Title: Bi-directional and multi-axial fabrics and fabric composites
Abstract: Bi-directional and multi-axial fabrics, fabric composites, ballistically resistant assemblies thereof, and the methods by which they are made. The fabrics are comprised of sets of strong, substantially parallel, unidirectional yarns lying in parallel planes, one above the other, with the direction of the yarns in a given plane rotated at an angle to the direction of the yarns in adjacent planes; and one or more sets of yarns having lower strength and higher elongation interleaved with the strong yarns. The fabrics of the invention provide superior ballistic effectiveness compared to ordinary woven and knitted fabrics but retain the ease of manufacture on conventional looms and knitting machines.
Patent Number: 6,841,492 Issued on 01/11/2005 to Bhatnagar, et al.
| Inventors:
|
Bhatnagar; Ashok (Chester, VA);
Parrish; Elizabeth Stroud (Blackstone, VA)
|
| Assignee:
|
Honeywell International Inc. (Morristown, NJ)
|
| Appl. No.:
|
179715 |
| Filed:
|
June 25, 2002 |
| Current U.S. Class: |
442/135; 2/2.5; 28/140; 428/911; 442/134; 442/182; 442/206; 442/207; 442/209; 442/239; 442/246; 442/255; 442/261; 442/286; 442/290 |
| Intern'l Class: |
D03D 015/08 |
| Field of Search: |
28/140
428/911
442/134,135,181,239,246,255,261,286,290,210,301,304,182,206,207,209
2/2.5
|
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|
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| |
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|
Other References
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|
Primary Examiner: Morris; Terrel
Assistant Examiner: Piziali; Andrew T
Attorney, Agent or Firm: Szigeti; Virginia
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of provisional application Ser. No.
60/387,201 entitled "Bi-Directional Fabric and Fabric Composites" filed
Jun. 7, 2002, and is related to U.S. Pat. No. 6,642,159 filed Aug. 16,
2000, entitled "Impact Resistant Rigid Composite and Method of
Manufacture" and co-pending application Ser. No. 10/126,202 filed Apr. 19,
2002, entitled, "Ballistic Fabric Laminates".
Claims
What is claimed is:
1. A woven fabric comprising:
a) a first set of continuous filament unidirectional yarns lying in a first
plane;
b) a second set of continuous filament unidirectional yarns lying in a
second plane above said first plane and arranged transversely to said
first set of yarns;
c) a third set of yarns arranged transversely to said first set of yarns
and interlaced with said first set of yarns, each yarn of the third set
lying above some and below the remaining yarns of said first set;
d) a fourth set of yarns arranged transversely to said second set and said
third set of yarns and interlaced with said second and thirds sets of
yarns, each yarn of the fourth set lying above some and below the
remaining yarns of said second and third sets of yarns;
wherein each of said first and second sets of yarns have tenacity's equal
to or greater than about 15 g/d, initial tensile moduli equal to or
greater than about 400 g/d and energies-to-break equal to or greater than
about 22 J/g as measured by ASTM D2256; and
wherein each of said first and second sets of yarns, in proportion to the
yarns comprising each of said third and fourth sets of yarns have at least
twice the breaking strength, and half the elongation to break.
2. The woven fabric of claim 1, wherein the yarns of said first and second
sets are each selected independently from the group consisting of
continuous filament highly oriented high molecular weight polyolefins,
aramids, polybenzazoles and blends thereof.
3. The woven fabric of claim 1, wherein the yarns of said first and second
sets of yarns are each selected independently from the group consisting of
continuous filament highly oriented high molecular weight polyethylene,
poly(p-phenylene terephthalamide, poly(m-phenylene isophthalamide),
poly(benzobisoxazole, poly(benzobisthiazole), poly(benzobisimidazole) and
blends thereof.
4. The woven fabric of claim 1, wherein the yarns of said third and fourth
sets are each selected independently from the group consisting of
polyamide, polyester, polyvinyl alcohol, polyolefin, polyacrylonitrile,
polyurethane, cellulose acetate, cotton, wool, and copolymers and blends
thereof.
5. The woven fabric of claim 1, wherein the yarns of at least one of said
third and fourth sets of yarns is comprised of an elastomeric fiber.
6. The woven fabric of claim 1, wherein the yarns of at least one of said
third and fourth sets of yarns is comprised of staple fibers.
7. The woven fabric of claim 1, wherein the yarns of each of said first and
second sets of yarns, in proportion to the yarns comprising each of said
third and fourth sets of yarns, have at least three times the breaking
strength, and one-third the elongation to break.
