composite chainplates

[benz]

Of course it can be done, if you use enough material. But to get the same strength as SS or bronze, you'd have to make the chainplate a lot thicker. I work with fiberglass a lot (in fact, I just made a set of chainplates pretty much like you've described). You'd want to make it mostly of unidirectional fibers, with an occasional layer of biaxial cloth to tie them all together. I don't think there's fatigue or load-cycle issues with fiberglass or carbon fiber, but you'd want to check with the engineer who also will tell you how thick and what sort of glass schedule to use. A look at G-10 specifications might give you an idea of glass compared to steel or bronze.
Ben