Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
FABRIC ARCHITECTURES FOR IMPROVED
BALLISTIC IMPACT PERFORMANCE
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to fabric architectures and soft body
armors constructed therefrom.
2. Description of the Related Art
Protective body armors such as those providing protection against
ballistic and stab type threats have long been an area of significant
interest. One challenge for body armor manufacturers is to provide
adequate protection from a particular threat or threats that the wearer may
be subjected to in the field, while minimizing the weight, or areal density of
the protective garment so as not to impede the dexterity of the wearer.
Characterization of the protective capabilities of any armor material
against ballistic projectile threats, such as deformable bullets and non-
deformable shrapnel, requires some determination of the ballistic velocity
limit with respect to the material's areal density and size, as well as the
properties of the projectile (mass, hardness, shape, etc.). One common
ballistic limit performance criteria is the ballistic V50, or the velocity at
which 50% of the projectiles can be defeated by the armor. Specific
testing and calculation protocols for determining V50 of body armors are
outlined by the National Institute of Justice (NIJ) Standard-0101.04
Ballistic Resistance of Personal Body Armor, dated September 2000.
Beyond the ability of armor to stop the penetration of a projectile, the need
to minimize blunt trauma associated with the ballistic impact for
concealable body armors worn by police, security, and correctional
officers, becomes an additional safety requirement set forth by NIJ
Standard-0101.04. This standard outlines the testing protocol and
performance requirements for an acceptable level of blunt trauma through
measurement of the backface signature associated with ballistic impact of
armors placed upon a clay witness simulation material. In NIJ Standard-
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0101.04, the acceptable amount of backface deformation is defined as
being no greater than 44 mm in a clay witness (Roma Plastilina clay, 5.5 in
(140 mm) clay witness depth).
The NIJ Standard-0101.04 provides ballistic requirements specific
to different types of projectiles and impact energy levels. Three common
NIJ threat levels for soft body armor include Threat Level II, 11A, and IIIA.
Threat level II relates to higher velocity 357 magnum, 10.2 g (158 gr) and
9 mm, 8.Og (124 gr) bullets (impact velocities of less than about 1400 ft/s
(427 m/s) and 1175 ft/s (358 m/s), respectively). Level IA relates to lower
velocity 40 S&W caliber full metal jacket bullets, with a nominal mass of
11.7 g (180 gr) and 9 mm 8.0 g (124 gr) bullets, (impact velocities of less
than about 1025 ft/s (312 m/s) and 1090 ft/s (332 m/s), respectively).
Threat level IIIA relates to 44 magnum, 15.6 g (240 gr) and sub machine
gun 9 mm (124 gr) bullets having impact velocities of less than about 1400
ft/s).
While the ballistic performance requirements set forth above can be
achieved using any of several commercially available anti-ballistic
materials, or combinations of said materials, the challenge for soft body
armor manufactures is the selection and arrangement of ballistic layers
required to prevent penetration with an acceptable safety margin and
minimize backface deformation while also minimizing the weight, bulk and
stiffness of the armor to improve comfort.
Commercially available anti-ballistic materials include a variety of
woven ballistic fiber yarn fabrics, ballistic fabric reinforced composites,
ballistic fiber unidirectional laminates and nonwovens. Of these various
constructions, woven fabrics fabricated from high tenacity fiber yarns have
the longest history of use in soft body armor fabrication. Weaving has
long been a relatively inexpensive means of uniformly generating fabric
ballistic resistant plies from high tenacity fiber yarns, relying on
mechanical
interlocking or "interlacing" of the yarns to hold the yarns in place instead
of chemical locking by adhesive resins which can contribute additional
weight and stiffness to a garment. Soft body armors fabricated from
ballistic resistant fabrics are very often more conformable and flexible
during use, providing greater comfort than hybrid armors containing stiff
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backface control layers such as unidirectional fiber laminates or resin
impregnated fabrics. Additionally, it has been shown that ballistic resistant
garments generated entirely of woven high tenacity fiber yarns maintain
ballistic resistant properties after years of service and wear. Alternatives
to an all woven ballistic resistant vest are in commerce. Such articles are
prepared from combinations of high tenacity fibers, matrix resins and films,
often making them more costly to produce. Additionally, by virtue of the
component materials having temperature and strain dependent physical
properties (eg. coefficient of thermal expansion, modulus, etc.) dissimilar
to that of the ballistic fiber, these composite layers often have a useable
life cycle dictated by the weakest of the materials selected.
Typical biaxial woven ballistic resistant fabrics (fabrics consisting of
interwoven interlaced yarns having two yarn orientations within the plane
of the fabric) are generated on automated looms. These looming
operations generate woven fabrics having interwoven fill fiber yarns
oriented 90 degrees to those yarns in the warp, or machine direction. The
fabric properties are largely governed by four basic variables: yarn denier,
thread count, weave pattern and fabric finish. Several styles of woven
fabrics exist, including plain, satin, twill, basket, and leno weaves. Meeting
the minimum ballistic performance requirements using only the above
woven fabrics presents a challenge for ballistic armor manufacturers.
