Fracture and fatigue in a 3-D woven carbon fiber/epoxy composite

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:412089

Wigent, D E; Mohamed, M H ^[1]; Fahmy, A A ^[1]

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1. North Carolina State Univ., Raleigh, NC (United States)

To further understand fracture and fatigue in 3-D textile composites, plates of carbon fiber/epoxy composite were consolidated using 3-D woven preforms woven at the Mars Mission Research Center. Subsequent compact tension specimens were prepared and tested by methods based in part on ASTM test method E 647-78T. Stress intensities required to propagate a crack were determined with crack planes at 0, 90, and 45 degrees with respect to the production direction. Failure modes were related to 3-D preform structure and orientation. Fatigue testing was conducted at incremental stress intensity levels. Sequential radiographs were made in conjunction with compliance measurements on both fatigue and static specimens to monitor progressive damage. Results show that the stress intensity, K, required to propagate under static load ranged from 19.8MPa m{sup .5} to 29MPa m{sup .5} and a fatigue threshold yielding lifetimes above 10{sup 7} cycles was observed at roughly 65% of the static stress intensities. The failure modes observed in the 3-D woven composites were significantly different from those common in laminated structures. Fatigue did not result in fiber failure or delamination. High toughness, lack of delamination, and resistance to edge induced failures implies that the 3-D reinforcement yields advantages in durability, machinability, repair, and safety over laminated structures.

• OSTI ID: 412089
• Report Number(s): CONF-960310--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON FIBERS
COMPOSITE MATERIALS
CRACKS
EPOXIDES
FAILURES
FATIGUE
MECHANICAL PROPERTIES
STRESS INTENSITY FACTORS