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Comparison of Intralaminar and Interlaminar Mode-I Fracture Toughness of Unidirectional IM7/8552 Graphite/Epoxy CompositeThe intralaminar and interlaminar mode-I fracture-toughness of a unidirectional IM7/8552 graphite/epoxy composite were measured using compact tension (CT) and double cantilever beam (DCB) test specimens, respectively. Two starter crack geometries were considered for both the CT and DCB specimen configurations. In the first case, starter cracks were produced by 12.5 micron thick, Teflon film inserts. In the second case, considerably sharper starter cracks were produced by fatigue precracking. For each specimen configuration, use of the Teflon film starter cracks resulted in initially unstable crack growth and artificially high initiation fracture-toughness values. Conversely, specimens with fatigue precracks exhibited stable growth onset and lower initiation fracture toughness. For CT and DCB specimens with fatigue precracks, the intralaminar and interlaminar initiation fracture toughnesses were approximately equal. However, during propagation, the CT specimens exhibited more extensive fiber bridging, and rapidly increasing R-curve behavior as compared to the DCB specimens. Observations of initiation and propagation of intralaminar and interlaminar fracture, and the measurements of fracture toughness, were supported by fractographic analysis using scanning electron microscopy.
Document ID
20120016494
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Czabaj, Michael W.
(NASA Langley Research Center Hampton, VA, United States)
Ratcliffe, James
(National Inst. of Aerospace Hampton, VA, United States)
Date Acquired
August 26, 2013
Publication Date
October 1, 2012
Subject Category
Composite Materials
Report/Patent Number
NF1676L-15094
Meeting Information
Meeting: 15th US-Japan Conference on Composite Materials
Location: Arlington, TX
Country: United States
Start Date: October 1, 2012
End Date: October 3, 2012
Funding Number(s)
WBS: WBS 877868.02.07.07.05.01.01
Distribution Limits
Public
Copyright
Public Use Permitted.
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