JPH04325527A - Prepreg - Google Patents

Abstract

PURPOSE:To obtain a prepreg excellent in heat resistance, impact resistance, etc., and further in toughness by mixing a high-modulus reinforcing fiber with a fibrous thermoplastic resin and a thermosetting resin-based matrix resin and molding the mixture. CONSTITUTION:A reinforcing fiber (A) (e.g. carbon fiber) of a modulus of 200GPa or above, a fibrous thermoplastic resin (B) (e.g. multifilament of nylon 12), and a thermosetting resin-based matrix resin (C) (e.g. bisphenol A epoxy resin) in amounts to give a component A to component C ratio of 60/40-75/25 and a component B to component C ratio of 0.5-/100-20/100 are prepared. A prepreg which contains component B on the external surface and in which a separated phase of at least 90% of component B added is formed in a composite after molding is produced by preparing a unidirectional prepreg from component A and component C by, e.g. the hot melt process and winding component B around the surface of the unidirectional prepreg.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD 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. Molded products obtained from the prepreg of the present invention are suitably used as structural materials for aircraft, etc.

0002

[Prior Art and Problems to be Solved by the Invention] Composite materials using high-strength, high-modulus fibers such as carbon fibers as reinforcing materials are
It has been widely used mainly in sports applications due to its 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. A common method to improve 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 a large amount; This resulted in a decrease in solvent resistance, etc.

[0003] This can also be achieved by adding a thermoplastic resin in powder form to a matrix resin, as proposed in JP-A-63-162732. If it is uniformly dispersed or dissolved in the liquid, problems such as a decrease in process passability during prepreg production due to an increase in the viscosity of the entire system and a decrease in the tack level of the prepreg cannot be avoided.

Furthermore, for example, JP-A-1-110537 discloses that the toughness of a composite material is effectively improved by localizing spherical fine particles from the surface of the prepreg to a depth within 30% of the thickness of the prepreg. However, even in this case, not only is a significant decrease in prepreg tack unavoidable, but new problems such as complication of the process and complication of quality control arise. A method of inserting a type of adhesive layer called an interleaf between layers has also been proposed, but it has not been put into widespread practical use for reasons such as the inability to increase the fiber content.

[0005]

OBJECTS OF THE INVENTION The object of the present invention is to impart excellent toughness to molded products obtained from the matrix resin without impairing its excellent thermal and mechanical properties, and to provide sufficient tack level drapability and impregnation properties. The object of the present invention is to provide a prepreg for fiber-reinforced composite materials that has the following characteristics and excellent handling properties.

[0006]

[Means for Solving the Problems] The present invention provides (A) elastic modulus 2
00GPa or more reinforcing fiber (B) elastic modulus 100GPa
In the prepreg for fiber-reinforced composite materials made of the following fibrous thermoplastic resin (C) thermosetting resin-based matrix resin, the ratio of each component (A), (B), and (C) is within the following range, And (B) fibrous thermoplastic resin exists on the outer surface of the prepreg, and by adding (B) in the composite after molding, 9 of the added volume of (B)
The present invention relates to a prepreg in which 0% or more of a separated phase is formed. (A)/(C)=60/40~75/25(B)/(C
)=0.5/100~20/100

[0007] As the reinforcing fiber (A) with an elastic modulus of 200 GPa or more in the present invention, reinforcing fibers used in ordinary fiber-reinforced composite materials such as carbon fiber, graphite fiber, and boron fiber can be used as they are, but the tensile strength Carbon fibers and graphite fibers having a strength of 3500 MPa or more are preferably used. Especially tensile strength 4500M
High strength and high elongation carbon fibers and graphite fibers with Pa or more and elongation of 1.7% or more are most preferably used.

As the thermosetting resin matrix resin (C) in the present invention, epoxy resins or polyfunctional maleimide resins using amines or phenols as precursors are preferably used. Specifically, examples of epoxy resins include tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, various isomers of triglycidylaminocresol, bisphenol A type epoxy resin, and bisphenol F type epoxy resin. Examples include epoxy resins, bisphenol S type epoxy resins, phenol novolak type epoxy resins, cresol novolak type epoxy resins, and mixtures of two or more of these.

[0009] Polyfunctional maleimide resins include resin compositions containing 1,2-bismaleimidododecane, 1,6-bismaleimide-(2,2,4-trimethyl)hexane, etc. as main components. However, it is of course not limited to these thermosetting resins, and thermoplastic resins, elastomer components, and inorganic resins may be used as long as they do not adversely affect the moldability, tackiness, drapability, etc. of the prepreg or the handling properties of the matrix resin. It is also possible to add system fine particles and the like to form a matrix resin.

[0010]Although the ratio of (A) and (C) can be set appropriately depending on the purpose, (A)
A suitable range is /(C)=55/45 to 85/15, and a more preferable range is (A)/(C)=60/40 to
It is 75/25.

The fibrous thermoplastic resin (B) may be fibrous in the composite after molding, or may not retain its fibrous shape depending on the molding conditions and the melting point of the fibrous thermoplastic resin ( By adding B), a separated phase must be formed with a volume of 90% or more of the volume of added (B). However, as for the component of the separated phase, (B) may not be used alone. If the ratio of the separated phase is less than 90% of the added (B), the effect on the toughness of the composite is not great, but it is not preferable because it reduces the heat resistance and mechanical strength of the composite.

[0012] As a specific evaluation method, a special prepreg is prepared by aligning (B) and (A) in parallel, and the prepregs are laminated in one direction to form a unidirectional material. Next, a 5 x 10 mm sample was cut out so that the cross section was perpendicular to the fibers. If necessary, stain the specimen using a staining agent and take a photograph of the entire surface of the specimen at an appropriate magnification. Once phase separation is confirmed, the phase separation area S1 within the cross section of the specimen is determined by copying it onto tracing paper, etc., cutting it out, and measuring its weight. On the other hand, the area S0 is determined by calculation from the amount of charge, assuming that all (B) has phase-separated as it is. In this way, the image S1 obtained from the cross-sectional areas of at least five locations
In the present invention, the average values S1' and S0 must satisfy the following formula.

[Math. 1] S1 ′/S0 × 100≧90 (%)

00
13] The form of the fibrous thermoplastic resin is preferably monofilaments or bundles thereof, but is not necessarily limited thereto. The fiber diameter is preferably 100μ or less, particularly preferably 50μ or less. The ratio of the fibrous thermoplastic resin is preferably 0.5 to 20 parts by weight per 100 parts by weight of the epoxy matrix resin (C). 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 20 parts by weight or more of a 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. Undesirable.

[0014] In the present invention, it is important 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.

[0015] There is no particular restriction on the direction in which the reinforcing fibers are drawn, and they may exist at any angle with respect to the reinforcing fibers, but it is easiest in the process to align them in the same direction as the reinforcing fibers. There are no particular restrictions on the method for manufacturing such prepregs from reinforcing fibers, matrix resins, and fibrous thermoplastic resins. It can be manufactured by various methods, such as a method of preparing prepreg using the same method as manufacturing prepreg, or a method of aligning and integrating a fibrous thermoplastic resin with a prepreg manufactured by a normal method.

[0016]

[Effects of the Invention] The molded product obtained from the prepreg of the present invention is endowed with excellent toughness without impairing the excellent thermal properties and mechanical properties of the matrix resin, and is resistant to the propagation of cracks that occur. Because of these characteristics, it is suitably used as a structural material for aircraft. Furthermore, the prepreg of the present invention has sufficient tack level, drapeability, and impregnability, and is excellent in handling, so it is fully compatible with lamination in an autolayup machine and has extremely high industrial applicability. It's expensive.

[0017]

[Examples] The present invention will be specifically explained below with reference to Examples. Examples 1 to 2 A unidirectional prepreg was made by hot melting from the resin composition shown in Table 1 and high strength and medium elastic carbon fiber (Mitsubishi Rayon, MR60P, tensile strength 5600 MPa, elastic modulus 310 GPa, elongation 1.9%). Manufactured by. The CF basis weight of the prepreg was 190 g/m2, and the resin content was 34% by weight. This prepreg is coated with nylon 12 multifilament (
81d/36fil, elastic modulus of about 2 GPa) was wound on both sides of the prepreg at a pitch of 3 mm using a filament winding method to produce the prepreg of the present invention.

[0018] 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). The cross section of the test piece was observed using an optical microscope, and it was confirmed that 99% of the added nylon had undergone phase separation. Using this test piece, the compressive strength after 270 lb-in impact was measured in accordance with SACMA's SRM2-88. Also, RDA-700 manufactured by Rheometrics has a frequency of 10 rad.
/sec, Temp. Dynamic viscoelasticity measurements were performed in Step mode, tan δ was tracked against temperature, and the temperature at the peak of tan δ was examined as a measure of Tg. The results are shown in Table 1.

Comparative Examples 1 and 2 A unidirectional prepreg was produced in the same manner as in Example 1, except that a resin film was used so that the resin content of the prepreg was 36% by weight. Using this prepreg, nylon 1
Evaluation was conducted in the same manner as in Example 1 without attaching the two fibers. The results are shown in Table 1.

Comparative Examples 3 and 4 The procedure was carried out in the same manner as in Example 1, except that the nylon 12 fibers were replaced with semi-IPNized nylon fibers having the composition shown below, TR-55 (
Mitsubishi Kasei amorphous nylon) / EP828 / Tomide #296 = 96/3/1 part by weight (81d /36fil
, elastic modulus of about 2 GPa) was used, a prepreg was manufactured in the same manner as in Example 1, a test piece was molded and evaluated, and the cross section of the test piece was observed under a microscope, and the results shown in Table 1 were obtained. . As is clear from Table 1, the molded product obtained from the prepreg of the present invention has higher compressive strength after impact than the comparative example, has excellent impact resistance, and has a very good retention rate of heat resistance. I understand that.

[Table 1]

Claims (4)

[Claims] Claim 1. In a prepreg for fiber reinforced composite material consisting of (A) reinforcing fibers having an elastic modulus of 200 GPa or more, (B) a fibrous thermoplastic resin, and (C) a thermosetting resin matrix resin, (A), ( B),
The ratio of (C) is within the following range and the fibrous thermoplastic resin (B) is present on the outer surface, and by adding (B) in the composite after molding, the added volume of (B) is A prepreg characterized in that 90% or more of separated phases are formed. (A)/(C)=60/40~75/25(B)/(C
)=0.5/100~20/100 [Claim 2] (
2. The prepreg according to claim 1, wherein A) is carbon fiber or graphite fiber having a tensile strength of 3500 MPa or more. 3. The prepreg according to claim 1, wherein (B) is a mono- or multifilament of thermoplastic resin. 4. The prepreg according to claim 1, wherein the fibrous thermoplastic resin (B) is embedded in its outer surface at regular intervals in one direction.