JP6722471B2 - Carbon fiber sheet, composite material, and method for manufacturing composite material - Google Patents
Carbon fiber sheet, composite material, and method for manufacturing composite material Download PDFInfo
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Landscapes
- Reinforced Plastic Materials (AREA)
- Nonwoven Fabrics (AREA)
Description
本発明は、炭素繊維シート、複合材料及び複合材料の製造方法に関する。 The present invention relates to a carbon fiber sheet, a composite material, and a method for manufacturing the composite material.
繊維強化プラスチック（Ｆｉｂｅｒ Ｒｅｉｎｆｏｒｃｅｄ Ｐｌａｓｔｉｃ、ＦＲＰ）は、軽量かつ高強度の複合材料として、浴槽、小型船舶、自動車、鉄道車両等の材料として幅広く利用されている。近年では、炭素繊維を用いた複合材料である炭素繊維強化プラスチック（Ｃａｒｂｏｎ Ｆｉｂｅｒ Ｒｅｉｎｆｏｒｃｅｄ Ｐｌａｓｔｉｃ、ＣＦＲＰ）が、航空機、自動車等の軽量かつ高強度であることが特に要求される分野において注目され、更なる軽量化、高強度化（特に、高弾性化）を目的とした開発が進められている。 BACKGROUND OF THE INVENTION Fiber reinforced plastic (FRP) is widely used as a lightweight and high-strength composite material as a material for bathtubs, small boats, automobiles, railway vehicles, and the like. In recent years, carbon fiber reinforced plastics (CFRPs), which are composite materials using carbon fibers, have attracted attention in fields such as aircrafts and automobiles that are particularly required to be lightweight and have high strength. Development is underway for the purpose of weight reduction and higher strength (in particular, higher elasticity).
ＣＦＲＰのような複合材料の製造方法としては、例えば、あらかじめ炭素繊維基材に熱硬化性樹脂を含浸させたプリプレグとよばれる中間基材を複数枚積層し、オートクレーブとよばれる耐圧容器内で加圧及び加熱することで熱硬化性樹脂を硬化させる方法がある。この方法の場合、プリプレグとしては、連続した炭素繊維の束を織って作製したクロス材に、エポキシ樹脂を含浸したクロスプリプレグ又は連続した炭素繊維束を一方向に配列したＵＤ（Ｕｎｉ−Ｄｉｒｅｃｔｉｏｎ）材にエポキシ樹脂を含浸したＵＤプリプレグを用いることが多い。このようなプリプレグを用いて製造された複合材料は、高強度（特に、高弾性）であるため、航空機の部品等に用いられている。しかし、この方法は、複合材料を立体的な形状に成形しにくい、生産性が低くコストが高い等の問題がある。 As a method for producing a composite material such as CFRP, for example, a plurality of intermediate base materials called prepregs, which are carbon fiber base materials impregnated with a thermosetting resin in advance, are laminated and added in a pressure resistant container called an autoclave. There is a method of curing the thermosetting resin by applying pressure and heating. In the case of this method, as the prepreg, a cloth material made by weaving a bundle of continuous carbon fibers, a cloth prepreg impregnated with an epoxy resin, or a UD (Uni-Direction) material in which continuous carbon fiber bundles are arranged in one direction Often, a UD prepreg impregnated with an epoxy resin is used. A composite material manufactured using such a prepreg has high strength (particularly, high elasticity), and is therefore used for parts of aircraft. However, this method has problems that it is difficult to mold the composite material into a three-dimensional shape, productivity is low, and cost is high.
上記の方法よりも生産性が高く、コストを低減できる方法として、樹脂を含浸させていないクロス材又はＵＤ材を所望の形状の金型に入れ、そこに樹脂を流し込むＲＴＭ（Ｒｅｓｉｎ Ｔｒａｎｓｆｅｒ Ｍｏｌｄｉｎｇ）法という方法がある。しかし、連続した炭素繊維を用いたクロス材又はＵＤ材は形状追従性に劣り、立体的な形状の複合材料を作製しにくいという問題がある。 As a method having higher productivity and cost reduction than the above method, a RTM (resin transfer molding) method in which a cloth material or a UD material not impregnated with a resin is put into a mold having a desired shape and the resin is poured therein There is a method. However, a cloth material or a UD material using continuous carbon fibers is inferior in shape conformability, and there is a problem that it is difficult to manufacture a composite material having a three-dimensional shape.
炭素材料の形状追従性を向上させることを目的として、ある程度の長さに切断された不連続な炭素繊維を用いた不織布をＲＴＭ法の基材として用いる方法が開発されている。この方法によれば、連続した炭素繊維を用いたＣＦＲＰの製造方法よりも立体的な形状の複合材料を作製しやすい。一方、不連続な炭素繊維を用いた不織布は、クロス材又はＵＤ材に比べて強度に劣る傾向にある。そこで、不連続な炭素繊維を用いて作製される炭素繊維材料の強度をより向上させる方法として、特許文献１及び特許文献２に示されるような、不連続な繊維を概略同じ方向にそろえた繊維材料が提案されている。 For the purpose of improving the shape conformability of a carbon material, a method has been developed in which a non-woven fabric using discontinuous carbon fibers cut into a certain length is used as a base material for the RTM method. According to this method, it is easier to produce a three-dimensionally shaped composite material than in the method for producing CFRP using continuous carbon fibers. On the other hand, a non-woven fabric using discontinuous carbon fibers tends to be inferior in strength as compared with a cloth material or a UD material. Therefore, as a method of further improving the strength of a carbon fiber material produced by using discontinuous carbon fibers, fibers obtained by aligning discontinuous fibers in substantially the same direction as shown in Patent Document 1 and Patent Document 2 Materials have been proposed.
近年の複合材料の用途の拡大と多様化に伴い、複合材料に用いる炭素繊維材料にはいっそうの形状追従性の向上と、炭素繊維材料を用いて作製される複合材料の高強度化（特に高弾性化）とが求められている。
本発明は上記事情に鑑み、形状追従性に優れ、かつ強度に優れる複合材料を作製可能な炭素繊維シート、複合材料及び複合材料の製造方法を提供することを課題とする。
With the expansion and diversification of applications of composite materials in recent years, the carbon fiber material used for the composite material has further improved shape conformability, and the composite material produced using the carbon fiber material has high strength (especially high strength). Elasticization) is required.
In view of the above circumstances, it is an object of the present invention to provide a carbon fiber sheet, a composite material, and a method for manufacturing the composite material, which are capable of producing a composite material having excellent shape followability and strength.
上記課題を解決するための手段には、以下の実施態様が含まれる。
＜１＞一方向に配向した炭素繊維を含み、前記炭素繊維と、前記炭素繊維の表面に存在する有機物の総質量に占める有機物の割合が０質量％〜３質量％である、炭素繊維シート。
＜２＞前記炭素繊維の平均長さが２０ｍｍ〜１５０ｍｍである、＜１＞に記載の炭素繊維シート。
＜３＞さらに樹脂繊維を含む、＜１＞又は＜２＞に記載の炭素繊維シート。
＜４＞前記炭素繊維と前記樹脂繊維の合計質量中の前記炭素繊維の割合が２０質量％以上９９質量％未満である、＜３＞に記載の炭素繊維シート。
＜５＞前記樹脂繊維が熱可塑性樹脂の繊維を含む、＜３＞又は＜４＞に記載の炭素繊維シート。
＜６＞一方向に配向した実質的に有機物を有しない炭素繊維を含む炭素繊維シートと、樹脂と、を含む複合材料。
＜７＞前記樹脂は、炭素繊維シートに含まれる樹脂繊維に由来する樹脂を含む、＜６＞に記載の複合材料。
＜８＞＜１＞〜＜５＞のいずれか１項に記載の炭素繊維シートに対し、加圧及び加熱からなる群より選択される少なくとも１つを実施する工程を含む、複合材料の製造方法。
＜９＞前記炭素繊維シートに樹脂を含浸する工程をさらに含む、＜８＞に記載の複合材料の製造方法。
Means for solving the above problems include the following embodiments.
<1> A carbon fiber sheet containing unidirectionally oriented carbon fibers, wherein the proportion of the organic substances present in the carbon fibers and the organic substances present on the surface of the carbon fibers is 0% by mass to 3% by mass.
<2> The carbon fiber sheet according to <1>, wherein the carbon fibers have an average length of 20 mm to 150 mm.
<3> The carbon fiber sheet according to <1> or <2>, further including resin fibers.
<4> The carbon fiber sheet according to <3>, wherein the ratio of the carbon fibers in the total mass of the carbon fibers and the resin fibers is 20% by mass or more and less than 99% by mass.
<5> The carbon fiber sheet according to <3> or <4>, wherein the resin fibers include a thermoplastic resin fiber.
<6> A composite material containing a resin and a carbon fiber sheet containing carbon fibers that are oriented in one direction and substantially free of organic matter.
<7> The composite material according to <6>, wherein the resin includes a resin derived from resin fibers contained in a carbon fiber sheet.
<8> A method for producing a composite material, which includes a step of performing at least one selected from the group consisting of pressurization and heating on the carbon fiber sheet according to any one of <1> to <5>. ..
<9> The method for producing a composite material according to <8>, further including a step of impregnating the carbon fiber sheet with a resin.
本発明によれば、形状追従性に優れ、かつ強度に優れる複合材料を作製可能な炭素繊維シート、複合材料及び複合材料の製造方法が提供される。 According to the present invention, there are provided a carbon fiber sheet, a composite material, and a method for producing the composite material, which are capable of producing a composite material having excellent shape-following property and excellent strength.
