Re: NEC-LIST: EM simulation of carbon fibers

Yannick Trovel wrote:

> I am currently looking for a method to simulate the interaction of an
> EM wave on some carbon fibers. Is there any special development for
> this kind of material? Or should we consider that it's a normal
> conducting material and simply use a program like NEC with the
> appropriate conducting value?
 
We have developed a method to model lossy surfaces by using lumped
resistive loading in the wire grid. The paper below gives the details
- I can certainly make it available to anybody who may be interested
and have difficulty getting hold of the paper.

  J Dresel, A P C Fourie, O Givati and A R Clark. "The modelling of
  lossy surfaces using a wire method-of-moments code" ANTEM 96,
  Quebec, Canada, 1996, pp 793-796.

We specifically applied the method described in the paper to modelling
carbon fibre woven material used in aircraft construction. A very
careful measurement procedure confirmed the validity of the method.

In short: one loads each arm in a gridded (ass. appr. square grid
elements) surface with a resistor with value equal to the
resistance/square of the surface. Normal wire gridding guidelines
(tenth of wavelength spacing and wire surface area = 2 x actual
surface area). We believe that this method should allow a wire MoM
package, such as NEC, to be used to model lossy surfaces and in
principle even lossy volumetric objects. It should in principle be
possible to use the technique to model lossy layers, inhomogeneous
surfaces AND anisotropic characteristics.

Intuitive reasoning even suggests that permittivity and permeability
may possibly be modelled using lumped capacitors and inductors in a
wire grid model - this is speculation however and we have not
attempted to do so yet. I would like any comments from users on the
approach however, because it does promise to add significant "punch"
to MoM wire programs which employ simple theory in comparison to some
of the different approaches normally required to handle especially
small lossy/dielectric components (radomes, coatings etc) on an
otherwise conductive structure.

Regards and a prosperous New Year to all.

Andre Fourie
Tel: Intl + 27 11 4030380
Fax: Intl + 27 11 4030381
Website: http://www.poynting.co.za
email: fourie_at_poynting.co.za
Papermail: Dr APC Fourie, PO Box 318, Wits, 2050, South Africa
Received on Tue Jan 06 1998 - 09:36:36 EST