Note: Descriptions are shown in the official language in which they were submitted.
~ 31 2487
~ALLISTIC-RESISTANT COMPOSITE ARTICLE
... . _ _ _
DESCRIPTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ballistic resistant
composite articles. More particularly, this invention
relates to such articles having improved ballistic
protection.
2. Prior Art
Ballistic articles such as bulletproo~ vests,
helmets, structural members of helicopters and other
military equipment, vehicle panels, briefcases, rain-
coats and umbrellas containing high strength fibers are
known. Fibers conventionally used include aramid fibers
such as poly(phenylenediamine terephthalamide), graphite
fibers, nylon fibers, ceramic fibers, glass fibers and
the like. For many applications, such as vests or parts
of vests, the fibers are used in a woven or knitted
fabric. For many of the o~her applications, the fibers
are encapsulated or embedded in a composite material.
In "The Application of High Modulus Fibers to
Ballistic Protection" R. C. Laible et al., J.
Macromol. Sci.-Chem. A7(1), pp. 295-322 1973, it is
indicated on p. 298 that a fourth requirement is that
the textile material have a high degree of heat resis-
tance; for example, a polyamide material with a melting
point of 255C appears to possess better impact proper-
ties ballistically than does a polyolefin fiber with
equivalent tensile properties but a lower melting
point. In an NTIS publication, AD-A018 gsa "New
Materials in Construction for Improved Helmets", A. L.
Alesi et al., a multilayer highly oriented polypropylene
film material (without matrix), referred to as "XP", was
evaluated against an aramid fiber (with a phenolic/poly-
vinyl butyral resin matrix). The aramid system was
judged to have the most promising combination of
superior performance and a minimum of problems for
combat helmet development.
'~
.,
.~
1312487
USP 4,403,012 and USP 4,457,985 disclose ballistic-
resistant composite articles comprised of networks of
high molecular wei~ht polyethylene or polypropylene
fibers, and matrices composed of olefin polymers and
copolymers, unsaturated polyester resins, epoxy resins,
and other resins curable below the melting point of the
fiber.
A.L. Lastnik, et al.; "The Effect of Resin Con-
centration and Laminating Pressures on KEVLAR~ Fabric
Bonded with Modified Phenolic Resin", Technical Report
NATICK/TR-84/030, ~une 8, 1984, disclose that an inter-
stitial resin, which encapsulates and bonds the fibers
of a fabric, reduces the ballistic resistance of the
resultant composite article.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a
ballistic-resistant rigid or flexible composites
comprised of one or more layers, at least one of said
layers comprising a network of high strength filaments
having a tenacity of at least about 7 grams~denier, a
tensile modulus of at least about 160 grams/denier and
an energy-to-break of at least about 8 joules~gram in a
i matrix material, the ratio of the thickness of said
layer to an Hequivalent diameter" of said filaments is
equal to or less than about 12.8. As used herein the
"equivalent diameter" of a filament is the diameter of a
circle having a cross-sectional area equal to the
average cross-sectional area of the filaments in the
layer. As used herein, a filament is an elongated body,
the length dimension of which is much greater than the
transverse dimensions o~ width and thickness.
Accordingly, the term filament includes simple filament,
ribbon, strips and the like having regular or irregular
' cross-section.
It has also been discovered that the equivalent
diameter of the filament, and the thickness of the layer
containing network of the filament has an effect on the
-2-
., ~
. .
,
1312487
degree of ballistic protection provided, particularly
against small caliber ballistic projectiles, i.e. 50
caliber or less, preferably, projectiles o~ 30 caliber
or less and more particularly, projectiles Oe 15 caliber
or less. In general, the smaller the equivalent
diameter of the filaments and the thinner the layer, the
greater the degree of protection provided, when compared
to the protection provided by a composite of comparable
weight but having thicker layers and filaments having
larger equivalent diameters. Ideally, filaments having
the minimum equivalent diameters formed into layers
having the minimum thickness will be used.
Compared to conventional ballistic-resistant armor
structures, the composite article of the present inven-
tion can advantageously provide a selected level of bal-
listic protection while employing a reduced weight of
protective material, alternatively, the article of the
present invention can provide increased ballistic pro-
tection when the article has a weight equal to the
weight of a conventionally constructed piece of com-
posite armor.
Another aspect of this invention relates to a novel
process for forming a network comprising a sheet-like
array of filaments in which said filaments are aligned
substantially parallel to one another along a common
filament direction such as a prepreg, a pultruded sheet
and the like, said filaments having a tenacity of at
least about 7 grams/denier, a tensile modulus of at
least about 160 grams/denier and an energy-to-break of
at least about 8 joules/gram in a matrix material
wherein the ratio of the thickness of said sheet-like
array to the equivalent diameter of said filaments
contained therein is equal to or less than about 12.8,
which comprises the steps of:
(a) aligning bundles of high strength filaments
comprising a plurality of high strength filaments said
filaments having a tenacity Oe at least about 7
grams/denier, a tensile modulus of at least about 160
1 31 2487
grams/denier and an energy-to-break of at least about 8
joule/gram in a sheet like array in which said filaments
are arranged substantially parallel to one another along
a common filament direction;
(b) passing said aligned bundles of filaments
through a plurality of spreading means under tension to
align individual filaments contained in said bundles of
filaments in a substantially coplanar fashion such that
tension upstream of said spreading means (Tl) is equal
to or less than about 0.3 grams per denier ("gpd"), and
tension downstream of said spreading means (T2) is equal
to or less than about 0.6 gpd, and Tl and T2
individually are not greater than the tensile strangth
of the weakest filament and said spreading means
comprising at least one of elongated body having a
substantially circular cross-section positioned
substantially perpendicular to the longitudinal axis of
said aligned bundles of filaments and positioned
relative to said aligned bundles filaments such that the
arc of contact ~,etween said means and said aligned
bundles of filament is equal to or ~reater than about
30, thereby spreading said bundles of filaments to
increase the coplanarity of filaments contained in said
bundles to any extent
(c) coating said spread filaments with a matrix
material; and
(d) consolidating said coated filaments to form a
layer comprising a network of said filaments dispersed
in said matrix material such that the ratio of the
thickness of said layer to the e~uivalent diameter of
said filaments is equal to or less than about 12.~.
8RIEF DESCRIPTION O_ THE DRAWINGS
The invention will be more fully understood and
further advantages will become apparent when reference
is made to the following detailed description of the
invention and the accompanying drawings in which:
~ -4-
v
~' ,
.
1 31 2487
FIG. 1 to 13 are various cross-sections of various
multilobal fibers.
FIG. 14 illustrates in schematic eorm an embodiment
of the process of this invention.
FIG. 15 is a detailed view of the spreading means
used to spread a bundle of filaments into aligned
~ilaments.
FIG. 16 is a cross-section of a bundle o~ filaments
prior to spreading.
FIG. 17 is a cross-section of the bundle of
filaments after spreading.
DETAILED DESCRIPTION OF THE INVENTION
Composites of this invention include one or more
layers of a filament network, at least one of which is
said that the ratio of the thickness of the layer to the
equivalent diameter of the filaments is equal to or less
than about 12.8. Surprisingly, we have discovered that
the value of this ratio has a significant effect on the
ballistic protection provided by the composite. In
general, the closer the ratio approaches to 1, the
greater the ballistic protection provided, and
conversely, the further the ratio diverges from 1, the
less ballistic protection provided. In the preferred
embodiments of the invention, the filament is a mono-
25 filament,
The cross-sections of filaments ~or use in this
invention may vary widely. They may be of circular or
of oblong or 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
; filament. In the particularly preferred embodiments of
the invention, the filaments are of substantially
circular or oblong cross-section and and in the most
preferred embodiments are circular or substantially
~` 35 circular cross-section.
In the preferred embodiments of the invention, the
ratio of the thickness of the layer to the equivalent
.,
1312487
diameter of the filament is equal to or less than about
10, and in the particularly preferred embodiments of the
invention, the ratio is equal to or less than about 8.
