JP3204627B2 - Fiber reinforced plastic molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced plastic molded product used for sports goods such as racket frames, golf club shafts, fishing rods, etc., and industrial goods such as robot arms.

[0002]

2. Description of the Related Art Fiber-reinforced plastic moldings used as various sports goods and industrial goods are required to have properties such as light weight, high strength and high vibration damping. You.

[0003] The strength (bending strength, impact strength, etc.) affects the durability of a molded article. If the strength is high, the durability of the molded article is improved. On the other hand, when the molded product is a tennis racket, the vibration damping has a large effect on the feel at impact and the impact applied to the human body at the time of hitting the ball. Damage to the human body can be suppressed. In addition, when the molded product is a robot arm, if the vibration damping property is excellent, the time required for the motion of the robot to stand still can be reduced, and the working efficiency can be reduced.

[0004] Many proposals have been made on modifying a matrix resin in order to improve the strength and vibration damping properties (vibration damping properties) of a fiber-reinforced plastic molded article using an epoxy resin as a matrix resin. I have.

[0005]

For example, use of a hardener having a long aliphatic group or rubbery properties, addition of a compound having an elastomeric property, addition of a plasticizer such as asphalt substance, glycols, etc., to epoxy compounds Attempts to increase toughness by introducing a molecular group exhibiting rubber elasticity <Koichi Ochi, “Polymer” 38 (3), 200 (1989), Shin Horiuchi, “Functional Materials” 15 (7) 22 (199)
5)>. Further, in order to achieve toughness, a fiber-reinforced composite epoxy resin composition comprising a phenolic hydroxyl group-containing aramid-polybutadiene-acrylonitrile block copolymer, an epoxy resin, a curing agent, and an inorganic or organic fiber has been proposed (Japanese Patent Laid-Open Publication No. HEI 9-26139). 4-328116). However, although the molded articles according to these proposals have excellent strength and rigidity, favorable results regarding vibration damping properties have not been obtained.

On the other hand, Japanese Patent Application Laid-Open No. Hei 6-155644 discloses a racket using an epoxy resin impregnated carbon fiber prepreg in which a vibration damping resin film containing butyl rubber as a main component is embedded in a layer in order to improve vibration damping properties. Has been proposed. However, in the racket according to such a proposal, the strength and rigidity of the molded article are greatly reduced due to poor adhesion between the vibration damping resin film and the epoxy resin impregnated carbon fiber layer.

As described above, various proposals have conventionally been made to improve the performance of a fiber-reinforced plastic molded article using an epoxy resin as a matrix resin, but the molded article is satisfactory in both strength and vibration damping properties. It is the fact that is not obtained.

The present invention has been made in view of the above-mentioned circumstances, and is a fiber-reinforced plastic molded article in which a matrix resin is made of an epoxy resin, wherein the fiber-reinforced plastic is excellent in both strength and vibration damping properties. It is an object to provide a molded product.

[0009]

The mainstream of fiber-reinforced plastic moldings such as tennis rackets and golf clubs is formed by laminating resin-impregnated reinforcing fiber layers and molding them into a hollow pipe shape. In such a hollow molded article, not only a simple bending mode but also a mode including torsion is important for its shock resistance and vibration damping properties. For example, in the case of a tennis racket frame, twisting occurs in the hollow frame in order to follow the deformation in an out-of-plane bending, that is, a bending in a direction perpendicular to the racket face surface. Also, in the case of a golf club shaft, the deformation is not limited to simple bending, but also to the origin in which torsion is compounded. Then, when such a twist is generated, a shear force 2 is generated between the resin-impregnated reinforcing fiber layers vertically overlapping with respect to the force 1 in the twist direction inside the hollow molded article as shown in FIG. That is, the shear strength generated between the laminated resin-impregnated reinforcing fiber layers has a great effect on the impact resistance and vibration damping properties of the hollow molded article.

