Re: cuting plexi
 

We were hauling a piece of lexan into the new building (4x8) and we thought hmmm. lets test something. Secured a 0.5" thick scarp piece to it, went inside and asked a worker to drop a piece of rebar from the 3rd story. Didnt phase the lexan.

Re: cuting plexi
 

I like doing a demo where I clamp 1/4" thick pieces of acrylic and polycarbonate to a work bench and wail on them them both with a medium sized hammer. The acrylic shatters into smithereens while the polycarbonate dents slightly (if you hit it just right on an edge). I think it gets the point across. :)

-Vivek