U.S. patent application number 11/726069 was filed with the patent office on 2011-09-15 for cross-plied composite ballistic articles.
Invention is credited to Henry G. Ardiff, Brian D. Arvidson, Ashok Bhatnagar, David A. Hurst, Lori L. Wagner.
Application Number | 20110219943 11/726069 |
Document ID | / |
Family ID | 39712226 |
Filed Date | 2011-09-15 |
United States Patent
Application |
20110219943 |
Kind Code |
A1 |
Arvidson; Brian D. ; et
al. |
September 15, 2011 |
CROSS-PLIED COMPOSITE BALLISTIC ARTICLES
Abstract
A multilayered composite fabric, the composite fabric comprising
a first fabric comprising first and second non-woven
unidirectionally oriented fiber layers. Each of the fiber layers is
in a resin matrix and the fibers comprise high tenacity fibers. The
fibers in the two fiber layers are disposed at an angle with
respect to each other. The composite fabric includes a second
fabric comprising multi-directionally oriented fibers optionally in
a resin matrix. The second fabric also comprises high tenacity
fibers. The first and second fabrics are bonded together to form
the composite fabric, which has improved ballistic resistant
properties. Plastic films may be adhered to one or both outer
surfaces of the first fabric and can serve as the bonding agent
between the two fabrics. Also described is a method of making a
composite fabric.
Inventors: |
Arvidson; Brian D.;
(Chester, VA) ; Ardiff; Henry G.; (Chesterfield,
VA) ; Bhatnagar; Ashok; (Richmond, VA) ;
Hurst; David A.; (Richmond, VA) ; Wagner; Lori
L.; (Richmond, VA) |
Family ID: |
39712226 |
Appl. No.: |
11/726069 |
Filed: |
March 21, 2007 |
Current U.S.
Class: |
89/36.02 ;
156/60; 442/71 |
Current CPC
Class: |
B32B 27/12 20130101;
B32B 27/32 20130101; Y10T 442/2615 20150401; Y10T 156/10 20150115;
B32B 27/02 20130101; B32B 25/02 20130101; B32B 27/34 20130101; F41H
5/0485 20130101; B32B 5/12 20130101; B32B 5/26 20130101; Y10T
428/24058 20150115; Y10T 442/2098 20150401; Y10S 428/911 20130101;
B32B 27/04 20130101; B32B 5/28 20130101; B32B 25/14 20130101 |
Class at
Publication: |
89/36.02 ;
442/71; 156/60 |
International
Class: |
F41H 5/04 20060101
F41H005/04; B32B 5/02 20060101 B32B005/02; B32B 37/02 20060101
B32B037/02; B32B 37/14 20060101 B32B037/14 |
Claims
1. A multilayered composite fabric, said composite fabric
comprising: (a) a first fabric comprising a first fiber layer and a
second fiber layer, said first fiber layer comprising non-woven
unidirectionally oriented fibers in a first resin matrix, said
fibers comprising high tenacity fibers, said first fiber layer
comprising first and second surfaces, said second fiber layer
comprising non-woven unidirectionally oriented fibers in a second
resin matrix, said fibers comprising high tenacity fibers, said
second fiber layer comprising first and second surfaces, said first
surface of said second fiber layer being adjacent to said second
surface of said first fiber layer, said fibers in said second fiber
layer being arranged at an angle with respect to the direction of
the unidirectionally oriented fibers of said first fiber layer; and
(b) a second fabric comprising multi-directionally oriented fibers
optionally in a third resin matrix, at least about 50 percent by
weight of said fibers of said second fabric comprising high
tenacity fibers, said high tenacity fibers being selected from the
group consisting of high tenacity polyethylene fibers, aramid
fibers, and blends thereof, said second fabric having first and
second surfaces, said first surface of said second fabric being
adjacent to said second surface of said second fiber layer, and
said second fabric being directly or indirectly bonded to said
first fabric thereby forming said composite fabric.
2. The composite fabric of claim 1 wherein said second fabric
comprises a fabric selected from the group consisting of woven
fabrics, knitted fabrics, braided fabrics, felted fabrics and paper
fabrics.
3. The composite fabric of claim 1 wherein said first and second
fabrics are bonded by an adhesive.
4. The composite fabric of claim 1 further comprising at least one
plastic film, said plastic film being located between said first
and said second fabric layers, said plastic film bonding said first
and second fabrics together.
5. The composite fabric of claim 4 further comprising a plastic
film bonded to said first surface of said first fiber layer.
6. The composite fabric of claim 1 wherein said high tenacity
fibers of said first fabric are selected from the group consisting
of polyolefin fibers, aramid fibers, polybenzazole fibers,
polyvinyl alcohol fibers, polyacrylonitrile fibers, liquid crystal
copolyester fibers, polyamide fibers, polyester fibers, glass
fibers, graphite fibers, carbon fibers, basalt or other mineral
fibers, rigid rod polymer fibers, and blends thereof.
7. The composite fabric of claim 1 wherein said high tenacity
fibers of said first fabric are selected from the group consisting
of high tenacity polyethylene fibers, aramid fibers, and blends
thereof.
8. (canceled)
9. The composite fabric of claim 1 wherein said high tenacity
fibers of said first fabric are chemically the same as the high
tenacity fibers of said second fabric.
10. The composite fabric of claim 1 wherein said second fabric is
in the form of a woven fabric.
11. The composite fabric of claim 1 wherein said high tenacity
fibers of said first fabric comprise aramid fibers and said high
tenacity fibers of said second fabric comprise aramid fibers.
12. The composite fabric of claim 11 wherein said second fabric is
in the form of a woven fabric.
13. The composite fabric of claim 1 wherein said first and second
fiber layers are disposed such that the fiber direction of said
first fiber layer is at an angle of about 90.degree. with respect
to the fiber direction of said fibers of said second fiber
layer.
