JPH0575575B2 - - 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. The intermediate of the present invention can impart toughness to a molded product without impairing the excellent mechanical and thermal properties of the matrix resin, especially when high-strength carbon fiber or the like is used as a reinforcing material. ,Also,
The molded product of the present invention obtained from this intermediate is suitably used as an aircraft structural material. [Prior art and problems] In recent years, composite materials reinforced with carbon fibers, aromatic polyamide fibers, etc. have been widely used as structural materials for aircraft, etc., due to their high non-strength and specific stiffness. . 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 forming and processing steps such as heating and pressing. 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 have been 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 excellent impact properties in addition to good heat resistance and mechanical properties, but the handling properties as a prepreg, such as the drapability of the prepreg, are poor. Therefore, 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 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. Although it is necessary, it has been considered difficult to improve impact resistance without compromising heat resistance. When trying to improve prepreg with impact resistance, it is necessary to improve the elongation of the reinforcing material itself such as carbon fiber, increase the toughness of the matrix resin used in the prepreg, and optimize the interface between reinforcing fiber and matrix resin. This has been pointed out as an important point and research has been carried out, but in addition to this, controlling the higher-order structure of the laminated material that is the molded product is also considered to be important for improving impact properties and suppressing crack propagation. By increasing the toughness of the matrix resin for prepreg,
Composite materials are a technology that improves impact resistance.
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.
Prepreg compositions have also been developed that improve the toughness and impact properties of composite materials, but the impact resistance of composite materials has not been completely 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 achieved. The current situation is that there is no such thing. 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, fabrics are difficult to manufacture, resin impregnation is poor, and fiber volume content cannot be controlled. There are many problems such as difficulty, and it has not yet achieved a remarkable effect in practical terms. Regarding the technology of inserting different materials between the laminated layers of composite materials, materials in which scrim 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, for example.
It is also possible to use thermoplastic resin films such as polyetherimide, polyethersulfone, polyetheretherketone 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 since 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, and the resin flow 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 composite material is relatively thick, the volume ratio of the thermoplastic resin film to the matrix resin becomes high, which sometimes causes a corresponding deterioration in the performance of the composite material. [Object of the invention] The object of the present invention is to overcome the above-mentioned problems,
Provides an intermediate (prepreg) that provides a composite material with a molded product that has excellent heat resistance, excellent toughness and impact properties (impact strength), and has the ability to suppress crack propagation during impact, and the molded product. It's about doing. In a prepreg using a thermoplastic matrix resin, a thin layer made of a material different from the matrix resin is provided on the surface of the prepreg, and the different material is inserted between the laminated layers of the 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 having excellent impact strength 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 fabric with a fiber area weight of 1 to 25 g/m ² made from fibers with a tensile modulus of 10,000 Kgf/mm ² or less is attached to the surface of a thermosetting resin prepreg based on reinforcing fibers. Fiber-reinforced resin laminate molded intermediate. (2) A fiber-reinforced resin laminate molded product in which a woven fabric with a fiber basis weight of 1 to 25 g/m ² made from fibers with a tensile modulus of elasticity of 10,000 Kgf/mm ² or less 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 fibers forming the fabric adhered to the surface of the thermosetting resin prepreg have a melting point of 200°C or higher. . (c) The fiber-reinforced resin laminate molded intermediate according to claim 1, wherein a cured matrix resin used in the thermosetting resin prepreg has an elongation of 4.0% or more. The molded product of the present invention has excellent impact strength and has the property that cracks that occur are difficult to propagate. In the present invention, the fibers constituting the fabric include:
Fibers having a tensile modulus of elasticity of 10,000 Kgf/mm ² or less, preferably 5,000 Kgf/mm ² or less are used. If the tensile modulus of the fiber exceeds 100,000 Kgf/mm ² , the effect of suppressing crack propagation and improving impact properties is small. There are no restrictions on the type of fiber used; it can be either inorganic fiber or organic fiber.
Further, either natural polymer fiber or synthetic polymer fiber may be used. In particular, glass fibers and aromatic aramid fibers are preferably used. These fibers may be used alone or in combination. The form of the fiber is not particularly limited, and filament, spun yarn, blended yarn, etc. are used. There is no particular limitation regarding the twist of the thread, and it is sufficient to use a thread having the same number of twists as is usually commercially available. The thickness of the fibers used is usually 20 to 500 μm, and the above-mentioned fibers are run on a loom in the form of single threads or twisted threads, and processed into woven fabrics. As for the thermal properties of the fiber, the curing temperature of the thermosetting resin composition that is the matrix resin is 100 to 200℃.
