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Local Relative Density Modulates Failure and Strength in Vertically Aligned Carbon Nanotubes

Pathak, Siddhartha and Mohan, Nisha and Decolvenaere, Elizabeth and Needleman, Alan and Bedewy, Mostafa and Hart, A. John and Greer, Julia R. (2013) Local Relative Density Modulates Failure and Strength in Vertically Aligned Carbon Nanotubes. ACS Nano, 7 (10). pp. 8593-8604. ISSN 1936-0851. doi:10.1021/nn402710j.

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Micromechanical experiments, image analysis, and theoretical modeling revealed that local failure events and compressive stresses of vertically aligned carbon nanotubes (VACNTs) were uniquely linked to relative density gradients. Edge detection analysis of systematically obtained scanning electron micrographs was used to quantify a microstructural figure-of-merit related to relative local density along VACNT heights. Sequential bottom-to-top buckling and hardening in stress–strain response were observed in samples with smaller relative density at the bottom. When density gradient was insubstantial or reversed, bottom regions always buckled last, and a flat stress plateau was obtained. These findings were consistent with predictions of a 2D material model based on a viscoplastic solid with plastic non-normality and a hardening–softening–hardening plastic flow relation. The hardening slope in compression generated by the model was directly related to the stiffness gradient along the sample height, and hence to the local relative density. These results demonstrate that a microstructural figure-of-merit, the effective relative density, can be used to quantify and predict the mechanical response.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Hart, A. John0000-0002-7372-3512
Greer, Julia R.0000-0002-9675-1508
Additional Information:© 2013 American Chemical Society. Received for review May 29, 2013 and accepted September 3, 2013. Published online September 03, 2013. The authors acknowledge financial support from the Institute for Collaborative Biotechnologies (ICB) through Grant W911NF-09-0001 from the U.S. Army Research Office. The content of the information does not necessarily reflect the position or the policy of the Government, and no official endorsement should be inferred. S.P. gratefully acknowledges support from the W.M. Keck Institute for Space Studies Postdoctoral Fellowship program for this work.
Group:Keck Institute for Space Studies
Funding AgencyGrant Number
Army Research Office (ARO)W911NF-09-0001
Keck Institute for Space Studies (KISS)UNSPECIFIED
Subject Keywords:vertically aligned carbon nanotubes; compression; mechanical properties; energy storage; finite element simulation
Issue or Number:10
Record Number:CaltechAUTHORS:20131204-145203712
Persistent URL:
Official Citation:Local Relative Density Modulates Failure and Strength in Vertically Aligned Carbon Nanotubes Siddhartha Pathak, Nisha Mohan, Elizabeth Decolvenaere, Alan Needleman, Mostafa Bedewy, A. John Hart, and Julia R. Greer ACS Nano 2013 7 (10), 8593-8604
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42838
Deposited By: Tony Diaz
Deposited On:05 Dec 2013 00:34
Last Modified:10 Nov 2021 16:29

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