JP2009220392A - Drape forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drape forming method for producing high quality shaped articles free of wrinkles or voids when bending a prepreg laminate. <P>SOLUTION: The drape forming method in which the prepreg laminate laminated into a planar shape is shaped into a columnar shape having bent portions in a crosssection on a desired mold and thereafter solidified by heating is characterized in that the viscosity of matrix resin used in prepregs at 40°C is 1,500 Pa s or more and 30,000 Pa s or less and the prepreg laminate is solidified by heating after shaping the same into the desired shape in 3 min or more and 25 min or less, using a vacuum degassing method, after heating the prepreg laminated bodies at 50°C or more and 100°C or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drape molding method in which a prepreg laminate laminated in a flat plate shape is shaped into a column having at least one bent portion in a cross section on a desired mold, and then heat-cured.

  Fiber reinforced composite materials (hereinafter sometimes abbreviated as FRP) are widely used from the aerospace industry to general industrial applications because of their excellent specific strength and specific rigidity. In particular, carbon fiber reinforced composite materials (hereinafter sometimes abbreviated as CFRP) using carbon fibers as reinforcing fibers are widely used in the aviation industry as represented by civil aircraft because they are particularly lightweight and have excellent strength and rigidity. In recent years, it is also used for large and long members such as main wings and fuselage.

As a method for forming a long and large-sized member having a bent section, a prepreg is laminated one by one along the mold, and a hand lay-up method for forming, or an uncured prepreg is laminated and obtained. Place the laminated body on a mold, etc., cover the whole with a bag film, heat or vacuum deaerate at room temperature, mold it, shape it into a mold, etc. The method (hereinafter sometimes simply referred to as drape molding) (for example, see Patent Documents 1 and 2) is employed. In the former method of hand lay-up, a molded product having a uniform thickness without yarn disturbance can be obtained, but it takes time to laminate and causes a cost increase. On the other hand, the latter drape forming method does not take much time for lamination and eliminates the cost increase factor, but is wrinkle generated during drape forming and is it difficult to shape the laminate to a predetermined shape? Even when shaped, the resulting laminate often wrinkles and voids and did not become a good laminate.
Japanese Patent Laid-Open No. 6-071763 Japanese Patent Laid-Open No. 6-071742

  An object of the present invention is to solve the above-mentioned problems, that is, to provide a drape forming method for obtaining a high-quality formed body free from wrinkles and voids when bending a prepreg laminate.

In order to achieve the above object, the drape forming method of the present invention has the following configuration. That is,
A draping molding method in which a prepreg laminate laminated in a flat shape is shaped into a column having a bent portion in a cross-section on a desired mold and then heat-cured, and the matrix resin used in the prepreg at 40 ° C. After the viscosity is 1500 Pa · s or more and 30000 Pa · s or less and the prepreg laminate is heated to 50 ° C. or more and 100 ° C. or less, a desired mold is formed over a period of 3 minutes or more and 25 minutes or less using a vacuum degassing method. A drape forming method characterized by heat-curing after forming into a shape.

  According to the present invention, in a draping molding method in which a columnar member having at least one bent portion in a cross section is formed into a desired mold by bending the prepreg laminate, and then heat-cured, a high quality molding free from wrinkles and voids. A body is obtained, which brings about an effect of improving physical properties and significantly reducing molding costs.

  The present invention is applied to a drape forming method in which a prepreg laminate laminated in a flat plate shape is heat-cured after a columnar member having at least one bent portion in a cross section on a desired die is formed into a desired die. Is. The prepreg used in the present invention refers to a prepreg in a state where resin is impregnated in a reinforcing fiber generally used as an advanced composite material.

  As the prepreg reinforcing fiber, carbon fiber, glass fiber, boron fiber, aramid fiber, high-strength polyethylene fiber, or the like is used. Among these, carbon fibers (hereinafter sometimes abbreviated as CF) having excellent strength and rigidity are preferably used.

  The matrix resin of the prepreg is not particularly limited, but a thermosetting resin that is cured by heat is preferably used. Specific examples of thermosetting resins include epoxy resins, benzoxazine resins, vinyl ester resins, unsaturated polyester resins, urethane resins, phenol resins, melamine resins, maleimide resins, cyanate ester resins, and urea resins. It is done. Among these, epoxy resins, benzoxazine resins, vinyl ester resins, unsaturated polyester resins, phenol resins and mixtures of these resins have high mechanical properties and are preferably used. In particular, the epoxy resin is preferably used because it has a good balance between the mechanical properties required for the member and the viscosity and tack required in the prepreg manufacturing process.

  As the epoxy resin, a compound having a plurality of epoxy groups in the molecule is used. For example, bisphenol A type epoxy resin, bisphenol AD type epoxy resin, bisphenol S type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, naphthalene type epoxy resin, and a copolymer of a phenol compound and dicyclopentadiene are used as raw materials. Glycidyl ether type epoxy resins such as epoxy resins, naphthalene type epoxy resins and novolak type epoxy resins, glycidyl amine type epoxy resins, and combinations of these resins are preferably used.

  In particular, an epoxy resin selected from bisphenol A type epoxy resin, bisphenol AD type epoxy resin, bisphenol S type epoxy resin and bisphenol F type epoxy resin, or a combination thereof, preferably 5 to 50 parts by weight, and glycidyl An epoxy resin containing 50 to 95 parts by weight of an amine type epoxy resin is excellent in the balance between mechanical properties and handleability, and is particularly preferably used.

  Examples of the curing agent used in combination with the epoxy resin include aromatic amines, aliphatic amines, carboxylic anhydrides, and Lewis acid complexes. These curing agents can be used in combination with an appropriate curing aid in order to increase the curing activity. Preferred examples of the case where a curing aid is combined with an epoxy resin include an example of combining dicyandiamide with a urea derivative such as 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU) as a curing aid, Examples include combining a group amine with a boron oxyfluoride ethylamine complex as a curing aid, and combining a tertiary amine with a carboxylic acid anhydride or a novolak resin as a curing aid.

  In the matrix resin after curing, the matrix resin may contain a thermoplastic resin that is dissolved and does not form particles. Such thermoplastic resins include carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, urea bonds, thioether bonds, sulfone bonds, imidazole bonds, and carbonyl bonds in the main chain. Those having a bond selected from the group consisting of: In particular, at least one resin selected from the group consisting of polysulfone, polyethersulfone, polyetherimide, and polyimide is preferably used. When the thermoplastic resin is mixed, an appropriate viscoelasticity and mechanical properties can be imparted to the epoxy resin by preferably mixing 1 to 20 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the epoxy resin.

  In addition, if a resin layer containing fine particles is further present on the surface of the prepreg, a layer in which fine particles are present between the layers is formed after the prepreg is laminated and cured, and it is more preferable that curing such as impact resistance is further imparted. . The fine particles to be used are not particularly limited, but fine particles comprising at least one thermoplastic resin selected from the group consisting of polyamide, polyarylate, polyamideimide, polyimide, polyetherimide, polysulfone, polyethersulfone and polyaramid are preferred. Used.

  In a field where high performance characteristics are required as a form of prepreg, a so-called UD (Uni Directional) prepreg in which reinforcing fibers are aligned in one direction is preferable, but depending on the application, use of a prepreg in which the reinforcing fibers are woven is also possible. Is possible.

  In the present invention, the prepreg is laminated in a flat plate shape, and then shaped into a column shape having at least one bent portion in a cross section on a desired mold. When the UD prepreg is used, the laminated structure of the prepreg laminated body can take various laminated structures including pseudo-isotropy. Further, the laminated structure is not particularly limited even in the prepreg laminate in the case of using the woven prepreg. Depending on the application, a prepreg laminate in which UD prepregs and woven prepregs are laminated regularly or irregularly may be used. When laminating using a UD prepreg, at least one layer is 10 to 90 degrees, preferably 30 to 90 degrees with respect to a thickness of 5 mm or less of a 0 degree layer arranged in the longitudinal direction of a long object such as a “beam”. A laminated structure in which fiber layers arranged at an angle of less than or equal to a degree are preferable in order to suppress the inter-fiber spread of the 0 degree layer when forming a column having a bent portion on a desired mold.

  The thickness of the prepreg laminate is preferably 3 mm or more and 100 mm or less, and more preferably 5 mm or more and 50 mm or less because rigidity and strength as a member can be easily secured.

  Drape molding can be applied to various cross-sectional shapes, and specific examples include L-shaped, concave, I-shaped, fan-shaped, semi-elliptical, Z-shaped, etc. L-shaped, concave, I The shape is used particularly frequently. A combination of these is also preferably used. For example, a combination of the flat plate 12 and the two L-shaped pillars 13 as shown in FIG. 4, and two flat plates 12 and two concave columns as shown in FIG. The shape which combined the body 14, the shape which combined the flat plate 12, the Z-shaped column 15, and the concave column 14 as shown in FIG. 6, etc. are mentioned. Both have at least one bent portion in the cross section of any one of the flat plate and the columnar body to be combined.

  In drape molding, the pressure source required to shape a prepreg laminate laminated in a flat shape into a shape having a bent portion on a desired mold is by removing air in a closed system. Vacuum pressure, pressurization with gas from the outside, or the combined use of liquid gravity and external pressurization can be applied. If the liquid is heated, it will be under pressure. Among these, the vacuum degassing method under heating is mentioned as the most simple forming method.

  When drape forming by a vacuum degassing method, it is preferable to carry out by the following method. Referring to FIG. 1, first, the jig 4 is placed in the center of the bottom of the box 1, the prepreg laminate 5 is placed on the jig 4, and the whole including the box 1 is covered with the bag film 6. The end of the bag film 6 is attached to and the laminate is shaped into the jig 4 in such a manner that the air in the box 1 is removed (the state after shaping is shown in FIG. 3). It is preferable that the whole box is put in an oven or the like and heated, because slippage between the prepregs laminated at the time of shaping becomes good and wrinkles are hardly formed. At this time, it is preferable to set the height of the wall of the box 1 to a height that is half or more of the height of the prepreg laminated body placed on the jig because wrinkles are less likely to occur in the prepreg laminated body.

  And, the present inventors diligently studied the conditions for obtaining a good-quality molded product without wrinkles and voids in this drape molding, the time required for shaping, the temperature of the prepreg laminate during shaping, the matrix resin It has been found that a molded article of good quality can be obtained when the viscosity is within a specific range.

  In order to obtain a high-quality molded article free from wrinkles and voids, it is important to form the molded article by taking a time of 3 minutes to 25 minutes using a vacuum degassing method. Although the reason for this has not been fully elucidated yet, it is considered that if the time for shaping is 25 minutes or less, the resin does not flow out of the prepreg, so that a high-quality molded article free from wrinkles and voids can be obtained. . The shorter the shaping time, the more difficult the resin flows out, and 20 minutes or less is particularly preferable. However, if it is too short, the prepreg laminate does not completely conform to the mold, and voids may occur due to uneven molding pressure. Is important. If the shaping time exceeds 25 minutes, the resin may flow and flow out of the prepreg, and voids may occur due to insufficient resin.

  The temperature of the prepreg laminate during shaping is preferably 50 ° C. or higher and 100 ° C. or lower, and more preferably 60 ° C. or higher and 80 ° C. or lower. If the temperature of the prepreg at the time of shaping is less than 50 ° C., wrinkles will occur without slipping between the prepregs, and if it exceeds 100 ° C., the resin may flow and flow out of the prepreg at the time of shaping.

  The viscosity of the matrix resin used in the prepreg is measured, and the resin viscosity at 40 ° C. of the matrix resin is preferably 1500 Pa · s or more and 30000 Pa · s or less. If the resin viscosity exceeds 30000 Pa · s, the slidability between prepregs may be reduced and wrinkles may occur. If it is less than 1500 Pa · s, the resin may flow and flow out of the prepreg during molding. The resin viscosity was measured using DSR-200 manufactured by Rheometrics Co., Ltd. or a measuring instrument having equivalent performance under the condition of a shear rate of 10 rad / sec. The value measured while increasing the temperature from 40 ° C. to 80 ° C. at a rate of temperature increase of 2 ° C./min.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
a. Preparation of Particles 90 parts by weight of a polyamide containing 4,4′-diamino-3,3′dimethyldicyclohexylmethane (“Milamide (registered trademark, same applies hereinafter)”-TR55 manufactured by Mzavelke), epoxy resin (Japan Epoxy Resin Co., Ltd.) ) “JER (registered trademark, same applies hereinafter)” 828) 8 parts by weight and a curing agent (“Fuji Kasei Kogyo Co., Ltd.“ Tomide (registered trademark) same applies below ”# 296) 2 parts by weight of chloroform 300 parts by weight The mixture was added to 100 parts by weight of methanol to obtain a homogeneous solution. Next, the solution was made into a mist using a spray gun for coating, and sprayed toward the wall surface of 3000 parts by weight of n-hexane, which was well stirred, to precipitate a solute. The precipitated solid was separated by filtration, washed well with n-hexane, and then vacuum dried at 100 ° C. for 24 hours to obtain transparent polyamide particles.
b. Preparation of resin composition The following raw materials were kneaded to obtain an epoxy resin composition, which was used as a primary resin. First, polyethersulfone was dissolved under heating in a mixture of tetraglycidyldiaminodiphenylmethane and bisphenol A type epoxy resin, cooled to 70 ° C., and 3,3′-diaminodiphenylsulfone was dispersed therein.
Tetraglycidyldiaminodiphenylmethane (ELM434, manufactured by Sumitomo Chemical Co., Ltd.) 85.0 parts Bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., “jER (registered trademark)” 828) 15.0 parts polyethersulfone ( PES5003P, manufactured by Sumitomo Chemical Co., Ltd.) 12.3 parts 3,3′-diaminodiphenylsulfone (manufactured by Wakayama Seika Co., Ltd.) 36.0 parts c. The primary resin prepared in Preparation of the prepreg (b) the coating amount onto release paper using a reverse roll coater and coated so as to be 45.1 g / m ² to prepare a primary resin film.

