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The Prime Importance of Second-Order Effects in Rigid-Rod Polymers

Published online by Cambridge University Press:  26 February 2011

Steven J. Deteresa
Affiliation:
Lawrence Livermore National Lab., University of California, P.O. Box 808, L-338, Livermore, CA 94550
Richard J. Farris
Affiliation:
University of Massachusetts, Polymer Science and Engineering Dept., Amherst, MA 01003
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Abstract

The torsion modulus of high performance rigid-rod polymer fibers is shown to be dependent on axial tensile stress. This behavior is one of at least second-order elasticity. Fiber ultimate tensile strengths are of the same magnitude as torsion moduli, and increases in torsion moduli in excess of 200% were observed for fibers under tension. Consideration of the effect of an axial compressive stress on fiber torsion modulus leads to a prediction of an elastic shear instability that initiates at a compressive stress approximately equal in magnitude to the zero-stress torsion modulus. Hence, it is concluded that the compressive strengths of high performance polymer fibers are limited by the onset of an elastic microstructural instability.

Type
Research Article
Copyright
Copyright © Materials Research Society 1989

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References

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