While many low cover factor (loosely woven) ballistic resistant fiber yarn
fabrics provide satisfactory V50 performance at the desired areal density
(vests fabricated therefrom can be shown to repeatedly impede projectiles
from penetrating the vest material at velocities safely above the threshold
values outlined in NIJ Standard-0101.04), they do not provide adequate
backface deformation resistance. Conversely, the use of higher cover
factor (more tightly woven) ballistic resistant fiber yarn fabrics at the same
vest areal density while improving backface deformation performance,
often results in significant reduction in V50 performance, sometimes falling
below the NIJ Standard-0101.04 velocities required for backface signature
measurement. Currently no all p-aramid fiber yarn (such as that sold
under the trade name Kevlar or Twaron ) woven fabric vests are
available commercially at an areal density of less than 1 lb/ft2, that can
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meet the NIJ Standard-0101.04 level IIIA backface requirement for a 44
magnum ballistic threat.
One common method for reducing the backface signature in soft
body armors is through incorporating rigid plies of high tenacity fiber or
fabric reinforced resin composite plies to impede deformation during
impact. This includes bonding polymeric films or applying polymeric
coatings to woven ballistic fabrics, or bonding two woven ballistic fabric
layers using a low melting temperature polymer film, or pressure sensitive
adhesive to provide an anti-ballistic ply that can be added to ballistic body
armor constructions to improve backface signature, as described in WO
00/08411, US Pat. No. 5,677,029, and US 2003/0109188. Resin or
elastomer impregnated ballistic fiber fabric is another type of composite
ply added to ballistic vest constructions to improve ballistic backface
signature. While the addition of these layers has been shown to improve
the backface signature performance of an armor material, they can often
have a deleterious effect on V50 performance. In addition, the resin adds
to the weight and stiffness of the ballistic vest assembly.
Unidirectional fiber laminates, comprised of a first plurality of
oriented parallel high tenacity fibers in a polymeric matrix adhesively
bound to a second plurality of oriented parallel high tenacity fibers in a
polymeric matrix, where the fiber orientation of the second plurality is often
90 degrees rotated relative to the orientation of the first plurality, have
become popular anti-ballistic materials that can provide good backface
trauma control while maintaining safe V50 performance. Methods of
making these unidirectional fiber laminates are generally described in U.S.
Pat. Nos. 4,916,000; 4,748,064; 4,737,401; 4,681,792; 4,650,710;
4,623,574; 4,563,392; 4,543,286; 4,501,854; 4,457,985, and 4,403,012.
These unidirectional laminates are commercially available under the trade
names Spectra Shield Plus Flex, and Gold FIexTM, from Honeywell
International, Inc. and Dyneema UD from DSM. While these
unidirectional fiber laminates can be used alone to provide ballistic
protection, it has been shown that further reductions in areal density
without performance loss can be achieved when these materials are used
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in conjunction with woven ballistic fiber yarn fabrics, as illustrated in U.S.
Patent 6,119,575
Performance improvements associated with using unidirectional
fiber or fabric and resin composite layers in vests can be very dependent
on their location within the multi-ply construction, as discussed in U.S.
Patent 6,119,575. In many documented instances, the placement of these
stiffer composite layers behind traditional ballistic fabrics provides the
optimum in backface signature and V50 performance. Due to this
"sidedness" these hybrid ballistic vest constructions can be inadvertently
worn inside-out, or inserted the wrong way into a tactical vest, providing
less than optimal protection from projectile threats. Hence there is value
in monolithic (comprised of all the same plies of anti-ballistic material) or
front-back symmetric ballistic resistant armor constructions.
The need exists for a lightweight, all woven fabric body armor that
can reduce the blunt trauma associated with ballistic impact. Prior to the
advent of the inventive biaxial (comprised of interlaced fiber yarns having
two distinct orientations within the plane of the fabric) fabric
architectures,
and soft body armor constructions described herein, no documented, all-
woven, p-aramid fabric ballistic body armors had existed having an areal
density less than about 1 Ib/ft2 fulfilling the NIJ Standard-0101.04 backface
requirement for a 44 caliber deformable projectile (backface signature
below 44 mm for projectile velocities of 1430 30 ft/s (436 9 m/s)).
SUMMARY OF THE INVENTION
In one embodiment, the invention is directed to a biaxial fabric
woven from yarn for use in the manufacture of ballistic projectile or
puncture resistant articles, said biaxial fabric, comprising a first plurality
of yarns oriented parallel within the plane of the fabric, interwoven with
a second plurality of parallel oriented yarns within the plane of the
fabric having a direction/orientation within the plane of the fabric
different from that of the first plurality, where the crossing of any fiber
yarn from the first plurality with a fiber yarn from the second plurality
forms a pair of acute vertical angles having an angular measurement
less than 90 degrees.
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In another embodiment, the invention is directed a multi-layer
ballistic projectile or puncture resistant article assembled from a
plurality of substantially unattached non-woven or woven fabric layers
comprising yarns selected, either alone or in combination, from the
group comprising aromatic polyamide, polyolefin, polyareneazole,
polyester, rayon, liquid crystal polymer, fiberglass, carbon fiber,
ceramic, polyacrylonitrile and polyvinyl alcohol, in which at least one of
the layers in the assembly is a biaxial fabric comprising a first plurality
of yarns oriented parallel within the plane of the fabric, interwoven with
a second plurality of parallel-oriented yarns within the plane of the
fabric having a direction/orientation within the plane of the fabric
different from that of the first plurality, where the crossing of any fiber
yarn from the first plurality with a fiber yarn from the second plurality
forms a pair of acute vertical angles having an angular measurement
less than 90 degrees.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a prior art example of a woven fabric.
