What Makes Stab and Spike Vests Resistant?


By Chris Taylor

Stab proof vests provide the wearer some protection that bullet proof vests don’t– protection from knife attacks. Knives and needles have sharper points than bullets and require a different kind of material construction. Stab proof vests protect from slashes and jabs, preventing sharp-edged weapons from penetrating more than a few millimeters.

Most stab proof vests are made from a material called Kevlar. Kevlar is very resistant to impact and is made from strong, tightly woven together threads. The blade of a knife is very thin and sharp, concentrating the force of the impact on a tiny edge. Therefore, Kevlar threads in a stab vest are woven together particularly tight in order to catch the blade in their net.

The damage inflicted from a knife is directly dependent upon the amount of force the knife is being thrust with. The more momentum the knife has when it contacts the skin, the more damage it will cause. A stab vest works by allowing the knife to pass through the layers of the Kevlar without breaking the threads– each layer displaces the force of the blade and slows the blade’s progress. By the time the blade nears or meets the wearer’s skin, most of the energy of the momentum has been absorbed by forcing its way through the Kevlar.

Sheer-Thickening Fluid (STF)

Kevlar can be treated with sheer-thickening fluid (STF) to make it even stronger. STF is a technologically advanced chemical that allows the Kevlar to maintain flexibility until an object strikes it forcefully. Then it hardens within milliseconds, making the Kevlar up to 14 times stronger than without the fluid. This prevents the Kevlar from bending backwards upon impact, offering greater protection for the wearer and allowing vests with fewer layers of Kevlar to be made.



While treated, tightly-woven Kevlar will protect against nearly all edged blades, it’s not impenetrable. Weapons with very tiny points such as needles, syringes or prison-style shivs are so small that they can pass right through the Kevlar threads. If facing these improvised weapons, which are common threats to prison guards and law enforcement officers, the wearer will need a higher level of protection. By attaching a metal platelet to the outside of the Kevlar, the vest will provide additional protection from these pointy but weak weapons, shattering them before they even meet the Kevlar.

Stab Protection Levels

The NIJ rates stab and spike protection vests at levels I, II and III. The higher levels protect against harder thrusts and sharper blades. Metal platelets for spike protection begin at level II and higher. Make sure you have a clear understanding of the threats you face so you can get the best protection for your situation. These levels can be found here: http://www.safeguardclothing.com/articles/nij-levels/

Many people focus on threats posed by firearms, but stabbings are very common. In close quarters, desperate individuals or criminals are far more likely to stab, and can do so with improvised or concealed objects, giving you little to no warning. Be ready with a stab proof vest!

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2 thoughts on “What Makes Stab and Spike Vests Resistant?”

  1. John, about five years ago I drove armored truck collecting money from the schools and purchased a vest that was good up to nine mm and level one for knives, it was costly but I still have it.


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