1. Tao Zheng Supervisor: Professor Harry Bhadeshia Richard Kemp
Configurational Entropy as a function of Material Dimensions: A theory for strong ropes
Tao Zheng
Supervisor: Professor Harry Bhadeshia
Richard Kemp

2. Outline space elevator.
are carbon nanotube ropes ideal materials for space elevator project?
1 Configurational entropy
2 Stored energy and energy release rate
3 size-dependence of materials strength
Conclusion

3. D.V.Smitherman 2005

4. High strength Lightweight > 62.5 GPa Carbon nanotubes Steel Kevlar
Density
1300 kg m-3
7900 kg m-3
1440 kg m-3
Tensile strength
130 GPa
< 5 GPa
3.6 GPa
Bradley C. Edwards 2004

5. Steven L.Mielke et al (2004)

6. Equilibrium defect density
Fromhold,Albert Thomas (1976)

7. Regular or ideal solution model
Quasichemical solution model
Lecture notes of Thermodynamics H K D H Bhadeshia (2004)

8. Energy release rate ( sound velocity):
Stored energy
Energy release rate ( sound velocity):

9. strength 130 GPa modulus 0.63 TPa
Stored energy (J g-1)
Energy release rate (m s-1)
Dynamite
4650
6000
Nanotube
5420
21500
Bradley C. Edwards 2004

10. Different tensile strength value with different ropes length.
Data from M.-F. Yu et al (2000); Min-Feng et al (2000); Z. W. Pan et al (1999)

11. Conclusion
1. By applying quasichemical solution model, more accurate configurational entropy and equilibrium defect density can be obtained.
2. Because of high strength and low density, carbon nanotubes have quite high stored energy and energy release rate which may make them not very safe in engineering application.
3. Strength of nanotube ropes will decrease sharply with increase of length of ropes.

12. Thank you!