JP2004346190A - Prepreg and fiber reinforced resin composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg and the like which solve the drawbacks inherent in a vacuum bag-molded FRP that it is void-prone and inferior in mechanical properties as compared to an autoclave-molded FRP. <P>SOLUTION: Multifilaments not fully impregnated with a thermosetting resin composition are adhered to at least one side of the outer surfaces of the prepreg consisting of reinforcing fibers and the thermosetting resin composition. The volume of the thermosetting resin composition impregnated among the multifilaments is ≤ 20 volume% of the multifilaments. The fiber-reinforced composite is obtained by laminating and thermosetting the prepreg by vacuum bag molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３９】
【発明の効果】
本発明のプリプレグは、真空バッグ成形法で成形した場合でもボイドが少なく、オートクレーブで成形した場合と同等の機械的性質を有し、かつ優れた成形性を有するため、航空機用構造材料等として好適に使用される。
【００４０】
【図面の簡単な説明】
【図１】本発明のプリプレグ１の断面（強化繊維の長手方向に対して直角方向の断面）の模式図である。
【図２】本発明のプリプレグを積層した積層体の断面の模式図を示す。
【図３】実施例でおこなったＦＲＰ成形の真空バッグの断面（部分）図である。
【図４】実施例でおこなったＦＲＰ成形の温度プロファイルを示すグラフである。
【符号の説明】
１ 本発明のプリプレグ
２ プリプレグ
３ マルチフィラメント[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a prepreg capable of obtaining a low void fiber reinforced resin composite material (hereinafter, referred to as FRP) even by a vacuum bag molding method without impairing handleability of the prepreg, and an FRP using the prepreg.
[0002]
[Prior art]
Because of its excellent mechanical properties, FRP has been widely used in sports and leisure applications such as fishing rods and golf shafts, and as a member of aircraft and automobiles. As a method of molding these FRPs, several methods are actually performed.When carbon fibers are used as the reinforcing fibers, an intermediate material called a prepreg, which is previously impregnated with the resin composition in the reinforcing fibers, is used. The method used is the most widely used.
[0003]
FRP is formed by compression molding using a mold, autoclave molding using a pressure cooker, vacuum bag molding using atmospheric pressure, or sheet wrap molding in which a prepreg is wound and laminated on a mandrel, and a film tape is wound thereover and molded. And so on. Above all, autoclave molding is generally used in applications such as aircraft parts where mechanical strength is prioritized because FRP having few voids (defects) and excellent mechanical strength is obtained. .
[0004]
However, the installation of an autoclave requires a huge investment, and the size of the obtained FRP is limited by the capacity of the autoclave. In order to obtain a large FRP, it is necessary to form the structure by dividing the structure. There is a major problem in terms of cost and productivity, for example, a large autoclave is required.
[0005]
Therefore, in recent years, de-autoclave, in which FRP is formed without using an autoclave, has been advanced due to cost and productivity problems. Above all, vacuum bag molding, in which molding is performed under only atmospheric pressure, has a small pressure at the time of molding, so that an inexpensive mold can be used as compared with an autoclave, and the heating equipment is simple. Since the size limitation of the apparatus is small, a large FRP can be integrally molded. For example, attention has been paid to advantages in cost and productivity as compared with autoclave molding.
[0006]
However, FRP molded by vacuum bag molding has a problem that since the molding pressure is smaller than that of autoclave molding, voids are easily generated in the FRP and mechanical properties are inferior to FRP molded by autoclave. . Voids are broadly classified into two types: intra-layer voids generated in the prepreg layer and interlayer voids generated between the prepreg layers, and are particularly problematic because relatively large interlayer voids greatly reduce mechanical properties. Causes of voids include volatiles due to water and solvents contained in the prepreg resin, and air bubbles remaining in the resin.The biggest cause of interlayer voids is that It is considered that the air pool was left between the layers due to the tack. Therefore, when attempting to obtain a large number of laminated FRPs in a void-free state, the air taken in each time the prepreg is laminated is punched out with a pin tip or a cutter blade or the like, or expelled every few plies. Work such as bagging with a plastic film or the like and degassing by vacuum degassing was required.
[0007]
As a method for eliminating voids, Patent Literature 1 discloses a method in which prepregs are stacked in a state where the prepregs are maintained at a tack-free temperature or lower of the resin in the prepreg, and the inside of the bag is depressurized to remove air pockets between layers. ing.
