JP2018172474A - Method for manufacturing fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a composite material exhibiting an excellent dynamic characteristic without deteriorating its appearance even when there is large difference in curing characteristics of a substrate to be used, in hybrid molding where a plurality of fiber-reinforced resin sheet-like substrates containing reinforced fibers and a thermosetting resin composition are laminated and compression-molded.SOLUTION: A method for manufacturing a fiber-reinforced composite material for compression molding by laminating a plurality of fiber-reinforced resin sheet-like substrates containing at least reinforcing fiber and a thermosetting resin composition comprises compression molding after repeating input of the fiber-reinforced resin sheet-like substrates having a longest gelling time of the fiber-reinforced resin sheet-like substrates different in a gelling time of the thermosetting resin composition into a metal mold and input of the fiber-reinforced resin sheet-like substrates having a secondly longest gelling time of the fiber-reinforced resin sheet-like substrates into a metal mold while providing further time difference.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a fiber-reinforced composite material.

  Composite materials made of fiber reinforced resin are used in a wide range of fields such as sports and leisure applications and industrial applications such as aircraft, because they are high in strength and high in rigidity. In addition, such a fiber-reinforced composite material is widely manufactured by compression molding. As the molding material, a prepreg in which a reinforcing fiber is impregnated with a thermosetting resin composition, a sheet molding compound (hereinafter referred to as SMC), or the like is used.

  Since SMC has a short fiber length, the strength of a fiber-reinforced composite material is generally lower than that of a prepreg, but it is suitable for forming a complicated shape such as a ridge. In the manufacture of fiber-reinforced composite materials using SMC, for example, in the publication of Japanese Patent No. 5950149, when forming a complicated shape such as a ridge, the quality of appearance is good by defining the difference in the curing time of the two materials It is stated that the substrate can be molded.

  In addition, in JP 2001-96573 A, JP 7-276560 A, JP 3617807 A, etc., the thermosetting resin composition is used as an adhesive or a film agent, and the heating time is controlled to control its appearance and shear. It is stated that the peel strength can be controlled.

Japanese Patent No. 5950149 JP 2001-96573 A JP-A-7-276560 Japanese Patent No. 3617807 JP-B 61-46295

  In hybrid molding using two types of fiber-reinforced resin sheet-like base materials containing reinforcing fibers and a thermosetting resin composition, high-quality fiber reinforcement can be formed by defining the difference in the curing time of the base materials used Is known in the prior art. However, when the two impregnation bodies are simultaneously charged into the molding machine, if the difference in curing time is too large, the base material using the thermosetting resin composition having a long curing time becomes uncured and the appearance deteriorates. I knew that.

  Therefore, in the present invention, in hybrid molding in which a plurality of fiber-reinforced resin sheet-like base materials containing reinforcing fibers and a thermosetting resin composition are laminated and compression-molded, even when there is a large difference in the curing characteristics of the base materials used, the appearance An object of the present invention is to provide a method for producing a composite material that exhibits high mechanical properties without deterioration.

  In order to solve the above problems, the method for producing a fiber-reinforced composite material according to the present invention is a fiber in which a plurality of fiber-reinforced resin sheet-like base materials including at least reinforcing fibers and a thermosetting resin composition are laminated and compression-molded. A method for producing a reinforced composite material, and among the fiber reinforced resin sheet-like base materials having different gel times of the thermosetting resin composition, the fiber reinforced resin sheet-like base material having the longest gel time is put into a mold. Further, after repeating the introduction of a fiber-reinforced resin sheet-like base material having the next longest gelation time into the mold after providing a time difference, compression molding is performed.

In the method for charging the substrate in the present invention, A1, A2... A (n), A (n + 1) from the thermosetting resin composition having a long gelation time,
In the case where the gelation time of the thermosetting resin composition is Tg1, Tg2,... Tg (n), Tg (n + 1),
The time from when the fiber-reinforced resin sheet-like base material containing the thermosetting resin composition A (n) is added to when the fiber-reinforced resin sheet-like base material containing the thermosetting resin composition A (n + 1) is added When Th (s)
If Th (s) satisfies at least one of the following formulas (1) to (3), the adhesion of the substrate is improved, and higher mechanical properties can be expressed.
When t ≧ 300 (s), t−t / 8 ≦ Th ≦ t + t / 8 Equation (1)
When 300 (s)> t ≧ 30 (s), t−30 (s) ≦ Th ≦ t + 30 (s) (2)
When 30 (s)> t ≧ 0 (s), 0 (s) ≦ Th ≦ t + 5 (s) (3)
Here, t (s) is the fiber containing the gelation time Tg (n) of the fiber-reinforced resin sheet-like substrate containing the thermosetting resin composition A (n) and the thermosetting resin composition A (n + 1). It is the difference (t = Tg (n) −Tg (n + 1)) from the gelation time Tg (n + 1) of the reinforced resin sheet-like substrate.

  At this time, if Th exceeds the upper limit of the range of the above formula, the previously charged base material is cured and the adhesion with the base material that has been input with a time difference is lowered, and the lower limit of the range of the above formula is reduced. If it is less, the difference in charging time is small, so that curing of the base material using the thermosetting resin composition having a long gelation time tends to be delayed, resulting in poor curing and poor appearance.

  Moreover, it is preferable that the form of the fiber reinforced resin sheet-like substrate according to the present invention is any one of a unidirectionally arranged sheet, a woven fabric, a nonwoven fabric, and a random mat. In particular, when a base material with different fluidity such as a woven fabric and a random mat is used, the surface of the woven base material tends to be broken due to the flow of the random mat base material. Since it can be suppressed in the invention, it becomes possible to obtain a fiber-reinforced composite material excellent in appearance and mechanical properties in all combinations of the above-mentioned substrate forms.

  The thermosetting resin composition according to the present invention is preferably either a vinyl ester resin or an epoxy resin. In general, the epoxy resin tends to have a longer gelation time than the vinyl ester resin. Therefore, when both resins are used, it is preferable to form the epoxy resin first. In addition, even when there is a difference in gelation time between epoxy resins and vinyl ester resins depending on the structure and additives, fiber reinforcement with excellent mechanical properties and appearance can be achieved by forming the injection sequence and injection time difference as described above. A composite material can be obtained.

  Even when a plurality of base materials having different gelation times of the thermosetting resin composition are used by the production method of the present invention, the adhesion between the base materials regardless of the difference in the gelation time of the thermosetting resin composition. Therefore, it is possible to suppress the fracture starting from the interface and to mold a composite exhibiting high mechanical properties.

It is an example of the hybrid-molded composite material manufactured with the manufacturing method of this invention. It is a schematic diagram of an example of the metal mold | die used for the manufacturing method of this invention, and its manufacturing method.

  Hereinafter, the present invention will be described in detail.

  The fiber-reinforced resin sheet-like substrate that can be used in the production method of the present invention is a fiber-reinforced composite material in which a reinforcing fiber is impregnated with a thermosetting resin composition. Examples of the fiber reinforced composite material include a material in which substantially continuous reinforcing fibers are impregnated with a thermosetting resin composition (prepreg), and a material in which short fiber reinforcing fibers are impregnated with a thermosetting resin composition ( SMC). The form of the prepreg is not particularly limited, and examples thereof include a unidirectionally arranged sheet prepreg in which reinforcing fibers are aligned in one direction, and a woven prepreg in which reinforcing fibers are woven. In order to improve the design of the fiber reinforced composite material, the surface of the fiber reinforced composite material may be a woven prepreg, and the inside of the fiber reinforced composite material may be a unidirectionally arranged sheet prepreg. .

  On the other hand, since short fibers having a fiber length of about 5 to 40 mm are used for SMC, the strength of fiber-reinforced composite materials is generally lower than that of prepreg, but it is suitable for forming complex shapes such as ridges. . In the method for producing a fiber reinforced composite material of the present invention, a prepreg obtained by impregnating a continuous reinforced fiber excellent in strength improvement into a fiber reinforced resin sheet base material (A) with a thermosetting resin composition, and a fiber reinforced resin sheet base It is preferable to use together the SMC which impregnated the thermosetting resin composition in the short fiber-like reinforcing fiber excellent in formation of complicated shapes, such as a protruding item | line, to a material (B).

