My supplier has something called kevlar honeycomb, as far as I know it is made out of kevlar paper(?) pre-impregnated with phenol resin. It is realyyyy expensive 70euro exl.vat for 2mm x 2550mmx1250mm and 48kg/m^2, he claims that it is the lightest sandwich in the world. I don't have money to buy it, but when I have some $ I will make some reviev of that, this is how it looks like :

You can see this type of material a lot on different expo's and so on. They use it for aero-projects and racecar-seats. mostly as a core-material to add some stiffness but keep te lightweight.