Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02746403 2011-07-15
Attorney Docket No.: 10036.0029-0000
MULTILAYER ARMOR SYSTEM FOR DEFENDING AGAINST MISSILE-BORNE AND
STATIONARY SHAPED CHARGES
DESCRIPTION OF THE INVENTION
Field of the Invention
[001] The present invention relates to an armor system that is resistant to
penetration by high energy solid projectiles and jets of material from hollow
charge
weapons such as rocket propelled grenades ("RPG's") and stationary shaped
charger.
Background of the Invention
[002] Conventional armor such as for protecting vehicles is subjected to a
variety of projectiles designed to defeat the armor by either penetrating the
armor with a
solid or jet-like object or by inducing shock waves in the armor that are
reflected in a
manner to cause spalling of the armor such that an opening is formed and the
penetrator (usually stuck to a portion of the armor) passes through, or an
inner layer of
the armor spalls and is projected at high velocity without physical
penetration of the
armor.
[003] Some anti-armor weapons are propelled to the outer surface of the armor
where a shaped charge is exploded to form a generally linear "jet" of metal
that will
penetrate solid armor; these are often called Hollow Charge (HC) weapons. A
second
type of anti-armor weapon uses a linear, heavy metal penetrator projected at
high
velocity to penetrate the armor. This type of weapon is referred to as EFP
(explosive
formed projectile), or SFF (self forming fragment), or a "pie charge," or
sometimes a
"plate charge."
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[004] In some of these weapons the warhead behaves as a hybrid of the HC
and the EFP and produces a series of metal penetrators projected in line
towards the
target. Such a weapon will be referred to herein as a Hybrid warhead. Hybrid
warheads behave according to how much "jetting" or HC effect it has and how
much of
a single big penetrator-like an EFP it produces.
[005] Various projection systems are effective at defeating HC jets. Among
different systems the best known are reactive armors that use explosives in
the
protection layers that detonate on being hit to break up most of the HC jet
before it
penetrates the target. The problem is that these explosive systems are poor at
defeating EFP or Hybrid systems.
[006] Another type of anti-armor weapon propels a relatively large, heavy,
generally ball-shaped solid projectile (or a series of multiple projectiles)
at high velocity.
When the ball-shaped metal projectile(s) hits the armor the impact indices
shock waves
that reflect in a manner such that a plug-like portion of the armor is sheared
from the
surrounding material and is projected along the path of the metal
projectile(s), with the
metal projectile(s) attached thereto. Such an occurrence can, obviously, have
very
significant detrimental effects on the systems and personnel within a vehicle
having its
armor defeated in such a manner.
[007] While the HC type weapons involve design features and materials that
dictate they be manufactured by an entity having technical expertise, the
later type of
weapons (EFP and Hybrid) can be constructed from materials readily available
in a
combat area. For that reason, and the fact such weapons are effective, has
proved
troublesome to vehicles using conventional armor.
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[008] The penetration performance for the three mentioned types of warheads is
normally described as the ability to penetrate a solid amount of RHA (Rolled
Homogeneous Armor) steel armor. Performances typical for the weapon types are:
HC
warheads may penetrate 1 to 3 ft thickness of RHA, EFP warheads may penetrate
1 to
6 inches of RHA, and Hybrids warheads may penetrate 2 to 12 inches thick RHA.
These estimates are based on the warheads weighing less than 15 lbs and fired
at their
best respective optimum stand off distances. The diameter of the holes made
through
the first inch of RHA would be; HC up to an inch diameter hole, EFP up to a 9
inch
diameter hole, and Hybrids somewhere in between. The best respective optimum
stand
off distances for the different charges are: standoff distances for an HC
charge is good
under 3 feet but at 10 ft or more it is very poor; for an EFP charge a stand
off distance
up to 30 feet produces almost the same (good) penetration and will only fall
off
significantly at very large distances like 50 yards; and for Hybrid charges
penetration is
good at standoff distances up to 10 ft but after 20 feet penetration starts
falling off
significantly. The way these charges are used are determined by these stand
off
distances and the manner in which their effectiveness is optimized (e.g., the
angles of
the trajectory of the penetrator to the armor). These factors effect the
design of the
protection armor.
[009] Conventional armor is subjected to a variety of projectiles designed to
defeat the armor by penetrating the armor. Some anti-armor weapons are
propelled to
the outer surface of the armor where a shaped charge is exploded to form a
generally
linear "jet" of metal that will penetrate solid armor. Such weapons are often
called
Hollow Charge (HC) weapons. A rocket propelled grenade ("RPG") is such a
weapon.
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An RPG 7 is a Russian origin weapon that produces a penetrating metal jet, the
tip of
which hits the target at about 8000m/s. When encountering jets at such
velocities solid
metal armors behave more like liquids than solids. Irrespective of their
strength, they
are displaced radially and the jet penetrates the armor.
[010] Various protection systems are effective at defeating HC jets. Among
different systems the best known are reactive armors that use explosives in
the
projection layers that detonate on being hit to break up most of the HC jet
before it
penetrates the target. Also known are "bulging armor" components which upon
impact
by the jet, distort into the jet path to deflect or break up the jet to some
extent. Both
such systems are often augmented by what is termed "slat armor," a plurality
of metal
slats or bars disposed outside the body of the vehicle to prevent the firing
circuit for an
RPG from functioning.
[011] Also, as recently disclosed by the Foster-Miller company as part of its
RPG Net (TM) Defense Systems, a net suspended alongside and spaced from the
surface of an armored vehicle can act to disrupt RPGs by breaking and/or
defeating the
RPGs. These nets are reported to be able to crush the foreword conical surface
of the
RPG 7 to render the fuze inoperative and thereby prevent detonation and shaped
charge formation in a significant percentage of RPG 7 impacts.
[012] While any anti-armor projectile can be defeated by metal armor of
sufficient strength and thickness, extra metal armor thickness is heavy and
expensive,
adds weight to any armored vehicle using it which, in turn, places greater
strain on the
vehicle engine, and drive train.
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[013] Armor solutions that offer a weight advantage against these types of
weapons can be measured in how much weight of RHA it saves when compared with
the RHA needed to stop a particular weapon penetrating. This advantage can be
calculated as a protection ratio, the ratio being equal to the weight of RHA
required to
stop the weapon penetrating, divided by the weight of the proposed armor
system that
will stop the same weapon. Such weights are calculated per unit frontal area
presented
in the direction of the anticipated trajectory of the weapon.
[014] Thus, there exists a need for an armor system that can defeat
projectiles
and jets from anti-armor devices, particularly rocket propelled grenades,
without
requiring an excess thickness of metal armor. Preferably, such an armor system
would
be made of materials that can be readily fabricated and incorporated into a
vehicle
design at a reasonable cost, and even more preferably, can be added to
existing
vehicles.
[015] As the threats against armored vehicles increase and become more
diverse, combinations of armor systems are needed to defeat the various
threats. An
armor system that raises the protection level of an armored vehicle to include
HC
charges, both missile-borne and stationary, is described.
SUMMARY OF THE INVENTION
[016] Additional objects and advantages of the invention will be set forth in
part
in the description which follows, and in part will be obvious from the
description, or may
be learned by practice of the invention. Some or all of the objects and
advantages of
the invention will be realized and attained by means of the elements and
combinations
particularly pointed out in the appended claims.
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[0171 In accordance with a first aspect of the present invention, there is
disclosed an armor system for defeating missile-borne and stationary shaped
charges
directed against a vehicle, the missile having a forward conical component and
a tip-
mounted electric fuze, the vehicle having a hull with outer and inner
surfaces. The
armor system includes a grid layer located outside of, and spaced away from,
the outer
surface of the armored vehicle, the grid layer having grid members separated
one from
the other a distance disposed to engage and disrupt the electrical firing
mechanism of
the tip-mounted fuze. The armor system further includes a shaped layer having
plurality
of tapered members formed of a fiber-reinforced material between the grid
layer and the
outer surface of the vehicle defining depressions configured to receive the
forward
conical portion of an unexploded missile and to attenuate a high velocity jet
emanating
from an exploded missile and/or a stationary shaped charge.
[0181 In accordance with a second aspect of the present invention, there is
disclosed an armor system for defeating a rocket propelled grenade directed at
a
vehicle, the vehicle having a hull with outer and inner surfaces, the rocket
propelled
grenade of the type having a forward conical section and a tip-mounted
piezoelectric
fuze component. The armor system includes a net layer having a plurality of
cord
members spaced from the outer surface of the vehicle by support members, and a
shaped layer having plurality of tapered members formed from a fiber-
reinforced
material and a layer of fiber-reinforced material abutting the base ends of
the tapered
members. The tapered members are positioned between the net layer and the
vehicle
outer surface and have respective apex ends proximate the net layer and
opposite base
ends, the tapered members defining with adjacent tapered members a plurality
of
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depressions opening in a direction away from the vehicle outer surface. A mesh
size of
the net layer is selected to allow passage of the fuze component and to engage
and
deform the conical section of the missile to short-circuit the fuze component.
The armor
system further includes bulging-type reactive elements disposed on surfaces of
the
tapered members defining the depressions.
[019] In accordance with a third aspect of the present invention, there is
disclosed a method of defeating missile-borne and stationary shaped charges
directed
at a vehicle, the missile of the type having a conical forward portion,
relative to its
trajectory, and a tip-mounted electric fuze component, the vehicle having a
hull with an
outer surface. The method includes the steps of interposing a grid layer
comprised of a
net or spaced bar/slat configuration in the missile trajectory spaced from the
outer
surface of a vehicle, the grid layer having a grid mesh size to engage the
conical section
to short circuit the fuze on a missile not detonating on the grid layer;
interposing a
shaped fiber-reinforced material layer downstream of the grid layer relative
to the
trajectory, the shaped fiber-reinforced layer having depressions therein and
bulging
armor with metal plates disposed on the surfaces forming the depressions, the
depressions configured such that a jet formed by a missile detonating on the
grid layer
next encounters the bulging armor and the shaped layer material; moving the
metal
plates of the bulging armor obliquely into the path of the jet by a reaction
of the
impinging jet; deflecting the jet with the metal plates moved into its path;
and attenuating
the deflected jet in the fiber-reinforced materials of the shaped layer.
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[020] Preferably, the armor systems also include one or more metal layers
and/or one or more additional fiber-reinforced material layers disposed
between the
shaped fiber-reinforced material layer and the vehicle outer surface.
[021] In embodiments of the invention the fiber in the fiber-reinforced
material
may consist essentially of a material selected from the group consisting of:
poly-
paraphenylene terephthalamide, stretch-oriented high density polyethylene,
stretch-
oriented high density polypropylene, stretch-oriented high density polyester,
a polymer
based on pyridobisimidazole, and silicate glass. Presently preferred
embodiments of
the invention include fiber-reinforced materials having high density stretch-
oriented
polypropylene fibers consolidated by heat and pressure in a lower density
polypropylene polymer.
[022] The accompanying drawings, which are incorporated in and constitute a
part of this specification, illustrate several embodiments of the invention
and together
with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[023] Figure 1 is a schematic, cross-sectional view of an outer portion of a
first
embodiment of the disclosed armor system illustrating the configuration of the
depressions in shaped layer formed by tapered members of a fiber-reinforced
material
downstream of a section of a net layer supported by "slat" armor, relative to
a trajectory
of a missile or jet;
[024] Figure 2 is a schematic, cross-sectional view depicting performance of
the
armor system outer portion shown in Fig. 1, with incident RPG-type missile
warheads
having conventional piezoelectric fuzes;
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[025] Figure 3 is a schematic, cross-sectional view depicting performance of
the
armor system outer portion shown in Fig. 1, with an incident RPG warhead
having a
counter-measure fuze;
[026] Figure 4 is a schematic, cross-sectional view of the entire first
embodiment of the disclosed armor system of Fig. 1, shown in relation to a
vehicle hull;
[027] Figure 5 is a schematic cross-sectional view of a second embodiment of
the disclosed armor system shown in relation to a vehicle hull;
[028] Figure 6 is a schematic cross-sectional view of a third embodiment of
the
disclosed armor system where slat armor constitutes the grid layer and wherein
fiber-
reinforced material layers and layers of sheet metal armor are disposed behind
the
shaped layer;
[029] Figure 7 is a schematic cross-sectional view of the outer portion of a
fourth
embodiment where the slat armor constitutes the grid layer and wherein
multiple layers
of metal armor separated by dispersion spaces are disposed behind the shaped
layer;
[030] Figure 8 is a schematic top view of an outer portion of a fifth
embodiment
of the disclosed armor system; and
[031] Figure 9 is a photograph of a vehicle that includes conventional slat
armor.
DESCRIPTION OF THE DISCLOSED EMBODIMENTS
[032] Reference will now be made in detail to embodiments of the invention,
examples of which are illustrated in the accompanying drawings. Wherever
possible,
the same reference numbers will be used throughout the drawings to refer to
the same
or like parts.
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[033] In accordance with the invention, there is provided an armor system for
defeating a range of anti-armor weapons. While the invention and its
embodiments may
impede penetration of relatively non-elongated, heavy, solid metal projectiles
formed
and propelled by either manufactured explosive devices or improvised explosive
device,
its primary utility is to defeat devices generating elongated metal "jets,"
produced by
shaped charges whether missile borne or stationary, along with the heavy solid
projectiles.
[034] The parameters of the system can be selected to defeat a particular
projectile if its weight, density, velocity, and size are known. The
parameters of the
system are the mechanical properties (ultimate tensile strength, hardness,
elastic
modulus, fracture toughness, and velocity of forced shock) of the layers of
material
comprising the layers of the invention, the spacing of the layers (the
distance between
layers, i.e. the thickness of the dispersion space) and the nature of any
materials placed
in the space between the layers.
[035] Where the system contains a layer of fibrous material it attenuates the
energy of the penetrating material by resisting the enlargement of an opening
therein by
virtue of the extremely high tensile strengths of the fibers comprising the
fibrous sheet.
Even if penetrated by an elongated penetrator, the initial opening resists
enlargement
and exerts high shear forces on the lateral surfaces of the elongated
penetrator. This
slows the penetrator and reduces the energy in the penetrator. This increases
the
probability that the next layer in the armor system will either defeat the
penetrator, or
further slow the penetrator such that layers of the system that will encounter
the
penetrator may have a better chance of defeating it.
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[036] In accordance with an aspect the present invention there may be provided
a plurality of rigid members located outside of and spaced from the outer
surface of a
vehicle. An array of rigid members configured as slats elongated in the
direction
parallel to a vehicle surface that are suitable for use in the armor system is
conventionally called "slat armor," and a vehicle using such armor is depicted
in Fig. 9.
In a first aspect of the present invention, the "slat armor" is used as a
support for the
net-type grid layer to be discussed henceforth in relation to Figures 1-5.
However, in
another aspect of the present invention to be discussed later in relation for
Figures 6
and 7, the "slat armor" can itself comprise the grid layer, to be used in
conjunction with
the shaped layer of fiber-reinforced tapered members, and preferably with
other armor
layers, between the grid layer and the vehicle hull outer surface. The present
invention
thus improves the performance of existing types of slat armor and provides a
layered
armor system which includes tapered members of a fiber-reinforced material
configured
in a shaped layer, and which may further include reactive armor elements (all
to be
discussed hereinafter), integrated with the slat armor.
[037] As depicted schematically in Figs. 1 and 2, the slats 10 are elongated
members separated one from the other along their length by a distance d1, and
spaced
a distance d2 from the outer surface 46a of vehicle hull 46. The individual
slats 10,
which typically are formed from mild steel and have cross-sectional dimensions
of about
mm x 50 mm, could be replaced by elongated bars of a rectangular or round
cross-
section, but slats may be preferred as they have a better stiffness to weight
ratio for the
same material and cross sectional dimension. As shown in Fig. 2 the distance
d1
between each adjacent slat 10 may be configured to allow the tip 12 of forward
conical
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section 13 of a missile such as RPG 7 to pass between the slats 10. The fuze
mechanism of certain types of RPGs such as the RPG 7 includes a piezoelectric
element 16 located at tip 12 that generates an electric pulse that is
conducted to the
rearwardly located fuze component (not shown) through the conical portion 13
of the
RPG. When the conical section 13 of the RPG is crushed or deformed by the
slats 10,
the electric pulse generated by the piezoelectric element of the firing
mechanism is
electrically short-circuited or otherwise prevented from reaching the rear
fuze
component, and the RPG warhead (the shaped charge that creates the jet) does
not
detonate.
[038] Approximately 60% of the RPG 7s having piezoelectric fuze components
that impact conventional slat armor (e.g. as shown in Fig. 9) do not detonate
because
the tip and fuze pass between two adjacent slats which "pinch" or crush the
trailing
conical section and disrupt the firing circuit. If the slats are too close,
the probability of
the RPG detonating on a slat increases, and if the slats are too far apart the
RPG round
will pass between the slats without being short circuited and detonate on the
armor
surface. Slat-slat spacings of about 68 mm have typically been used in
conventional
slat armor systems, but the spacing may be substantially increased in the
presently
disclosed system due to the net-type grid layer to be discussed below. The
remaining
40% of the RPG rounds hit a slat and detonate. In most conventional slat armor
systems the space behind the slats that must accommodate the length of the
conical
portion and tip-mounted fuze component without activating the fuze, is empty.
Typically
the slats are supported from the vehicle by side support members (see Fig. 9)
to
achieve a stand-off distance of about 275 mm.
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[039] In accordance with the invention, a layer of netting is positioned in
front of
and covering the rigid members. The net layer may be configured to be
supported by
the rigid members against deflection toward the vehicle surface. Conventional
mechanical fasteners may be used for attaching the net to the rigid member
supports, to
provide both axial (toward the vehicle body surface) as well as lateral
(parallel to the
body surface) restraints on the net.
[040] An embodied herein, and as depicted schematically in Figs. 1-5, layer 50
of a net material is positioned to cover, and be supported by, slats 10. The
net layer is
intended to provide essentially the same function as the conventional slat
armor, that is,
to laterally crush or otherwise deform the conical tip portion of an RPG to
disable and/or
short circuit the fuze, the mesh or grid size of net 50 may be made smaller
than the
spacing between the rigid members, namely slats 10 in Figs. 1-5. Moreover, the
mesh
size may be selected in view of the dimensions of the RPG type(s) expected in
the
battle theater. It is presently contemplated that mesh sizes of about 1" - 3"
may be
useful, with the smaller mesh sizes used with existing slat armor (slat-slat
spacing of
about 68 mm). The larger mesh sizes may be useful when the rigid members are
spaced apart by distances d, greater than conventional separation distances,
that is,
when the rigid members are intended to provide primarily a support function
for net 50,
and not provide a back-up intercept and crush function. Also, conventional
mechanical
fasteners (pins, bolts/washers, rivets, screws/washers, etc.) may be used to
attach net
layer 50 to the rigid member supports, and may allow the net layer component
to be
readily replaced if different RPG types with different conical tip sizes are
encountered or
the net is damaged.
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[041] The net layer 50 may be formed from high strength, low stretch material
such as Zytel , a nylon material available from DuPont. Other net materials
may be
used including metal mesh fabricated from e.g., conventional braided steel
cable of
about 1/8" diameter. The higher weights for metal-based nets may be
acceptable,
because a metal mesh may be more durable and less prone to cutting. In either
case,
the crossing strands of the net material may be welded or otherwise bonded
together at
the crossing points to resist enlargement of the mesh openings by the RPG 7
conical
section.
[042] In accordance with the invention, a shaped layer comprising tapered
members formed from a fiber-reinforced material are placed between the rigid
members
and the outer surface of the vehicle. The adjacent tapered members define
cavities or
depressions configured to receive the forward conical portion of a rocket
propelled
grenade before fuze contact can occur. As here embodied and depicted in Figs.
1 and
2, the system includes shaped layer 18 having tapered members 20 with sides
20c
defining depressions 22 disposed to receive the conical section 13 of the RPG
7
including tip 12 with fuze component 16. In Fig. 1, tapered members are
configured in a
wedge-shape and aligned with a respective slat 10 in a direction generally
perpendicular to the vehicle surface, each with an apex 20a abutting a rear
edge 24 of
slat 10. However, armor system configurations having some tapered members 20
not
aligned with a respective rigid member are specifically contemplated. See
discussion of
the embodiment in Fig. 8, below. In such configurations, all the tapered
members and
resulting depressions would nevertheless be covered by the net layer.
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[043] If an RPG round hits a slat 10 and detonates, the fiber-reinforced
material
in the shaped layer 18 behind the slat attenuates the jet and increases the
probability
that the total armor system, including metal layers and fiber-reinforced
material layers to
be discussed hereinafter, will survive the challenge of the jet and the
vehicle receiving
the RPG hit will not be breached, or the severity of the breach will be
significantly
reduced.
[044] The length dimensions of tapered members 20 may be conservatively set
to receive the full length of conical portion 13 of the specific RPG type of
concern
(typically 8 inches for an RPG 7). Also, the bases 20b of adjacent tapered
members 20
may be separated as depicted in Fig. 1 to accommodate the width of a forward-
mounted
RPF fuze element, without contact with sides 20c such as about 20 mm, the
diameter of
the piezoelectric fuze component in RPG 7s. However, if the net layer 50 is
configured
with a mesh size less than the rigid member spacing (i.e., the spacing between
slats 10
in Fig. 1), the length dimensions of tapered members 20 may be reduced, as
crushing
(and fuze disablement) engagement of conical section 13 by the net layer may
occur at
a location closer to tip 12. This reduction in tapered member length may
result in a
more "compact" armor system, or the ability to use more or thicker layers of
fiber-
reinforced material and/or sheet type metal armor between the tapered members
20
and the vehicle hull 46, as discussed in more detail below.
[045] It is believed that the fiber-reinforced material of shaped layer 18
attenuates the energy of the penetrating jet following impact on a slat (see
Fig. 2, lower
portion) by resisting the enlargement of an opening therein by virtue of the
extremely
high tensile strengths of the fibers comprising the fibrous material. Even if
penetrated,
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the initial opening resists enlargement and exerts high shear forces on the
lateral
surfaces of the penetrating jet material. This increases the probability that
subsequent
layers in the armor system will either defeat the jet before it engages the
vehicle hull, or
slow it such that layers interior to the hull that will encounter the jet may
have a better
chance of defeating it.
[046] The fiber-reinforced material may be comprised of a plurality of fibers
having an ultimate tensile strength greater than 2.5 GPa bonded to form the
sheet by a
polymer surrounding the fibers. Without being bound by theory, it is believed
that any
jet of material penetrating the fibrous layer must separate the fibers
laterally and hence
apply a tensile load on the fibers. When the fibers are sufficiently strong
(have a high
tensile strength), the material surrounding the jet constricts the jet and
slows it
substantially. Because the jet defeats armor by the inertia of an elongated
(explosive
formed) molten metal penetrator, the reduction of the velocity of the jet
significantly
reduces its effectiveness. Hence, due to jet attenuation by the tapered member
20
formed of such fiber-reinforced material the subsequent layers in the armor
system of
the present invention can more readily defeat the jet.
[047] Recent developments in fiber technology have created fibers having
tensile strengths in relatively light materials that are in excess of 3GPa. In
a preferred
embodiment, the fiber in the fiber-reinforced sheet armor consists essentially
of a
material selected from the group consisting of: poly-paraphenylene
terephthalamide,
stretch-oriented high density polyethylene, stretch-oriented high density
polypropylene,
stretch-oriented high density polyester, a polymer based on pyridobisimidzole,
and
silicate glass.
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[048] Preferably the fiber-reinforced material consists essentially of stretch-
oriented, high molecular weight polyethylenes, especially linear
polyethylenes, having
an ultrahigh molecular weight of 600,000 to 6,000,000 g/mol and higher. Such
fibers
are bound together such as with a polymer matrix by heat and pressure to form
a sheet-
like product with polymeric matrix materials, for example thermosetting resins
such as
phenolic resins, epoxy resins, vinyl ester resins, polyester resins, acrylate
resins and
the like, or polar thermoplastic matrix materials such as polymethyl
(meth)acrylate. A
particularly preferred fiber-reinforced sheet armor of this type is known
commercially as
Dyneema , a product of DSM Dyneema, Mauritslaan 49, Urmond, P.O. Box 1163,
6160
BD Geleen, the Netherlands.
[049] Another preferred fiber-reinforced material consists essentially of a
composite made of high molecular weight polypropylene. In such a product, tape
yam
of high molecular weight stretch-oriented polypropylene is woven into a
fabric. Multiple
layers of fabric are stacked and consolidated with heat and pressure to form
rigid sheets
using low molecular weight polypropylene as a matrix. A particularly preferred
fiber-
reinforced sheet armor made of this type material is known commercially as
Tegris , a
product of Milliken & Company, 920 Milliken Road, P.O. Box 1926, Spartansburg,
South
Carolina, 29303 USA. Such a material is described in U.S. Patent 7,300,691 to
Callaway et al., the content of which is specifically incorporated by
reference herein.
[050] Preferably, shaped layer 18 includes at least one continuous sheet of
the
fiber-reinforced material abutting the bases of the tapered members. As here
embodied, and as depicted in Figs. 1-5, sheet 30 of fiber-reinforced material
abuts
bases 20b of tapered members 20. Sheet 30 may consist essentially of the same
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material as that used in the tapered members 20. The fiber-reinforced
materials
disclosed to be used in the tapered members 20 can be used in sheet 30 and
those
materials provide similar benefits with respect to impeding projectiles and
jets as are
provided when used in tapered members 20. The thickness of fiber-reinforced
material
sheet 30 in the embodiments in Figs. 1-5 may be about 3".
[051] The wedge-shaped tapered members 20 depicted in Fig. 1 may be formed
from stacked layers of sheets of the fiber-reinforced material. The
cavities/depressions
22 can be formed by stacking different width sheets cut at an angle (e.g.
about 7 in the
Fig. 1 embodiment). While the embodiment depicted shows fiber-reinforced
material
sheets laminated to form tapered members 20 and a sheet-like layer of fiber-
reinforced
material 30 abutted thereto, these elements alternatively may be combined into
a
unitary shaped layer with depressions 22 and no interface between the members
forming the depressions (shown here as 20) and the rear portion (shown here as
sheet
30).
[0521 Because multi-layer armor embodiments for protecting against EFP
penetrators work better against slower penetrators (e.g. about 2000m/s or
less) than
against faster penetrators like about 2500m/s and above, lower density
materials can be
used to slow the penetrator rather than metallic layers with spacings towards
the rear of
the assemblies, where those materials and spacings work better e.g. such as in
the
embodiment depicted in Fig. 7 and also in Fig. 4, Fig. 5, and Fig. 6. Suitable
"tough"
(high elongation of fracture) titanium alloys may be used for the metal armor
layers of
the present invention, as well.
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[053] Still further in accordance with the present invention, the armor system
may include reactive elements positioned on the surfaces of the adjacent
tapered
elements that form the depressions. As embodied herein, and with reference
again to
Fig. 1, reactive elements 60 are positioned on the side surfaces 20c of
tapered
members 20. Each element 60 is a "bulging armor" type reactive element, which
may
comprise a layer of a rubber material sandwiched between two metal plates as
depicted
in Fig. 1. The plates may be mild steel plates each of about 2 mm in
thickness, and the
rubber layer about 1 mm in thickness. Alternatively, explosive reactive armor
elements
(not shown) may be substituted for "bulging armor" elements 60. See U.S.
4,368,660 to
Held, the disclosure which is hereby incorporated by reference, for a
discussion of the
principles of such reactive elements.
[054] The purpose of the reactive elements is to deflect the metal plates into
the
trajectory of a HC jet upon impact by the jet, and thus break up and/or
attenuate the jet.
It is believed that the bulging occurs due to the shockwave reflections at the
steel plate-
rubber layer interface, as depicted by the heavy dashed lines in Fig. 3. The
deflected
plates act to disperse trailing portions of the jet and thus increase the
chance that the
remainder of the armor system can defeat the (smaller) lead portion of the
jet.
[055] As one skilled in the art would appreciate, stationary HC devices would
be
detonated and the high speed molten metal jet formed away from the armor
system,
which jet would then be incident on or between the net strands of net layer 50
or the
slats 10, which may have little effect in deflecting the jet from its original
trajectory or
attenuating the jet. Moreover, even optimum performance of net layer 50 and
rigid
members such as slats 10 would not disable all RPGs before detonation and jet
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formation. Also, the percentage of RPGs not disabled before detonation may
also
increase over the 30% - 40% values characteristic of RPGs with piezoelectric-
based
fuzes, when RPGs with "countermeasure fuzes" as depicted in Fig. 3 are being
used.
These latter RPGs may detonate upon encountering the webbing in layer net 50
at
locations offset from the slats 10 and generate a high yield jet. This jet may
be
deflected and/or attenuated by reactive elements 60 and then further
attenuated by the
fiber-reinforced material in tapered members 20. The reactive elements 60 thus
provide
further protection to compensate for the diminished length of fiber reinforced
material at
locations away from slat 10.
[056] It may also be preferred to provide in the armor system of the present
invention, one or more sheet-like layers of metal armor between the shaped
layer of
fiber-reinforced material and the vehicle hull, to provide increased
protection against
solid projectiles accompanying the HC jets, such as in hybrid shaped charges.
As here
embodied and depicted in Fig. 4, there is provided a layer of aluminum armor
plate 32
abutting the rear surface 34 of the first layer of fiber-reinforced material
sheet 30.
Preferably, the aluminum plate consists essentially of an aluminum alloy
having an
elongation at fracture of at least 7% and more preferably 10%. Examples of
preferred
aluminum alloys include: 7017, 7178-T6, 7039 T-64, 7079-T6, 7075-T6 and T651,
5083-
0, 5083-Hl 13, 5050 H116, and 6061-T6. It is preferred that the aluminum plate
have a
thickness in the range of from 8 to 40 millimeters, and in the Fig. 4
embodiment a
thickness of about 25 mm may be used.
[057] As used herein, the term armor in connection with a metal plate does not
restrict the metal plate to metals and alloys that are known as armor
materials. In
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certain applications ductile metals having high fracture toughness may be used
and
referred to as a "metal armor layer."
[058] It may also be preferred to provided a steel plate between the first
aluminum plate and the hull, with the steel plate abutting the rear surface of
the first
aluminum plate. As here embodied and depicted in Fig. 4, there is provided a
layer of
steel plate 36 abutting the rear surface 38 of aluminum armor plate layer 32.
Preferably, the steel plate has an elongation at fracture of at least 7% and
more
preferably 10%. The steel can be SSAB Weldox 700; SSAB Armox 500T (products of
SSAB Oxelosund of Oxelosund, Sweden); ROQ-TUF, ROQ-TUF AM700 (products of
Mittal Steel, East Chicago, Indiana, USA); ASTM A517; and steels that meet
U.S.
Military specification MIL-46100. Steels normally used for the construction of
boilers
like A517, A514 and other steels having similar yield strengths and elongation
to break
comparable to ROQ-tuf and Weldox 700 may also be used. It is preferred that
the steel
armor plate layer have a thickness in the range of from 5 to 20 millimeters,
and in the
Fig. 4 embodiment a thickness of about 10 mm may be used.
[059] It may be further preferred to include an additional sheet-like layer of
fiber-
reinforced material between the steel armor layer and the hull, with the
additional fiber-
reinforced material layer abutting the rear surface of the steel armor layer.
As here
embodied and depicted in Fig. 4, there is provided a sheet-like layer 40 of
fiber-
reinforced material abutting steel layer 36. The sheet-like layer of fiber-
reinforced
material 40 may consist essentially of the same material as that used in the
fiber-
reinforced components 20 and 30. Whether or not the material of components 40,
20
and 30 are the same, the materials disclosed to be used in the fiber-
reinforced
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components 20 and 30 can be used in the second sheet-like layer 40 and those
materials provide similar benefits with respect to impeding projectiles and
jets as are
provided when used in components 20 and 30. The thickness of the fiber-
reinforced
material layer 40 may be about 3" in the Fig. 4 embodiment.
[060] It may also be preferred to provide a second sheet-like layer of
aluminum
armor plate between the steel armor plate layer and the hull. The second sheet-
like
layer of aluminum plate abuts the rear surface of the additional sheet-like
layer of fiber-
reinforced material. As here embodied and depicted in Fig. 4, second layer 42
of
aluminum armor plate abuts rear surface 44 of the additional or second layer
40 of fiber-
reinforced material and also abuts the outside surface 46a of hull 46.
Preferably, the
aluminum plate consists essentially of an aluminum alloy having an elongation
at
fracture of at least 7% and more preferably 10% and can be a material selected
from
the alloys disclosed above for use in the aluminum plate 32. For the Fig 4
embodiment,
an aluminum plate thickness of about 25 mm can be used for layer 42.
[061] Alternatively, the armor system can include, between the first sheet-
like
layer of aluminum armor plate and the hull, an additional or second sheet-like
layer of
fiber-reinforced material directly abutting the first aluminum armor plate
layer, a second
sheet-like layer of aluminum plate abutting the second sheet-like layer of
fiber-
reinforced material, a third sheet-like layer of fiber-reinforced material
abutting the
second aluminum armor plate layer, and a third sheet-like layer of aluminum
armor plate
abutting the third fiber-reinforced material layer. As embodied herein, and
with
reference to Fig. 5, second fiber-reinforced material layer 40 directly abuts
first
aluminum plate layer 32 (i.e., without a steel plate as in the Fig. 4
embodiment),
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followed by second aluminum armor plate layer 42, third fiber-reinforced
material layer
80, and third aluminum armor plate layer 82. Aluminum plate layer 82 may
directly abut
hull 46 and may be formed of the same material as aluminum plate layers 32 and
42,
and have similar functions. Similarly, fiber-reinforced material layer 80 may
be formed
of the same material as layers 30 and 40, and tapered elements 20, and have
similar
functions. Also, layer 80 in the Fig. 5 embodiment may be about 3" thick.
[062] It may also be preferred that the hull of the vehicle be formed of sheet-
like
armor metal for each of the embodiments shown in Figs. 4 and 5. The material
used to
form the hull may be at least two different sheet materials. The hull of the
vehicle, a
portion of which is depicted in Fig. 4 as element 46 may be formed of a tough
sheet
material. As used herein the word "tough" is a material that resists the
propagation of a
crack there though, generally referred to as a material that has a high
fracture
toughness. When a tough sheet material is used for the hull it is preferred to
use steel
known as "ROQ-tuf AM700 (a product of Mittal Steel, East Chicago, Indiana).
Another
material known as SSAB Weldox 700 (a product of SSAB Oxelosund of Oxeli sund,
Sweden) can also be used. Steels normally used for the construction of boilers
like
A517, A514 and other steels having similar yield strengths and elongation to
break
comparable to ROQ-tuf and Weldox 700 may also be used. Where the hull is to be
of
high strength armor plate, SSAB Armox 400 (a product of SSAB Oxelosund of
Oxelosund, Sweden), or an armor meeting U.S. MIL-A-46100 can be used.
[063] It may also be preferred to provide a third sheet-like layer of fiber-
reinforced material inside the hull, to attenuate the velocity of any
projectile and jet
fragments penetrating the hull. As here embodied and depicted in Fig. 4, there
is
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provided a sheet-like layer of fiber-reinforced material 48 abutting the inner
surface 46b
of the hull 46. Preferably, the sheet-like layer of fiber-reinforced material
48 may consist
essentially of the same material as the material used in the fiber-reinforced
components
20, 30, and 40. Whether or not the material of elements 20, 30, 40, and 42 are
the
same, the materials disclosed to be used in the fiber-reinforced components
20, 30, and
40 can also be used in the sheet-like layer 48. The primary purpose of the
layer 48,
however, is to stop or attenuate any fragments penetrating the hull so as to
minimize
lethality.
[064] Also, as depicted in Fig. 4, there may be provided a rigid sheet-like
layer
of material consisting essentially of a high strength aramid fiber, e.g.
Kevlar, in a
polymer matrix abutting the rear surface of fiber-reinforced material layer
48. The rigid
layer 70 forms the interior-most layer of the overall armor system of the
vehicle. Like
the layer 48, the purpose of layer 70 is to retain any fragments that have
passed
through layer 48 to minimize risk from fragments to those in the vehicle.
[065] One skilled in the art would appreciate that the protective layers
positioned
adjacent the inner surface 46b of hull 46 in Fig. 4 could be used in
conjunction with the
other disclosed embodiments.
[066] As mentioned previously, the array of slats in conventional slat armor,
as
depicted in Fig. 9, without a net layer can serve as the grid layer in the
armor systems of
the present invention. Fig. 6 depicts such an embodiment, which is similar to
that of
Fig. 4 (but without net 50), having essentially the same combination of sheet
metal
armor layers and additional fiber-reinforced material layers between the
shaped layer
and the hull outer surface, as well as fiber-reinforced material layers
adjacent the hull
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inner surface. Fig. 7 depicts an embodiment also utilizing "slat armor" as the
grid layer,
but includes an array of spaced metal armor plates 32, 42 and 82, where the
spaces
between plates 32, 42 and 82 are configured as "dispersion spaces" 90, 92, and
94, as
disclosed in co-pending applications of the present inventor, namely S.N.
11/521,3607
filed September 15, 2006; S.N. 11/713,012 filed March 2, 2007, and S.N.
12/010,268,
filed January 3, 2008. The disclosures in each of these co-pending
applications is
hereby expressly incorporated herein by reference.
[067] As is clear from the above discussion, the armor system of the present
invention can use a grid layer of rigid members configured as elongated slats
or rods,
and thus be readily integrated with conventional slat armor. However, as
mentioned
previously, the present invention is not restricted to the use of slat or rod-
type rigid
members, nor is it restricted to use of a net-type grid layer with support
members
elongated in a direction parallel to the vehicle surface.
[068] For example, Fig. 8 depicts a top view of an armor system having an
array
of post-like support members 110. Each post extends generally perpendicular to
the
vehicle hull surface, and may be mounted, such as by a threaded end post,
directly to
the hull or to an intermediate metal armor layer (both not depicted in Fig. 8,
but see hull
46 and aluminum armor-plate layer 32 in Figs. 4 and 5). Posts 110 may be a
metal
such as structural steel or aluminum and may be of a diameter sufficient to
support net
layer 150, which may be attached to the ends of posts 110 with mechanical
fasteners
(e.g. screw and washer 152), preferably removable. Although the posts 110 are
shown
having a round cross-section, other shapes are contemplated, as are non-metal
structural post materials. Materials and mesh sizes for net layer 150 may be
the same
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as those for net layer 50 in the embodiments shown in Figs. 1-5, as the
respective net
layers have essentially the same functions.
[069] Further provided in the Fig. 8 embodiment, is a shaped layer 118 formed
from pyramid-shaped tapered members 120 constructed of a fiber-reinforced
material
such as the materials identified for tapered members 20 in the embodiments of
Figs. 1-
5. In the Fig. 8 embodiment, each tapered member 120 surrounds a respective
post
110 and has four generally planar, triangular sides extending down to a common
sheet-
like layer 130, which also may be formed from a fiber-reinforced material as
in layers 30
of Figs. 1-5.
[070] As can also be appreciated from Fig. 8, the sides 120c of adjacent
pyramid members 120 form depressions 122 for receiving the leading conical
sections
of RPGs. In this regard, depressions 122 can have the same depth dimension as
the
depth dimension of tapered member 20 in the Fig. 1 - Fig. 5 embodiments. Also,
the
bases 120b of pyramid members 120 can be spaced apart a distance sufficient to
accommodate an RPG fuze component.
[071] Still further, triangular or trapezoidal-shaped bulging armor-type
reactive
elements 160 are disposed on the side surfaces of the pyramid-shaped tapered
members 120. Reactive elements 160 may be of essentially the same construction
and
have the same intended function as reactive elements 60 of the embodiments
depicted
in Figs. 1-5.
[072] It is contemplated that the balance of the armor system for the Fig. 8
embodiment, that is, the portion of the armor system between the fiber-
reinforced sheet
130 and the vehicle hull, would include layers corresponding to the
combinations of
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sheet-like metal armor layers and fiber-reinforced material layers disclosed
in the Fig. 4
and Fig. 5 embodiments between fiber-reinforced sheet 30 and hull 46. It is
further
contemplated that an overall vehicle armor system may include one or more
armor
layers inside the vehicle hull, such as corresponding to layers 48 and 70
disclosed in
Fig. 4.
[073] It is still further contemplated that the rigid support posts 110 need
not be
included in every tapered pyramid member 120. That is, if sufficient tension
can be
provided in net layer 150 using fewer posts 110, such as using only the middle
post 110
in the top and bottom rows and the outside posts in the middle row of the 3x3
pyramid
module, post ends shown darkened in Fig. 8, the chance of RPG impact and
detonation
on the rigid post component of the armor system may be further reduced.
[074] It may be still further preferred to provide portions or all of the
above-
described armor systems as replaceable modules, to facilitate installation and
repair,
including field repair. For example, and with reference to Fig. 4, tapered
members 20,
together with reactive elements 60, fiber-reinforced material sheet 30, and
aluminum
armor plate layer 32 may be configured as a replaceable module 90.
Additionally, the
remaining steel armor layer 36, adjacent fiber-reinforced material layer 40,
and final
aluminum plate layer 42 can be configured as a replaceable module 92. Each of
modules 90 and 92 may be of any convenient size, e.g. 2' x 2', or be sized and
configured geometrically for a particular area on the vehicle hull. Other
modular
configurations for the Fig. 4 embodiment would, of course, occur to the
skilled artisan
given the present disclosure, as well as modular configurations for the
embodiments of
Figs. 1-7. For a Fig. 8 embodiment module, the rigid post elements may be
included if
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mounted on a metal armor plate layer corresponding e.g. to metal armor plates
32, 36,
or 42 in Fig. 4, depending upon the configuration of the module, as one
skilled in the art
would appreciate.
[075] Finally, presently disclosed embodiments as well as the co-pending
applications, namely S.N. 11/521,3607 filed September 15, 2006; S.N. 11/71-012
filed
March 2, 2007 and S.N. 12/010,268 filed January 3, 2008, layered armor
assemblies,
where space allows an advantage gained by angling the armor layers with
respect to
the path of penetration for both HC jets and EFP penetrators, particularly for
the slower
velocity (e.g. be low 2000ms) penetrators.
[076] It will be apparent to those skilled in the art that various
modifications and
variations can be made to the present invention. The present invention
includes
modifications and variations of this invention which fall within the scope of
the following
claims and their equivalents.
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