14. A multilayered ballistic resistant composite fabric, said
composite fabric comprising: (a) a first fabric comprising a first
fiber layer and a second fiber layer, said first fiber layer
comprising non-woven unidirectionally oriented fibers in a first
resin matrix, said fibers comprising high tenacity fibers, said
first fiber layer comprising first and second surfaces, said second
fiber layer comprising non-woven unidirectionally oriented fibers
in a second resin matrix, said fibers comprising high tenacity
fibers, said second fiber layer comprising first and second
surfaces, said first surface of said second fiber layer being
adjacent to said second surface of said first fiber layer, said
fibers in said second fiber layer being arranged at an angle with
respect to the direction of the unidirectionally oriented fibers of
said first fiber layer; (b) optionally a first plastic film bonded
to said first surface of said first fiber layer of said first
fabric; (c) a second plastic film bonded to said second surface of
said second fiber layer of said first fabric; and (d) a second
fabric comprising multi-directionally oriented fibers optionally in
a third resin matrix, at least about 50 percent by weight of said
fibers of said second fabric comprising high tenacity fibers, said
high tenacity fibers being selected from the group consisting of
high tenacity polyethylene fibers, aramid fibers, and blends
thereof, said second fabric having first and second surfaces, said
first surface of said second fabric being bonded to said second
plastic film.
15. The composite fabric of claim 14 wherein said high tenacity
fibers of said first fabric comprise high tenacity polyethylene
fibers and/or aramid fibers.
16. The composite fabric of claim 15 wherein said first and second
fiber layers are disposed such that the fiber direction of said
first fiber layer is at an angle of about 90.degree. with respect
to the fiber direction of said fibers of said second fiber
layer.
17. The composite fabric of claim 16 wherein said second fabric is
In the form of a woven fabric.
18. A ballistic article comprising the multilayered composite
fabric of claim 1.
19. A ballistic article comprising from about 2 to about 60 layers
of said multilayered composite fabric of claim 1.
20. A method of forming a composite fabric structure, said method
comprising: (a) supplying a first fiber layer comprising non-woven
unidirectionally oriented fibers in a first resin matrix, said
fibers comprising high tenacity fibers, said first fiber layer
comprising first and second surfaces; (b) supplying a second fiber
layer comprising non-woven unidirectionally oriented fibers in a
second resin matrix, said fibers comprising high tenacity fibers,
said second fiber layer comprising first and second surfaces; (c)
bonding said first and second fiber layers together such that said
first surface of said second fiber layer is adjacent to said second
surface of said first fiber layer, said fibers in said second fiber
layer being arranged at an angle with respect to the direction of
the unidirectionally oriented fibers of said first fiber layer; (d)
optionally applying a first plastic film to said first surface of
said first fiber layer; (e) applying a second plastic film to said
second surface of said second fiber layer; (f) supplying a second
fabric comprising multi-directionally oriented fibers optionally in
a third resin matrix, at least about 50 percent by weight of said
fibers of said second fabric comprising high tenacity fibers, said
high tenacity fibers being selected from the group consisting of
high tenacity polyethylene fibers, aramid fibers, and blends
thereof, said second fabric having first and second surfaces; and
(g) bonding said first surface of said second fabric to said second
plastic film to thereby form said composite fabric.
21. The method of claim 20 wherein said second fabric comprises a
woven fabric.
22. The method of claim 20 wherein said high tenacity fibers of
said first fabric comprise high tenacity polyethylene fibers and/or
aramid fibers.
23. The composite fabric of claim 1 wherein said high tenacity
fibers of said first fabric comprise high tenacity polyethylene
fibers and said high tenacity fibers of said second fabric comprise
high tenacity polyethylene fibers.
24. The composite fabric of claim 1 wherein said second fabric
contains no matrix resin.
25. The composite fabric of claim 1 wherein said fibers of said
first fiber layer are fully embedded in said first resin matrix and
said fibers of said second fiber layer are fully embedded in said
second resin matrix.
26. The composite of claim 11 wherein said fibers of said second
fabric layer comprise aramid fibers.
27. The composite of claim 1 wherein substantially all of said
fibers of said second fabric are said high tenacity fibers.
28. The composite of claim 1 where said high tenacity fibers of
said first fabric and said high tenacity fibers of said second
fabric have a tenacity of at least about 22 g/d.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to composite materials which are
useful for ballistic and other applications, and to a method for
their manufacture.
[0003] 2. Description of the Related Art
[0004] Ballistic resistant products are known in the art. They may
be of the flexible or rigid type. Many of these products are based
on high tenacity fibers, and are used in such applications as body
armor, such as bullet-resistant vests.
[0005] One popular type of ballistic resistant product is made from
unidirectionally oriented high tenacity fibers, such as high
tenacity polyethylene fibers or aramid fibers. Although such
products have desirable ballistic resistant properties, there
continues to be a need to provide products with enhanced
properties.
[0006] Accordingly, it would be desirable to provide a ballistic
resistant product that has improved ballistic properties.
SUMMARY OF THE INVENTION
[0007] In accordance with this invention, there is provided a
multilayered composite fabric, the composite fabric comprising:
[0008] (a) a first fabric comprising a first fiber layer and a
second fiber layer, the first fiber layer comprising non-woven
unidirectionally oriented fibers in a first resin matrix, the
fibers comprising high tenacity fibers, the first fiber layer
comprising first and second surfaces, the second fiber layer
comprising non-woven unidirectionally oriented fibers in a second
resin matrix, the fibers comprising high tenacity fibers, the
second fiber layer comprising first and second surfaces, the first
surface of the second fiber layer being adjacent to the second
surface of the first fiber layer, the fibers in the second fiber
layer being arranged at an angle with respect to the direction of
the unidirectionally oriented fibers of the first fiber layer;
and
[0009] (b) a second fabric comprising multi-directionally oriented
fibers optionally in a third resin matrix, the second fabric
comprising high tenacity fibers, the second fabric having first and
second surfaces, the first surface of the second fabric being
adjacent to the second surface of the second fiber layer, and the
second fabric being directly or indirectly bonded to the first
fabric thereby forming the composite fabric.
[0010] Further in accordance with this invention, there is provided
a multilayered composite fabric, the composite fabric
comprising:
[0011] (a) a first fabric comprising a first fiber layer and a
second fiber layer, the first fiber layer comprising non-woven
unidirectionally oriented fibers in a first resin matrix, the
fibers comprising high tenacity fibers, the first fiber layer
comprising first and second surfaces, the second fiber layer
comprising non-woven unidirectionally oriented fibers in a second
resin matrix, the fibers comprising high tenacity fibers, the
second fiber layer comprising first and second surfaces, the first
surface of said second fiber layer being in contact with the second
surface of the first fiber layer, the fibers in the second fiber
layer being arranged at an angle with respect to the direction of
the unidirectionally oriented fibers of the first fiber layer;
[0012] (b) optionally, a first plastic film bonded to the first
surface of the first fiber layer of said first fabric;
[0013] (c) a second plastic film bonded to the second surface of
the second fiber layer of the first fabric; and
[0014] (d) a second fabric comprising multi-directionally oriented
fibers optionally in a third resin matrix, the second fabric
comprising high tenacity fibers, the second fabric having first and
second surfaces, the first surface of the second fabric being
bonded to the second plastic film.
