 2). ).
JP 2003-334836 A

However, if an attempt is made to obtain an FRP molded product having a precise shape using a prepreg, the conventional means / method may not always provide a sufficient product. For example, in the case of forming a rectangular parallelepiped square pipe, when a strict rectangular parallelepiped is required, there is a problem that the conventional prepreg molding does not produce a corner and tends to have R. .

An object of the present invention is to provide a method of obtaining a square pipe, which is a hollow member made of FRP having a square cross section, by a compression molding method using a prepreg as a molded body having an accurate corner.

In the present invention, when an FRP square pipe is formed using a die or mold with a top and bottom split mold and a bagging film, the lower mold is placed inside the outermost layer of a prepreg wound around a mandrel having a square cross section. Alternatively, a prepreg made of a unidirectionally arranged fiber reinforcing material is arranged in a portion corresponding to the corner of the mold so that the fiber axis direction coincides with the axial direction of the mandrel, and then the mold is clamped or molded mold This is a method of forming an FRP square pipe, wherein a bagging film is sealed and compression molded.

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 is not limited to each corner, for example, a precise triangle, quadrangle, pentagon, or hexagon, but may have a rounded corner, that is, an R shape. However, the wall cross section of the square pipe having the hollow portion corresponding to the mandrel must have at least one corner portion of the outer wall having 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 diagram in the case of forming a square pipe having a square outer surface. In FIG. 1, reference numeral 1 denotes an upper die of a two-part upper and lower split mold having a shape corresponding to a square pipe shape, 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 of forming with a mold using a prepreg, the prepreg is stretched in the vicinity of the lower mold, and in the portion 5 corresponding to the corner of the lower mold, the angle is not accurately formed and becomes an R shape. There is a problem of end.

Therefore, in order to solve such a problem, a device as shown in FIG. 2 is devised. In FIG. 2, 3 is a mandrel, 4 is a prepreg wound a plurality of times, that is, a cross section of a square pipe wall, and 6 is a prepreg made of a unidirectionally arranged fiber reinforcement. In the present invention, a portion corresponding to the corner of the lower mold (5 in FIG. 1) is formed of a unidirectionally arranged fiber reinforcing material inside the outermost layer of the prepreg 4 wound around the mandrel 3 having a quadrangular cross section. The prepreg 6 is arranged so that the fiber axis direction thereof coincides with the axial direction of the mandrel 3. Then, the upper and lower molds of the mold are clamped to compress the prepreg. When such a molding method is adopted, the prepreg made of the unidirectionally aligned fiber reinforcement is easily deformed in the cross-sectional direction with a relatively small pressure, so that the wall cross-section as shown in FIG. A square pipe is obtained. At this time, since the outermost layer is wound around the mandrel 3, the integrity of the molded body is maintained.

In the present invention, typically, an upper and lower split mold having a shape corresponding to a shape of an outer surface of a target square pipe, for example, a triangle, a quadrangle, a pentagon, or a hexagon is used. 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 mold and mandrel are not particularly limited in material and others.

In the present invention, when the shape of the square pipe requires a strict angle only in the part corresponding to the lower mold, the molding die is used corresponding to the lower mold, and the bagging film corresponding to the upper mold is used. It is also possible to obtain a desired square pipe by vacuum forming. In such a case, the mold and the bagging film are hermetically sealed and reduced in pressure, and, for example, heated in a curing furnace, as a result, compression molding is performed, and at least the portion of the prepreg laid on the mold is accurate. It becomes a square pipe having an angle. Or what sealed the shaping | molding die and the bagging film may be heated and pressurized with an autoclave. In the present invention, the term “compression molding” includes not only the case where pressure is applied from the outside, but also that the inside is evacuated or decompressed.

In the present invention, the prepreg wound around the mandrel a plurality of times 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 to improve handling properties except for fluidity and adhesiveness. In this invention, there is no restriction | limiting in particular about the form of the fiber reinforcement which forms the prepreg wound around a mandrel several times. 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.

