JPH0583072B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to an intermediate for producing a molded product having excellent impact resistance and the ability to suppress crack propagation upon impact, and to the molded product. More specifically, it is an intermediate for providing molded products with toughness without impairing the excellent mechanical and thermal properties of matrix resin when high-strength carbon fiber or the like is used as a reinforcing material. ,
The present invention also relates to the molded product. [Prior art and problems] In recent years, composite materials using carbon fibers, aromatic polyamide fibers, etc. as reinforcing materials have been developed due to their high specific strength,
Due to its specific stiffness, it has been widely used as a structural material for aircraft etc. These composite materials are often actually used after forming a prepreg, which is an intermediate product in which reinforcing fibers are impregnated with a matrix resin, through molding and processing steps such as heating and pressurization. As matrix resins in prepreg, thermosetting resins such as epoxy resins, bismaleimide resins, unsaturated polyester resins, and polyimide resins are used, and recently thermoplastic resins such as polyether ether ketone have also been used. No matter which resin is used, composite materials are characterized by their excellent heat resistance, mechanical properties, dimensional stability, chemical resistance, and weather resistance. When a thermoplastic resin is used as a matrix resin, it is expected that the composite material will have good impact properties in addition to good heat resistance and mechanical properties. Moreover, it is a material that is difficult to handle with current molding technology, making it difficult to apply it to complex-shaped objects. 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 it shows good performance in terms of heat resistance and mechanical properties, but on the other hand, the elongation of the matrix resin is low. It has been pointed out that composite materials have inferior toughness and impact resistance due to their brittleness, and improvements have been sought. In particular, when composite materials made from these prepregs are used as primary structural materials for aircraft, they must have the ability to withstand external impacts such as those caused by pebbles being thrown up during takeoff and landing, and tools falling during maintenance. However, it has been considered difficult to improve impact resistance without reducing heat resistance. When improving impact resistant prepreg,
Improving the elongation of reinforcing materials such as carbon fiber,
Increasing the toughness of the matrix resin used in prepreg and optimizing the reinforcing fiber/matrix resin interface have been pointed out as important points, and research has been progressing. Controlling the higher-order structure is also considered important for improving impact properties and suppressing crack propagation. By increasing the toughness of the matrix resin for prepreg,
Technologies to improve the impact resistance of composite materials include:
JP-A-58-120639, JP-A No. 62-250021, JP-A No. 62-
As known from publications such as No. 36421 and No. 62-57417, a matrix resin is blended with a specific elastomer component, a high molecular weight rubber component, and a thermoplastic resin.
Although prepreg compositions with improved toughness (impact properties) of composite materials have been developed, the impact resistance of composite materials has not yet been satisfactory. Regarding optimizing the reinforcing fiber/matrix resin interface, research is being conducted on the surface treatment conditions of the fibers and the selection of the type of sizing agent, but it is still at the research stage and the desired effect has not yet been obtained. do not have. Possible techniques for controlling the higher-order structure of a composite material and improving its impact resistance include a method of controlling the material form of reinforcing fibers, and a method of inserting different materials between laminated layers. Attempts have been made to use three-dimensional fabrics as reinforcing materials to create uniform materials, but so far the fabrics are difficult to manufacture, resin impregnation is poor, and it is difficult to control the fiber volume content. There are many problems such as these, and it has not yet reached the point where it has a significant effect in practical terms. Regarding the technology of inserting different materials between the laminated layers of composite materials, materials in which scream cloth is pasted on the surface of prepreg are known, as shown in Japanese Patent Application Laid-Open Nos. 51-33162 and 61-135712. However, the scrim cloth in this case is rather used for the purpose of reinforcing the prepreg itself, such as preventing transverse cracking of the prepreg and preventing fiber disorder. Japanese Patent Laid-Open Publication No. 2003-19911 has developed a technology to improve the impact properties of composite materials by inserting different materials between the laminated layers of composite materials.
