Note: Descriptions are shown in the official language in which they were submitted.
7~
B ISTIC-RESISTANT FINE WEAVE FABRIC ARI'ICLE
DESCRIPTION
BACKGROUND OF THE INVENTION
_
Ballistic resistant articles such as bulletproof
5 vests, curtains, mats, raincoats and umbrellas con-
taining high strength fibers are known. Fibers
conventionally used include aramid fibers such as
poly(phenylenediamine terephthalamide), nylon fibers,
glass fibers and the like. For many applications, such
10 as vests or parts of vests, the fibers are used in a
woven or knitted fabric.
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 an important requirement is
that the textile material have a high degree of heat
resistance; for example, a polyamide material with a
melting point of 255C appears to possess better impact
properties ballistically than does a polyolefin fiber
with equivalent tensile properties but a lower melting
point.
R. C. Laible; "Fibrous armor," Ballistic Materials
and Penetration Mechanics, Elsevier Scientific Pub-
lishing Co~, 1980; provides an overview of the ballistic
resistance performance of various fabrics. Liable
discloses that among different silk fabrics, a fabric
having a lower areal density would exhibit a small
increase in ballistic resistance to .22 caliber frag-
ments. See in particular, pp. 73-90 thereof. J. W. S.
Hearle, et al.; "Ballistic Impact Resi5tance of Multi-
Layer Textile Fabrics," NTIS Acquisition No. AD A127641,
(1981); disclose that among nylon abrics, those having
greater areal density exhibited increased ballistic
resistance. The findings of R. Sarson, et al.; 11th
Commonwealth Defense Conference on Operational Clothing
and Combat Equipment, India ~1975); were in agreement
with the findings of Hearle, et al. Weiner, et al.;
"Materials Evaluation Report No. 2781," ~.S. Army Natick
47~.
-2- ~
RSD Command Ma. ~1950); found no significant effect of
fabric areal density on balli5tic resistancQ, Figucia;
"En~rgy Absorption o~ Kevla~ Fabrics under ~alli~tic
Impact" NTIS Acguisition No. AD A090390, (1980); dis-
5 closes a limited study ~mploying Kevla~ fabric in which
balli tic resistance increased with a decrease in fabric
areal den~ity. However, thes~ reqult3 are not readily
interpreted becauc~ the type of fabric weavs was no~
held constant.
It is, thereforo, appar~nt that there i~ no gen-
erally applicabl0 relationship b~tween fabric areal
den ity and b~lli3tic re~istanc~O
~RIEF DESCRIPT~ON OF THE INVENTION
__ _ _ _ =
The pre ent invention provides an improved, flexi-
15 ble, ballistic-r~-Ri3tant ~ot~ fabric armor. The
fabric i3 compri~ed of ~t lea~t on~ network layer o~
high ~trength, ext~nded chain polyolefin ~ECP~ fibers
~elected ~rom the group consist~ng of ~xt~nded chain
polyethylen~ ~CPE3 and ext~nded chain polypropylene
t~CPP) flbers, extanded chain polyvinyl alcohol (PVA)
fiber, and e%~ended chain polyacrylonitrile fiber. The
fibers may be employe~ as such or arranged and con-
figured ~o form y~rn, th~ d~n~er of the fiber or yarn
being no more than about 500 and h~ving a tQn~ile modu-
lus of at 1~3t ~bout 200 g/d~nior. Th~ fiber or y~rnof the i3 ~mployod to fonm the fabric. Th~ fiber or
yarn o~ tho ~ab~lc arfl optionally coated with a low
modulu~ el~tomorlc mat0rl~1 which ha3 a ten~ile modulus
of le~s than about 6,000 p~i ~41,300 kPa).
Compared ~o conventionsl balli~tic-resistant fabric
structures, th~ fabric of th~ present invention can
advanta~eou31y provido a sel~ct~d l~vel o~ ballistic
protection whil~ employing a reduced weight o~ pro~ec-
tive material. Alternatively, the fabri~ o~ the pre~ent
3r invention can provid0 incr~a~ed ballistic protoction
when the ar~icl~ h~ a weight equal to the wei~h~ ef a
conventionally constructed piece of flexible fabric-
type, soft armor.
*Indicates Trademark
--3--
DETAILED DESCRIPTION OF THE INVENTION
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
5 thickness~ Accordingly, the term fiber includes mono-
filament and multifilament fiber, ribbon, strip, and the
like having regular or irregular cross-section.
A ballistic resistant fabric of the present inven-
tion includes at least one network comprised of a high
10 strength, ultra-high molecular weight, extended chain
polyolefin (ECP) fiber, extended chain polyvinyl alcohol
(PVA) fiber, and extended chain polyacrylonitrile ~PAN)
fiber. The fiber may be arranged and configured to form
a yarn, provided the yarn denier is not more than about
500 and has a tensile modulus of at least about 200
g/denier. This yarn can be employed to form the fabric.
To further improve the ballistic resistance of the
fabric, the fiber and yarn preferably have a denier of
less than about 300, and more preferably have a denier
f less than about 250. In addition, the fiber and yarn
have a tensile modulus which preferably is at least
about 1200 g/den, and more preferably is at least about
1800 g/den.
