Note: Descriptions are shown in the official language in which they were submitted.
CA 02271707 2004-04-30
BARRIER UNITS AND ARTICLES MADE THEREFROM
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to barrier units and to articles made
therefrom. More particularly, this invention relates to various constraining
bands
of high strength and low weight for containing articles such as logs or
containers.
Most particularly, this invention relates to blast resistant container
assemblies for
receiving explosive articles and preventing or minimizing damage in the event
of an
explosion. These container assemblies have utility as containment and
transport
devices for hazardous materials such as gunpowder and explosives, e.g., bombs
and grenades, particularly in aircraft where weight is an important
consideration,
and more particularly in the cargo holds and passenger cabins of the aircraft.
They
15 are also particularly useful to bomb squad personnel in combating terrorist
and _
other threats.
2. The Prior Art ,
In response to the 1988 terrorist bombing of a Pan American flight over
Lockerbie, Scotland, experts in explosives and aircraft-survivability
techniques
2o have studied ways to make commercial airliners more resistant to terrorist
bombs.
One result of these studies has been the development and deployment of new
generations of explosive detection devices. As a practical matter, however,
there
remains a threshold bomb size above which detection is relatively easy but
below
which an increasing fraction of bombs will go undetected. An undetected bomb
25 likely would find its way into luggage either carried on board (in cabin)
by a
passenger or stored in an aircraft cargo container. Cargo containers, shaped
as
cubic boxes with a truncated edge, have typically been made of aluminum, which
is
lightweight hut not explosion-proof. As a consequence, there has been
tremendous
focus in recent years on redesigning containers to be both blast resistant to
bombs
30 that are below this threshold size and lightweight.
CA 02271707 2004-04-30
2
A good overview on redesigned aircraft cargo containers is found in
Ashley, S., SAFETY IN THE SKY: Designing, Bomb-Resistant Bae~aQe
Containers, Mechanical Engineering, v 114, n 6, Jun 1992, pp 81-86.
One type of container disclosed by this article is
designed to suppress shock waves and contain exploding fragments while safely
bleeding off or venting high pressure gases, while another type is designed to
guide
explosive products overboard by channeling blast forces out of and away from
the
airplane hull. Several of the new designs utilize composite materials that are
both
strong and lightweight. In one such design, a hardened luggage container is
to wrapped in a blanket woven from low density materials such as SPECTRA~
fibers, commercially available from AlliedSignal Inc., and lined with a rigid
polyurethane foam and perforated aluminum alloy sheet. A sandwich of this
material covers four sides of the container in a seamless shell. In this
regard, see
also U.S.P. 5,267,665.
Access to a container's interior is necessary for loading and unloading and
is typically provided by doors. Doors provide a significant weak point for the
container during an explosion since a blast from within the container forces a
typical door outward. If the door is connected through a hinge and metal pin
arrangement, the pins can become dangerous projectiles. If the door slides in
2o grooves or channels, the grooves or channels may bend or distort to cause
failure
of the container. It would thus be desirable to have a container design-that
eliminates the aforesaid problems with doors for access to the container's
interior.
U.S.P. 5,312,182 discloses hardened cargo containers wherein the door
engages by sliding in groovesltracks with an interlock that ostensibly
responds to
such an explosive blast by gripping tighter to resist rupture of the device.
CA 02271707 2004-04-30
3
Other blast resistant andlor blast directing containers are described in
European Patent Publication 0 572 965 A1 and in U.S.P. Nos. 5,376,426;
5,249,534; and 5,170,690. Other relevant art is represented by
U.S.P. Nos. 5,333,532; 5,238,305; 4,809,402; 4,231,135.
The present invention, which was developed to overcome the deficiencies
of the prior art, provides barrier units, constraining bands, and blast
resistant
container assemblies made therefrom.
BRIEF DESCRIPTION OF THE INVENTION
to This invention is a barrier unit, for use alone or with other barrier
units.
The barrier unit comprises a surface having a regular polygonal perimeter,
preferably rectangular, with a plurality of substantially parallel sides, each
of which
terminates in at least one loop integral with the surface. There are
preferably a
plurality of spaced coaxial loops integral with the surface on each side. The
15 surface comprises at least one network of fiber, preferably in a polymeric
matrix,
and having a tenacity of at least about 10 g/d and a tensile modulus of at
least
about 200 g/d. At least about 50, more preferably about 80, weight percent of
the
fiber comprises substantially continuous lengths of fiber aligned in the hoop
direction of the loops. Preferably, a plurality of barner units are used with
one
2o another, connected via their integral loops which function as the knuckles
of a
hinge through which a connecting pin is inserted.
The present invention is also a constraining band for constraining loads of
articles, e.g., steel rods or logs, or for constraining a container assembly
to enhance
its blast resistance. The constraining band has a length and a width, and
comprises
25 at least one network of fiber having a tenacity of at least about 10 g/d
and a tensile
modulus of at least about 200 g/d, preferably in a resin matrix. At least
about S0,
more preferably about 80, weight percent of the fiber comprises substantially
continuous lengths of fiber along the length of the band. The band is
interrupted
across its length in at least one place to create two ends, each of which
3o cori~priseslterminates in at least one integral loop, preferably a
plurality of spaced,
coaxially aligned loops. A pin is used to connect the loops of the two ends to
one
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4
another. The pin comprises a rigid or flexible material. Preferred rigid
materials
_ are rigid metal and rigid fiber-reinforced composites. Preferred flexible
materials
comprise fibers in the form of rope, roving unitape, shield, braid , belt
(strapping),
fabric and combinations thereof. The constraining bands can be made rigid or
flexible as desired. If the bands are polygonal in section, they can be made
with
flexible edges and rigid faces so that they can be collapsed for more
efficient
storage and transportation for subsequent assembly and use
The preferred blast resistant container assembly utilizing the constraining
band comprises at least three bands, one of which is the
discontinuous/interrupted
1o constraining band which is connected as set forth above to provide strength
and
energy absorption chaf~cteristics comparable to that of uninterrupted bands
using
continuous fiber. More-than one constraining/interrupted band can be used in
arr
assembly; it is preferred, however, that the constraining band be nested at
its point
or points of connection within a continuous band of material. The assembly
also
1s preferably comprises blast mitigating material located within the
container.
In a particularly preferred embodiment the blast resistant container
assembly comprises a cover, a container, and connecting means. The cover
comprises a polygonal perimeter, having first and second sub~antially parallel
sides, each of which terminates in at least one integral loop, preferably a
plurality
20 of spaced, coaxiaily aligned loops. The cover comprises at least one
network of
_ high strength fibers having a tenacity of at least about 10 g/d and a
tensile modulus
of at least about 200 g/d, preferably in a resin matrix. At least about 50,
preferably
about 80, weight percent of the fiber comprises substantially continuous
lengths of
fiber that are substantially perpendicular to the first and second sides and
aligned in
25 the hoop direction of the loops. The container comprises a wall and an
access
opening in the wall. The wall comprises at least two integral loops on
opposing
first and second sides of the access opening. Means is provided for connecting
the
loop on the first side of the cover with the loop on the first side of the
access
opening, and means is provided for connecting the loop on the second side of
said
3o cover with the loop on the second side of the access opening, with the
cover
overlaying the access opening. The connecting means can be a single means or a
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plurality of means. Rigid pins are preferred when a plurality of means is
utilized
whereas flexible pins are preferred when a single means is utilized. It is
preferred
that the perimeter shape be that of a regular polygon; as long as opposing
parallel
sides of the cover are the same length, even though the -length may differ'
from that
5 of other opposed pairs within the cover, then the polygon is deemed to be
regular.
