Hey David, Welcome to the Forum. You should go over to the introduction page and introduce yourself.
I have never cut fiberglass so I can't give you any firsthand advice. The most important factor is to wear a respirator as fiberglass dust is very nasty stuff.
What kind of blade are you using? It seams you need to go to a bigger size blade.
1mm is less than 1/16th", So I would sandwich the FG between two layers of 1/8" Baltic birch plywood and use a larger blade than you were using. Maybe a #3 or #5 skip tooth blade.