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

When you say „Kevlar is stronger than steel“, you refer to pulling a string (I think). But a bullet approaching a plate (or a vest) is not the same thing. This is more of a push/pressure situation which may depend a lot on the shape of the bullet.