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

It’s because all of the soundbites exclude key information that only engineers would understand.

Kevlar is stronger than steel… but in tension? compression? by weight? by volume? And what does “stronger” mean? Elastic modulus? Toughness/deformation?

Kevlar is not stronger than steel vs a very sharp knife, for example.