JP2850165B2 - Pitch based carbon fiber reinforced composite molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article of carbon fiber reinforced composite material (CFRP) having high bending strength.

[0002]

2. Description of the Related Art CFRP is widely used industrially in its applications such as golf shafts, tennis rackets and other sports / leisure articles, space / aircraft structural materials and industrial materials, etc., taking advantage of its features such as light weight and high rigidity. ing.

[0003] Among them, CFRP using pitch-based carbon fiber
Although they exhibit high strength and high elastic modulus under a tensile load, there is a problem that the strength on the compressive load side is not sufficient under a bending or compressive load.

[0004]

SUMMARY OF THE INVENTION In view of such circumstances, the present inventors have developed an elastic modulus of a pitch-based carbon fiber composite material for use in sports goods, structural materials such as space and aircraft, and industrial materials. While maintaining, it was examined to achieve high bending strength. An object of the present invention is to provide a bending strengthening method by co-laminating and co-curing a pitch-based carbon fiber prepreg and a high-strength carbon fiber prepreg, and to provide a molded article thereof.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned object, and as a result, have arranged a substantially small amount of carbon fiber prepreg having high compressive strength on the surface layer of the pitch-based carbon fiber prepreg. The inventors have found that a composite material having a high elastic modulus and a high strength can be obtained by laminating and curing, and the present invention has been achieved.

That is, the present invention relates to (A) a strand having a tensile strength of 250 kgf / mm ² or more and a tensile modulus of 20
CFRP having a pitch-based carbon fiber having a ton f / mm ² or more (hereinafter referred to as “pitch-based carbon fiber (a ′)”) in a reinforcing fiber and having a Vf (fiber content) of 60 vol%.
A prepreg (hereinafter referred to as “prepreg (a)”) having a compressive strength equal to or less than の of the tensile strength at the time of (b) is laminated on the tensile control side under a bending load, and (B) the tensile strength of the strand is 120 kgf. / mm ² or more, a tensile modulus of 15 ton f / mm carbon fiber having ^two or more (hereinafter, referred to as "carbon fibers (b ')".) the include reinforcing fibers, the compressive strength when formed into a Vf60vol% of CFRP tensile A prepreg (hereinafter, referred to as “prepreg (b)”) having a strength larger than １ ／ of the strength is laminated on one or both surface layers subjected to stress under a bending load, and a volume of the prepreg (a) versus the prepreg (b). The ratio is 100:
2 to 25.

Hereinafter, the present invention will be described in more detail.

[0008] The pitch-based carbon fiber (a ') used in the present invention has a strand tensile strength of 250 kgf.
/ Mm ² or more, for example, 250 to 550 Kg f / m
m ² , preferably 280 to 500 kg f / mm ² , and a tensile elastic modulus of 20 ton f / mm ² or more, for example, 20 to 8
5 ton f / mm ² , preferably 25 to 80 ton
f / mm ² , and the compressive strength when converted to Vf60 vol% CFRP is 以下 or less of the tensile strength when converted to vf60 vol% CFRP, preferably 0.5 to 0.1%.
2, more preferably 0.45 to 0.25.

The type of the carbon fiber is not particularly limited as long as it is a pitch-based carbon fiber satisfying conditions such as the tensile strength, the tensile modulus and the compressive strength.
Tar-based carbon fibers can be mentioned, but pitch-based carbon fibers produced from optically anisotropic pitch are particularly preferred. As a method for producing the pitch-based carbon fiber, for example, among coal-based or petroleum-based pitches having a softening point of 100 to 400 ° C, preferably 150 to 350 ° C, optically isotropic pitch or anisotropic pitch is used. Pitch, preferably the content of the optically anisotropic phase is 60 to 100 vol%, particularly 80 to 100 vol%.
Using an optically anisotropic pitch of 100 vol%, the pitch is first melt-spun into a pitch fiber by a well-known method, and then, under an oxidizing gas atmosphere, usually 50 to 400 ° C., preferably 100 to 350 ° C. A fusion treatment is performed, and then a carbonization treatment is performed at 800 to 3,000 ° C. in an inert gas atmosphere to obtain carbon fibers. Examples of the oxidizing gas include air, oxygen, nitrogen oxide, sulfur oxide, halogen, and a mixture thereof. As the inert gas, for example Ar, He, Xe, _{N 2} gas, and the like.

