EP4662358A1

EP4662358A1 - Method for preparing a compos ite material for ballistic protection in the form of a flexible sheet and related compos ite material obtainable with said method

Info

Publication number: EP4662358A1
Application number: EP24707285.3A
Authority: EP
Inventors: Adalberto Lorenzo Montagna; Mauro Vernocchi; Marcin DOMBROWSKI
Original assignee: Pro-Systems SpA; Pro Systems SpA
Current assignee: Pro-Systems SpA; Pro Systems SpA
Priority date: 2023-02-10
Filing date: 2024-02-09
Publication date: 2025-12-17
Also published as: WO2024166051A1; IT202300002268A1

Abstract

The present invention relates to a method for preparing a composite material for ballistic protection in the form of a flexible sheet comprising : a. providing a woven fabric comprising interwoven weft yarns and warp yarns, said weft yarns and warp yarns being ballistic yarns having a l inear density equal to or higher than 800 dtex; said woven fabric having a Wal z fabric density equal to or higher than 5% and lower than or equal to 25%; b. applying a binding polymeric material on at least one face of said woven fabric to bind said weft yarns and said warp yarns and obtain a reinforced woven fabric; c. sub j ecting said reinforced woven fabric to a mechanical softening treatment comprising sub j ecting said reinforced woven fabric to movement so as to cause repeated impacts of said reinforced woven fabric against a rigid impact surface. The present invention also relates to the composite material obtainable with the aforementioned method as well as to the ballistic protective articles which include it.

Description

METHOD FOR PREPARING A COMPOSITE MATERIAL FOR BALLISTIC

PROTECTION IN THE FORM OF A FLEXIBLE SHEET AND RELATED

COMPOSITE MATERIAL OBTAINABLE WITH SAID METHOD

The present invention concerns a method for preparing a composite material for ballistic protection in the form of a flexible sheet and the related composite material obtainable with said method.

The present invention originates in the field of materials used for the production of articles for ballistic protection, i.e. articles having properties of resistance to the penetration of bodies, such as projectiles, splinters, blades, etc.

Articles for ballistic protection known in the state of the art generally comprise a plurality of overlapping layers of ballistic fabrics. Ballistic fabrics are textile substrates that include ballistic fibers, i.e. fibers having high resistence, toughness and elastic modulus. These fibers, also known as high perfomance fibers, include, by way of example, aramid, para-aramid, polyethylene or other synthetic fibres. In textile substrates, the fibers or yarns comprising said fibers can be bonded together in various ways, so as to form for example a warp and weft fabric, a non-woven fabric (NWF) , a unidirectional or multidirectional fabric and others .

The overlapping layers of ballistic fabrics (also called "ballistic packages") can be held together in various ways, for example: through stitchings, by laminating the fabrics together using thermoplastic films or by impregnation with binding polymeric materials (e.g. thermoplastic or thermosetting resins) . In general, the number of layers of ballistic fabrics that make up a ballistic package varies depending on the type and level of protection sought for the final article (e.g. bulletproof, knifeproof, multi-protection, etc.) , the type of ballistic fiber and how the article is used (e.g. protective articles to wear, rigid protective shields, etc.) .

For the manufacture of bulletproof vests, for example, a multi-layer package comprising 20 to 50 layers of ballistic fabric is generally used. In particular, in the case of protection class SKI bulletproof vests (Technische Richtlinie Ballistische Schutzwesten (2009) ) , i.e. capable of stopping steel- j acketed projectiles (e.g. 9 mm DM41 pro ectiles, .) , the most effective textile-based solution currently known in the state of the art is based on the use of a ballistic package comprising at least 36 layers of a light ballistic fabric (approx. 100 - 150 g/m²) having a warp/weft type weave (plain) and a Walz fabric density- as defined below - greater than 20%, generally in the range 22% - 30%.

The high fabric density of the ballistic package layers gives the final product the ability to absorb and disperse the kinetic energy of the projectile. Furthermore, the high Walz fabric density makes the layers of fabric adequately processable, i.e. the individual layers of fabric can easily be subjected to cutting to size and packaging operations of the ballistic package (e.g. overlapping of the layers) , typically carried out using automated machinery, in particular avoiding fraying of the fabrics along the edges. The use of the aforementioned high Walz fabric density, however, has the disadvantage of requiring very fine ballistic yarns , generally having a linear density in the range 300 - 700 dtex, the cost of which is signi ficantly higher than that of yarns with higher linear density .

Furthermore , to meet the most stringent ballistic protection standards , as in the case of protection class SKI bulletproof vests , it is often necessary to overlap the layers of fabric in the ballistic package in a particular arrangement . For example , adj acent fabric layers are overlapped on each other such that the warp and weft yarns of one are arranged along respective directions that form an angle of +45 ° /-45 ° with respect to the directions along which the respective warp and weft yarns of the other are arranged . This operation of cross-overlapping the layers , however, is rather complex and increases the costs of the production process , as well as giving rise to non-negligible amounts of textile material waste .

Regardless of the type of application, an important requirement of articles for ballistic protection is represented by the relationship between the ballistic resistance features and the overall weight of the article , this ratio having to be as high as possible . The ballistic resistance/weight ratio is particularly relevant in the case of ballistic protective articles intended to be worn, such as protective clothing for military and police personnel . In this case , in fact , the articles must guarantee ef fective protection and at the same time maximum freedom of movement for the wearer .

Furthermore , wearable ballistic protective articles must be perceived as comfortable by the wearer . The comfort property o f an article can be evaluated in terms of the drapability of the ballistic fabrics used, which must be as high as possible .

In consideration of the aforementioned state of the art , the Applicant has addressed the problem of providing a composite material for ballistic protection and a related preparation process that overcome the drawbacks of the prior art .

In particular, the Applicant has addressed the problem of providing a composite material in the form of a flexible sheet with which it is possible to manufacture protective articles having adequate ballistic resistance properties , relatively low weight and a reduced production cost . Furthermore , the composite material must allow the preparation of wearable protective articles ( e . g . bulletproof vests ) , which are comfortable to wear .

A further technical problem faced by the Applicant is that of providing a method of preparing the aforementioned composite material which is easy to produce and economical .

It has now been found that the above and other obj ects , which will be better illustrated in the following description, can be achieved by a composite material in the form of a flexible sheet and the related preparation process , wherein the composite material comprises a textile substrate comprising a warp and weft fabric made of yarns with relatively high linear density ( denier ) ( greater than 800 dtex ) and characteri zed by a relatively low Wal z fabric density index ( e . g . equal to or less than 25% ) ; the fabric is mechanically reinforced via a surface coating of a binding polymeric material ; the binding polymeric material has the function of binding the yarns together to form a substrate having suf ficient dimensional stability to make it adequately workable during the production process of the ballistic packages and the related multilayer protective articles .

The fabric reinforced with the binding polymeric material has good drapeability, a feature which is obtained by subj ecting the reinforced fabric to a mechanical softening treatment . It was also surprisingly observed that the mechanical softening treatment also improves the ballistic resistance properties of the material .

Thanks to the use of yarns of relatively high linear density, which are easier to prepare and more economical , the composite material described here allows ballistic packages and related protective articles having the required level of ballistic resistance to be manufactured more simply and economically than to solutions known in the state of the art . Furthermore , the preparation process is also simpli fied, as it is possible to achieve a certain level of ballistic protection, with the same overall weight of the multilayer package , without resorting to crossoverlapping the layers of composite material .

Thanks to the aforementioned features , the composite material in laminar form described herein is suitable for making articles for ballistic protection of di f ferent kinds , such as : bulletproof vests , multiprotection j ackets , bomb-proof suits and blankets , antitrauma protection, panels and slabs for rigid ballistic protection and armoring of vehicles and buildings , etc . In particular, the material is suitable for preparing wearable protective articles with bulletproof properties , even of protection class Ballistische Schutzwesten - SKI .

Therefore , according to a first aspect , the present invention refers to a method for preparing a composite material for ballistic protection in the form of a flexible sheet comprising : a . providing a woven fabric comprising interwoven weft yarns and warp yarns , said weft yarns and warp yarns being ballistic yarns having a l inear density equal to or higher than 800 dtex ; said woven fabric having a Wal z fabric density equal to or higher than 5% and lower than or equal to 25% ; b . applying a binding polymeric material on at least one face of said woven fabric to bind said weft yarns and said warp yarns and obtain a reinforced woven fabric ; c . subj ecting said reinforced woven fabric to a mechanical softening treatment comprising subj ecting said reinforced woven fabric to movement so as to cause repeated impacts of said reinforced woven fabric against a rigid impact surface .