[0008]
However, there is no problem in the case of a flat and small FRP, but in the case of manufacturing a large FRP, it is difficult to reduce the temperature of a prepreg having substantially the same area as the FRP to a uniform low temperature. In order to achieve a free state, it is necessary to lower the temperature considerably, so that it becomes more difficult to control the temperature. On the other hand, at low temperatures, the draping property of the prepreg is also lost, so that lamination is difficult, and when the FRP has a curved structure, tack-free, prepreg without drape is difficult to laminate in addition to lamination. .
[0009]
On the other hand, Patent Documents 2 and 3 disclose prepregs in which fibers of a type different from the reinforcing fibers are compounded in order to impart strength and impact resistance to the final FRP. In these prepregs, it is conceivable that the tackiness is reduced by compounding different kinds of fibers, and the formability in vacuum bag forming is improved.However, these are made by completely or almost completely burying the different kinds of fibers in the prepreg. Also, since the thermosetting resin composition is impregnated in the different kinds of fibers, the decrease in tack is small. Therefore, it cannot be said that the vacuum bag formability is necessarily improved. In order to obtain FRP with few voids, autoclave molding is required. Had to be used.
[0010]
Patent Document 4 discloses a method in which a plurality of grooves arranged continuously in the longitudinal direction are provided on at least one surface of a one-way prepreg to secure an air passage and prevent air from being trapped. I have.
[0011]
However, when trying to obtain a curved FRP, depending on the type of the thermosetting resin composition that is the matrix resin of the prepreg, the prepreg may be cracked, the groove portion is closed, and the air passage cannot be sufficiently secured. Could be problematic in terms of
[0012]
[Patent Document 1]
JP-A-6-226874 [Patent Document 2]
Japanese Patent Application Laid-Open No. Hei 3-19909 [Patent Document 3]
JP-A-5-17603 [Patent Document 4]
JP-A-2-227212
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, has a small interlayer void even when molded by vacuum bag molding, has the same mechanical properties as when molded by an autoclave, and has excellent moldability. And a FRP using the same.
[0014]
[Means for Solving the Problems]
The gist of the present invention is a prepreg in which a multifilament that is not completely impregnated with a thermosetting resin composition is attached to at least one outer surface of a prepreg composed of a reinforcing fiber and a thermosetting resin composition. It is in.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
(Reinforced fiber)
The reinforcing fiber used in the present invention is not particularly limited as long as it is used for a general fiber-reinforced composite material. Preferable examples include carbon fiber, boron fiber, aramid fiber, glass fiber and the like.
[0016]
(Thermosetting resin composition)
As the thermosetting resin composition used in the present invention, any resin can be used as long as it is cured by external energy such as heat or light to form at least partially three-dimensional crosslinks.
[0017]
(Form of prepreg)
The form of the prepreg before attaching the multifilament (described later) in the present invention is not particularly limited, and a so-called UD prepreg in which reinforcing fibers are aligned in one direction and impregnated with a thermosetting resin composition, A prepreg in which a reinforcing fiber is woven into a woven fabric and impregnated with a thermosetting resin composition may be used, and there is no particular limitation. The present invention is particularly suitable for a UD prepreg because the effect of reducing interlayer voids is great when laminating and molding a UD prepreg in which interlayer voids are likely to occur.
[0018]
(Multifilament)
The type of fiber of the multifilament used in the present invention is not particularly limited as long as the mechanical properties of the finally obtained FRP are not extremely reduced. When impact resistance is required for FRP, thermoplastic resin fibers are preferably used for the purpose of improving impact resistance and the like. As such a thermoplastic resin fiber, a fiber obtained by shaping an engineering plastic such as polyamide, polyimide, or polyamideimide into a fibrous shape is preferably used.
[0019]
When FRP is required to have good mechanical properties such as tensile strength and compressive strength, carbon fibers, aramid fibers, fibers having excellent mechanical properties, such as glass fibers, are preferably used. It is more preferably used because it has excellent mechanical properties such as modulus and strength.
[0020]
In the present invention, the diameter of the monofilament forming the multifilament is not particularly limited. The diameter of the monofilament is preferably in the range of 5 to 150 μm for obtaining the effects of the present invention. When the diameter of the monofilament is more than 150 μm, the unevenness of the FRP surface becomes large, which is not preferable. On the contrary, when it is less than 5 μm, the bulk of the multifilament becomes small, and it becomes difficult to secure a passage for air.
