KR20180087995A - Prepreg with high toughness and high tensile strength - Google Patents

Abstract

Provided is a high toughness prepreg which is composed of: (a) a reinforcing fiber; (b) a resin composition composed of an epoxy resin containing bisphenol A type, aminophenol type, and tetraglycidyl diaminodiphenylmethane, and a curing agent containing dicyandiamide and 3-(3,4-dichlorophenyl) -1,1-dimeth-K urea; (c) polyether sulfone as a solubility toughening agent; and (d) a nylon 12 fine particle as an insoluble toughening agent. At least 50% of the component (c) and at least 95% of the component (d) are distributed within a 20% depth of the thickness of the prepreg. According to the present invention, the prepreg ensures excellent effects such as high toughness, high strength, and high heat resistance.

Description

[0001] Prepreg with high toughness and high tensile strength [

The present invention relates to a 350 ℉ curable high toughness prepreg, and more particularly, to a resin composition and compounding technique suitable for use as a material for advanced transport equipment such as aerospace parts and structures, Hardness tough toughness prepreg having high strength and high heat resistance.

The prepreg is a fiber-reinforced composite material produced by a combination of a fiber and a matrix mainly composed of a resin. The carbon fiber reinforced composite material composed of carbon fiber and resin has excellent mechanical strength characteristics and is widely used in general industrial applications such as sports, aerospace, automobile body, and the like.

Composite materials typically consist of a resin matrix and continuous reinforcing fibers as two major components. Composites are often needed to perform tasks in demanding environments, such as aerospace, where the physical limitations and characteristics of composite components are critically important.

 Pre-impregnated composites (prepregs) are widely used in the manufacture of composite parts. A prepreg is a combination of an uncured resin matrix and a fiber reinforcement, which is a form that is easy to shape and cure into a final composite part. By pre-impregnating the fiber reinforcement with resin, the manufacturer must carefully control the amount and location of the resin impregnated with the fiber network. It is well known that the relative amount of fibers and resin in a composite part and the distribution of resin in the fiber network have a great influence on the structural characteristics of the part. Pre-pressures are a preferred material for use in the manufacture of load-bearing structural components and specifically aerospace composite components such as wings, fuselages, partitions and maneuvers. It is important that these components have sufficient strength, damage tolerance and other requirements generally established for this.

Conventional prepresses are well suited for intentional use in providing strong, damage-tolerant composite parts, but require a higher level of strength (e.g., tensile and compressive strength), damage tolerance (CAI) And interlaminar fracture toughness (GIc and GIIc). It is still a continuing need to provide prepregs that can be used to prepare composite parts having interlaminar fracture toughness (GIc and GIIc).

The present invention has been made to solve the above problems and provides a prepreg having tensile strength, compressive strength, damage tolerance and interlaminar fracture toughness.

(B) an epoxy resin composed of bisphenol A type, aminophenol type and tetraglycidyldiaminodiphenylmethane, and 4,4'-diaminodiphenylsulfone, dicyandiamide, and 3 (C) a polyether sulfone as a soluble toughening agent, and (d) an insoluble toughening agent as essential components. Wherein the content of component c is not less than 50% and the content of d is not less than 95% is distributed within a range of 20% of the thickness of the prepreg at the surface of the prepreg.

The reinforcing fibers constituting the prepreg of the present invention include one or more fibers selected from the group consisting of carbon fiber, glass fiber, aramid fiber, boron fiber, and graphite fiber, and the content of the reinforcing fiber is greater than the total weight of the prepreg Preferably 35 to 65 parts by weight.

The content of the epoxy resin constituting the resin composition for producing the prepreg of the present invention is 60 to 80 parts by weight, the content of the curing agent is 10 to 20 parts by weight, the content of the soluble toughening agent and the insoluble toughening agent is 10 to 30 parts by weight .

The prepreg of the present invention is characterized in that the interlayer toughness GIIc is 10 to 13 in-lbf / in ² and the compressive strength at the time of wet heating is 1200 MPa or more.

The prepreg according to the present invention has an excellent effect of high toughness, high strength and high heat resistance.

Hereinafter, the present invention will be described in detail.

Composite materials typically consist of a resin matrix and continuous reinforcing fibers as two major components. Composites are often needed to perform tasks in demanding environments, such as aerospace, where the physical limitations and characteristics of composite components are critically important.

The tensile strength of the cured composite material is largely dependent on the individual properties of the reinforcing fibers and the matrix resin as well as by the interaction between these two components. In addition, fiber-resin composition ratio is an important factor. The cured composites under tensile forces tend to fail through the mechanism of cumulative loss resulting from multiple tensile failure of individual fiber filaments located in the reinforcing tow. If the stress level of the resin adjacent to the broken filament end becomes very large, the entire composite can be broken. Therefore, the fiber strength, the strength of the matrix, and the stress dissipation efficiency near the destroyed filament end will contribute to the tensile strength of the cured composite.

In many applications, it is desirable to maximize the tensile strength properties of the cured composite. Attempts to maximize tensile strength, however, can often have negative effects on other desirable properties, such as compressive performance and damage tolerance of the composite structure. In addition, attempts to maximize tensile strength can have unexpected effects on the tack and outlife of the prepreg. The stickiness or tackiness of the uncured prepreg is generally referred to as "tack ". The viscosity of the uncured prepreg is an important consideration in lay up and molding operations. A prepreg with little or no viscosity is difficult to fabricate with a laminate that can be molded to make structurally robust composite parts. On the contrary, a prepreg having a very high viscosity is difficult to handle, and it may also be difficult to position it on a mold. The prepreg preferably has a suitable amount of viscosity to ensure easy handling and excellent laminate / molding characteristics. In any attempt to increase the strength and / or damage tolerance of the cured composite material provided, it is important to maintain the viscosity of the uncured prepreg within acceptable limits to ensure proper prepreg handling and molding.

The "out-life" of the prepreg is a period during which the prepreg can be exposed to ambient conditions before it is cured to an unacceptable degree. The out-life of the prepreg can vary widely depending on various factors, but is mainly controlled by the resin formulation used. The prepreg out-life should be long enough so that routine handling, layup, and molding operations are performed without curing the prepreg to an unacceptable degree. In any attempt to increase the strength and / or damage tolerance of the cured composite material provided, the out-life of the uncured prepreg allows sufficient time for processing, handling and laying up the prepreg before curing It is important to be as long as possible.

The most common way to increase the tensile performance of a composite is to change the surface of the fiber to weaken the bond strength between the matrix and the fiber. This can be achieved by reducing the amount of electro-oxidized surface treatment of the fibers after graphitization. Reducing the matrix fiber bond strength causes a mechanism for stress dissipation at the filament ends exposed by interfacial separation. This interfacial separation increases the amount of tensile loss that a composite component can withstand before it loses its tensile strength.

Alternatively, applying a coating or "size" to the fibers can reduce the resin-fiber bond strength. This method is well known in glass fiber composites, but can also be applied to composites reinforced with carbon fibers. By using these strategies, it is possible to significantly increase the tensile strength. However, this improvement entails a decrease in properties such as compression after impact (CAI) strength, which requires a high bond strength between the resin matrix and the fibers.

Another alternative is to use a lower coefficient matrix. Having a low coefficient resin reduces the stress level to be formed in the vicinity of the broken filament. This may be accomplished by selecting a resin that is usually inherently lower in modulus (e.g., cyanate ester) or by selecting an elastomer (carboxy-terminated butadiene-acrylonitrile [CTBN], amine- terminated butadiene- acrylonitrile [ATBN], etc.). Combinations of these various methods are also known.

Choosing a lower coefficient resin may be effective in increasing the composite tensile strength. However, this can lead to propensity for damage tolerance, which is typically measured by compression properties, such as impact-after-compression (CAI) strength and reduced open hole compression (OHC) strength. Therefore, it is very difficult to simultaneously increase both the tensile strength and the damage tolerance.

