Paper number 551


Masaki Hojo1 , Satoshi Matsuda2 , Shojiro Ochiai1 , Atsushi Murakami2 and Hideo Akimoto3

1Mesoscopic Materials Research Center, Graduate School of Engineering,
Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
2Dept. Chemical Engineering, Himeji Institute of Technology
Shosha, Himeji 671-2201, Japan
3Technical Center, Du Pont-Mitsui Polychemicals Co., Ltd.
Chigusa-kaigan, Ichihara 299-0108, Japan

Summary Interlaminar fracture toughness under mode I and II loadings was investigated for unidirectional CF/epoxy laminates with ionomer interleaf of the thickness of 12 to 200 micrometers. Ethylene based ionomer resin used in this study has high bonding strength with base epoxy resin. EPMA analysis revealed that interphases were formed between the ionomer layer and the base laminas. These interphases contain a mixture of ionomer, epoxy and carbon fibers. The fracture toughness of ionomer interleaved CF/epoxy laminates was much higher than that of base CF/epoxy laminates both under mode I and II loadings. For mode I loading, the high level of the toughness was kept constant with the crack growth. For mode II loading, the toughness reached 9 to 10 kJ/m2 , which is one of the highest among already reported results. Microscopic observation showed that the crack path was at the interface of the ionomer/interphase or inside the interphase region, arrested by fibers. Thus, cracks never propagated through the non-toughened region and this is responsible for the higher toughness, giving a new concept of interleaf toughening.
Keywords delamination, interlaminar fracture toughness, CFRP, interleaf, CF/epoxy, ionomer, interphase, mesoscopic fracture mechanism.

Theme : Mechanical and Physical Properties ; Fracture Mechanics and Failure

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