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Other TitleStudy of out-of-plane (interlaminar) tensile test method for CFRP laminates
Author(jpn)原 栄一; 横関 智弘; 八田 博志; 石川 隆司
Author(eng)Hara, Eiichi; Yokozeki, Tomohiro; Hatta, Hiroshi; Ishikawa, Takashi
Author Affiliation(jpn)航空宇宙技術振興財団; 東京大学 大学院工学系研究科; 宇宙航空研究開発機構 総合技術研究本部 複合材技術開発センター; 宇宙航空研究開発機構 航空プログラムグループ
Author Affiliation(eng)Foundation for Promotion of Japanese Aerospace Technology; University of Tokyo School of Engineering; Japan Aerospace Exploration Agency Advanced Composite Technology Center, Institute of Aerospace Technology; Japan Aerospace Exploration Agency Aviation Program Group
Issue Date2007-03-30
PublisherJapan Aerospace Exploration Agency (JAXA)
Publication date2007-03-30
AbstractAlthough several out-of-plane test methods are proposed in MIL-HDBK-17 (MILitary-HanDBooK-17) and in research publications, their reliability remains to be established. The present study focuses on the flatwise tension test. Finite element analyses and experiments were carried out to find the most suitable specimen configuration to evaluate out-of-plane stiffness and strength. Several variations of specimen configuration (cylindrical column and spool column) were examined. Nine types of cylindrical model were investigated, with the diameter fixed at 25 mm and the thickness varied between 2 mm and 100 mm. The numerical calculations indicated stress concentrations near the adhesive layer and a multi-axial stress state in the cylindrical model. The 'stress ratio' is defined as a representative value in which the nominal stress is divided by the maximum stress in order to describe the apparent strength. Based on stress ratios, the best configuration among the cylindrical column models was determined to be the thinnest. In the case of spool specimens, stress concentration near the minimum diameter at the center of a specimen was predicted. Through these calculations, it was concluded that the degree of multi-axial stress was lower in the spool specimens than in the column specimens, and the stress ratio approaches unity as the minimum diameter approaches zero. This suggests that the strength of a spool specimen increases as the center diameter decreases. Several experimental tests were also carried out on cylindrical and spool specimens. Failure (including delamination in the adhesive layer) was confirmed for cylindrical specimens, whereas failure at the center of the specimen was confirmed for spool specimens.
複合材料の面内特性や破壊靱性を評価するための試験は各団体(JIS(Japanese Industrial Standards)、ISO(International Organization for Standardization)、ASTM(American Society for Testing and Materials))により定められているが、面外引張特性(層間引張特性)を評価するための直接負荷試験は未だ規格化されていない。本研究では、炭素繊維強化プラスチック(Carbon Fiber Reinforced Plastic: CFRP)の面外方向の引張特性を取得するための試験方法を検討した。負荷形態はハニカムサンドイッチ板のフラットワイズ試験と同様の直接負荷方式とし、最初に試験片形状の検討のため、有限要素解析を実施した、CFRPの0度1方向積層板を対象とし、供試体形状は円柱と板厚中心部がくびれたスプール状円柱(糸巻き形状)を検討した。有限要素法ソフトABAQUSを使用して供試体内の応力状態や供試体の各位置の歪みによる見かけの弾性率を検討した。解析結果より円柱形状の供試体の場合、治具接着面近傍の特定の位置で応力集中が発生することが予測された。また、スプール状円柱形状供試体の場合、板厚中心部で応力集中が発生し、供試体評定部内での破断が予測された。中心部の直径を減少させることで、この応力集中の度合いが緩和されることが予測された。次に解析で検討した形状の供試体を製作し、検証試験を実施した。スプール状円柱の供試体の各試験結果は応力集中が予測された位置での破断が確認され、最小断面部の直径の違いによる破断強度の違いも解析予測と同様の傾向を得た。なお、円柱形状では試験実施の不安定性が確認され、標準化する試験法としては採用しがたいことも明らかにした。
DescriptionJAXA Research and Development Report
KeywordsCFRP; tensile strength; mechanical property; test method; finite element method; cylindrical column; adhesive layer; interlaminar stress; stress ratio; tensile test; CFRP; 引張強度; 機械的性質; 試験法; 有限要素法; 円柱; 接着層; 層間応力; 応力比; 引張試験
Document TypeTechnical Report
JAXA Category研究開発報告
Report NoJAXA-RR-06-025

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