Multiple layers of prepreg are typically used to produce composite parts having laminated structures. The detachment of such composite parts is an important failure mode. Peeling occurs when the two layers are separated from each other. Important design constraints include both the energy required to initiate delamination and the energy required to propagate delamination. The onset and advancement of delamination is often determined by examining Method I and Method II fracture toughness. Fracture toughness is usually measured using a composite material with unidirectional fiber orientation. The interlaminar fracture toughness of the composite material is quantified using Glc (Double Cantilever Beam) and G2c (End Notch Flex) tests. In Method I, the pre-cracked laminate fracture is subjected to a peel force, and in Method II, the crack is advanced by a shear force. G2c interlaminar fracture toughness is related to CAI. The prepreg material exhibiting high damage tolerance also has a high CAI and G2c value.

A simple way to increase the interlaminar fracture toughness was to increase the ductility of the matrix resin by introducing a thermoplastic sheet as an insert between the prepreg layers. However, in this method, it is easy to obtain a hard and viscous material which is difficult to use. Another method is to include a layer of hard resin between about 25 to 30 microns thick between the fibrous layers. The prepreg product comprises a resin rich surface containing fine, hard thermoplastic particles. For layer-hardened materials, the initial value of the Method II fracture toughness is about four times higher than the value of the carbonless prepreg without the interlayer, but the fracture toughness value decreases as the crack spreads and converges at low values, It is almost identical to the value of the system without inserts. As a result, the average G2c value becomes highest as the cracks move from the very hard interlayer (resin-enriched) region of the composite to the less hard interlayer (fiber) region.

Conventional prepresses are well suited for intentional use in providing strong, damage-tolerant composite parts, but require a higher level of strength (e.g., tensile and compressive strength), damage tolerance (CAI) And interlaminar fracture toughness (GIc and GIIc). It is still a continuing need to provide prepregs that can be used to prepare composite parts having interlaminar fracture toughness (GIc and GIIc).

The resin composition suitable for the prepreg of the present invention can be selected from the resin compositions discussed below. The bifunctional epoxy resin and the trifunctional epoxy resin include those based on the following materials by way of example.

Examples of the bifunctional epoxy resin include diglycidyl ethers of bisphenols such as bisphenol A and bisphenol F (so-called bisphenol-based epoxy resins), epoxyphenol novolacs, polyfunctional epoxy resins, and halogenated derivatives thereof . Chlorine and bromine are the most commonly used halogens for the production of halogenated derivatives. The brominated epoxy resin may impart nonflammability to the composition. More preferably, diglycidyl ether bisphenol F is suitable as the bifunctional epoxy resin.

The trifunctional epoxy resin is most preferably, for example, triglycidyl p-aminophenol and triglycidyl m-aminophenol. Other examples of the tetrafunctional epoxy resin include tetraglycidyl-4,4'-diaminodiphenylmethane and tetraglycidyl-3,3'-diaminodiphenylmethane.

In the present invention, an epoxy resin composed of bisphenol A type, aminophenol type and tetraglycidyldiaminodiphenylmethane is preferable. In the resin composition, the content of the epoxy resin is preferably 60 to 80 parts by weight. When the content of the epoxy resin is less than 60 parts by weight, moldability is poor. When the amount is more than 80 parts by weight, the epoxy resin does not have adequate physical properties such as tensile strength for composites.

As the curing agent used in the epoxy resin composition, a compound having an active group capable of reacting with an epoxy group can be used. Examples of the amine-based curing agent include aliphatic amines such as ethylenediamine, ethylenetriamine, triethylenetetramine, hexamethylenediamine and m-xylenediamine, meta-phenylenediamine, diaminodiphenylmethane, diaminodiethyldiphenyl Aromatic amines such as methane and diamino diethyldiphenyl sulfone, tertiary amines such as benzyldimethylamine, tetramethylguanidine and 2,4,6-tris (dimethylaminomethyl) phenol, and basic amines such as dicyandiamide Hydrogen compounds and organic acid dihydrazides such as adipic acid dihydrazide, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole. Examples of the acid anhydride-based curing agent include aliphatic acid anhydrides such as polyadipic acid anhydride, poly (ethyloctadecanedioic acid) anhydride and poly sebacic acid anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylcyclohexene dicarboxylic acid anhydride Alicyclic acid anhydrides such as trimellitic anhydride, trimellitic anhydride, pyromellitic anhydride, and glycerol tristrimellitate, and halogen-based acid anhydrides such as anhydrous hic acid and tetrabromophthalic anhydride. have. In the present invention, since it is cured at a relatively low temperature and the storage stability is good, a basic active hydrogen compound can be preferably used in the amine curing agent as a curing agent. In addition, as a curing agent suitable for the prepreg of the present invention, 4,4'-diaminodiphenylsulfone (DDS) is included.

As the curing accelerator, it is preferable to use dicyandiamide, preferably 0.1 to 10 parts by weight, and most preferably 1 to 5 parts by weight. The curing can be caused by the latent amine type curing agent, but the curing time can be greatly shortened by a small amount of catalyst, that is, a curing accelerator. As such, it is to be understood that the term catalyst and cure accelerator refers to a chemical that shortens the curing time achievable with the curing agent alone. As a urea-based catalyst used to complete the shortening of the curing time exceeding the previous prediction, there is a 3,3 '- (4-methyl-1,3-phenylene) bis (1,1-dimethylurea) . The catalyst is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, most preferably 0.5 to 3 parts by weight.

The curing agent containing the curing accelerator is preferably 10 to 20 parts by weight based on 100 parts by weight of the total of the resin composition. If the amount of the curing agent containing the curing accelerator is less than 10 parts by weight, the curing rate will be adversely affected. If the amount is more than 20 parts by weight, the moldability is poor.

The toughening agent usable in the present invention includes thermoplastic resins, cured thermosetting resins, and elastomers. These fine particles are effective for improving the toughness of the resin and improving the impact resistance of the fiber-reinforced composite material. The amount of the toughening agent to be used is generally 10 to 30 parts by weight, and most preferably 14 to 25 parts by weight, based on 100 parts by weight of the total resin composition. If the amount is less than 10 parts by weight, sufficient toughness required in the present invention is difficult to be exhibited. If the amount is more than 30 parts by weight, blending with the epoxy resin becomes difficult, and the tackiness of the prepreg may be deteriorated.

 Thermoplastic resins preferably usable as toughening agents include polyamides. Thermosetting resins which can be preferably used include epoxy resins, phenol resins and the like. The elastomer fine particles which can be preferably used include core-shell type rubber microparticles obtained by graft polymerizing cross-linked rubber microparticles and other polymers on the surfaces of cross-linked rubber microparticles. The use of toughening agents provides greater damage tolerance (CAI) and interlaminar toughness to the composite material. That is, toughening agents increase impact-to-impact (CAI) performance and interlayer toughness (GIIc).

The toughening agents may be composed solely or in combination and may be selected from the group consisting of polyamides, copolyamides, polyimides, aramids, polyketones, polyetheretherketones, polyesters, polyurethanes, polysulfones, polyethersulfones, high performance hydrocarbon polymers, , PTFE, elastomers, and segmented elastomers. In the present invention, a mixed toughening agent of a soluble toughening agent and an insoluble toughening agent is used. The soluble toughening agent is preferably polyethersulfone (PES), and the insoluble toughening agent is most preferably nylon 12. In the present invention, the size of the toughening agent particle is not particularly limited, but particles made of polyether sulfone particles and nylon 12 particles ball-milled to 10 탆 or less are preferable.

The composite polyamide fine particles of the present invention can be mixed with other resins to such an extent that the effect is not impaired. The other resin that can be mixed is not particularly limited, and examples of the thermoplastic resin include a vinyl polymer, a polyester, a polyamide, a polyarylene ether, a polyallylen sulfide, a polyether sulfone, a polysulfone, a polyether Ketone, polyether ether ketone, polyurethane, polycarbonate, polyamideimide, polyimide, polyetherimide, polyacetal, silicone, and copolymers thereof. Examples of the thermosetting resin include epoxy resin, benzoxazine resin , A vinyl ester resin, and the like. These resins may be used alone or in combination of two or more.

