I happened to be shopping for acoustic treatment for my in-progress home video recording studio and ran into this stuff
It’s a fiberglass acoustic treatment blanket.
Shows up in many spots in TNG, but most prominently as part of the warp core assembly.
Starship Mine 21:00
I’ve always assumed these were the coolant tanks, but that’s not necessarily based on anything other than the fact that it looks like material designed for thermal insulation.
Here on the elevator as well
“Schizoid man” 39:28