JPH02133632A - Sewing yarn for forming preform material for reinforcing resin - Google Patents

Abstract

PURPOSE:To obtain a sewing yarn for FRP preform material having excellent endurance and reliability by using a carbon fiber multifilament based yarn as core yarn and winding and applying a thermoplastic multifilament yarn around the surface of the core yarn at a specific ratio based on total volume of the yarn. CONSTITUTION:A carbon fiber multifilament yarn and thermoplastic multifilament yarn are each used as a core yarn and coating yarn and the thermoplastic yarn is wound and applied around the surface of the core yarn at the ratio of surface area of 90% and the ratio of volume of 25-50% based on the total volume of yarn to form the sewing yarn. The sewing yarn is free from end breakage and fluffing in formation of preform material and thermal strain and thermal stress generated around or inside the sewing yarn are relaxed when molded to FRP and generation of thermal crack is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sewing thread used for forming a preform material used for molding fiber reinforced plastic (FRP).

(Prior Art) When molding FRP, carbon fiber fabric is often used as a reinforcing base material for resin. In that case, for example, as described in Japanese Patent Publication No. 62-27184@, woven fabrics may be laminated and sewn together with sewing thread to form a preform material. This not only saves the trouble of laminating fabrics during molding, but also improves the strength of the preform material, such as the interlaminar shear strength and delamination strength of the FRP, due to the sewing thread.

However, the sewing thread used to form such a carbon fiber preform material is glass fiber thread,
Organic fiber yarns such as polynisder fibers are sometimes used, but these have high water absorption, low heat resistance, poor adhesion to the FRP matrix resin, and are difficult to form into textiles. There are problems such as the large difference in thermal expansion between FRP and carbon fiber, which causes deterioration of FRP properties due to thermal cycle fatigue, and poor mechanical properties such as strength and elastic modulus. less carbon
ft multifilament yarn is said to be most preferred. However, when FRP is actually molded using carbon fiber multifilament yarn as a sewing thread and the cross section is observed under a microscope, thermal cracks are often found around and inside the sewing thread. The reason for this is that carbon fiber has a thermal turgor coefficient of almost zero, so when it is cooled to room temperature after molding, there is almost no contraction in the longitudinal direction of the sewing thread, whereas in the direction perpendicular to the longitudinal direction, It is presumed that this is because the thickness of the sewing thread tends to become smaller due to the influence of the resin, and shrinkage is not suppressed in the in-plane direction of the fabric in the lamination direction as well. As thermal cracks grow with fatigue,
FRP has poor durability.

In addition, carbon fiber is very brittle, so if multifilament thread is used as a suture thread in its original form, the
The reliability of the Glyph 4-me material and, by extension, the FRP cannot be easily improved because the single threads break or become fluffy due to the oversight.

(Problems to be Solved by the Invention) An object of the present invention is to solve the problems of conventional sewing threads made of multifilament threads of carbon fibers, and
A resin reinforcing plastic that not only makes it possible to use highly durable FRP with less risk of thermal cracks occurring around or inside the sewing threads, but also improves reliability. We provide sewing threads for forming renovation materials.

(Means for Solving the Problems) This invention to achieve the above object 1) uses a multifilament yarn of carbon fiber as a core yarn, and connects the core yarn to a multifilament yarn of thermoplastic fibers with a covered yarn consisting of a yarn. The covered yarn covers at least 90% of the surface of the core yarn and occupies 25 to 50% by volume of the entire core yarn, forming a preform material for resin reinforcement. It features sewing thread for

The sewing thread of this invention uses a carbon fiber multifilament thread as a core thread. Preferably, the tensile modulus is 23x 1
03 kg/mm2 or more, tensile strength is 30Qkg/mm
Use one that is 2 or more.

The core yarn has a fineness of about 300 to 3,600 denier. In addition, the single threads constituting the core thread should have a denier of 0.5 denier or less and a breaking elongation of 1.8% or more, in order to prevent single threads from breaking when sewing the laminate. Preferably.

Further, the core yarn may be untwisted or may have a light twist of about 15 tans per meter or less. However, the core yarn is 2 to 3 multifilament yarns with a first twist.
It may be a twisted yarn formed by real twisting.

Now, the core thread connected to - is wound and covered with a covering thread made of a multifilament thread of thermoplastic fiber. This covered thread remains as it is even after the FRP is molded, and acts to alleviate the thermal distortion and thermal stress that occurs around and inside the sewing thread when it is cooled after molding, and to prevent the above-mentioned thermal cracks in that part. It is something to do.

As mentioned above, the covered yarn remains in the FRP after molding, but it does not essentially become the matrix of the FRP, so it is important to reduce the quality properties such as heat resistance and water resistance of the FRP as much as possible. The melting point is 240'C or higher to prevent
The moisture content in the standard state of 0°C and 65% Rl-1 is 1.
Preferably, it consists of less than 0% thermoplastic polymer. In addition, the dry heat shrinkage rate at 100'C is 15%.
The following are preferred. Dry heat shrinkage rate is 15%
If the core yarn exceeds the 71-Lix resin during molding, the core yarn will be caulked due to shrinkage during molding, and the density of the single yarn will become denser, resulting in poor impregnation of the 71-Rix resin or stress concentration on the FRP (B). Specifically, polyester lli fibers, aromatic polyester fibers, polyether ether ketone II, borifuenylene sulfide 11li fibers, etc. can be used.

