Note: Descriptions are shown in the official language in which they were submitted.
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MULTILAYER ARMOR SYSTEM FOR DEFENDING AGAINST MISSILE-BORNE
AND STATIONARY SHAPED CHARGES
DESCRIPTION OF THE INVENTION
Related Applications
[001] Priority is claimed to U.S. Provisional Applications No. 61/006,600,
filed January 23, 2008; No. 61/006,601, filed January 23, 2008; No.
61/006,643,
filed January 24, 2008; No. 61/006,649, filed January 25, 2008; and No.
61/064,234, filed February 22, 2008, the disclosures of each of which being
incorporated by reference.
Field of the Invention
[002] 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
[003] 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.
[004] 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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[005] 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.
[006] 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.
[007] 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.
[008] 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.
[009] 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
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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.
[010] 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. 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.
[011 ] 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.
[012] 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.
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[013] 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.
[014] 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.
[015] 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.
[016] 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
[017] 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.
[018] 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
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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.
[019] 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 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.
[020] 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
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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.
[021] 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.
[022] 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.
[023] 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
[024] 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;
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[025] 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;
[026] 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;
[027] 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;
[028] Figure 5 is a schematic cross-sectional view of a second embodiment
of the disclosed armor system shown in relation to a vehicle hull;
[029] 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;
[030] 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;
[031] Figure 8 is a schematic top view of an outer portion of a fifth
embodiment of the disclosed armor system; and
[032] Figure 9 is a photograph of a vehicle that includes conventional slat
armor.
DESCRIPTION OF THE DISCLOSED EMBODIMENTS
[033] 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.
[034] 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
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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.
[035] 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.
[036] 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.
[037] 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
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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.
[038] 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 10 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 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.
[039] 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
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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.
[040] 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.
[041] 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 d1 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.
[042] 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
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welded or otherwise bonded together at the crossing points to resist
enlargement of
the mesh openings by the RPG 7 conical section.
[043] 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.
[044] 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.
[045] 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
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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.
[046] 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, 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.
[047] 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.
[048] 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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[049] 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.
[050] Another preferred fiber-reinforced material consists essentially of a
composite made of high molecular weight polypropylene. In such a product, tape
yarn 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.
[051] 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
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".
[052] 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
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angle (e.g. about 70 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).
[053] 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.
[054] 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.
[055] 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.
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[056] 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 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.
[057] 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-H 113, 5050 H 116, 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.
[058] 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 certain applications ductile metals having high fracture toughness may be
used
and referred to as a "metal armor layer."
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[059] 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
mm may be used.
[060] 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 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.
[061] 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
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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.
[062] 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), 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.
[063] 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 Oxelosund, 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,
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SSAB Armox 400 (a product of SSAB Oxelosund of Oxelosund, Sweden), or an
armor meeting U.S. MIL-A-46100 can be used.
[064] 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
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.
[065] 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.
[066] 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.
[067] 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 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-
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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.
[068] 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.
[069] 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 as those for net layer 50 in the
embodiments shown in Figs. 1-5, as the respective net layers have essentially
the
same functions.
[070] 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.
[071] 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
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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.
[072] 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.
[073] 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 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.
[074] 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.
[075] 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
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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 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.
[076] 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.
[077] 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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