The preferred shape is a rectangle wherein the third and fourth sides of the
cover
each terminate in at least one loop and wherein the wall further comprises at
least
an additional two integral loops on opposing third and fourth sides of the
access
opening. Means is provided for connecting the loop on the third side of the
cover
1o with the loop on the third side of the access opening, and means is also
provided
for connecting the loop on the fourth side of the cover with the loop on the
fourth
side of the access opening.
The present invention also comprises an improvement in a hinge comprised
of a pair of hinge halves terminating in coaxially aligned knuckles for
connection
with one another by a rigid pin. The improvement comprises a connecting pin
comprising a flexible material selected from the group consisting of rope,
roving,
unitape, shield, braid, belt, fabric and combinations thereof.
In an alternate embodiment, the present invention is an improved container
assembly comprising a container having a wall and an access opening in the
wall.
Zo The improvement comprises a hinge formed of fibrous material. The hinge
comprises a pair of hinge halves terminating in spaced, coaxially aligned
knuckles
which are joined together by a pin to cover the access opening. A portion of
each
of the hinge halves is integral with and covers a portion of the container
wall.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages will
become apparent when reference is made to the following drawing figures and
the
accompanying description of the preferred embodiments wherein:
FIGURE I is a plan view of a barrier unit 20 of the present invention,
connected via pin 25 to another barrier unit 20';
3o FIGURE 2 is a three dimensional view of constraining bands 3I and 3 I',
used with posts 32 to form a fence 30;
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G
FIGURE 3A is a three dimensional view of constraining band 40;
FIGURE 3B is an enlarged three dimensional partial view of loops 41
forming part of band 40;
FIGURE 3C is an enlarged three dimensional partial view of loops 41 and
41' connected with one another; _
FIGURE 3D is a three dimensional view of an alternate constraining band
40' ;
FIGURE 4 is a partial three dimensional view of loops 42 reinforced with
hinge half 45 and tubes 46;
1o FIGURE 5 is a partial three dimensional view of alternate, consolidated
loops 42;
FIGURE 6 is a side view of constraining bands 50 of the present invention
utilizing a soft/flexible pin 55 to connect loops 51;
FIGURE 7 is a side view of a plurality of constraining bands 50' of the
present invention, also utilizing a soffilflexible pin 55' to connect loops
51';
FIGURE 8A is a three dimensional view of band 11 which forms part of
container assembly 10 of FIGURE 8F;
FIGURE 8B is a three dimensional view of band 12 which forms part of
container assembly 10 of FIGURE 8F;
2o FIGURE 8C is a three dimensional view of band 13 which forms part of
container assembly 10 of FIGURE 8F;
FIGURE 8D is a three dimensional partial assembly view which together
with FIGURE 8E illustrates the assembly sequence for container assembly 10;
FIGURE 8E is a three dimensional partial assembly view which together
with FIGURE 8D illustrates the assembly sequence for container assembly 10;
FIGURE 8F is a three dimensional assembly view of container assembly 10;
FIGURE 8G is a three dimensional view of an optional support structure
for use with any of the container assemblies 10 depicted;
FIGURE 9 is a three dimensional view of an in-airport container assembly
60 for containing and transporting luggage 69 containing an explosive;
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7
FIGURE l0A is a three dimensional view of sub-bands 71 which form part
of container assembly 70 of FIGURE 10E;
FIGURE l OB is a three dimensional view of partially assembled container
assembly 70 with interrupted band 72 wrapped in place; -
FIGURE l OC is a three dimensional view of partially assembled container
assembly 70 with sub-bands 73 in place;
FIGURE l OD is a three dimensional view of partially assembled container
assembly 70 with band 78 in place;
FIGURE l0E is a three dimensional assembled view of container assembly
l0 70 with third band 70 oriented for closure of container assembly 70 with
step 77 in
place;
FIGURE 1 lA is a three dimensional view of a container with interrupted
band 90 thereon with a rigid pin 91 for mechanical closure;
- FIGURE 11B is a three dimensional view of a container with interrupted
band 95 thereon with a rigid composite pin 96 for mechanical closure;
FIGURE 11C is a three dimensional view of a container with interrupted
band 100 thereon with a flexible rope 101 for mechanical closure;
FIGURE 12 is a three dimensional view of a container 1 i 0 formed from six
separate panels/barrier un~s 111 connected with twelve pins i 12 at its edges;
and
2o FIGURE 13 is a three dimensional view of a container 115 formed from a
five-sided box 116 having a removable door 117 located with four pins 118.
DETAILED DESCRIPTION OF THE INVENTION
The preferred invention will be better understood by those of skill in the art
with reference to the above figures. The preferred embodiments of this
invention
illustrated in the figures are not intended to be exhaustive or to limit the
invention
to the precise form disclosed. It is chosen to describe or to best explain the
principles of the invention and its application and practical use to thereby
enable
others skilled in the art to best utilize the invention. In particular, the
bands of
blast resistant material are shown in the accompanying drawings with parallel
lines
3o representing substantially continuous fibers/filaments in the hoop
direction of the
bands, i.e., as unidirectional fibrous bands. This representation is for ease
in
CA 02271707 2004-04-30
understanding the invention - while it constitutes one fabric contemplated for
use in
the present invention, it is not the exclusive fabric.
Initial discussion of the drawing figures will be directed to design
considerations followed by a discussion of appropriate materials and how they
affect blast resistance ardor blast-directing capabilities of the structures.
Referring to FIGURE 1, barrier unit 20 comprises a surface 21 having a
regular polygonal perimeter, i.e., essentially a square, with a plurality of
pairs of
substantially parallel sides 22 and 23. Each of parallel sides 22 and 23
terminates
in at least one loop 24 integral with surface 21, in this instance 2 loops 24
per side
1o 22, 23. In FIGURE 1, barrier unit 20 is shown affixed to another, similar
varrier
unit 20' via pin 25. Pin 25 may be rigid or flexible (soft), according to end
use and
desired properties.
This barrier unit 20 of FIGURE 1 can be used to close a blast resistant
container (see FIGURE 13 and accompanying discussion),or as a window
protector if affixed in front of a conventional window with pins into a mating
sill.
Such a protector would provide protection against thrown missiles, bullets,
hurricanes and so forth. The connecting pins/rods could be locked into place
with
stops (not shown).
With reference to FIGURE 2, a fencelbarrier i s shown . The fence
comprises a plurality of constraining bands 31 and 31' which can be used to
confine animals or to provide, protection against a wide variety of threats,
including
vehicles, avalanches, and trespassing snowmobiles, etc. Bands 31 and 31' have
a
length and a width. Bands 31 and 31' are interrupted across the length thereof
to
create two ends 32 and 32', respectively. Ends 32 and 32' comprise at least
one
integral loop 33 and 33', respectively. In FIGURE 2, each end comprises only
one
integral loop 33 or 33'. The fence is formed by connecting the loops 33 and
33'
with a pin 34, depicted as a post. In this instance, pin 34 would desirably be
formed of a rigid material, e.g., wood.
