U.S. patent application number 10/801795 was filed with the patent office on 2004-11-04 for formed metal armor assembly.
Invention is credited to Dickson, Lawrence J..
Application Number | 20040216595 10/801795 |
Document ID | / |
Family ID | 33313348 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040216595 |
Kind Code |
A1 |
Dickson, Lawrence J. |
November 4, 2004 |
Formed metal armor assembly
Abstract
A formed metallic armor assembly is disclosed, wherein a backing
portion is adhered to a durable, formed metallic facing element.
The metallic facing element has a reduced effective density to
reduce the weight of the assembly without reducing the
effectiveness of defeating penetration threats. The backing portion
is selected to have a predetermined thickness to be effective
against predetermined penetration threats.
Inventors: |
Dickson, Lawrence J.;
(Granville, OH) |
Correspondence
Address: |
CALFEE HALTER & GRISWOLD, LLP
800 SUPERIOR AVENUE
SUITE 1400
CLEVELAND
OH
44114
US
|
Family ID: |
33313348 |
Appl. No.: |
10/801795 |
Filed: |
March 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60455292 |
Mar 17, 2003 |
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Current U.S.
Class: |
89/36.02 |
Current CPC
Class: |
F41H 5/0464
20130101 |
Class at
Publication: |
089/036.02 |
International
Class: |
F41H 005/02 |
Claims
I claim:
1. A metallic armor assembly comprising a metallic facing element
formed to have an effective density reduced by at least about 20%
and a backing having at least one layer comprising a fiber
composite substrate.
2. The metallic armor assembly of claim 1, wherein the metallic
facing element comprises a plurality of perforations.
3. The metallic armor assembly of claim 2, wherein at least about
20% of the surface area of the metallic facing element is
perforated.
4. The metallic armor assembly of claim 2, wherein the perforations
have a diameter of between about 3.0 mm and about 3.5 mm.
5. The metallic armor assembly of claim 2, wherein the perforations
have a diameter of between about 3.0 mm and about 3.5 mm and a
spacing of between about 4.0 mm and about 4.5 mm.
6. The metallic armor assembly of claim 2, wherein the perforations
have a diameter less than about 1.2 times a diameter of a core of a
projectile that is to be defeated.
7. The metallic armor assembly of claim 6, wherein the perforations
have a diameter less than about 0.9 times a diameter of a core of a
projectile that is to be defeated.
8. The metallic armor assembly of claim 2, wherein the perforations
are arranged to be spaced apart about between about 4.0 mm and
about 4.5 mm edge-to-edge.
9. The metallic armor assembly of claim 1, wherein the metallic
facing element comprises a plurality of projections.
10. The metallic armor assembly of claim 1, wherein the metallic
facing element comprises a plurality of indentations.
11. The metallic armor assembly of claim 1, wherein the metallic
facing element is corrugated.
12. The metallic armor assembly of claim 1, wherein the metallic
facing element comprises a plurality of perforated metal
plates.
13. The metallic armor assembly of claim 1, wherein the fiber
composite substrate comprises fibers having a diameter, and wherein
the ratio of thickness of at least one layer of the backing to an
equivalent diameter of the fibers is no more than about 20.0.
14. The metallic armor assembly of claim 13, wherein the fiber
composite substrate comprises fibers having a diameter, and wherein
the ratio of thickness of at least one layer of the backing to the
equivalent diameter of the fibers is between about 3.5 and about
10.0.
15. The metallic armor assembly of claim 1, wherein the fiber
composite substrate comprises a plurality of fiber layers.
16. The metallic armor assembly of claim 15, wherein at least two
fiber layers comprise fibers having a longitudinal axis arranged in
a parallel array.
17. The metallic armor assembly of claim 16, wherein the at least
two fiber layers are adjacent and the longitudinal axes of the
fibers are aligned at 90 degree angles with respect to the
longitudinal axes in adjacent layers.
18. The metallic armor assembly of claim 1, wherein the fiber
composite substrate has an areal density of at least about 2.5
pounds per square foot.
19. The metallic armor assembly of claim 1, wherein the fiber
composite substrate has a fiber content of at least about 75% by
weight or by volume.
20. The metallic armor assembly of claim 1, further comprising an
adhesive layer between the metallic facing element and the fiber
composite substrate.
21. The metallic armor assembly of claim 1, further comprising a
protective outer cover.
