Have you ever wondered why protective vests on the market are divided into stab proof vests and bulletproof vests? Normally, as long as the items that can be bulletproof are generally harder and more protective than ordinary items, why should they be divided into bulletproof and stab proof?
Even some types of bulletproof vests can be cut by high-quality daggers. Why?
In theory, as long as the protective material is thick enough, or so to speak, as long as the material is thick enough, bulletproof and stab proof are not a problem.
For example, when fighting in the past, it was incredible to wet the quilt and put several layers together to prevent the killing of bomb shrapnel.
Can bulletproof vests only be bulletproof but not stab proof? My answer is: if it is thick enough, it can be prevented.
This involves a contradiction or dilemma faced by bulletproof clothing manufacturers.
Wearability (weight, softness) and protection ability (protection level) are in conflict in essence, which is an inevitable contradiction.
The lightest protective clothing is “the emperor’s new clothes”, which is especially breathable, light and comfortable. A child will understand that the emperor has no clothes, and his protective ability is zero. Of course, it’s a joke.
In fact, there is also a triangular relationship among wearability, protective ability and price. For such problems, please refer to our previous articles, which have a detailed introduction
The design of a protective suit must coordinate the relationship and balance between the three. Let’s take a look and discuss this problem today.
Why Can’t The Existing Soft Bulletproof Vests Be Stab Proof
The main reason is that the working principles of bulletproof and stab proof are different
The main protective material of soft bulletproof clothing is usually fabric, which has gaps. For the sake of aerodynamics, that is, the bullet flies stably and accurately, the front of the bullet must be designed into a circular arc.
The circular arc surface will be a surface in the impact during the bullet impact. During the live bullet test, the front end of the warhead will always contact 2-4 fiber wires to play a role.
The principle is similar to placing countless pieces of paper in front of the bullet to continuously provide friction. Help the bullet slow down and finally stop him.
The working principle of stab proof clothing is completely different. The front-end details of the cutting tool used in the standard test are sharp, similar to the tip or spear of the triangular scraper.
The main protective function is completed by shearing and cutting. The direction of shear stress generated by the cutting tool is perpendicular to the protective material, and the energy density of the tool tip is much higher than that of the warhead.
Therefore, the protective material of stab proof clothing is usually denser or glued than that of bulletproof clothing. From the test sample, the impact area after bulletproof test is basically a circle with a diameter of more than 5cm, while the impact area after stab test is usually a circle with a diameter of 2-3cm.
The comparison between bullet and tool is as follows
The comparison between bullet and tool is as follows:
Bullet: small weight, fast speed, large kinetic energy and not sharp.
Cutting tools: heavy, slow, low kinetic energy, very sharp
You can’t underestimate stab proof. Do you dare to let a 1kg metal block fall from a meter high and hit your feet?
What’s more, this metal block also has a sharp three edge scraper!
Of course, the standards of stab proof clothing in each country are completely different. Let’s compare the standards of China and the United States.
The standard of Chinese stab proof clothing is that sharp objects of the same grade are not allowed to pierce the stab proof clothing, and the corresponding protective articles of different grades are in detail.
However, the standards for stab proof clothing in the United States are completely different. The American NIJ standard is that stab proof clothing is allowed to penetrate up to 7mm. However, the grade span of stab proof clothing is relatively large, and the protection effect and type are relatively vague. Therefore, when purchasing American standard protective clothing, high-grade protective clothing will be selected as much as possible.
