1.
S Fang ZF Liu, FA Moura
Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles Journal Article
In: Science, vol. 349, no. 6246, pp. 404-404, 2015.
@article{Liu2015,
title = {Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles},
author = {ZF Liu, S Fang, FA Moura, JN Ding, N Jiang, J Di, M Zhang, X Lepró, DS Galvão, CS Haines, NY Yuan, SG Yin, DW Lee, R Wang, HY Wang, W Lv, C Dong, RC Zhang, MJ Chen, Q Yin, YT Chong, R Zhang, X Wang, MD Lima, R Ovalle-Robles, D Qian, H Lu, RH Baughman},
url = {http://www.sciencemag.org/content/349/6246/400.full.pdf},
doi = {10.1126/science.aaa7952},
year = {2015},
date = {2015-07-24},
journal = {Science},
volume = {349},
number = {6246},
pages = {404-404},
abstract = {Superelastic conducting fibers with improved properties and functionalities are needed
for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%)
sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in
the fiber direction on stretched rubber fiber cores. The resulting structure exhibited
distinct short- and long-period sheath buckling that occurred reversibly out of phase
in the axial and belt directions, enabling a resistance change of less than 5% for a
1000% stretch. By including other rubber and carbon nanotube sheath layers, we
demonstrated strain sensors generating an 860% capacitance change and electrically
powered torsional muscles operating reversibly by a coupled tension-to-torsion
actuation mechanism. Using theory, we quantitatively explain the complementary effects
of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation
and electronic properties.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Superelastic conducting fibers with improved properties and functionalities are needed
for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%)
sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in
the fiber direction on stretched rubber fiber cores. The resulting structure exhibited
distinct short- and long-period sheath buckling that occurred reversibly out of phase
in the axial and belt directions, enabling a resistance change of less than 5% for a
1000% stretch. By including other rubber and carbon nanotube sheath layers, we
demonstrated strain sensors generating an 860% capacitance change and electrically
powered torsional muscles operating reversibly by a coupled tension-to-torsion
actuation mechanism. Using theory, we quantitatively explain the complementary effects
of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation
and electronic properties.
for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%)
sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in
the fiber direction on stretched rubber fiber cores. The resulting structure exhibited
distinct short- and long-period sheath buckling that occurred reversibly out of phase
in the axial and belt directions, enabling a resistance change of less than 5% for a
1000% stretch. By including other rubber and carbon nanotube sheath layers, we
demonstrated strain sensors generating an 860% capacitance change and electrically
powered torsional muscles operating reversibly by a coupled tension-to-torsion
actuation mechanism. Using theory, we quantitatively explain the complementary effects
of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation
and electronic properties.
2.
Machado, Leonardo D; Legoas, Sergio B; Galvao, Douglas S
Multi-Million Fully Atomistic Molecular Dynamics Simulations of Yarn Formation from Carbon Nanotube Forests Proceedings
Cambridge University Press, vol. 1407, 2012.
@proceedings{machado2012multi,
title = {Multi-Million Fully Atomistic Molecular Dynamics Simulations of Yarn Formation from Carbon Nanotube Forests},
author = {Machado, Leonardo D and Legoas, Sergio B and Galvao, Douglas S},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8537115&fulltextType=RA&fileId=S1946427412007105},
year = {2012},
date = {2012-01-01},
journal = {MRS Proceedings},
volume = {1407},
pages = {mrsf11--1407},
publisher = {Cambridge University Press},
abstract = {In this work we present preliminary results from multi-million fully atomistic classical molecular dynamics simulations carried out to test different existing mechanisms that have been proposed in the literature to explain the drawing of yarns from carbon nanotube forests. Despite the fact that it has been almost ten years since yarns were first drawn, there are still controversies on the mechanisms and necessary conditions that can produce yarns and sheets drawn from carbon nanotube forests. Moreover, few works have tried to understand at atomistic level the details of yarn drawing mechanisms, and no fully atomistic simulations have been carried out so far on this particular subject. Our preliminary results suggest that only direct van der Waals interactions among large bundles seem not to be enough to explain the yarn drawing process. Bundle interconnectors (such as small bundles connecting large bundles) were observed to play a critical role in our simulations. Depending on the topology of these interconnectors it was possible to observe from the simulations fibers/yarn formation from proposed structural models. These models were built based on structural information inferred from scanning electron microscopy data.},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
In this work we present preliminary results from multi-million fully atomistic classical molecular dynamics simulations carried out to test different existing mechanisms that have been proposed in the literature to explain the drawing of yarns from carbon nanotube forests. Despite the fact that it has been almost ten years since yarns were first drawn, there are still controversies on the mechanisms and necessary conditions that can produce yarns and sheets drawn from carbon nanotube forests. Moreover, few works have tried to understand at atomistic level the details of yarn drawing mechanisms, and no fully atomistic simulations have been carried out so far on this particular subject. Our preliminary results suggest that only direct van der Waals interactions among large bundles seem not to be enough to explain the yarn drawing process. Bundle interconnectors (such as small bundles connecting large bundles) were observed to play a critical role in our simulations. Depending on the topology of these interconnectors it was possible to observe from the simulations fibers/yarn formation from proposed structural models. These models were built based on structural information inferred from scanning electron microscopy data.