  Examples of the reinforcing fiber contained in the prepreg or SMC that can be used in the production method of the present invention include carbon fiber, glass fiber, aramid fiber, boron fiber, silicon carbide fiber, high-strength polyethylene, and polyparaphenylene benzobisoxazole (PBO). Examples thereof include fiber, nylon fiber, and stainless steel fiber. Among these, carbon fiber is preferable because it is lightweight and has high rigidity. In addition, examples of the reinforcing fibers include long fibers and short fibers. In the reinforcing fibers included in SMC, short fibers having a length of about 5 to 40 mm are usually used. In the prepreg, long fibers are preferable from the viewpoint of rigidity. Examples of the form of the long fiber include one aligned in one direction, a woven fabric made of long fibers, and the like.

  Examples of the thermosetting resin composition contained in the prepreg and SMC that can be used in the production method of the present invention include epoxy resins, vinyl ester resins, unsaturated polyester resins, polyimide resins, maleimide resins, and phenol resins. When carbon fibers are used as reinforcing fibers, prepregs containing continuous reinforcing fibers are used to increase the mechanical properties and heat resistance of the fiber reinforced composite material, and SMCs containing short fibers are used to enable the formation of complex shapes. Since excellent fiber-reinforced composite materials can be obtained by performing hybrid molding, epoxy resin generally used for prepregs containing carbon fibers and SMCs containing carbon fibers are used in the present invention. It is preferable to perform molding in combination with a vinyl ester resin used for general purposes. Furthermore, the epoxy resin is not particularly limited, but it is preferable to use a bisphenol A type or a novolac type as a basic skeleton because it is easy to control the physical properties and physical properties of a cured product, and molding at a high cycle is possible. Therefore, it is preferable to use a fast curing type having a curing time of less than 15 minutes. The vinyl ester resin is not particularly limited, but it is desirable to use a bisphenol A type as the basic skeleton in order to make the fiber-reinforced composite material molded body have high mechanical properties.

"Method of manufacturing fiber-reinforced composite material"
Molding by combining or combining multiple fiber reinforced resin sheet-like base materials according to the shape and application in order to obtain a complex shaped composite material or a material with high strength at a low cost. When performing the above, the curing behavior of the base material is greatly different depending on the difference in gelation time, the adhesion between the base materials is lowered, and the mechanical properties and the appearance may be deteriorated. In order to prevent such deterioration of mechanical properties and deterioration of appearance, in the present invention, the thermosetting resin composition contained in the base material is charged into the mold with a time difference from the long gelation time. This makes it possible to obtain a fiber-reinforced composite material having a uniform curing timing, high adhesion between substrates, and excellent mechanical properties and appearance.

As a specific method for producing the fiber-reinforced composite material in the present invention, for example, when the gelation time of the thermosetting resin composition (A2) is short with respect to the thermosetting resin composition (A1), thermosetting The fiber-reinforced resin sheet-like base material (B1) containing the resin composition (A1) is first charged into the mold, and the fiber-reinforced resin sheet-like base material (B2) containing the thermosetting resin composition (A2) is obtained. It is preferable to provide a manufacturing method in which a time difference is provided and the composite material is integrally molded by being put into a mold and compressed at a time. The gelation time of the thermosetting resin composition (A1) contained in the fiber reinforced resin sheet-like substrate (B1) is Tg1 (s), and the thermosetting resin composition contained in the fiber reinforced resin sheet-like substrate (B2). When the gelation time of the product is Tg2 (s) and the time difference Tg1-Tg2 (s) is t (s), the fiber reinforced resin sheet-like base material (B1) containing the thermosetting resin composition A1 is added. Then, when the time from when the fiber reinforced resin sheet-like base material (B2) containing the thermosetting resin composition A2 is added is Th (s), the difference Th (s) in the heating time is (1 ) To (3) are preferable because the adhesion between the substrates is improved.
When t ≧ 300 (s), t−t / 8 ≦ Th ≦ t + t / 8 Equation (1)
When 300 (s)> t ≧ 30 (s), t−30 (s) ≦ Th ≦ t + 30 (s) (2)
When 30 (s)> t ≧ 0 (s), 0 (s) ≦ Th ≦ t + 5 (s) (3)

