Armour plate composite with ceramic impact layer.

DESCRIPTION

The present invention relates to a composite shielding plate, comprising at least one hard impact layer based on ceramic material and an energy absorbing sublayer, fixed to the impact layer and formed by a laminate containing several layers of fibers impregnated with some material, preferably a synthetic material.

German DE-A-2,943,680 refers to an armor plate of the type indicated above and comprising two basic elements, namely: a hard impact layer bonded to a laminate. The impact layer is preferably based on a ceramic material such as aluminum oxide and the laminate comprises a large number of layers of woven fabric (on loom) consisting of aramine fibers. Although tissues made of aramina fibers have better baltic properties, compared with fabrics made of usual fibers such as Nylon 6, polyester or somewhatdodan, in many cases the stiffness of these will be too low to absorb the kinetic energy of a projectile due to plastic deformation. According to DE-A-2,943,680, it is proposed to reduce this disadvantage by using a large number of layers - for example, 45 ... 50 (see examples) - of fabric. Now this still leads to improper armor and nothing practical. Another disadvantage of this already known technique armor structure is that the woven fabric textile laminate provides insufficient backing support for the hard impact layer of ceramic material, which cannot then dull the tip of a projectile. Therefore, the armor structure according to DE-A-2,943,680 is considered very far from the optimum for many of the applications.

Reference FR-A-1,102,646 concerns a shielding structure comprising a laminate of three sheets a, b and c consisting of woven fabrics made of glass fibers and impregnated with a synthetic resin, said sheets a, b and c separated by very thin dye movies (see page 2 on the left, paragraphs 5 and 6). Such films may consist of various materials such as cellulose, paper or possibly very thin metal sheets (see page. two on the right, paragraphs 2 and 3). Since the armor structure according to this reference does not comprise any hard impact layer, it would be inappropriate anyway for many purposes, because the function of dulling the projectile tip is almost completely absent.

Reference US-A-3,179,553 describes an armor plate laminate whose upper and final layers, and a middle layer, are beryllium and said three metal layers alternate with a polycarbonate resin layer and a rubber layer of Isocyanate that may be reinforced with fiberglass cloth. These layers may be bonded or bonded between them with epoxy resin. In this well-known technical armor structure, the front layer of metal beryllium is intended to function as a hard impact layer. However, in view of the very high temperatures that develop locally when the impact of a projectile occurs, the beryllium front layer will lose its hardness, so that its blunt function will be reduced. Another drawback of this already known technique armor structure is that the relatively thick beryllium plates placed in both the core or middle part and the back side will make the laminate too stiff for sufficient plastic deformation to absorb the kinetic energy of the projectile. Therefore, the armor structure according to US-A-3,179,553 will be inadequate for many purposes.

Also known is an armor plate, of the type indicated above, by US-A-3,516,898 whose claim 1- specifies an armor plate which on its side of impact is provided with a hard ceramic boron carbide layer or silicon carbide, backed by a plurality of layers of fiberglass fabric impregnated with resin. The layer of ceramic material may be composed of a certain number of adjacent tiles located in the same plane. Or the ceramic layer may be provided, on its impact side, with a flexible layer that may consist, for example, of a fiberglass fabric impregnated with resin.

In the work "Ballistic Materials and Penetration Mechanics" by Roy C. Laible, Elsevier Scientific Publishing Company, 1980, p. 142, a description is given of the above-mentioned shield plates, in which the back support of the hard layer of ceramic material may consist of a single thick aluminum plate, or two thinner aluminum plates that together give the same total thickness as the thick Uranic plate, or of a fiberglass laminate. It concludes that the use of a backing support consisting of a single layer of relatively thick aluminum is preferable to the use of two aluminum plates that give the same overall thickness as the utanic plate. Well, in the case of the two aluminum plates the ballistic limit was 100 m / s lower. Although the results obtained with said composite shielding plates already known may be reasonable, which in part depends on the intended use of them, they cannot be considered optimal. For example, an armor plate having an impact layer of ceramic material and a backrest consisting entirely of woven fiberglass will generally require the use of a number of inadmissibly high layers of fabric. The shielding materials according to DE-GM-78 27 301 are mainly of the same type as the shielding plates described above with reference to US-A-3,516,898 and the work of RC Laible.

Reference FR-A-2,447,272 describes a shield plate for a vehicle. The armor plate comprises a laminate of low-weight metal sheets - for example, aluminum sheets - in alternation with possibly reinforced synthetic sheets. This laminate is backed by a package of aramina fiber fibers. A disadvantage of this well-known armor plate is that the pla2

016 333 cas of synthetic material insufficiently dampens the impact of a projectile, particularly due to the fact that the synthetic lamines of thermoplastic material cease to have adequate mechalenic properties, as a result of the local increase in temperature. In addition, the impact faces or sides lack an impact layer of ceramic material.

Reference NL-A-7.803.506 describes a shield plate on whose impact side there is a hard layer of steel or glass and a backing or sublayer of electrostatic material, such as polyvinyl chloride, polycarbonate, Nylon , fabric bonded with synthetic resin, polypropylene or fiber. A backing of such a composition is considered of insufficient capacity to absorb the kinetic energy of various projectiles.

Reference US-A-4,404,889 describes various forms of shield plate execution, all of which, both on their impact side and inside, are provided with a steel plate having a thickness of about 12.5 mm . Among these outer layers of steel plate there may be several other layers and plates, such as one or more layers of balsa wood, a layer of steel sheet covered aramina fibers, a honeycomb structure or an air damper. Apart from the complexity of its structure, this well-known armor plate has the disadvantage of comprising a heavy steel impact plate. In addition, the steel loses much of its hardness and resistance due to the development of local heat produced by heavy projectiles, as a result of which the tip of the projectile will not become dull, or insufficiently. The combination of high weight and many layers leads to a less efficient form of armor plate construction.

Reference FR-A-864.844 describes a shield plate laminate composed of three alternating steel plates with layers of a less hard, cellulose-based material.

Reference FR-A-1,566,488 describes a shield plate composed of a metal matrix containing overlapping tiles of a ceramic material.

Reference FR-A-1,146,389 describes a shielding plate made of a laminate of thin metal sheets - made of steel or of an aluminum alloy - between which there are thick metal sheets that can be made of some natural or synthetic rubber and in some cases they can be reinforced with tissues.

Reference FR-A-2,469,277 describes a protective laminate made of inorganic or organic fiber fabrics, such as those of aromatic polyamides, which are adhered to a viscoelastic, thermoset or thermoplastic synthetic material, which has a tg loss factor δ from 0.5 to 1.5 and a modulus of elasticity of 10⁶ a10⁹ N / m² at a frequency of 100 Hz and at the operating temperature.

Reference FR-A-1,144,062 describes a shield plate laminate composed of a reinforced sheet made of a synthetic material, a sheet of steel or fabrics.

GB-A-1,142,689 describes a shield plate whose impact side contains ceramic tiles, whose upper and lower sides are covered with fiberglass cloth, the backing of the shield plate consisting of a thick metal plate.

US-A-3,577,836 describes a protective trim formed by a laminate of curved polytetrafluoroethylene curved plates and covered with a Nylon fabric, followed by a few layers of polyurethane foam separated by a layer of honeycomb units.

EP-O 168 746 describes a shield plate laminate comprising a metallic or ceramic front layer bonded to a bundle of fiber layers with a particular adhesive. The fiber layers are interconnected with a different glue or binder, which has less adhesive power than the previous adhesive.

EP-O 169 432 describes a protective material that essentially consists of a laminate of fabrics composed of aramina fibers. The adhesive is mainly provided between the layers of fabric, while the interior of the fabrics is substantially free of adhesive. Various types of adhesive are mentioned, such as polyvinyl, polycarbonate, epoxy resin, polyurethane, etc.

US-A-3,616,115 describes an armor plate formed by a laminate of titanium sheet followed by two layers of blocks of alternating ceramic material (three-sided). The backing plate can consist of several layers of fibers.

US-A-4,131,053 describes a shield plate consisting of three layers of different materials joined together by means of an adhesive. The first layer is of a hard surface or facing material, such as aluminum oxide, silicon carbide or the like. The second layer can be beryllium or some other material that has a high elasticity modulus but less hardness than the first layer. The third layer is made of a synthetic material reinforced with high strength fibers.

Finally, US-A-2,279,110 describes a shield plate composed of three steel plates joined together by means of two layers of adhesive.

Reference is also made to US Pat. 4,529,640, which describes a composite armor plate comprising a thick, steel impact plate, successively backed by a honeycomb plate, preferably paper, and a package of fiberglass or aramina fiber fabrics impregnated with a material Synthetic Also this already known armor plate has the disadvantage of the thick steel impact plate. In addition, the thick steel plate will deform, in general, to a limited extent so that the kinetic energy of the projectile is insufficiently absorbed.

The present invention aims to offer a composite shield plate, of the type indicated above in the introduction paragraph, which ceases to present the drawbacks of known shield plates. The composite shielding plate according to this invention is characterized by the features defined in the characterizing portion of claim 1^to. In claims 2^to...16^to subor3

016 333 dynades define a preferred embodiments. The aforementioned combination of metal sheets and alternating fiber layers as a backup sublayer of the impact layer of ceramic material, in the armor plate according to this invention, leads to a surprisingly optimal use of the baosically required properties of the metal plates and fiber layers. A particularly effective way of executing the shielding plate according to this invention is characterized by the fact that the laminate that acts as a sublayer is fixed to a joint layer, consisting of supporting or supporting element, which on the remote side of The impact face is fixed to a backing layer formed by a laminate of fibers impregnated with, for example, a synthetic material. On its impact side and on the oil side, the ceramic layer was advantageously provided, according to the invention, with a relatively thin layer of anti-fragmentation, such as a fiber layer in the form of a woven fabric or some other fabric impregnated with a synthetic material. The impact ceramic layer has a total thickness of 3 mm. An armor plate that offers better protection against a second bullet impact is characterized, according to the invention, for being the ceramic impact layer composed of two, three or more constitutive plates, of ceramic material, interconnected, superimposed and / or adjacent , the superimposed constituent layers being fixed, according to the invention, by means of a layer of interposed fibers in the form of woven fabric (on loom) or some other fabric, preferably impregnated with synthetic material. According to this invention, the constitutive, interconnected, superimposed and adjacent ceramic material plates were located in the successive layers in position such that the plates of each layer are staggered or three-sided with respect to those of the next layer, whereby it is communicated an additional damping power to the layer of ceraomic material. A very simple form of execution is characterized, according to the invention, by the fact that the impact layer of ceramic material was substantially composed of grains of one or more ceramic materials with which a coherent mass has been formed, for example, by sintering .

Of the armor plate according to the invention, the impact ceraomic layer has a total thickness of 5 to 15 mm, in particular about 10 mm; a hardness in the range of 1000 to 10,000 deca N / mm², preferably from 1500 to 3000 deca N / mm², determined by Vickers hardness measurement; and the ceramic material was substantially formed of one or more of the following materials: aluminum oxide, boron carbide, silicon carbide or mixtures thereof.

An effective embodiment of the armor plate according to the invention is characterized by the fact that the laminate constituting the sublayer was composed of three or more, with more particularity of five to twenty and preferably of about ten, metal plates in alternation with one or more layers of fibers, such as woven fabrics or some other textile fabric. The metal plates are advantageously made of steel or an aluminum alloy with a tensile strength greater than 300 N / mm², and the metal plates may have a thickness of 0.1 to 2.0 mm each, and preferably about 0.3 to 0.9 mm. The metal plates may be made of copper and aluminum alloy, in particular of type n^° . 2024-T3 of the AA (USA), or an alloy of aluminum and zinc, in particular of type n^°. 7075-T6 of the AA (USA), or an aluminum-magnesium-silicon alloy, in particular of type n^°. 6061-T6 of the AA (USA). According to the invention, the successive metal plates have a total thickness of 0.3 to 5 mm.

A preferred embodiment of the shielding plate according to the present invention is characterized by the fact that the fibers of the sublayer laminate have a total thickness of 5 to 20 mm, preferably about 10 mm, an elastic modulus comprised in the interval ranging from 1^.10⁴ a25^.10⁴ N / mm², preferably of 8^.10⁴ to 15^.10⁴ N / mm², and the fibers of the sublayer laminate are in the form of strands of poly (paraphenylene terephthalamide) filaments, for example, of the type of dtex 1680 / f 1000. Under the invention, the fibers of the sublayer laminate are in woven fabric form with a ligament or fabric of the right type for ballistic purposes, such as the taffeta ligament or the panamaó ligament. A favorable form of execution of the armor plate according to the invention is characterized in that the layers of fibers of the backing laminate are fixed to the metal plates and impregnated with a viscoelastic substance whose loss factor (tangent of the δ angle of loss) , measured at 20^°C and at a frequency of 1 Hz, has values ​​of 0.01 <tgδ <100 and more in particular 0.3 <tgδ <2, and whose G-modulus of loss-shear, also measured at 20^°C and at the frequency of 1 Hz, has the values ​​10²Pa <G ”<10⁹Pa, and more specifically 10⁴Pa <G ”<10⁶Pa.

Favorable results can be obtained with a shield plate which, according to the invention, is characterized in that the viscoelastic substance from which the layers of fiber are impregnated in the sublayer laminate is a synthetic material based on alkyl (meth) acrylate or a synthetic material based on a copolymer of 80 to 95 parts by weight of an alkyl acrylate having an alkyd group containing 6 to 10 carbon atoms, and 20 to 5 parts by weight of at least one monoomer taken from the group of acroic acid, methacrylic acid, acrylonitrile, methacrylonitrile, acrylamide and methacrylamide. According to the invention it is preferred that the viscoelastic substance be a synthetic material of 20% to 25% by weight of 2-ethylhexyl acrylate, 65% to 70% by weight of isooctyl acrylate and 5% to 15% by weight of Acrylic Acid. In accordance with the invention it is also possible, in principle, that for the impregnation of the fiber layers contained in the mixed laminate, use of viscoelastic substances based on polyurethane or polyvinyl chloride. According to the invention, the viscoelastic substance may contain

016 333 a plasticizer, for example in an amount not exceeding 50% by weight. According to the invention, the viscoelastic substance from which the fiber layers contained in the mixed laminate are impregnated can also, advantageously, be made of substantially or partially amorphous polymers or copolymers, such as natural or synthetic rubber, or polyvinyl rubber. alcohol), polypropylene, glycol diisocyanate co-numbers and similar materials.

The shielding plate according to the invention is advantageously characterized in that the forming layer of the support or support element has a total thickness of 5 to 50 mm, preferably 10 to 30 mm, and a stag formed by a plate of an alloy of aluminum having an open structure, such as a honeycomb structure, the open structure being covered on either side with, for example, an aluminum alloy plate of small thickness with respect to the support element. In principle, favorable results can also be obtained if, according to the invention, the forming layer of the stump support element composed of an expanded plastic or of a fibrous mass (marana) of open structure and made of synthetic fibers, said marana, for example , of the commercially obtainable type under the registered name of "Enkamat". When a past projectile collides with the armor plate in accordance with this invention, said layer forming a support element acts in a unique way (unique in its genre) as a crushing zone (wrinkle), which allows deformation of the sublayer and as a consequence of which kinetic energy of the projectile can be absorbed to a considerable extent. The support element, which can be in the form of a honeycomb, also offers the advantage of being able to be fixed easily, since it can be attached to the object to be protected, for example, by adhesive or glue.

A preferred embodiment of the shielding plate is characterized, according to the invention, by the fact that the back layer is constituted by a laminate of, for example, 3 ... 20 layers of fabrics joined between them and impregnated with a synthetic material , and a loom-woven fabric of the type that is usually used for balustic uses, such as tafetaún ligament or Panamanian ligament, the fabrics being made of poly (paraphenylene terephthalamide) yarns (filaments).

Particularly favorable results are those expected from a composite shield plate characterized, in accordance with the invention, by the fact that:

- the impact layer of ceramic material, such as aluminum oxide, is constituted by one or more component, superimposed and / or adjacent layers;

- The impact layer has a total thickness of 5 to 15mm:

- the impact layer has a hardness in the range of 1000 to 10,000 deca N / mm², and preferably from 1500 to

3000 daN / mm², determined by Vickers hardness measurement;

- The ceramic tile (s) are covered on each side with an antifragmentation layer that has a total thickness of 0.1 to 2 mm, such as a composite impregnated with a synthetic glue based on epoxy resin and which has a ligament (mesh) of the type commonly used for baltic uses. and composed of threads, particularly filaments, having a modulus of elasticity of 1^.10⁴ a25^.10⁴ N / mm², such as poly (paraphenylene terephthalamide) (PPDT), polyethylene (PE), glass, polyacrylonitrile (PAN), poly (vinyl alcohol) (PVA) or a similar material;

- the laminate that forms the sublayer consists of 5 to 15 plates of a metal, such as an aluminum alloy with a tensile strength of at least 300 N / mm², in alternation with a woven fabric impregnated with a viscoelastic substance and having a ligament of the type commonly used for baltic purposes, such as a taffeta ligament or a Panamanian ligament, and is composed of threads - particularly filament wires - of a module of elasticity between 1^.10⁴ and 25^.10⁴ N / mm², of a material such as PPDT, PE, glass, PAN, PVA or the like;

- the laminate of the sublayer has a total thickness of 5 to 25 mm, and each of the metal plates has a thickness of 0.2 to 1 mm;

- the laminate of the sublayer is fixed to a layer forming a support element, such as an aluminum alloy plate having a honeycomb structure, an expanded plastic plate or an open structure fibrous marana composed of synthetic fibers;

- the support element has a total thickness of 5 to 30 mm;

- the support element is fixed to a back or back layer made of a laminate of 3 ... 20 woven and impregnated fabrics, of a ligament of the type commonly used for baltic purposes, such as a taffetaun ligament or a panamaú ligament, and a compound made up of threads - in particular, filaments - of a modulus of elasticity in the range of 1^.10⁴ a25^.10⁴ N / mm², of a material such as PPDT, PE, glass, PAN, PVA or the like;

- the backing layer has a total thickness in the range of 2 to 20 mm.

An effective embodiment of the shielding plate according to the invention is that characterized by the fact that the mass of the compound

016 333 is in total from 35 to 350 kg / m², and more particularly about 55 kg / m² approximately for protection against small firearms.

The preferred embodiment of the composite shielding plate according to the invention is made of four main components, namely: the impact ceramic layer, the sublayer laminate, the support element and the backing layer. The impact ceraomic layer is excellently suitable for dulling the tip of a projectile, in particular because the ceramic materials applied will retain their hardness and resistance despite the high temperature increase that occurs in the region hit by a projectile. The sublayer laminate is perfectly suited to absorb the kinetic energy of the projectile by plastic deformation, and the support layer provides a sufficient means of admission for said plastic deformation. The backing layer of the armor plate compound according to the invention, on the far side from which it receives the impact, continues to offer additional protection and remains proactively colorless even though the impact layer is attacked with fairly heavy ammunition, such as 7 , 62 mm AP (piercing, hard core). Since the shield plate compound according to the invention contains an optimal combination of said main components, the resulting shield plate offers a high degree of protection with a limited weight per unit of surface area. This shield plate compound, therefore, is particularly suitable for various uses. Among the fields of application for the armor plate compound may be mentioned armor of combat vehicles, warships, fighters and helicopters. However, the shield plate compound according to the invention is also very suitable for use in the civil area; for example, for the additional protection of passenger vehicles, money transport vans and for other purposes that require special safety precautions.

Even though the shielding plate compound according to the invention is of an essentially simple construction, the special composition of the sublayer laminate made of alternating metal plates with fabrics impregnated with the appropriate viscoelastic substance is, among other things, what contributes to a particularly effective protection of the present shield plate against various projectiles or flying fragments. On the basis of what was said in page 142 of the Roy C. Laible book mentioned above, it could be expected that the use of a single aluminum plate, thicker, would be more favorable than the use of two aluminum plates Same total thickness. Surprisingly, according to the invention, it turns out that the use, for an armor plate, of said sublayer laminate composed of several metal plates, in particular an aluminum alloy, with the presence between each of these two plates of a cloth layer impregnated with a synthetic viscoelastic material, is particularly effective.

The invention will be described in greater detail in the following, referring to the photographs and the accompanying schematic drawings, in which:

- Figure 1 is a view in straight section and in side elevation of an armor plate according to the invention;

- Figure 2 is a view of depiezo ordered, in some way, of the form of construction according to fig. one;

- Figure 3 is a view in straight section and in side elevation of a somewhat modified embodiment;

- Figure 4 illustrates a modified form of execution of the layer of ceraomic material; ^Y

- Figures 5 and 6 are photographs of the armor plates following Figs. 1 and 3, respectively, after receiving the impact of a projectile.

In fig. 1, the number 1 generally indicates a shield plate compound. Plate 1, as illustrated in the drawing, comprises four main components, namely: an impact layer 2, of ceraomic material; a sublayer 3; a support layer 4; and a backing layer 5. The impact layer 2 consists substantially of a fine and sintered powder of aluminum oxide (Al2O3) with a total thickness of, for example, about 10 mm. The impact layer 2 was coated on both sides with layers 6, 7 of antifragmentation, which consist of a weave of taffeta ligament, made with fiberglass threads or threads of aramina and impregnated with a synthetic material. This synthetic material, which can be an epoxy resin based glue, should be such that it can be used to properly bond the antifragmentation layers 6, 7 to the ceramic impact layer 2, at elevated pressure and temperature. For the synthetic material, for example, the glue type AF 163-2 put on the market by the Minnesota Mining and Manufacturing Company can be used.

The sublayer 3 comprises ten plates 8 of a cuproaluminium alloy of type no. 2024-T of AA (USA), each plate having a thickness of 0.5 mm. Between each two successive metal plates 8 there is a layer of fabric 9, so that the ten metal plates 8 of the sublayer 3 alternately interspersed a total of nine layers 9 of fabric, each indicated by a thick line.

The fabrics 9 are impregnated with a synthetic material that has viscoelastic properties. This viscoelastic synthetic material contains approximately 22.5% by weight of ethylhexyl acrylate, about 67.5% by weight of isooctyl acrylate and approximately 10% by weight of acrylic acid, and is marketed by the Minnesota Mining and Manufacturing Company under the registered designation of "Scotch Damp" 15D112. In a sample of the visco-elastic synthetic material used, it was found that the tangent of the δ loss angle was approximately 0.8 at a temperature of 20^°C and a

016 333 frequency of 1 Hz. In addition, a value of approximately 10 was measured in the sample of the synthetic viscoelastic substance⁵ for module G "of loss-shear, also at a temperature of 20 ^ C and a frequency of 1 Hz. Both weft and warp threads of fabrics 9 were made of poly (paraphenylene terephthalamide) (PPDT) filaments . The PPDT threads used are those marketed by Enka under the registered denomination of "Twaron" 1000. These threads have a tensile strength of about 2750 MPa, an electrostatic modulus of approximately 3.3%. In particular, the following two types of fabric were used:

<td>Type 1</td><td>Plot</td><td>Warp</td>

<td>Linear Density (Tex)</td><td> 126</td><td> 126</td>

<td>Density (threads / cm)</td><td> 11,8</td><td> 11,8</td>

<td>Ligament</td><td colspan="2">Tafetan 1/1</td>

<td>Torsion (turns per meter)</td><td> 60</td><td> 0</td>

<td>Weight (g / cm²)</td><td colspan="2"> 271...288</td>

<td>Type 2 Linear Density (Tex)</td><td> 168</td><td> 168</td>

<td>Density (threads / cm)</td><td> 13,4</td><td> 13,0</td>

<td>Ligament</td><td colspan="2">panama 2/2</td>

<td>Torsion (turns per meter)</td><td> 60</td><td> 0</td>

<td>Weight (g / cm²)</td><td colspan="2"> 458...492</td>

The sublayer 3 can be made in a separate process of manufacturing a plurality of layers of fabric 9 in alternation with metal plates 8. Each fabric of aramina fibers has a thickness of, for example, about 0.15 mm and is covered by each side with a thin film of viscoelastic synthetic material. The resulting laminate becomes a sublayer 3 under the influence of heat and pressure. The sublayer 3, in the armor plate, serves first of all to absorb the kinetic energy of a projectile by plastic deformation of the metallic plates of the sublayer laminate 3, by exfoliation, by the viscoelastic behavior of the synthetic material from which the fabrics are impregnated 9, and by the breaking energy of the thread. During such deformation, the shear forces between the fabric layers 9 and the metal plates 8 must not be unduly large. For this purpose it is necessary to make use of said synthetic material of viscoelectric properties in order to impregnate the fabrics 9 and fix said fabrics to the metal plates 8. The use of the synthetic material of viscoelectric properties results in such a connection between the layers of fabric 9 and the metal plates 8, which will communicate a coherence, to the sublayer 3, sufficient to absorb the desired degree of kinetic energy by plastic deformation, but I will not give a bond as strong as that obtained by a good type of glue (glue) or adhesive, generally heat stable.

The support plate 4 represented in the drawing of the shield plate 1 consists of an open honeycomb structure 10, made of aluminum alloy. The honeycomb structure 10 is covered on both sides with thin metal plates 11, 12 attached thereto with glue, each of which has a thickness of, for example, 0.5 mm and consists of an aluminum alloy. The total thickness of the honeycomb structure 10 and the plates 11, 12 that cover it is, for example, about 10 mm. At the discretion, instead of the honeycomb structure, a layer of expanded hard synthetic material or a tangle-shaped layer of synthetic and open-structure threads can be used.

The backing layer 5 is composed of a package of fifteen fabrics 13 joined together, of filament threads of PPDT, contained in a matrix of synthetic material. The fabrics 13 can be formed in the same manner and impregnated with the same synthetic viscoelastic material as the fabrics 9 of the sublayer 3. The total thickness of the backing layer 5 can be, for example, 6 mm.

Said four main components of the shield plate compound 1, that is, the impact ceramic layer 2, the sublayer 3, the support layer 4 and the backing layer 5 can, after being manufactured separately, be assembled into one unity by resorting to joining or pasting them between one to a certain external pressure.

Fig. 3 illustrates a composite shield plate 14 which differs only from the shield plate 1 of figs. 1 and 2 as regards the construction of the impact ceramic layer, the corresponding parts being designated with equal reference numbers. In the shield plate 14, the impact ceramic layer 2 is composed of three overlapping constituent layers 15, 16 and 17. On their contact surfaces, these constituent layers or components are joined together by a glued joint, by means of cloth 18 and 19 glass fabric or PPDT wires impregnated with a synthetic glue. With the exception of the impregnating agent, fabrics 18 and 19 and fabrics 6 and 7 may be made in the same manner as tissue layers 9 of sublayer 3.

Fig. 4 shows a construction variant of the impact ceramic layer 2. The impact layer 2, here also, consists of three component layers 20, 21 and 22 also in alternation with the fabrics 23 and 24 impregnated with a synthetic tail. In contrast to the construction according to fig. 3, each of the component layers 20, 21, 22 of the construction according to alafig. 4It is composed of adjacent tiles 25, the tiles of each component layer being run to the treadmill with respect to those of the successive immediate component layer.

The composite armor plate according to the invention was ballastically tested against a light automatic rifle (FAL) and 7.62 mm AP (hard core) ammunition, the armor plate of the invention being 25 mm away from the weapon of fire. Figs. 5 and 6 are two natural-sized photographs of the armor plates of fig. 1 and of figure 3, respectively, after having been fired at them in the

016 333 trials indicated above. Although the two armor plates are damaged by the projectile, they were not pierced by oil. The impact hole 2 of ceramic material, which primarily serves to blunt the tip of the projectile, is the one that was mostly destroyed in each case (figs. 5 and 6), as expected by the very function of the impact ceramic layer . In both armor plates, the sublayer laminate 3 made of alternating fabric layers with aluminum plates, has been clearly subjected to plastic deformation but has only suffered little damage and does not show any penetration at all, which should be considered as a Particularly favorable result in ballistic trials with this type of ammunition. The photographs also clearly demonstrate that the sublayer laminate 3 performs its function of primarily absorbing the kinetic energy of the projectile. The support layer 4 in the form of an aluminum honeycomb structure acted as a wrinkle zone and leaves enough space for the plastic deformation of the sublayer laminate 3. Under the impact area of ​​the projectile, the backing layer 5 was only slightly warped and in no way damaged.

The comparison of the photographs of fig. 5 and 6 show that the division of the impact ceramic 2 layer into three component layers 15, 16 and 17 superimposed and fixed between them constitutes a considerable improvement, since the hole produced in the impact ceramic 2 layer is much smaller in the shield plate illustrated in the photo of fig. 6. The shield plate 14 of the type according to fig. 3 (photo of fig. 6) It would offer better protection when the armor plate receives impacts from several projectiles at close range from each other (multi-impact). The backing layer 5 of the shield plate 14 of fig. 3 deforms even less than in the case of plate 1 of fig. 1, as can be seen from the comparison of the photographs in figs. 5 and 6. From fig. 6 it follows that the honeycomb layer performs a more effective function.

The above-mentioned mechanical properties of the fibers, such as tensile strength, elastic modulus and elongation at breakage were measured in accordance with ASTMD-885.

It should be added that by said G "module of shear-shearing, the quadrature part of the complex dynamic module G * of shear in the plane of the viscoelastic layer must be understood. This complete dynamic module G^* it is the quotient of dividing the amplitude τ or of the sinsoidal shear stress τ (shear) by the amplitude γ_ο of the γ sinusoidal shear applied:

G * = τo / Yo

The G "drop module" is then:

G ”= G^* sin γ, where δ is the phase angle between the shear stress τ and the shear γ. Said cutting or shearing modulus G "and a drop angle δ are measured in a dynamic rheometer, in which the viscoelastic material consisting of one or more layers was between two round parallel plates of a radius R. Starting from the amplitude θ_ο of the torque angle θ (θ = θ_ο sin 2nft) sinusoidal at time t of one of the plates with respect to the other plate, and of the amplitude Mo of the pair M, also in sinusoidal but outdated [M = M_or sin (2Πίΐ + δ)], the complex module G can be calculated^* as follows:

G * 2^.h Mo ^G _ nR⁴ . θο^, where h is the thickness of the viscoelastic layers between the plates, and f is the frequency of the sinusoidal vibration (Hz). Sliding or sliding between the layers and between the plates and the viscoelastic material should be avoided.

The aromatic polyamides to be used according to the invention are polyamides totally or substantially composed of repetitive units of the general formula

-C- A1 -C, -N- A2 -N- C- A3 -NII II II and / or || I

OOHHOH in which A1, A2 and A3 represent divalent rigid radicals, different or the same, containing one or more aromatic rings, which may contain a heterocyclic ring, the chain extension bonds of these radicals being in "para" position with each other, or parallel and directed in opposite directions. Examples of such radicals are 1,4-phenylene, 4,4'-biphenylene, 1,5-naphthalene and 2,6-naphthylene. They may or may not carry substituents, such as halogen atoms or alkyl groups. In addition to the amide groups and aromatic radicals mentioned above, the chain molecules of the aromatic polyamides may, at their discretion, contain up to 50 mol% of other groups, such as m-phenylene groups, of non-rigid groups such such as alkylic groups, or of ether, urea or ester groups, such as the 3,4'-diaminodiphenyl ether groups. According to the invention it is preferred that the yarn consists, totally or substantially, of poly (p-phenylene terephthalamide) or (PPDT). The manufacture of PPDT threads is described in US Pat. 4,320,081.

Although favorable results can be obtained with the shield plate compounds indicated in the drawings, the invention is not limited thereto. Various modifications can be made within the scope of the invention. For example, the thickness of layers and the number of plates can be varied according to the intended use. In the sublayer laminate 3 the layers of fabric 9 impregnated with synthetic tendon material will, in general, be less thick than the metal plates 8. Although the metal plates 8 will generally be all of the same thickness, this is not absolutely necessary. Although the fabrics applied are preferably of PPDT filament threads, it is also possible, in principle, to use other filament threads of the desired high modulus and good tensile strength, such as glass threads or polyethylene (PE) threads, of poly (vinyl alcohol) (PVA) or polyacrylonitrile (PAN) obtained by spinning with solvent, or Nylon and polyester threads of the ballistic type. The manufacture of PE filaments by spinning with solvent

016 333 can be performed as described, for example, in documents GB20.42.414, GB 2.051.667 or EP 64.167. The manufacture of PVA filaments by solvent spinning can be performed as described, for example, in US Pat. 4,440,711. The manufacture of PAN filaments by solvent spinning can be carried out as described, for example, in EP 144,983 or in the patent application

JP 70449/83. Although said fibrous layers, such as cloth, are preferably composed of filamentary threads, in some circumstances it is also possible to use spinning threads. It should be noted that in US Pat. 4,034,639 and 3,799,025 describe various viscoelastic materials, more particularly synthetic materials that have favorable damping properties.

016 333