JPS62286729A - Manufacture of hollow pipe made of fiber reinforced plastic - Google Patents

Abstract

PURPOSE:To manufacture easily a hollow pipe which is made of fiber rinforced plastic and possesses a complicated form, by a method wherein a core metal heated at the fusion temperature or more is sweeped away from the inside of a processed pipe and a tape or a tube made of a material having elasticity is removed off from the outside circumference of the said processed pipe. CONSTITUTION:A thermosetting prepreg sheet curing at the temperature a little lower than the fusion temperature of a core metal is wound round the outside circumference of the core metal manufactured of a metal fusing at a low temperature. Then the circumference of the prepreg sheet is surrounded by a material having elasticity. The core metal, prepreg sheet and the material which has the elasticity are processed into a desired form by applying press processing to them and they are heated up to a setting temperature of the prepreg sheet. The core metal is carried away from the inside of a processed pipe by heating members each, which include the processed pipe made of the prepreg sheet cured through heating, up to the fusion temperature or more and a tape or tube made of the material having the elasticity is removed from the outside circumference of the processed pipe made of the prepreg.

Description

Detailed description of the invention 3. Detailed description of the invention a. Object of the invention (industrial application field) Tubes made by rolling sheets can be used to mass produce bent tubes with relatively complex shapes, such as bicycle handles or fork blades, as well as for automobiles, which require strong and lightweight construction. It can be used to manufacture base materials for drive shafts and extremely high frequency waveguides for air and space equipment that require strong, lightweight, and strict dimensional accuracy.

(Prior Art and Its Problems) For example, in the case of a bicycle handle, conventionally, a metal tube made of iron or aluminum is bent into a desired shape.

By the way, for example, in the case of bicycle handles, there is constant research into making them from lighter materials, mainly for bicycle handles used for competitions.

An example of a lightweight and durable material that can be formed into a hollow tube shape is a material made by rolling a prepreg sheet reinforced with glass fiber or carbon fiber and forming it into a tube shape.

However, in the case of bicycle handlebars, the shape is complex and bending is troublesome, and in the case of drop handlebars, which are assembled on bicycles for competitions and sports, it is impossible to obtain handlebars made of prepreg sheets using conventional techniques. There wasn't.

That is, when processing a prepreg sheet reinforced with glass fibers or carbon fibers into a tube shape, during the heat curing of a portion of the thermosetting resin binder, the portion corresponding to the completed hollow tube is separated from the inside of the tube. It is necessary to maintain the desired shape from the outside and at the same time apply pressure to the portion corresponding to the hollow tube in order to improve the finished appearance.

However, in the case of bent pipes or hollow pipes whose cross-sectional shape changes midway through, if we use steel or brass core metals, which have been widely used for forming prepreg sheets, it is difficult to wrap the pipes around the core metal. Not only is it extremely difficult to bend the prepreg sheet, which has low mechanical strength, without damaging it, but it also becomes impossible to remove the core metal after the prepreg sheet has been heat-cured.

The method for manufacturing a fiber-reinforced plastic hollow tube of the present invention includes:
This invention was invented in view of the above-mentioned circumstances.

b. Structure of the invention (means for solving the problem) The method for manufacturing a fiber-reinforced plastic hollow tube of the present invention consists of the following five steps (a) to (e), first to fifth. There is.

That is, (a) a first step of wrapping a thermosetting prepreg sheet that hardens at a temperature slightly lower than the melting temperature of the metal constituting the core around the outer periphery of a core made of a metal that melts at low temperatures; .

(b) A tape made of an elastic material is spirally wound around the prepreg sheet formed into a tubular shape surrounding the outer periphery of the core metal in the first step, or a tube made of an elastic material is fitted around the prepreg sheet. The second step is to surround the outer periphery of this prepreg sheet with an elastic material.

(C) The core metal, the prepreg sheet formed into a tubular shape in the first step, and the resilient material surrounding the prepreg sheet in the second step are bent or shaped to have a cross-sectional shape. The third step is to process it into the desired shape by applying press processing.

(d) A fourth step in which each member bent or pressed in the third step is further heated to the curing temperature of the prepreg sheet.

(e) Each member including the thermoset prepreg sheet processed tube is further heated to a temperature higher than the melting temperature of the metal core, and the molten core is flowed out from the inside of the prepreg sheet processed tube. The fifth step is to remove the tape or tube made of elastic material from the outer periphery of the processed pipe made of prepreg sheet.

By sequentially performing the first to fifth steps shown in (a) to (e) above, the prepreg sheet is made into a hollow tube shape with a desired shape as a whole, but when the prepreg sheet is cured, Since it is elastically restrained from the outer periphery by a tape or tube made of an elastic material, the strength of the bent pipe after hardening is increased. Furthermore, during bending, the presence of the core metal prevents the cross section of the hollow tubular prepreg sheet from being crushed.

In addition, as the prepreg sheet used when carrying out the present invention, various conventionally known prepreg sheets can be used, but in the case of a prepreg sheet reinforced with carbon fiber, for example, Kasei Fiberlite Co., Ltd. MSX7714/2534 (curing temperature: 121°C), etc. manufactured by Manufacturer Co., Ltd., can be used.

