Yes . It will not show up in the finished board .Its perforated for use with resin infusion .Always wet out your core first. I would not use it for a core as it has a tendancy to break within the laminates without you knowing .
There are two ways of sublimating ,flat bed or roller flat bed if it comes in sheets or roller if it comes on a roll .You need to find a company that can sublimate the required size graphic in one hit . Hope that makes sense .
Go down to the local fabric shop and pick what you want .If you want your own design simply get some polyester fabric ,and get it dye sublimated on .The fun starts if you want a clear or white background when you wet out the fabric .