[0021]
There is no particular limitation on the form of application of the multifilament to the outer surface of the prepreg. The alignment direction of the multifilament is not particularly limited, and may be present at any angle with respect to the reinforcing fibers in the prepreg. If they are not adhered at an appropriate interval, a sufficient invention effect cannot be obtained, and therefore, it is preferable that they are present at equal intervals.
[0022]
(Method for producing prepreg of the present invention)
There is no particular limitation on the method for producing the prepreg of the present invention from the reinforcing fiber, the thermosetting resin composition and the multifilament, and the method of aligning and integrating the multifilament with the prepreg produced by a known method, and a drum winder To produce a prepreg, and then a multifilament is wound thereover and integrated.
[0023]
FIG. 1 shows a schematic view of a cross section of the prepreg 1 of the present invention (a cross section perpendicular to the longitudinal direction of the reinforcing fibers).
[0024]
FIG. 2 shows a schematic diagram of a cross section of a laminate in which the prepregs 1 of the present invention are laminated. As shown in FIG. 2, a portion of the multifilament 3 existing between the layers and between the filaments, which is not impregnated with the thermosetting resin composition, becomes an air passage, and air can be released to the outside. No air pockets. At the time of heat molding, the space between the filaments in the multifilament becomes a moving path of the thermosetting resin composition whose viscosity has been reduced by heating, and the thermosetting resin composition containing air or volatile matter causing voids Is discharged outside the laminate. Finally, the thermosetting resin composition spreads between the filaments, and a good FRP free of interlayer voids can be obtained even in vacuum bag molding.
[0025]
In the present invention, it is important that the multifilament is present on the outer surface of the prepreg, and that the thermosetting resin composition is not completely impregnated in the multifilament. Here, the state where the thermosetting resin composition is not completely impregnated means that the volume of the thermosetting resin composition contained in the multifilament arranged on the outer surface of the prepreg is 20 to the volume of the multifilament. % Is preferable. If the multifilament is completely impregnated with the thermosetting resin composition, a path for air between the layers cannot be secured, and a sufficient invention effect cannot be obtained. In order to obtain a sufficient inventive effect, the volume of the thermosetting resin composition in the multifilament is preferably 20% or less, more preferably 15% or less.
[0026]
The volume of the thermosetting resin composition contained in the multifilament (based on the volume of the multifilament) V _R (vol%) is the weight WF _{+ R} (g) when the multifilament on the prepreg surface is carefully peeled off with tweezers. And a solvent that dissolves the thermosetting resin composition and does not dissolve the multifilament, for example, acetone or MEK, removes the thermosetting resin composition impregnated in the multifilament, and cleans and dries the multifilament. W measured _F (g), is calculated using the following equation.
[0027]
_{V R = (ρ F (W} F + R -W F) / ρ R W F) × 100 ( vol%)
here,
ρ _F : density of multifilament (g / cm ³ )
ρ _R : density of the thermosetting resin composition (g / cm ³ )
[0028]
The multifilament may be attached to only one outer surface of the prepreg, or may be attached to both outer surfaces. Is more preferable because the effect of suppressing the generation of voids is large.
[0029]
(Method of Forming FRP Using Prepreg of the Present Invention)
The prepreg of the present invention is preferably used in autoclave molding, but is more preferably used in a vacuum bag molding in which voids are easily generated during molding because a large void suppression effect is obtained.
[0030]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited by the embodiments.
[0031]
(Example 1)
A carbon fiber (Carbon Fiber MR50K manufactured by Mitsubishi Rayon Co., Ltd., fiber density: 1.80 g / cm ² ) was used as a reinforcing fiber, and an epoxy resin composition cured at 180 ° C. was used as a thermosetting resin composition. (Reinforcement fiber weight: 190 g / cm ² , resin content: 34% by weight, resin density: 1.25 g / cm ² ).
On both surfaces, using a drum winder, nylon 12 fibers prepared as multifilaments (monofilament diameter: 35 μm, number of filaments: 24, fiber density: 1.12 g / cm) at intervals of 3 mm in the same direction as the reinforcing fiber direction using a drum winder ² ) was wound, and a nylon 12 fiber on the surface was pressure-bonded to a unidirectional fiber-reinforced prepreg using a roller to prepare a prepreg of the present invention.