Figure 2 is a magnified image of one embodiment of the inventive
ballistic resistant fabric construction.
Figure 3A is an illustration of the preparation of bias-oriented fabric
strips from a roll of conventional woven fabric
Figure 3B shows the fabric cut from the roll shown in 3A clamped in
a trellising apparatus.
Figure 3C shows the fabric clamped in the trellising apparatus and
extended.
DETAILED DESCRIPTION OF THE INVENTION
Glossary Of Terms Used Herein
Acute angles - angles measuring less than 90 degrees.
Woven fabric - a fabric comprised of one plurality of fiber yarns oriented in
one direction, interwoven with a second plurality of yarns oriented in a
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direction different from that of the first plurality. The first plurality of
parallel yarns aligned in the machine direction are referred to as warp
yarns. Those interwoven yarns oriented 90 degrees to the warp are
referred to as the fill or weft yarns.
Bias woven or bias-oriented fabric- a two dimensional woven or braided
fabric that when oriented in the XY plane, where X is the machine direction
(length), and Y is the transverse direction (width) of the fabric, contains
interlaced yarns that are oriented in a different direction from the X and Y
axes within the plane of the fabric.
Bias orientation - In a biaxial woven fabric comprised of a plurality of yarns
oriented in one direction within the plane of the fabric, interwoven with a
second plurality of yarns having an orientation different from the first, the
direction parallel to any ray bisecting any angle formed between a fiber
yarn from the first plurality with that of a yarn from the second plurality.
Unidirectional fiber layer - a layer having fibers arranged substantially
parallel along a common fiber direction
Composite fabric ply- a combination of one woven fabric layer and at least
one second layer which could be another fabric layer, a unidirectional fiber
layer, a polymeric film, a polymeric resin impregnated into the fabric
structure, etc. The one woven fabric layer can be united with the second
layer through stitching, melt adhesives, pressure sensitive adhesives,
compression molding, coating.etc.
Supplementary angle - Two angles are called supplementary angles if the
sum of their degree measurements equals 180 degrees. One of the
supplementary angles is said to be the supplement of the other.
Vertical angles- For any two lines (rays) that cross, such as in the diagram
below, angle A and angle B are called vertical angles. Vertical angles
have the same degree measurement. Angle C and angle D are also
vertical angles.
C
A B
D
Trellis angle - in biaxial fabrics, the acute angle formed between any two
yarns having different orientation within the plane of the fabric, observed in
biaxial braided structures or achieved by in-plane extension of biaxial
woven structures in either bias direction.
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Trellis direction - a direction parallel with the line bisecting acute
vertical
angles..
Cover Factor - the fraction of the surface area of the fabric that is covered
by yarns assuming a round yarn shape.
V50 - V50 ballistic limit testing is a statistical test, originally developed
by
the U.S. military to evaluate hard armor. V50 testing experimentally
identifies the velocity at which a bullet has a 50 percent chance of
penetrating the test object.
Backface signature (BFS) - The depth of the depression made in the
backing material, created by a non-penetrating projectile impact. The
backface signature is measured from the plane defined by the front edge
of the backing material fixture. In accordance with the National Institute of
Justice (NIJ) Standard-0101.04 Ballistic Resistance of Personal Body
Armor, the value is not allowed to exceed the limit of 44 mm.
The present invention is directed in various embodiments at a new
class of ballistic resistant fabric architectures, as well as ballistic layers
and multi-layer body armor constructions made therefrom that exhibit
improved ballistic backface deformation over traditional woven ballistic
fabrics. One embodiment of this invention involves generating ballistic
fabric architectures that can impart significant backface signature
improvements to body armor that have never been achieved using
traditional ballistic fabrics. A second embodiment of this invention is the
generation of balanced ballistic layers from the ballistic fabric architecture
for use in body armor assembly. A third embodiment of this invention is
the fabrication of specific multilayer vest constructions incorporating the
inventive ballistic fabric architectures.
The first embodiment of this invention can be described by first
referring to Fig 1 that shows a prior art example of a woven fabric 10. The
figure shows a magnified example of a plain weave construction
comprised of multifilament yarns, where the intersection of a first set of
yarns 1 parallel in direction within the plane of the fabric as indicated by
line X is interwoven with a second set of yarns 2 parallel within the plane
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of the fabric and oriented 90 degrees from that of the first set as indicated
by line Y. Intersections of yarns from the first set with those in the second
set form angles A - D, each measuring 90 degrees. A line L is shown as
bisecting angles A and B.
