U.S. patent application number 13/545503 was filed with the patent office on 2013-10-31 for composite material; a ballistic resistant article made from same and method of making the article.
This patent application is currently assigned to E I Du Pont De Nemours and Company. The applicant listed for this patent is Jeffrey Alan Hanks, John Henry McMinn, Bryce Vanarsdalen, Brian Charles West. Invention is credited to Jeffrey Alan Hanks, John Henry McMinn, Bryce Vanarsdalen, Brian Charles West.
Application Number | 20130284004 13/545503 |
Document ID | / |
Family ID | 49476193 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130284004 |
Kind Code |
A1 |
Hanks; Jeffrey Alan ; et
al. |
October 31, 2013 |
COMPOSITE MATERIAL; A BALLISTIC RESISTANT ARTICLE MADE FROM SAME
AND METHOD OF MAKING THE ARTICLE
Abstract
A fiber reinforced resin composite for ballistic protection
comprising a plurality of first and second plies wherein the first
and second plies further comprise a woven fabric and a polymeric
resin. The fabric has a Russell tightness factor of from 0.2 to 0.7
and a cover factor of at least 0.45, The fabric is impregnated with
the resin, the resin comprising from 5 to 30 weight percent of the
total weight of fabric plus resin. The fabric of each first and
second ply comprises regions wherein the fabric is distorted from
an orthogonal woven state by a distortion angle of least 30
degrees. The composite may further comprising a third ply having a
surface area no greater than 50% of the surface area of a first and
second ply. The ratio of the number of first plus second plies to
the number of third plies is from 2:1 to 12:1.
Inventors: |
Hanks; Jeffrey Alan;
(Midlothian, VA) ; West; Brian Charles;
(Wilmington, DE) ; McMinn; John Henry; (Newark,
DE) ; Vanarsdalen; Bryce; (Cherry Hill, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hanks; Jeffrey Alan
West; Brian Charles
McMinn; John Henry
Vanarsdalen; Bryce |
Midlothian
Wilmington
Newark
Cherry Hill |
VA
DE
DE
NJ |
US
US
US
US |
|
|
Assignee: |
E I Du Pont De Nemours and
Company
Wilmington
DE
|
Family ID: |
49476193 |
Appl. No.: |
13/545503 |
Filed: |
July 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13274590 |
Oct 17, 2011 |
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13545503 |
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Current U.S.
Class: |
89/36.02 ;
156/264; 428/212 |
Current CPC
Class: |
B32B 2571/02 20130101;
A42B 3/063 20130101; F41H 5/0485 20130101; B32B 5/024 20130101;
B32B 5/26 20130101; F41H 1/08 20130101; B32B 7/02 20130101; B32B
2260/021 20130101; B32B 5/12 20130101; B32B 38/0004 20130101; A42C
2/00 20130101; B32B 2260/046 20130101; B32B 2307/718 20130101; Y10T
156/1075 20150115; B32B 2305/188 20130101; B32B 2309/06 20130101;
Y10T 428/24942 20150115; B29L 2031/4821 20130101; B29L 2031/768
20130101; B29C 70/222 20130101; B29C 70/56 20130101 |
Class at
Publication: |
89/36.02 ;
428/212; 156/264 |
International
Class: |
F41H 1/08 20060101
F41H001/08; B32B 38/00 20060101 B32B038/00; B32B 5/12 20060101
B32B005/12; B32B 7/02 20060101 B32B007/02 |
Claims
1. A contoured fiber reinforced resin composite for ballistic
protection comprising a plurality of first and second plies
arranged such that a plurality of first plies is followed by a
plurality of second plies, wherein, yarn orientations in the weave
of each plurality of plies, are substantially aligned to each
other, and wherein the plurality of first and second plies further
comprise (i) a woven fabric made from a plurality of polymeric
yarns having a yarn tenacity of from 15 grams per dtex to 50 grams
per dtex and a modulus of from 200 grams per dtex to 2200 grams per
dtex, and (ii) a polymeric resin, wherein (a) the fabric has a
Russell tightness factor of from 0.2 to 0.7, (b) the fabric has an
areal weight of from 80 gsm to 510 gsm, (c) the fabric has a cover
factor of at least 0.45, (d) the fabric is impregnated with the
resin, the resin comprising from 5 to 30 weight percent of the
total weight of fabric plus resin, and (e) the fabric of each first
and second ply comprises regions wherein the fabric is distorted
from an orthogonal woven state by a distortion angle of least 30
degrees.
2. The composite of claim 1 wherein the number of plies comprising
the plurality of first or second plies is from 2 to 250.
3. The composite of claim 1 wherein the polymer of the yarns of the
fabric of the first and second plies is para-aramid, polyethylene,
polyazole or mixtures thereof.
4. The composite of claim 1 wherein the fabric of each first and
second ply comprises regions wherein the fabric is distorted from
an orthogonal woven state by a distortion angle of least 40
degrees.
5. The composite of claim 1 wherein the yarn orientation of a
second ply is offset at an angle of from 20 to 70 degrees with
respect to the yarn orientation of a first ply.
6. The composite of claim 5 wherein the yarn orientation of a
second ply is offset at an angle of from 40 to 50 degrees with
respect to the yarn orientation of a first ply.
7. The composite of claim 5 further comprising a third ply, the
third ply comprising (i) a woven fabric made from a plurality of
polymeric yarns having a yarn tenacity of from 15 grams per dtex to
50 grams per dtex and a modulus of from 200 grams per dtex to 2200
grams per dtex, and (ii) a polymeric resin, wherein, (a) the
surface area of a third ply is no greater than 50% of the surface
area of a first and second ply, (b) the fabric has a Russell
tightness factor of from 0.2 to 0.7, (c) the fabric has an areal
weight of from 80 gsm to 510 gsm, (d) the fabric has a cover factor
of at least 0.45, (e) the fabric is impregnated with the resin, the
resin comprising from 5 to 30 weight percent of the total weight of
fabric plus resin, and (f) the ratio of the number of first plus
second plies to the number of third plies in the composite is in
the range of from 2:1 to 12:1.
8. The composite of claim 7 wherein a third ply located between any
two first plies has the same yarn orientation as the yarns of a
first ply.
9. The composite of claim 7 wherein a third ply located between any
two second plies has the same yarn orientation as the yarns of a
second ply.
10. The composite of claim 7 wherein a third ply is located at the
intersection between a plurality of first plies and a plurality of
second plies.
11. The composite of claim 7 wherein there are no cuts, darts,
pleats or folds in the first, second and third plies.
12. The composite of claim 7 wherein the geometric shape of the
third ply is circular, oval, square, rectangular, diamond,
pentagonal, hexagonal, octagonal or cross shaped.
13. The composite of claim 7 wherein the polymer of the yarns of
the third ply is para-aramid, polyethylene, polyazole or mixtures
thereof.
14. A ballistic resistant article comprising the composite of claim
1.
15. A ballistic resistant article comprising the composite of claim
7.
