JP4104413B2

JP4104413B2 - RTM molding method

Info

Publication number: JP4104413B2
Application number: JP2002295933A
Authority: JP
Inventors: 俊英関戸; 一章北岡; 浩司小谷; 西山　　茂; 正彦清水
Original assignee: Mitsubishi Heavy Industries Ltd; Toray Industries Inc
Current assignee: Mitsubishi Heavy Industries Ltd; Toray Industries Inc
Priority date: 2002-10-09
Filing date: 2002-10-09
Publication date: 2008-06-18
Anticipated expiration: 2022-10-09
Also published as: JP2004130598A

Description

【０００１】
【発明の属する技術分野】
本発明は、繊維強化プラスチック（以下、ＦＲＰと言う。）製構造体を成形する際に用いられるResin Transfer Molding（以下、ＲＴＭと言う。）成形方法の改良に関し、とくに、成形されるＦＲＰ成形体の繊維体積含有率（以下、Ｖｆと略称することもある。）を向上させ、より強度、軽量性に優れた成形体を得ることが可能なＲＴＭ成形方法に関する。
【０００２】
【従来の技術】
例えば、航空機や自動車用途のＦＲＰ成形体においては、高強度化、軽量化、低コスト化のために、ＦＲＰ成形体全体に占める強化繊維の体積含有率（Ｖｆ）を５５％〜６５％程度のいわゆる高Ｖｆ化することが望ましい。このようなＦＲＰ成形体の高Ｖｆ化技術に関する従来技術としては、例えば特許文献１に記載の技術が提案されている。
【０００３】
この特許文献１に記載のＲＴＭ成形方法では、強化繊維材の積層体からなる強化繊維基材の両面に、ピールプライ／樹脂分散メディアを配置し、これらを成形型（ツール）面上に配置して、全体をバッグ材で覆うとともに、バッグ材によりシールされた内部に対し樹脂注入ゲートと減圧のための吸引ゲートを設けてＲＴＭ成形する方法が記載されている。
【０００４】
しかし、このＲＴＭ成形方法では、強化繊維基材の繊維体積含有率（Ｖｆ）が５５％以上のいわゆる高Ｖｆ状態、つまり、強化繊維間の隙間が小さい状態で樹脂の注入を行った場合は、最終成形体の繊維体積含有率自体は高くなるが、樹脂の成形体内への浸透性が悪いため、板厚がたとえば２５ｍｍ以上となるような厚い成形体の場合は、成形体内の隅々にまで樹脂が到達せず、構造物としては樹脂の未含浸部分の残る欠陥のあるものしか製造できなかった。
【０００５】
一方、強化繊維のＶｆが例えば４５％と、強化繊維間の隙間が比較的大きい場合には、樹脂の浸透性は良いが最終成形体の繊維体積含有率は低くなるため、強度、軽量性に劣るものしか製造できなかった。つまり、樹脂の含浸性と繊維体積含有率Ｖｆは相反する関係にあり、樹脂の含浸性向上と繊維体積含有率向上との両立は困難であった。さらに、成形体によっては品質安定化の必要性から繊維体積含有率をコントロールすることが好ましいが、このような要求を満たすことも困難であった。
【０００６】
【特許文献１】
米国特許５，０５２，９０６号明細書（請求項１、第１図）
【０００７】
【発明が解決しようとする課題】
本発明の課題は、上記のような従来技術における問題を解消し、樹脂の含浸性向上と繊維体積含有率向上との両立を可能ならしめて、ＦＲＰ成形体をより高強度化、軽量化することが可能なＲＴＭ成形方法を提供することにある。
【０００８】
【課題を解決するための手段】
上記課題を解決するために、本発明に係るＲＴＭ成形方法は、成形型内に強化繊維基材を配置し、該成形型内に連通する樹脂注入ラインと吸引ラインを設け、該成形型内を吸引により減圧するとともに樹脂を成形型内に注入し強化繊維基材に含浸させてＦＲＰ成形体を成形するＲＴＭ成形方法において、ＦＲＰ成形体の目標繊維体積含有率よりも低い繊維体積含有率となるように樹脂を強化繊維基材に含浸させた後、樹脂の注入を停止し、しかる後に目標繊維体積含有率になるまで樹脂の吸引を継続することを特徴とする方法からなる。つまり、樹脂が基材全域に流動して含浸された後に硬化させるに際し、樹脂が硬化するまでに、目標繊維体積含有率となるまで樹脂の吸引を継続して、強化繊維基材内から余分な樹脂を吸引し、それによって繊維体積含有率を目標値まで上げるようにしたＲＴＭ成形方法である。
【０００９】
このＲＴＭ成形方法においては、樹脂の注入を停止した後、樹脂注入ラインの少なくとも１ラインを吸引ラインに変更して、目標繊維体積含有率になるまで樹脂の吸引を継続することができる。
【００１０】
上記目標繊維体積含有率としては、高Ｖｆ化のために、例えば５５％〜６５％の範囲内にあることが好ましい。この場合、上記目標繊維体積含有率よりも低い繊維体積含有率としては、例えば４５％〜５５％の範囲内にあることが好ましい。
【００１１】
目標繊維体積含有率に到達したか否かの判定は、例えば強化繊維基材の厚みの測定により行うことができ、上記樹脂吸引継続中に、この厚みを測定し、余分の樹脂が所定量吸引除去されたか否かを判定すればよい。
【００１２】
また、本発明に係るＲＴＭ成形方法においては、樹脂の注入量あるいは吸引量を予め設定しておくことも可能である。すなわち、上記目標繊維体積含有率よりも低い繊維体積含有率に相当する樹脂の注入量を予め設定し、該設定注入量になった時点で、樹脂の注入を停止することができる。また、樹脂注入量に対し上記目標繊維体積含有率に到達するための樹脂の吸引量を予め設定し、該設定吸引量になった時点で、樹脂の吸引を停止することができる。
【００１３】
また、本発明に係るＲＴＭ成形方法において、高強度、軽量なＦＲＰ成形体を得るためには、強化繊維基材の少なくとも１層が炭素繊維層からなることが好ましい。この炭素繊維層が織物、例えば、炭素繊維が一方向に配向された一方向織物に形成することができる。
【００１４】
上記のような本発明に係るＲＴＭ成形方法においては、まず、ＦＲＰ成形体の目標繊維体積含有率よりも低い繊維体積含有率となるように樹脂が強化繊維基材に含浸させるので、強化繊維基材の全域にわたって十分に樹脂が含浸され、この時点で樹脂未含浸部の発生は防止される。この樹脂含浸後、樹脂の注入が停止され、しかる後に、樹脂が硬化するまでに、目標繊維体積含有率になるまで樹脂の吸引が継続され、強化繊維基材内から余分な樹脂が吸引されて目標とする成形体の高Ｖｆ化が達成される。
【００１５】
【発明の実施の形態】
以下に、本発明の望ましい実施の形態について、図面を参照して説明する。
図１は、本発明の一実施態様に係るＲＴＭ成形方法に用いる成形装置の一例を示している。図１において、ベースとなる成形型１は、たとえば、ステンレスから作製され、平板状のものに構成される。この成形型１内に、図示例では成形型１上に、強化繊維基材２が配置される。強化繊維基材２は、例えば、強化繊維の織物を積層したものからなる。本実施態様では、強化繊維基材２の上に、樹脂を拡散させるための媒体３がピールプライ２４を介して配置される。樹脂拡散媒体３には、樹脂の流動抵抗が強化繊維基材２内を流れる場合の流動抵抗に比べ１／１０以下の低い抵抗をなす媒体であることが好ましく、具体的には、ポリエチレンやポリプロピレン樹脂製のメッシュ織物で、目開きが＃４００以下のものが好ましい。これら成形型１上に配置された部材全体が、気密材料からなるバッグ材４で覆われる。バッグ材４としては、気密性および耐熱性を考慮して、例えばナイロン製のフィルムを用いることが好ましい。５は粘着性の高い合成ゴム製のシーラントで、バッグ材４内を減圧状態に保つことができるよう、外部からの空気の流入を防止する。なお、第１のバッグ材をさらに第２のバッグ材で覆い二重バッグとすることで、空気漏れを防ぐことができ、その結果、Ｖｆを向上させることができる。
【００１６】
シールされたバッグ材４内に、樹脂注入口７と、吸引によりバッグ材４内を減圧するための吸引口６が設けられ、各々、樹脂注入ラインと吸引ラインに接続されている。樹脂注入口７、吸引口６には、例えばアルミニウム製のＣチャンネル材等を使用することができ、これらチャンネル材を、樹脂注入ライン、吸引ラインを形成するプラスチック製のチューブを介して外部部材と接続すればよい。８は、ＦＲＰ成形体のマトリックス樹脂となる熱硬化性樹脂であり、該樹脂は例えばプラスチック製のポット内に収容される。９は真空トラップで、吸引口６より吸引した成形体内からの余分な樹脂を蓄積させる。１０は真空ポンプであり、真空トラップ９、吸引口６を介して、バッグ材４で覆われた内部から吸引し、内部を減圧状態に保持する。ピールプライ２４は、成形体から樹脂拡散媒体３を容易に除去するために介装され、例えば、ナイロン製タフタのように離型の機能を有する織物が用いられる。
【００１７】
強化繊維基材２を形成する強化繊維の材質としては特に限定されるものではないが、例えば、ガラス繊維、炭素繊維、アラミド繊維等が挙げられる。また、それらを少なくとも２種類使用あるいは積層したハイブリッド構造のものでもよい。また、強化繊維の間に、例えば発泡材や中空コアなどのコア材を挟んだサンドイッチ構造のものを用いてもよい。樹脂拡散媒体３としては、例えば網状体を用いることもできるし、成形型１に溝等により樹脂流路を形成し、その樹脂流路が形成された成形型１の面自体を樹脂拡散媒体に構成することも可能である。また、強化繊維基材自体を樹脂拡散媒体として使用することも可能である。マトリックス樹脂としては、例えば、ポリエステル樹脂、ビニルエステル樹脂、エポキシ樹脂、フェノール樹脂等が挙げられる。
【００１８】
図２は、本発明の別の実施態様に係るＲＴＭ成形方法に用いる成形装置を示しており、強化繊維基材の下面側に、樹脂拡散媒体を別途配置する代わりに成形型に溝を加工して実質的に樹脂拡散媒体を構成するとともに、樹脂の吸引中にダイヤルゲージで板厚（成形体あるいは樹脂が含浸された強化繊維基材の厚みに想到する板厚）を測定できるようにした装置を示している。図１の装置に比べて異なる点は以下の通りである。
【００１９】
２１は、ダイヤルゲージで、樹脂の吸引中に強化繊維基材の板厚の測定を行う。２２は、樹脂拡散媒体の代わりに樹脂拡散用に成形型に加工した溝で、幅が０．５ｍｍ〜５ｍｍ、深さが１ｍｍ〜６ｍｍ、配設ピッチが２ｍｍ〜２５ｍｍの矩形または逆台形または三角形などの断面形状を有することが好ましい。より好ましくは、幅が約１ｍｍ、深さが約３ｍｍの矩形断面を有し、ピッチが約８ｍｍであることが望ましい。ダイヤルゲージ２１以外の成形品の厚みの測定機器としては、定尺、マイクロメータまたはレーザ測定器などが挙げられる。
【００２０】
上記のような成形装置を用いて本発明に係るＲＴＭ成形方法は次のように行われる。