With reference to FIGURES 3A-3D, formation of an interrupted
3o constraining band 40 is shown. Unitape or other fabric may be used to
create such
an interrupted band 40. A belt 41 of unitape is created by winding a length of
same
CA 02271707 2004-04-30
9
around two rods (not shown) separated by an appropriate distance. The big
fabric
wraps at either end are separated into a number of segments of width b. The
yarn
is pushed together to produce loops 42 of width b/2 (see FIGURE 3B). It-is
desirable that all of the fibers be continuous across loops 42 as depicted.
The band
5 may be constructed from a variety of materials, including rope, roving,
unitape,
shield, braid, belt (strapping), fabric, and combinations thereof. Details on
unitape
and shield may be found in the accompanying examples of the invention. Pin 43
can be used to connect interleaved, coaxiaily aligned loops 42 and 42'. Pin 43
may
be formed of rigid or flexible (soft) material, as desired. In FIGURE 3D, is
shown
1o an alternate interrupted band 40' wherein fabric 41, preferably unitape,
forms
several discrete sub-bands which are reinforced across the main body thereof,
i.e.,
that portion exclusive of loops 42", with fabric 44, preferably having
continuous
length fiber normal to that of the unitape, sewn thereto.
With reference to FIGURE 4, an actual hinge half 45 with short
15 tubesrnserts 46, may be inserted within the loops 42 to provide rigidity.
These
tubes may be formed from plastic, metal, ceramic, composites or wood.' All of
the
tubes on each end of the band preferably are linked together to create a hinge
system which will keep the openings in register and allow a pin 43 to be
easily
inserted or removed to close or open the band. The tubes, or hinge knuckles,
may
2o be circular or oblong in cross-section. FIGURE 5 depicts another way to
form
rigid~loops 42 wherein the wrapped material is consolidated to form loops 42.
With reference to FIGURES 6 and 7, the interrupted band 50, 50' can be
closed by lacing it up with a strong flexible material, such as soft pin 55 ,
55 ~ ,
respectively. In this case the loops 51 can be coaxially aligned per end and
25 adjacent the loops of the other end for lacing, e.g., like a shoelace.
FIGURES 6
and 7 differ from one another in that the interrupted band 50' of FIGURE 7
actually comprises a plurality of discrete sub-bands wherein each sub-band end
terminates in a single loop. In both instances, the loops can be in register,
or not,
as desired, and can cover anywhere from about 20 to about 95 % of the band.
The
3o closure of the band may leave little distance between the mating
ends/edges, as in
FIGURE 6, or may leave a considerable distance, as in FIGURE 7, all according
to
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-- end use. Appropriate strong knots, sockets, and/or stops (not shown) can be
used
to effect closure. Optionally, yokes or flanges (not shown) can be used to
keep _
loops in appropriate register. .
Referring to FIGURE 8F, the numeral 10 indicates a blast resistant
5 container assembly. The container comprises a set of at least three nested
and
mutually reinforcing four-sided continuous bands of material I 1, 12, and 13
assembled into a cube. See FIGURES 8A, 8B, and 8C. By "band" is meant a thin,
flat, volume-encircling strip. The cross-section of the encircled volume may
vary ,
although polygonal is preferred to circular, with rectangular being more
preferred
and square being most preferred, as depicted. With reference to FIGURES 8D and
8E, a first inner band 11 may be filled with blast mitigating mate~al (e.g.,
an
aqueous foam) and then nested within a slightly larger second- band 12 which
is
nested within a slightly larger third band 13, all bands with their respective
longitudinal axes perpendicular to one another. In this fashion, each of the
six
panels fornung the faces of the cubic container will have a thickness
substantially
equivalent to the sum of the thicknesses of at least two of the bands 11, I2
and 13,
where they overlap, and every edge 15 of the container is covered by at least
one
band of material, 11, 12, or 13. Stated differently, after the load (explosive
or
luggage) is placed in the first band 11, blast mitigating material (not shown)
is
optionally placed or dispersed around the load within the first band 11. The
second
structurally similar band 12 of slightly larger dimensions is placed over the
first so
that its longitudinal axis is perpendicular to that of first band 11 (see
FIGURE 8D).
The third, similar yet larger, band 13 is slid over the second band 12, so
that its
longitudinal axis is perpendicular to the axes of both bands 11 and 12 (see
FIGURE 8E). The third band 13 completes the blast resistant container assembly
10. The fit between bands 11, I2 and 13 is not intended to be a gastight seal,
but is
a close fit to permit gas to vent gradually, in the event of an explosion,
from the
corners 16 of the cubic container. It is preferred that the bands slide on one
another, and therefore the fiictional characteristics of their surfaces may
need to be
3o modified, as will be discussed in more detail later. Container assembly 10
does not
have a separate entry door and thus avoids all of the limitations presented by
the
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11
same in the prior art. FIGURE 8G depicts a weight/load bearing frame I7 which
may optionally be nested within container assembly 10 in the event that
container
assembly 10 is insu~ciently rigid for bearing the items to be loaded therein.
Inner
band 11 is slipped over the frame initially, and then assembly proceeds as
earlier
s discussed. Frame 17 may be made from metal, wood or structural composite
rods
designed in a way to optimize the load bearing capacity of the structure and
to
minimize container weight.
As previously stated, however, assembly 10 requires movement of the
bands to operate which is not always user friendly, especially when there are
space
1o constraints as with aircraft. The interrupted band of the present invention
is
designed to be mechanically closed so as to provide strength and energy
absorption
characteristics similar to that of unir~terrupted%continuous bands using
continuous
fiber. The interrupted band may be used to contain blast, either alone or in
conjunction with other bands, continuous or interrupted. The interrupted band
1s may be used in conjunction with a conventional blast resistant container;
possibly
steel if weight is not a concern, to prvide a closure system. Such bands may
also
be used for a variety of other applications, such as constraining loads of
steel rods
or logs on a truck bed, for instance. These bands can be closed with rigid
and/or
flexible pins, discussed in further detail later.
2o With regard to FIGURE 9, in-airport blast resistant container assembly 60
is depicted. Luggage 68 containing an explosive is detected by a device (not
shown) used by airport security personnel. It is placed inside container
assembly
60 and taken to a place where the explosive can be safely removed or
detonated.
A rigid rectangular shell prism (not shown) is formed with one face missing. A
- ---
2s first band 6I is formed and interrupted across the length thereof. Loops 64
are
formed at the two ends of first band 61, which is wrapped around the shell so
as to
center the band interruption on the access opening of the shell. Second,
continuous band 65 of slightly larger dimensions is placed over closed first
band 61
so that its longitudinal axis is perpendicular to that of first band 61. The
third,
3o continuous and yet larger, band 66 is slid over the second band 65, so that
its
longitudinal axis is perpendicular to the axes of both bands 61 and 65.
Casters 67
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12
can be attached to the base of the assembly 60 for mobility. In use, band 66
is slid
to one side of assembly 60 to expose band 61 which is mechanically closed
thereacross by connection of loops 64. Loops 64 are disconnected to open band
61. Luggage 68 is placed within assembly 66, and thereafter, blast mitigating
material is optionally is placed or dispersed around the load within first
band 61.
Second band 65 is either slid onto first band 61 or is permanently affixed
with the
orientation as shown in FIGURE 9. Third band 66 is then rolled horizontally to
cover the mechanically closed, interrupted band 61.
With reference to FIGURES l0A-10E, a hardened aircraft luggage
to container assembly 70 of the LD3 type is shown. The container is a
rectangular
box with a step 76 created at the bottom of one side to facilitate band
wrapping.
The box was constructed as detailed in Example 2 set forth below. The
structural
shell had an access opening 80 to the interior thereof on the front side. The
blast
containment function is primarily provided by three mutually reinforcing,
perpendicular bands 72, 78, and 79 (two continuous bands 78 and 79 forming the
middle and outer bands, respectively, and one interrupted/discontinuous band
72
having a pin joint and forming the inner band along with sub-bands 71). The
interrupted band 72overlaps the side edges of access opening 80 slightly. The
hinge connection is created by subdividing band 72 into a plurality of parts
which
2o are used to form loops/knuckles 81, 81' which are spaced and coaxially
aligned on
each end of band 72. The loops 81 and 81' are aligned as in a hinge for
connecting
pin 82 to be placed therethrough.
With reference to FIGURES l0A and IOC, it can be seen that continuous
sub-bands, narrower in width than the box, are wound to either side of access
opening 80 in a front, top, back, bottom orientation (see FIGURE l0A), after
which the interrupted inner band 72 is placed over the box with pin 82
connecting
ends across the middle of access opening 80. The pin is horizontal in
orientation.
Two additional continuous sub-bands 73, similar to the others, are formed on
the
box on either side of access opening 80 in a front, side, back, side
orientation (see
3o FIGURE lOC). These sub-bands 73 are permanently attached to the box. A
triangular wedge 77 is placed in step 76 with its base located to the exterior
prior
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13 _
to wrapping of middle band 78. This wedge, in conjunction with the stepped
box,
forms the truncated side of the aircraft LD3 container 70. Middle band 78 is
permanently attached to the box since it does not interfere with the opening
of the
box. Outer band 79 is a removable band, placed on assembly 70 perpendicular to
s the other primary bands 72 and 78.
FIGURE 11 A depicts a partially assembled container with interrupted band
90 thereon with a rigid pin 91 for mechanical closure. FIGURE 11B shows a
partially assembled container with interrupted band 95 thereon with a rigid
composite pin 96 for mechanical closure. Composite pin 96 is formed by
wrapping
1o a fibrous composite layer, 98 around a rigid pin 97. Pin 96 is then
threaded through
the loops of interrupted band 90 with its tails 99 folded to either side for
closure by
yet another band of material (not shown). FIGURE 11C shows a partially
assembled container with interrupted band 100 thereon with a flexible rope 101
for
mechanical closure. Rope 101 is knotted at one end 102 to keep it from sliding
15 through the loops of the interrupted band 100.
FIGURE 12 shows a container 110 formed from six separate panels/barrier
units 111 connected with twelve pins 112 at its edges. FIGURE 13 shows a
container 115 formed from a five-sided box 116 having a removable door 117
located with four pins 118.
20 Many differing container shapes are contemplated by the present invention. -
-
For instance, the container assembly of FIGURE 1 OE encloses a non-cubic
rectangular prism due to the differing rectangular cross-sections of its three
bands.
The preference for the bands to have a polygonal cross-section is derived from
the
tendency for the container to deform to increase the internal volume during an
25 explosion. A regular polygon is preferred, more preferably a rectangle, and
most
preferably a square. ~t is desirable to have opposed parallel sides of
substantially
equal length although it is not necessary that all sets of opposed parallel
sides in the
regular polygon be of substantially equal length, i.e., with a rectangular
surface, a
set of opposed sides canl be longer than the other set of opposed sides, as
long as
3o the surface is not a square.
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14
It should be appreciated by now that substantially more than three bands
can readily be utilized in the present invention, even with the basic cube (or
rectangular prism) design of the container. Theoretically an unlimited number
of
coaxial bands can be used in parallel, preferably abutting one another, to
substitute
for any one band in the basic three-band container concept of the invention.
It is preferred, however, that the outermost band comprises a single
continuous
band. Furthermore, a large number of coaxial bands can also be coaxially
nested
one within the other to substitute for any one band in the basic three band
container
concept of the invention; the number of bands utilized as an equivalent may
depend
1o upon the desired rigidity of the equivalent. _ It is possible to have
several flexible
bands which, when nested coaxially, become rigid.
In the various embodiments depicted, a rigid inner liner or band can be
constructed using one or more of the techniques and/or material to follow. The
_ inner liner/band may be rotationally molded using polyethylene, cross-
linkable
polyethylene, nylon 6, or nylon 6,6 powders. Technology described in Plastics
World, p.60, July, 1995, hereby incorporated by reference, can also be used.
Tubes, rods and connectors may be used, preferably formed from thermoplastic
or
thermoset resins, optionally fiber reinforced, or low density metals such as
aluminum. The inner liner/band may utilize a continuous four-sided metal band.
2o Sandwich constructions consisting of honeycomb, balsa wood or foam core
with
rigid facings may be used. The honeycomb may be constructed from aluminum,
cellulose products, or aramide polymer. Weight can be minimized by using
construction techniques well known in the aerospace industry. (Carbon fiber
reinforced epoxy composites may be used.) A rigid inner shell/band can be
constructed from wood using techniques well known to the carpentry trades.
(Flame retardant paipts may usefully be used.) The rigid inner liner/band may
serve
as a mandrel onto which the bands are wound and can form part of the final
blast
container. Alternatively the inner liner can be inserted into the inner band
after the
band has been constructed.
As used herein with respect to bands, "rigid" means that a band is inflexible
across the face or faces thereof. If the band comprises a plurality of faces
and
CA 02271707 1999-OS-07
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edges, then it may be substantially inflexible across the faces but retain its
flexibility
- at the edges and still be considered "rigid." Such a band is also considered
"collapsible" since its flexible edges act as pin-less hinges connecting the
substantially inflexible faces, and the band can be essentially flattened by
folding at
5 least two of its edges. With respect to the faces as well as the pins,
flexibility is
determined as follows. A length of the material is clamped horizontally along
one
side on a flat support surface with an unsupported overhang portion of length
"L"
The vertical distance "D" that the unclamped side of the overhang portion
drops
below the flat support surface is measured. The ratio D/L gives a measure of
1o drapability. When the ratio approaches 1, the structure/face is highly
flexible, and
when the ratio approaches 0, it is very rigid or inflexible. Structures are
considered
rigid when D/L is less than about 0.2, more preferably less than about 0.1. '
The structural designs of the present invention, especially the three band
cube design, enhance the blast containment capability of the container. Blast -
15 containment capability is also enhanced with increased areal density of the
container. The "areal density" is the weight of a structure per unit area of
the
structure in kg/m2, as discussed in more detail in conjunction with the
examples
which follow below.
