why can’t kevlar stop rifle bullets even though it’s strong than steel on an equal weight basis?

Question

Ar500 steel plate can stop rifle bullets. In my brain I’m thinking like “well if kevlar is stronger than steel, then slab of kevlar of the same size of an ar500 plate should stop rifle bullets too”. Clearly it doesn’t and I don’t understand why

In: Engineering

Answer 1

The problem is it’s stronger on a weight basis, not necessarily a volume basis. The reason Kevlar works as body armor is because you can have a vest that’s not excessively heavy with the ability to stop certain rounds. It also acts in a way that disperses the impact across your torso. So it’s possible to make a Kevlar vest that can stop a high-energy rifle bullet. The problem is the vest would be too big and too heavy.