U.S. patent application number 13/826424 was filed with the patent office on 2014-05-22 for spall liners in combination with blast mitigation materials for vehicles.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. The applicant listed for this patent is HONEYWELL INTERNATIONAL INC.. Invention is credited to CHARLES ARNETT, ROY ARTHUR ASH, ANDREW ASHLEY, ANTONIO BRUCO, LORI L. WAGNER.
Application Number | 20140137726 13/826424 |
Document ID | / |
Family ID | 49882568 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140137726 |
Kind Code |
A1 |
WAGNER; LORI L. ; et
al. |
May 22, 2014 |
SPALL LINERS IN COMBINATION WITH BLAST MITIGATION MATERIALS FOR
VEHICLES
Abstract
Spall suppressing ballistic resistant vehicular armor. More
particularly, a lightweight spall suppressing ballistic resistant
vehicular armor system incorporating both a spall resistant liner
and a blast mitigating material. The blast mitigating material is
positioned contiguous to a vehicle hull to thereby space the spall
resistant liner from the vehicle hull, thereby improving the
performance of the liner and the overall system.
Inventors: |
WAGNER; LORI L.; (RICHMOND,
VA) ; ASH; ROY ARTHUR; (MIDLOTHIAN, VA) ;
ARNETT; CHARLES; (RICHMOND, VA) ; ASHLEY; ANDREW;
(ARLINGTON, VA) ; BRUCO; ANTONIO; (HANOVER,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONEYWELL INTERNATIONAL INC.; |
|
|
US |
|
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
49882568 |
Appl. No.: |
13/826424 |
Filed: |
March 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61618107 |
Mar 30, 2012 |
|
|
|
Current U.S.
Class: |
89/36.02 ;
156/60 |
Current CPC
Class: |
F41H 5/023 20130101;
F41H 5/0471 20130101; Y10T 156/10 20150115; F41H 5/0478 20130101;
F42D 5/045 20130101; F41H 7/02 20130101 |
Class at
Publication: |
89/36.02 ;
156/60 |
International
Class: |
F41H 5/04 20060101
F41H005/04; F41H 7/02 20060101 F41H007/02 |
Claims
1. A ballistic resistant article comprising: a) an elastically
deformable blast mitigating material having first and second
surfaces; and b) a spall resistant substrate coupled with at least
one of said first and second surfaces of said blast mitigating
material, said spall resistant substrate comprising fibers having a
tenacity of about 7 g/denier or more and a tensile modulus of about
150 g/denier or more.
2. The article of claim 1 wherein said elastically deformable blast
mitigating material comprises a material that is at least partially
hollow.
3. The article of claim 1 wherein said elastically deformable blast
mitigating material comprises an elastically deformable sheet
comprising a plurality of integrally formed elastically deformable
protrusions.
4. The article of claim 1 wherein said elastically deformable blast
mitigating material comprises at least one pair of elastically
deformable sheets spaced from each other to define a cavity
therebetween, each sheet having a plurality of inwardly facing,
opposing, elastically deformable protrusions extending into the
cavity.
5. The article of claim 4 wherein said elastically deformable blast
mitigating material comprises at least one additional elastically
deformable sheet comprising a plurality of integrally formed
elastically deformable protrusions, said at least one additional
sheet comprising a plurality of outwardly and/or inwardly facing
elastically deformable protrusions, and said at least one
additional sheet being attached to at least one surface of said
pair of spaced apart elastically deformable sheets.
6. The article of claim 1 wherein a spall resistant substrate is
coupled with only one of said first and second surfaces of the
elastically deformable blast mitigating material.
7. The article of claim 1 wherein a spall resistant substrate is
coupled with both of said first and second surfaces of the
elastically deformable blast mitigating material.
8. The article of claim 1 wherein said spall resistant substrate is
adhesively attached to said elastically deformable blast mitigating
material.
9. The article of claim 1 wherein said elastically deformable blast
mitigating material has a thickness of at least about 1-inch (2.54
cm).
10. The article of claim 1 wherein said elastically deformable
blast mitigating material has a thickness of at least about
2-inches (5.08 cm).
11. The article of claim 1 wherein said spall resistant substrate
comprises fibers having surfaces that are at least partially
covered with a polymeric binder material.
12. The article of claim 1 wherein said spall resistant substrate
comprises a consolidated plurality of woven fibrous plies.
13. The article of claim 1 wherein said spall resistant substrate
comprises a consolidated plurality of non-woven fibrous plies.
14. The article of claim 1 wherein said spall resistant substrate
comprises a consolidated plurality of cross-plied, non-woven
fibrous plies wherein each non-woven fibrous ply comprises a
plurality of unidirectionally oriented fibers.
15. The article of claim 1 wherein said spall resistant substrate
has an areal density of from about 0.5 lb/ft.sup.2 to about 5.0
lb/ft.sup.2.
16. The article of claim 1 further comprising a protective cover on
an outer surface of the spall resistant substrate.
17. A reinforced object which comprises an object coupled with a
ballistic resistant article, the ballistic resistant article
comprising: a) an elastically deformable blast mitigating material
having first and second surfaces; b) a spall resistant substrate
coupled with at least one of said first and second surfaces of said
blast mitigating material, said spall resistant substrate
comprising fibers having a tenacity of about 7 g/denier or more and
a tensile modulus of about 150 g/denier or more; and optionally c)
a protective cover on an outer surface of the spall resistant
substrate; wherein the blast mitigating material is contiguous to
the object.
18. The reinforced object of claim 17 wherein said object is a
vehicle.
19. The reinforced object of claim 17 wherein the elastically
deformable blast mitigating material comprises a material that is
at least partially hollow, wherein at least a portion of the volume
between the object and the spall resistant substrate is occupied by
air.
20. A method of forming a ballistic resistant article which
comprises: a) providing an elastically deformable blast mitigating
material having first and second surfaces; b) adjoining at least
one of said first and second surfaces of the blast mitigating
material with at least one spall resistant substrate, said spall
resistant substrate comprising fibers having a tenacity of about 7
g/denier or more and a tensile modulus of about 150 g/denier or
more; and c) optionally covering an outer surface of the at least
one spall resistant substrate with a protective cover.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of co-pending U.S.
Provisional Application Ser. No. 61/618,107, filed on Mar. 30,
2012, the disclosure of which is incorporated by reference herein
in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The invention relates to spall suppressing ballistic
resistant vehicular armor. More particularly, the invention
pertains to a lightweight spall suppressing ballistic resistant
vehicular armor system incorporating anti-spall and blast
mitigating elements.
[0004] 2. Description of the Related Art
[0005] Vehicles intended for use in combat environments are often
armored to protect the vehicle occupants from ballistic threats.
Harm to vehicle occupants from ballistic threats may occur, for
example, from the penetration of ballistic rounds or other such
projectiles through the vehicle hull and into the vehicle interior,
and/or as a result of the impact of high pressure blast energy from
improvised explosive devices (IEDs). Equipping vehicles with armor
reduces the likelihood that ballistic threats will breach the hull
and penetrate the vehicle, while coupling armor with blast
mitigating materials helps suppress shock waves and reduce the
impact of high pressure blast energy. Blast mitigating materials
also help to contain exploding fragments from IEDs as well as
fragments from fractured projectiles.
[0006] It is also recognized that high velocity fragments of metal
released from the inside surface of a vehicle hull due to a high
velocity impact with the vehicle, also known as spall, is a primary
cause of vehicular casualties in combat. To control such metal
spall that may occur when a threat impacts or penetrates the hull
of a vehicle, a spall resistant liner is typically used directly
behind the vehicle hull material, serving as a barrier to incoming
projectile fragments or debris. For example, U.S. Pat. No.
4,664,967 discloses a ballistic spall resistant liner for military
vehicles where the liner has multiple and repeating layers made of
high tensile strength fabric and steel. U.S. Pat. No. 4,739,690
discloses ballistic resistant armor with a spall resistant liner
containing an outer layer of a plasticized resin. This disclosure
does not specify vehicular use of the spall resistant liner.
[0007] It is also known that incorporating a space between a spall
resistant liner and a vehicle hull can increase spall resistant
liner performance. For example, U.S. Pat. No. 4,934,245 states that
spall resistant liners should optimally be spaced from the inner
wall of a vehicle by 4 to 17 inches to maximize their
effectiveness, noting however that such a construction is
unrealistic due to limited useable space within most vehicles. To
overcome these spatial limitations, U.S. Pat. No. 4,934,245 teaches
attaching an armor plate backed with a spall resistant liner
directly to a vehicle hull. U.S. Pat. No. 6,622,608 teaches that
armor mass efficiency of vehicle armor can be enhanced by
incorporating a standoff plate separated from the base armor
material. The standoff plate creates a distance of separation from
the base armor in which shell fragments can be turned, shattered,
and caught. See also U.S. Pat. No. 6,912,944 which teaches ceramic
armor systems with a front spall layer bonded to a front surface of
a ceramic plate and a shock absorbing layer bonded to a rear
surface of the ceramic plate. This assembly may be bolted into the
hull of a vehicle, preferably with an air gap between the
shock-absorbing layer and the hull of the vehicle.
[0008] Although it is desirable to equip armored vehicles with both
a blast mitigating material and a spall resistant liner, space
limitations within the vehicle are restrictive, resulting in no
space available to separate the spall resistant liner from the
hull. Therefore, there is a need in the art for an improved vehicle
armor construction that permits the use of both a blast mitigating
material and a spall resistant liner within a vehicle, while also
allowing the spall resistant liner to be beneficially spaced from
the vehicle hull. This disclosure provides a solution to this need
in the art.
SUMMARY
[0009] Provided is a ballistic resistant article comprising:
[0010] a) an elastically deformable blast mitigating material
having first and second surfaces; and
[0011] b) a spall resistant substrate coupled with at least one of
said first and second surfaces of said blast mitigating material,
said spall resistant substrate comprising fibers and/or tapes
having a tenacity of about 7 g/denier or more and a tensile modulus
of about 150 g/denier or more.
[0012] Also provided is a reinforced object which comprises an
object coupled with a ballistic resistant article, the ballistic
resistant article comprising:
[0013] a) an elastically deformable blast mitigating material
having first and second surfaces;
[0014] b) a spall resistant substrate coupled with at least one of
said first and second surfaces of said blast mitigating material,
said spall resistant substrate comprising fibers and/or tapes
having a tenacity of about 7 g/denier or more and a tensile modulus
of about 150 g/denier or more; and optionally
[0015] c) a protective cover on an outer surface of the spall
resistant substrate;
[0016] wherein the blast mitigating material is contiguous to the
object.
[0017] Further provided is a method of forming a ballistic
resistant article which comprises:
[0018] a) providing an elastically deformable blast mitigating
material having first and second surfaces;
[0019] b) adjoining at least one of said first and second surfaces
of the blast mitigating material with at least one spall resistant
substrate, said spall resistant substrate comprising fibers and/or
tapes having a tenacity of about 7 g/denier or more and a tensile
modulus of about 150 g/denier or more; and
[0020] c) optionally covering an outer surface of the at least one
spall resistant substrate with a protective cover.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is an edge view schematic representation of ballistic
resistant article of the invention including a blast mitigating
material positioned between a spall resistant liner and a surface
of a reinforced object with a protective cover on the spall
resistant liner, where the blast mitigating material comprises a
plurality of protrusions.
[0022] FIG. 2 is an edge view schematic representation of ballistic
resistant article of the invention including a blast mitigating
material that is formed from a pair of sheets having a plurality of
inwardly facing, opposing protrusions.
[0023] FIG. 3 is a perspective view of the top and bottom sheets of
a prior art blast mitigating material incorporating a pair of
elastically deformable sheets having a plurality of inwardly
facing, opposing, hemispherical elastically deformable
protrusions.
[0024] FIG. 4 is a cross-section view of the inwardly facing,
opposing, hemispherical elastically deformable protrusions from
FIG. 3.
[0025] FIG. 5 is a perspective view of a prior art blast mitigating
material of FIG. 3 having a wall member along the periphery of the
sheet surfaces.
[0026] FIG. 6 is an edge view schematic representation of an
alternative prior art blast mitigating material.
[0027] FIG. 7 is a graph showing spall resistant liner protection
performance in overmatch testing with varied spacing between the
spall resistant liner and an object hull.
[0028] FIG. 8 is a graph showing spall resistant liner protection
performance in overmatch testing with varied spall resistant liner
areal densities.
[0029] FIG. 9 is a cross-section view schematic representation from
the prior art of metal armor without a spall resistant liner or
blast mitigation material attached thereto being contacted by a
high velocity projectile and showing metal spall being discharged
therefrom.
[0030] FIG. 10 illustrates the method of measuring 1/2 spall cone
angle .alpha. for the Inventive and Comparative Examples.
DETAILED DESCRIPTION
[0031] In the context of the present invention, spallation (or
spalling) describes the material failure and fragmentation of a
surface due to a high velocity impact, such as shockwave impact
from a detonated IED or the impact of a high velocity projectile,
including rocket propelled grenades and other shaped charge
threats. The spallation of a metal armor surface due to the impact
of a high velocity projectile is schematically illustrated in FIG.
9. As shown in this prior art figure, a projectile contacting an
outer surface of metal armor impacts the armor with sufficient
force to dislodge fragments from the inner surface of the armor.
The fragments, referred to as spall, are propelled from the inner
surface of the armor along a conical path referred to in the art as
the spall angle or spall cone angle. When the armor impacted is a
vehicle hull, such spall fragments are a threat to harm and
significantly injure vehicle occupants. The ballistic resistant
articles of the invention minimize this threat, reinforcing the
vehicle or other object with articles that combine both a blast
mitigating material and a spall resistant substrate, also referred
to herein as a spall resistant liner. As used herein, a "spall
resistant" substrate or liner is a material that will absorb the
energy from the spall and either stop it completely or reduce its
velocity. The spall resistant substrate may be fibrous, being
formed from fabrics or other fibrous materials, including fibrous
tapes, which includes both non-woven fibrous tapes and woven
fibrous tapes, or the spall resistant substrate may be formed from
non-fibrous materials, such as non-fibrous tapes. As used herein,
the term "tape" refers to a narrow strip of fibrous or non-fibrous
material. Tapes are generally flat structures having a
substantially rectangular cross-section and having a thickness of
about 0.5 mm or less, more preferably about 0.25 mm or less, still
more preferably about 0.1 mm or less and still more preferably
about 0.05 mm or less. In the most preferred embodiments, the
polymeric tapes have a thickness of up to about 3 mils (76.2
.mu.m), more preferably from about 0.35 mil (8.89 .mu.m) to about 3
mils (76.2 .mu.m), and most preferably from about 0.35 mil to about
1.5 mils (38.1 .mu.m). Thickness is measured at the thickest region
of the cross-section. A tape generally has a width less than or
equal to about 6 inches (15.24 cm), with a preferred width of from
about 2.5 mm to about 50 mm, more preferably from about 5 mm to
about 50 mm, still more preferably from about 5 mm to about 25.4 mm
(1 inch), even more preferably from about 5 mm to about 20 mm, and
most preferably from about 5 mm to about 10 mm. These dimensions
may vary but the polymeric tapes formed herein are most preferably
fabricated to have dimensions that achieve an average
cross-sectional aspect ratio, i.e. the ratio of the greatest to the
smallest dimension of cross-sections averaged over the length of
the tape article, of greater than about 3:1, more preferably at
least about 5:1, still more preferably at least about 10:1, still
more preferably at least about 20:1, still more preferably at least
about 50:1, still more preferably at least about 100:1, still more
preferably at least about 250:1 and most preferred polymeric tapes
have an average cross-sectional aspect ratio of at least about
400:1.
[0032] As illustrated in FIG. 1 and FIG. 2, the ballistic resistant
articles 10 are coupled with a surface of an object 16 such that a
spall resistant substrate 12 is spaced apart from the surface of
the object 16, wherein a blast mitigating material 14 is positioned
contiguous to the object surface.
[0033] For the purposes of the invention, ballistic resistant
articles describe those which exhibit excellent properties against
the penetration of deformable projectiles, such as bullets, and
against penetration of fragments, such as shrapnel and spall. A
"fiber layer" as used herein may comprise a single-ply of
unidirectionally oriented fibers, a plurality of non-consolidated
plies of unidirectionally oriented fibers, a plurality of
consolidated plies of unidirectionally oriented fibers, a woven
fabric, a plurality of consolidated woven fabrics, or any other
fabric structure that has been formed from a plurality of fibers,
including felts, mats and other structures, such as those
comprising randomly oriented fibers. A "layer" describes a
generally planar arrangement. A fiber layer will have both an outer
top surface and an outer bottom surface. A "single-ply" of
unidirectionally oriented fibers comprises an arrangement of
substantially non-overlapping fibers that are aligned in a
unidirectional, substantially parallel array. This type of fiber
arrangement is also known in the art as a "unitape",
"unidirectional tape", "UD" or "UDT." As used herein, an "array"
describes an orderly arrangement of fibers or yarns, which is
exclusive of woven fabrics, and a "parallel array" describes an
orderly parallel arrangement of fibers or yarns. The term
"oriented" as used in the context of "oriented fibers" refers to
the alignment of the fibers. The term "fabric" describes structures
that may include one or more fiber plies, with or without molding
or consolidation of the plies. For example, a woven fabric or felt
may comprise a single fiber ply. A non-woven fabric formed from
unidirectional fibers typically comprises a plurality of fiber
plies stacked on each other and consolidated. When used herein, a
"single-layer" structure refers to any monolithic fibrous structure
composed of one or more individual plies or individual layers that
have been merged, i.e. consolidated by low pressure lamination or
by high pressure molding, into a single unitary structure,
optionally together with a polymeric binder material. By
"consolidating" it is meant that a polymeric binder material
together with each fiber ply is combined into a single unitary
layer. Consolidation can occur via drying, cooling, heating,
pressure or a combination thereof. Heat and/or pressure may not be
necessary, as the fibers or fabric layers may just be glued
together, as is the case in a wet lamination process. The term
"composite" refers to combinations of fibers or tapes, typically
with at least one polymeric binder material. A "complex composite"
as used herein refers to a consolidated combination of a plurality
of fiber layers. As described herein, "non-woven" fabrics include
all fabric structures that are not formed by weaving. For example,
non-woven fabrics may comprise a plurality of unitapes that are at
least partially coated with a polymeric binder material,
stacked/overlapped and consolidated into a single-layer, monolithic
element, as well as a felt or mat comprising non-parallel, randomly
oriented fibers that are preferably coated with a polymeric binder
composition.
[0034] The spall resistant substrate 12 preferably comprises one or
more layers, each layer comprising a plurality of high-strength,
high tensile modulus polymeric fibers and/or non-fibrous
high-strength, high tensile modulus polymeric tapes. As used
herein, a "high-strength, high tensile modulus" fiber or tape is
one which has a preferred tenacity of at least about 7 g/denier or
more, a preferred tensile modulus of at least about 150 g/denier or
more, and preferably an energy-to-break of at least about 8 J/g or
more, each as measured by ASTM D2256 for fibers and ASTM D882 (or
another suitable method as determined by one skilled in the art)
for polymeric tapes. As used herein, the term "denier" refers to
the unit of linear density, equal to the mass in grams per 9000
meters of fiber/yarn or tape. As used herein, the term "tenacity"
refers to the tensile stress expressed as force (grams) per unit
linear density (denier) of an unstressed specimen. The "initial
modulus" of a fiber or tape is the property of a material
representative of its resistance to deformation. The term "tensile
modulus" refers to the ratio of the change in tenacity, expressed
in grams-force per denier (g/d) to the change in strain, expressed
as a fraction of the original fiber or tape length (in/in).
[0035] In embodiments where the spall resistant substrate 12 is a
fibrous material, particularly suitable high-strength, high tensile
modulus fibers include polyolefin fibers, including high density
and low density polyethylene. Particularly preferred are extended
chain polyolefin fibers, such as highly oriented, high molecular
weight polyethylene fibers, particularly ultra-high molecular
weight polyethylene fibers, and polypropylene fibers, particularly
ultra-high molecular weight polypropylene fibers. Also suitable are
aramid fibers, particularly para-aramid fibers, polyamide fibers,
polyethylene terephthalate fibers, polyethylene naphthalate fibers,
extended chain polyvinyl alcohol fibers, extended chain
polyacrylonitrile fibers, polybenzoxazole (PBO) fibers,
polybenzothiazole (PBT) fibers, liquid crystal copolyester fibers,
rigid rod fibers such as M5.RTM. fibers, and glass fibers,
including electric grade fiberglass (E-glass; low alkali
borosilicate glass with good electrical properties), structural
grade fiberglass (S-glass; a high strength
magnesia-alumina-silicate) and resistance grade fiberglass
(R-glass; a high strength alumino silicate glass without magnesium
oxide or calcium oxide). Each of these fiber types is
conventionally known in the art. Also suitable for producing
polymeric fibers are copolymers, block polymers and blends of the
above materials.
[0036] The most preferred fiber types include polyethylene,
particularly extended chain polyethylene fibers, aramid fibers, PBO
fibers, liquid crystal copolyester fibers, polypropylene fibers,
particularly highly oriented extended chain polypropylene fibers,
polyvinyl alcohol fibers, polyacrylonitrile fibers and rigid rod
fibers, particularly M5.RTM. fibers. Specifically most preferred
fibers for use in the fabrication of spall resistant liner 12 are
aramid fibers, polyethylene fibers, polypropylene fibers and glass
fibers.
[0037] In the case of polyethylene, preferred fibers are extended
chain polyethylenes having molecular weights of at least 300,000,
preferably at least one million and more preferably between two
million and five million. Such extended chain polyethylene (ECPE)
fibers may be grown in solution spinning processes such as
described in U.S. Pat. Nos. 4,137,394 or 4,356,138, which are
incorporated herein by reference, or may be spun from a solution to
form a gel structure, such as described in U.S. Pat. Nos.
4,413,110; 4,536,536; 4,551,296; 4,663,101; 5,006,390; 5,032,338;
5,578,374; 5,736,244; 5,741,451; 5,958,582; 5,972,498; 6,448,359;
6,746,975; 6,969,553; 7,078,099; 7,344,668 and U.S. patent
application publication 2007/0231572, all of which are incorporated
herein by reference. Particularly preferred fiber types for use in
the spall resistant substrate 12 of the invention are any of the
polyethylene fibers sold under the trademark SPECTRA.RTM. from
Honeywell International Inc. SPECTRA.RTM. fibers are well known in
the art. Other useful polyethylene fiber types also include and
DYNEEMA.RTM. UHMWPE yarns commercially available from Royal DSM
N.V. Corporation of Heerlen, The Netherlands.
[0038] Preferred are aramid (aromatic polyamide) or para-aramid
fibers are commercially available and are described, for example,
in U.S. Pat. No. 3,671,542. For example, useful poly(p-phenylene
terephthalamide) filaments are produced commercially by DuPont
under the trademark of KEVLAR.RTM.. Also useful in the practice of
this invention are poly(m-phenylene isophthalamide) fibers produced
commercially by DuPont of Wilmington, Del. under the trademark
NOMEX.RTM. and fibers produced commercially by Teijin Aramid Gmbh
of Germany under the trademark TWARON.RTM.; aramid fibers produced
commercially by Kolon Industries, Inc. of Korea under the trademark
HERACRON.RTM.; p-aramid fibers SVM.TM. and RUSAR.TM. which are
produced commercially by Kamensk Volokno JSC of Russia and
ARMOS.TM. p-aramid fibers produced commercially by JSC Chim Volokno
of Russia.
[0039] Suitable PBO fibers for the practice of this invention are
commercially available and are disclosed for example in U.S. Pat.
Nos. 5,286,833, 5,296,185, 5,356,584, 5,534,205 and 6,040,050, each
of which is incorporated herein by reference. Suitable liquid
crystal copolyester fibers for the practice of this invention are
commercially available and are disclosed, for example, in U.S. Pat.
Nos. 3,975,487; 4,118,372 and 4,161,470, each of which is
incorporated herein by reference, and including VECTRAN.RTM. liquid
crystal copolyester fibers commercially available from Kuraray Co.,
Ltd. of Tokyo, Japan. Suitable polypropylene fibers include highly
oriented extended chain polypropylene (ECPP) fibers as described in
U.S. Pat. No. 4,413,110, which is incorporated herein by reference.
Suitable polyvinyl alcohol (PV-OH) fibers are described, for
example, in U.S. Pat. Nos. 4,440,711 and 4,599,267 which are
incorporated herein by reference. Suitable polyacrylonitrile (PAN)
fibers are disclosed, for example, in U.S. Pat. No. 4,535,027,
which is incorporated herein by reference. Each of these fiber
types is conventionally known and is widely commercially
available.
[0040] M5.RTM. fibers are formed from
pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene) and are
manufactured by Magellan Systems International of Richmond, Va. and
are described, for example, in U.S. Pat. Nos. 5,674,969, 5,939,553,
5,945,537, and 6,040,478, each of which is incorporated herein by
reference.
[0041] Fiberglass spall resistant substrates preferably comprise
composites of glass fibers, preferably S-glass fibers, which are
impregnated with a thermosetting or thermoplastic polymeric resin,
such as a thermosetting epoxy or phenolic resin. Such materials are
well known in the art and are commercially available. Preferred
examples non-exclusively include spall resistant liners comprising
S2-Glass.RTM. commercially available from AGY of Aiken, S.C.; spall
resistant liners formed from HiPerTex.TM. E-Glass fibers,
commercially available from 3B Fibreglass of Battice, Belgium. Also
suitable are glass fiber materials comprising R-glass fibers, such
as those commercially available under the trademark VETROTEX.RTM.
from Saint-Gobain of Courbevoie, France. Also suitable are
combinations of all the above materials, all of which are
commercially available. Also suitable are any spall resistant liner
materials within the specifications of Department of Defense
specification MIL-DTL 64152B.
[0042] In embodiments where the spall resistant substrate 12 is a
fibrous tape, the tape may comprise a strip of woven fabric, or may
comprise a plurality of fibers or yarns which may be arranged in a
generally unidirectional array of generally parallel fibers. In
embodiments where the spall resistant substrate 12 is a non-fibrous
tape material, particularly suitable high-strength, high tensile
modulus polymeric tape materials are polyolefin tapes. Preferred
polyolefin tapes include polyethylene tapes, such as those
commercially available under the trademark TENSYLON.RTM., which is
commercially available from E. I. du Pont de Nemours and Company of
Wilmington, Del. See, for example, U.S. Pat. Nos. 5,091,133;
7,964,266 and 7,964,267 which are incorporated herein by reference.
Also suitable are polypropylene tapes, such as those commercially
available under the trademark TEGRIS.RTM. from Milliken &
Company of Spartanburg, S.C. See, for example, U.S. Pat. No.
7,300,691 which is incorporated herein by reference. Polyolefin
tape-based composites that are useful as spall resistant substrates
herein are also commercially available, for example under the
trademark DYNEEMA.RTM. BT10 from Royal DSM N.V. Corporation of
Heerlen, The Netherlands and under the trademark ENDUMAX.RTM. from
Teijin Aramid Gmbh of Germany.
[0043] Methods for fabricating fibrous tapes are described, for
example, in U.S. Pat. No. 8,236,119 and U.S. patent application
Ser. Nos. 13/021,262; 13/494,641; 13/568,097; 13/647,926 and
13/708,360, the disclosures of which are incorporated herein by
reference. Other methods for fabricating fibrous tapes are
described, for example, in U.S. Pat. Nos. 2,035,138; 4,124,420;
5,115,839, or by use of a ribbon loom specialized for weaving
narrow woven fabrics or ribbons. Useful ribbon looms are disclosed,
for example, in U.S. Pat. Nos. 4,541,461; 5,564,477; 7,451,787 and
7,857,012, each of which is assigned to Textilma AG of Stansstad,
Switzerland, and each of which is incorporated herein by reference
to the extent consistent herewith, although any alternative ribbon
loom is equally useful. Polymeric tapes may also be formed by other
conventionally known methods, such as extrusion, pultrusion, slit
film techniques, etc. For example, a unitape of standard thickness
may be cut or slit into tapes having the desired lengths. An
example of a slitting apparatus is disclosed in U.S. Pat. No.
6,098,510 which teaches an apparatus for slitting a sheet material
web as it is wound onto said roll. Another example of a slitting
apparatus is disclosed in U.S. Pat. No. 6,148,871, which teaches an
apparatus for slitting a sheet of a polymeric film into a plurality
of film strips with a plurality of blades. The disclosures of both
U.S. Pat. No. 6,098,510 and U.S. Pat. No. 6,148,871 are
incorporated herein by reference to the extent consistent herewith.
Methods for fabricating non-woven, non-fibrous polymeric tapes are
described, for example, in U.S. Pat. Nos. 7,300,691; 7,964,266 and
7,964,267, which are incorporated herein by reference. For each of
these tape embodiments, multiple layers of tape-based materials may
be stacked and consolidated/molded in a similar fashion as the
fibrous materials, with or without a polymeric binder material.
[0044] The fibers and tapes may be of any suitable denier. For
example, fibers may have a denier of from about 50 to about 3000
denier, more preferably from about 200 to 3000 denier, still more
preferably from about 650 to about 2000 denier, and most preferably
from about 800 to about 1500 denier. Tapes may have deniers from
about 50 to about 30,000, more preferably from about 200 to 10,000
denier, still more preferably from about 650 to about 2000 denier,
and most preferably from about 800 to about 1500 denier. The
selection is governed by considerations of ballistic effectiveness
and cost. Finer fibers/tapes are more costly to manufacture and to
weave, but can produce greater ballistic effectiveness per unit
weight.
[0045] As stated above, a high-strength, high tensile modulus
fiber/tape is one which has a preferred tenacity of about 7
g/denier or more, a preferred tensile modulus of about 150 g/denier
or more and a preferred energy-to-break of about 8 J/g or more,
each as measured by ASTM D2256. Preferred fibers have a preferred
tenacity of about 15 g/denier or more, more preferably about 20
g/denier or more, still more preferably about 25 g/denier or more,
still more preferably about 30 g/denier or more, still more
preferably about 40 g/denier or more, still more preferably about
45 g/denier or more, and most preferably about 50 g/denier or more.
Preferred tapes have a preferred tenacity of about 10 g/denier or
more, more preferably about 15 g/denier or more, still more
preferably about 17.5 g/denier or more, and most preferably about
20 g/denier or more. Wider tapes will have lower tenacities.
Preferred fibers/tapes also have a preferred tensile modulus of
about 300 g/denier or more, more preferably about 400 g/denier or
more, more preferably about 500 g/denier or more, more preferably
about 1,000 g/denier or more and most preferably about 1,500
g/denier or more. Preferred fibers/tapes also have a preferred
energy-to-break of about 15 J/g or more, more preferably about 25
J/g or more, more preferably about 30 J/g or more and most
preferably have an energy-to-break of about 40 J/g or more. Methods
of forming each of the preferred fiber and tape types having these
combined high strength properties are conventionally known in the
art.
[0046] The fibers and/or tapes forming the spall resistant
substrate 12 are preferably, but not necessarily, at least
partially coated with a polymeric binder material. A binder is
optional because some materials, such as high modulus polyethylene
tapes, do not require a polymeric binder to bind together a
plurality of said tapes into a molded layer or molded article.
Useful spall resistant liners may also be formed from, for example,
soft woven tapes or fibrous products that require neither a
polymeric/resinous binder material nor molding.
[0047] As used herein, a "polymeric" binder or matrix material
includes resins and rubber. When present, the polymeric binder
material either partially or substantially coats the individual
fibers/tapes of the spall resistant substrate 12, preferably
substantially coating each of the individual fibers/tapes. The
polymeric binder material is also commonly known in the art as a
"polymeric matrix" material. These terms are conventionally known
in the art and describe a material that binds fibers or tapes
together either by way of its inherent adhesive characteristics or
after being subjected to well known heat and/or pressure
conditions.
[0048] Suitable polymeric binder materials include both low
modulus, elastomeric materials and high modulus, rigid materials.
As used herein throughout, the term tensile modulus means the
modulus of elasticity, which for fibers is measured by ASTM D2256
and by ASTM D638 for a polymeric binder material. The tensile
properties of polymeric tapes may be measured by ASTM D882 or
another suitable method as determined by one skilled in the art.
The rigidity, impact and ballistic properties of the articles
formed from the composites of the invention are affected by the
tensile modulus of the polymeric binder polymer coating the
fibers/tapes. A low or high modulus binder may comprise a variety
of polymeric and non-polymeric materials. A preferred polymeric
binder comprises a low modulus elastomeric material. For the
purposes of this invention, a low modulus elastomeric material has
a tensile modulus measured at about 6,000 psi (41.4 MPa) or less
according to ASTM D638 testing procedures. A low modulus polymer
preferably is an elastomer having a tensile modulus of about 4,000
psi (27.6 MPa) or less, more preferably about 2400 psi (16.5 MPa)
or less, more preferably 1200 psi (8.23 MPa) or less, and most
preferably is about 500 psi (3.45 MPa) or less. The glass
transition temperature (Tg) of the elastomer is preferably less
than about 0.degree. C., more preferably the less than about
-40.degree. C., and most preferably less than about -50.degree. C.
The elastomer also has a preferred elongation to break of at least
about 50%, more preferably at least about 100% and most preferably
has an elongation to break of at least about 300%.
[0049] A wide variety of materials and formulations having a low
modulus may be utilized as the polymeric binder. Representative
examples include polybutadiene, polyisoprene, natural rubber,
ethylene-propylene copolymers, ethylene-propylene-diene
terpolymers, polysulfide polymers, polyurethane elastomers,
chlorosulfonated polyethylene, polychloroprene, plasticized
polyvinylchloride, butadiene acrylonitrile elastomers,
poly(isobutylene-co-isoprene), polyacrylates, polyesters,
polyethers, fluoroelastomers, silicone elastomers, copolymers of
ethylene, polyamides (useful with some fiber/tape types),
acrylonitrile butadiene styrene, polycarbonates, and combinations
thereof, as well as other low modulus polymers and copolymers
curable below the melting point of the fiber. Also preferred are
blends of different elastomeric materials, or blends of elastomeric
materials with one or more thermoplastics.
[0050] Particularly useful are block copolymers of conjugated
dienes and vinyl aromatic monomers. Butadiene and isoprene are
preferred conjugated diene elastomers. Styrene, vinyl toluene and
t-butyl styrene are preferred conjugated aromatic monomers. Block
copolymers incorporating polyisoprene may be hydrogenated to
produce thermoplastic elastomers having saturated hydrocarbon
elastomer segments. The polymers may be simple tri-block copolymers
of the type A-B-A, multi-block copolymers of the type (AB).sub.n
(n=2-10) or radial configuration copolymers of the type
R--(BA).sub.x (x=3-150); wherein A is a block from a polyvinyl
aromatic monomer and B is a block from a conjugated diene
elastomer. Many of these polymers are produced commercially by
Kraton Polymers of Houston, Tex. and described in the bulletin
"Kraton Thermoplastic Rubber", SC-68-81. Also useful are resin
dispersions of styrene-isoprene-styrene (SIS) block copolymer sold
under the trademark PRINLIN.RTM. and commercially available from
Henkel Technologies, based in Dusseldorf, Germany. Particularly
preferred low modulus polymeric binder polymers comprise styrenic
block copolymers sold under the trademark KRATON.RTM. commercially
produced by Kraton Polymers. A particularly preferred polymeric
binder material comprises a
polystyrene-polyisoprene-polystyrene-block copolymer sold under the
trademark KRATON.RTM..
[0051] While low modulus polymeric binder materials are preferred
for the formation of flexible armor materials, high modulus
polymeric binder materials are preferred for the formation of rigid
armor articles. Preferred high modulus, rigid materials generally
have a higher initial tensile modulus than 6,000 psi. Preferred
high modulus, rigid polymeric binder materials useful herein
include polyurethanes (both ether and ester based), epoxies,
polyacrylates, phenolic/polyvinyl butyral (PVB) polymers, vinyl
ester polymers, styrene-butadiene block copolymers, as well as
mixtures of polymers such as vinyl ester and diallyl phthalate or
phenol formaldehyde and polyvinyl butyral. A particularly preferred
rigid polymeric binder material for use in spall resistant
substrate 12 is a thermosetting polymer, preferably soluble in
carbon-carbon saturated solvents such as methyl ethyl ketone, and
possessing a high tensile modulus when cured of at least about
1.times.10.sup.6 psi (6895 MPa) as measured by ASTM D638.
Particularly preferred rigid polymeric binder materials are those
described in U.S. Pat. No. 6,642,159, the disclosure of which is
incorporated herein by reference. The polymeric binder, whether a
low modulus material or a high modulus material, may also include
fillers such as carbon black or silica, may be extended with oils,
or may be vulcanized by sulfur, peroxide, metal oxide or radiation
cure systems as is well known in the art.
[0052] Most specifically preferred are polar resins or polar
polymer, particularly polyurethanes within the range of both soft
and rigid materials at a tensile modulus ranging from about 2,000
psi (13.79 MPa) to about 8,000 psi (55.16 MPa). Preferred
polyurethanes are applied as aqueous polyurethane dispersions that
are most preferably co-solvent free. Such includes aqueous anionic
polyurethane dispersions, aqueous cationic polyurethane dispersions
and aqueous nonionic polyurethane dispersions. Particularly
preferred are aqueous anionic polyurethane dispersions, and most
preferred are aqueous anionic, aliphatic polyurethane dispersions.
Such includes aqueous anionic polyester-based polyurethane
dispersions; aqueous aliphatic polyester-based polyurethane
dispersions; and aqueous anionic, aliphatic polyester-based
polyurethane dispersions, all of which are preferably cosolvent
free dispersions. Such also includes aqueous anionic polyether
polyurethane dispersions; aqueous aliphatic polyether-based
polyurethane dispersions; and aqueous anionic, aliphatic
polyether-based polyurethane dispersions, all of which are
preferably cosolvent free dispersions. Similarly preferred are all
corresponding variations (polyester-based; aliphatic
polyester-based; polyether-based; aliphatic polyether-based, etc.)
of aqueous cationic and aqueous nonionic dispersions. Most
preferred is an aliphatic polyurethane dispersion having a modulus
at 100% elongation of about 700 psi or more, with a particularly
preferred range of 700 psi to about 3000 psi. More preferred are
aliphatic polyurethane dispersions having a modulus at 100%
elongation of about 1000 psi or more, and still more preferably
about 1100 psi or more. Most preferred is an aliphatic,
polyether-based anionic polyurethane dispersion having a modulus of
1000 psi or more, preferably 1100 psi or more.
[0053] Methods for applying a polymeric binder material to fibers
and tapes to thereby impregnate fiber or tape layers with the
binder are well known and readily determined by one skilled in the
art. The term "impregnated" is considered herein as being
synonymous with "embedded," "coated," or otherwise applied with a
polymeric coating where the binder material diffuses into the layer
and is not simply on a surface of the layer. Any appropriate
application method may be utilized to apply the polymeric binder
material and particular use of a term such as "coated" is not
intended to limit the method by which it is applied onto the
filaments/fibers. Useful methods include, for example, spraying,
extruding or roll coating polymers or polymer solutions onto the
fibers/tapes, as well as transporting the fibers/tapes through a
molten polymer or polymer solution. Most preferred are methods that
substantially coat or encapsulate each of the individual
fibers/tapes and cover all or substantially all of the fiber/tape
surface area with the polymeric binder material.
[0054] Fibers and tapes that are woven into woven fibrous layers or
woven tape layers are preferably at least partially coated with a
polymeric binder, followed by a consolidation step similar to that
conducted with non-woven layers. Such a consolidation step may be
conducted to merge multiple woven fiber or tape layers with each
other, or to further merge a binder with the fibers/tapes of said
woven layers. For example, a plurality of woven fiber layers do not
necessarily have to be consolidated, and may be attached by other
means, such as with a conventional adhesive, or by stitching,
whereas a polymeric binder coating is generally necessary to
efficiently consolidate a plurality of non-woven fiber plies.
[0055] Woven fabrics may be formed using techniques that are well
known in the art using any fabric weave, such as plain weave,
crowfoot weave, basket weave, satin weave, twill weave and the
like. Plain weave is most common, where fibers are woven together
in an orthogonal 0.degree./90.degree. orientation. Typically,
weaving of fabrics is performed prior to coating the fibers with a
polymeric binder, where the woven fabrics are thereby impregnated
with the binder. However, the invention is not intended to be
limited by the stage at which the polymeric binder is applied. Also
useful are 3D weaving methods wherein multi-layer woven structures
are fabricated by weaving warp and weft threads both horizontally
and vertically. Coating or impregnation with a polymeric binder
material is also optional with such 3D woven fabrics, but a binder
is specifically not mandatory for the fabrication of a multilayer
3D woven spall resistant substrate 12.
[0056] Methods for the production of non-woven fibrous materials
and non-woven tape materials are well known in the art. For
example, in a preferred method for forming non-woven fabrics, a
plurality of fibers are arranged into at least one array, typically
being arranged as a fiber web comprising a plurality of fibers
aligned in a substantially parallel, unidirectional array. In a
typical process, fiber bundles are supplied from a creel and led
through guides and one or more spreader bars into a collimating
comb, followed by coating the fibers with a polymeric binder
material. A typical fiber bundle will have from about 30 to about
2000 individual fibers. The spreader bars and collimating comb
disperse and spread out the bundled fibers, reorganizing them
side-by-side in a coplanar fashion. Ideal fiber spreading results
in the individual filaments or individual fibers being positioned
next to one another in a single fiber plane, forming a
substantially unidirectional, parallel array of fibers without
fibers overlapping each other.
[0057] After the fibers are coated with an optional binder material
the coated fibers are formed into non-woven fiber layers that
comprise a plurality of overlapping, non-woven fiber plies that are
consolidated into a single-layer, monolithic element. In a
preferred non-woven fabric structure for the spall resistant
substrate 12, a plurality of stacked, overlapping unitapes are
formed wherein the parallel fibers of each single ply (unitape) are
positioned orthogonally to the parallel fibers of each adjacent
single ply relative to the longitudinal fiber direction of each
single ply. The stack of overlapping non-woven fiber plies is
consolidated under heat and pressure, or by adhering the coatings
of individual fiber plies, to form a single-layer, monolithic
element which has also been referred to in the art as a
single-layer, consolidated network where a "consolidated network"
describes a consolidated (merged) combination of fiber plies with
the polymeric matrix/binder. The spall resistant substrate 12 may
also comprise a consolidated hybrid combination of woven fabrics
and non-woven fabrics, as well as combinations of non-woven fabrics
formed from unidirectional fiber plies and non-woven felt
fabrics.
[0058] Most typically, non-woven fiber layers or fabrics include
from 1 to about 6 plies, but may include as many as about 10 to
about 20 plies as may be desired for various applications. The
greater the number of plies translates into greater ballistic
resistance, but also greater weight. As is conventionally known in
the art, excellent ballistic resistance is achieved when individual
fiber plies are cross-plied such that the fiber alignment direction
of one ply is rotated at an angle with respect to the fiber
alignment direction of another ply. Most preferably, the fiber
plies are cross-plied orthogonally at 0.degree. and 90.degree.
angles, but adjacent plies can be aligned at virtually any angle
between about 0.degree. and about 90.degree. with respect to the
longitudinal fiber direction of another ply. For example, a five
ply non-woven structure may have plies oriented at a
0.degree./45.degree./90.degree./45.degree./0.degree. or at other
angles. Such rotated unidirectional alignments are described, for
example, in U.S. Pat. Nos. 4,457,985; 4,748,064; 4,916,000;
4,403,012; 4,623,574; and 4,737,402, all of which are incorporated
herein by reference to the extent not incompatible herewith.
[0059] Methods of consolidating fiber plies/layers to form complex
composites are well known, such as by the methods described in U.S.
Pat. No. 6,642,159. Consolidation can occur via drying, cooling,
heating, pressure or a combination thereof. Heat and/or pressure
may not be necessary, as the fibers or fabric layers may just be
glued together, as is the case in a wet lamination process.
Typically, consolidation is done by positioning the individual
fiber plies on one another under conditions of sufficient heat and
pressure to cause the plies to combine into a unitary fabric.
Consolidation may be done at temperatures ranging from about
50.degree. C. to about 175.degree. C., preferably from about
105.degree. C. to about 175.degree. C., and at pressures ranging
from about 5 psig (0.034 MPa) to about 2500 psig (17 MPa), for from
about 0.01 seconds to about 24 hours, preferably from about 0.02
seconds to about 2 hours. When heating, it is possible that the
polymeric binder coating can be caused to stick or flow without
completely melting. However, generally, if the polymeric binder
material is caused to melt, relatively little pressure is required
to form the composite, while if the binder material is only heated
to a sticking point, more pressure is typically required. As is
conventionally known in the art, consolidation may be conducted in
a calender set, a flat-bed laminator, a press or in an autoclave.
Consolidation may also be conducted by vacuum molding the material
in a mold that is placed under a vacuum. Vacuum molding technology
is well known in the art. Most commonly, a plurality of orthogonal
fiber webs are "glued" together with the binder polymer and run
through a flat bed laminator to improve the uniformity and strength
of the bond. Further, the consolidation and polymer
application/bonding steps may comprise two separate steps or a
single consolidation/lamination step.
[0060] Alternately, consolidation may be achieved by molding under
heat and pressure in a suitable molding apparatus. Generally,
molding is conducted at a pressure of from about 50 psi (344.7 kPa)
to about 5,000 psi (34,470 kPa), more preferably about 100 psi
(689.5 kPa) to about 3,000 psi (20,680 kPa), most preferably from
about 150 psi (1,034 kPa) to about 1,500 psi (10,340 kPa). Molding
may alternately be conducted at higher pressures of from about
5,000 psi (34,470 kPa) to about 15,000 psi (103,410 kPa), more
preferably from about 750 psi (5,171 kPa) to about 5,000 psi, and
more preferably from about 1,000 psi to about 5,000 psi. The
molding step may take from about 4 seconds to about 45 minutes.
Preferred molding temperatures range from about 200.degree. F.
(.about.93.degree. C.) to about 350.degree. F. (.about.177.degree.
C.), more preferably at a temperature from about 200.degree. F. to
about 300.degree. F. and most preferably at a temperature from
about 200.degree. F. to about 280.degree. F. The pressure under
which the fiber layers are molded has a direct effect on the
stiffness or flexibility of the resulting molded product.
Particularly, the higher the pressure at which they are molded, the
higher the stiffness, and vice-versa. In addition to the molding
pressure, the quantity, thickness and composition of the fiber
plies and polymeric binder coating type also directly affects the
stiffness of the spall resistant substrate 12.
[0061] While each of the molding and consolidation techniques
described herein are similar, each process is different.
Particularly, molding is a batch process and consolidation is a
generally continuous process. Further, molding typically involves
the use of a mold, such as a shaped mold or a match-die mold when
forming a flat panel, and does not necessarily result in a planar
product. Normally consolidation is done in a flat-bed laminator, a
calendar nip set or as a wet lamination to produce soft (flexible)
body armor fabrics. Molding is typically reserved for the
manufacture of hard armor, e.g. rigid plates. In either process,
suitable temperatures, pressures and times are generally dependent
on the type of polymeric binder coating materials, polymeric binder
content, process used and fiber type.
[0062] In the preferred embodiments where the spall resistant layer
12 is a fibrous substrate, the total weight of the binder/matrix
comprising the spall resistant substrate 12 preferably comprises
from about 2% to about 50% by weight, more preferably from about 5%
to about 30%, more preferably from about 7% to about 20%, and most
preferably from about 11% to about 16% by weight of the fibers plus
the weight of the coating. A lower binder/matrix content is
appropriate for woven fabrics, wherein a polymeric binder content
of greater than zero but less than 10% by weight of the fibers plus
the weight of the coating is typically most preferred, but this is
not intended as limiting. For example, phenolic/PVB impregnated
woven aramid fabrics are sometimes fabricated with a higher resin
content of from about 20% to about 30%, although around 12% content
is typically preferred.
[0063] The spall resistant substrate 12 may also optionally
comprise one or more thermoplastic polymer layers attached to one
or both of the outer surfaces of the spall resistant substrate 12.
Suitable polymers for the thermoplastic polymer layer
non-exclusively include polyolefins, polyamides, polyesters
(particularly polyethylene terephthalate (PET) and PET copolymers),
polyurethanes, vinyl polymers, ethylene vinyl alcohol copolymers,
ethylene octane copolymers, acrylonitrile copolymers, acrylic
polymers, vinyl polymers, polycarbonates, polystyrenes,
fluoropolymers and the like, as well as co-polymers and mixtures
thereof, including ethylene vinyl acetate (EVA) and ethylene
acrylic acid. Also useful are natural and synthetic rubber
polymers. Of these, polyolefin and polyamide layers are preferred.
The preferred polyolefin is a polyethylene. Non-limiting examples
of useful polyethylenes are low density polyethylene (LDPE), linear
low density polyethylene (LLDPE), medium density polyethylene
(MDPE), linear medium density polyethylene (LMDPE), linear very-low
density polyethylene (VLDPE), linear ultra-low density polyethylene
(ULDPE), high density polyethylene (HDPE) and co-polymers and
mixtures thereof. Also useful are SPUNFAB.RTM. polyamide webs
commercially available from Spunfab, Ltd, of Cuyahoga Falls, Ohio
(trademark registered to Keuchel Associates, Inc.), as well as
THERMOPLAST.TM. and HELIOPLAST.TM. webs, nets and films,
commercially available from Protechnic S.A. of Cernay, France. Such
a thermoplastic polymer layer may be bonded to the substrate 12
surfaces using well known techniques, such as thermal lamination.
Typically, laminating is done by positioning the individual layers
on one another under conditions of sufficient heat and pressure to
cause the layers to combine into a unitary structure. Lamination
may be conducted at temperatures ranging from about 95.degree. C.
to about 175.degree. C., preferably from about 105.degree. C. to
about 175.degree. C., at pressures ranging from about 5 psig (0.034
MPa) to about 100 psig (0.69 MPa), for from about 5 seconds to
about 36 hours, preferably from about 30 seconds to about 24 hours.
Such thermoplastic polymer layers may alternatively be bonded to
the substrate 12 surfaces with hot glue or hot melt fibers as would
be understood by one skilled in the art.
[0064] In embodiments where the spall resistant substrate does not
include a polymeric binder material coating the fibers or tapes
forming the substrate, it is preferred that a one or more
thermoplastic polymer layers as described above be employed to bond
fiber/tape plies together or improve the bond between adjacent
fiber/tape plies. In one embodiment, a spall resistant substrate
comprises a plurality of unidirectional fiber plies or tape plies
wherein a thermoplastic polymer layers is positioned between each
adjacent fiber ply or tape ply. For example, in one preferred
embodiment the spall resistant substrate has the following
structure: thermoplastic polymer film/binder-less 0.degree.
UDT/thermoplastic polymer film/90.degree. binder-less UDT
thermoplastic polymer film. In this exemplary embodiment, the spall
resistant substrate may include additional binder-less UDT plies
where a thermoplastic polymer film is present between each pair of
adjacent UDT plies. In addition, in this exemplary embodiment, a
unitape (UDT) may comprise a plurality of parallel fibers or a
plurality of parallel tapes. This exemplary embodiment is not
intended to be strictly limiting. For example, the UDT elongate
bodies (i.e. fiber or tapes) of the UDT plies may be oriented at
other angles, such as thermoplastic polymer film/0.degree.
binder-less UDT/thermoplastic polymer film/45.degree. binder-less
UDT/thermoplastic polymer film/90.degree. binder-less UDT
thermoplastic polymer film/45.degree. binder-less UDT/thermoplastic
polymer film/0.degree. binder-less UDT/thermoplastic polymer film,
etc., or the plies may be oriented at other angles. The outermost
thermoplastic polymer films may also be optionally excluded as
determined by one skilled in the art. Such binder-less structures
may be made by stacking the component layers on top of each other
in coextensive fashion and consolidating/molding them together
according to the consolidation/molding conditions described
herein.
[0065] The thickness of the spall resistant substrate 12 will
correspond to the thickness of the individual fibers/tapes and the
number of fiber/tape plies or layers incorporated into the spall
resistant substrate 12. For example, a preferred woven fabric will
have a preferred thickness of from about 25 .mu.m to about 600
.mu.m per ply/layer, more preferably from about 50 .mu.m to about
385 .mu.m and most preferably from about 75 .mu.m to about 255
.mu.m per ply/layer. A preferred two-ply non-woven fabric will have
a preferred thickness of from about 12 .mu.m to about 600 .mu.m,
more preferably from about 50 .mu.m to about 385 .mu.m and most
preferably from about 75 .mu.m to about 255 .mu.m. Any
thermoplastic polymer layers are preferably very thin, having
preferred layer thicknesses of from about 1 .mu.m to about 250
.mu.m, more preferably from about 5 .mu.m to about 25 .mu.m and
most preferably from about 5 .mu.m to about 9 .mu.m. Discontinuous
webs such as SPUNFAB.RTM. non-woven webs are preferably applied
with a basis weight of 6 grams per square meter (gsm). While such
thicknesses are preferred, it is to be understood that other
thicknesses may be produced to satisfy a particular need and yet
fall within the scope of the present invention.
[0066] The spall resistant substrate 12 comprises multiple
fiber/tape plies or layers, which layers are stacked one upon
another and optionally, but preferably, consolidated. The spall
resistant substrate 12 will have a preferred composite areal
density of from about 0.2 psf to about 8.0 psf, more preferably
from about 0.3 psf to about 6.0 psf, still more preferably from
about 0.5 psf to about 5.0 psf, still more preferably from about
0.5 psf to about 3.5 psf, still more preferably from about 1.0 psf
to about 3.0 psf, and most preferably from about 1.5 psf to about
2.5 psf. It has been unexpectedly found that when the spall
resistant substrate 12 is coupled with a blast mitigating material
14, thereby spacing the substrate 12 from a surface of a reinforced
object 16, the ballistic resistant article 10 exhibits improved
ballistic resistance. As a result, consistent levels of ballistic
performance may be achieved with a spall resistant substrate 12
having a lower areal density than liners of the related art,
thereby reducing the weight of the reinforcing armor.
[0067] It is also fully within the scope of the invention that the
spall resistant substrate 12 of the ballistic resistant articles 10
may comprise any conventionally known and commercially available
spall resistant liner material, such as the HiPerTex.TM. and
S2-Glass.RTM. fiberglass based spall resistant liners mentioned
previously herein, as well as any commercially available
KEVLAR.RTM. reinforced plastic (KRP) spall resistant liner.
[0068] The blast mitigating material 14 may be formed from any
suitable flexible material that is most preferably an elastically
deformable, shock absorbing material, including commercially
available blast mitigating materials that would be known to one
skilled in the art. As used herein, an "elastically deformable"
material is a material, typically a polymeric material, that is
capable of elastic deformation, wherein "elastic deformation" is a
temporary and reversible deformation rather than a permanent
deformation, such that when forces causing deformation are no
longer applied, the material (or object) returns to its original,
non-deformed shape. Particularly preferred are elastically
deformable, shock absorbing materials commercially available from
Skydex Technologies, Inc. of Englewood, Colo. (formerly known as
Retama Technology Corporation) under the trademark SKYDEX.RTM.,
particularly the shock absorbing materials taught in U.S. Pat. Nos.
5,976,451; 6,029,962; 6,098,313; 6,777,062; 7,033,666 and
7,574,760, each of which are incorporated herein by reference to
the extent compatible herewith. Examples of such preferred
commercially available structures from Skydex Technologies, Inc.
are illustrated in the figures. FIG. 3, FIG. 4 and FIG. 5 each
illustrate cushioning materials as described and illustrated in
U.S. Pat. No. 6,029,962. FIG. 6 illustrates an alternative useful
cushioning material as described and illustrated in U.S. Pat. No.
7,574,760.
[0069] As described in U.S. Pat. No. 6,029,962, the blast
mitigating material 14 preferably comprises a pair of sheets
comprising first and second surfaces with a plurality of integrally
formed, inwardly extending indentations protruding from the first
and second surfaces. As described therein, the pair of elastically
deformable sheets is spaced from each other to define a cavity
therebetween, each sheet having a plurality of inwardly facing,
opposing, elastically deformable protrusions extending into the
cavity, such that the elastically deformable protrusions extend
between the first and second surfaces. In a preferred embodiment,
at least some of the protrusions are hemispherical, but they may
have alternative shapes, such as illustrated in FIG. 6 and as
described in U.S. Pat. No. 7,574,760. The protrusions are
preferably hollow, but may alternatively be solid nodules or may be
filled with a material, such as foam, a polymeric material such as
rubber, or a particulate material, such as rubber particles. The
surfaces may optionally be formed of mesh material to allow the
passage of gas or fluid therethrough, and one or more inserts may
be placed in the protrusions. The blast mitigation material 14 may
be constructed by molding upper and lower elastically deformable
sheets wherein the molds are configured to provide indentations in
the top and bottom surfaces. The upper and lower sheets are then
joined to complete the blast mitigating material 14. The point of
contact can be fixed or non-fixed. If fixed, the indentations can
be joined at their contact point such as by gluing, fusing, welding
or the like. The blast mitigating material 14 may also include a
wall member coextensive with the top and bottom surfaces, as shown
in FIG. 5. The blast mitigating material 14 may also comprise at
least one additional elastically deformable sheet comprising a
plurality of integrally formed elastically deformable protrusions,
where said at least one additional sheet is adhered or otherwise
attached to at least one surface of said pair of spaced apart
elastically deformable sheets. Means for the fabrication of these
preferred commercially available blast mitigation materials are
described in detail in the Skydex Technologies, Inc. patents which
are incorporated herein by reference.
[0070] The blast mitigation material 14 is preferably formed from a
flexible high polymer thermoplastic resin, including both
crystalline and amorphous thermoplastic polymers. Such
thermoplastic polymers non-exclusively include
acrylonitrile-butadiene-styrene copolymers, styrene, cellulosic
polymers, polycarbonates, nylons, polyethylene, polypropylene and
polyurethane. Particularly preferred thermoplastic polymers for use
in the blast mitigating material 14 of the present invention are
thermoplastic polyurethanes, nylons, polyesters, polyethylenes,
polyamides and combinations thereof.
[0071] The blast mitigation material 14 is not limited to the
commercially available constructions available from Skydex
Technologies, Inc. and may comprise other suitable constructions as
would be determined by one skilled in the art wherein the blast
mitigation material 14 is capable of being attached to a spall
resistant substrate 12. For example, blast mitigating material 14
may comprise flexible, elastically deformable polymeric
particulates or foams, elastically deformable balloons, elastically
deformable micro-balloons, elastically deformable bladders,
elastically deformable hollow spheres, as well as combinations of
these materials and sheets formed from said materials. The blast
mitigating material may also comprise alternative hollow structures
formed from an elastically deformable polymeric material. All of
these materials are considered to have first and second surfaces
represented by the outermost areas of the materials, where one side
of the material is capable of being attached to the spall resistant
substrate 12 and another side of the material is capable of being
attached to an object 16. The composition and structure of the
blast mitigation material is not intended to be strictly limiting
but for the capability of being attached to the spall resistant
substrate 12. In most preferred embodiments, however, the blast
mitigating material comprises a material that is elastically
deformable. It is also most preferred that such an elastically
deformable blast mitigating material be at least partially hollow
such that at least a portion of the volume between the spall
resistant substrate 12 and a reinforced object 16 is occupied by
air.
[0072] It should also be understood that in embodiments where the
blast mitigating material 14 comprises protrusions or other
non-flat elements, the outermost area of the protrusions constitute
a surface to which the spall resistant substrate 12 may be coupled
with or attached. For example, in embodiment where the blast
mitigating material 14 comprises a single sheet of the SKYDEX.RTM.
material or three sheets of the SKYDEX.RTM. material rather than a
pair of sheets of said SKYDEX.RTM. material, the spall resistant
substrate 12 may be coupled with or attached to either side of the
sheet, and the outermost area of the protrusions constituting a
surface (or surfaces) that is suitable for contact with and
attachment with the spall resistant substrate 12.
[0073] The thickness of the blast mitigating material 14 may vary
as would be determined by one skilled in the art in view of the
spatial limitations of the object to be reinforced with the
ballistic resistant articles 10. In a preferred embodiment, the
blast mitigating material 14 has a thickness of at least about
1-inch (2.54 cm), more preferably at least about 2-inches (5.08
cm). Where the blast mitigating material 14 is a commercially
procured SKYDEX.RTM. material, the thickness of the material 14
will depend on the number of sheets of SKYDEX.RTM. material
incorporated. While such thicknesses are preferred, it is to be
understood that other thicknesses may be produced to satisfy a
particular need and yet fall within the scope of the present
invention.
[0074] The spall resistant substrate 12 and the blast mitigating
material 14 may be coupled with each other without attaching them
to each other, or they may be attached to each other using any
suitable means in the art. The spall resistant substrate 12 and the
blast mitigating material 14 are preferably attached to each other
with an adhesive. Any suitable adhesive material may be used.
Suitable adhesives non-exclusively include elastomeric materials
such as polyethylene, cross-linked polyethylene, chlorosulfonated
polyethylene, ethylene copolymers, polypropylene, propylene
copolymers, polybutadiene, polyisoprene, natural rubber,
ethylene-propylene copolymers, ethylene-propylene-diene
terpolymers, polysulfide polymers, polyurethane elastomers,
polychloroprene, plasticized polyvinylchloride using one or more
plasticizers that are well known in the art (such as dioctyl
phthalate), butadiene acrylonitrile elastomers,
poly(isobutylene-co-isoprene), polyacrylates, polyesters,
unsaturated polyesters, polyethers, fluoroelastomers, silicone
elastomers, copolymers of ethylene, thermoplastic elastomers,
phenolics, polybutyrals, epoxy polymers, styrenic block copolymers,
such as styrene-isoprene-styrene or styrene-butadiene-styrene
types, and other suitable adhesive compositions conventionally
known in the art. Particularly preferred adhesives include
methacrylate adhesives, cyanoacrylate adhesives, UV cure adhesives,
urethane adhesives, epoxy adhesives and blends of the above
materials. Of these, an adhesive comprising a polyurethane
thermoplastic adhesive, particularly a blend of one or more
polyurethane thermoplastics with one or more other thermoplastic
polymers, is preferred. Most preferably, the adhesive comprises
polyether aliphatic polyurethane. Such adhesives may be applied,
for example, in the form of a hot melt, film, paste or spray, or as
a two-component liquid adhesive. Other suitable means for
attachment non-exclusively include stitching them together, bolting
or screwing them together, as well as attachment with hook-and-loop
fasteners such as VELCRO.RTM. brand products commercially available
from Velcro Industries B.V. of Curacao, The Netherlands, or 3M.TM.
brand hook and loop fasteners, and the like.
[0075] The blast mitigating material 14 may be coupled with only
one spall resistant substrate 12, said substrate 12 being coupled
with only one of said first and second surfaces of the blast
mitigating material 14, or it may be coupled with more than one
spall resistant substrate 12 on one or both of its surfaces. The
articles 10 may also comprise more than one blast mitigating
material 14 attached to one or both outer surfaces of the spall
resistant substrate 12. To minimize the weight of the ballistic
resistant article, it is most preferred that only one spall
resistant substrate 12 is coupled with only one of said first and
second surfaces of the blast mitigating material 14.
[0076] It is also preferred that one or both of the outer surfaces
of the ballistic resistant articles of the invention be covered
with a protective cover 18. In a most preferred embodiment, a
protective cover 18 is positioned on or attached to an outer
surface of the spall resistant substrate 12. Suitable protective
covers 18 include, for example, fabric materials such upholstery
fabrics, as well as polymeric surface covers, such as molded rubber
or non-molded rubber sheets. An example of a suitable upholstery
fabric useful as a protective cover 18 is CORDURA.RTM. brand fabric
or covers fabricated from CORDURA.RTM. brand nylon fibers, each of
which are commercially available from Invista S.a r.l. of Wichita,
Kans.
[0077] The ballistic resistant articles of the invention are
suitable for reinforcing or armoring any type of object as may be
desired by one skilled in the art, but are particularly useful for
reinforcing vehicles such as automobiles, military tanks, aircraft
and marine vessels. As stated above, it is known that incorporating
a space between a spall resistant liner and a vehicle hull can
increase spall resistant liner performance, and it has been
unexpectedly found that when the spall resistant substrate 12 is
coupled with a blast mitigating material 14, particularly an
elastically deformable blast mitigating material, thereby spacing
the substrate 12 from a surface of a reinforced object 16, the
ballistic resistant article 10 exhibits improved ballistic
resistance. Accordingly, objects are to be reinforced are
reinforced with the ballistic resistant articles 10 of the
invention by positioning the articles 10 such that the blast
mitigating material 14 is contiguous to the object 16, such that at
least a portion of the volume between the object and the spall
resistant substrate is occupied by air. Articles 10 may be attached
to the object to be reinforced or may be loosely placed into a
desired position without being attached or otherwise secured to the
object. For example, articles 10 may be bolted into the hull of a
vehicle, adhered to the hull of the vehicle, or otherwise attached
by another means that would be readily determined by one skilled in
the art. Suitable adhesives include those previously described
herein.
[0078] While such designs are most preferred, alternate designs may
also be effective for the purposes described herein. For example,
depending on spatial limitations and desired ballistic resistance
requirements, it may be possible and desirable to space the
ballistic resistant articles 10 from the vehicle hull such that an
open space is present between the articles 10 and the hull. The
essential feature is the removal of the spall resistant liner from
direct placement with the hull and providing an air space, but most
preferably achieving the air space with a blast mitigating
material, as it has been found by the Examples below to outperform
having only an open air space. This ordering improves the
performance and also importantly reduces the necessary weight of
the system.
[0079] The following examples serve to illustrate the
invention.
Examples 1-5
[0080] Overmatch testing was conducted to measure the performance
of a spall resistant liner with and without a blast mitigating
material attached to one of its surfaces. A strike face of high
hard steel (15 mm of ARMOX.RTM. 440T steel commercially available
from SSAB Technology AB of Stockholm, Sweden) was used as
representative of a vehicle hull. In all examples, the spall
resistant liner was constructed from the same material, comprising
19 consolidated layers of a 4-ply, non-woven aramid-fiber based
composite fabric identified herein as GV-2018. THE GV-2018
composite included a polyurethane binder material with a total
binder content of 13% by weight of the layer. In each example, the
spall resistant liner had an areal density of 2.0 lb/ft.sup.2
(psf). In Example 1 (Comparative), the spall resistant liner tested
was placed directly behind the strike face hull and clamped in
place. In Example 2 (Comparative), the spall resistant liner tested
was spaced apart from the strike face hull by 13.5 mm. In Example 3
(Comparative), the spall resistant liner tested was spaced apart
from the strike face hull by 30 mm. In Example 4, the spall
resistant liner was adhered to one article of SKYDEX.RTM. blast
mitigating material, where the SKYDEX.RTM. material comprised a
pair of sheets comprising hemispherical-shaped protrusions as
described in U.S. Pat. No. 6,029,962. In Example 5, the spall
resistant liner was adhered to two articles of SKYDEX.RTM. blast
mitigating material, where the SKYDEX.RTM. material comprised a
pair of sheets comprising hemispherical-shaped protrusions as
described in U.S. Pat. No. 6,029,962. In each of Examples 4 and 5,
the SKYDEX.RTM. material was positioned between the spall resistant
liner and the strike face hull, and the thickness of each sheet of
the SKYDEX.RTM. material was approximately 30 mm. Testing was
conducted using an RPG-7 stimulant as the ballistic threat. A
witness plate was placed behind the samples and the perforations in
the witness plate were collected and measured to determine the 1/2
spall cone angle (.alpha.). FIG. 10 illustrates how angle .alpha.
was measured.
[0081] The 1/2 spall cone angle .alpha. was then used to compare
the cone angle reduction in degrees relative to the 1/2 spall cone
angle .alpha. on a baseline metal with no spall resistant liner.
For each test shot, four angles were calculated based on
percentages (100%, 99%, 95% and 90%) of the total number of
perforations in the witness plate. The results are summarized in
Table 1 and are graphically illustrated in FIG. 7.
TABLE-US-00001 TABLE 1 Example Test 100% 99% 95% 90% 1 Liner
Directly on Hull 7.25 4.05 0.2 -1.15 (Comp.) 2 Liner with 13.5 mm
air gap 10.7 8.9 4.5 2.5 (Comp.) 3 Liner with 30 mm air gap 18.2
10.7 7.0 6.8 (Comp.) 4 Liner with one SKYDEX .RTM. 22.2 15.5 11.7
11.0 BMM sheet between Liner and Hull 5 Liner with two SKYDEX .RTM.
40.2 31.7 23.5 19.8 BMM sheets between Liner and Hull
[0082] The results from Examples 1-5 illustrate that spall
resistant liner performance was improved when spaced from the
ARMOX.RTM. hull, but the performance of the system was
significantly better when the SKYDEX.RTM. material was in the gap
space.
Examples 7-12
[0083] In Examples 6-11 the testing described for Comparative
Example 1 was repeated where the test was performed with the spall
resistant liner placed directly behind the strike face hull and
clamped in place, but in these Examples the performance of spall
resistant liners having varying areal densities were compared.
Example 6 (Comparative) and Example 7 (Comparative) are duplicates
of Example 1 (Comparative), testing a spall resistant liner having
an areal density of 2.0 psf. In Examples 8 and 9, the spall
resistant liner had an areal density of 3.5 psf. In Examples 10 and
11, the spall resistant liner had an areal density of 5.0 psf.
Inventive Example 12 is a duplicate of Inventive Example 4, where a
2.0 psf spall resistant liner was adhered to one article of
SKYDEX.RTM. blast mitigating material having a thickness of
approximately 30 mm. In all examples, the spall resistant liner was
constructed from the same materials and comprised GV-2018 as per
Examples 1-5. The results are summarized in Table 2 and are
graphically illustrated in FIG. 8.
TABLE-US-00002 TABLE 2 Example Test 100% 99% 95% 90% 6 2.0 psf
Liner Directly on Hull 8.7 5.9 0.7 -1.4 (Comp.) 7 2.0 psf Liner
Directly on Hull 5.8 2.2 -0.3 -0.9 (Comp.) 8 3.5 psf Liner Directly
on Hull 16.0 8.5 3.3 2.1 (Comp.) 9 3.5 psf Liner Directly on Hull
19.3 11.0 6.0 3.6 (Comp.) 10 5.0 psf Liner Directly on Hull 11.9
10.9 5.3 4.4 (Comp.) 11 5.0 psf Liner Directly on Hull 21.2 14.7
7.8 6.0 (Comp.) 12 Liner with one SKYDEX .RTM. 22.2 15.5 11.7 11.0
BMM between Liner and Hull
[0084] The results from Examples 7-12 illustrate that the use of a
2.0 psf spall resistant liner together with the SKYDEX.RTM. blast
mitigating material outperformed a 5.0 psf liner, thereby providing
a significant weight savings.
[0085] While the present invention has been particularly shown and
described with reference to preferred embodiments, it will be
readily appreciated by those of ordinary skill in the art that
various changes and modifications may be made without departing
from the spirit and scope of the invention. It is intended that the
claims be interpreted to cover the disclosed embodiment, those
alternatives which have been discussed above and all equivalents
thereto.
* * * * *