Effect of fiber volume fraction on the fracture behavior of Nb-1 wt pct Zr/218W composites at elevated temperatures |
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Authors: | S V Raj L J Ghosn |
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Affiliation: | (1) NASA-Glenn Research Center at Lewis Fields, 44136 Cleveland, OH;(2) Eveready Battery Company, Inc., 44145 Westlake, OH |
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Abstract: | Nb-1 wt pct Zr/218W long-fiber composite monotapes, nominally containing 0 to 70 vol pct of 218 tungsten fibers, were fabricated
by arc spraying the Nb-1 pct Zr matrix onto the tungsten fibers. The monotapes were consolidated by hot pressing and hot isostatic
pressing techniques. Tensile tests conducted between 1400 and 1600 K, under engineering strain rates varying between 1.5×10−5 and 1.5×10−3 s−1, demonstrated that composites containing 70 vol pct of fibers had the highest strength-to-density ratio. Microstructural
observations of specimens tested at 1400 K revealed that composites containing less than 50 vol pct of fibers showed extensive
matrix cavitation, fiber-matrix debonding, and necking of the fibers. Above 50 vol pct, the composite matrix was less prone
to cavitation, with an increasing tendency toward shear deformation of the fibers as the fiber volume fraction increased.
No fiber damage was observed at 1400 K away from the fractured end, but significant fiber damage was observed at higher temperatures.
A phenomenological model is presented to rationalize these observations.
L.J. GHOSN, formerly Researcher with Case Western Reserve University, Cleveland, OH 44115
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. |
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