[quote=Beta]
I can attest to this. I used to do medieval-style combat with people from an SCA Heavy Fighting Unit. The armor we wore was patterned on Roman Lorica Segmentata, and made from High-Density Polyetheline with light padding beneath. And that shit stopped both impacts and the rare sharp weapon ( in the case of a weapon breaking, as all weapons were blunted and wooden... but a break still happened now and then and made a pointy thing. ) very effectively. Making a similar material out of an even heavier element would produce substantially more durable and protective armor.
[/quote]

Until you see me hit something with a mace this study is inconclusive. 

Plus, it doesn't really matter how good your armour is at absorbing impacts, because physics dictates I can still hit you hard enough that you fall over, at which point your face is mine. 

And main characters don't wear face armour, unless they're Khans.