8. The woven fabric of claim 1, wherein the yarns of each of said first and
second sets of yarns, in proportion to the yarns comprising each of said
third and fourth sets of yarns, have at least three times the breaking
strength, and one-tenth the elongation to break.
9. The woven fabric of claim 1, wherein the spacing of each of said first,
second, third, and fourth sets of yarns is independently from about 5
ends/in (1.97 ends/cm) to about 50 ends/in (19.7 ends/cm).
10. The woven fabric of claim 1, wherein the spacing of each of said first
second, third, and fourth sets of yarns is independently from about 8
ends/in (3.15 ends/cm) to about 20 ends/in (7.87 ends/cm).
11. The woven fabric of claim 1, wherein said woven fabric has been
calendered.
12. A fabric composite comprising a woven fabric having the characteristics
as recited in claim 1 embedded in a matrix selected from the group
consisting of an elastomeric matrix having an initial tensile modulus less
than about 6,000 psi (41.3 MPa) and a rigid matrix having an initial
tensile modulus at least about 300,000 psi (2068 MPa) as measured by ASTM
D638.
13. The fabric composite of claim 12, wherein said matrix is a rigid matrix
having an initial tensile modulus of at least about 300,000 psi (2068 MPa)
as measured by ASTM D638, and wherein coated on at least a portion of one
surface of said fabric composite is an elastomeric material having an
initial tensile modulus less than about 6,000 psi (41.3 MPa) as measured
by ASTM D638.
14. The fabric composite of claim 12, wherein the fabric is calendered.
15. The fabric composite of claim 14, wherein a plastic film bonded to at
least a portion of one of the surfaces of said fabric composite.
16. The fabric composite of claim 14, wherein an elastomer is coated on at
least a portion of at least one surface of said fabric, said elastomer
having an initial tensile modulus equal to or less than about 6,000 psi
(41.3 MPa), as measured by ASTM D638; and a plastic film is bonded to at
least a portion of said elastomer coated surface.
17. A fabric composite comprising a calendered woven fabric having the
characteristics as recited in claim 11 with a plastic film bonded to at
least a portion of at least one of said fabric surfaces.
18. A ballistically resistant article comprised of a plurality of fabric
sheets plied together in a stacked array, wherein at least a majority of
said fabric sheets are a woven fabric having the characteristics as
recited in claim 1.
19. The ballistically resistant article of claim 18, wherein the fabric has
been calendered.
20. The ballistically resistant article of claim 19, wherein at least a
portion of said fabric sheets are fabric composite sheets embedded in a
matrix selected from the group consisting of an elastomeric matrix having
an initial tensile modulus less than about 6,000 psi (41.3 MPa) and a
rigid matrix having an initial tensile modulus at least about 300,000 psi
(2068 MPa), as measured by ASTM D638.
21. The ballistically resistant article of claim 20, wherein the matrix is
a rigid matrix having an initial tensile modulus at least about 300,000
psi (2068 MPa), as measured by ASTM D638, and coated on at least a portion
of one surface of said fabric composite sheets is an elastomeric material
having an initial tensile modulus less than about 6,000 psi (41.3 MPa), as
measured by ASTM D638.
22. The ballistically resistant article of claim 16 or 21 additionally
comprising a hard face member selected from the group consisting of a
metal, a ceramic, a glass, a metal filled composite, a ceramic filled
composite or a glass filled composite.
23. A method of producing a ballistically resistant article comprising the
steps of: weaving a fabric with the characteristics as recited in claim 1;
and plying sheets of said fabric in a stacked array.
24. A method of producing a ballistically resistant article comprising the
steps of: weaving a fabric with the characteristics as recited in claim
11; and plying sheets of said fabric in a stacked array.
25. The method recited in claim 23 or 24 additionally comprising the step
of joining said fabric sheets together by joining means.
26. A method of producing a ballistically resistant article comprising the
steps of:
a) weaving a fabric with the characteristics as recited in claim 11;
b) embedding the fabric in a matrix selected from the group consisting of
an elastomer having an initial tensile modulus less than about 6,000 psi
(41.3 MPa) and a rigid resin having an initial tensile modulus at least
300,000 psi (2068 MPa), as measured by ASTM D638, to produce a fabric
composite;
d) plying sheets of said fabric composite in a stacked array; and
e) bonding and curing said sheets of said fabric composite together to form
a unitary article.
27. A method as recited in claim 26 additionally including the step of
bonding a plastic sheet to at least a portion of one surface of said
fabric composite prior to plying sheets of said fabric composite in
stacked array.
