To improve the strength of a badminton racket shaft without changing rigidity and to enable the racket shaft to generate a flexible bending as designed by laminating a fiber-reinforced layer comprising reinforcing fiber with tensile elasticity within a specific range and a fiber-reinforced resin layer comprising reinforcing fiber with a specific tensile elasticity value.
The shaft of a badminton racket is constituted of a bias layer 7 and a straight layer 6. The bias layer 7 is made of fiber-reinforced resin layer comprising reinforcing fiber with 200-400 GPa of tensile elasticity and is formed by winding two bias prepreg sheets several times around a mandrel. On the other hand, the straight layer 6 is constituted of a fiber reinforced resin layer comprising reinforcing fiber with tensile elasticity lower than 60 GPa and is similarly formed by winding two straight prepreg sheets. As the reinforcing fiber with tensile elasticity within the range 200-400 GPa, carbon fiber is most preferable since it is light.
KOZUKA AKIHIRO
TAKENAKA TOSHIMASA
