Re: Re: Carbon fiber cloth for Treger's vp prop hub?

From: Tapio Linkosalo <tapio.linkosalo_at_iki.fi>
Date: Sat, 08 Jan 2011 14:37:40 +0200

On 8.1.2011 11:29, Phedon Tsiknopoulos wrote:
> Thanks Tapio. Your definition proves once and for all that the epoxy in
> the prepreg results in a heavier component than just TOW (loose fibers
> with nothing applied to them) and Duco, Testors or Ambroid cements which
> weigh considerably less than even thinned down epoxy resin. I wouldn't
> even think of autoclaving my 3.3 lb. balsa wood. Case closed.

Case closed? Not quite so.

Any composite consist of two elements, the fibers that take the load,
and matrix that holds the fibers together, in proper position to take
the loads, and also transfer load from one fiber to another. If you glue
loose carbon fibers directly to the component, you are actually using
the celluloid cement as matrix. The question is now, if celluloid is
better matrix that epoxy? I firmly believe that it is not, as it is
first of all heavier (celluloid has a density of 1.4g/cm3 while typical
laminating epoxies are under 1.2). More importantly, a good laminate has
a rather strict ratio of fibers to the matrix, in case of carbon it is
about 50-50. That is practically impossible to achieve on "open air"
lamination (such as gluing loose fibers to balsa); for carbon/epoxy
laminates it requires high pressure on a closed mold. So I claim that
you get much better strength-to-weight ratio when you first laminate the
carbon with epoxy into suitable form, and then use this laminate, cut to
proper shape and glued onto the structure.



-Tapio-
Received on Sat Jan 08 2011 - 04:37:53 CET