3.
Coluci, Vitor R; Fonseca, Alexandre F; Galvao, Douglas S; Daraio, Chiara
Entanglement and the nonlinear elastic behavior of forests of coiled carbon nanotubes Journal Article
In: Physical Review Letters, vol. 100, no. 8, pp. 086807, 2008.
@article{coluci2008entanglement,
title = {Entanglement and the nonlinear elastic behavior of forests of coiled carbon nanotubes},
author = {Coluci, Vitor R and Fonseca, Alexandre F and Galvao, Douglas S and Daraio, Chiara},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.086807},
year = {2008},
date = {2008-01-01},
journal = {Physical Review Letters},
volume = {100},
number = {8},
pages = {086807},
publisher = {American Physical Society},
abstract = {Helical or coiled nanostructures have been objects of intense experimental and theoretical studies due to their special electronic and mechanical properties. Recently, it was experimentally reported that the dynamical response of a foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The physical origin of this unusual behavior is not yet fully understood. In this Letter, based on analytical models, we show that the entanglement among neighboring coils in the superior part of the forest surface must be taken into account for a full description of the strongly nonlinear behavior of the impact response of a drop ball onto a forest of coiled carbon nanotubes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Helical or coiled nanostructures have been objects of intense experimental and theoretical studies due to their special electronic and mechanical properties. Recently, it was experimentally reported that the dynamical response of a foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The physical origin of this unusual behavior is not yet fully understood. In this Letter, based on analytical models, we show that the entanglement among neighboring coils in the superior part of the forest surface must be taken into account for a full description of the strongly nonlinear behavior of the impact response of a drop ball onto a forest of coiled carbon nanotubes.
4.
Coluci, Vitor R; Hall, Lee J; Kozlov, Mikhail E; Zhang, Mei; Dantas, Socrates O; Galvao, Douglas S; Baughman, Ray H
Modeling the auxetic transition for carbon nanotube sheets Journal Article
In: Physical Review B, vol. 78, no. 11, pp. 115408, 2008.
@article{coluci2008modeling,
title = {Modeling the auxetic transition for carbon nanotube sheets},
author = {Coluci, Vitor R and Hall, Lee J and Kozlov, Mikhail E and Zhang, Mei and Dantas, Socrates O and Galvao, Douglas S and Baughman, Ray H},
url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.78.115408},
year = {2008},
date = {2008-01-01},
journal = {Physical Review B},
volume = {78},
number = {11},
pages = {115408},
publisher = {APS},
abstract = {A simple model is developed to predict the complex mechanical properties of carbon nanotube sheets (buckypaper) [L. J. Hall et al., Science 320, 504 (2008)]. Fabricated using a similar method to that deployed for making writing paper, these buckypapers can have in-plane Poisson’s ratios changed from positive to negative, becoming auxetic, as multiwalled carbon nanotubes are increasingly mixed with single-walled carbon nanotubes. Essential structural features of the buckypapers are incorporated into the model: isotropic in-plane mechanical properties, nanotubes preferentially oriented in the sheet plane, and freedom to undergo stress-induced elongation by both angle and length changes. The expressions derived for the Poisson’s ratios enabled quantitative prediction of both observed properties and remarkable new properties obtainable by structural modification.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A simple model is developed to predict the complex mechanical properties of carbon nanotube sheets (buckypaper) [L. J. Hall et al., Science 320, 504 (2008)]. Fabricated using a similar method to that deployed for making writing paper, these buckypapers can have in-plane Poisson’s ratios changed from positive to negative, becoming auxetic, as multiwalled carbon nanotubes are increasingly mixed with single-walled carbon nanotubes. Essential structural features of the buckypapers are incorporated into the model: isotropic in-plane mechanical properties, nanotubes preferentially oriented in the sheet plane, and freedom to undergo stress-induced elongation by both angle and length changes. The expressions derived for the Poisson’s ratios enabled quantitative prediction of both observed properties and remarkable new properties obtainable by structural modification.
