Anti Ballistic Fabric: An Overview

Anti Ballistic Fabric: An Overview
Authors: Ubair Shah, Muhammad Ali Uddin Alvi, Areesha Nadeem, Asmat Kalwar, Iftikhar Ahmed Rajpoot, Maria Urooj, Rizwan Haid and Teena Tarwani
Department Of Textile Engineering, 
Mehran University of Engineering & Technology, Jamshoro, Pakistan



ANTI BALLISTIC:

Introduction
Anti Ballistic or Ballistic protection is a class of protective. Clothing which aims at protecting the individuals. From the bullets and steel fragments from hand- held weapons and exploding munitions.

A silicon-infiltrated ceramic based on a reaction-bonded silicon carbide body is a popular anti-ballistic material. Apart from anti ballistic properties, it also offers excellent protection against knife and ice pick threats. One attribute of this fabric is its ability to reduce the trauma conventionally caused by the impact of a ballistic projectile, even though the projectile is stopped from penetrating the fabric. Fabrics in para aramid fibers and Polyethylene HT fabrics are also often used in manufacture of anti ballistic textiles.

There are many natural and synthetic fibers, which are used for ballistic protection, but only two types of synthetic fibers can be regarded as high-performance – aramid (kevlar) and UHMWPE (Ultra High Molecular Weight Polyethylene), carbon, ceramic fibers. UHMWPE fibers, also known as HPPE (High Performance Polyethylene) fibers, are characterized with parallel molecules orientation along the fiber axis greater than 95% and a high level of crystallinity as opposed to conventional polyethylene fibers. This results in fibers with a very high strength and modulus of elasticity. In this study, we have investigated HPPE composites based on woven fabrics and unidirectional (UD) fibers under the high-speed ballistic impact. The fibers we have used were produced by the inventor of these fibers, the Dutch company DSM, and are known under the trade name Dyneema.

HISTORY
In 1538, Francesco Maria della Rovere commissioned Filippo Negroli to create a bulletproof vest. In 1561, Maximilian II, Holy Roman Emperor is recorded as testing his armor against gun-fire. Similarly, in 1590 Sir Henry Lee expected his Greenwich armor to be "pistol proof". Its actual effectiveness was controversial at the time. The etymology of "bullet" and the adjective form of "proof" in the late 16th century would suggest that the term "bulletproof" originated shortly thereafter. During the English Civil War Oliver Cromwell’s Ironside cavalry were equipped with Capeline helmets and musket-proof cuirasses which consisted of two layers of armor plate (in later studies involving X-ray a third layer was discovered which was placed in between the outer and inner layer). The outer layer was designed to absorb the bullet's energy and the thicker inner layer stopped further penetration. The armor would be left badly dented but still serviceable. One of the first recorded descriptions of soft armor use was found in me dieval Japan, with the armor having been manufactured from silk.

Simple ballistic armor was sometimes constructed by criminals. The suits were roughly made on a creek bed using a makeshift forge and a stringy-bark log as a muffled anvil. They had a mass of around 44 kg (96 lb), making the wearer a spectacular sight yet proved too unwieldy during a police raid at Glen rowan. Their armour deflected many hits with none penetrating, but eventually was of no use as the suits lacked protection for the legs and hands.

1st WORLD WAR
The first official attempts at commissioning body armor were made in 1915 by the British Army Design Committee, in particular a 'Bomber's Shield' for the use of bomber pilots who were notoriously under-protected in the air from anti-aircraft bullets and shrapnel. The Experimental Ordnance Board also reviewed potential materials for bullet and fragment proof armor, such as steel plate. A 'necklet' was successfully issued on a small scale (due to cost considerations), which protected the neck and shoulders from bullets traveling at 600 feet per second with interwoven layers of silk and cotton stiffened with resin. The Day field body shield entered service in 1916 and a hardened breastplate was introduced the following year. The British army medical services calculated towards the end of the War, that three quarters of all battle injuries could have been prevented if an effective armor had been issued.

Testing a bulletproof vest
Figure-1: Testing a bulletproof vest in Washington, D.C. September 1923
2nd WORLD WAR
In 1940, the Medical Research Council in Britain proposed the use of a lightweight suit of armor for general use by infantry, and a heavier suit for troops in more dangerous positions, such as anti-aircraft and naval gun crews. By February 1941, trials had begun on body armor made of manganese steel plates. Two plates covered the front area and one plate on the lower back protected the kidneys and other vital organs. Five thousand sets were made and evaluated to almost unanimous approval - as well as providing adequate protection; the armor didn't severely impede the mobility of the soldier and were reasonably comfortable to wear. The armor was introduced in 1942 although the demand for it was later scaled down. The Canadian Army in northwestern Europe also adopted this armor for the medical personnel of the 2nd Canadian Infantry Division.