[0015] Also in accordance with this invention, there is provided a
method of forming a composite fabric structure, the method
comprising:
[0016] (a) supplying a first fiber layer comprising non-woven
unidirectionally oriented fibers in a first resin matrix, the
fibers comprising high tenacity fibers, the first fiber layer
comprising first and second surfaces;
[0017] (b) supplying a second fiber layer comprising non-woven
unidirectionally oriented fibers in a second resin matrix, the
fibers comprising high tenacity fibers, the second fiber layer
comprising first and second surfaces;
[0018] (c) bonding the first and second fiber layers together such
that the first surface of the second fiber layer is bonded to the
second surface of the first fiber layer, the fibers in the second
fiber layer being arranged at an angle with respect to the
direction of the unidirectionally oriented fibers of the first
fiber layer;
[0019] (d) optionally applying a first plastic film to the first
surface of the first fiber layer;
[0020] (e) applying a second plastic film to the second surface of
the second fiber layer;
[0021] (f) supplying a second fabric comprising multi-directionally
oriented fibers optionally in a third resin matrix, the second
fabric comprising high tenacity fibers, the second fabric having
first and second surfaces; and
[0022] (g) bonding the first surface of said second fabric to the
second plastic film to thereby form the composite fabric.
[0023] The invention provides a first fabric which comprises two
fibrous layers of unidirectionally oriented fibers that are
arranged at an angle with respect to each other (commonly referred
to as "cross plied"). The first fabric is bonded to a second fabric
which comprises multi-directionally oriented fibers. Additionally
layers can be present in the composite structure, such as plastic
films on one or both surfaces of the first fabric. When present on
the bottom surface of the second fibrous layer, the plastic film
bonds the first and second fabrics together. Other layers may be
employed and several layers of the composite fabric may be used to
form desired products, such as ballistic resistant products.
[0024] Surprisingly, it has been found that the composite structure
has improved ballistic performance when compared to a similar
structure in which the first and second fabrics are not bonded
together. In addition, it has been surprisingly found that the back
face deformation can be reduced by bonding the two fabric layers
together.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention comprises a multilayered composite
fabric which is formed from at least a first fabric layer and a
second fabric layer. The fibers in both of the first and second
fabric layers comprise high tenacity fibers, and the layers are
bonded together, directly or indirectly.
[0026] For the purposes of the present invention, a fiber is an
elongate body the length dimension of which is much greater that
the transverse dimensions of width and thickness. Accordingly, the
term "fiber" includes monofilament, multifilament, ribbon, strip,
staple and other forms of chopped, cut or discontinuous fiber and
the like having regular or irregular cross-sections. The term
"fiber" includes a plurality of any of the foregoing or a
combination thereof. A yarn is a continuous strand comprised of
many fibers or filaments. Fibers may also be in the form of split
film or tape.
[0027] The cross-sections of fibers useful herein may vary widely.
They may be circular, flat or oblong in cross-section. They may
also be of irregular or regular multi-lobal cross-section having
one or more regular or irregular lobes projecting from the linear
or longitudinal axis of the fibers. It is preferred that the fibers
be of substantially circular, flat or oblong cross-section, most
preferably circular.
[0028] As used herein, the term "high tenacity fibers" means fibers
which have tenacities equal to or greater than about 7 g/d.
Preferably, these fibers have initial tensile moduli of at least
about 150 g/d and energies-to-break of at least about 8 J/g as
measured by ASTM D2256. As used herein, the terms "initial tensile
modulus", "tensile modulus" and "modulus" mean the modulus of
elasticity as measured by ASTM 2256 for a yarn and by ASTM D638 for
an elastomer or matrix material.
[0029] Preferably, the high tenacity fibers have tenacities equal
to or greater than about 10 g/d, more preferably equal to or
greater than about 16 g/d, even more preferably equal to or greater
than about 22 g/d, and most preferably equal to or greater than
about 28 g/d.
[0030] High strength fibers useful in the yarns and fabrics of the
invention include highly oriented high molecular weight polyolefin
fibers, particularly high modulus (or high tenacity) polyethylene
fibers and polypropylene fibers, aramid fibers, polybenzazole
fibers such as polybenzoxazole (PBO) and polybenzothiazole (PBT),
polyvinyl alcohol fibers, polyacrylonitrile fibers, liquid crystal
copolyester fibers, polyamide fibers, polyester fibers, glass
fibers, graphite fibers, carbon fibers, basalt or other mineral
fibers, rigid rod polymer fibers, and mixtures and blends thereof.
Preferred high strength fibers useful in this invention include
polyolefin fibers (more preferably high tenacity polyethylene
fibers), aramid fibers, polybenzazole fibers, graphite fibers, and
mixtures and blends thereof. Most preferred are high tenacity
polyethylene fibers and/or aramid fibers.
[0031] U.S. Pat. No. 4,457,985 generally discusses such high
molecular weight polyethylene and polypropylene fibers, and the
disclosure of this patent is hereby incorporated by reference to
the extent that it is not inconsistent herewith. In the case of
polyethylene, suitable fibers are those of weight average molecular
weight of at least about 150,000, preferably at least about one
million and more preferably between about two million and about
five million. Such high molecular weight polyethylene fibers may be
spun in solution (see U.S. Pat. No. 4,137,394 and U.S. Pat. No.
4,356,138), or a filament spun from a solution to form a gel
structure (see U.S. Pat. No. 4,413,110, German Off. No. 3,004, 699
and GB Patent No. 2051667), or the polyethylene fibers may be
produced by a rolling and drawing process (see U.S. Pat. No.
5,702,657). As used herein, the term polyethylene means a
predominantly linear polyethylene material that may contain minor
amounts of chain branching or comonomers not exceeding about 5
modifying units per 100 main chain carbon atoms, and that may also
contain admixed therewith not more than about 50 weight percent of
one or more polymeric additives such as alkene-l-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,
ultraviolet screening agents, colorants and the like which are
commonly incorporated.
[0032] High tenacity polyethylene fibers (also referred to as
extended chain or high molecular weight polyethylene fibers) are
preferred and are available, for example, under the trademark
SPECTRA.RTM. fibers and yarns from Honeywell International Inc. of
Morristown, N.J., U.S.A.