16. A method of forming a curved fiber reinforced resin composite
article comprising the steps of (i) providing a roll of resin
impregnated fabric composite comprising a woven fabric made from a
plurality of polymeric yarns having a yarn tenacity of from 15
grams per dtex to 50 grams per dtex and a modulus of from 200 grams
per dtex to 2200 grams per dtex, and a polymeric resin, wherein (a)
the fabric has a Russell tightness factor of from 0.2 to 0.7, (b)
the fabric has an areal weight of from 80 gsm to 510 gsm, (c) the
fabric has a cover factor of at least 0.5, and, (d) the fabric is
impregnated with the polymeric resin, the resin comprising from 5
to 30 weight percent of the of the total weight of fabric plus
resin, (ii) cutting a plurality of plies from the fabric composite
roll to provide first and second plies such that the plies have a
shape profile similar to the final shape profile of the article
being formed, (iii) cutting a plurality of plies from the fabric
composite roll to provide third plies such that the surface area of
a third ply is no greater than 50% of the surface area of the first
or second plies, (iv) tensioning the corners or edges of the first
and second plies to cause regions of the ply to distort by a
distortion angle of at least 30 degrees, (v) assembling a plurality
of first plies followed by a plurality of second plies with third
plies interspersed at a pre-determined frequency within the
pluralities of first and second plies such that the ratio of the
number of first plus second plies to the number of third plies is
in the range of from 2:1 to 12:1 and the orientation of a second
ply is offset at an angle of from 20 to 70 degrees with respect to
the orientation of a first ply, and (vi) consolidating the assembly
of step (v) at a temperature of from 115.degree. C. to 230.degree.
C. and an applied force of from 34 to 800 tonnes for between 5 to
60 minutes to form a cured composite article.
17. The method of claim 16 wherein the polymer of the yarns of the
first, second and third plies is para-aramid, polyethylene,
polyazole or mixtures thereof.
18. The method of claim 16 wherein the fabric of each first and
second ply comprises regions wherein the fabric is distorted from
an orthogonal woven state by a distortion angle of least 40
degrees.
19. A method of forming a curved fiber reinforced resin composite
article comprising the steps of (i) providing a roll of resin
impregnated fabric composite comprising a woven fabric made from a
plurality of polymeric yarns having a yarn tenacity of from 15
grams per dtex to 50 grams per dtex and a modulus of from 200 grams
per dtex to 2200 grams per dtex, and a polymeric resin, wherein (a)
the fabric has a Russell tightness factor of from 0.2 to 0.7, (b)
the fabric has an areal weight of from 80 gsm to 510 gsm, (c) the
fabric has a cover factor of at least 0.5, and, (d) the fabric is
impregnated with the polymeric resin, the resin comprising from 5
to 30 weight percent of the of the total weight of fabric plus
resin, (ii) cutting a plurality of plies from the fabric composite
roll to provide first and second plies such that the plies have a
shape profile similar to the final shape profile of the article
being formed, (iii) cutting a plurality of plies from the fabric
composite roll to provide third plies such that the surface area of
a third ply is no greater than 50% of the surface area of the first
or second plies, the third plies having at least two different
shapes, (iv) tensioning the corners or edges of the first and
second plies to cause regions of the ply to distort by a distortion
angle of at least 30 degrees, (v) assembling a plurality of first
plies followed by a plurality of second plies with third plies
interspersed at a pre-determined frequency within the pluralities
of first and second plies such that the ratio of the number of
first plus second plies to the number of third plies is in the
range of from 2:1 to 12:1, the yarn orientation of a second ply is
offset at an angle of from 20 to 70 degrees with respect to the
yarn orientation of a first ply, the third plies interspersed
within a plurality of first or second plies have the same
orientation as the plies between which they are interspersed, and
(vi) consolidating the assembly of step (v) at a temperature of
from 115.degree. C. to 230.degree. C. and an applied force of from
34 to 800 tonnes for between 5 to 60 minutes to form a cured
composite article.
20. The method of claim 19 further comprising the step of
positioning a third ply at the intersection of a plurality of first
plies and a plurality of second plies.
Description
RELATED APPLICATION
[0001] The present patent application is a continuation-in-part of
Ser. No. 13/274,590 filed 17 Oct., 2011.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] This invention pertains to a fiber reinforced resin
composite having anti-ballistic properties and armor articles made
therefrom.
[0004] 2. Description of Related Art
[0005] Anti-ballistic armor articles comprising high tenacity
polymeric yarns have been in use for some time. There is a
continuing need to provide hard body armor articles with increased
resistance to bullets and fragments while at the same time reducing
the total weight of the anti-ballistic article.
[0006] Current composites used for ballistic helmets and other
complex curved ballistic articles are based on the assembly of
layers of high strength fabrics or non-woven packets of
uni-directional fibers and resins. Composites and processes for
fabrication of ballistic helmets and the like are detailed in U.S.
Pat. No. 3,582,990, U.S. Pat. No. 4,596,056, U.S. Pat. No.
4,656,674, U.S. Pat. No. 4,778,638 U.S. Pat. No. 4,953,234, and
U.S. Pat. No. 7,228,571. In each of these examples, the high
strength fabric or non-woven packet is cut and darted to allow the
fabric to take on the shape of the doubly curved article such as a
helmet. These cuts and darts create a discontinuity in the
protective article or cause wrinkling in the article if too few
cuts and darts are used. The cuts, darts and wrinkles result in a
decrease in the penetrative resistance in the article. The art
describes proposed shapes, patterns, pre-forming processes,
off-setting approaches and stitching of the seams, as some means to
minimize these defects.
[0007] A significant need exists for a ballistic helmet, or other
doubly curved article, with a minimum of cut and wrinkle flaws to
allow a weight reduction and/or performance increase in the
article.
[0008] The present invention provides for an anti-ballistic hard
armor composite article of low areal weight and having acceptable
ballistic resistance. The article can be produced without the need
for folds or pleats in the fabric layers and with no or minimal cut
or wrinkle flaws. The invention is particularly suitable for highly
contoured articles such as a helmet, a knee protector, an arm
protector and the like.
SUMMARY OF THE INVENTION
[0009] This invention pertains to a contoured fiber reinforced
resin composite for ballistic protection comprising a plurality of
first and second plies arranged such that a plurality of first
plies is followed by a plurality of second plies, wherein, yarn
orientations in the weave of each plurality of plies, are
substantially aligned to each other, and wherein the plurality of
first and second plies further comprise (i) a woven fabric made
from a plurality of polymeric yarns having a yarn tenacity of from
15 grams per dtex to 50 grams per dtex and a modulus of from 200
grams per dtex to 2200 grams per dtex, and (ii) a polymeric resin,
wherein [0010] (a) the fabric has a Russell tightness factor of
from 0.2 to 0.7, [0011] (b) the fabric has an areal weight of from
80 gsm to 510 gsm, [0012] (c) the fabric has a cover factor of at
least 0.45, [0013] (d) the fabric is impregnated with the resin,
the resin comprising from 5 to 30 weight percent of the total
weight of fabric plus resin, and [0014] (e) the fabric of each
first and second ply comprises regions wherein the fabric is
distorted from an orthogonal woven state by a distortion angle of
least 30 degrees.
[0015] The invention is further directed to a composite comprising
first, second and third plies, the third ply comprising (i) a woven
fabric made from a plurality of polymeric yarns having a yarn
tenacity of from 15 grams per dtex to 50 grams per dtex and a
modulus of from 200 grams per dtex to 2200 grams per dtex, and (ii)
a polymeric resin, wherein, [0016] (a) the surface area of a third
ply is no greater than 50% of the surface area of a first and
second ply, [0017] (b) the fabric has a Russell tightness factor of
from 0.2 to 0.7, [0018] (c) the fabric has an areal weight of from
80 gsm to 510 gsm, [0019] (d) the fabric has a cover factor of at
least 0.45, [0020] (e) the fabric is impregnated with the resin,
the resin comprising from 5 to 30 weight percent of the total
weight of fabric plus resin, and [0021] (f) the ratio of the number
of first plus second plies to the number of third plies in the
composite is in the range of from 2:1 to 12:1.