In the present invention, it is preferable that the above-mentioned toughening agent particles are formed in the vicinity of the surface of the prepreg.

Specifically, it takes a structure in which 50% of polyethersulfone as a soluble toughening agent and 95% or more of nylon 12 fine particles as an insoluble toughening agent are distributed and distributed in a range of 20% of the thickness of the prepreg on the surface of the prepreg More preferable.

By adopting such a structure, a resin layer is likely to be formed between the composite material layers, and as a result, the adhesion and adhesion between the composite material layers become high, so that a high interlayer toughness and impact resistance can be exhibited in the obtained reinforcing fiber composite material It is.

Next, the prepreg of the present invention will be described. By impregnating the reinforcing fiber with the embodiment of the resin composition, a prepreg containing the embodiment of the epoxy resin composition as a matrix resin in the form of a cured product can be obtained.

The prepreg of the present invention is obtained by impregnating the resin composition with the reinforcing fiber. There are no specific limitations or restrictions on the type of reinforcing fibers used and a wide variety of fibers are used, including glass fibers, carbon fibers, graphite fibers, aramid fibers, boron fibers, alumina fibers and silicon carbide fibers. Two or more of these fibers may be used in combination. The shape and arrangement of the reinforcing fibers are not limited, and for example, fibrous structures such as long fibers aligned in one direction, single tows, fabrics, knits, nonwoven fabrics, mats and braids are used.

Particularly, in applications where the weight of the material is required to be high or the strength thereof is high, carbon fibers can be suitably used because of its excellent non-elasticity ratio and non-elasticity. Therefore, carbon fiber is preferred in the present invention.

The carbon fiber preferably used in the present invention may be any kind of carbon fiber, but is preferably carbon fiber having a tensile modulus in the range of 200 to 300 GPa from the viewpoint of interlayer toughness and impact resistance. The resin composition preferably has a minimum viscosity at 100 to 150 DEG C of not more than 25 Poise in 10 Poise.

The resin composition is expected to have a viscosity of 50,000 to 100,000 Paise or less at 30 占 폚. A resin composition having a viscosity of 100,000 Poise or less is preferable, and has various desirable characteristics of a prepreg.

It is also preferable that the average epoxy equivalence of the resin composition is 200 to 300. To achieve this preferred range of average epoxy equivalents, a high molecular weight resin (e.g., molecular weight greater than 1,000) and a low molecular weight (e.g., less than 200 molecular weight) resin are mixed.

The prepreg of the present invention is preferably impregnated with the reinforcing fiber, and the reinforcing fiber mass fraction of the prepreg is preferably 35 to 65 parts by weight. If the weight of the reinforcing fiber is excessively low, the resultant composite material becomes excessively massive, and the advantage of the fiber reinforced composite material excellent in the non-rigidity and the non-elasticity ratio adversely affects. If the weight of the carbon fiber is excessively high, , The resulting composite material tends to have a large void, and its mechanical properties may be significantly lowered.

The prepreg prepared by the above-mentioned method has a interlayer toughness GIIC of 10 to 13 in-lbf / in ² and a compressive strength of 1200 MPa or higher at the time of wet heat, and is excellent in toughness and wet heat compression strength and thus used as a composite material for aerospace components .

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are for illustrating the present invention specifically, and the scope of the present invention is not limited to these examples.

Example 1

Epoxy resin composed of bisphenol A type, aminophenol type and tetraglycidyldiaminodiphenylmethane was mixed at room temperature (25 ° C) and then heated to 120 ° C at a rate of 2 ° C / min. Then, solvay PES was charged, Keep 120 ° C for 1-2 hours and mix until the PES particles are completely dissolved. After the PES particles are completely melted, add 12 nylon particles and mix them uniformly for 0.5 to 1 hour. The PES and nylon 12 microparticles used herein were a mixture of PES particles having a particle diameter of 30 占 퐉 and nylon 12 particles having a particle diameter of 20 占 퐉, which were pulverized through a ball-mill and mixed with particles having a particle size of 10 占 퐉 or less. The slope is 0.2 poise / min, the viscosity at 30 ° C is 50,000 ~ 100,000 poise, and at 130 ° C it is 10 ~ 20 posie. After the temperature of the mixture was lowered to 2 캜 / min, a curing agent containing 4,4'-DDS, dicyanodiamine and 3- (3,4-dichlorophenyl) -1,1-dimeth-K urea was allowed to react within 10 min And stirred well.