28. A method of producing a ballistically resistant article comprising the
steps of:
a) weaving a fabric with the characteristics as recited in claim 11;
b) bonding a plastic film to at least a portion of at least one of said
fabric surfaces to produce a fabric composite;
c) plying sheets of said fabric composite in a stacked array; and
d) bonding said sheets of said fabric composite together to form a unitary
article.
29. A method of producing a ballistically resistant article comprising the
steps of:
a) weaving a fabric with the characteristics as recited in claim 11;
b) embedding the fabric in a matrix consisting essentially of a rigid resin
having an initial tensile modulus at least about 300,000 psi (2068 MPa),
as measured by ASTM D638, to produce a fabric composite;
b) applying to the surface of said fabric composite an elastomeric material
having a tensile modulus less than about 6000 psi (41.3 MPa), as measured
by ASTM D638, to produce an elastomeric coated fabric composite;
c) plying sheets of said elastomeric coated fabric composite in a stacked
array; and
d) bonding and curing said sheets of said elastomeric coated fabric
composite together to form a unitary article.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to bi-directional and multi-axial fabrics, fabric
composites, ballistically resistant assemblies thereof, and the methods by
which they are made.
2. Description of the Related Art
Ballistically resistant fabric-based composites have typically been formed
from layers of fabrics that are plied together. The fibers in a fabric can
be woven, knitted and/or non-woven. Where the individual fabric plies
include non-woven and unidirectionally oriented fibers, successive plies
are usually rotated relative to one another, for example at angles of
0.degree./90.degree. or 0.degree./45.degree./90.degree./45.degree.. The
individual fabric plies are generally either uncoated or else embedded in
a polymeric matrix material which fills the void spaces between the
fibers. If no matrix is present, the fabric or fiber sheet is inherently
flexible. A contrasting type of construction is a composite consisting of
fibers and a single major matrix material. To construct rigid composites
of this type, individual plies are bonded together using heat and pressure
to adhere the matrix in each ply, forming a bond between them, and
consolidating the whole into a unitary article.
These earlier constructions have several disadvantages. Woven or knitted
fabrics generally have poorer ballistic resistance than cross-plied
unidirectional fiber composites. On the other hand, woven or knitted
fabrics can be produced at lower cost and greater ease of manufacture with
more commonly available equipment than can cross-plied unidirectional
fiber composites.
A need therefore exists for a fabric construction that retains the
advantages of lower cost and greater ease of manufacture, but that has
ballistic resistance superior to conventional fabrics. Ideally, the fabric
construction would be highly flexible and capable of being bonded to
itself or to hard facings to form rigid panels.
U.S. Pat. No. 4,737,401 discloses ballistic resistant fine weave fabric
articles. U.S. Pat. Nos. 5,788,907 and 5,958,804 disclose ballistically
resistant calendered fabrics. U.S. Pat. No. 4,623,574 discloses simple
composites comprising high strength fibers embedded in an elastomeric
matrix. U.S. Pat. No. 5,677,029 discloses a flexible penetration resistant
composite comprising at least one fibrous layer comprised of a network of
strong fibers, and at least one continuous polymeric layer coextensive
with, and at least partially bound to a surface of one of the fibrous
layers. Aramid fabrics rubber coated on one or both sides are commercially
produced by Verseidag Industrietextilien Gmbh. under the product name
UltraX. Rigid panels formed by bonding the rubber-coated fabrics together
under heat and pressure are also available.
In another context, U.S. Pat. No. 2,893,442 discloses a bi-directional
woven fabric having transverse sets of straight and parallel high
strength, high modulus yarns interleaved with thin binder yarns. A
bi-directional knitted fabric having transverse sets of straight and
parallel high strength, high modulus yarns interleaved with thin binder
yarns is disclosed in a publication by S. Raz, "Eine Auswahl optimaler
Geotextilien," Tettilinfomationen Kettenwir-Praxis, (2), 35-39 (1990). A
multi-axial warp knit fabric is disclosed in "Wellington Sears Handbook of
Industrial Textiles", S. Adanur, Ed., Technomic Publishing Co., Inc.,
Lancaster, Pa., 246-247 (1995).
Each of the constructions cited above represented progress toward the goals
to which they were directed. However, none described the specific
constructions of the fabrics, fabric composites and assemblies of this
invention, and none satisfied all of the needs met by this invention.
SUMMARY OF THE INVENTION
This invention relates to novel fabrics and fabric composites, assemblies
thereof having superior ballistic resistance to penetration by ballistic
projectiles, and the method by which they are made. The bi-directional and
multi-axial articles of the invention provide superior ballistic
effectiveness compared to ordinary woven and knitted fabrics but retain
the ease of manufacture on conventional looms and knitting machines.