Amongst these particularly preferred embodiments of the
invention, most preferred are those embodiments in which
the ratio of the thickness of the layer to the
equivalent diameter of the filament is equal to or less
than about 6, with a ratio of between about 1 and about
5 being the ratio of choice.
The equivalent diameter of the filaments and the
thickness of the layer may vary widely. In general, the
smaller the equivalent diameter and the thinner the
layer, the greater the ballistic protection provided;
and conversely, the greater the equivalent diameter of
the filament and the greater the thickness of the
layers, the lower the ballistic protection provided.
In the preferred embodiments of the invention, the
equivalent diameter of the filaments is equal to or less
than about 0.01 cm, and the thickness of the layer is
equal to or less than abGut 0.04 cm. In the
particularly preferred embodiments of the invention, the
equivalent diameter of the filaments is from about 0.001
cm to about 0.008 cm, and the thickness of the layer is
equal to or less than abouc 0.03cm. Amongst these
particularly preferred embodiments, most preferred are
those embodiments in which the thickness of the layer is
from about 0.0007 cm to about 0.02 cm, with a thickness
of from about 0.002 cm to about 0.02 cm being the
thickness of choice; and the equivalent diameter of the
filaments is from about 0.002 cm to about O.OOS cm.
In the composite articles of our invention, the
filaments may be arranged in networks having various
configurations. For example, a plurality of filaments
can be grouped together to form a twisted or untwisted
yarn bundles in various alignment. In preferred
embodiments of the invention, the filaments in each
layer are aligned substantially parallel and
unidirectionally in which the matrix material
--6--
.~
.
1 31 2487
substantially coats the individual filaments Oe the
filaments. The filaments or yarn may be formed as a
felt, knitted or woven (plain, basket, satin and crow
~eet weaves, etc.) into a network, fabricated into non-
woven fabric, arranged in parallel array, layered, or
~ormed into a fabric by any of a variety of conventional
techniques. Among these techniques, for ballistic
resistance applications we prefer to use those
variations commonly employed in the preparation of
aramid fabrics for ballistic-resistant articles. For
example, the techniques described in U.S. Patent No.
4,181,768 and in M.R. Silyquist et al. J. Macromol Sci.
Chem., A7(1), pp. 203 et. seq. ~1973) are particularly
suitable.
The type of filaments used in the fabrication of
the article of this invention may vary widely and can be
metallic filaments, semi-metallic filaments, inorganic
filaments and/or organic filaments. Preferred filaments
for use in the practice of this invention are those
having a tenacity equal to or greater than about 10 g/d,
a tensile modulus equal to or greater than about 150 g/d
and an energy-in-break equal to or greater than about 8
joules/grams. Particularly preferred filaments are
those having a tenacity equal to or greater than about
20 g/d, a tensile modulus equal to or greater than about
500 g/d and energy-to-break equal to or greater than
about 30 joules/grams. Amongst these particularly
preferred embodiments, most preferred are those embodi-
ments in which the tenacity of the filaments are equal
to or greater than about 25 g/d, the tensile modulus is
equal to or greater than about 1000 g/d, and the energy-
to-break is equal to or greater than about 35 joules/
gram. In the practice of this invention, filaments of
choice have a tenacity equal to or greater than about 30
g/d, the tensile modulus is equal to or greater than
about 1300 g/d and the energy-to-break is equal to or
greater than about 40 joules/gram.
;
,.
:
1 31 2487
Filaments for use in the practice o~ this invention
may be metallic, semi-metallic, inorganic and/or
organic. Illustrative of useful inorganic filaments are
those formal from S-glass, silicon carbide, asbestos,
basalt, E-glass, alumina, alumina-silicate, quartz,
zirconia-silica, ceramic filaments, boron filaments,
carbon filaments, and the like. Exemplary of useful
metallic or semi-metallic filaments are those composed
o~ boron, aluminum, steel and titanium. Illustrative of
useful organic filaments are those composed of aramids
(aromatic polyamides), poly(m-xylylene adipamide),
poly(p-xylylene sebacamide), poly(2,2,2-
trimethylhexamethylene terephthalamide), poly(piperazine
sebacamide), poly(metaphenylene isophthalamide) (Nomex)
and poly(p-phenylene terephthalamide) (Kevlar) and
aliphatic and cycloaliphatic polyamides, such as the
copolyamide of 30~ hexamethylene diammonium isophthalate
and 70% hexamethylene diammonium adipate, the
copolyamide of up to 30% bis-(-amidoclyclohexyl)
methylene, tarephthalic acid and caprolactam, polyhexa-
methylene adipamide (nylon 66), poly(butyrolactam)
(nylon 4), poly(9-aminonoanoic acid) nylon 9),
poly(enantholactam) (nylon 7), poly(capryllactam) (nylon
8), polycaprolactam (nylon 6), poly(p-phenylene tere-
phthalamide), polyhexamethylene sebacamide ~nylon 6,10),
polyaminoundecanamide (nylon 11), polydodecanolactam
(nylon 12), polyhexamethylene isophthalamide,
polyhexamethylene terephthalamide, polycaproamide,
poly(nonamethylene azelamide) Nylon 9,9),
poly(decamethylene azelamide) (nylon 10,9),
poly(decamethylene sebacamide) (nylon 10,10), poly[bis-
(4-aminocyclohexyl)methane l,10-decanedicarboxamide]
(Qiana)(trans), or combination thereof; and aliphatic,
cycloaliphatic and aromatic polyesters such as poly(l,4-
i cyclohexylidene dimethyl eneterephathalate) cis and
trans, poly(ethylene-1,5-naphthalate), poly(ethylene-
2,6-naphthalate), poly(l,4-cyclohexane dimethylene
terephthalate) (trans), poly(decamethylene
_ ~_
,
."
13124~7
terephthalate), poly(ethylene terephthalate),
poly(ethylene isophthalate), poly(ethylene oxybenzoate),
poly(para-hydroxy benzoate), poly( C~C , C~c
dimethylpropiolactone), poly(decamethylene adipate),
poly(ethylene succinate) and the like.
Also illustrative of useful organic filaments are
those composed of extended chain polymers formed by
polymerization of c~ , ~ -unsaturated monomers of the
formula:
Rl R2-C = CH2
wherein:
Rl and R2 are the same or different and are
hydrogen, hydroxy, halogen, alkylcarbonyl, carboxy,
alkoxycarbonyl, heterocycle or alkyl or aryl either
unsubstituted or substituted with one or more
substituents selected from the group consisting of
alkoxy, cyano, hydroxy, alkyl and aryl. Illustrative of
such polymers of c~ unsaturated monomers are
polymers including polystyrene, polyethylene,
polypropylene, poly(l-octadecene), polyisobutylene,
poly(l-pentene), poly(2-methylstyrene), poly(4-
methylstyrene), poly(l-hexene), poly(l-pentene), poly(4-
methoxystrene), poly(5-methyl-1-hexene), poly(4-
methylpentene), poly(l-butene), poly(3-methyl-1-butene),
poly(3-phenyl-1-propene), polyvinyl chloride, polybuty-
lene, polyacrylonitrile, poly(methyl pentene-l),
poly(vinyl alcohol), poly(vinylacetate), poly(vinyl
butyral), poly(vinyl chloride), poly(vinylidene
chloride), vinyl chloride-vinyl acetate chloride
copolymer, poly(vinylidene fluoride), poly~methyl
acrylate, poly(methyl methacrylate),
poly(methacrylonitrile), poly(acrylamide), poly(vinyl
fluoride), poly(vinyl formal), poly(3-methyl-1-butene),
poly(l-pentene), poly(4-methyl-1-butene), poly(l-
pentene), poly(4-methyl-1-pentene), poly(l-hexane),
poly(5-methyl-1-hexene), poly(l-octadecene), poly(vinyl
1 31 2487
cyclopentane), poly(vinylcyclohexane),
poly(a-vinylnaphthalene), poly(vinyl methyl ether),
poly(vinylethylether), poly(vinyl propylether),
polytvinyl carbazole), poly(vinyl pyrrolidone),
5 poly(2-formate), poly(vinyl butyl ether), poly(vinyl
octyl ether), poly(vinyl methyl ketone),
poly(methylisopropenyl ketone), poly(4-phenylstyrene)
and the like.