[0033] Depending upon the formation technique, the draw ratio and
temperatures, and other conditions, a variety of properties can be
imparted to these fibers. The tenacity of the polyethylene fibers
are at least about 7 g/d, preferably at least about 15 g/d, more
preferably at least about 20 g/d, still more preferably at least
about 25 g/d and most preferably at least about 30 g/d. Similarly,
the initial tensile modulus of the fibers, as measured by an
Instron tensile testing machine, is preferably at least about 300
g/d, more preferably at least about 500 g/d, still more preferably
at least about 1,000 g/d and most preferably at least about 1,200
g/d. These highest values for initial tensile modulus and tenacity
are generally obtainable only by employing solution grown or gel
spinning processes. Many of the filaments have melting points
higher than the melting point of the polymer from which they were
formed. Thus, for example, high molecular weight polyethylene of
about 150,000, about one million and about two million molecular
weight generally have melting points in the bulk of 138.degree. C.
The highly oriented polyethylene filaments made of these materials
have melting points of from about 7.degree. C. to about 13.degree.
C. higher. Thus, a slight increase in melting point reflects the
crystalline perfection and higher crystalline orientation of the
filaments as compared to the bulk polymer.
[0034] Preferably the polyethylene employed is a polyethylene
having fewer than about one methyl group per thousand carbon atoms,
more preferably fewer than about 0.5 methyl groups per thousand
carbon atoms, and less than about 1 weight percent of other
constituents.
[0035] Similarly, highly oriented high molecular weight
polypropylene fibers of weight average molecular weight at least
about 200,000, preferably at least about one million and more
preferably at least about two million may be used. Such extended
chain polypropylene may be formed into reasonably well oriented
filaments by the techniques prescribed in the various references
referred to above, and especially by the technique of U.S. Pat. No.
4,413,110. Since polypropylene is a much less crystalline material
than polyethylene and contains pendant methyl groups, tenacity
values achievable with polypropylene are generally substantially
lower than the corresponding values for polyethylene. Accordingly,
a suitable tenacity is preferably at least about 8 g/d, more
preferably at least about 11 g/d. The initial tensile modulus for
polypropylene is preferably at least about 160 g/d, more preferably
at least about 200 g/d. The melting point of the polypropylene is
generally raised several degrees by the orientation process, such
that the polypropylene filament preferably has a main melting point
of at least 168.degree. C., more preferably at least 170.degree. C.
The particularly preferred ranges for the above described
parameters can advantageously provide improved performance in the
final article. Employing fibers having a weight average molecular
weight of at least about 200,000 coupled with the preferred ranges
for the above-described parameters (modulus and tenacity) can
provide advantageously improved performance in the final
article.
[0036] In the case of extended chain polyethylene fibers,
preparation and drawing of gel-spun polyethylene fibers are
described in various publications, including U.S. Pat. Nos.
4,413,110; 4,430,383; 4,436,689; 4,536,536; 4,545,950; 4,551,296;
4,612,148; 4,617,233; 4,663,101; 5,032,338; 5,246,657; 5,286,435;
5,342,567; 5,578,374; 5,736,244; 5,741,451; 5,958,582; 5,972,498;
6,448,359; 6,969,553 and U.S. patent application publication
2005/0093200, the disclosures of which are expressly incorporated
herein by reference to the extent not inconsistent herewith.
[0037] In the case of aramid fibers, suitable fibers formed from
aromatic polyamides are described, for example, in U.S. Pat. No.
3,671,542, which is incorporated herein by reference to the extent
not inconsistent herewith. Preferred aramid fibers will have a
tenacity of at least about 20 g/d, an initial tensile modulus of at
least about 400 g/d and an energy-to-break at least about 8 J/g,
and particularly preferred aramid fibers will have a tenacity of at
least about 20 g/d and an energy-to-break of at least about 20 J/g.
Most preferred aramid fibers will have a tenacity of at least about
23 g/d, a modulus of at least about 500 g/d and an energy-to-break
of at least about 30 J/g. For example, poly(p-phenylene
terephthalamide) filaments which have moderately high moduli and
tenacity values are particularly useful in forming ballistic
resistant composites. Examples are Twaron.RTM. T2000 from Teijin
which has a denier of 1000. Other examples are Kevlar.RTM. 29 which
has 500 g/d and 22 g/d as values of initial tensile modulus and
tenacity, respectively, as well as Kevlar.RTM. 129 and KM2 which
are available in 400, 640 and 840 deniers from du Pont. Aramid
fibers from other manufacturers can also be used in this invention.
Copolymers of poly(p-phenylene terephthalamide) may also be used,
such as co-poly(p-phenylene terephthalamide 3,4' oxydiphenylene
terephthalamide). Also useful in the practice of this invention are
poly(m-phenylene isophthalamide) fibers sold by du Pont under the
trade name Nomex.RTM..
[0038] High molecular weight polyvinyl alcohol (PV-OH) fibers
having high tensile modulus are described in U.S. Pat. No.
4,440,711 to Kwon et al., the disclosure of which is hereby
incorporated by reference to the extent it is not inconsistent
herewith. High molecular weight PV-OH fibers should have a weight
average molecular weight of at least about 200,000. Particularly
useful PV-OH fibers should have a modulus of at least about 300
g/d, a tenacity preferably at least about 10 g/d, more preferably
at least about 14 g/d and is most preferably at least about 17 g/d,
and an energy to break of at least about 8 J/g. PV-OH fiber having
such properties can be produced, for example, by the process
disclosed in U.S. Pat. No. 4,599,267.
[0039] In the case of polyacrylonitrile (PAN), the PAN fiber should
have a weight average molecular weight of at least about 400,000.
Particularly useful PAN fiber should have a tenacity of preferably
at least about 10 g/d and an energy to break of at least about 8
J/g. PAN fiber having a molecular weight of at least about 400,000,
a tenacity of at least about 15 to 20 g/d and an energy to break of
at least about 8 J/g is most useful; and such fibers are disclosed,
for example, in U.S. Pat. No. 4,535,027.
[0040] Suitable liquid crystal copolyester fibers for the practice
of this invention are disclosed, for example, in U.S. Pat. Nos.
3,975,487; 4,118,372 and 4,161,470. Liquid crystal copolyester
fibers are available under the designation Vectran.RTM. fibers from
Kuraray America Inc.
[0041] Suitable polybenzazole fibers for the practice of this
invention are disclosed, for example, in U.S. Pat. Nos. 5,286,833,
5,296,185, 5,356,584, 5,534,205 and 6,040,050. Polybenzazole fibers
are available under the designation Zylon.RTM. fibers from Toyobo
Co.