5.
Hall, Lee J; Coluci, Vitor R; Galvao, Douglas S; Kozlov, Mikhail E; Zhang, Mei; Dantas, Socrates O; Baughman, Ray H
Sign change of Poisson's ratio for carbon nanotube sheets Journal Article
In: Science, vol. 320, no. 5875, pp. 504–507, 2008.
@article{hall2008sign,
title = {Sign change of Poisson's ratio for carbon nanotube sheets},
author = {Hall, Lee J and Coluci, Vitor R and Galvao, Douglas S and Kozlov, Mikhail E and Zhang, Mei and Dantas, Socrates O and Baughman, Ray H},
url = {http://www.sciencemag.org/content/320/5875/504.short},
year = {2008},
date = {2008-01-01},
journal = {Science},
volume = {320},
number = {5875},
pages = {504--507},
publisher = {American Association for the Advancement of Science},
abstract = {Most materials shrink laterally like a rubber band when stretched, so their Poisson's ratios are positive. Likewise, most materials contract in all directions when hydrostatically compressed and decrease density when stretched, so they have positive linear compressibilities. We found that the in-plane Poisson's ratio of carbon nanotube sheets (buckypaper) can be tuned from positive to negative by mixing single-walled and multiwalled nanotubes. Density-normalized sheet toughness, strength, and modulus were substantially increased by this mixing. A simple model predicts the sign and magnitude of Poisson's ratio for buckypaper from the relative ease of nanofiber bending and stretch, and explains why the Poisson's ratios of ordinary writing paper are positive and much larger. Theory also explains why the negative in-plane Poisson's ratio is associated with a large positive Poisson's ratio for the sheet thickness, and predicts that hydrostatic compression can produce biaxial sheet expansion. This tunability of Poisson's ratio can be exploited in the design of sheet-derived composites, artificial muscles, gaskets, and chemical and mechanical sensors.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Most materials shrink laterally like a rubber band when stretched, so their Poisson's ratios are positive. Likewise, most materials contract in all directions when hydrostatically compressed and decrease density when stretched, so they have positive linear compressibilities. We found that the in-plane Poisson's ratio of carbon nanotube sheets (buckypaper) can be tuned from positive to negative by mixing single-walled and multiwalled nanotubes. Density-normalized sheet toughness, strength, and modulus were substantially increased by this mixing. A simple model predicts the sign and magnitude of Poisson's ratio for buckypaper from the relative ease of nanofiber bending and stretch, and explains why the Poisson's ratios of ordinary writing paper are positive and much larger. Theory also explains why the negative in-plane Poisson's ratio is associated with a large positive Poisson's ratio for the sheet thickness, and predicts that hydrostatic compression can produce biaxial sheet expansion. This tunability of Poisson's ratio can be exploited in the design of sheet-derived composites, artificial muscles, gaskets, and chemical and mechanical sensors.
2015
5.
S Fang ZF Liu, FA Moura
Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles Journal Article
In: Science, vol. 349, no. 6246, pp. 404-404, 2015.