In the most preferred embodiments of the invention,
10 composite articles include a filament network, which may
include a high molecular weight polyethylene filament, a
high molecular weight polypropylene filament, an aramid
filament, a high molecular weight polyvinyl alcohol
filament, a high molecular weight polyacrylonitrile
- 15 filament or mixtures thereof. USP 4,457,985 generally
discusses such high molecular weight polyethylene and
polypropylene filaments, and the disclosure of this
patent is hereby incorporated by reference to the extent
that it is not inconsistent herewith. In the case of
20 polyethylene, suitable filaments are those of molecular
weight of at least 150,000, preferably at least one
million and more preferably between two million and five
million. Such extended chain polyethylene (ECPE)
filaments may be grown in solution as described in U.S.
25 Patent No. 4,137,394 to Meihuzen et al., or U.S. Patent
No. 4,356,138 of Kavesh et al., issued October 26, 1982,
or a filament spun from a solution to form a gel
! structure, as described in German Off. 3,004,699 and GB
2051667, and especially as described in U.S. Patent No.
30 4,551,296 of Kavesh et al (see EPA 64,167, published
$ Nov. 10, 1982). As used herein, the term polyethylene
shall mean a predominantly linear polyethylene material
that may contain minor amounts of chain branching or
comonomers not exceeding 5 modifying units per 100 main
35 chain carbon atoms, and that may also contain admixed
therewith not more than about 50 wt% of one or more
~ polymeric additives such as
--10--
. . .
:
t312487
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 anti-oxidants, lubricants, ultra-violet
screening agents, colorants and the like which are
commonly incorporated by reference. Depending upon the
formation technique, the draw ratio and temperatures,
and other conditions, a variety of properties can be
imparted to these filaments. The tenacity of the
filaments should be at least 15 grams/ denier,
preferably at least 20 grams/denier, more
preferably at least 25 grams/denier and most preferably
at least 30 grams/denier. Similarly, the tensile
modulus of the filaments, as measured by an Instron
tensile testing machine, is at least 300 grams/denier,
preferably at least 500 grams/denier and more preferably
at least 1,000 grams/denier and most preferably at least
1,200 grams/denier. These highest values for tensile
modulus and tenacity are generally obtainable only by
employing solution grown or gel filament 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
polyethylenes of 150,000, one million and two million
generally have melting points in the bulk of 138C. The
highly oriented polyethylene filaments made of these
materials have melting points of from about 7 to about
13C 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. Nevertheless, the melting points of
these filaments remain substantially below nylon; and
the efficacy of these filaments for ballistic resistant
articles is contrary to the various teachings cited
above which indicate temperature resistance as a
critical factor in selecting ballistic materials.
--11--
1 3 1 2487
Notwithstanding the contrary teachings in the prior art,
improved ballistic resistant articles are formed when
polyethylene filaments having a weight average molecular
weight of at least about 150,000, a modulus of at least
5 about 500 and a tenacity of at least about 15 g/denier are
employed. Cf. John V. E. Hansen and Roy C. Laible in
"Flexible Body Armor Materials," Filament Frontiers ACS
Conference, June 10-12, 1974 ~ballistically resistent high
strength filaments must exhibit high melting point and
10 h~gh resistance to cutting or shearing); Roy C. Laible,
Ballistic Materials and Penetration Mechanics, 1980
(noting that nylon and polyester amy be limited in their
ballistic effectiveness due to the lower melting point);
and "The Application of High Modulus Filaments to
15 Ballistic Protection", R.C. Laible, et al., J. Macromel.
Sci. Chem., A7(1), pp. 295-322, 1973 (the importance of a
high degree of heat resistance is again discussed).
Similarly, highly oriented polypropylene filaments of
molecular weight at least 200,000, preferably at least one
20 million and more preferably at least two million may be
used. Such high molecular weight polypropylene may be
formed into reasonably well oriented filaments by the
techniques prescribed in the various references referred
to above, and esp~cially by the technique of U.S. Patent
25 No. 4,551,296 of Kavesh et al. and commonly assigned.
Since polypropylene is a much less crystalline material
than polyPthylene and contains pendant methyl groups,
tenacity values achievable with polypropylene are
generally substantially lower than the corresponding
30 values for polyethylene. Accordingly, a suitable tenacity
is at least 8 grams/denier, with a preferred tenacity
being at least 11 grams/denier. The tensile modulus for
polypropylene is at least 160 grams/denier, preferably at
least 200 grams/denier. The melting point of the
35 polypropylene is generally raised several degrees by the
orientation process, such that the polypropylene
i,.
... ..
~ -12-
.,
.,
1 31 24~7
filament preferably has a main melting point of at least
168C, more preferably at least 170C. The particularly
preferred ranges for the above-described parameters can
advantageously provide improved performance in the final
5 article. Employing filaments having a weight average
molecular weight of at least about 200,00 coupled with the
preferred ranges for the above-described parameters
(modulus and tenacity) can provide advantageously improved
performance in the final article especially in ballistic
10 resistant articles, notwithstanding the contrary teachings
in the prior art). C.f. Laible, Ballistic Materials and
Penetration Mechanics, supra, at p. 81 (no successful
treatment has been developed to bring the ballistic
resistance of polypropylene up to levels predicated from
15 the yarn stress-strain properties); and The relative
effectiveness of NTIS publication AD-AO18 958, "New
Materials in Construction for Improved Helmets", A.L Alesi
et al. [wherein a multi-layer highly oriented
polypropylene film material (without matrix), referred to
20 as "XP", was evaluated against an aramid filament (with a
phenolic/polyvinyl butyral resin matrix); the aramid
system was judged to have the most promising combination
of superior performance and a minimum of problems for
combat helmet development~.
, 25 High molecular weight polyvinyl alcohol filaments
having high tensile modulus are described in USP 4,440,711
to Y. Kwon et al. In the case of polyvinyl alcohol
(PV-OH), PV-OH filament of molecular weight of at least
about 200,000. Particularly useful PV-OH filament should
30 have a modulus of at least about 300 g/d, a tenacity of at
least 7 g/d (preferably at least about 10 g/d, more
preferably at about 14 g/d, and most preferably at least
about 17 g/d), and an energy to break of at least about 8
joules/gram. PV-OH filaments having a weight average
35 molecular weight of at least about 200,000, a tenacity of
at least about 10 g/denier,
.,
, ~ ~ -13-
.,.
1 31 24~7
a modulus of at least about 300 g/denier, and an energy to
break of about 8 joules/gram are more useful in producing
a ballistic resistant article. PV-OH filament having such
properties can be produced, for example, by the process
5 disclosed in u.S. Patent No. 4,599,267.
In the case of polyacrylonitrile (PAN), PAN filament
of molecular weight of at least about 400,000.
Particularly useful PAN filament should have a tenacity of
at least about 10 g/denier and an energy to break of at
10 least about 8 joule/g. PAN filament having a molecular
weight of at least about 400,000, a tenacity of at least
about 15 to about 20 g/denier and an energy to break of at
least 8 joule/g is most useful in producing ballistic
resistant articles; and such filaments are disclosed, for
15 example, in U.S. 4,535,027.
In the case of aramid filaments, suitable aramide
filaments formed principally from aromatic polyamide are
described in USP 3,671,542. Preferred aramid filament
will have a tenacity of at least about 20 g/d, a tensile
20 modulus of at least about 400 g/d and an energy to break
at least about 8 joules/gram, and particularly preferred
aramid filaments will have a tenacity of at least about 20
g/d, a modulus of at least about 480 g/d and an energy to
break of at least about 20 joules/gram. Most preferred
25 aramid filaments will have a tenacity of at least about 20
g/denier, a modulus of at least about 300 g/denier and an
energy to break of at least about 30 joules/gram. For
example, poly(phenylenediamine terephalamide) filaments
produced commercially by Dupont Corporation under the
30 trade name of Kevlar~ 29 and 49 and having moderately high
moduli and tenacity values 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 modulus and
35 tenacity, respectively). Also useful in the practice of
this invention is poly(metaphenylene isophthalamide)
-14-
A`~
.;
,
1312487
filaments produced commercially by Dupont under the
tradename Nomex~.
