Modern helmets — protective structure and production technology

Personal protective equipment soldier on the battlefield has not used a thousand years, and its components are well known to historians and archaeologists, investigated in great detail. Since the dawn of the century an important part of military defense is broneshlem (BS).

In this article, be subject to review some nuances related to modern materials and construction of battleships.

The design and geometry of the battleships changed over time, regardless of the constant improvement of tools and weapons, from which it was necessary to protect the person. But the material of construction for housing BS — its main structural part is actually not changed in centuries. This material was homogeneous narrow sheet metal — first copper and bronze, and later iron and steel. Until the early 80-ies of XX century, only iron battleships were used in all the armies of the world.

Modern helmets - protective structures and manufacturing technologies

The soldiers in helmets

The overarching task BS, formulated by military leading global powers, is to protect the head from the fighter on the battlefield mass destruction factor — the fragments of natural fragmentation high-explosive shells, mines and grenades, the protection of the skull from shock loads.

In the middle of the XX century, when we analyzed the results of the 1st and 2nd world wars and the following local conflicts (Korea and Vietnam) has become evident that the metal homogeneous BS can not provide protection for the head of a soldier of the range of the mass flow of shrapnel damage on the modern the battlefield. Level of ballistic resistance (PIC) was very low and did not exceed V50% = 300-350 m / s for the fragment mass of 1 g (50% probability. Possibility of non-penetration housing BS). I must say that to do with the protection of a superior POS can only be achieved by increasing the thickness of the housing BS that immediately lead to a significant increase in weight worn on the head. So, for instance, to raise the PIC SB with iron V50% = 300 m / s to V5o% = 600 m / s to almost double the thickness of the shell from 1.6 mm to 2.5 mm, which is in the physical density of steel rst = 7.85 g / cm3 lead to higher body mass BS from 2350g to 1500g. This is unacceptable, because there are medical and technical limitations on the allowable weight worn battleship that require maximum limit for combined arms BS in 1600g.

Such a restriction based on the fact that the pilot experiment was determined by the doctors getting the heavy injuries of the cervical spine area in excess of wearable distributed mass BS on his head over 1600g.

So Makar, at the turn of the 60s — 70s XX century saw the creation of the task low-density polymer materials possessing commensurate with durable steel tensile strength, which would come to replace the iron sheet steel in the creation of BS and have allowed to significantly increase the PIC housing without increasing its weight. In addition, polymeric materials, because of their own physical and mechanical properties, better absorb and dissipate the energy of the shock-wave interaction means of destruction with a protective barrier structure than homogeneous high-carbon steel.

Such material was first developed by the American company «Dupont» and has been called "para-aramid fiber", who had the ultimate strength is the same as that of structural steel, and the physical density of the pap. = 1.43 g/cm3, which is more than five times lighter steel. Fibers made from para-aramid yarn linear density of 110 tex. (Yarn mass in grams per 1000 meters of length), which won the brand «Kevlar ® 29" and woven fabric specific weight 255 g/m2. Of this tissue has been made quasi-homogeneous multilayer tissue-polymer structure, which is equivalent to the weight of the homogenous solid steel showed more than twice as much higher PIC and the least dynamic deflection of the track with the help of the simulator standard fragments and 9mm pistol bullet caliber.

First in the world of tissue-polymer helmet appeared in the United States. It was developed natikskaya Research Laboratory of the U.S. Army in the late 1970s. First-1980s, he was adopted by the Army. Helm received the title of Personnel Armor System, Ground Troops (PASGT). It was made from a fabric-based fiber, and Kevlar ® 29 binder — a phenolic resin or PVB. Weight BS was 1.4 (3.1 lbs) -1.9 kg (4.2 lb)} have 5 sizes — XS, S, M, L, XL. Level determined by the PIC helmet military standard MIL-STD-662E, police NIJ 0106 and was V50% = 600 m / s in the standard splinter STANAG 2920, which is approximately the same level as in the V50% = 570 … 580 m / s on an iron ball weighing 1 , 03 g, which tested all the Russian helmets. Shock-proof properties are regulated standard MIL-H44099A.

Development of the production of these helmets is quite ordinary. Cloth soaked in resin bonding, simply put, the resin is placed in several layers to form. The resulting preform is compressed at a certain temperature, binding polymerized hardens. From upressovannoy shells are cut burr, set podtupeynoe device — a helmet ready. Because cloth soaked in resin, referred to as "prepreg", the development and production of helmets received the title of "prepreg". The main advantage of this technology — simplicity and low dependence on the accuracy of the final result of compliance regimes pressing. Because quite rapidly helmets like PASGT, was started in almost all countries. For 30 years, made several million pieces of helmets type PASGT, it is accepted as the main NATO and to this day used by the U.S. Army. In the armies of many countries around the world is used or that the helmet, or its analogs. Number of firms such as PASGT helmet in the several hundreds. Accordingly, the dispersion characteristics of these helmets, as in the mass, and on the protective features is quite large.

Modern helmets - protective structures and manufacturing technologies

Soldier in helmets with a small strap

Although the overall helmet satisfies the requirements of the military, work to improve it started in the late 90s. These works were initiated in the beginning of the implementation of almost all countries of the world programs to equip fighter coming century. These program notes fighter and his equipment are considered as a single system, which interacts with other systems must be very good to do battle puzzle. Means of protection, and a helmet that is, applets are accepted as an element that is not counting the protective functions should be complexed with other elements of the system. Virtually all programs from "soldier of the future" considering the helmet as a platform for the installation of night vision devices, communications, navigation, and monitors for self-control and information functions, which inevitably leads to an increase in mass, the loading head.

Because back in 1996, the U.S. DoD was proposed two-year programm SEP (Soldier Enhancement Program — The program increases the fighter combat abilities), in which was to be developed and tested a helmet with a light foundation. As the goal was tasked to reduce the weight of the helmet by 25%.

But to realize these goals
zabugornom developers manage with great difficulty. The main reason is just to made and operated by technology. Has long since become clear that the ballistic fabric more works fine when its individual strands have the opportunity for elastic stretch, reaching the yield point, which occurs at the highest loads on the material. The fabric itself for itself already limits the elasticity of the filaments and the type of fabric weaving resistance can vary considerably. If the cloth impregnated with a wetting adhesive composition and reincarnate into a hard composite, the ballistic properties of such composites will be worse than that of an equivalent mass of tissue in no way associated package.

Yet, using new, more effective than Kevlar ® 29 materials, zabugornom developers have 10-15% lower and raise the weight of the helmet and his pic. Thus, the application of new and improved aramid fiber «Kevlar ® KM2» and the ready threads of his more linear low density (44teks, 67teks.) Enabled reduce the weight of the helmet by 8-10%.

Follow-up studies on the reduction of weight led to the development and adoption by the U.S. Army in 2002, the latest, as aramid, helmet ACH (Advanced Combat Helmet), which has the lowest weight yet. However, the decrease in weight was provided, in the main, a decrease of 8% of the area of protection, but the developers managed to increment by 6% of the pic.

Hard at work on the problem of reducing the mass of the helmet and the last developer helmet PASGT — Research Laboratory NATICK. So it is at the present time to learn two new materials that can solve the problem of weight reduction. One of them — a recognizable material «Zyion». Using this material, company has managed to get a helmet weighing only 800 g (1.79 lb). However, this material was not stable to sunlight, water, and therefore not applicable for use with helmets. At the moment, the company will explore new material on the basis of M5 fiber, developed by Magellan Systems Int. Calculations show that at the same level of protection will allow the introduction of material M5 downsize helmet 35%. But while the South American soldier at war in the helmet, the weight of which more than 1.3-1.5 kg, and the PIC does not exceed 680-700 m / s on STANAG-2920.

Our home much later many foreign countries began to think about the substitution of the metal helmets CLU-68 on the tissue-polymer, although work on creating such helmets began at the Institute of Steel in an active manner since the mid-80s. The developers of the Institute began to develop a fundamentally different technology — the technology of thermoplastic extrusion quasi-homogeneous multilayer film structures, or, as it is often at this point is called — "film" technology. The essence of its ordinariness — layers of ballistic fabric are laid narrow thermoplastic film. Then the stack is placed in a mold, heated, compressed and cooled. The film melts and connects the fabric layers. After cooling down is a tough homogeneous shell helmet shell. Estimated developer film soften, not wet filament fabric, leaving them to actually limit the freedom of elastic deformation, and hence resistance, such compositions should be higher than the equivalent mass of prepreg. Practice has shown that the calculation was correct. However, to arrive at the desired result institute took almost 10 years. Specifically, there was so much testing of high-performance technologies for industrial helmets desired property. But the developers appeared a vast field for the optimization of the composition. By varying the set of tissues in the front and back layers, changing the thickness and material of the film binding could find a more balanced version of the criteria. In 1999, the first serial helmet produced by the Research Institute of Steel under the symbol "6B7", entered the armed forces of the Russian army. According to its features it immediately eclipsed own zabugorny analog: weight — less than 1.3-1.35 kg, Ballistic resistance -560 m / s, corresponding to 600-610 m / s over a STANAG. By 2005, the Institute became developed and passed into service has 3 models of helmets — 6B26, 6B27 and 6B28. They all were, and to this day holds the record for weight and durability. Optimizing the package, Steel Research Institute managed to make a helmet weighing less than 1.1 kg with a pic above 700 m / s (STANAG — 730-740 m / s), while not in experimental models and in mass production. This layout design combined arms BS 2nd generation.

