History of Bullet Proof Vest

Body Armor in Middle Age at England

The principle of bullet-proof armor has been developed since the early Middle Ages. Starting from the knight  with iron armor, which can reduce puncture wounds sword or shooting an arrow. Unfortunately with the development of firearms, the protection becomes useless.

Aramid (Kevlar™)

This material was found in 1964, by Stephanie Kwolek, an American chemist, who worked as a researcher at the DuPont company.

Stephanie Kwolek

Aramid is stand for aromatic polyamide. Aramid has a strong structure, tough, has a good impact and also vibration damping, acid and alkaline resistant and besides that can be heated up to 370°C (so is not flammable). Because of that advantages, aramid is also used in the aircraft, tanks, and aerospace (rocket). The products was known as Kevlar™. Kevlar™ is light, and 5 times stronger than steel.

Structure Molecule of Aramid

This fiber is commonly known as Kevlar™ 

The thickness of Kevlar™ layer is less than 1 mm, generally in standard body armor, it contain up to 32 layers and the weight can reach 10 kg.

 
Basic Principle of Bullets Proof Vest

The basic principle of bullets proof vest is reduce as much as possible of kinetic energy of the bullet, by using layers of kevlar, it can absorb energy, so that energy is not enough anymore to make a bullet break through the vest. In absorbing the kinetic energy of bullet, Kevlar™ will deformed inwards and it will be transferred into the pressure to the user's body. The maximum limit pressure should not be more than 4.4 cm (44 mm). If that limit is exceeded, the user will have internal organs injury, which is very dangerous.

Bullet Strike in Bullet Proof Vest

Kevlar™ Deformation

This analogy like goal's net which can hold the kinetic energy of moving ball. The net is contain thight structure of the rope. If the moving ball go through the net, the kinetic energy of the ball will absorb by the net and the rope around will extending and the pressure of the rope will discarged the goal post.
 

The picture above show if the bullet proof armor can fully protect the user but sometime if user is not lucky, something bad will happen. The main purpose of bullet proof armor is only decrease the kinetic energy from the moving bullet then the user will not dead. No matter because of this reducing pressure from bullet, the user will suffer blunt force trauma or broken bone.

Bullet Proof Vest or Ballistic Vest ? 
Bullet Proof Vest divided by Soft Body Armor and Hard Body Armor.

Soft Body Armor

Soft Body Armor type 1

Soft Body Armor type 2

In everyday duty of cop / detective in undercover work prefers a lightweight bulletproof clothing like that. Soft body armor is now mostly made of Aramid Fibers.

Hard Body Armor

Hard Body Armor

Hard body armor is like soft body armor but it adding with several special layer. The layer that used is ceramic (Al2O3 "Alumina"), metal slab, or composite. The weight is heavy and thick and uncomfortable, so no matter is rarely used in daily duty. It only use in high risk duty like military operation or SWAT team operation.

SWAT Team Operation

Standart Level of The Type of Bullet Proof Armor
Standard measurement of bullet proof armor commontly is using NIJ Standart (National Institute of Justice) in America. In this standard, bullet proof armor can devided by several level which is :

• Level I, 
• Level II-A, 
• Level II, 
• Level III-A, 
• Level III, and 
• Level IV. 

Level I is the lowest level. This armor only proofing low caliber bullet.

Level of Bullet Proof Armor

Type of bullet and which level that can protect the user

With using new composite material, the safety level is increasing time by time. But it still have the weakness that is "If you want to safe, use the thick one, but you must carrying that heavy vest". For this condition, the scientist and the military always create new product which is lighter and stronger.