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Indentation Creep and Relaxation Measurements of Polymers

Published online by Cambridge University Press:  01 February 2011

Mark R. VanLandingham ,
Peter L. Drzal  and
Christopher C. White
Mark R. VanLandingham
Affiliation:
U. S. Army Research Laboratory, Weapons & Materials Research Directorate, Aberdeen Proving Ground, MD 21005–5069
Peter L. Drzal
Affiliation:
National Institute of Standards and Technology, Building and Fire Research Laboratory, Gaithersburg, MD 20899–8615
Christopher C. White
Affiliation:
National Institute of Standards and Technology, Building and Fire Research Laboratory, Gaithersburg, MD 20899–8615
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Abstract

Instrumented indentation was used to characterize the mechanical response of polymeric materials. A model based on contact between a rigid probe and a linear viscoelastic material was used to calculate values for creep compliance and stress relaxation modulus for epoxy, poly(methyl methacrylate) (PMMA), and two poly(dimethyl siloxane) (PDMS) elastomers. Results from bulk rheometry studies were used for comparison to the indentation creep and stress relaxation results. For the two glassy polymers, the use of sharp pyramidal tips produced responses that were considerably more compliant (less stiff) than rheometry values. Additional study of the deformation remaining in epoxy after creep testing revealed that a large portion of the creep displacement measured was due to post-yield flow. Indentation creep measurements of the epoxy using a rounded conical tip also produced nonlinear responses, but the creep compliance values appeared to approach linear viscoelastic values with decreasing creep force. Responses measured for the PDMS were mainly linear elastic, but the filled PDMS exhibited some time-dependence and nonlinearity in both rheometry and indentation measurements.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 841: Symposium R – Fundamentals of Nanoindentation and Nanotribology III , 2004 , R5.5
Copyright
Copyright © Materials Research Society 2005

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References

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