In composite articles containing such filaments,
the filaments are arranged in a network which can have
various configurations. For example, a plurality of
filaments can be grouped together to form a twisted or
untwisted yarn. The filaments or yarn may be formed as
a felt, knitted or woven (plain, basket, satin and crow
feet weaves, etc.) into a network, or formed into a
network by any of a variety of conventional
techniques. In the preferred embodiments of the
invention, the filaments are untwisted mono-filament
yarn wherein the filaments are parallel,
unidirectionally aligned. For example, the filaments
may also be formed into nonwoven cloth layers by
conventional techniques.
The filaments are dispersed in a continuous phase
of a matrix material which preferably substantially
coats each filament contained in the bundle o~
fil~ment. The manner in which the filaments are
dispersed may vary widely. The filaments may be aligned
in a substantially parallel, unidirectional fashion, or
filaments may be aligned in a multidirectional fashion
with filaments at varying angles with each other. In
the preferred embodiments of this invention, filaments
in each layer are aligned in a substantially parallel,
unidirectional fashion such as in a prepreg, pultraded
sheet and the like.
The matrix material employed may vary widely and
may be a metallic, semi-metallic material, an organic
material and/or an inorganic material. The matrix
material may be flexible ~low modulus) or rigid (high
modulus)~ Illustrative of useful high modulus or rigid
matrix materials are polycarbonates;
polyphenylenesulfides polyphenylene oxides; polyester
carbonates; polyesterimides; polyimides; and thermoset
resins such as epoxy resins, phenolic resins, modified
phenolic resins, allylic resins, alkyd resins,
.,
-15-
!.
.,
1312487
unsaturated polyesters, aromatic vinylesters as ~or
example the condensation produced o~ bisphenol A and
methacrylic acid diluted in a vinyl aromatic monomer
(e.g. styrene or vinyl toluene), urethane resins and
amino (melamine and urea) resins. The major criterion
is that such material holds the filaments together, and
maintains the geometrical integrity of the composite
under the desired use conditions.
In the preferred embodiments of the invention, the
matrix material is a low modulus elastomeric material.
A wide variety of elastomeric materials and formulations
may be utilized in the preferred embodiments of this
invention. Representative examples of suitable
elastomeric materials for use in the formation of the
matrix are those which have their structures,
properties, and formulations together with crosslinking
procedures summarized in the Encyclopedia of Polymer
Science, Volume 5 in the section Elastomers-Synthetic
(John Wiley & Sons Inc., 1964). For example, any of the
following elastomeric materials may be employed:
polybutadiene, polyisoprene, natural rubber, ethylene-
propylene copolymers, ethylene-propylene-diene
terpolymers, polysulfide polymers, polyurethane
elastomers, chlorosulfonated polyethylene,
polychloroprene, plasticized polyvinylchloride using
dioctyl phthate or other plasticers well known in the
art, butadiene acrylonitrile elastomers,
poly(isobutylene-co-isoprene), polyacrylates,
polyesters, polyethers, fluoroelas~omers, silicone
elastomers, thermoplastic elastomers, copolymers of
ethylene.
Particularly useful elastomers are block copolymers
of conjugated dienes and vinyl aromatic monomers.
Butadiene and isoprene are preferred conjugated diene
elastomers. Styrene, vinyl toluene and t-butyl styrene
are preferred conjugated aromatic monomers. Block
copolymers incorporating polyisoprene may be hydrogena-
ted to produce thermoplastic elastomers having saturated
.,
''
-16-
1 31 2487
hydrocarbon elastomer segments. The polymers may be
simple tri-block copolymers of the type A-B-A, multi-
block copolymers o~ the type (AB)n(n=2-10) or radial
confi~uration copolymers of the type R-~sA)x(x=3-I5o);
wherein A is a block from a polyvinyl aromatic monomer
and B is a block from a conjugated diene elastomer.
~any of these polymers are produced commercially by the
Shell Chemical Co. and described in the bulletin "Kraton
Thermoplastic Rubber", SC-68-81.
Most preferably, the elastomeric matrix material
consists essentially of at least one of the above-men-
tioned elastomers. The low modulus elastomeric matrices
may also include fillers such as carbon black, silica,
glass microballons, and the like up to an amount
preferably not to exceed about 50~ by volume of the
elastomeric material, preferably not to exceed about 40
by weight, and may be extended with oils, may include
fire retardants such as halogenated parafins, 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 elastomer
materials may be blended with one or more
thermoplastics. High density, low density, and linear
low density polethylene may be cross-linked to obtain a
matrix material of appropriate properties, either alone
or as blends. In every instance, the modulus of the
elastomeric matrix material should not exceed about
6,000 psi (41,300 kPa), preferably is less than about
5,000 psi (34,500 kPa), more preferably is less than
1000 psi (6900 kPa) and most preferably is less than 500
psi ~3450 kPa).
In the preferred embodiments of the invention, the
matrix material is a low modulus, elastomeric
material. The low modulus elastomeric material has a
tensile modulus, measured at about 23C, of less than
about 6,000 psi (41,300 kPa). Preferably, the tensile
modulus of the elastomeric material is less than about
-17-
1 ~ 1 2487
5,000 psi (34,500 kPa), more preferably, is less than
1,000 psi (6900 kPa) and most preferably is less than
about 500 psi (3,450 kPa) to provide even more improved
performance. The glass transition temperature (Tg) of
the elastomeric material (as evidenced by a sudden drop
in the ductility and elasticity of the material) is less
than about 0C. Preferably, the Tg of the elastomeric
material is less than about -40C, and more preferably
is less than about -50C. The elastomeric material also
has an elongation to break of at least about 50%.
Preferably, the elongation to break of the elastomeric
material is at least about 100%, and more preferably is
at least about 300~.
The proportions of matrix to filament in the
composite is not critical and may vary widely depending
on a number of factors including, whether the matrix
material has any ballistic-resistant properties of its
own twhich is generally not the case) and upon the
rigidity, shape, heat resistance, wear resistance,
flammability resistance and other properties desired for
the composite article. In general, the proportion of
matrix to filament in the composite may vary from
relatively sma~ll amounts where the amount of matrix is
about 10% by volume of the filaments to relatively large
amounts where the amount of matrix is up to about 90% by
volume of the filaments. In the preferred embodiments
of this invention, matrix amounts of from about 15 to
about 80% by volume are employed. All volume percents
are based on the total volume of the composite. In the
particularly preferred embodiments of the invention,
ballistic-resistant articles of the present invention
contain a relatively minor proportion of the matrix
(e.g., about 10 to about 30% by volume of composite),
since the ballistic-resistant properties are almost
entirely attributable to the filament, and in the
particularly preferred embodiments of the invention, the
proportion of the matrix in the composite is from about
10 to about 30% ~y weight of filaments.
.,.
-18-
.,
.,
13124~7
The articles of this invention can be ~abricated
using a number of procedures. In general, the layers
are formed by molding the combination of the matrix
material and filaments in the desired configurations and
amounts by subjecting them to heat and pressure.
