TECHNICAL FIELD

The present invention relates to a structure for producing ballistic protection which can combine high bullet-stopping performance and trauma reduction with high flexibility.

PRIOR ART

A primary aim in the production of ballistic protections is that of combining high performance levels in terms of stopping the bullet, and limiting the trauma induced by the energy thereof with suitable flexibility, not only in order to provide good comfort, but also to allow the necessary freedom of movement during any action phase. In the field of ballistic protections that must be able to withstand the penetration of bullets even with a ferrous core whose speed is greater than 600 m/sec such as, for example, those relating to bullets identified as Kalashnikov caliber 7.62 x 39 mm, rigid monolithic structures are usually used, preferably made with overlapping laminates based on high resistance threads consolidated with each other by the application of pressure and temperature.

If, instead, the protection must be able to withstand the penetration of bullets whose speed is greater than 900 m/sec as is the case, for example, with the bullets indicated as SS 109 with caliber 5.56 mm whose cross-section is smaller than the cross-section of the bullets with caliber 7.62 mm and therefore more penetrating, monolithic structures made with consolidated textile laminates are possible but are associated with an unacceptable weight per m ² and a very high cost. Therefore, to be able to obtain adequate protection against this threat, monolithic and rigid composite structures are used, which are made with a combination of ceramic elements and textile elements stably connected to one another.

Where such items of protection are used for personal protection, in order to be sufficiently comfortable, they must be in some way pre-formed; but as the physical structure of every individual is different, for example, in terms of shape and size, a high number of mutually different moulds would need to be provided. To overcome such limitations, different solutions have been proposed as contained in patent US 875 77041 B1 , which describes a partially flexible structure composed of a series of ceramic discs which are overlapped with one another over a portion of the surface thereof, then encapsulated in glass fiber. The structure thus obtained has numerous drawbacks including that of not offering protection against bullets that hit surfaces even at moderate angles. The bullet can penetrate into the overlapping points between one disc and another, therefore not fulfilling the expected task.

Patent application EP 3098560 A1 describes an item of protection provided with a ceramic protective structure composed of a series of plates, and having different shapes, glued to at least one layer of contiguous ballistic laminate. The plates are partially free to move between one another, but as the ballistic laminate to which they are glued is practically non-extendable, the flexibility of the ballistic protection is hindered in some directions. In patent application EP 0967453 A1 a series of ceramic plates are glued to a completely rigid substrate. This structure is then connected to a series of flexible ballistic laminates, but the assembly is rigid in any case. OBJECT OF THE INVENTION

The main aim of the present invention is that of proposing a ballistic protection element that reduces the disadvantages of the prior art.

SUMMARY OF THE INVENTION

This result was achieved, in accordance with the present invention, by making a flexible ballistic structure comprising a textile component and a ceramic component, the textile component comprising a plurality of multilayer packages, wherein each of the packages has a plurality of textile layers comprising ballistic fibers pressed together and subjected to a flexibilization process by means of yelding, the ceramic component being placed outside the structure so as to have one face facing the direction of impact of an incident bullet and the other face facing the textile component and in contact with it, characterized in that the ceramic component comprises: a protective layer comprising a plurality of plates of ceramic material, the plurality of plates being arranged substantially on a plane with the plates being arranged substantially adjacent to each other, each of the plurality of plates having a gap of less than 0.5 mm from the adjacent ones, the plates being free to move so as to be able to tilt with respect to the plane and with respect to the other plates in all directions; an elastic element on each face of the ceramic component arranged in contact with the plurality of small plates, the elastic material including a gluing material filling the gap between adjacent plates so that the plates are kept substantially in position in relation to each other but with mutual freedom of movement, allowing them to be inclined with respect to the plane. The shape of the plates must however enable their contiguity so as to substantially cover the whole surface on which they are applied (e.g. the outer surface of the ballistic structure). In a preferred embodiment, the plates have an equilateral regular hexagonal shape. The distance between the contiguous sides of the plates is preferably substantially comprised between 0 and 0.2 mm, more preferably around 0.1 mm.

In one embodiment the elastic element comprises, for each face of the ceramic component, an elastic textile layer and a layer of gluing material suitable for gluing the elastic textile layer to the plurality of plates.

In an alternative embodiment, the elastic element includes a polymeric film placed on each of the two faces of the ceramic element. In the structure assembly step, the ceramic element, covered by the two films, is subjected to the action of heat and pressure. The polymeric film is partially melted and attaches itself to the ceramic element; the partially melted film can also penetrate into the space (gaps) between the plates, filling it at least in part. In another embodiment, the polymer film can be reinforced with elastic threads or be discontinuous.

The textile part placed behind the ceramic structure, according to a preferred embodiment, is composed of a plurality of laminates made using structures which are preferably unidirectional, appropriately impregnated with polymers, for example thermoplastic or thermohardening, made using so-called ballistic threads which comprise aramid, polyethylene, copolyaramid, polybenzoxazole, polybenzothiazole, glass, carbon, polyvinyl, polyvinyl alcohol threads, also mixed together and also with different count (thread sizes). In a second aspect of the present invention, a process is provided for producing a ballistic laminate as described above.

According to a further aspect of the present invention an item of ballistic protection is provided comprising the ballistic structure described above.

One of the advantages obtained from a structure according to the present invention is flexibility without directional limits. The textile substrate, normally very rigid, to which the flexible ceramic layer is added, is subjected to mechanical yielding cycles, which are also able to make it manually flexible in every direction. BRIEF DESCRIPTION OF THE FIGURES

These and further advantages, aims and characteristics of the present invention shall become clearer to a person skilled in the art from the following description and appended drawing, relating to examples of non-limiting embodiments, wherein:

- Figure 1 shows a perspective view of a structure for making ballistic items of protection according to a possible embodiment of the present invention;

- Figure 2 shows a perspective view of a structure for making ballistic protections according to a possible alternative embodiment of the present invention;

- Figure 3a shows a front view of the ceramic layer comprised in a ballistic protection according to the present invention;

- Figure 3b shows a side view of the structure of Figure 1 .

DETAILED DESCRIPTION

The ballistic structure according to a preferred embodiment of the present invention is made by combining a textile component, comprising a plurality of ballistic packages

107 overlapping with each other and a ceramic layer 105, comprising a plurality of ceramic elements, e.g. hexagonal plates, placed substantially adjacent to each other.

The plurality of ceramic elements is covered and held together by elastic elements

101 (one on each side). The elastic elements 101 may for example be elastic textiles, glued to the plurality of ceramic elements 105 by means of a gluing layer 103, as shown in Figure 1 and in Figure 3b. The gluing material penetrates in the gaps among the plates. In this way, the ceramic elements 105 are held together by the combined action of the elastic textiles and the gluing material, but are free to move with respect to an ideal plane. Alternatively, the elastic element can be comprised of, for example, a polymeric film 201 (see Figure 2) directly glued to the ceramic elements 105, therefore obtaining a similar effect on the ceramic elements, but without needing the gluing layer 103, as the polymeric film melts, by means of heating during the assembly step, and becomes welded to the plates (ceramic elements 105) penetrating in the gaps an filling them at least in part.

The textile component comprises a plurality of ballistic packages 107 obtained by consolidating a series of ballistic textile layers to each other. Every individual consolidated ballistic package, which is initially rigid, is subjected to a flexibilization process so as to make it flexible in every direction. The combination of the ceramic elements and the textile elements is therefore flexible in every direction.

Flexible ceramic component

In a preferred embodiment of the present invention, the ceramic layer 103 comprises a series of ceramic plates 105, preferably hexagon shaped and with dimensions that can be contained in a circle whose diameter is preferably comprised between 5 mm and 100 mm and whose thickness is preferably comprised between 1 mm and 12 mm. The plates 105 are substantially arranged on an ideal plane, adjacent to one another with the sides in contact with those of the adjacent plates or with a very small space comprised between 0 mm and 0.5 mm, preferably between 0 and 0.2 mm, more preferably around 0.1 mm. It should also be noted that, when plates are placed in contact with the adjacent ones, the irregularity of the side edges allows the plates to move in relation to each other, deviating from the substantially planar direction and enabling curved shapes to be created. The plates 105, as previously mentioned, are held together by an elastic layer 101 , placed on each side and glued by means of a gluing layer 103. The layer 101 may be any elastic material which enables the movement of the plates, e.g. a polymeric film, non-woven fabric, textile mesh, felt, netting, and is glued to the plates. In a preferred embodiment of the invention, the layer 101 is comprised of a flexible elastic mesh fabric, which is extendable, even manually, in every direction.

