JP2012193469A - Fiber reinforcement sheet and method for producing the same, and fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a unidirectional reinforcement fiber sheet which has a structure excellent in resin impregnation in VaRTM molding in spite of having a heavy basis weight, has carbon fibers arranged with reduced crimps, and can be produced without using a weaving or knitting machine, or a multiaxial weaving machine.SOLUTION: A fiber reinforcement sheet with a basis weight of 600-1000 g/mincludes: a plurality of sheet-like objects each obtained by arranging in parallel a plurality of yarns 1 each of which is formed of a plurality of carbon fibers arranged in parallel and has a fineness within a certain range; a plurality of pairs of auxiliary yarns 3; and a plurality of weft yarns 2. The plurality of sheet-like objects are arranged in parallel with spaces between the sheet-like objects adjacent to each other. The weft yarns 2 are arranged in the direction intersecting the sheet-like objects, and the auxiliary yarns 3 are arranged in the spaces. The auxiliary yarns 3 are used as warp yarns to form a leno weave structure with the weft yarns, thereby integrally holding a group of the yarns 1 substantially without bending.

Description

  The present invention relates to a fiber-reinforced sheet using reinforcing fibers, a method for producing the same, and a fiber-reinforced composite material. More specifically, the present invention relates to RTM molding (resin injection) used in various applications in various industrial fields such as windmill blade applications and automobile applications. The present invention relates to a fiber reinforced sheet excellent in strength expression suitable for molding), a method for producing the same, and a fiber reinforced composite material.

  As a reinforcing material for a structure for earthwork, a seismic reinforcement method is known in which a fiber sheet-like material in which reinforcing fibers such as carbon fibers are arranged in one direction is impregnated with resin and adhered to the structure. This method is widely adopted because it has a high reinforcing effect and is excellent in durability, and is easy to reinforce. For example, Patent Documents 1 to 3 and the like are often used in woven fabrics and knitted fabrics using typical carbon fibers of a fiber sheet in which carbon fibers are arranged in one direction. On the other hand, as industrial applications that require higher strength than wind turbine blades, automobile applications, etc., for example, Patent Document 4 proposes multiaxial fabrics such as woven fabrics, woven fabrics, UD prepregs, and the like that have structurally less carbon fiber bending. Yes.

  However, a fabric such as the following Patent 1 is structurally formed by crossing warps and wefts. At this time, the carbon fibers arranged in the warp are crimped at the time of crossing with the weft. For this reason, it is already well known that the crimp concentrates stress and causes a decrease in strength properties as a reinforced fiber fabric. On the other hand, in order to solve these problems, a knitted or knitted fabric having a structure in which stress is not concentrated is proposed as in Patents 2 and 3 below. On the other hand, VaRTM molding or the like is often used in industrial applications such as windmill blades, and a multiaxial fabric sheet as shown in Patent 4 below has been proposed. In industrial applications, the weight of the fabric tends to be particularly high, so that the resin impregnation property and the multi-axis loom necessary for manufacturing the fabric require a very expensive capital investment.

  In general, a unidirectional fiber fabric is composed of carbon fibers for warps and auxiliary fibers having a fineness smaller than that of warps, and is a so-called plain weave structure in which warp yarns and weft yarns are repeatedly crossed. For this reason, stress is concentrated by bending at a place where the warp and the weft intersect, which causes a decrease in strength. This tendency naturally becomes stronger as the crimp angle is larger. Further, a woven fabric that suppresses these bendings as much as possible is provided. However, as long as it is a woven or knitted fabric, crossing is essential as long as it is finished into a sheet-like material, bending is inevitable, and mechanical properties are not unavoidably reduced. In addition, these fiber sheets require special machines such as looms and knitting machines.

Further, the composite material that can generally obtain the highest physical property is a so-called UD prepreg in which a unidirectional material in which carbon fibers are arranged in one direction is impregnated with a resin. The prepreg is difficult to fabricate in production, and the limit is 500 to 600 g / m ² . Therefore, at the time of the prepreg, the impregnation state of the resin is not perfect and is almost semi-impregnated, but depending on the molding method, a completely impregnated composite is finally obtained. However, since the prepreg is already impregnated with resin, the molding method is limited to AC molding, oven molding, etc., and is not suitable for RTM molding used in large-scale molding such as windmill applications. Woven, knitted and multiaxial fabrics are used.

