IL115397A - Light-weight compact armor panel - Google Patents

Description

A LIGHT-WEIGHT COMPACT ARMOR PANEL WD l DID* VIWO The present invention relates to a light-weight, compact armor panel.

More particularly, the invention is concerned with providing a panel giving protection to mobile equipment and vehicles against fire-arm projectiles.

Mobile military equipment has long been provided with protective armor. Said armor usually comprises a thick layer of alloy steel which is intended to provide protection against the blast and fragmentation from projectiles. Due to its weight, such armor is unsuitable for light vehicles such as automobiles, jeeps, light boats, or aircraft whose performance is unacceptably compromised by steel panels of more than a few millimeters thickness.

Armor for light vehicles is expected to prevent penetration of fire-arm bullets of various types, and prevent perforation of fragments and blast hazards in case an explosive charge detonates near the vehicle.

The maximum armor weight which is acceptable for use on light vehicles varies with the type of vehicle, but generally falls in the range of 16 to 100 kilogram per square meter depending on the protection level required, vehicle type and limitations, cost/performance of armor, etc..

A second consideration is cost; overly complex arrangements, particularly those depending entirely on synthetic fibers, can be responsible for a notable proportion of the total vehicle cost and make manufacture of the whole vehicle non-acceptable.

A third consideration in armor design is compactness. A thick armor panel, including air spaces between its various layers, increases installation costs and sometimes it is impossible to install due to the vehicle's space limitations. In the case of civilian retrofitted armored automobiles which are outfitted with internal armor, there is no room for a thick panel in most areas requiring protection.

A large number of armor systems are described in U.S. Patents, fairly recent examples being Patent 4,836,084, disclosing an armor plate composite, including a supporting plate consisting of an open honeycomb structure of aluminium, and Patent 4,868,040, disclosing an antiballistic composite armor, including a shock-absorbing layer. Also of interest is U.S. Patent 4,529,640, disclosing spaced armor, including a hexagonal honeuycomb core member.

It has long been known that a spaced deflector unit, which acts to tilt an incoming projectile before contact with the main armor, will enable said armor to receive a impact/hit from the side of the projectile instead of its nosetip and thus prevent penetration. Spacing of the deflector unit is required outside the main armor to allow time and space for tilting of the projectile; such spacing is typically in the range of 5 to 30 centimeters.

Accordingly, several systems have been developed using either a series of outer sloping plates, or plates which include various patterns of voids, spaced outside the main armor. Such voids typically comprise a series of holes, ridges or slots (i.e. the German patent DE 9421063 Ul) .

On impact, projectile yaw is achieved due to the statistical improbability of contact being made in the precise centre of one of the voids or of one of the connectors between the voids. In advanced systems, voids are non-symmetrical with projectile shape, providing asymmetrical resistance when perforated.

Systems using this tilting principle are made in France and Germany, and in Israel by Rafael (TOGA Protection System) , TAAS and Urdan Industries, as well as the P-900 by USA/ARL (formerly BRL) .

The inherent disadvantages of the described systems are easily understood. The external deflector units must be attached and supported on spacers, which increase the cost and weight of the system. The large volume of the armor system inhibits its use on some types of vehicle, particularly on small road vehicles. These systems are unsuitable for submarines due to high skin-friction drag, and even more unsuitable for aircraft. A thick armor increases the likelihood of a vehicle becoming visible and a target to a hostile force, as vehicle internal dimensions must be maintained for crew, cargo and machinery function and the thicker armor therefor expands vehicle external dimensions . _4- 115,397/2 It is therefore one of the objects of the present invention to obviate the disadvantage of the prior-art armor and to provide a compact armor panel which is effective against fire-arm projectiles, yet is of light weight and low bulk.

A further object of the invention is the provision of an armor panel which can be used on vehicles requiring a limited volume armor kit.

Thus, according to the present invention there is provided a light-weight compact armored panel, comprising an outer layer made of at least one sheet of hard metal, an intermediate, projectile-deflection layer, adjacent to said outer layer and comprising a surface including voided spaces and a protective backing layer, which panel, when impacted by an incoming projectile, reduces the kinetic energy of said projectile during penetration of said outer layer and the formation of a sheared mass therefrom, said voided spaces causing tilting of said sheared mass, extended contact between said sheared mass and projectile and axial misalignment between said projectile and said mass, further kinetic energy being absorbed in said sheared mass during said extended contact and in said intermediate layer, during which extended contact said projectile is increasingly misaligned as a result of the forces imparted thereto by said sheared mass, following which said inner layer is impacted by the misaligned projectile after displacement and separation from said sheared mass and absorbs by deflection the remaining kinetic energy of said misaligned projectile and said sheared mass.

In a preferred embodiment of the present invention there is provided a steel composite armored panel wherein said intermediate deflection layer is made of a hard aluminium alloy, or of a hard plastic composite material, and said protective backing or inner layer comprises a thick layer of a tough woven textile material such as multiple layers of evlar .

In especially preferred embodiments of the present invention said intermediate deflection layer is constructed of an array of tubes, bars or rods, or of silica plates.

As will become clear from the description, and particularly with referenced to FIGS. 4a-4d, the novel armor of the present invention absorbs projectile kinetic energy by a combination of shear and various deflection modes. In contradistinction to prior-art armor, the armor of the present invention makes use of the sheared mass or plug produced when the outer layer is penetrated, and uses said mass or plug to wedge against the side of the projectile, thereby increasing the armor area being deflected and thus enabling the inner layer to arrest both items in an effective manner. Misalignment of the projectile and shear plug causes lateral local deflection of the intermediate layer, this being a desirable mode of energy absorption. While in prior-art armor the generated shear plug may enter the vehicle interior and cause damage therein, in the present invention said shear plug is utilized as part of the projectile arresting mechanism.

The projectile interacts for an extended period with the hard layer material (even after the first hard layer failed and was sheared by the entering projectile) , and in case of non- AP bullets, it adds significant projectile erosion, and thus adds to the target's significant resistance.

The intermediate layer is also designed to permit proper backing to the frontal hard layer to increase resistance by extending the time of its operation before failure occurs and also by providing further support and resistance to counter the bulging thereof.

Preferably, said intermediate projectile-deflection layer is formed of punched, drilled, slotted or grooved plates and induces extensive asymmetric loads on the projectile, directly and/or through the sheared mass of the frontal layer in order to tilt and rotate the same.

Alternately, said layer can be formed from a non-homogenous structure such as an array of bars and/or tubes arranged in several forms (horizontal or vertical) .

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings: FIG. 1 is a perspective, fragmented view of a preferred embodiment of the armor panel according to the invention; FIGS. 2a, 2b, and 2c are elevational views, and 2d is a sectional view of four embodiments of voided spaces in an intermediate, projectile-deflection layer of the armor panel ; FIG. 3 is an elevational view of an intermediate projectile-deflection layer constructed of an array of rods; and FIGS. 4a, 4b, 4c and 4d are sectional views showing a bullet impacting and being arrested by the armor panel of the present invention (four stages of the penetration process) , and FIGS. 5 and 6 are fragmented perspective views of further embodiments of intermediate projectile-deflection layers constructed of an array of short cylinders.

There is seen in FIG. 1 a light-weight compact armored panel 10, made of three layers 12, 14, 16. Layer thicknesses are determined by considering the protection level required (threat specifications) , the likely kinetic energy of the projectile, its type, and weight restraints applying to the vehicle requiring protection.

An outer layer 12 is made of a sheet of hard metal, preferably a tough, heat-treated steel. Ultraservice low-carbon Alloy Steels, such as ASTM A543 and ASTM A579, ultra high hardness steel (UHH) like MARS 300R or ARMOX 600S, hardened alloy tool steels such as SAE 2842 hardened to 58-63 Rc, and also high hardness (HHS) armor steels like the MARS 240 , steel of CLI in France, or steel 500S to 560S of SSAB in Sweden, are examples of suitable steels for this application. Many additional high hardness steels have been developed for use as armor and are suitable for the outer layer 12.

An intermediate backing layer which serves as projectile-deflection layer 14, is directly adjacent to the outer layer 12, and can, for convenience, be attached thereto. It is also possible to attach layer 14 to 12 through a few layers of fiberglass or aramid, or a thin, aluminum layer (all of those less than 1mm. thick) .

The layer 14 comprises a surface including voided spaces 18, which are shown in the prsent embodiment as an array of punched-through holes. Details of preferred hole spacing are given with reference to FIG 2a.

Suitable materials for the intermediate deflection layer 14 include ceramics, metals or hard composites.

Particularly preferred for use on vehicles where low weight and low price are important is a hard aluminium alloy, for example, aluminium alloy 7075 T6, which in its 2 hard cold-worked state has a shear strength of 3200 kg/cm .

A titanium alloy, such as ΤΪ-155Α (alpha-beta) will provide enhanced performance, and its cost can be justified for some aircraft applications.

A ceramic layer (i.e. Silica Sand type) will also perform well.

Adjacent to the intermediate layer 14 is an inner backing layer 16 comprising a thick multi-ply, tough blanket of a tough woven textile material.

Suitable fiber materials are fiberglass, S2 glass, R R R R Kevlar /Twaron polyethelyne-Spectra , Dynima or Famostone .

Particularly preferred is a tough blanket composed of multiple layers of Kevlar ^™^ , made by Du Pont De Nemours, hot pressed with plastic resin.

EXAMPLE Armor designed to resist bullets fired at close range by M16, AK-47 and M14 rifles.

Outer Layer Armor steel, 4-5 mm. thick, steel type Mars (TM) ' , manufacturer CLI, France.

Intermediate Layer Aluminium alloy 7075-T6, thickness 5-8 mm.

Voids: 5 mm. circular, through-punched apertures, 8-10 mm. centre to centre spacing.

Inner Layer 10-20 layers Kevlar ^™^ type 3000 fibers.

Total Weight; 48-58 kg/sq. meter.

Referring now to FIGS. 2a, 2b, 2c, and 2d, there are seen four embodiments of plates 20, 22, 24, 26 provided with voided spaces for use in an intermediate, projectile-deflection layer of the armor panel, providing punch resistance due to its asymmetrical configuration.

In the following description and/or in the figures similar parts are designated by similar numerals.

FIG.2a shows a plate 20 with the voids 18 referred to in EXAMPLE 1, 5 mm. dia, through-going holes, 8 mm. centre to centre. Circular voids achieve lowest production costs, particularly when the metal is perforated by a piercing die; the punched-out stock can sometimes be utilized for other purposes. Small quantities can be produced by drilling, lazer cutting or water jet cutting machines.

FIG.2b depicts a plate 22 having shaped-hole through-going apertures 28, also produced by a piercing die, or laser/water jet cutting machines. Aperture length/width ratio is about 2, and metal width between apertures is 0.5 -0.9 of aperture width.

Seen in FIG. 2c is a plate 24 provided with rounded-end through-going slot voids 30, also produced by a piercing die, or laser/water jet cutting machines. Slot length is about 3-10 times slot width, metal between slots is 0.5-0.9 slot width.

Long parallel grooves 32 are seen in the plate 26 FIG. 2d, alternate round-bottom grooves 32 being positioned on each surface 34, 36 of the plate 26. Groove centre to centre distance, combining grooves on the two sides, is between 1.3 to 2 times groove width. Groove depth is about half the material thickness. Small quantities are produced by milling, large quantities by hot forging.

FIG. 3 shows an intermediate projectile-deflection layer 38 constructed of an array of tough rods 40. The spaces 42 between the rods 40 act as voids. In the embodiment shown the rods 40 are made of a metallic or ceramic material and two rod tiers 44, 46, oriented at 90° to each other, are held in place by an epoxy 48 or other plastic resin.

FIGS. 4a, 4b, 4c and 4d are sectional views showing succeeding stages of a bullet projectile 50 impacting and being arrested by the armor panel 10 of the present invention. While the precise modes of energy dispersion will vary slightly according to the relationship between the projectile flight axis and the void axis, the following description represents a typical chain of events occurring in use of the current invention.

The panel 10 is impacted by an incoming projectile 50 in FIG. 4a. Projectile kinetic energy is reduced, being absorbed in the dynamic plastic penetration, bulging and succession shearing action taking place in the hard outer layer 12. The sheared, truncated cone or disk-like mass 52 advances to contact the intermediate layer 14 , which in this embodiment is made of a tough material having some ductility, such as an aluminium alloy.

A void 54 in the intermediate layer 14, whose centre in this example lies below the centre of projectile impact, allows a first portion 56 of the shear disk 52 to advance, while a second portion 58 of the shear disk 52 is retarded by contact with solid material 60 at the side of the void 54. The disk 52 consequently moves in a down-sloping path in the example shown.

In FIG. 4b the projectile nosetip 62 is now misaligned relative to the centre of the sheared disk 52, which slopes further downward, being driven to enter an available void 54. Energy is absorbed by deformation of the sheared disk 52 which is being rammed into the intermediate layer 14 and plastic deformation of 14. The projectile 50 is therefore slowed and tilted down.

In FIG. 4c a side 64 of the projectile nose 62 is rammed against the sheared disk 52, which suffers further deformation itself and is now driven substantially downwards to further deform the intermediate layer 14; further energy is absorbed thereby. The projectile 50 is now seen tilted upwards, and it is also starting to deform the intermediate layer 14 on an upper side 66 of the void 54 opposite to that being deformed by the sheared disk 52. The projectile 50 is now wedged between the side 66 and the sheared disk 52.

FIG. 4d shows the projectile 50 after having caused severe deformation of the void upper side wall 66, which now cushions impact against the inner layer 16 and causes deflection thereof. Further energy has been absorbed as the body of the projectile 50 has increasingly deformed the sheared disk 52 and also an edge 68 of the aperture 70 formed by piercing the outer layer 12.

By combination of the various energy absorption mechanisms described, by tilting and misaligning the projectile 50 and by the enlarged contact areas 72, 74 causing deformation of the inner layer 16, the projectile 50 is safely halted inside the compact armor panel 10 described.

Seen in FIG. 5 is a further embodiment of an intermediate deflection layer 76, which here is constructed of an array of short solid cylinders 78. Those shown in the figure are held with the cylinder axis perpendicular to the major face of the layer, in a matrix 80 constructed of a strong and rigid resin such as epoxy, phenolic polycarbonate, polyurethane, or polyester. The cylinders 78 are suitably made either of a hard metal alloy of aluminium or of titanium, or of a ceramic material. Cylinder diameter is typically in the range of 4 to 12 m"m. Centre to centre cylinder spacing is between 1 to 1.5 of cylinder diameter.

The intermediate deflection layer 82 seen in FIG. 6 is similar to the layer 76 except that the cylinders are thick-wall hollow cylinders 84, i.e. made of tough aluminum alloy or Kevlar , having an outer diameter in the range 6 to 16 mm. The matrix 80 material is, for weight-reduction purposes, excluded from entering the hollow cylinder cores 86; this can be achieved by filling the cores 86 before casting with a disposable material such as a light plastic foam or a wax which can later be removed by moderate heating of the completed layer 82 or by its immersion in a suitable solvent.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as schematic illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. o

Claims (11)

-15- 115,397/3 WHAT IS CLAIMED IS:

1. . A light-weight compact armored panel, comprising: a) an outer layer made of at least one sheet of hard metal; b) an intermediate, projectile-deflection layer, adjacent to said outer layer and comprising a surface including voided spaces; and c) a protective backing layer; which panel, when impacted by an incoming projectile, reduces the kinetic energy of said projectile during penetration of said outer layer and the formation of a sheared mass therefrom, said voided spaces causing tilting of said sheared mass, extended contact between said sheared mass and projectile and axial misalignment between said projectile and said mass, further kinetic energy being absorbed in said sheared mass during said extended contact and in said intermediate layer, during which extended contact said projectile is increasingly misaligned as a result of the forces .imparted thereto by said sheared mass, following which said ianer layer is impacted by the misaligned projectile after displacement and separation from said sheared mass and absorbs by deflection the remaining kinetic energy of said misaligned projectile and said sheared mass.

2. The armored panel as claimed in claim 1 , wherein said outer layer comprises heat-treated steel.

3. The armored panel as claimed in claim 1 , wherein said intermediate layer is formed of punched, drilled, slotted or grooved plates.

4. The armored panel as claimed in claim 1 , wherein said intermediate deflection layer is made of a ceramic material. -16- 115,397/2

5. The armored panel as claimed in claim 1, wherein said intermediate deflection layer is made of a metal.

6. The armored panel as claimed in claim 1 , wherein said intermediate deflection layer is made of hard aluminum metal alloys.

7. The armored panel as claimed in claim 1 , wherein said intermediate deflection layer is made of a hard, plastic composite.

8. The armored panel as claimed in claim 1 , wherein said intermediate deflection layer is constructed of silica plates.

9. The armored panel as claimed in claim 1 , wherein said intermediate deflection layer is constructed of an array of tubes, bars or rods.

10. The armored panel as claimed in claim 1 , wherein said protective backing layer comprises a thick layer of a tough woven textile material.

11. The armored panel as claimed in claim 1 , wherein said protective backing layer is made of multiple layers of Kevlar ™. For the Applicant WOLFF, BREGMAN AND GOLLER