[0022] The invention also describes a method of forming a curved
fiber reinforced resin composite article comprising the above
plies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1A shows a perspective view of a helmet comprising a
first ply.
[0024] FIGS. 1B and 1C show in further detail features of FIG.
1A.
[0025] FIG. 2 shows a perspective view of a helmet comprising a
second ply.
[0026] FIG. 3 shows a perspective view of a helmet comprising a
third ply.
[0027] FIG. 4 represents a cross shaped ply of Example 3.
[0028] FIG. 5 represents a circular shaped ply of Example 3.
[0029] FIGS. 6A and 6B represent a cross section through a resin
composite.
[0030] FIGS. 7A and 7B represent an alternative cross section
through a resin composite.
DETAILED DESCRIPTION
[0031] This invention pertains to a fiber reinforced resin
composite comprising a woven fabric and a polymeric resin. In some
embodiments the composite may comprise more than one type of woven
fabric. Other embodiments may comprise a combination of woven
fabric and unidirectional non-woven packets.
Woven Fabric
[0032] The term "woven" is meant herein to be any fabric that can
be made by weaving; that is, by interlacing or interweaving at
least two yarns typically at right angles. Generally such fabrics
are made by interlacing one set of yarns, called warp yarns, with
another set of yarns, called weft or fill yarns. The woven fabric
can have essentially any weave, such as, plain weave, crowfoot
weave, basket weave, satin weave, twill weave, unbalanced weaves,
and the like. In some embodiments, a satin or plain weave is
preferred.
[0033] In some embodiments, each woven fabric layer has a basis
weight of from 50 to 800 g/m.sup.2 (1.4 to 23.5 oz./sq. yd.). In
other embodiments the basis weight of each woven layer is from 70
to 600 g/m.sup.2 (2.9 to 17.6 oz./sq. yd). In yet some other
embodiments the basis weight of a woven layer is from 80 to 510
g/m.sup.2(4.0 to 14.7 oz./sq. yd). In some embodiments, the fabric
yarn count in the warp is 2 to 39 ends per centimeter (5 to 100
ends per inch) or even 3 to 24 ends per centimeter (8 to 60
ends/inch). In some other embodiments the yarn count in the warp is
4 to 18 ends per centimeter (10 to 45 ends/inch). In some
embodiments, the fabric yarn count in the weft or fill is 2 to 39
ends per centimeter (5 to 100 ends per inch) or even 3 to 24 ends
per centimeter (8 to 60 ends/inch). In some other embodiments the
yarn count in the weft or fill is 4 to 18 ends per centimeter (10
to 45 ends/inch).
[0034] The fabric has a Russell tightness factor of from 0.2 to
0.7. In some embodiments the Russell tightness factor is from 0.3
to 0.5. The Russell tightness factor is a measure of the degree of
fabric tighness that is present in any particular woven structure.
Seyam [Textile Progress, Vol 31, No. 3, 2002] provides a review of
a number of dimensionless indices that can be used to determine the
tightness or firmness of a particular fabric, including Russell's
Tightness Factor. The factor is calculated by the following
formula:
C.sub.fabric=n.sub.w+n.sub.f)/(n.sub.wmax+n.sub.f max)
where [0035] n.sub.w=warp density in the fabric (ends/cm) [0036]
n.sub.f=fill density in the fabric (picks/cm) [0037]
n.sub.wmax=maximum theoretical warp density [0038]
n.sub.fmax=maximum theoretical fill density
[0039] The maximum theoretical end and pick density are calculated
using Ashenhurst's Theory of ends plus intersections also detailed
in the Seyam reference. The maximum theoretical end or pick density
can be determined from the following formula;
n.sub.max=M/(Md+d)
where [0040] n.sub.max=theoretical maximum warp or fill density
[0041] M=weave factor [0042] =(ends per weave
repeat)/(intersections per weave repeat) [0043] d=Diameter of the
yarn when forced into a circular cross-section.
[0044] For calculation of the yarn diameter of multifilament yarn,
a packing factor must be determined. For synthetic continuous
filament yarns, such as those utilized in this invention, a packing
factor of 0.65 is recommended by Seyam and should be used.
[0045] If the Russell tightness is below 0.2 the fabric becomes too
loosely connected to evenly form into the shape of a uniform
ballistic article such as a helmet. If the tightness factor is
above 0.7 the fabric structure will create excessive wrinkles or
buckles as it is formed into highly complex double curvature
articles such as a helmet, and ballistic performance will be
reduced.
[0046] The fabric must also have a cover factor of at least 0.45.
Cover factor is defined as the ratio of projected fabric surface
area covered by yarns to the fabric surface area, and is given by
the following equation:
CF=(C.sub.w+C.sub.f-C.sub.wC.sub.f)
Where:
[0047] C.sub.w=warp cover factor=n.sub.w.times.d [0048]
C.sub.f.sup.=fill cover factor=o.sub.f.times.d
[0049] If the cover factor is below 0.45 then the fabric becomes
too open to effectively stop small sized ballistic fragments at
high velocities.
Yarns and Filaments
[0050] Fabrics are woven from multifilament yarns having a
plurality of filaments. The yarns can be intertwined and/or
twisted. For purposes herein, the term "filament" is defined as a
relatively flexible, macroscopically homogeneous body having a high
ratio of length to width across its cross-sectional area
perpendicular to its length. The filament cross section can be any
shape, but is typically circular or bean shaped. Herein, the term
"fiber" is used interchangeably with the term "filament", and the
term "end" is used interchangeably with the term "yarn".
[0051] The filaments can be any length. Preferably the filaments
are continuous. Multifilament yarn spun onto a bobbin in a package
contains a plurality of continuous filaments. The multifilament
yarn can be cut into staple fibers and made into a spun staple yarn
suitable for use in the present invention. The staple fiber can
have a length of about 1.5 to about 5 inches (about 3.8 cm to about
12.7 cm). The staple fiber can be straight (i.e., non crimped) or
crimped to have a saw tooth shaped crimp along its length, with a
crimp (or repeating bend) frequency of about 3.5 to about 18 crimps
per inch (about 1.4 to about 7.1 crimps per cm).
[0052] The yarns have a yarn tenacity of at least 7.3 grams per
dtex. In some embodiments the yarns have a yarn tenacity in the
range of from 10 to 65 grams per dtex or even 15 to 50 grams per
dtex. The yarns have a yarn modulus of at least 100 grams per dtex.
In some embodiments the yarns have a yarn modulus in the range of
from 150 to 2700 grams per dtex or even 200 to 2200 grams per dtex.
The yarns have a linear density of from 50 to 4500 dtex or even
from 100 to 3500 dtex. The yarns have an elongation to break of
from 1 to 8 percent or even from 1 to 5 percent.
[0053] The filaments of the yarns are solid, that is, they are not
hollow.
Fabric Fiber Polymer
[0054] The yarns of the present invention may be made with
filaments made from any polymer that produces a high-strength
fiber, including, for example, polyamides, polyolefins, polyazoles,
and mixtures of these.