The preferred blast resistant materials utilized in forming the containers and
- 2o bands of the present invention are oriented films, fibrous layers, and/or
a
combination thereof. A resin matrix may optionally be used with the fibrous
layers,
and a film (oriented or not) may comprise the resin matrix.
Uniaxially or biaxially oriented films acceptable for use as the blast
resistant
material can be single layer, bilayer, or multilayer films selected from the
group
' 25 consisting of homopolymers and copolymers of thermoplastic polyolefins,
thermoplastic eiastomers, crosslinked thermopiasti~s, crosslinked elastomers,
polyesters, polyamides, fluorocarbons, urethanes, epoxies, polyvinylidene
chloride,
polyvinyl chloride, and blends thereof. Films of choice are high density
polyethylene, polypropylene, and polyethylene/elastomeric blends. Film
thickness
CA 02271707 1999-OS-07
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16
preferably ranges from about 0.2 to 40 mils, more preferably from about 0.5 to
20
mils, most preferably from about 1 to 1 S mils.
For purposes of this invention, a fibrous layer comprises at least one
network of fibers either alone or with a matrix. Fiber denotes an elongated
body,
s the length dimension of which is much greater than the transverse dimensions
of
width and thickness. Accordingly, the term fiber includes monofilament,
multifilament, braid, rope, ribbon, strip, staple and other forms of chopped,
cut or
discontinuous fiber and the like having regular or irregular cross-sections.
The -
term fiber includes a plurality of any one or combination of the above.
to The cross-sections of filaments for use in this invention may vary widely.
They may be circular, flat or oblong in cross-section. They also may be of
irregular
or regular multi-lobal cross-section having o~r~.e or more regular or
irregular lobes
projecting from the linear or longitudinal axis of the-fibers. - It is
particularly
preferred that the filaments be of substantially circular, flat or oblong
cross-section,
Is most preferably the former.
By network is meant a plurality of fibers arranged into a predetermined
configuration or a plurality of fibers grouped together to form a twisted or
untwisted yarn, which yarns are arranged into a predetermined configuration.
For
example, the fibers or yarn may be formed as a felt or other nonwoven, knitted
or
2o woven (plain, basket, satin and crow feet weaves, etc.) into a network, or
formed
into a network by any conventional techniques. According to a particularly
preferred network configuration, the fibers are unidirectionally aligned so
that they
are substantially parallel to each other along a common fiber direction.
Continuous
length fibers are most preferred although fibers that are oriented and have a
length
2s of from about 3 to 12 inches (about 7.6 to about 30.4 centimeters) are also
acceptable and are deemed "substantially continuous" for purposes of this
invention.
It is preferred that within a fibrous layer at least about 50 weight percent
of
the fibers , more preferably at least about 80 weight percent, be
substantially
3o co~ttinuous lengths of fiber that encircle the volume enclosed by the
container. By
encircle the volume is meant in the band or hoop direction, i.e.,
substantially
CA 02271707 1999-OS-07
WO 98/21542 PCT/US97/06054
17
parallel to or in the direction of the band, as band has been previously
defined and
shown. By substantially parallel to or in the direction of the band is meant
within +
10°. ~ The'preferred fibrous material comprises substantially
continuous, parallel
lengths of fiber perpendicular to the edge.
The continuous bands can be fabricated using a number of procedures. In
one preferred embodiment, the bands, especially those without resin matrix,
are
formed by winding fabric around a mandrel and securing the shape by suitable
securing means, e.g., heat and/or pressure bonding, heat shrinking, adhesives,
staples, sewing and other securing means known to those of skill in the art.
1o Sewing can be either spot sewing, line sewing or sewing with intersecting
sets of
parallel lines. Stitches are typically utilized in sewing, but no specific
stitching type
or method constitutes a preferred securing means for use in this invention.
Fiber
used to form stitches can also vary widely. Useful fiber may have a relatively
low
modulus or a relatively high modulus, and may have a relatively low tenacity
or a
relatively high tenacity. Fiber for use in the stitches preferably has a
tenacity equal
to or greater than about 2 g/d and a modulus equal to or greater than about 20
g/d. -
All tensile properties are evaluated by pulling a 10 in (25.4 cm.) fiber
length
clamped between barrel clamps at 10 in/min (25.4 cm/min) on an Instron Tensile
Tester. In cases where it is desirable to make the band somewhat more rigid,
pockets can be sewn in the fabric into which rigid plates may be inserted, or
the
plates themselves can be sewn into the band between wraps of material. This is
another "collapsible" embodiment of rigid bands, i.e., the faces are rigid due
to the
presence of the rigid plates, but the edges are flexible due to the flexible
fabric
forming the bands or can be bent by, e.g., the weight of the rigid face
portion. An
2s advantage to the collapsible embodiments of the present invention is that
the
apparatus can be transported flat and set up immediately prior to use. Another
way
to make wraps of fabric selectively rigid within a band is by way of stitch
patterns,
e.g.,'parallel rows of stitches can be used across the face portions of the
band to
make them rigid while leaving the joints/edges unsewn to create another
"collapsible" rigid band.
CA 02271707 1999-OS-07
WO 98/21542 PCT/LTS97/06054
18
The type of fibers used in the blast resistant material may vary widely and
can be inorganic or organic fibers. Preferred fibers for use in the practice
of this
invention, especially for the substantially continuous lengths, are those
having a
tenacity equal to or greater than about 10 grams/denier (g/d) and a tensile
modufus
equal to or greater than about 200 g/d (as measured by an Instron Tensile
Testing
machine). Particularly preferred fibers are those having a tenacity equal to
or
greater than about 20 g/d and a tensile modulus equal to or greater than about
500
g/d. Most preferred are those embodiments in which the tenacity of the fibers
is
equal to or greater than about 25 g/d and the tensile modulus is equal to or
greater
to than about 1000 g/d. In the practice of this invention, the fibers of
choice have a
tenacity equal to or-greyer than about 30 g/d and a tensile modulus equal to
or
greater than about 1200~/d. J
High performance fibers can be incorporated into bands together and/or in
conjunction with other fibers which may be inorganic, organic or metallic.
Preferably the high performance fiber is the continuous (warp) fiber and the
other
fiber is the fill fiber. Optionally the other fiber can be incorporated in
both warp
and fill. Such fabrics are designated hybrid fabrics. Hybrid fabrics can be
used to
construct one or more bands of the container. Preferably, hybrid fabrics would
be
used to construct part or all of the outer band. Bands can also be created by
2o simultaneously or serially wrapping one or more fabrics made with
conventional
fibers with one or more fabrics made from high performance fibers.
The denier of the fiber may vary widely. In general, fiber denier is equal to
or less than about 8,000. In the preferred embodiments of the invention, fiber
denier is from about 10 to about 4000, and in the more preferred embodiments
of
the invention, fiber denier is from about 10 to about 2000. In the most
preferred
embodiments of the invention, fiber denier is from about 10 to about 1500.
Fabrics
made with coarser (tughef) denier fibers will allow more venting of gases,
which
may be desirable in some cases.