The first embodiment of this invention is a woven fabric architecture
comprising a first plurality of parallel oriented yarns within the plane of
the
fabric, interwoven with a second plurality of parallel oriented yarns within
the plane of the fabric having a direction/orientation within the plane of the
fabric different from that of the first plurality, where the intersection of
any
fiber yarn from the first plurality with a fiber yarn from the second
plurality
forms a pair of acute vertical angles, having an angular measurement less
than 90 degrees and necessarily a pair of obtuse vertical angles,
supplementary to the aforementioned acute angles, having a
measurement greater than 90 degrees. This inventive ballistic fabric
arrangement 10' is shown in Fig. 2. comprised of a first plurality of parallel
yarns 1' oriented within the plane of the fabric as indicated by line X',
interwoven with a second plurality of parallel yarns 2' within the plane of
the fabric as indicated by line Y' having orientation different from the first
plurality where the intersection of any fiber yarn from the first plurality 1'
with any fiber yarn from the second plurality 2' forms a pair of vertical
angles within the plane of the fabric, where the angular measurements of
the acute vertical angles A' and B' are equal in value and less than 90 ,
and the angular measurements of the obtuse vertical angles C' and D' are
equal in value and greater than 90 . This inventive fabric can be achieved
by extending the original woven fabric in the trellis direction as explained
below by reference to Figs 3A-3C. For the purpose of this disclosure, we
will refer to the orientation, or trellis extension direction, of these
fabrics as
the directions parallel to the line L' bisecting the acute vertical yarn
crossing angles A' and B' as illustrated in Fig. 2
The scope of this invention is not limited to a construction
consisting of yarns interlaced in a one over-one under every other yarn
alternating structure as illustrated in Fig. 2, analogous to the interlacing
for
plain woven fabric illustrated in Fig. 1.. Rather, the scope of this invention
includes, but is not limited to architectures where yarns in one direction in
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the plane of the fabric may alternatively pass over the top of, or beneath
two or more adjacent yarns oriented in the second direction in any
particular repeat pattern conceivable, including, for example fabric
architectures which can be constructed through bias-direction extension of
satin weaves (including but not limited to 3-harness satin weaves, 4-
harness satin weaves (crow's foot), 5-harness satin weaves, and 8-
harness satin weaves, etc.), basket weaves, and twill weave structures..
The fiber yarns used in constructing the ballistic resistant
architectures described in this disclosure, would have a tensile strength
greater than about 8 g/denier or more preferably greater than about 12
g/denier. In an embodiment of this invention, the fibers in the fabric yarn
will be made of an aromatic polymeric material. Aromatic polymers
include aromatic polyamides such as poly(para-phenylene
teraphthalamide), sold under the trade names Kevlar available from E.I.
du Pont de Nemours and Company, Wilmington, DE (DuPont) and
Twaron available from Teijin, and poly(metaphenylene isophthalamide)
sold under the trade name Nomex , p-phenylene benzobisoxazole (PBO
available from Toyobo), polybenzoxazole, polybenzothiazole. Other
aromatic polymers include aromatic unsaturated polyesters such as
polyethylene terephthalate, liquid crystalline thermotropic polyesters such
as those sold under the trade name Vectran available from Kuraray,
aromatic polyimides, aromatic polyamideimides, aromatic
polyesteramideimides, aromatic polyetheramideimides and aromatic
polyesterim ides. Copolymers of any of the above mentioned classes of
materials can also be used.
Other ballistic grade fiber yarns having tenacity greater than 12
g/denier that could be used to fabricate these woven architectures include
polyolefins, most notably high molecular weight polyethylene, sold under
the trade names Dyneema available from DSM and Spectra available
from Honeywell International, high molecular weight polypropylene and
copolymers thereof.
For the example cases presented in this disclosure, bias-oriented
fabric strips were obtained through cutting ballistic fabrics from fabric
rolls
having warp fibers oriented in the machine (longitudinal) direction, and fill
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fiber yarns oriented 90 degrees to that of the warp direction (transverse to
the machine direction, parallel to the axis of the fabric roll). These strips
were prepared through cutting along a bias direction, as illustrated in Fig.
3A. The fabrics were then extended to form the ballistic resistant bias
fabric architecture once clamped into the trellising apparatus illustrated in
Figs. 3B and 3C.
While the above method was adequate for generating the examples
herein, a process to economically generate these structures would require
the manufacture of bias-oriented fabric extended to create the desired
trellis angle having continuous running lengths and enough width to
provide for vests to be cut therefrom. Methods of generating bias-oriented
fabrics have been disclosed in the patent literature. Examples include US
6,494,235, US 6,494,238, US 4,907,323 and WO 99/55519. Bias-oriented
woven structures can also be generated using braiding processes known
in the industry, to either directly generate continuous fabric sheets, or
tubular constructions that can be slit along one side parallel to the axis of
the tube to produce a flat continuous sheet of bias-oriented fabric. A
second means of fabricating a continuous sheet of bias oriented fabric
would be to helically cut a tubular fabric generated from a tubular loom,
where warp fibers are oriented parallel to the axis of the tube and fill fiber
is oriented circumferentially, also described in US Pat. 4,299,878
A second embodiment of this invention is the generation of a free-
standing trellised fabric architecture, or trellised fabric composite ply that
can be used in the construction of a ballistic body armor. Such a
stabilized layer of the trellised ballistic architecture could be provided as
a
continuous rolled good for use by ballistic body armor manufacturers. It
must be understood that individual fabric layers having this inventive
architecture with no means of stabilization are inherently unbalanced due
to their anisotropic nature. That is, the fabric layers have the tendency to
readily revert (bounce back) to a more balanced structure (as represented
by an increase in acute angle measurement) with little perturbation. This
makes these fabric architectures difficult to handle without unwanted
reversion during body armor assembly. One method used to maintain the
trellised state in an individual fabric layer is stitching through a sewing
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operation once the desired trellis angle is achieved. Though stitching in
any direction may afford some stability to the ballistic fabric, most
effective
stitching to impede the "bounce-back" tendency is stitching in a direction
perpendicular to that of the trellis direction. Stitching in this fashion at
regular intervals across a long piece of bias-oriented fabric extended to
the desired acute trellis angle provides a stabilized single fabric sheet.