The filaments may be premolded by subjecting them
to heat and pressure. For ECPE filaments, molding
temperatures range from about 20 to about 150C,
preferably from about 80 to about 145C, more preferably
from about 100 to about 135C, and more preferably from
about 110 to about 130C. The pressure may range from
aboùt 10 psi (69 kpa) to about 10,000 psi (69,000
kpa). A pressure between about 10 psi (69 kpa) and
about 100 psi (690 kpa), when combined with temperatures
below about 100C for a period of time less than about
1.0 min., may be used simply to cause adjacent filaments
to stick together. Pressures from about 100 psi to about
10,000 psi (69,000 kpa), when coupled with temperatures
in the range of about 100 to about 155C for a time of
between about 1 to about 5 min., may cause the filaments
to deform and to compress together (generally in a film-
like shape). Pressures from about 100 psi (690 kpa) to
about 10,000 psi ~69,000 kpa), when coupled with
temperatures in the range of about 150 to about 155C
for a time of between 1 to about 5 min., may cause the
film to become translucent or transparent. For
polypropylene filaments, the upper limitation of the
temperature range would be about 10 to about 20C higher
than ~or ECPE filament.
In the preferred embodiments of the invention, the
filaments (premolded if desired) are precoated with the
desired matrix material prior to being arranged in a
network and molded as described above. The coating may
be applied to the filaments in a variety of ways and any
method known to those of skill in the art for coating
filaments may be used. For example, one method is to
apply the matrix material to the stretched high modulus
filaments either as a liquid, a sticky solid or
--19--
,
1 3 1 24~7
particles in suspension, or as a fluidized bed.
Alternatively, the matrix material may be applied as a
solution or emulsion in a suitable solvent which does
not adversely affect the properties of the filament at
the temperature of application. In these illustrative
embodiments, any liquid capable of dissolving or
dispersing the matrix material~may be used. However, in
the preferred embodiments of the invention in which the
matrix ~aterial is an elastomeric material, preferred
groups of solvents include water, paraffin oils,
ketones, alcohols, aromatic solvents or hydrocarbon
solvents or mixtures thereof, with illustrative specific
solvents including paraffin oil, xylene, toluene and
octane. The techniques used to dissolve or disperse the
matrix in the solvents will be those conventionally used
for the coating of similar elastomeric materials on a
variety of substrates.
Other techniques for applying the coating to the
filaments may be used, including coating of the high
modulus precursor (gel filament) before the high
temperature stretching operation, either before or after
removal of the solvent from the filament. The filament
may then be stretched at elevated temperatures to
produce the coated filaments. The gel filament may be
5 passed through a solution of the appropriate matrix
material, as for example an elastomeric material
dissolved in paraffin oil, or an aromatic or aliphatic
solvent, under conditions to attain the desired
coating. Crystallization of the polymer in the gel
0 filament may or may not have taken place before the
filament passes into the cooling solution.
Alternatively, the filament may be extruded into a
fluidized bed of the appropriate matrix material in
powder form.
r'.' 35 The proportion of coating on the coated filaments
or fabrics may vary from relatively small amounts (e.g.
1~ by weight of filaments) ~o relatively large amounts
(e.g. 150% by weight of filaments), depending upon
,
.~
-20-
13124~7
whether the coating material has any impact or
ballistic-resistant properties of its own (which is
generally not the case) and upon the rigidity, shape, heat
resistance, wear resistance, flammability resistance and
5 other properties desired for the complex composite
article. In general, ballistic-resistant articles of the
present invention containing coated filaments should have
a relatively minor proportion of coating (e.g., about 10
to about 30 percent by volume of filaments), since the
10 ballistic-resistant properties are almost entirely
attributable to the filament. Nevertheless, coated
filaments with higher coating contents may be employed.
Generally, however, when the coating constitutes greater
than about 60% (by volume of filament), the coated
15 filament is consolidated with similar coated filaments to
form a simple composite without the use of additional
matrix material.
Furthermore, if the filament achieves its final
properties only after a stretching operation or other
20 manipulative process, e.g~ solvent exchanging, drying or
the like, it is contemplated that the coating may be
applied to a precursor material of the final filament. In
such cases, the desired and preferred tenacity, modulus
and other properties of the filament should be judged by
25 continuing the manipulative process on the filament
precursor in a manner corresponding to that employed on
the coated filament precursor. Thus, for example, if the
coating is applied to the xerogel filament described in
U.S. Patent 4,551,296 of Kavesh et al., and the coated
30 xerogel filament is then stretched under defined
temperature and stretch ratio conditions, then the
filament tenacity and filament modulus values would be
measured on uncoated xerogel filament which is similarly
stretched.
It is a preferred aspect of the invention that each
filament be substantially coated with the matrix material
for the production of composites having improved impact
; protection and/or having maximum
-21-
. ~.
.~. ....
.
:.
1 3 1 ~4~7
ballistic resistance. A filament is substantially
coated by using any of the coating processes described
above or can be substantially coated by employing any
other process capable of producing a filament coated
5essentially to the same degree as a filament coated by
the processes described heretofore (e.g., by employing
known high pressure molding techniques).
The filaments and networks produced therefrom are
formed into "simple composites" as the precursor to
1 preparing the complex composite articles of the present
invention. The term, "simple composite", as used herein
is intended to mean composites made up of one or more
layers, each of the layers containing filaments as
described above with a single major matrix material,
15 which material may include minor proportions of other
materials such as fillers, lubricants or the like as
noted heretofore.
The proportion of elastomeric matrix material to
filament is variable for the simple composites, with
matrix material amounts of from about 5% to about 150
Vol %, by volume of the filament, representing the broad
general range. Within this range, it is preferred to
use composites having a relatively high filament
content, such as composites having only about 10 to
about 50 Vol ~ matrix material, by volume of the
composite, and more preferably from about 10 to about 30
Vol % matrix material by volume of the composite.
Stated another way, the filament network occupies
different proportions of the total volume of the simple
composite. Preferably, however, the filament network
comprises at least about 30 volume percent of the simple
composite. For ballistic protecting, the filament
network comprises at least about 50 volume percent, more
preferably about 70 volume percent, and most preferably
at least about 75 volume percent, with the matrix
occupying the remaining volume.
A particularly effective technique for preparing a
' preferred composite of this invention comprised of sub-
-22-
..~
!
1~12487
stantially parallel, unidirectionally aligned filaments
includes the steps of pulling a filament or bundles of
filaments through a bath containing a solution of a
matrix material preferably, an elastomeric matrix
5material, and circumferentially winding this filament
into a single sheet-like layer around and along a bundle
of filaments the length of a suitable form, such as a
cylinder. The solvent is then evaporated leaving a
sheet-like layer of filaments embedded in a matrix that
can be removed from the cylindrical form.
Alternatively, a plurality of filaments or bundles of
filaments can be simultaneously pulled through the bath
containing a solution or dispersion of a matrix material
and laid down in closely positioned, substantially
15 parallel relation to one another on a suitable
surface. Evaporation of the solvent leaves a sheet-like
layer comprised of filaments which are coated with the
matrix material and which are substantially parallel and
aligned along a common filament direction. The sheet is
suitable for subsequent processing such as laminating to
another sheet to form composites containing more than
one layer.
Similarly, a yarn-type simple composite can be
produced by pulling a group of filament bundles through
2 a dispersion or solution of the matrix material to
substantially coat each of the individual filaments, and
then evaporating the solvent to form the coated yarn.
The yarn can then, for example, be employed to form
fabrics, which in turn, can be used to form more complex
30 composite structures. Moreover, the coated yarn can
also be processed into a simple composite by employing
conventional filament winding techniques; for example,
the simple composite can have coated yarn formed into
overlapping filament layers.
In the most preferred embodiments of this inven-
tion, the layers comprising a network of substantially
parallel, undirectionally aligned filaments in the
matrix material wherein the ratio of the thickness of
-23-
!
. .
.
