U.S. patent application number 12/220910 was filed with the patent office on 2012-08-30 for pultruded composite frangible projectile or penetrator.
This patent application is currently assigned to KaZaK Composites, Incorporated. Invention is credited to Stephen C. Ellis, Jerome P. Fanucci.
Application Number | 20120216699 12/220910 |
Document ID | / |
Family ID | 46718117 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120216699 |
Kind Code |
A1 |
Fanucci; Jerome P. ; et
al. |
August 30, 2012 |
Pultruded composite frangible projectile or penetrator
Abstract
A composite penetrator or projectile is formed of a core of
uniaxial tungsten wires embedded in a matrix material. The core may
be overwrapped to improve hoop or radial strength. The core is
mounted in a sabot for use as an ordnance projectile. The
penetrator is frangible and can include a detonatable energetic
resin to provide a self-destruct capability. A pultrusion process
is provided to manufacture the penetrator.
Inventors: |
Fanucci; Jerome P.;
(Lexington, MA) ; Ellis; Stephen C.; (Lexington,
MA) |
Assignee: |
KaZaK Composites,
Incorporated
Woburn
MA
|
Family ID: |
46718117 |
Appl. No.: |
12/220910 |
Filed: |
July 28, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60962037 |
Jul 26, 2007 |
|
|
|
Current U.S.
Class: |
102/473 ;
102/520; 86/52 |
Current CPC
Class: |
F42B 12/207 20130101;
F42B 33/00 20130101; F42B 12/06 20130101; F42B 14/064 20130101;
F42B 12/74 20130101 |
Class at
Publication: |
102/473 ;
102/520; 86/52 |
International
Class: |
F42B 12/20 20060101
F42B012/20; F42B 33/00 20060101 F42B033/00; F42B 14/06 20060101
F42B014/06 |
Claims
1. A composite penetrator comprising: a core comprising tungsten
wires disposed uniaxially, the tungsten wires embedded in a matrix
material, the uniaxial tungsten wires defining a longitudinal
direction of the core; an overwrapping over the core, the
overwrapping comprising a filament winding wound in a hoop
direction around the core at a wind angle of 90.degree. or close to
90.degree. to the longitudinal direction of the core to increase
the transverse strength of the core; and a sabot containing the
core and the overwrapping.
2. The penetrator of claim 1, wherein the matrix material comprises
a detonatable energetic resin.
3. The penetrator of claim 1, further comprising a pusher plate and
a nose cap maintaining the core, a rod disposed through the core,
and a detonatable energetic resin.
4. The penetrator of claim 1, wherein the matrix material comprises
a eutectic alloy.
5. The penetrator of claim 1, wherein the matrix material comprises
a Cerro alloy.
6. The penetrator of claim 1, wherein the matrix material comprises
a Woods metal.
7. The penetrator of claim 1, wherein the matrix material comprises
a lead-tin-bismuth alloy or a tin-bismuth alloy.
8. The penetrator of claim 1, wherein the overwrapping is comprised
of boron fibers.
9. The penetrator of claim 1, wherein the overwrapping is comprised
of graphite fibers.
10. The penetrator of claim 1, further comprising boron fibers
disposed uniaxially with the tungsten wires in the core.
11. The penetrator of claim 1, further comprising graphite fibers
disposed uniaxially with the tungsten wires in the core.
12. A method of manufacturing the composite penetrator of claim 1,
comprising: collimating a plurality of tungsten wires through a
forming card in a desired layout; wetting out the collimated
tungsten wires with a matrix material; pulling the tungsten wires
through a pultrusion die for a selected time and at a selected
temperature to form a pultruded length of composite material;
cutting the composite material into segments; and mounting the
segments into sabots.
13. The method of claim 12, further comprising wetting out the
collimated tungsten wires in a bath of resin.
14. The method of claim 13, wherein the resin comprises a
detonatable energetic resin.
15. The method of claim 12, further comprising wetting out the
collimated tungsten wires in a bath of a eutectic alloy.
16. The method of claim 12, further comprising providing an
overwrapping over the tungsten wires.
17. The method of claim 16, wherein the overwrapping is wound over
the pultruded length after exiting the pultrusion die.
18. The method of claim 16, wherein the overwrapping is wound over
the tungsten wires prior to entering the pultrusion die.
19. The penetrator of claim 1, wherein the matrix material
comprises a resinous material.
20. The penetrator of claim 1, wherein the matrix material
comprises a resinous material or a low-melt eutectic alloy.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application No. 60/962,037,
filed Jul. 26, 2007, the disclosure of which is incorporated by
reference herein.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] N/A
BACKGROUND OF THE INVENTION
[0003] Penetrating weapons effectively use projectiles or
penetrators formed of monolithic metal, such as depleted uranium or
tungsten. Depleted uranium (DU) performs well as a penetrator due
to its very high density, relatively low modulus-to-density ratio,
and a shear failure characteristic that tends to cause penetrators
fabricated from DU to be "self-sharpening." The use of DU can,
however, present an environmental hazard. Monolithic tungsten alloy
penetrators are slightly less dense than DU penetrators, with
approximately twice the elastic modulus and four times the
compressive strength. Monolithic tungsten penetrators perform well,
although not as well as DU penetrators.
