FR2628831A1 - Armour plating includes compressible and deformable plastics layers - to reduce shrapnel penetration by energy absorption and slattering - Google Patents

Abstract

Composite armour plate for protection against explosive charges by including a layer of ceramic material between two layers of metal (steel) is provided with an external covering comprising an additional sheet of metal between a layer of compressible material (I), and a layer of highly deformable material (II) sufficiently deep to allow (2) to distort and deflect the path of incident shrapnel and reduce its penetration. The compressible material (I) is pref. of polyethylene rubber. The deformable material may be an air gap or a low density cellular material, such as expanded polyethylene or polyurethane at least 10 times as thick as the adjacent layer of metal nearer to the incoming shrapnel. Opt. the armour has an additional external layer of sheet metal. ADVANTAGE - Lighter and/or more resistant than an equivalent panel not including a ceramic layer. Layer allows considerable distortion of before is affected or inhibits such distortion, and spreads the effect of a group of impinging particles which would otherwise maintain a relatively concentrated impulse on all the successive layers of the armour plating.

Description

(d) FRENCH REPUBLIC Publication No. 2 628 831 (use only

  for NATIONAL INSTITUTE reproduction orders)

INDUSTRIAL PROPERTY

  ) OF THE INDUSTRIELLN PROPERTY of national registration 79 20178 PARIS

(i) Int CI'4: F 41 H 5/04.

@ A1 PATENT APPLICATION

  (È Filing date August 7, 1979. (Applicant (s): FRANCO-GERMAN INSTITUTE OF RE-

CHERCHES DE SAINT-LOUIS. - FR.

Priority

  (Inventor (s) Claude Fauquignon: Claus-Peter Woid-

  neck. ) Date of public availability of the

  application: BOPI "Patents" n 38 of September 22, 1989.

  References to other national documents appearing

Renter (s) Holder (s)

  (Agent (s) Cabinet André Bouju.

  Shield for protection against shaped charges.

  The shielding for protection against hollow charges, comprises an outer layer 1, 2 comprising on its face exposed to the effects of the hollow charge 8, a plate 1 of compressible material, behind which is fixed a plate 2 of thick steel at more equal to that of the 8 D plate

compressible material.

  This outer layer 1, 2 is separated from a layer 4 of ceramic or glass-based material rigidly confined between two metal plates 5, 6, by a release layer 3 of a material of low density and rigidity 1 2 3 6 relative to those of the materials constituting the other layers.

  Application to protection against anti-tank projectiles.

  1p = N N D Sale of booklets' IMPRIMERIE NATIONALE. 27 rue deConvention75732 PARIS CEDEX 15 OL. The present invention relates to armor for the protection against hollow charges, in particular the protection of self-propelled military vehicles such as the sale of leaflets to the IMPRIMERIE NATIONALE, 27, rue de la Convention

than tanks.

  It is known that hollow charges generate fine metallic jets which penetrate at a very high speed into shielding materials by forming deep and narrow craters. As an indication, a good hollow charge can perforate 600 millimeters of steel,

  the average diameter of the perforation obtained being less

laughing at 20 millimeters.

  We can consider the jet as consisting of a

  series of elements. each spray element increases the perfo-

  ration by consuming its kinetic energy at the bottom of the

  crater already formed by the elements that preceded it.

  To be effective, the jet must remain perfectly aligned so that the last jet elements can reach

  the bottom of the crater without coming to lose their energy by rubbing

  tement and rebound on the wall of this crater.

  We already know the practical interest of very hard materials, such as alumina-based ceramic, in the realization of shieldings for protection against hollow charges. Elementary considerations of the physics of the perforation of materials by very high-speed projectiles that constitute the head elements of jets whose displacement speed is between approximately 5,000 and 8,000 meters per second, make it possible to determine that the hardness of the material constituting the shielding, is primarily responsible for the

  formation of small diameter craters.

  Thus, approximate calculations make it possible to determine for example that with a given hollow charge, the diameter of the crater formed in a ceramic is comprised substantially between a third and half of that formed

in steel.

  Furthermore, it results from the mode of action of the jet

  on very hard materials, such as ceramics

  that their effectiveness in protection against charges

  hollow is all the greater as alignment defects

  ment are created in the jet formed by the shaped charge. It is the same, in the case of the use of glass plates instead of ceramic plates.xxteis, in the case of glass plates it is not only the hardness of the material which explains the effectiveness of the protection obtained against hollow charges, but also the bringing into play of a crater tightening effect due to a

  local modification of the density of the glass.

  To avoid the bursting of ceramic or glass, under the effect of the impact of the jet, these materials are used in shields, rigidly confined between two metal plates. The use of such ceramic or glass plates in a shield, replacing steel, makes it possible to obtain, for a given efficiency, a notable reduction in mass.

total shielding.

  As already mentioned above, the efficiency

  shielding can be increased by disrupting the pro-

  gression of the jet inside the shield, and in particular, by creating misalignments between the different elements of the jet. In this regard, we already know the disturbing effect produced on a jet by its interaction with a thin and movable metal plate in an oblique direction relative to the jet. The setting in motion of this

  plate is obtained either by the action of a layer of explosive

  sif, placed on this plate, that is when a compressible material attached to this plate is released under

  the effect of the shock generated on impact.

  262883i This compressible material can be a metal that is more compressible than steel, and preferably a highly compressible organic material, such as

polyethylene or rubber.

  The implementation of the aforementioned disturbing effect in a shield, makes it possible to increase it appreciably

Efficiency.

  The object of the present invention is to create a

  shielding against shaped charges, pre-

  feeling a still improved efficiency compared to the shields using the aforementioned disturbing effect, or comprising, instead of steel, plates of

ceramic or glass.

  The shielding for protection against hollow charges targeted by the invention comprises an outer layer comprising on its face exposed to the effects of the hollow charge, a plate of compressible material behind which is fixed a thick steel plate

  at most equal to that of the plate of compressible material.

  According to the invention, this shielding is characterized in that this outer layer is separated from a layer of material based on ceramic or glass, rigidly confined between two metal plates, by a release layer made of a material of density and rigidity weak relative to those of materials

constituting the other layers.

  The shielding according to the invention combines the disturbing effect with respect to the jet obtained thanks to the outer layer with the very narrow crater formation effect created by the layer constituted by a plate

ceramic or glass.

  It was surprisingly found that the overall effect, generated against the jet, was significantly greater than the sum of the effects specific to the two aforementioned layers, when the latter two were separated in accordance with the invention by a release layer made of a material of low density and rigidity. This surprising effect can be explained a posteriori as follows: The release layer of low density and stiffness material allows the steel plate of the outer layer to "fly", that is to say move almost freely and at high speed, under the effect O10 of the expansion of the compressible material of the outer layer. This possibility of moving the plate

  steel, allows to obtain a disturbance or defect of a-

  jet alignment over a distance which corresponds appreciably-

  the thickness of the density and stiffness layer

weak.

  According to a preferred version of the invention, the layer of material of low density and rigidity is

  constituted by a space filled with air.

  The realization of such a space does not cause any practical difficulty and allows to obtain a high efficiency, since the air allows the plate of the outer layer to move freely after expansion.

  compressible material of the outer layer.

  According to an advantageous version of the invention, the thickness of the space filled with air is at least equal

  ten times that of the steel plate of the outer layer

  better. The thickness of the air-filled space is thus sufficient for, that during its "flight" towards the ceramic or glass layer, the steel plate of the outer layer intercepts and disturbs a large part, otherwise

the entire jet.

  Other features and advantages of the

  vention will appear again in the description below.

  In the appended drawings, given by way of nonlimiting examples:

Z628831

  - Figure 1 is a schematic cross-sectional view of a shield according to the invention - Figure 2 is a view similar to the figure

  1 concerning another shielding embodiment.

  In the diagram of Figure 1, the shielding according to the invention comprises a series of parallel layers 1, 2, 3, 4, 5, 6 arranged obliquely to the

  direction D of impact of the shaped charge 8.

  Layer 1, directly exposed to the effects of the jet, is made of a material much more compressible than steel, such as polyethylene or rubber, which also have the advantage of having a low density. Behind the layer 1 is fixed, for example by gluing, a plate 2 of hard steel, of relatively small thickness, preferably between 3 and 5 millimeters. The thickness of the steel plate 2 is

  less than or at most equal to that of the compressed layer

sible 1.

