GB2279902A

GB2279902A - Method for manufacturing a fiber reinforced thermoplastic resin composite racket frame

Info

Publication number: GB2279902A
Application number: GB9314429A
Authority: GB
Inventors: Kun-Nan Lo
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-07-13
Filing date: 1993-07-13
Publication date: 1995-01-18
Also published as: FR2708863A1; GB9314429D0

Abstract

A method for manufacturing a racket frame, made of a thermoplastic resin composite material formed from unidirectional prepreg, includes the steps of: (a) cutting a thermoplastic resin composite fabric formed of unidirectional prepreg into sheets (10) of predetermined size and fiber orientation angle; (b) pre-forming a tube (30) by stacking the sheets (10) of thermoplastic resin composite fabric; heating the stacked sheets (10) to the softening temperature of the stacked sheets (10); wrapping the heated sheets (10) around a mandrel (20) to form the tube (30); cooling the tube (30) at room temperature to harden the tube (30); and withdrawing the tube (30) from the mandrel (20); and (c) shaping the tube (30) into a racket frame by placing the tube (30) inside a mold. The tube may be shaped by heating it and blowing air into it. The racket frame is then finished by painting and so on. <IMAGE>

Description

METHOD FOR MANUFACTURING A FIBER REINFORCED THERMOPLASTIC RESIN COMPOSITE RACKET FRAME The invention relates to a method for manufacturing a racket frame, more particularly to a method for manufacturing a fiber reinforced thermoplastic resin composite racket frame.

Fiber composite materials have gradually replaced metal alloys as the primary material in the manufacture of exercise equipments. Fiber composite materials are lightweight and can be cast to form a wide variety of exercise equipments. For example, different kinds of fiber resin composite racket frames are now available in the market. Because each type of fiber resin composite material has a specific characteristic, the type of fiber resin composite material to be used in an exercise equipment should be selected in order to correspond with the desired qualities of the latter.

Conventional methods for forming fiber reinforced composite material include injection forming, braiding, filament winding and the unidirectional prepreg method.

Injection forming requires the use of a thermoplastic fiber resin composite material. Braiding, filament winding and the unidirectional prepreg method can use either thermoplastic or thermosetting fiber resin composite material. When a thermosetting resin composite material is used, heat is applied until a curing temperature is reached in order to harden the composite material. When a thermoplastic resin composite material is used, heat is applied until a softening temperature is reached. The composite material is then cooled in order to harden the same.

Although thermoplastic resin materials can be recycled, they are relatively hard, thereby increasing the difficulty in forming the same. The following is a brief description of the above mentioned composite material forming methods: 1. The forming speed of the injection forming method is relatively fast. However, since only short fibers can be used, the structure of the finished product is relatively poor. Therefore, high strength is difficult to achieve.

2. The forming speed of the braiding method is average. Although long fibers can be used in this method, braided fibers have a mesh-like structure, thereby resulting in the uneven distribution of resin at the mesh openings. This makes it difficult to achieve a high specific strength and a high specific modulus.

3. The forming speed of the filament winding method is also average. The characteristics of this method and those of the braiding method are almost similar. The filament winding method, however, is slightly better than the braiding method.

4. The forming speed of the unidirectional prepreg method is relatively slow. However, due to the presence of good fiber and resin distribution, products made with the use of this method tend to exhibit high specific strength and high specific modulus. However, forming of a product with the use of this method is relatively difficult since the raw thermoplastic resin composite material is relatively hard.

Presently, majority of the racket frames that are available in the market are made of a fiber reinforced thermosetting resin composite material which is formed of unidirectional prepreg. There are also racket frames which are made of a thermoplastic resin composite material that is formed by injection forming, braiding or by filament winding. A thermoplastic resin composite racket frame formed of unidirectional prepreg is nonexistent, until now, due to difficulties in producing the same.

Therefore, the objective of the present invention is to provide a method for manufacturing a fiber reinforced thermoplastic resin composite racket frame with a high specific strength and a specific modulus.

Accordingly, the method of the present invention is directed to the manufacture of a racket frame which is made of a thermoplastic resin composite material that is formed of unidirectional prepreg and comprises the steps of: (a) cutting a thermoplastic resin composite fabric formed of unidirectional prepreg into sheets of predetermined size and fiber orientation angle; (b) pre-forming a tube including: stacking the sheets of thermoplastic resin composite fabric; heating the stacked sheets to a predetermined softening temperature of the stacked sheets; wrapping the heated sheets around a mandrel to form the tube; cooling the tube at room temperature to harden the tube; and withdrawing the tube from the mandrel; and (c) shaping the tube into a racket frame by placing the tube inside a mold.

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment, with reference to the accompanying drawings, of which: Figure 1 is a flow diagram illustrating the preferred embodiment of a racket frame manufacturing method of the present invention; and Figure 2 illustrates the process steps involved in the pre-forming of a tube in accordance with the racket frame manufacturing method of the present invention.

The raw material used in the method of the present invention is a thermoplastic resin composite material formed of unidirectional prepreg. In this embodiment, the thermoplastic resin material is nylon 6. Referring to Figure 1, the process steps of the racket frame manufacturing method of the present invention are as follows: 1. Tailoring: A thermoplastic resin composite fabric formed of unidirectional prepreg is cut into sheets of predetermined size and fiber orientation angle.

2. Tube pre-forming: Referring to Figure 2, the tube pre-forming step includes the following sub-steps: 2.1 Stacking: The sheets 10 of thermoplastic resin composite fabric are stacked together.

2.2 Heating: The stacked sheets are heated to a softening temperature of the thermoplastic resin composite material. In this embodiment, the softening temperature is 2300C.

2.3 Wrapping: The softened sheets 10 are wrapped around a mandrel 20 to form a tube 30.

2.4 Cooling: The tube 30 is cooled at a temperature which is at least 20 below the softening temperature, preferably at room temperature, for at least one minute in order to harden the same.

2.5 Drawing: Finally, the tube 30 is withdrawn from the mandrel 20.

3. Racket frame shaping: The tube is heated before placing the same in a mold. The mold is heated, and air is charged into the same in order to shape the tube in a conventional manner. The mold is then cooled, and a semi-finished racket frame is thus obtained.

4. Finishing: The semi-finished racket frame undergoes several finishing operations, such as grinding, spray-painting, printing, etc., in order to obtain a finished racket frame.

In the method of the present invention, the number of stacked sheets and the fiber orientation angle, which may range from 0 to 3600, are selected in order to correspond with the desired racket frame characteristics. Heating of the stacked sheets and the resulting tube can help overcome the difficulties usually encountered due to the hardness of the raw thermoplastic resin composite material. Furthermore, the characteristics of each of the stacked sheets, such as the fiber orientation angle, may be varied in order to vary the properties of the racket frame and so as to achieve a high specific strength and specific modulus.

Claims

CLAIM:

1. A method for manufacturing a racket frame which is made of a thermoplastic resin composite material that is formed of unidirectional prepreg, comprising the steps of: (a) cutting a thermoplastic resin composite fabric formed of unidirectional prepreg into sheets of predetermined size and fiber orientation angle; (b) pre-forming a tube including: stacking said sheets of thermoplastic resin composite fabric; heating said stacked sheets to a predetermined softening temperature of said stacked sheets; wrapping said heated sheets around a mandrel to form said tube; cooling said tube at room temperature to harden said tube; and withdrawing said tube from said mandrel; and (c) shaping said tube into a racket frame by placing said tube inside a mold.

2. The method for manufacturing a racket frame as described substantially hereinbefore with reference to the accompanying drawings.