In addition, various metals such as solder can be used as the low-temperature melting metal for making the core metal, but the eutectic alloy of bismuth and lead described in metal manuals has a melting temperature of 124.
℃ can be preferably used in combination with the above MSX7714/2534. The above-mentioned eutectic alloy has extremely small expansion and contraction during casting, and can be rapidly cooled after casting to obtain a cast product with a beautiful surface, so it can achieve extremely high dimensional accuracy without the need for machining after casting. Since it is possible to obtain a good core metal and has excellent ductility and malleability, it has the advantage of being easy to bend and press to change the cross-sectional shape.

Furthermore, polyethylene, polypropylene, or the like can be used as the elastic material constituting the tape or tube that restrains the prepreg sheet from its outer periphery when the prepreg sheet is heated and cured. Furthermore, heat-shrinkable synthetic resins such as fluororesin can also be used as long as they can maintain elasticity during heat curing.

(Application example) In the above section (Means for solving the problem), we mainly described the essential elements when manufacturing hollow tubes made of prepreg sheets. When manufacturing a hollow tube made of a sheet, a release agent may be further applied to the outer circumferential surface of the core metal, or a release agent may be further applied to the outer circumferential surface of the prepreg sheet wound around the outer circumference of the core metal in the second step. Wrapping release tape is effective.

Among these, the release agent applied to the outer peripheral surface of the core metal prevents adhesion between the core metal and the prepreg sheet, and is applied from the inside of the hollow tube made of heat-cured prepreg sheet after bending, etc. This is to ensure that the molten metal is completely washed away and to prevent metal from remaining inside the completed hollow tube. This is to facilitate and reliably remove an elastic tape or tube from the outer circumferential surface of a hollow tube made of plastic.

As these release agents and release tapes, conventionally commercially available products can be used.

However, if it is okay for a small amount of metal to remain inside the hollow tube after completion, a release agent on the outer circumferential surface of the core bar is not necessarily necessary, and the outer circumferential surface of the hollow tube made of prepreg sheet may be Because of the polishing process, the tape or tube can be completely removed from the outer peripheral surface of the hollow tube without necessarily winding the release tape.

Additionally, prepreg sheets used to make hollow tubes that are reinforced with carbon fiber are preferred in terms of strength, but hollow tubes that are used for purposes other than bicycle handles require such strength. If not, the hollow tube can be made by reinforcing it with fibers of a material such as glass fiber, and then machining the surface of the core metal such as cutting. It is also possible to form reinforcing spiral strips or ribs on the inside of the tube, or to integrally form a flange for a joint on the open end of the hollow tube. In other words, if a groove is formed on the surface of the core metal, and when a prepreg sheet is wound around the outer circumferential surface of the core metal, a part of the prepreg sheet enters the inside of the groove. After curing, it becomes a reinforcing spiral strip or lip, or a flange for a joint.

In order to further improve the quality of the hollow tube produced by the method of the present invention, if the prepreg sheet wound around the core metal is further fitted into the outer mold during heat curing in the fourth step,
It is possible to prevent thermal distortion or elastic return from occurring in the completed hollow tube, which would cause the dimensional accuracy of the hollow tube to become inconsistent. At this time, if necessary, if the pressure inside the heating furnace is made high, it is possible to completely prevent the resin contained in the binder of the prepreg sheet from flowing out, and it is possible to obtain a hollow tube of even better quality.

C1 Effects of the Invention The method for manufacturing a fiber-reinforced plastic hollow tube of the present invention is configured as described above, and it is possible to manufacture a fiber-reinforced plastic hollow tube with a complicated shape, which has been considered difficult in the past. It is easy to perform and plays a large role in reducing the weight of various products such as bicycle handles.

Claims (1)

[Scope of Claims] A method for manufacturing a fiber-reinforced plastic hollow tube comprising the first to fifth steps described in the following (a) to (e). (a) A first step of wrapping a thermosetting prepreg sheet that hardens at a temperature slightly lower than the melting temperature of the metal constituting the core around the outer periphery of a core made of a metal that melts at low temperatures. (b) A tape made of an elastic material is spirally wound around the prepreg sheet formed into a tubular shape surrounding the outer periphery of the core metal in the first step, or a tube made of an elastic material is fitted around the prepreg sheet. The second step is to surround the outer periphery of this prepreg sheet with an elastic material. (c) The core metal, the prepreg sheet formed into a tubular shape in the first step, and the elastic material surrounding the prepreg sheet in the second step are bent or shaped to have a cross-sectional shape. The third step is to process it into the desired shape by applying press processing. (d) A fourth step in which each member bent or pressed in the third step is further heated to the curing temperature of the prepreg sheet. (e) Each member including the thermoset prepreg sheet processed tube is further heated to a temperature higher than the melting temperature of the metal core, and the molten core is flowed out from the inside of the prepreg sheet processed tube. The fifth step is to remove the tape or tube made of elastic material from the outer periphery of the processed pipe made of prepreg sheet.