I have somehow managed to DAMAGE my Modular Powersuit Helmet. I have no idea how this happened - the last thing I did before I noticed the helm was damaged was fight a few bosses in the Twilight Forest: The Boss Minotaur, the Twilight Lich (twice) and Ur-ghast.
Also, I'm running FTB Unleashed v1.0.3, as v1.1.x is currently too glitchy for my tastes. (Funny how a beta version's less glitchy, eh?)