Interface effects on the viscoelastic characteristics of carbon nanotube polymer matrix composites

Y. Pan, G. J. Weng, S. A. Meguid, W. S. Bao, Z. H. Zhu, A. M.S. Hamouda

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

Highlights: A theory of interface effects in viscoelastic response of CNT composites is developed. CNT loadings of 0.3, 0.6 and 2.8 vol.% in polypropylene are examined. From creep tests, load transfer from CNTs to polymer is found to be indeed imperfect. It leads to enhanced creep, and affects stress relaxation and strain-rate sensitivity. Cyclic loading causes higher interfacial sliding and greatly affects the loss modulus. It is generally known that load transfer from the polymer matrix to carbon nanotubes (CNTs) can be greatly hindered due to the pristine CNT surface condition. This imperfect condition can have a profound influence on the effectiveness of CNT reinforcement. In order to address this issue in the context of viscoelastic response, an effective medium theory is first presented, and then applied to study the effect of interfacial sliding on the time-dependent creep, stress relaxation, strain-rate sensitivity, and storage and loss moduli of a multi-walled CNT/polypropylene nanocomposite. We show that, without accounting for the imperfect load transfer at the interface, the predicted creep compliances are too stiff, but with the introduction of a weakened interface, the measured creep curves at various CNT loading can be well captured. Both stress relaxation and stress-strain relations are also found to greatly depend on the interface condition. Under low-frequency harmonic loading our calculations also reveal that the interface condition is further weakened and that a larger interface sliding parameter is required to reflect the measured storage and tangent moduli. We conclude that the viscoelastic characteristics of a CNT nanocomposite are very sensitive to the interface condition, and that continued improvement in surface functionalization is necessary to realize the full potential of CNT reinforcement.

Original languageEnglish (US)
Pages (from-to)1-11
Number of pages11
JournalMechanics of Materials
Volume58
DOIs
StatePublished - Jan 1 2013

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Instrumentation
  • Materials Science(all)

Keywords

  • Carbon nanotube
  • Interface effects
  • Micromechanics
  • Polymer matrix
  • Viscoelastic characteristics

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