Alternatively, a polymeric layer (having an adequate degree of
dimensional stability/reversion resistance to oppose the tendency of the
trellis fabric "bounce-back") could be adhered to the trellised fabric layer
to
help maintain the structure. Such a polymeric layer could be in the form of
a thin film that is melt-bonded to the fabric (via heated platen compression
or heated calendering) or a polymer coating (solvent based or
emulsion/latex) applied and then dried to one or both sides of the fabric
while held in the extended state. Such polymeric layers could be
continuous in that they cover the entire surface of the fabric, or could be
discontinuous across the surface of the fabric architecture to minimize
weight and stiffness contribution to the ballistic layer. Discontinuous
coatings of resins include open patterns or lines of resin on the fabric, or
discrete spots. This can be achieved using melt adhesive films cut into
open patterns that can be welded to the fabric surface. Alternatively,
solvent based polymer coatings or polymer emulsions/latexes can be
transfer printed in the aforementioned discontinuous fashion onto the
trellised fabrics using gravure printing processes or the like.
The individual inventive trellised fabric layers and/or composite
plies described above can be used to construct the entire ballistic body
armor, or could be used in conjunction with other anti-ballistic materials in
a ballistic body armor. The sewn or adhered polymer film or coating
stabilized structures could be stacked in various arrangements within the
body armor.
Balanced composite fabric plies can also be generated by the union
of two of the trellised fabric architectures, assembled in such a way to
have the acute angle or trellis direction of one fabric (defined as being
parallel to the line bisecting the acute vertical angles formed by two
interwoven yarns) oriented at a 90 degree angle with respect to the acute
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angle direction of the second trellised fabric architecture. The resulting
two layers of fabric could be bound together through stitching with a
sewing operation, adhesive bound using a pressure sensitive adhesive,
adhered together through melt adhesion by placing a polymeric or
thermoplastic elastomer films between the layers, compressing the layers
together in a press or via a calendaring operation while heating above the
melting point to promote adhesion. Thermosetting resins or elastomers
could also be used to unite the two layers of materials together. As with
the polymer coating stabilized single fabric layer architectures,
discontinuous coatings are most preferred as a means of reducing
stiffness and weight of these two fabric sandwich structure laminates.
EXAMPLES
Comparative Example 1.
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 25 layers of style 726 greige fabric available from JPS Industries Inc,
Anderson, SC. This is a plain weave fabric made from 840 denier Kevlar
129 fiber yarns, having a yarn count of 26 ends per inch warp and 26 ends
per inch fill, measured extracted yarn tenacities of 27 g/denier warp and
26 g/denier fill, and an areal density of 6.04 oz/yd2 (205 g/m2). Individual
square fabric layers were generated by cutting along the warp and fill
direction (having warp and fill fiber yarns parallel to the sides of the
square). Fabric layers were arranged with warp and fill fibers oriented in
the same direction for all fabric layers in the stack. The fabric layers were
stitched together about the perimeter of the panel 1/2 in (1.27 cm) from the
edge. A 2 in x 2 in (5.1 x 5.1 cm) quilt pattern was also sewn through the
thickness of the panel to mechanically bind the layers together. Ballistic
backface signature impact testing was performed using 44 magnum
bullets at velocities of 1430 30 ft/s on targets placed against a clay
witness (Roma plastilina clay) following the protocol outlined by NIJ
Standard 0101-04. The ballistic V50 for 44 magnum bullets was
determined for this test panel. The backface signature and V50 results for
44 Magnum bullet ballistic testing at 1430 30 ft/s against a clay witness
appear in Table 1.
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Comparative Example 2
A 15 in x15 in (38 x 38 cm) square ballistic test panel was prepared
from 36 layers of a plain weave fabric made from 840 denier Kevlar 129
fiber yarns by JPS Industries Inc., having a yarn count of 18 ends per inch
warp and 18 ends per inch fill, measured extracted yarn tenacities of 27
g/denier warp and 26 g/denier fill, and an areal density of 4.04 oz/yd2 (137
g/m2). Individual fabric layers were cut from the fabric roll having warp and
fill yarns parallel to the sides of the square. Fabric layers were arranged
with warp and fill fiber yarns oriented in the same direction for all fabric
layers in the stack. The fabric layers were stitched together about the
perimeter of the panel 1/2 in (1.27 cm) from the edge. A 2 in x 2 in (5.1 x
5.1 cm) quilt pattern was also sewn through the thickness of the panel to
mechanically bind the layers together. The backface signature and V50
results for 44 Magnum bullet ballistic testing at 1430 30 ft/s against a clay
witness appear in Table 1.
Comparative Example 3
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 37 layers of style 726 greige fabric having the properties described in
Comparative Example 1. The target was fabricated having an alternating
fabric orientation for every other layer with 19 fabric squares having the
sides of the square oriented parallel with the warp and fill fiber yarn
directions (0-90), and 18 layers oriented 45 degrees rotated from that of
the previous fabric (-45, +45). The fabric layers were stitched together
about the perimeter of the panel 1/2 in (1.27 cm) from the edge. A 2 in x 2
in (5.1 x 5.1 cm) quilt pattern was also sewn through the thickness of the
panel to mechanically bind the layers together. The backface signature
and V50 results for 44 Magnum bullet ballistic testing at 1430 30 ft/s
against a clay witness appear in Table 1.