However, when the basis weight of the fiber reinforced sheet is 600 g / m ² or more, the carbon fiber multifilament yarn used is also 32670 dtex or more, and the conventional unidirectional woven fabric such as Patent Document 1 is crimped by weft. Occurring, the straightness of the fiber is lacking, and the mechanical properties are clearly reduced. Further, even in the woven fabric of Patent Document 2 in which the stress is not concentrated, auxiliary yarns are arranged on both sides adjacent to the warp yarn, and the weft yarn and the auxiliary yarn are interlaced to form the woven fabric. However, since the auxiliary yarns are arranged, the process becomes very complicated.

  Furthermore, when trying to obtain by the methods of Patent Documents 1 and 2, since the fabric density is high, the gaps between the fibers are reduced as a whole, and naturally, the impregnation property of the resin is greatly influenced in the step of impregnating the resin. In order to prevent strength reduction, a fabric having a structure that eliminates stress concentration has been proposed. However, when such a structure is made thick, almost no voids are generated between the carbon fiber multifilament yarns, so that the impregnation property of the resin is deteriorated, and further, large irregularities are formed on the surface after molding.

Japanese Patent No. 3122295 Japanese Patent No. 3279049 JP 2008-7871 A JP 2007-182661 A

  The present invention has a structure with good resin impregnation even in the case of a thick fabric, has a good structure of resin impregnation, reduces the crimp of arranged carbon fibers, and can be produced without using a loom, a knitting machine or a multi-axis loom The purpose is to provide a sheet.

The first gist of the present invention is a fiber reinforced sheet having a basis weight of 600 to 1000 g / m ² ,
A plurality of carbon fibers arranged in parallel, and a yarn having a fineness within a range of 32670 to 65340 dtex;
A sheet-like product in which a plurality of the yarns are aligned in parallel;
A set of two auxiliary threads,
Each having a plurality of wefts,
A plurality of the sheet-like objects are arranged with a gap between the parallel and adjacent sheet-like objects,
The weft is arranged in a direction intersecting the sheet-like material,
The auxiliary yarn is arranged in the gap,
It is a fiber reinforced sheet that uses the auxiliary yarn as a warp, forms a woven structure entangled with the weft, and holds the yarn group integrally in a state having substantially no bending.
Moreover, the 2nd summary of this invention is the fiber reinforced composite material containing the said fiber reinforced sheet | seat and 30-70 mass% matrix resin.
Moreover, the third gist of the present invention is a yarn in which a plurality of carbon fibers are aligned in parallel, and the fineness is within the range of 32670 to 65340 dtex,
A plurality of the yarns are drawn in parallel to form a sheet,
Arranging a plurality of the sheet-like materials with a gap between the parallel and adjacent sheet-like materials,
Arrange the wefts in the direction intersecting the sheet-like material,
Arrange a set of two auxiliary yarns in the gap,
Using the auxiliary yarn as a warp, weaving and weaving with the weft to hold the group of yarns in a substantially unbent state to obtain a fiber reinforced sheet having a basis weight of 600 to 1000 g / m ^2. A method for producing a fiber-reinforced sheet.

  The fiber reinforced sheet of the present invention has a structure that allows good resin impregnation in VaRTM molding even when it is thick, and the carbon fiber is held in a substantially buckling-free state. Further, a unidirectional reinforcing fiber sheet can be produced without using a special loom, knitting machine or multi-axis loom. The fiber reinforced composite material using the reinforced fiber sheet thus obtained is a composite material suitable for a wide range of fields such as windmill applications and the like.

It is the schematic which shows an example of the fiber reinforcement sheet | seat of this invention. It is the schematic which shows the structure of the weft and auxiliary yarn of this invention.

