How To Make Bulletproof Glass

Bulletproof glass, balastic glass, transparent armor .......... we all know them, we know what they do and where are they used.

Now, How this brittle crystal glass become so tough?

Let's start from very initial thinking.... 

TAKE some balls (football, stone, metal ball) and glass plates  (better if square) then attach them to a firm. 

Then attach a glass plate and through a stone from very close, the glass is not broken of flexed.

Then through from a bit farther, not flexed. But cracked not broken. And check the area of crack region. Almost all over the plate. The area is vast larger then contact surface between ball and glass.

Then through the ball from more distance. Glass is broken(a hole). And also cracked. But check, this time few number of crack.  And cracking region is smaller then before.

Now through the ball from far distance and ensure enough kinetic energy (like a bullet). This time just a hole and this hole is also bit larger then the ball.

....................................

This time we'll perform this experiment with football. We may need it later. 

Through the football from long distance and with enough kinetic fore, ensure to cross the previous one. No hole. Maybe not cracked yet, or some minor crack. 

From these experiments we've seen that, glass increase the acting surface area of force. But if kinetic force is too high comparing to hitting surface area, it's brittle limit  (stiffness) cross and then the forced portion be detached. But if the hitting surface is big enough comparing to hitting surface, the glass at least will not be broken.

NOW THE NEXT EXPERIMENT. 

This time Take a polycarbonate glass plate and through the metallic ball with heavy kinetic force. Little flexed and some crack. 

But when we'll fire bullet, it will be teared , for sure.

Because the stress is too big that polymer bonds will break down.

NOW THINK WIDELY.

If we gluten a crystal glass plate with a polycarbonate glass, then we fire bullet? 

First the bullet will hit the crystal glass. And the acting forced area will be increased. And glass will pretend to break and detach. But for resistance of another plate it can't but increase in area to decrease the stress. 

Then the force will hit (force not the bullet) in large area and small stress.

THIS WILL NOT BREAK.

For tougher performance several glass plate of crystal glasses and polycarbonate glasses are attached one by one by heating and cooling reciprocally .

BULLETPROOF GLASSES MAY BE 2 cm TO 10 cm THICK. 

But they are not completely invincible, reciprocating hitting may destroy bulletproof glasses.