Patent Publication Number: US-2007094760-A1

Title: Ballistic protective armor and ballistic protective helmet and protective vest

Description:
The present invention relates to ballistic protective armour according to the preamble of claim  1 , and a corresponding ballistic protective helmet and protective vest.  
      Ballistic protective armour of this type is a component of ballistic protective clothing or head coverings such as military helmets, bullet-proof vests and suchlike. For reasons to do with saving weight, such protective armour is generally made from technical fabrics such as high-molecular polyethylene, aramid or other highly durable yarns. Individual layers of fabric are laminated with the help of an adhesive matrix by applying an adhesive, a resin or a film between the individual textile layers, and the entire packet of layers is then pressed to create a textile laminate.  
      The properties of the protective armour may be varied as a function of the material properties of the yarns used for the textile layers, the different types of weave and fabric weights, and the percentage of resin or adhesive in the connection matrix. Besides form stability, i.e. resistance to deformation, which is particularly important in protective helmets, resistance to an impacting projectile or fragments naturally plays a primordial role. In addition to exerting force in the layering direction, which will be referred to below as the Z direction, the impacting missile also exercises forces in the directions within the plane of the layers, i.e. in the X and Y directions perpendicular to the Z direction. These forces are absorbed by the yarns or fibres of the textile layers, whilst the forces in the Z direction are absorbed by the bonding of the textile layers. This means that the adhesive strength of the matrix makes a decisive contribution to preventing the missile from penetrating the armour.  
      It is possible to completely embed the layers of textile fabric in the matrix so that the adhesive force holding the layers to each other is very high. In general, the forces occurring in the X and Y directions upon impact of a missile cause the fabric fibres to stretch, thereby absorbing energy. As this happens, the protective armour may bulge in the direction of impact. If, however, a certain force or extension of the fibres is exceeded the fibres are abruptly sheared and the missile penetrates the corresponding layer. This shearing effect is exacerbated by completely embedding the fabric in the resin or adhesive matrix as this restricts the fibres in their capacity for longitudinal extension. This reduces resistance to perforation of the armour. Besides this effect, a high percentage of resin or adhesive increases the weight of the protective armour.  
      Attempts have therefore been made to construct ballistic protective armour with a reduced application of resin between the textile layers. This saves weight, and the energy absorption within the individual textile layers is increased as the fabric fibres not embedded in the matrix can stretch unhindered. On the other hand, the hold between the layers is reduced. Hence the following effect occurs upon impact of a projectile: as a result of the shearing effect, the outer textile layers are smoothly penetrated by the projectile, which is greatly deformed in the process. The following layers stop the projectile, whose kinetic energy is already greatly reduced by this point, thanks to the stretching of the fibres within the textile layers. As this happens, these stopping layers of the laminate bulge substantially towards the inside of the protective armour because the projectile-stopping layers detach more easily from the perforated layers due to the reduced application of resin, and delamination occurs between these layers. The pronounced bulging effect can, however, cause serious injury to the wearer of the ballistic protective clothing. The wearer of a ballistic protective helmet which is subjected to substantial inward deformation upon impact of a missile may, for example, suffer head injuries.  
      When designing conventional ballistic protective armour one must, therefore, prevent the above described effect of complete perforation on the one hand, whilst also preventing excessive deformation of the inner layers of the textile laminate on the other hand. This is done by appropriately matching the stretch properties of the textile fabric and the percentage of resin or adhesive, so that the load uptake in the various directions can be predetermined. This is only possible to a limited extent, however, because the conditions are difficult to reproduce during production of the protective armour, and because the delamination effect that occurs as the deforming stopping layers detach from the perforated layers is sudden and virtually uncontrollable. These circumstances render it extremely difficult to select, in particular, the percentage of resin or adhesive to use in the connection matrix.  
      The task of the present invention is therefore to provide ballistic protective armour of the above-mentioned type which reliably prevents penetration by projectiles or impacting fragments but at the same time reduces the above-described deformation effect on the inside of the armour opposite the impact side to an acceptable degree, whilst keeping the weight of the protective armour as low as possible.  
      This task is solved according to the invention by means of ballistic protective armour with the features of claim  1 .  
      The ballistic protective armour according to the invention comprises a number of wire or thread binders which pass through the textile laminate in the layering direction, i.e. in the direction of the surface normals, which is perpendicular to the textile layers. These binders give the individual textile layers of the laminate additional hold relative to each other in that in addition to the prior art adhesive matrix, a further mechanical connection is created. By selecting an appropriate tensile strength, i.e. elasticity, of the binders it is possible to improve the perforation and deformation properties of the textile laminate and its resistance to an impacting projectile.  
      In particular, the above-described bulging effect in the inner stopping layers of the laminate which are deformed on projectile impact is greatly reduced as the binders can absorb large tensile forces in the direction of the missile, and can prevent an uncontrolled detaching of the layers from each other (delamination). Instead, the delamination effect is restricted to the immediate vicinity of the missile channel. In this region the tensile forces on the binders are so high that they break and the inner stopping layers can become detached. In the directions within the layers, i.e. in the directions perpendicular to the layering direction, the force finally decreases until it drops below the force required to snap the binders, so that the binders are merely stretched. The adhesive coatings on the layers may become detached from each other, but the layers themselves are held together in a stable manner by the stretched binders. This substantially reduces the degree of inward bulging in the protective armour, and hence the risk of injury. And there is still sufficient absorption of the kinetic energy from the missile to ensure that the projectile is unable to completely penetrate the textile laminate. The percentage of resin or adhesive in the textile laminate can be substantially reduced without excessive deformation occurring, which results in weight savings and improved wearer comfort.  
      Advantageous embodiments of the ballistic protective armour according to the invention are disclosed in subclaims  2  to  18 .  
      A ballistic protective helmet, whose helmet shell is formed by ballistic protective armour according to the invention, is claimed in claim  19 .  
      Claim  20  is further directed at a ballistic protective vest comprising hard segments or hard inserts, each of which is formed by ballistic protective armour according to the invention.  
      Further embodiments of this protective vest are disclosed in claims  21  and  22 . 
    
    
      Preferred examples of embodiments of the invention will be described in more detail below with reference to the drawings, in which  
       FIG. 1  shows a side partial section through a ballistic protective helmet whose helmet shell is formed by ballistic protective armour according to the invention;  
       FIG. 2  shows a top plan view of a section of the surface of the helmet shell of  FIG. 1 ;  
       FIG. 3  shows a partial section through a helmet shell according to a further embodiment of the invention;  
       FIG. 4  shows a top plan view of a section of the helmet shell of  FIG. 3 ;  
       FIG. 5  shows the helmet shell of  FIG. 3  in a deformed state after impact by a projectile, and  
       FIG. 6  shows a partial section through a helmet shell according to a third embodiment of the invention. 
    
    
      The helmet shell  10  shown in  FIG. 1  is a component of a ballistic protective helmet, for example a helmet for military use. The concave inside of the protective helmet closest to the helmet wearer&#39;s head (not illustrated) is shown at the bottom of the Figure, whilst a projectile may impact from the convex outer side. The term “projectile” as used hereafter includes all possible ballistic missiles, such as grenade or missile fragments or suchlike in addition to projectiles from firearms in the narrowest sense.  
      Other devices inside the protective helmet such as a basket-shaped lining attached to the inside of the helmet shell  10 , which ensures a gap between the helmet wearer&#39;s head and the inside of the helmet shell  10  and improves wearer comfort, is not shown in this or any of the following figures.  
       FIG. 1  shows the helmet shell  10  in intact condition. It is formed by ballistic protective armour  12  comprising a textile laminate  14  made from a number of textile layers which are laminated together. The layers run along the curve of the helmet surface, parallel to each other, between the inner and outer surfaces of helmet shell  10 , i.e. the layering direction coincides with the surface normals, which is perpendicular to the surfaces of the textile layers. In  FIG. 1 , the layering direction is designated by an arrow Z, which coincides with the normals of the outer helmet surface at a certain point of curvature, whilst the individual textile layers run in the X and Y directions inside helmet shell  10 , perpendicular to layering direction Z. For the sake of completeness, the X direction (to the right in  FIG. 1 ) is also indicated by an arrow X.  
      For reasons of clarity, the textile layers are shown in cross-section in a region confined to the right of the Figure. The layers actually run through the entire helmet shell  10 . The present embodiment specifically includes ten layers  16  to  34 , layered on top of each other in the Z direction. In practice it is usual to use an even larger number of layers; the person skilled in the art will, however, be able to select an appropriate number of layers. Each of textile layers  16  . . .  34  comprises a fabric made of aramid, polyethylene or carbon fibres, that is a synthetic material with high tensile strength in the directions X and Y, in which the layer stretches. It is further possible to weave the textile layers out of yarns, or to produce them using other textile techniques.  
      Textile layers  16  . . .  34  are laminated together in that they are pressed with a connection matrix disposed layer by layer between the individual textile layers. This connection matrix may be, for example, an adhesive, a resin or a pressable film. To produce the textile laminate  14 , textile layers  16  . . .  34  and adhesive or resin layers, or film layers, are thus alternately positioned one on top of the other and pressed under high pressure so that the textile laminate  14  is created as a composite made of textile layers and the connection matrix. The individual layers of the connection matrix are not shown in more detail in  FIG. 1  or the following Figures. The stability of this packet of layers  14 , i.e. its resistance to forces in the Z direction, which act to detach textile layers  16  . . .  34  from each other, and the weight of helmet shell  10  can be determined by the quantity of adhesive or resin applied, or the thickness of the pressable film between the textile layers. Basically, the greater the weight percentage of the connection matrix in relation to the total weight, the greater its strength, meaning that the strength can be increased by, for example, applying more resin. Doing so may, however, cause an effect whereby the material used for the connection matrix penetrates at least partially into the fabric of the textile layers  16  . . .  34  when the laminate is pressed, causing the fibres of the textile layers to become embedded in the matrix. This severely restricts the fibres&#39; ability to stretch in the X and Y directions.  
      According to the invention, the ballistic protective armour  12  forming helmet shell  10  comprises a number of wire or thread binders  40 , which pass through the textile laminate  14  in the layering direction Z from the inner surface of helmet shell  10  to the outer surface, i.e. through all the textile layers  16  . . .  34 . These binders, which are spaced apart from each other in directions X, Y in which textile layers  16  . . .  34  run, ensure additional hold between the textile layers  16  . . .  34 . Hence layers  16  . . .  34  are not held together solely by the adhesive force of the connection matrix, but also mechanically, by binders  40 . This ensures greater stability of laminate  14  in the layering direction Z and, in the event of impact by a projectile, offers advantageous properties in case of delamination of the inner textile layers, as will be described in more detail below.  
      Binders  40 , of which only the left-hand binder  40  is provided with a reference numeral in  FIG. 1 , can be made of any suitable material which exhibits the desired properties, i.e. appropriate tensile strength and elasticity in particular. Binders  40  may, for example, be made of a metal or a synthetic material, and possibly flexible reinforcing threads formed from a single fibre or a number of fibres which may further be spun or drilled to form a yarn. Highly durable materials such as aramid, polyethylene or carbon fibres are possibilities. Although not shown in  FIG. 1 , it is conceivable that the ends of the individual binders  40  on the outside and inside of helmet shell  10  be provided with anchoring devices such as protuberances or suchlike to prevent binders  40  from simply being pulled out of the packet of layers in the event of delamination of the textile laminate  14 .  
      To allow binders  40  to fulfil their function according to the invention it is not essential that binders  40  run precisely in the layering direction Z or −Z, i.e. in the direction of the surface normals of textile layers  16  . . .  34  at the point of penetration of binders  40 , rather it is sufficient that the stretching direction of binders  40  includes a component which coincides with the layering direction Z, so that textile layers  16  . . .  34  are penetrated. Hence it is permissible to include a certain angle with the normals. If such deviations are desired for constructive reasons, the person skilled in the art will be able to determine a suitable size for the angle of deviation through tests not involving a great deal of work.  
       FIG. 2  shows a top plan view of helmet shell  10  with the inserted binders  40 . In this figure all that is visible is a section of the surface of the uppermost textile layer  34 , inside which lie the outermost ends of the wire or thread binders  40 . The layering direction Z thus points out of the plane of the drawing in  FIG. 2 . Binders  40  are arranged in a regular quadratic grid pattern, i.e. binders  40  are disposed in both the X and Y directions to coincide with the stretching direction of textile layer  34 , positioned in rows at equal distances, a, from each other. Distances a may be freely selected in order to influence the stability of the textile laminate  14  and its delamination behaviour.  
       FIG. 3  shows a lateral partial section through another helmet shell  50  which is also made from a textile laminate  14  comprising individual textile layers  16  . . .  34 . The structure of the individual layers  16  . . .  34  made from a highly endurable fabric, their layering in the Z direction and their connection by means of layer-upon-layer pressing with a connection matrix correspond to the helmet shell  10  of  FIGS. 1 and 2 , so that reference is made to the preceding sections of the description with regard to the structure of textile laminate  14 .  
      According to the invention, helmet shell  50  comprises thread binders formed here by sections  52 , running in the layering direction Z, of a reinforcing thread  54  which runs as an endless thread between the inner and outer surfaces of helmet shell  50  meandering through textile laminate  14  in direction X, i.e. in the direction in which textile layers  16  . . .  34  stretch. Starting out on the left-hand side of  FIG. 3 , a section  52  of reinforcing thread running in layering direction Z initially passes from the inside to the outside where it is joined by a connecting section  56 , which rests on top of the outer surface of helmet shell  50 , of reinforcing thread  54 . This is in turn followed by a reinforcing thread section  52  which runs from the outside to the inside (opposite direction −Z), followed by a connecting section  56  which rests against the inside of the helmet shell. From here on, this sequence of sections of the reinforcing thread  54  between the inside and the outside repeats itself continuously in the stretching direction X of the textile layers  16  . . .  34 . Hence the individual reinforcing thread sections  52  forming the binders are connected by connecting sections  56  to form an endless thread which creates a seam which can run through the entire textile laminate  14  and helmet shell  50 . Reinforcing thread  54  can be pulled taut to give the individual textile layers  16  . . .  34  increased stability.  
      Reinforcing thread  54  may be a textile fibre made from a highly durable synthetic material such as aramid, polyethylene or carbon fibre, and several fibres of reinforcing thread  54  can be spun or drilled together to form a yarn. Basically, the same materials can be used for binders  40  in the first embodiment and for reinforcing thread  54 , respectively sections  52  of it acting as binders. Given that in the case of the endless reinforcing thread  54 , the thread path undergoes deflections at the inner and outer surfaces of helmet shell  50 , the thread material needs to exhibit a certain pliancy and flexibility.  
       FIG. 4  shows a top plan view of a section of the outermost textile layer  34  from the same perspective as in  FIG. 2 . Resting on the surface of the textile layer  16  one can recognise connecting sections  56  of reinforcing thread  54 , whilst at the ends of connecting sections  56 , reinforcing thread sections  52  run in the layering direction and opposite thereto (directions Z and −Z) into textile laminate  14  and out again. In  FIG. 4 , the seams of endless threads  54  run from left to right, and connecting sections  56  are the same length on the inside and outside of helmet shell  50 . Endless threads  54  are spaced apart in the direction perpendicular to the direction in which the seams run, and connecting sections  56  of adjacent connecting threads  54  are each staggered by the length of one connecting section  56  in relation to each other in the direction in which the seams run.  
      It is understood that a different seam path may also be selected, for example by forming loops within the path of reinforcing thread  54 , as will be explained below. Furthermore, as in the previously described embodiment, it is not necessary for reinforcing thread sections  52  to run precisely in the direction of the surface normals; deviations from this direction can be tolerated. For example, consecutive reinforcing thread sections  52  may be inclined in relation to each other such that a W or zigzag type path results in the perpendicular sectional plane through laminate  14 .  
       FIG. 5  shows the functioning principle of the ballistic protective armour according to the invention with reference to the second embodiment depicted in  FIGS. 3 and 4 . In this case it is assumed that helmet shell  50  is shot at with a projectile  60  which impacts absolutely perpendicular to helmet shell  50 , i.e. in a missile direction −Z. Upon impact projectile  60  penetrates a number of outer textile layers, whereupon the fibres inside the textile layers are sheared smoothly, producing an approximately cylindrical missile channel  62 . The projectile  60  is greatly deformed as this happens and its kinetic energy is partially absorbed until the energy is no longer sufficient to penetrate further layers. This causes a deformation in the form of an inward bulge in the remaining textile layers on the inside of helmet shell  50  because the remaining energy from projectile  60  stretches the fibres of the textile layers which are not penetrated. Projectile  60  then remains inside a cavern  64  between the outer and inner textile layers. This cavern  64  is formed because the outer penetrated textile layers essentially retain their outwardly curved shape whilst the deformation of the inner layers causes a detaching or delaminating effect in that the outer and inner layer packets become detached from each other in the vicinity of missile channel  62 .  
      In  FIG. 5 , the three outermost textile layers  30 , 32 , 34  are smoothly penetrated and missile channel  62  forms inside them whilst the four innermost layers  16  to  22  bulge inwards. The fabric of these textile layers  16  to  22  remains intact, the fibres of the fabric are merely stretched so that the bulge is formed towards the inside of helmet shell  50 . Between the penetrated layers  30 , 32 , 34  and the deformed layers  16  to  22 , which are also referred to as stopping layers, there are three textile layers  24 , 26 , 28  which are destroyed in the immediate vicinity of missile channel  62 , absorbing energy as a result.  
      When stopping layers  16  to  22  detach, the inner stability of textile laminate  14  provided by the connection matrix is destroyed and there is a risk that uncontrolled detaching of the layers may cause substantial bulging and hence injury to the helmet wearer. According to the invention, this disadvantageous effect is prevented by reinforcing thread  54 . The sections  52  of reinforcing thread  54  running in the layering direction Z are able to absorb the tensile forces occurring in the Z direction upon impact, which stretches reinforcing thread  54  along sections  52 , so that additional energy is absorbed. If the forces exceed a certain value, reinforcing thread section  52  snaps. As the force decreases in the lateral direction, i.e. in the X and Y directions in relation to the direction of the missile, this snapping effect only occurs in the vicinity of the missile channel  62 , as shown in  FIG. 5 . Further away from missile channel  62  the tensile forces decrease and can be absorbed by the sections  52  of reinforcing thread without snapping thread  54 . In this fashion the adhesive layer of the connection matrix between the penetrated layers  30 , 32 , 34  and the stopping layers  16  to  22  can be prevented from giving way uncontrollably. The reinforcing thread sections  52  at the outer regions of cavern  64  reliably limit the delamination effect. The absorption of the tensile forces by the reinforcing thread sections  52  is facilitated by the outer ends of sections  52  being anchored in the outer textile layers  30 , 32 , 34  which retain their curved shape and hence exhibit high stability against the tensile forces exerted by reinforcing thread sections  52 . This anchoring effect in the outer layers  30 , 32 , 34  gives greater stability to sections  52 , and hence to the inwardly deformed region of the inner stopping layers  16  to  22 .  
      It is understood that the effect of the binders according to the invention as shown in  FIG. 5  is illustrated through reinforcing thread sections  52  merely by way of example, and is similarly achieved by all kinds of binders as defined in the present invention, in particular by binders  40  according to the first embodiment.  
      The energy absorption within textile laminate  14  can be advantageously increased by configuring the outer layers  30 , 32 , 34  in which missile channel  62  is formed to be very hard in comparison to the subsequent middle layers  24 , 26 , 28  which are destroyed in the region of cavern  64 , thereby absorbing energy. The great hardness of outer layers  30 , 32 , 34  greatly deforms projectile  60 , which has to form a larger penetration channel to allow it to penetrate more deeply into textile laminate  14 . In order to guarantee good deformability, the hardness of stopping layers  16  to  22  on the inside of helmet shell  50  should advantageously be selected so that it lies somewhere between the hardness of outer layers  30 , 32 , 34  and that of the soft middle layers  24 , 26 , 28 . The hardnesses of the various layers  16  . . .  34  can be influenced by the choice of fabric, and in particular, by the percentage of resin or adhesive in the connection matrix in the textile layers  16  . . .  34 .  
      Finally,  FIG. 6  shows a helmet shell  70  similar to the helmet shell  50  of FIGS.  3  to  5 , in which the seams of reinforcing threads  54  follow a different path. On the opposite surfaces of textile laminate  14 , reinforcing threads  54  run as endless threads, of which each endless thread comprises a number of loops  72  projecting into textile laminate  14 , said loops being interlooped with the loops  72  of an endless thread running across the opposite surface of textile laminate  14 . That means loops  72  of the reinforcing thread  54  that rests against the outside of helmet shell  70  point into textile laminate  14  counter to layering direction Z through a channel not shown in more detail and in the region of the middle textile layers engage in the loops  72  of another endless thread  54  running in a similar manner along the inside of the helmet. Each pair of interlooped loops  72  therefore forms a binder according to the invention. The loops  72  can be tensioned more or less tautly to permit adjustment of the elastic properties of the tensioning.  
      Ballistic protective armour  12  of the type described here is suitable not only for helmet shells  10 , 50  of ballistic protective helmets, but also for other kinds of ballistic protective clothing, in particular for protective vests designed to protect their wearer from projectiles or fragments. As such protective vests need to exhibit a certain flexibility for reasons to do with wearer comfort, the prior art vests usually include hard segments or hard inserts at points which are particularly at risk. These hard segments or inserts can also be formed from the ballistic protective armour according to the invention. To guarantee unbroken protection without restricting the vest wearer&#39;s freedom of movement it is advantageous to select an arrangement whereby the hard segments or hard inserts overlap each other, but can be displaced with respect to each other, or engage with each other.