There is an interleaf technique as shown in the publications No. 60-63229 and No. 60-231738. As interleaf material, thickness 0.03~0.06
It is common to use a highly flexible epoxy resin layer with a thickness of 0.01 to 0.05 mm, but thermoplastic films such as polyetherimide, polyether sulfone, and polyether ether ketone films with a thickness of 0.01 to 0.05 mm are used. It is also possible to use resin films. When using an epoxy resin with excellent flexibility as an interleaf material, for example, an epoxy resin layer containing a large amount of elastomer component, it is necessary to incorporate a large amount of elastomer component in order to improve the impact properties. Depending on the type and amount of the elastomer component, the heat resistance and mechanical properties of the composite material may deteriorate, and because restrictions are placed on the type and amount, sufficient effects are often not achieved. When a thermoplastic resin film is inserted between the laminated layers of a composite material, it is effective to improve the impact resistance of the composite material, but since the resin film completely blocks adjacent layers, the matrix There may be problems with the adhesion between the resin and the thermoplastic resin film, or the flow of resin in the direction between the laminated layers may be blocked, resulting in uneven resin flow, leading to deformation of the molded product, or the thermoplastic resin film may be damaged. Since the film is relatively thick, the volume ratio of the thermoplastic resin film to the matrix resin becomes high, which sometimes causes a corresponding decrease in composite material performance. [Object of the invention] The object of the present invention is to overcome the above-mentioned problems,
To provide a prepreg that imparts a molded product to a composite material that has excellent heat resistance, excellent toughness and impact strength, and has the ability to suppress crack propagation during impact, and to provide the molded product, In prepregs using thermosetting matrix resin, impact strength is improved by providing a thin layer made of a material different from the matrix resin on the surface of the prepreg, and inserting the different material between the laminated layers of composite material after molding. An object of the present invention is to provide a molded intermediate for a hot melt type fiber-reinforced composite material, which has excellent properties and the ability to suppress crack propagation upon impact, and a molded product obtained therefrom. [Structure of the Invention] The present invention is as described in claims (1) and (2) below. (1) A fiber-reinforced resin laminate molded intermediate formed by adhering a thermoplastic resin film having through holes to a thermosetting resin prepreg based on reinforcing fibers. (2) A fiber-reinforced resin laminate molded product in which a thermoplastic resin film having through holes is interposed between the laminates. Preferred embodiments of the invention are as follows. (a) The fiber-reinforced resin laminate molded intermediate according to claim 1, wherein carbon fibers having an elongation of 1.3% or more are used as reinforcing fibers. (b) The fiber-reinforced resin laminate molded intermediate according to claim 1, wherein the thermosetting resin of the prepreg forms a continuous layer through the through holes of the thermoplastic resin film. (c) The fiber-reinforced resin laminate molded intermediate according to claim 1, which is a thermoplastic resin film having a glass transition temperature of 100° C. or higher. (d) Claim 1, wherein the through hole is a perforation or a slit.
The fiber-reinforced resin laminate molded product intermediate described above. (e) The fiber-reinforced resin laminate molded intermediate according to claim 1, wherein the area of each perforation is 0.5 to 50 ^mm2 . (f) The fiber-reinforced resin laminate molded intermediate according to claim 1, wherein the slit film has a width of 5 to 20 mm and a gap between the slits of 0.1 to 1 mm. (g) The fiber-reinforced resin laminate molded intermediate according to claim 1, wherein the thermoplastic resin film has a thickness of 1 to 30 μm. The molded product of the present invention has excellent impact resistance and has the property that cracks that occur are difficult to propagate. The reinforcing fibers used in the present invention are preferably carbon fibers, glass fibers, or aromatic polyamide fibers having an elongation of 1.3% or more. Glass fibers and aromatic polyamide fibers usually have an elongation of 2.5% or more. If carbon fiber with an elongation of less than 1.3% is used, the impact properties of the composite material tend to be somewhat insufficient. Particularly in the present invention, the effect is great when carbon fibers, particularly high modulus carbon fibers, are used as the reinforcing material. Carbon fibers are not particularly limited, such as acrylic carbon fibers and pitch carbon fibers, and have a tensile strength of 350.
