A+-+How+do+Bulletproof+Vests+Work?

How Do Modern Armor and Bulletproof Vests Work?

 * By: Daniel Branescu**
 * Teacher: Mr. Erik Lindala**
 * Course: SCH4U1**

__**Who invented Armor in the first place? How was it used?**__

Body armor was //**a collective invention**// - humans have been wearing armor for //**thousands of years**//, in order to protect themselves from injury and death. It took many forms over the ages - from animal skins, woven plant fibers, leather, to forged ironplate armor which made knights almost invincible.

All that changed with //**the development of cannons and guns**// in the 1500s. These weapons' projectiles have enough energy to penetrate thin layers of metal. Armorers could make the metal armor thicker, but that made it heavy and uncomfortable. It seemed like body armor was futile against these new, devastating weapons... Or so it was thought. It wasn't //**until the 1960s**// that engineers developed a reliable bullet-resistant armor that a person could wear comfortably. There are two types of body armor currently used by the military, law enforcement - and sometimes civilians - today: The //**HARD BODY ARMOR**// and the //**SOFT BODY ARMOR.**//

__**Why do we need bulletproof vests in the first place?**__

Before I start explaining the ins and outs of bulletproof vests, I'll first explain very shortly why bullets are so lethal:

If you remember your //**Grade 11 Physics**//, you know that kinetic energy is much more influenced by the velocity of an object that by its mass. Bullets travel very fast, and rifle rounds do so at speeds of __//** over 700 meters per second!!! **//__ This massive amount of energy is focused in a small, sharp bullet; it can easily pass through various materials - including humans. //**Bullets can easily rip organs, shatter bones, sever arteries, send overpressure waves in your whole body, and cause an untimely death.**//

Bulletproof vests have been designed to minimize and/or prevent the damage caused by bullets, by placing a strong material in the way of the bullet, and shielding its wearer from harm. The concept is simple, but the production and materials are quite complex, as the armors need to withstand tremendous forces.

__**Hard Body Armor (HBA)**__


 * //Hard Body Armors (abbreviated HBA's)//** are usually made out of //**thick ceramic plates, steel plates,**// or materials such as //**titanium alloys**// and //**advanced polymers.**// In essence, they're a far more advanced version of the iron armor worn by medieval knights. The plates are hard enough that even multiple bullet hits will be deflected, with very few chances of the plate being structurally compromised. This deflection is particularily spectacular in slow-motion, as you can see how the bullet transfers its massive kinetic energy into the plate, disintegrating itself in the process. //**Often, the wearer is left with very minor bruises or skin rashes - and a good scare!**//

However, these plates are //**heavy and inflexible**//, so they only cover vital areas such as the back and front of the torso and abdomen, in order to maintain the wearer's mobility. Because of this, there are vulnerable spots. But this added weight has an advantage - these armor plates can easily stop //**multiple direct impacts**// from many projectiles, ranging from pistol rounds to the devastating __7.62x39mm__ //**AK-47**// bullet.

...You might ask yourselves - //**"Why ceramics? My bathroom tiles are ceramics, and I'm pretty sure they're not even close to being bulletproof..."**// Now, before you go shooting a gun in your bathroom, it's good to know that ceramics are more than your bath tiles and coffee mug... The ceramic used in body armor is called //**Alumina (Al2O3)**//... //**Sapphires**// are made out alumina, and sapphires are so durable they are often used alongside with diamond in advanced cutting machines.

With the strong protection of //**HBA elements**// in //**mixed suits (HBA plus Kevlar fabric)**// such as the US-made //**Interceptor Body Armor,**// today's soldiers can endure punishment that would completely neutralize any unarmored target, and still be fully capable of retaliation. **//Superheavy armors//** like the //**Explosive Ordnance Disposal (EOD) suits**// are extremely complex and expensive, but also almost invincible, allowing their users to survive //**small bomb blasts and point-blank detonations!!!**//


 * //**Interesting Fact: The Dragonskin HBA - Pretty tough, yet not enough.**//
 * Another special type of HBA was created in 2007, **//the Dragonskin Armor//**. This armor is comprised of many ceramic disks - each one about 5cm across - that are assembled in such a way that they form a layer of overlapping, tough scales - just like a dragon's skin! But, despite being more flexible, the armor failed multiple ballistic tests, and the adhesive holding the disks together failed under high temperature conditions, and when exposed to non-polar liquids such as motor oil, gasoline and diesel. It is currently being improved.