The present inventor has focused on the shearing force generated between the laminated resin-impregnated reinforcing fiber layers of such a hollow molded article, to reduce the deviation in the shearing direction between the laminated resin-impregnated reinforcing fiber layers, and to reduce the shearing force. So that it can be effectively absorbed
The present inventors have made intensive studies on the material of the molded article and the laminated structure and completed the present invention.

That is, the present invention is a molded article of a fiber reinforced plastic in which the matrix resin is an epoxy resin, wherein an ionomer film is interposed at least partially between the vertically overlapping layers of the epoxy resin impregnated reinforced fibers. The present invention provides a fiber-reinforced plastic molded product characterized in that:

As the above-mentioned ionomer film, a film obtained by crosslinking the molecules of an ethylene-methacrylic acid copolymer with metal ions, for example, Himilan (trade name, manufactured by Dupont Mitsui Chemicals, Inc.) is preferably used. (Claim 2). This ionomer film has high reactivity with an epoxy group and exhibits excellent adhesiveness to an epoxy resin, and itself has high elasticity, is tough, and has excellent impact resistance.

The metal ions include Na, K, Mg,
An ion such as Zn can be mentioned. In particular, a Zn ion is preferable in that the adhesion of the ionomer film to the epoxy resin can be improved. The thickness of the ionomer film is not particularly limited, but may be 30 to 100.
It is preferable that the thickness be in the range of μm.

In such a fiber-reinforced plastic molded article of the present invention, the ionomer film interposed between the epoxy resin-impregnated reinforced fiber layers is firmly adhered to the epoxy resin of the epoxy resin-impregnated reinforced fiber layer, and the epoxy resin layer vertically overlaps. The displacement in the shearing direction between the impregnated reinforcing fiber layers is reduced, and vibration caused by the shearing force generated between the epoxy resin impregnated reinforcing fiber layers can be effectively absorbed by the elasticity of the ionomer film. Therefore, the impact resistance and vibration damping properties of the molded product can be greatly improved.

The glass transition temperature of the ionomer film is preferably in the range of 0 to 60 ° C. (claim 3). Generally, the ionomer has a large loss coefficient (tan δ) near the glass transition temperature. Therefore, when an ionomer film having a glass transition temperature of 0 to 60 ° C. is used, the temperature at the time of actual use (in general, the outdoor or indoor environmental temperature at which a tennis racket, golf club, robot arm, or the like is actually used: about 5 to 5) (35 ° C.), the vibration absorption by the ionomer film appears more remarkably.

Further, the molded article is obtained by adhering an ionomer film to one surface of a prepreg sheet in which a reinforcing fiber is impregnated with an epoxy resin to form a composite sheet, winding the composite sheet in a hollow pipe shape, and curing the epoxy resin. It is preferably formed into a hollow pipe (claim 4). In this way, the ionomer film is placed between the lower epoxy resin-impregnated reinforced fiber layer and the upper epoxy resin-impregnated reinforced fiber layer without winding the ionomer film into direct contact with the ionomer film just by winding the composite sheet. Therefore, the ionomer film and the epoxy resin react efficiently, and the impact resistance and vibration damping properties of the molded product are further improved.

As the epoxy resin to be impregnated into the reinforcing fibers, an epoxy resin having a precursor of an amine, a phenol, or a compound having a carbon-carbon double bond is used. In particular, those having two or more epoxy groups in one molecule are preferable. Specific examples of epoxy resins using amines as precursors include tetraglycidyldiaminodiphenylmethane, triglycidyl-P-aminophenol,
Various isomers of triglycidyl-m-aminophenol and triglycidylaminocresol are exemplified. Specific examples of epoxy resins using phenols as precursors include:
Examples include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, and resorcinol novolak epoxy resin. Specific examples of the epoxy resin using a compound having a carbon-carbon double bond as a precursor include an alicyclic epoxy resin.

As the so-called latent curing agent for epoxy resin to be blended for curing the epoxy resin, amines, acid anhydrides, imidazoles and the like are suitable. Specific examples of the amines include 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone,
Dicyandiamide and the like. Specific examples of the acid anhydrides include tetrahydrophthalic anhydride.
Examples of imidazoles include 2-n-heptanedecylimidazole. In addition to these amines, acid anhydrides, and imidazoles, for example, N, N-dialkylurea derivatives, N, N-dialkylurea derivatives,
N, N-dialkylthiourea derivatives, N-aminoethylpiperazine, melamine, guanamine, boron trifluoride complex compounds, trisdimethylaminomethylphenol and the like may be used. These curing agents may be used alone or in combination of two or more.

Examples of the curing accelerator include alcohol, phenol, mercaptan, dimethylurea, alicyclic, imidazole and the like. Also,
Examples of fillers that are commonly blended for cost reduction include calcium carbonate, silica, talc, mica, celite, perlite, asbestos, and alumina.

The curing temperature of the epoxy resin can be changed depending on the type of the curing agent, and is not particularly limited. However, in consideration of the moldability, the reactivity with the ionomer film, the melting point of the ionomer film, and the like, the curing temperature is in the range of 140 to 160 ° C. Is preferred.

As the reinforcing fibers, those known in the field of this type and conventionally generally known as high-performance reinforcing fibers can be used. For example, carbon fibers (carbon fibers), graphite fibers, glass fibers, Examples thereof include aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, glass fiber, steel fiber, amorphous metal fiber, and organic fiber, and these can be used alone or in combination of two or more. In addition, the shape of the fiber is continuous fiber, long fiber,
It may be in the form of short fibers or a composite of these. Further, the arrangement form and fiber direction of the reinforcing fibers are not particularly limited, and may be, for example, any one of a single direction, a random direction, a sheet shape, a mat shape, a woven (cross) shape, and a braided shape.

The method for producing the molded article is not particularly limited, but the following method is preferred. A prepreg in which an epoxy resin is impregnated into reinforcing fibers is laminated, and the epoxy resin is cured while applying pressure to the laminate. In this case, an ionomer film is interposed between the prepregs at the stage of laminating the prepregs. As the prepreg, it is preferable to use a unidirectional continuous fiber prepreg produced by winding continuous fibers impregnated with an epoxy resin by drum winding around a drum in one direction.

[0023] A sleeve-shaped braid is laminated to form a pipe, and the pipe is impregnated with epoxy resin.
Next, the epoxy resin is cured while applying pressure to the pipe impregnated with the epoxy resin. In this case, an ionomer film is interposed between the sleeve-shaped braids at the stage of laminating the sleeve-shaped braids. Note that the ionomer film does not exist in the entire area between the lower sleeve-shaped braid and the upper sleeve-shaped braid so that the epoxy resin impregnation spreads over the entire laminate, and the path through which the epoxy resin passes It is preferable to provide it.

Using a roving previously impregnated with an epoxy resin and winding a reinforcing fiber impregnated with a resin by a filament winding method, the epoxy resin is cured while applying pressure. In this case, the ionomer film cut into a sheet or a tape is wrapped while the reinforcing fibers are wound, and the ionomer film is interposed between the reinforcing fiber layers.

In any of the above manufacturing methods, molding is performed by winding a laminate of a resin-impregnated reinforcing fiber layer having an ionomer film interposed between layers on an outer peripheral surface of a flexible tube in a mold, and forming the laminate. The material is heat-formed while applying pressure with a flexible tube, so-called internal pressure method, or a pressure tape is wound around the outer periphery of the resin-impregnated reinforcing fiber layer with an ionomer film interposed between the layers, and the laminate is wrapped. A so-called external pressure method in which heat molding is performed while applying pressure with a pressure tape can be used. In the internal pressure method, excess resin flows into the mold parting line, and in the external pressure method, it is necessary to flow the excess resin from the gap of the pressing tape, so an ionomer film that obstructs the flow of such excess resin Arrangement must be avoided. That is, it is preferable to avoid completely wrapping the outermost periphery of the laminate with the ionomer film or to arrange the ionomer film so that the upper and lower ionomer films are in contact with each other.

In the case where the ionomer film is not used in the molded article, it is preferable that the ionomer film be interposed between the fiber layers at the position where the displacement of the vibration is greatest.