[0010] The carbon fiber (b ') used in the present invention comprises:
The strand tensile strength 120 kg f / mm ² or more, for example 120~550Kg f / mm ^2, preferably 150~500Kg f / mm ^2, tensile modulus 15 t
on f / mm ² or more, for example, 15 to 85 ton f /
mm ² , preferably 17 to 80 ton f / mm ² , and the compression strength when converted to 60 vol% CFRP is greater than １ ／ of the tensile strength when converted to 60 vol% CFRP, preferably 0.5 Greater than 0.9 and more preferably greater than 0.55 and 0.8
The type is not particularly limited as long as it is 5 or less and the condition is satisfied. Specifically, for example, PAN
Among the carbon fibers, rayon-based carbon fibers, pitch-based carbon fibers, and the like, those satisfying the above-mentioned conditions are exemplified.

[0011] Here, if the elastic modulus of the pitch-based carbon fiber (a ') used for the prepreg (a) and the elastic modulus of the carbon fiber (b') used for the prepreg (b) are selected to be close to each other, the resulting molding is obtained. This is preferable because the elastic modulus of the body is relatively high and the material can be easily designed.

Further, the pitch-based carbon fiber (a ′) and / or the carbon fiber (b ′) may contain aramid fiber, boron fiber, polyethylene fiber or the like, usually 50 vol% or less.
Preferably, they can be used together in a range of 40 vol% or less.

For example, the form of the reinforcing fiber in the prepreg (a) may be one of pitch-based carbon fiber / glass fiber, pitch-based carbon fiber / aramid fiber, pitch-based carbon fiber / boron fiber, pitch-based carbon fiber / polyethylene fiber, etc. Directional and cross hybrids. Examples of the form of the prepreg (b) include, for example, carbon fiber / glass fiber, carbon fiber / aramid fiber, carbon fiber / boron fiber,
Unidirectional and cloth hybrids such as carbon fiber / polyethylene fiber can also be used.

The prepreg (a) of the present invention is a prepreg containing pitch-based carbon fibers (a ') in reinforcing fibers, and the prepreg (b) is a prepreg containing carbon fibers (b') in reinforcing fibers.

The matrix resin used for the prepreg (a) and / or the prepreg (b) is not particularly limited. For example, thermosetting of an epoxy resin, a phenol resin, an unsaturated polyester resin, a vinyl ester resin, a bismaleimide resin, a holocyanate resin, or the like. Resin, polycarbonate resin, nylon resin, PPO, PPS, PEEK
The matrix resin used for the prepreg (a) and the prepreg (b) may be the same or different.

The method of impregnating the reinforcing fiber with the above matrix resin is not particularly limited. For example, a method of introducing the reinforcing fiber into a resin bath, a hand lay-up method of applying a resin to the reinforcing fiber with a brush and impregnating the resin, It can be performed by a hot melt method using a film, a resin injection method, or other known methods.

The ratio between the reinforcing fibers and the matrix resin is appropriately selected depending on the purpose, but the fiber content in the impregnated material is usually 30 to 75 vol%, preferably 40 to 65 vol%.
It is desirable that

Prepreg (a) and prepreg (b)
Is desirably oriented in one direction.

Thus, prepreg (a) and prepreg (b) are obtained.

The laminate of the present invention can be obtained by laminating and molding a prepreg (a) and a prepreg (b), and further curing when a thermosetting resin is used.

At this time, the prepreg (a) is on the side where a tensile stress is applied (tensile dominant side) when a bending load is applied during use of the molded article, and the prepreg (b) is on the side where the bending load is applied during use of the molded article. Are laminated on the side to which a compressive stress is applied (compressed load portion).

For example, one side or both sides of the prepreg (a), one side, both sides of the molded body, a surface layer, an inner layer and the like can be mentioned.