22. A small arms protective insert to provide a protective barrier
against projectile penetration, comprising a metallic facing
element formed to have an effective density reduced by at least
about 20% and a backing layer comprising a fiber composite
substrate.
23. The small arms protective insert of claim 22, wherein the
metallic facing element comprises a plurality of perforations.
24. An armor plate for use as a small arms protective insert,
comprising: a. at least one metallic facing element having a
thickness between about 0.02 inches and about 0.50 inches, a
hardness no less than 30 on the Rockwell C scale, and at least
about 20% perforated; b. a backing portion comprising a fiber
composite substrate with a thickness between about 0.06 inches and
about 3.00 inches, the substrate having at least one layer
comprising a network of filaments having a tensile modulus of at
least about 150 g/denier, an energy to break of at least about 8
j/g, and a tenacity of at least about 7 g/denier, wherein the ratio
of thickness of at least one substrate layer to an equivalent
diameter of the filaments is no more than about 20.0; c. an
optional adhesive layer between the metallic facing element and the
backing portion, the adhesive layer having a thickness of between
about 0.0005 inches and about 0.090 inches; and d. an optional
protective outer cover for at least a portion of the metallic
facing element or the backing portion.
25. An armor plate, comprising: a. at least one metallic facing
element; b. a backing portion comprising a fiber composite
substrate, the substrate having at least one layer wherein the
ratio of thickness of the layer to an equivalent diameter of the
filaments is no more than about 20.0; wherein a ratio of thickness
of the backing portion to thickness of the metallic facing element
is selected to be effective against a predetermined penetration
threat.
26. The armor plate of claim 25, wherein the ratio of thickness of
the backing portion to thickness of the metallic facing element is
at least about 7.
27. The armor plate of claim 25, wherein the ratio of thickness of
the backing portion to thickness of the metallic facing element is
between about 4 and about 10.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e) of U.S. Provisional Application 60/455,292 filed Mar. 17,
2003, titled FORMED METAL ARMOR ASSEMBLY, which application is
hereby incorporated by reference in its entirety.
BACKGROUND
[0002] The present invention relates to metallic armor and, more
particularly, to a durable, formed metallic armor assembly for
protection against multiple small arms bullets.
[0003] Various materials are used to make armor to protect against
projectile penetration. Historically, metal-based armor was used
for most armor applications. More recently, ceramic-based armor has
been used for body armor, because of weight considerations.
Metallic- or ceramic-based armor is typically used for coverings
for vehicles. For ceramic-based armors, typically tiles of ceramic
are bonded to a substrate and often secured in an outer cover to
form a plate. The plates are then secured to a vehicle, or, in the
case of body armor, placed in a fabric pocket. The plates may be
designed to provide protection against a single penetration threat
or against multiple penetration threats.
[0004] The penetration protection afforded by a particular armor
must be balanced against weight constraints, particularly for body
armor. One manner in which this balance has been achieved is by the
use of relatively thin (less than 0.25 inch) ceramic facings with
composite backing layers. Hard ceramics, such as silicon carbides
or boron carbides, have been found necessary for the facings to
allow weight efficient solutions.
[0005] The use of these ceramics with appropriate backing layer
materials provides protection against multiple penetration threats.
The use of metal plates, while providing protection against some
penetration threats, is often disfavored because of the weight
associated with the metal plates.
[0006] The hard, thin ceramics suffer from brittle fracture and
cracking in use. Cracking of the ceramic facing prior to ballistic
impact can result in ballistic failure of the armor in the field,
an undesirable occurrence.
SUMMARY OF THE INVENTION
[0007] The present invention is an armor assembly with a durable,
formed metallic material facing element combined with a backing
portion to defeat multiple penetration threats at minimal weight
while providing adequate durability for in field use. The formed
metallic facing element preferably has a thickness of between about
0.02 inches and about 0.50 inches, a hardness no less than 30 on
the Rockwell C scale, and the metal is formed in such a way that
its effective density is reduced by at least about 20%.
[0008] The backing portion includes a fiber composite substrate
with a thickness of between about 0.06 inches and about 3.00
inches, the substrate having at least one layer with a network of
filaments having a tensile modulus of at least about 150 g/denier,
an energy to break of at least about 8 j/g, and a tenacity of at
least about 7 g/denier wherein the ratio of the thickness of the
layer to an equivalent diameter of the filaments is no more than
about 20.0.