[0042] Rigid rod fibers are disclosed, for example, in U.S. Pat.
Nos. 5,674,969, 5,939,553, 5,945,537 and 6,040,478. Such fibers are
available under the designation M5.RTM. fibers from Magellan
Systems International.
[0043] Preferably, the fibers in the first fabric layer are
selected from the group of high tenacity polyolefin fibers (more
preferably high tenacity polyethylene fibers), aramid fibers, PBO
fibers, graphite fibers and blends thereof. Likewise, the fibers in
the second fabric layer are selected from the same group of
fibers.
[0044] The fabric layers of this invention are preferably formed
from all or substantially all high tenacity fibers. Alternatively,
at least about 50% by weight of the fibers in the fabric layers are
high tenacity fibers and more preferably at least about 75% by
weight of the fibers in the fabric layers are high tenacity
fibers.
[0045] The first fabric is in the form of a non-woven fabric of
high tenacity unidirectionally oriented fibers. The first fabric
has a plurality of fiber layers, and each of the fiber layers
includes unidirectionally oriented fibers. As is known, in such an
arrangement the unidirectionally oriented fibers of each layer are
aligned parallel to one another along a common fiber direction. The
unidirectionally oriented fiber layers may include a minor amount
of a material which provides some cross-directional stability to
the product; such material may be in the form of fibers, yarns or
adhesive yarns all of which are not high tenacity materials, or
resins, adhesives, films and the like that may be spaced along the
length of the unidirectionally oriented fiber layer but extend at
an angle thereto. Such materials, if present, may comprise up to
about 10%, more preferably up to about 5%, by weight of the total
weight of each fiber layer.
[0046] The first fabric may be constructed via a variety of
methods. Each of the fiber layers forming the first fabric is
preferably formed by supplying yarn bundles of the high tenacity
filaments from a creel and led through guides and into a
collimating comb. The collimating comb aligns the filaments
coplanarly and in a substantially unidirectional fashion. The
fibers may then be led into one or more spreader bars which may be
included in the coating apparatus, or may be located before or
after the coating apparatus.
[0047] The fiber layers of the first fabric are coated with a
matrix resin composition. As used herein, the term "coating" is
used in a broad sense to describe a fiber network wherein the
individual fibers either have a continuous layer of the matrix
composition surrounding the fibers or a discontinuous layer of the
matrix composition on the surfaced of the fibers. In the former
case, it can be said that the fibers are fully embedded in the
matrix composition. The terms coating and impregnating are
interchangeably used herein. Preferably the matrix resin of each of
the fiber layers of the first fabric has the same or similar
chemical structure so that the layers can be readily bonded to each
other.
[0048] Typical methods for forming each of the fiber layers are
described, for example, in U.S. Pat. Nos. 5,552,208 and 6,642,159,
the disclosures of which are expressly incorporated herein by
reference to the extent not inconsistent herewith.
[0049] At least two of the fiber layers of the first fabric are
combined in a manner such that the angles of orientation of the
layers are different. These fiber layers may be cross-plied in a
manner known in the art. For example, the fibers in the first fiber
layer extend preferably 90.degree. from the fibers in the second
fiber layer. The angles of rotation of the fibers in the various
fiber layers may be any chosen angles, such as
0.degree./90.degree., 0.degree./90.degree./0.degree./90.degree., or
0.degree./45.degree./90.degree./45.degree./0.degree. or other
angles. Such rotated unidirectional alignments are described, for
example, in U.S. Pat. Nos. 4,623,574; 4,737,402; 4,748,064; and
4,916,000.
[0050] The first and second fiber layers of the first fabric may be
bonded together by any desired technique. For example, the matrix
resin or resins of the two layers may be employed as the bonding
agent. Alternatively, the two fiber layers may be bonded by means
of an adhesive, a plastic film, or any other suitable means.
[0051] In one preferred embodiment, two fiber layers are
cross-plied in a 0.degree./90.degree. configuration or in an
approximate 0.degree./90.degree. configuration and then
consolidated to form the first fabric layer. The two fiber network
layers can be to continuously cross-plied, preferably by cutting
one of the fiber layers into lengths that can be placed
successively across the width of the other network in a
0.degree./90.degree. orientation. Equipment for the continuous
cross-plying of fibrous layers is known, and such is described, for
example, in U.S. Pat. Nos. 5,173,138 and 5,766,725. The resulting
continuous two-ply first fabric can then be wound into a roll,
preferably with a layer of separation material between each
adjacent two-ply structure.
[0052] The high tenacity fibers of the first fiber layer and the
second fiber layer may be the same or be chemically different
fibers. For ease of manufacturing, the high tenacity fibers of each
fiber layer is the same, but in some constructions it may be
desired to have the fibers in each fiber layer to be different so
as to combine the different properties of the each fiber material.
Examples of the first fabric construction include high tenacity
polyethylene fibers used as the fibers in both fiber layers, aramid
fibers used as the fibers in both fiber layers, high tenacity
polyethylene fibers used as the fibers in a first fiber layer and
aramid fibers used as the fibers in a second fiber layer, aramid
fibers used as the fibers in a first fiber layer and high tenacity
polyethylene fibers used as the fibers in the second fiber layer,
as well as other constructions using any of the high tenacity
fibers mentioned above.
[0053] As mentioned above, the first fabric may be formed from more
than two fiber layers, and any desired number of fiber layers may
be employed in the first fabric. For example, the first fabric may
be a four ply structure, in which adjacent fiber layers are
oriented with respect to each other, preferably at 90.degree..
[0054] With respect to the second fabric, it is preferred that the
second fabric layer is not coated with a matrix resin.
Alternatively, the second fabric may be coated with a matrix resin,
preferably of the same or similar chemical structure as are in the
fiber layers of the first fabric.
[0055] The matrix resin composition may be applied as a solution,
dispersion or emulsion, or the like, onto the fibers of the fiber
layers that form the first fabric layer. The matrix resin may be
applied by any desired technique, such as by spraying, dipping,
roller coating, hot melt coating, or the like. The coated fabric
layer or layers may then be passed through an oven for drying in
which they are subjected to sufficient heat to evaporate the water
or other solvent in the matrix resin composition.
[0056] The second fabric layer is also formed from high tenacity
fibers, but the fibers are oriented in multiple directions in the
fabric. That is, the fibers in the second fabric are
multi-directionally oriented. This means that there are sufficient
fibers which extend in a second direction from the major direction
of the fabric to provide some degree of cross direction strength to
the fabric. The term "multi-directionally oriented fibers" is
distinct from "unidirectionally oriented fibers".