Examples 2 to 4 and Comparative Examples 1 to 2

A resin composition was prepared in the same manner as in Example 1, except that the content of the resin composition and the particle size of the composite polyamide fine particles were changed as shown in Table 1.

Measurement of flexural modulus of cured resin

The resin compositions prepared in Examples and Comparative Examples were defoamed in a vacuum and then injected into a mold set to have a thickness of 3 mm by a 3 mm thick spacer made of Teflon (registered trademark). And cured at 180 ° C for 2 hours to obtain a resin cured product having a thickness of 3 mm. Test pieces having a width of 12.7 mm and a length of 61 mm were cut out from the thus-obtained resin cured product, and three-point bending at 48 mm between spans was measured, and the bending elastic modulus was determined according to ASTM D 790.

Toughness measurement of cured resin

The resin compositions prepared in Examples and Comparative Examples were defoamed in a vacuum and then injected into a mold set to have a thickness of 6 mm by a spacer made of "Teflon (registered trademark)" having a thickness of 6 mm. And cured at 180 ° C for 2 hours to obtain a resin cured product having a thickness of 6 mm. This cured product of the resin was cut into a size of 12.7 x 150 mm to obtain a test piece. A test piece was processed and tested according to ASTM D5045 (1999) using an Instron universal testing machine (manufactured by Instron) to evaluate toughness.

Preparation of prepreg

The resin composition thus compounded is applied to a release paper to prepare a resin sheet.

The resin unit weight applied to release paper was 53 g / m 2 resin paper. Next, a unidirectional prepreg was obtained by impregnating both sides of the carbon fiber with resin paper in one direction by heating and pressing.

Measure the presence rate of PES and nylon 12 particles in the range of 20% depth of prepreg thickness

The prepreg was sandwiched between two sheets of smooth polysafluoride ethylene resin plates and brought into close contact with each other and gelled and cured by gradually raising the temperature to 150 ° C over a period of 7 days to prepare a platelet-shaped resin cured product. After curing, the section was cut from a direction perpendicular to the contact surface, and the cross section thereof was polished and then enlarged to 200 times or more by an optical microscope to take a picture so that the upper and lower surfaces (both surfaces) of the prepreg were within the visual field. The photograph was taken such that the longitudinal direction of the photograph was the thickness direction of the prepreg and the lateral direction was the surface direction of the prepreg. The spacing between the polysafused ethylene resin plates at five locations in the transverse direction of the cross-sectional photograph was measured by the same operation, and the average value (n = 5) was determined as the thickness of the prepreg. Two lines parallel to the surface of the prepreg are drawn at the 20% depth position of the thickness from the surface of the prepreg cured product on both surface sides of the prepreg cured product on the photograph of the prepreg cured product, The total area of each of the PES grains and nylon 12 fine grains existing over the total area of each of the PES grains and the nylon 12 grains present between the lines and the thickness of the prepreg was obtained and the total area of the prepreg The existence ratio of each of the PES particles and the nylon 12 fine particles existing in the depth range of 20% from the surface of the noble metal particles was calculated. Here, the total area of each of the PES particle and the nylon 12 particle was obtained by cutting out the PES particle and the nylon 12 fine particle portion in the cross-sectional photograph and converting the mass of the PES particle and the nylon 12 particle.