In a first embodiment, an article of the invention comprises a
bi-directional woven fabric comprised of a first set of continuous
filament unidirectional yarns lying in a first plane; a second set of
continuous filament unidirectional yarns lying in a second plane above
said first plane and arranged transversely to said first set of yarns; a
third set of yarns arranged transversely to said first set of yarns and
interlaced with said first set of yarns, each yarn of the third set lying
above some and below the remaining yarns of said first set; a fourth set
of yarns arranged transversely to said second set and said third set of
yarns and interlaced with said second and thirds sets of yarns, each yarn
of the fourth set lying above some and below the remaining yarns of said
second and third sets of yarns; wherein each of the yarns comprising said
first and second sets of yarns have tenacity's equal to or greater than
about 15 g/d, initial tensile moduli equal to or greater than about 400
g/d and energies-to-break equal to or greater than about 22 J/g as
measured by ASTM D2256; and wherein each of the yarns comprising said
first and second sets of yarns, in proportion to the yarns comprising each
of said third and fourth sets of yarns, have at least about twice the
breaking strength and at most about one-half the percent elongation to
break.
In a second embodiment, an article of the invention comprises a
bi-directional knitted fabric comprised of a first set of continuous
filament unidirectional yarns lying in a first plane; a second set of
continuous filament unidirectional yarns lying in a second plane above
said first plane and arranged transversely to said first set of yarns; a
third set of interlacing yarns forming interlocking loops interlaced with
said first set and said second set of yarns, each yarn of the third set
lying above some and below the remaining yarns of said first set and said
second set of yarns; wherein each of the yarns comprising said first and
second sets of yarns have tenacity's equal to or greater than about 15
g/d, initial tensile moduli equal to or greater than about 400 g/d and
energies-to-break equal to or greater than about 22 J/g as measured by
ASTM D2256; and wherein each of the yarns comprising said first and second
sets of yarns, in proportion to the yarns comprising said third set of
yarns has at least about twice the breaking strength and, at most, about
one-half the percent elongation to break.
In a third embodiment, an article of the invention is a multi-axial knitted
fabric comprised of: a set of continuous filament unidirectional yarns in
a bottom plane; a plurality of intermediate planes above said bottom plane
each defined by a set of continuous filament unidirectional yarns; a set
of continuous filament unidirectional yarns in a top plane; a set of
interlacing yarns forming interlocking loops, said loops binding the sets
of unidirectional yarns in all planes; wherein the set of unidirectional
yarns in each said plane is rotated at an angle relative to the set of
unidirectional yarns in adjacent planes; wherein the yarns of each said
set of unidirectional yarns have tenacity's equal to or greater than about
15 g/d, initial tensile moduli equal to or greater than about 400 g/d and
energies-to-break equal to or greater than about 22 J/g, all as measured
by ASTM D2256; and wherein the yarns of each said set of unidirectional
yarns, in proportion to said interlacing yarns have at least about twice
the breaking strength and, at most, about one-half the percent elongation
to break.
In another embodiment, a fabric composite of the invention comprises a
fabric embedded in a matrix. The fabric is selected from the group
consisting of the woven and the knitted fabrics described, respectively,
in the first, second and third embodiments above. The matrix is selected
from the group consisting of an elastomeric matrix having an initial
tensile modulus less than about 6,000 psi (41.3 MPa), and a rigid matrix
having an initial tensile modulus at least about 300,000 psi (2068 MPa)),
as measured by ASTM D638.
In another embodiment, a fabric composite of the invention comprises a
fabric selected from the group consisting of the woven and the knitted
fabrics described, respectively, in the first, second and third
embodiments above, embedded in a rigid matrix having an initial tensile
modulus at least about 300,000 psi (2068 MPa)) and coated on at least a
portion of one surface with an elastomeric material matrix having an
initial tensile modulus less than about 6,000 psi (41.3 MPa), both as
measured by ASTM D638.
In yet another embodiment, a fabric composite of the invention comprises: a
fabric, as described above, embedded in a matrix and a plastic film bonded
to at least a portion of one surface of said embedded fabric.
In another embodiment, a fabric composite of the invention comprises a
fabric, as described above, with a plastic film bonded to at least a
portion of at least one surface of said fabric.
In other embodiments, ballistically resistant articles of the invention are
comprised of a plurality of sheets plied together, wherein at least a
majority of said sheets are selected from the group consisting of the
inventive fabrics and the inventive fabric composites described above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a woven fabric of the invention.
FIG. 2 is a schematic representation of a knitted fabric of the invention.