The ceramic plates are obtained, according to the prior art techniques known to a person skilled in the art, for example by sintering ceramic powders, and are comprised of oxides, carbides, nitrides such as, for example, aluminium oxide, boron carbide, silicon carbide, boron nitride, silicon nitride. As a result of the composition and sintering conditions, and purity of the ceramic powders, different degrees of hardness can be obtained. For the purpose of the present invention, greater hardness values than HV 1200 are particularly advantageous.

In a preferred embodiment of the present invention, the layer 101 should preferably be manually extendable, even simultaneously, in every direction by at least 20%, more preferably by at least 200%. If a polymeric film is used to make the flexible layer 101 , this film is able to perform the dual function of support and gluing. Therefore, it is not necessary to use a separate glue, but the film itself is glued to the ceramic plates (by means of heating). Examples of materials for making the polymeric film are: polythene, polypropylene, polyurethane, acrylic, epoxides, phenols, polyamides, polyvinylalcohols, also in the form of copolymers with weights preferably comprised between 5 and 200 g/m ²

In a preferred embodiment, the elastic element 101 is represented by a mesh with an open structure made with traditional threads such as cotton, polyester, polyamide and viscose. Since the mesh intrinsically has elasticity in every direction, due to its type of textile construction, high-resistance threads may also be used, also of the ballistic type with resistances for example greater than 10 g/dtex such as, for example, aramid threads commercially known as Kevlar ^® , Twaron ^® , copolyaramids known as Rusar ^® , Artec ^® , Ruslan ^® , threads based on polyethylene polymers with high molecular weight, for example Spectra ^® , Dyneema ^® , glass, carbon, basalt. In order to glue the ceramic plates to the support 101 , gluing materials are used which can be easily found on the market (see the layer 103 in Figure 1 ). The glues can have high elongation values and are preferably higher than the support element.

Examples of such materials are: poly-isoprene, polyurethane, polyamide, poly butylene, poly-iso-butylene glues in the form, for example, of pastes, liquids, gels, also diluted with solvents or in aqueous dispersion.

In a preferred embodiment of the present invention, the amount of glue is preferably comprised between 5 g/m ² and 100 g/m ² The ceramic plates glued onto the support are then further covered on the opposite face by a glue which is the same or similar to the glue of the first face with the application of a further support (e.g. polyethene film). Preferably, the glue must have a sufficiently limited viscosity to enable it to penetrate between the plates and have an elasticity so as not to compromise the malleability of the final structure. The penetration of the gluing system between the plates contributes to the attenuation of the shockwave between the plates, caused by the impact of the bullet confining the damaged zone to the individual plate. This enables the nearby plates that are still intact to absorb the energy of any further impacts.

Textile component

The ceramic structure described above is not enough alone to provide sufficient ballistic protection, as it does not have the necessary characteristics required of an item of ballistic protection. On the other hand, the aim of the ceramic layer is to fragment or deform the bullet, also attenuating the energy thereof, but not to retain the deformed bullet or its fragments. Therefore, to obtain suitable protection, e.g. for personal protection, or for the armor-plating of aircraft, helicopters and so on, further elements need to be added which can compensate for such shortcomings. For that purpose, in the prior art systems, rigid, monolithic elements (laminated blocks) are normally used, made with elements glued together and consolidated with pressure and temperature.

It has surprisingly been found that the replacement of a single monolithic laminated blocks with a plurality of monolithic laminated blocks whose total weight per m ² corresponds to the weight of the single monolithic laminated blocks, the same ballistic characteristic can be obtained and, furthermore, after appropriate mechanical yielding treatment of each of the plurality of laminated blocks, advantageous flexibility in every direction can also be obtained.

In a preferred embodiment of the invention, to make such textile elements, laminates are used, based on threads in which the tensile strength values are greater than 15 g/dtex, more preferably greater than 30 g/dtex and even more preferably greater than 45 g/dtex, modulus values greater than 30 GPa and more preferably greater than 130 GPa with titers comprised between 200 and 8000 dtex.

Different ways are known for making such ballistic laminates. Particularly useful for the purpose of the present invention are the so-called laminates in which the threads are arranged without being interwoven, indicated as unidirectional, as happens on the contrary in warp and weft textiles or in semi-unidirectional laminates in which the ballistic threads are interwoven with much thinner non-ballistic threads than the ballistic threads.