[0055] When the polymer is polyamide, aramid is preferred. The term
"aramid" means a polyamide wherein at least 85% of the amide
(--CONH--) linkages are attached directly to two aromatic rings.
Suitable aramid fibers are described in Man-Made Fibres--Science
and Technology, Volume 2, Section titled Fibre-Forming Aromatic
Polyamides, page 297, W. Black et al., Interscience Publishers,
1968.
[0056] A preferred aramid is a para-aramid. A preferred para-aramid
is poly(p-phenylene terephthalamide) which is called PPD-T. By
PPD-T is meant a homopolymer resulting from mole-for-mole
polymerization of p-phenylene diamine and terephthaloyl chloride
and, also, copolymers resulting from incorporation of small amounts
of other diamines with the p-phenylene diamine and of small amounts
of other diacid chlorides with the terephthaloyl chloride. As a
general rule, other diamines and other diacid chlorides can be used
in amounts up to as much as about 10 mole percent of the
p-phenylene diamine or the terephthaloyl chloride, or perhaps
slightly higher, provided only that the other diamines and diacid
chlorides have no reactive groups which interfere with the
polymerization reaction. PPD-T, also, means copolymers resulting
from incorporation of other aromatic diamines and other aromatic
diacid chlorides such as, for example, 2,6-naphthaloyl chloride or
chloro- or dichloroterephthaloyl chloride or
3,4'-diaminodiphenylether.
[0057] Additives can be used with the aramid and it has been found
that up to as much as 10 percent or more, by weight, of other
polymeric material can be blended with the aramid. Copolymers can
be used having as much as 10 percent or more of other diamine
substituted for the diamine of the aramid or as much as 10 percent
or more of other diacid chloride substituted for the diacid
chloride or the aramid.
[0058] Another suitable fiber is one based on aromatic copolyamide
prepared by reaction of terephthaloyl chloride (TPA) with a 50/50
mole ratio of p-phenylene diamine (PPD) and 3,4'-diaminodiphenyl
ether (DPE). Yet another suitable fiber is that formed by
polycondensation reaction of two diamines, p-phenylene diamine and
5-amino-2-(p-aminophenyl) benzimidazole with terephthalic acid or
anhydrides or acid chloride derivatives of these monomers.
[0059] When the polymer is polyolefin, polyethylene or
polypropylene is preferred. The term "polyethylene" means a
predominantly linear polyethylene material of preferably more than
one million molecular weight that may contain minor amounts of
chain branching or comonomers not exceeding 5 modifying units per
100 main chain carbon atoms, and that may also contain and mixed
therewith not more than about 50 weight percent of one or more
polymeric additives such as alkene-1-polymers, in particular low
density polyethylene, propylene, and the like, or low molecular
weight additives such as anti-oxidants, lubricants, ultra-violet
screening agents, colorants and the like which are commonly
incorporated. Such is commonly known as extended chain polyethylene
(ECPE) or ultra high molecular weight polyethylene (UHMWPE
[0060] In some preferred embodiments polyazoles are polyarenazoles
such as polybenzazoles and polypyridazoles. Suitable polyazoles
include homopolymers and, also, copolymers. Additives can be used
with the polyazoles and up to as much as 10 percent, by weight, of
other polymeric material can be blended with the polyazoles. Also
copolymers can be used having as much as 10 percent or more of
other monomer substituted for a monomer of the polyazoles. Suitable
polyazole homopolymers and copolymers can be made by known
procedures.
[0061] Preferred polybenzazoles are polybenzimidazoles,
polybenzothiazoles, and polybenzoxazoles and more preferably such
polymers that can form fibers having yarn tenacities of 30 gpd or
greater. If the polybenzazole is a polybenzothioazole, preferably
it is poly(p-phenylene benzobisthiazole). If the polybenzazole is a
polybenzoxazole, preferably it is poly(p-phenylene benzobisoxazole)
and more preferably poly(p-phenylene-2,6-benzobisoxazole) called
PBO.
[0062] Preferred polypyridazoles are polypyridimidazoles,
polypyridothiazoles, and polypyridoxazoles and more preferably such
polymers that can form fibers having yarn tenacities of 30 gpd or
greater. In some embodiments, the preferred polypyridazole is a
polypyridobisazole. A preferred poly(pyridobisozazole) is
poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d']bisimidazole
which is called PIPD. Suitable polypyridazoles, including
polypyridobisazoles, can be made by known procedures.
Polymeric Resin
[0063] By "polymeric resin" is meant an essentially homogeneous
resin or polymeric material in which the yarn is embedded. The
polymeric resin may be thermoset or thermoplastic or a mixture of
the two. Suitable thermoset resins include phenolic, epoxy,
polyester, vinyl ester and the like. Suitable thermoplastic resins
include a blend of elastomeric block copolymers, polyvinyl butylral
polyethylene copolymers, polyimides, polyurethanes, polyesters and
the like. In some embodiments, the polyethylene copolymers comprise
from 50 to 75 weight percent and the elastomeric block copolymers
comprise from 25 to 50 weight percent of the resin. For example
ethylene copolymers with acid monomers can be used, or
alternatively any polyester of polyamide may be used. Ethylene
acrylic acid copolymer is one suitable material. One skilled in the
art will be able with minimal experimentation to specify a suitable
polymer.
[0064] The ethylene copolymers that may be utilized in the present
invention can be neutralized with an ion selected form the group
consisting of sodium, potassium, lithium, silver, mercury, copper
and the like and mixtures thereof. Useful divalent metallic ions
include, but are not limited to, ions of beryllium, magnesium,
calcium, strontium, barium, copper, cadmium, mercury, tin, lead,
iron, cobalt, nickel, zinc and the like and mixtures therefrom.
Useful trivalent metallic ions include, but are not limited to,
ions of aluminum, scandium, iron, yttrium and the like and mixtures
therefrom. Useful multivalent metallic ions include, but are not
limited to, ions of titanium, zirconium, hafnium, vanadium,
tantalum, tungsten, chromium, cerium, iron and the like and
mixtures therefrom. It is noted that when the metallic ion is
multivalent, complexing agents, such as stearate, oleate,
salicylate, and phenolate radicals may be included, as disclosed
within U.S. Pat. No. 3,404,134. The metallic ions used herein are
preferably monovalent or divalent metallic ions. More preferably,
the metallic ions used herein are selected from the group
consisting of ions of sodium, lithium, magnesium, zinc and mixtures
therefrom. Yet more preferably, the metallic ions used herein are
selected from the group consisting of ions of sodium, zinc and
mixtures therefrom. The parent acid copolymers of the invention may
be neutralized as disclosed in U.S. Pat. No. 3,404,134.
[0065] By "degree of neutralization" is meant the mole percentage
of acid groups on the ethylene copolymer that have a counterion.
The ethylene acid copolymer utilized in the present invention is
neutralized to a level of about 70% to slightly greater than 100%
with one or more metal ions selected from the group consisting of
potassium, sodium, lithium, magnesium, zinc, and mixtures of two or
more thereof, based on the total carboxylic acid content of the
acid copolymer.
[0066] A polymer or copolymer may also be applied to the fabric
surface in the form of a dispersion, or a solution. The polymer or
copolymer may also be plasticized. Any suitable plasticizer may be
selected by one skilled in the art, for example the plasticizer is
selected from the group consisting of fatty acids or fatty
alcohols. A polymer or co-polymer may also be applied to the fabric
in the form of a film or dry powder. Several methods may be
selected by one skilled in the art to laminate the polymer to the
fabric substrate.