Next, carbon fibers ("Treka" (registered trademark) T800SC-24K-10E (manufactured by Toray Industries, Inc.)) aligned in one direction are sandwiched between the primary resin films from both sides, and heated and pressed to impregnate the resin. Furthermore, 6 g / m ^{2 of the} particles prepared in a were sprayed on both sides of the particles and sandwiched between release papers, followed by heating and pressurization, and thus a carbon fiber basis weight of 190 g / m ² and a carbon fiber content of 55. 6% prepreg was obtained.
d. Viscosity measurement of resin The primary resin adjusted in (b) was measured by using DSR-200 manufactured by Rheometrics Co. The viscosity at each temperature was measured while increasing the temperature from 40 ° C. to 80 ° C. at a rate of temperature increase of 2 ° C./min.
e. Cut and Lamination of Prepreg Eight prepregs prepared in (c) were cut into a longitudinal direction of 0 degree and a 0 degree material having a width of 5 cm and a length of 50 cm. Similarly, the longitudinal direction was set to 0 degree, and the 45 degree material, the -45 degree material, and the 90 degree material were each cut into 8 pieces each having a width of 5 cm and a length of 50 cm. A total of 32 prepregs were laminated in a laminated configuration of [45/90 / −45 / 0] 4s (s represents mirror symmetry).
f. The laminate laminated by drape molding (e) was placed on a mold as shown in FIG. FIG. 1 is a cross-sectional view perpendicular to the longitudinal direction of the jig for this drape forming apparatus, and FIG. 2 is a cross-sectional view in the longitudinal direction of the jig. A hole was made in the wall of the stainless steel box 1 for drape molding, and the entire hole was made from the inside of the wall with the nonwoven fabric 2 in order to make it easy to vent the air in the box, and the nonwoven fabric was applied to the wall with the heat-resistant tape 3. After placing the jig 4 at an equal interval with respect to the wall of the box and fixing it with double-sided tape, the prepreg laminate 5 was placed on the jig. The positions of the prepreg laminate were set at an equal interval with respect to the jig. The peel ply 7 was placed on the bag film 6 side of the prepreg laminate. The height of the upper surface of the prepreg laminated base material was the same as the height of the box 1. The entire top of the box 1 was covered with a bag-like bag film 6, and the end of the film was affixed to the outside of the box wall with double-sided tape 8 so as not to leak air. The holed portion of the box was welded with a pipe 9 and the tip was connected with a pressure-resistant rubber tube 10 and connected to the vacuum pump 11 via the pressure-resistant rubber tube. Then, the air in a box was extracted with the vacuum pump so that a bag film might come to the vicinity of a prepreg laminated body (this state is FIG. 1). The whole box was heated in a drier heated to 60 ° C. for 1 hour as it was, and then the air in the box was again drawn by a vacuum pump and draped. At this time, the vacuum valve was gradually pulled so that the vacuum pressure was applied in 20 minutes by adjusting the leak valve of the vacuum pump. FIG. 3 shows a state in which the laminated base material follows the shape of the jig and the drape forming is finished. The box was removed from the dryer, the vacuum state was released, and the product was cooled to room temperature. After taking out the shaped laminated base material from the jig and removing the sheet material, the shaped laminated equipment is placed on the jig again, and using an ordinary autoclave molding method, 180 ° C. under a pressure of 0.6 MPa. A molded body was produced under curing conditions for 2 hours. The resulting molded plate was cut with a diamond cutter perpendicular to the longitudinal direction and observed for wrinkles. As a result, no wrinkles were found. Further, when the cut surface was buffed and observed under a microscope, no void was confirmed.

(Example 2)
Drape molding was performed in the same manner as in Example 1 except that the time for vacuum degassing was changed to 5 minutes and the temperature during shaping was changed to 80 ° C. The obtained molded product was cut with a diamond cutter and buffed in the same manner as in Example 1 to confirm the presence or absence of wrinkles and voids.

(Comparative Example 1)
Drape molding was performed in the same manner as in Example 1 except that the vacuum degassing time was changed to 1 minute. The obtained molded product was cut with a diamond cutter and buffed in the same manner as in Example 1 to confirm the presence or absence of wrinkles and voids.

(Comparative Example 2)
Drape molding was performed in the same manner as in Example 1 except that the vacuum degassing time was changed to 30 minutes. The obtained molded product was cut with a diamond cutter and buffed in the same manner as in Example 1 to confirm the presence or absence of wrinkles and voids.

(Comparative Example 3)
The composition of the primary resin
Tetraglycidyldiaminodiphenylmethane (ELM434, manufactured by Sumitomo Chemical Co., Ltd.) 85.0 parts Bisphenol A type epoxy resin (manufactured by Tohto Kasei Co., Ltd., “YD (registered trademark) 128) 15.0 parts polyethersulfone (PES5003P) 16.0 parts 3,3′-diaminodiphenyl sulfone (manufactured by Wakayama Seika Co., Ltd.) Except for changing to 36.0 parts, drape molding was carried out in the same manner as in Example 1. went. The obtained molded product was cut with a diamond cutter and buffed in the same manner as in Example 1 to confirm the presence or absence of wrinkles and voids.

(Comparative Example 4)
Drape molding was performed in the same manner as in Example 1 except that the temperature at the time of molding was changed to 40 ° C. The obtained molded product was cut with a diamond cutter and buffed in the same manner as in Example 1 to confirm the presence or absence of wrinkles and voids. The obtained results are shown in Table 1.

  From comparison between Example 1 and Comparative Examples 1 and 2, it can be seen that voids are generated when the vacuum degassing time is less than 3 minutes or more than 25 minutes.

  From comparison between Example 1 and Comparative Example 3, it can be seen that wrinkles are generated when the resin viscosity at 40 ° C. exceeds 30000 Pa · s even when the time of vacuum degassing and the temperature at the time of molding are the same.

  From comparison between Example 2 and Comparative Example 4, it can be seen that wrinkles occur when the temperature during shaping is less than 50 ° C.

It is sectional drawing of a direction perpendicular | vertical with respect to the longitudinal direction of the jig | tool of the shaping | molding apparatus used for the drape shaping | molding method which concerns on one embodiment of this invention. It is sectional drawing of the longitudinal direction of the jig | tool of the shaping | molding apparatus used for the drape shaping | molding method which concerns on one embodiment of this invention. It is sectional drawing of the direction perpendicular | vertical with respect to the longitudinal direction of the jig | tool after shaping | molding by the drape forming method which concerns on one embodiment of this invention. It is a figure which shows an example of the cross-sectional shape of the molded object which combined the columnar body obtained by the drape forming method which concerns on one embodiment of this invention. It is a figure which shows another example of the cross-sectional shape of the molded object which combined the columnar body obtained by the drape molding method which concerns on one embodiment of this invention. It is a figure which shows another example of the cross-sectional shape of the molded object which combined the columnar body obtained by the drape molding method which concerns on one embodiment of this invention.

Explanation of symbols

1: Stainless steel box for drape molding 2: Nonwoven fabric
3: Heat-resistant tape 4: Jig 5: Pre-preg laminate 6: Bag film 7: Peel ply 8: Double-sided tape
9: Pipe 10: Pressure rubber tube 11: Vacuum pump 12: Flat plate 13: L-shaped column 14: Concave column 15: Z-shaped column

Claims (1)

A draping molding method in which a prepreg laminate laminated in a flat shape is shaped into a column having a bent portion in a cross section on a desired mold and then heat-cured, and the matrix resin used in the prepreg at 40 ° C. After the viscosity is 1500 Pa · s or more and 30000 Pa · s or less and the prepreg laminate is heated to 50 ° C. or more and 100 ° C. or less, a desired mold is formed over a period of 3 minutes or more and 25 minutes or less using a vacuum degassing method. A drape forming method characterized by heat-curing after forming into a shape.

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