Abstract | Links | BibTeX | Tags: Carbon Nanotube Forests, Finite Elements, Superelastic, top20
@article{Liu2015,
title = {Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles},
author = {ZF Liu, S Fang, FA Moura, JN Ding, N Jiang, J Di, M Zhang, X Lepró, DS Galvão, CS Haines, NY Yuan, SG Yin, DW Lee, R Wang, HY Wang, W Lv, C Dong, RC Zhang, MJ Chen, Q Yin, YT Chong, R Zhang, X Wang, MD Lima, R Ovalle-Robles, D Qian, H Lu, RH Baughman},
url = {http://www.sciencemag.org/content/349/6246/400.full.pdf},
doi = {10.1126/science.aaa7952},
year = {2015},
date = {2015-07-24},
journal = {Science},
volume = {349},
number = {6246},
pages = {404-404},
abstract = {Superelastic conducting fibers with improved properties and functionalities are needed
for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%)
sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in
the fiber direction on stretched rubber fiber cores. The resulting structure exhibited
distinct short- and long-period sheath buckling that occurred reversibly out of phase
in the axial and belt directions, enabling a resistance change of less than 5% for a
1000% stretch. By including other rubber and carbon nanotube sheath layers, we
demonstrated strain sensors generating an 860% capacitance change and electrically
powered torsional muscles operating reversibly by a coupled tension-to-torsion
actuation mechanism. Using theory, we quantitatively explain the complementary effects
of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation
and electronic properties.},
keywords = {Carbon Nanotube Forests, Finite Elements, Superelastic, top20},
pubstate = {published},
tppubtype = {article}
}
Superelastic conducting fibers with improved properties and functionalities are needed
for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%)
sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in
the fiber direction on stretched rubber fiber cores. The resulting structure exhibited
distinct short- and long-period sheath buckling that occurred reversibly out of phase
in the axial and belt directions, enabling a resistance change of less than 5% for a
1000% stretch. By including other rubber and carbon nanotube sheath layers, we
demonstrated strain sensors generating an 860% capacitance change and electrically
powered torsional muscles operating reversibly by a coupled tension-to-torsion
actuation mechanism. Using theory, we quantitatively explain the complementary effects
of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation
and electronic properties.
for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%)
sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in
the fiber direction on stretched rubber fiber cores. The resulting structure exhibited
distinct short- and long-period sheath buckling that occurred reversibly out of phase
in the axial and belt directions, enabling a resistance change of less than 5% for a
1000% stretch. By including other rubber and carbon nanotube sheath layers, we
demonstrated strain sensors generating an 860% capacitance change and electrically
powered torsional muscles operating reversibly by a coupled tension-to-torsion
actuation mechanism. Using theory, we quantitatively explain the complementary effects
of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation
and electronic properties.
2012
4.
Machado, Leonardo D; Legoas, Sergio B; Galvao, Douglas S
Multi-Million Fully Atomistic Molecular Dynamics Simulations of Yarn Formation from Carbon Nanotube Forests Proceedings
Cambridge University Press, vol. 1407, 2012.
Abstract | Links | BibTeX | Tags: Carbon Nanotube Forests, Carbon Nanotubes, Molecular Dynamics, Yarns
@proceedings{machado2012multi,
title = {Multi-Million Fully Atomistic Molecular Dynamics Simulations of Yarn Formation from Carbon Nanotube Forests},
author = {Machado, Leonardo D and Legoas, Sergio B and Galvao, Douglas S},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8537115&fulltextType=RA&fileId=S1946427412007105},
year = {2012},
date = {2012-01-01},
journal = {MRS Proceedings},
volume = {1407},
pages = {mrsf11--1407},
publisher = {Cambridge University Press},
abstract = {In this work we present preliminary results from multi-million fully atomistic classical molecular dynamics simulations carried out to test different existing mechanisms that have been proposed in the literature to explain the drawing of yarns from carbon nanotube forests. Despite the fact that it has been almost ten years since yarns were first drawn, there are still controversies on the mechanisms and necessary conditions that can produce yarns and sheets drawn from carbon nanotube forests. Moreover, few works have tried to understand at atomistic level the details of yarn drawing mechanisms, and no fully atomistic simulations have been carried out so far on this particular subject. Our preliminary results suggest that only direct van der Waals interactions among large bundles seem not to be enough to explain the yarn drawing process. Bundle interconnectors (such as small bundles connecting large bundles) were observed to play a critical role in our simulations. Depending on the topology of these interconnectors it was possible to observe from the simulations fibers/yarn formation from proposed structural models. These models were built based on structural information inferred from scanning electron microscopy data.},
keywords = {Carbon Nanotube Forests, Carbon Nanotubes, Molecular Dynamics, Yarns},
pubstate = {published},
tppubtype = {proceedings}
}
In this work we present preliminary results from multi-million fully atomistic classical molecular dynamics simulations carried out to test different existing mechanisms that have been proposed in the literature to explain the drawing of yarns from carbon nanotube forests. Despite the fact that it has been almost ten years since yarns were first drawn, there are still controversies on the mechanisms and necessary conditions that can produce yarns and sheets drawn from carbon nanotube forests. Moreover, few works have tried to understand at atomistic level the details of yarn drawing mechanisms, and no fully atomistic simulations have been carried out so far on this particular subject. Our preliminary results suggest that only direct van der Waals interactions among large bundles seem not to be enough to explain the yarn drawing process. Bundle interconnectors (such as small bundles connecting large bundles) were observed to play a critical role in our simulations. Depending on the topology of these interconnectors it was possible to observe from the simulations fibers/yarn formation from proposed structural models. These models were built based on structural information inferred from scanning electron microscopy data.