FIG. 3 is a schematic representation of a multi-axial knitted fabric of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to novel fabrics and fabric composites, assemblies
thereof having superior ballistic resistance to penetration by ballistic
projectiles, and to the methods by which they are made.
In one embodiment, an article of the invention comprises a bi-directional
woven fabric comprised of a first set of continuous filament
unidirectional yarns lying in a first plane; a second set of continuous
filament unidirectional yarns lying in a second plane above said first
plane and arranged transversely to said first set of yarns; a third set of
yarns arranged transversely to said first set of yarns and interlaced with
said first set of yarns, each yarn of the third set lying above some and
below the remaining yarns of said first set; a fourth set of yarns
arranged transversely to said second set and said third set of yarns and
interlaced with said second and third sets of yarns, each yarn of the
fourth set lying above some and below the remaining yarns of said second
and third sets of yarns; wherein each of the yarns comprising said first
and second sets of yarns have tenacity's equal to or greater than about 15
g/d, initial tensile moduli equal to or greater than about 400 g/d and
energies-to-break equal to or greater than about 22 J/g as measured by
ASTM D2256; and wherein each of the yarns comprising said first and second
sets of yarns, in proportion to the yarns comprising each of said third
and fourth sets of yarns, have at least about twice the breaking strength
and at most about one-half the percent elongation to break.
FIG. 1 is a schematic representation of a bi-directional woven fabric 10 of
the invention. A first set of continuous filament unidirectional yarns 11
lies in a first plane. A second set of continuous filament unidirectional
yarns 12 lies in a second plane above the first plane and arranged
transversely to the first set of yarns 11. A third set of yarns 13 is
arranged transversely to the first set of yarns 11 and is interlaced with
the first set of yarns 11. A fourth set of yarns 14 is arranged
transversely to the second set and the third set of yarns (12 and 13,
respectively) and is interlaced with the second and thirds sets of yarns,
12 and 13, respectively.
In a second embodiment, an article of the invention comprises a
bi-directional knitted fabric comprised of a first set of continuous
filament unidirectional yarns lying in a first plane; a second set of
continuous filament unidirectional yarns lying in a second plane above
said first plane and arranged transversely to said first set of yarns; a
third set of interlacing yarns forming interlocking loops interlaced with
said first and said second set of yarns, each yarn of the third set lying
above some and below the remaining yarns of said first set and said second
set of yarns; wherein each of the yarns comprising said first and second
sets of yarns have tenacity's equal to or greater than about 15 g/d,
initial tensile moduli equal to or greater than about 400 g/d and
energies-to-break equal to or greater than about 22 J/g as measured by
ASTM D2256; and wherein each of the yarns comprising said first and second
sets of yarns, in proportion to the yarns comprising said third set of
yarns have at least about twice the breaking strength and at most about
one-half the percent elongation to break.
FIG. 2 is a schematic representation of a bi-directional knitted fabric 20
of the invention. A first set of continuous filament unidirectional yarns
21 lies in a first plane. A second set of continuous filament
unidirectional yarns 22 lies in a second plane above the first plane
arranged transversely to the first set of yarns 21. A third set of yarns
23 is interlaced with the first and second sets of yarns, 21 and 22
respectively, in interlocking loops. FIG. 2 shows a tricot knit but other
knit configurations that stabilize the first and second sets of yarn, 21
and 22, are suitable such as interlocking weft chain stitches.
In a third embodiment, an article of the invention is a multi-axial knitted
fabric comprised of: a set of continuous filament unidirectional yarns in
a bottom plane; a plurality of intermediate planes above said bottom plane
each defined by a set of continuous filament unidirectional yarns; a set
of continuous filament unidirectional yarns in a top plane; a set of
interlacing yarns forming interlocking loops, said loops binding the sets
of unidirectional yarns in all planes; wherein the set of unidirectional
yarns in each said plane is rotated at an angle relative to the set of
unidirectional yarns in adjacent planes; wherein the yarns of each said
set of unidirectional yarns have tenacity's equal to or greater than about
15 g/d, initial tensile moduli equal to or greater than about 400 g/d and
energies-to-break equal to or greater than about 22 J/g, all as measured
by ASTM D2256; and wherein the yarns of each said set of unidirectional
yarns, in proportion to said interlacing yarns have at least about twice
the breaking strength and, at most, about one-half the percent elongation
to break.
FIG. 3 is a schematic representation of a multi-axial knitted fabric 30 of
the invention. A first set of continuous filament unidirectional yarns 31
defines a bottom plane of the fabric. In the embodiment illustrated, two
intermediate planes above the bottom plane are defined by sets of
continuous filament unidirectional yarns 32 and 33. A continuous filament
unidirectional yarn set 34 defines a top plane of the fabric. A set of
interlacing yarns 35 form interlocking loops that enclose the
unidirectional yarns in all planes.