Kgf/mm ² and tensile modulus of 24T/mm ² are usually used. In order to improve the mechanical properties of the composite material, the tensile strength is 400Kgf/ ^mm2 or more and the elastic modulus is 30T/
It is also possible to use so-called medium-modulus high-strength carbon fibers of mm ² level. These prepregs based on reinforcing fibers are prepared by impregnating an uncured thermosetting resin composition between the fibers of a base material such as a unidirectional sheet of reinforcing fibers, a woven fabric, or a short fiber mat. The thermosetting resin composition as the matrix resin is an epoxy resin, a bismaleimide resin, an unsaturated polyester resin, a polyimide resin, etc., and the content of the resin composition is suitably 30 to 50% by volume.
If the elongation of the matrix resin is improved due to resin modification or the like, the molded product will have characteristics that make it difficult for cracks to propagate. The basic prepreg of the thermosetting resin composition can be manufactured by a conventionally known method. Examples of the thermoplastic resin film in the present invention include films of polyether sulfone, polyetherimide, polyether ether ketone, and polyimide. These films preferably have little orientation due to stretching, but their surfaces may be subjected to physical or chemical etching treatment. In particular, a thermoplastic resin film with a glass transition temperature of 100°C or higher is preferred, and the film thickness is 1
~30 μm is preferred. The holes in the film are perforations or slits. The shape of the perforation is not particularly limited and may be round, oval, triangular, polygonal, etc. In the case of a slit, it is a notch provided in the film, and the direction of the slit is preferably continuous in the winding direction of the film. The present invention will be explained with reference to the drawings. In the drawings, FIG. 1 shows a perspective view of the molded product intermediate of the present invention. FIG. 2 shows plan views A to D of the film portion of the molded intermediate of the present invention. FIG. 3 schematically shows a cross-sectional view of the molded product intermediate of the present invention. In FIG. 1, 1 is a prepreg, and 2 is a film. The prepreg 1 is made by impregnating and retaining an uncured thermosetting resin between the fibers of a fiber sheet such as a unidirectional fiber sheet, a woven fabric, or a random mat. These include maleimide resin, unsaturated polyester resin, polyimide resin, etc. Film 2 is a thermoplastic resin film. The film has holes. FIG. 2 shows an example of the form of this through hole. In Fig. 2, A shows a circular through hole, B shows an oval through hole, C shows a rectangular through hole, and D shows a slit (a cut with no width in the through hole). FIG. 3 schematically shows a state in which a film with such holes is attached to a prepreg and a continuous layer is formed by passing the holes in the film through the resin. In FIG. 3, the prepreg 1 is mainly composed of fibers 1-1 and resin 1-2, and the resin 1-2 passes through the through holes 2-1 of the film 2 and wraps around the back side of the film to form a continuous layer. ing. The film 2 having the through hole 2-1 is the prepreg 1
Although it may be attached to both sides, it is usually attached only to one side. Conventionally, a film was attached to prepreg, but this was done to protect the prepreg, and when laminating, the film was peeled off and only the prepreg was laminated to form a molded product. However, the intermediate molded product of the present invention is a molded product that is molded without peeling off the film and has a film interposed between the laminations of the molded product. When laminating the molded product intermediate of the present invention, all layers do not need to be composed of the molded intermediate of the present invention, and can also be laminated in combination with a normal prepreg to which no film is attached. At this time, it is preferable to laminate the molded product intermediate of the present invention so as to form the surface layer of the molded product. Such a molded product has excellent impact resistance and is less likely to cause peeling between laminated layers. The molded product intermediate of the present invention can be produced, for example, by the following method. First, a prepreg is prepared by a conventional method such as a hot melt method or a solvent method. Then,
A film having through holes is combined with the prepreg and pressed with a plate, roller, etc. to integrate the film. At this time, heating can be done, but the heating temperature is 60°C.
The temperature is preferably ~120°C. [Effects of the Invention] The molded product intermediate and molded product obtained by the present invention have excellent mechanical properties, thermal properties, and toughness, and are difficult to propagate cracks that occur. Because of these characteristics, it is suitable for use in aircraft structural materials, space structure materials, etc. [Examples and Comparative Examples] Example 1 and Comparative Example 1 Carbon fiber unidirectional prepregs made of resin compositions shown in Table 1 below were produced by a hot melt method. The carbon fiber (CF) used is besuphite.
