I’m not sure I understand the armor mechanic. I thought if Average Armor was greater than the weapon penetration there was no damage,bBut If I create a Puma Frigate with 4 Frigate Armor III modules I get an average armor of something like 18.1 but then when I post a challenge to myself and send fighters with basic lasers on them, the armor takes damage and is evertually brought down. Can someone explain this to me? I would have thought that with an average armor of 18 the ship would be invulnerable to fighter lasers.
I gather that there are critical hits that bypass armor deflection.
I’m starting to wonder if we need a seperate subforum about game mechanics. Or just about armor mechanics. 
Anyway yeah it’s the critical hits that eventually chew through your frigate. I think thicker armor may reduce the chance of a critical hit, but it may simply buy you more time by allowing you absorb more critical hits. Cruisers with armor above 8 and a repair module are fairly safe against fighters. At least until your repair supplies run out…