以下、本発明を実施するための形態について詳細に説明する。但し、本発明は以下の実施形態に限定されるものではない。以下の実施形態において、その構成要素（要素ステップ等も含む）は、特に明示した場合を除き、必須ではない。数値及びその範囲についても同様であり、本発明を制限するものではない。
本明細書において「工程」との語には、他の工程から独立した工程に加え、他の工程と明確に区別できない場合であってもその工程の目的が達成されれば、当該工程も含まれる。
本明細書において「〜」を用いて示された数値範囲には、「〜」の前後に記載される数値がそれぞれ最小値及び最大値として含まれる。
本明細書中に段階的に記載されている数値範囲において、一つの数値範囲で記載された上限値又は下限値は、他の段階的な記載の数値範囲の上限値又は下限値に置き換えてもよい。また、本明細書中に記載されている数値範囲において、その数値範囲の上限値又は下限値は、実施例に示されている値に置き換えてもよい。
本明細書において組成物中の各成分の含有率は、組成物中に各成分に該当する物質が複数種存在する場合、特に断らない限り、組成物中に存在する当該複数種の物質の合計の含有率を意味する。
本明細書において組成物中の各成分の粒子径は、組成物中に各成分に該当する粒子が複数種存在する場合、特に断らない限り、組成物中に存在する当該複数種の粒子の混合物についての値を意味する。
本明細書において「層」との語には、当該層が存在する領域を観察したときに、当該領域の全体に形成されている場合に加え、当該領域の一部にのみ形成されている場合も含まれる。
本明細書において「積層」との語は、層を積み重ねることを示し、二以上の層が結合されていてもよく、二以上の層が着脱可能であってもよい。
本明細書において「炭素繊維シート」とは、炭素繊維シート（炭素繊維シートが他の部材を有する場合は、炭素繊維シートに相当する部分）の全質量に占める炭素繊維の割合が１０質量％以上であるシート状の物体を意味する。
Hereinafter, modes for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and does not limit the present invention.
In the present specification, the term “process” includes not only a process independent of other processes but also the process even if the process is not clearly distinguishable from other processes as long as the purpose of the process is achieved. Be done.
In the present specification, the numerical range indicated by using "to" includes the numerical values before and after "to" as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another stepwise described numerical range. Good. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present specification, the content rate of each component in the composition is the total of the plurality of types of substances present in the composition, unless a plurality of substances corresponding to each component are present in the composition. Means the content rate of.
In the present specification, the particle size of each component in the composition is a mixture of particles of the plurality of types present in the composition, unless a plurality of types of particles corresponding to each component are present in the composition, unless otherwise specified. Means a value for.
In the present specification, the term "layer" refers to a case where when a region in which the layer exists is observed, in addition to the case where it is formed in the entire region, it is formed in only a part of the region. Is also included.
As used herein, the term "laminate" refers to stacking layers, two or more layers may be joined together or two or more layers may be removable.
In the present specification, the “carbon fiber sheet” means that the proportion of carbon fibers in the total mass of the carbon fiber sheet (the portion corresponding to the carbon fiber sheet when the carbon fiber sheet has other members) is 10% by mass or more. Is a sheet-like object.
＜炭素繊維＞
本実施形態の炭素繊維シートは、一方向に配向した炭素繊維を含み、前記炭素繊維と、前記炭素繊維の表面に存在する有機物の総質量に占める有機物の割合が０質量％〜３質量％である。
<Carbon fiber>
The carbon fiber sheet of the present embodiment includes unidirectionally oriented carbon fibers, and the ratio of the carbon fibers to the total mass of the organic substances existing on the surface of the carbon fibers is 0% by mass to 3% by mass. is there.
本実施形態の炭素繊維シートが形状追従性に優れている理由は明らかではないが、炭素繊維が一方向に配向していることにより、炭素繊維が縦横方向に配向している場合に比べて形状追従性に優れていることがひとつの要因として挙げられる。また、炭素繊維が実質的に有機物を有しておらず、集束体を形成せずに単繊維の状態で独立しているため、炭素繊維シートを作製する際に炭素繊維同士の絡み合いが抑制されて一方向に配向させやすいことが別の要因として挙げられる。 Although the reason why the carbon fiber sheet of the present embodiment is excellent in shape following property is not clear, since the carbon fibers are oriented in one direction, the shape of the carbon fibers is larger than that in the case where the carbon fibers are oriented in the vertical and horizontal directions. One of the factors is the excellent followability. In addition, since the carbon fibers are substantially free of organic matter and are independent in a single fiber state without forming a bundle, the entanglement of the carbon fibers is suppressed when producing the carbon fiber sheet. Another factor is that it is easily oriented in one direction.
本実施形態の炭素繊維シートが強度に優れる複合材料を作製可能である理由は明らかではないが、炭素繊維が一方向に配向していることにより、炭素繊維が特定の方向に配向していない場合に比べて強度（特に、炭素繊維の配向方向の曲げ弾性率）が得られやすいことがひとつの要因として挙げられる。また、炭素繊維の表面に存在する有機物の割合が０質量％〜３質量％であり、集束体を形成せずに単繊維の状態で独立しているため、複合材料を作製する際に炭素繊維間に樹脂が入り込みやすく、空隙が発生しにくいことが別の要因として挙げられる。 It is not clear why the carbon fiber sheet of the present embodiment can produce a composite material having excellent strength, but when the carbon fibers are oriented in one direction, the carbon fibers are not oriented in a specific direction. One of the factors is that the strength (in particular, the bending elastic modulus in the orientation direction of the carbon fibers) can be easily obtained as compared with the above. In addition, the proportion of organic substances existing on the surface of the carbon fiber is 0% by mass to 3% by mass, and the carbon fiber is independent in a single fiber state without forming a bundle. Another factor is that the resin easily enters between them and voids are less likely to occur.
本明細書において炭素繊維シートが「一方向に配向した炭素繊維を含む」とは、炭素繊維シート中の炭素繊維が配向している方向（縦方向）と、これと直交する方向（横方向）との、引張り強度の比（炭素繊維シートの縦方向の引張り強度／炭素繊維シートの横方向の引張り強度）が４以上であることを意味する。引張り強度は、例えば、炭素繊維シートから幅（横方向の長さ）１０ｍｍ、厚さ２．５ｍｍ程度、長さ（縦方向の長さ）８０ｍｍの大きさの試験片を１０枚作製し、１枚ずつ引張試験装置（例えば、株式会社島津製作所、商品名「ＡＵＴＯＧＲＡＰＨ ＡＧ−Ｘ １ｋＮ」）を用いて、２０ｍｍのチャック間距離、５ｍｍ／ｍｉｎの引張り速度で引っ張りながら測定し、１０枚の試験片から得られた引張り強度の数平均値を求めることで測定できる。 In the present specification, the carbon fiber sheet “includes carbon fibers oriented in one direction” means a direction in which the carbon fibers in the carbon fiber sheet are oriented (longitudinal direction) and a direction orthogonal thereto (horizontal direction). Means that the ratio of tensile strength (longitudinal tensile strength of carbon fiber sheet/lateral tensile strength of carbon fiber sheet) is 4 or more. Tensile strength is, for example, 10 pieces of a test piece having a width (horizontal length) of 10 mm, a thickness of about 2.5 mm and a length (longitudinal length) of 80 mm are prepared from a carbon fiber sheet, and 1 Using a tensile tester (for example, Shimadzu Corporation, trade name "AUTOGRAPH AG-X 1kN") one by one, measurement is performed while pulling at a distance between chucks of 20 mm and a pulling speed of 5 mm/min, and 10 test pieces. It can be measured by obtaining the number average value of the tensile strength obtained from
複合材料の強度向上の観点からは、上記測定で得られる「引張り強度の比」は、５以上であることが好ましく、７以上であることがより好ましく、８以上であることが更に好ましい。本明細書において炭素繊維が配向している方向（縦方向）は、図１の矢印で示す方向を意味する。なお、本明細書にて述べる「一方向に配向した状態」は、上述した引張り強度の比によって定義されるものであり、全ての炭素繊維が一方向に配向した状態であることを意味するものではない。 From the viewpoint of improving the strength of the composite material, the “ratio of tensile strengths” obtained by the above measurement is preferably 5 or more, more preferably 7 or more, and further preferably 8 or more. In the present specification, the direction in which the carbon fibers are oriented (longitudinal direction) means the direction indicated by the arrow in FIG. The "unidirectionally oriented state" described in the present specification is defined by the above-described tensile strength ratio, and means that all carbon fibers are unidirectionally oriented. is not.
本実施形態の炭素繊維シートに含まれる炭素繊維は、炭素繊維と、炭素繊維の表面に存在する有機物の総質量に占める有機物の割合が０質量％〜３質量％である（以下、「実質的に有機物を有しない」ともいう）。有機物の割合は、例えば、炭素繊維を１００℃で２０分間の条件で乾燥し、次いでマッフル炉（例えば、ヤマト科学株式会社の商品名「ＦＰ３１１」）にて、５００℃で４５分の条件で空気中で熱処理し、熱処理前後の質量の減少分から算出することができる。具体的には「（熱処理前の質量−熱処理後の質量）／熱処理前の質量×１００％」の式によって計算される値を有機物の割合とする。有機物の割合は、２．５質量％以下であることが好ましく、２質量％以下であることがより好ましい。 As for the carbon fibers contained in the carbon fiber sheet of the present embodiment, the proportion of the carbon fibers and the organic substances in the total mass of the organic substances present on the surface of the carbon fibers is 0% by mass to 3% by mass (hereinafter, “substantially It also has no organic matter."). The ratio of the organic matter is, for example, drying the carbon fiber at 100° C. for 20 minutes, and then airing at 500° C. for 45 minutes in a muffle furnace (for example, Yamato Scientific Co., Ltd.'s trade name “FP311”). It can be calculated from the amount of decrease in mass before and after heat treatment. Specifically, the value calculated by the formula “(mass before heat treatment−mass after heat treatment)/mass before heat treatment×100%” is taken as the ratio of organic substances. The proportion of the organic substance is preferably 2.5% by mass or less, and more preferably 2% by mass or less.
炭素繊維が実質的に有機物を有しないか否かを確認するための別の方法としては、炭素繊維が集束体を形成しているか否かを調べる方法が挙げられる。すなわち、炭素繊維は通常、複数の単繊維（フィラメント）が集まって集束体(ストランド）を形成した状態で製造され、集束体を形成した状態を維持するために樹脂等の有機物が付着している。従って、炭素繊維が集束体を形成していない場合は、炭素繊維に付着していた有機物が除去された等の理由により、実質的に有機物を有しない状態であると判断できる。炭素繊維シート中の炭素繊維が集束体を形成しているか否かは、例えば、光学顕微鏡等を用いて調べることができる。 As another method for confirming whether or not the carbon fibers have substantially no organic substance, there is a method for examining whether or not the carbon fibers form a bundle. That is, carbon fibers are usually manufactured in a state in which a plurality of single fibers (filaments) are gathered to form a bundle (strand), and an organic substance such as a resin is attached to maintain the state in which the bundle is formed. .. Therefore, when the carbon fibers do not form a bundle, it can be determined that the carbon fibers are substantially free of organic substances because the organic substances attached to the carbon fibers have been removed. Whether or not the carbon fibers in the carbon fiber sheet form a bundle can be examined using, for example, an optical microscope.
本明細書において炭素繊維が「集束体を形成していない」とは、炭素繊維が集束体を形成せず、独立した単繊維として存在していることを意味する。「集束体を形成していない炭素繊維」には、まったく集束体を形成していない炭素繊維と、部分的に集束体を形成していない炭素繊維の両方が含まれる。 In the present specification, "the carbon fiber does not form a bundle" means that the carbon fiber does not form a bundle and exists as an independent single fiber. "Carbon fibers that do not form a bundle" include both carbon fibers that do not form a bundle at all and carbon fibers that partially form a bundle.
集束体を形成していない炭素繊維を用いて作製される炭素繊維シートは、加圧熱プレス、樹脂含浸等の工程において任意の形状に成形する際の形状追従性に優れる。また、樹脂中への炭素繊維の分散性が向上するため、得られる複合材料の強度のバラつきが抑制される傾向にある。また、炭素繊維シートが後述する樹脂繊維をさらに含む場合、樹脂繊維と混合した際のバラつきが抑制され、得られる複合材料中での樹脂繊維の分布のバラつきが抑制され、得られる複合材料の強度のバラつきが抑制される傾向にある。 A carbon fiber sheet produced by using carbon fibers that do not form a bundle has excellent shape-following properties when it is formed into an arbitrary shape in a process such as pressure hot pressing and resin impregnation. Further, since the dispersibility of the carbon fiber in the resin is improved, the strength variation of the obtained composite material tends to be suppressed. Further, when the carbon fiber sheet further contains a resin fiber described below, variation when mixed with the resin fiber is suppressed, variation in the distribution of the resin fiber in the resulting composite material is suppressed, the strength of the resulting composite material Variation tends to be suppressed.
炭素繊維シートの形状追従性の観点からは、炭素繊維が不連続であることが好ましい。本明細書において炭素繊維が「不連続である」とは、炭素繊維がある程度の長さ（一定であっても一定でなくてもよい）に切断（破断を含む）された状態であることを意味する。炭素繊維の長さは特に制限されないが、例えば、１５０ｍｍ以下であることが好ましい。炭素繊維の平均長さは、炭素繊維又は炭素繊維シートから任意の１００本を選択し、測定した長さの数平均値として得られる。 From the viewpoint of the shape conformability of the carbon fiber sheet, the carbon fibers are preferably discontinuous. In the present specification, the term “discontinuous” means that the carbon fiber is in a state in which the carbon fiber is cut (including break) into a certain length (which may or may not be constant). means. The length of the carbon fiber is not particularly limited, but is preferably 150 mm or less, for example. The average length of the carbon fibers is obtained as a number average value of the lengths measured by selecting any 100 carbon fibers or carbon fiber sheets.
複合材料の強度向上の観点からは、炭素繊維の平均長さは２０ｍｍ以上であることが好ましい。また、炭素繊維シートの形状追従性の観点からは、炭素繊維の平均長さは１５０ｍｍ以下であることが好ましい。炭素繊維の平均長さは、３０ｍｍ〜１００ｍｍであることがより好ましく、３５ｍｍ〜８０ｍｍであることが更に好ましい。 From the viewpoint of improving the strength of the composite material, the average length of the carbon fibers is preferably 20 mm or more. Further, from the viewpoint of the shape following property of the carbon fiber sheet, the average length of the carbon fibers is preferably 150 mm or less. The average length of the carbon fibers is more preferably 30 mm to 100 mm, further preferably 35 mm to 80 mm.
複合材料の場所による強度のムラを抑制するする観点からは、炭素繊維の個々の長さが概ねそろっていることが好ましい。具体的には、例えば、炭素繊維又は炭素繊維シートから選択した任意の１００本の炭素繊維の長さの測定値のうち最大値と最小値が、平均長さ±２０％の範囲内であることが好ましく、平均長さ±１０％の範囲内であることがより好ましい。 From the viewpoint of suppressing the unevenness of strength depending on the location of the composite material, it is preferable that the individual lengths of the carbon fibers are substantially the same. Specifically, for example, the maximum value and the minimum value of the measured values of the length of any 100 carbon fibers selected from the carbon fibers or the carbon fiber sheets are within the range of the average length ±20%. Is preferred, and it is more preferred that the average length is within ±10%.
炭素繊維の材質は特に制限されず、ポリアクリロニトリル（ＰＡＮ）を原料とする炭素繊維、異方性ピッチ、等方性ピッチ等のピッチを原料とする炭素繊維などが挙げられる。中でも、ＰＡＮを原料とする炭素繊維は、繊維径のバラつきが少なく、炭素繊維を切断したときの長さをそろえやすく、カード等で梳られても比較的しなやかで折れにくいことから、炭素繊維が配向した状態のシートを作製しやすい傾向にある。炭素繊維は１種のみであっても、２種以上であってもよい。 The material of the carbon fibers is not particularly limited, and examples thereof include carbon fibers made of polyacrylonitrile (PAN) as a raw material, carbon fibers made of pitch such as anisotropic pitch, isotropic pitch, and the like. Among them, the carbon fiber made from PAN has a small variation in the fiber diameter, the length when the carbon fiber is cut is easily aligned, and the carbon fiber is relatively flexible and difficult to break even if it is carded with a card or the like. It tends to be easy to produce an oriented sheet. The carbon fiber may be only one kind or two or more kinds.
炭素繊維の太さは特に制限されず、得られる複合材料の用途等に応じて選択できる。例えば、単繊維の状態での太さが３μｍ〜１０μｍの範囲内であってもよく、４μｍ〜８μｍの範囲内であることが好ましい。 The thickness of the carbon fiber is not particularly limited and can be selected according to the application of the obtained composite material. For example, the thickness of the single fiber may be in the range of 3 μm to 10 μm, and is preferably in the range of 4 μm to 8 μm.
実質的に有機物を有しない炭素繊維の具体例としては、有機物で表面処理された炭素繊維であって、炭素繊維と、当該炭素繊維に付着している有機物の総質量の３質量％以下である炭素繊維が挙げられる。あるいは、廃材となった複合材料の再生処理工程において樹脂から分離した炭素繊維であって、樹脂の付着量が炭素繊維と、当該炭素繊維に付着している樹脂の総質量の３質量％以下である炭素繊維が挙げられる。 A specific example of the carbon fiber having substantially no organic substance is a carbon fiber surface-treated with an organic substance, which is 3% by mass or less of the total mass of the carbon fiber and the organic substance attached to the carbon fiber. Carbon fiber may be used. Alternatively, when the carbon fibers are separated from the resin in the step of recycling the waste composite material and the amount of the resin adhered is 3% by mass or less of the total mass of the carbon fibers and the resin adhered to the carbon fibers. There is a carbon fiber.
通常、工業的に製造される炭素繊維には、複合材料としたときに炭素繊維と接触するマトリックス樹脂に対する接着性の向上を目的とする接着性向上剤、単繊維が集束した状態の維持及び取り扱い性の向上を目的とするサイジング剤等の有機物を含む表面処理剤が付着している。表面処理剤が付着している炭素繊維としては、例えば、東レ（株）製、商品名「Ｔ７００」等が挙げられる。 Usually, industrially produced carbon fibers include an adhesion improver for the purpose of improving the adhesion to the matrix resin that comes into contact with the carbon fibers when it is made into a composite material, and maintenance and handling of single fibers in a bundled state. A surface treatment agent containing an organic substance such as a sizing agent for the purpose of improving the property is attached. Examples of the carbon fiber to which the surface treatment agent is attached include Toray Co., Ltd., trade name “T700”, and the like.
