JPH10158417A - Prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a prepreg excellent in toughness, resistances to impact and heat, and mechanical properties by forming a prepreg from a thermosetting matrix resin, a nonwoven fabric, and a fibrous reinforcement made from long fibers and by positioning the nonwoven fabric at the surface of the prepreg. SOLUTION: This prepreg comprises a thermosetting matrix resin, a nonwoven fabric, and a fibrous reinforcement made from long fibers, and the nonwoven fabric is positioned at the surface of the prepreg. For instance, nonwoven fabric layers 1 are positioned at both the surfaces and a carbon fiber layer 2 is positioned between the nonwoven fabric layers. Pref. the nonwoven fabric forms a separate phase after the curing of the matrix resin and, though embedded in and unified with the resin, exhibits a distinct boundary, enabling the nonwoven fabric part to be distinguished from the resin part. Pref. the nonwoven fabric is one made from poly-p-phenylenebenzobisoxazole fibers and/or polybenzimidazole fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high impact resistance
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg / molded article for producing a molded article capable of suppressing crack propagation upon impact and a molding method therefor. More specifically, the present invention relates to a prepreg for obtaining a molded article to which toughness (toughness) is imparted without impairing excellent mechanical and thermal properties of a matrix resin when a high-strength carbon fiber or the like is used as a reinforcing fiber. Things.

[0002]

2. Description of the Related Art In recent years, composite materials using carbon fibers, aromatic polyamide fibers, and the like as reinforcing fibers have been widely used as structural materials for aircraft and the like by utilizing their high specific strength and specific rigidity.

[0003] These composite materials are often used from a prepreg, which is an intermediate product in which a reinforcing material is impregnated with a matrix resin, through molding and processing steps such as heating and pressing.

As a matrix resin in a prepreg, a thermosetting resin such as an epoxy resin, a bismaleimide resin, an unsaturated polyester resin, or a polyimide resin is used, and recently, a thermoplastic resin such as polyether-terketone is also used. It is becoming possible. Regardless of which resin is used, the composite material is characterized by its excellent mechanical properties, dimensional stability, heat resistance, chemical resistance, and weather resistance.

[0005] When a thermoplastic resin is used as a matrix resin, it is expected that the composite material has excellent impact properties in addition to good heat resistance and mechanical properties. However, handleability as a prepreg, for example, drape Due to poor properties, it is a material that is difficult to handle with current molding technology, and it is difficult to apply it to complicated shapes.

On the other hand, when a thermosetting resin such as an epoxy resin prepreg is used as a matrix resin, it has been recognized that heat resistance and mechanical properties are good.
On the other hand, it has been pointed out that the matrix material has low elongation and is brittle, so that the toughness and impact resistance of the composite material are inferior, and improvement thereof has been demanded. Therefore, toughness,
Various techniques have been proposed to impart impact resistance.

For example, (1) Japanese Patent Laid-Open No. 58-1 discloses a technique for improving the toughness of a matrix resin for prepreg and improving the impact resistance of a composite material.
No. 20639, No. 61-250021, No. 62-36
Nos. 421 and 62-57417;
As known from Japanese Patent Publication No. 25, etc., a prepreg composition in which a specific elastomer component, a high molecular weight rubber component, and a thermoplastic resin fine powder are blended with a matrix resin to enhance the toughness (impact resistance) of the composite material is also provided. Is being developed.

(2) Japanese Patent Application Laid-Open Nos. 60-63229 and 63-162733 disclose a technique for improving the impact characteristics of a composite material by inserting a different material between the composite materials.
There is an interleaf technique as disclosed in Japanese Patent Application Publication No.
The thickness of the interleave material is generally from 0.03 to 0.03.
An epoxy resin layer having excellent flexibility of 0.06 mm is used, or a thermoplastic resin film having a thickness of 0.01 to 0.05 mm, for example, a film of polyetherimide, polyethersulfone, or polyetheretheroketone is used. I'm using

(3) Japanese Patent Application Laid-Open Nos. 4-292634, 4-292912 and 4-292912 disclose a technique for improving the toughness of a composite material by disposing a fibrous thermoplastic resin on the outer surface of a prepreg for a composite material. 4-306238, 4-3
Nos. 25527 and 8-92392 are disclosed.

[0010]

However, each of these methods has many problems. For example, (1) The method of blending a specific elastomer component and a high molecular weight rubber component into the matrix resin has problems such as a low effect of improving the impact resistance of the composite material and a significant increase in the viscosity of the matrix resin. doing.

According to the method of blending the thermoplastic resin fine powder with the matrix resin, although the impact resistance is improved, there is a problem that the tack of the prepreg changes with time (gradual decrease) due to exposure in an air atmosphere. Was.

(2) In the method using an interface, when an epoxy resin excellent in flexibility, for example, an epoxy resin layer containing a large amount of an elastomer component is used as an interface material, the impact characteristics are improved. In order to achieve this, it is necessary to incorporate a large amount of an elastomer component, but if this is done, the heat resistance and mechanical properties of the composite material may be reduced depending on the type and amount of the elastomer component. Is often limited to a sufficient effect.

[0013] When a thermoplastic resin film is inserted between the laminated layers of the composite material, the effect of improving the impact resistance of the composite material has been recognized, but the resin film completely interposed between adjacent layers. Therefore, there is a problem in tackiness of the prepreg or adhesion between the matrix resin and the thermoplastic resin film, and there is a defect that the toughness of the composite, particularly, the strain energy release rate (GIC) is low. Further, since the resin flow in the direction between the laminations is blocked, uneven resin flow occurs, causing deformation of the molded product,
Alternatively, since the thickness of the thermoplastic resin film is relatively large, the ratio of the thermoplastic resin film to the matrix resin is increased, and the performance (composite performance) of the composite material may be reduced accordingly.

(3) In the method of arranging the fibrous thermoplastic resin, a method of arranging the fibrous thermoplastic resin on the outer surface of the prepreg in an aligned state in one direction is exemplified. In this method, in order to improve toughness, many fibrous thermoplastic resins must be arranged on the outer surface of the prepreg. As a result, there is a problem that the tackiness of the prepreg is reduced.

Also, as exemplified in Japanese Patent Application Laid-Open No. 4-325527, in order to obtain a sufficient toughness improving effect, care should be taken that the aligned fibrous thermoplastic resin is not completely buried in the center of the prepreg. There was a restriction that it had to be manufactured. Furthermore, when a fibrous thermoplastic resin is used, when the molded product is exposed to heat, there is a problem that the thermoplastic resin is softened, and the excellent heat resistance inherent to the matrix resin is impaired.

[0016]

[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result of using the following methods, the viscosity of the resin, handleability such as tackiness, toughness of composite materials, impact resistance, heat resistance, An excellent prepreg having both mechanical properties was found, and the present invention was achieved.

That is, the present invention relates to a prepreg comprising (A) a reinforcing fiber composed of long fibers, (B) a nonwoven fabric, and (C) a thermosetting matrix resin, wherein (B) is disposed on the surface of the prepreg. It is characterized by.

More specifically, the present invention includes the following aspects. That is, the present invention relates to: 1. A prepreg comprising (A) a reinforcing fiber composed of long fibers, (B) a nonwoven fabric, and (C) a prepreg composed of a thermosetting matrix resin, wherein (B) is disposed on the surface of the prepreg.

2: (B) has a thermal decomposition onset heat temperature of 300
2. The prepreg according to 1 above, wherein the prepreg is a nonwoven fabric made of organic fibers having a temperature of not less than ° C.

(3) The prepreg as described in (1) or (2) above, wherein (B) forms a separated phase after curing of (C).

4: The prepreg according to the above-mentioned items 1 to 3, wherein (B) is a non-woven fabric of polyparaphenylene benzobisoxazole fiber and / or polybenzimidazole fiber.

5: (B) is a non-woven fabric made of polyparaphenylene benzobisoxazole fiber, and (C) is a bismaleimide resin.
The prepreg described.

6: A molded article comprising a cured (C) thermosetting matrix resin containing (A) a reinforcing fiber composed of long fibers and (B) a nonwoven fabric, wherein (A) and (B) are (B) and (C) comprising layers arranged adjacent to each other.
A molded article having excellent impact resistance, characterized by forming phases separated from each other, and capable of suppressing crack propagation upon impact.

7: (B) is a thermal decomposition start heat temperature of 300 ° C.
It is a nonwoven fabric made of the above organic fibers, and (B) and (C) form phases separated from each other, and is excellent in impact resistance and has the ability to suppress crack propagation upon impact. 7. The molded article according to the above item 6.

8: (B) is a polyparaphenylene benzobisoxazole fiber and / or a polybenzimidazole fiber, and (B) the nonwoven fabric and the cured (C) form separate phases. 7. The molded article according to the above item 6, which is excellent in impact resistance and has an ability to suppress crack propagation upon impact.

9: (B) and (C) are polyparaphenylene benzobisoxazole fibers and bismaleimide resin, respectively, and (B) and (C) form phases separated from each other. 7. The molded article according to the above item 6, which is excellent in impact resistance and has an ability to suppress crack propagation upon impact.

10: (A) a reinforcing fiber comprising a long fiber;
A prepreg comprising (B) a non-woven fabric and (C) a thermosetting matrix resin, wherein (B) is formed by laminating a prepreg disposed on the surface of the prepreg to produce a molded product, and comprises (A) a long fiber. The above-mentioned item 6, which is excellent in impact resistance and has an ability to suppress crack propagation upon impact, characterized in that the reinforcing fiber layer and the (B) nonwoven fabric layer are arranged so as to be adjacent to each other and laminated and molded. Method for producing molded articles. 11: The non-woven fabric according to the above item 6, wherein the (B) non-woven fabric is a non-woven fabric made of an organic fiber having a thermal decomposition onset temperature of 300 ° C or higher, and has excellent impact resistance and ability to suppress crack propagation upon impact. Manufacturing method of molded product.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The reinforcing fibers composed of long fibers (A) used in the present invention are single or a combination of two or more organic or inorganic fibers such as carbon fibers, glass fibers and aramid fibers. In particular, in the present invention, a tensile strength of 4
00 kgf / mm ² or more, tensile modulus of elasticity 29 × 10 ³ kg
It is preferable to use a so-called high-strength medium-elasticity carbon fiber of f / mm ² or more. As the form of the fiber, a long fiber monofilament or a bundle thereof is used.

The nonwoven fabric (B) in the present invention is preferably an organic fiber having a thermal decomposition initiation temperature of 300 ° C. or higher. For example, it is a non-woven fabric made of organic fibers such as meta-type aramid fiber, para-type aramid fiber, and polyparaphenylene benzobisoxazole fiber. A non-woven fabric of polyparaphenylene benzobisoxazole fiber is particularly preferable because it has heat resistance and a large effect of imparting toughness.

When a fibrous thermoplastic resin is used as the organic fiber, the thermoplastic resin is softened when the molded product is exposed to heat, and the excellent heat resistance inherent to the matrix resin is impaired. Absent. As used herein, the term “thermoplastic resin” refers to the reversible property of having fluidity by heating and solidifying by cooling, as defined in Okamura et al. The resin is a resin which is shaped by being pressed into a mold or the like by utilizing its fluidity, and then cooled and molded as it is.

To explain in more detail, thermoplasticity is described in “Latest heat-resistant polymer” General Technology Center (198), supervised by Mita.
In 7), it is defined as a property that can be molded by being melt-plasticized by heating and flowing, and when a fibrous thermoplastic resin is used as an organic fiber, a part of the molded product is melt-plasticized. It is not preferable because it has unstable factors. Therefore, it is preferable to use an organic fiber having no distinct melting point.

In the present invention, the nonwoven fabric (B) composed of organic fibers having a thermal decomposition onset temperature of 300 ° C. or higher is a nonwoven fabric comprising (C)
It is preferred to form a separate phase after curing of the thermosetting matrix resin. That is, (B) a nonwoven fabric composed of organic fibers having a thermal decomposition initiation temperature of 300 ° C. or higher is (C)
It is preferably embedded in the thermosetting matrix resin and integrated, but has a clear boundary so that the nonwoven fabric portion and the matrix resin portion can be distinguished.

In this case, the nonwoven fabric does not have to keep the fiber shape, but it is preferable that 90% or more of the volume of the arranged nonwoven fabric is clearly phase-separated from the matrix resin. In order to form a separated phase, it is preferable to select a thermosetting matrix resin having no nonwoven fabric dissolving ability. Although the basis weight of the nonwoven fabric is not particularly limited,
0 g / m ² is preferred. The reason is that if it is less than 10 g / m ² , the effect of imparting toughness is insufficient, and if it exceeds 50 g / m ² , the mechanical properties deteriorate.

The thermosetting matrix resin (C) in the present invention is not particularly limited, but includes bismaleimide resin,
A polyimide resin and a polyisoimide resin having an acetylene terminal, a polyimide resin having a nadic acid terminal and the like are preferably used. The content of the resin composition (excluding the nonwoven fabric) in the prepreg is preferably 20 to 60% by weight, more preferably 25 to 45% by weight.

