JP6550573B2 - Method of manufacturing fiber reinforced composite without autoclave and fiber reinforced composite manufactured by this method - Google Patents

Description

  The present invention relates to a method for producing a fiber-reinforced composite material in which a fiber material is mixed into a resin material to improve strength, and in particular, a fiber obtained by heat curing and forming a laminated prepreg without using a large scale autoclave. The present invention relates to a method of producing a reinforced composite and a fiber reinforced composite produced by this method.

  A fiber reinforced composite material is lightweight by mixing reinforcing fiber such as carbon fiber with thermosetting resin as a base material, in addition to the characteristics of thermosetting resin, the strength and heat resistance etc. of the reinforcing fiber are compounded. It is widely used as a structural material for aircraft, ships, vehicles, etc. because of its excellent properties. As a method of manufacturing such a fiber reinforced composite material, for example, a sheet-like prepreg in which a carbon fiber is impregnated with a thermosetting resin is used, and the prepreg is laminated to a desired thickness and then thermally cured to be integrated. By forming the fiber reinforced composite material.

  When the prepreg is laminated in multiple layers, air is easily taken in between the layers of the prepreg, and when it is thermally cured in this state, a trace as a void is left inside the formed fiber reinforced composite material, and strength is increased at this portion. Problems such as loss of uniformity may occur. In addition, a slight volatile material contained in the thermosetting resin, moisture in the air, and the like may be vaporized due to heating, which may cause generation of voids.

Thus, when prepregs are laminated in multiple layers, a molding method using an autoclave is often employed as disclosed in, for example, Patent Document 1 in thermosetting. An autoclave is a cylindrical pressure vessel. By pressing and heating the laminated prepreg in this pressure vessel, air taken in between the layers is drawn out of the laminated prepreg, or the autoclave Since the vaporization component in the prepreg is suppressed from being vaporized by applying pressure, the generation rate of the void can be sufficiently suppressed, and there is an advantage that high strength characteristics can be obtained for the molded article.

JP-A-7-214679

  In the molding method using an autoclave as described in Patent Document 1, for example, in order to form a large-sized molded product such as a wing portion of a passenger aircraft, a huge pressure vessel capable of accommodating the entire wing inside is required. It becomes. In particular, in a pressure vessel that requires high pressure control such as an autoclave, strict installation standards are imposed on the container itself, and the larger the container is, the more difficult it is to achieve the standards. Furthermore, a large amount of cost is required to install these facilities such as a heating device and a pressurizing device that uniformly adjust and control the temperature of the huge internal space in the pressure vessel. On the other hand, in the case of producing a fiber-reinforced composite material having a greater thickness, the number of laminated prepregs increases, and air is more easily taken in between the layers, and in order to suppress the generation of voids, such an autoclave is used. I had to rely on the manufacturing method using

On the other hand, although it is possible to adopt a manufacturing method in which a molded product is divided into parts and molded using a small-sized autoclave and then assembled later to form a molded product, the joining process of parts is separately Not only it becomes necessary, but it also causes problems such as the need for a new construction method and a strict inspection system for securing the reliability of the joint portion.
In short, in the conventional method for producing a fiber reinforced composite material, it is necessary to create a large autoclave in order to solve the problem of voids, especially when trying to obtain a large molded product, and the labor and cost are very high. There was a problem of getting bigger.

  The present invention has been made to solve such problems, and the object of the present invention is to sufficiently suppress the generation of voids even when manufacturing a large-sized fiber-reinforced composite material by a simple and simple device configuration. It is an object of the present invention to provide a method for producing a fiber reinforced composite material which can be manufactured at low cost and a fiber reinforced composite material produced by this method.

  The inventors of the present invention conducted intensive studies to solve the above problems, and after laminating the prepreg and the fiber, using an autoclave also by degassing and reducing the pressure in the atmosphere where the laminate is present instead of pressurizing. In the same manner, the inventors have found that the generation of voids can be prevented, and the present invention has been completed.

That is, the present invention provides the following inventions.
1. A laminating step of alternately laminating a prepreg in which a first fiber base material is impregnated with a matrix resin, and a second fiber base material to form a laminate of the prepreg and the second fiber base material;
A degassing step of covering the laminate with a sealing sheet to form a hermetic container and degassing the air in the hermetic container;
A heating step of heating the sealed container and integrating the prepreg and the second fiber base;
A method of producing a fiber reinforced composite without using an autoclave, comprising:
2. The method for producing a fiber-reinforced composite material according to claim 1, wherein the second fiber base material is a fiber assembly in which long fibers are aligned in one direction.
3. The method for producing a fiber-reinforced composite material according to claim 1 or 2, wherein the second fiber base material is a fiber aggregate made of the same kind of fiber material as the first fiber base material.
A fiber-reinforced composite manufactured by any of the methods of 4.1 to 3.

According to the method for producing a fiber-reinforced composite material of the present invention, when producing a large-sized fiber-reinforced composite material, generation of voids can be sufficiently suppressed by a simple and simple apparatus configuration, and the production can be performed at low cost. Can. That is, since the layer of the second fiber base is interposed between the prepreg and the prepreg in the laminating step, when the matrix resin is impregnated on the second fiber base in the degassing step and the heating step. The air between the layers is released to the outside of the laminate through the layer of the second fiber base material, and generation of voids can be sufficiently suppressed to thermoform the fiber reinforced composite material. For this reason, even when forming a large-sized fiber reinforced composite such as an aircraft wing, a fiber reinforced composite that can obtain high strength characteristics without requiring a large and expensive facility such as an autoclave, It becomes possible to manufacture at a low cost with a simple and simple apparatus configuration.
And the fiber reinforced composite material of this invention does not generate | occur | produce a void in the layer formed with the 2nd fiber base material, has high intensity | strength uniformity, and was excellent in the intensity | strength as a molded object.
As described above, the production method of the present invention is a production method called a so-called de-autoclave method, which is a production method which has not been achieved so far. In the conventional manufacturing method, the limit is about VF 50%, but 60% or more can be realized.

FIG. 1 is a cross-sectional view schematically showing a degassing step in the method for producing a fiber-reinforced composite material according to the example. FIG. 2 is a plan view schematically showing the state of the laminating step. FIG. 3 is a sectional view in the thickness direction showing one embodiment of the fiber-reinforced composite material of the present invention.

10: laminate, 12: UD prepreg (prepreg), 14: spread dry carbon fiber substrate (second fiber substrate), 20: bottom breather, 22: top breather, 24: inside breather, 30/32: separation Mold film, 40 · 42: peel ply, 60: partition member, 62: breathable yarn, 70: bagging film (sealing sheet), 100: jig plate, 110: sealant, 120: hermetically sealed container

Hereinafter, the method for producing a fiber-reinforced composite material according to the present invention will be described.
In the method for producing a fiber-reinforced composite material of the present invention, a first fiber base material is impregnated with a matrix resin impregnated prepreg (UD prepreg 12) and a second fiber base material (opened dry carbon fiber base material 14) alternately. Laminate (10), which has been subjected to a lamination step, to form a laminate (10) of the prepreg (UD prepreg 12) and the second fiber base (opened dry carbon fiber base 14). Is covered with a sealing sheet (bagging film 70) to form a sealed container (120), and the degassing step of degassing the air in the sealed container (120) is performed by heating the inside of the sealed container (120) It can carry out by performing the heating process which unifies a prepreg (UD prepreg 12) and the 2nd fiber base material (open fiber dry carbon fiber base material 14).

In the following, first, an article (a member for forming a fiber-reinforced composite material) used in the present invention will be described.
(Prepreg)
The prepreg used in the present invention is in the form of a sheet, in which a first fiber base made of the following reinforcing fibers is impregnated with a matrix resin. Here, impregnation means filling a matrix resin between each fiber in a fiber assembly composed of a large number of reinforcing fibers.
In the present invention, setting the content of the matrix resin to be higher than that in the case where only the prepreg is laminated and the fiber-reinforced composite material is heat-formed is the second fiber base material in the degassing step and heating step described later. In order to effectively impregnate the matrix resin. The matrix resin is preferably 40 to 70, particularly preferably 50 to 60 with respect to the reinforcing fiber 100 in a volume ratio.
The thickness of the prepreg is preferably 0.05 to 1 mm from the viewpoint of resin impregnation efficiency into the second fiber base material, and more preferably 0.1 to 0.3 mm.
(First fiber substrate)
The first fiber base is an aggregate of reinforcing fibers. The reinforcing fiber is not particularly limited as long as it is a reinforcing fiber used for a fiber reinforced composite material, and fiber materials such as carbon fiber, glass fiber, aramid fiber, boron fiber and the like are used, and any of them The fiber material can be used alone or in combination of a plurality of types of fiber materials.

The form of the fiber material constituting the first fiber base material is not particularly limited. For example, the form of the spread yarn as an aggregate in which the long fibers are aligned in one direction, the form in which the long fibers are woven, These forms of fiber materials such as non-woven fabrics using fibers or mats can be used alone or in combination, and can be regularly or irregularly arranged in the matrix resin.
The fiber diameter of the reinforcing fiber used for the first fiber base material is optional, but preferably 0.001 mm to 1 mm, and more preferably 0.002 mm to 0.01 mm.