1312487
the layer to the equivalent diameter of the filaments is
equal to or less than about 12.8 is formed by the
process of this invention. This process can be more
readily appreciated from the FIG's. FIG. 14 illustrates
5in schematic ~orm a preferred embodiment of this
inventionc As shown in FIG. 14, a plurality of creels
11 containing high strength filaments, preferably high
strength polyethylene, polypropylene, boron, polyvinyl
alcohol, graphite, polyacrylonitrile, poly aramid or S-
glass, more preferably polyethylene and aramid, and most
preferably polyethylene are deployed. The yarn
preferably consist of bundles of from about 30 to about
2000 individual filaments of less than about 12 denier,
and more preferably are bundles of from about 100
1 filaments of less than about 7 denier. Individual
filaments are aligned coplanarly and in a substantially
parallel, and unidirectional fashion by pulling the
filaments through a first and second set of combs,
identified in the drawings by the numerals 12 and 13
respectively. As shown in FIG. 14, the average distance
between aligned filaments is controlled by the distance
between neighboring pins of combs 12 and 13. The
distance between neighboring pins of the second set of
combs is generally equal to or less than about twice the
25"equivalent diameter of the filament", times the number
of filaments in a bundle of filaments. In the preferred
embodiments of the invention, the distance between
neighboring pins is equal to or less than about 1.5
times the product of the equivalent diameter of the
30 filament and the number of filaments in the bunder of
filaments. The aligned filaments are then pulled
through spreading means 14 for spreading the filaments
bundle to its maximum width so that the thickness of
' bundle approaches the equivalent diameter of filaments
` in the bundle and to simultaneously improve the
alignment of individual filaments within the filament
bundle. As shown in FIG. 15, normally yarn consist of
bundles of filaments in which the equivalent diameter of
-24-
c~
'
1 3 1 2487
the bundle of filaments or the width of the filament
bundle is very much greater than the equivalent diameter
of the filaments contained in the bundle. As shown in
FIGs. 16 and 17, after treatment with the spreading
means, the filament bundle is spread out, and this
difference is reduced, and the equivalent diameter of
the filaments more closely approximates the thickness of
the filament bundle. The operation of the spreading
means may be more readily appreciated from FIG. 14. As
shown in FIG. 14, spreading ~eans in ~his preferred
embodiment of the invention consists of two spread bars,
15 and 16 positioned such that the center of axis of the
bars are parallel. This relative position insures that
the aligned filaments 17 emerging from combs 13 will on
passing through the spread bars 15 and 16 as shown in
FIG. 14 will maintain an angle of contact with spread
bar 15 of Sl, and an angle of contact with spread bar
16 of S2, while the aligned filaments upstream of
spreading means 14 is maintained under a tension Tl and
the aligned filaments downstream of spreading means 14
20 is maintained under a tension T2. In general, at
constant Tl or T2, the greater the value of the contact
angles Sl and S2, the greater the value of T2 and the
greater the degree to which the filaments are spread out
so that the thickness of the filament bundle more
closely approximates the equivalent diameter of the
filaments; and at constant Sl and S2, the greater the
value of Tl and T2, the greater the degree to which the
filaments are spread out so that the equivalent diameter
of the ~ilament more closely approximates that of the
individual filaments. In general, Tl and T2 are
di~ferent and are less than about the tensile strength
of the filaments, comprising the filament, and S1 and
, S2 are the same or different and are equal to or
greater than about 30. In the preferred embodiments
using the preferred polyethylene, polypropylene, aramid,
S-glass, polyvinylalcohol and polyacrylonitrile
filaments Tl and T2 are different and are from about 0.3
:
' -25-
.
',
1 31 2487
gpd to about 0.9 gpd, and S1 and S2 are the same or
different and are equal to or greater than about 30.
In the particularly preferred embodiments of the
invention employing the particularly preferred
polyethylene and aramid filaments, Tl and T2 are
different and are from about 0.3 gpd to about 0.6 gpd
provided that ~T , the difference between Tl and T2
is from about 0.1 gpd to about 0.5 gpd; and S1 and S2
are the same or different and are from about 30 to
about 270. Amongst these particularly preferred
embodiments, most preferred are those embodiments in
which Tl and T~ are different and are from about 0.2 gpd
to about 0.5 gpd and ~T is from about 0.2 gpd to
about 0.4 gpd; and in which 51 and S2 are the same or
different and are from about 40 to about 250.
After passing through spreading means 14, the
aligned filaments which have been spread are fed onto
support means, as for example release on wheel paper 18
such as silicone release paper, to support the aligned
filaments. Release paper 18 is fed onto wheel 19 from
20 paper substrate 20. The combination of release paper
supported align filaments are pulled through the
apparatus at a tension T2 supplied by pull rolls 21 to a
position directly under a matrix material applying means
22, which in FIG. 14 is a combination of reciprocating
cylinder 23 connected to a source of matrix material
(not shown) and a resin applicator tube 24 for applying
the resin material to the supported and aligned
filaments in a manner such that preferably each filament
of the aligned filaments is substantially coated with
the matrix. The filaments may be coated with the matrix
material using any convenient method. For example, the
material can be applied as a dispersion of the material
in a suitable solvent or in the form of an emulsion or
as a low molecular material which on consolidation
cross-links to form the desired matrix material; or
sprayed on as fine discrete particles of the matrix
material. In the preferred embodiments of the
.~
:
~ -26-
':
,.
1 31 2487
invention, the matrix ~aterial is a low modulus material
such as a block copolymer of conjugated dienes, e.g.,
butadiene, isoprene, and vinyl aromatic ~ono~ers, e.g.,
styrene, vinyl toluene and t-butyl-styrene, which is
applied as a dispersion in a solvent such as water.
After application of the desired matrix material, the
coated filaments are consolidated into the desired
composite. Consolidation methods may vary widely
depending on a number of factors, as for example, the
type of matrix material and the manner in which it is
applied to the filaments and the type of filament. In
the preferred embodiments after application of the
~aterial, the supported and coated aligned filaments are
consolidated by conveying same to a leveling means 25
which spreads and substantially levels the applied
material to the desired level such that the ratio of the
thickness of the layer to the equivalent diameter of the
filaments is after drying less than about 12.8, and in
which, in addition, functions to complete the
substantial coating of any uncoated filaments. In FIG.
14, leveling means are two pairs of adjustable nip rolls
26 and 27, and 31 and 32. However, other leveling means
such as doctor blades and the like can be used. Under
tension from pull rolls 21, the coated filaments are
then converted to solvent removal means 28 to remove all
or substantially all of the solvent from the matrix
material coating the filaments. In FIG. 14, solvent
removal means is a gas fired oven which heats the coated
filaments above the vaporization temperature of the
solvent and below the degradation temperature and/or
melting point of the filaments and matrix material.
However, any solvent removal means known to those of
skill in the art can be used, as for example such oven
in conjunction with a vacuum means to allow for removal
of the solvent at lower temperatures. The dried layer
of coated filaments in which the ratio thickness of the
layer (combination of filaments and coat.ings), and the
equivalent diameter of the filaments is equal to or less
,.,
. -27-
.
~'
1 31 2487
than about 12.8, together with release paper 18 are
pulled from drying means 27 by pull roll 21, and wound
on a rewind assembly 23 for further use in the
manufacture of composites of this invention having more
than one layer.
The number of layers included in the composite of
this invention may vary widely depending on the uses of
the composite, for example, in those uses where the
composite would be used as ballistic protection, the
number of layers would depend on a number of factors
including the degree of ballistic protection desired and
other factors known to those of skill in the ballistic
protection art. In general for this application, the
greater the degree of protection desired the greater the
number of layers included in the article for a given
weight of the article. Conversely, the lessor the
degree of ballistic protection required, the lessor the
number of layers required for a given weight of the
article. It is convenient to characterize the
geometries of such composites by the geometries of the
filaments and then to indicate that the matrix material
may occupy part or all of the void space left by the
network of filaments. One such suitable arrangement is
a plurality of layers or laminates in which the coated
filaments are arranged in a sheet-like array and aligned
parallel to one another along a common filament
direction. Successive layers of such coated,
undirectional filaments can be rotated with respect to
the previous layer. An example of such laminate
structures are composites with the second, third, fourth
and fifth layers rotated +45, -45, 90 and 0, with
respect to the first layer, but not necessarily in that
order. Other examples include composites with 0/909
layout of yarn or filaments.
One technique for forming composites of this
invention having more than one layer includes the steps
of arranging coated filaments into a desired network
structure, and then consolidating and heat setting the
-28-
,.
