Note: Descriptions are shown in the official language in which they were submitted.
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LIGHTWEIGHT ARMOR AGAINST
MULTIPLE HIGH VELOCITY BULLETS
BACKGROUND OF 'THi~ INVENTION
1. Field of the Invention
The invention relates to fiber reinforced articles having utility for
ballistic resistance to multiple high velocity bullets, impact absorption and
penetration resistance in body armor, helmets, breast plates, helicopter
seats, spall shields and other applications.
2. Description of the Re6atec! Art
lo Modern body armor designed for protection against hand-gun
arnmunition at velocities of about 1000 ft/sec (305 m/sec) is usually formed
from thin layers of woven fabrics or non-woven sheets of fibers that are
plied together in a flexible bundle. However, body armor designed to
defeat heavy rifle bullets with velocities over 2000 ft/sec (610 m/sec)
generally requires a more complex construction in order to satisfy
conflicting requirements of weight, thickness, flexibility, multiple hit
performance, transient deformation (blunt trauma) and durability. The
armor may incorporate rigid front and/or back elements to deform the bullet
or to absorb its energy. Inorganic materials such as ceramics have found
use in such armor because of their high hardness and low density relative
to metals. Plates and tiles, commonly used forms of ceramics, often
shatter in the process of deforming a bullet, and thus offer relatively little
protection against subsequent bullet hits. This problem is particularly
manifested when the bullet contains a steel penetrator designed to
penetrate armor.
There are numerous ballistic-resistant constructions described in
the prior art, although most are not directed at protection against rifle
bullets or multiple hit performance. USP 4,111,097 describes a laminated
multi-layer armor comprising steel and tungsten wire mesh in a foamed
plastic. USP 4,868,040 describes a three-element composite comprising a
frontal woven fabric composite, a ceramic tile energy absorbing body and a
rearward woven fabric composite. USP 5,221,807 describes an armor
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comprising a frontal ceramic plate having a regular array of cells, an
intermediate layer having a honeycomb structure and a rear plate that may
be Kevlar fiber, ceramic matrix composite or steel. USP 5,545,455
describes a rigid composite comprising polymeric fibrous layers stitched
together and continuously encircled by a fibi-ous girdle. The stitching fibers
may be inorganic fibers. USP 5,456,156 describes an armor compi-ising
metal reinforced ceramic and a tough backup plate. USP 5,635,288
describes a rigid composite comprising a monolithic frontal plate consisting
of ceramic, steel, glass, aluminum, titanium or graphite and a rearward
io layer comprising unidirectionally oriented polymeric-fibers bonded at their
outer surfaces by plastic films.
USP 5,677,029 describes a flexible fiber composite armor with
surfaces comprising tessellated triangular or hexagonal shaped hard
bodies positioned such that multiple seams are formed and the armor is
flexible along the seam directions. The hard bodies may be reinforced with
polymeric or inorganic fibers. USP 6,035,438 describes a body armor
comprising ceramic disks laid out in an imbricate pattern sandwiched
between layers of high strength fibers. USP 6,510,777 describes a vehicle
armor of similar construction. USP 6,127,291 describes a flexible
penetration-resistant composite comprising woven sub-plies of polymeric or
inorganic ballistic fibers. USP 6,323,145 B1 describes a penetration-
resistant interlaced yarn structure of high strength polymeric or inorganic
fibers. USP 6,389,594 describes an anti-ballistic article comprising a
ceramic plate maintained under isostatic pressure of at least 10
atmospheres by a resin enclosure.
USP 6,408,733 B1 describes an armor for multiple bullet
protection comprising a monolithic ceramic frontal element and an aramid
fiber composite substrate. USP 6,532,857 B1 describes a ceramic array
armor comprising elastomer-encapsulated ceramic tiles spaced from one
3o another and an optional metal backing plate. USP 6,601,497 B2 describes
an armor component comprising a polygonal ceramic tile confined in a
wrapping material wherein the wrapping material may comprise one of a
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high-strength fiber, a high-strength fiber in a polymer composite matrix, a
high-strength fiber in a metal matrix, a high-strength metallic band, and a
high-strength metallic wire.
USP Application 2001/0053645 Al describes a multi-layered
ballistic resistant article comprising at least one hard armor layer and at
least one fibrous armor layer, wherein the fibers of one fibrous ply are at an
angle of less than 45 to the fibers of the adjacent fibrous ply. The material
of the hard armor layer is a metal, a metal/ceramic composite, a ceramic, a
hardened polymer or combinations thereof.
30 Each of the articles in the patents cited above represents
improvements in the state of the art. However, none describes the specific
constructions of the articles of this invention and none satisfies all of the
needs met by this invention. It is a principal objective of this invention to
provide lightweight, ballistic-resistant and penetration-resistant composites
1; having multiple hit capability against high velocity bullets.
SUMMARY OF THE INVENTION
The invention is a bailistic-resistant and penetration-resistant
article comprising:
20 a) a frontal laminate comprising one or more plies, the frontal
laminate having at least a frontal ply comprising a plurality of laminae of
unidirectional inorganic fibers in a polymeric matrix, the laminae in a ply
having the same composition and construction, the laminae in adjacent
plies of the frontal laminate differing in composition and/or construction
25 from one another, the inbrganic fibers being comprised of filaments having
a tensile strength of at least 2.0 GPa and a density of less than 4.0 g/cm3,
whei-ein the fiber direction in each lamina is at an angle to the fiber
direction in adjacent laminae; and
b) a second laminate united in face-to-face relationship with-the
30 frontal laminate, the second laminate comprising one or more plies, each
ply comprising a plurality of laminae of polymeric fibers in a network, the
polymeric fibers having a tenacity of at least 17 g/d, the network optionally
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containing a polymeric matrix material, a ply in the second laminate being
defined by laminae having the same composition and construction which
differs from the composition and/or construction of the laminae in adjacent
plies.
BRIEF DESCRIPTION OF THE DRAWINGS
(n the accompanying drawing figures:
FIGURE 1 is a cross-section of a two-ply embodiment of an
article of the invention having one ply of unidirectional inorganic fibers in
a
io frontal laminate, and one ply of polymeric fibers in a second laminate.
FIGURE 2 is a cross-section of a five-ply embodiment of an
article of the invention having two plies of unidirectional inorganic fibers
in a
frontal laminate, each ply having different compositions or constructions,
two plies of polymeric fibers in a second laminate, each ply having different
cornpositions or constructions, and one ply of inorganic fibers in a third
laminate.
FIGURE 3 is a cross-section of a five-ply embodiment of an
article of the invention having:
a) a frontal laminate consisting of a frontal ply of unidirectional
2a inorganic fibers, a second ply consisting of a titanium metal plate,
and a third ply of unidirectional inorganic fibers, the titanium metal
plate being embedded on all surfaces by the frontal and third plies;
b) a second laminate consisting of one ply of polymeric fibers; and
c) a third laminate consisting of one ply of polymeric fibers of a
composition or construction different from those in the second
laminate.
FIGURE 4 is a schematic representation of a process for making
a lamina.
DETAILED DESCRIPTION OF THE INVENTION
The invention is fiber reinforced articles having utility for ballistic
resistarice to multiple high velocity bullets, impact absorption and
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penetration-resistance in body armor, helmets, breast plates, helicopter
seats, spall shields and other applications. The invention is a ballistic-
resistant and penetration-resistant article comprising:
a) a frontai laminate and b) a second laminate, united face-to-
5 face. The frontal laminate comprises one or more plies, the frontal ply of
which comprises a plurality of laminae of unidirectional inorganic fibers in a
matrix. A ply is defined by laminae having the same composiLion and
construction and. differing in composition and/or construction from the
laminae in adjacent plies. The inorganic fibers comprise filaments having a
zo tensile strength of at least 2.0 GPa and a density of.iess than 4.0 g/cm3.
The fiber direction in each lamina is at an angle to the fiber direction in
adjacent laniinae.
The second laminate comprises one or more plies, each of
which comprises a plurality of laminae of polymeric fibers in a network.
The polymeric fibers have a tenacity of at least 17 g/d. The network
optionally contains a matrix material. A ply is defined by laminae having
the same composition and construction and differing in composition and/or
construction from the laminae in adjacent plies.
As used herein "laminate" denotes a structure wherein
superposed sheet-like elements (laminae) are united, either loosely, for
example by sewing around their edges or at their corners, or rigidly, for
example by full areal bonding, or at any intermediate level, for example by
stapling, riveting, sewing, partial bonding, or other suitable means.
For purposes of the present invention, a fiber is an elongate body
the length dimension of which is much greater than the transverse
dimensions of width and thickness. Accordingly, "fiber" as used herein
includes one or a piurality of filaments, ribbons, strips, and the like having
regular or irregular cross-sections in continuous or discontinuous lengths.
A yarn is an assemblage of continuous or discontinuous fibers.
As used herein, "fiber network" or "network" denotes a plurality of
fibers arranged into a predetermined configuration, or a plurality of fibers
grouped together to form a twisted or untwisted yarn, which yarns are
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arranged into a predetermined configuration. The fiber network can have
various constructions. For example, the fibers or yarn may be structured
as a felt, knit, braid, weave, randomly oriented non-woven (e.g. air-laid),
unidirectionally oriented non-woven, or formed into a network by any
conventional techniques. According to a particularly preferred network
configuration, the fibers are unidirectionally aligned so that they are
substantially parallel to each other along the longitudinal direction of the
network layer. This is not meant, however, to preclude the use of an
insubstantial number of parallel and/or non-parallel fibers for the purpose of
io stabilizing the other fibers, as is known in the art.
In a further embodiment, an article of the invention comprises:
a)' a frontal laminate and b) a second laminate, as described
above and united face-to-face, in combination with c) a third laminate,
which is stacked face-to-face with the second laminate.
ls The third laminate also comprises one or more plies, each of which
comprises a plurality of laminae of polymeric fibers in a network not
containing a matrix. The polymeric fibers have a tenacity of at least 17 g/d,
and a ply is defined by laminae having the same composition and
construction and differing in composition and/or construction from the
20 laminae in adjacent plies;
In another embodiment, the article of the invention comprises:
a) a frontal laminate and b) a second laminate, as previously described and
united face-to-face, in combination with c) a third laminate, united face-to-
face to the second laminate. This third laminate also comprises one or
25 niore plies, each of which compi-ises a plurality of laminae of
unidirectional
inorganic fibers in a polymeric matrix. A ply is here defined by laminae
having the same composition and construction and differing in composition
and/or construction from the laminae in adjacent plies. The inorganic fibers
havea tensile strength of at least 2.0 GPa and a density of less than 4.0
g/cm3. The fiber direction in each lamina is at an angle to the fiber
direction
in adjacent laminae.
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In yet another embodiment, the article of the invention
comprises:
a) a frontal laminate united face-to-face to b) a second laminate, and c) a
third laminate stacked face-to-face with the second laminate.
s In this embodiment, the first laminate comprises at least three
plies, the frontal ply comprising a plurality of unidirectional inorganic
fibers,
a second ply comprising a titanium metal plate, and a third ply comprising a
pluraltiy of unidirectional inorganic fibers. The titanium metal plate forming
the second ply is embedded on all surfaces by the first and third plies. A
io ply is defined by laminae having the same composition and construction
and differing in composition and/or construction from the laminae in
adjacerit plies. The inorganic fibers are comprised of filaments having a
tensile strength of at least 2.0 GPa, and a density of less than 4.0 g/cm3.
As in previous embodiments, the fiber direction in each lamina is at an
1s angle to the fiber direction in adjacent laminae.
The second and third laminates of this embodiment
independently comprise one or more plies, each of which comprises a
plurality of laminae of polymeric fibers in a network. The polymeric fibers
have a tenacity at least 17 g/d, and the network optionally contains a
20 polymeric matrix material. As in previous embodiments, a ply is defined by
laminae having the same composition and construction and differing in
composition and/or construction from the laminae in adjacent plies.
It will be understood that in each embodiment the frontal laminate
faces the direction of the incoming threat.
?5 Figure 1 is a cross-sectional view of one article 100 of the
invention comprising a frontal laminate 50 and a second laminate 60. In
the article illustrated, the frontal larninate 50 is comprised of a single ply
which comprises a plurality of laminae of unidirectional inorganic fibers in a
polymeric rnatrix. The fiber direction in each lamina is at an angle to the
30 fiber direction in adjacent laminae, and the composition and construction
in
each lamina is identical. The second laminate 60 is bonded face-to-face to
the frontal laminate 50. The second laminate 60 is also comprised of a
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single ply which comprises a plurality of laminae of unidirectional polymeric
fibers in a polymeric matrix. The fiber direction in each lamina is at an
angle to the fiber direction in adjacent laminae, and the composition and
construction in each lamina is identical.
Figure 2 is a cross-sectional view of another article 200 of the
invention comprising a frontal laminate 50, consisting of two plies 10 and
20; a second laminate 60 consisting of two plies 30 and 40; and a third
laminate 70 consisting of one ply. Plies 10 and 20 of the first laminate 50
are distinguished from one another by consisting of laminae of different
io inorganic fibers and/or different matrices and/or different constructions.
Plies 30 and 40 of the second laminate 60 are distinguished from one
another by consisting of laminae of different polymeric fibers and/or
different or no matrices and/or different constructions. Laminate 70
consists of a single ply wherein the composition and construction in each
lamina is identical.
Figure 3 is a cross-sectional view of yet another article 300 of the
invention comprising a frontal laminate 80, a second laminate 85, and a
third laminate 90. The frontal laminate 80 is comprised of three plies. A
frontal ply 81 consists of a plurality of laminae of unidirectional inorganic
fibers in a polymeric matrix, wherein the fiber direction in each lamina is at
an angle to the fiber direction in adjacent laminae and the composition and
construction in each lamina is identical. A second ply of the first laminate
82 is a titanium metal plate embedded on all surfaces by the first and third
plies (81 and 83). The third ply 83 of the first laminate 80 consists of a
plurality of laminae of unidirectional inorganic fibers in a polymeric matrix,
wherein the fiber direction in each lamina is at an angle to the fiber
direction in adjacent laminae and the composition and construction in each
lamina is identical. The second laminate 85 is comprised of a single ply
that consists of a plurality of laminae of unidirectional polymeric fibers in
a
polymeric matrix, wherein the fiber direction in each lamina is at an angle to
the fiber direction in adjacent laminae and the composition and construction
in each lamina is identical. The third laminate 90 is also comprised of a
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single ply that consists of a plurality of laminae of unidirectional polymeric
fibers in a polymeric matrix, wherein the fiber direction in each lamina is at
an angle to the fiber direction in adjacent laminae and the composition and
construction in each lamina is identical.
Preferably, each of the laminates in an article of the invention
has balanced construction. A balanced laminate construction is one in
which all laminae are found only in 8 pairs relative to the centerline of
the laminate, or at 0/90 . Preferably, the angle between the fibers in
adjacent laminae is from 45 to 90 degrees.
Preferably, the filaments comprising the inorganic fibers have a
tensile strength of at least 2.4 GPa and a density of less than 3.4 g/cm3,
more preferably, a tensile strength of at least 3.4 GPa and a density of less
than 3.4 g/cm3, and most preferably, a tensile strength of at least 4.0 GPa
and a density of less than 3.1 g/cm3.
Some examples of inorganic fibers useful in a laminate of the
invention are listed in Table E. The abbreviation "CVD" in Table I means
chemically vapor deposited.
The plies may be constructed with the fibers listed in Table l,
singly or in combination. The filaments of different composition may be
combined in a single fiber/yarn, or the unidirectional laminae may be
constructed with fibers/yarns of different composition laid down parallel to
one another in regular or irregular array. A ply is defined by laminae having
the same composition and construction and differing from the composition
and/or construction of laminae in adjacent plies. A laminate may be
25- constructed with several plies each having a different fiber and/or a
different matrix. A laminate may also be constructed with several plies
each having the same inorganic fiber and matrix but having different
filament and/or matrix concentrations.
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TABLE !
Designation and Composition Strength, ~ensity,
Supplier GPa g/cm3
SCS (a) CVD SiC on carbon 3.4 - 5.8 2.8 - 3.0
Boron fiber (a) CVD boron on tungsten 3.4 - 4.5 2.6 - 3.4
Nicalon NL-200 (b) (3-SiC in Si-O-C amorphous phase 3.0 2.55
Hi Nicalon (b) (3-SiC, carbon 2.8 2.74
Hi Nicalon-S (b) (3-SiC, carbon 2.6 3.10
Tyranno Lox M(c) 54.4% Si, 32.4% C, 10.2% O, 2% Ti 3.3 2.48
Tyranno ZM (c) 55.3% Si, 33.9% C, 9.8% 0, 1.0% Zr 3.3 2.48
SiBN (d) SiBNaC with 1-3% O 3.0 1.8 -- 1.9
E - Glass (e) Si, A{, Ca oxide glass 2.4 2.54
S- Glass (e) Si, Al, Ca oxide glass _ 3.45 2.55
Nextel 720 (f) 85/15 A1203/Si02 2.1
a) Specialty Materials, Inc., Lowell, MA
b) Nippon-Carbon Co., Ltd., Tokyo, Japan
c) UBE America Inc., New York, NY
s d) Bayer AG, Leverkusen, Germany
e) Owens Corning, Toledo, OH
f) 3M Co., Minneapolis, MN
Preferably, the inorganic fibers comprising a laminate are
jo chemically vapor deposited boron on tungsten or chemically vapor
deposited silicon carbide on carbon, and combinations thereof. Preferably,
the inorganic fibers comprise from 60 to 95 percent by weight of the
laminate.
The polymeric fibers comprising the plies of the second laminate
or a third laminate are preferably selected from the group consisting of high
molecular weight polyethylene, aramid, polybenzazole, rigid rod polymeric
fibers (such as M5 brand) and combinations thereof.
As used herein, the term polyethylene means a predominantly linear
polyethylene material that may contain minor amounts of chain branching
or comonomers not exceeding 5 modifying units per 100 main chain carbon
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atoms, and that may also contain admixed therewith not more than about
50 wt % of one or more polymeric additives such as alkene-i-polymers, in
particular low density polyethylene, polypropylene or polybutylene,
copolymers containing mono-olefins as primary monomers, oxidized
polyolefins, graft polyolefin copolymers and polyoxymethylenes, or low
molecular weight additives such as antioxidants, lubricants, ultra-violet
screening agents, colorants and the like.
High molecular weight polyethylene for the purposes of this
invention has an intrinsic viscosity in decalin at 135 C of from about 5
io deciliter/gram (di/g) to about 35 dl/g. Such high molecular weight
polyethylene fibers may be grown in solution as described in USP
4,137,394 or USP 4,356,138, or a filament spun from a solution to form a
gel structure, as described in German Off. No. 3,004, 699 and GB No.
2051667, and especially as described in USP 4,413,110 and sold under the
Is SPECTRAO trademark by Honeywell International Inc. The disclosure of
USP 4,413,110 is hereby incorporated by reference to the extent that it is
not inconsistent herewith. The polyethylene fibers may also be produced
by a rolling and drawing process as described in UPS 5,702,657 and sold
under the TENSYLONO trademark by ITS Industries Inc.
20 In the case of aramid fibers, suitable fibers formed from aromatic
polyamides are described in USP's 3,671,542 and 5,010,168 which are
hereby incorporated by reference. Aramid fibers are produced
commercially by E. 1. Dupont Co. under the KEVLARO and NOMEXO
trademarks; by Teijin Twaron BV under the TV1(ARONO, TECHNORAO
and TEI.IINCONEXO trademarks; by JSC Chim Volokno under the name
ARMOS; and by Kamensk Volokno JSC under the names RUSAR and
SVM. Poly(p-phenylene terephthalamide) and p-phenylene
terephthalamide aramid co-polymer fibers having moderately high moduli
and tenacity values are particularly useful in the present invention. An
30 example of a p-phenylene terephthalamide copolymer aramid useful in the
invention is co-poly-(paraphenylene 3,4'-oxydiphenylene terephthalamide).
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Also useful in the practice of this invention are poly(m-phenylene
isophthalamide) fibers.
Suitable polybenzazole fibers for the practice of this invention are
disclosed for example in USP's 5,286,833, 5,296,185, 5,356,584,
5,534,205 and 6,040,050 hereby incorporated by reference. Preferably,
the polybenzazole fibers are ZYLONO poly(p-phenylene-2,6-
benzobisoxazole) fibers from Toyobo Co.
Suitable rigid rod polymers having the structure of the M5 brand
of fiber are disclosed in USP's 5,674,969, 5,939,553, 5,945,537 and
io 6,040,478, hereby incorporated by reference. A preferred fiber is M50
brand available from Magellan Systems International, LLC.
The fiber networks in the plies of the second laminate or a third
laminate may be constructed with the polymeric fibers listed above singly or
in combination. The filaments of different composition may be combined in
1s a single fiber. Unidirectional fiber networks may be constructed with
fibers
of different composition laid down parallel to one another in regular or
irregular array. Felts, braids, knits and woven fabrics may employ different
fibers in different directions. A ply is defined by laminae having the same
composition and construction differing in composition and/or construction
20 from the laminae in adjacent plies. The second laminate or a third laminate
may be constructed with several plies each having a different polymeric
fiber, a different or no matrix, or a different fiber network construction. As
different polymeric fibers have differing ballistic effectiveness to
projectiles
of differing velocities, it is preferred to construct the second laminate with
25 plies containing the fiber that is most effective against high velocity
projectiles nearest the frontal laminate.
Preferably, the polymeric fibers comprise from 75 to 100 percent
by weight of the second laminate, the balance being a matrix material. .
The polymeric matrices employed in the inorganic fiber networks
30 preferably have initial tensile moduli of at least 400,000 psi (2.76 GPa)
as
measured by ASTM D638-94b. More preferably, the polymeric matrix in at
least one ply of the frontal laminate has an initial tensile modulus of at
least
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1 x 106 psi (6.9 GPa), as measured by ASTM D638-94b. High modulus
matrix resins useful in a laminate of the invention include thermoset allyls,
aminos, cyanates, epoxies, phenolics, urisaturated polyesters,
bismaleimides, rigid polyurethanes, silicones, vinyl esters and their
copolymers and blends. It is important only that the matrix resin possesses
the necessary initial tensife modulus. Thermoset vinyl ester resins are
preferred.
Preferably, the vinyl ester is one produced by the esterification of
a polyfunctional epoxy resin with an unsaturated monocarboxylic acid,
io usually methacrylic or acrylic acid. Illustrative vinyl esters include
diglycidyl
adipate, diglycidyl isophthalate, di-(2,3-epoxybutyl) adipate, di-(2,3-
epoxybutyl) oxalate, di-(2,3-epoxyhexyl) succinate, di-(3,4-epoxybutyl)
maleate, di-(2,3-epoxyoctyl) pimelate, di-(2,3-epoxybutyl) phthalate, di-(2,3-
epoxyoctyl) tetrahydrophthalate, di-(4,5-epoxydodecyl) maleate, di-(2,3-
1s epoxybutyl) terephthalate, di-(2,3-epoxypentyl) thiodiproprionate, di-(5,6-
epoxytetradecyl) diphenyldicarboxylate, di-(3,4-epoxyheptyl)
suphonyldibutyrate, tri-(2,3-epoxybutyl)-1,2,4- butanetricarboxylate, di-(5,6-
epoxypentadecyi) maleate, di-(2,3-epoxybutyl) azelate, di-(3,4-
epoxypentadecyl) citrate, di-(4,5-epoxyoctyl) cyclohexane-1,3-
2o dicarboxylate, di-(4,5-epoxyoctadecyl) malonate, bisphenol-A-fumaric acid
polyester and similar materials.
Most preferred are epoxy-based vinyl ester resins, such as the
DERAKANEO resins manufactured by Dow Chemical Company.
The polymeric matrices that are optionally eirrployed in the plies
25 of the second laminate are preferably elastomEirs having initial tensile
moduli of less than 6000 psi (41.3 MPa) as measured by ASTM D638-94b.
A wide variety of elastomeric materials and formulations having
appropriately low modulus may be utilized in this invention. For example,
any of the following materials may be employed: polybutadiene,
30 polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-
propylene-diene terpolymers, polysulfide polymers, polyurethane
elastomers, cholorosulfinated polyethylene, polychloroprene, plasticized
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polyvinylchloride using dioctyl phthalate or other plasticizers well known in
the art, butadiene acrylonitrile elastomers, poly(isobutylene-co-isoprene),
polyacrylates, polyesters, polyethers, fluoroelastomers, silicone elastomers,
thermoplastic elastomers, copolymers of ethylene. Preferred are block
copolymers of conjugated dienes and vinyl aromatic copolymers. Many of
these polymers are produced commercially by Kraton Polymers, Inc.
Alternatively, if the article of the invention is to be used in hard
armor, or has a structural role, the polymeric matrix optionally employed in
the plies of the second laminate preferably has an initial tensile moduli
least
io 400,000 psi (2.76 GPa), more preferably 1 x'E 106 psi (6.9 GPa) as
measured by ASTM D638-94b. Thermoset vinyl ester resins are preferred.
As used herein, the term "matrix" does not imply any particular
degree of filling of void volume in or between the laminae. As the impact
properties of a laminate are determined almost entirely by the fiber conterit,
1s and it is desirable to minimize the weight of the laminate, the matrix
content
is preferably kept as low as possible consistent with the requirements of
particular manufacturing processes. The level of matrix necessary to
stabilize the laminae and to maintain a robust manufacturing operation will
be known to the man skilled in the art.
20 The matrix resin may be applied to the fibers in a variety of ways
and any method known to those skilled in the art may be used. Preferably,
a unidirectional fiber lamina in a matrix is formed in a continuous process
illustrated schematically in Figure 4. Fibers are supplied from a creel 102
and passed through a combing station 104 to form a unidirectional network.
25 Different fibers may be arranged on the creel so a to produce a fiber
network with a periodic or other arrangement of the fibers in a transverse
direction. The fiber network is then placed on a carrier web that can be a
paper or a plastic film or plastic sheet substrate 106. The matrix
composition is applied to the fiber network at 108. The matrix composition
A may contain a solvent diluent or it may in the form of an aqueous
dispersion for ease of application. The coated fiber network is then passed
through a pair of roliers 110. The rollers spread the matrix composition
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among the fibers. The rollers may be designed to create a non-uniformly
distributed matrix as described in USP 5,093,158 hereby incorporated by
reference to the extent not incompatible herewith. The coated fiber network
is then passed through a heated oven 112 to evaporate any solvent or
5 water in the matrix composition. A nip roller 116 is used to pull the
carrier
web and prepreg through the system. The substrate and the prepreg that
will becorne a lamina can then be wound on a roller 118 in preparation for
construction of an article of the invention.
A ply of a preferred laminate is preferably produced from
io continuous rolls of unidirectional prepregs as described above by a
continuous cross-plying operation employing the method of USP 5,173,138
or 5,766,725, hereby incorporated by reference to the extent not
incompatible herewith, or by hand lay-up, or by any suitable means. With
reference to the apparatus and drawings of USP 5,173,138, one prepreg
15 roll is placed on the let off roll 11 of the cross-plying machine and a
second
prepreg roll is placed on the let off roll 17. The carrier web may be stripped
from the prepreg or it may become part of the final laminate.
The fiber compositions of the prepreg rolls may be the same or
different. The prepregs (laminae) are consolidated by the application of
heat and pressure in the cross-plying apparatus. Cross-linkable matrix
resins are generally not cured at this stage of construction.
To construct plies of the preferred laminates with more than one
pair of laminae, the cross-plied product may itself be cross-plied, and
cross-plied again a plurality of times to produce a desired laminate
construction. In each cross-plying operation, the number of laminae may
be doubled. Alternatively, the second and subsequent cross-plying
operations may be done with different numbers of lamina in the prepregs to
be cross-plied. When the number of laminae becomes too great for
continuous roll formation, the cross-plying may be conducted by hand or by
3o any suitable means.
Finally, the plies are assembled by stacking together face-to-
face. The plies may be united by bonding under pressure and at a
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16
temperature sufficient to cure any thermosetting matrix resins.
Temperatures from about 90 to about 160 C and pressures of from about
100 psi to about 2500 psi (69 -- 17,000 kPa) are employed, depending
upon the types of fibers and matrix present.
The articles of the invention possess in heretofore unseen
combination light weight and ballistic-resistance to multiple high velocity
bullets. One measure of weight efficiency is the specific energy absorption
of the laminate at the V50 velocity. The V50 velocity is that velocity at
which 50% of bullets will penetrate the laminate as determined by M4L-STD
lo 662E. Preferably, a laminate of the invention, when impacted by M80 ball,
7.62 X 51, 147 grain (9.53 g) bullets, has a specific energy absorption at
the V50 velocity of at least 100 j-m2/Kg.
Remarkably, the resistance of an article of the invention to
penetration by subsequent bullets impacting in a small area remains
unaffected even after multiple hits. Even more remarkably, an article of the
invention maintains its resistance to penetration by multiple hits from
bullets
containing steel cores designed to penetrate armor. This is in marked
contrast to articles having unreinforced monolithic ceramic elements that
are shattered by the first bullet. Preferably, an article of the invention,
when serially impacted by M80 ball, 7.62 X 51, 147 grain (9.53 g) bullets at
a velocity of at least 2000 ft/sec (610 m/sec) within a iateral area of 15 cm
x
15 cm, has a minimum penetration velocity for a third bullet of not less than
90% of the minimuni penetration velocity of a first bullet, more preferably
not less than 95% of the minimum penetration velocity of a first bullet.
Yet more preferably, an article of the invention, when serially
impacted by M80 ball, 7.62 X 51, 147 grain (9.53 g) bullets at a velocity of
at least 2000 ft/sec (610 m/sec) within a lateral area of 15 cm x 15 cm, has
a minimum penetration velocity for a fifth bullet of not less than 90% of the
minimum penetration velocity of a first bullet, again more preferably nof
less than 95% of the minimum penetration velocity of a first bullet.
Still more preferably, an article of the invention, when serially
impacted by M80 ball, 7.62 X 51, 147 grain (9.53 g) bullets at a velocity of
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at least 2000 ft/sec (610 m/sec) within a lateral area of 15 cm x 15 cm, has
a minimum penetration velocity against a seventh bullet of not less than
90% of the minimum penetration velocity of a first bullet, most preferably
not less than 95% of the minimum penetration velocity of a first bullet.
Preferably also, an article of the invention, when serially
impacted by 7.62 X 39 ball type 56, 123gr. (7.97 g) (Russian AK-47) bullets
with steel penetrator cores, at a velocity of at least 1900 ft/sec (579 m/sec)
within a lateral area of 15 cm x 15 cm, has a minimum penetration velocity
for a third, fifth or seventh bullet of not less than 90% of the minimum
io penetration velocity of a first bullet.
Without being held to a particular theory of why the invention
works, it is believed that the high hardness of the inorganic fibers in the
frontal laminate act to deform and slow the bullet in the same manner as
would a monolithic plate of the same material. However, because the
fibers are arranged in unidirectional array, the fracturing of the fibers is
confined to a small distance along their lengths. Also in contrast to a
woven network where there is direct connection between fibers, the ballistic
shock wave is attenuated when transmitted through the matrix to laterally
adjacent but unconnected fibers. Thus, many fibers in a given area of the
frontal laminate remain intact and are available to perform the same
function of deforming and slowing subsequent bullets.
The following examples are presented to provide a more
complete understanding of the invention. The specific techniques,
conditions, materials, proportions and reported data set forth to illustrate
the principles of the invention are exemplary and should not be construed
as limiting the scope of the invention.
EXAMPLES
Comparative Example
A laminate panel was constructed consisting of a front plate of
monolithic silicon carbide (SiC) and a rear laminate bonded to the SiC plate
consisting of laminae of unidirectional high molecular weight polyethylene
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fibers. The SiC front plate had dimensions of 15.2 cm x 15.2 cm x 0.587
cm and it had an areal density of 3.76 ibs/ft2 (18.38 Kg/m2). The SiC plate
was manufactured by Saint-Gobain Advanced Ceramics, Niagra Falls, NY.
It was a sintered form of a-SiC having a density of 3.10 g/cm3, a modulus
of elasticity of 410 GPa and a Knoop Hardness of 2800 kg/mm2.
The rear laminate consisted of 56 SPECTRA SHIELD PCR
sheets from Honeywell International Inc. bonded together under heat and
pressure, each sheet consisting of two unidirectional laminae of high
molecular weight polyethylene fibers in a thermoplastic elastomeric matrix,
io and cross-plied 0 /90 . The thickness of the rear laminate was 0.3 inch
(0.76 cm), and it had an areal density of 1.51 Ibs/ft2 (7.38 Kg/m2). The total
areal density of the laminate panel was 5.27 Ibsfft2 (25.75 Kg/rn 2).
The 1.35 cm thick laminate panel was fired on in succession by
two M80 ball, 7.62 X 51 mm, 147 grain (9.53 g) bullets. The first bullet fired
1s at a velocity of 3081 ft/sec (939 m/sec) did not penetrate the laminate
panel
but shattered the front SiC plate. The second bullet fired at a velocity of
only 1625 ft/sec (495 m/sec) penetrated the laminate panel.
Example 1
Chemically vapor deposited (CVD) boron fiber on tungsten
20 unidirectional prepreg tape was obtained from Specialty Materials, Inc,
Lowell, MA. The CVD boron filaments were of 0.004 inch (0.0102 cm)
diameter, and had a density of 2.60 g/cm3 and a tensile strength of 3.44
GPa. The CVD boron fibers were 67 percent by weight of the prepreg tape
with the balance being epoxy resin. Thirty-four of the CVD boron
25 fiber/epoxy unidirectional tapes were cross-plied 0 /90 and formed into a
frontal laminate in a press at 121 C, and 1.0 MPa. The areal density of this
15.2 cm x 15.2 cm x 0.526 cm laminate was 2.0 Ibs/ft2 (9.77 Kg/m2).
A second laminate was formed of 74 SPECTRA SHIELD PCR
sheets from Honeywell International Inc. bonded together under heat and
3o pressure, each sheet consisting of two inner unidirectional laminae of high
molecular weight polyethylene fibers in a matrix, cross-plied 0 /90 and
having an outer plastic film on each surface. The matrix was a styrene-
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isoprene-styrene thermoplastic elastomer having a tensile modulus of 200
psi (1.4 MRa). The high molecular weight polyethylene fibers had a
tenacity of 30 g/d and comprised 80 percent by weight of the laminae. This
second laminate was united (bonded) face-to-face to the first laminate to
create a panel article of the invention having an areal density of 4.0 Ebs/ft2
(19.6 Kg/mZ).
This 1.54 cm thick panel was serially fired on by 7.62 X 51 mm,
147 grain (9.53 g) steel jacketed bullets in the sequence and with the
results shown in Table fl below. The bullets impacted the frontal laminate
io of the panel.
TABLE el
Velocity Bullet No. ftisec n1lsec Penetration
1 2719 829 Yes
2 2521 768 Yes
3 2379 725 No
4 2422 738 Yes
5 2336 712 No
6 2419 737 Yes
7 2412 735 No
8 2441 744 Yes
9 2391 729 No
2495 760 Yes
11 2400.. 732 No
The first two bullets at veiocities of 2719 ft/sec (829 m/sec) and
2521 ft/sec (768 m/sec) penetrated the article of the invention. The third
bullet fired at a velocity of 2379 ft/sec (725 m/sec) did not penetrate the
panel. Therefore, the minimum penetration velocity for the first bullet was
known to be at least 2379 ft/sec (725 m/sec). Remarkably, the fifth,
seventh, ninth and eleventh bullets fired into this same panel at velocities
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no less than 98 % of the minimum penetration velocity of the first bullet also
did not penetrate the panel.
The article of the invention was also resistant to penetration
meeting at least the requirements of NIJ Standard 0115.00 for Type 1 stab
s protection.
Example 2
Chemically vapor deposited (CVD) boron fiber on tungsten
unidirectional prepreg tape was obtained from Specialty Materials, Inc,
Lowell, MA. The CVD boron filaments were of 0.004 inch (0.0102 cm)
io diameter, and had a density of 2.60 g1cm3 and a tensile strength of 3.44
GPa. The CVD boron fibers were 67 percent by weight of the prepreg tape
with the balance being epoxy resin. Thirty-four of the CVD boron
fiberlepoxy unidirectional tapes were cross-plied 0 /90 and formed into a
frontal laminate in an autoclave at a temperature of 116 C, 344 KPa
15 external pi-essure and 96 KPa vacuum. The areal density of this 15.2 cm x
14.0 cm x 0.526 cm laminate was 2.0 Ibs/ft2 (9.77 Kg/mZ).
A second laminate was formed of 112 SPECTRA SNlELD
PLUS PCR consolidated sheets, bonded together under heat and pressure,
each sheet consisting of two inner unidirectional laminae of high molecular
20 weight polyethylene fibers in a matrix, cross-plied 0 /90 , and having an
outer plastic film on each surface. The matrix was a styrene-isoprene-
styrene thermoplastic elastomer having a tensile modulus of 200 psi (1.4
MPa). The high molecular weight polyethylene fibers had a tenacity of 30
g/d. The areal density of this laminate was 3 Ibs/ft2 (14.66 Kg/m2).
The second laminate was bonded face-to-face with the frontal
laminate to create a panel article of the invention 1.49 cm thick and having
an areal density of 5.0 Ibs/ft2 (24.4 Kg/m2).
This panel was serially fired on by 7.62 X 39 mm ball type 56;
123 gr. (7.97 g) (Russian AK-47) bullets with steel penetrator cores, in the
'o sequence and with the results shown in Table Ill. The bullets impacted the
frontal laminate of the panel.
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Table lEl
ity
Bullet No. I ftfsec m/sec Penetration
1 2347 715 Yes
2 2231 680 Yes
3 2100 640 Yes
4 ~ 1908 582 No
1975 602 Yes
6 1922 586 No
7 1982 604 No
8 2042 622 No
9 2084 635 No
2078 633 Yes
The panel article of the invention maintained its minimum
penetration velocity of at least 1908 ft/sec (582 m/sec) even after nine
5 bullets had been fired into it.
Example 3
A frontal laminate was formed identical to the frontal laminate in
Example 2. The areal density of this frontal laminate, having dimensions of
15.2 cm x 14.0 cm x 0.526 cm, was 2.0 [bs/ft2 (9.77 Kg/m2).
10 A second laminate was formed of 172 SPECTRA SHIELD
PLUS PCR consolidated sheets, bonded together under lieat and pressure,
each sheet consisting of two inner unidirectional laminae of high molecular
weight polyethylene fibers in a matrix, cross-plied 0 /90 , and having an
outer plastic film on each surface. The matrix was a styrene-isoprene-
styrene thermoplastic elastomer having a tensile modulus of 200 psi (1.4
MPa). The high molecular weight polyethylene fibers had a tenacity of 30
g/d, and the areal density of this laminate was 3.99 lbs/ft2 (19.5 Kg/m2).
The second laminate was bonded face-to-face with the frontal
laminate creating a panel article of the invention of 2.76 cm thickness and
2o an areal density of 5.99 Ibs/ft2 (29.3 Kg/m2). This panel was serially
fired
on by M80 ball, 7.62 X 51 mm, 147 grain (9.53 g) steel jacketed bullets in
the sequence and with the results shown in Table IV. The bullets impacted
the frontal laminate of the article.
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Table IV
Velocif
Bullet No. fvsec m/sec Penetration
1 3239 987 Yes
2 3018 920 No
3 3093 943 No
4 3134 955 No
3205 977 Yes
The panel article of the invention maintained its minimum
penetration velocity of at least 3018 ft/sec (920 m/sec) even after four
bullets had been fired into it.
Example 4
A frontal laminate was formed identical to the frontal laminate in
Example 2. The areal density of this frontal laminate, having dimensions of
15.2 cm x 14.0 cm x 0.526 cm, was 2.0 Ibs/ft2 (9.77 Kg/m2).
A second laminate was formed identical to the second laminate
in Example 3. The areal density of this laminate was 3.99 Ibs/ft2 (19.5
Kg/m2).
A third laminate was formed of 24 sheets of GOLDFLEXO
material from Honeywell International stacked face-to-face and sewn
is together around their edges, each sheet consisting of four inner
unidirectional laminae of aramid fibers in a matrix, cross-plied 0 /90 , and
having an outer plastic film on each surface. The matrix was a styrene-
isoprene-styrene thermoplastic elastomer having a tensile modulus of 200
psi (1.4 MPa). The aramid fibers had a tenacity of 22 g/d. The areal
2o density of this laminate was 1.14 Ibs/ft2 (5.57 Kg/m2).
The second laminate was bonded face-to-face with the frontal
laminate and the third lamiriate was stacked face-to-face with the second
laminate to create an article of the invention 3.48 cm thick and having an
areal density of 5.99 Ibs/ft2 (29.3 Kglm).
25 This article was serially fired on by 7.62 X 39 ball type 56, 123 gr.
(7.97 g) (Russian AK-47) bullets with steel penetrator cores, in the
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sequence and with the results shown in Table V. The bullets impacted the
frontal laminate of the article.
Table V
Velocity
Buiiet No. fitPsec M/sec Penetration
1 2432 741 No
2 2460 750 No
3 2651 808 No
4 2714 827 No
2716 828 No
6 3111 948 No
7 3331 1015 Yes
5 The article of the invention maintained its minimum penetration
velocity of at least 3111 ft/sec (948 m/sec) even after six bullets had been
fired into it.
Example 5
A frontal laminate was formed identical to the frontal laminate in
la Example 1. The areai density of this frontal laminate having dimensions of
15.2 cm x 15.2 cm x 0.526 crn was 2.0 Ibs/ft2 (9.77 Kg/m2).
A second laminate was formed of 27 sheets of an aramid woven
fabric containing 15 percent by weight of a vinyl ester matrix resin. The
fabric was a plain weave having 21 x 21 ends/ inch (8.27 ends/cm) woven
1s from 1500 denier KEVLARO 29 yarn and was obtained from Barrday, Inc.
The matrix resin was Dow Chemical Co. Derekane 411 containing 1.5% 2,5
dimethyl-2,5di(2-ethylhexanoyl peroxy) hexane curing agent. Impregnated
fabric sheets were stacked and bonded together by heating and curing the
resin at 120 C under a pressure of 500 psi (3.45 MPa). The initial tensile
?o niodulus of the neat resin in the cured state is 460,000 psi (3.17GPa). The
areal density of the second larninate was 1.72 lbs/ft2 (9.77 Kg/m2).
A third laminate was formed of 24 sheets of GOLDFLEXO
material (Honeywell International Inc.) stacked face-to-face and sewn
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24
together around their edges, each sheet consisting of four inner
unidirectional laminae of aramid fibers in a matrix, cross-plied 01/901, and
having an outer plastic film on each surface. i'he matrix was a styrene-
isoprene-styrene thermoplastic elastomer having a tensile modulus of 200
psi (1.4 MPa). The aramid fibers had a tenacity of 22 g/d. The areal
density of this laminate was 1.14 ibs/ft2 (5.57 Kgfm2).
The second laminate was bonded face-to-face with the frontal
laminate and the third laminate was stacked face-to-face with the second
laminate to create an article of the invention having an areal density of 4.86
io ibs/ftz (23.8 Kg/m2).
This article was serially fired on by M80 ball, 7.62 X 51 mm, 147
grain (9.53 g) steel jacketed bullets in the sequence and with the results
shown in Table VI. The bullets impacted the frontal laminate of the article.
Table VI
Velocity
Bullet No. ft/sec rn/sec Penetration
1 2484 757 Yes
2 2366 721 Yes
3 2006 611 No
4 2013 614 Yes
5 2100 640 Yes
6 1965 599 Yes
7 1950 594 No
8 1969 600 No
9 2011 613 Yes
The article of the invention maintained its minimum penetration
velocity of at least 1950 ft/sec (594 misec) even after eight bullets had
been fired into it.
Example 6
Chemically vapor deposited (CVD) boron fiber on tungsten
unidirectional prepreg tape was obtained from Specialty Materials, Inc,
Lowell, MA. The CVD boron filaments were of 0.004 inch (0.0102 cm)
diameter, had a density of 2.60 g/cm3 and a tensile strength of 3.44 GPa.
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The CVD boron fibers were 67 percent by weight of the prepreg tape with
the balance being epoxy resin. Seventeen of the CVD boron fiber/epoxy
unidirectional tapes were stacked together, cross-plied at 0 /90 to form the
frontal ply. An 11 cm x 11 cm titanium plate of 1.8 mm thickness was
5 placed on this stack to form a second ply, and an additional seventeen of
the CVD boron fiber/epoxy unidirectional tapes were placed on the stack,
cross-plied at 0 /90 to form a third ply. The entire stack with the titanium
plate in the center was then forrned into a frontal laminate in an autoclave
at a temperature of 116 C, 344 KPa external pressure and 96 KPa
io vacuum. The areal density of this 15.2 cm x 14.0 cm x 0.526 cm laminate
was 2.86 Ibs/ft2 (14.0 Kg/m2). The titanium plate was embedded on all
surfaces by the frontai and third piies of the frontal laminate.
A second laminate was formed of 103 SPECTRA SHIELD
PLUS PCR consolidated sheets, bonded together under heat and pressure,
is each sheet consisting of two inner unidirectional laminae of high molecular
weight polyethylene fibers in a matrix, cross-plied 0 /90 , and having an
outer plastic film on each surface. The matrix was a styrene-isoprene-
styrene thermoplastic elastomer having a tensile modulus of 200 psi (1.4
MPa). The high molecular weight polyethylene fibers had a tenacity of 30
20 g/d. The areal density of this laminate was 2.0 Ibs/ft2 (9.77 Kg/mz).
A third laminate was formed of 24 sheets of GOLDFLEX
material (Honeywell International Inc.) stacked face-to-face and sewn
together around their edges, each sheet consisting of four inner
unidirectional laminae of aramid fibers in a matrix, cross-plied 0 /90 , and
25 having an outer plastic film on each surface. The matrix was a styrene-
isoprene-styrene thermoplastic elastomer having a tensile niodulus of 200
psi (1.4 MPa). The aramid fibers had a tenacity of 22 g/d. The areal
density of this laminate was 1.14 Ibs/ftZ (5.57 Kg/rn2).
The second laminate was bonded face-to-face with the frontai
laminate and the third laminate was stacked face-to-face with the second
laminate to create an article of the invention having an areal density of 6.0
lbs/ft2 (29.3 Kg/m2).
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This article was serially fired on by 7.62 x 54R ball type 56, 149
grain (9.66 g),
(Russian Dragriov, LPS) bullets with steel penetrator cores, in the
sequence and with the results shown in Table \t'll. The bullets impacted
the frontal laminate of the article.
Table Vil
Velocity
Buifet No. ftfsec mlsec Penetration
1 2170 661 No
2 2281 695 No
3 2403 732 Yes
4 2344 714 No
The article of the invention maintained a minimum penetration
velocity of at least 2344 ft/sec (714 m/sec) after four bullets had been fired
into it.
Example 7
A frontal laminate is formed identical to the frontal laminate in
Example 1. The areal density of this frontal laminate having dimensioi;s of
15.2 cm x 15.2 cm x 0.526 cm was 2.0 lbs/ft2 (9.77 Kg/m2).
A second laminate is formed from five sheets of PBO (poly(p-
phenylene-2,6-benzobisoxazole) felt having a KEVLAR scrim. The PBO
felt is designated PBO/KR-KR from Bayrische Wollfilz Fabrik and has an
areal density of 0.27 Ibs/ft2 (1.35 Kg/m2) and an initial thickness of 4 mm.
The felt sheets are stacked together face-to-face with polyethylene films of
0.35 mm thickness between the sheets and on both sides of the stack, and
the stack is molded at 120 C under a pressure of 100 psi (0.69 MPa). The
second laminate has a thickness of 10 mm and an areal density of 1.38
lbs/ft'' (6.75 Kg/m2).
A third laminate is formed of 24 sheets of GOLDFLEXO material
stacked face-to-face and sewn together around their edges, each sheet
consisting of four inner unidirectional laminae of aramid fibers in a matrix,
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cross-plied 00/900, and having an outer plastic film on each surface. The
matrix is a styrene-isoprene-styrene thermoplastic elastomer having a
tensile modulus of 200 psi (1.4 MPa). The aramid fibers have a tenacity of
22 g/d. The areal density of this laminate is 1.14 Ibs/ft2 (5.57 Kg/m2).
The second laminate is bonded face-to-face with the frontal
laminate and the third laminate is stacked face-to-face with the second
laminate to create an article of the invention having an areal density of 4.52
lbs/ft2 (22.1 Kg/r"r~2).
It is believed that this panel when serially impacted on the frontal
io laminate by M80 ball, 7.62 X 51, 147 grain (9.53 g) bullets at a velocity
of at
least 2000 ft/sec (610 m/sec), within a lateral area of 15 cm x 15 cm, would
have a minirnum penetration velocity for a third bullet of not less than 90%
of the minimum penetration velocity of a first bullet.
Example 8
ts SCS-ULTRAO chemically vapor deposited silicon carbide on
carbon fibers are obtained from Specialty Materials, Inc. The CVD SiC
fibers are of 0.0056 inch (0.0142 cm) diameter and have a tensile strength
of 5.86 GPa and a density of 3.0 g/cm3. The fibers are formed into a
unidirectional prepreg using the apparatus illustrated in Figure 3. A
~o DERAKANEO epoxy vinyl ester resin having a tensile modulus of 450,000
psi (3.1 GPa) is applied as the matrix. The CVD SiC fibers constitute 90
percent by weight of the prepreg. The prepreg is cross-plied 0 /90 using
the method and apparatus described in USP 5,173,138. Sixteen of the
cross-plied sheets (32 laminae) are bonded together to form a frontal
25 laminate, having an areal density of 2.70 Ibs/ft2 (13.2 Kg/m2).
A second laminate is formed of 37 SPECTRA SHIELDO PCR
sheets bonded together under heat and pressure, each sheet consisting of
two unidirectional laminae of high molecular weight polyethylene fibers in a
thermoplastic elastomeric matrix, and cross-plied 0 /90 . The high -
30 molecular weight polyethylene fibers have a tenacity of 30 g/d. The areal
density of the second laminate is 2 Ibs/ft2 (9.77 Kg/n,2).
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A third laminate is formed by a method identical to that used to
form the frontal laminate except that only eight of the CVD SiC cross-plied
sheets (16 laminae) are bonded together. The areal density of the third
laminate is 1.35 Ibs/ft2 (6.60 Kg/m2).
The frontal laminate, the second laminate and the third laminate
are bonded together face-to-face to create a laminate panel of the invention
having an areal density of 5.64 ibs/ft2 (27.6 Kg/m2).
It is believed that this panel, when serially impacted on the
frontal laminate by M80 ball, 7.62 X 51, 147 grain (9.53 g) bullets at a
io velocity of at least 2000 ft/sec (610 m/sec) within a lateral area of 15 cm
x
cm, would have a minimum penetration velocity for a third bullet of not
less than 90% of the minimum penetration velocity of a first bullet.
Having thus described the invention in rather full detail, it will be
understood that such detail need not be strictly adhered to but that further
15 changes and modifications may suggest themselves to one skilled in the
art, all failing with the scope of the invention as defined by the subjoined
claims.
