Tuesday, May 15, 2007

continuing the detour - finding Young's modulus of a carbon nanotube along the long axis

While I am waiting for the latest simulation of Movement 114 to complete, I thought I would try another experiment. This time I am trying to find Young's modulus, or the modulus of elasticity, of a carbon nanotube positioned as shown. This tube is 20A long and 9A in diameter. Just like before it is being subjected to 1000pN of force. Here is the elongation/time plot:

Again you can see that eventually the tube starts to break up just like in the last experiment. Before it does it makes an average elongation of .38A. I have calculated the stress applied as 1.59e9 N/m^2 and strain as .02. This gives a Young's modulus of 75 GPa and a spring constant of 24.1 N/m.

I believe that the generally accepted value for the Young's modulus of a single wall carbon nanotube is approximately 1000 GPa, so I am off by more than an order of magnitude with this one. However I am not sure of the physical properties of the tubes used in these other experiments, and I do believe the Young's modulus of single wall nanotubes is heavily dependent on its size and chirality. Hopefully I can find these others experiments and find out exactly what type of tubes were used.

No comments: