Basic Mechanical Properties of Carbon Nanotubes

SkepticJ

I'm looking for information on the maximum possible strength of SWNTs.
What effect do thermodynamically inevitable(over macro scale lengths) lattice faults have on the tensile and compressive strength of the tubes?
What effect does tube chirality and diameter have on tensile and compressive strength? What is the probability that composites will ever be as strong as single tubes? There is an undue level of contradictory information on them online for my taste. Thanks in advance for the help.

so-crates

As carbon nanotubes are pretty much at the cutting edge of chemistry/materials science, that info is going to be hard to find. Have you tried looking in journal publications?

PerennialII

Remember seeing somewhere that nanotube sheets had an axial elastic modulus of about/up to 1 TPa (in that case, would consider there to be some scatter(?)).

slider527

to look up in the journals try... scholar.google.com

SkepticJ

Is the Young's modulus a practical strength or for theoretically perfect crystals?
What is scatter?

PerennialII

I remember reading from some journal that single wall nanotubes have Young's modulus of about 1 TPa and multi-wall constructs some hundred GPas higher. The theoretical tensile strength is around 120 to 150 GPa, in practise what has been measured in lab and as such has been attained so far is 63 GPa (remember seeing a bit of this probably in Nature or something). What I meant by scatter was that there may be considerably lot of it since we're talking about cutting edge stuff and there are different constructs available (someone knowing more about these things can enlighten this quantitatively ?).

SkepticJ

Hmmmmm, seems the tensile strength has been circumcised a bit since I last found data on them. A Nasa page had them at 200GPa. Or maybe it's just in flux because it's still so new and we don't yet have precise data on them.

PerennialII

I'd go for the flux interpretation ... even doing any sort of material characterization for them feels like quite a boggle.

SkepticJ

How would I callculate how stiff a composite member of NTs could be? For example nylon makes nice strong flexible ropes but can also make hard plastic gears. Carbon fiber is flexible stringy stuff but put it in an epoxy and it's very light and stiff. Fiberglass same thing. What exactly is the Young's modulus if it's not the practical tensile strength? I'm not a mechanical engineer, just on a learning quest.

PerennialII

Young's modulus is a material parameter essentially characterizing stiffness. Young's modulus is typically defined and understood via Hooke's law:

http://physics.uwstout.edu/StatStr/s...ess/strs32.htm

Its important not to mix structural stiffness and material stiffness. Like in your examples, if you simply take a large enough block of material of suitable geometry and apply a force to it, if the block is large enough, it is bound to have some stiffness (resistance to the applied force).

If you have a case like above where you essentially have a composite of two or more materials, a simple way to derive condensed ("homogenized") material properties is often the rule of mixtures, used quite a bit in composite stuff for one (like when you got fiberglass fibres mixed to a plastic matrix):

http://islnotes.cps.msu.edu/trp/back/est_rule.html
http://www.matter.org.uk/glossary/detail.asp?dbid=341