(Matrix resin)
As the matrix resin used in the present invention, a thermoplastic resin, a thermosetting resin, or the like can be used without particular limitation as long as the viscosity can be controlled. Specifically, an epoxy resin, a phenol resin, Polyimide resin, polyamideimide resin, cyanate ester resin, bismaleimide triazine resin (BT resin), etc. are used. As for the viscosity of the resin, it is desirable that the viscosity of the resin is so high that the adjacent second fiber base layer can suitably function as an air passage in the degassing step, but there is no upper limit on the viscosity and there is no upper limit at the end of the lamination. It may be a resin which becomes solid. However, at the time of lamination in use, the application of the fiber shaping and lamination process is easy, and the viscosity to such an extent that the laminated form is maintained is preferable, specifically 1000 to 5000 mPa · s is preferable, and 3000 to 5000 More preferably, it is 4000 mPa · s.
Further, in the heating resin melt impregnation step of the next step, the resin viscosity is reduced to a viscosity that impregnates the second fiber base material under conditions such as heating, and the resin viscosity at the time of heat melt impregnation is preferably as low as possible. There is no limit to the viscosity at the time of melt impregnation.

(2nd fiber base material)
The 2nd fiber base material used by this invention is an aggregate | assembly of a reinforced fiber similarly to a 1st fiber base material. The reinforcing fiber used at this time is not particularly limited as long as it is a reinforcing fiber used in the fiber-reinforced composite material as in the first fiber base material. Carbon fiber (dry carbon fiber), glass fiber, aramid fiber, boron A fiber material such as a fiber is used, and any of these fiber materials can be used alone or in combination of a plurality of types of fiber materials.
Although it does not specifically limit also as a form of the fiber material which comprises a 2nd fiber base material, The form of the opening yarn as an aggregate | assembly which arranged the long fiber in one direction, the form which woven the long fiber, and a short fiber These forms of fiber materials such as non-woven fabrics or mat-like forms can be arranged regularly or irregularly in the matrix resin alone or in combination.

In the present invention, the second fiber base is in a state in which air or the like in the laminate is discharged to the outside of the laminate through the layer of the second fiber base during the degassing step and the heating step. The second fiber base layer functions as a degassing path. Therefore, the second fiber base material is preferably a spread fiber material composed of an assembly in which long fibers are used as reinforcing fibers and the long fibers are aligned in one direction, from the viewpoint of air permeability. Etc. have the advantage of being easily exhausted to the outside of the laminate along the long fibers.
In addition, it is desirable that the molded fiber-reinforced composite material has a uniform internal composition, and in this respect, the second fiber base material is a fiber material of the same type and form as the first fiber base material. preferable.
Moreover, although the fiber diameter of the reinforcement fiber used for a 2nd fiber base material is arbitrary, it is preferable to set it as 0.001 mm-1 mm, and it is more preferable to set it as 0.002 mm-0.01 mm. The length of the reinforcing fiber is appropriately adjusted according to the required length. Moreover, it is preferable that the thickness as a fiber assembly of a 2nd fiber base material sets it as 0.01 mm-0.3 mm from a viewpoint of the ease of the impregnation of resin which comprises a prepreg.

The manufacturing method of the present invention will be described below with reference to the attached drawings.
FIG. 1 schematically shows the state of the degassing step shown in the example, but with reference to FIG. 1, a method of manufacturing a fiber reinforced composite material will be described in order of steps.

  First, the sealed container 120 will be described. The hermetic container 120 is formed of the bagging film 70 and the jig plate 100, and the bagging film is contracted in the deaeration process so that the deaerated state inside is maintained. Specifically, on the flat jig plate 100, a polyester bottom breather 20 functioning as a degassing mat is disposed so that the outer edge portion of the jig plate 100 is exposed. The release film 30 and the peel ply 40 are laminated in order. The peel ply 40 is formed of a polyester fiber fabric coated with a release agent. The jig plate is preferably made of metal such as stainless steel, and specifically made of SUS304 or 303. The bagging film can be a commercially available flexible vacuum bagging film without particular limitation, but it is elongated. It is preferable to use one having a high rate of heat resistance at high temperatures. Hereinafter, the sealed container 120 will be described while describing each process.

(Lamination process)
On the peel ply 40, a UD (Uni Direction) prepreg 12 as a prepreg and a sheet-like open fiber dry carbon fiber substrate 14 as a second fiber substrate are alternately laminated in turn, and the UD prepreg 12 is laminated on the uppermost layer. To form a laminate 10 (lamination process). The UD prepreg 12 uses, as a reinforcing fiber material (first fiber base material), an open fiber material in which threadlike carbon fibers are thinly aligned in one direction, and is impregnated with a matrix resin to semisolidify it. It is formed into a sheet as a state.
The resin and first fiber base material used for the UD prepreg can be appropriately selected from the above-mentioned ones, and the fiber diameter of the line dry carbon fiber base material can also be selected as appropriate. Further, the thickness of the prepreg and the thickness of the second fiber base material are also appropriately selected from the above range.
The open-fiber dry carbon fiber base 14 is a thin carbon fiber bundle drawn in one direction, opened, and formed into a sheet, and an open-fiber material of carbon fibers used for reinforcing the UD prepreg 12. It is the same kind of fiber material.

  Such a UD prepreg 12 and the spread dry carbon fiber base material 14 are alternately laminated to form the laminated body 10, and when laminating each layer, particularly when there are a plurality of layers of the second fiber base material The fiber reinforced composite material is formed by laminating the layers such that 0 °, 90 °, 45 °, etc. are combined by shifting the fiber orientation direction of the open fiber material to different directions in each layer, for example, by 45 °. It is possible to enhance the strength and rigidity as a molded article.

(Degassing process)
After the laminate 10 is formed in this manner, the peel ply 42, the glass cross bleeder 50 that absorbs an excess resin, and the release film 32 are sequentially laminated on the uppermost UD prepreg 12, and then the laminate 10 is obtained. An inner breather 24 is provided so as to surround the four outer sides, and a rubber partition member 60 is disposed in a frame shape on the outer peripheral portion. The partition member 60 covers the entire side surface of the laminate of the prepreg and the second fiber base, and the height of the partition member at least as high as that of the laminate is a loss of resin of the prepreg. Is preferable in that the shape of the obtained molded body is kept in a predetermined shape. By providing the partition member 60, it is possible to prevent the resin from leaking out to the entire inside of the sealed housing portion and losing the shape of the molded body in the subsequent heating step.

  In addition, when arrange | positioning the inner breather 24 and the partition member 60, as shown in FIG. 2, the ventilation yarn 62 is arrange | positioned in multiple places. One end of the aeration yarn 62 is connected to the inner breather 24, and the other end extends to the outside of the partition member 60 via the lower end of the partition member 60 and the bottom surface breather 20. Thereby, even if the partition member 60 is provided, sufficient air permeability can be secured and the air and the like in the second fiber base material can be discharged.

  Subsequently, the upper surface breather 22 is disposed to cover the upper end surface of the partition member 60. As a result, the laminate 10 is disposed in the space surrounded by the partition member 60 and the upper surface breather 22. Then, they are entirely covered by the bagging film 70, and the outer edge of the bagging film 70 is brought into close contact with the outer edge of the jig plate 100 by the sealant 110. Thereby, the laminated body 10 on the jig plate 100 and all the members surrounding them are sealed in a hermetic housing portion 120 formed by the bagging film 70 and the jig plate 100.

  The bagging film 70 is provided with exhaust ports 72 at a plurality of locations, and a deaeration circuit including an exhaust path, a vacuum pump, etc. (not shown) is connected to the exhaust ports 72. The air is exhausted to the outside of the sealed housing portion 120 through the exhaust port 72.

  Subsequently, the air in the sealed housing 120 is deaerated to the outside by such a degassing circuit, and the pressure is reduced until the pressure difference between the inside of the sealed housing 120 and the atmospheric pressure becomes about 0.87 atm (degassing). Process). In addition, this pressure is an example and it is not restrict | limited in particular to this, The said differential pressure can be made into the range of 0.1 atm-1 atm. By this deaeration process, the bagging film 70 that has been subjected to atmospheric pressure is bent toward the jig plate 100, contracts the space of the hermetic housing portion 120, the upper surface breather 22 is pressed downward, and the lower layer from the upper surface breather 22 is laminated. The body 20, the partition member 60, etc. are pressurized by atmospheric pressure. At this time, the air inside the frame-shaped partition member 60 is exhausted outside the frame of the partition member 60 through the breathable upper surface breather 22 and the bottom surface breather 20, and also through the breathable thread 62. The air is exhausted to the outside of the frame 60 and further to the outside of the bagging film 70 through the exhaust port 72, that is, to the outside of the closed container 120.