In another aspect of the invention, the fiber or
yarn of the network is coated with a low modulus elasto-
meric material comprising an elastomer to provide
improved ballistic resistance. This elastomeric
material has a tensile modulus oE less than about 6,000
psi (41,300 kPa), measured at about 23C. Preferably,
- 30 the tensile modulus of the elastomeric material is less
than about S,000 psi t34,500 kPa), more preferably, i5
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 elastomer of the elastomeric material (as
evidenced by a sudden drop in the ductility and
elasticity of the material) i5 less than about 0C.
Preferably, the Tg of the elastomer is less than about
~X747~1
-~ooc, and more preferably is less than about -50C.
The elastomer also has an elongation to breals (measured
at about 23C) of at least about 50%. Preferably, the
elongation to break is at least about 100%, and more
preferably, ;t is about 300% for improved pecformance.
USP 4,457,9~5 generally di6cusses the high
streng~h, high molecular weight, extended chain polyole-
fin fibers, employed in the present inven-tion, and the
disclosure of this patent is hereby incorporated by ref-
erence to the extent that it is not inconsistent here-
with. More particularly, suitable polyethylene fibers
are those having a molecular weight of at least 500,000,
preferably at least one million and more preferably
between two million and five million. Such extended
chain polyethylene (ECPE) fibers may be grown in
solution such as described in U.S. Patent No. 4,137,39
~o Meihuzen et al., or U.S. Patent No. 4,356,138 of
Kavesh et al., issued October 26, 1982, or a fiber spun
from a solution to form a gel structure, as described in
Germany Off. 3,004,699 and GB 2051667, and especially as
described in U.S. Patent No. 4,551,296 issued Nov.5,
1985 of Kavesh (see EP~, 64,167, published Nov. 10,
1982). 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 grams/
denier, preferably at least 20 grams/denier, more pref-
erab].y at least 25 grams/ denier and most preferably at
least 30 grams/denier. Similarly, the tensile modulus
of the fibers, 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 1,500
grams/denier. These highest values for tensile modulus
and tenacity are generally obtainable only by employing
solution grown or gel fiber processes. Many of the
fibers have melting points higher than the melting point
of the polymer from which they were formed. Thus, for
*Indicates Trademark
7~
example, ultra-high molecular ~eight polyethylenes of
500,000, one millio~ and two million generally have
melting points in the bulk of 138C. The highly
oriented polyethylene fibers made of these materials
5 have melting points 7 - 13C higher. Thus, a slight
increase in melting point reflects the crystalline per-
fection of the fiber~O Nevertheless, the melting points
of ~hese fibers remain substantially below nylon; and
the efficacy of these fibers for ballistic resistant
10 articles is contrary to the various teachings cited
above which indicate temperature resistance as a criti-
cal factor in selecting ballistic materials.
Similarly, highly oriented, extended chain poly-
propylene (ECPP) fibers of molecular weight at least
750,000, preferably at least one million and mor~ pref-
erably at least two million may be used. Such ultra
high molecular weight polypropylene may be formed into
reasonably well oriented fibers by the techniques pre-
scribed in ths various references referred to above, and
especially be the technique of U.S. Patent No. 4,551,296
filed January 20, 1984, of ~avesh et al. and commonly
as~igned. Since polypropylene is a much less crystal
line material than polyethylene and contains pendant
methyl group~ tenacity values achievable with poly-
propylene ara g~nerally subctantially lswer than thecorresponding values for polyethylene. Accordingly, a
suitable tenacity is at least 8 yrams/denier, with a
preferred tenacity being at least 11 grams/denier. The
ten ile modulus for polypropylene i~ at least 160
grams/denier, preferably at least 200 grams/denier. The
melting point of the polypropylene i5 generally raised
several degrees by the orientation proces3, such that
the polypropylene fiber preferably has a main melting
point o~ a~ least 168C, more preerably at least
170C. The particularly preferred ranges for the above-
described parameters can advantageously provide improved
performance in the final article.
B
~L~7~75~
~ s used herein, the terms polyethylene and poly--
propylene mean predominantly linea~ polyethylene and
polypropylene materials that may contain minor amounts
oE chain b~anching or comonomees not exceeding 5 modi-
fying units per lOO main chain carbon atom~, an-l that
may also contain admixed therewi~h not more than about
25 wt% of one or more polymeric additives such as
alkene-l-polymers: in particular, low density polyethy-
lene, polypeopylene or polybu~y]ene, copolymers con-
taining mono-olefins as primary monomers, oxidized
polyole-Eins, graft polyolefin copolymers and polyoxy-
methylenes, or low molecular weight additives such as
anti-oxidants, lubricants, ultra-violet screening
agents, colorants and the like which are commonl~ incor-
porated therewith.
In the case of polyvinyl alcohol (PV-O~I), PV-OH
fiber of molecular weight of at least about 500,000,
preferably at least about 750,000 more preferably
between about l,OOO,OOO and about 4,000,000, and most
preferably between about 1,500,000 and about 2,500,000
may be employed in the present invention. Particularly
useful PV-OH fibec should have a modulus of at least
about 300 g/denier, a tenacity of at least about 7
g/denier (preferably at least about lO g/denier, more
preferably at about 14 g/denier, and mo~t preeerably at
least about 17 g/denier), and an eneegy to break oE at
least about 22 joules/g. PV--OH fibers having a weight
average molecular weight of at least about 500,000 a
tenacity of at least about 300 g/denier, a modulus of at
least about 10 g/denieL, and an energy to break of about
Z2 joll].es/g are more useEul in producing a ballistic
resistant article. PV-OH fiber having such properties
can be produced, f OL e~ample, by the process disclosed
in U.S. Patent No. ~,599,267, filed January ll, L9~4
issued July 8, 19~6 to Kwon et al. and commonly assigned.
In the case of polyacrylonitrile (PAN), PAN fiber
of molecular weight of at least about ~OO,000, and
preferably at least l,OOO,OO0 may be employed.
.~
~7~7S~
Particularly useful PAN fiber should have a tenacity o~
at least about 10 g/denier and an energy to break o at
least about 22 joule/g. PAN fiber having a mol~cular
weight of at leas~ about 400,000, a tenacity oS at least
5 about 15-20 g/denier and an energy to break of at least
about 22 joule/g is most useful in producing ballistic
resistant articles; and such fibers are disclosed, for
example, in U.S. 4,535,027.
For improved ballistic resistance of the fabric
10 article, the fiber has a tensile modulus which pref-
erably is at least about 500 g/den, more preferably is
at least about 1000 g/den and mo5t preferably is at
least about 1300 g/den. Additionally, the ECP fiber has
an energy-to-break which preferably is at least about ~2
15 J/9~ more preferably is at least about 50 J/g and most
preferably is at least about 55 J/g.
In the fabric of the invention, the fiber network
can have various configurations. For example, a
plurality of fibers can be grouped together to form a
twisted or untwist~d yarn. The fibers or yarn may be
formed a~ a felt, knitted or woven ~plain, basket, satin
and crow ~eet weaves~ etc.) into a network~ or ~ormed
into a network by any of a variety of conventional tech-
nique~. For example, the fiber~ may be formed into
25 wo~en or nonwoven cloth layers by conventional tech-
niques.
A preferred embodiment of the present invention
includes multiple laycrs of ~lastomeric material coated
fiber networks. The l~yer~ individually retain the hi~h
flexibility char~cteristic of textile fabrics and remain
separate ~rom each other. The multilayer article exhi-
~its the flexibility o~ plied fabric~, and is readily
dis~inguishable from the compositc structure6 de-ccribed
in co-pending U.S. Patent No. 4,623,574
of Harpell, et al. and entitled "Ballistic Resistant
Composite Article~ ~Attorney Docket No. 82-2334). Vests
and other articles of clothing comprised of multiple
layers o fabric constructed in accordance with the pre~
~ ;~7D~75~
--8--
sent invention have good flexibility and comfort coupled
with excellent ballistic protection.
The flexibility of the ballistic resistant fabric
structures of the present invention is demonstrated by
5 the following test: A 30 cm square fabric sample com-
prised o~ multiple fabric layers having a total areal
density of 2 kg/m2, when clamped in a horizontal orien-
tation along one side edge, will drape so that the oppo-
site side edge is at least 21 cm below the level of the
10 clamped side.
The multiple layers of fabric may be stitched
together to provide a desired level of ballistic pro-
tection; for example, as against multiple ballistic
impacts. However, stitching can reduce the flexibility
Coated fibers may be arranged (in the same fashion
as uncoated fibers) into woven, non-woven or knitted
fabrics. The fabric layers may be arranged in parallel
arrays and/or incorporated into multilayer fabric arti-
cles. Furthermore, the fibers, used either alone orwith coatings, may be wound or connected in a conven-
¦ tional fashion.
The proportion of coating in the fabric may varyfrom relatively small amounts (e.g. 0.1~ by weight of
fibers) to relatively large amounts (e.g. 60% by weight
of fibers), depending upon whether the coating material
has any ballistic-resistant properties of its own (which
is generally not the case) and upon the rigidity, shape,
heat resistance, wear resistance, flammability resis-
tance and other properties desired for the fabric. Ingeneral, ballistic-resistant fabrics of the present
invention containing coated fibers should have a rela-
tively minor proportion of coating (e.g. 0.1-30%, by
weight of fibers), since the ballistic-resistant proper-
ties are almost entirely attributable to the fiber.Nevertheless, coated fabrics with higher coating con-
tents may be employedl
~7~751
_g
The coating may be applied to the fiber in a
variety of ways. One method is to apply the neat resin
of the coating material to the stretched high modulus
fibers either as a li~uid, a sticky solid or particles
5 in suspension or as a fluidized bed. Alternatively, the
coating may be applied as a solution or emulsion in a
suitable solvent which does not adversely affect the
properties of the Eiber at the temperature of applica-
tion. While any liquid capable of dissolving or dis-
10 persing the coating polymer may be used, preferredgroups of solvents include water, paraffin oils,
aromatic solvents or hydrocarbon solvents, with illus-
trative specific solvents including paraffin oil,
xylene, toluene and octane. The techniques used to
15 dissolve or disperse the coating polymers in the sol-
vents will be those conventionally used for the coating
of similar elastomeric materials on a variety of sub-
strates.
j Other techniques for applying the coating to the
i 20 fibers may be used, including coating of the high modu-
lus precursor (gel fiber) before the high temperature
stretching operation, either before or after removal of
the solvent from the fiber. The fiber may then be
stretched at elevated temperatures to produce the coated
fibers. The gel fiber may be passed through a solution
of the appropriate coating polymer (solvent may be
paraffin oil, aromatic or aliphatic solvent) under
conditions to attain the desired coating~ Crystalliza-
tion of the high molecular weight polyethylene in the
~ 30 gel fiber may or may not have taken place before the
fiber passes into the cooling solution. Alternatively,
the fiber may be extruded into a fluidized bed of the
appropriate polymeric powder.
