Advanced spall liner system

Abstract: The invention provides a three layer liner for armor to reduce spall and the spall angle. The liner provides a high impedance.

Description: The invention relates to an apparatus for an armour according to claim 1 and to a method of producing an armour liner according to claim 10. From EP-A-0 334 263 there is known a primary spall backing plate which contacts the inner wall of the armour. The backing plate material is formed as a polymeric matrix having metal or ceramic powders therein which form particles of low mass, low kinetic energy and low penetration capability. A secondary spall backing plate may be spaced from the primary plate for reducing the angle of dispersement from fragments released from the armour and the weapon. Spall is defined as the tensional failure of an area around a hole created by a projectile or shaped charge jet that has penetrated an armour plate. The penetrating projectile or shaped charge may result in a relatively small amount of damage inside an armoured vehicle. The spall created by this penetration however, spreads out in a wide cone angle and can cause severe and lethal damage to soft targets within the vehicle. The invention provides an improved multilayer liner that reduces the cone angle and the amount of spall created by penetrating projectiles or shaped charged jets. Figure 1 is a cross sectional view of part of an armour system using a preferred embodiment of the inventive spall liner. Figure 2 is a cut away view of the inventive spall liner in a frame. Figure 3 is a side view of a testing procedure of the inventive spall liner. Figure 1 is a cross sectional view of part of an armour layer 10 attached to a preferred embodiment of the inventive system comprising a first layer 11, a second layer 12, and a third layer 13. The first layer 11 comprises a soft and low density material such as silastic rubber, which contains a fine grained filler material of high density such as tungsten powder. The concentration of the tungsten powder in the silastic rubber is of a quantity that provides a nearly matching shock impedance to the armor layer 10 to allow most of the energy to be transferred from the armor layer 10 to the first layer 11. The second layer 12 comprises the soft and low density material with a lower concentration of the filler material and a reinforced high strength fabric such as Spectra™ fabric or Kevlar™ fabric. The second layer 12 provides a nearly matching impedance with the first layer 11, so that most of the energy is transferred from the first layer 11 to the second layer 12. The third layer 13 comprises the soft low density material with little or no filler material and the reinforced high strength fabric. The third layer 13 provides a nearly matching impedance with the second layer 12, so that most of the energy is transferred from the second layer 12 to the third layer 13. A soft material is defined as an elastic or pliable material such as silastic rubber or polyurethane or polyethylene. An example of the manufacture of a preferred embodiment of the invention comprises first pouring a mixture of silastic rubber and tungsten powder into a mold. The rubber and tungsten powder is then pressed to form a sheet 11 as shown in Figure 2, which shows a cut away few of the inventive system. The sheet 11 is placed at the bottom of a frame 15. A first wet layer of silastic rubber 16 with a smaller concentration of tungsten powder than the concentration of tungsten powder in the sheet 11 is applied to one side of the sheet 11. A first layer of fabric 17 is placed on the first wet layer of silastic rubber 16. The first layer of fabric 17 is wetted with a second wet layer 18 of silastic rubber with a smaller concentration of tungsten powder than the concentration of tungsten powder in the sheet 11. This process is repeated several times until the second layer 12 is completed. The third layer 13 continues the above described layers, but the wet layers of silastic rubber have little or no tungsten powder. The system is removed from the frame 15, and an adhesive such as a silastic rubber with a tensile strength higher that the tensile strength of the first layer 11 is used to attach the first layer to the armor 10. Figure 3 is a side view of a test to illustrate the spall reduction of the inventive system. In Figure 3 a shaped charge 22 warhead is directed at the armour layer 10 mounted on a test stand 23. The shaped charge 22 produces a high velocity jet of metal that is able to pierce the armour layer 10. Such a piercing bv the jet creates a spall cone angle in excess of 90° in the prior art. The piercing by a jet of an armour layer 10 with the first layer 11, second layer 12, and third layer 13 produces a spall cone angle α of approximately 30°. The particles created by the spall impact a witness sheet 25 located on the side of the armour layer 10 opposite from the shaped charge 22. The pattern impact that the particles from the spall make on the witness board 25 helps to determine the spall cone angle α. A first example for the inventive spall liner for steel armor uses a first layer that is 3,8mm (0.15 inches) thick and comprises silastic rubber homogeneously mixed with 30% by volume fine-grained tungsten powder that is cured at 65,5°C (150° Fahrenheit) and with 2 032,09 Kp (2 tons) of pressure. The second layer is 7.62 mm (0.30 inches) thick and comprises a wetting agent comprised of silastic rubber homogeneously mixed with 15% by volume tungsten powder. This wetting agent is used as an interlayer material between approximately 15 plies of Spectra™ fabric. The third layer is 7,62 mm (0.30 inches) thick and comprises a wetting agent comprised of silastic rubber alone that is used as an interlayer material between approximately 20 plies of Spectra™ fabric. The overall weight of this example is 58,6 Kp/m 2 (12 pounds per square foot). A second example for the inventive spall liner for aluminum uses a first layer that is 6,35 mm (0.25 inches) thick that comprises silastic rubber homogeneously mixed with 7% by volume fine-grained tungsten powder that is cured at 65,5°C (150° Fahrenheit) and at 2 032,09 Kp (2 tons) of pressure. The second layer is 6,35 mm (0.25 inches) thick and consists of a wetting agent comprised of silastic rubber homogeneously mixed with 5% by volume tungsten powder. The wetting agent is used as an interlayer material between approximately 15 plies of Spectra™ fabric. The third layer is 6,35 mm (0.25 inches) thick and comprises a wetting agent comprised of silastic rubber alone, which is used as an interlayer material between approximately 20 plies of Spectra™ fabric. The over all weight of this example is 34,17 Kp/m 2 (7 pounds per square foot). In both examples, a silastic rubber adhesive is used as the bonding agent to apply the liner to the armor. While a preferred embodiment of the present invention has been shown and described herein, it will be appreciated that various changes and modifications may be made therein without departing from the invention as defined by the scope of the appended claims.