[0009] There may also be an adhesive layer between the metallic
facing element and the backing portion having a thickness of
between about 0.0005 inches and about 0.090 inches. A protective
outer cover also may be provided.
[0010] An armor assembly in accordance with the present invention
is a durable yet light-weight armor assembly that can sustain
multiple ballistic attacks without failure. The armor assembly may
be used as a stand-alone armor or for use as ballistic inserts in
conjunction with a ballistic vest and affords a new and useful
manner of penetration protection against ballistic attack.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In the accompanying drawings, which are incorporated in and
constitute a part of the specification, embodiments of the
invention are illustrated, which, together with a general
description of the invention given above, and the detailed
description given below, serve to exemplify the embodiments of this
invention.
[0012] FIG. 1 is a perspective view, partially broken away and
partially in section, of one embodiment of an armor assembly in
accordance with the present invention;
[0013] FIG. 2 is a view in partial section of an embodiment of the
present invention taken along line 2-2 of FIG. 1;
[0014] FIG. 3 is a perspective view, partially broken away and
partially in section, of another embodiment of an armor assembly in
accordance with the present invention;
[0015] FIG. 4 is a perspective view of an embodiment of the present
invention; and
[0016] FIG. 5 is a perspective view of an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention is directed to an armor assembly
having at least a formed metallic facing and a fiber composite
substrate backing attached or adjacent thereto. It has been found
that use of a formed metallic facing with the appropriate fiber
composite substrate adjacent thereto provides a weight-efficient
alternative to conventional ceramic-based facings adjacent to a
composite substrate backing. Without intending to be limited by the
description of preferred embodiments herein, the invention will be
described in an exemplary manner as it relates to personal body
armor, such as small arms protective inserts (SAPI).
[0018] Use of the term "metal" herein includes pure metal or
metals, metal alloys, inter-metallic compounds, and mixtures
thereof. Use of the term "ceramic" herein is defined as inorganic,
nonmetallic materials, typically crystalline in nature, and
generally are compounds formed between metallic and nonmetallic
elements, such as aluminum and oxygen (alumina-Al.sub.2O.sub.3),
boron and carbon (boron carbide-B.sub.4C), silicon and carbon
(silicon carbide-SiC), and other analogous oxides, nitrides,
sulfides, and carbides. Use of the term "or" herein is the
inclusive, and not the exclusive, use. See BRYAN A. GARNER, A
DICTIONARY OF MODERN LEGAL USAGE 624 (2d Ed. 1995). Use of the term
"fiber" herein is defined as an elongated body, the length
dimension of which is much greater than the dimensions of width and
thickness. Accordingly, the term fiber as used herein includes a
monofilament elongated body, a multifilament elongated body,
ribbon, strip, and the like having regular or irregular cross
sections. The term fibers includes a plurality of any one or
combination of the above. The "equivalent diameter" of the fibers
is the approximate average of the diameters of individual fibers in
a layer of fibers.
[0019] FIG. 1 illustrates an armor assembly 10 in accordance with
the present invention in which a formed metallic armor assembly 12
includes a metallic facing element 14, an adhesive layer 16, and a
composite fiber substrate/backing 18. The composite fiber
structure/backing 18 may have one or more than one layer.
Preferably, there is more than one layer. The metallic facing
element 14 has a plurality of perforations 20. The assembly may
include an encapsulating cover 22 with or without a rear portion
24, as illustrated in FIG. 2.
[0020] The cover 22 may be constructed of any suitable conventional
material, including nylon fabric, or may be a combination of
materials, such as fabric, rigid plastic, and foam, that protects
the formed metallic armor assembly 12 from wear-and-tear and
provides added durability.
[0021] The formed metallic facing element 14 may be constructed of
any suitable metals, including nickel, manganese, tungsten,
magnesium, titanium, aluminum, copper, brass, bronze, and steel
plate. Illustrative of useful steels are carbon steels which
include mild steels of grades AISI 1005 to AISI 1030, medium-carbon
steels of grades AISI 1030 to AISI 1055, high-carbon steels of the
grades AISI 1060 to AISI 1095, free-machining steels,
low-temperature carbon steels, rail steel, and superplastic steels;
high-speed steels such as tungsten steels, molybdenum steels,
chromium steels, vanadium steels, and cobalt steels; hot-die
steels; low-alloy steels; low-expansion alloys; mold-steel;
nitriding steels for example those composed of low-and
medium-carbon steels in combination with chromium and aluminum, or
nickel, chromium and aluminum; silicon steel such as transformer
steel and silicon-manganese steel; ultra high-strength steels such
as medium-carbon low alloy steels, chromium-molybdenum steel,
chromium-nickel-molybdenum steel, iron-chromium-molybdenum-cobalt
steel, quenched-and-tempered steels, cold-worked high-carbon steel;
and stainless steels such as iron-chromium alloys austenitic
steels, and chromium-nickel austenitic stainless steels, and
chromium-manganese steel.