[0032]
This prepreg was cut into a square of 10 × 10 mm so that the reinforcing fibers were parallel to the edges, the multifilaments on the outer surface of the prepreg were carefully peeled off with tweezers, and the mass was measured. The peeled multifilament was put into a beaker containing acetone, and washed for 2 minutes while slightly stirring with tweezers. This washing operation was performed three times by replacing acetone, and the washed multifilament was dried by a dryer set at 80 ° C. for 3 hours, and then the mass was measured. From these weight measurement results, the volume of the thermosetting resin composition contained in the multifilament (based on the bulk of the multifilament) V _R (vol%) was calculated, and the results are shown in Table 1.
[0033]
The prepreg has a laminated structure (based on the orientation of the reinforcing fibers) of (+ 45 ° / 0 ° / −45 ° / 90 ° / + 45 ° / 0 ° / −45 ° / 90 ° / + 45 ° / 0 ° / −). 45 ° / 90 ° / 90 ° / -45 ° / 0 ° / + 45 ° / 90 ° / -45 ° / 0 ° / + 45 ° / 90 ° / -45 ° / 0 ° / + 45 °) Then, the bag was sealed with the nylon bag shown in FIG. 4 and vacuum-packed with the temperature profile shown in FIG. 5 while evacuating to a vacuum degree of 750 mmHg or more (the size of the laminate was 200 mm (length) × 250 mm ( (Width) x about 4.5 mm (thickness).
[0034]
After cutting the obtained FRP at an arbitrary place, polishing the cut surface, observing from the upper part to the lower part of the panel cut surface with a width of about 1 mm by an optical microscope, counting the number of interlayer voids having a width of 50 μm or more, The results are shown in Table 1.
[0035]
(Example 2)
The UD prepreg obtained in Example 1 and carbon fibers (TR40S, manufactured by Mitsubishi Rayon Co., Ltd., fiber diameter: about 7 μm, number of filaments: 1000, fiber density: 1.80 g / cm ² ) prepared as multifilaments were prepared. A multifilament was wound around both surfaces of the UD prepreg using a drum winder at an interval of about 6 mm in the same direction as the reinforcing fiber direction, and the fibers on the surface were pressed using a roller to produce a prepreg of the present invention.
Using this prepreg, it was molded in the same lamination configuration as in Example 1, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.
[0036]
(Comparative Example 1)
Using the UD prepreg obtained in Example 1, an FRP was formed in the same laminated configuration as in Example 1. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.
[0037]
(Comparative Example 2)
After the prepreg of the present invention was obtained in Example 1, using a fusing press (manufactured by Asahi Textile Industry Co., Ltd.), a multi-filament was impregnated with the thermosetting resin composition to prepare a prepreg integrally formed.
Using this prepreg, it was molded in the same lamination configuration as in Example 1, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.
[0038]
[Table 1]

[0039]
【The invention's effect】
The prepreg of the present invention has few voids even when molded by a vacuum bag molding method, has the same mechanical properties as when molded by an autoclave, and has excellent moldability, so it is suitable as a structural material for aircraft, etc. Used for
[0040]
[Brief description of the drawings]
FIG. 1 is a schematic view of a cross section (a cross section perpendicular to the longitudinal direction of a reinforcing fiber) of a prepreg 1 of the present invention.
FIG. 2 shows a schematic diagram of a cross section of a laminate obtained by laminating the prepreg of the present invention.
FIG. 3 is a cross-sectional (partial) view of an FRP-molded vacuum bag performed in an example.
FIG. 4 is a graph showing a temperature profile of FRP molding performed in an example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pre-preg 2 Pre-preg 3 Multifilament of this invention

Claims (5)

A prepreg in which a multifilament that is not completely impregnated with a thermosetting resin composition is attached to at least one outer surface of a prepreg made of a reinforcing fiber and a thermosetting resin composition. The prepreg according to claim 1, wherein the volume of the thermosetting resin composition impregnated in the multifilament is 20% by volume or less based on the volume of the multifilament. The prepreg according to claim 1 or 2, wherein the reinforcing fibers are aligned in one direction. The prepreg according to any one of claims 1 to 3, wherein the multifilament is a multifilament made of a thermoplastic resin. A fiber-reinforced resin composite material obtained by laminating the prepregs according to any one of claims 1 to 4 and curing by heating by a vacuum bag molding method.

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