Further, it is preferable that the covered yarn has a single yarn diameter of 10 to 30 L1m and a fineness of about 50 to 150 denier. If the yarn is too thin, it is possible to cover the core yarn with a small amount, but the gaps between the single yarns become small, which may hinder the impregnation of the matrix resin during molding. On the other hand, if it is too thick, the impregnating property of the matrix resin will be improved, but the amount used will be too large, which may reduce the heat resistance of the FRP. The covered yarn may also be untwisted or may have a light twist of about 15 tangs or less per meter.

Covering the core yarn with the covering yarn is performed by winding the covering yarn around the core yarn in a Z twist, a J twist, and then an S twist. -Of course, it is not necessary to use both the Z twist and the S twist, and only one of them may be used.

However, the burr type 1 can reduce the displacement of the covered thread during suturing, and also prevents thermal cracks from forming around the core thread, which rarely occur. This is preferable because it allows you to Hey, when using 7 twist and S twist (71,
It is also possible to roughen the hyphae. In addition, when using Z twist and S twist 01, the cross section of the sewing thread becomes almost circular, but depending on the thickness, circular sewing thread increases the unevenness on the surface of the preform material, and when it is made into FRP, it becomes resin-rich. It is also preferable to flatten the dough using a hot roll, as this makes it easier to create the rounded parts. The flatness (thickness 7 width) is 0.3 to 0.
About 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%, it becomes impossible to alleviate the thermal strain and thermal stress generated in the resin around and inside the core yarn, and thermal cracks occur frequently. The more the instep of the covered thread is, the more complete prevention of thermal cracking becomes possible, but on the other hand, if the number of insteps is too large, the impregnating properties of the matrix resin will be poor, and the surroundings and internal parts of the thread may become difficult to absorb. Since the heat resistance will be greatly reduced in the above, it is necessary to limit the amount to 25 to 50% by volume.

Now, the sewing thread of the present invention is used to stitch together 14 pseudo-isotropically laminated carbon fibers, for example, woven fabrics, by, for example, single chainstitch to form a preform material. Preform materials can be used not only in plate form, but also in the form of
l'' type as described in Publication No.-23139, I
It is possible to adopt a girder shape such as a type, a T-shape, or any other arbitrary shape.

Then, this glyph 4-me material is impregnated with resin and molded using a normal molding method, such as a resin injection method, to form FRP.

Note that instead of impregnating the preform material with resin, it is also possible to use prepreg as the preform material.

(Embodiment) In FIG. 1, a core yarn 1 made of a multifilament yarn of carbon fiber is covered with a covering yarn 2 made of a multifilament type of thermoplastic fiber with a Z twist,
The sewing thread 4 is roughly wound and covered with a covering thread 3 made of a multifilament thread of thermoplastic fibers with an S twist.

The coating system 2.3 accounts for 25-50% by volume and covers at least 90% of the surface of the core yarn 1.

Figure 2 shows seven pseudo-isotropically laminated carbon fiber fabrics 5 to 1.
This figure shows a plate-shaped preform material made by sewing 1 with a single chain stitch using the sewing thread 4 shown in FIG.

FIG. 3 shows that a hat-shaped laminate consisting of carbon fiber fabrics 16 and 19 is placed on a plate-shaped laminate of carbon fiber fabrics 12 to 15, and these two laminates are connected to the sewing thread 4 shown in FIG. in!
It is made of preform material made by chain stitching. Such a preform material is suitable, for example, when molding FRP used as an air compensation panel or the like.

(Effects of the Invention) The sewing thread of the present invention is made by using a multifilamen l-based carbon fiber as a core thread, and winding and covering the core thread with a covering thread consisting of a thermoplastic fiber multifilamen thread. Since the covered yarn covers at least 90% of the surface of the core yarn and accounts for 25 to 50% by volume of the whole -C, it is used to form a preform material. When doing 1. Not only can it prevent single thread breakage and fuzzing of the sewing thread, but it can also alleviate the thermal stress that occurs around and inside the sewing thread when it is attached to FRP. , it is possible to suppress the occurrence of thermal cracks in that part, and it becomes possible to greatly improve the durability and reliability of FRP.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing one embodiment of the sewing thread of the present invention, and FIGS. 2 and 3 show different embodiments of preform materials formed using the sewing thread shown in FIG. 1 above. It is a V schematic perspective view which shows. 1: Core yarn 2: Covered yarn 3: Covered yarn 4: N yarn 5-19: Carbon fiber fabric

Claims (3)

[Claims] (1) A multifilament yarn made of carbon fiber is used as a core yarn, and the core yarn is wound and covered with a covered yarn made of a multifilament yarn made of thermoplastic fiber, and the covered yarn covers at least the surface of the core yarn. A sewing thread for forming a resin reinforcing preform material, which covers 90% of the material and occupies 25 to 50% by volume of the entire material. (2) A resin reinforcing preform material having the sewing thread according to claim (1). (3) A fiber-reinforced plastic comprising the preform material according to claim (2).