If the fiber achieves its final properties only
after a stretching operation or other manipulative
process, e.g. solvent exchanging, drying or the like, it
is contempIated that the coating may be applied to the
prec~rsor material. In this embodiment, the desired and
--10--
preferred tenacity, modulu~ and other propertie~ o~ the
fiber should be judged by continuing the manipulative
process on tha fib~r precur~or in a manner corr~ponding
to ~hat employed on the coated fiber precur~or. Thus,
5 for example, if the coating i~ applied to the xorog~l
fiber described in U.S.Patent No. 4,623,574
of Kave~h et al,, and th~ coated xerogel fiber i9 then
stretched under d~fined temp~rature and ~tretch ratio
condition~, th~ applicable fib~r tena~ity and fiber
10 modulu~ value~ would b~ the m~ured values of ~n
uncoated xorogel ~ib~r which i3 ~imilarly strQtched.
A preferr~d co~ting t~chnique i~ to fonm a n~twork
layer and thon dip tho n~t~ork into a bath of ~ ~olution
containing th~ 1GW modulu~ ~la~tomeric co~ting
15 mat~rial. Evaporation of the ~olv2nt produce~ an
ela~tomeric materlal coae~d f~bric. Th~ dip~ing pro-
cedure ~ay b~ rop~at~d a~ r~quired to plac~ a d~3ired
amount of ol~tom~ric coAting on th~ fibor~.
A wide vari~ty of ~la~tomeric materials and
formulation~ ~ay b~ utiliz~d in this inv~ntion. The
e ~ential r0quircm~nt i~ th~t th~ elastomeric material
havo th~ ~propr~aSoly low ~odulu~. Repr~ntative
ex~mple~ o ~u~t~bl~ ela~to~0r~ of tho olautom~ric
mat~ri~l h~v~ th~ir ~tructur~ rop~rti~ ormulations
tog~th~r with ~ro~linking procedur~ ~u~marized ~n th2
~ 9~L __ ~ , Volumo 5 in the ~ction
~lA~o~r~-Syn~hQtic~ (Jolln ~ y ~ Son~ Inc., 1964).
Fo~ ~xampl~, any of tho ollowlng ~a~eri~l~ m~y be
employads polybut~dl~n~, polyi~opren~, natur~l rubber,
sthyl~n~-pro~yl~n~ copolym~r~, e~hyl~n~-propylene-diene
terpolymor~, poly3ulfid~ polym~rs, ~olyur~than~ ol~to-
mar~, chloro~ulfonated polye~hylen~, polychloropr0ne,
plaeticized polyvinylchlorido u~ing dioctyl phtha~ or
oth~r pla~ic~r~ w~ll known in tho art, but~di~ne
~crylonitril~ ola~tomer~, poly(l~obutyl~n~-co-is0pr~no),
polyacrylat~3, polyo3~rs, poly~th~r~, ~luoro~la~tom~r5,
~ilicone ~la~tom~rs, thQrmopla3~ic ~ tom~r~, copoly-
m~rs o~ ethyl~n~.
4~5~L
Particularly u~ful ela~tomers ar~ block copolym~rs
o~ con~ugat~d di~ne~ and vinyl aromatic ~onomers.
Butadien~ ~nd isopren~ ar~ prQ~rred conJugated dl~n~
ela~tomers. 5tyr~ne, vinyl toluene and t~bu~yl ~tyrene
5 are preferr~d conjugate~ aromatic monomer~. alock
copolym~r~ lncorporating polyi~oprene may b~ hydrogena-
t~d to produc~ th~rmopla~tic ~la~tomer~ having saturated
hydsocarbon ~la~tomor s~g~a~t~. Th~ polymers may be
simpl~ tri~block copolymer~ o the type A-~-A, multi-
10 block copolym~r~ of the typ~ ~AB)n(n~2-10) or radial
configuration copolymers of th~ typ~ R-(~A)x(x~3-150);
wh~rcin A i~ a block from a polyvinyl aromatic monomer
~nd ~ i~ a block from a conjugatsd di~n~ ~la~tomer.