The proportion of the prepreg (a) and the prepreg (b) is appropriately selected usually by adjusting the number of laminations depending on the shape and properties of the target molded article and the properties of the reinforcing fibers to be used. The ratio of the prepreg (b) to the prepreg (a) 100 is 2 to 25, preferably 4 to 12 in a ratio.
It is. At this time, if the proportion of the prepreg (b) is less than 2, the effect of improving the compressive strength of the compact is insufficient.

The laminating direction is not particularly limited. However, the laminating direction is such that the direction of the reinforcing fibers contained in the prepreg (a) is the same as the direction of the reinforcing fibers contained in the prepreg (b).
Unidirectional lamination is preferred. There are other combinations such as 0/90 ° lamination and quasi-isotropic lamination, among which unidirectional lamination is most effective.

The shape of the molded article is not particularly limited and is appropriately selected according to the purpose of use of the molded article. Examples thereof include a flat plate, a curved surface, a tube, a rod, and a shape to which these are applied.

[0026]

According to the present invention, it is possible to obtain a molded article having improved compressive strength while maintaining high tensile strength and high elastic modulus of the pitch-based high elastic carbon fiber.

[0027]

EXAMPLES The present invention will now be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Examples 1 to 3 Tensile strength in the state of a strand was 350 kgf / mm.
² , having a tensile modulus of 50 ton f / mm ² and a Vf
Tensile strength 150K when made into 60 vol% CFRP
g f / mm ² , tensile elastic modulus is 29 ton f / m
A pitch-based carbon fiber (a ′) having m ² and a compressive strength of 45 Kg f / mm ² was impregnated with a 250 ° F. curable epoxy resin composition to prepare a unidirectional prepreg having a basis weight of 75 g / mm ² (Vf 60 vol%, Hereinafter, it is referred to as “prepreg (a)”.)

Next, the tensile strength in the state of a strand is 35.
0Kg f / mm ² , tensile modulus of 23 ton f / m
has m ^2, tensile degree 170 kg f / mm ² when the Vf60vol% of CFRP, the tensile modulus 13t
A PAN-based carbon fiber (b ') having an on f / mm ² and a compressive strength of 120 kgf / mm ² was impregnated with a 250 ° F. curable epoxy resin composition to prepare a unidirectional prepreg having a basis weight of 75 g / mm ² (Vf60vol). %, Hereinafter referred to as “prepreg (b)”).

28 to 32 prepregs (a) are laminated,
One to four prepregs (b) are laminated thereon, and
For 1 hour. A three-point bending test was performed according to JIS with the side on which the prepreg (b) was laminated being the compression load side. Table 1 shows the results. Comparative Example 1 Using only the pitch-based carbon fiber (a ') used in the example, lamination and curing were performed, and three-point bending was measured. Table 1 shows the results. Comparative Example 2 Using only the carbon fiber (b ') used in the example, lamination and curing were performed in the same manner, and three-point bending was measured. Table 1 shows the results.

[0030]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-135232 (JP, A) JP-A-60-145030 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. The tensile strength of a strand (A) is 250 kg.
f / mm ² or more, tensile elastic modulus 20 ton f / mm ²
The pitch-based carbon fiber having the above is contained in a reinforcing fiber, and Vf
(Fiber content) Pre-preg (a) having a compression strength of not more than の of the tensile strength when made into 60 vol% CFRP
Is laminated on the tensile control side under a bending load, and (B) a carbon fiber having a strand tensile strength of 120 kgf / mm ² or more and a tensile elastic modulus of 15 ton f / mm ² or more is included in the reinforcing fiber, and the CFRP having a Vf of 60 vol% is formed. The prepreg (b) having a compressive strength greater than 引 張 of the tensile strength when laminated is laminated on one or both surface layers subjected to stress under a bending load, and the volume ratio of the prepreg (a) to the prepreg (b) is adjusted. 100: A pitch-based carbon fiber reinforced composite material molded body characterized by having a ratio of 2 to 25. 2. The molded article according to claim 1, wherein the reinforcing fibers contained in the prepreg (a) and the reinforcing fibers contained in the prepreg (b) are laminated in the same direction.