[0004] Rapid fire gun systems have been designed as point defense
weapons, for example, to protect Navy ships against high speed
anti-ship missiles, by destroying incoming rounds prior to impact.
These systems rely on very high rates of fire combined with
automatic adjustment of the aim point based on projectile
trajectory tracking to maximize the probability that at least one
projectile will hit an incoming missile. Such projectiles rely on
kinetic energy to ensure target destruction, so extremely dense
monolithic penetrator materials such as depleted uranium or
tungsten are used to maximize lethality.
[0005] Because this strategy relies on a high rate of fire, a
significant number of projectiles miss the target. This creates a
potential for collateral damage and casualties from the projectiles
that miss the target when used, for example, in urban or heavily
populated areas. One approach for reducing collateral damage is to
use projectiles with integral self-destruct mechanisms. This
approach currently precludes the use of kinetic energy penetrators,
however, because the monolithic metal penetrator remains lethal for
personnel throughout the projectile flight path. Another
alternative is to use a much less lethal high explosive round with
a self-destruct mechanism. However, the effectiveness in destroying
an incoming missile is lowered. Also, composite or axially
reinforced penetrators have not generally been found to be
effective at surviving centrifugal forces generated in rifled gun
systems.
SUMMARY OF THE INVENTION
[0006] A composite projectile or penetrator is provided that is
formed of unidirectional tungsten or other wires embedded in a
matrix material. Tungsten wires are a readily available commodity.
The matrix material constituents preferably can be processed at
relatively low temperatures. Suitable low temperature matrix
constituents can be epoxy or other polymer resins or low melting
point eutectic alloys. Unidirectional composite penetrators can be
over-wrapped with graphite or other fibers to provide improved
hoop-radial strength, which improves the penetrator's capability in
rifled gun systems.
[0007] In one aspect, a composite projectile is provided that
includes a self-destruct mechanism that reduces or eliminates the
potential for collateral damage while retaining the ability to
successfully destroy targets. The self-destruct mechanism breaks
the penetrator into small, non-lethal elements with a lower kinetic
energy that minimizes the potential for collateral damage or
injury.
[0008] A cost-effective automated pultrusion manufacturing process
in combination with commodity components provides a simpler, lower
cost production process than current monolithic metal
processing.
DESCRIPTION OF THE DRAWINGS
[0009] The invention will be more fully understood by reference to
the following detailed description of the invention in conjunction
with the drawings, of which:
[0010] FIG. 1 illustrates an embodiment of a composite material
penetrator according to the present invention;
[0011] FIG. 2 illustrates the penetrator of FIG. 2 mounted in a
sabot;
[0012] FIG. 3A is an isometric view of a frangible self-destruct
penetrator according to the present invention;
[0013] FIG. 3B is a cross-sectional view of the penetrator of FIG.
3A;
[0014] FIG. 3C is an exploded view of the penetrator of FIG.
3A;
[0015] FIG. 4A is one embodiment of a wire bundle layout for a
self-destruct penetrator of the present invention;
[0016] FIG. 4B is a further embodiment of a wire bundle layout for
a self-destruct penetrator of the present invention;
[0017] FIG. 5 is a schematic illustration of a pultrusion process
for the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The disclosure of U.S. Provisional Application No.
60/962,037 is incorporated by reference herein.
[0019] A composite material penetrator 10 or projectile 12 are
illustrated in FIGS. 1 and 2. The composite penetrator is formed of
multiple unidirectional strands of wire 14, preferably tungsten,
embedded in a matrix material 16 that binds the wires together. An
overwrapping 18 is preferably provided around the wire-matrix
composite. The composite penetrator forms a core which can be held
within a sabot 22 of any desired design, as known in the art. See
FIG. 2. Any suitable projectile configuration may be employed.
[0020] The unidirectional wires are preferably tungsten or
substantially tungsten, as tungsten is generally effective in
ordnance projectiles, and tungsten wire is a commodity readily
available for light bulbs. Boron, graphite, or other fibers or
wires can be added in both the longitudinal direction and the
hoop-bias direction (as the overwrapping) to improve
weight-specific bending strength and rigidity of the
penetrator.
[0021] The matrix material may be an epoxy resin or other polymer
or a metal. In one embodiment, the matrix material is an energetic
polymer resin, as would be known in the art, to provide a
self-destruct mechanism, discussed further below. Suitable
energetic resins are known in the art. Strength characteristics are
best provided by a plastic matrix material having a large strain to
failure ratio and good adhesion to the tungsten or other wires. The
class of soft metals known as Cerro alloys or Woods metals
possesses these attributes as well as superior density and modulus
compared with polymer matrix materials. Other suitable matrix
materials may include low temperature melting eutectic alloys, such
as lead-tin-bismuth or tin-bismuth alloys. These alloys have
melting temperatures in a range (approximately 200-400.degree. F.)
similar to the cure temperatures for epoxy and other polymers, so
they are suitable for low temperature processing. If necessary, the
surface of the tungsten wires can be suitably prepared to improve
the wetting of the metal matrix material and bonding to the wires,
to minimize wire pullout.
[0022] The radial/hoop strength is important for penetrators
launched by rifled gun systems (e.g., spin-stabilized projectiles).
Spin-stabilized projectiles are often launched at rotational speeds
in excess of 100,000 rpm, leading to hoop and radial stresses often
well in excess of 5000 psi. While the applied rotational stresses
vary widely with the particular ordnance application, they can
easily exceed the transverse strength capability of unidirectional
composite materials having a resinous or low-melt eutectic alloy
matrix. Thus, the resistance of spin stabilized projectiles to the
centrifugal-load-induced stresses is an important consideration for
composite penetrators. In one embodiment, radial/hoop strength can
be improved by an overwrapping of graphite, boron, or other fibers,
discussed further below.
[0023] The particular size and configuration of the core of the
composite penetrator is based on target effect, post self-destruct
lethality (if present), and load requirements. Specific
considerations include wire diameters; wire lay-up pattern;
penetrator size; external elements including sabot, pusher plate
and nose cap (described below); firing loads; target impact induced
loads; and projectile dynamic stability during flight. The design
must meet lethality requirements both before and after the
self-destruct mechanism function as well as all aerodynamic and
dynamic flight stability requirements.
[0024] Other considerations relevant to penetrator design include
selection of materials and configuration so that the penetrator
exhibits sufficiently high hardness and compressive strength and
high density. Additionally, a reasonably large value of transverse
strain to failure is desirable to ensure a stable penetration.
Sleeving or otherwise improving penetrator bending rigidity and
strength is also desirable, especially on a weight-specific basis.
The use of boron fiber in addition to the tungsten wires can be
helpful in this regard, as it provides a higher modulus (58 Msi)
and lower density (2.2 g/cc) compared to tungsten (59 Msi and 19.65
g/cc).
[0025] In one embodiment, a composite kinetic energy penetrator
includes multiple unidirectional strands of tungsten wire embedded
in an energetic polymeric resin to provide a self-destruct
mechanism that breaks the penetrator into small individual wire
elements that fall to the ground with significantly lower potential
for damage or injury than a more conventional monolithic
penetrator. These segments rapidly bleed off energy as they become
unstable and tumble. The inclusion of a sufficient amount of
energetic resin to support self-destruction introduces a trade-off
between optimum wire packing for self-destruction versus maximum
weight and density of the penetrator.
[0026] FIGS. 3A-3C illustrate an embodiment of a frangible
self-destruct projectile 26 in which a core bundle 32 of pultruded
wires embedded in a matrix material is shown with a pusher plate 34
and a central rod 36 supporting an energetic material insert 38
inside a light-weight nose fairing or cap 42. The pusher plate
assists in maintaining penetrator integrity during firing, and the
nose cap is provided for both penetrator integrity and ballistic
performance. After a pre-determined, chemically triggered time, the
energetic material detonates, in any suitable manner, as would be
known in the art. Detonation splits the nose fairing and drives the
rod backwards to split the wires apart, while also splitting the
pusher plate. During a target impact, the energetic material is
designed to resist detonation until the penetrator has almost or
fully penetrated the target. This results in another mechanism
(beside the impact impulse) to destroy the target safely above the
ground. After self-destruction, the individual pieces have a lesser
kinetic energy (KE), so that they do not cause inappropriate damage
upon impact with the ground.
[0027] An embodiment of a layout of a composite wire bundle 52 is
illustrated in FIG. 4A, in which an energetic resin 54 binds the
wires 56 together. This embodiment imposes a minimum gap size
between wires to allow sufficient resin for effective self-destruct
functioning, which may limit the overall density.
[0028] A further embodiment of a layout of a composite wire bundle
62 is illustrated in FIG. 4B. In this embodiment, the energetic
material is concentrated by utilizing a pultrusion process
(discussed below) to leave out individual wires to create a larger
space between the wires 66. The penetrator is pultruded with a
placeholder material in place of selected wires. The placeholder is
then removed, for example, by heating or chemical action, leaving
passage(s) for the self-destruct pyrotechnic material 64 to be
placed.