For example, in recent years, the weight of a tennis racket has been reduced, and a racket having a total weight of 250 to 270 g has appeared. Since such a lightweight racket has poor resilience, the balance should be top heavy. The flying performance is maintained. That is, the weight distribution of the fiber reinforced plastic layer is increased so as to increase in the face portion of the racket, especially in the top portion (see FIG. 9). However, players have heard that such lightweight rackets have poor vibration damping properties, and as a result of studying this,
In order to increase the weight of the face part, the amount of fiber on the grip side is smaller than the amount of fiber on the face side. Therefore, the displacement at the antinode of the secondary vibration mode in the out-of-plane direction increases. I knew it was.

FIGS. 10A and 10B show the primary vibration mode and the secondary vibration mode in the out-of-plane direction of the racket frame, and the antinode of the secondary vibration mode corresponds to R in FIG. 10B.
1 (near the 3 o'clock position when the vertex P is 12 o'clock when the gut plane is regarded as the clock face) and R2 (near the boundary between the grip G and the throat portion). Therefore, in such a racket, antinode portions R1 and R1 of the secondary vibration mode are provided.
When an ionomer film is interposed between the two fiber layers,
Vibration damping can be greatly improved.

In the case of a lightweight golf club shaft having a total weight of 55 g or less, a normal shaft (total weight:
56 to 90 g). In this case, particularly, when the ionomer film is inserted into a portion where the stress is concentrated, the bending strength is increased, and the durability of the club shaft can be greatly improved.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to Examples and Comparative Examples. (Example 1) Using an epoxy resin impregnated carbon fiber prepreg (T800: P2053-122) manufactured by Toray Industries, Inc.
By the following steps, the overall diameter is 600 mm and the outer diameter (φ) is 18.
A circular pipe having a cross section of 4 mm was produced. First, length 600
200 mm length x 59 m width on an epoxy resin impregnated carbon fiber prepreg sheet having a size of 59 mm × 59 mm width.
m, tensile strength (JIS K-6760) is 245kg
/ Cm ² , elongation at break (JIS K-6760) is 56
0%, flexural modulus (JIS K-7106) 1480
kg / cm ² , a glass transition temperature of 40 ° C. and a Zn ion type ionomer film (manufactured by Du Pont-Mitsui Co., Ltd.)
A composite sheet to which Himilan 1652 (trade name) was attached was prepared.

Similarly, an ionomer film (Himilan 1652 (trade name, manufactured by Mitsui Dupont), having a length of 600 mm and a width of 60 mm) was attached to an epoxy resin impregnated carbon fiber prepreg sheet having a length of 600 mm and a width of 60 mm. Composite sheet, epoxy resin-impregnated carbon fiber prepreg sheet having a length of 600 mm x width of 62 mm and an ionomer film (manufactured by Mitsui Dupont Co., Ltd.
1652 (trade name)) and an epoxy resin-impregnated carbon fiber prepreg sheet having a length of 600 mm and a width of 63 mm and an ionomer film of 600 mm in length and 63 mm in width (DuPont Mitsui)
Manufactured by Himilan 1652 (trade name) manufactured by Toshiba Corporation.

Next, each of the four composite sheets prepared above has the same dimensions (length × width) as the composite sheet so that the fiber direction is ± 24 ° between the prepreg sheet and the prepreg sheet. The oxy resin impregnated carbon fiber prepreg sheet was further overlapped.

Next, as shown in FIG.
A 66 mm nylon tube 22 is put on a 5 mm mandrel 21, and the four composite sheets 23 </ b> A to 23 </ b> D are sequentially wound on the 66 mm nylon tube 22.
As shown in (B), the mandrel 21 was pulled out to form a lay-up 24. In addition, in the winding of each composite sheet, the overlap amount was set to 7 mm, and as shown in FIG. 1C, the overlap portion 25 of the composite sheet was prevented from overlapping between the winding layers. This is to prevent a portion having an extremely large thickness from being formed on the lay-up 24 so that the pressing force is applied to the lay-up 24 as uniformly as possible in the next molding step.

