Tuesday, 12 October 2004 - 4:20 PM

This presentation is part of : Damage and Composites II

Experimental study on dynamic delamination toughness of a graphite-fiber/epoxy composite with interface modified by nanofibers

Xiangfa Wu and Yuris A. Dzenis. Department of Engineering Mechanics, University of Nebraska-Lincoln, W317 Nebraska Hall, 900N 17th Street, Lincoln, NE 68588-0526

Experimental study was performed to evaluate the toughening effect of polymer nanofibers on dynamic delamination toughness of a graphite-fiber/epoxy composite made of unidirectional P7051S-20Q-1000 prepreg (Toray). Polymer composite panels with and without nanofiber reinforcement at interfaces were produced. Polyacrylonitrile (PAN) continuous nanofibers were manufactured by electrospinning technique and directly placed at interfaces of the laminated panels before curing. Modified dynamic three-point-bending and compact shearing test configurations based on Hopkinson pressure bar (HPB) and crack detection gage (CDG) were used for the determination of the dynamic mode I and mode II delamination toughness of the composite samples. Transient loading history was measured by the HPB instrumented with a high-resolution digital oscilloscope, while the crack initiation and delay times were captured using the CDG. Using dynamic finite-element analysis (FEA) of the impact process, the critical dynamic stress intensity factors, KIDC and KIIDC, were extracted from numerical results of the crack opening displacements. Results show that under the present transient loadings, the PAN nanofibers substantially increase the critical DSIFs in both mode I and mode II cases up to 60% and 40%, respectively. Dynamic toughening mechanisms were further explored in details by fractographical analysis of failed samples using scanning electron microscopy (SEM). The present research indicates that continuous nanofibers have a potential as dynamic interface reinforcement in advanced polymer composites.

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