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Comparative Example 4
A 15 in x 15 in (38 cm x 38 cm) square ballistic test panel was
prepared from 53 layers of plain woven Kevlar KM2, 600 denier fiber
yarns, having a yarn count of 17 ends per inch warp and 17 ends per inch
fill, extracted yarn tenacities of 25 g/denier warp, and 22 g/denier fill, and
an areal density of 2.64 oz/yd2 (89.5 g/m2). Individual square fabric layers
were generated by cutting along the warp and fill direction (having warp
and fill fiber yarns parallel to the sides of the square). Fabric layers were
arranged with warp and fill fibers oriented in the same direction for all
fabric layers in the stack. The fabric layers were stitched together about
the perimeter of the panel 1/2 in (1.27 cm) from the edge. A 2 in x 2 in
(5.1 x 5.1 cm) quilt pattern was also sewn through the thickness of the
panel to mechanically bind the layers together. The backface signature
and V50 results for 44 Magnum bullet ballistic testing at 1430 30 ft/s
against a clay witness appear in Table 2.
Comparative Example 5
A 15 in x 15 in (38 cm x 38 cm) square ballistic test panel was
prepared from 26 layers of plain woven Kevlar KM2, 600 denier fiber
yarns, having a yarn count of 34 ends per inch warp and 34 ends per inch
fill, extracted yarn tenacities of 21 g/denier warp, and 23 g/denier fill, and
an areal density of 5.50 oz/yd2 (186 g/m2). Individual square fabric layers
were generated by cutting along the warp and fill direction (having warp
and fill fiber yarns parallel to the sides of the square). Fabric layers were
arranged with warp and fill fibers oriented in the same direction for all
fabric layers in the stack. The fabric layers were stitched together about
the perimeter of the panel 1/2 in (1.27 cm) from the edge. A 2 in x 2 in
(5.1 x 5.1 cm) quilt pattern was also sewn through the thickness of the
panel to mechanically bind the layers together. Backface signature and
V50 results for 44 Magnum bullet ballistic testing at 1430 30 ft/s against a
clay witness appear in Table 2.
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Comparative Example 6
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 33 layers of a 4-harness satin (crow's foot) weave fabric made from
840 denier Kevlar 129 fiber yarns by JPS Industries Inc, having a yarn
count of 20 ends per inch warp and 20 ends per inch fill, a warp yarn
tenacity of 27 g/denier, a fill yarn tenacity of 25 g/denier, and an areal
density of 4.43 oz/yd2 (150 g/m2). Individual fabric layers were cut from
the fabric roll having warp and fill yarns parallel to the sides of the
square.
Fabric layers were arranged with warp and fill fibers oriented in the same
direction for all fabric layers in the stack. The fabric layers were stitched
together about the perimeter of the panel 1/2 in (1.27 cm) from the edge.
A 2 in x 2 in (5.1 x 5.1 cm) quilt pattern was also sewn through the
thickness of the panel to mechanically bind the layers together. The
backface signature and V50 results for 44 Magnum bullet ballistic testing
at 1430 30 ft/s against a clay witness appear in Table 3.
Comparative Example 7
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 12 composites fabricated by bonding two layers of style 726 greige
fabric described in Comparative Example 1, the second layer being
rotated 45 degrees relative to the first. The layers were bonded together
using a nonwoven polymeric fabric adhesive ( Pellon Wonder-Under
805 fusible nonwoven interfacing web available from Pellon Consumer
Products Group, LLC of Tucker, Georgia), at a temperature of about
130 C and compressed using a hand iron to melt the adhesive and effect
a bond between the fabric layers. The 12 composite layers were stacked
and sewn about the perimeter and with a 2 in x 2 in (5.1 x 5.1 cm) quilt
stitch to generate the test panel. The backface signature and V50 results
for 44 Magnum bullet ballistic testing at 1430 30 ft/s against a clay
witness appear in Table 4.
Comparative Example 8
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 12 layers of the style 726 greige fabric having properties described in
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Comparative Example 1, and 6 of the two 726 greige fabric layer
composites described in Comparative Example 7. The panel was
assembled with the 12 non-bonded layers in front (first impacted by the
bullet), and the six composites in the rear (nearest the clay witness). The
resulting stack was sewn about the perimeter and with a 2 in x 2 in (5.1 x
5.1 cm) quilt stitch to generate the test panel. The backface signature and
V50 results for 44 Magnum bullet ballistic testing at 1430 30 ft/s against a
clay witness appear in Table 4.
Comparative Example 9
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from a stack of 17 composites fabricated by bonding two layers of the 840
denier, 18 ends per inch warp, 18 ends per inch fill greige fabric described
in Comparative Example 2, the second layer being rotated 45 degrees
relative to the first. The layers were bonded together using a nonwoven
polymeric fabric adhesive (Pellen 805 Wonder-Under ) under similar
conditions to Comparative Example 7 to melt the adhesive and effect a
bond between the fabric layers. The 17 composite layers were stacked
and sewn about the perimeter and with a 2 in x 2 in (5.1 x 5.1 cm) quilt
stitch to generate the test panel. The backface signature and V50 results
for 44 Magnum bullet ballistic testing at 1430 30 ft/s against a clay
witness appear in Table 4.