The prepreg of the present invention is shown in FIGS. 1, 2 and 3. As shown in FIGS. 1 and 2, in the present invention,
(A) a reinforcing fiber composed of a long fiber, (B) a nonwoven fabric composed of an organic fiber having a thermal decomposition initiation temperature of 300 ° C. or higher, and (C) a prepreg composed of a thermosetting matrix resin,
(B) is placed on one side (FIG. 1) or both sides (FIG. 2) of the prepreg surface.

The prepreg composed of (A), (B) and (C) is unidirectionally aligned, and an uncured thermosetting resin composition is impregnated between fibers of a base material such as a unidirectional fabric or a woven fabric. It is a thing.

The method for producing the prepreg of the present invention is not particularly limited. For example, it can be produced by a hot melt method or a solvent method. When applying the hot melt method, first, the prepared thermosetting resin composition is formed into a resin film using a film coater or the like. Next, a reinforcing fiber composed of long fibers and a nonwoven fabric are supplied on the resin film,
The prepreg is heated and pressurized with a roller and a roller.

When the solvent method is applied, a resin solution is prepared using a solvent that does not dissolve the nonwoven fabric, the reinforcing fibers and the nonwoven fabric are supplied to the resin solution, dried, and then prepreg.

The molded article molded using the prepreg of the present invention has a laminated structure in which (A) a reinforcing fiber composed of long fibers and (B) a nonwoven fabric composed of organic fibers are arranged adjacent to each other. You. Specifically, the prepreg lamination structure of the present invention is not particularly limited when (B) is disposed on both surfaces of the prepreg surface and two or more prepregs are laminated. (B)
Is placed on one side of the prepreg surface, and when two sheets are laminated, the second carbon fiber layer is attached to the first nonwoven fabric layer of the prepreg, and the nonwoven fabric layer is disposed between the two prepreg layers. Are laminated as follows.

Alternatively, a second non-woven fabric layer may be attached to the first non-woven fabric layer of the prepreg, and the two prepregs may be laminated so that the non-woven fabric layer is disposed between the two layers.

(B) is placed on one side of the prepreg surface,
When two or more sheets, for example, three sheets are stacked, the layers are stacked such that the (B) layer is always arranged between the layers of the prepreg as shown in FIG.

The prepreg of the present invention may be laminated in one direction, or may be quasi-isotropic, for example,
(+45 ^O / 0 ^O / 45 ^O / 90 ^O ) _4S may be laminated.

In the case where three or more prepregs are laminated, the prepreg of the present invention is laminated only on a portion where cracks are likely to occur, and a prepreg without (B) is laminated on other portions. Is also good. For example, if the laminate is composed of 0 ^O x5 layer / 90 ^O x1 layer / 0 ^O x5 layer, prepreg of the present invention to three layers of 0 ^O layer / 90 ^O layer / 0 ^O layer in the center portion May be laminated.

After lamination as described above, molding is performed at a curing temperature of the matrix resin in accordance with a usual molding method to obtain a molded product.

[0045]

The prepreg obtained according to the present invention is a prepreg from which a molded article having excellent mechanical and thermal properties, toughness and impact resistance can be obtained, and molded using this prepreg. The formed article has a property that the generated crack is hardly propagated, and thus is suitably used for an aircraft structural material, a space structural material, and the like.

[0046]

Example 1 Using a resin composition having the following composition, a resin film was prepared by a film coater. Next, a non-woven fabric is supplied to one surface of the carbon fibers uniformly arranged in one direction by a hot melt method, and a hot roller at 100 ° C.
And a non-cured thermosetting resin was impregnated between the fibers and the non-woven fabric to produce a molded product intermediate (prepreg).

1) Bismaleimide resin (manufactured by Shell, Co.
mpimide 796) -60 parts by weight 2) 4,4'-bis (o-fluorophenylphenoxy) benzophenone (Compimide TM-123 by Shell) -40 parts by weight
The carbon fiber (CF) used was Vesfight IM-600 (manufactured by Toho Rayon Co., Ltd., tensile strength 5
80 kgf / mm ² and tensile modulus of elasticity 29 × 10 ³ kgf / mm ² ).

The non-woven fabric has a thermal decomposition onset temperature of 650 ° C.
Nonwoven fabric made of polyparaphenylene benzobisoxazole fiber (manufactured by Nippon Virgin Co., Ltd .: PBO nonwoven fabric)
Was used.

The prepreg has a basis weight of 150 g / m ² ,
The basis weight of the PBO nonwoven fabric was 25 g / m ² , and the resin content of the entire prepreg was 32% by weight (excluding the PBO nonwoven fabric). The obtained prepreg had good tack and drapability.

Twenty prepregs are laminated in one direction so that the PBO nonwoven fabric layer is always arranged between the layers of the prepreg, and the temperature is increased by autoclave molding at a rate of 2 ° C./min.
The composition was cured at 0 ° C. for 2 hours. Then 210 ° C
For 9 hours, and after-curing at 250 ° C. for 10 hours (heating rate 2 ° C./min) to produce a molded plate.

A test piece was cut out from this molded plate, and the strain energy release ratio (GIC) was measured in accordance with NASARP1092. The 14 prepregs were laminated in one direction so that the PBO non-woven fabric layer was always arranged between the layers of the prepreg, and molded under the same conditions.
S) and glass transition temperature (Tg) were determined by ASTM
D2344 and ASTM D3418.

Further, a second carbon fiber layer is bonded to the first non-woven fabric layer of the prepreg, and is laminated in one direction so that the PBO non-woven fabric layer is disposed between the two prepreg layers. After molding under the conditions, the T-peel strength was measured according to JIS K6.
Laminated according to 854.

Tg is 310 ° C., GIC is 790 J / m
^2. T-peel strength is 17.4N / 25mm width, ILSS
Was 12.0 kgf / mm ² .

[0054]

Example 2 The PBO nonwoven fabric shown in Example 1 had a basis weight of 1
The procedure was the same as in Example 1, except that the pressure was 0 g / m ² .
The obtained prepreg had good tack and drapability. The molded product obtained by curing this prepreg in the same manner as in Example 1 had a Tg of 312 ° C., a GIC of 762 J / m ² ,
T-peel strength is 10.2N / 25mm width, ILSS is 1
It was 3.5 kgf / mm ² .

[0055]

Example 3 The PBO nonwoven fabric shown in Example 1 had a basis weight of 4
The same procedure as in Example 1 was repeated at 5 g / m ² .
The obtained prepreg had good tack and drapability. The molded product obtained by curing this prepreg in the same manner as in Example 1 had a Tg of 313 ° C., a GIC of 885 J / m ² ,
The T-peel strength was 19.2 N / 25 mm width and the ILSS was 9.5 kgf / mm ² .

[0056]

Comparative Example 1 A prepreg was prepared in the same procedure as in Example 1 without adding a nonwoven fabric. CF of the obtained prepreg
The basis weight was 150 g / m ² , the resin content was 32%, and it had good tack and drapability. This prepreg was cured in the same manner as in Example 1. The Tg of this molded product is 31
0 ° C, GIC: 115 J / m ² , T-peel strength: 2.2
The N / 25 mm width and the ILSS were 13.0 kgf / mm ² .

The measurement results are shown in Table 1. In Examples 1 to 4, when compared with Comparative Example 1, heat resistance (Tg) and mechanical properties (ILSS) were maintained at the same excellent level. , Toughness (GIC) and adhesion (T-peel strength) were found to be good.

[0058]

[Table 1]

Comparative Example 2 A prepreg was prepared in the same procedure as in Example 1 using a nonwoven fabric made of polyester fiber having a thermal decomposition initiation temperature of 260 ° C.
The molded plate was peeled off during after-curing at 50 ° C. for 10 hours, and a test piece could not be obtained.

[0059]

The prepreg obtained according to the present invention has excellent mechanical and thermal properties, as well as toughness and impact resistance, and has the property that cracks generated are difficult to propagate. It is suitably used for aircraft structural materials, space structure materials, and the like.

[0060]

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of a prepreg of the present invention.

FIG. 2 is a perspective view of an example of the prepreg of the present invention.

FIG. 3 is a perspective view of an example of the prepreg of the present invention.

[Explanation of symbols]

 1 non-woven fabric layer 2 carbon fiber layer

Claims (3)

[Claims] 1. A prepreg comprising (A) a reinforcing fiber composed of long fibers, (B) a nonwoven fabric and (C) a thermosetting matrix resin, wherein (B) is disposed on the surface of the prepreg. 2. A prepreg according to claim 1, wherein (B) forms a separate phase after curing of (C). 3. The prepreg according to claim 1, wherein (B) is a non-woven fabric of polyparaphenylene benzobisoxazole fibers and / or polybenzimidazole fibers.