[quote=@Skallagrim]
The armor isn't that strong. It spreads the kinetic force out. But it does not stop a concentrated attack. Since he likens it to kevlar a directed, focused attack will pretty much negate the armor.
[/quote]

I was under the impression that's -how- it stops a concentrated attack though, by dispersing that force across a larger surface area, unless you mean a sustained attack, like someone forcing a knife through it. In which case the armour would only be good at reducing kinetic impacts of projectiles, like Rilla said. 

Does anyone know if an arrow would pierce a Kevlar Vest? Apparently an arrow can punch through bullet proof glass so I was wondering if the same logic applies to a vest.