M~ny o tho~ polym~rs ~o produc~d commerci~lly by the
15 Shell Ch~mlc~l CoO and d~crib~d $n th~ bull~tin ~Rraton*
Th~rmopl~tic Rubbor~, SC 68~
Mo~t pref~rably, th~ ~la3to~sric mat~rial consi~ts
o at l~aRt ono o~ ths abov~ m~ntion~d ela~tomer~. Th~
low modulus ~1~ to~oric ~at~rial m~y ~l~o include fil-
lar~ such as ca~bon black, ~ilica, et~. and m~y b~ext~nd~d with oil~ and vulc~nl2~d by ~ulfur, peroxide,
m~tal oxid~, or radiation curo ~y$tom~ u~ing msthod~
w~ll known to rubbor t~chnologi~t~ nd~ of differ~n~
ela~tomeric matorial~ m~y b~ u~d tog~ther or on~ or
25 mor~ ~lA~to~r ~at~ri~l~ ~ay b~ bl~ndod with on~ or ~ore
th0r~0~1a~tlc~. High d~n~ity, low d~n~ity, and linaar
low don~ity polyothylon~ ~ay bo ~ros~-llnk~d to obtain a
~atrlx mat~rial o~ appropri~t~ prcport~o~, ~ith~r alone
or a~ bl~nd~. In ~ry ~n~tanco, th~ ~odulu~ o~ the
co~tin~ 3hould not ~xc~d ~bout 6000 p~i (41,300 kPa),
pr~f~rably i~ s than about 5000 p~i (34,500 kPa),
more preferably 1~ than 100 p~i ~6900 kP~) and mo~t
pref~rably i~ l~ss than abou~ 500 p~i (3~50 kPa).
A coatod yarn can b2 produc0d by pulling a group of
fibers through th~ ~olution o low modulu~ olastomoric
mat~ri~l to ~u~t~nti~lly coat ~ch of tho lndi~idual
fib~r~, and then ~v~por~ting t~ ~olv~nt to form th~
coat~d yarn. Th~ yarn can th~n ~ employ~d to form
*Indicates Trademark
75~
coated fabric layers which in turn, can be used to form
desired multilayer fabric structures.
Multilayer fabric articles may be constructed and
arranged in a variety of forms. It is convenient to
5 characterize the geometries of such multilayer fabrics
by the geometries of the fibers and then to indicate
that substantially no matri~x material, elastomeric or
otherwise, occupies the region between fabric layers.
One such suitable arrangement is a plurality of layers
10 in which each layer is comprised of coated fabric fibers
arranged in a sheet-like array and successive layers of
such fabrics are rotated with respect to the previous
layer. An example of such multilayer fabric structures
is a five layered structure in which the second, third,
fourth and fifth layers are rotated +45~, -45, 90 and
o, with respect to the first layer, but not necessarily
in that order. Other exarnples include multilayer fab-
rics with alternating fabric layers rotated 90 with
respect to each other.
In various forms of the fabric of the invention,
I the fiber network occupies different proportions of the
total volume of the fabric layer. Preferably, however,
the fiber network comprises at least about 50 volume
percent of the fabric layer, more preferably between
about 70 volume percent, and most preferably at least
j about 90 volume percent. Similarly, the volume percent
I of low modulus elastomeric material in a fabric layer is
preferably less than about 15 Vol %, more preferably is
less than about 10 Vol %, and most preferably is less
than about 5 Vol %.
The specific weight of the fabric layer is
expressed in terms of the areal density (AD)o This
areal density corresponds to the weight per unit area of
the fabric layer. Preferably, the fabric layer areal
density is less than about 0.3 kg/m2; more preferably
the areal density is less than about 0.2 kg/m2 and most
preferably, the areal density is less than about 0.1
kg/m2 -
75~
-13-
It has been discovered that coated fabric comprised
of strip or ribbon tfiber with an aspect ratio, ratio of
fiber width to thickness, of at least about 5) can be
even more effective than other forms of fiber or yarn
5 when producing ballistic resistant articles. In
particular embodiments of the invention the aspect
ratio of the strip is at least 50, preferably is at
least 100 and more preferably is at least 150 for
improved performance~ Surprisingly, even though an ECPE
10 strip material had significantly lower tensile proper-
ties than an ECPE yarn material of the same denier but
generally circular cross section, the ballistic resis-
tance of the coated fabric ccnstructed from ECPE strip
was significantly higher than the ballistic resistance
15 of the coated fabric constructed from the ECPE yarn.
Most screening studies of ballistic composites
; employ a .22 caliber, non-deforming steel fragment of
specified weight, (19 grains) hardness and dimensions
! (Mil-Spec. MIL-P-46593A(ORD)). Limited studies were
20 made employing .22 caliber lead bullet weighing 40
grains. The protective power of a structure is normally
expressed by citing the impacting velocity at which 50%
of the projectiles are stopped, and is designated the
V50 value.
Usually, a flexible fabric, "soft" armor is a
multiple layer structure. The specific weight of the
multilayer fabric article is similarly expressed in
terms of the areal density (AD). This areal density
corresponds to the weight per unit area of the multiple
layer structure.
To compare structures having different V50 values
and different areal densities, the following examples
state the ratios of (a) the kinetic energy tJoules) of
the projectile at the V50 velocity, to (b) the areal
density of the fabric tkg/m2). This ratio is designated
as the Specific Energy Absorption tSEA).
The following examples are presented to provide a
more complete understanding of the invention. The
~7~
-14-
~,pecific technique~, conditions, materials, proportion~
and reported data ~et forth to illustrate the principles
of the invention ar~ exemplary and should not be con-
strued a~ limiting the ~cope of th~ invention,
EX~MPLE F-l
A low areal den ity (0.1354 kg~m~) pl~in weave
fabric having 70 end~/inch (28 end3/cm) in both the warp
and fill direetion was pr~pared from untwisted yarn
si2~d with low mol~cular weight polyvinyl~lcohol on a
10 Crompton and Rnowl~ *box loom. After weaving, the
sizing was removed by washing in hot water (60 72~C).
