An Overview on Bulletproof Jacket
Md. Ferdus Alam
Department of Textile Engineering
Facebook: Ferdus Alam
Department of Textile Engineering
Facebook: Ferdus Alam
A bulletproof jacket, bulletproof vest, ballistic vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso. Soft vests are made from many layers of woven or laminated fibers and can be capable of protecting the wearer from small-caliber handgun and shotgun projectiles, and small fragments from explosives such as hand grenades. This textiles are commonly worn by police forces, private citizens who are at risk of being shot (e.g., national leaders), security guards, and bodyguards, whereas hard-plate reinforced vests are mainly worn by combat soldiers, police tactical units, and hostage rescue teams.It is also called safety textile.
|Fig: Bulletproof jacket.|
|Fig: A test in 1901.|
How does it work?
When a handgun bullet strikes body armor, it is caught in a “web” of very strong fibers. These fibers absorb and disperse the impact energy that is transmitted to the bullet proof vest from the bullet, causing the bullet to deform or “mushroom.” Additional energy is absorbed by each successive layer of material in bullet proof vests, until such time as the bullet has been stopped.
|Fig: Additional energy is absorbed by each successive layer of material in the ballistic panel.|
A bulletproof vest consists of a panel, a vest-shaped sheet of advanced plastics polymers that are composed of many layers of either Kevlar, Spectra Shield, or, in other countries, Twaron (similar to Kevlar) or Bynema (similar to Spectra). The layers of woven Kevlar are sewn together using Kevlar thread, while the nonwoven Spectra Shield is coated and bonded with resins such as Kraton and then sealed between two sheets of polyethylene film. The panel provides protection but not much comfort. It is placed inside of a fabric shell that is usually made from a polyester/cotton blend or nylon. The side of the shell facing the body is usually made more comfortable by sewing a sheet of some absorbent material such as Kumax onto it. A bulletproof vest may also have nylon padding for extra protection. For bulletproof vests intended to be worn in especially dangerous situations, built-in pouches are provided to hold plates made from either metal or ceramic bonded to fiberglass. Such vests can also provide protection in car accidents or from stabbing. Various devices are used to strap the vests on. Sometimes the sides are connected with elastic webbing. Usually, though, they are secured with straps of either cloth or elastic, with metallic buckles or Velcro closures.
The Manufacturing Process:
|Manufacturing process of Bulletproof Jacket|
Making the panel cloth
To make Kevlar, the polymer poly-para-phenylene terephthalamide must first be produced in the laboratory. This is done through a process known as polymerization, which involves combining molecules into long chains. The resultant crystalline liquid with polymers in the shape of rods is then extruded through a spinneret (a small metal plate full of tiny holes that looks like a shower head) to form Kevlar yarn. The Kevlar fiber then passes through a cooling bath to help it harden. After being sprayed with water, the synthetic fiber is wound onto rolls. The Kevlar manufacturer then typically sends the fiber to throwsters, who twist the yarn to make it suitable for weaving. To make Kevlar cloth, the yarns are woven in the simplest pattern, plain or tabby weave, which is merely the over and under pattern of threads that interlace alternatively.
Unlike Kevlar, the Spectra used in bulletproof vests are usually not woven. Instead, the strong polyethylene polymer filaments are spun into fibers that are then laid parallel to each other. Resin is used to coat the fibers, sealing them together to form a sheet of Spectra cloth. Two sheets of this cloth are then placed at right angles to one another and again bonded, forming a nonwoven fabric that is next sandwiched between two sheets of polyethylene film. The vest shape can then be cut from the material.
Cutting the panels:
|Fig: Cutting the panels.|
Sewing the panels:
While Spectra Shield generally does not require sewing, as its panels are usually just cut and stacked in layers that go into tight fitting pouches in the vest, a bulletproof vest made from Kevlar can be either quilt-stitched or box-stitched. Quilt-stitching forms small diamond of cloth separated by stitching, whereas box stitching forms a large single box in the middle of the vest. Quilt-stitching is more labor intensive and difficult, and it provides a stiff panel that is hard to shift away from vulnerable areas. Box-stitching, on the other hand, is fast and easy and allows the free movement of the vest. To sew the layers together, workers place a stencil on top of the layers and rub chalk on the exposed areas of the panel, after the cloth is made, it must be cut into the proper pattern pieces. These pieces are then sewn together with accessories to form the finished vest making a dotted line on the cloth. A sewer then stitches the layers together, following the pattern made by the chalk. Next, a size label is sewn onto the panel.
Finishing the Vest
The shells for the panels are sewn together in the same factory using standard industrial sewing machines and standard sewing practices. The panels are then slipped inside the shells, and the accessories—such as the straps—are sewn on. The finished bulletproof vest is boxed and shipped to the customer.
|Fig: It is checked for defects by National Institute for Justice (N.I.J.)|
|Fig: Future development (High comfort, protection and low garment weight).|
- The Defence Department of Canada posted a contract tender Monday asking companies for proposals for high- tech body suits that could help Canadian soldiers carry bigger loads into battle.
- The Pentagon agency eventually awarded a contract to Sarcos, a Salt Lake City, Utah, and company now owned by Raytheon that produced a test version this year. Known as the XOS Exoskeleton, it uses a single engine and hydraulics to assist movement. Included in the Pentagon's Future Warrior Concept are a powerful exoskeleton, a self-camouflaging outer layer that adapts to changing environments and a helmet which translates a soldier's voice into any foreign language. The future soldier will also benefit from 'intelligent' armour, which remains light and flexible until it senses an approaching bullet, then tenses to become bullet proof.
- Bullet-proof brassieres designed to be comfortable and injury-proof have been issued to 3,000 policewomen in Germany for their protection. The brassieres are made of cotton or polyester and are padded. Unlike bullet-proof vests, they have no metal or plastic under-wire or fasteners that can pierce skin and injure the wearer when a bullet hit the body armor.
- Super carbon nanotube vest which bounces back the incoming projectiles have been developed in the University of Sydney.
|Fig: Carbon nanotube|
- Dragon Skin is a type of ballistic vest made by Pinnacle Armor. It is currently produced in Fresno, California. It’s characteristic two-inch-wide circular discs overlap like scale armor, creating a flexible vest that allows a good range of motion and can allegedly absorb a high number of hits compared with other military body armor. The discs are composed of silicon carbide ceramic matrices and laminates, much like the larger ceramic plates in other types of bullet resistant vests.
|Fig: Dragon skin|
- The armor is available in three basic protection levels: SOV-2000, which has previously had certification to Level III protection; SOV-3000, which is rated as Level IV by the manufacturer, but has not officially certified as such; and a rating-unspecified "Level V" variant not available to the general public.
- SOV-2000 armor is made of an imbricated overlapping configuration of high tensile steel discs encased in an aramid textile cover. Different layout configurations with variations in coverage are available.