Depending on the layers, and how tight the weave is, could be anywhere from 1.5lb's (light armor for shrapnel), or all the way up to 10lb's, which would be used for close-combat SWAT teams and Special Forces US army members who work in close quarters combat, which usually consists of gunfire. I imagine the ones plating the car door would weigh (in total) about 12-15lbs. The car already has a steel panel in front of it anyway, which would help disform the bullet and bounce it around a tad.
And if you feel like buying yourself a Kevlar vest, you can pick one up for a cheap
$309.00!.
Also, note that some high-end sports cars use kevlar as a body panel. Pound-for-pound kevlar is about 1.5x as rigid as carbon fibre, and I believe there's an entire Toyota Supra (last gen I think) body conversion kit made entirely out of kevlar. Only problem is, because this is so rigid, the edges can be a bit grainy or sharp because it doesn't cut/sand off as well as carbon fibre. Not quite as easy to mold.
Of course there are different grades, and the sheets/plies used in vests is just like the seat-belt fabric, only the weave is tighter (2000 fibre count vs 600 for example).
Meow! (='.'=)
