I'm a bit of an insomniac and all sorts of random stuff goes through my head!  This time its composite related.  My thought is this:

We spend some effort considering fibre orientation for strength.  Has anyone ever considered resin orientation?  The resin is just polymer chains which we infuse into the fibre and link in a completely random orientation.  Whilst this gives a uniformly random matrix is this the best option?  If we could align resin chains and then cure or cross link in a certain orientation could we achieve better / stronger parts?  Could we 'grow' polymers through the fibre?  When I get work experience students we make nylon and I have them pull the fibre continuously out of the beaker as it grows so it should be possible. 

Anyways, enough of my ramblings for a pseudo friday.  What do you guys think?

Oh to be inside the mind of a chemist I was out of my depth after the third sentence if I'm honest, sounds interesting though.

Warren

Carbon Copies Ltd

Damn.  Looks like I am a geek after all

Very interesting idea! I in no way understand the full ins and outs, but in what way would be best to orientate the polymer chains? If their primary purpose is to transmit the load to the fibres, would you try and increase their strength there, or orientate the chains in the same direction as the fibre to further increase the strength

My thought for orientation was mostly electrostatic.  Apply a voltage, allow some time for alignment and then cure.  The other alternative would be control of the polymerisation, start it at one end and propagate to the other.  The idea was, as you say, to increase the strength. 

The theory is possible.  You have to balance the strength difference between the polymer chains themselves, and the links/bonds between the chains. 

The difficulties of this are all down to practicality.  You are trying to align long molecular chains in such a restricted environment around another element.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

There is probably not a good dependable way to "orient" the epoxy polymer chains, but my experiments seem to suggest that I can orient the content of carbon nanotubes that I'm adding to reinforce the polymer (Epocyl, made by Nanocyl, a Belgian specialist in Carbon Nanotubes)

Since the Epocyl makes the actual resin conductive to electricity, I've tried to add a low voltage potential from end to end in some test "bars" made from unidirectional CF and EC laminating epoxy (EL2) with Epocyl added.

Simple bending tests seem to indicate that the bars subjected to the electric field during curing are stiffer along the line of current travel through the material, however I still have no real measurements from this experiment.

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This is not possible for several reasons. The usual resins do not cure into individual chains, they cure into three dimensional networks producing essentially one huge molecule the size of the whole resin batch. In theory you could "walk" from one end of a part to any desired position by following the polymer backbone. The resins cannot be melted once cured, they aren't thermoplastics.

There are ways to achieve orientation in polymers, e.g. by stretching a fiber. You can do this at home with polypropylene. If you pull a strip of sheet PP it will stretch  and elongate and get much stiffer due to crystallization of the polymer chains and finally it will yield and tear. But this is only possible since PP is pretty much a straight chain polymer. There are other ways to achieve orientation and a bunch of other interesting effects in certain polymers, like liquid crystals, micelle formation, phase separation in copolymers and a bunch more (don't remember right now). But none of them are terribly interesting for composites, since the strength of a composite is almost exclusively caused by the physical properties and orientation of the fibers. The physical properties of the usual cured resins are one to several orders of magnitude lower than those of the fibers, you can easily crumbe a thin cured piece of resin between two fingers, meaning even if it was possible to make the resin matrix 100% stronger the resulting composite wouldn't be any better.