.,.
1 3 1 2487
overall structure to cause the coating material to flow
and occupy the remaining void spaces, thus producing a
continuous matrice. Another technique is to arrange
layers or other structures of coated or uncoated
filament adjacent to and between various forms, e.g.
films, of the matrix material and then to consolidate
and heat set the overall structure. In the above cases,
it is possible that the matrix can be caused to stick or
flow without completely melting. In general, if the
matrix material is caused to melt, relatively little
pressure is required to form the composite; while if the
matrix material is only heated to a sticking point,
generally more pressure is required. Also, the pressure
and time to set the composite and to achieve optimal
properties will generally depend on the nature of the
matrix material (chemical composition as well as
molecular weight) and processing temperature.
The composites of this invention comprising one or
more layers may be incorporated into complex
composites. For example, such composites may be
incorporated into more complex composites to provide a
rigid complex composite article suitable, for example,
as structural ballistic-resistant components, such as
helmets, structural members of aircraft, and vehicle
panels. The term "rigid" as used in the present
specification and claims, is intended to include semi-
flexible and semi-rigid structures that are capable of
being free standing, without collapsing. To form the
complex composite, at least one substantially rigid
layer is bonded or otherwise connected to a major
surface of the mono or multi-layer composite. The
resultant complex composite article is capable of
standing by itself and is impact resistant. Where there
is only one layer, the composite of this invention
ordinarily forms a remote portion of the complex
composite article; that is a portion that is not
initially exposed to the environment, e.g., the impact
of an oncoming projectile. Where there is more than one
-29-
.,. I
-.
1312487
layer, the simple composite may form, for example, a
core portion that is sandwiched between two rigid
layers, as is particularly useful, for example, in
helmet applications. Other forms of the complex
composite are also suitable, for example a composite
comprising ~ultiple alternating layers of simple
composite and rigid layer.
In the preferred embodiments of the invention,
rigid layers are preferably comprised of an impact
resistant material, such as steel plate, composite armor
plate, ceramic reinforced metallic composite, ceramic
plate, concrete, and high strength filament composites
(for example, an aramid filament and a high modulus,
resin matrix such as epoxy or phenolic resin vinyl
ester, unsaturated polyester, thermoplastics, Nylon~ 6,
nylon 6, 6 and polyvinylidine halides). Most
preferably, the rigid impact resistant layer is one
which is ballistically effective, such as ceramic plates
or ceramic reinforced metal composites. A desirable
embodiment of our invention is the use of a rigid impact
resistant layer which will at least partially deform the
initial impact surface of the projectile or cause the
projectile to shatter such as aluminum oxide, boron
carbide, silicon carbide and beryllium oxide (see
Laible, supra, Chapters 5-7 for additional useful rigid
layers). For example, a particularly useful ballistic
resistant complex composite comprises a simple composite
comprising highly-oriented high molecular weight
polyethylene filament in an elastomeric matrix on which
is formed at least one layer comprising highly-
orientated ultra-high molecular weight polyethylene
filament in a rigid matrix, such as an epoxy resin.
Other suitable materials for the face sheets include
materials which may be heat resistant, flame resistant,
solvent resistant, radiation resistant, or combinations
thereof such as stainless steel, copper, aluminum
oxides, titanium, etc.
As a portion of the rigid impact resistant com-
-30-
.
,
.
., .
:
1 31 2487
posite, the volume percent of the simple composite is
variable depending upon the desired properties of the
final product. The volume percent of the simple com-
posite to the complex composite is ordinarily at least
5 about 10%, preferably at least about 15~, and most pref-
erably at least about 20% (for maximizing ballistic
resistance). The volume percent of the simple composite
to the complex composite is ordinarily at least about
5%, preferably at least about 10~, and most preferably
10 at least about 15% (for maximizing ballistic resis-
tance). The examples illustrate the effectiveness of a
simple composite in a complex structure at various per-
centages of the simple composite to the total. For
example, various compromises between structural rigidity
and ballistic performance are attainable depending upon
the specific material choices and the relative proper-
ties of the simple composites and rigid layers.
Studies of ballistic composites frequently employ a
22 caliber, non-deforming steel fragment of specified
weight, hardness and dimensions (Mil-Spec. MIL-P-
46593A(ORD)). The protective power of a structure is
normally expressed by citing the impacting velocity at
which 50% of the projectiles are stopped, and is desig-
nated the V50 value.
Usually, a composite armor has the geometrical
shape of a shell or plate. The specific weight of the
shells and plates can be expressed in terms of the areal
density (ADT). This areal density corresponds to the
weight per unit area of the structure. In the case of
filament reinforced composites, the ballistic resistance
of which depends mostly on the filament, another useful
weight characteristic is the filament areal density of
composites. This term corresponds to the weight of the
filament reinforcement per unit area of the composite
35 (AD).
The following examples are presented to provide a
more complete understanding of the invention. The
; specific techniques, conditions, materials, proportions
~;
-31-
,
1312487
and reported data set ~orth to illustrate the principles
of the invention are exemplary and should not be
construed as limiting the scope of the invention.
EXAMPLE 1
A ballistic panel was prepared by molding a
plurality of sheets comprised of uni-directional high
strength extended chain polyethylene (ECPE) yarn
impregnated with a Kraton D1107 thermoplastic elastomer
matrix ( a polystyrene-polyisoprene-polystrene-block co-
polymer having 14 wt % styrene and a product of Shell
Chemical). This yarn had a tenacity of 30g/denier, a
modulus of 1,20Gg/denier and energy-to-break 55
joules/g. The elongation to break of the yarn was 4~,
15denier was 1,200 and an individual filament denier was
10, or 118 filaments per yarn end. Each filament has
a diameter of 0.0014" (0.0036 cm). Thermoplastic
elastomer impregnated sheets were prepared using the
device depicted in FIGs 14 and 15.
Resin coating system consisted of a resin
applicator tube moving reciprocatingly across the width
of the aligned Spectra ~00 yarn (a high strength
polyethylene yarn manufactured by Allied Corporation)
while the resin wa~ pumped through the tube. Liquid
resin comprised of a homogeneous blend of 50% Airflex~
120 and 50~ Airflex~ 410 by volume was used. Airflex
products, manufactured by Air Products and Chemicals,
Inc. Airflex~ 120 is a self-crosslinking vinyl acetate-
ethylene in the form of water based emulsion. The resin
30 coated prepreg was pulled through a pair of nip rolls
with a gap setting of 0.026" (0.066 cm), a gas fired hot
air oven of 12 feet (366 cm) long X 2 feet (61 cm) wide
at an air temperature of approximately 90C and after
drying wound on a spooler. The resin preimpregnated
sheet was peeled from the silicone release paper and
measured to be approximately 8" (20.3 cm) wide and the
equivalent diameter of the filament was 0.001~" (0.0036
cm). The ra~io of the thickness of the layer to the
. . .
:
, !
.:
1 31 2487
equivalent diameter o~ the filaments was 1.2 to 1.5. It
contained 74% Spectra-900 uniaxially oriented yarn and
26% AirflexD resin by weight.
The prepreg sheet was then cut into 8" (20.3 cm)
5 squares. A total of 164 layers were prepared, and were
stacked or laminated together with a O/90 yarn
orientation with each layer having filament length
perpendicular to the filament length of the adjacent
layers.
The laminated composite panel was then molded
between two parallel plates of 12" (30.5 cm) X 12" (30.5
cm) square at a temperature of 124C and a pressure of
420 psi (2900 kpa) for a period of 40 minutes. After
molding the panel and allowed to cool to room
temperature over a 30 minute period. The molded panel
was measured 8" (20.3 cm) X 8" (20.3 cm) X 0.249~ (0.632
cm) thick and weighed 248 grams which was equivalent to
an nADT" (total panel weight divided by surface area of
the panel) of 1.23 lbs/ft2 (6 kg/m2). The panel
contained approximately 74~ ECPC yarn with a yarn areal
density (AD) of 0.91 lbs-yarn / ft2 (4.44 kg-yarn/m2).
