Hi Welcome to the forum,
I've spotted you've gone unanswered on this one, you might have had more responses if you had posted in one of the technical sections.
1) If any of the members would be kind enough to throw some light on a material relatively new to me, called Vectran, that I have looking up and studying.
Vectran is liquid crystal aromatic polyester fibre, it is generally not used in rigid composite applications, inflatables and sail-cloth applications seem to be the most common, looking at it's performance it is likely to give performance that is similar to that of diolen or kevlar, however it is likely that the fibre will need to have been treated to offer a good bond with epoxy resin systems. If you do explore it's performance in a rigid composites I would be very interested in hearing about you results.
2) Please distinguish between aluminium honeycomb and PP (polypropylene) hex in terms of their areas of application (both being used in a carbon fiber sandwich configuration).
As a broad answer; aluminium will provide a stiffer core for a given weight, it is however more difficult to work with than the polypropylene, PP has excellent impact resilience and can prove to be more cost effective to process.
3) While using Kevlar to provide strength to a structural member, is a hybrid Kevlar-cf weave preferred or a sandwich?
This completely depends upon you application, the hybrid shares the properties of the to fibre types so you will lose in some areas but gain in others. Look forward to hearing from you in the forum!
Paul StathamEasy Composites / Carbon Mods - Technical