[0022] Useful materials also include alloys such a manganese
alloys, such as manganese aluminum alloy or manganese bronze alloy;
nickel alloys, such as nickel bronze, nickel cast iron alloy,
nickel-chromium alloys, nickel-chromium steel alloys, nickel copper
alloys, nickel-molybdenum iron alloys, nickel-molybdenum steel
alloys, nickel-silver alloys, or nickel-steel alloys;
iron-chromium-molybdenum-cobalt-steel alloys; magnesium alloys;
aluminum alloys such as those of aluminum alloy 1000 series of
commercially pure aluminum, aluminum-manganese alloys of aluminum
alloy 300 series, aluminum-magnesium-manganese alloys,
aluminum-magnesium alloys, aluminum-copper alloys,
aluminum-silicon-magnesium alloys of 6000 series,
aluminum-copper-chromiu- m of 7000 series, or aluminum casting
alloys; aluminum brass alloys; and aluminum bronze alloys. Most
useful are double hard steels, ballistic armor steels that meet the
specifications set forth in Mil A 46100 and super high hard steels
sold under the trade name Mars 240 and Mars 300 and Mars 300 Nickel
Plus, available from Usinor Industeel. Steels that can be formed
and hardened such as D2, A2, M4, PM-M4, Maximat150, S-5, S-7,
Rex121, T15, M42, 4340, and spring steel are also useful.
[0023] Metals have long been known as good ballistic material,
especially hardened metals. It is known to heat treat metal to
increase its hardness and improve its ballistic performance. The
use of metallic strike faces have been used where cost is
important, but weight is secondary. Where weight is critical,
ceramics, such as boron carbide, silicone carbide, or aluminum
oxide, are used due their excellent performance and low weight.
Historically, materials having the highest hardness to density
ratios have yielded the most weight-efficient ballistic solutions
when used as facing materials. Boron carbide facings are
conventionally used to produce the lightest armor assemblies, with
silicon carbide facings producing slightly heavier assemblies, and
aluminum oxide facings used where ultimate weight is not required
and cost is important. The following table illustrates the
hardness-to-density ratios for typical materials.
1TABLE 1 Hardness-to-Density Ratios Boron Carbide Silicon Carbide
Aluminum Oxide Armor steel Hardness 3200 2300 1600 750 (Vickers)
Density 2.5 3.2 3.98 7.8 (g/cc) Hardness-to- 1280 718 402 96.1
density ratio
[0024] Defeating multiple penetration threats, such as those
defined by the United States military specifications for SAPI
plates, have required the use of both a fiber composite backing and
ceramic facing. Some penetration threats are more readily defeated
by the hard facing and some penetration threats are more readily
defeated by a fiber composite backing.
[0025] Conventionally, boron carbide facings with a composite
backing or silicon carbide facings with a composite backing have
been used to provide the desired multiple penetration protection.
Surprisingly, applicant determined that by reducing the effective
density of a high hardness steel, thereby increasing its
hardness-to-density ratio to between about 120 and about 300, the
steel can be made to perform similarly to boron carbide and silicon
carbide assemblies with ratios of between 700 and 1300. Such
reduction in effective density is realized by perforating the metal
or other geometric forming of the strike face, as discussed in
greater detail below.
[0026] Small arms rounds like the M-80 ball and the LPS ball are
weight efficiently stopped by the use of fibrous backings alone.
The 7.62.times.39 PS ball, the SS-109, the M-80 ball, and the LPS
ball can be defeated at an areal density of 3.8 pounds per square
foot (psf), without the use of a hard facing. To stop the M-855
projectile, however, which contains a hard core, additional
material must be provided, which affects the ability to meet the
5.1 psf weight requirement of the SAPI plate. Testing revealed that
the most currently advanced backings, (e.g., raw material produced
by Honeywell Corporation under the trade name Spectra Shields and
molded at processing pressures of 3000 psi, yielded failures on the
M-855 against the SAPI threats at the 5.1 pound per square foot
areal density.
[0027] Testing the M-855 on a Mars 300 steel facing having a
hardness of Rockwell C 55, adjacent the Spectra Shields fiber
composite backing, yielded the following results:
2TABLE 2 Solid Metal Test Results Facing Backing Result .022 inch
4.1 psf Fail .040 inch 3.36 psf Fail .062 inch 2.45 psf Fail .080
inch 1.72 psf Fail
[0028] Surprisingly, these failures can be reversed by forming the
metal in a way that achieves a reduction in the effective density
or a corresponding increase in metallic thickness for a given
density, such as by perforation of the metal. This increase in
hardness to areal weight (pounds per sq ft) or hardness to
thickness by perforation in combination with sufficient advanced
composite backing yields an armor assembly that can be as weight
effective as boron carbide and silicon carbide ceramics based
assemblies. This increases the specific hardness, or
hardness-to-density ratio, of the metal.
[0029] While density is weight of the material divided by the
displaced volume of the material, the effective density is the
actual weight divided by the volume that the material would occupy
if the material were solid between its outer dimensions. For
example, in a facing of outer dimensions x (length), y (width), and
z (thickness), the volume of the facing is x times y times z, and
the density is the weight of the facing divided by this volume. In
a perforated facing of the same outer dimensions, the effective
density is the weight of the perforated facing (which is less than
that of the non-perforated facing) divided by the same volume (x
times y times z), without accounting for the reduction in volume of
the material that would be caused by the perforations.
[0030] Surprisingly, the holes in the metal perforation can be
larger than the steel pin in the projectile and still provide
acceptable results.
[0031] Increasing the fiber content of the backing material from
the traditional 80% to a higher percentage, allows the fiber
backing to work more weight efficiently in conjunction with the
metallic facing.
[0032] Encapsulating the thin steel in a carbon fiber composite
will increase its specific stiffness (stiffness to weight), which
may also affect its effectiveness as a strike face.
[0033] It is known that steel armor can be made more weight
effective by putting holes in the steel in a defined pattern and at
a preferred spacing. Prior art also teaches that steel alone, when
encased in rubber, can be an effective ballistic material.
Moreover, the shape of the perforations can also have an effect on
ballistic performance, especially when used in conjunction with
additional perforated metal plates. Surprisingly, however, the use
of a metallic facing element 14 having perforations along with a
composite fiber substrate 18 is effective in providing protection
against multiple penetration threats, as an alternative to a
ceramic-based facing element.
[0034] For the present invention, optimization of hole pattern and
spacing for every specific threat or group of threats that is
anticipated may be conducted without undue experimentation, and
will produce an armor assembly with minimal weight. The
perforations may be round, square, hexagonal, slotted, etc., in any
uniform pattern, a staggered pattern, or a random pattern without
departing from the spirit or scope of the invention. For example,
FIG. 1 illustrates round perforations while FIG. 3 illustrates
square perforations. One embodiment of the present invention
includes hole diameter of about 4 mm, with the holes spaced about 6
mm in a staggered pattern. Other embodiments include hole diameters
of about 3 mm to 3.5 mm, with spacing of the holes about 4 mm to
about 4.5 mm in a staggered pattern.
[0035] The perforations may be made in any conventional manner
without departing from the spirit and scope of the invention. The
perforations could be caused by expanding metal or cast at an
obliquity to the surface of the armor plate. The perforations can
be formed into the plate in the pre-hardened material and then
hardened, or the steel can be hardened and the perforations formed
with a laser or water-jet.
[0036] Surprisingly, when perforated metal materials are combined
with fiber composite backings, as described below, the hole
diameter can actually exceed the diameter of the core of the
projectile and still be an effective armor assembly. This is
possible because of the low probability of the core and the steel
target lining up perfectly, and thus the desired effect on the
projectile is accomplished as long as the core of the projectile
touches any portion of the metallic strike face or side of the
hole.
[0037] A preferred hole diameter for the present invention is less
than 1.2 times the diameter of the core of the projectile that is
to be defeated. A more preferred hole diameter is equal to the
diameter of the core of the projectile that is to be defeated. A
most preferred hole diameter is less than 90% of the diameter of
the core of the projectile that is to be defeated. A hole diameter
of about 3.2 mm has been found to be effective for multiple
penetration threats.
