JP2764957B2 - Carbon fiber reinforced plastic - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a carbon fiber reinforced plastic formed of a proform material sewn with a sewing thread and having excellent durability and improved reliability. .

(Prior Art) When molding FRP, a carbon fiber fabric is often used as a substrate for reinforcing a resin. In this case, as described in, for example, Japanese Patent Publication No. 62-27184, woven fabrics are sometimes laminated and sewed together with sewing threads to form a preform material. This not only saves time and effort for laminating the woven fabric at the time of molding, but also improves the interlaminar strength, such as the interlaminar shear strength and the interlaminar peel strength, of the preform material and, by extension, the FRP.

However, as a sewing thread used for forming such a carbon fiber preform material, an organic fiber thread such as a glass fiber thread or a polyester fiber may be used, but these are not water absorbing. High heat resistance, low heat resistance, poor adhesion of the FRP to the matrix resin, too large thermal expansion difference with the carbon fibers that make up the woven fabric, leading to deterioration of FRP characteristics due to thermal cycle fatigue. In addition, there is a problem that the mechanical properties such as strength and elastic modulus are inferior. Therefore, it is most preferable to use a carbon fiber multifilament yarn having less concern. However, when an FRP is actually formed using a carbon fiber multifilament thread as a sewing thread and a cross section is observed with a microscope, thermal cracks often occur around and inside the sewing thread. The reason is that the carbon fiber has a coefficient of linear thermal expansion of almost zero, so when it is cooled to room temperature after molding, there is almost no shrinkage in the longitudinal direction of the sewing thread, whereas in the direction perpendicular to the longitudinal direction, the resin does not shrink. Because of the effect, the thread tries to reduce its thickness,
It is presumed that shrinkage is not suppressed as much as in the in-plane direction of the woven fabric in the laminating direction. Thus, thermal cracks grow with fatigue, making the FRP less durable.

Also, since carbon fiber is very brittle, if the multifilament yarn is used as it is as a sewing thread, a single thread breakage or fuzzing may occur due to rubbing at the time of suturing, and the reliability of the preform material and ultimately the FRP Does not improve easily.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above-mentioned problems of the conventional sewing thread composed of a multifilament yarn of carbon fiber,
It is made of a preform material that has a low risk of generating thermal cracks around and inside the sewing thread, and can not only obtain a highly durable FRP, but also improve reliability. To provide carbon fiber reinforced plastic.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method in which a multifilament yarn of carbon fiber is used as a core yarn, and the core yarn is wound with a covering yarn made of a multifilament yarn of a thermoplastic fiber. The coated yarn has a moisture content of 1.
0% or less, occupies 25-50% by volume of the whole, and
A carbon fiber reinforced plastic molded with a preform formed by sewing a plurality of laminated carbon fiber fabric substrates with a sewing thread in which the covering yarn covers at least 90% of the surface of the core yarn. Things.

The sewing thread used in the present invention has a multifilament thread of carbon fiber as a core thread. Preferably, the tensile modulus is
Use a material with 23 × 10 ³ kg / mm ² or more and tensile strength of 300 kg / mm ² or more.

The core yarn has a fineness of about 300 to 3600 denier. Further, the single yarn constituting the core yarn is preferably one having a denier of 0.5 denier or less and a breaking elongation of 1.8% or more in order to make it difficult for the single yarn to break when the laminate is sewn.

The core yarn may be untwisted or may have a light twist of about 15 turns or less per meter. However, the core yarn may be a ply-twisted yarn obtained by ply-twisting two or three multifilament yarns having a lower twist.

Now, the above-mentioned core yarn is wound and covered with a covering yarn composed of a multifilament yarn of a thermoplastic fiber. This coated thread remains as it is even after the molding of the FRP, acts to relieve the thermal strain and thermal stress that occurs around and inside the sewing thread during cooling after molding, and acts to prevent the above-described thermal cracks in that part. Is what you do.

The coated yarn remains in the FRP even after molding as described above, but since it is not essentially a matrix of the FRP, it is possible to reduce various properties such as heat resistance and water resistance of the FRP as much as possible. Melting point above 240 ℃, 20 ℃, 65
It is preferably made of a thermoplastic polymer having a water content of 1.0% or less in a standard condition of% RH. Also, 100
Those having a dry heat shrinkage at 15 ° C. of 15% or less are preferred. If the heat shrinkage exceeds 15%, use FRP
The core yarn is swaged by the shrinkage during molding of the resin, the density of the single yarn becomes dense, and the impregnating property of the matrix resin deteriorates.
It becomes easy to create defects that cause stress concentration in P. Specifically, polyester resin, wholly aromatic polyester fiber, polyetheretherketone fiber, polyphenylene sulfide fiber, and the like can be used.

The coated yarn has a single yarn diameter of 10 to 30 μm and a fineness of 50 to 50 μm.
Those having a density of about 150 denier are preferred. If it is too thin, the core yarn can be coated with a small amount, but the gap between the single yarns becomes small, and the impregnation of the matrix resin during molding may be hindered. On the other hand, when the thickness is too large, the impregnating property of the matrix resin is improved, but the amount used is too large and the heat resistance and the like of the FRP may be reduced.
In addition, even if the covering yarn is also untwisted,
It may have a light twist of about the turn or less.

The covering of the core yarn with the covering yarn is performed by winding the covering yarn by Z twist and further by S twist. However, it is not necessary to use both Z twist and S twist, and only one of them may be used. However, the combined use can reduce the displacement of the covering thread at the time of suturing, and can suppress the occurrence of a thermal crack around the core thread when it occurs. Is preferable. In addition, when Z twist and S twist are used together, it is also possible to form a braided covering yarn. When the Z twist and the S twist are used in combination, the cross section of the sewing thread becomes substantially circular, but the circular sewing thread increases the unevenness of the surface of the preform material depending on the thickness, and becomes resin-rich when made into FRP. It is also preferable to flatten it with a hot roll, because it makes it easier to make the part. The flatness (thickness / width) of about 0.3 to 0.6 is sufficient.

Now, the covering yarn must cover at least 90% of the surface of the core yarn. If the coverage is lower than 90%,
Thermal strain and thermal stress generated around and inside the core yarn cannot be reduced, and thermal cracks occur frequently. Thus, the more the amount of the covering thread, the more complete prevention of thermal cracks becomes possible, but if too much, on the other hand, the impregnating property of the matrix resin becomes extremely poor, Since heat resistance is greatly reduced, it is necessary to limit the heat resistance to 25 to 50% by volume.

The sewing thread used in the present invention is used to form a preform material by suturing a carbon fiber, for example, a laminate obtained by quasi-isotropically laminating a woven fabric by, for example, single-ring sewing. Preform materials include not only plate materials but also H-type and I-type as described in JP-B-62-23139.
The shape of the girder material such as a mold and a T-shape, and other arbitrary shapes can be adopted. Then, the preform material is impregnated with a resin by a normal molding method, for example, a resin injection method, and is molded to obtain FRP. Instead of impregnating the preform material with a resin, the preform material can be formed using a prepreg.

(Embodiment) In FIG. 1, a core yarn 1 composed of a multifilament yarn of a carbon fiber is first wound and covered with a coating yarn 2 composed of a multifilament yarn of a thermoplastic fiber by Z twisting.
Furthermore, a sewing thread 4 is formed by winding and covering with a coating thread 3 made of a multifilament thermoplastic fiber by S twist. The covering yarns 2 and 3 occupy 25 to 50% by volume and cover at least 90% of the surface of the core yarn 1.

FIG. 2 shows seven carbon fiber woven fabrics 5 to 5 which are quasi-isotropically laminated.
11 shows a plate-shaped preform material formed by single-ring sewing with the sewing thread 4 shown in FIG.

FIG. 3 shows a plate-like laminate of carbon fiber fabrics 12 to 15,
This is a preform material in which a hat-shaped laminate made of carbon fiber fabrics 16 to 19 is placed, and the two laminates are sewn in a single ring with the sewing thread 4 shown in FIG. Such preforms are used, for example, in FRPs used as aircraft panels, etc.
Suitable for molding.

(Effect of the Invention) The carbon fiber reinforced plastic of the present invention can reduce thermal strain and thermal stress generated around and inside the sewing thread by the thermoplastic fiber yarn wound around and coated around the carbon fiber,
The occurrence of thermal cracks can be prevented, and the covering yarn wound around and covered around the core yarn is a thermoplastic fiber yarn having a water content of 0.1% or less in a standard state. Even if it is in the preform,
Since the fiber yarn hardly absorbs moisture, when the preform is impregnated with a resin and molded at a high temperature, moisture does not generate voids due to vaporization and volume expansion, and a highly reliable CFRP can be obtained. .

 This effect has been successfully achieved.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an embodiment of a sewing thread used in the present invention, and FIGS. 2 and 3 show different forms of a sewing thread formed using the sewing thread shown in FIG. It is a schematic perspective view which shows a reforming material. 1: Core thread 2: Coated thread 3: Coated thread 4: Sewing thread 5 to 19: Carbon fiber fabric

──────────────────────────────────────────────────続 き Continued on the front page (58) Investigated field (Int.Cl. ⁶ , DB name) D02G 3/38 D02G 3/46 D02G 3/02 D02J 1/22 D04B 21/14 B29B 11/16 B22D 19 / 14 C08J 5/04

Claims (1)

(57) [Claims] 1. A multifilament yarn of carbon fiber is used as a core yarn, and the core yarn is wound and covered with a coating yarn of a multifilament yarn of a thermoplastic fiber. Is not more than 1.0%, occupies 25 to 50% by volume of the whole, and a plurality of carbon fiber fabric base materials are laminated by a sewing thread in which the coating yarn covers at least 90% of the surface of the core yarn. A carbon fiber reinforced plastic molded with a preform obtained by sewing.