Next, the lay-up was placed in a mold having a circular cross section, and heated at 150 ° C. for 40 minutes to form a circular pipe. At this time, an air pressure of 7 kgf / cm ² was applied to the 66 nylon tube.

Example 2 As an ionomer film, a Na ion type tensile strength (JIS K-676) was used.
0) is 305 kg / cm ² , and the elongation at break (JIS K-
6760) is 430% and the flexural modulus (JIS K-71)
06) is 2040 kg / cm ² , and the glass transition temperature is 0 ° C.
Example 1 except that an ionomer film (Himilan 1601 (trade name) manufactured by Du Pont-Mitsui Co., Ltd.) was used.
A pipe having a circular cross section having the same structure as that of the above (the dimensions of the epoxy resin impregnated carbon fiber prepreg sheet, the ionomer film, the composite sheet, and the like, the lamination structure, and the like) are the same.

Example 3 A circular pipe was formed in the same manner as in Example 1 except that the length of the ionomer film in each of the four composite sheets was changed to 600 mm.

(Comparative Example 1) A process similar to that of Example 1 was carried out using four composite sheets obtained by laminating two prepreg sheets so that the fiber direction was ± 24 ° without attaching an ionomer film. A circular pipe was created. Each of the four composite sheets is 600 m long
A stack of two sheets of mx 63 mm width, length 600
2 x 62 mm sheets, length 60
A stack of two sheets of 0 mm x 60 mm width, length 6
Two sheets of 00 mm × 59 mm width were stacked.

(Comparative Example 2) An ionomer film (manufactured by Du Pont-Mitsui Co., Ltd., Himilan 1)
652), and a pipe having a circular cross section was prepared in the same manner as in Comparative Example 1 except for the above.

(Comparative Example 3) Instead of the ionomer film, a coating layer made of an emulsion-like butyl rubber-based vibration damping paint (Anglen manufactured by Daicel Industries Ltd.) having the same dimensions as the ionomer film was used. Four composite sheets were produced in the same manner as in Example 1, and a circular pipe having a circular cross section was produced by the same steps as in Example 1 using the four composite sheets.

The above-prepared Examples 1 to 3 and Comparative Examples 1 to
3 was measured for its strength and vibration damping properties.

As shown in FIG. 2, the bending strength was measured according to JIS-
Length supported by jig 10 according to K7055 (span)
Is set to 300 mm, the center of the entire length of the circular pipe 11 is aligned with the center of the span, and a load is applied from above the center point P by the pressurizing tool 25 so that the test speed is 50 mm /
It was measured by performing a three-point bending test in minutes.

As shown in FIG. 3, the impact characteristics (maximum impact load and impact energy) were obtained by cutting out the center of a pipe having a circular cross section, and supporting the cut out pipe 12 with a support length (span) of 185 mm using a jig 10. The weight 32 having the load cell 32 attached to the center of the support length (span) was dropped freely, and the maximum load required for breaking and the impact energy required for breaking were calculated from the load value and the initial acceleration at each time.

As shown in FIG. 4, the vibration damping rate is determined by fixing the center of the pipe 11 having a circular cross section to the vibrator 41,
, Vibrations of various frequencies are given to the pipe, and the vibration of the aluminum foil 42 affixed to a portion 20 mm from the end of the pipe is measured by a laser displacement type 43, and the measured value is measured by the laser displacement type 43 with a DFC (Doppler Frequency).
cy Tracker) and FFT (Fast F)
(ourier Transfer Analyzer)
And the damping rate of the primary vibration mode was measured.

Table 1 below shows the results.

[Table 1] As shown in Table 1, the circular cross-section pipes of Examples 1 to 3 in which the ionomer films were interposed between the epoxy resin-impregnated carbon fiber prepreg sheets that vertically overlapped each other had a higher bending strength and resistance than the circular pipes of the comparative example. The impact properties (impact maximum load, impact energy) were clearly improved. In addition, the vibration damping properties were greatly improved as compared with the circular pipes of Comparative Examples 1 and 2. The circular pipe having a circular cross section of Comparative Example 3 in which an application layer of an emulsion-shaped butyl rubber-based vibration damping paint was interposed between epoxy resin-impregnated carbon fiber prepreg sheets that vertically overlapped each other showed extremely good vibration damping properties, but had a high bending strength and The impact resistance (impact maximum load, impact energy) was extremely poor. From the above results, it was found that both the strength and the vibration damping property of the molded product can be improved by interposing the ionomer film between the epoxy resin-impregnated carbon fiber prepreg sheets that are vertically stacked.

(Embodiment 4) Length 1680 mm × 70 mm
Eight pieces of epoxy resin impregnated carbon fiber prepreg (T800: P2053-122) 5 manufactured by Toray Industries, Inc.
As shown in FIG. 5A, 66A nylon tube 22 covered with mandrel 21 was used.
Fiber direction is 0 °, 0 °, 30 °, 30
゜, 45 ゜, 45 ゜, 45 ゜, 45 よ う, and, for prepregs of 30 ゜ and 45 積 層, after laminating and winding so that the fiber direction intersects between adjacent prepregs, As shown in FIG. 5 (B), the mandrel 2
1 was pulled out to create a lay-up 52. Before laminating the carbon fiber prepreg impregnated with the epoxy resin, the first, third, fifth, and seventh prepregs from the inside had Zn on their outer surfaces that had a length of 1680 mm and a width of 70 mm. An ionomer ionomer film (Himilan 1652 (trade name), manufactured by Du Pont-Mitsui Co., Ltd.) was laminated after attaching the ionomer film 50.

Then, as shown in FIG. 6, the lay-up 52 is placed in the racket
Apply 7 kgf / cm ² air pressure to the nylon tube,
By heating at 150 ° C. for 40 minutes and molding, a tennis racket low frame was prepared. The yoke portion 54 was made of foamed polyurethane as a core material, and the core material was covered with a prepreg. The face area of the prepared low frame was 110 in ² , the weight was 190 g, and the balance was 360 mm.

Comparative Example 4 A tennis racket low frame having a weight of 194 g and a balance of 358 mm was prepared in the same manner as in Example 4 except that no ionomer film was interposed. The vibration damping rates of the tennis racket low frames of Example 4 and Comparative Example 4 manufactured as described above were measured by the method shown in FIG.

As shown in FIG. 7A, a racket frame 70 with a gut is hung with a string 71, and the frame is hit with an impact hammer 72, and the racket frame 70 is attached to a force pickup (not shown) attached to the impact hammer 72. While measuring a vibration input (force F), a vibration response (acceleration α) is measured by an acceleration pickup 73 fixed to a portion 4 cm from the grip end perpendicular to the frame surface, and these measured values (α / F) are calculated. The frequency is analyzed by a frequency analyzer (Dynamic Signal Analyzer HP3562A manufactured by Hewlett-Packard) 76 via the amplifiers 74 and 75, and the out-of-plane primary natural frequency and the out-of-plane secondary natural frequency are obtained by obtaining a transfer function in the frequency domain. I asked.

Then, the attenuation rate (ζ) was calculated by the following equations (1) and (2) based on FIG. 7 (B).

Ζ = (１ ／) × (△ ω / ω _n ) × 100 (1)

T ₀ = T _n / √2 (2)

In FIG. 7B and equations (1) and (2), ω
_n is the frequency of the resonance point, T ₀ is the width at T _n / √2,
T _n is the peak value of the resonance point.

The primary vibration damping rate (%) of the racket frame of the fourth embodiment is 0.649, and the secondary vibration damping rate (%) is 1.49.
409. On the other hand, the primary vibration damping rate (%) of the racket frame of Comparative Example 4 was 0.237, and the secondary vibration damping rate (%) was 0.438.

From the above results, it was confirmed that by shaping the ionomer film with the ionomer film interposed between the epoxy resin-impregnated carbon fiber prepreg sheets stacked vertically, the vibration damping property of the racket frame was significantly improved.

