Method for manufacturing fiber-reinforced composite material and fiber-reinforced composite material
The purpose of the present invention is to obtain a fiber-reinforced composite material having excellent appearance or mechanical characteristics, whereby a three-dimensional shape is molded with high productivity while appearance defects such as fiber meandering or wrinkling are suppressed. In this method for manufacturing a fiber-reinforced composite material, when a stack in which a plurality of sheet-shaped prepregs (X) in which a plurality of continuously arranged reinforcing fibers are impregnated with a matrix resin composition are layered in different fiber directions is molded into a three-dimensional shape by a molding die ( 100 ) provided with a lower die ( 110 ) and an upper die ( 112 ), a stretchable sheet ( 10 ) or a resin film (Y) used in the stack ( 12 ) is utilized. In this method for manufacturing a fiber-reinforced composite material, the stack may be pre-molded to obtain a preform, and the preform may be furthermore compression-molded to obtain a fiber-reinforced composite material.
1. A method for manufacturing a fiber-reinforced composite material, the method comprising:
laminating a plurality of sheet-shaped prepregs (X), each of which comprises a plurality of consecutively arranged reinforcing fibers impregnated with a matrix resin composition, such that fiber directions differ among at least two of the prepregs (X), thereby obtaining a stack;
forming the stack into a preform by preliminary molding, using a pair of the dies; and
further subjecting the preform to compression molding to obtain a fiber-reinforced composite material having a three-dimensional shape,
wherein, in the preliminary molding, at least a part of the stack is pressed between the pair of dies, with a stretchable resin or rubber sheet disposed between the at least a part of the stack and one of the pair of dies, in a state in which a tensile force is applied to the at least a part of the stack by tensioning the stretchable sheet from outside the pair of dies such that an angle formed by a fiber direction of each prepreg (X) in the stack and a direction in which the stretchable sheet is tensioned is from 15° to 75°.
2. The method for manufacturing a fiber-reinforced composite material according to claim 1 , wherein the angle formed by the fiber direction of each prepreg (X) in the stack and the direction in which the stretchable sheet is tensioned is from 30° to 60°.
3. The method according to claim 1 , wherein the stack comprises a UD (unidirectional) prepreg.
4. The method according to claim 1 , wherein the stack comprises a cloth prepreg.
5. The method according to claim 1 , wherein the stack comprises a resin film.
6. The method according to claim 1 , wherein the stretchable resin or rubber sheet exhibits adhesive property to the stack.
7. The method according to claim 1 , wherein the stretchable resin or rubber sheet has a modulus of elasticity in tension of 0.1 MPa or more and 40 MPa or less.
8. The method according to claim 1 , wherein the product of a thickness (in mm) and a modulus of elasticity in tension (in MPa) in the stretchable resin or rubber sheet is in a range of 1 to 6.