In combat aircraft, in particular helicopters, dry bays are filled with ballistic foam to prevent fires and reduce damage from shrapnel. Principally it's polyurethane foam about 2 pound, with fiberglass strand mixed in.
The fiberglass adds some structural integrity to the foam.
With that in mind, we attempted to reproduce it with chopped strand mat and pour foam.
We started with a section of CSM and pulled it apart. Then mixed up some pour foam and added the fibers to the mix while waiting for it to rise.