  As a reason why the range of Th (s) must be changed depending on the value of t (s) as in the above formulas (1) to (3), the gelling time is several tens of minutes for the thermosetting resin composition. It can be mentioned that there are members exceeding several tens of seconds.

  For example, when the difference in gelation time t (s) of a plurality of base materials is 40 seconds, the range of the formula (2) is satisfied. By setting the difference in the input time from 10 seconds to 70 seconds, the mechanical properties and the appearance quality are improved. Although a good molded body can be obtained, if molding of a plurality of base materials with a difference in gelation time of 40 minutes within the same range of formula (2) is performed, the molding is performed between 49.5 minutes and 40.5 minutes. Without it, you will not get a good product. In fact, since the latter has a sufficient gelation time, it is possible to mold good products within the range of Th (min) of about 40 min ± 5 min. doing. In addition, when the difference in gelation time t (s) of a plurality of base materials is less than 30 seconds, the state of the base material changes in a short time. It is defined as (3).

  In addition, when laminating a plurality of base materials as well as two base materials, in the present invention, the base material having the longest gelation time is introduced in contact with the lower mold, and the other bases are arranged in the order of long gelation time. It is preferable to laminate the materials.

"Curing time"
The curing time in the present invention is a time required from the closing of the mold during press molding to the hardness at which the mold can be removed.

"Measuring method of gelation time"
In the present invention, the curing behavior is measured under the condition of 150 ° C. using ALPHA (manufactured by ALPHA TECHNOLOGIES, ATD 1000) as the target material, and the first inflection point at which the torque value rapidly increases is defined as the gel time. .

[Fiber-reinforced composite materials]
As described above, a plurality of fiber-reinforced resin sheet-like base materials can be laminated or combined to form the fiber-reinforced composite material 10. As an example, as shown in FIG. 1, a flat fiber-reinforced composite material 10 (substrate) having a prepreg surface 11 on one side and an SMC surface 12 on the other side can be used.

[Mold for compression molding]
The mold 20 includes an upper mold 21 and a lower mold 22, and both molds have a smooth surface. By bringing the upper mold 21 and the lower mold 22 close to each other, a flat plate cavity for forming the fiber-reinforced composite material 10 is formed.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not limited by the following description. First, the prepreg, the raw material and production method of SMC, the manufacturing method of the fiber reinforced composite material using both materials, and the evaluation method used in the Examples are described.

(1) Raw material Woven fabric prepreg: Twill weave a continuous carbon fiber bundle (manufactured by Toray Industries, Inc., "Torayca (registered trademark)" T300-3K-50E) with a fiber diameter of 7 μm, a tensile modulus of 230 GPa, and a single yarn number of 3,000. A mat that was impregnated with an epoxy resin composition having a gelation time of 60 seconds so that the fiber weight ratio (W _f ) = 60% was used. The curing time of this prepreg at 150 ° C. was 8 minutes.

  SMC base material: A continuous carbon fiber bundle (manufactured by ZOLTEK, “Panex 35 (registered trademark)”) having a fiber diameter of 7.2 μm, a tensile modulus of 240 GPa, and a single yarn number of 50,000, and a vinyl ester resin (Dow Chemical) 100 parts by weight of “Deraken (registered trademark) 790” manufactured by KK, and both parts of tert-butyl peroxybenzoate (manufactured by NOF Corporation, “Perbutyl (registered trademark) Z”) as a curing agent 4 parts by weight of magnesium oxide (Kyowa Chemical Industry Co., Ltd., MgO # 40) as a thickening agent, and 2 parts by weight of zinc stearate (manufactured by Sakai Chemical Industry Co., Ltd., SZ-2000) as an internal mold release agent A resin composition obtained by thoroughly mixing and stirring was used. The gel time of this resin composition was 30 seconds, and the curing time at 150 ° C. was 3 minutes.

(2) Manufacturing method After cutting out the woven prepreg into a width of 300 mm and a length of 300 mm and cutting out two SMC substrates into 200 mm squares, only the SMC substrate was laminated in two layers and prepared. The upper and lower molds 21, 22 were heated to 150 ° C., and first, the fabric prepreg 23 was put into the lower mold 22. Thereafter, the mold is kept waiting for a certain time (Th (s)), and the two-layer laminated SMC base material 24 is placed on the fabric prepreg 23, the upper mold 21 is lowered, and the mold is clamped for 10 minutes at 150 ° C. The pressure was increased at 15 MPa while maintaining the temperature. After a certain period of time, the fiber reinforced composite material 10 was removed from the mold 20.

(3) Evaluation method (Adhesion evaluation between base sheet)
A bending test was performed in accordance with JIS K7074, and evaluation was performed based on the following criteria by observing the fracture surface. In the present invention, 3 or more was considered acceptable.
1: Interfacial peeling between the woven prepreg and the SMC substrate occurred without causing fiber breakage of the prepreg in the entire fractured portion.
2: Although the fiber rupture of the prepreg was observed in a part of the rupture part, interfacial peeling between the fabric prepreg and the SMC substrate occurred.
3: Although fiber breakage occurred at the broken part, interfacial peeling was observed in the test piece.
4: Destruction due to fiber breakage occurred, and no interfacial peeling was observed.

(Appearance evaluation)
The fiber-reinforced composite material after molding was observed from the prepreg side, and the degree of misalignment of the fabric prepreg accompanying the flow of the SMC base material was evaluated based on the following criteria.
1: Misalignment occurred in the entire molded plate.
2: The misalignment occurred at the end of the charge portion of the SMC substrate and the end of the mold.
3: Yarn meandering occurred at several locations along the edge of the charge portion of the SMC substrate.
4: Yarn meandering occurred on only one side of the end of the charged portion of the SMC substrate.
5: No misalignment of the fabric prepreg occurred.

[Example 1]
A fiber reinforced composite material was molded using a woven prepreg and an SMC base material according to the manufacturing method described above, and evaluated by the evaluation method described above. At this time, the difference Th in charging time was 30 seconds.

[Examples 2 and 3]
The raw materials were prepared in the same manner as in Example 1, and a fiber reinforced composite material was molded according to the manufacturing method described above, and evaluated by the evaluation method described above. At this time, the difference Th in charging time was 60 seconds and 100 seconds, respectively.

[Comparative Example 1]
The raw material was prepared in the same manner as in Example 1, the woven prepreg was cut into a width of 300 mm and a length of 300 mm, and two SMC substrates were cut into 200 mm squares, and then the SMC substrate was placed in the center of the woven prepreg. Two sheets were laminated to prepare a three-layer laminate. The upper and lower molds 21 and 22 were heated to 150 ° C., and the fabric prepreg was charged so as to hit the lower mold. The upper mold 21 was immediately lowered and the mold was clamped and pressurized at 15 MPa while maintaining the temperature at 150 ° C. for 10 minutes. . After a lapse of a certain time, the fiber reinforced composite material 10 was removed from the mold 20. The obtained fiber reinforced composite material was evaluated by the previous evaluation method.

[Comparative Example 2]
The raw materials were prepared in the same manner as in Example 1, and the upper and lower molds 21 and 22 were heated to 150 ° C., and then the SMC base material 24 laminated in two layers was first put into the lower mold 22. After waiting for 30 seconds, the fabric prepreg 23 was put on the SMC base material 24, the upper mold 21 was lowered, the mold was clamped, and the pressure was maintained at 150 ° C. for 10 minutes and pressurized at 15 MPa. . After a certain period of time, the fiber reinforced composite material 10 was removed from the mold 20.

