Well, what could I do with a low budget (100-150) and not make cardboard...preferably some type of plastic, fiberglass...something tough. I am probally going to dedicate this to my summer....so I'd like it to be badass when I roll into the the town with the ONLY suit of MJOLNIR within a 25 mile radius. And I'll have my freaking rocket launcher. Major cool.
Right now I'm working on a helmet using foam board and poster board. As these guys will tell you, it will definately make putting a hard exterior on it difficult but I'll probably figure something out.
Anyways, I spent $15 for 3 sheets of poster size foam board, 3 sheets of poster board, 1 pad of graph paper, and 1 X-Acto knife.
I suppose if you bought like puddy or something (not bondo) and filled the cracks (cuz you'll have them unless you are a surgeon with the X-Acto knife) then filled the inside with a cheap foam filling, spray painted it for color..... You could do that for under $100 I would think. (Granted I haven't bought a visor for mine yet)
I used posterboard I purchased at wal mart, more expensive than cardboard which is readily given away free. But you can run it through a printer and print up your layout directly on it.
Another option alot of the 501st star wars guys use is sintra, its that plastic stuff for sale signs are made of. It can be bought in large sheets for little money, and is fairly easy to work with. I reccomend using AC glue found only at hobby stores as it causes a type of plastic welding when it cures.
as far as bonding agent for cardboard, I would reccomend, bondo (the green stuff not the red) its easy to smear on, and sand down, and will make a nice helmet when completed. And its hard and durable. Fiberglass it messy and takes along time to cure.
Then later you can sand out the card board, and your left with the bondo shell. Use the cardboard for the basic structure, and do all the detail work with the bondo. But remeber go for the green stuff, not the red. That is unless you like sanding a rock. LOL
It all depend how fine the particle it's got to filter are. Not having used Bondo I can't say definitively. Im sure someone will jump in in a moment.
Respirators and filters. The finer the particles the more expensive. Straightforward sanding on inert materials is fine with one of the fibre paper filters. A wet bandanna when sanding outside would do in a pinch.