Before we embark on seeing the science behind how a bullet proof glass works, we need to be clear on the terminology. The term bullet proof glass is not correct. The glass which we call bullet proof is actually only bullet resistant. But, for convenience, we will call it bullet proof.
How Does It Work?
How does bullet proof glass work? It works by spreading the impact. When we want to catch a fast-moving ball what we do is to move our hand back as the ball hits our palm. This reduces the impact of the ball on our palm. What we are doing is to reduce the momentum of the ball so that we feel lesser pain. When we move our hand back we are reducing the momentum of the ball till it stops completely.
Ordinary glass can’t move back. So, it shatters on impact by a bullet. The bullet passes through the glass with hardly any reduction in the momentum. Anyone behind the glass is going to get hurt badly. So, how does bullet proof glass work? Before seeing that we need to see how the bullet proof glass is made.
Making Of The Bullet Proof Glass
While ordinary glass is just one layer of glass, bullet proof glass has layers of glass with layers of polycarbonate in between. Sometimes it is made by sandwiching other plastic layers in between and the final middle layer being made of polycarbonate. The number of layers and the thickness depends on how much resistance you need.
Nowadays another kind of bullet proof glass is made. This is called the one-way bullet proof glass. In this kind of glass, there is solid glass on one side and polycarbonate on the other side. This allows the bullet to pass when shot from the polycarbonate side, but not the other way.
Now let us see how does bullet proof glass work. The glass breaks but doesn’t shatter because of the plastic layers inside. The plastic layers help to slow down the bullet. When so many layers are there it reduces the momentum of the bullet enough not to cause any harm.
The one-way glass works in a different way. The glass breaks towards the polycarbonate layer which reduces the momentum and polycarbonate doesn’t allow the bullet to pass. From the other side when a bullet is shot the polycarbonate gives way due to short distance impact and the glass breaks allowing the bullet to pass.