炭素繊維の表面処理に用いられる接着性向上剤としては、例えば、各種油剤が挙げられる。サイジング剤としては、例えば、脂肪族エポキシ化合物、芳香族エポキシ化合物（ポリアルキレングリコールのエポキシ付加物、ビスフェノールＡのジグリシジルエーテル、ビスフェノールＡのポリアルキレンオキサイド付加物、ビスフェノールＡのポリアルキレンオキサイド付加物にエポキシ基を付加した化合物等）等が挙げられる。 Examples of the adhesion improver used for the surface treatment of carbon fibers include various oil agents. Examples of the sizing agent include aliphatic epoxy compounds, aromatic epoxy compounds (epoxy adducts of polyalkylene glycol, diglycidyl ether of bisphenol A, polyalkylene oxide adducts of bisphenol A, polyalkylene oxide adducts of bisphenol A). Examples thereof include compounds having an epoxy group added thereto.
例えば、炭素繊維の表面にエポキシ化合物を含むサイジング剤が付着している場合、この炭素繊維はエポキシ樹脂との密着性には優れるが、その他の樹脂（例えば、ポリプロピレン、ポリエチレンテレフタレート、ナイロン６、ナイロン６６、ポリカーボネート、ポリスチレン等）との密着性には劣ると考えられる。そのため、サイジング剤が実質的に付着していない炭素繊維の方が、サイジング剤が付着している炭素繊維に比べ、複合材料を成形した際に、溶融した樹脂に対する良好な密着性が得られると考えられる。 For example, when a sizing agent containing an epoxy compound is attached to the surface of carbon fiber, the carbon fiber has excellent adhesion to an epoxy resin, but other resins (for example, polypropylene, polyethylene terephthalate, nylon 6, nylon) 66, polycarbonate, polystyrene, etc.). Therefore, the carbon fiber to which the sizing agent is not substantially attached is better than the carbon fiber to which the sizing agent is attached, when the composite material is molded, good adhesion to the molten resin is obtained. Conceivable.
さらに、有機物で表面処理された状態の炭素繊維は、多数の単繊維が集合して会合状態、束状態、強固に結合した状態等で存在する。このため、炭素繊維シートを作製する際にカード機（梳綿（「そめん」又は「りゅうめん」）機）、ギル機（繊維を櫛で梳り、繊維方向が揃った綿状の塊にする機械）、練条機（ローラーでドラフトをかけ、方向性を向上させる機械）等での取扱いが難しく、単繊維の状態になっていないため一方向に配向させにくい傾向にある。 Further, the carbon fibers surface-treated with an organic substance are present in a state in which a large number of single fibers are aggregated to be in an association state, a bundle state, a tightly bound state, or the like. For this reason, when making carbon fiber sheets, a card machine (carding (“somen” or “ryumen”) machine), gil machine (combing the fibers with a comb, and forming a cotton-like lump with aligned fiber directions) Machine), a drawing machine (a machine for drafting with a roller to improve the directionality), and the like, and it tends to be difficult to orient in one direction because it is not in a single fiber state.
さらに、炭素繊維シートが炭素繊維に加えて樹脂繊維を含む場合、炭素繊維が集束体を形成した状態であると、樹脂繊維と炭素繊維の混合状態にバラつきが生じやすく、樹脂繊維と炭素繊維の一本一本とが接触する面積が減少する傾向にある。この場合、複合材料の作製の際に樹脂斑、空隙等が形成されやすく、複合材料の機械特性等の物性が低下する傾向にある。 Furthermore, when the carbon fiber sheet contains resin fibers in addition to carbon fibers, if the carbon fibers are in the state of forming a bundle, the mixed state of the resin fibers and the carbon fibers is likely to vary, The area of contact with each other tends to decrease. In this case, resin unevenness, voids and the like are likely to be formed during production of the composite material, and physical properties such as mechanical properties of the composite material tend to be deteriorated.
実質的に有機物を有しない炭素繊維は、例えば、有機物が付着している炭素繊維から当該有機物を除去することによって得ることができる。炭素繊維から有機物を除去する方法としては、有機物が付着している炭素繊維又は当該炭素繊維を含む複合材料を、有機溶媒とアルカリ金属化合物、金属水酸化物等の分解触媒で処理して有機物を除去する方法（例えば、特開２００１−１７２４２６号公報参照）、有機物が付着している炭素繊維又は当該炭素繊維を含む複合材料を、有機物が分解する温度で熱処理して有機物を除去する方法（例えば、特開２０１３−２３７７１６号公報を参照）等が挙げられる。 The carbon fiber having substantially no organic substance can be obtained, for example, by removing the organic substance from the carbon fiber to which the organic substance is attached. As a method for removing organic matter from carbon fiber, carbon fiber to which organic matter is attached or a composite material containing the carbon fiber is treated with a decomposition catalyst such as an organic solvent and an alkali metal compound or a metal hydroxide to remove the organic matter. A method of removing (for example, Japanese Patent Laid-Open No. 2001-172426), a method of heat treating a carbon fiber to which an organic substance is adhered or a composite material containing the carbon fiber at a temperature at which the organic substance is decomposed (for example, , Japanese Patent Laid-Open No. 2013-237716) and the like.
炭素繊維の損傷を少なくできる、有機物の残存量を少なくできる、単繊維が独立した状態を得やすい等の観点からは、有機溶媒と分解触媒を用いて有機物を除去する方法が好ましい。実質的に有機物を有しない炭素繊維の作製コストの観点からは、廃材となった複合材料からマトリックス樹脂等の有機物を上記の方法で除去して、炭素繊維を得る方法が好ましい。 From the viewpoints of reducing damage to the carbon fibers, reducing the amount of organic matter remaining, and easily obtaining a state in which the single fibers are independent, a method of removing the organic matter using an organic solvent and a decomposition catalyst is preferable. From the viewpoint of the production cost of carbon fiber substantially free of organic matter, a method of obtaining carbon fiber by removing organic matter such as matrix resin from the waste composite material by the above method is preferable.
炭素繊維シートは、樹脂繊維をさらに含んでもよい。樹脂繊維をさらに含むことで、炭素繊維シートの取り扱い性と形状追従性がより向上する傾向にある。これは、樹脂繊維が炭素繊維とよく絡み、炭素繊維シートの形状が保持されやすくなるためと考えられる。炭素繊維シートが樹脂繊維を含む場合、炭素繊維シート中の樹脂繊維は、炭素繊維が有する「有機物」には該当しないものとする。 The carbon fiber sheet may further include resin fibers. By further containing the resin fiber, the handling property and the shape following property of the carbon fiber sheet tend to be further improved. It is considered that this is because the resin fibers are often entangled with the carbon fibers and the shape of the carbon fiber sheet is easily maintained. When the carbon fiber sheet contains resin fibers, the resin fibers in the carbon fiber sheet do not correspond to “organic substances” included in the carbon fibers.
炭素繊維シートが樹脂繊維を含む場合、樹脂繊維によって複合材料のマトリックス樹脂を形成してもよい。例えば、樹脂繊維として熱可塑性樹脂を用い、成形工程における加熱及び加圧により樹脂繊維を溶融させることにより、複合材料を作製してもよい。この場合は、成形工程で樹脂含浸を行う必要がないため、簡便な手法で複合材料を作製することができる。 When the carbon fiber sheet contains resin fibers, the resin may form the matrix resin of the composite material. For example, a thermoplastic resin may be used as the resin fiber, and the composite material may be produced by melting the resin fiber by heating and pressurizing in the molding step. In this case, since it is not necessary to impregnate the resin in the molding step, the composite material can be manufactured by a simple method.
樹脂繊維の材質は特に制限されず、炭素シート又は複合材料の作製条件等に応じて選択できる。例えば、熱可塑性樹脂、熱硬化性樹脂等の合成繊維及びレーヨン等の再生繊維が挙げられる。炭素繊維シートの取り扱い性と形状追従性の観点からは、樹脂繊維の材質は熱可塑性樹脂であることが好ましい。熱可塑性樹脂としては、ポリプロピレン等のポリオレフィン、ポリエチレンテレフタレート等のポリエステル、ナイロン６、ナイロン６６等のポリアミド、ポリカーボネート、ポリスチレンなどが挙げられる。樹脂繊維は１種のみであっても、２種以上であってもよい。 The material of the resin fiber is not particularly limited and can be selected according to the production conditions of the carbon sheet or the composite material. Examples thereof include synthetic fibers such as thermoplastic resins and thermosetting resins, and regenerated fibers such as rayon. From the viewpoints of handleability and shape conformability of the carbon fiber sheet, the material of the resin fiber is preferably a thermoplastic resin. Examples of the thermoplastic resin include polyolefin such as polypropylene, polyester such as polyethylene terephthalate, polyamide such as nylon 6 and nylon 66, polycarbonate, polystyrene and the like. The resin fiber may be only one kind or two or more kinds.
炭素繊維シートが樹脂繊維を含む場合、炭素繊維と樹脂繊維の合計質量中の炭素繊維の割合（炭素繊維の質量／（炭素繊維の質量＋樹脂繊維の質量）×１００）は、２０質量％以上９９質量％未満であることが好ましい。 When the carbon fiber sheet contains a resin fiber, the ratio of the carbon fiber in the total mass of the carbon fiber and the resin fiber (mass of carbon fiber/(mass of carbon fiber+mass of resin fiber)×100) is 20% by mass or more. It is preferably less than 99% by mass.
炭素繊維の割合が２０質量％以上であると、複合材料としたときの充分な強度が得られる傾向にあり、炭素繊維の割合が９９質量％未満であると、炭素繊維シートの取り扱い性と形状追従性の向上効果が充分に得られる傾向にある。炭素繊維の割合は、３０質量％以上９０質量％未満であることがより好ましく、３３質量％以上８０質量％未満であることがさらに好ましい。 When the proportion of carbon fibers is 20% by mass or more, a sufficient strength as a composite material tends to be obtained, and when the proportion of carbon fibers is less than 99% by mass, the handleability and shape of the carbon fiber sheet are improved. There is a tendency that the effect of improving the followability is sufficiently obtained. The proportion of carbon fibers is more preferably 30% by mass or more and less than 90% by mass, and further preferably 33% by mass or more and less than 80% by mass.
炭素繊維シートが樹脂繊維を含む場合、樹脂繊維の長さは特に制限されない。炭素繊維シートの作製のしやすさの観点からは、樹脂繊維の平均長さは２０ｍｍ〜１５０ｍｍの範囲内であることが好ましく、３０ｍｍ〜１００ｍｍの範囲内であることがより好ましい。樹脂繊維の平均長さは、樹脂繊維又は樹脂繊維を含む炭素繊維シートから任意の１００本を選択し、測定した長さの数平均値として得られる。 When the carbon fiber sheet contains resin fibers, the length of the resin fibers is not particularly limited. From the viewpoint of easy production of the carbon fiber sheet, the average length of the resin fibers is preferably in the range of 20 mm to 150 mm, more preferably in the range of 30 mm to 100 mm. The average length of the resin fibers is obtained as a number average value of the lengths measured by selecting any 100 fibers from the resin fibers or the carbon fiber sheets containing the resin fibers.
炭素繊維シートが樹脂繊維を含む場合、樹脂繊維の長さは特に制限されない。炭素繊維シートの作製のしやすさの観点からは、樹脂繊維の太さは０．１ｄｔｅｘ〜１０ｄｔｅｘの範囲内であってもよく、１ｄｔｅｘ〜７ｄｔｅｘの範囲内であることが好ましい。 When the carbon fiber sheet contains resin fibers, the length of the resin fibers is not particularly limited. From the viewpoint of easy production of the carbon fiber sheet, the thickness of the resin fiber may be in the range of 0.1 dtex to 10 dtex, and is preferably in the range of 1 dtex to 7 dtex.
炭素繊維シートの目付けは、特に制限されない。炭素繊維シートの取り扱い性及び形状追従性の観点からは、例えば、２ｇ／ｍ２〜５０００ｇ／ｍ２の範囲内であることが好ましい。 The basis weight of the carbon fiber sheet is not particularly limited. From the viewpoint of handling properties and conformality of the carbon fiber sheet, for example, it is preferably in the range of 2g / m 2 ~5000g / m 2 .
（炭素繊維シートの製造方法）
本実施形態の炭素繊維シートの製造方法の一例を以下に説明する。ただし、本実施形態の炭素繊維シートの製造方法はこれに制限されない。
(Method of manufacturing carbon fiber sheet)
An example of the method for manufacturing the carbon fiber sheet of this embodiment will be described below. However, the method for manufacturing the carbon fiber sheet of the present embodiment is not limited to this.
まず、実質的に有機物を有しない炭素繊維（以下、単に炭素繊維ともいう）をカード機等で開繊し、スライバーとよばれるやや配向した紐状の繊維集合体の篠状物を得る。樹脂繊維を加える場合は、炭素繊維とともに樹脂繊維をカード機に投入し、混綿及び開繊を行い、炭素繊維と樹脂繊維とが混合したスライバーを得る。なお、樹脂繊維を加える場合は、炭素繊維と樹脂繊維とができるだけ均一に混合されたスライバーとなっていることが好ましい。 First, carbon fibers having substantially no organic matter (hereinafter, also simply referred to as carbon fibers) are opened by a card machine or the like to obtain a slightly oriented string-shaped fiber aggregate called a sliver. In the case of adding resin fibers, the resin fibers are put into a card machine together with the carbon fibers, and mixed and opened to obtain a sliver in which the carbon fibers and the resin fibers are mixed. When the resin fiber is added, it is preferable that the sliver is made by mixing the carbon fiber and the resin fiber as uniformly as possible.
次に、ギルレデューサー等で、上記の方法で得られたスライバーを複数並べてギルに投入し、櫛状の多数の移動ギルフォーラー（バーに針を植え、これを運動させて繊維に梳り作用を与えるもの）で上下から並んだ櫛状のフォーラーでスライバーをつかみながら移動させ、フロントのニップローラーでギルフォーラーでの移動スピードの数倍スピードでドラフトして引き伸ばし、より配向した篠状のスライバー（以下、配向スライバーともいう）を作製する。必要に応じ、この工程を複数回行ってもよい。この工程を複数回行うことで、より配向性の高い配向スライバーを得ることができる。ギルレデューサーに複数の配向スライバーを投入し、ギルのフロントローラーからスライバー状に収束しないで、ドラフトされたままシート状に取出し、炭素繊維が一方向に配向した炭素繊維シートを得る。この炭素繊維シートをそのまま又は複数並べて広幅にした状態で、複合材料の材料として使うことができる。 Next, using a gil reducer etc., arrange multiple slivers obtained by the above method and put them in the gil, and move a large number of comb-like moving gilforers (planting needles on the bars and moving them to give a carding action to the fibers. Sliver is moved while grasping the sliver with comb-shaped forlers arranged from the top and bottom, and drafted and stretched at the front nip roller at a speed several times faster than the movement speed of the gilforer. Sliver). You may perform this process multiple times as needed. By performing this step a plurality of times, it is possible to obtain an oriented sliver having higher orientation. A plurality of oriented slivers are put into a gil reducer, and the draft is taken out into a sheet shape without being converged into a sliver shape from the front roller of the gil, to obtain a carbon fiber sheet in which carbon fibers are oriented in one direction. This carbon fiber sheet can be used as a material for a composite material as it is or in a state where a plurality of the carbon fiber sheets are arranged side by side to be wide.
必要に応じ、上記の工程で得られた配向スライバーの太さが所望の範囲になるよう調節し、複数並べて、シート状にすることで炭素繊維シートを得ることも好ましい実施態様である。
炭素繊維シートに樹脂バインダーを付与し、乾燥させることで、炭素繊維を樹脂バインダーで結合させた炭素繊維シートとしてもよい。炭素繊維シートの作製後に付与される樹脂バインダーは、炭素繊維が有する「有機物」には該当しないものとする。
あるいは、炭素繊維シートに含まれる樹脂繊維の融点付近の温度に加熱して樹脂繊維を溶融させることで、炭素繊維を樹脂で結合させた炭素繊維シートとしてもよい。
さらに、必要に応じ、複数の炭素繊維シート又は配向スライバーを面方向に並べたり、積層したりして、ステッチング、ニードルパンチ等の手段で絡合させてもよい。
It is also a preferred embodiment to obtain a carbon fiber sheet by adjusting the thickness of the oriented sliver obtained in the above step to a desired range and arranging a plurality of sheets to form a sheet, if necessary.
A carbon fiber sheet may be obtained by binding a carbon fiber with a resin binder by applying a resin binder to the carbon fiber sheet and drying. The resin binder applied after the production of the carbon fiber sheet does not correspond to the “organic substance” of the carbon fiber.
Alternatively, the carbon fiber sheet may be formed by bonding the carbon fibers with a resin by heating the resin fibers contained in the carbon fiber sheet to a temperature near the melting point to melt the resin fibers.
Further, if necessary, a plurality of carbon fiber sheets or oriented slivers may be arranged in a plane direction or laminated, and entangled by means such as stitching or needle punching.
上述した炭素繊維シートの製造方法は、ローラーで行う練条機でも同様に行うことができる。この場合、複数本のスライバーを並べて、練条機に導入し、フィードニップローラーのスピードより早いスピードのデリバリーニップローラーでドラフトする方法により、ドラフトされたところで収束し、配向性を高めて配向スライバーとする。場合により、上記の工程を複数回行って、配向度をさらに高めてもよい。このようにして配向スライバーを作製した後、収束しないでシート状で繊維を取出し、ギルを用いた方法と同様にしてシート化する。配向スライバーをさらにドラフトすることで、より一方向性に揃った配向炭素繊維シートを得ることができる。 The above-described method for producing a carbon fiber sheet can be similarly performed with a kneading machine using rollers. In this case, a plurality of slivers are arranged side by side, introduced into a kneading machine, and a method of drafting with a delivery nip roller having a speed faster than the speed of the feed nip roller is converged at a drafted position to enhance the orientation and the orientation sliver. To do. In some cases, the degree of orientation may be further increased by performing the above-mentioned steps a plurality of times. After the oriented sliver is produced in this manner, the fibers are taken out in a sheet form without being converged and formed into a sheet in the same manner as the method using a gil. By further drafting the oriented sliver, a more unidirectionally oriented carbon fiber sheet can be obtained.
