JPH04292909A - prepreg - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg for fiber-reinforced composite materials that can impart excellent toughness to molded products obtained from it without impairing the excellent thermal and mechanical properties of the matrix resin.

0002

BACKGROUND OF THE INVENTION Composite materials using high-strength, high-modulus fibers such as carbon fibers as reinforcing materials have been widely used mainly in sports applications, taking advantage of their excellent specific strength and specific elasticity. Thermosetting resins such as epoxy resins, which are commonly used as matrix resins, have various features but have the disadvantage of poor toughness, which has considerably limited their use.

[0003] A common method for improving the drawbacks of thermosetting resins is to add rubber components or thermoplastic resins, but in order to achieve a sufficient effect of improving toughness, it is necessary to add large amounts. This resulted in a decrease in heat resistance, solvent resistance, etc. A method of inserting a type of adhesive layer called interleaf between layers has also been proposed, but it has not been widely put into practical use for reasons such as the inability to increase the fiber content.

0004

OBJECTS OF THE INVENTION The object of the present invention is to provide a prepreg for fiber-reinforced composite materials that can impart excellent toughness to molded products obtained from it without impairing the excellent thermal and mechanical properties of the matrix resin. It is about providing.

[0005]

[Means for solving the problems] The gist of the present invention is (A)
Reinforcing fiber with elastic modulus of 200 GPa or more (B) elastic modulus of 10
(B
) The short fibrous thermoplastic resin is localized on the outer surface of the prepreg, and the short fibrous thermoplastic resin has a concealment ratio of the prepreg surface of 1.0 or less.

[0006] The elastic modulus of (A) in the present invention is 200GP
As reinforcing fibers of a or higher, reinforcing fibers used in ordinary fiber-reinforced composite materials, such as carbon fibers, graphite fibers, and boron fibers, can be used as they are, but the tensile strength is 3500 MPa.
The above carbon fibers and graphite fibers are preferably used. Among them, carbon fibers and graphite fibers with high strength and high elongation, such as a tensile strength of 4500 MPa or more and an elongation of 1.7% or more, are most preferably used. As the thermosetting resin in the present invention, any resin can be used as long as it is cured by external energy such as heat or light to at least partially form a three-dimensional cured product.

Epoxy resin is used as a thermosetting resin suitable for the present invention. As the epoxy matrix resin (C) in the present invention, epoxy resins using amines or phenols as precursors are preferably used. Specifically, tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, various isomers of triglycidyl aminocresol, bisphenol A type epoxy resin,
Bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin,
Examples include, but are not limited to, cresol novolac type epoxy resins and mixtures of two or more thereof.

There are no particular restrictions on the curing agent for epoxy resins, and any compound having a functional group that can react with an epoxy group such as an amino group or an acid anhydride group can be used as appropriate. Aromatic amines such as dicyandiamide and dicyandiamide are preferably used. As the matrix resin in the present invention, it is also possible to use the above-mentioned epoxy resin to which a thermoplastic resin or an oligomer thereof is added. As the thermoplastic resin component, those having a so-called engineering plastic skeleton such as polyimide, polyetherimide, polysulfone, polyethersulfone, and polyetheretherketone are preferable from the viewpoint of heat resistance, and those having a functional group that can react with the epoxy resin are preferable. It is preferable to have the following at the molecular end or in the molecular chain.

The amount of thermoplastic resin added to the epoxy resin is preferably 30% by weight or less, more preferably 0 to 15% by weight. If more than 30% by weight of thermoplastic resin is used, the viscosity of the system becomes too high, which not only causes poor impregnation during prepreg formation, but also reduces the tack properties of the prepreg.
It also causes deterioration of drape characteristics. It is also possible to mix a small amount of inorganic particles such as finely powdered silica or an elastomer with the epoxy resin.

[0010] The ratio of the reinforcing fiber (A) to the epoxy matrix resin (C) can be set as appropriate depending on the purpose, but the weight ratio is (A)/(C) = 60/40. A range of 75/25 is particularly preferred.

Examples of the fibrous thermoplastic resin (B) having an elastic modulus of 100 GPa or less include polyaramid, polyester, polyacetal, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polyarylate, polybenzimidazole, polyimide, polyetherimide, polysulfone, and polyamide. So-called engineering plastics such as polyamide-imide, and super engineering plastics shaped into fibers are preferably used; Particularly preferred are those having the following.

Examples of such thermoplastic resins include polyamides, polyamideimides, etc., as well as engineering plastics, super engineering plastics, polyamides, polyamideimides, etc. in which functional groups are introduced at the ends or into molecular chains by means such as copolymerization. engineering plastics, polymer alloys with super engineering plastics, etc. are suitably used.

[0013] As for the form of the short fibrous thermoplastic resin, monofilaments or bundles of monofilaments that are cut into short fibers are preferably used, and although it is preferable that the fiber length is constant, it is not necessarily limited to these. It is not something that will be done. The diameter of the fiber is preferably 100μ or less,
Particularly preferred is 50μ or less.

