What is a bulletproof vest made of & how does that stop a massively fast bullet?
To keep it as simple as possible, there are two main types of bulletproof vests; soft and hard.
Soft vests are made of woven kevlar. These are tiny strands of extremely strong fabric. They’re woven and layered up to create a relatively soft, flexible panel.
This stops bullets by slowing them down as they impact the kevlar, losing energy as they rip through the layers of fabric.
Think of it like a speeding car plowing into a bunch of buckets filled with water.
These soft vests are the type typically worn by police. They’re designed to stop most handgun rounds.
The second type of bulletproof vest is hard armor. This is typically in the form of steel or ceramic plates.
Basically these are just strong enough to withstand the impact of a bullet. Ceramic plates shatter and spread out the force of the impact much like kevlar does, but on a higher level.
These type of vests are worn by military. They’re designed to stop rifle rounds. Increasingly, police will carry these in their cars as well.
It’s made of kevlar, a synthetic fiber that is very strong, or related material. When woven into a fabric it makes a very strong fabric that is resistant to the type of damage incurred when shot by a bullet. However the kevlar fabric is often not good enough as the force of the bullet is strong enough it wont penetrate the fabric but it’ll still penetrate you and just bring the fabric with. So a vest will also include inserts made of ceramic, fiberglass or metal, and padding. So the plating stops the bullet from penetrating and the fabric protects you from damage caused by shrapnel caused by a plate breaking or the bullet breaking on impact.
Usually they’re a Kevlar fabric containing sheets of lead with thin ceramic plates in front.
Kevlar resists being punctured and spreads the force out through the entire fabric. Ceramic converts kinetic energy into the ceramic turning to powder, slowing the projectile. And lead… is really dense. It just stops things from going any further, which works really well in combination with the Kevlar.
 the truck is that while bullets have a lot of kinetic energy, they don’t have much mass — so a sheet of lead often has enough stopping power by itself to pancake the projectile, spreading the kinetic force out through accelerating the inertial state of the entire lead plate.