The yarn used for ~abri~ preparation had 1~ filaments,
yarn denier of 203, modulu~ of 1304 g~denier, tenacity
of 28,4 g/denier, alongation of 3.1~ and energy~o-break
15 f 47 J/9. A multilayer fabric targct F-l wa compri ed
of 13 layer3 o f~bric and had a total areal density
(AD) o~ 1.76 kg/m2O All yarn tcn~ile properti~ wera
me~sured on an In~tron te~ter using tire cord b~rrel
clamp~, gauge lsngth of 10 inch~ (25.4 cm), and cross-
head speed of 10 inches/~inute (25.4 cm/min).XAMPLE F-2
Fabric wa~ woven in a manner similar to that u3ed
for pr~paration o fabric F~ xc~pt that a higher
deni~r yarn (de3ignat0d SY-l) having 118 filament~ and
approxim~tely 1200 d~niar, 1250 9 denier modulu~, 30 9
denier tenacity, and 60 J/g ener~y-to-break) wa~ used to
produce ~ pl~in wea~e ~abric having areal den~ity of
approximately 0.3 kg/m2 and 28 end~/inch (11 ends/cm).
Slx layer~ of this fabric were a3semblad to prepare a
balli~tic targot F-2.
* Indicates Trademark
~, ~
~.~'7~'75~
-15-
EXAMPLE F-3
A 2 x 2 basket weave fabric was prepared from our
standard yarn (SY-l) having 34 ends/inch (13.4
ends/cm)~ The yarn had approximately 1 turnJinch and
5 was woven without sizing. The fabric areal density was
0,434 kg/m2 t and a target F-3 comprised of 12 fabric
layers had an ar~al density of 5.21 kg/m2.
EXAMPLE F-4
This fabric was prepared in an identical manner to
10 that of Example F-l except that the yarn used had the
following properties- denier 270~ 118 filaments, modulus
700 g/denier, tenacity 20 g/denier and energy-to-break
52 J/9O The fabric had an areal density of 0.1722
kg/m2~ ~ target F-4 was comprised of 11 layers of this
fabric.
EXAMPLE F 5
Yarn SY-l wa~ used to prepare a high denier non-
crimped fabric in the following manner. Four yarns were
combined to form single yarnQ of approximately 6000
denier and these yarns were used to form a nvn-crimped
fabric having 2B ends~inch in both the warp and fill
~irection. Yarn SY 1, having yarn denier of 1200 was
used to knit together a multilayer structure. Fabric
areal density was OL705 kg/m2. A ballistic target F-5
25 wa~ compri~ed of seven layers of this fabric.
EXAMPLE F- 6
Eight one-foot-square pieces of Kcvla~ 29 ballistic
fabric, manufactured by Clark Schwebel, were assembled
to produce a target F-6 having an areal den~ity of 2.32
kg/m2, The fabric waR designated Style 713 and was a
plain weave fabric comprised of 31 ends per inch of
untwisted 1000 denier yarn in both the warp and fill
direction.
EXAMPLE F-7
This sample was substantially identical to sample
F-6, except that ~ix layers of ~evla~ 29 were used to
produce a target F-7 having a total target areal density
of 1.74 kg/m2.
*Indica-tes Trademark
~L~7~75~
-16-
EXAMPLE FB 1
Ballistic Results Against .22 Caliber Fragments
Fabric targets one-foot-square (30.5 cm) and
comprised of multiple layers of fabric were tested
against .22 caliber fragments to obtain a V50 value.
Fabric properties are shown in Table lA and ballistic
results are shown in Table lB.
TABLE lA
FABRIC PROPERTIES
10 E~m~le Yarn Yarn Yarn W~ave
Denier Modulus Energy-
(g/den) to-break (J/g)
F-l 203 1304 47 Plain
F-4 270 700 52 Plain
15 F-2 1200 1250 60 Plain
F-3 1200 1250 60 2x2 Lasket
F-5 6000 1250 60 non-cr~ed
TABLE lB
Ballistic Results Against .22 Caliber Fra~ments
~le Fabric AD Target ~D V50 SEA
No. (kg/m2) _ (kg/m ) _ (ft/sec) (J/m2
F-l 0.1354 1.76 1318 50.5
F-4 0.1722 1.89 951 24.4
25 E`-2 0.316 1.90 1165 36.9
F-3 0.434 5.21 1318 17.1
F-5 0.705 4.95 1333 18.0
Sample F-l gave the best ballistic results, sug-
gesting that a combination of high modulus yarns and
~ 30 fine weave fabric comprised of low denier yarn has par-
ticular merit.
Example FB-2
Ballistic Results A2~1n .22 Caliber Lead Bullets
Sample targets were evaluated against .22 caliber
lead bullets, and the striking and exit velocities of
the bullets were individually recorded. ~abric proper-
ties are shown in Table 2A, and ballistic results are
shown in Tables 2B and 2C.
~ ~7~75~
~17~
Table 2A
Properties o Plain Weave Fabric~
Example Yarn
TypeD~nier Mbdulus Energy~to-Bre~k
(g/den.) _(J/~?
