MIT OpenCourseWarehttp://ocw.mit.edu3.22 Mechanical Properties of MaterialsSpring 2008For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.3.22 Mechanical Behavior of MaterialsCarbon Nanotube MechanicsMark MascaroRobert MitchellMIT Department of Materials Science and EngineeringCambridge, MA 02139 USAMay 2008Image removed due to copyright restrictions. Please see http://en.wikipedia.org/wiki/Image:Kohlenstoffnanoroehre_Animation.gif3.22 Mechanical Behavior of MaterialsBig Picture• Macroscopic description of the phenomenon• Very high tensile strength, but buckles easily in compression (11-63 GPA, 100-1000x better than ASTM 1040 steel) [1]• Very high Young’s Modulus (~1 TPa)• Buckling behavior very similar to deformation of cylindrical shells [2]•Engineering applications of Carbon Nanotubes• Composite materials to take advantage of high tensile strength• Cell nano-injection - Delivery of chemical load into cells without solvents and without damage of the cell membrane [3][1] Pantano, A., et al. “Mechanics of deformation of single- and multi-wall carbon nanotubes.” Journal of the Mechanics and Physics of Solids 52 (2004): 789-821[2] Poncharal P., et al. “Electrostatic Deflections and Electromechanical Resonances of Carbon Nanotubes.” Science 283 (1999): 1513-1516[3] Chen, X., et al. “A cell nanoinjector based on carbon nanotubes.” PNAS 104 (20 May 2007): 8218-8222Courtesy of National Academy of Sciences, U. S. A. Used with permission. Source: Chen, Xing, et al. "A cell nanoinjector based on carbon nanotubes." PNAS 104 (20 May 2007): 8218-8222. Copyright 2007 National Academy of Sciences, U.S.A.Image removed due to copyright restrictions. Please see Fig. 3b,c,d in [2].3.22 Mechanical Behavior of MaterialsMicroscopic mechanism• Microscopic behavior of Carbon Nanotube Failure•Failure proceeds via breaking of C-C bonds•Fracture propagation direction is a function of chirality [4]•Sword-in-Sheath Failure predominant in MWCNT structures [5][4] Belytschko, T., et al. “Atomistic Simulations of Nanotube Fracture.” Physical Review B 65 (2002): 235430.[5] Yu, M. F., et al. “Controlled sliding and pullout of nested shells in individual multiwalled carbon nanotubes.” Journal of Physical Chemistry B 104 (2000): 8764-8767Images removed due to copyright restrictions. Please see Fig. 6 in [4] and Fig. 1 in [5]3.22 Mechanical Behavior of MaterialsPrediction & Optimization•Prediction• Resonance can be modeled as a thin-walled cylindrical cantilever beam [2]•Optimization of CNT Mechanical Properties• Minimization of crystalline defects is critical• Chirality has a lesser influence on strength [4]Case: Failure Strain:Pristine Armchair 18.7%Pristine Zig-Zag 15.5%5/7/7/5 Armchair 14.3%One Atom Removed 10%Images removed due to copyright restrictions. Please see Fig. 2 in [2] and Fig. 8 and 9 in