Carbon fiber thermoplastic resin prepreg, carbon fiber composite material and producing method
Provided are a carbon fiber thermoplastic resin prepreg which is a carbon fiber prepreg obtained by impregnating a PAN-based carbon fiber in which the average fiber fineness of a single fiber is 1.0 dtex to 2.4 dtex with a thermoplastic resin, wherein the thermoplastic resin satisfies 20≤(FM/FS)≤40 (where FM: flexural modulus (MPa) of a resin sheet comprising only the thermoplastic resin, and FS: flexural strength (MPa) of the resin sheet), a method for manufacturing the same, and a carbon fiber composite material employing the carbon fiber prepreg.
1. A carbon fiber thermoplastic resin prepreg formed by impregnating a carbon fiber bundle formed from plural carbon fibers having an average single fiber fineness of 1.0 dtex to 2.4 dtex, with a thermoplastic resin composition, wherein a weight per area of the carbon fiber thermoplastic resin prepreg is 75 g/m 2 or more, and a single fiber of the carbon fiber that constitutes the carbon fiber bundle has plural surface asperity structures extending over 2 μm or more in the fiber longitudinal direction, and the difference of elevation between the peak and the bottom (Rp−v) in a region having a circumferential length of the single fiber of 2000 nm×a length in the fiber axial direction of 2000 nm is in the range of 60 nm to 200 nm.
2. The carbon fiber thermoplastic resin prepreg according to claim 1 , wherein the thermoplastic resin composition is a thermoplastic resin that satisfies the following Formula (1):
20≤(FM/FS)≤40 (1)
wherein in Formula (1), FM represents the flexural modulus (MPa) of a resin plate formed from this thermoplastic resin composition only; and FS represents the flexural strength (MPa) of the resin plate.
3. The carbon fiber thermoplastic resin prepreg according to claim 1 , wherein the thermoplastic resin composition is a thermoplastic resin composition that satisfies the following Formula (2):
25≤(FM/FS)≤35 (2)
wherein in Formula (2), FM represents the flexural modulus (MPa) of a resin plate formed from this thermoplastic resin composition only; and FS represents the flexural strength (MPa) of the resin plate.
4. A carbon fiber composite material formed from the carbon fiber thermoplastic resin prepreg according to claim 1 .
5. The carbon fiber thermoplastic resin prepreg according to claim 1 , wherein the carbon fiber bundle is a PAN-based carbon fiber bundle.
6. The carbon fiber thermoplastic resin prepreg according to claim 1 , wherein the degree of circularity of a single fiber of the carbon fiber that constitutes the carbon fiber bundle is 0.70 to 0.90,
provided that the degree of circularity is determined by the following Formula (4), wherein S represents the cross-sectional area of the single fiber; and L represents the circumferential length of a cross-section of the single fiber:
Degree of circularity=4π S/L 2 (4).
7. The carbon fiber thermoplastic resin prepreg according to claim 6 , satisfying the following Formula (5):
β×( Tc− 25)×(100− Vf )>0.5 (5)
wherein β represents the coefficient of linear expansion (1/° C.) of the thermoplastic resin composition; Tc represents the lower limit temperature for molding (° C.) of the thermoplastic resin composition, while regarding the lower limit temperature for molding, in a case in which the thermoplastic resin composition has a melting point, the lower limit temperature for molding represents the melting point of the composition, and in a case in which the thermoplastic resin composition does not have a melting point, the lower limit temperature for molding represents a temperature at which the viscosity of the composition is 1×10 4 Pa·s; and Vf represents the fiber volume percentage content (% by volume) of the carbon fiber thermoplastic resin prepreg.
8. The carbon fiber thermoplastic resin prepreg according to claim 6 , wherein the thermoplastic resin composition is at least one kind of resin selected from the group consisting of a polypropylene resin, a polyamide resin, a modified resin of a polypropylene resin, and a modified resin of a polyamide resin.
9. A carbon fiber thermoplastic resin prepreg flakes, obtained using the carbon fiber prepreg according to claim 6 .
10. A carbon fiber-reinforced composite material, obtained using the carbon fiber thermoplastic resin prepreg flakes according to claim 9 .
11. A carbon fiber-reinforced composite material, obtained using the carbon fiber thermoplastic resin prepreg according to claim 6 .
12. An automobile part, obtained using the carbon fiber-reinforced composite material according to claim 11 .
13. A method for producing a carbon fiber thermoplastic resin prepreg, the method comprising a step of impregnating a PAN-based carbon fiber bundle having an average single fiber fineness of from 1.0 dtex to 2.4 dtex, with a thermoplastic resin composition, and thereby obtaining a carbon fiber prepreg,
wherein the thermoplastic resin composition is a thermoplastic resin composition that satisfies the following Formula (3):
20≤(FM/FS)≤40 (3)
wherein in Formula (3), FM represents the flexural modulus (MPa) of a resin plate formed from this thermoplastic resin composition only; and FS represents the flexural strength (MPa) of the resin plate, and wherein
a weight per area of the carbon fiber thermoplastic resin prepreg is 75 g/m 2 or more, and a single fiber of the carbon fiber that constitutes the PAN-based carbon fiber bundle has plural surface asperity structures extending over 2 μm or more in the fiber longitudinal direction, and the difference of elevation between the peak and the bottom (Rp−v) in a region having a circumferential length of the single fiber of 2000 nm×a length in the fiber axial direction of 2000 nm is in the range of 60 nm to 200 nm.
14. The method for producing the carbon fiber thermoplastic resin prepreg according to claim 13 , wherein the thermoplastic resin composition is in a film form.