Is Kevlar really a stab-proof material?

Kevlar is advertised all over the internet as being a ‘Stab Proof’ Material that will resist stabs and save lives, but is this really the case?

Kevlar (or Aramid Fibre) Comes in many different forms, DuPont Kevlar, Heracron Nomex or Technora. It is a material that is comprised of Kevlar and other fabrics woven together. These combined qualities make it very difficult to cut through.

I have been doing some detailed research into Kevlar. I have seen Heracron samples and many other samples that claim to be ‘Kevlar’ But I have not seen a single sample that I haven’t been able to get my knife through after a few goes.

But why is this? Why is it that a material that is so famous for saving lives can be cut through?

Take for example armour protection. Look at the difference here between a ‘stab proof’ jacket and a slash proof shirt

This is the reason:

Stab proof vests are very thick. They are made up of many layers of Kevlar. These layers put together create such a thick barrier that a knife would take a hell of a lot of force to get through it.

Effectively, the material catches and resists the knife’s blow because the fibre is very strong. But this does not mean the material cannot be penetrated.

A mistake that is often also made with bulletproof vests is that they are also stab proof. This is very wrong. Bullets are very blunt objects and a vest softens the blow to a blunt object due to the material absorbing the impact, despite the speed. However a pointy sharp object can get through the weaves of the material and cause damage.

Kevlar by itself is not stab proof. It is merely ‘slash resistant’ This means you can run the edge of the blade over the material multiple times without any problem. This is still a great quality and has many uses, however it cannot save lives as people think.
Kevlar can be a great use for products that need a hard wearing material. Seatbelts are often made of a Kevlar material. This is because seatbelts often get worn and to avoid the breakage of a seatbelt in an accident, it can be assured that the seatbelt will stay unbreakable.

Stab  proof jackets are extremely thick and rigid and resists stabbing but the tshirt is able to protect you from the threat of blade edges and sharp cuts. Which is better? That purely depends on the application.  You cannot wear a thick stabproof jacket all the time and still have the flexibility to run all over the place.

It will be exciting when materials become developed enough for us to have flexible suits than can make us invincible to knives and bullets!

Here is an eyeopening video that shows just how effective stab proof jackets can be
http://www.youtube.com/watch?v=4x8AJYDrFlU

Blog by Alice Parlett