The directions of the unidirectional yarns in each plane of the fabric are
rotated at an angle to the unidirectional yarns in adjacent planes. In the
specific embodiment illustrated, the yarn set 32 in the first intermediate
plane is rotated at an angle of 90.degree. to the yarns 31 in the bottom
plane. The yarns 33 in the second intermediate plane are rotated at an
angle of 45.degree. to the yarns 32 in the first intermediate plane. The
yarns 34 in the top plane are rotated at an angle of 90.degree. to the
yarns 33 in the second intermediate plane.
It will be evident that the multi-axial fabric of the invention may be
comprised of greater numbers of intermediate planes and/or different
angles of rotation between yarn planes than is illustrated in FIG. 3.
Preferably, the number of yarn planes and the angles between the
unidirectional yarns are chosen to provide symmetrical properties to the
fabric.
For the purposes of the present invention, a fiber is an elongate body the
length dimension of which is much greater than the transverse dimensions
of width and thickness. Accordingly, the term fiber includes filament,
ribbon, strip, and the like having regular or irregular cross-section. A
yarn is a continuous strand comprised of many fibers or filaments. The
fibers comprising the yarn may be continuous through the length of the
yarn or the fibers may be staple fibers of lengths much shorter than the
yarn.
The continuous filament unidirectional yarns are the primary structural
components of the bi-directional and multi-axial fabrics of the invention.
The interlacing yarns provide integrity to the fabrics without deforming
the unidirectional sets of yarns from an essentially planar configuration.
The continuous filament unidirectional yarns may be comprised of the same
or different fiber materials, fiber forms, tensile properties and deniers.
Preferably, the continuous filament unidirectional sets of yarns are each
selected independently from the group consisting of continuous filament
highly oriented, high molecular weight polyolefins, aramids,
polybenzazoles and blends thereof. Most preferably, the continuous
filament unidirectional sets of yarns are each selected independently from
the group consisting of continuous filament highly oriented, high
molecular weight polyethylene, poly(p-phenylene terephthalamide,
poly(m-phenylene isophthalamide), poly(benzobisoxazole,
poly(benzobisthiazole), poly(benzobisimidazole) and blends thereof.
U.S. Pat. No. 4,457,985 generally discusses high molecular weight
polyethylene and polypropylene fibers. In the case of polyethylene,
suitable fibers are those of weight average molecular weight of at least
150,000, preferably at least one million and more preferably between two
million and five million. Such high molecular weight polyethylene fibers
may be grown in solution as described in U.S. Pat. No. 4,137,394 or U.S.
Pat. No. 4,356,138, or may be filament spun from a solution to form a gel
structure, as described in U.S. Pat. No. 4,413,110, or may be produced by
a rolling and drawing process as described in 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 5 modifying units per 100 main chain carbon
atoms, and that may also contain admixed therewith not more than about 50
wt % of one or more polymeric additives such as alkene-I-polymers, in
particular low density polyethylene, polypropylene or polybutylene,
copolymers containing mono-olefins as primary monomers, oxidized
polyolefins, graft polyolefin copolymers and polyoxymethylenes, or low
molecular weight additives such as anti-oxidants, lubricants, ultra-violet
screening agents, colorants and the like.
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 fibers should be at least 15 g/denier,
preferably at least 20 g/denier, more preferably at least 25 g/denier and
most preferably at least 30 g/denier. Similarly, the initial tensile
modulus of the fibers, as measured by an Instron tensile testing machine,
is at least 300 g/denier, preferably at least 500 g/denier and more
preferably at least 1,000 g/denier and most preferably at least 1,200
g/denier.
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, polyethylene
of weight average molecular weights from about 150,000 to two million
generally have melting points in the bulk of about 138.degree. C. The
highly oriented polyethylene filaments made of these materials have
melting points of from about 7 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.
In the case of aramid fibers, suitable fibers formed from aromatic
polyamides are described in U.S. Pat. No. 3,671,542. 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 20
g/denier, a modulus of at least about 900 g/denier and an energy-to-break
of at least about 30 J/g. For example, poly(p-phenylene terephalamide)
filaments produced commercially by DuPont Corporation under the
KEVLAR.RTM. trademark are particularly useful in forming ballistic
resistant composites. KEVLAR 29 has 500 g/denier and 22 g/denier and
KEVLAR 49 has 1000 g/denier and 22 g/denier as values of initial tensile
modulus and tenacity, respectively. Also useful in the practice of this
invention is poly(m-phenylene isophthalamide) fibers produced commercially
by DuPont under the NOMEX.RTM. trademark.