RECENT YEARS
Kevlar soft armor had its shortcomings because if "large fragments or high velocity bullets hit the vest, the energy could cause life-threatening, blunt trauma injuries in selected, vital areas. Ranger Body Armor was developed for the American military in 1991. Although it was the second modern US body armor that was able to stop rifle caliber rounds and still be light enough to be worn by infantry soldiers in the field, it still had its flaws: "it was still heavier than the concurrently issued PASGT (Personal Armor System for Ground Troops) anti-fragmentation armor worn by regular infantry.

ANTI-BALLISTIC Materials/ Fibers

1. Aramid Fibre

Introduction:
  • Aramids are heat resistance and strong synthetic fibre .
  • They are used in aerospace and millitry applications for body armour bicycle tires
The following characterstics distinguish them from other polymers:
  • High strength
  • Non conductive
  • No melting point
  • Good resistance to organic solventThe production of aramid fibre known under :
  • Kevlar(para-aramid)
  • Nomex (meta-aramid)
Types of Aramid Polymers:
  1. Nomex (meta aramid)
  2. Kevlar (Para-aramid)
  3. Twaron
  4. Technora
  5. Heracron
2. KEVLAR
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, this high-strength material was first commercially used in the early 1970s as a replacement for steel in racing tires. Typically it is spun into ropes or fabric sheets that can be used as such or as an ingredient in composite material components. Currently, Kevlar has many applications, ranging from bicycle tires and racing sails to body armor, because of its high tensile strength-to-weight ratio; by this measure it is 5 times stronger than steel. It is also used to make modern drumheads that withstand high impact. When used as a woven material, it is suitable for mooring lines and other underwater application A similar fiber called Twaron with roughly the same chemical structure was developed by Akzo in the 1970s; commercial production started in 1986, and Twaron is now manufactured by Teijin.(11,12).

Properties of Kevlar fiber
Figure-2: Properties of Kevlar fiber
Poly-paraphenyleneterephthalamide – branded Kevlar – was invented by Polish-American chemist Stephanie Kwolek while working for DuPont, in anticipation of a gasoline shortage. In 1964, her group began searching for a new lightweight strong fiber to use for light but strong tires. The polymers she had been working with at the time, poly-p-phenylene-terephthalate and polybenzamide, formed liquid crystal while in solution, something unique to those polymers at the time.

The solution was "cloudy, opalescent upon being stirred, and of low viscosity" and usually was thrown away. However, Kwolek persuaded the technician, Charles Smullen, who ran the "spinneret", to test her solution, and was amazed to find that the fiber did not break, unlikenylon. Her supervisor and her laboratory director understood the significance of her accidental discovery and a new field of polymer chemistry quickly arose. By 1971, modern Kevlar was introduced. However, Kwolek was not very involved in developing the applications of Kevlar.(12)

STRUCTURE-PROPERTIES:

Kevlar: bold represents a monomer unit, dashed lines indicate hydrogen
Figure-3: Kevlar: bold represents a monomer unit, dashed lines indicate hydrogen
3. DYNEEMA FIBER
UHMWPE (Ultra-high-molecular-weight polyethylene) is a type of polyolefin. It is made up of extremely long chains of polyethylene, which all align in the same direction. It derives its strength largely from the length of each individual molecule (chain). Van der Waals bonds between the molecules are relatively weak for each atom of overlap between the molecules, but because the molecules are very long, large overlaps can exist, adding up to the ability to carry larger shear forces from molecule to molecule. Each chain is bonded to the others with so many van der Waals bonds that the whole of the inter-molecule strength is high.

4. TWARON FIBER
Twaron is Teijin Aramid’s flagship para-aramid, a high-performance man-made fiber. Offering well-balanced performance in terms of mechanical properties, chemical resistance and thermal stability, it is widely recognized in many industries as an extremely valuable component with excellent durability. Our experience of more than 30 years, not only guarantees a technically mature product, it is also the basis for developments – often in close cooperation with our customers to tailor Twaron to the specific requirements in various applications.