In accordance with a second aspect , the present invention refers to a composite material for ballistic protection in the form of a flexible sheet comprising a fabric comprising interwoven weft yarns and warp yarns , said weft yarns and warp yarns being ballistic yarns having a linear density equal to or greater than 800 dtex ; said fabric having a Wal z fabric density equal to or higher than 5% and lower than or equal to 25% ; said fabric being coated with at least one binding polymeric material which binds said weft yarns and said warp yarns ; said composite material having a sti f fness , measured according to the ASTM D4032 standard, equal to or lower than 10 N.

In accordance with a third aspect, the present invention relates to a ballistic protective article comprising a plurality of overlapping layers of the composite material in the form of a flexible sheet according to the first aspect of the present invention.

The composite material according to the present invention comprises a woven fabric comprising or consisting of interwoven weft yarns and warp yarns.

The warp and weft yarns are ballistic yarns. For the purposes of this description, "ballistic yarn" means a yarn having a toughness equal to at least 15 g/denier and an elastic modulus (tensile modulus) equal to at least 400 g/denier.

In accordance with the present invention, ballistic yarns have an effective linear density, also called yarn titer, greater than 800 dtex, more preferably in the range 850 - 3400 dtex, even more preferably in the range 900 - 2500 dtex.

Examples of usable ballistic yarns are yarns based on aramid and para-aramid fibers (e.g. Twaron®, Kevlar®, Technora®, etc.) , ultra-high molecular weight polyethylene, e.g. Spectra® , Dyneema®) , polybenzoxazole (poly (p-phenylene-2 , 6, benzobisoxazole, e.g. Zylon®) , liquid crystal polymers (e.g. Vectran®) , glass fibers, carbon fibers and the like.

Preferably, the ballistic yarns are selected from aramid and para-aramid yarns.

Ballistic yarns are multifilament yarns; the number of filaments per yarn is not subject to particular restrictions .

The fabric of the composite material comprises weft yarns arranged along a weft direction and warp yarns arranged along a warp direction, the warp and weft yarns being interwoven to form the woven fabric.

The fabric weave can be chosen from those generally used for warp and weft ballistic fabrics. Preferably, the weave is chosen from: plain, twill, satin and basket. More preferably, the weave is a plain weave.

The ballistic fabric has a Walz fabric density index equal to or greater than 8% and less than or equal to 25%, preferably in the range 10% - 20%.

Walz fabric density, expressed as a percentage (%) , is determined using the following formula:

DG (%) = (dk + d_s)²-f -f_s wherein : dk = substance diameter of the warp yarn in mm; df = substance diameter of the weft yarn in mm; fk = number of warp yarns /cm; f_s = number of weft yarns /cm.

The yearn substance diameter dk and/or ds is determined through the following formula: d = -

88,5 wherein : d represents dk or d_s; titer and density represent , respectively, the titer in dtex and the density in g/cm³ of the corresponding yarn k or s.

The above formula for determining Walz fabric density (DG) applies to plain weave woven fabrics . For fabrics woven with special weaves, i.e. different from plain weave, a correction factor must be introduced into the formula . Below are the corrective factors to use for some special weave:

The Walz fabric density of a special weave is determined by multiplying the DG density of the plain weave by the correction factor of the special weave.

In one embodiment, the number of weft yarns per cm is in the range 2 - 20/cm, preferably 4 - 10/cm.

In one embodiment, the number of warp yarns per cm is in the range 2 - 20/cm, preferably 4 - 10/cm.

The weave can be balanced, i.e. have the same number of yarns/cm in the weft and warp direction, or unbalanced, with a number of yarns/cm in the weft direction different from the number of yarns/cm in the warp direction.

The yarns used can have the same or different linear density .

In one embodiment, the ballistic fabric has the following characteristics:

- plain weave; aramid and/or para-aramid yarns with linear density in the range 850 - 3400 dtex;

- number of warp yarns per cm of weft in the range 4 - 10/cm;

- number of weft yarns per cm of warp in the range 4 - 10/cm.

Preferably, the weight of the fabric is in the range 80 g/m² - 200 g/m², more preferably in the range 120 g/m² - 160 g/m², the weight values being referred to the fabric before the application of the binding polymeric material .

