(Frag Damage)*(Anti-Armor/(anti-armor + armor))

Here, this is as far as I got with the armor formulas (now enter your own numbers!):

https://docs.google.com/spreadsheets/d/1ZlC2ZkiuB0fs5VSDXsmxJy30uRqqZ6oWCQ0ifsvUS9c/edit#gid=0The basic formula is something like:

Damage = DMG*Type * (DMG*Type)/(DMG*Type+armor)

The armor reduction chooses the weakest of DMG*type / (DMG*Type+armor) vs. 85% reduction cap. Armor chooses the strongest of (5%+Impact Mitigation 1), or current armor strength. I don't know how low armor works, but even a single point of leftover armor can absorb a ton of kinetic or frag damage.

Damage type gets counted TWICE, once for armor strength and again for armor damage. The 25% frag damage multiplier renders it practically useless even against the thinnest armor, and extremely weak against 5% armor. The flat +150 armor will basically leave you always armor capped against frag damage, even with 0 armor plates.