JPH0375340B2 - - Google Patents

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to polyester resin, epoxy resin,
It is an FRP tube made by reinforcing thermosetting resin such as vinyl ester resin with high strength fibers such as carbon fiber, aramid fiber, glass fiber, and single crystal fiber. Regarding how to manufacture quality FRP pipes.

B. Prior Art Conventionally, methods for manufacturing FRP pipes have been disclosed, for example, in Japanese Patent Application Laid-Open No. 50-62271 (hereinafter referred to as Conventional Example 1) and Japanese Patent Application Laid-Open No. 51-23575 (hereinafter referred to as Conventional Example 2).
A method of manufacturing a bent pipe of reinforced plastic using a flexible core mold is known, as disclosed in JP-A-55-11867 (hereinafter referred to as Conventional Example 3). As a countermeasure against excess air generated during the FRP pipe manufacturing process, a narrow groove is provided along the axial direction on the surface of the core mold, and air is directed toward the shaft core through a ventilation path led from the narrow groove. The one that collects and releases from the end face is also disclosed in JP-A-55-
As disclosed in Publication No. 101421 (hereinafter referred to as Conventional Example 4), in order to improve the slippage between the spirally manufactured FRP pipe and the core rod, a spiral groove is provided on the surface of the core rod. Various inventions are known in which a small hole is bored in the bottom and the air inside the core rod is blown out from the small hole.

C. Problems to be Solved by the Invention In the above-mentioned conventional methods for manufacturing FRP pipes, both Conventional Examples 1 and 2 are inventions of methods for manufacturing bent FRP pipes using a flexible core mold. However, since this method only applies external pressure to the uncured FRP pipe to harden it, no consideration is given to the removal of air bubbles and excess resin that remain in the FRP layer and deteriorate the physical properties of the product. As a result, the expected high strength may not be obtained, or
The characteristics of FRP could not be fully demonstrated as it became heavy. Conventional Example 3 was developed to prevent air from being trapped by the release tape between the core mold and the FRP pipe, and this also has problems with the treatment of air bubbles and resin that are squeezed out from the surface of the pipe. There was no consideration given to this. Furthermore, regarding Conventional Example 4, the structure was adopted to improve workability in the FRP pipe manufacturing process, and there was also no countermeasure against the above-mentioned surplus material.

In this way, FRP pipes are used in aircraft, sports equipment,
Although it is expected to be used in a wide range of applications such as vehicles, the presence of the above-mentioned surplus materials makes it difficult to obtain products of uniform quality and high strength, and the current situation has been that its widespread adoption has been hindered.

D. Means for Solving the Problems Therefore, the present invention provides a method for manufacturing an FRP pipe, which aims to effectively remove air bubbles and excess resin, which are factors that cause deterioration of the physical properties of FRP. The structure is such that a rod-shaped core mold is inserted through a core material that is normally kept straight and can be bent and expanded, and then a rod-shaped core mold is inserted around the core material.
After forming an FRP layer and covering the FRP layer with an outer cover having a bleeder hole, the core mold is removed.
While the FRP is still uncured, it is set in a shape-retaining mold with a two-part structure, which has a discharge path consisting of a thin groove and a through hole penetrating to the outside in the recesses of both the upper and lower molds. Or expand the core material by injecting gas,
Alternatively, by using a material with expandable properties such as synthetic resin foam that has undergone primary foaming as a core material and utilizing its expansion action, excess resin and gas can be removed from the discharge path by applying external pressure from the inside of the FRP layer. It is characterized by squeezing out more, waiting for the FRP to harden, shrinking the core material, and removing the mold.

E Action By expanding the core material, external pressure is applied to the inner surface of the FRP layer, and this pressure causes air bubbles and excess resin in the FRP layer to pass through the bleeder hole in the outer cover and squeeze out to the surface. The released air bubbles and resin are further discharged to the outside of the shape-retaining mold through a discharge path. After waiting for the FRP to harden, the core material is removed from the shape-retaining mold, resulting in a high-strength, high-quality, lightweight product with no excess material.

F. Example Next, the method for manufacturing an FRP pipe according to the present invention will be explained based on the drawings by giving an example in which the method was applied to a drop handlebar of a bicycle.

First, a straight core mold 1 made of steel with high roundness is inserted into a urethane hose 2 which is a core material, and a carbon fiber braid impregnated with epoxy resin is coated around it, and the epoxy resin is applied on top of the straight core mold 1 made of steel. The FRP layer 3 is formed by winding the impregnated unidirectional carbon fiber prepreg to a predetermined thickness and further covering the carbon fiber braid thereon. Here, the core mold 1 can be made of not only steel but also a solid body such as reinforced plastic or hard rubber, or a hollow body, and it is preferable that the surface thereof be subjected to mold release treatment. Also, instead of urethane hose, use polypropylene,
Polystyrene tubes can also be used. Next, the FRP layer 3 is covered with an outer cover 4 made of a tubular knitted fabric made of polypropylene, and the core mold 1 is removed while remaining uncured and set in a shape-retaining mold 5. The outer cover 4 may be a flexible tube made of polypropylene or polyethylene with pores, as long as it has a bleeder hole that can squeeze out air bubbles and excess resin contained in the FRP layer. It is also possible to use The shape-retaining mold 5 has a structure made of heat-resistant epoxy and is divided into upper and lower halves, and U-shaped bent recesses 6 and 6' are formed on each opposing surface, respectively, and the outer cover 4 is formed in the recess 6 of the lower mold. A coated, uncured FRP tube can be set therein, and a heater is built into the mold, so that the entire shape-retaining mold 5 can be heated. A discharge passage 7 consisting of a narrow groove and a through hole penetrating to the outside is formed on each inner surface of the recesses 6, 6'.

Next, both the upper and lower molds are fixed, couplers 8, 8 are attached to both ends of the urethane hose 2, and hot water of about 80°C and 5 kg/cm ² is circulated inside the urethane hose 2. Then, the urethane hose 2 expands, external pressure is applied to the FRP layer 3 from its inner surface, and the air bubbles and excess resin in the FRP layer 3 are pushed out through the bleeder hole of the outer cover and the discharge path 7 of the shape-retaining mold. , at the same time FRP layer 3
is heated. After about 4 hours, the mold is removed, the urethane hose 2 is pulled out, and the outer cover 4 is peeled off.Finally, it is put into a curing oven and hardened at about 130 degrees Celsius for 2 hours. After curing, the surface was treated with sandpaper and a urethane clear coating was applied to produce the product.

In order to improve the product appeal by preventing cracking and increasing torsional strength, the bicycle drop handlebar of this embodiment has an FRP layer 3 consisting of a carbon fiber braid impregnated with epoxy resin and a unidirectional epoxy resin impregnated carbon fiber braid. Although the fiber structure is made up of three layers consisting of carbon fiber prepreg and carbon fiber braid, the layers and thickness of the fibers can be increased or decreased as appropriate depending on the required strength, and if there are parts that need reinforcement. For example, the thickness may be increased by increasing the number of turns of the unidirectional carbon fiber prepreg in only that part.

It has been confirmed that the bicycle drop handle manufactured in this way is 40% lighter and 120% stronger than conventional aluminum handles.

Although the above embodiment describes a method for manufacturing a bent bicycle drop handle, it does not necessarily have to be bent or have a circular cross section, and the shape can be appropriately determined by the shape-retaining mold. It can be widely used in parts where weight reduction is desired, such as marine sports equipment, automobile parts, and aircraft parts.

According to the present invention, excess resin is squeezed out when external pressure is applied to the FRP layer, so even if the recesses of the shape-retaining mold have different sizes, the pressure is evenly applied as shown in Figure 7, resulting in uniform flesh. A thick, high-strength product can be obtained, and by changing the number of turns of the unidirectional carbon fiber prepreg, for example, it is possible to make the outer diameter or inner diameter uniform and partially thicken the product.

In the above embodiment, the core material is normally kept straight by inserting the core mold 1,
When the core mold 1 is removed, a urethane hose 2 with high flexibility and expandability is used, but a simple flexible cylinder may be used as long as it has the minimum strength necessary for FRP molding. In addition to circulating hot water, the means for applying expansion force include using air pressure or oil pressure, or using a synthetic resin foam that has undergone primary foaming as the core material and utilizing the expansion force caused by secondary foaming. You can also do that. Furthermore, the shape-retaining mold 5 can discharge resin and air bubbles seeping from the outer cover to the outside of the mold.
As long as the FRP layer can be kept in a desired shape, the material can be selected as appropriate, such as resin, metal, or plaster. For example, it is also possible to use an open-cell structure.

G. Effect of the invention According to the present invention, the
By adding a discharge function to the shape-retaining mold, surplus materials from FRP pipe manufacturing can be efficiently removed during the curing stage, making it easy to produce high-quality, high-strength, yet lightweight FRP pipes of arbitrary shapes. Since it can be manufactured in a number of steps, its range of use is greatly expanded and the practical benefits brought to industry are enormous.

[Brief explanation of drawings]

Figures 1 to 5 are explanatory diagrams showing the manufacturing process of the FRP pipe according to the present invention, and Figure 6 is an explanatory diagram showing how to apply external pressure to the FRP layer to squeeze out excess resin and air bubbles.
FIG. 7 is a cross-sectional view of the FRP layer when there is a difference in diameter. 1... core type, 2... urethane hose, 3...
FRP layer, 4... Outer cover, 5... Shape-retaining type, 6,
6'... recess, 7... discharge path, 8... coupler.

Claims (1)

[Claims] 1. A rod-shaped core mold is inserted into a core material that is normally kept straight but can be bent and expanded to form an FRP layer around the core material, and the FRP layer is used as a bleeder. After covering with an outer cover with holes, the core mold was removed, and while the FRP was still uncured, the recesses of both the upper and lower molds had a discharge path consisting of a narrow groove and a through hole penetrating to the outside. Set into a shape-retaining mold with a two-part structure,
By applying fluid pressure to the core material to cause it to expand, external pressure is applied from the inner surface of the FRP layer to squeeze out excess resin and gas from the discharge passage, and after waiting for the FRP to harden, the core material is contracted and demolded. characterized by
How to manufacture FRP pipes. 2. The expansion of the core material is performed by injecting gas into the core material.
The method for manufacturing FRP pipes described in section. 3. The expansion of the core material is achieved by using a synthetic resin foam that has undergone primary foaming as the core material and utilizing the expansion force of the secondary foaming.
The method for manufacturing FRP pipes described in section.