A racket frame including a first laminate composed of a plurality of first prepregs consisting of fiber reinforced resin and a second prepreg, consisting of fiber reinforced resin, which is layered on the first laminate. The first laminate has a loss factor (=tan δ) set to not less than 0.005 nor more than 0.02, when the loss factor is measured at a temperature of 10° C. and a frequency of 10 Hz. The second prepreg has a loss factor (=tan δ) set to not less than 0.10 nor more than 0.50, when the loss factor is measured at a temperature of 10° C. and a frequency of 10 Hz.
1. A racket frame comprising a first laminate composed of a plurality of first prepregs consisting of fiber reinforced resin; and a second prepreg, consisting of fiber reinforced resin, which is layered on said first laminate,
wherein said first laminate has a loss factor (=tan δ) set to not less than 0.005 nor more than 0.02, when said loss factor is measured at a temperature of 10° C. and a frequency of 10 Hz, and
said second prepreg has a loss factor (=tan δ) set to not less than 0.10 nor more than 0.50, when said loss factor is measured at a temperature of 10° C. and a frequency of 10 Hz.
2. The racket frame according to claim 1 , wherein a weight of said second prepreg is set to not less than 1% nor more than 10% of a weight of said first prepreg.
3. The racket frame according to claim 2 , wherein supposing that an overall thickness of a layer of said fiber reinforced resin is 100%, said second prepreg is disposed in a thickness range not more than 20% at both sides of a central position of said thickness.
4. The racket frame according to claim 2 , wherein a composition of a matrix resin of said second prepreg contains epoxy resin and one or more activators selected from compounds having benzotriazole groups and compounds having diphenyl acrylate groups; and
a tensile modulus of elasticity of a reinforcing fiber of each of said first prepreg and said second prepreg is set to not less than 150 GPa nor more than 600 GPa.
5. The racket frame according to claim 2 , comprising a head part forming an outline of a ball-hitting face thereof and a bifurcated throat part connected to said head part, wherein supposing that said ball-hitting face is regarded as a clock surface and that a top position of said ball-hitting face is 12 o'clock, said second prepreg is disposed at one position or two or more positions selected from among a first position in a range of 11 o'clock to one o'clock, a second position in a range of three o'clock to five o'clock (nine o'clock to seven o'clock), and a third position disposed at said left and right throat parts.
6. The racket frame according to claim 1 , wherein supposing that an overall thickness of a layer of said fiber reinforced resin is 100%, said second prepreg is disposed in a thickness range not more than 20% at both sides of a central position of said thickness.
7. The racket frame according to claim 6 , wherein a composition of a matrix resin of said second prepreg contains epoxy resin and one or more activators selected from compounds having benzotriazole groups and compounds having diphenyl acrylate groups; and
a tensile modulus of elasticity of a reinforcing fiber of each of said first prepreg and said second prepreg is set to not less than 150 GPa nor more than 600 GPa.
8. The racket frame according to claim 6 , comprising a head part forming an outline of a ball-hitting face thereof and a bifurcated throat part connected to said head part, wherein supposing that said ball-hitting face is regarded as a clock surface and that a top position of said ball-hitting face is 12 o'clock, said second prepreg is disposed at one position or two or more positions selected from among a first position in a range of 11 o'clock to one o'clock, a second position in a range of three o'clock to five o'clock (nine o'clock to seven o'clock), and a third position disposed at said left and right throat parts.
9. The racket frame according to claim 1 , wherein a composition of a matrix resin of said second prepreg contains epoxy resin and one or more activators selected from compounds having benzotriazole groups and compounds having diphenyl acrylate groups; and
a tensile modulus of elasticity of a reinforcing fiber of each of said first prepreg and said second prepreg is set to not less than 150 GPa nor more than 600 GPa.
10. The racket frame according to claim 1 , comprising a head part forming an outline of a ball-hitting face thereof and a bifurcated throat part connected to said head part, wherein supposing that said ball-hitting face is regarded as a clock surface and that a top position of said ball-hitting face is 12 o'clock, said second prepreg is disposed at one position or two or more positions selected from among a first position in a range of 11 o'clock to one o'clock, a second position in a range of three o'clock to five o'clock (nine o'clock to seven o'clock), and a third position disposed at said left and right throat parts.