  Layer 4 consisting of a ceramic plate

  hard mique (for example based on alumina) or by a glass plate, rigidly confined between two plates, 6 metallic (for example steel), is separated from the steel plate 2 by a clearance space 3 filled with 'air. The thickness of the air-filled space 3 varies depending on the protection sought. In theory, the more the thickness of space 3 is increased, the more effective the shielding. Excellent results are obtained when this thickness is greater than ten times that of the steel plate 2. The maximum thickness of this space 3 is limited only by practical problems

  raised by the bulk of the shielding.

  The technical effects of shielding according to

  the invention are set out below.

  During the impact of the shaped charge jet 8

  with compressible layer 1, the latter is per-

  drilled and subjected to a supersonic shock wave which

  moves steel plate 2 to layer 4, perpendicular

  in layer 1, either in a direction D

  oblique to the direction D of the jet.

  The displacement of this plate 2 disturbs the jet by creating defects in the alignment of the various elements constituting this jet, and consequently, by reducing

  notably the perforating efficiency of this jet.

  The steel plate 2 can move almost freely towards the layers 5, 4 thanks to the filled space

  air 3, located at the rear of this plate 2.

  After having crossed the space filled with air 3, the elements of the jet, highly disturbed and misaligned with respect to each other, have a very reduced perforation power when arriving on the hard ceramic plate 4 confined between the two plates

metallic 5 and 6.

  Experiments carried out on a shield conforming to FIG. 1, and at a jet incidence angle equal to 60 have shown that the total mass of the shield guaranteeing protection was reduced by at least 15% compared to a similar shield without space filled with air 3. Such a reduction in mass can be considered very important in the case of shields. 3P In addition, it was surprisingly found that in the case of the shielding according to the invention, the dispersion of the results was very significantly reduced compared to a similar shielding without air-filled space. 3 This last advantage is particularly important because it allows relatively reliable materials to be used in shields

expensive such as ceramic.

  In a preferred embodiment of the invention, (see FIG. 2) the compressible layer 1 is covered externally by a hard steel pre-shielding layer 7. This pre-shielding layer 7 ensures the protection of layers 1 and 2, and especially of layer 4 of ceramic or glass, against attack by conventional projectiles capable of spraying

the materials of these layers.

  Of course, the invention is not limited to the examples which have just been described, and many modifications can be made to them, without going beyond the ambit

of the present invention.

  Thus, the air-filled space 3 can be replaced by a release layer of density material and

  low stiffness such as for example polyurethane foam

  thylene or polyurethane. Because of their low rigidity and their high compressibility, such materials allow, like air, the steel plate 2 to move at high speed towards the layers 5, 4 during the impact of the jet. The air-filled space 3 nevertheless constitutes the

  simplest and most effective embodiment.

  Furthermore, the compressible layer 1 which

  covers the plate 2, instead of being made of poly-

  thylene or rubber, can also be made of a preferably light metal, such as aluminum or its alloys whose compressibility is greater than that of steel. In this case, the disturbing effect is less intense, and the higher density of such materials relative to polyethylene and rubber, affects

  substantially the total mass of the shield.

Claims (5)

  1. Shield for protection against hollow charges, comprising an outer layer comprising on its face exposed to the effects of the hollow charge a plate of compressible material, behind which is fixed a steel plate of thickness at most equal to that of the plate of compressible material, characterized in that this outer layer is separated from a layer of ceramic or glass-based material rigidly confined between two metal plates, by a release layer of a material of low density and rigidity relative to those materials constituting the other layers.   2. Shielding according to claim 1, charac-   terized in that the layer of density and stiffness material   weak is constituted by a space filled with air.   3. Shielding according to claim 2, characterized in that the thickness of the air-filled space is at least ten times that of the steel plate of the outer layer.   4. Shielding in accordance with any of   Claims 1 to 3, characterized in that the plate in   compressible material is polyethylene or rubber.   5. Shielding in accordance with any of   claims 1 to 4, characterized in that the plate in   compressible material of the outer layer is covered   externally by a steel pre-shielding plate.   Go I sC c I% <4.'eU i -L ai2i c i I.-o C