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. Preferably, the polybenzazole fibers are selected
from the group consisting of poly(benzobisoxazole, poly(benzobisthiazole),
and poly(benzobisimidazole). Most preferably, the polybenzazole fibers are
ZYLON.RTM. poly(p-phenylene-2,6-benzobisoxazole) fibers from Toyobo Co.
The deniers of the continuous filament unidirectional sets of yarns are
independently selected in the range of from about 100 to about 3000, more
preferably in the range of from about 750 to about 1500.
The spacing of the yarns within each set of unidirectional yarns may be the
same or different from that of yarns within other unidirectional yarn
sets. By "spacing" is meant the distance between parallel yarn ends within
the set. The spacing between yarns will be greater for heavier denier
yarns and smaller for lower denier yarns. Preferably the yarn spacing for
each of the unidirectional sets of yarns is independently selected in the
range of from about 5 ends/in (2 ends/cm) to about 50 ends/in (20
ends/cm), more preferably in the range of from about 8 ends/in (3.2
ends/cm) to about 20 ends/in (7.9 ends/cm). A yarn spacing of about 8
ends/in (3.2 ends/cm) to about 12 ends/in (4.7 ends/cm) is preferred for
1200 denier SPECTRA.RTM. highly oriented high molecular weight
polyethylene yarns from Honeywell International Inc.
In the bi-directional woven fabrics of the invention, the spacing of the
yarns in the third set is generally an integral multiple of the yarn
spacing within the set having yarns parallel thereto, i.e., the first set
in FIG. 1. The spacing of the yarns in the fourth set is also generally an
integral multiple of the yarn spacing within the set having yarns parallel
thereto, i.e., the second set of yarns in FIG. 1. For example, if the
space between yarn ends in the first set is 0.1 inches, the space between
yarn ends in the third set may be 0.1, 0.2, 0.3, 0.4 . . . inches.
Preferably, the yarn spacing of the third and fourth sets is the same as
that of the yarn set to which they are parallel.
The following comments are directed to the sets of interlacing yarns in a
fabric of the invention, i.e., the third and fourth yarn sets in a woven
bi-directional fabric of the invention, the third yarn set in a knitted
bi-directional fabric of the invention, and the interlacing and
loop-forming yarn set in a knitted multi-axial fabric of the invention.
The sets of interlacing yarns, where more than one, may be formed of
different fiber materials and fiber forms. Preferably, the interlacing
sets of yarns are each selected independently from the group consisting of
polyamides, polyesters, polyvinyl alcohol, polyolefins, polyacrylonitrile,
polyurethane, cellulose acetate, cotton, wool, and copolymers and blends
thereof. Most preferably, the interlacing sets of yarns are selected from
the group consisting of nylon 6, nylon 66, polyethylene terephthalate
(PET), polyethylene naphthalate, (PEN), polybutylene terephthalate (PBT),
polytrimethylene terephthalate (PTT), polypropylene, polyvinyl alcohol and
polyurethane. The interlacing sets of yarns may be comprised of
elastomeric fibers or staple fibers.
The yarns in the interlacing yarn sets are selected so as not to possess
more than about one-half the breaking strength (load at break, lbs (Kg))
and have no less than about twice the percent elongation to break of each
of the unidirectional yarns. Preferably, the breaking strengths of each of
the interlacing sets of yarns do not exceed about one-third of the
breaking strength and have no less than about six times the percent
elongation at break of each of the unidirectional sets of yarns. Most
preferably, the breaking strengths of each of the interlacing sets of
yarns do not exceed about one-third of the breaking strength and have no
less than ten times the percent elongation of each of the unidirectional
sets of yarns. These choices insure that the unidirectional yarns will
remain essentially unrestrained during a ballistic impact and will be best
able to participate in absorbing the energy of a projectile.
Yarns comprised of staple fibers generally have lower tenacity's than
continuous filament yarns and may be used at higher deniers than
continuous filament yarns in the interlacing sets of yarns.
The fibers in all sets of yarns may be twisted or entangled as disclosed in
U.S. Pat. No. 5,773,370. Preferably, the unidirectional sets of yarns in
each embodiment have minimum twist, from about zero turns/in to about 2
turns/in (0.78 turns/cm). Ballistics are typically better with a zero
twist structural yarn. Greater twist levels are preferred for the yarns in
interlacing yarn sets, from about 2 turns/in (0.28 turns/cm) to about 10
turns/in (3.9 turns/cm).
