JPH04251714A - Manufacture of carbon fiber reinforced composite material - Google Patents

Abstract

PURPOSE:To enhance interlaminar fracture toughness and improve tensile strength, fatigue strength and the like by laminating a composite sheet composed of carbon fibers impregnated with thermosetting resin in the semi-cured state and thermoplastic resin sheet, heating, pressurizing and curing the laminate. CONSTITUTION:A composite sheet (prepreg sheet) 2 composed of carbon fibers impregnated with epoxy resin and semi-cured is cut in consideration of the size, shape and the like of a component to be manufactured when a carbon fiber reinforced composite material (CFRP) provided with vibration-damping property useful for a structure such as space structure, aircraft, automobile or the like. The prepreg sheet 2 and a thermoplastic resin sheet having a heat bonded layer, for example, a polyolefin sheet 1 are laminated in the required laminating order and fiber direction. Then, a release film, a pressurized sheet and the like are placed on the laminate in the bagging process and covered with a vacuum bag. Then, the constitution is cured in an autoclave to complete the manufacture.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon fiber reinforced composite material having vibration damping properties particularly useful for structures such as space structures, aircraft, automobiles, and leisure equipment.

0002

[Prior Art] Fiber-reinforced composite materials (CFRP) based on carbon fibers are different from fiber-reinforced composite materials using other reinforcing fibers such as glass, aramid, and boron fibers in terms of specific strength and specific modulus. It is superior to other materials and has come to be widely used as a structural material for aviation, space, automobiles, leisure goods, etc.

The main method for producing CFRP is to solidify unidirectional or crossed carbon fibers with an epoxy resin. CFRP using epoxy resin is a material that is laminated in a flexible semi-cured state and the resin is cured, and has features such as being able to be integrally molded into complex shapes.

0004

Problems to be Solved by the Invention As the performance of carbon fiber itself increases, the brittle characteristics of epoxy resins become a problem. The epoxy resin conventionally used in CFRP is brittle, so when tensile, repeated, or compressive loads are applied, it breaks before the reinforcing fibers. C
The destruction of the entire FRP was triggered by the destruction of the fibers.

[0005] Furthermore, the brittle characteristics of epoxy resin
This also has the disadvantage of increasing the safety factor when designing a structure because it increases the variation in the strength characteristics of RP. Therefore, thermoplastic resins such as polyetheretherketone (PEEK) are expected to be used to change the toughness of resins. However, it has the disadvantage that the molding temperature is much higher than that of epoxy resin, and it cannot be manufactured using existing equipment.

The object of the present invention is to solve the problems of carbon fiber reinforced composite materials produced by such conventional techniques and to provide a technique for imparting excellent mechanical strength.

[0007]

[Means for Solving the Problems] The method for producing a carbon fiber reinforced composite material of the present invention includes a composite sheet (prepreg sheet) in which carbon fibers are impregnated with an epoxy resin and subjected to semi-curing treatment, and a thermoplastic resin having a thermal adhesive layer. Laminate the sheets, heat and
It is hardened by applying pressure.

[0008]

[Operation] In the manufacturing method of the present invention, a thermoplastic resin sheet and a prepreg sheet are laminated and cured by heating and pressurizing, so a carbon fiber reinforced composite material in which a prepreg sheet and a thermoplastic resin sheet are laminated and integrated is produced. realizable. In the composite material, since the elongation at break of the thermoplastic resin sheet between the layers is generally larger than that of the epoxy resin, it is possible to improve the interlayer fracture toughness. This suppresses the progress of damage such as delamination, and improves mechanical properties such as tensile strength and fatigue strength.

[0009] The thermoplastic resin sheet having thermal adhesive properties used in the present invention may be one having good thermal adhesive properties with the prepreg sheet and high toughness. For this purpose, various thermoplastic resins can be used, and among them, those containing polyolefin as a main component are desirable. Examples of the polyolefin include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene, and pentene, and mixtures thereof. As components other than polyolefin, various rubbers, inorganic fillers, etc. can be combined as necessary. However, the glass transition temperature (Tg) is preferably about 60° C. when used at a temperature higher than the environmental temperature, for example, room temperature.

0010

[Example] As an example of the present invention, a case in which curing was performed by heating and pressurizing in an autoclave will be described below. FIG. 1 is a process diagram for explaining one embodiment of the present invention.

The prepreg sheet 2 is cut in consideration of the size, shape, number of layers, etc. of the member to be manufactured. This prepreg sheet and polyolefin sheet 1 are laminated according to the required lamination order and fiber direction. Then, in the banking process, these laminates are covered with a release film, pressure sheet, etc., and then covered with a vacuum bag. Next, this composition is placed in an autoclave and heated and cured under pressure.

In this example, heat and pressure curing was carried out in an autoclave, but methods such as press molding can be used as well. The polyolefin sheet used here has an outer layer of adhesive polypropylene modified with unsaturated carboxylic acid,
The inner layer used was a three-layered copolymer mainly composed of propylene and butene and having a Tg of 60° C. and a molecular weight of about 600,000, which did not show a melting point. Hereinafter, the case where the length direction of the carbon fibers is aligned with the direction in which the tensile force is applied will be explained as 0°.

FIG. 2 shows a cross-sectional view of a carbon fiber composite material manufactured using the manufacturing method of the example shown in FIG. In this example, the prepreg sheet is cured at 0° of the composite material layer 3.
It has a structure in which the polyolefin sheet 1 is sandwiched between the 45° layers 3A and 3B, and are laminated and integrated. Similarly, FIG. 3 shows a cross-sectional view of a carbon fiber reinforced composite material in which a polyolefin sheet 1 is sandwiched between -45° and 90° layers 3C and 3D, FIG. 4 shows a 90° layer 3D, and FIG. 5 shows a polyolefin sheet 1 between all layers. Figure 2
~ Table 1 shows the tensile breaking loads of the carbon fiber composite material shown in Figure 5 and the conventional composite material without a polyolefin sheet sandwiched between them.
Shown below. All test pieces were in the form of strips with a width of 25 mm.

As shown in Table 1, the carbon fiber composite material produced in this example has a greater breaking strength than the conventional material. It can also be seen that the coefficient of variation, which represents variations in strength, has become smaller, indicating that reliability has improved.

[0015]

[0016]

[Effects of the Invention] As described above, according to the present invention, it is possible to realize a carbon fiber reinforced composite material with excellent mechanical strength, and the variation in strength can be reduced. This has the effect of improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for explaining one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a composite material produced according to an example.

FIG. 3 is a cross-sectional view of a composite material produced according to an example.

FIG. 4 is a cross-sectional view of a composite material produced according to an example.

FIG. 5 is a cross-sectional view of a composite material produced according to an example.

[Explanation of symbols]

1 Polyolefin sheet 2 Prepreg sheet 3 Composite material layer

Claims (1)

[Claims] 1. A carbon fiber-reinforced composite material characterized in that a composite sheet in which carbon fibers are impregnated with a semi-cured thermosetting resin and a thermoplastic resin sheet are laminated and cured by heating and pressurizing the composite sheet. Fabrication method.