Fabric Manufacturing Techniques for Anti Ballistics Fabric:

Anti ballistics fabric is made from woven, nonwoven and knitted technique.


Woven Fabric: Woven Fabric is any textile formed by weaving. Woven fabrics are often created on a loom, and made of many threads woven on a warp and a weft. Technically, a woven fabric is any fabric made by interlacing two or more threads at right angles to one another.

Example: Button up shirts, trousers, jeans, denim jackets.


Non-woven fabric: Non-woven fabric is a fabric -like material made from staple fiber (short) and long fibers (continuous long), bonded together by chemical, mechanical, heat or solvent treatment. The term is used in the textile manufacturing industry to denote fabrics, such as felt, which are neither woven nor knitted. Some non-woven materials lack sufficient strength unless densified or reinforced by a backing. In recent years, non woven have become an alternative to polyurethane foam.

Example: Tea bag paper, Face cloths, Shingling and Synthetic fiber paper.


Knitted fabric: Knitted fabric is a textile that results from knitting. Its properties are distinct from woven fabric in that it is more flexible and can be more readily constructed into smaller pieces, making it ideal for socks and hats.

Types of Ballistic Protective Material/Body Armor
Body armor is the clothing worn by army and police personnel to protect against gunfire.Modern body armor can be broadly divided into two categories, which are hard body armor and soft body armor, depending on the type of material used and also depend on the end application.

  1. Hard body armor
  2. Soft body armor.
Hard Body Armour:
As the name indicates, hard body armor is made from rigid materials such as ceramics, reinforced plastics, metal plates and composites. Standard hard body armour is made with multiple layers, commonly including ceramic plates (to blunt and fracture projectiles) and laminated composite panels (to stop projectiles). Hard body armor may include an anti-trauma layer too, which reduces the potential injury caused by dynamic deformation of the armour into the wearer’s body.

Hard body armour may be hard enough so that a bullet or other high velocity fragment is deflected on impact. Advances in ceramic/composite armour materials have resulted in lightweight body armour systems that provide a significant amount of protection. However, increasing threats in the form of large caliber and armour-piercing rounds have led to a need for increased levels of protection. In theory, the thickness of existing body armour could increase up to the point where an armour piercing round would be defeated. However, the necessary increase in the weight of the armour to achieve the required performance level may not be acceptable.

Hard body armour absorbs the energy of the projectile by a plastic deformation mechanism by dissipating the kinetic energy of the projectile through the fracture of the hard material in the armour. Ceramics are considered to be important materials for improved armour. However, the amount of protection by ceramics alone is limited. Hence, ceramic armour hybrid systems have been developed, which consist of a monolithic ceramic or a composite ceramic-metal body form covered with ballistic nylon and bonded to a high performance textile fabric. Similarly, the hybrid armour systems consisting of layers of ceramics and fabrics bonded together have also been developed. The layers that form the hybrid armour serve specific purposes in preventing projectile penetration. The function of the ceramic composite facing is to flatten or fragment the tip of an incoming projectile, thereby distributing the load over a large area and decelerating the projectile.

Some hard armour can also consist of multilayers of steel in addition to the ceramic plates and stiff fiber-reinforced materials. The main disadvantages of the steel containing hard body armour remain heavyweight and inflexibility.

Soft Body Armor:
As the name suggests, soft body armor is soft and flexible, though its components can be many times stronger than steel. Because it is typically not as bulky as hard body armor, it’s more likely to be worn underneath a uniform or in addition to some other kind of gear. In some cases, soft armor is used in conjunction with hard armor to provide the user with as much protection as possible.

Soft armor is usually made of a fabric-like material with extreme strength such as Kevlar, Spectra, Twaron, and so on. Soft armor can come in many shapes and forms, but it is most commonly worn as a vest.

Although it is flexible and easy-to-wear, soft body armor is not as strong as its hard counterpart. Typically rated to stop pistol-caliber ammunition, soft body armor is generally not rated to protect the wearer against rife-caliber shots.

Both hard and soft armor are generally strong enough to protect the human body from sharp or fast-moving threats. The best protection is multi-layered protection; gear made up of both soft and hard armor components.