  One of the points of the fabric structure of the present invention is to form a sheet-like material by arranging a plurality of yarns made of a plurality of carbon fibers arranged in parallel, and to provide a gap between the sheet-like materials. The resin impregnation speed is greatly influenced by the presence or absence of the gap. In general VaRTM molding, a plurality of materials such as woven fabrics are stacked, a peel ply and a resin diffusion medium are arranged and covered with a back material, and a resin is injected from the other while vacuum suctioning from one side. The basic resin flow is that the resin diffuses between the resin diffusion medium and the peel ply arranged on the upper surface, and at the same time, the resin gradually penetrates through the gaps in the yarn from the top to the bottom of the laminated material. Impregnate. That is, it is greatly influenced by the fabric structure. As the fiber voids shown in FIG. 1-a are larger and the number is larger, the impregnation property becomes better. However, when the gap exceeds 5 mm, the fiber holding portion of the molded plate has a large variation, and the resin becomes rich and unevenness in strength occurs. On the other hand, if the thickness is less than 0.5 mm, the penetration of the resin is poor and a long impregnation time is required. Therefore, the range of 0.5-5 mm is preferable, More preferably, 0.2-2 mm is favorable. The resin impregnation property is evaluated by the speed and time until the whole laminated material is impregnated.

  Next, a method of crossing warp and weft is described. In the present invention, a set of two auxiliary yarns that are thinner than the yarn are arranged in the gap of the yarn, and the weft and the two auxiliary yarns are entangled and interlaced by a structure. . As shown in FIG. 2, the entangled structure here refers to passing a weft thread between two sets of auxiliary yarns, and when passing the next weft yarn, each individual yarn constituting the auxiliary yarn is twisted once. And the weft thread is passed between the two threads and securely gripped. When a plain weave structure is used, the length of the weft in FIG. 1-b is about 10 to 15 times longer than that of the woven structure part of the present invention, and the weave structure is not restrained and difficult to be held in a straight line. The weft yarn becomes unstable before, causing a large meandering phenomenon. This is also affected by the pitch between the auxiliary yarns. The method of arranging the pitch for each yarn is most stable without meandering of the weft, but arranging a large number of auxiliary yarns becomes very complicated in the process, and the weight per unit becomes difficult.

  Therefore, in the present invention, in order to enable thickening, a plurality of yarns are arranged in parallel to form a sheet, and a gap is formed between the sheets to arrange the auxiliary yarn. The pitch of the auxiliary yarn is preferably arranged at an interval of 50 to 100 mm. Furthermore, the fineness of the auxiliary yarn is narrower than the yarn, preferably a yarn of 1100 dtex or less, and is not limited to glass fiber, aramid fiber, nylon fiber, polyester fiber or the like. Further, if the pitch of the weft exceeds 50 mm, the adjacent carbon fiber multifilament yarn is likely to spread because of the thickness, and the straightness of the fiber is impaired. The wefts are preferably alternately arranged in the longitudinal direction at a pitch in the range of 5 to 50 mm on the front and back surfaces of the yarn. It is preferable that a low melting point polymer is combined with the weft. Generally, a heat-bonding fiber is combined with the weft. The composite method is not particularly limited, such as drawing, twisting, and covering. The inserted weft is combined with the portion that contacts the yarn and the auxiliary yarn that intersects.

  Next, the manufacturing method of this invention is demonstrated. The present invention is usually manufactured by using a loom for manufacturing a warp woven fabric, and although not shown, the yarns arranged in the warp are supplied in a horizontal direction so as not to be unwound and twisted from the creel. The drawn yarn is successively passed through a guide and a nip roll that is actively supplied to a heald for moving the warp up and down and a kite for driving the weft. On the other hand, two entangled yarns (auxiliary yarns) arranged between sheet-like materials made of yarn are supplied from the creel, passed through a tension device different from the yarn, and then passed through a simple entanglement device installed on the heald. Passed to the pass. The gap between the sheet-like materials can be easily regulated by adjusting the space of the wings.

  Next, the weft yarns are usually arranged on the front and back surfaces of the sheet-like material by weaving with a plain weave of a rapier loom, and the gap portions are firmly held by two entangled yarns. Further, the wefts containing the fusion fibers are bonded by heating rolls arranged above and below the fabric, and then wound by a winding roll. Note that the bonding method may be bonding with a heating roll or a non-contact far infrared heater.