In life, everything has a price. Naturally, as the highest properties of the helmet has been made a corresponding price. So strict requirements for quality ballistic fabric used, the smallest deviation from the devil sends the passport cloth the marriage. The development allows for the introduction of the packages only solid pieces, whereas in prepreg technology can be used packages, recruited from pieces of ballistic fabric. This leads to increased consumption of expensive fabrics and accordingly the final price of the product. The very process of compression is also asking for more time than the prepreg technology as well as the controlled heating of the workpiece and its cooling occur specifically in the press snap. True his latest works developers Steel Institute showed that the reserves in the optimization of this technology is and they are not small. We find solutions to reduce the cycle of heating and cooling of the workpiece. Do not forget a number of important points. Since the development of film does not use harmful resins, it is on the order of environmentally cleaner, which manifests itself in the workplace, and the operation of the helmet. Oh, and for the organization of large-scale production film development progressive prepreg as it allows automate the process of assembling tissue-plastic bags for pressing, while the prepreg technology, this operation is done manually.

Modern helmets - protective structures and manufacturing technologies

Soldier in helmets pass the obstacle

Following from the above, and zabugornye and Russian design tissue-polymer SB is used as a protective structure multilayer quasi-homogeneous composition is based on a strong aramid fabric and polymeric thermoset or thermoplastic binder that holds the layers of fabric over the entire thickness of the structure and forces the body to work as a continuous solid BS elastic shell — "polymer armor."

Very important to note the fact that the solid homogeneous shell casing prevents normal use of physical and mechanical characteristics of the material structure — namely, to dissipate the shock wave formed by the penetration of high-speed pulse means of destruction, and it created a wave of elastic deformation of the composite material, providing a permissible value of the dynamic deflection shell. A specific value of dynamic deflection shell BS when no penetration protective structure is a determining factor zapregradnogo contusion impact on a person's head. Because very permissible value of the dynamic deflection of the shell is always defined in the municipal test samples BS with rentgenoimpulsnoy settings in real-time.

Apart from the technology of thermoplastic film applied to the creation of a homogeneous solid shell cases battleships in Russia has developed a "mixture shannaya" design, which incorporates elements of prepreg technology in combination with the "dry" layered aramid fabric bags. With all of this external tissue layers protective structure impregnated with a thermosetting resin bonding, and the inner layers remain dry. Such a structure has received the
title of their own developers (JSC CVM "Armokom") — "discrete fabric structure" (TPA).

Since 2000., Russian aircraft bought tissue-polymer battleships and produced by film technology and technology TPA approximately similar amounts. Exceptionally in 2010 — 2011. they were produced and delivered to the army of around 70,000 units. At the same time, fighting protective and performance properties of homogeneous and discrete tissue BS is exactly the same, the cost of both samples are single. What's the difference after all?

And the difference is just BS and lies in the structure of the polymer protective composition obtained as a result of other processes molding shell casing. In the case of the thermoplastic film, as noted, is a homogeneous solid shell structure and interactions with such ordnance in general obstacle lies in the conventional theory of elasticity and strength of materials. Housing BS acquired technology TPA has expressed a heterogeneous structure consisting of two relatively hard outer shell and thin, giving the firmness of the assembly, and dry flaky package aramid fabric, located between the membranes. This structure called "diversity", because a high-density layers are at a distance from each other, and between them is placed low-density material. Diversity scheme protective structure has advantages, for example, more effective absorption and dissipation of the shock wave due to the presence of the interfaces between layers of different-density material composition. But this advantage is achieved greater width combined body battleships with TPA — up to 15 mm, while the thickness of the film of a homogeneous body in the most cumbersome podtuleynoy area does not exceed 8 mm.

But apart from that merits no more protective benefits development TPA does not, not to mention the relatively low productivity of the production of such structures, at first, due to the large bit of manual labor used in the assembly of tissue package. Together with the fact TPA has one significant drawback — a very small thickness of hard-elastic inner shell BS, the task of which is, that by absorbing the energy of elastic deformation of dry cloth bags to reduce the amount of dynamic deflection of the polymer composition. But because dry cloth packet is associated with a narrow resilient pressurization of prepreg, the whole elastic energy pas ¬ keta have a local affected area narrow prepreg coating rather than moderately distributed throughout the thickness of layers as in the structure of the homogeneous tissue-polymeric housing. In this case, if the criteria are equivalent to associate values of the dynamic deflection of 2-technologically different BS — homogeneous and DTS, it appears that the TPA value of dynamic deflection of more than homogeneous thermoplastic film.

The question "which technology is more preferred and progressive?" Is the responsibility of the customer, which in step municipal tests led to detail all the performance characteristics of the two battleships, each separately, and made serially in both the creation of the standard.

As long as the mass creation of tissue-polymer battleships of the first generation could not focus on the technological qualities of the production of different designs, all the more that the establishment is conducted under the current working design documentation letter "O1", approved by the customer. But with the development of military equipment 2nd generation customer demanded the development of a single design, and means and protective structure, combined arms BS.

Becomes relevant "deferred" customer question: "What is the protective structure of the polymer composition meets the modern requirements for ballistic and anti-bullet resistance in a most? What structure provides a more useful value zapregradnogo contusion impact? "

Quite obviously, the answer to this question is the customer can get only after the overarching comparative tests of different battleships, including zabugornogo production, first of biomedical research results of the dynamic effects of weapons on housing BS and a human head. Without answering this question, it can not be reconciled, and to take an informed decision in the field of military equipment in the long term.

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