IM-500 (manufactured by Toho Rayon Co., Ltd., tensile strength 500Kg
f/mm ² , elastic modulus 30T/mm ² ). of prepreg
The CF area weight was 150 g/m ² and the resin content was 32% by weight. On the other hand, there are through holes with a diameter of 2 mmφ on the entire surface, and the area ratio is 20.
A polyetherimide film (abbreviated as PEI, glass transition temperature 216° C.) with a thickness of 5 μm and having a thickness of 5 μm was prepared. The prepreg and film were stacked and passed through a hot roller at 80°C to adhere them together to obtain a molded intermediate. From this molded intermediate, small pieces of a predetermined size and number were cut, laminated, and cured by autoclave molding at a heating rate of 2° C./min at 180° C. for 2 hours to produce a molded plate. A test piece was cut out from this, and the 0° interlaminar shear strength, 0° compressive strength,
The compressive strength after impact of 1500 in-lb/in was measured and the results shown in Table 1 were obtained. Further, for comparison, carbon fiber unidirectional prepregs made of the resin compositions shown in Table 1 were made in the same manner as in Example 1. A molded plate was prepared from this prepreg under the same conditions without attaching a polyetherimide film, and the molded plate was tested. From the physical properties shown in Table 1, the molded plate of Example 1 has the following properties:
Compared to Comparative Example 1, there is no difference in 0° interlaminar shear strength and 0° compressive strength, but at 1500 in-lb/in
It was revealed that the compressive strength after impact was high and the impact resistance was excellent. Example 2 and Comparative Example 2 A carbon fiber unidirectional prepreg made of the resin composition shown in Table 1 was made in the same manner as in Example 1, and a 5 μm thick polyether film was used as a thermoplastic resin film to be attached to the prepreg. Imide film (abbreviated as PEI, glass transition temperature 216℃) is arranged in the form of 10mm slit tape on the surface of the prepreg so that the gap between the tapes is 0.5 to 1mm, and the two are pasted through a hot roller at 80℃. A molded intermediate was obtained. A molded plate was prepared from this molded intermediate in the same manner as in Example 1, and the 0° interlaminar shear strength, 0° compressive strength, and compressive strength after 1500 in-lb/in impact were measured. The results shown in Table 1 were obtained. Further, for comparison, a prepreg was made in the same manner as in Example 2. Molding was performed in the same manner using only this prepreg without attaching a film, and a composite test was conducted on the molded plate. As shown in Table 1, compared to Comparative Example 2, the molded plate of Example 2 showed no difference in 0° interlaminar shear strength and 0° compressive strength, but It became clear that the compressive strength after the test was high and the impact resistance was excellent. Example 3 and Comparative Example 3 A carbon fiber unidirectional prepreg made of the resin composition shown in Table 1 was made in the same manner as in Example 1, and a rectangular shape was applied to the entire surface as a thermoplastic resin film to be attached to the prepreg. The area of the through hole is 25mm ²
A polyether sulfone film (abbreviated as PES, glass transition temperature 223°C) with a thickness of 10 μm and an area ratio of 50% was arranged on the surface of the prepreg, and
The mixture was passed between hot rollers at 0.degree. C. to adhere the two to obtain a molded intermediate. This molded intermediate was prepared for molding in the same manner as in Example 1, and then cured by autoclave molding at a heating rate of 2° C./min and at 130° C. for 1.5 hours to produce a molded plate. The 0° interlaminar shear strength, 0° compressive strength, and compressive strength after impact at 1500 in-lb/in were measured for the molded plates, and the results shown in Table 1 were obtained. Further, for comparison, a prepreg was made in the same manner as in Example 3. Using only this prepreg without attaching a film, molding was carried out in the same manner.