[0067] The amount of resin in the composite is from 5 to 30 weight
percent of the composite based on the total weight of resin plus
fabric. In some embodiments, the resin content is from 5 to 20
weight percent. In other embodiments the resin content is from 5 to
15 weight percent. In yet another embodiment, the resin content is
from 8 to 12 weight percent. The resin may be coated onto the
surface of the fabric or impregnated between the yarn filaments by
well known prepregging methods such as those described in section
2.9 of "Manufacturing Processes for Advanced Composites" by F. C.
Campbell, Elsevier, 2004 or may be film or powder laminated to the
fabric.
Preform Manufacture
[0068] For handling and process efficiency purposes, a fiber
reinforced resin composite article may be assembled from a preform
or a plurality of preforms. A preform is a fomed but not fully
consolidated resin coated or impregnated fabric (prepreg) which has
the contour of the finished product. There may be a plurality of
fabric layers in a preform.
[0069] Prepreg ply shapes are cut from prepreg roll stock using a
knife and template, a cutting die or some other means. One layer of
cut prepreg stock is called a ply. The number of shapes to be cut
and the dimensions of each shape will depend on the final design of
and the materials to be used in the final article. In some
embodiments, there is more than one ply shape in a preform
assembly.
[0070] Cut plies are stacked in the desired sequence on a
preforming tool, which may be flat or contoured and made of
materials such as wood, metal, plastic, fiber-reinforced plastic or
ceramic. In some instances, the layers comprising the preform are
bonded under temperature and pressure. Within a stack, the yarn
orientations in the weave of each plurality of plies are
substantially aligned to each other. By substantially aligned is
meant that the yarn orientations are aligned except that some yarn
non-alignment of a few degrees may arise in a ply during the ply
lay-up process. Typically this non-alignment is less than ten
degrees and more typically less than five degrees. One convenient
processes for achieving pre-consolidation is vacuum forming or
matched mold shaping. These processes are well known in the art.
The amount of heat and pressure to bond the ply stack should be
sufficient to allow the particular resin to reach a melt stage
which permits the polymer to be infused into and through the fabric
thus adhering multiple plies together and providing a cohesive and
semi-rigid preform. By semi-rigid we mean that the preform is both
noticeably stiffer than the prepreg and sufficiently stiff to
prevent individual fabric layers from buckling and causing wrinkles
during final consolidating in the molding tool. A single preforming
step is sufficient to provide the desired compaction and inter-ply
coherence to the preform.
[0071] In some instances, bonding of the layers comprising the
preform is achieved by saturation with a liquid resin in a process
commonly know as wet lay-up. These processes are well know in the
art. The wet resin soaked layers are layered on the preforming tool
to create the desired contoured shape, and solvents are removed
and/or the resin level of cure is advanced to create the rigid
preform.
Article Manufacture
[0072] A plurality of individual plies or preforms are stacked in a
desired sequence on a molding tool having the dimensions of the
finished article. The tool is contoured and made of materials such
as metal, plastic, fiber-reinforced plastic or ceramic. The desired
number of preforms in the final assembly will vary according to the
laminate design and the number of plies in each preform. The number
of plies in a laminate varies from 2 to 500, or from 20 to 150 or
even from 30 to 120. In a preferred embodiment, there are from 10
to 70 plies in the final assembly. In some embodiments, the number
of plies comprising the plurality of first or second plies is from
2 to 250 or from 5 to 35 or from 10 to 75 or even from 15 to 60. In
some other embodiments, the number of plies comprising the
plurality of first or second plies is from 2 to 50 or from 5 to
50.
[0073] Final consolidation is carried out under temperature and
pressure. The temperature can be from 115.degree. C. to 230.degree.
C., or from 120.degree. C. to 170.degree. C. or even from
140.degree. C. to 160.degree. C. The desired consolidation pressure
is achieved by applying a force of from 34 to 800 tonnes or from
200 to 600 tonnes or even from 400 to 650 tonnes. Once at
temperature, the temperature is maintained for a specified number
of minutes before cooling is initiated. The temperature hold time
can be from 5 min to 60 min, or from 5 min to 30 min or even from 7
min to 22 min. The molding of the composite laminate may be carried
out in a platen press, an autoclave, a matched mold or under vacuum
in an oven, such techniques being well known to those skilled in
the art. For a thermoplastic polymeric resin, the amount of heat
required should be sufficient to allow the particular thermoplastic
to reach a melt stage. The applied pressure should be sufficient to
cause good compaction of the plies such that there are minimal
voids in the finished laminate. Voids may be detected by methods
such as ultrasonic scanning or x-rays. Preferably, the finished
laminate is removed from the mold after it has cooled to room
temperature. This allows the resin to fully solidify before removal
from the mold. After removal of the cured laminate from the mold,
the laminate is trimmed and sent for finishing operations such as
installation of fittings and painting.
[0074] In one embodiment, the fiber reinforced resin composite
article is formed from first and second plies. FIG. 1A shows
generally at 10 the contoured shape of a helmet comprising a first
ply. The warp and fill (weft) yarns are shown respectively at 11
and 12. Over the majority of the surface area of the first ply, the
warp and fill yarns are orthogonal or essentially orthogonal to
each other. By "`essentially" orthogonal is meant that the warp and
fill yarns are within a few degrees of being orthogonal to each
other, for example within five or ten degrees. An example of an
orthogonal yarn intersection is shown at 13 in FIG. 1B. Extending
or trellising the corners or edges of a ply produces a ply having
regions where the warp and fill yarns become distorted from an
orthogonal intersection as in the original woven state. This angle
of yarn distortion is referred hereto as a distortion angle and is
shown as .PSI., at 14 in FIG. 1C. It is preferable that the
distortion angle is at least 30 degrees or even 40 degrees. A
phantom center reference line for the first ply is shown at 15. It
is not unusual for significant distortion and folding to occur at
and/or around the outer edges of the finished article, resulting
from manufacturing imperfections. For this reason, when determining
the distortion angle present in any article, the regions within
25.4 mm (1 inch) of the edges should be excluded.
[0075] FIG. 2 shows generally at 20 a second ply having warp yarns
21 and fill yarns 22. The majority of the warp and fill yarns are
oriented orthogonally or essentially orthogonally to each other
but, as described for FIG. 1, trellising the fabric of a second ply
produces regions in the ply wherein the fabric is distorted from an
orthogonal woven state by a distortion angle of least 30 degrees. A
phantom center reference line for the second ply is shown at
23.
[0076] During assembly of the composite article, it is preferable
that the yarn orientation of the second ply is offset at an angle,
alpha, of from 20 to 70 degrees with respect to the yarn
orientation of the first ply. More preferably, the second ply is
offset at an angle, alpha, of from 40 to 50 degrees with respect to
the first ply. In an even more preferred embodiment, the second ply
is offset at an angle, alpha, of from 45 degrees with respect to
the first ply. This offset angle is shown at 24 in FIG. 2 with
respect to centre reference lines 15 for the first ply and 23 for
the second ply.
[0077] In one embodiment, the first and second plies are stacked in
an alternating sequence and are oriented at from 20 to 70 degrees
with respect to each other. The first and second plies have a shape
profile similar to the final shape profile of the article being
formed.
[0078] In another embodiment, the composite comprises a plurality
of first plies followed by a plurality of second plies. Such a
composite may comprise a single plurality of first plies followed
by a single plurality of second plies or the composite may comprise
a repeat pattern of alternating pluralities of first and second
plies. FIGS. 6A and 6B show generally at 60 a cross section through
a resin composite comprising a plurality of first plies 61 as per
FIG. 1A followed by a plurality of second plies 62 as per FIG. 2.
The plurality of first plies 61 is facing the projectile 63. FIGS.
7A and 7B show generally at 70 a cross section through a resin
composite comprising a plurality of first plies 71a followed by
plurality of second plies 72a followed by a plurality of first
plies 71b followed by plurality of second plies 72b.
[0079] In yet another embodiment, the fiber reinforced resin
composite article comprises a third ply which is shown at 33 in
FIG. 3. Also shown in this figure are the principal warp 11 and
fill 12 yarn directions of a first ply. A requirement of the third
ply is that it has a surface area no greater than 50% of the
surface area of a first or second ply, If the surface area of the
third ply is greater than 50% uniformity in material distibution
will not be maintained. During assembly of the first, second and
third plies, the number of third plies is such that the ratio of
the number of first plus second plies to the number of third plies
in the composite is in the range of from 2:1 to 12:1 or 3:1 to 12:1
or even 4:1 to 12:1, The third plies are interspersed at a
predetermined frequency throughout the assembly of first and second
plies, for example as every fifth or sixth ply. Preferably, the
orientation of the yarns of the third ply is similar to the
orientation of yarns in an adjacent ply. For example, if a third
ply is located between any two first plies, then the yarn
orientation in the third ply is the same as the orientation of
yarns of a first ply. Similarly, if a third ply is located between
any two second plies, then the yarn orientation in the third ply is
the same as the orientation of yarns of a second ply. The prime
function of the third ply is to maintain uniformity in the
distribution of material throughout the article. The shape of the
third play may be any convenient shape such as circular, oval,
square, rectangular, diamond, pentagonal, hexagonal, octagonal or
cross shaped.
[0080] A third ply may also be located at the intersection between
a plurality of first plies and plurality of second plies as
exemplified by 64 and 74 in FIGS. 6B and 7B respectively. A third
ply located at the intersection between a plurality of first plies
and plurality of second plies may take the shape of any third ply
located between any of the first plies or between any of the second
plies or it may be different from both.
[0081] Preferably, the number of first, second and, optionally,
third plies is such that in the regions of the fabric assembly
where the yarns are not distorted, there is an equal balance of
yarn orientation between the different plies.
[0082] In one embodiment, a method of making a curved fiber
reinforced resin composite article comprises the steps of
[0083] (i) providing a roll of resin impregnated fabric composite
comprising a woven fabric made from a plurality of polymeric yarns
having a yarn tenacity of from 15 grams per dtex to 50 grams per
dtex and a modulus of from 200 grams per dtex to 2200 grams per
dtex, and a polymeric resin, wherein [0084] (a) the fabric has a
Russell tightness factor of from 0.2 to 0.7, [0085] (b) the fabric
has an areal weight of from 80 gsm to 510 gsm, [0086] (c) the
fabric has a cover factor of at least 0.5, and, [0087] (d) the
fabric is impregnated with the polymeric resin, the resin
comprising from 5 to 30 weight percent of the of the total weight
of fabric plus resin,
[0088] (ii) cutting a plurality of plies from the fabric composite
roll to provide first and second plies such that the plies have a
shape profile similar to the final shape profile of the article
being formed,
[0089] (iii) cutting a plurality of plies from the fabric composite
roll to provide third plies such that the surface area of a third
ply is no greater than 50% of the surface area of the first or
second plies,
[0090] (iv) tensioning the corners or edges of the first and second
plies to cause regions of the ply to distort by a distortion angle
of at least 30 degrees,
[0091] (v) assembling a plurality of first plies followed by a
plurality of second plies with third plies interspersed at a
pre-determined frequency within the pluralities of first and second
plies such that the ratio of the number of first plus second plies
to the number of third plies is in the range of from 2:1 to 12:1
and the orientation of a second ply is offset at an angle of from
20 to 70 degrees with respect to the orientation of a first ply,
and
[0092] (vi) consolidating the assembly of step (v) at a temperature
of from 115.degree. C. to 230.degree. C. and an applied force of
from 34 to 800 tonnes for between 5 to 60 minutes to form a cured
composite article.
[0093] In another embodiment, a method of making a curved fiber
reinforced resin composite article comprises the steps of
[0094] (i) providing a roll of resin impregnated fabric composite
comprising a woven fabric made from a plurality of polymeric yarns
having a yarn tenacity of from 15 grams per dtex to 50 grams per
dtex and a modulus of from 200 grams per dtex to 2200 grams per
dtex, and a polymeric resin, wherein [0095] (a) the fabric has a
Russell tightness factor of from 0.2 to 0.7, [0096] (b) the fabric
has an areal weight of from 80 gsm to 510 gsm, [0097] (c) the
fabric has a cover factor of at least 0.5, and, [0098] (d) the
fabric is impregnated with the polymeric resin, the resin
comprising from 5 to 30 weight percent of the of the total weight
of fabric plus resin,
[0099] (ii) cutting a plurality of plies from the fabric composite
roll to provide first and second plies such that the plies have a
shape profile similar to the final shape profile of the article
being formed,
[0100] (iii) cutting a plurality of plies from the fabric composite
roll to provide third plies such that the surface area of a third
ply is no greater than 50% of the surface area of the first or
second plies, the third plies having at least two different
shapes,
[0101] (iv) tensioning the corners or edges of the first and second
plies to cause regions of the ply to distort by a distortion angle
of at least 30 degrees,
[0102] (v) assembling a plurality of first plies followed by a
plurality of second plies with third plies interspersed at a
pre-determined frequency within the pluralities of first and second
plies such that the ratio of the number of first plus second plies
to the number of third plies is in the range of from 2:1 to 12:1,
the orientation of a second ply is offset at an angle of from 20 to
70 degrees with respect to the orientation of a first ply, the
third plies interspersed within a plurality of first or second
plies have the same orientation as the plies between which they are
interspersed, and
[0103] (vi) consolidating the assembly of step (v) at a temperature
of from 115.degree. C. to 230.degree. C. and an applied force of
from 34 to 800 tonnes for between 5 to 60 minutes to form a cured
composite article.
[0104] A contoured fiber reinforced resin composite article having
a uniform distribution of material can be produced from first,
second and third plies as described above without the need for
cuts, darts, pleats or folds in any of the plies.
[0105] An antiballistic article may also be produced as a hybrid
construction comprising composites as described above plus fabrics
of another construction. One example of another construction is a
nonwoven fabric comprising polyolefin yarns oriented in a
unidirectional arrangement, These nonwoven materials may be
obtained from DSM Dyneema or Honeywell. In a preferred embodiment
of a hybrid construction, the layers of polyolefin yarns are in a
strike facing direction and the layers of woven fabrics in a body
facing direction.
Test Methods
[0106] Ballistic Penetration Performance:
[0107] Ballistic tests of the composite laminate were conducted in
accordance with standard procedures MIL STD-662F (V50 Ballistic
Test for Armor, 18 Dec., 1997) and NIJ STD 0106.01 (Ballistic
Helmets). Tests were conducted using 16 grain fragment simulating
projectiles (FSPs) against the composite laminate targets. The
projectiles were compliant with MIL DTL 46593B. One article was
tested for each examples with 10 shots, at zero degree obliquity,
fired at each target. The reported V50 values are average values
for the number of shots fired for each example. V50 is a
statistical measure that identifies the average velocity at which a
bullet or a fragment penetrates the armor equipment in 50% of the
shots, versus non penetration of the other 50%. The parameter
measured is V50 at zero degrees where the degree angle refers to
the obliquity of the projectile to the target.
