glueing 18 gauge s/s sheets to aluminum honeycomb backing
I would make test samples using Silicone I, Lexel, and metal epoxy to determine the best product for your application.

Permatex Cold Weld is the 2 part metal epoxy adhesive that I would try first. The other two are sealants and technically not adhesives, but they might still work.

Permatex Steel Weld is another option, it says it has a greater temperature range but sets in only 4 minutes so it might be hard to use.