まず、成形型１の成型面の上に強化繊維基材２を配置し、その上に離型用ピールプライ２４（例えばナイロン製タフタ）と樹脂拡散媒体３を配設する。また、強化繊維基材２に対し、例えば、端部と中央部（図２）や、両端部（図１）に、樹脂注入口７と吸引口６を配置し、それらに樹脂注入ラインと吸引ラインを接続する。これら樹脂注入口７および樹脂注入ライン、吸引口６および吸引ラインは、それぞれ、少なくとも１ライン配設する。次に上記のように成形型１上に積層された各部材の上部から全体を覆うようにバッグ材４（フィルム材）を被せ、外部から強化繊維基材２等の内部を減圧状態に維持するために周囲をシーラント５でシールする。そして、バルブＡ１、Ａ２を閉じ、バルブＡ３を開いて、吸引口６、真空ライン、真空トラップ９を介して真空ポンプ１０により吸引することによって、キャビティ内（バッグ材４で覆われた内部）を０．１ＭＰａ以下の減圧状態にする。
【００２１】
次に成形型１を加熱用オーブン内に設置して、成形型全体を所定の温度まで加熱する。成形型１が所定の温度まで上昇したら、バルブＡ１を開き、樹脂注入口７より所定の樹脂８をキャビティ内に注入する。樹脂は吸引ラインに向かって樹脂拡散媒体３内を拡散し、樹脂拡散媒体３内の樹脂は強化繊維基材２内に含浸し始める。そして、基材２内の全領域に樹脂が含浸された時、あるいは基材２内の全領域に樹脂が含浸されていなくとも、予め設定した所定量の樹脂が注入された時、バルブＡ１を閉じて樹脂の供給を中止する。この樹脂注入停止時点での繊維体積含有率Ｖｆは４５％〜５５％の範囲内、より好ましくは５０〜５５％の範囲内となるように設定するのが望ましい。これは、吸引排出による樹脂のロスを極力少なく抑えるためである。そして、真空ラインを連通した真空トラップ９を介して吸引口６および、Ａ２を開いて樹脂注入口７から、真空トラップ９に所定の繊維体積含有率になるまで樹脂の吸引を行う。樹脂の吸引は樹脂がゲル化あるいは硬化するまで継続してもよいが、最終的に目標繊維体積含有率である５５％〜６５％になるまで吸引を行う。目標繊維体積含有率をこのような範囲に設定するのは、例えば、航空機部材の場合、対金属材料とのコスト・性能比較では、Ｖｆを５５％以上にする必要があり、また、繊維体積含有率が６５％を越えるような高Ｖｆとなった場合には、含浸不良となってボイドを発生したり、成形体における層間剪断強度が低下する等の問題が生じやすくなるためである。
【００２２】
本発明において、目標繊維体積含有率Ｖｆは、例えば、以下の方法により設定できる。
すなわち、次式により、強化繊維基材の厚みから、成形体の繊維体積含有率の予測が可能である。
Ｖｆ＝ＦＡＷ×ＰＬＹ／（ρ×ｔ）
Ｖｆ：繊維体積含有率（％）
ＦＡＷ：強化繊維基材を構成する強化繊維材の目付（ｇ／ｃｍ²）
ＰＬＹ：強化繊維材の積層数
ρ：強化繊維基材の密度（ｇ／ｃｍ³）
ｔ：板厚（ｃｍ）
【００２３】
積層体（強化繊維基材）の厚みを測定する機器を予め設置して、積層体の厚みの測定を行いながら、目標繊維体積含有率に相当する板厚に達した時に、バルブＡ２とＡ３を閉じてもよい。もしくは、繊維体積含有率は、積層体内の繊維と樹脂の量で定義できるため、予め所定の繊維体積含有率に相当する樹脂の注入量と吸引量を設定しておき、目標の注入量で樹脂の注入を中止し、目標の吸引量となった段階で樹脂の吸引を停止することもできる。
【００２４】
その後、所定の温度と時間で樹脂を硬化させる。硬化が終了した後、バッグ材やピールプライと共に樹脂拡散媒体や樹脂注入、吸引ラインに用いた部材など全ての副資材を成形体表面から取り除き、最後に成形型面上より成形体を脱型する。得られた成形体は、必要に応じて所定の温度と時間にてアフターキュアを行うこともできる。
【００２５】
【実施例】
実施例１
図１および図２のＲＴＭ成形装置を用い、縦５００ｍｍ、横５００ｍｍに裁断した炭素繊維織物をステンレス製平板からなる成形型１上にレイアップした。用いた強化繊維基材形成用の強化繊維材は、東レ（株）製”トレカ”Ｔ８００Ｓの一方向織物（目付：２８５ｇ／ｍ²）であり、トータルで９６ｐｌｙレイアップした。該強化繊維基材２の上に、ピールプライ２４（ナイロン製タフタ）及び樹脂拡散媒体３（ポリプロピレン製メッシュ材）を配設して、基材に対し樹脂注入口７と吸引口６を配設して、全体をバッグ材４（ナイロン製フィルム）を被せて周囲を粘着性の高い合成ゴム製のシーラント５でシールした（なお、この図では省略しているが、二重バッグとした）。
【００２６】
この状態で、バルブＡ１、Ａ２を閉じ、バルブＡ３を開いて、真空ライン、真空トラップ９を介して吸引口から吸引し、キャビティ内を０．１ＭＰａ以下まで減圧した。その後、電気オーブン内に該成形型を設置し、オーブン内を７０℃に加温する。強化繊維基材全体が７０℃に達した後に、バルブＡ１を開放して真空圧にて樹脂注入口７よりマトリックス樹脂８を注入した。樹脂としてはエポキシ樹脂（７０℃（注入温度）における樹脂粘度が１３０ｍＰａ・ｓ、７０℃で１時間経過後の樹脂粘度が３２０ｍＰａ・ｓ）を使用した。注入された樹脂は流動抵抗の低い樹脂拡散媒体３内を流れながら基材２内に含浸していく。所定の樹脂量の３７５０ｃｍ³を注入した時点で、バルブＡ１を閉じて樹脂の供給を停止した。この時の強化繊維基材の厚みから推測しうる基材の繊維体積含有率は５２％程度であった。
【００２７】
次に、バルブＡ２を開放して、真空トラップを介して樹脂注入ラインを真空側に開放し、強化繊維基材の端部から強化繊維基材内の余分な樹脂を真空トラップ９に吸引した。その後、樹脂の吸引量が所定量の７００ｃｍ³になった時点で、バルブＡ２、Ａ３を閉じ、樹脂の吸引を停止した。その後、電気オーブン内の温度を１３０℃まで昇温して、約２時間加熱硬化させた。加熱硬化後、バッグ材等の副資材を取り除き、ＣＦＲＰ（炭素繊維強化プラスチック）成形体を型面上より脱型した。ＣＦＲＰ成形体について、樹脂注入側、吸引側、両者の中間点で繊維体積含有率を測定した結果、５７．２％〜５８．２％の範囲内であった。すなわち、樹脂含浸直後の樹脂吸引前に比べ、繊維体積含有率を目標値の範囲内まで向上させることができた。
【００２８】
実施例２
樹脂の流路として＃形の溝２２（幅１ｍｍ、深さ４ｍｍ、ピッチ１５ｍｍ）を加工したステンレス製の成形型１上に、ピールプライ２４を介して縦５００ｍｍ、横５００ｍｍに裁断した炭素繊維織物２をレイアップした。用いた炭素繊維織物２は、東レ（株）製”トレカ”Ｔ８００Ｓの一方向織物（目付：２８５ｇ／ｍ²）であり、トータルで８８ｐｌｙレイアップした。この基材の上に、ピールプライ２４を介して通気性材料２３（ポリエステル製不織布）を配設し、その上に吸引口６を配設した。また、成形型１に形成された樹脂流路用溝２２の上に樹脂注入口７を配設して、全体にバッグ材４（ナイロン製フィルム）を二重に被せて周囲を粘着性の高い合成ゴム製のシーラント５でシールした。
【００２９】
この状態でバルブＡ１、Ａ２を閉じ、バルブＡ３を開いて、真空ライン、真空トラップ９を介して吸引口６から吸引し、キャビティ内を０．１ＭＰａ以下まで減圧した。その後、電気オーブン内に成形型を設置し、オーブン内を７０℃に加温した。強化繊維基材全体が７０℃に達した後、バルブＡ１を開放して真空圧にて樹脂注入口７よりマトリックス樹脂８を注入した。樹脂には実施例１のエポキシ樹脂を使用した。注入された樹脂は樹脂拡散用型溝内に拡散して、溝内の樹脂が基材内に含浸していった。樹脂が強化繊維基材全体に含浸した後の板厚を測定した結果、２７．５ｍｍであり、繊維体積含有率は５０．７％であった。
【００３０】
次に、バルブＡ１を閉じ、バルブＡ２を開放し、吸引口６と樹脂注入口７を介して、強化繊維基材内の余分な樹脂を真空トラップ９に吸引した。本実施例の場合、ＣＦＲＰ成形体の目標繊維体積含有率を５５〜６０％とした。成形体の厚み方向の硬化収縮が約１．２％であることが、事前の実験結果で得られていたので、板厚が２４．１ｍｍとなった時に、Ａ２とＡ３を閉じ、樹脂の吸引を停止した。その後、炉の温度を１３０℃まで昇温して、約２時間、加熱硬化させた。加熱硬化後、バッグ材等の副資材を取り除き、ＣＦＲＰ成形体を型面上より取り出した結果、上記目標とする繊維体積含有率内の５７．１〜５９．３％（板厚２３．８ｍｍ）のＣＦＲＰ成形体が得ることができた。
【００３１】
【発明の効果】
以上説明したように、本発明に係るＲＴＭ成形方法によれば、まず強化繊維基材の全域にわたって十分に樹脂を含浸させ、樹脂の供給を停止後、目標繊維体積含有率になるまで樹脂の吸引を継続して余分な樹脂を除去するようにしたので、ボイド等の不都合を発生させることなく、成形体の高い繊維体積含有率を達成でき、高Ｖｆ化を達成して、強度、軽量性に優れたＦＲＰ成形体を得ることができる。
【００３２】
また、例えば、航空機部材のように、構造強度部材にＦＲＰを適用する場合には、Ｖｆが５５％〜６５％で、そのばらつきは小さいことが要求される。このような要求に対しても、樹脂の供給ラインを吸引ラインに変更し、樹脂吸引口、注入口の両方から樹脂を吸引することで、Ｖｆのばらつきを小さく抑えることができる。また、樹脂の吸引中に、例えば板厚や注入量や吸引量から繊維体積含有率を推測して、目標繊維体積含有率に相当する時点で樹脂の吸引を停止すれば、成形体の繊維体積含有率を目標値に対して、より正確にコントロールすることが可能となる。
【図面の簡単な説明】
【図１】本発明の一実施態様に係るＲＴＭ成形方法に用いる成形装置の概略縦断面図である。
【図２】本発明の別の実施態様に係るＲＴＭ成形方法に用いる成形装置の概略縦断面図である。
【符号の説明】
１成形型
２強化繊維
３樹脂拡散媒体
４バッグ材
５シーラント
６吸引口
７樹脂注入口
８樹脂
９真空トラップ
１０真空ポンプ
２１ダイヤルゲージ
２２樹脂拡散用型溝
２３通気性材料
２４ピールプライ
Ａ１、Ａ２、Ａ３バルブ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a resin transfer molding (hereinafter referred to as RTM) molding method used for molding a fiber reinforced plastic (hereinafter referred to as FRP) structure, and in particular, an FRP molded body to be molded. It is related with the RTM shaping | molding method which can improve the fiber volume content rate (henceforth Vf), and can obtain the molded object which was more excellent in intensity | strength and lightweight.
[0002]
[Prior art]
For example, in an FRP molded body for aircraft and automobile applications, the volume content (Vf) of reinforcing fibers in the entire FRP molded body is about 55% to 65% in order to increase strength, reduce weight, and reduce costs. It is desirable to increase the so-called high Vf. For example, a technique described in Patent Document 1 has been proposed as a conventional technique related to a technique for increasing the Vf of such an FRP molded body.
[0003]
In the RTM molding method described in Patent Document 1, peel ply / resin dispersion media are arranged on both sides of a reinforcing fiber base made of a laminate of reinforcing fiber materials, and these are arranged on a molding die (tool) surface. In addition, a method is described in which the whole is covered with a bag material, and a resin injection gate and a suction gate for pressure reduction are provided in the interior sealed by the bag material to perform RTM molding.
[0004]
However, in this RTM molding method, when the resin is injected in a so-called high Vf state in which the fiber volume content (Vf) of the reinforcing fiber base is 55% or more, that is, the gap between the reinforcing fibers is small, Although the fiber volume content of the final molded body itself is high, the penetration of the resin into the molded body is poor, so in the case of a thick molded body with a plate thickness of, for example, 25 mm or more, it reaches every corner of the molded body. The resin did not reach, and as the structure, only those with defects remaining in the unimpregnated portion of the resin could be produced.
[0005]
On the other hand, when the reinforcing fiber Vf is 45%, for example, and the gap between the reinforcing fibers is relatively large, the resin permeability is good, but the fiber volume content of the final molded product is low, so that the strength and light weight are reduced. Only inferior products could be produced. That is, the resin impregnation property and the fiber volume content Vf are in a contradictory relationship, and it is difficult to achieve both the resin impregnation property and the fiber volume content improvement. Furthermore, although it is preferable to control the fiber volume content from the necessity of quality stabilization depending on a molded object, it was also difficult to satisfy such requirements.
[0006]
[Patent Document 1]
US Pat. No. 5,052,906 (Claim 1, FIG. 1)
[0007]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems in the prior art, and to make it possible to achieve both improvement in resin impregnation and fiber volume content, thereby making the FRP molded body stronger and lighter. An object of the present invention is to provide an RTM molding method capable of
[0008]
[Means for Solving the Problems]
In order to solve the above problems, an RTM molding method according to the present invention includes a reinforcing fiber base disposed in a molding die, a resin injection line and a suction line communicating with the molding die, and the inside of the molding die. In the RTM molding method in which the pressure is reduced by suction and the resin is injected into the mold and impregnated into the reinforcing fiber base to form the FRP molded body, the fiber volume content is lower than the target fiber volume content of the FRP molded body. After the resin is impregnated into the reinforcing fiber base, the injection of the resin is stopped, and then the suction of the resin is continued until the target fiber volume content is reached. In other words, when the resin is cured after flowing and being impregnated throughout the base material, the resin is continuously sucked until the target fiber volume content is reached before the resin is cured, so that the excess of the reinforcing fiber base material This is an RTM molding method in which resin is sucked to increase the fiber volume content to a target value.
[0009]
In this RTM molding method, after stopping the resin injection, at least one of the resin injection lines can be changed to a suction line, and the resin suction can be continued until the target fiber volume content is reached.
[0010]
The target fiber volume content is preferably in the range of 55% to 65%, for example, in order to increase Vf. In this case, the fiber volume content lower than the target fiber volume content is preferably in the range of 45% to 55%, for example.
[0011]
Whether or not the target fiber volume content has been reached can be determined, for example, by measuring the thickness of the reinforcing fiber substrate. While the resin suction is continued, the thickness is measured and a predetermined amount of excess resin is sucked. What is necessary is just to determine whether it was removed.
[0012]