Mechanism of Protection:
The principles on which the ballistic protective materials work can be broadly divided into two categories that are (1) absorption of impact energy and (2) redistribution of impact energy. A protective material should absorb the energy of a projectile before it completely penetrates the material. Energy absorption is achieved by stretching, compressing or destroying the material. In other words, the principle on which body armour operates is based on the rapid conversion and dispersion of the kinetic energy from a striking bullet into strain energy within the ballistic body armour. The protection provided by body armour is achieved by three different methods namely:
  1. The armour decelerates and stops theballistic projectile by dissipating its kinetic energy along the plane of the material impacted;
  2. The armour completely bounces the projectile, which is very rare; and
  3. A possible combination of the above (1) and (2).
When a bullet strikes a fabric, or a number of layers of fabric, two waves, namely longitudinal and transverse waves, are propagated from the point of impact on the outer surface. The longitudinal wave travels in the plane of the fabric and the transverse wave propagates perpendicular to the fabric (Figure-3).
longitudinal wave travels in the plane of the fabric
Figure-3
As the tensile waves propagate away from the impact point, the material behind the wave front moves towards the point of impact, which is deflected in the direction of motion by the impacting bullet. The velocities at which the longitudinal and transverse waves are propagated in the ballistic panel during an impact of a projectile are dependent on the energy absorption capability of the fabric layers. The shock wave affecting the ballistic structure propagates at higher speeds in materials with higher moduli and lower weights per unit area. The major parameters that affect the way in which impact energy is dissipated are dependent on the tensile strength of the fabrics and yarns, the fabric structures and the number of layers of fabric.

During an impact of a bullet, the fibres in the fabric absorb and disperse the impact energy, which is transmitted to the armour from the projectile, causing the bullet to deform or to ‘mushroom’. Each successive layer in the vest absorbs energy, until the bullet is stopped (Figure-4). The energy spreads across the surface of the armour at a tremendous speed, which can be up to 900 m/s.

The Mechanism of Bullet Penetration in An Impact
Figure-4: The Mechanism of Bullet Penetration in An Impact
In the case of hard body armour, metal and reinforced plastic provide protection by partially bouncing the bullet as well as absorbing the impact energy. Upon impact, the impact pulse on the surface of the armour is reflected as a tensile or pulling wave. When the amount of tensile stress exceeds the tensile strength of the armour material, fractures occur leading to mechanical failure of the hard body armour and the creation of a hole. If the magnitude of the stress pulse after the fracture still exceeds the tensile strength of the material, multiple fractures can occur. If the material is driven beyond its elastic limit as the applied load increases, the material becomes plastic.

As indicated in Figure-3, impact of a projectile produces a cone shaped deformation in layers of protective fabric, As an impact progresses, the radius and height of the deformation cone increase with time and the cone grows as the projectile moves forward resulting in an increase in the cone height.

Properties of Anti Ballistic Fabric:
  • Strength to weight ratio is more.
  • Withstands temperatures upto 450°C to as low as -196°C.
  • Self extinguish able.
  • 2.5 to 4% elongation.
  • Resistant to almost all types of chemicals.
  • Negative co-efficient of thermal expansion.
  • Abrasion Resistance.
  • Poor Cut and Drill.
  • Poor Compressive Strength.
  • Absorbs Moisture upto 4.3 to 4.5%.
Benefits of Anti-Ballistic Fabrics:
  • Reduces back and front face trauma
  • Lightweight
  • Puncture resistant
  • Breathable
  • Abrasion resistant
  • Durable
APPLICATION OF ANTI-BALLISTICS
As mentioned, these advanced textiles are commonly used in defense and low enforcement applications. Military may incorporate these fabrics into protection garments such as vest, helmets, soft armor, hard armor and body armor. These materials are also often used in the construction of personal armor systems and shields. These are also used in application requiring superior rugged less and durability to withstand heavy use such as luggage, bag packs, motorcycle apparels and work where employees material to ensure optimal longevity and performance.

Following are some application of antiballistic:
  1. Military Vehicles
  2. Bomb suits
  3. Bullet Proof Glass
  4. Bullet Proof Vest
  5. Bank Vault
  6. Liquid Armor
  7. Riot Shield
  8. Panic Room or Safe Room.
Conclusion
We feel good to collaborate with each other. We really learn lot of things, regardinghigh performance or technical fibers/fabrics and their applications, manufacturing, properties.

Resources:
  1. https://textilelearner.blogspot.com/2015/10/ballistic-protection-of-textile.html
  2. https://www.researchgate.net/publication/304506225_Recent_Trends_in_Ballistic_Protection#pfb
  3. http://info.veltye.com/blog/soft-vs-hard-body-armor
  4. https://www.thomasnet.com/insights/how-textiles-are-used-for-ballistic-materials
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