[0057] The second fabric may be in the form of a woven fabric, a
knitted fabric, a braided fabric, a felted fabric, a paper fabric,
and the like. Preferably the second fabric is in the form of a
woven fabric. This second fabric layer may be referred to as a
ballistic textile product.
[0058] As mentioned above, the high tenacity fibers in the second
fabric layer are chosen from the same group of fibers mentioned
above with respect to the first fabric layer. Preferably, the
fibers in the second fabric layer are also selected from the group
of high tenacity polyolefin fibers (more preferably high tenacity
polyethylene fibers), aramid fibers, PBO fibers, graphite fibers
and blends thereof. Most preferably, such fibers are high tenacity
polyethylene fibers and/or aramid fibers.
[0059] If a woven fabric is employed, it may be of any weave
pattern, including plain weave, basket weave, twill, satin, three
dimensional woven fabrics, and any of their several variations.
Plain and basket weave fabrics are preferred and more preferred are
such fabrics having an equal warp and weft count. In one embodiment
as mentioned above, the woven fabric does not include a resin
matrix. In another embodiment, the woven fabric may include a resin
matrix prior to bonding to the first fabric.
[0060] The yarns of the woven fabric may be twisted, over-wrapped
or entangled. The second fabric may be woven with yarns having
different fibers in the warp and weft directions, or in other
directions. For example, a woven fabric may be formed with aramid
fibers in the warp direction and high tenacity polyethylene fibers
in the weft direction, or vice versa.
[0061] As mentioned above, the second fabric may alternatively be
in the form of a knitted fabric. Knit structures are constructions
composed of intermeshing loops, with the four major types being
tricot, raschel, net and oriented structures. Due to the nature of
the loop structure, knits of the first three categories are not as
suitable as they do not take full advantage of the strength of a
fiber. Oriented knitted structures, however, use straight inlaid
yarns held in place by fine denier knitted stitches. The yarns are
absolutely straight without the crimp effect found in woven fabrics
due to the interlacing effect on the yarns. These laid in yarns can
be oriented in a monoaxial, biaxial or multiaxial direction
depending on the engineered requirements. It is preferred that the
specific knit equipment used in laying in the load bearing yarns is
such that the yarns are not pierced through.
[0062] The second fabric may alternatively be formed from a
non-woven fabric such as a fabric in the form of a felt, such as
needle punched felts. A felt is a non-woven network of randomly
oriented fibers, preferably at least one of which is a
discontinuous fiber, preferably a staple fiber having a length
ranging from about 0.25 inch (0.64 cm) to about 10 inches (25 cm).
These felts may be formed by several techniques known in the art,
such as by carding or fluid laying, melt blowing and spin laying.
The network of fibers is consolidated mechanically such as by
needle punching, stitch-bonding, hydro-entanglement, air
entanglement, spun bond, spun lace or the like, chemically such as
with an adhesive, or thermally with a fiber to point bond or a
blended fiber with a lower melting point.
[0063] Alternatively, the second fabric may be in the form of a
paper fabric that may be formed, for example, by pulping a liquid
containing the high tenacity fibers.
[0064] In another embodiment, the second fabric may be in the form
of a multilayer composite fabric, such as a fabric that includes a
third layer which is may be a unidirectionally oriented fabric or a
multi-directionally oriented fabric. The third layer is also
preferably formed from high tenacity fibers.
[0065] The yarns useful in the various fibrous layers may be of any
suitable denier, and may be of the same or different deniers in
each layer. For example, the yarns may have a denier of from about
50 to about 3000.
[0066] The selection is governed by considerations of ballistic
effectiveness, other desired properties, and cost. For woven
fabrics, finer yarns are more costly to manufacture and to weave,
but can produce greater ballistic effectiveness per unit weight.
The yarns are preferably from about 200 denier to about 3000
denier. More preferably, the yarns are from about 400 denier to
about 2000 denier. Most preferably, the yarns are from about 500
denier to about 1600 denier.
[0067] The matrix resin for the fiber layers of the first fabric
and of the second or additional fabrics (if present) may be formed
from a wide variety of thermoplastic, thermosetting or elastomeric
materials having desired characteristics. In one embodiment, the
elastomeric materials used in such matrix possess initial tensile
modulus (modulus of elasticity) equal to or less than about 6,000
psi (41.4 MPa) as measured by ASTM D638. More preferably, the
elastomer has initial tensile modulus equal to or less than about
2,400 psi (16.5 MPa). Most preferably, the elastomeric material has
initial tensile modulus equal to or less than about 1,200 psi (8.23
MPa). These resinous materials are typically thermoplastic in
nature.
[0068] Alternatively, the matrix resin may be selected to have a
high tensile modulus when cured, as at least about 1.times.10.sup.5
psi (690 MPa). Examples of such materials are disclosed, for
example, in U.S. Pat. No. 6,642,159, the disclosure of which is
expressly incorporated herein by reference to the extent not
inconsistent herewith.
[0069] The proportion of the resin matrix material to fiber in the
composite layers may vary widely depending upon the end use. The
resin matrix material preferably forms about 1 to about 98 percent
by weight, more preferably from about 5 to about 95 percent by
weight, and still more preferably from about 5 to about 40 percent
by weight, and most preferably from about 10 to about 25 percent by
weight, based on the total weight of the fibers and resin
matrix.
[0070] A wide variety of elastomeric materials may be utilized as
the resin matrix. For example, any of the following materials may
be employed:
[0071] polybutadiene, polyisoprene, natural rubber,
ethylene-propylene copolymers, ethylene-propylene-diene
terpolymers, polysulfide polymers, polyurethane elastomers,
chlorosulfonated polyethylene, polychloroprene, plasticized
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,
and copolymers of ethylene. Examples of thermosetting resins
include those which are soluble in carbon-carbon saturated solvents
such as methyl ethyl ketone, acetone, ethanol, methanol, isopropyl
alcohol, cyclohexane, ethyl acetone, and combinations thereof.
Among the thermosetting resins are vinyl esters, styrene-butadiene
block copolymers, diallyl phthalate, phenol formaldehyde, polyvinyl
butyral and mixtures thereof, as disclosed in the aforementioned
U.S. Pat. No. 6,642,159. Preferred thermosetting resins for
polyethylene fiber fabrics include at least one vinyl ester,
diallyl phthalate, and optionally a catalyst for curing the vinyl
ester resin.