EXAMPLES
Materials:
[0108] A 4-harness satin weave Kevlar.RTM. fabric was aquired from
JPS Composites, Anderson, S.C. The fabric had an areal weight of
146.4 gsm, a yarn count of 7.87 ends per cm (20 ends per inch) in
the warp, a yarn count of 7.87 ends per cm (20 ends per inch) in
the weft, a cover factor of 0.48 and a Russell tightness factor of
0.35. The fabric was woven from Kevlar.RTM. 129, 840 denier
para-aramid yarn available from E. I. DuPont de Nemours and
Company, Wilmington, Del. The yarn had a nominal yarn tenacity of
29 grams per dtex and a yarn modulus of 820 grams per dtex
[0109] A plain weave Kevlar.RTM. fabric was aquired from JPS
Composites, Anderson, S.C. The fabric had an areal weight of 152.1
gsm, a yarn count of 7.87 ends per cm (20 ends per inch) in the
warp, a yarn count of 7.87 ends per cm (20 ends per inch) in the
weft, a cover factor of 0.48 and a Russell tightness factor of
0.56. The fabric was woven from Kevlar.RTM. 129, 840 denier
para-aramid yarn available from E. I. DuPont de Nemours and
Company, Wilmington, Del. The yarn had a nominal yarn tenacity of
29 grams per dtex and a yarn modulus of 820 grams per dtex
[0110] Dyneema.RTM. HB 26 is a roll product consisting of four
crossed plies of unidirectionally oriented polyethylene yarns
embedded in resin. This nonwoven material was obtained from DSM
Dyneema, Stanley, N.C. This four-ply sheet had an areal weight of
260 gsm, (0.053 psf). The type of fiber used in this material is
reported in the literature to have a nominal tenacity of about 44
grams per dtex and a modulus of about 1400 grams per dtex.
Example 1
[0111] The 4 harness satin weave fabric described above was
impregnated with a thermoplastic resin dispersion, Michem.RTM.
Prime 2960, to make a suitable wet prepreg for manufacture of a
helmet shaped composite. The resin is available from Michelman
Inc., Cincinnati, Ohio. The dry resin content of the prepreg was 8
percent by weight of the fabric plus the dry resin. The resin is an
ethylene/acrylic acid copolymer. Plies for creating a helmet shaped
article were made by cutting either 432 mm.times.432 mm squares or
230 mm diameter circles.
[0112] A first fabric square ply was draped over a male mold plug
that modeled the shape of a medium sized Personnel Armor System for
Ground Troops (PASGT) helmet. Each of the 4 corners of the first
ply were tensioned so as to cause the fabric to distort and conform
to the shape of the helmet mold as it was draped in place. A second
fabric ply was then placed on top of the first fabric ply. This
second ply was also conformed to the shape of the mold by
distorting the fabric plies through tensioning of the corners. The
orientation of the second ply was, prior to draping, rotated by 45
degrees with respect to the orientation of the first ply. A total
of 46 square plies were positioned in a similar alternating manner
between the two orientations of first and second plies to create
the shaped helmet preform. In addition to the distorted square
plies, a total of nine circular crown plies, third plies, 230 mm in
diameter, were also added, one crown ply for each five of the
square plies. The circular crown plies were centered on the top of
the article. Each crown ply had and area of approximately 410
square centimeters. These plies covered approximately 33% of the
molded PASGT helmet shape or approximately 40% of the surface area
of the first and second plies.
[0113] The assembly of 55 plies was removed from the mold plug and
was placed in a vacuum oven, heated to 110 degrees C. and dried for
3 hours to remove the water from the polymer coating. The dried
assembly of polymer coated fabrics was placed in a matched die
PASGT helmet compression mold with a gap of 6.86 mm and pressed at
a temperature of 141 degrees C. and with 455 tonnes force. The
molded was bumped open once during the molding process to release
any volatiles and then held under those conditions for 15 minutes.
While still under pressure, the compressed assembly was rapidly
cooled to 38 degrees C. to complete consolidation of the structure.
The shell had a molded weight of 1.04 kg, with an average thickness
of 7.19 mm. This weight translates to a PASGT helmet weight of 0.95
kg.
[0114] The outer plies of the formed helmet were examined and a
maximum distortion angle of 55 degrees was noted in the regions of
the helmet that had been distorted to create the seamless contoured
ply shape. The regions within 25.4 mm of the trimmed helmet edge
were ignored for this measurement to exclude any edge effects in
the measurement. The helmet was assembled without cuts, darts,
pleats or folds in the first, second and third plies.
[0115] The molded helmet was tested to determine its ballistic
resistance against a 16 grain Right Circular Cylinder (RCC)
Fragment Simulated Projectile (FSP). The lightweight helmet had a
V.sub.50 value of 831 m/s that surpassed by 91 m/s the performance
standard published by MSA for ACH TC2000 series helmets
Example 2
[0116] The plain weave fabric described above was impregnated with
a thermoplastic resin dispersion, Michem.RTM. Prime 2960, to make a
suitable wet prepreg. The dry resin content of the prepreg was 8.5
percent by weight of the fabric plus the dry resin. Plies for
creating a helmet shaped article were made by cutting either 432
mm.times.432 mm squares or 230 mm diameter circles.
[0117] A medium sized PASGT helmet preform was created as described
in Example 1, by wet lay-up of the square and circular ply shapes.
A total of 55 plies were again used to create the helmet preform.
The ply sequencing and orientation of the first, second and third
plies was as in Example 1. The preform was similarly dried, and
pressed as in Example 1 to create a medium PASGT shaped helmet
shell. A finished helmet was cut to the contours of a typical
Advanced Combat Helmet. The final helmet had a trimmed weight of
1.06 kg, with an average thickness of 7.06 mm. The outer plies of
the formed helmet were examined and a maximum distortion angle of
40 degrees was noted in the regions of the helmet that had been
distorted to create the seamless contoured ply shape. The regions
within 25.4 mm of the trimmed helmet edge were ignored for this
measurement to exclude any edge effects in the measurement. The
helmet was assembled without cuts, darts, pleats or folds in the
first, second and third plies.
[0118] The molded helmet was tested to determine its ballistic
resistance against a 16 grain Right Circular Cylinder Fragment
Simulated Projectile. The lightweight helmet had a V.sub.50 value
of 832 m/s that surpassed by 92 m/s the performance standard given
by MSA for ACH TC2000 series helmets.
Example 3
[0119] Eight sheets of Dyeema.RTM. HB-26 were cut into circular
plies having a diameter of 483 mm. Four slots each having a length
of 165 mm were cut into each circular ply as shown at 50 in FIG. 5.
A further eight sheets were cut in the shape of a cross. Plies cut
in the shape of a cross all had a length of 483 mm and a width of
108 mm as shown as L and W respectively in FIG. 4. The sixteen
plies (8 circles and 8 crosses) were lightly tacked into a net
helmet shape with an ultrasonic welding tool and stacked in an
alternating fashion. The assembled stack was placed into a matched
die PASGT helmet compression mold with a gap of 8.13 mm which was
preheated to 129 degrees C. and the mold closed for 15 seconds,
just long enough to make a partially consolidated first
sub-assembly which was then immediately removed from the mold.
