What modern flak jackets are made of: Construction, protection principle

The body armour https://uarmprotection.com/shop/category/body-armor/ is one of the basic protective equipment worn by security guards or internal affairs officers on special assignments today. It covers the upper part of the torso against the impact of cold or firearms and against various shrapnel wounds as a result of an explosion. A good civilian bullet-proof waistcoat is composed of fabrics capable not only of deterring bullets, but also of dissipating projectile energy. Such a design prevents serious wounds from the inertia of the bullet or fragment itself.

The predecessor of modern body armour is the breastplate worn by knights. In the sixth century, the requirements for such protection were as follows: the breastplate had to stop a bullet from a musket, and the back from a pistol. Over time, the lethality of weapons has increased and modern flak jackets are made of better materials.

Concealed body armour

Such models are made of ballistic fabric which has high toughness and tensile strength. Kevlar or aramid, these materials are capable of stopping a blunt bullet, buckshot or a fragment with low velocity. However, this flak jacket can be cut with a knife and will not protect against sharp shrapnel from mines or grenades, so modern ballistic fabric is combined with metal or polymer plates.

Kevlar fibres are a crystallising polymer. Their structure is characterised by the highest degree of rigidity. This is due to the presence of benzene rings. The structure of Kevlar belongs to the mesh polymers.

Fibre-forming polymers are processed by polycondensation in solution at low temperature. Reagents are added to the latter and actively mixed. The polymer is released from this solution as a crumb or gel. The polymer is then washed and dried. The polymer is then dissolved in strong acids (e.g. sulphuric acid). The solution is extruded to form strands and fibres. The yarns and fibres are then deposited in a settling tank and washed and dried again.

Kevlar is made in the form of technical yarns of different linear density and structure. The number of fibres in the yarns can vary from 130 to 1,000 for Kevlar fabrics and from 500 to 10,000 for cord and rope. This material is available as roving, fabric and yarn. The fibres are opaque and have an average cross section of 11 microns.

Semi-rigid and rigid flak jackets

These are considered external or concealed wear waistcoats and combine ballistic fabric and hard plates. This “sandwich” holds back blunt-pointed bullets, buckshot, protects against shrapnel and edged weapons. Unlike soft body armour there is practically no risk of latent injuries caused by projectile inertia.

In the manufacture of body armour, the plates are made of the following materials

• ultra-high modulus polyethylene;
• boron carbide or silicon
• corundum or aluminium alloys;
• titanium alloys with other materials;
• armour steel.

The last type of plate is used less and less often because of its weight – a soldier wearing body armour has to move, sometimes he has to run and perform other physical tasks. The manoeuvrability is very important, which is why lightweight semi-rigid or rigid body armour is one of the most popular waistcoats.