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carbon nanotube-reinforced composite materials

Henry Tan's picture

The effect of van der Waals-based interface cohesive law on carbonnanotube-reinforced composite materials

H. Tan, L. Y. Jiang, Y. Huang, B. Liu, and K. C. Hwang
Composite Science and Technology, 2007, accepted.

The nonlinear cohesive law derived from the weak van der Waals force for carbonnanotube/polymer interfaces is incorporated in present study of CNT-reinforced composites.

Carbon nanotubes can indeed improve the mechanical behavior of composite at the small strain, but such improvement disappears at relatively large strain because the completely debonded nanotubes behave like voids in the matrix and may even weaken the composite.

The increase of interface adhesion between carbon nanotubes and polymer matrix may significantly improve the composite behavior at the large strain.

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Henry Tan's picture

Dear Xiaodong,

Our modeling is still in its infancy, and will be more useful after incorporate some of your experimental observations.

I will comment more after a thorough reading and understanding of your very nice work.

Dear Henry,

I would like to point out the following paper by Hashin (2002) on thin interfaces you might find interesting. As an example, he considers a fiber reinforced composite material using the Generalized Self-Consistent scheme, rather than Mori-Tanaka that you used. I think the van der Waals forces could be inncorporated into this model as well.

Here is the link

http://dx.doi.org/10.1016/S0022-5096(02)00050-9

Sincerely,

Vladimir Vinogradov

Henry Tan's picture

Dear Vladimir,

Thanks for being interested in out work.

Generalized Self-Consistent scheme is more accurate than Mori-Tanaka in dealing with the interaction between inclusions; this is important when the volume fraction of the inclusions is high.

The volume fraction of nanotubes in a polymeric matrix is usually low, around 1% only, therefore Mori-Tanaka is more suitable for this case for its simplicity. We enjoyed the elegancy of the method which enabled us to focus more on the physics of the interface bonding.

Sincerely,

Henry Tan

Dear Henry,

Thanks for your reply. You are absolutely right.
In fact, the Hashin's paper is more general than I mentioned. It first develops the general theory of thin elastic interfaces in curvilinear coordinates, then applies the problem of an isolated cylinder with  interface/interphase (which is your case), and applies both the composite cylinder assemblage and the GSCS for finite volume fractions (which you don't need).

Your paper deals with hydrostatic tension. With radial symmetry the nonlinear CNT-polymer matrix interface changes its properties in an angle-independent way. This wouldn't occurs under transverse shear or transverse unidirectional tension, for example. The problem is much more complicated in this case due to the interface nonlinearity. Are you going to deal with this in the future?

Regards
Vladimir

Henry Tan's picture

Dear Vladimir,

What you said is exactly what we have concerned. The angle-independent way wouldn't occur under transverse shear or transverse unidirectional tension. We chose the simplest case, hydrostatic loading, to avoid the shear/tension coupling on the interfaces.

You are right that the problem is much more complicated in this case due to the interface nonlinearity. We have already done some work in this direction, and the paper was published two months ago.

Tan et al (2007) The uniaxial tension of particulate composite materials with nonlinear interface debonding. Int. J. Solids Struct 44, 1809-1822.

For the future research in this direction, I will apply the method to both small systems like nanotube (or nanoparticle) reinforced composite materials, and big systems like solid propellants for rockets.

Regards
Henry.

Thank you for the reference.

Regards,

Vladimir

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