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Nanoindentation-derived elastic modulus of an amorphous polymer and its sensitivity to load-hold period and unloading strain rate

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Abstract

An amorphous polymer was contacted by a Berkovich indenter using the same loading history but with four different unloading rates following a wide range of load-hold time periods. The strain-rate sensitivity index of the creeping solid was determined at each load-hold period based on two readily determinable parameters, which are the effective contact stiffness and strain rate at the onset of unloading. The measured strain-rate sensitivity index was found to increase with decreasing load-hold period, suggesting that the elastic moduli of the amorphous polymers determined by nanoindentation (together with the true contact area) depends significantly on the selection of the load-hold period. The rheological condition of the creeping solid under constant load changes substantially with time to affect the subsequent unloading recovery process. It is therefore advisable to control not only the unloading strain rate but also the load-hold period when testing time-dependent materials.

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References

  1. I.N. Sneddon: The relation between load and penetration in the axisymmetric Boussinesq problem for a punch of arbitrary profile. Int. J. Eng. Sci. 3, 47 1965

    Article  Google Scholar 

  2. W.C. Oliver, G.M. Pharr: Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology. J. Mater. Res. 19, 3 2004

    Article  CAS  Google Scholar 

  3. W.C. Oliver, G.M. Pharr: An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res. 7, 1564 1992

    Article  CAS  Google Scholar 

  4. A. Bolshakov, G.M. Pharr: Influences of pileup on the measurement of mechanical properties by load and depth-sensing indentation techniques. J. Mater. Res. 13, 1049 1998

    Article  CAS  Google Scholar 

  5. A.H.W. Ngan, H.T. Wang, B. Tang, K.Y. Sze: Correcting power-law viscoelastic effects in elastic modulus measurement using depth-sensing indentation. Int. J. Solids Struct. 42, 1831 2005

    Article  Google Scholar 

  6. J. Menčík, G. Rauchs, J. Bardon, A. Riche: Determination of elastic modulus and hardness of viscoelastic-plastic materials by instrumented indentation under harmonic load. J. Mater. Res. 20, 2660 2005

    Article  Google Scholar 

  7. N. Fujisawa, M.V. Swain: Effect of unloading strain rate on the elastic modulus of a viscoelastic solid determined by nanoindentation. J. Mater. Res. 21, 708 2006

    Article  CAS  Google Scholar 

  8. Y-T. Cheng, C-M. Cheng: Relationships between initial unloading slope, contact depth, and mechanical properties for conical indentation in linear viscoelastic solids. J. Mater. Res. 20, 1046 2005

    Article  CAS  Google Scholar 

  9. Y-T. Cheng, C-M. Cheng, W. Ni: Methods of obtaining instantaneous modulus of viscoelastic solids using displacement-controlled instrumented indentation with axisymmetric indenters of arbitrary smooth profiles. Mater. Sci. Eng., A 423, 2 2006

    Article  Google Scholar 

  10. N. Fujisawa, M.V. Swain: On the indentation contact area of a creeping solid during constant-strain-rate loading by a sharp indenter. J. Mater. Res. 22, 893 2007

    Article  CAS  Google Scholar 

  11. G. Feng, A.H.W. Ngan: Effects of creep and thermal drift on modulus measurement using depth-sensing indentation. J. Mater. Res. 17, 660 2002

    Article  CAS  Google Scholar 

  12. M.J. Mayo, W.D. Nix: A micro-indentation study of superplasticity in Pb, Sn, and Sn-38 wt% Pb. Acta Metall. 36, 2183 1988

    Article  CAS  Google Scholar 

  13. B. Tang, A.H.W. Ngan: Accurate measurement of tip-sample contact size during nanoindentation of viscoelastic materials. J. Mater. Res. 18, 1141 2003

    Article  CAS  Google Scholar 

  14. D.L. Goble, E.G. Wolff: Strain-rate sensitivity index of thermoplastics. J. Mater. Sci. 28, 5986 1993

    Article  CAS  Google Scholar 

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Acknowledgments

The authors wish to acknowledge the Australian Research Council for funding this project. We also wish to thank Hysitron, Inc., for access to a Ub1 instrument to undertake this research.

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Authors and Affiliations

  1. Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra, Australian Capital Territory, 0200, Australia

    N. Fujisawa

  2. Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Surry Hills, New South Wales, 2010, Australia

    M.V. Swain

Authors
  1. N. Fujisawa
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  2. M.V. Swain
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Correspondence to N. Fujisawa.

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Fujisawa, N., Swain, M. Nanoindentation-derived elastic modulus of an amorphous polymer and its sensitivity to load-hold period and unloading strain rate. Journal of Materials Research 23, 637–641 (2008). https://doi.org/10.1557/JMR.2008.0079

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  • DOI: https://doi.org/10.1557/JMR.2008.0079

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