Preferably, the woven and knitted fabrics of the invention are calendered.
Preferably, the calendering is conducted by passing the fabric through
opposed rolls rotating at the same speed and applying a pressure of about
800 lbs/inch (140 kN/m) to about 1200 lbs/inch (210 kN/m) of fabric width
at a temperature ranging from about 100.degree. C. to about 130.degree. C.
Preferably the calendering pressure is about 900 lbs/inch (158 kN/m) to
about 1000 lbs/inch (175 kN/m) of fabric width, and the temperature ranges
from about 115.degree. C. to about 125.degree. C.
In another embodiment, a fabric composite of the invention comprises a
fabric, selected from the group consisting of the inventive woven and
knitted fabrics described above, embedded in a matrix selected from the
group consisting of an elastomeric material having an initial tensile
modulus less than about 6,000 psi (41.3 MPa), and a rigid resin having an
initial tensile modulus at least about 300,000 psi (2068 MPa), as measured
by ASTM D638.
The matrix preferably comprises about 5 to about 30, more preferably about
10 to about 20, percent by weight of the fabric composite. The matrix
material is preferably applied by applying an uncured liquid matrix or a
solution of the matrix material onto the fabric by means of a wetted roll
and doctoring the liquid into the fabric to accomplish complete
impregnation. Alternatively, dipping or immersion of the fabric into a
liquid bath may be employed.
A wide variety of elastomeric materials and formulations having
appropriately low modulus may be utilized as the matrix. For example, any
of the following materials may be employed: polybutadiene polyisoprene,
natural rubber, ethylene-propylene copolymers, ethylene-propylene-diene
terpolymers, polysulfide polymers, polyurethane elastomers,
cholorosulfinated 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,
copolymers of ethylene.
Preferably, the elastomeric material does not bond too well or too loosely
to the fabric material. Preferred for polyethylene 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 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. Many of these polymers are
produced commercially by Kraton Polymers, Inc.
The low modulus elastomer may be compounded with fillers such as carbon
black, silica, etc., and may be extended with oils and vulcanized by
sulfur, peroxide, metal oxide or radiation cure systems using methods well
known to rubber technologists. Blends of different elastomeric materials
may be used together or one or more elastomers may be blended with one or
more thermoplastics.
A rigid matrix resin useful in a fabric composite of the invention
preferably possesses an initial tensile modulus at least 300,000 psi (2068
MPa) as measured by ASTM D638. Preferred matrix resins include at least
one thermoset vinyl ester, diallyl phthalate, and optionally a catalyst
for curing the vinyl ester resin.
Preferably, the vinyl ester is one produced by the esterification of a
polyfunctional epoxy resin with an unsaturated monocarboxylic acid,
usually methacrylic or acrylic acid. Illustrative vinyl esters include
diglycidyl adipate, diglycidyl isophthalate, di-(2,3-epoxybutyl)adipate,
di-(2,3-epoxybutyl)oxalate, di-(2,3-epoxyhexyl)succinate,
di-(3,4-epoxybutyl)maleate, di-(2,3-epoxyoctyl)pimelate,
di-(2,3-epoxybutyl)phthalate, di-(2,3-epoxyoctyl)tetrahydrophthalate,
di-(4,5-epoxy-dodecyl)maleate, di-(2,3-epoxybutyl)terephthalate,
di-(2,3-epoxypentyl)thiodipropronate,
di-(5,6-epoxy-tetradecyl)diphenyldicarboxylate,
di-(3,4-epoxyheptyl)sulphonyldibutyrate,
tri-(2,3-epoxybutyl)-1,2,4-butanetricarboxylate,
di-(5,6-epoxypentadecyl)maleate, di-(2,3-epoxybutyl)azelate,
di(3,4-epoxypentadecyl)citrate,
di-(4,5-epoxyoctyl)cyclohexane-1,3-dicarboxylate,
di-(4,5-epoxyoctadecyl)malonate, bisphenol-A-fumaric acid polyester and
similar materials. Particularly preferred are the epoxy vinyl esters
available from Dow Chemical Company under the DERAKANE.RTM. trademark.
In another embodiment, a fabric composite of the invention comprises a
fabric selected from the group consisting of the woven and the knitted
fabrics described, respectively, in the first, second and third
embodiments described above, embedded in a rigid matrix having an initial
tensile modulus at least about 300,000 psi (2068 MPa)) and coated on at
least a portion of one surface with an elastomeric material having an
initial tensile modulus less than about 6,000 psi (41.3 MPa), both as
measured by ASTM D638.
In another embodiment, a fabric composite of the invention comprises:
