Higher Recovery and Better Energy Dissipation at Faster Strain Rates in Carbon Nanotube Bundles: An in-Situ Study
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- 作者：Siddhartha Pathak ; Ee J. Lim ; Parisa Pour Shahid Saeed Abadi ; Samuel Graham ; Baratunde A. Cola ; Julia R. Greer
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：March 27, 2012
- 年：2012
- 卷：6
- 期：3
- 页码：2189-2197
- 全文大小：565K
- 年卷期：v.6,no.3(March 27, 2012)
- ISSN：1936-086X
文摘
We report mechanical behavior and strain rate dependence of recoverability and energy dissipation in vertically aligned carbon nanotube (VACNT) bundles subjected to quasi-static uniaxial compression. We observe three distinct regimes in their stress鈥搒train curves for all explored strain rates from 4 脳 10鈥? down to 4 脳 10鈥? /sec: (1) a short initial elastic section followed by (2) a sloped plateau with characteristic wavy features corresponding to buckle formation and (3) densification characterized by rapid stress increase. Load鈥搖nload cycles reveal a stiffer response and virtually 100% recoverability at faster strain rates of 0.04/sec, while the response is more compliant at slower rates, characterized by permanent localized buckling and significantly reduced recoverability. We propose that it is the kinetics of attractive adhesive interactions between the individual carbon nanotubes within the VACNT matrix that governs morphology evolution and ensuing recoverability. In addition, we report a 6-fold increase in elastic modulus and gradual decrease in recoverability (down to 50%) when VACNT bundles are unloaded from postdensification stage as compared with predensification. Finally, we demonstrate energy dissipation capability, as revealed by hysteresis in load鈥搖nload cycles. These findings, together with high thermal and electrical conductivities, position VACNTs in the 鈥渦nattained-as-of-to-date-space鈥?in the material property landscape.