必要に応じ、炭素繊維シート中に必要に応じて含まれる樹脂繊維、複合材料を成形する際に注入する樹脂等の樹脂成分と、炭素繊維との接着性を向上させる観点から、サイジング剤を炭素繊維シートに付与してもよい。炭素繊維シートの作製後に付与されるサイジング剤は、炭素繊維が有する「有機物」には該当しないものとする。 If necessary, resin fibers optionally contained in the carbon fiber sheet, a resin component such as a resin injected when molding the composite material, and from the viewpoint of improving the adhesiveness between the carbon fibers, the sizing agent is carbon. You may give to a fiber sheet. The sizing agent applied after the production of the carbon fiber sheet does not correspond to the “organic substance” of the carbon fiber.
＜複合材料＞
本実施形態の複合材料は、上記の実施形態の炭素繊維シートと、樹脂と、を含む。
本明細書では、複合材料に含まれる樹脂が完全に又は不完全に硬化又は固化していない状態のもの（プリプレグ）と、プリプレグに含まれる樹脂を硬化又は固化させた状態のものの両方を「複合材料」と称する。
<Composite material>
The composite material of the present embodiment includes the carbon fiber sheet of the above embodiment and a resin.
In the present specification, both a state in which the resin contained in the composite material is not completely or incompletely cured or solidified (prepreg) and a state in which the resin contained in the prepreg is cured or solidified are "composite". Material".
複合材料に含まれる樹脂は、熱硬化性樹脂であっても、熱可塑性樹脂であってもよい。熱硬化性樹脂として具体的には、エポキシ樹脂等が挙げられる。熱可塑性樹脂として具体的には、樹脂繊維の材質として例示したもの等が挙げられる。 The resin contained in the composite material may be a thermosetting resin or a thermoplastic resin. Specific examples of the thermosetting resin include epoxy resin. Specific examples of the thermoplastic resin include those exemplified as the material of the resin fiber.
複合材料に含まれる炭素繊維シートが樹脂繊維を含むものである場合は、複合材料に含まれる樹脂は、当該樹脂繊維に由来する樹脂を含んでいてもよい。すなわち、炭素繊維シートに含まれていた樹脂繊維が溶融し、再び硬化又は固化した状態の樹脂を含んでいてもよい。 When the carbon fiber sheet contained in the composite material contains resin fibers, the resin contained in the composite material may contain resin derived from the resin fibers. That is, the resin fibers contained in the carbon fiber sheet may contain the resin in a state of being melted and then cured or solidified again.
＜複合材料の製造方法＞
本実施形態の複合材料の製造方法は、上述した実施形態の炭素繊維シートに対し、加圧及び加熱からなる群より選択される少なくとも１つを実施する工程（以下、成形工程ともいう）を含む。複合材料に含まれる炭素繊維シートが樹脂繊維を含むものである場合は、当該樹脂繊維が溶融する条件で加圧加熱工程を実施してもよい。上記方法は、加圧加熱工程の前に、炭素繊維シートに樹脂を含浸する工程（以下、樹脂含浸工程ともいう）をさらに含んでもよい。
<Method for manufacturing composite material>
The method for manufacturing the composite material of the present embodiment includes a step of performing at least one selected from the group consisting of pressurization and heating (hereinafter, also referred to as a molding step) on the carbon fiber sheet of the above-described embodiment. .. When the carbon fiber sheet contained in the composite material contains resin fibers, the pressurizing and heating step may be carried out under the condition that the resin fibers are melted. The above method may further include a step of impregnating the carbon fiber sheet with a resin (hereinafter, also referred to as a resin impregnation step) before the pressure heating step.
成形工程を実施する方法は、特に制限されない。例えば、炭素繊維シートを単独で、又は複数枚を積層した状態で、上下の熱盤を油圧でプレスする加圧プレス成型機等で、加圧しながら任意の温度で熱プレスすることにより行ってもよい。
樹脂含浸工程を実施する方法は、特に制限されない。例えば、硬化前の熱硬化性樹脂又は溶融した熱可塑性樹脂を炭素繊維シートの炭素繊維間に入り込ませる公知の手段により行うことができる。樹脂含浸工程は、成形工程の前に実施しても、成形工程と並行して実施してもよい。
The method for carrying out the molding step is not particularly limited. For example, the carbon fiber sheets may be used alone or in a state where a plurality of carbon fiber sheets are laminated by hot pressing at an arbitrary temperature while applying pressure with a pressure press molding machine or the like that presses the upper and lower heating plates hydraulically. Good.
The method for carrying out the resin impregnation step is not particularly limited. For example, it can be carried out by a known means for allowing the thermosetting resin before curing or the molten thermoplastic resin to enter between the carbon fibers of the carbon fiber sheet. The resin impregnation step may be performed before the molding step or in parallel with the molding step.
複合材料の作製方法は上記の方法に限定されず、ＲＴＭ（Ｒｅｓｉｎ Ｔｒａｎｓｆｅｒ Ｍｏｌｄｉｎｇ、樹脂注入成形法）、ＶａＲＴＭ（Ｖａｃｕｕｍ Ａｓｓｉｓｔｅｄ Ｒｅｓｉｎ Ｔｒａｎｓｆｅｒ Ｍｏｌｄｉｎｇ、真空樹脂注入成形法）等の方法でも得ることができる。 The method for producing the composite material is not limited to the above-mentioned method, and the composite material can also be obtained by a method such as RTM (resin transfer molding, resin injection molding), VaRTM (vacuum assisted resin transfer molding, vacuum resin injection molding).
以下、実施例を参照して本実施形態の炭素繊維シート及び複合材料について具体的に説明する。ただし、下記の実施例は本実施形態を制限するものではない。 Hereinafter, the carbon fiber sheet and the composite material of the present embodiment will be specifically described with reference to examples. However, the following examples do not limit the present embodiment.
＜実質的に有機物を有しない炭素繊維の作製＞
高分子中のエステル結合を分解しうる分解触媒として水酸化ナトリウムを、含有率が０．５ｍｏｌ／Ｌとなるようにベンジルアルコール中に投入し、撹拌することで処理液を調製した。この処理液を、コンデンサ、温度計、窒素導入口及び撹拌機を取り付けたフラスコに入れ、窒素気流中で穏やかに撹拌しながら、オイルバスを使用して処理液を１９０℃に加熱した。この処理液中に、３５ｍｍの長さに切断したサイジング剤で表面処理された炭素繊維（東レ株式会社、商品名「Ｔ７００Ｓ」）を、処理液５０ｇに対し０．５ｇの割合で投入し、処理液の温度を１９０℃に維持しながら５時間放置した後に取り出した。取り出した炭素繊維を水で洗浄し、乾燥した。
<Preparation of carbon fiber substantially free of organic matter>
Sodium hydroxide was added as a decomposition catalyst capable of decomposing the ester bond in the polymer into benzyl alcohol so that the content rate was 0.5 mol/L, and the mixture was stirred to prepare a treatment liquid. This treatment liquid was placed in a flask equipped with a condenser, a thermometer, a nitrogen inlet and a stirrer, and the treatment liquid was heated to 190° C. using an oil bath while gently stirring in a nitrogen stream. Into this treatment liquid, carbon fibers surface-treated with a sizing agent cut to a length of 35 mm (trade name "T700S", Toray Industries, Inc.) were added at a ratio of 0.5 g to 50 g of the treatment liquid, and treated. It was taken out after being left for 5 hours while maintaining the temperature of the solution at 190°C. The carbon fiber taken out was washed with water and dried.
上記工程を経た炭素繊維を１００℃で２０分間乾燥した後、マッフル炉（ヤマト科学株式会社、商品名「ＦＰ３１１」）にて５００℃で４５分の条件で、空気中で熱処理した。熱処理の前後における炭素繊維の質量から有機物の含有量（（熱処理前の質量−熱処理後の質量）／処理前の質量×１００％）を算出したところ、有機物の含有量は１．３質量％であり、実質的に有機物を有していないことが確認された。 After the carbon fibers that had undergone the above steps were dried at 100° C. for 20 minutes, they were heat-treated in air in a muffle furnace (Yamato Scientific Co., Ltd., trade name “FP311”) at 500° C. for 45 minutes. When the content of organic matter ((mass before heat treatment-mass after heat treatment)/mass before treatment×100%) was calculated from the mass of carbon fibers before and after heat treatment, the content of organic matter was 1.3 mass %. Yes, it was confirmed that there was substantially no organic matter.
＜実施例１＞
上記の方法で得られた実質的に有機物を有しない炭素繊維５．７ｋｇと、樹脂繊維としてポリプロピレン（ＰＰ）の繊維（ＪＮＣ株式会社、商品名「ＲＰ−２７０」、繊維の太さ：６．６Ｄｔ、繊維の平均長さ：５１ｍｍ）４．３ｋｇとを混合し、カード機で開繊し、スライバーを作製した。次に、得られたスライバーをギルレデューサーに８本投入し、約８倍の長さとなるように一方向へ引き伸ばす工程を６回行い、配向スライバーを作製した。得られた配向スライバーを、ギルレデューサー（ＯＫＫ株式会社）に通し、所定の目付になるようなドラフトでスライバー化することなく、より繊維の方向性の揃ったシートとして取り出すことで、炭素繊維シート基材を得た。
<Example 1>
5.7 kg of substantially organic-free carbon fiber obtained by the above method and polypropylene (PP) fiber as resin fiber (JNC Corporation, trade name "RP-270", fiber thickness: 6. 6 Dt, average length of fiber: 51 mm, and 4.3 kg were mixed and opened by a card machine to prepare a sliver. Next, 8 steps of the obtained sliver were put into a Gil reducer, and a process of stretching in one direction so as to have a length of about 8 times was performed 6 times to prepare an oriented sliver. The obtained oriented sliver is passed through a Gil reducer (OKK Co., Ltd.) and taken out as a sheet in which the directionality of the fibers is more uniform without slicing into a sliver with a draft that gives a predetermined basis weight. I got the material.
得られた炭素繊維シート基材を観察したところ、集束体を形成せずに単繊維の状態となっている炭素繊維が存在していた。また、炭素繊維シート基材中の炭素繊維の状態は均一性が高いものであった。この炭素繊維シート基材を、コンベア式熱風乾燥器で、１７０℃で２分間加熱した後、冷却ローラーで軽くプレスすることで、炭素繊維シート１を得た。炭素繊維シート１の目付けは、２００ｇ／ｍ２であった。 When the obtained carbon fiber sheet base material was observed, there were carbon fibers in a single fiber state without forming a bundle. The state of the carbon fibers in the carbon fiber sheet base material was highly uniform. The carbon fiber sheet base material was heated at 170° C. for 2 minutes with a conveyor hot air dryer and then lightly pressed with a cooling roller to obtain a carbon fiber sheet 1. The basis weight of the carbon fiber sheet 1 was 200 g/m 2 .
炭素繊維シート１を観察したところ、炭素繊維が概ね一方向に配向していた。また、炭素繊維シート１の炭素繊維の配向方向（縦方向）と直交する方向（横方向）の引張り強度の比（炭素繊維シートの縦方向の引張り強度／炭素繊維シートの横方向の引張り強度）は１０．１であった。これらの結果より、炭素繊維シート１における炭素繊維は一方向に配向していると判断した。 Observation of the carbon fiber sheet 1 revealed that the carbon fibers were oriented in one direction. Further, the ratio of the tensile strength in the direction (horizontal direction) orthogonal to the orientation direction (longitudinal direction) of the carbon fibers of the carbon fiber sheet 1 (longitudinal tensile strength of carbon fiber sheet/horizontal tensile strength of carbon fiber sheet). Was 10.1. From these results, it was determined that the carbon fibers in the carbon fiber sheet 1 were oriented in one direction.
炭素繊維シート１の縦方向及び横方向の引張り強度は、炭素繊維シート１から幅（横方向の長さ）１０ｍｍ、厚さ２．５ｍｍ程度、長さ（縦方向の長さ）８０ｍｍの大きさの試験片を１０枚作製し、１枚ずつ引張試験装置（株式会社島津製作所、商品名「ＡＵＴＯＧＲＡＰＨ ＡＧ−Ｘ １ｋＮ」）を用いて、２０ｍｍのチャック間距離、５ｍｍ／ｍｉｎの引張り速度で引っ張りながら測定し、１０枚の試験片から得られた引張り強度の数平均値を求めることで測定できる。 The tensile strength in the longitudinal direction and the transverse direction of the carbon fiber sheet 1 is 10 mm in width (lateral length), about 2.5 mm in thickness, and 80 mm in length (longitudinal length) from the carbon fiber sheet 1. 10 pieces of test pieces were prepared, and one by one, using a tensile tester (Shimadzu Corporation, trade name “AUTOGRAPH AG-X 1kN”), while pulling at a chucking distance of 20 mm and a pulling speed of 5 mm/min. It can be measured by measuring and obtaining the number average value of the tensile strengths obtained from the 10 test pieces.
次に、炭素繊維シート１を目付けが２５００ｇ／ｍ２になるように複数枚積層し、小型熱プレス機（ＡＳ ＯＮＥ製）に配置した。次いで、仕上がりの厚みが２．７ｍｍになるようにスペーサをプレス板間に挟み、４３ｋｇ／ｃｍ２の圧力で加圧しながら、２００℃で熱プレスすることにより、炭素繊維間にポリプロピレン樹脂が含浸した状態の複合材料としてＣＦＲＰ−１を作製した。 Next, a plurality of carbon fiber sheets 1 were laminated to have a basis weight of 2500 g/m 2 and placed in a small heat press machine (made by AS ONE). Next, a spacer was sandwiched between the press plates so that the finished thickness was 2.7 mm, and the polypropylene resin was impregnated between the carbon fibers by hot pressing at 200° C. while applying a pressure of 43 kg/cm 2 . CFRP-1 was prepared as a composite material in the state.
作製したＣＦＲＰ−１から、長さ（炭素繊維の配向方向）が８ｃｍ、幅（炭素繊維の配向方向に直交する方向）が２．５ｃｍの試験片を１０枚作製した。試験片の作製は、回転カッター（マキタ株式会社）に回転刃（株式会社谷テック）を装着したものを用いて行った。作製した試験片について、試験機（株式会社島津製作所、商品名「ＡＵＴＯＧＲＡＰＨ ＡＧ−Ｘ １ｋＮ」）を用いて、ＪＩＳ Ｋ ７１７１法に準じ、３点曲げにより、曲げ強度と曲げ弾性率を計測した。１０枚の試験片について得られた値の平均値を表１に示す。 From the CFRP-1 thus produced, 10 test pieces having a length (orientation direction of carbon fibers) of 8 cm and a width (direction orthogonal to the orientation direction of carbon fibers) of 2.5 cm were prepared. The test piece was manufactured using a rotary cutter (Makita Co., Ltd.) equipped with a rotary blade (Tanitec Co., Ltd.). About the produced test piece, the bending strength and the bending elastic modulus were measured by three-point bending according to JIS K 7171 method using a testing machine (Shimadzu Corporation, trade name "AUTOGRAPH AG-X 1kN"). Table 1 shows the average values of the values obtained for the 10 test pieces.
（実施例２）
有機物を有していない炭素繊維の量を４ｋｇに変更し、樹脂繊維の量を６ｋｇに変更下以外は実施例１と同様の方法で、炭素繊維シート基材を作製した。炭素繊維シート基材を観察したところ、集束体を形成せずに単繊維の状態となっている炭素繊維が存在していた。また、炭素繊維シート基材は均一性が高いものであった。次いで、炭素繊維シート基材を用いて実施例１と同様にして炭素繊維シート２と、複合材料としてＣＦＲＰ−２を作製し、実施例１と同様の測定を実施した。結果を表１に示す。
(Example 2)
A carbon fiber sheet base material was produced in the same manner as in Example 1 except that the amount of carbon fiber having no organic substance was changed to 4 kg and the amount of resin fiber was changed to 6 kg. When the carbon fiber sheet base material was observed, there were carbon fibers in the state of single fibers without forming a bundle. Further, the carbon fiber sheet base material was highly uniform. Then, using the carbon fiber sheet base material, carbon fiber sheet 2 and CFRP-2 as a composite material were produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1.
（実施例３）
実施例１におけるＰＰ繊維に代えて同量のポリエチレンテレフタレート（ＰＥＴ）の繊維（帝人株式会社、商品名「ＴＡ０４ ＳＤ」、繊維の太さ：３．３Ｄｔ、繊維の平均長さ：５１ｍｍ）を樹脂繊維として用いたことと、熱プレスの温度を２９０℃としたこと以外は実施例１と同様の方法で、炭素繊維シート基材を作製した。炭素繊維シート基材を観察したところ、炭素繊維が概ね一方向に配向し、集束体を形成せずに単繊維の状態となっている炭素繊維が存在していた。また、炭素繊維シート基材中の炭素繊維の状態は均一性が高いものであった。次いで、炭素繊維シート基材を用いて実施例１と同様にして炭素繊維シート３と、複合材料としてＣＦＲＰ−３を作製し、実施例１と同様の測定を実施した。結果を表１に示す。
(Example 3)
Instead of the PP fiber in Example 1, the same amount of polyethylene terephthalate (PET) fiber (Teijin Co., Ltd., trade name "TA04 SD", fiber thickness: 3.3 Dt, average fiber length: 51 mm) was used as the resin. A carbon fiber sheet base material was produced in the same manner as in Example 1 except that the carbon fiber sheet was used as a fiber and the hot press temperature was 290°C. When the carbon fiber sheet base material was observed, it was found that the carbon fibers were oriented in almost one direction, and there were carbon fibers in a single fiber state without forming a bundle. The state of the carbon fibers in the carbon fiber sheet base material was highly uniform. Next, using the carbon fiber sheet base material, carbon fiber sheet 3 and CFRP-3 as a composite material were produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1.
（実施例４）
スライバーの引き伸ばし工程を実施する回数を４回に変更した以外は実施例１と同様の方法で、炭素繊維シート基材を作製した。炭素繊維シート基材を観察したところ、炭素繊維が概ね一方向に配向し、集束体を形成せずに単繊維の状態となっている炭素繊維が存在していた。また、炭素繊維シート基材中の炭素繊維の状態は均一性が高いものであった。次いで、炭素繊維シート基材を用いて実施例１と同様にして炭素繊維シート４と、複合材料としてＣＦＲＰ−４を作製し、実施例１と同様の測定を実施した。結果を表１に示す。
(Example 4)
A carbon fiber sheet substrate was produced in the same manner as in Example 1 except that the number of times the sliver stretching step was performed was changed to 4. When the carbon fiber sheet base material was observed, it was found that the carbon fibers were oriented in almost one direction, and there were carbon fibers in a single fiber state without forming a bundle. The state of the carbon fibers in the carbon fiber sheet base material was highly uniform. Then, using the carbon fiber sheet base material, carbon fiber sheet 4 and CFRP-4 as a composite material were produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1.
（実施例５）
スライバーの引き伸ばし工程を実施する回数を２回に変更した以外は実施例１と同様の方法で、炭素繊維シート基材を作製した。炭素繊維シート基材を観察したところ、炭素繊維が概ね一方向に配向し、集束体を形成せずに単繊維の状態となっている炭素繊維が存在していた。また、炭素繊維シート基材中の炭素繊維の状態は均一性が高いものであった。次いで、炭素繊維シート基材を用いて実施例１と同様にして炭素繊維シート５と、複合材料としてＣＦＲＰ−５を作製し、実施例１と同様の測定を実施した。結果を表１に示す。
(Example 5)
A carbon fiber sheet substrate was produced in the same manner as in Example 1 except that the number of times the sliver stretching step was performed was changed to 2. When the carbon fiber sheet base material was observed, it was found that the carbon fibers were oriented in almost one direction, and there were carbon fibers in a single fiber state without forming a bundle. The state of the carbon fibers in the carbon fiber sheet base material was highly uniform. Next, using the carbon fiber sheet base material, carbon fiber sheet 5 and CFRP-5 as a composite material were produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1.
（実施例６）
炭素繊維として、処理液に放置する時間を１５分間に変更した以外は実施例１と同様の工程を経たものを実施例１と同じ量で使用した以外は実施例１と同様の方法で、炭素繊維シート基材を作製した。炭素繊維シート基材を観察したところ、炭素繊維が概ね一方向に配向し、集束体を形成せずに単繊維の状態となっている炭素繊維が存在していた。また、炭素繊維シート基材中の炭素繊維の状態は均一性が高いものであった。次いで、炭素繊維シート基材を用いて実施例１と同様にして炭素繊維シート６と、複合材料としてＣＦＲＰ−６を作製し、実施例１と同様の測定を実施した。結果を表１に示す。なお、炭素繊維シート基材の作製に用いた炭素繊維の有機物の含有量を、実施例１と同様にして算出したところ、有機物の含有量は２．１質量％であり、実質的に有機物を有していないことが確認された。
(Example 6)
Carbon fiber was prepared in the same manner as in Example 1 except that the same amount of carbon fiber as in Example 1 was used, except that the time for leaving in the treatment liquid was changed to 15 minutes. A fiber sheet base material was produced. When the carbon fiber sheet base material was observed, it was found that the carbon fibers were oriented in almost one direction, and there were carbon fibers in a single fiber state without forming a bundle. The state of the carbon fibers in the carbon fiber sheet base material was highly uniform. Next, using the carbon fiber sheet base material, carbon fiber sheet 6 and CFRP-6 as a composite material were produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1. In addition, when the content of the organic matter of the carbon fiber used for producing the carbon fiber sheet base material was calculated in the same manner as in Example 1, the content of the organic matter was 2.1% by mass, and the organic matter was substantially contained. It was confirmed that they did not have it.
（比較例１）
実施例１で用いたものと同じ有機物を実質的に有していない炭素繊維５．７ｋｇと、実施例１で用いたものと同じ樹脂繊維４．３ｋｇと、を混合し、カード機で開繊し、ウェブとよばれる薄い綿状のシートを作製した。作製したウェブを炭素繊維シート基材として用いた以外は実施例１と同様にして、炭素繊維シートＡと、複合材料としてＣＦＲＰ−Ａを作製し、実施例１と同様の測定を実施した。結果を表１に示す。なお、ウェブを観察したところ、炭素繊維が特定の方向に配向せず、ランダムに配置されておいた。
(Comparative Example 1)
5.7 kg of carbon fibers substantially free of the same organic substances as those used in Example 1 and 4.3 kg of the same resin fibers used in Example 1 were mixed and opened with a card machine. Then, a thin cotton-like sheet called a web was prepared. Carbon fiber sheet A and CFRP-A as a composite material were produced in the same manner as in Example 1 except that the produced web was used as the carbon fiber sheet base material, and the same measurement as in Example 1 was performed. The results are shown in Table 1. When the web was observed, the carbon fibers were not oriented in a specific direction and were randomly arranged.
（比較例２）
炭素繊維として、実施例１で用いたものと同じ炭素繊維であってサイジング剤で表面処理されたままのものを実施例１と同じ量で使用した以外は実施例１と同様の方法で、炭素繊維シート基材を作製した。炭素繊維シート基材を観察したところ、炭素繊維は概ね一方向に配向していたが、実施例１よりも配向の度合いは低かった。また、集束体を形成した状態の単繊維が多く存在していた。次いで、炭素繊維シート基材を用いて実施例１と同様にして炭素繊維シートＢと、複合材料としてＣＦＲＰ−Ｂを作製し、実施例１と同様の測定を実施した。結果を表１に示す。また、炭素繊維シート基材の作製に用いた炭素繊維の有機物の含有量を、実施例１と同様にして算出したところ、有機物の含有量は３．６質量％であり、有機物を有していることが確認された。
(Comparative example 2)
As the carbon fibers, the same carbon fibers as those used in Example 1 which were still surface-treated with a sizing agent were used in the same manner as in Example 1 except that the same amount was used. A fiber sheet base material was produced. Observation of the carbon fiber sheet substrate revealed that the carbon fibers were oriented in one direction, but the degree of orientation was lower than that in Example 1. Moreover, many single fibers in the state of forming a bundle were present. Next, using the carbon fiber sheet base material, carbon fiber sheet B and CFRP-B as a composite material were produced in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1. Moreover, when the content of the organic matter of the carbon fiber used for the production of the carbon fiber sheet base material was calculated in the same manner as in Example 1, the content of the organic matter was 3.6% by mass, and the organic matter was contained. Was confirmed.
表１に示すように、一方向に配向した実質的に有機物を有しない炭素繊維を含む実施例の炭素繊維シートは、炭素繊維配向方向の曲げ強度及び曲げ弾性率の値が良好であった。また、実施例１〜６で作製したＣＦＲＰの断面（炭素繊維の配向方向に直交する方向に沿って切断したときの断面）を目視で観察したところ、炭素繊維の一本一本の周りに樹脂が浸透し、視認可能な空隙は存在しなかった。 As shown in Table 1, the carbon fiber sheets of Examples containing the unidirectionally oriented carbon fibers having substantially no organic matter had good values of bending strength and bending elastic modulus in the carbon fiber orientation direction. Further, when the cross-sections (cross-sections when cut along the direction orthogonal to the orientation direction of the carbon fibers) of the CFRP produced in Examples 1 to 6 were visually observed, resin around each carbon fiber was observed. Penetrated and there were no visible voids.
炭素繊維が一方向に配向していない比較例１の炭素繊維シートは、炭素繊維配向方向の曲げ強度及び曲げ弾性率の値が実施例よりも低かった。また、比較例１で作製したＣＦＲＰの断面（炭素繊維の配向方向に直交する方向に沿って切断したときの断面）を目視で観察したところ、炭素繊維が交差する場所等で樹脂が浸透せず、空隙となっている箇所が存在していた。このことから、炭素繊維が一方向に配向していないことにより、樹脂が炭素繊維間に充分に入り込めないため、炭素繊維配向き方向の曲げ強度及び曲げ弾性率の値が低くなったと推察される。 The carbon fiber sheet of Comparative Example 1 in which the carbon fibers were not oriented in one direction had lower values of bending strength and bending elastic modulus in the carbon fiber orientation direction than in the examples. Further, when the cross section of the CFRP prepared in Comparative Example 1 (the cross section when cut along the direction orthogonal to the orientation direction of the carbon fibers) was visually observed, the resin did not permeate at the places where the carbon fibers intersect. , There was a void. From this, it can be inferred that since the carbon fibers are not oriented in one direction, the resin cannot sufficiently enter between the carbon fibers, and thus the values of the bending strength and the bending elastic modulus in the carbon fiber orientation direction become low. It
有機物を有しない炭素繊維を用いて作製した比較例２の炭素繊維シートは、炭素繊維配向方向の曲げ強度及び曲げ弾性率の値が実施例よりも低かった。また、比較例２で作製したＣＦＲＰの断面（炭素繊維の配向方向に直交する方向に沿って切断したときの断面）を目視で観察したところ、炭素繊維が束になっており、束の内部に樹脂が入り込まずに空隙となっている部分が多く観察された。このことから、炭素繊維の表面に有機物があることで、炭素繊維が集束体を形成しており、集束体の内部に樹脂が充分に入り込めないため、炭素繊維配向き方向の曲げ強度、及び曲げ弾性率が低くなったと推察される。 The carbon fiber sheet of Comparative Example 2 produced using carbon fibers having no organic matter had lower values of bending strength and bending elastic modulus in the carbon fiber orientation direction than those of the examples. Further, when the cross section of the CFRP produced in Comparative Example 2 (the cross section when cut along the direction orthogonal to the orientation direction of the carbon fibers) was visually observed, it was found that the carbon fibers were in a bundle and were inside the bundle. Many voids were observed without the resin entering. From this, since there is an organic substance on the surface of the carbon fiber, the carbon fiber forms a bundle, and since the resin cannot sufficiently enter the inside of the bundle, the bending strength in the carbon fiber orientation direction, and It is presumed that the flexural modulus became low.
Claims (7)
前記炭素繊維の平均長さが２０ｍｍ〜１５０ｍｍであり、
さらに樹脂繊維を含む炭素繊維シート。 Including unidirectionally oriented carbon fibers, the proportion of organic matter in the total mass of the carbon fibers and the organic matter present on the surface of the carbon fibers is 0% by mass to 3% by mass,
The average length of the carbon fiber is 20 mm to 150 mm,
A carbon fiber sheet that further contains resin fibers .
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