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Strain gradient plasticity effect in indentation hardness of polymers

Published online by Cambridge University Press:  31 January 2011

Arthur C. M. Chong  and
David C. C. Lam
Arthur C. M. Chong
Affiliation:
Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
David C. C. Lam
Affiliation:
Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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Abstract

Plasticity in material is typically described as a function of strain, but recent observations from torsion and indentation experiments in metals suggested that plasticity is also dependent on strain gradient. The effects of strain gradient on plastic deformation in thermosetting epoxy and polycarbonate thermoplastic were experimentally investigated by nanoindentation and atomic force microscopy in this study. Both thermosetting and thermoplastic polymers exhibited hardening as a result of imposed strain gradients. Strain gradient plasticity theory developed on the basis of a molecular kinking mechanism has predicted strain gradient hardening in polymers. Comparisons made between indentation data and theoretical predictions correlated well. This suggests that strain gradient plasticity in glassy polymers is determined by molecular kinking mechanisms.

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Type
Articles
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Journal of Materials Research , Volume 14 , Issue 10 , October 1999 , pp. 4103 - 4110
Copyright
Copyright © Materials Research Society 1999

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