__**Soft Body Armor (SBA)**__

Soft Body Armors (abbreviated SBA's) trade heavy plates for **//advanced woven fibers//** that form a tight interlaced net which disperses the energy of the bullet, reducing its speed until it stops. The most effective material used in body armor is //**Kevlar**// - it's light as cloth, but __**// FIVE TIMES STRONGER //**__ than a piece of steel of the same weight!!! **//Other materials include artificial spider silk (interestingly enough, produced by bio-engineered goats), feathers, and carbon nanotubes.//**

SBA's are designed to spread the energy **//laterally//** over the whole vest while //**deforming the bullet**// at the same time. It's like a soccer net - it bends inwards to stop the ball, but doesn't whip it back out. This, though, poses both advantages and disadvantages. On one hand, //**Kevlar**// is //**flexible**// and often //**thin**// enough to be //**concealed under other clothing**//, making it useful for people such as undercover policemen. On the other hand, //**Kevlar does not RESIST bullets**//, but instead flexes on impact to trap the bullet... the impact itself can still transmit its kinetic energy through the vest and to the wearer.

Often, even "slow", //**low-caliber handgun rounds**// like the widespread __9x19MM Parabellum__ and __.40-caliber__ ammunition will cause //**medium to severe bruising**//, as well as //**various levels of internal trauma**// to muscles and organs. //**Assault rifle bullets**// can force the Kevlar strands apart to make their way through the vest.

But, despite their disadvantage over HBA's, Kevlar vests have found other uses, too: They are used by //**helicopter pilots**// and //**out-of-combat soldiers,**// because of their excellent capability of stopping //**low-velocity objects**// - such as //**shrapnel from grenades, RPG's, and explosive anti-aircraft projectiles (flak).**//

__**Useful Videos**__

Here are a couple of videos presenting the capabilities of body armor:

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__** Special Note: **__

Most of the information present here was already known to me at the time this project was made - since military technology happens to be one of my areas of special interest. Because this presentation required a minimum of 3 sources complying with the YMCI database, I added several relatively useful sources; Relevant data on modern body armor was hard to find, and even these 3 sources provide only fragmented information.

__**References:**__

Armor. (2010). Encyclopedia Americana. Retrieved November 13, 2010, from Grolier Online http://ea.grolier.com/article?id=0021390-00

Solis, M.W. (June 6, 2007). Defense logistics: army and marine corps' body armor requirements, controls, and other issues [GAO 2007 release]. Retrieved from http://books.google.com/books?id=4Sb3zIRJBaQC&pg=PP2&dq=Interceptor+armor&hl=en&ei=DjnfTMq4MeDtnQfU8KSyDw&sa=X&oi=book_result&ct=result&resnum=7&ved=0CEIQ6AEwBjgK#v=onepage&q=Interceptor%20armor&f=false

Booker, R. (2005). Nanotechnology for dummies [page 99]. Retrieved from http://books.google.com/books?id=_flVj1rz6CQC&pg=PA99&dq=kevlar+bullet&hl=en&ei=QzzfTNvfLZS8ngeduInKDw&sa=X&oi=book_result&ct=result&resnum=10&ved=0CFMQ6AEwCQ#v=onepage&q=kevlar%20bullet&f=false

National Research Council. (1999). //Reducing the logistics burden for the army: doing more with less// [page 130]. (Body Armor Info), Retrieved from http://books.google.com/books?id=XDHt6C1mnPwC&pg=PA129&dq=body+armor&hl=en&ei=DizjTN-7FIrAnAfy0cTFDg&sa=X&oi=book_result&ct=result&resnum=9&ved=0CFAQ6AEwCDgK#v=onepage&q=body%20armor&f=false