BE902435A - COMPOSITE MATERIAL FOR MECHANICAL SHIELDING. - Google Patents

Abstract

The invention relates to a composite material for the mechanical shielding of structures, infrastructures or vehicles. The material 1 of the invention comprises an element 2 made of a material with high hardness, such as a ceramic tile, coated in a layer 3 of lower hardness material. This layer 3 is made of a material with viscoelastic property. To achieve the shielding, it suffices to glue the elements 1 to the surface to be shielded, thereby forming a covering by tiling. The material of the invention makes it possible to reduce the surface mass of the shielding, and to limit the damage caused to the shielding by a projectile, at the point of impact of the projectile, due to the damping effect of the viscoelastic material and to the distribution of the constraints. The present invention is particularly applicable in the field of making armored structures.

Description

Composite material for mechanical shielding

The present invention relates to a composite material for the mechanical shielding 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 and other infrastructure which can resist and stop projectiles, in particular large caliber. These shields are generally made up either of metal such as a steel alloyed with Nickel-Chromium-Molybdenum sold by the company "Creusot-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 with "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 relatively difficult to use, in particular for the shielding of existing structures. In addition, when part of this shield is damaged, its restoration is relatively difficult and expensive.

Also known, in particular from French patents Nos. 1,581,760 and 1,604,806, composite mechanical shields constituted by elements made of ceramic material embedded in a synthetic resin which is generally reinforced. These shields which have a lower "surface mass" than those described above also have the drawbacks of a difficult implementation to achieve the protection of existing structures, and of a large damaged surface under the effect of impact of a projectile resulting in 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 is therefore a function of the density of the materials used as well as the thickness necessary to obtain the stop of the projectile.

The object of the present invention is in particular to remedy the drawbacks mentioned above by proposing a composite material having high protective properties for a low surface mass, which can be arranged using a simple and easy technique on the structure to be protected. In addition, the material proposed by the invention 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 structures of 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 adjacent elements hard material, and the rear layers of the shielding if they exist.

Thus, damage caused by the projectile is limited to the vicinity of the starting point. In addition, as the stresses are distributed 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 calibers of projectiles, this additional shielding may be eliminated.

According to another characteristic of the invention, the element made of hard material is coated in the layer of viscoelastic material, with the exception 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 made of hard material are ceramic elements, advantageously 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 to 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 of viscoelastic material, the shielding material being obtained by vulcanization of the material viscoelastic.

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 thermosetting resin plate reinforced with fibers, fabrics or the like, thus forming a rear shielding wall. Other characteristics, advantages and aims of the invention will appear more clearly on reading the detailed description which follows, given with reference to the appended drawings given solely by way of illustration, and in which: - Figure 1 is a cross section schematic of a first embodiment of a shielding material according to the invention, - Figure 2 is a schematic sectional view of a structure protected by a 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 material 2 is coated in a layer 3 of material of lower hardness 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, the thickness of which is determined according to the degree of protection sought.

Examples of suitable ceramics include ceramics based on aluminum oxide, ceramics based on beryllium oxide or zirconium oxide, silicon carbide, or 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 tgS greater than 0.05 and advantageously having a hardness less than 60 shA. By way of example of viscoelastic materials, mention may be made of polyisoprene elastomers, and more particularly the 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 depending on the face of the covered tile. Thus, according to a preferred embodiment of the invention, the thickness of the layer on the four sides of the tile (only two 2c, only 2d of which are visible) is slightly less than that of the layer covering the two large faces 2a, 2b 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 according to the desired degree of damping and stress distribution.

It is also possible, without departing from the scope of the invention, not to cover one of the large faces of the pane 2.

However, this uncovered face must be that which receives the impact of the projectile, in other words the front face 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 tiled floor.

The adhesive suitable for making this coating is any adhesive compatible with the viscoelastic material forming the layer 3 and of course the material forming the structure 8.

Suitable adhesives are, for example, araldite, neoprene, polyurethane adhesives, such as, for example, the adhesive sold by the applicant under the brand "Népurane".

It is also possible, within the framework of the invention, to make the shielding of the structure 8 by bonding several superimposed layers 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 reinforced resin, according to the same laying method as that mentioned above.

This front wall makes it possible on the one hand to reduce the necessary thickness of the rear plates 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 stresses generated by the impact of the projectile on the ceramic tile 2.

Thus to restore this shielding, it will only be necessary to replace the damaged tile (s) by the impact.

According to a second embodiment of the invention, illustrated in FIG. 3.1, 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 high hardness elements 6 embedded in a layer of viscoelastic material 7.

The elements 6 are made of the same material, described above, as the elements 2 of FIG. 1.

The first layer 4 may consist, for example, of steel such as the "Mars 240" steel mentioned above, or a reinforced resin, such as an epoxy resin reinforced by a fabric or aramid fibers sold under the brand "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 face not being covered, or completely embedded in it.

The resin is then vulcanized by heat for example. The assembly 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 bond the layer 5 to a structure to be protected, if its protective power is sufficient.

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

As in the first embodiment, it is possible to have several superposed layers 5.

Firing tests show that under the impact of the projectile, the square 2 or 6 having supported the impact is destroyed, the adjacent squares do not

This result proves the damping and stress distribution effect of the viscoelastic material, which significantly reduces the cost of repairing the shields.

In addition, with a shield conforming 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 the layer 4 of resin reinforced with a Kevlar fiber fabric is 18 millimeters, a reduction in the surface mass of the order of 50% is obtained compared to that of an armor made of "Mars 240" steel for an equivalent degree of protection against a 5.56 caliber projectile.

Decreases in surface mass of the same order are obtained for protection against 7.62 and 12.7 caliber projectiles.

Furthermore, as the shielding material of the invention is in the form of elements of small dimension, it is very easy to arrange these elements on structures having complicated shapes.

Claims (8)

Claims 1. Composite material for mechanical shielding of a structure comprising 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 viscoelastic property material, 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 damping coefficient (tg &) greater than 0.05, and is preferably an elastomer. 3. Material according to claim 1 or 2, characterized in that the above elements (2, 6) of hard material are surrounded by the layer (3, 7) of viscoelastic material on. all of its faces except 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 material with high hardness consists of a 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 the above-mentioned element or elements made of high hardness material are arranged in a layer (7) of viscoelastic elastomer before vulcanization, the joints between two elements (6) adjacent 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 bonded 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 of about a millimeter.