  As can be seen from Table 1, in the case of an SMC base material in which the difference t in gelation time from the fabric prepreg is 30 seconds, the time difference Th from the introduction of the fabric prepreg to the introduction of the SMC base material is 30 seconds (implementation) In the case of Example 1), it was possible to obtain a high-quality fiber-reinforced composite material having good adhesion between the base sheets and having little misalignment in the appearance seen from the prepreg surface. In Examples 2 and 3, molding was carried out in the same manner with an input time difference Th of 60 seconds and 100 seconds, respectively, and when evaluated, no misalignment of the prepreg was observed, and the fiber-reinforced composite material in which the adhesion was slightly inferior to that of Example 1. I was able to get.

  On the other hand, as shown in Table 2, in Comparative Example 1, two substrates were simultaneously added to perform molding, and as a result of evaluation, the SMC substrate was first cured, so that the adhesion at the interface was lowered, and the prepreg The misalignment has also increased. In Comparative Example 2, when the SMC base material was introduced 30 seconds ahead of the fabric prepreg, the SMC base material did not flow sufficiently, and the appearance of the prepreg surface was greatly misaligned.

  The present invention makes it possible to obtain a composite with high mechanical properties in hybrid molding of a material using a fiber-reinforced resin sheet-like base material. Therefore, other reinforcing fibers and other matrices that are expected in the automotive field and the like are used. However, the application range is not limited to these.

10: Fiber reinforced composite material 11: Pre-preg surface 12: SMC surface 20: Mold 21: Upper mold 22: Lower mold 23: The fiber reinforced resin sheet base material 24:23 having a longer gelation time than 23:24 Short fiber reinforced resin sheet substrate

Claims (4)

  A method for producing a fiber-reinforced composite material comprising compression-molding a plurality of fiber-reinforced resin sheet-like base materials comprising at least reinforcing fibers and a thermosetting resin composition, wherein the gelation time of the thermosetting resin composition Among the fiber reinforced resin sheet-like base materials having different values, the fiber reinforced resin sheet-like base material having the longest gelation time is introduced into a mold, and a time difference is further provided to make the fiber reinforced resin sheet having the second longest gel time. A method for producing a fiber-reinforced composite material, comprising repeatedly compressing and molding a shaped substrate into a mold. In the method for charging the substrate in the present invention, A1, A2... A (n), A (n + 1) from those having a long gelation time among the thermosetting resin composition,
In the case where the gelation time of the thermosetting resin composition is Tg1, Tg2,... Tg (n), Tg (n + 1), respectively.
Until the fiber-reinforced resin sheet-like substrate containing the thermosetting resin composition A (n + 1) is introduced after the fiber-reinforced resin sheet-like substrate containing the thermosetting resin composition A (n) is introduced. When the time is Th (s),
Th (s) satisfy | fills at least any one of following formula (1)-(3), The manufacturing method of the fiber reinforced composite material of Claim 1 characterized by the above-mentioned.
When t ≧ 300 (s), t−t / 8 ≦ Th ≦ t + t / 8 Equation (1)
When 300 (s)> t ≧ 30 (s), t−30 (s) ≦ Th ≦ t + 30 (s) (2)
When 30 (s)> t ≧ 0 (s), 0 (s) ≦ Th ≦ t + 5 (s) (3)
Here, t (s) is the gelation time Tg (n) of the fiber-reinforced resin sheet-like substrate containing the thermosetting resin composition A (n), and the thermosetting resin composition A (n + 1). The difference (t = Tg (n) −Tg (n + 1)) from the gelation time Tg (n + 1) of the fiber reinforced resin sheet-like base material.   The method for producing a fiber-reinforced composite material according to claim 1 or 2, wherein the fiber-reinforced resin sheet-like base material is any one of a unidirectional array sheet, a woven fabric, a nonwoven fabric, and a random mat.   The said thermosetting resin composition is either a vinyl ester resin or an epoxy resin, The manufacturing method of the fiber reinforced composite material in any one of Claims 1-3 characterized by the above-mentioned.