Comparative Example 10
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 17 layers of the 840 denier Kevlar 129 yarn, 18 yarns per inch
warp, 18 ends per inch fill greige fabric described in Comparative Example
2, and 9 of the two layer composite fabric plies described in Comparative
Example 9. The panel was assembled with the 17 non-bonded layers in
front (first impacted by the bullet), and the six composites in the rear
(nearest the clay witness). The resulting stack was sewn about the
perimeter and with a 2 in x 2 in (5.1 x 5.1 cm) quilt stitch to generate the
test panel. The backface signature and V50 results for 44 Magnum bullet
ballistic testing at 1430 30 ft/s against a clay witness appear in Table 4.
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Comparative Example 11.
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared
from 30 layers of plain weave fabric type S-17114G with a CS811 finish
woven by JPS Industries Inc. from ultra high molecular weight
polyethylene yarn made by the Beijing Tongyizhong Specialty Fiber
Technology & Development Company Ltd., Beijing, China. This 800
denier yarn reinforcement had a yarn count of 24 ends per inch (94 ends
per 10 cm.) in warp and fill and had an areal density of 4.86 oz/yd2 (165
g/m2). Individual square fabric layers were generated by cutting along the
warp and fill directions (having warp and fill fibers parallel to the sides of
the square). The fabric layers were arranged with warp and fill fibers
oriented in the same direction for all fabric layers in the stack. The fabric
layers were stitched together about the perimeter of the panel 1/2 in (1.27
cm) from the edge. A 2 in x 2 in (5.1 x 5.1 cm) quilt pattern was also sewn
through the thickness of the panel to mechanically bind the layers
together. Ballistic backface signature impact testing was performed using
44 magnum bullets at velocities of 1430 30 ft/s on targets placed against
a clay witness (Roma plastilina clay) following the protocol outlined by NIJ.
The ballistic V50 for 44 magnum bullets was determined for this test panel.
The backface signature and V50 results appear in Table 5.
Example 1
Diagonal strips were cut from a 63 in (160 cm) wide roll of the 840
denier Kevlar 129 yarn, 18 ends per inch warp, 18 ends per inch fill
greige fabric described in Comparative Example 2. The diagonal cuts
were oriented along the bias direction of this plain weave fabric as shown
in Fig. 3A; generating bias-oriented fabric strips 28 in (71 cm) in width.
The fabric was clamped in a trellising frame as illustrated in Fig. 3B and
extended to achieve a 45 degree acute trellis angle. The trellised fabric
was cut into equal sections and cross-laid (stacked in an alternating layer
fashion, with every layer having a trellis direction rotated 90 degrees
relative to the one before it). The stack was constructed with the aid of a
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square pinning frame that held the trellis angle of individual fabric layers
fixed during construction. This alternating cross-laid arrangement of fabric
layers was repeated to create a stack with 26 trellised fabric layers. The
stack of fabric layers were stitched together about their perimeter, and a 2
in x 2 in (5.1 x 5.1 cm) quilt pattern was also sewn through the thickness of
the panel to mechanically bind the layers together, while the fabric layers
were held in place in the pinning frame. The panel was then trimmed to
have a 15 in x 15 in (38 x 38 cm) end construction. The backface
signature and V50 results for 44 Magnum bullets at 1430 30 ft/s against a
clay witness appear in Table 1. These panels fabricated from the
inventive fabric architecture demonstrated a reduction in backface
signature over Comparative Examples 1-3. V50 performance was also not
compromised for these panels with this novel construction, remaining
comparable in value to Comparative Examples 1-3.
Example 2
Diagonal strips were cut from a 63 in (160 cm) wide roll of the 600
denier Kevlar KM2 yarn, 17 ends per inch warp, 17 ends per inch fill
greige fabric described in Comparative Example 2. The diagonal cuts
were oriented along the bias direction of this plain weave fabric as shown
in Fig. 3A, generating bias-oriented fabric strips. The fabric was clamped
in a trellising frame as illustrated in Fig. 3B and extended to achieve a 30
degree acute trellis angle. The trellised fabric was cut into equal sections
and cross-laid (stacked in an alternating layer fashion, with every layer
having a trellis direction rotated 90 degrees relative to the one before it).
The stack was constructed with the aid of a square pinning frame that held
the trellis angle of individual fabric layers fixed during construction. This
alternating cross-laid arrangement of fabric layers was repeated to create
a stack with 27 trellised fabric layers. The stack of fabric layers were
stitched together about their perimeter, and a 2 in x 2 in (5.1 x 5.1 cm)
quilt
pattern was also sewn through the thickness of the panel to mechanically
bind the layers together, while the fabric layers were held in place in the
pinning frame. The panel was then trimmed to have a 15 in x 15 in (38 x
38 cm) end construction. The backface signature and V50 results for 44
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Magnum bullets at 1430 30 ft/s against a clay witness appear in Table 1.
This trellised fabric construction exhibited improved V50 performance over
both the target fabricated of the base 17 end per inch warp, 17 end per
inch fill fabric (Comparative example 5) and the plain woven fabric target
of the same 600 denier yarn exhibiting equivalent individual fabric layer
areal density (Comparative Example 6). The first backface measurement
performed on this inventive construction also demonstrated improvement
over both Comparative Examples 5 and 6, yet the integrity of this
construction after this first backface test was reduced, which may have
resulted in the increased deformation resistance observed in the second
backface signature measurement.
Example 3
A multilayer panel comprised of a trellised fabric architecture generated
using the 20 x 20 ends per inch, 840 denier Kevlar 129 yarn crow's foot
weave fabric described in Comparative Example 6 , was generated using
the procedure described for Experimental example 1 above. The finished
test panel was comprised of 23 layers, each having a 45 degree trellis
angle, the layers being stacked in a 0 degree - 90 degree alternating
orientation as done in experimental example 1. The panel was sewn
about the perimeter and with a 2 in x 2 in (5.1 x 5.1 cm) quilt pattern. The
backface signature and V50 results for 44 Magnum bullets at 1430 30 ft/s
against a clay witness appear in Table 3.
This example exhibited improved backface without significant loss in V50
when compared with the target fabricated from the base fabric in
Comparative Example 6.
Example 4
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared from
12 composites fabric plies fabricated by bonding two layers of the
inventive trellised fabric architecture fabricated as described in Example 1,
the second fabric layer being rotated 90 degrees relative to the first with
respect to trellis direction. The layers were bonded together using a
nonwoven polymeric fabric adhesive (Pellen 805) under similar
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conditions to Comparative Example 7 to effect a bond between the fabric
layers. The 12 composite layers were stacked and sewn about the
perimeter and with a 2 in x 2 in (5.1 x 5.1 cm) quilt stitch to generate the
test panel. As shown in Table 4, this construction demonstrated higher
V50 than the comparative composite fabric ply panels described in
Comparative Examples 7 through 10, while consistently demonstrating
satisfactory backface signatures even after 5 backface tests performed
with the 44 magnum bullet at 1430 30 ft/s.
Example 5
A 15 in x 15 in (38 x 38 cm) square ballistic test panel was prepared from
18 layers of the 840 denier Kevlar 129 fiber yarn greige fabric described
in Comparative example 2, and 6 trellised fabric composite plies fabricated
from this same fabric as described in experimental example 4. The panel
was assembled with the 18 fabric layers in front (first impacted by the
bullet), and the six composite plies in the rear (nearest the clay witness).
The resulting stack was sewn about the perimeter and with a 2 in x 2 in
(5.1 x 5.1 cm) quilt stitch to generate the test panel. The backface
signature and V50 results for 44 Magnum bullets at 1430 30 ft/s against a
clay witness appear in Table 4.
Experimental Example 6
Diagonal strips were cut from a roll of style S-1 7114G, CS811
polyethylene fabric of Comparative Example 11. The diagonal cuts were
oriented along the bias direction of this plain weave fabric as shown in Fig.
3A, generating bias-oriented fabric strips. The fabric was clamped in a
trellising frame as illustrated in Fig. 3B and extended to achieve a 50
degree acute trellis angle. The trellised fabric was cut into equal sections
and cross-laid (stacked in an alternating layer fashion, with every layer
having a trellis direction rotated 90 degrees relative to the one before it).
The stack was constructed with the aid of a square pinning frame that held
the trellis angle of individual fabric layers fixed during construction. This
alternating cross-laid arrangement of fabric layers was repeated to create
a stack with 22 trellised fabric layers. The stack of fabric layers was
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stitched together about the perimeter and a 2 in x 2 in (5.1 x 5.1 cm) quilt
pattern was also sewn through the thickness of the panel to mechanically
bind the layers together, while the fabric layers were held in place in the
pinning frame. The panel was then trimmed to have a 15 in x 15 in (38 x
38 cm) end construction. The backface signature and V50 results for 44
Magnum bullets at 1430 30 ft/s against a clay witness appear in Table 5.
The trellis fabric construction had a 27% reduction in backface signature
compared to the conventional 0/90 plain weave construction fabric.
Table 1
Example Areal V50 Backface Performance
density (fps) Velocity BFS
Ibs/ft (fps) (mm)
Comparative 1.034 1535 1444 50
Example 1 1421 51
Comparative 1.008 1558 1429 49
Example 2 1405 56
Comparative 1.040 1590 1434 51
Example 3 1428 45
Example 1 1.034 1559 1428 39
1414 36
Table 2
Example Areal V50 Backface performance
density (fps) Velocity BFS
(lbs/ft (fps) (mm)
Comparative 1.03 1589 1430 52
Example 4 1426 55
Comparative 1.03 1548 1435 48
Example 5 1425 49
Example 2 1.033 1602 1444 42
1448 48
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Table 3
Example Areal V50 Backface performance
densi j (fps) Velocity BFS
(lbs/ft (fps) (mm)
Comparative 1.021 1617 1435 59
Example 6 1426 63
Example 3 1.033 1602 1432 39
1422 48
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Table 4
Example Areal V50 Backface Performance
density (fps) Velocity BFS
Ibs/ft (fps) (mm)
Comparative 1.034 1472 1427 37
Example 7 1444 39
1433 35
1405 34
Comparative 1.014 1473 1443 Complete
Example 8 **
1408 40
Comparative 1.018 1408 1439 Complete
Example 9 1424 Complete
Comparative 1.011 1471 1427 43
Example 10 1435 56
Example 4 0.992 1510 1408 35
1440 40*
1417 40
1424 36
1446 40
Example 5 0.999 1515 1434 47
1441 42
denotes impact 2.5" from edge of target
** "Complete" denotes bullet passed straight through the target
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Table 5
Example Areal V50 Backface Performance
densi (fps) Velocity BFS
(lbs/ft (fps) (mm)
Comparative 1.090 1450 1432 51
Example 11 1430 52
Example 6 1.020 1435 1444 39
1442 36