[0029] A composite penetrator can be built up from tungsten or
other wires, and possibly other structural fiber such as carbon or
glass, in a pultrusion process, which is well suited to low cost,
high volume production. An automated low temperature process such
as pultrusion coupled with low cost, commodity components such as
tungsten wire suitable for light bulbs provides a simpler
production process that makes tungsten projectiles much more cost
effectively than current technology for making large diameter
monolithic tungsten rods.
[0030] Pultrusion processing is capable of automating the
manufacture of cost-effective constant cross section parts with
little labor cost. A composite design, optimized for pultrusion
production, can reduce the cost of the system components to a
minimum, approaching raw material cost, for sufficiently large
production runs. The process is illustrated schematically in FIG.
5, in this case using an injection system to impregnate a fiber
preform with resin. In the pultrusion process, reinforcing
materials in the form of dry unidirectional fibers, cloth,
multi-axial stitch bonded materials, braided pre-forms and
specially-produced 2-D and 3-D reinforced materials are
continuously pulled from spools or woven using in-line winders and
braiders prior to being passed through an optional preheating
furnace.
[0031] Preheating serves to dry the materials and improves resin
wet-out. The collation of dry reinforcing material then passes
through forming cards before entering a heated steel die. Tungsten
wires or rods should be properly collimated before entering the
die, as they are not sufficiently flexible to redistribute
themselves once in the die or upstream guides. Similarly, the wires
should be packed as tightly as possible with no or little free
space to prevent shifting and crossover of wires in the die. One or
more forming cards or guide plates include holes drilled for each
individual wire in the appropriate wire pattern to collimate the
wires. The die compresses the material into the final geometry.
Resin is applied to the preform, either by pulling it through a
wet-bath or by directly injecting liquid matrix into the die. The
wet fiber/resin assembly is then cured as it moves through the
heated portion of the die. The resin inside the die is exposed to
the appropriate temperature and pressure conditions required to
achieve a nearly complete cure before the material exits the
downstream end of the tool.
[0032] The epoxy resin can be filled with a fine kaolin clay to
raise the viscosity to a paste-like or near paste-like consistency.
The increased viscosity helps to prevent loss of resin from between
the wires, maintain a resin film between wire contact points, and
minimize shrinkage and microcracking. A mold release agent can be
used when the resin contacts the die surface, such as on outer
carbon fibers.
[0033] Line speed and temperature can be regulated to obtain the
desired cure properties and overall composite properties. A set of
hydraulic gripping plates alternately grab and pull the material
through the system at a constant speed. Tractor-puller systems are
also used for simpler part geometries.
[0034] The composite core can be overwrapped, for example, with
graphite or other fibers, for greater transverse strength and to
provide a desired outer diameter, either before or after passage
through the pultrusion die. For example, a pultruded length of core
can be wet filament wound with a yarn of carbon fiber at a suitable
wind angle, preferably as close to 90.degree. (hoop direction) as
practical. The same resin used for pultrusion of the core can be
used for the filament winding. The pultruded core surface can be
lightly sanded and solvent wiped prior to winding. Any suitable
number of layers of the overwrapping fiber can be wound. The part
is then wrapped with shrink film and cured at a suitable
temperature. After removal of the shrink wrap, the part can be
lightly sanded to removed ridges left by the shrink film and to
bring the diameter down to the correct size to fit the sabot. The
resulting overwrapped composite wire bundle is cut into pieces of
the desired length. The wire bundle segments are mounted in sabots
of the desired caliber. If the segments are intended for
self-destruct projectiles, the other components for the
self-destruction mechanism (as discussed above) are assembled with
the segments. A more aerodynamic shape and better stability of the
projectile can be provided using suitable components, for more
effective penetration into the various missile threats if
desired.
[0035] The composite tungsten wire penetrator can also be made by
batch processes, such as pressure casting.
[0036] Hybrid penetrators can also be provided that combine
composite materials with metal, such as steel. For example, the
penetrator can be longitudinally segmented such that some portion
of the wall thickness of a metal penetrator is replaced with a
composite material to improve compression strength and modulus.
[0037] The present frangible projectile is advantageous for several
reasons. Its use reduces the likelihood that expended projectiles
fall to earth and injure unintended victims or damage building and
equipment that were not specifically targeted. Also, the composite
projectile eliminates or reduces difficult and expensive processing
required to manufacture a monolithic tungsten penetrator, replacing
it with a readily available, low cost material that retains the
ability to penetrate armored targets.
[0038] The design of the penetrator allows for a weight of 55-75%
of that of a monolithic penetrator, depending on wire size and
materials used, while providing a simple means for breaking the
penetrator into fragments that are significantly less lethal.
[0039] The projectile is useful for military application, civilian
law enforcement agencies, and hunters who use high power
rifles.
[0040] The invention is not to be limited by what has been
particularly shown and described, except as indicated by the
appended claims.
* * * * *