[QUOTE=VxZeroKnots;20738585]Have you used a compressed nitrogen/air welding rig or are you extrapolating the performance of using a heat gun as a welder to be equal? I'd go carbon fiber long before fiberglass just for looks alone, fiberglass is ugly and this piece will be pretty visible. There are already ugly options out there should I decide to be less vain.
Yes. I started welding with a nitrogen gun (worked in the modeling shop at Rubbermaid Commercial, Pretty big projects like the rolliing garbage bins). They're nice, but costly. The heatgun rig I have now works OK and I've done some projects with it, Sinks, etc.
I agree on transferring force, A rigid GRP plate is just like steel in that respect. But you can soft mount it on rubber bumpers if you want. (maybe something like ethafoam blocks.) it may be a thin flexible peice will work fine. it may flex back far enough to touch the cases but it will prevent abrasion of the metal and spread the blow enough to prvefent puncture of the case.
Carbon fiber is a pain in the ass to work with. (I have some along with some carbon/aramid blends). it is a LOT more difficult to turn a corner with it than glass (often you need special clamping or a vacuum setup) because it is so stiff. it also transfers stresses all over the place making design with it tricky. On top of all that, those slick carbon fiber things you see are complete crap. They are made by taking the resin/fiber ratio way up (to the resin side) to give that smooth glossy surface. This makes for a heavier, weaker part. Properly done FRP has a very spare resin ratio, you should be able to see each strand in the finished surface. of course this doesn't look all that great despite being the strongest way to go. Also, the CF stuff you see has been vacuum bagged, again to give that sheet-of-glass-with CF-in-it look. It's window dressing.
Personally if I was going to use sheet material I would use riveted construction. You can do that very cleanly so it looks right. use big head pop rivits and backing washers. The trick is to work out the shape of your plates so when you assemble everything comes together into the right shape. Use thin cardboard (construction board from the craft shop or some office supply places) or 1/8" foamcore board to sort this out. A combination of thermoforming and riviting can be very effective.
If you're determined to weld having a hot air gun (self contained blower) will definitely do you. And they are handy as a spot heat gun (rusted on nuts) as well. The only trick I can really offer beyound following the directions and using native material as rod, is to use a small planer blade as a scraper to clean up exterior welds. You want one about 1" wide by 3" or so if you can find it. they come in sets of 2 or 3 for portable hand (electric) planers). Stiffer than a utility knife blade and very sharp. I use them for finishing the edges of plexi too.
Kydex is killer stuff. Used to line hockey rinks among many other things, You may have difficulty finding it in thick sheets however. http://en.wikipedia.org/wiki/Kydex
You bend nice strait lines with a plexi bender (from platic supply place) or if you have a vacuum source you can vacuum form it in your kitchen (the largest sheet being the size of your oven unless you want to build a heater)