Bullet resistant glass may seem like complex technology. But the scientific explanation behind it is quite simple.
Bullet resistant glass consists of many layers. Between each layer is a polycarbonate layer. This polycarbonate layer is what stops the bullet. When the bullet hits the glass, the polycarbonate layer inside the glass absorbs the bullet’s energy, spreading its impact around.
Broken glass can cause various other damages. These glasses are made stronger so that the glass does not break easily. This is why bullet resistant glass has a layer of hard plastic. This layer absorbs the energy of the bullet and slows it down. As a result, the risk of glass breakage is also greatly reduced.
Suppose you are in a fatal collision. Enemies are shooting wildly around, you are dodging them. You need urgent help. Can’t seem to survive that many shells for long.
The safest way to protect yourself from this situation is to hide behind something transparent and solid. It will protect you from incoming bullets. This barrier will require a material that is tough enough to withstand bullet impact. This is why “bullet resistant” glass is made. This article contains the scientific explanation of bullet resistant glass.
Not truly bulletproof
If you are an avid action movie buff, you may have seen the use of bullet resistant glass in many movies. Bulletproof glasses are shown in movies as indestructible. No matter how many guns or bullets are used, the bullet resistant glass is always intact in these action-packed scenes. No bullet can penetrate them.
‘Bulletproof’ glass is a strong enough material, but from a scientific point of view it is not really ‘bulletproof’. Because no glass is unbreakable forever.
Bullet resistant glass usually slows down the speed of bullets. It reduces the impact of bullets on the glass. That’s why it takes a few shots to break bullet resistant glass. Therefore, the bullet resistant glass you see in high-security systems is actually this type of glass. But, sellers call them ‘bullet resistant’ to make their glass seem invulnerable to buyers. The ballistic glass industry is worth billions of dollars.
History of bullet resistant glass
Many historians credit 17th-century Prince Rupert of the Rhine with the invention of bulletproof glass. He accidentally put molten glass in a bowl of cold water one day. To his surprise, the glass became almost impossible to break. However, in 1909, the first patented bullet resistant glass was created by the French chemist Edouard Benedictus. It was a simpler form of laminated safety glass. In 1937 a magazine called ‘Popular Science’ speculated on the possible use of “bullet resistant glass” in police cars.
How does bullet resistant glass work?
If you have any experience of watching cricket, you might know how difficult it is to catch fast balls. The trick to catch such a fast ball is to follow the trajectory of the ball with the hands following the ball, so as to slow the ball down to stop the ball.
Catching the ball in this way will reduce the pressure on the hand, making the impact of the ball less painful. From a physics point of view, the pressure exerted by the ball on the hand will be proportional to the rate of change of the ball’s velocity.
Simply put, the force generated by a moving ball hitting the hand can be reduced if you slowly or gradually change the ball’s speed. Let’s understand this better with an example.
Imagine trying to stop and catch a ball instantly, in just half a second. In such a situation there will be severe pain in the hands. Imagine, the same thing happened again, but this time you catch the ball slowly, taking two seconds to complete the whole process. Since the ball takes four times longer to change speed than before, it will also take four times less time to hit the ball in the hand than before.
But glass is not like our hands. Glass cannot move like a hand. It may offer little protection against impact. So, if a person fires a shot at an ordinary piece of glass, the glass cannot bend, nor can it slowly absorb the energy. Rather, the bullet hit the glass with great force and shattered it into pieces.
The broken pieces of glass are very sharp and sharp. Serious damage can be caused by broken glass. Even if the bullet survives, these broken pieces of glass can cause loss of life. This is why ordinary glass cannot provide any protection against bullets. It also fails to slow down the bullet.
Bullet resistant glass is different from ordinary glass. Bullet resistant glass looks like ordinary glass but has significant differences in structure and properties. How many bullets a bullet resistant glass can withstand depends on the thickness of the glass and the caliber of the bullet.
Ordinary glasses also have many layers. An additional layer of poly-carbonate material is added in between to essentially make bullet resistant glass. This process is commonly called lamination. Poly-carbonate material makes the glass strong and flexible. It can be up to 10 times thicker and heavier than normal glass.
When someone fires a shot at bullet resistant glass, the energy of the bullet is dispersed between the different layers of the glass. Because there are so many layers, this energy is split between different layers of glass and plastic. Thus, bullet resistant glass quickly absorbs the force of the bullet. Poly-carbonate slows down the bullet and prevents the glass from shattering.
But if several shots are fired at the same spot in succession, the glass will break. But because bullet resistant glasses have a layer of plastic inside, the glass does not break into pieces like normal glass. If you think of bullet resistant glass as “energy absorbing” glass, you’ll get a better idea of ​​how it works.
Thickness and cost of bullet resistant glass
How strong bullet resistant glass is depends a lot on its thickness. These glasses are usually designed to protect against a bullet or a round of bullets. Thicker bullet resistant glass is required based on the degree of bullet injury and the type of gun used.
For example, sniper rifles have much higher firing speed and power than normal pistols. As a result, stopping a rifle shot requires a thicker bullet resistant glass than stopping a pistol shot. Generally, bullet resistant glass thickness can range from 0.25 inches to 3 inches.
Development of bullet-resistant glass
When a bullet hits bullet resistant glass, the outer layer is perforated, but the inner polycarbonate layer absorbs the bullet’s energy and spreads the impact of the bullet’s kinetic energy around. Because of this the bullet cannot penetrate all layers of glass and hit the target.
Interestingly, some companies have recently developed “one-way” bullet-resistant glass. Through this the incoming shots can be stopped as well as the counter shots can be done as well.
This glass has a tough but easily breakable glass on the top layer. It also uses a tough polymer layer inside. The brittle layer is on the outside of the glass and breaks when a bullet hits it. Thus the bullet impact spreads over a large volume, which is then absorbed by the hard (polycarbonate) layer behind. On the other hand, a bullet coming from the other direction can easily pierce the polymer layer before breaking the glass, resulting in a slight reduction in bullet speed.
Application of bullet resistant glass
Businesses like jewelry stores, banks, etc. that have a lot of cash and valuables use bullet resistant glass to protect them from potential gunmen. In many countries, bullet resistant glass is also used in administrative departments such as local police stations and court buildings.
Bullet resistant glass used in critical installations is much stronger than bullet resistant glass in bank cashiers or executive rooms. They are specially designed to withstand the impact of being fired from a high velocity rifle.
Limitation of bullet resistant glass
As stated earlier, bulletproof glass is not truly bulletproof. Another problem with bullet resistant glass is its heavy weight. The thick and heavy structure of the glass does not cause problems in frames like windows or cubicles. However, the application of this glass in the case of cars is quite difficult.
It’s not just the thickness or the weight that creates engineering constraints in the design of the car, but the other side has to make concessions to keep it strong enough. Because the harder the glass, the less clear it is. Then the front glass of the car becomes almost impossible to make bullet resistant. Because if the glass is thick, the driver may not see many things clearly while driving.
But despite these limitations, scientists and researchers continue to strive to make bullet resistant glass even stronger. Bullet resistant glass is an important innovation. It is constantly protecting the lives of thousands of people from the armed forces to the highest levels of various institutions and states.
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