[0014] The ratio of fibrous thermoplastic resin is (C)
0.0% per 100 parts by weight of epoxy matrix resin.
5 to 20 parts by weight is preferred. If the amount is less than 0.5 parts by weight, a sufficient toughness improvement effect cannot be obtained. On the other hand, even if more than 20 parts by weight of short fibrous thermoplastic resin is used, not only will the toughness improvement effect reach a plateau, but depending on the type of resin used, properties such as heat resistance and solvent resistance may drop significantly. can be,
Undesirable.

It is important in the present invention that the fibrous thermoplastic resin be present near the outer surface of the prepreg. If it is completely buried in the center of the prepreg, a sufficient toughness improvement effect cannot be obtained. However, it is still undesirable for the fibrous thermoplastic resin to completely protrude from the surface of the prepreg, and it is preferable that most of the fibrous thermoplastic resin be buried in the resin.

[0016] Furthermore, it is preferable that the short fibrous thermoplastic resin has a concealing rate of 100% or less on the surface of the prepreg. When the hiding rate exceeds 100%, it becomes difficult for the thermosetting resin (C) to appear on the prepreg surface, reducing tack,
Ease of handling decreases.

[0017] There are no particular restrictions on the method for producing prepreg from the reinforcing fibers, the matrix resin, and the fibrous thermoplastic resin. A method of producing prepreg using the same method as producing normal prepreg, or a method of layering short fiber thermoplastic resin in the form of a mat on a prepreg produced by a normal method, or spreading it in a mat form, and then impregnating it with heat. It can be manufactured in

[0018]

[Effects of the Invention] Molded products using the prepreg obtained by the prepreg manufacturing method of the present invention are endowed with excellent toughness without impairing the excellent thermal properties and mechanical properties of the matrix resin, and moreover, Because it has the property of making it difficult for cracks to propagate, it is suitably used as a structural material for aircraft.

[0019]

[Examples] The present invention will be explained in detail with reference to Examples below. The "hiding rate (%)" is calculated from the amount of short fibers when it is assumed that all the fibers in the layer made of short fibers are dispersed on the prepreg without overlapping, and is expressed by the following formula.

[Math 1]

Examples 1 to 3 Unidirectional prepregs were made from the resin compositions shown in Table 1 and high-strength/high-elasticity carbon fibers (manufactured by Mitsubishi Rayon, MR60P, tensile strength 5600 MPa, elastic modulus 310 GPa, elongation 1.9%). was manufactured by hot melt method. The CF basis weight of the prepreg was 190 g/m2, and the resin content was 34% by weight. Cut 12 nylon fibers (elastic modulus of about 2 GPa) with an apparent thickness of about 20μ into this prepreg to a length of 8
Cut into mm pieces and make short fibers, fiber weight per side is 3g
/m2 and attached to both sides of the prepreg to produce the prepreg of the present invention. The concealment rate at this time was 10%.

[0021] Small pieces of predetermined dimensions were cut out from this prepreg, and after lamination, test pieces for measuring compressive strength after impact were molded in an autoclave (curing conditions: 180°C x 2 hours). Using this test piece, SACMA (Suppli
ers of Advanced Compos
ite Materials Association
on) Recommended Method S
The compressive strength after 270 lb-in impact was measured according to RM2-88, and the results shown in Table 1 were obtained.

Comparative Examples 1 to 3 Unidirectional prepregs were produced in the same manner as Examples 1 to 3, except that a resin film was used such that the resin content of the prepreg was 36% by weight. This prepreg was evaluated in the same manner as in Example 1 without attaching nylon 12 fibers. The results are also shown in Table 1.

Example 4 A prepreg was produced in the same manner as in Example 1, except that the fiber basis weight of Nylon 12 was changed as shown in Table 2, and the compressive strength after impact was measured. The results obtained are shown in Table 2.

Example 5 Polyetherimide (about 3 in diameter) was used instead of nylon 12.
A prepreg was produced in the same manner as in Example 1, except that the prepreg was used (with a cut length of 8 mm, a cut length of 8 mm, and an elastic modulus of about 4 GPa), and the compressive strength after impact was measured. The obtained compressive strength after impact was 31
It was 1 MPa.

[0025]

[Table 1]

[0026]

[Table 2]

Claims (2)

[Claims] Claim 1: In a prepreg for fiber-reinforced composite materials consisting of (A) reinforcing fibers with an elastic modulus of 200 GPa or more, (B) short fibrous thermoplastic resin with an elastic modulus of 100 GPa or less, and (C) a thermosetting matrix resin, (B
) A prepreg characterized by having short fibrous thermoplastic resin localized on the outer surface. 2. The prepreg according to claim 1, wherein the concealment rate of the prepreg surface by the short fibrous thermoplastic resin is 100% or less.