On the other hand, in the present invention, the prepreg made of a unidirectionally arranged fiber reinforcing material used in a portion corresponding to the corner of the lower mold or the mold is formed into a sheet shape by aligning fiber bundles (strands) in one direction in parallel. This is impregnated with a resin, or a tape-like prepreg (bias tape prepreg) in which fiber bundles are arranged at ± 45 degrees and impregnated with resin. A bundle of 1K to 12K of carbon fiber or a bias tape prepreg of carbon fiber is preferable. In the present invention, the arrangement of the unidirectionally arranged fiber reinforcing material or the prepreg comprising the same is such that the fiber bundle is arranged at ± 45 degrees like a bias tape, for example, when the fiber axis direction coincides with the mandrel axial direction. In this case, the average arrangement direction is one direction, or the direction is matched with the axial direction of the mandrel.

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.

In the present invention, a prepreg made of a unidirectionally arranged fiber reinforcing material is formed on the inner side of the outermost layer of a prepreg wound around a mandrel having a square cross section and corresponding to the corner of the lower mold or the mold. Arrange so that the axial direction matches the axial direction of the mandrel. In the case of a bias tape prepreg in which fiber bundles are arranged at ± 45 degrees, the direction of 0 degrees may be arranged so as to coincide with the axial direction of the mandrel. The outermost layer prepreg is preferably one (one layer), but if the prepreg is sufficiently thin and flexible and can form an accurate angle, the outermost layer consists of two or more prepregs. Also good.

In the present invention, the upper and lower molds of the mold are then clamped or the mold and the bagging film are sealed, and the prepreg is compression molded. The compression molding may be performed by a method such as normal autoclave molding, hot pressing, vacuum molding, elastomeric molding, or the like. 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 heated and cured, the mold and the mold are cooled, and the molded product is removed from the mold and taken out.

Hereinafter, the present invention will be described by way of examples.

An example of forming a FRP hollow member having a square cross section as shown in FIG. 2 will be described. First, as shown in FIG. 1, a carbon fiber prepreg 4 was wound around a mandrel 3 having a quadrangular cross section. Carbon fiber prepregs include plain woven fabric (W-3101 / Q-195, manufactured by Toho Tenax Co., Ltd.) using carbon fiber HTA3K (manufactured by Toho Tenax Co., Ltd., general-purpose grade carbon fiber, 3000 filaments) as an epoxy resin. (Resin content: 40%) was used. Five prepregs were stacked so that the laminated pattern was (0/90), (± 45), (30/120), (± 45), (0/90) and wound around a mandrel. Then, a prepreg made of a unidirectionally arranged fiber reinforcing material was arranged in a portion 5 corresponding to the corner portion of the lower mold inside one sheet of the outermost layer so that the fiber axis direction coincided with the axial direction of the mandrel. As the prepreg made of the unidirectionally arranged fiber reinforcing material, five prepregs made of a unidirectionally arranged carbon fiber bundle (6K strand) and an epoxy resin were laminated and used.

Thereafter, the mold is clamped, placed 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 demolded to obtain a square pipe having a cross section as shown in FIG. Obtained. The four corners of the obtained square pipe were precisely formed at right angles.

It is explanatory drawing of the conventional shaping | molding method and the shaping | molding method of this invention. It is a figure which shows the cross-sectional shape of the molded article obtained in this invention.

Explanation of symbols

1 Upper mold of mold 2 Lower mold of mold 3 Mandrel 4 Prepreg wound around mandrel 5 Corner of lower mold (part where prepreg is not laid)
6 Corner of molded product corresponding to the corner of the lower mold (cross section of the prepreg of the unidirectionally arranged fiber reinforcement)

Claims (2)

When forming an FRP square pipe using an upper and lower split mold or mold and a bagging film, inside the outermost layer of the prepreg wound around a square mandrel, the lower mold or the mold Place a prepreg made of unidirectionally aligned fiber reinforcement on the corner corresponding to the corner so that the fiber axis direction coincides with the mandrel axis direction, and then clamp the mold or seal the mold and bagging film And forming a FRP square pipe, which is compression-molded. The method for forming an FRP square pipe according to claim 1, wherein the prepreg is made of carbon fiber as a fiber reinforcing material.

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