Further, in the RTM molding method according to the present invention, it is also possible to set a resin injection amount or a suction amount in advance. That is, a resin injection amount corresponding to a fiber volume content lower than the target fiber volume content is set in advance, and the resin injection can be stopped when the set injection amount is reached. In addition, a resin suction amount for reaching the target fiber volume content is set in advance with respect to the resin injection amount, and when the set suction amount is reached, the resin suction can be stopped.
[0013]
Further, in the RTM molding method according to the present invention, in order to obtain a high-strength and lightweight FRP molded body, it is preferable that at least one layer of the reinforcing fiber base is composed of a carbon fiber layer. This carbon fiber layer can be formed into a woven fabric, for example, a unidirectional woven fabric in which carbon fibers are oriented in one direction.
[0014]
In the RTM molding method according to the present invention as described above, first, the resin is impregnated into the reinforcing fiber base so that the fiber volume content is lower than the target fiber volume content of the FRP molded body. The resin is sufficiently impregnated over the entire area of the material, and at this point, the occurrence of the resin non-impregnated portion is prevented. After the resin impregnation, the resin injection is stopped, and then the resin is continuously sucked until the target fiber volume content is reached until the resin is cured, and excess resin is sucked from the reinforcing fiber base. High Vf of the target molded product is achieved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a molding apparatus used in an RTM molding method according to an embodiment of the present invention. In FIG. 1, a mold 1 serving as a base is made of, for example, stainless steel and is configured in a flat plate shape. In the mold 1, a reinforcing fiber base 2 is disposed on the mold 1 in the illustrated example. The reinforcing fiber base 2 is made of, for example, a laminate of reinforcing fiber fabrics. In this embodiment, the medium 3 for diffusing the resin is disposed on the reinforcing fiber base 2 via the peel ply 24. The resin diffusion medium 3 is preferably a medium in which the flow resistance of the resin is lower than 1/10 of the flow resistance when flowing through the reinforcing fiber substrate 2, and specifically, polyethylene or polypropylene. A resin mesh fabric with an opening of # 400 or less is preferred. The entire members arranged on the mold 1 are covered with a bag material 4 made of an airtight material. As the bag material 4, for example, a nylon film is preferably used in consideration of airtightness and heat resistance. 5 is a highly adhesive synthetic rubber sealant that prevents the inflow of air from the outside so that the bag 4 can be kept in a reduced pressure state. In addition, air leakage can be prevented by further covering the first bag material with the second bag material to form a double bag, and as a result, Vf can be improved.
[0016]
The sealed bag material 4 is provided with a resin injection port 7 and a suction port 6 for decompressing the interior of the bag material 4 by suction, and is connected to the resin injection line and the suction line, respectively. For example, an aluminum C channel material or the like can be used for the resin injection port 7 and the suction port 6, and these channel materials are connected to an external member via a plastic tube forming the resin injection line and the suction line. Just connect. Reference numeral 8 denotes a thermosetting resin that becomes a matrix resin of the FRP molded body, and the resin is accommodated in a plastic pot, for example. A vacuum trap 9 accumulates excess resin from the molded body sucked from the suction port 6. A vacuum pump 10 sucks from the inside covered with the bag material 4 through the vacuum trap 9 and the suction port 6 and keeps the inside in a reduced pressure state. The peel ply 24 is interposed to easily remove the resin diffusion medium 3 from the molded body. For example, a woven fabric having a releasing function such as a nylon taffeta is used.
[0017]
