[engunneer]

Originally Posted by cadandcookies

This. So many people just call clear plastic "plexi" or "plexiglas"-- whether it's the right thing or not. For competitive robotics, it is just about always the wrong thing.

Also, since nobody explicitly stated what will go wrong:
Lexan basically doesn't shatter. They use specific compositions of it for bulletproof "glass" for this reason. You can even cold-bend the stuff (though I wouldn't generally recommend it) and depending on the use it can be fine. Acrylic on the other hand... well, drop it or hit it with something or try to bend it and see what happens. It shatters. Something into sharp shards. A quite undesirable characteristic for robots. So, polycarbonate, Lexan, or Makrolon are generally good for robot use. Acrylic, Plexiglas, Acrylite, Lucite or Perspex = bad news.

To reiterate everyone else:

Make sure what you are using is polycarbonate and not acrylic or it may very well literally shatter your dreams.

That being said, (and all of it accurate) you can also weaken polycarbonate significantly with some chemicals. Threadlock in particular can make even polycarbonate brittle.