  Next, examples relating to the fiber reinforced sheet will be described below based on the above manufacturing method.

Hereinafter, the present invention will be described more specifically with reference to examples.
Threads made of carbon fiber (Mitsubishi Rayon Co., Ltd. Pyrofil, number of filaments: 50000) are arranged in parallel to form a sheet-like material and arranged in the warp direction so as to have a gap of 2 mm, and the gap is entangled. A glass fiber of 675 dtex (manufactured by Unitika Glass Fiber Co., Ltd.) was arranged as an auxiliary yarn for yarn, and the pitch of the auxiliary yarn was 50 mm. Further, a fiber reinforced sheet was obtained by weaving glass fiber (manufactured by Unitika Glass Fiber Co., Ltd.) and heat-bonding fiber (manufactured by Toray) as weft at a pitch of 25 mm. The yarns arranged in the warp direction of the obtained sheet have straightness, and the wefts are bonded and solidified at the intersections with the front and back surfaces of the yarn and the auxiliary yarns, and the sheet shape is as designed. It was a fiber reinforced sheet having a basis weight of 600 g / m ² with a gap between the objects.
Next, the obtained fiber reinforced sheet was cut into 300 × 300 mm, three sheets were laminated, VaRTM molding was performed, and the results of evaluating the resin impregnation property are shown in Table 1 below. In molding, an epoxy resin having a viscosity of 260 mPa · S was used as the resin.

<Comparative Example 1>
A warp woven fabric was woven in a plain weave with a basis weight of 600 g / m ² using the same yarn as in Example 1 as the warp, and using the same composite yarn of glass fiber and heat fusion fiber as the weft. The obtained woven fabric had almost no gaps between the yarns arranged in the warp direction, and some crimps were seen on the yarns by the wefts.
Table 1 below shows the results obtained by performing VaRTM molding on the knit fabric obtained in the same manner as in Example 1 and evaluating the resin impregnation property.

  As is apparent from the results shown in Table 1, the fiber-reinforced sheet of the present invention has a gap, so that the resin impregnation property is impregnated in less than half the time of the conventional woven fabric, and is very good. Show.

1 Yarn 2 Weft 3 Auxiliary Thread a Clearance b Weft continuation length

Claims (6)

A fiber reinforced sheet having a basis weight of 600 to 1000 g / m ² ,
A plurality of carbon fibers arranged in parallel, and a yarn having a fineness within a range of 32670 to 65340 dtex;
A sheet-like product in which a plurality of the yarns are aligned in parallel;
A set of two auxiliary threads,
Each having a plurality of wefts,
A plurality of the sheet-like objects are arranged with a gap between the parallel and adjacent sheet-like objects,
The weft is arranged in a direction intersecting the sheet-like material,
The auxiliary yarn is arranged in the gap,
A fiber-reinforced sheet comprising the auxiliary yarn as a warp, forming a woven structure entangled with the weft, and integrally holding the yarn group without substantially bending. The fiber-reinforced sheet according to claim 1, wherein the wefts are alternately arranged in the longitudinal direction on the front and back surfaces of the sheet-like material.   The fiber reinforced sheet according to claim 1 or 2, wherein a low melting point polymer is combined with the weft.   The fiber-reinforced sheet according to claim 3, wherein the weft and the sheet-like material and / or the auxiliary yarn are fused via the low melting point polymer.   A fiber-reinforced composite material comprising the fiber-reinforced sheet according to claim 1 and 30 to 70% by mass of a matrix resin. By arranging a plurality of carbon fibers in parallel, the yarn has a fineness within the range of 32670 to 65340 dtex,
A plurality of the yarns are drawn in parallel to form a sheet,
Arranging a plurality of the sheet-like materials with a gap between the parallel and adjacent sheet-like materials,
Arrange the wefts in the direction intersecting the sheet-like material,
Arrange a set of two auxiliary yarns in the gap,
Using the auxiliary yarn as a warp, weaving and weaving with the weft to hold the group of yarns in a substantially unbent state to obtain a fiber reinforced sheet having a basis weight of 600 to 1000 g / m ^2. The manufacturing method of a fiber reinforced sheet.

Images