The material of the reinforcing fiber forming the reinforcing fiber substrate 2 is not particularly limited, and examples thereof include glass fiber, carbon fiber, and aramid fiber. Moreover, the thing of the hybrid structure which used those at least 2 types or laminated | stacked may be used. Moreover, you may use the thing of the sandwich structure which pinched | interposed core materials, such as a foam material and a hollow core, between reinforcement fibers, for example. As the resin diffusion medium 3, for example, a mesh body can be used, or a resin flow path is formed in the mold 1 by a groove or the like, and the surface of the mold 1 on which the resin flow path is formed is used as the resin diffusion medium. It is also possible to configure. It is also possible to use the reinforcing fiber substrate itself as a resin diffusion medium. Examples of the matrix resin include polyester resin, vinyl ester resin, epoxy resin, and phenol resin.
[0018]
FIG. 2 shows a molding apparatus used in an RTM molding method according to another embodiment of the present invention, in which grooves are formed in a mold instead of separately placing a resin diffusion medium on the lower surface side of a reinforcing fiber substrate. A device that substantially constitutes a resin diffusion medium and that can measure the plate thickness (the thickness that is conceivable to the thickness of a molded fiber or a reinforcing fiber base impregnated with resin) with a dial gauge during resin suction. Is shown. Differences from the apparatus of FIG. 1 are as follows.
[0019]
21 is a dial gauge, which measures the plate thickness of the reinforcing fiber base during resin suction. 22 is a groove processed into a mold for resin diffusion instead of a resin diffusion medium, and is a rectangle or inverted trapezoid or triangle having a width of 0.5 mm to 5 mm, a depth of 1 mm to 6 mm, and an arrangement pitch of 2 mm to 25 mm. It is preferable to have a cross-sectional shape such as More preferably, it has a rectangular cross section with a width of about 1 mm and a depth of about 3 mm, and a pitch of about 8 mm. Examples of the measuring device for the thickness of the molded product other than the dial gauge 21 include a standard, a micrometer, and a laser measuring instrument.
[0020]
The RTM molding method according to the present invention using the molding apparatus as described above is performed as follows.
First, the reinforcing fiber base 2 is disposed on the molding surface of the mold 1, and the release peel ply 24 (for example, nylon taffeta) and the resin diffusion medium 3 are disposed thereon. Moreover, with respect to the reinforcing fiber base 2, for example, a resin injection port 7 and a suction port 6 are arranged at an end portion and a central portion (FIG. 2) and both end portions (FIG. 1), and a resin injection line and a suction port are provided to them. Connect the lines. At least one line is provided for each of the resin injection port 7 and the resin injection line, and the suction port 6 and the suction line. Next, the bag material 4 (film material) is covered so as to cover the whole from the upper part of each member laminated on the mold 1 as described above, and the inside of the reinforcing fiber base 2 and the like is maintained in a reduced pressure state from the outside. Therefore, the periphery is sealed with a sealant 5. Then, the valves A1 and A2 are closed, the valve A3 is opened, and suction is performed by the vacuum pump 10 through the suction port 6, the vacuum line, and the vacuum trap 9, so that the inside of the cavity (the interior covered with the bag material 4) is obtained. The pressure is reduced to 0.1 MPa or less.
[0021]
Next, the mold 1 is placed in a heating oven, and the entire mold is heated to a predetermined temperature. When the mold 1 rises to a predetermined temperature, the valve A1 is opened, and a predetermined resin 8 is injected into the cavity from the resin injection port 7. The resin diffuses in the resin diffusion medium 3 toward the suction line, and the resin in the resin diffusion medium 3 begins to impregnate the reinforcing fiber base 2. When the entire region in the base material 2 is impregnated with the resin, or even when the entire region in the base material 2 is not impregnated with the resin, when a predetermined amount of resin is injected, the valve A1 is turned on. Close and stop supplying resin. It is desirable to set the fiber volume content Vf at the time of stopping the resin injection to be in the range of 45% to 55%, more preferably in the range of 50 to 55%. This is to suppress resin loss due to suction and discharge as much as possible. Then, the suction port 6 and A2 are opened through the vacuum trap 9 communicating with the vacuum line, and the resin is sucked from the resin injection port 7 into the vacuum trap 9 until a predetermined fiber volume content is obtained. The suction of the resin may be continued until the resin is gelled or cured, but the suction is finally performed until the target fiber volume content is 55% to 65%. Setting the target fiber volume content in such a range is, for example, in the case of aircraft parts, Vf needs to be 55% or more in the cost / performance comparison with metal materials, and the fiber volume content This is because, when the Vf is as high as 65%, impregnation is poor and voids are likely to occur, and the interlaminar shear strength of the molded article is likely to decrease.