2008
3.
Coluci, Vitor R; Fonseca, Alexandre F; Galvao, Douglas S; Daraio, Chiara
Entanglement and the nonlinear elastic behavior of forests of coiled carbon nanotubes Journal Article
In: Physical Review Letters, vol. 100, no. 8, pp. 086807, 2008.
Abstract | Links | BibTeX | Tags: Carbon Nanotube Forests, Entanglement, Mechanical Properties, top20
@article{coluci2008entanglement,
title = {Entanglement and the nonlinear elastic behavior of forests of coiled carbon nanotubes},
author = {Coluci, Vitor R and Fonseca, Alexandre F and Galvao, Douglas S and Daraio, Chiara},
url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.086807},
year = {2008},
date = {2008-01-01},
journal = {Physical Review Letters},
volume = {100},
number = {8},
pages = {086807},
publisher = {American Physical Society},
abstract = {Helical or coiled nanostructures have been objects of intense experimental and theoretical studies due to their special electronic and mechanical properties. Recently, it was experimentally reported that the dynamical response of a foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The physical origin of this unusual behavior is not yet fully understood. In this Letter, based on analytical models, we show that the entanglement among neighboring coils in the superior part of the forest surface must be taken into account for a full description of the strongly nonlinear behavior of the impact response of a drop ball onto a forest of coiled carbon nanotubes.},
keywords = {Carbon Nanotube Forests, Entanglement, Mechanical Properties, top20},
pubstate = {published},
tppubtype = {article}
}
Helical or coiled nanostructures have been objects of intense experimental and theoretical studies due to their special electronic and mechanical properties. Recently, it was experimentally reported that the dynamical response of a foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The physical origin of this unusual behavior is not yet fully understood. In this Letter, based on analytical models, we show that the entanglement among neighboring coils in the superior part of the forest surface must be taken into account for a full description of the strongly nonlinear behavior of the impact response of a drop ball onto a forest of coiled carbon nanotubes.
2.
Coluci, Vitor R; Hall, Lee J; Kozlov, Mikhail E; Zhang, Mei; Dantas, Socrates O; Galvao, Douglas S; Baughman, Ray H
Modeling the auxetic transition for carbon nanotube sheets Journal Article
In: Physical Review B, vol. 78, no. 11, pp. 115408, 2008.
Abstract | Links | BibTeX | Tags: Auxetics, Carbon Nanotube Forests, Carbon Nanotubes, CNT sheets
@article{coluci2008modeling,
title = {Modeling the auxetic transition for carbon nanotube sheets},
author = {Coluci, Vitor R and Hall, Lee J and Kozlov, Mikhail E and Zhang, Mei and Dantas, Socrates O and Galvao, Douglas S and Baughman, Ray H},
url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.78.115408},
year = {2008},
date = {2008-01-01},
journal = {Physical Review B},
volume = {78},
number = {11},
pages = {115408},
publisher = {APS},
abstract = {A simple model is developed to predict the complex mechanical properties of carbon nanotube sheets (buckypaper) [L. J. Hall et al., Science 320, 504 (2008)]. Fabricated using a similar method to that deployed for making writing paper, these buckypapers can have in-plane Poisson’s ratios changed from positive to negative, becoming auxetic, as multiwalled carbon nanotubes are increasingly mixed with single-walled carbon nanotubes. Essential structural features of the buckypapers are incorporated into the model: isotropic in-plane mechanical properties, nanotubes preferentially oriented in the sheet plane, and freedom to undergo stress-induced elongation by both angle and length changes. The expressions derived for the Poisson’s ratios enabled quantitative prediction of both observed properties and remarkable new properties obtainable by structural modification.},
keywords = {Auxetics, Carbon Nanotube Forests, Carbon Nanotubes, CNT sheets},
pubstate = {published},
tppubtype = {article}
}
A simple model is developed to predict the complex mechanical properties of carbon nanotube sheets (buckypaper) [L. J. Hall et al., Science 320, 504 (2008)]. Fabricated using a similar method to that deployed for making writing paper, these buckypapers can have in-plane Poisson’s ratios changed from positive to negative, becoming auxetic, as multiwalled carbon nanotubes are increasingly mixed with single-walled carbon nanotubes. Essential structural features of the buckypapers are incorporated into the model: isotropic in-plane mechanical properties, nanotubes preferentially oriented in the sheet plane, and freedom to undergo stress-induced elongation by both angle and length changes. The expressions derived for the Poisson’s ratios enabled quantitative prediction of both observed properties and remarkable new properties obtainable by structural modification.
1.
Hall, Lee J; Coluci, Vitor R; Galvao, Douglas S; Kozlov, Mikhail E; Zhang, Mei; Dantas, Socrates O; Baughman, Ray H
Sign change of Poisson's ratio for carbon nanotube sheets Journal Article
In: Science, vol. 320, no. 5875, pp. 504–507, 2008.
Abstract | Links | BibTeX | Tags: Artificial Muscles, Auxetics, Carbon Nanotube Forests, sheets, top20
@article{hall2008sign,
title = {Sign change of Poisson's ratio for carbon nanotube sheets},
author = {Hall, Lee J and Coluci, Vitor R and Galvao, Douglas S and Kozlov, Mikhail E and Zhang, Mei and Dantas, Socrates O and Baughman, Ray H},
url = {http://www.sciencemag.org/content/320/5875/504.short},
year = {2008},
date = {2008-01-01},
journal = {Science},
volume = {320},
number = {5875},
pages = {504--507},
publisher = {American Association for the Advancement of Science},
abstract = {Most materials shrink laterally like a rubber band when stretched, so their Poisson's ratios are positive. Likewise, most materials contract in all directions when hydrostatically compressed and decrease density when stretched, so they have positive linear compressibilities. We found that the in-plane Poisson's ratio of carbon nanotube sheets (buckypaper) can be tuned from positive to negative by mixing single-walled and multiwalled nanotubes. Density-normalized sheet toughness, strength, and modulus were substantially increased by this mixing. A simple model predicts the sign and magnitude of Poisson's ratio for buckypaper from the relative ease of nanofiber bending and stretch, and explains why the Poisson's ratios of ordinary writing paper are positive and much larger. Theory also explains why the negative in-plane Poisson's ratio is associated with a large positive Poisson's ratio for the sheet thickness, and predicts that hydrostatic compression can produce biaxial sheet expansion. This tunability of Poisson's ratio can be exploited in the design of sheet-derived composites, artificial muscles, gaskets, and chemical and mechanical sensors.},
keywords = {Artificial Muscles, Auxetics, Carbon Nanotube Forests, sheets, top20},
pubstate = {published},
tppubtype = {article}
}
Most materials shrink laterally like a rubber band when stretched, so their Poisson's ratios are positive. Likewise, most materials contract in all directions when hydrostatically compressed and decrease density when stretched, so they have positive linear compressibilities. We found that the in-plane Poisson's ratio of carbon nanotube sheets (buckypaper) can be tuned from positive to negative by mixing single-walled and multiwalled nanotubes. Density-normalized sheet toughness, strength, and modulus were substantially increased by this mixing. A simple model predicts the sign and magnitude of Poisson's ratio for buckypaper from the relative ease of nanofiber bending and stretch, and explains why the Poisson's ratios of ordinary writing paper are positive and much larger. Theory also explains why the negative in-plane Poisson's ratio is associated with a large positive Poisson's ratio for the sheet thickness, and predicts that hydrostatic compression can produce biaxial sheet expansion. This tunability of Poisson's ratio can be exploited in the design of sheet-derived composites, artificial muscles, gaskets, and chemical and mechanical sensors.
http://scholar.google.com/citations?hl=en&user=95SvbM8AAAAJ
