Tuesday, 12 October 2004 - 5:10 PM

This presentation is part of : Damage and Composites II

Advanced Laminated Composites with Nanofiber Reinforced Interfaces

Yongkui Wen, University of Nebraska-Lincoln, Department of Engineering Mechanics, Lincoln, NE 68588 and Yuris A. Dzenis, Department of Engineering Mechanics, University of Nebraska-Lincoln, W315 Nebraska Hall, 900N 17th Street, Lincoln, NE 68588-0526.

Delamination is a serious and persistent problem of advanced laminated composites. It is caused by interlaminar stresses at weak, non-reinforced ply interfaces and can lead to catastrophic failure of composite structures. Different approaches have been tried over the years to suppress delamination, including resin toughening, interleaving, stitching or wrapping free edge regions, altering the mechanical properties of certain layers, optimizing composite layups, etc. However, most were expensive and technologically complicated. In addition, some methods reduced the primary in-plane properties of composites and resulted in significant increase of laminate thickness and weight. Nanoreinforcement of interfaces between plies in laminated composites was recently proposed to suppress delamination by one of the co-authors. The concept has been recently demonstrated experimentally using several polymer nanofibers. In the present study, carbon nanofibers were applied for interface nanoreinforcement in advanced commercial carbon/epoxy composite for the first time. These nanofibers were compared with as-spun polyacrylonitrile (PAN) nanofibers and stabilized PAN nanofibers. Static interlaminar fracture analysis was performed under Mode I and Mode II loadings by the DCB and ENF tests. The results showed substantial increase in interlaminar fracture toughness with nanoreinforcement. The highest improvement was observed with carbon nanofiber reinforcement. The improvements were achieved with negligible increase in weight. Fractographic analysis of the failed specimens showed that nanofiber pull-out and crack bridging were the major nanomechanisms of toughening. The results indicate that carbon nanofiber may have superior mechanical properties.

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