[0120] The 4 harness satin weave aramid fabric previously described
was impregnated with Michem.RTM. Prime 2960 resin to make a wet
prepreg. The dry resin content of the prepreg was 8 weight percent
based on the total weight of fabric plus resin. The prepreg was cut
into either 432 mm.times.432 mm squares or 230 mm diameter circles.
There were 22 square and 4 circular plies that were assembled over
a male mold plug in a similar manner as described in Example 1 to
form a second sub-assembly comprising first, second and third
plies. The circular crown plies were centered on the top of the
second sub-assembly. This second sub-assembly was then removed from
the mold plug and placed in a vacuum oven, heated to 110 degrees C.
and dried for 3 hours to remove the water from the polymer coating.
The second sub-assembly was placed into a matched die PASGT helmet
compression mold with a gap of 8.13 mm which was preheated to 129
degrees C. and the mold closed for 15 seconds, just long enough to
make a partially consolidated second sub-assembly which was then
immediately removed from the mold
[0121] A final helmet assembly was made by inserting the second
sub-assembly inside the first sub-assembly and placing the combined
assembly into a matched die PASGT helmet compression mold with a
gap of 8.13 mm. The mold was preheated to a temperature of 129
degrees C. and held for 20 minutes to consolidate the two
sub-assemblies into a final assembly. While still under pressure,
the compressed assembly was rapidly cooled to 38 degrees C. and
this temperature maintained for 40 minutes to complete
consolidation of the structure. The resulting helmet shell was cut
to the contours of a typical Advanced Combat Helmet. The final
helmet shell had a molded weight of 0.85 kg. Fifty percent of this
weight was comprised of Dyneema.RTM.HB 26 and fifty percent of this
weight was comprised of the resin impregnated aramid fabric. The
average thickness of the shell was 7.95 mm. The inner plies of the
formed helmet shell were examined and a maximum distortion angle of
40 degrees was noted in the regions of the helmet that had been
distorted to create the seamless contoured ply shapes. The regions
within 25.4 mm of the trimmed helmet edge were ignored for this
measurement to ignore any edge effects in the measurement. The
helmet was assembled without cuts, darts, pleats or folds in the
woven fabrics of the second sub-assembly.
[0122] The molded helmet shell was tested to determine its
ballistic resistance against a 16 grain Right Circular Cylinder
Fragment Simulated Projectile. The layers of polyethylene formed
the outer strike facing section of the final assembly and the
layers of aramid fabric formed the inner back facing section. The
lightweight helmet had a V.sub.50 value of 767 m/s that surpassed
by 53 m/s the performance standard given by MSA for ACH TC2000
series helmets.
[0123] The ballistic results for these examples are summarized in
Table 1.
TABLE-US-00001 TABLE 1 Shell Weight V50 Example Helmet Description
(kg) (m/s) Control ACH TC2000 Series Datasheet 1.10 739 Value 1
Aramid Satin Weave Fabric 0.95* 831 2 Aramid Plain Weave Fabric
1.05 832 3 Hybrid of Polyethylene and Aramid 0.85 767 *indicates an
ACH equivalent weight.
Example 4
[0124] The 4-harness satin weave fabric previously described was
impregnated with a thermoplastic resin dispersion, Michem.RTM.
Prime 2960, to make a suitable wet prepreg for manufacture of a
helmet shaped composite. The dry resin content of the prepreg was 8
percent by weight of the fabric plus the dry resin. Plies for
creating a helmet shaped article were made by cutting either 432
mm.times.432 mm squares or 230 mm diameter circles.
[0125] A fabric square ply (first ply) was draped over a male mold
plug that modeled the shape of a medium sized light weight advanced
combat helmet (LW ACH). Each of the 4 corners of the first ply were
tensioned so as to cause the fabric to distort and conform to the
shape of the helmet mold as it was draped in place. A further three
first plies were then placed, in the same orientation, on top of
the first fabric ply. These additional plies were also conformed to
the shape of the mold by distorting the fabric plies through
tensioning of the corners. A circular ply (third ply) was then
placed on top of the four first plies. The ply lay-up process was
repeated four times to give a first stack comprising a total of
twenty first plies and five third plies, the first plies all having
a common yarn alignment. A fabric square ply (second ply) was
draped on to the first stack such that the yarn orientation of the
second ply was, prior to draping, at an angle of 45 degrees with
respect to the yarn orientation of the first plies. A further three
second plies were added in exactly the same manner followed by a
circular ply (third ply). The ply lay-up process was repeated four
times to give a second stack comprising a total of twenty second
plies and five third plies, the second plies all having a common
yarn alignment. All third plies in the first and second stacks were
centered on the top of the article and covered approximately 40% of
the surface area of the first and second plies.
[0126] The combined first and second stacks formed the shaped
helmet preform.
[0127] The helmet preform was removed from the mold plug and was
placed in a vacuum oven, heated to 110 degrees C. and dried for 3
hours to remove the water from the polymer coating. The dried
assembly of polymer coated fabrics was placed in a matched die ACH
style helmet compression mold with a gap of 6.2 mm and pressed at a
temperature of 141 degrees C. and with 455 tonnes force. The mold
was opened once during the molding process to release any volatiles
and then held under those conditions for 15 minutes. While still
under pressure, the compressed assembly was rapidly cooled to 38
degrees C. to complete consolidation of the structure. The shell
had a molded weight of 0.813 kg and had an average thickness of
6.28 mm. After cutting to roughly ACH contours, the helmet weighed
0.766 kg.
[0128] The outer plies of the formed helmet were examined and a
maximum distortion angle of 55 degrees was noted in the regions of
the helmet that had been distorted to create the seamless contoured
ply shape. The regions within 25.4 mm of the trimmed helmet edge
were ignored for this measurement to exclude any edge effects in
the measurement. The helmet was assembled without cuts, darts,
pleats or folds in the first, second and third plies.
[0129] The molded helmet was tested to determine its ballistic
resistance against a 16 grain Right Circular Cylinder (RCC)
Fragment Simulated Projectile (FSP). The lightweight helmet had a
V.sub.50 value of 777 m/s that surpassed by 37 m/s the performance
standard published by MSA for ACH TC2000 series helmets
Example 5
[0130] Example 5 is similar to Example 4 except that the preform
can comprise a total of forty eight plies of fabric arranged in a
repeat sequence of three first plies followed by three second
plies, this pattern being repeated eight times. The yarn
orientation of the second plies is, prior to draping, at an angle
of 45 degrees with respect to the yarn orientation of the first
plies.
Example 6
[0131] Example 6 is similar to Example 4 except that the preform
can comprise a total of forty nine plies of fabric arranged in a
repeat sequence of three first plies followed by three second plies
followed by one third ply, this pattern being repeated seven times.
The yarn orientation of the second plies is, prior to draping, at
an angle of 45 degrees with respect to the yarn orientation of the
first plies.
[0132] The results show that a helmet construction comprising woven
fabrics having a Russell tightness factor of from 0.2 to 0.7 and a
cover factor of at least 0.45 meet the specified anti-ballistic
performance standards. Since the helmets are made without cuts,
darts, pleats or folds in the plies there is a reduction in the
number of potential weak zones that could adversely impact
performance in the field.
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