[0055]

As is apparent from the above description, according to the present invention, in a molded article of a fiber-reinforced plastic in which the matrix resin is an epoxy resin, at least a portion of the ionomer between the epoxy resin-impregnated reinforcing fiber layers which are vertically stacked. The interposition of the film increases the bonding force between the layers of epoxy resin-impregnated reinforced fibers that overlap vertically, making it less likely to shift in the shear direction, and occurs between the layers of epoxy resin-impregnated reinforced fibers that overlap vertically due to the elasticity of the ionomer film. Vibration caused by the shearing force can be effectively absorbed. Therefore, both the impact resistance and the vibration damping property of the molded product can be greatly improved, and a high-performance fiber-reinforced plastic molded product can be obtained. In particular, an ionomer film is adhered to one side of a prepreg sheet in which a reinforcing fiber is impregnated with an epoxy resin to form a composite sheet, the composite sheet is wound into a hollow pipe shape, and the epoxy resin is cured to form a hollow pipe molded product. Thereby, the ionomer film and the epoxy resin react efficiently, and the impact resistance and the vibration damping property of the molded product are further improved.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views showing a manufacturing process up to the creation of a lay-up of a fiber-reinforced plastic molded product (circular cross-section pipe) of Example 1 of the present invention.

FIG. 2 is a diagram showing a method for measuring the bending strength of a fiber-reinforced plastic molded product.

FIG. 3 is a diagram showing a method for measuring impact characteristics (impact maximum load and impact energy) of a fiber-reinforced plastic molded product.

FIG. 4 is a diagram showing a method for measuring a vibration damping rate of a fiber-reinforced plastic molded product.

FIGS. 5A to 5C are fiber-reinforced plastic molded products (tennis racket low frame) of Example 4 of the present invention.
FIG. 7 is a cross-sectional view showing a manufacturing process up to the creation of the lay-up.

6 is a perspective view showing a molding step of molding the lay-up shown in FIG. 5 into a racket low frame shape using a mold.

FIG. 7A is a diagram showing a method of measuring a vibration damping rate of a fiber-reinforced plastic molded product, and FIG. 7B is a graph showing a relationship between a frequency obtained by frequency analysis of a racket vibration input and a vibration stress and a transfer function. FIG.

FIG. 8 is a schematic diagram showing a relationship between a force in a twisting direction of a fiber-reinforced plastic hollow pipe molded product and a shearing force generated between resin-impregnated reinforcing fiber layers that overlap vertically.

FIG. 9 is a diagram illustrating components of a racket.

FIGS. 10A and 10B are diagrams showing a primary vibration mode and a secondary vibration mode in an out-of-plane direction of a racket frame.

[Explanation of symbols]

 21 Mandrel 22 66 Nylon tube 23A-23D Composite sheet 24 Lay-up 25 Overlap

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B29B 11/16 B29B 15/08-15/14 C08J 5/04-5/10 C08J 5 / 24 A63B 49/02-49/14 A63B 53/00-53/16

Claims (4)

(57) [Claims] 1. A fiber-reinforced plastic molded article in which a matrix resin is made of an epoxy resin, wherein an ionomer film is interposed at least partially between layers of the epoxy resin-impregnated reinforcing fibers which are vertically stacked. Plastic molded products. 2. The method according to claim 1, wherein the ionomer film is ethylene-
The fiber-reinforced plastic molded product according to claim 1, wherein the methacrylic acid copolymer is obtained by crosslinking between molecules of a metal ion. 3. The fiber-reinforced plastic molded article according to claim 1, wherein the glass transition temperature of the ionomer film is in the range of 0 to 60 ° C. 4. An ionomer film is attached to one side of a prepreg sheet in which a reinforcing fiber is impregnated with an epoxy resin to form a composite sheet, the composite sheet is wound into a hollow pipe shape, and the epoxy resin is cured to form a hollow pipe. The fiber-reinforced plastic molded product according to any one of claims 1 to 3, which is molded.