[0038] Preferably, the effective density of the metallic facing
element 14 is reduced by at least about 20% compared to the solid,
flat metal. But, the metallic facing element 14 need not be
perforated to achieve the desired effective density reduction.
Other geometric formations for the metallic facing element are also
effective for reducing the effective density and providing the
reduced weight of the metallic facing element 14. For example, FIG.
4 illustrates an embodiment in which the metallic facing element 14
is provided with indentations 26 that do not completely penetrate
the metallic facing element 14. Indentations 26 may be discrete, as
in pits, or continuous, as in grooves, or a combination thereof,
and may be in any or no pattern and of any shape, depth, or other
dimension. Metallic facing element 14 may also be corrugated to
reduce the effective density.
[0039] Also, FIG. 5 illustrates pyramidal or conical projections 28
that are affixed to or formed as part of the metallic facing
element 14. Projections 28 may be of any shape and the projections
28 may be arranged in any uniform pattern, a staggered pattern, or
a random pattern. Other geometries may also be used without
departing from the spirit and scope of the invention.
[0040] The areal weight of the metallic facing element 14 can be
any value, and depends on the threat or group of threats that the
element is to protect against. Preferably, at least 20% of the
surface area of the metallic facing element 14 is perforated. The
thickness of the metallic facing element 14 can be of any
dimension, such as between about 0.02 inches and about 0.5 inches,
and is tailored to the threats that are to be defeated. For the
SAPI threat, a preferred thickness is less than about 0.125 inches,
a more preferred thickness is less than about 0.10 inches and a
most preferred thickness is less than or equal to about 0.080
inches.
[0041] For the SAPI threats, a preferred areal weight of the
metallic facing element 14 is less than about 2.5 psf, a more
preferred areal weight is less than about 2.0 psf, and a most
preferred areal weight is about equal to 1.8 psf.
[0042] In a preferred embodiment of the invention for the SAPI
plate, the hardness of the metallic facing element 14 is in excess
of Rockwell C 25, is preferred to be in excess of Rockwell C 45, is
more preferred to be in excess of Rockwell C 55, and is most
preferred to be greater than or equal to Rockwell C 60.
[0043] In one embodiment, the metallic facing element 14 is a
continuous monolithic plate that is generally flat. In other
embodiments, the metallic facing element 14 has a single, double,
or compound curvature.
[0044] In one embodiment, the metallic facing element 14 includes
multiple individual plates made as described above that are
arranged in a staggered or non-staggered array as tiles to cover
the surface of the composite fiber substrate/backing 18.
[0045] The composite fiber substrate/backing 18 is any high
performance backing involving a network of fibers with or without a
resin matrix. Suitable backings include composite ballistic
laminates as described by U.S. Pats. No. 4,916,000; 5,677,029; or
5,443,883. The use of highly oriented tapes or films that are
cross-plied at 0/90 degrees and laminated would also provide a
suitable backing. The tapes or films also may have more than one
ply or layer. If the tapes or films have more than one layer, the
layers may be arranged such that lines of plies are disposed at
angles greater than zero relative to the lines of adjacent
plies.
[0046] Preferably, the thickness of the composite fiber
substrate/backing 18 is between about 0.06 inches and about 3.00
inches, but any thickness is within the spirit and scope of the
invention. The thickness of the backing 18 is preferably such that
the ratio of the thickness of at least one individual composite
layer of the backing to the equivalent diameter of filaments in the
backing 18 is equal to or less than about 20.0, and most preferably
between about 3.5 and about 10.0. The appropriate thickness for a
particular application is determined based on the threat or threats
to be defeated, weight considerations, cost considerations, and
other considerations.
[0047] In one embodiment, the thickness of the backing 18 is at
least 7 times the thickness of the metallic facing element 14. This
will provide effective performance against selected penetration
threats regardless of whether the metallic facing element 14 has a
reduced effective density as provided above. Another embodiment
effective against selected penetration threats is an assembly 10 in
which the backing 18 has a thickness between about 4 and about 10
times the thickness of the metallic facing element 14. Preferably,
the thickness of the backing 18 is between about 7 and about 9
times the thickness of the metallic facing element 14, and most
preferably about 8 times the thickness of the metallic facing
element 14.
[0048] These backings include fibers sold under the trademarks
Spectra Shield.RTM. (Honeywell Corp.), Kevlar.RTM. (E.I. Du Pont de
Nemours and Company), Twaron.RTM. (Teijin Limited), Vectran.RTM.
(Celanese), M5.RTM. (Magellin Systems Int'l), Tensylon.RTM.
(Integrated Textile Systems, Inc.), Borosilicate (E) glass fiber,
S-2 glass fiber (Advanced Glassfiber Yarns) and carbon or graphite
fiber.
[0049] The cross-section of fibers for use in the present invention
may vary widely. Useful fibers may have a circular cross-section,
oblong cross-section, or irregular or regular multi-lobal
cross-section having one or more regular or irregular lobes
projecting from the linear or longitudinal axis of the fibers. In
particularly preferred embodiments of the invention, the fibers are
of substantially circular or oblong cross-section and in the most
preferred embodiments are of circular or substantially circular
cross-section.
[0050] The fibrous network may be formed from fibers alone, or from
fibers coated with a suitable polymer, such as, for example, a
polyolefin, polyamide, polyester, polydiene such as a
polybutadiene, urethanes, diene/olefin copolymers such as
poly(styrene-butadiene-styrene) block copolymers, and a wide
variety of elastomers. The composite fiber substrate element 18 may
also include a network of a fibers dispersed in a polymeric matrix
such as, for example, a matrix of one or more of the above
referenced polymers to form a flexible composite. The composite
fiber substrate may also include a network of fibers that is bonded
together without the use of a matrix.
[0051] Useful organic fibers for this invention include aramid,
(Kevlar.RTM., Twaron.RTM.), polyethylene (Spectra Shield.RTM.),
liquid crystal polymers (Vectran.RTM.), fiberglass, carbon, and
M5.RTM..
[0052] Useful inorganic fibers include S-glass fibers, E-glass
fibers, carbon fibers, boron fibers, alumina fibers,
zirconia-silica fibers, alumina-silica fibers and the like.
[0053] The fibers in composite fiber substrate 18 may be arranged
in networks having various configurations. For example, a plurality
of filaments can be grouped together to form twisted or untwisted
yarn bundles in various alignments. The filaments or yarn may be
formed as a felt, knitted, or woven (plain, basket, satin, and crow
feet weaves, etc.) into a network, fabricated into non-woven
fabric, arranged in parallel array, layered, or formed into a woven
fabric by any of a variety of conventional techniques.
[0054] Composite fiber substrate/backing 18 may be more than one
layer. In one preferred embodiment, composite fiber
substrate/backing 18 has more than one layer, with the fibers of
the layers arranged in a parallel array and having the longitudinal
axis of the parallel fibers aligned at a 90 degree angle with
respect to the longitudinal axis of the parallel fibers in the
adjacent layers.
[0055] Fibers having a tenacity equal to or greater than about 7
grams per denier, a tensile modulus equal to or greater than about
150 g/denier, and an energy to break equal to or greater than about
8 g/joule are preferred.
[0056] Fibers having a tenacity equal to or greater than about 25
grams per denier, a tensile modulus equal to or greater than 1000
g/denier, and an energy to break equal to or greater than about 20
g/joule are more preferred.
[0057] Fibers having a tenacity equal to or greater than about 30
grams per denier, a tensile modulus equal to or greater than about
1300 g/denier and an energy to break equal to or greater than about
30 g/joule are even more preferred.
[0058] Fibers of polyethylene having a tenacity equal to or greater
than about 30 grams per denier, a tensile modulus equal or greater
than about 800 g/denier and an energy to break of at least about 35
g/joule are most preferred.
[0059] In a preferred embodiment of the invention, for the SAPI
plate requirements, the areal density of the backing is greater
than 2.5 psf. The more preferred areal density of the backing is
greater than 3.0 psf, and the most preferred areal density of the
backing is greater than or equal to 3.2 psf.
[0060] Preferably, the composite fiber substrate 18 has a fiber
content of at least about 75% by weight or by volume, a more
preferred fiber content of more than about 80% by weight or by
volume, and a most preferred fiber content exceeding about 85% by
weight or by volume.
[0061] A preferred backing includes a network of fibers in a resin
matrix. The resin type is any resin suitable for use in the making
of a composite fiber substrate/backing 18e without departing from
the spirit and scope of the invention. These resins include:
phenolics, urethanes, epoxies, acrylics, polyesters, vinyl esters,
liquid crystal polymers, and thermoplastic resins such as
polyolefins, polyamides, and polyesters. Most preferred polymeric
resin materials are polyolefins, such as polyethylene,
polypropylene, and the like, and polyamides, such as nylon 6 and
nylon 66.
[0062] In one embodiment, the matrix, either resin, polymeric, or
of another material, is rigid and has a tensile modulus of less
than about 6000 psi (41,300 kPa) at 25.degree. C. In one embodiment
the composite fiber substrate 18 is rigid and has a tensile modulus
of less than about 6000 psi (41,300 kPa) at 25.degree. C.
[0063] A suitable backing includes a monolithic material or a
hybrid of materials or resin types to allow the most efficient
dissipation of energy from the projectile.
[0064] In a preferred embodiment of the invention, the metallic
facing element 14 is bonded in intimate contact with the composite
fiber substrate/backing 18, such as by use of adhesive layer 16.
Preferably, the thickness of the adhesive layer 16 is between about
0.0005 inches and about 0.09 inches. Adhesive layer 16 may be any
conventional adhesive without departing from the spirit and scope
of the invention. Suitable adhesives include epoxies, polysulfides,
polyurethanes, polyolefins, and acrylics. Acceptable results,
however, are also possible by spacing the metallic facing element
14 at some distance from the composite fiber substrate/backing
18.
[0065] In one embodiment, an armor assembly 10 in accordance with
the present invention includes a steel metallic facing element 14
having a hardness greater than about 40 on the Rockwell C scale, a
thickness of no more than about 0.010 inches, and an areal density
of no more than about 2.2 psf. The armor assembly 10 also includes
a composite fiber substrate/backing 18 with an areal density
greater than about 2.8 psf and a cover 22. The overall total
thickness of the armor assembly 10 is no more than about 1.25
inches.
[0066] In one embodiment, the armor assembly 10 includes at least a
metallic facing element 14, an adhesive layer 16, and a composite
fiber substrate/backing 18 with a combined weight between about 4.5
psf and about 10.0 psf, and, prefereably, in the range of from
about 4.5 psf to about 5.5 psf.
[0067] While a preferred embodiment of the invention is described
in terms of use for a SAPI plate, this armor assembly has many
applications where enhanced ballistic production at minimum weight
is required. This could include, for example, aircraft armor,
helicopter armor, vehicle armor, helmets, and shields for civilian
use at various areal densities, facing, and backing thicknesses. In
addition to the ballistic and cost advantages of this armor, the
armor assembly can be manufactured more easily, with all of the
components of the armor assembly co-cured in one molding step,
eliminating the need for post-assembly of the metallic facing
element and the composite fiber substrate backing.
EXAMPLE
[0068] Hard steel having a nominal Rockwell C 57 hardness sold
under the trade name Mars 300 and available from Usinor Industeel,
was perforated with a staggered hole pattern 5 mm diameter.times.7
mm between holes, heat treated, then ground from 125" to 0.08
inches thick. The resulting metallic facing element was placed in
intimate contact with a high performance backing.
[0069] The backing raw material is sold by Honeywell Corporation
under the trade name, Spectra Shield.RTM. Plus. One hundred and
fifty-seven (157) layers of Spectra Shield.RTM. Plus were stacked
and molded at a pressure of 3000 psi, at a molding temperature of
250 degrees F. until the center of the laminate reached 240 degrees
F. for fifteen minutes, and was then cooled under pressure. The
perforated Mars 300 facing element was cut into 2".times.2" tiles
and adhesively bonded to the face of the Spectra Shield.RTM. using
adhesive sold under the trade name Spray 77, available from 3M
Corporation. The resulting laminate was ballistically tested and
yielded the following results. The core diameter of the M-855
bullet was 4.5 mm while the perforated hole diameter was 5 mm, 11%
larger than the core of the projectiles. Testing was done per Mil
STD 662F with all shots laser-aligned with the holes, which is
considered the worst case scenario.
3TABLE 3 Perforated Steel Test Results Threat Result M-80 ball No
penetration M-855 No penetration LPS ball No penetration PS ball No
penetration
[0070] While the present invention has been illustrated by the
above description of embodiments, and while the embodiments have
been described in some detail, it is not the intention of the
applicant to restrict or in any way limit the scope of the
invention to such detail. Additional advantages and modifications
will readily appear to those skilled in the art. Therefore, the
invention in its broader aspects is not limited to the specific
details, representative apparatus and methods, and illustrative
examples shown and descried. Accordingly, departures may be made
from such details without departing from the spirit or scope of the
applicant's general or inventive concept.
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