Tests were conducted on molded plates. As shown in Table 1, the molded plate of Example 3 showed no difference in 0° interlaminar shear strength and 0° compressive strength compared to Comparative Example 3, but It became clear that the compressive strength after the test was high and the impact resistance was excellent. Example 4 and Comparative Example 4 A carbon fiber unidirectional prepreg made of the resin composition shown in Table 1 was made in the same manner as in Example 1, and a 5 μm thick polyether film was used as a thermoplastic resin film to be attached to the prepreg. Ether ketone film (abbreviated as PEEK, glass transition temperature 143℃)
It is a slit tape shape with a width of mm, and the gap between the tapes is
Arrange them on the prepreg surface so that they are 0.5 to 1 mm apart,
Both were pasted together by passing between hot rollers at 80°C to obtain a molded intermediate. A molded plate was prepared from this molded intermediate in the same manner as in Example 1, and the 0° interlaminar shear strength, 0° compressive strength, and compressive strength after 1500 in-lb/in impact were measured. The results shown in Table 1 were obtained. Further, for comparison, a prepreg was made in the same manner as in Example 4. Molding was carried out in the same manner using only this prepreg without attaching a film.
Tests were conducted on molded plates. As shown in Table 1, compared to Comparative Example 4, the molded plate of Example 4 showed no difference in strength in 0° interlaminar shear strength and 0° compressive strength, but It became clear that the compressive strength after the test was high and the impact resistance was excellent. Example 5 and Comparative Example 5 Carbon fiber unidirectional prepreg made in the same manner as in Example 1 (CF basis weight of the prepreg is 150 g/m ² ,
A polyetherimide film (abbreviated as PEI, glass transition temperature 216°C) with a thickness of 10 μm, which has through holes with a diameter of 2 mmφ on the entire surface and an area ratio of 20%, is arranged on the surface of the prepreg. , 80
The mixture was passed between hot rollers at 0.degree. C. to adhere the two to obtain a molded intermediate. For comparison, a similar film (thickness: 8 μm) without holes was arranged on the surface of the prepreg, and a molded intermediate was obtained in the same manner. In order to control the fiber volume content after molding (targeting 60% by volume), the two types of molded intermediates are molded using a method that allows 5 to 10% by weight of the resin component in the prepreg to flow out during mold curing. A molded plate was prepared (curing conditions were the same as in Example 1). In the case of Example 5, the resin component flowed out as planned during molding, resulting in a good molded plate with a controlled fiber volume content and a relatively small thickness. There was almost no flow of resin in the vicinity, the fiber volume content was not controlled, the molded plate was distorted, and the mechanical properties were not good. Examples 6 to 10 and Comparative Examples 6 to 10 Carbon fiber unidirectional prepregs were made in the same manner as in Example 1 using the resin compositions shown in Table 2, and thermoplastic resin films with holes shown in Table 2 were prepared in the prepreg. They were arranged on the surface and passed between hot rollers at 80°C to stick them together to obtain a molded intermediate. A molded plate was made from this molded intermediate under the molding conditions shown in Table 2, and the 0° interlaminar shear strength, 0° compressive strength, and compressive strength after 1500 in-lb/in impact were measured for the molded plate. As a result, the results shown in Table 2 were obtained. Moreover, in Comparative Examples 6 to 10, prepregs were made in the same manner as in Examples 6 to 10. Molding was performed in the same manner using only prepreg without attaching a film, and tests were conducted on the molded plates. As shown in Table 2, the molded plates of Examples 6 to 10 have 0° interlaminar shear strength,
Although no strength difference was observed in the 0° compressive strength,
It was revealed that the compressive strength after impact of 1500 in-lb/in was high and the impact resistance was excellent.

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【table】 [Brief explanation of the drawing]

FIG. 1 shows a perspective view of an intermediate molded product of the present invention. FIG. 2 shows plan views A to D of the film portion of the molded intermediate of the present invention. FIG. 3 schematically shows a cross-sectional view of the molded product intermediate of the present invention. Explanation of symbols in the drawings, 1...prepreg,
1-1...Fiber, 1-2...Resin, 2...Film, 2-1...Through hole.

Claims (1)

[Scope of Claims] 1. A fiber-reinforced resin laminate molded intermediate formed by adhering a thermoplastic resin film having through holes to a thermosetting resin prepreg made of reinforcing fibers as a base material. 2. A fiber-reinforced resin laminate molded product in which a thermoplastic resin film having through holes is interposed between the laminates.