Claims: An apparatus for an armour with a first side and a second side, comprising a first layer (11) of a soft material with a first tensile strength and a first density and mixed with a first concentration of filler material with a second density, wherein the second density is significantly greater than the first density, wherein the first layer (11) has a first side and a second side, wherein the first side of the first layer (11) is adjacent to the second side of the armour (10), characterized by a second layer (12) of the soft material mixed with a second concentration of the filler material and provided with a fabric, the second layer having a first and a second side, wherein the first side of the second layer (12) is adjacent to the second side of the first layer (11) and a third layer (13) of the soft material mixed with a third concentration of the filler material and provided with the fabric, the third layer (13) having a first side and a second side, wherein the first side of the third layer (13) is adjacent to the second side of the second layer (12). An apparatus, as claimed in claim 1, further comprising, an adhesive with a tensile strength greater than or equal to the first tensile strength between the armour and the first layer for bonding the first layer to the armour. An apparatus, as claimed in claim 2, wherein the first concentration of filler material is greater than the second concentration of the filler material. An apparatus, as claimed in claim 3, wherein the third concentration of filler material is less than the second concentration of filler material and is substantially zero. An apparatus, as claimed in claim 3, wherein the filler material is tungsten powder. An apparatus, as claimed in claim 3, wherein the soft material is silastic rubber. An apparatus, as claimed in claim 3, wherein the soft material is polyurethane. An apparatus, as claimed in claim 3, wherein the fabric is Kevlar™ fabric. An apparatus, as claimed in claim 3, wherein the fabric is Spectra™ fabric. A method of producing an armour liner, comprising the steps of: casting a layer of soft material with a first tensile strength and a first density and mixed with a first concentration of filler material with a second density wherein the second density is significantly greater than the first density into a mold; pressing the cast layer into a sheet with a first side and a second side; wetting the second side of the sheet with a first wet layer of soft material with a second concentration of the filler material; placing a first fabric layer with a first side and a second side on the first wet layer of soft material with a first side of the first fabric layer adjacent to the first wet layer; wetting the second side of the first fabric layer with a second wet layer of soft material with a third concentration of the filler material; and placing a second fabric layer with a first side and a second side on the second wet layer of soft material with a first side of the second fabric layer adjacent to the second wet layer. A method, as claimed in claim 10, further comprising the step of adhering the first side of the sheet to the armour with an adhesive with a tensile strength greater than or equal to the first tensile strength.

Inventors: DROTLEFF JAMES E, DROTLEFF, JAMES E.
Applicants: FMC CORP, FMC CORPORATION
Application year: 1993
Main classification: F41H5
IPC codes: F41H5