Each layer thickness was 0.0015n (0.0038 cm). The ratio
of the thickness of the layer to the equivalent diameter
of the filaments was 1.07.
The panel was then submitted to H. P. White
Laboratory, Inc. for ballistic testing. A V50 value of
2,131 ft/sec (650 m/sec) was obtained.
EXAMPLE 2
Example 1 was repeated with the exception that the
thickness of each layer in the molded composite panel
was 0.0032" ~0.008 cm) and the effective thickness of
; the filaments was 0.0014n (0.0036 cm). The ratio of the
thickness of the layer to the equivalent diameter of the
filament was 2.28. A total of 82 layers was used to
mold a panel of 8n (20.3 cm) X 8n (20.3 cm) X 0.259"
(O.658 cm) The panel weighed 273 grams which was
equivalent to an ADT of 1.35 lbs/ft2 (6.6 kg/m2). The
-33-
., I
..
1312487
panel contained approximately 68~ ECPE yarn with a yarn
areal density (AD) of 0.92 lbs-yarn / ft2 (4.5 kg-
yarn/m2). Each layer thickness of the molded panel was
0.0032" (0.0081 cm) which was approximately double the
layer thickness of 0.0015" (0.0038 cm) shown in Example
1. Ballistic testing showed that the panel has a V50 of
1,944 ft/sec (593 m/sec)
Example 3
A composite was prepared by dipping fabrics
composed of polyethylene in an ethylene vinylacetate
emulsion (Airflex 105 - a product of Air Products
Corporation). The fabrics used were plain weave, 14 x
14 ends/inch (5.5 x S.5 ends/cm) r Thirty (30) layers of
the dipped and coated fabrics were dried and were
subsequently molded together at 30 tons (27,240 kg)
force at 125C to produce a panel which was 12" x 12" x
0.25" (30.5 cm x 30.5 cm x 0.64 cm) thick. The panel
weighed approximately 595 grams which was equivalent to
an ADT of 1.31 lbs/ft2 (6.39 kg/m2). The panel
contained approximately 71% ECPC yarn with a yarn areal
density (AD) of 0.93 lbs-yarn/ft2 (4.55 kg-yarn/m2).
The thickness of each layer was 0.008" (0.02 cm) and the
equivalent diameter of the filament was 0.0014~ (0.0036
cm). The ratio of the thickness of the layer to the
equivalent diameter Oe the filaments was 5.7. The panel
was tested against ballistic projectiles and exhibits a
V50 of 1,570 ft/sec (480 cm/sec). The results indicate
that ballistic performance for fabric based composites
were far inferior to those of the composites of Examples
1 and 2.
,
Example 4
', Example 3 was repeated with the exception ~hat 22
layers of fabrics of plain weave 18 x 18 ends/inch (7 x
7 ends/cm) were used. The panel areal density was 6.02
kg/m2 and yarn areal density was 4.41 kg/m2 which are
-34-
.'
1 31 2487
composite o~ Comparative Example I. The ratio of layer
thickness to the equivalent diameter of the filament is
8.14. The panel has a measured V50 of 1,582 fps (483
m/sec).
Exa.~ple 5
A ballistic panel was prepared by molding a
plurality of sheets comprised of uni-directional high
strength extended chain polyethylene (ECPE) yarn, using
the procedure of Example 1, with a rigid thermoset
matrix Thermoset Epon 828, manufactured by Shell
Chemical Company. Impregnated sheets were prepared with
an EN-Tech filament winding machine manufactured by
Engineering Technology Inc. Using an En-Tech filament
winding machine, a CTC type yarn tension compensator and
a fluid metering pump, a liquid resin consisting of 100
parts by weight of Epon 828, 9.5% parts o~ TETA
(triethylenetetramine) and 15 parts of xylene was pumped
into a resin-container where the ECPE yarns were
coated. The coated yarns were then wound on a rotating
drum, 30" (76.2 cm) diameter, 48N (122 cm) length to
form a prepeg sheet. An infra-red lamp was used to
slightly heat the drum, and the sheet to approximately
50C for two hours to "B" stage the liquid epoxy
resin. The sheet was then cut into squares 112" x 12" x
0.005") ( 30.5 cm x 30.5 cm x 0.0127 cm). A total of 56
layers were prepared. The layers were oriented and
laminated in a 0, 90 configuration in which the linear
filament axis of adjacent layers was perpendicular. The
'~! laminated sheets were molded into a panel (12" x 12" x
0.279n) (30.5 cm x 30.5 cm x 0.709 cm) under a pressure
of 30 tons (27,2~0 kg) at a temperature of 125C for a
period of 1 hour, afterwhich the molded sheets were
cooled for 1 hr. The panel weighed 638 grams which was
equivalent to an ADT of 1.4 lbs/ft2 (6.9 kg/m2) and an
A~ of 0.92 lbs-yarn/ft2 (4.5 kg-yarn/m2). The
composition of the panel was approximately 66% yarn and
34~ r~sin. The thickness of each layer was 0.005"
-35-
' !
~,.
1 ~1 2487
(0.0127 cm). The ratio o~ the thickness of the layer to
the equivalent diameter of the filament was 3.57.
The panel was submitted to H. P. White Laboratory,
Inc. for ballistic testing. AV50 value of 1,969 fps
(597 m~sec) was obtained.
ComParative Ex mple I
Example 3 was repeated with the exception that 14
layers of fabrics of plain weave 28 x 28 ends/inch (11 x
11 ends/cm) were used. The panel areal density was 6.12
kg/m2 yarn areal density of the panel was 4.51 kg/m2
which are similar to the yarn areal density of the
composite of Comparative Example I. The ratio of layer
thickness to the equivalent diameter of the filament is
12.8 and the measured V50 was 1,448 fps (442 m/sec).
ComParative Example II
Using the procedure of Example 5, fourteen prepeg
layers having a ~hickness of 0.018" (0.046 cm) and in
which the ratio of the thickness of the layer to the
equivalent diameter of the filament is 13 were formed.
The layers were laminated in a 0, 90 configuration and
the laminated sheets were molded into (12" x 12~ x
0.256n) (30.5 cm x 30.5 cm x 30.5 cm). The panel
weighed 578 gram~ which was equivalent to an ADT of 1.3
lbs/ft2 (6.2. kg/m2) and an AD of 0.92 lbs-yarn/ft2
(4.~kg-yarn/m2). The composition of the panel was
approximately 72.5~ yarn and 27.5~ resin. The measured
V50 of the p~nel was 1,348 fps (408m/sec).
Comparative Example III
To better illustrate the advantages of this
invention and the critical relationship between the
ratio of thickness of the layer to the equivalent
diameter of the filament to the effectiveness of the
composite as protection against ballistics, the results
of the previous examples are set forth in a side by side
:,
. -36-
,
.
. . .
~ 3 1 2487
comparision in the following Table I. In the Table the
abbreviations have the following meanings:
(a) "T/ED" is the ratio o~ the thickness of the
layer to the equivalent diameter of the filament.
(b) "AD" is the total yarn weight divided by the
surface area of the panel expressed in Kg-yarn/m2.
(c) "ADT" is total panel weight divided by the
surface area of the panel.
(d) "V50" is the projectile velocity at which 50%
of the total projectiles wil be de~eated by the panels
being tested.
Table I
Exp No ~le T/ED 2 2 V o V50
(ka/m ) ~m ) (ft~sec) (m/sec?
1 Ex 1 1.07 4.44 6.0 2,131 650
2 Ex 2 2.28 4.5 6.6 1,944 593
3 ~ 3 5.17 4.55 6.39 1,570 480
: .20 4 Ex 4 8.14 4.43 6.02 1,582 483
Ex 5 3.57 4.5 6.9 1,969 597
6 ~ Ex I 12.8 4.51 6.12 1,448 442
7 ~ ~ II 13 4.5 6.2 1,348 408
i
;;
?
.
--37--
/
!
.,
:
