SYMPOSIA PAPER Published: 01 January 1992

Open Hole and Postimpact Compressive Fatigue of Stitched and Unstitched Carbon-Epoxy Composites


This investigation evaluates the fatigue performance of a stitched uniweave fabric composite and a toughened tape composite. It also addresses the effects of stitching on compression fatigue life. Postimpact compressive fatigue and open hole fatigue tests were run on an AS4/3501-6 uniweave with stitching and a toughened IM7/8551-7 tape without stitching. Stitching was found to increase the thickness and, consequently, the weight of the composite material. The two materials were compared on an equal carbon content basis as well as on an equal weight basis. The excess thickness in the stitched uniweave composite was responsible for the lower fatigue life, on an equal carbon basis, compared to the toughened resin tape composite. Comparison of fatigue lives on an equal carbon fiber areal weight basis indicated that puncture or crimp damage from stitching has very little effect on compression failure. Postimpact fatigue tests showed that, although the damage area in the stitched uniweave composite was twice that of the toughened tape composite, the fatigue lives of the stitched composite were significantly longer than those of the toughened composite. Thus, it appears that the increase in thickness from stitching is much more of a penalty than crimped fibers or puncture damage from stitching.

Author Information

Portanova, MA
Lockheed Engineering & Sciences Co., NASA Langley Research Center, Hampton, VA
Poe, CC
NASA Langley Research Center, Hampton, VA
Whitcomb, JD
NASA Langley Research Center, Hampton, VA
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Developed by Committee: D30
Pages: 37–53
DOI: 10.1520/STP20143S
ISBN-EB: 978-0-8031-5184-0
ISBN-13: 978-0-8031-1426-5