Center for Composite Materials - University of Delaware

Research Summary

Local Buckling Behavior of Vertically Aligned MWCNT Arrays with van der Waals Interaction

Authors: Yupeng Li and Jonghwan Suhr

OBJECTIVES

• Use compression experimental method and electronic microscope to characterize vertically aligned carbon nanotubes (VACNTs) in compression
• Use theoretical modeling and mechanical tools to analyze the buckling response of VACNTs
• Characterize the van der Waals interaction between VACNTs
• Use 3D finite element analysis to study the local buckling behavior of VACNT with lateral support

Terminology

• Instron, TA Q800: compressive machine which could control displacement and force and could have stress-strain response of material in test
• SEM, TEM: Electronic microscopic characterization method to have high magnitude view of VACNT
• Abaqus: Finite element analysis software for 3D CNT modeling

Local buckling behavior of VACNT

Local buckling behavior of VACNT
• Local buckling behavior in end region of VACNT
• Many short buckling waves in the end region and almost identical half wave length
• Progressive developed buckling waves in the longitudinal direction of VACNTs
• Wave damping effect seems to happen while a strain increases

Local buckling behavior with van der Waals interaction

• The van der Waals interaction between neighboring VACNT can provide a lateral support effect to each nanotube and could lead to distinctive local buckling behavior
• Due to van der Waals interaction, CNTs are constrained to some extent in the radial direction all along the length of the nanotube.
• Due to van der Waals interaction, CNTs are constrained to some extent in the radial direction all along the length of the nanotube.
• Within the buckled region, the buckling type is high mode buckling with many short half-waves, and the wave length is almost identical.

Finite element modeling on CNT buckling

• VACNTs with van der Waals interaction have high mode buckling in bottom region with many half waves, while the Euler CNT has classical 1st mode buckling with only one half wave.
• The half wave amplitude gradually decreases to zero upwards, which indicates the wave damping effect.

Conclusions

• In monotonic compression, VAMWCNT exhibits local buckling behavior with progressively developed half waves.
• Van der Waals interaction between adjacent CNTs within one bundle could provide the lateral support for each individual CNT.
• The lateral support effect from Van der Waals interaction could give rise to the local buckling behavior and the VACNTs will buckle collectively.
• The propagation of buckling will happen from the bottom and developing mechanism of VACNT buckling follows the wave damping effect.

Acknowledgements

Collaborators: Prof. Jae-boong Choi and Dr. Junmo Kang.
Lab members: Wenjie Zhao, Changsheng Shan, Hyung-ick Kim, Jaesoon Jang, Hong-Kyu Jang, James Sargianis and Joe Walsh.

National Science Foundation.

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