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 :

The best way to compare is with like laminate to start with.

This image from the FSAE website shows the relative performance:



As you can see its quite easy to roughly work out the relative difference between having a core and not.

Cored panels arent always necessary though so it depends on your situation.  Sometimes the added thickness can be a disadvantage, also core materials all have thier own way of being processed into the laminate and often the facilities available to you can limit that. eg you can easily resin infuse Lantor Soric and PVC closed cell foam cores, but you cannot infuse a honeycomb panel as the cells will fill with resin.

With honeycombs, the film adhesives needed for the minimum weight possible are expensive and hard to process, so manually making panels with bonding glue by hand can be heavier than expected.

So its all dependant on what is best for your situation.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant