FR2702272A1 - Composite material for mechanical armour - Google Patents

Abstract

The invention relates to a composite material for the mechanical armour of structures, infrastructures or vehicles. The material 1 of the invention comprises an element 2 made from a material with high hardness, such as a ceramic tile clad with a layer 3 of material having a lower hardness. This layer 3 is made from a material which has a visco-elastic property. In order to produce the armour, it suffices to glue the elements 1 on the surface to be armoured, in order thus to form a covering by tiling. The material of the invention makes it possible to reduce the mass per unit area of the armour, and to limit the damage caused to the armour by a projectile, at the point of impact of the projectile, due to the shock absorbing effect of the visco-elastic material and the distributing of stresses. The present invention applies particularly in the field of the manufacture of armoured structures.

Description

Composite material for mechanical shielding

  The present invention relates to a composite material for the

  mechanical aging of structures, infrastructures or vehicles.

  It relates, more particularly, to shielding materials for protection against objects with high kinetic energy, such as large caliber projectiles, shells, bullets, for example, which comprise elements of material of high hardness associated with

  elements with lower hardness material.

  It is known to make armor plating for vehicles, infrastruc-

  tures or others that can resist and stop projectiles including

  ment of large calibres These shields are generally made up either of metal such as a steel alloyed with Nickel-Chromium-Molybdenum marketed by the company "Creuset-Loire" under the name "Mars 240" or by a laminate formed by a resin reinforced by fibers or a fabric such as for example an epoxy resin reinforced by "Kevlar" fibers These materials have the following major drawbacks on the one hand of having a high "surface mass", and on the other hand of being a relatively difficult implementation in particular for the shielding of existing structures In addition, when part of this shielding is damaged, its restoration is

  relatively difficult and expensive.

  Also known, in particular from French patents N 1,581,760 and 1,604,806, composite mechanical shields constituted by elements of ceramic material embedded in a synthetic resin which

  is generally reinforced These shields which have a "surface mass

  cique "weaker than those described above also have the disadvantages of a difficult implementation to achieve the protection of existing structures, and a large damaged area under the effect of the impact of a projectile causing a

difficult and costly repair.

  By the expression "surface mass" is meant the mass of the shielding layer per unit area, necessary to obtain the desired degree of protection. This value therefore depends on the density of the materials used as well as on the thickness necessary for

get the projectile stopped.

  The object of the present invention is in particular to remedy the inconveniences

  previously mentioned by proposing a composite material having high protective properties for a low basis weight, which can be arranged using a simple and easy technique on

  the structure to be protected In addition, the material proposed by the invention

  tion is damaged only at the point of impact of the projectile, and the

  shielding can therefore be repaired easily, and inexpensively.

  To this end, the subject of the invention is a composite material for the mechanical shielding of a structure comprising at least one element made of hard material and a layer of material of lower hardness, this layer of material of lower hardness being constituted by a

  viscoelastic material.

  The element made of hard material is embedded in said layer of viscoelastic material. The viscoelastic material is a material whose intrinsic damping coefficient represented by the tg S is greater than 0.05. By structure is meant all infrastructure, all

  vehicles, ships, aircraft or the like.

  The viscoelastic material having a high damping coefficient, dampens the shock wave generated by the impact of a projectile on the element made of hard material, and distributes the stresses generated by this shock, to avoid their transmission to the elements in adjacent hard material, and to the rear layers of the shielding if they exist.

  Thus, the damage caused by the projectile is limited to the vicinity

  swim from the starting point Furthermore, as the constraints are re-

  parts and absorbed by the viscoelastic material, the additional necessary thickness of shielding constituted by layers of hard material will be greatly reduced, and even for certain sizes

  of projectiles, this additional armor can be removed.

  According to another characteristic of the invention, the element made of material

  hard is embedded in the layer of viscoelastic material, except

  tion of the surface receiving the impact of the projectile.

  The hard materials suitable for the invention can be steels, metals or alloys with high hardness, reinforced resins,

or ceramics.

  According to a preferred characteristic of the invention, the elements

  hard material elements are ceramic elements, advantageous-

ceramic tiles.

  Thus, each ceramic tile is coated with a layer of viscoelastic material and can be laid, for example by gluing, on the structure to be protected, the shielding surface being formed by laying several tiles side by side, in a manner similar

the tiling of floors or walls.

  According to yet another characteristic of the invention, the ceramic tiles are placed side by side in the layer of unvulcanized viscoelastic material, the joints between each tile being made up of the viscoelastic material, the shielding material.

  being obtained by vulcanization of the viscoelastic material.

  Advantageously, the layer of viscoelastic material comprising the elements of hard material, for example ceramic tiles or the elements of hard material coated with a layer of viscoelastic material are arranged on a plate of material with high hardness, such as a metal plate. , a plate of thermosetting resin reinforced by fibers, fabrics or the like, forming

  thus a rear shielding wall.

  Other characteristics, advantages and aims of the invention appear

  will appear more clearly in view of the detailed description which will

  follow made with reference to the accompanying drawings given solely by way of illustration, and in which: FIG. 1 is a schematic cross section of a first embodiment of a shielding material according to the invention, FIG. 2 is a schematic sectional view of a structure protected by shielding according to the first embodiment of the invention; and Figure 3 is a schematic cross section of a second embodiment of a shielding material according to the invention. According to a first embodiment of a shielding material 1

  according to the invention, illustrated in FIG. 1, an element made of

  hard riau 2 is coated in a layer 3 of material with less hardness

  high and having viscoelastic properties.

  Element 2 advantageously has the form of a plate or a tile.

  Suitable hard materials are metals, such as steel, alloys, for example, resins reinforced by fabrics or

fibers, or ceramics.

  Preferably, the elements 2 are ceramic tiles of which

  the thickness is determined according to the degree of protection re-

  sought. As suitable ceramics, mention may be made, by way of example, of ceramics based on aluminum oxide, ceramics based on beryllium oxide or on zirconium oxide, on silicon carbide, or on

boron carbide.

  The preferred ceramics of the invention are those based on aluminum oxide, such as for example the ceramic sold by the

  French company "Desmarquet" under the name "AF 920 / S".

  The viscoelastic material constituting layer 3 of lower hardness is an elastomer resin of tgc greater than 0.05 and advantageously having a hardness less than 60 sh A. By way of example of viscoelastic materials, mention may be made of polyisoprene elastomers, and more especially elastomers

  marketed by the applicant under the brand "Népurane".

  In the embodiment illustrated in FIG. 1, the ceramic tile 2 is completely coated in a layer 3 of viscoelastic elastomer, this layer being able to have a variable thickness.

  according to the face of the covered tile Thus, according to a mode of realization

  preferred sation of the invention, the thickness of the layer on the four sides of the tile (of which two 2 c, 2 d only are visible) is slightly less than that of the layer covering the two

  large faces 2 a, 2 b of square 2.

  Furthermore, the thickness of layer 3 is of the order of 1 to a few millimeters, generally However, this thickness is

  not critical and will be determined based on the desired degree of amor-

  stress distribution and distribution.

  It is also possible, without going beyond the scope of the information.

  Be careful not to cover one of the large faces of the tile 2.

  However, this uncovered face is the one that receives the impact of the

  projectile, in other words the front of the armor.

  To make the shielding of a structure 8, as illustrated in FIG. 2, with a material of the invention, each element 1 is glued on one of the faces of the structure to make a coating.

  of this face in the form of a tiling.

  The adhesive suitable for making this coating is any adhesive compatible with the viscoelastic material forming layer 3 and

  of course the material forming the structure 8.

  Suitable glues are, for example, araldite glues,

  neoprenes, polyurethanes, such as for example commercial glue

  specialized by the plaintiff under the brand "Népurane".

  It is also possible, within the framework of the invention, to produce

  the shielding of structure 8 by bonding several super layers

asked of elements 1.

  According to another variant, the shielding elements 1 according to the invention can form the front wall of a shield comprising on the rear wall one or more plates of metal or resin

  reinforced, using the same installation process as that mentioned above.

  This front wall allows on the one hand to reduce the thickness required

  to attach rear plates made of hard material and therefore to reduce the surface mass, and on the other hand to protect these rear plates

  against significant damage, by distributing and limiting the

  tracks caused by the impact of the projectile on the glass

ceramic 2.

  So to restore this shielding, it will only be necessary

  replace the damaged tile (s).

  According to a second embodiment of the invention, illustrated in FIG. 3, the shield is formed by a first layer 4 made of a material with high hardness, such as metal or a reinforced resin, and a second layer 5 constituted by elements 6 with hardness

  high coated in a layer of viscoelastic material 7.

  The elements 6 are made of the same material, described above.

  demment, that the elements 2 of figure 1.

  The first layer 4 can be constituted for example by steel such as the "Mars 240" steel mentioned above, or a reinforced resin,

  such as an epoxy resin reinforced by a fabric or ara fibers

  mides marketed under the brand name "Kevlar".

  To make layer 5, an elastomeric resin with a viscoelastic property, not vulcanized, is placed in a mold, forming layer 7. Then the tiles 6 are arranged in this resin, so that the joints between two adjacent tiles are formed by the resin. not vulcanized The tiles are either laid in the resin, the upper side not being covered, or

totally drowned in it.

  The resin is then vulcanized by heat, for example.

  ble thus produced is bonded to layer 4 with a polyurethane type adhesive, marketed by the applicant under the brand "Népurane". Of course, it is possible to directly glue layer 5 on

  a structure to be protected, if its protective power is sufficient.

  The resin constituting layer 7 is a resin similar to that forming the envelope 3 of element 1 illustrated in FIG. 1, for example a polyisoprene elastomer, sold under the brand

"Népurane" by the plaintiff.

  As in the first embodiment, it is possible to

  apply several superimposed layers 5.

  Firing tests show that under the impact of the projectile, the square 2 or 6 having supported the impact is destroyed, the squares

are not damaged.

  This result proves the damping and stress distribution effect of the viscoelastic material, which decreases so

  important the cost of repairing the shields.

  In addition, with a shield according to the second embodiment illustrated in FIG. 2, the thickness of the ceramic element 6 is 4 millimeters, the thickness of the elastomer 7 being one millimeter, and l thickness of layer 4 in resin reinforced by a

  Kevlar fiber fabric is 18 millimeters, we get a dimi-

  nution of the surface mass of the order of 50% compared to that of a shield made of "Mars 240" steel for a degree of protection

  equivalent against a 5.56 caliber projectile.

  We obtain decreases in surface mass of the same order for a

  protection against 7.62 and 12.7 caliber projectiles.

  Furthermore, since the shielding material of the invention is pre-

  feels in the form of small elements, it is very easy

  to place these elements on structures having com-

plicated.

Claims (8)

Claims   1 Composite material for mechanical shielding of a structure   taking at least one element consisting of a material of high hardness and a layer of material of lower hardness, characterized in that said layer (3, 7) of material of lower hardness consists of a material with viscoelastic property, the element (2, 6) of hard material being coated in said layer (3, 7) of viscoelastic material. 2 Material according to claim 1, characterized in that the   aforementioned viscoelastic material has an intrinsic coefficient of absorption   weaving (tgi) greater than 0.05, and is preferably an elasto-   mother. 3 Material according to claim 1 or 2, characterized in that the above-mentioned elements (2, 6) of hard material are surrounded by the layer (3, 7) of viscoelastic material on all of its faces except   of the face to receive the impact of a projectile.   4 Material according to one of the preceding claims, characterized   in that the aforementioned element (2, 6) of high hardness material is   made of ceramic material.   5 Material according to claim 4, characterized in that the aforementioned element (2, 6) of hard material is a ceramic tile, the shielding material consisting of the assembly of several tiles (2, 6) coated in the layer (3) of viscoelastic material   to form a tiling on the structure (8) to be protected.   6 Material according to one of claims 1 to 4, characterized in that   that the aforementioned element or elements made of high hardness material are arranged in a layer (7) of viscoelastic elastomer before vulcanization, the joints between two adjacent elements (6) being   formed by said viscoelastic elastomer.   7 Material according to one of the preceding claims, characterized   in that it comprises one or more layers (4) consisting of a material with high hardness chosen from the group comprising hard metals, alloys, reinforced resins or the like, forming a rear protection, the elements (1) or the layer ( 5) being glued to said   layer (4) of high hardness material.   8 Material according to one of the preceding claims, characterized   in that the layer (3, 7) of viscoelastic material has a thickness about a millimeter.