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Published April 1, 2012 | Published
Journal Article Open

Nonlinear viscoelasticity of freestanding and polymer-anchored vertically aligned carbon nanotube foams


Vertical arrays of carbon nanotubes (VACNTs) show unique mechanical behavior in compression, with a highly nonlinear response similar to that of open cell foams and the ability to recover large deformations. Here, we study the viscoelastic response of both freestanding VACNT arrays and sandwich structures composed of a VACNT array partially embedded between two layers of poly(dimethylsiloxane) (PDMS) and bucky paper. The VACNTs tested are ∼2 mm thick foams grown via an injection chemical vapor deposition method. Both freestanding and sandwich structures exhibit a time-dependent behavior under compression. A power-law function of time is used to describe the main features observed in creep and stress-relaxation tests. The power-law exponents show nonlinear viscoelastic behavior in which the rate of creep is dependent upon the stress level and the rate of stress relaxation is dependent upon the strain level. The results show a marginal effect of the thin PDMS/bucky paper layers on the viscoelastic responses. At high strain levels (ɛ = 0.8), the peak stress for the anchored CNTs reaches ∼45 MPa, whereas it is only ∼15 MPa for freestanding CNTs, suggesting a large effect of PDMS on the structural response of the sandwich structures.

Additional Information

© 2012 American Institute of Physics. Received 7 July 2011; accepted 1 March 2012; published online 10 April 2012. L. De Nardo and L. Lattanzi acknowledge Regione Lombardia and INSTM for the project "Metahouse." J.R. Raney thanks the U.S. Department of Defense for support via a National Defense Science & Engineering Graduate (NDSEG) fellowship. This work is supported by the Institute for Collaborative Biotechnologies under Contract No. W911NF-09-D-0001 with the Army Research Office.

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