Can figure out how to migrate post so I'll repost this the old fassion way.
I incorporate damage to armor in my game.
When a piece of armor takes a hit if the damage is greater than the combine value of TB and AP then the it takes what I call a Punch Through (PT). It has a total of six (6) PT's before it's useless unless it's Primitive then it only has three (3). After the first three (3) PT's it becomes Primitive armor. This shows that even though it's been damaged it still offers some protection. If it take three more PT's or starts out as Primitive then the armor is useless and offers no protection.
I do allow my PC's to try and repair the damage, but once it passes the last PT there's no point.
Exmaple. Damage=10 Pen=0 TB=4 AP=5 TB+AP=9 10-9=1 or 10>9 therefore 1 PT.