F~l ECPE 203 1304 47
F 4 ECPE 270 700 52
F 6 Kevlar*29 1000 700 29
F-7 Kevla~ 29 1000 700 29
13
Table 2B
Ballistic Results Against .22 Caliber Bullets
~xample Fabric AD Target AD V(in~ V(out) SEA
( kQhn ) _ _( ks~ (Jm2/kg
15 F-l 0.1354 1.76 1212 0 100.5
1198 9~2 32.2
1194 838 ~9.5
1193 958 34.6
11~1 0 93.8
1148 0 90 2
- 20
7 0.29 1.741175 0 95.8
11~6 760 57.5
120~ 1040 25.5
1176 963 31.6
1216 9~6 43.1
F-6 0.29 2.231198 0 74.6
1214 721 49.6
1181 0 72.5
1200 589 56.9
1181 0 72.5
F-4 0.1722 1.89 1200 1100 14.6
1184 1091 13.5
1225 1137 13.2
1144 1037 14.8
*Indicates Trademark
'~.
~.Z74~5~
--18--
TABLE 2C
Sample A~erage SEA 96 Bullets
__ ( iC~m2 ) _ Sto 2ped
F-l 66 .8 50
5F-7 50 . 0 20
F-6 65 . 2 60
F-4 14.0 0
A eomparison of the ballistic results of examples
F-l and F-4 indicates that higher modulus yarns are much
10 superior for ballistic protection against .22 caliber
bull~ts when woven into a fine weave fabric comprised of
low denier yarn. These data also indicate that the F-l
f~bric is ~uperior to Kevla~ ballistic fabric (F-7) in
current use, with respect to both the percen of bullets
15 stopped and the average SEAo
EXAMPLE C-l
The individual fabric layers of the target des-
cribed in Example F-l, after ballistic testing against
both 22 caliber fragments and .22 caliber bullets, was
20 soaked overnight in a toluene ~olution o~ Kraton*D1107
(50 g/litre). ~rato~ D1107, a commercial product of the
Shell Chemical Company, is a triblock copolymer of the
polystyrene~polyisoprene-polystyrene having about 14 wt
% styrene, a tensile modulus of about 200 p~i (measured
25 at 23C~ and having a Tg o~ approximately -60C. The
fabric layers w~re removed from the solvent and hung in
a fume hood to allow the solvcnt to cvaporate. A target
C-l, contalning 6 wt ~ elastomer, was reassembled with
13 fabrlc layer~ for additional ballistic testing.
EXAMPLE C-2A and C-2B
Six one~foot-square fabric layers of the type
describad in example F-2 were assembled together and
designated sample C-2A.
Six fabr1c layers identical to thos2 o~ example C-
2A, were immersed in a toluene solution of Xraton*G1650
(35 g/litre) for three days and were hung in a fume hood
to allow solvent evaporation. Xraton*G1650, a triblock
thermoplastic elastomer produced by Shell Chemical Co,
.~ *Indlcates Trademark
7S~
--lg--
has the structure polystrene-polyethylenebutylene-poly-
styrene and has about 29 wt ~ styrene. Its tensile
modulus is about 2000 psi ~measured at 23C), and its Tg
is approximately -60C. The panel layers each had an
5 areal density of 1.9 kg/m2 and contained 1 wt % rub-
ber. The layers were assembled together for ballistic
testing and were designated sample C-2B.
EXAMPLES C4 ~C10
Each target in this series was comprised of six
10 one-foot-square layers of the same fabric, which had
been prepared as described in example F-2. The f iber
areal density of these targets was 1.90 kg/m2.
Sample C-~ was compri~ed of untreated fabric.
Sample C-5 was eomprised of fabric coated with 5.7
15 wt % Krato* G1550. The fabric layers wsre soaked in a
toluene solution of the Krato~*1650 ~65 g/litre) and
~hen assembled after the solvent had besn evaporated.
Sample C-6 was prepared in a similar manner to
sample C-5 except that after the sampla had been dipped
and dried, it was redipped to produce a target having
11.0 wt % coating.
Sample C-7 was prepared by sequentially dipping the
fabric squares in three ~olutionq of ~raton*
D1107/dichloromethane to produce a target having 10.8 wt
25 % coating. Fabric layers were dried between succe~sive
coating~. Concantration~ of the Kraton*D1107 thermo-
plastic, low modulus elastomers in the three coating
solutions were 15 g/L, 75 g/L and 15 g~L, in that order,
Sample C-8 was prepared by dipping fabric layers
into a colloidal silica solution, prepared by adding
three volume parts of de-ionized water to one volume
part of Ludo~AM, a product of DuPont Corporation which
i9 an aqueou3 colloidal ~ilica dispersion having 30 wt
silica of average particle ~ize 12 nm and surface area
of 230 m2/~.
Sample C-9 was prepared from electron beam irradi-
ated fabric irradiated under a nitrogen atmosphere to 1
Mrad using an Electracurtain*apparatus manufactured by
*Indicates Trademark
~7~
-20-
Energy Sciences Corporation. The fabric squares were
dipped into a Eudox~AM solution diluted with an equal
volume of deionized water.
Sample C10 was prepared in a ~imilar manner to
5 ~xample C-9, except that the fabric was irradiated to 2
Mrads and was subsequently dipped into undiluted Ludox*
AMo Thi~ level of irradiation had no significant effect
on yarn tensile poroperties.