[0022]
In the present invention, the target fiber volume content Vf can be set by the following method, for example.
That is, it is possible to predict the fiber volume content of the molded body from the thickness of the reinforcing fiber base by the following formula.
Vf = FAW × PLY / (ρ × t)
Vf: Fiber volume content (%)
FAW: basis weight of reinforcing fiber material constituting reinforcing fiber substrate (g / cm ² )
PLY: Number of laminated reinforcing fiber materials ρ: Density of reinforcing fiber substrate (g / cm ³ )
t: Plate thickness (cm)
[0023]
When the thickness of the laminate (reinforcing fiber substrate) is set in advance and the thickness of the laminate is measured while the plate thickness corresponding to the target fiber volume content is reached, the valves A2 and A3 are You may close it. Alternatively, since the fiber volume content can be defined by the amount of fiber and resin in the laminate, the resin injection amount and suction amount corresponding to the predetermined fiber volume content are set in advance, and the resin is used at the target injection amount. The injection of the resin can be stopped and the suction of the resin can be stopped when the target suction amount is reached.
[0024]
Thereafter, the resin is cured at a predetermined temperature and time. After the curing is completed, all auxiliary materials such as the resin diffusion medium, the resin injection, and the members used for the suction line are removed from the surface of the molded body together with the bag material and peel ply, and finally the molded body is removed from the surface of the molding die. The obtained molded body can be after-cured at a predetermined temperature and time as required.
[0025]
【Example】
Example 1
Using the RTM molding device shown in FIGS. 1 and 2, a carbon fiber fabric cut into a length of 500 mm and a width of 500 mm was laid up on a mold 1 made of a stainless steel flat plate. The reinforcing fiber material used for forming the reinforcing fiber substrate was “Torayca” T800S unidirectional fabric (weight per unit: 285 g / m ² ) manufactured by Toray Industries, Inc., and a total of 96 ply layup was performed. A peel ply 24 (nylon taffeta) and a resin diffusion medium 3 (polypropylene mesh material) are disposed on the reinforcing fiber base 2, and a resin injection port 7 and a suction port 6 are disposed on the base material. Then, the whole was covered with a bag material 4 (nylon film) and the periphery was sealed with a highly adhesive synthetic rubber sealant 5 (note that although not shown in this figure, a double bag was used).
[0026]
In this state, the valves A1 and A2 were closed, the valve A3 was opened, and suction was performed from the suction port via the vacuum line and the vacuum trap 9, and the pressure in the cavity was reduced to 0.1 MPa or less. Thereafter, the mold is placed in an electric oven, and the inside of the oven is heated to 70 ° C. After the entire reinforcing fiber substrate reached 70 ° C., the valve A1 was opened and the matrix resin 8 was injected from the resin injection port 7 under vacuum pressure. As the resin, an epoxy resin (a resin viscosity at 70 ° C. (injection temperature) of 130 mPa · s, a resin viscosity after 1 hour at 70 ° C. of 320 mPa · s) was used. The injected resin is impregnated in the base material 2 while flowing in the resin diffusion medium 3 having low flow resistance. When 3750 cm ³ of a predetermined resin amount was injected, the valve A1 was closed to stop the resin supply. The fiber volume content of the base material that can be estimated from the thickness of the reinforcing fiber base material at this time was about 52%.
[0027]
Next, the valve A2 was opened, the resin injection line was opened to the vacuum side via a vacuum trap, and excess resin in the reinforcing fiber base was sucked into the vacuum trap 9 from the end of the reinforcing fiber base. Thereafter, when the resin suction amount reached a predetermined amount of 700 cm ³ , the valves A2 and A3 were closed to stop the resin suction. Thereafter, the temperature in the electric oven was raised to 130 ° C. and cured by heating for about 2 hours. After heat-curing, auxiliary materials such as bag materials were removed, and a CFRP (carbon fiber reinforced plastic) molded body was removed from the mold surface. As a result of measuring the fiber volume content of the CFRP molded body at the resin injection side, the suction side, and the midpoint between the two, it was within the range of 57.2% to 58.2%. That is, the fiber volume content could be improved to within the range of the target value compared to before the resin suction immediately after the resin impregnation.
[0028]
Example 2
A carbon fiber fabric 2 cut into a length of 500 mm and a width of 500 mm via a peel ply 24 on a stainless steel mold 1 having a # -shaped groove 22 (width 1 mm, depth 4 mm, pitch 15 mm) as a resin flow path. Laid up. Carbon fiber fabric 2 used was, Toray Industries Co., Ltd. "trading cards" T800S unidirectional fabric (basis weight: 285g / m ²⁾ a and was 88ply lay-up in total. A breathable material 23 (polyester nonwoven fabric) was disposed on the base material via a peel ply 24, and a suction port 6 was disposed thereon. In addition, the resin injection port 7 is disposed on the resin flow channel groove 22 formed in the mold 1 and the bag material 4 (nylon film) is covered over the whole so that the periphery is highly adhesive. Sealed with a sealant 5 made of synthetic rubber.
[0029]
In this state, the valves A1 and A2 were closed, the valve A3 was opened, and suction was performed from the suction port 6 through the vacuum line and the vacuum trap 9, and the pressure in the cavity was reduced to 0.1 MPa or less. Then, the shaping | molding die was installed in the electric oven, and the inside of an oven was heated at 70 degreeC. After the entire reinforcing fiber substrate reached 70 ° C., the valve A1 was opened, and the matrix resin 8 was injected from the resin injection port 7 under vacuum pressure. The epoxy resin of Example 1 was used for the resin. The injected resin diffused into the resin diffusion mold groove, and the resin in the groove was impregnated into the base material. As a result of measuring the plate thickness after the resin impregnated the entire reinforcing fiber substrate, it was 27.5 mm and the fiber volume content was 50.7%.
[0030]
Next, the valve A1 was closed, the valve A2 was opened, and excess resin in the reinforcing fiber base was sucked into the vacuum trap 9 through the suction port 6 and the resin injection port 7. In the case of this example, the target fiber volume content of the CFRP molded body was set to 55 to 60%. Since it was obtained in the previous experimental results that the shrinkage in the thickness direction of the molded body was about 1.2%, when the plate thickness reached 24.1 mm, A2 and A3 were closed and the resin was sucked. Stopped. Then, the temperature of the furnace was raised to 130 ° C. and cured by heating for about 2 hours. After heat curing, auxiliary materials such as bag materials were removed, and the CFRP molded body was taken out from the mold surface. As a result, 57.1 to 59.3% (plate thickness 23.8 mm) within the target fiber volume content. A CFRP molded product could be obtained.
[0031]
【The invention's effect】
As described above, according to the RTM molding method of the present invention, first, the resin is sufficiently impregnated over the entire area of the reinforcing fiber base, and after the resin supply is stopped, the resin suction is performed until the target fiber volume content is reached. Since the excess resin is continuously removed, it is possible to achieve a high fiber volume content of the molded body without causing inconveniences such as voids, to achieve high Vf, and to achieve strength and light weight. An excellent FRP molded product can be obtained.
[0032]
For example, when FRP is applied to a structural strength member such as an aircraft member, Vf is 55% to 65%, and the variation is required to be small. Even in response to such a requirement, the resin supply line is changed to a suction line, and the resin is sucked from both the resin suction port and the injection port, whereby the variation in Vf can be suppressed. Further, during the suction of the resin, for example, if the fiber volume content is estimated from the plate thickness, the injection amount, or the suction amount, and the resin suction is stopped at a time corresponding to the target fiber volume content, the fiber volume of the molded body It becomes possible to control the content rate more accurately with respect to the target value.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a molding apparatus used in an RTM molding method according to an embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view of a molding apparatus used in an RTM molding method according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mold 2 Reinforcing fiber 3 Resin diffusion medium 4 Bag material 5 Sealant 6 Suction port 7 Resin injection port 8 Resin 9 Vacuum trap 10 Vacuum pump 21 Dial gauge 22 Resin diffusion mold groove 23 Breathable material 24 Peel ply A1, A2, A3 valve

Claims

A reinforcing fiber base material is disposed in the mold, a resin injection line and a suction line communicating with the mold are provided, the inside of the mold is decompressed by suction, and a resin is injected into the mold to reinforce the fiber base material. In the RTM molding method of forming an FRP molded body by impregnating with a reinforced fiber substrate, the resin is impregnated into the reinforcing fiber base so that the fiber volume content is lower than the target fiber volume content of the FRP molded body, and then the resin is injected. The RTM molding method is characterized in that the suction of the resin is continued until the target fiber volume content is reached.

2. The RTM molding method according to claim 1, wherein after the resin injection is stopped, at least one of the resin injection lines is changed to a suction line, and the resin suction is continued until the target fiber volume content is reached.

The RTM molding method according to claim 1 or 2, wherein the target fiber volume content is in a range of 55% to 65%.

The RTM molding method according to claim 3, wherein a fiber volume content lower than the target fiber volume content is in a range of 45% to 55%.

The RTM shaping | molding method in any one of Claims 1-4 which determines the arrival to the said target fiber volume content rate by the measurement of the thickness of a reinforced fiber base material.

The injection amount of the resin corresponding to the fiber volume content rate lower than the target fiber volume content rate is preset, and the resin injection is stopped when the set injection amount is reached. The RTM molding method described in 1.

The resin suction amount for reaching the target fiber volume content is preset with respect to the resin injection amount, and when the set suction amount is reached, the resin suction is stopped. The RTM molding method described in 1.

The RTM molding method according to claim 1, wherein at least one layer of the reinforcing fiber base is composed of a carbon fiber layer.

The RTM molding method according to claim 8, wherein the carbon fiber layer is formed on a woven fabric.

The RTM molding method according to claim 9, wherein the woven fabric is a unidirectional woven fabric.