Therefore, the melting point of the substance that makes up the fiber is 200
It is desired that the temperature is at least ℃. In addition, in order to improve handling properties and compatibility with the thermosetting resin composition that is the matrix resin, the fibers may be subjected to physical treatment, chemical treatment, oil treatment, etc. that are commonly used for various fibers. I don't mind. Examples of the types of textile structures include plain weave, twill weave, satin weave, and Karame weave. It is also possible to use so-called mixed fabrics, which are woven using different types of fibers. The fiber basis weight (weight per unit area) of the fabric is
Since these fabrics will eventually be inserted between the laminated layers of the composite, it is necessary to have a weight that does not impair the mechanical properties of the molded product. m ² , preferably 5-5 g/
^m2 . If the fiber basis weight is less than 1 g/m ² , sufficient results such as improving impact properties cannot be achieved, while if it exceeds 25 g/m ² , the tensile strength and compressive strength required for the molded product itself cannot be achieved. Basic characteristics such as strength will be reduced. Specific types of fibers used in the fabrics used in the present invention include cotton, silk, rayon, organic synthetic polymer fibers (polyacrylonitrile, polyamide, polyester, polyetherimide, polyetheretherketone, aramid, polyester, etc.). fibers such as benzimidazole and polyimide), glass fibers,
There are aluminum fibers, etc., and fabrics made of several types of fibers may be used together in one molded product. The reinforcing fibers used in the present invention are preferably carbon fibers, glass fibers, aromatic polyamide fibers, etc. 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 elastic modulus of 24T/mm ² are preferably used. To improve the mechanical properties of composite materials,
It is also possible to use so-called medium-elastic high-strength carbon fibers having a tensile strength of 400 Kgf/mm ² or more and an elastic modulus of 30 T/mm ² . These reinforcing fiber-based intermediates (prepregs) are made by impregnating an uncured thermosetting resin composition between the fibers of a base material such as a unidirectional sheet of reinforcing fibers, woven fabric, or short fiber mat. be. 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.
The present invention is also effective when the elongation of the matrix resin is improved due to deformation of the resin or the like. If the fabric used in the present invention is applied to a prepreg made of a resin composition having high impact properties, the impact resistance of the composite will be further improved, and the composite will have characteristics that make it difficult for cracks to propagate. In particular, when the fabric of the present invention is used between composite layers in which the thermosetting resin composition used in the prepreg has an elongation of 4.0% or more after curing, the composite has a high impact resistance level.
The scope of application to aircraft primary structural material applications will also be expanded. The basic prepreg of the thermosetting resin composition can be manufactured by a conventionally known method. 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 examples (a), (b), and (c) of the texture of the fabric attached to 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 woven fabric. 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. Since the fabric 2 has through holes, the matrix resin 1-2 of the prepreg passes through the through holes 2-1 of the fabric 2 and wraps around the back side of the fabric to form a continuous layer. The fabric 2 may be attached to both sides of the prepreg 1, but
Usually attached to one side only. 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 woven fabric is attached. 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. Next, the woven fabric is combined with the prepreg and pressed with a plate, roller, etc. to integrate the fabric. At this time, heating can be performed, but the heating temperature is preferably 60 to 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 also have characteristics that prevent cracks that occur from propagating. Therefore, it is suitably used for aircraft structural materials, space structure materials, etc. [Examples and Comparative Examples] Example 1 A unidirectional carbon fiber prepreg made of a resin composition shown in Table 1 below was produced by a hot melt method. The carbon fiber CF used was Besphite IM-
500 (manufactured by Toho Rayon Co., Ltd., tensile strength 500Kgf/ ^mm2 ,
The elastic modulus is 30T/mm ² ). The prepreg had a CF area weight of 150 g/m ² and a resin content of 32% by weight. On the other hand, a plain weave with a fiber area weight of 10 g/m ² made from doubled polyether ether ketone fibers (abbreviated as PEEK fibers, tensile modulus of elasticity of about 600 Kgf/mm ² , melting point 334°C) with an apparent thickness of about 80 μm. The fibers were 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. Comparative Example 1 A carbon fiber unidirectional prepreg made of the resin composition shown in Table 1 was produced in the same manner as in Example 1. A molded plate was prepared under similar conditions from this prepreg to which no woven fabric made of polyetheretherketone fibers was attached, and the molded plate was tested. (Comparison of results) From the physical properties shown in Table 1, the molded plate of Example 1 has no difference in 0° interlaminar shear strength and 0° compressive strength compared to Comparative Example 1, but It is clear that the compressive strength after impact is high and the impact resistance is excellent. 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 fabric with an apparent thickness of approximately
Fiber area weight 15 g/m ² made from 200 μm doubled polyetherimide fibers (abbreviated as PEI, tensile modulus approximately 700 Kgf/mm ² , glass transition temperature 216°C).
Prepare a plain weave fabric and arrange it on the prepreg surface,
Pass them between hot rollers at 80℃ and stick them together.
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. Comparative Example 2 A prepreg was produced in the same manner as in Example 2. Molding was performed in the same manner using only this prepreg without attaching any fabric, and tests were conducted on the molded plates. (Comparison of results) As shown in Table 1, the molded plate of Example 2 was found to have no strength difference in 0° interlaminar shear strength and 0° compressive strength compared to Comparative Example 2. It was revealed that the compressive strength after -lb/in impact was high and the impact resistance was excellent. 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 fabric with an apparent thickness of approximately
100μm polyester fiber (Teflon, tensile modulus approx. 1200Kgf/mm ² , melting point 260℃)
A plain weave fabric with a fiber basis weight of 20 g/m ² was prepared, arranged on the surface of the prepreg, and passed between hot rollers at 80°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. Comparative Example 3 A prepreg was produced in the same manner as in Example 3. Molding was performed in the same manner using only this prepreg without attaching any fabric, and tests were conducted on the molded plates. (Comparison of results) As shown in Table 1, the molded plate of Example 3 has no difference in 0° interlaminar shear strength and 0° compressive strength compared to Comparative Example 3, but It was revealed that the compressive strength after -lb/in impact was high and the impact resistance was excellent. 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 fabric with an apparent thickness of approximately
A twill fabric with a fiber area weight of 25 g/m ² was prepared from 60 μm polyetherimide fibers (abbreviated as PEI, tensile modulus approximately 700 Kgf/mm ² , glass transition temperature 216°C), and this fabric was They were arranged on the surface of the prepreg and passed between hot rollers at 80°C to adhere them together 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 determined. The results shown in Table 1 were obtained. Comparative Example 4 A prepreg was produced in the same manner as in Example 4. Molding was performed in the same manner using only this prepreg without attaching any fabric, and tests were conducted on the molded plates. (Comparison of results) As shown in Table 1, the molded plate of Example 4 showed no difference in 0° interlaminar shear strength and 0° compressive strength compared to Comparative Example 3, but It was revealed that the compressive strength after -lb/in impact was high and the impact resistance was excellent. Examples 5 to 8 and Comparative Examples 5 to 8 Carbon fiber unidirectional prepregs were made in the same manner as in Example 1 using the resin compositions shown in Table 2, and fabrics shown in Table 2 (tensile modulus of PEI fibers of approximately 7000 kgf) were prepared. /
mm ² , glass fiber approx. 7000Kgf/mm ² , aramid fiber approx.
7000Kgf/mm ² , aluminum fiber approx. 7000Kgf/
mm ² ) were arranged on the surface of the Puipreg, passed between hot rollers at 80°C, and stuck 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 5 to 8, prepregs were made in the same manner as in Examples 5 to 8. Molding was performed in the same manner using only the prepreg without attaching the fabric, and tests were conducted on the molded plates. (Comparison of results) As shown in Table 2, the molded plates of Examples 5 to 8 have a 0° interlaminar shear strength, a 0°
Although there is no difference in compressive strength, 1500in
It was revealed that the compressive strength after -lb/in impact was high and the impact resistance was excellent.

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【table】 [Brief explanation of drawings]

FIG. 1 shows a perspective view of an intermediate molded product of the present invention. FIG. 2 shows examples (a), (b), and (c) of the fabric structure to be attached to the molded intermediate of the present invention. FIG. 3 schematically shows a cross-sectional view of the molded part intermediate body of the present invention. Explanation of symbols in the drawings, 1: Prepreg, 1
-1: Fiber, 1-2: Resin, 2: Textile, 2-1:
Through hole.

Claims (1)

[Claims] 1. A woven fabric with a fiber area weight of 1 to 25 g/m ² made from fibers with a tensile modulus of 10,000 Kgf/mm ² or less is pasted on the surface of a thermosetting resin prepreg based on reinforcing fibers. A fiber-reinforced resin laminate molded intermediate. 2. A fiber-reinforced resin laminate molded product in which a woven fabric with a fiber basis weight of 1 to 25 g/m ² made from fibers with a tensile modulus of 10000 Kgf/mm ² or less is interposed between the laminates.