(Heating process)
While performing such a deaeration process, the whole including the jig plate 100 is inserted into a heating device (not shown). The temperature inside the interlayer of the laminate 10 is measured by a thermocouple, and the temperature is raised to a temperature region where the matrix resin of the UD prepreg 12 can flow. For example, the temperature rising rate is preferably in the range of 0.5 ° C./min to 3 ° C./min. After reaching the softening temperature of the matrix resin, the temperature of the laminate 10 is kept constant for 0.5-2 hours. Thereafter, the heating device is controlled to raise the temperature of the laminate 10 to the curing temperature of the resin, and the temperature is maintained for a time required for the curing of the resin. Then, the temperature of the laminated body 10 is controlled by controlling the heating device, and the temperature is decreased at a temperature decrease rate of 0.5 ° C./min to 1 ° C./min. During this time, the deaeration process is continued until the laminate 10 is cooled to room temperature.
Heating may be performed with a jig manufactured from a heat conductor containing a heat source such as surface, linear, rod, or heat source pipe, or the jig and the laminate may be wrapped with a blanket-like heating element, or jig And if the stable heating can be done, such as putting the laminate in an oven or enclosing it with an oven-like heating panel, a large-scale device is not necessary.

  During the heating step in the present embodiment, the viscosity of the matrix resin constituting the UD prepreg 12 is lowered, and it is gradually impregnated on the adjacent open dry carbon fiber base 14 side, and finally the open dry The carbon fiber substrate 14 is also in a state of being filled with the thermosetting tree without voids. In this process, since air or the like taken into the layer of the opened dry carbon fiber base material 14 is drawn out to the outside of the laminate 10 through the layer of the opened dry carbon fiber base material 14, generation of voids is prevented. It can be sufficiently suppressed.

  Moreover, although the case where the inside of the frame formed of the partition member 60 is deaerated is illustrated by covering the upper part of the laminated body 10 by the upper surface breather 22 which has air permeability in this example, the upper surface breather 22 and separation are illustrated. Instead of the mold film 32, it is also possible to use a stainless steel pressure plate coated with a mold release agent on the lower surface side. In this case, although the pressure plate and the upper end surface of the partition member 60 are in close contact and closed, degassing of the inside of the frame formed by the partition member 60 is performed via the inner breather 24 and the air thread 62. It can be done sufficiently.

(Fiber reinforced composites)
As shown in FIG. 3, the fiber-reinforced composite material 200 of the present invention obtained by the production method of the present invention is formed by laminating a layer 210 formed of prepreg and a layer 220 formed of a second fiber base material. . Both are formed of a resin obtained by thermosetting the matrix resin constituting the prepreg, and the layer of the second fiber base material is cured with the resin in a state in which the generation of voids is suppressed. Further, since the constituent resins of the respective layers are the same, the integrity of the entire composite material is high and the strength is also excellent.
In addition, when a fiber reinforced composite material of 30 cm square was separately prepared by a conventional autoclave method, a composite material was obtained with a void generation rate substantially equal to that manufactured by the manufacturing method of the present invention.
However, since the shape of the autoclave is determined, only a composite material having a shape within the standard could be formed.
From this, it can be seen that according to the production method of the present invention, a composite material having performance equivalent to that produced by the conventional autoclave method can be obtained in a desired shape.

The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-mentioned embodiment, although the inner breather 24, the mold release films 30, 32, the peel plies 40, 42, and the glass cross bleeder 50 were used, you may use these selectively as needed.
Moreover, the matrix resin may be impregnated to some extent on the second fiber substrate side in advance.

Claims (4)

A laminating step of alternately laminating a prepreg in which a first fiber base material is impregnated with a matrix resin, and a second fiber base material to form a laminate of the prepreg and the second fiber base material;
A degassing step of covering the laminate with a sealing sheet to form a hermetic container and degassing the air in the hermetic container;
A heating step of heating the sealed container and integrating the prepreg and the second fiber base;
I have a,
In the laminating step, the second fiber base material is laminated in a plurality of layers, and each second fiber base material is laminated so that the fiber orientation direction is different in each layer. A fiber-reinforced composite material that does not use an autoclave. Manufacturing method.   The method for producing a fiber-reinforced composite material according to claim 1, wherein the second fiber base is a fiber assembly in which long fibers are aligned in one direction.   The method for producing a fiber-reinforced composite material according to claim 1 or 2, wherein the second fiber base material is a fiber aggregate made of the same kind of fiber material as the first fiber base material. The method for producing a fiber-reinforced composite material according to any one of claims 1 to 3, wherein the second fiber base materials are laminated such that orientation directions of fibers in each layer are different by 45 ° .

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