The composite material according to the present invention comprises at least one binding polymeric material that binds the warp and weft yarns of the ballistic fabric. Since the ballistic fabric has a relatively low Walz fabric density, in the absence of the binding polymeric material it would be unsuitable for being subjected to conventional cutting and packaging operations. The binding polymeric material is then applied to the fabric to form a reinforced fabric, i.e. to give it sufficient compactness and dimensional stability (a characteristic which is also referred to below as "stiffness") to make it easily processable, despite the relatively low Walz fabric density, avoiding in particular its excessive fraying.

Generally, the binding polymeric material can be selected from the polymeric materials generally used for the production of composite materials for ballistic protection .

The binding polymeric material can be either thermoplastic or thermosetting.

Preferably, the binding polymeric material is a soft material, having a Tg (glass transition temperature) lower than -10°C, more preferably in the range of -20°C to -50°C. Preferably the binding polymeric material comprises a resin selected from : polyacrylate , polyurethane , polyester, polybutadiene , polyisoprene , ethylenepropylene copolymers . The aforementioned resins can be used individually or in combination with two or more resins .

In one embodiment , the binding polymeric material comprises a mixture of at least one polyacrylate resin and at least one polyurethane resin . Preferably, the weight ratio between the polyacrylate resin and the polyurethane resin is in the range of 25 : 1 to 1 : 1 , more preferably in the range of 10 : 1 to 3 : 1 , the aforementioned ratios being referred to the weight of the dry resins .

In general , the binding polymeric material is present in the composite material in an amount suf ficient to give the fabric the desired compactness and dimensional stability . Preferably, the binding polymeric material is present in the composite material in the form of a thin and continuous surface coating . The coating can be applied on one or both faces of the fabric, more preferably on one face only .

Preferably, the binding polymeric material is present in the composite material in an amount by weight in the range 1 g/m² - 50 g/m² , more preferably in the range 1 g/m² - 30 g/m² , even more preferably in the range 2 g/m² - 10 g/m² , said amounts by weight being referred to the weight of the dry binding polymeric material .

In one embodiment , the thickness of the binding polymer material coating is in the range of 3-35 micrometers , more preferably in the range of 5- 15 micrometers . The binding polymeric material, in addition to the polymeric resin, can include additives of the type generally used in composite materials for ballistic use such as, for example, dyes, viscosifying agents, crosslinkers, abrasive particles and the like.

The binding polymeric material can be applied to the ballistic fabric in accordance with methods known in the art for the preparation of composite materials for ballistic protection. For example, the binding polymeric material can be applied by coating, extrusion, immersion, impregnation or spraying, depending on the viscosity of the polymeric material to be applied.

In one embodiment, the binding polymeric material is applied by the coating technique, for example according to one or more of the following methods: knife over roll, knife over air, engraved roll and others. The coating technique is particularly suitable, for example, for applying binding polymeric materials having a viscosity at 25 °C in the range of 1,000 - 20,000 cps, preferably 5,000 - 10,000 cps.

In another embodiment, the polymer resin may be applied in foam form, the aforementioned foam having, at the time of application, preferably a density in the range of 50 - 250 g/dm³, more preferably 150 - 200 g/ dm³.

The application process of the binding polymeric material can include, for example, the deposition of the polymeric material on at least one face of the fabric, for example via one of the techniques previously described, followed by a heat treatment step of the fabric coated with the binding polymeric material for evaporate any solvents (e.g. water or organic solvents) and harden or polymerize the polymer resin. The heat treatment can be carried out, for example, at a temperature of 50 °C to 250 °C, more preferably 80 °C to 200 °C. The heat treatment can be carried out, for example, in a "rameuse" apparatus, of the type known in the state of the art.

The fabric on which the covering is applied is generally processed into ribbon form and gathered into reels .

In general, the fabric reinforced with the binding polymeric material has a stiffness, measured according to ASTM D4032, in the range of 15 N - 35 N, preferably in the range of 15 N - 25 N, more preferably in the range of 15 N - 20 N, the stiffness depending, among other factors, on the characteristics of the fabric, the chemical composition of the polymeric material and the amount of polymeric material applied to the fabric.