Measurement of compressive strength during wet heat

The unidirectional prepregs prepared in the examples and the comparative examples were laminated 10 lines by aligning the fiber directions and molded at a temperature of 180 ° C for 2 hours under a pressure of 0.59 MPa at a temperature raising rate of 1.5 ° C / Thereby producing a laminate. A test piece having a tab having a thickness of 2 mm, a width of 12.8 mm, and a length of 38 mm was produced from this laminate. At this time, a test piece was prepared so that the longitudinal direction of the test piece and the fiber direction were parallel. This specimen was immersed in hot water at 71 ° C for 14 days. The test piece was measured at 0 ° compression strength at 82 ° C using a universal testing machine equipped with a thermostatic chamber according to JIS K 7076 (1991). The number of samples was 5.

Shear mode interlaminar fracture toughness (GIIc) test of composites

For preparing the GIIc specimen, 20 sheets of the prepreg were stacked in one direction, and molding with a normal autoclave was carried out at 180 DEG C for 2 hours and at a pressure of 6 bar. Thereafter, the specimens were prepared by cutting at a size of 0.5 inches in the direction of 13 degrees and 90 degrees in the direction of 0 degrees.

The test specimens were used to carry out the evaluation according to the test procedure of BMS 8-276. At this time, five specimens were evaluated and the average values were recorded in Table 1.

Measurement of compressive strength (CAI) after impact of composite material

Twenty-four prepregs were laminated with (+ 45/0 / -45 / 90) 3S to prepare a CAI specimen. Molding with a normal autoclave was carried out at 180 DEG C for 2 hours and at a pressure of 6 bar. The specimens were cut into 4 inches by 6 inches long.

After five test specimens were prepared, the impact test was carried out at a 270 in-lbf impact level, and a compression test was conducted. The average values were recorded in Table 1.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Composition content Epoxy 73 68 65 63 81 73 Hardener 17 16 15 14 19 17 A tough topic 10 16 20 23 - 10 Percentage of PES particle surface layer present in the prepreg (%) 51 50 52 55 - 40 Percentage of nylon 12 particle surface layer present in the prepreg (%) 96 97 98 95 - 91 Carbon Fiber IMS60 IMS60 IMS60 IMS60 IMS60 IMS60 Compressive strength during wet heat
(MPa) 1220 1250 1270 1210 980 1150 G _II c
(in-lbf / in ² ) Avg. 12.19 11.52 10.88 9.04 4.50 8.68 CAI (ksi) (270 in-lbf impact level) Avg. 48.97 46.69 45.07 46.08 38.81 43.33

As shown in Table 1, in Examples 1 to 4 according to the present invention, the interlaminar fracture toughness, the post-impact compressive strength and the compressive strength at the time of wet heat are superior to those of the comparative example.

Claims (6)

(a) reinforcing fibers,
(b) an epoxy resin composed of a bisphenol A type, an aminophenol type and tetraglycidyldiaminodiphenylmethane, and an epoxy resin composed of 4,4'-diaminodiphenylsulfone, dicyandiamide and 3- (3,4-dichlorophenyl) -1,1-dimethoxy-urea < / RTI >
(c) a polyether sulfone as a soluble toughening agent and
(d) Nylon 12 fine particles are used as an insoluble toughening agent,
Characterized in that at least 50% of component c and at least 95% of d are distributed within the range of 20% depth of prepreg thickness on the surface of the prepreg.
The method according to claim 1,
Wherein the reinforcing fiber comprises one or more fibers selected from the group consisting of carbon fiber, glass fiber, aramid fiber, boron fiber and graphite fiber, wherein the content of the reinforcing fiber is 35 to 65 parts by weight based on the total weight of the prepreg Characterized by a high toughness prepreg. The method according to claim 1,
Wherein the content of the epoxy resin in the resin composition is 60 to 80 parts by weight. The method according to claim 1,
Wherein the content of the curing agent in the resin composition is 10 to 20 parts by weight. The method according to claim 1,
Wherein the content of the soluble toughening agent and the insoluble toughening agent in the resin composition is 10 to 30 parts by weight. The method according to claim 1,
An interlaminar toughness GIIc of 10 to 13 in-lbf / in ² , and a compressive strength at the time of wet heating of 1200 MPa or more.