EXAMPLE C-ll
A plain weave ribbon fabric was pr2pared from poly-
ethylen2 ribbon 0.64 cm in width, having modulus of 865
g~denier and energy-to-break of 46 J/g. Fabric panels
~layers) one-foot-square (30.5 cm) were soaked in dich-
loromethane solution of Kraton~D1107 (lOg/litre) for 24
15 hour~ and then removed and driedO The 37 panels, having
a total ribbon areal density of 1.99 kg/m2 and 6 wt ~
rubber coating were as~embled into a multilayer target
sample C-ll for balliQtic testing.
EXAMPLE CB-l
As shown below, the damaged target C-l stopp~d all
.22 caliber bullets fired into it. TheRe results were
superior to those obtained for the same fabric before it
was rubb~r coated and much superior to the Revla~ bal-
listic fabrics. (See Example FB-2,)
25 V(in) V~out) SEA
~ft/sec)(ft~sec) ~Jm2
1218 0 101.5
1182 0 95.6
1172 0 94.0
1169 0 93O5
1159 0 91.9
Although this fabric wa~ highly damaged, a .22
calib2r fragment wa3 ~ired into thc target at an
impacting v210city of 1381 ft/sec and was stopped,
corresponding to an SEA of 55,5 Jm2/kg. This result
indicates that th~ low modulus rubber coating also
improves ballistic rssistance against .22 caliber
fragment~. The VS0 value or the uncoated fabric
*Indicates Trademark
75~L
-21-
(example F-l) was 1318 ft/sec, corresponding to an SEA
of 50.5 Jm2/kg. The highest partial penetration
velocity for Example F-l was 1333 ft/sec, corresponding
to an SEA of 51.7 Jm2~kg.
~inally, thi~ highly damaged sample was ballisti-
cally tested against .38 caliber bullets according to
test procedure NILECJ-5TD-0101.01. Three .38 caliber
bullets having impacting velocities of 780, 803 and 831
ft/sec, respectively, were stopped by the target, and
10 the bullet îndentations into the clay backing were less
than 1~2 inchesO The target sample easily me~ the
spacification. Even though this target had an areal
density of only 1.76 kg~m2, it met or exceeded the U.S.
Military specifications for Type 1 and Type lA Kevla~ 29
15 target~ having a greater areal density of 2.24 kg/m2
~Specification MIL-C-44050). This wae accomplished in
spite of the fact that the total number of ballistic
impacts on this single target greatly exceeded reguire-
ments. It is, therefore, quite apparent that the fabric
2~ articles of the present invention can provide required
levels of ballistic protection while employing a lighter
weight of material.
EXAMPLE B-2
Targets C-2A and C-2B were marked with a felt pen
to divide it ~nto two, 6in X 12in rectangles. The V50
value~ for each target wa~ determined against .22 cali
ber fragments using only one of tha rectangles (one half
of the target). Each target was immersed in watar for
ten minutes, and the hung for three minutes before
determination of a VS0 value using the undamaged rec-
tangle. Data shown below clearly indicate that the
small ammount of rubber coating ha~ a beneficial effect
on the balli~tic performance of the fabric tar~et when
wet.
*Indicates Trademark
~4~5~
-22-
V50 (~t/s~c)
Target C-2A Target C-2B
(untreated) _ (lwt ~ Elastomer)
DRY 1175 12S0
5 WET 985 1200
EXAMPLE CE--3
(Ballis~ic Studies uQing 28X28 plain
weave, coated fabrics)
Ballistic testing usin~ .22 caliber fragments
10 against six-layer fabric targets having fiber areal den
sity of 1.90 kg~m2 showed that elastomeric coatings
improved ballistic performance, but silica coatings were
inefective.
15 Sample CoatingV50 SEA
(ft/sec)(~m2/k~)
C-4 none 1165 36.9
C-5 Kraton*G1650 1228 41.0
(5,7 wt %)
20 C-6 Rrato~ G1650 1293 45.4
(11 wt %)
C-7 Krato~* D1107 1259 43.1
110.8 wt %)
C-8 Silica1182 38.0
(3.4 wt ~
C-9 Silica1150 3600
(7.2 wt %)
C-10 Silica1147 35.8
(17 wt ~)
EXAMPLE CB-4
Sample C-ll was tested ballistically and exhibited
a V50 value of 1156 ft/sec determined against .22
caliber fragments. This corresponded to a SEA value of
34.4 Jm2/kg. This target exhibited good ballistic
properties in spite of the fact that ribbon ~tress-
strain properties were inferior to those of most of ~he
ECPE yarns used in this studyO
*Indicates Trademark
a
'. ~ ~
;-
:~I.X~747~3
-23-
A V50 value of 1170 ft/sec against .22 caliber
bullets was obtained for sample C-ll, whereas samples C-
5, C-6 and C-7 allowed bullets having a striking
velocity of approximately 1150 ft/sec to pass through
5 the target with a velocity loss of less than 250
ft/sec. This indicates that the ribbon fabric is par~
ticularly effective against .22 caliber lead bullets~
Having thus described the invention in rather full
detail, it will be understood that these details need
10 not be strictly adhered to but that various changes and
modifications may suggest themselves to one skilled in
the art, all falling within the scope of the invention
as defined by the subjoined claims.
- 20
.1