To improve both the ballistic resistance properties and the drapeability, i.e. the comfort of the wearable ballistic protective articles, in accordance with the present invention the reinforced fabric is subjected to a mechanical softening treatment. This treatment includes the action of moving the reinforced fabric so as to cause repeated impacts of the reinforced fabric with at least one rigid impact surface. Repeated impacts of the reinforced fabric with an impact surface reduce the stiffness of the reinforced fabric, making it softer and increasing its drapability characteristics.

It was surprisingly observed that the aforementioned mechanical softening treatment also significantly improves the ballistic resistance properties of the composite material, especially towards non-def ormable proj ectiles , such as steel- acketed bullets . Presumably, the increase in resistance to proj ectile penetration of the composite material is due to the fact that , after the mechanical softening treatment , the composite material is able to conform more easily to a proj ectile , wrapping it at its point of impact with the composite material . This ef fect is ampli fied in a multilayer ballistic package comprising a plurality of layers of composite material according to the present invention .

The mechanical softening treatment can be achieved, in general , using any device or process capable of causing a plurality of impacts of the reinforced fabric on a rigid impact surface . For example , the softening treatment can be carried out using the finishing processes and machines known in the state of the art generally used to improve the feel and appearance of fabrics based on non-ballistic fibers and yarns ( e . g . cotton, linen, wool , etc . ) , such as the machines marketed under the names ENAIRGY® ( Pentek) , AIRO®quattro and AIRO®due (Biancalani ) and others .

In one embodiment , the mechanical softening treatment includes moving the reinforced fabric by means of an intense air flow, which accelerates the fabric at high speed against a rigid surface against which it discharges the accumulated kinetic energy . The exclusive use of air to move the fabric avoids rubbing the fabric against surfaces that may be abrasive or cause other surface defects . This operating principle , for example , is adopted in the AIRO® (Biancalani ) and ENAIRGY® ( Pentek) machines . Examples of machines that can be used to carry out the mechanical softening treatment according to the present invention are described in WO2006021978A1 , IT102007901586570 and IT102010901886619 .

The mechanical softening treatment can be carried out both in rope form and in open width form, more preferably in width.

Preferably, the mechanical softening treatment is carried out at a temperature of 20°C to 180°C, more preferably 20°C to 120°C.

The mechanical softening treatment can be carried out on the dry reinforced fabric (dry treatment) or after it has been previously wetted (wet treatment) with water or a liquid softening composition which favors the softening of the reinforced fabric. If the mechanical treatment of the fabric is carried out wet, at the end of the treatment a drying phase can be foreseen to evaporate the residual liquid present, for example at a temperature of 50 °C to 120 °C.

The mechanical softening treatment can be carried out continuously or discontinuously, for the time necessary to obtain the desired stiffness for the final composite material. For the purposes of this description, the stiffness of a fabric or fabric reinforced with the binding polymeric material is intended to be measured in accordance with ASTM D4032.

Preferably, the mechanical softening treatment is continued until the stiffness of the treated composite material is equal to or less than 70% of the stiffness of the reinforced fabric before being subjected to the treatment, more preferably equal to or less than 60%.

Preferably, the stiffness of the composite material at the end of the mechanical softening treatment is in the range 5 N - 24 N, more preferably in the range 5 N - 15 N, even more preferably in the range 8 N - 12 N .

As described below, a ballistic protective article preferably comprises a plurality of overlapping layers of the composite material in form of flexible sheet according to the present invention . Preferably, the mechanical softening treatment is conducted on single layers of composite material .

In accordance with the present invention, in a ballistic article the layers of composite material are advantageously held together enclosed within a textile envelope ( or "cover" ) , without being j oined together by means of adhesive resins . The envelope , which is closed by heat sealing or stitching, keeps the overlapping layers inside and in position without changing the drapeability of the ballistic package . Although not essential , inside the envelope the layers can still be j oined together using a limited number of stitchings ( for example from 2 to 4 stitchings with a length of 5- 8 cm) , provided that these do not change the multilayer structure and modi fy its drapeability .

Preferably, a ballistic protective article comprises at least 8 layers of composite material . The minimum number of layers , however, depends on the particular type of yarn used and the level of ballistic protection desired . In general , the ballistic protective article may comprise 8 to 100 layers of composite material , more preferably 8 to 80 layers , even more preferably 15 to 50 layers , even more preferably 25 to 40 layers . The layers of composite material can be used in combination with layers of material of another composition, for example layers of reinforced fabric not subjected to the softening treatment or layers of material other than the aforementioned composite materials or reinforced fabric (e.g. rigid anti-trauma inserts) .

The preparation processes of the composite material and the multilayer structure object of the present invention can be carried out continuously. The products obtained are then conveniently wrapped in reels and marketed in this form.

The composite material in the form of a flexible sheet described here is suitable for making different types of ballistic protective articles, without particular limitations. In particular, it is suitable for use to produce wearable ballistic protective articles, such as: bulletproof vests, multi-protection jackets, bomb-proof suits and blankets. In particular, the composite material described here is suitable for preparing wearable protective articles with bulletproof properties, even of protection class SKI.

EXAMPLES

The following examples are provided for illustrative purposes only of the present invention and are not to be considered as a limitation of the scope of protection defined by the accompanying claims.

EXAMPLE 1 - Preparation of a composite material according to the present invention

A composite material according to the present invention was prepared starting from a balanced fabric of paraaramid yarns (Twaron® type 2040, 930 dtex) . The Walz fabric density is 19.2. The fabric has a plain weave with 7.5 weft/cm of warp and 7.5 warp/cm of weft. The weight of the fabric, before the application of the binding polymeric material, is equal to 140 g/m².

A binding polymeric material was applied to only one side of the fabric by spreading it with a blade in the air. The binding polymeric material was formulated by mixing an aqueous dispersion of an acrylic resin (Dicrylan® AS, Tg approx. -30 °C) and an aqueous dispersion of a polyurethane resin (Dicrylan® PHR, Tg approx. 0 °C) in a weight ratio of acrylic resin: polyurethane resin equal to 1:4 (referring to the dry weight of the two resins) .

The mixture obtained has a dynamic viscosity at 25°C equal to 6500 cps (HAAKE VISCOTESTER 2 PLUS, fixed rotor speed, rotor N°2) .

The coated fabric was subjected to heating in a rameuse apparatus at a temperature of 180°C for 90 seconds.

The reinforced fabric was subsequently wet treated (aqueous solution containing a fabric softener) in an ENAIRGY® (Pentek) , with movement of the fabric carried out by means of a flow of hot air (110°C) .

The final composite material had a weight of 145 g/m² and a thickness of 0.30 mm.

Before being subjected to the mechanical softening treatment, the reinforced fabric had a stiffness measured by the "Pneumatic Stiffness Tester" in accordance with the ASTM D4032 standard of approximately 20.0 N. The stiffness of the composite material after the treatment was found to be approximately 10.0 N.

EXAMPLE 2 - Preparation of a ballistic protective article

A ballistic protective article (BP 1) was prepared by overlapping 35 layers of the composite material of Example 1 (without cross-overlapping the layers) . The layers of the package were enclosed within a heat-sealed fabric envelope .

The final weight of the multilayer package was 5 . 075 kg/m² . Experimental tests have shown that the aforementioned ballistic protection package guarantees resistance to penetration by SKI class proj ectile ( Technische Richtlinie Ballistische Schutzwesten ( 2009 ) ) . For comparison, the same multilayer package was prepared using layers of the reinforced fabric of Example 1 , which were not subj ected to the mechanical softening treatment (BP 2 ) .

The test results are shown in Table 1 . Table 1

¹ - test with 9 mm DM41 EMS J Ruag 8 . 0g bullet

In the case of the comparative package BP 2 , to obtain the SKI protection level, it was necessary to form a multilayer package containing 40 layers of reinforced fabric, for a total weight of the package equal to 5.80 kg/m².

From the comparison with the BP 2 reference ballistic protection package it can be seen that by using the BP 1 composite material according to the present invention it is possible to obtain the desired level of protection (e.g. SKI) with a lighter and less rigid multilayer package, therefore more comfortable.

The BP 1 package according to the invention also passed the "contact shot" test, which involves positioning the ballistic package in a contact position with the muzzle of the manometric barrel (projectile speed equal to 410 ± 10 m/s) , and the "edge shot" test, which involves the explosion of two shots in a corner position 30 mm from the surface of the ballistic package (ball speed equal to 410 ± 10 m/s) .

The comparative package BP 2 instead suffered a perforation when the first shot exploded.

It is also noted that to meet the penetration resistance requirements of SKI class projectile with prior art materials, a ballistic package consisting of at least 36 layers of fabric is required (with -45°/+45° cross-overlapping of the layers) having the following characteristics: plain weave with 11.0 weft /cm of warp and 11.0 warp /cm of weft, linear yarn density equal to 550 dtex, weight of the single layer of fabric equal to 126 g/m², for a total package weight of 4.536 kg/m². With the same performances, the relatively higher weight (approx. 11.8%) of the BP 1 ballistic package according to the invention compared to this prior art ballistic package is balanced by the advantages connected to the use of higher titer yarns and by the possibility of using a simpli fied ballistic package preparation process , which does not require cross-overlapping of the layers .

Claims

1. Method for preparing a composite material for ballistic protection in the form of a flexible sheet comprising : a. providing a woven fabric comprising interwoven weft yarns and warp yarns, said weft yarns and warp yarns being ballistic yarns having a linear density equal to or higher than 800 dtex; said woven fabric having a Walz fabric density equal to or higher than 5% and lower than or equal to 25%; b. applying a binding polymeric material on at least one face of said woven fabric to bind said weft yarns and said warp yarns and obtain a reinforced woven fabric; c. subjecting said reinforced woven fabric to a mechanical softening treatment comprising subjecting said reinforced woven fabric to movement so as to cause repeated impacts of said reinforced woven fabric against a rigid impact surface.

2. Method according to claim 1, wherein at the end of step c the stiffness of said composite material, measured according to the ASTM D4032 standard, is equal to or lower than 70% of the stiffness of the reinforced woven fabric.

3. Method according to claim 1 or 2, wherein the stiffness of said composite material, measured according to the ASTM D4032 standard, is in the range 5 - 24 N.

4. Method according to any one of claims 1 to 3, wherein said ballistic yarns have a linear density in the range 850 dtex - 3400 dtex, preferably in the range 900 dtex - 2500 dtex.

5. Method according to any one of claims 1 to 4, wherein said number of weft yarns per cm is in the range 2 - 20/cm and, independently, said number of warp yarns per cm is in the range 2 - 20/cm cm.

6. Method according to any one of claims 1 to 5, wherein said binding polymeric material comprises a resin selected from: polyacrylate, polyurethane, polyester, polybutadiene, polyisoprene, ethylenepropylene copolymers and combinations thereof.

7. Method according to any one of claims 1 to 6, wherein said binding polymeric material comprises a mixture of at least one polyacrylate resin and at least one polyurethane resin, the weight ratio between said at least one polyacrylate resin and said at least one polyurethane resin being preferably in the range of 25:1 to 1:1, more preferably in the range of 10:1 to 3:1.

8. Method according to any one of claims 1 to 7, wherein said binding polymeric material is applied in an amount by weight in the range 1 g/m² - 50 g/m², preferably in the range 1 g/m² - 30 g/m², more preferably in the range 2 g/m² - 10 g/m², said amounts by weight being referred to the weight of the dry binding polymeric material .

9. Method according to any one of claims 1 to 8, wherein said ballistic yarns comprise: aramid fibers, para-aramid fibers, ultra-high molecular weight polyethylene fibers, polybenzoxazole fibers, polyester fibers, glass fibers, carbon fibers, liquid crystal polymer fibers and combinations thereof.

10. Method according to any one of claims 1 to 9, wherein said reinforced woven fabric is moved by means of an air flow.

11. Composite material for ballistic protection in the form of a flexible sheet comprising a woven fabric comprising interwoven weft yarns and warp yarns , said weft yarns and warp yarns being ballistic yarns having a linear density equal to or higher than 800 dtex ; said woven fabric having a Wal z fabric density equal to or higher than 5% and lower than or equal to 25% ; said woven fabric being coated with at least one binding polymeric material which binds said weft yarns and said warp yarns ; said composite material having a sti f fness , measured according to the ASTM D4032 standard, in the range of 5 - 24 N .

12 . Ballistic protective article comprising a plurality of overlapping layers of a composite material according to claim 1 , preferably from 8 to 100 layers , more preferably from 8 to 80 , even more preferably from 15 to 50 layers , even more preferably from 25 to 40 layers .

13 . Article according to claim 12 , wherein said layers are enclosed within a textile envelope .

14 . Article according to claim 12 or 13 having a ballistic resistance of protection class SKI according to Technische Richtlinie Ballistische Schutzwesten

( 2009 ) .