[0072] One preferred group of materials for polyethylene fiber
fabrics are block copolymers of conjugated dienes and vinyl
aromatic copolymers. Butadiene and isoprene are preferred
conjugated diene elastomers. Styrene, vinyl toluene and t-butyl
styrene are preferred conjugated aromatic monomers. Block
copolymers incorporating polyisoprene and/or polybutadiene may be
hydrogenated to produce thermoplastic elastomers having saturated
hydrocarbon elastomer segments. The polymers may be simple
tri-block copolymers of the type R-(BA).sub.x(x=3-150); wherein A
is a block from a polyvinyl aromatic monomer and B is a block from
a conjugated diene elastomer, or an A-B-A type of elastomer. A
preferred resin matrix is an styrene-isoprene-styrene block
copolymer, such as Kraton.RTM. D1107 styrene-isoprene-styrene block
copolymer available from Kraton Polymer LLC.
[0073] One preferred matrix resin for aramid fibers is a
polyurethane resin, such as a water-based polyurethane resin.
[0074] In one preferred embodiment, the matrix resin is chosen such
that the composite fabric is flexible, and is useful in such
applications as soft armor products and the like.
[0075] The second fabric is bonded to the first fabric preferably
after the layers of the first fabric are bonded together. Any
suitable means of bonding the first fabric to the second fabric may
be employed. For example, where the second fabric is directly
attached to one of the fiber layers of the first fabric, the matrix
resin of the fiber layer may be used as the material that bonds the
two fabrics together. This may be achieved under suitable heat
and/or pressure. Alternatively, the first and second fabrics may be
bonded by means of a separate layer of adhesive, which may or not
be similar to the matrix resin employed in the first fabric. Such
adhesives may be applied by spraying, dipping, roller coating,
application as a film, extrusion coating, or any other suitable
technique. Again, heat and/or pressure may be used to bond the two
fabric layers together. Furthermore, if the second fabric includes
a matrix resin that resin may be the vehicle by which the two
fabric layers are attached. Other bonding techniques may also be
employed.
[0076] One or more plastic films can be included in the composite
structure for a variety of reasons, such as to permit different
adjacent composite layers to slide over each other. This permits
ease of forming into a body shape and ease of wearing, as well as
other desirable properties. These plastic films may typically be
adhered to one or both surfaces of the first fabric. Any suitable
plastic film may be employed, such as films made of polyolefins.
Examples of such films are linear low density polyethylene (LLDPE)
films, ultrahigh molecular weight polyethylene (UHMWPE) films,
polyester films, nylon films, polycarbonate films and the like.
These films may be of any desirable thickness. Typical thicknesses
range from about 0.1 to about 1.2 mils (2.5 to 30 .mu.m), more
preferably from about 0.2 to about 1 mil (5 to 25 .mu.m), and most
preferably from about 0.2 to about 0.5 mils (5 to 12.5 .mu.m). Most
preferred are films of LLDPE.
[0077] For example, the two unidirectionally oriented high tenacity
fiber layers which are bonded together and cross-plied may have
plastic films applied to one or preferably both sides. The inner
plastic film is then in contact with the second fabric and is used
as the material which bonds the first and second fabrics together.
This can be achieved under heat and/or pressure. The outer plastic
film provides the structure with a degree of slipperiness so that
when a plurality of composite fabrics are stacked together they can
slide over each other. A plastic film may also be applied to the
exposed outer surface of the second fabric, if desired
[0078] Following bonding of the first fabric and second fabrics
together, they may be cut to the desired shape or wound up in a
roll for further processing.
[0079] An article may be formed from a number of layers of the
composite fabric structure (whether it be a two fabric layer
structure, a three layer fabric structure, a four layer fabric
structure, or a structure with additional layers). The number of
layers of the composite fabric structure that are present in such
an article depends upon a variety of factors, including the type of
application, desired weight, etc. For example, in a ballistic
resistant article such as a vest, the number of layers of the two
fabric composite structure may range from about 2 to about 60, more
preferably from about 8 to about 50, and most preferably from about
10 to about 40. Such layers may be combined without bonding the
several layers together in a conventional manner, such as by
stitching only along the edges. To form such an article, the
composite fabric can be cut into the desired shape.
[0080] Various configurations of the composite fabric can be made
based on the desired application, ballistic threat and desirable
properties such as flame retardancy, durability and water
repellency, among others. For example, one can use aramid materials
for both the second multi-directionally oriented fabric layer and
for both of the fiber layers of the first unidirectional fabric
layer, or high tenacity polyethylene fibers for both such fabric
layers. Alternatively, the high tenacity polyethylene fibers and
aramid fibers may be combined in any desired combination, such as
the first fabric being an aramid fabric and the second fabric being
a high tenacity polyethylene fabric, or the first fabric being a
high tenacity polyethylene fabric and the second fabric being an
aramid fabric. In another embodiment, a graphite first fabric may
be attached to a high tenacity polyethylene fiber woven second
fabric, or a PBO first fabric may be attached to an aramid woven
second fabric. These materials could be arranged in any desired
configuration. Other combinations of high tenacity fibers may be
employed.
[0081] As mentioned above, additional fabric layers may be present
in the composite fabric, and such layers may be unidirectionally
oriented fabrics or multi-directionally oriented fabrics.
[0082] To form one preferred composite fabric of this invention, a
preferred method includes supplying first and second fiber layers
each comprising non-woven unidirectionally oriented fibers in a
resin matrix, with the fibers of each layer comprising high
tenacity fibers. The fibers may be of the same or different
chemical types. A first surface of the second fiber layer is bonded
to a second surface of the first fiber layer, and the layers are
cross-plied such that the fibers in the second fiber layer are
arranged at an angle with respect to the direction of the
unidirectionally oriented fibers of the first layer.
[0083] A plastic film may be applied to both outer surfaces of the
first and second fiber layers (namely the first surface of the
first layer and the second surface of the second layer) or just the
outer surface of the second fiber layer. A second fabric comprising
multi-directionally oriented, high tenacity fibers is bonded to the
first fabric by means of the contacting plastic film. As a result,
a composite fabric is formed. The second fabric may include a resin
matrix as well (third resin matrix).
[0084] The composite fabrics of this invention can be used in a
wide variety of applications, such as ballistic products,
structural products, components in the automotive and aerospace
industries, etc. Preferred applications are soft or hard armor
products, such as bullet resistant body armor (vests and the like),
vehicle panels, etc.
[0085] The following non-limiting 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
Example 1
[0086] A composite was formed from layers of unidirectionally
oriented aramid fibers and an aramid woven fabric. The
unidirectionally oriented non-woven fabric was in the form of a
cross-ply structure of unidirectional aramid fiber layers
(cross-plied at 0.degree./90.degree.. Each unidirectional aramid
layer is coated with a styrene-isoprene-styrene elastomer
(Kraton.RTM. D1107) having a tensile modulus of 200 psi (1.4 MPa).
Liner films of low density polyethylene were attached to the outer
layers of the fiber layers. The weight of the coating was 16.+-.2%.
After the fiber layers are cross-plied, the polyethylene films are
laminated on both sides of the material under heat and pressure.
Each film weighs 7 g/m.sup.2 and has a thickness of 7 microns. The
total areal density of this material is 124 g/m.sup.2 and the
thickness is 0.004 inch (0.01 cm).
[0087] As the woven fabric there was employed a plain weave aramid
fabric having 29 by 29 ends/inch (11.4 by 11.4 ends/cm) weighing
4.5 oz/square yard (152.6 g/m.sup.2). No resin was applied to the
aramid woven fabric.
[0088] All of the samples measured 18.times.18 inches
(45.7.times.45.7 cm).
[0089] Two of the unidirectionally oriented fiber layers were
employed and sandwiched the woven aramid fabric. The layers were
molded under heat and pressure by preheating in a mold for 10
minutes at 240.degree. F. (116.degree. C.), applying molding
pressure of 500 psi (3.5 MPa) for 10 minutes, cooling in the press
for 10 minutes until a temperature of 160.degree. F. (71.degree.
C.) is achieved, then removing the sample from the mold and
allowing it to cool to room temperature. The low density
polyethylene films bond all of the layers together.
[0090] Samples were prepared for ballistic resistance testing using
12 layers of the composite fabric. The combined structure had a
theoretical areal density of 0.98 psf (4.81 kg/m.sup.2) and an
weight of 2.19 pounds (0.99 kg). The sample was tested for
ballistic resistance in accordance with MIL-STD-662E using a 17
grain fragment simulating projectile (FSP) conforming to
MIL-P-46593A. The results are shown in Table 1, below.
[0091] The composite was tested for ballistic fragment protection
per test method MIL-STD-662E and the fragments used conformed to
MIL-P-46593A These fragments were 17 grain, 22 caliber, FSP
hardened fragment simulators. One measure of the protective power
of a sample composite is expressed by citing the impacting velocity
at which 50% of the projectiles are stopped. This velocity,
expressed in units of feet per second, is designated the
V.sub.50.
Example 2 (Comparative)
[0092] Samples were formed from 39 layers of the unidirectionally
oriented aramid non-woven fabric used in Example 1. The theoretical
areal density was 0.99 psf (4.85 kg/m.sup.2) and the weight was
2.22 pound (1.01 kg). The ballistic results are also shown in Table
1, below.
Example 3 (Comparative)
[0093] Samples were formed from 32 layers of the aramid woven
fabric layer used in Example 1. The theoretical areal density was
1.00 psf (4.90 kg/m.sup.2) and the weight was 2.28 pound (1.04 kg).
The ballistic results are also shown in Table 1, below.
Example 4 (Comparative)
[0094] A sample was formed from the unidirectionally oriented
aramid non-woven fabric used in Example 1, together with the aramid
fabric used in Example 1. The aramid fabric was sandwiched between
layers of the non-woven fabric but was not bonded thereto. A total
of 12 layers of the combined 3 layered structure was used. The
theoretical areal density was 0.98 psf (4.81 kg/m.sup.2) and the
weight was 2.22 pound (1.01 kg). The ballistic results are also
shown in Table 1, below.
TABLE-US-00001 TABLE 1 17 grain FSP V50, fps Example Layers (mps) 1
12 1917 (584.6) 2* 39 1762 (537.4) 3* 32 1983 (604.8) 4* 12 1862
(567.9) *= comparative example
Example 5
[0095] Samples were prepared from 12 layers of the combined fabric
as in Example 1. The samples had a theoretical areal density of
0.98 psf (4.81 kg/m.sup.2) and an weight of 2.20 pounds (1.00 kg).
The sample was tested for ballistic resistance in accordance with
MIL-STD-662E using a 9 mm full metal jacket (FMJ) 124 grain bullet.
The V50 ratings and back face deformation were determined. The
ballistic results are shown in Table 2, below.
Example 6 (Comparative)
[0096] Samples were formed from 39 layers of the unidirectionally
oriented aramid non-woven fabric used in Example 5. The theoretical
areal density was 0.99 psf (4.85 kg/m.sup.2) and the weight was
2.22 pounds (1.00 kg). The ballistic results are also shown in
Table 2, below.
Example 7 (Comparative)
[0097] Samples were formed from 32 layers of the aramid woven
fabric layer used in Example 5. The theoretical areal density was
1.00 psf (4.90 kg/m.sup.2) and the weight was 2.29 pound (1.04 kg).
The ballistic results are also shown in Table 2, below.
Example 8 (Comparative)
[0098] A sample was formed from the unidirectionally oriented
aramid non-woven fabric used in Example 6, together with the aramid
fabric used in Example 7. The aramid fabric was sandwiched between
layers of the non-woven fabric but was not bonded thereto. A total
of 12 layers of the combined 3 layered structure was used. The
theoretical areal density was 0.98 psf (4.81 kg/m.sup.2) and the
weight was 2.22 pound (1.01kg). The ballistic results are also
shown in Table 2, below.
TABLE-US-00002 TABLE 2 9 mm FMJ Backface V50, fps deformation,
Example Layers (mps) mm 5 12 1715 34 (523.0) 6* 39 1640 36 (500.2)
7* 32 1669 45 (509.0) 8* 12 1635 36 (498.6) *= comparative
example
[0099] The results show that by laminating a cross-ply
unidirectional non-woven fabric of high tenacity fibers with a
woven fabric of high tenacity fibers, the ballistic performance in
terms of V50 is surprisingly increased, and the backface
deformation is reduced.
[0100] The present invention provides a composite fabric that is
relatively simple to manufacture and has excellent ballistic and
other desirable properties. The fabrics are bonded together which
yields improved ballistic performance.
[0101] 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 changes and modifications may suggest
themselves to one skilled in the art, all falling within the scope
of the invention as defined by the subjoined claims.
* * * * *