Examples of ballistic laminates are those known with the commercial name of

Spectra ^® , Dyneema ^® , Endumax ^® , Goldshield ^® . An example of a laminate of the semi- unidirectional type is the one commercially known by the name of Twaron ^® L.F.T. The weight of these laminates is comprised between 80 g/m ² and 500 g/m ² A plurality of single layers is consolidated with the application of pressure and temperature, the pressure being comprised between 5 and 250 Bar and the temperature comprised between 50°C and 170°C. The resulting weights are comprised between 0.5 kg m ² and 10 kg m ² The weights and the composition of each consolidated laminate may also differ from one another. The individual consolidated laminates and sheets therefore undergo a flexibilization process to achieve the necessary flexibility objectives for the implementation of the present invention.

In a preferred embodiment, each ballistic laminate consolidated to become flexible is subjected to the passage through three duly spaced out rollers, for example with a device used for bending the laminates. The process can also be repeated several times, also introducing the package at different angles. The rollers can also be preheated and thus it is also possible to heat the package in order to reduce the initial rigidity. Alternatively, the consolidated product can be stressed, subjecting it to repeated bending with the same system used for the fatigue tests on the compounds.

In another embodiment, particularly in the presence of individual sheets whose weight is less than 5 kg/m ² , the yielding can also take place manually.

The sheets thus flexibilized are simply overlapped with one another preferably without any adhesive.

In another embodiment, a discontinuity element is positioned between at least two packages, represented by felts, non-woven fabrics, netting, polymer foams, meshes, for example. Advantageously, the thickness of such further elements is comprised between 1 mm and 5 mm. They must be characterized by much greater flexibility than the individual packages and by a compressibility such that the manual compressibility value is also greater than 10% with respect to the initial thickness. For the purposes of the present invention, closed cell polymer foams are particularly useful, in particular polyethylene foams having a density comprised between 30 and 100 kg/m ³ . Said discontinuity elements enable the shockwave, which is due to the energy triggered by the incident bullet, to be attenuated, enabling an increase in the ballistic protection.

The structure according to the present invention can be associated with a further item of ballistic protection generally with a larger surface area which is, however, able to withstand bullets whose speeds can be attributed to the specifications such as, for example, NiJ010104 levels I, II, III A or HOSDB levels H01 H02.

In an embodiment of the present invention, whenever used for personal defence, i.e. for example as a bullet-proof jacket, the various components of the structure of the present invention, as described above, are contained and held together by means of a textile package comprised of an “inner lining” which contains the item of ballistic protection which is then inserted into a textile package referred to as “outer lining”. The outer lining, for the purposes of the present invention, may be provided with pockets into which additional ballistic structures can be introduced which thus increase the level of protection of the system.

In another variant, the structure according to the present invention can be inserted directly into the inner lining. However, with this solution the modularity of the system is lost.

Whereas, in fact, in the presence of additional pockets the operator can decide at any time to introduce the further protection in consideration of the risk level to be faced, in the other case the system is not adjustable.

Figure 3b schematically shows the structure of Figure 1 in a sectional view. From top to bottom, the following can be seen: the elastic element 101 (Figures 1 and 3b show the special case of the elastic fabric glued to the plurality of plates 105 by means of a gluing layer 103; as mentioned above, in an alternative representation, the plates 105 are held together, but free to move, by a film, polymeric for example, which does not need any glue, as shown in the example of Figure 2); the gluing layer 103; the layer of ceramic plates 105; a second gluing layer 103 and a second elastic element 101. Associated with the ceramic element (comprised in Figure 3b by the sequence 101 , 103, 105, 103, 101) there is the textile component comprised of a plurality of packages 107.

Figure 3a shows a front view of the ceramic plates having an equilateral hexagon shape (but other geometries are possible). The plates may have different measurements; in a preferred embodiment, they should be contained in a circle having a diameter of about 20 mm. Figure 3a shows a separation between one plate and the adjacent ones: this space can have a maximum dimension of 0.5 mm, preferably less than 0.2 mm (the plates may also be in contact with one another, with the exception of any irregular edges). In a preferred embodiment, the space between the plates is filled, during the assembly step, with the glue of the layer 103 or with a polymeric film, which replaces the textile element + gluing layer 103, when it melts due to the temperature, and penetrates between the cracks.