How stab proof vests stop the blade/spike penetrating
Stab proof vests do something the bullet proof vest can’t– protecting their wearer from edged blades and spikes, which can be just as lethal as bullets.
Edged blade and spikes have very thin, sharp points of impact and require a different construction of material to neutralize. Because they can fit through such small spaces, the synthetic fabric, the vest is made of, needs to be woven far tighter than in a bullet-proof-only vest.
Much of the effectiveness of a knife depends on how much energy (measured in joules) can remain behind the blade as it strikes its victim. Knives not designed for stabbing, such as kitchen knives, generally will bend if stabbed, dispersing much of their energy and failing to penetrate. A knife that has been engineered for stabbing, on the other hand, is so strong that the blade doesn’t bend and the energy of the knife is maintained, pressing into its victim.
Multi-layered protection
The general strategy an edged blade and spike vest employs is to absorb as much energy from the knife or spike as possible before it passes into the skin. There are numerous layers to a stab proof vest, each designed to hinder the knife’s progress as much as possible.
Some stab-proof vests have a thin hard outer shell that the blade or spike meets first. Though this layer isn’t impenetrable, it will break weaker spikes, meaning it’s very effective against syringes. Though previously uncommon, syringe stabbings seem to be cropping up more frequently. This layer is usually made of proprietary synthetic material with metal elements. It will also damage the tip of a knife as it proceeds to lower layers.
Below the outer layer, some vests have an under-layer of a synthetic material designed to snag the blade, dissipating as much energy as possible. But the core of the stab-proof vest is the inner layer– usually made up of tightly woven synthetic fibers.
Synthetic fibers stronger than steel
This class of fibers, known as aramids, is the real secret behind edged blade and spike-proof vests. Aramids are light, as well as highly resistant to heat and abrasion.
The most well-known aramid, Kevlar, was first introduced in 1971 and is five times stronger than steel. Some vests are made of Twaron, a very chemically similar fiber, which was introduced shortly after Kevlar. The aramids are woven tightly together and then layered on top of one another. The knife needs to expend energy to break the aramid fibers or move through them. As it passes through each layer, the amount of energy behind the thrust decreases, and eventually the blade stops.
A newer technology on the market comes from a class of material known as high-performance polyethylene (HPE). This material is also highly resistant to abrasion– some forms are 15 times the strength of steel. HPE can be turned into fiber as well– two kinds used in body armor are Spectra and Dyneema, which have strength-to-weight ratios about 40% higher than aramid fibers.
The Dyneema fibers are bonded into sheets, and the sheets are then stacked at multiple angles for protections from all directions. Dyneema is particularly adept at stopping stabs and punctures– it is used in protective equipment in the sport of fencing as well.
Levels and classes of protection
Edged blade and spike vests are held to National Institute of Justice standards for protection. Vests are rated in two different areas of classification; edged blade and spike. Edged blades can generally be expected on the street and are blades that are engineered to inflict maximum damage. Spikes are more common in the corrections environment. These are lower quality and have been fashioned from improvised materials.
Within each class, there are three levels of protection. Each level is rated for a stab done in a common technique with a certain amount of joules (units of energy) behind the thrust.
In general, “level I” armor is low-level protection that can be worn for long periods of time and is easy to conceal under clothing. “Level II” vests are thicker and often worn by law enforcement officers for extended periods of time. “Level III” vests are usually so thick that they can’t be concealed, and only worn in the most high risk situations.
It’s important to take local threats into account when deciding what level of spike and edged blade protection is right for you. It’s not an either/or situation– many vests are rated for both edged blade and spike. Many even provide total protection– for edged blade, spike, and ballistic attacks.
Covert vs. Overt
It is just as important to decide whether or not to have your armor on display. While the more protection your armor gives you, the bigger and heavier it will be, the lower levels of soft armor can be worn with lightweight covert carriers. These are designed to be worn underneath clothes and provide maximum mobility. Many manufacturers offer covert stab proof vests with breathable materials, such as Gore-Tex or CoolMax technology designed to regulate the temperature of the wearer.
Of course, many may wish to wear an overt stab proof vest. This will offer the same protection, and will be easier to remove, and may act as a deterrent to an attacker. People will certainly think twice before attacking someone who is obviously prepared for an attack.
Both Covert and Overt styles offer the same level of protection and simply differ in the wearing. It is important to be properly prepared for the situation you will find yourself in and choose your body armor accordingly. Make sure to perform a careful assessment of the risks you are likely to face before purchasing body armor.
Communications Director
