The physics varies Depends on what part of the extended universe you're reading :) 

I prefer the original. The plastic armour of the stormtroopers mostly keeps you alive when you get hit by a blaster but disables you. Heavy armour made of durasteel takes a few hits but melts and weakens with each hit and there's no way of knowing how many hits you can take beyond the first. 

When it comes to Beskar'Gam, the legendary Mandalorian metal the effectiveness of the metal varies from what I listed above to making one utterly invulnerable and really, who wants an invulnerable protagonist?