- Useful inorganic fibers include S-glass fibers, E-glass fibers, carbon
fibers,
3o boron fibers, alumina fibers, zirconia-silica fibers, alumina-silica fibers
and the like.
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WO 98/21542 PCT/US97/06054
--r ~ 19
Illustrative of useful inorganic filaments for use in the present invention
are
glass fibers such as fibers formed from quartz, magnesia alumuninosilicate,
non-
alkaline aluminoborosilicate, soda borosilicate, soda silicate, soda lime-
aluminosilicate, lead silicate, non-alkaline lead boroalumina, non-alkaline
barium
boroalumina, non-alkaline zinc boroalumina, non-alkaline iron aluminosilicate,
cadmium borate, alumina fibers which include "saffil" fiber in eta, delta, and
theta
phase form, asbestos, boron, silicone carbide, graphite and carbon such as
those
derived-from the carbonization of saran, polyaramide (Nomex), nylon,
polybenzimidazole, polyoxadiazole, polyphenylene, PPR, petroleum and coal
to pitches (isotropic), mesophase pitch, cellulose and polyacrylonitrile,
ceramic fibers,
metal fibers as for example steel, aluminum metal alloys, and the like.
Illustrative of useful organic filaments are those composed of polyesters,
polyolefins, polyetheramides, fluoropolymers, polyethers, celluloses,
phenolics,
polyesteramides, polyurethanes, epoxies, aminoplastics, sili6ones,
polysulfones,
polyetherketones, polyetheretherketones, polyesterimides, polyphenylene
sulfides,
polyether acryl ketones, poly(amideimides), and polyimides. Illustrative of
other
useful organic filaments are those composed of aramids (aromatic polyamides),
such as poly(m-xylylene adipamide), polyp-xylylene sebacamide), poly(2,2,2-
trimethyl-hexamethylene tecephthalamide), poly(piperazine sebacamide),
2o poly(metaphenylene isophthalamide) and polyp-phenylene terephthalamide);
aliphatic and cycloaliphatic polyamides, such as the copolyamide of 30%
hexamethylene diammonium isophthalate and 70% hexamethylene diammonium
adipate, the copolyamide of up to 30% bis-(-amidocyclohexyl)methylene,
terephthalic acid and caprolactam, polyhexamethylene adipamide (nylon 66),
poly(butyrolactam) (nylon 4), poly(9-aminonoanoic acid) (nylon 9),
poly(enantholactam) (nylon 7), poly(capryllactam) (nylon 8), polycaprolactam
(nylon 6), polyp-phenyieae terephthalamide), polyhexamethylene sebacamide
(nylon 6,10}, polyaminoundecanamide (nylon 11 ), polydodecanolactam (nylon
12),
polyhexamethylene isophthalamide, polyhexamethylene terephthalamide,
3o polycaproamide, poly(nonamethylene azelamide (nylon 9,9),
poly(decamethylene
azelamide) (nylon 10,9), poly(decamethylene sebacamide) (nylon 10,10),
poly[bis-
CA 02271707 1999-OS-07
WO 98121542 PCT/US97/06054
(4-aminocyclohexyl)methane 1, I O-decanedicarboxamide] (Qiana) (traps), or
combinations thereof; and aliphatic, cycloaliphatic and aromatic polyesters
such as
poly( I,4-cyclohexylidene dimethyl eneterephthalate) cis and traps,
poly(ethylene-
I,5-naphthalate), polyethylene-2,6-naphthalate), poly(1,4-cyclohexane
5 dimethylene terephthalate) (traps), poly(decamethy(ene terephthalate),
polyethylene terephthalate), polyethylene isophthalate), polyethylene
oxybenzoate), poly(para-hydroxy benzoate), poly(dimethylpropiolactone),
poiy(decamethylene adipate), polyethylene succinate), polyethylene azelate),
poly(decamethylene sabacate), poly(a,a-dimethylpropiolactone), and the like.
Also illustrative of useful organic filaments are those of polybenzoxazoles
and polybenzothiazoles, as detailed in the Handbook of Fiber Science and
Technology: Volume II. High Technology Fibers. Part D, edited by Menachem
Lewin.
Also illustrative of useful organic filaments are those of liquid crystalline
~5 polymers such as lyotropic liquid crystalline polymers which include
polypeptides
such as poly-a-benzyl L-glutamate and the like; aromatic polyamides such as
poly(1,4-benzamide), poly(chloro-I-4-phenylene terephthalamide), poly(1,4-
phenylene fumaramide), poly(chloro-1,4-phenylene fumaramide), poly(4,4'-
-- benzanilide traps, traps-muconamide), poly(1,4-phenylene mesaconamide),-
2o poly(1,4-phenylene) (traps-1,4-cyclohexylene amide), poly(chloro-1,4-
phenylene)
(traps-1,4-cyclohexylene amide), poly(1,4-phenylene 1,4-dimethyl-traps-1,4-
cyclohexylene amide), poly(1,4-phenylene 2,5-pyridine amide), poly(chioro-1,4-
phenylene 2,5-pyridine amide), poly(3,3'-dimethyl-4,4'-biphenylene 2,5
pyridine
amide), poly( 1,4-phenylene 4,4'-stilbene amide), poly(chloro-1,4-phenylene
4,4'-
stilbene amide), poly(1,4-phenylene 4,4'-azobenzene amide), poly(4,4'-
azobenzene
4,4'-azobenzene amide), poly(1,4-phenylene 4,4'-azoxybenzene amide), poly(4,4'-
azobenzene 4,4'-azoxybenzene amide), poly(1,4-cyclohexylene 4,4'-azobenzene
amide), poly(4,4'-azobenzene terephthal amide), poly(3,8-phenanthridinone
terephthal am:,~e), poly(4,4'-biphenylene terephthal amide), poly(4,4'-
biphenylene
4a4'-bibenzo amide), poly( 1,4-phenylene 4,4'-bibenzo amide), poly( 1,4-
phenylene
4,4'-terephenylene amide), poly(1,4-phenylene 2,6-naphthal amide), poly(1,5-
CA 02271707 1999-OS-07
WO 98/21542 PCT/US97H16054
21
naphthalene terephthal amide), poly(3,3'-dimethyl-4,4-biphenylene terephthal
amide), poly(3,3'-dimethoxy-4,4'-biphenylene terephthal amide), poly(3,3'-
dimethoxy-4,4-biphenylene 4,4'-bibenzo amide) and the like; polyoxamides such
as
those derived from 2,2'-dimethyl-4,4'-diamino biphenyl and chloro-1,4-
phenylene
diamine; polyhydrazides such as poly chloroterephthalic hydrazide, 2,5-
pyridine
dicarboxylic acid hydrazide) poly(terephthalic hydrazide), poly(terephthalic-
chloroterephthalic hydrazide) and the like; poly(amide-hydrazides) such as
poly(terephthaloyl 1,4 amino-benzhydrazide) and those prepared from 4-amino-
benzhydrazide, oxalic dihydrazide, terephthalic dihydrazide and para-aromatic
1o diacid chlorides; polyesters such as those of the compositions include
poly(oxy-
trans-1,4-cyclohexyleneoxycarbonyl-trans-1,4-cyclohexylenecarbonyl-(3-oxy-1,4-
phenyl-eneox~teraphthaloyl) and poly(oxy-cis-1,4-cyclohe~xyleneoxycarbonyl-
trans-
1,4-cyclohexylenecarbonyl-(3-oxy-1,4-phenyleneoxyterephthaloyi) in methylene
chloride-o-cresol poly(oxy-trans-1,4-cyclohexylene oxycarbonyl-trans-1,4-
cyclohexylenecarbonyl-b-oxy-(2-methyl-1,4-phenylene)oxy-terephthaloyl) in
1,1,2,2-tetrachloroethane-o-chlorophenol-phenol (60:25:15 voUvol/vol),
poly[oxy-
trans-1,4-cyclohexyleneoxycarbonyl-trans-1,4-cyclohexylenecarbonyl-b-oxy(2-
methyl-1,3-phenylene)oxy-terephthaloyl] in o-chlorophenol and the like;
polyazomethines such as those prepared from 4,4'-diaminobenzanilide and
2o terephthalaldehyde, methyl-1,4-phenylenediamine and terephthalaldehyde and
the
like; polyisocyanides such as poly( -phenyl ethyl isocyanide), poly(n-octyl
isocyanide) and the like; polyisocyanates such as poly(n-alkyl isocyanates) as
for
example poly(n-butyl isocyanate), poly(n-hexyl isocyanate) and the like;
lyotropic
crystalline polymers with heterocyclic units such as poly(1,4-phenylene-2,6-
benzobisthiazole) (PBT), holy(1,4-phenylene-2,6-benzobisoxazole) (PEO),
poly(1,4-phenylene-1,3,4-oxadiazole), poly(1,4-phenylene-2,6-
benzobisimidazole),
poly[2,5(6)-benzimidazole] (AB-PBI), poly[2,6-(1,4-phenylene-4-
phenylquinoline],
poly[ 1,1'-(4,4'-biphenylene)-6,6'-bis(4-phenylquinoline)] and the like;
polyorganophosphazines such as polyphosphazine, polybisphenoxyphosphazine,
3o poly[bis(2,2,2' trifluoroethylene) phosphazine] and the like; metal
polymers such as
those derived by condensation of traps-bis(tri-n-butylphosphine)platinum
dichloride
CA 02271707 1999-OS-07
WO 98/21542 PCT/US97/06054
22
with a bisacetylene or trans-bis(tri-n-butylphosphine)bis( 1,4-
butadienyl)platinum
and similar combinations in the presence of cuprous iodine and an amide;
cellulose
and cellulose derivatives such as esters of cellulose as for example
triacetate
cellulose, acetate cellulose, acetate-butyrate cellulose, nitrate cellulose,
and sulfate
cellulose, ethers of cellulose as for example, ethyl ether cellulose,
hydroxymethyl
ether cellulose, hydroxypropyl ether cellulose, carboxymethyl ether cellulose,
ethyl
hydroxyethyl ether cellulose, cyanoethylethyl ether cellulose, ether-esters of
ceIlulosE as for example acetoxyethyl ether cellulose and benzoyloxypropyl
ether
cellulose, and urethane cellulose as for example phenyl urethane cellulose;
t0 thermotropic liquid crystalline polymers such as ceiluloses and their
derivatives as
for example hydroxypropyl cellulose, ethyl cellulose propionoxypropyl
cellulose;
thermotropic copolyesters as for example copolymers of 6-hydroxy-2-naphthoic
acid and p-hydroxy benzoic acid, copolymers of 6-hydroxy-2-naphthoic acid,
terephthalic acid and p-amino phenol, copolymers of 6-hydroxy-2-naphthoic
acid,
terephthalic acid and hydroquinone, copolymers of 6-hydroxy-2-naphthoic acid,
p
hydroxy benzoic acid, hydroquinone and terephthalic acid, copolymers 6f 2,6
naphthalene dicarboxylic acid, terephthalic acid, isophthalic acid and
hydroquinone,
copolymers of 2,6-naphthalene dicarboxylic acid and terephthalic acid,
copolymers
of p-hydroxybenzoic acid, terephthalic acid and 4,4'-dihydroxydiphenyl,
2o copolymers of p-hydroxybenzoic acid, terephthalic acid, isophthalic acid
and 4,4'-
dihydroxydiphenyl, p-hydroxybenzoic acid, isophthalic acid, hydroquinone and
4,4'-dihydroxybenzophenone, copolymers of phenylterephthalic acid and
hydroquinone, copolymers of chlorohydroquinone, terephthalic acid and p-
acetoxy
cinnamic acid, copolymers of chlorohydroquinone, terephthalic acid and
ethylene
dioxy-r,r'-dibenzoic acid, copolymers of hydroquinone, methylhydroquinone, p-
hydroxybenzoic acid.and isophthalic acid, copolymers of (1-
phenylethyl)hydroquinone, terephthalic acid and hydroquinone, and copolymers
of
polyethylene terephthalate) and p-hydroxybenzoic acid; and thermotropic
polyamides and thermotropic copoly(amide-esters).
CA 02271707 1999-OS-07
WO 98/21542 PCTlUS97/06054 -
23
Also illustrative of useful organic filaments are those composed of extended
chain polymers formed by polymerization of a,(3-unsaturated monomers of the
formula:
RtR2-C=CH2
wherein:
R, and R2 are the same or different and are hydrogen, hydroxy, halogen,
alkylcarbonyl, carboxy, alkoxycarbonyl, heterocycle or alkyl or aryl either
unsubstituted or substituted with one or more substituents selected from the
group
consisting of alkoxy, cyano, hydroxy, alkyl and aryl. Illustrative of such
polymers
to of a,(3-unsaturated monomers are polymers including polystyrene,
polyethylene,
polypropylene, poly(1-octadecene), polyisobutylene, poly(1-pentene), poly(2-
methylstyrene), poly(4-methylstyrene), poly(/-hexene), poly(4-methoxystyrene),
poly(5-methyl-1-hexene), poly(4-methyipentene), poly(/-butene), polyvinyl
chloride, polybutylene, polyacrylonitrile, poly(methyl pentene-1), polyvinyl
alcohol), poly(vinyl-acetate), poly(~inyl butyral), polyvinyl chloride),
poly(vinylidene chloride), vinyl chloride-vinyl acetate chloride copolymer,
poly(vinylidene fluoride), poly(methyl acrylate), poly(methyl methacrylate),
poly(methacrylonitrile), poly(acrylamide), polyvinyl fluoride), polyvinyl
formal),
poly(3-methyl-1-butene), poly(4-methyl-I-butene), poly(4-methyl-1-pentene),
2o poiy(1-hexane), poly(5-methyl-1-hexene), poly(/-octadecene), polyvinyl
cyclopentane), poly(vinylcyclohexane), poly(a-vinylnaphthalene), polyvinyl
methyl
ether), poly(vinylethylether), polyvinyl propylether), poiy(vinyl carbazole),
poly{vinyl pyrrolidone), poly(2-chlorostyrene), poly(4-chlorostyrene),
polyvinyl
for7nate), polyvinyl butyl ether), polyvinyl octyi ether); polyvinyl methyl
ketone),
poly(methylisopropenyl ketone), poly(4-phenylstyrene) and the like.
The most usefixl high strength fibers include extended chain polyolefin
fibers, particularly extended chain polyethylene (ECPE) fibers, aramid fibers,
polybenzoxazole fibers, polybenzothiazole fibers, polyvinyl alcohol fibers,
polyacrylonitrile fibers, liquid crystal copolyester fibers, polyamide fibers,
glass
3o fibers, carbon fibers and/or mixtures thereof. Particularly preferred are
the
polyolefin and aramid fibers. If a mixture of fibers is used, it is preferred
that the
CA 02271707 2004-04-30
24
fibers be a mixture of at least two of polyethylene fibers, aramid fibers,
polyamide
fibers, carbon fibers, and glass fibers.
U.S.P. 4,457,985 generally discusses such extended chain polyethylene and
polypropylene fibers, and the disclosure of this patent is hereby incorporated
by
reference to the extent that it is not inconsistent herewith. In the case of
polyethylene, suitable fibers are those of weight average molecular weight of
at
least 150,000, preferably at least one million and more preferably between two
million and five million. Such extended chain polyethylene fibers may be grown
in
solution as described in U. S.P. 4,137,394 or U. S.P. 4,356,13 8, or may be
spun
1o from a solution to form a gel structure, as described in German Off
3,004,699 and
GB 2051667, and especially as described in U.S.P. 4,413,110, 4,551,296 .
~As used herein, the term polyethylene
shall mean a predominantly linear polyethylene material that may contain minor
amounts of chain branching or comonomers not exceeding 5 modifying units per
100 main chain carbon atoms, and that may also contain admixed therewith not
more than about SO weight percent of one or more polymeric additives such as
alkene-1-polymers, in particular low density polyethylene, polypropylene or
polybutylene, copolymers containing mono-olefins as primary monomers, oxidized
polyolefins, graft polyolefin copolymers and polyoxymethylenes, or low
molecular
weight additives such as antioxidants, lubricants, ultraviolet screening
agents,
colorants and the like which are commonly incorporated by reference. Depending
upon the formation technique, the draw ratio and temperatures, and other
conditions, a variety of properties can be imparted to these filaments. The
tenacity
of the filaments is at least about 15 g/d, preferably at least 20 g/d, more
preferably
at least 25 g/d and mpst preferably at least 30 g/d. Similarly, the tensile
modules of
the filaments, as measured by an Instron tensile testing machine, is at least
about
200 g/d, preferably at least S00 g/d, more preferably at least 1,000 g/d, and
most
preferably at least 1,200 g/d. These highest values for tensile modules and
tenacity
are generally obtainable only by employing solution grown or gel filament
3o processes. Many of the filaments have melting points higher than the
melting point
of the polymer from which they were formed. Thus, for example, high molecular
CA 02271707 2004-04-30
weight polyethylene of 150,000, one million and two million generally have
melting
points in the bulk of 138°C. The highly oriented polyethylene filaments
made of
these materials have melting points of from about 7° to about
13°C higher. Thus, a
slight increase in melting point reflects the crystalline perfection and
higher
5 crystalline orientation of the filaments as compared to the bulk polymer.
Similarly, highly oriented extended chain polypropylene fibers of weight
average molecular weight at least 200,000, preferably at least one million and
more
preferably at least two million, may be used. Such extended chain
polypropylene
may be formed into reasonably well oriented filaments by techniques described
in
i0 the various references referred to above, and especially by the technique
ofU.S.P.'s
4,413,110, 4,551,296, 4,663,101, and 4 784 820 . Since polypropylene is
a much less crystalline material than polyethylene
and contains pendant methyl groups, tenacity values achievable with
polypropylene
are generally substantially lower than the corresponding values for
polyethylene.
15 Accordingly, a suitable tenacity is at least about 8 g/d, with a preferred
tenacity
being at least about 11 g/d. The tensile modulus for polypropylene is at least
about
160 g/d, preferably at least about 200 g/d. The melting point of the
polypropylene
is generally raised several degrees by the orientation process, such that the
polypropylene filament preferably has a main melting point of at least
168°C., more
20 preferably at least 170°C. The particularly preferred ranges for the
above-
described parameters can be advantageously provide improved performance in the
final article. Employing fibers having a weight average molecular weight of at
least
about 200,000 coupled with the preferred ranges for the above-described
parameters (modulus and tenacity) can provide advantageously improved
25 performance in the final article.
High molecular weight polyvinyl alcohol fibers having high tensile modulus
are described in U.S.P. 4,440,711 , High molecular
weight PV-OH fibers should
have a weight average molecular weight of at least about 200,000. Particularly
usefizl PV-OH fibers should have a modulus of at least about 300 g/d, a
tenacity of
at least about 7 g/d (preferably at least about 10 g/d, more preferably about
14 g/d,
CA 02271707 2004-04-30
26
and most preferably at least about 17 g/d), and an energy-to-break of at least
about
8 joules/g. PV-OH fibers having a weight average molecular weight of at Ieast
about 200,000, a tenacity of at least about 10 gJd, a modulus of at least
about 300
g/d, and an energy to break of about 8 jouleslg are likely to be more useful
in
producing articles of the present invention. PV-OH fibers having such
properties
can be produced, for example, by the process disclosed in U.S.P. 4,599,267 .
In the case of polyacrylonitrile (PAN), PAN fibers for use in the present
invention are of molecular weight of at least about 400,000. Particularly
useful
to PAN fiber should have a tenacity of at least about ~10 g/d and an energy-to-
break of
at least about 8 jouleslg. PAN fibers having a molecular weight of at least
about
400,000, a tenacity of at least about 15 to about 20 g/d and an energy-to-
break of
at least about 8 joules/g are most useful; such fibers are disclosed, for
example, in
U. S.P. 4,535,027 .
In the case of aramid fibers, suitable aramid fibers formed principally from
aromatic polyamide are described in U.S.P. 3,671,542_. preferred aramid
fiber will have a tenacity of at least about 20 g/d, a
tensile modulus of at least about 400 g/d and an energy-to-break at least
about 8
joules/g, and particularly preferred aramid fiber will have a tenacity of at
least
2o about 20 g/d, a modulus of at least about 480 g/d and an energy-to-break of
at
least about 20 joules/g. Most preferred aramid fibers will have a tenacity of
at least
about 20 g/d, a modulus of at least about 900 g/d and an energy-to-break of at
least about 30 joules/g. For example, poly(phenylenediamine terephthalamide)
filaments produced commercially by Dupont Corporation under the trade name of
KEVLAR~ 29, 49, 129 and 149 and having moderately high moduli and tenacity
values are particularly usefixl in forming articles of the present invention.
KEVLAR 29 has 500 g/d and 22 g/d and I~EVLAR 49 has 1000 g/d and 22 g/d as
values of modulus and tenacity, respectively. Also useful in the practice of
this
invention is poly(metaphenylene isophthaIamide) fibers produced commercially
by
. Dupont under the trade name NOMEX~.
CA 02271707 2004-04-30
27
In the case of liquid crystal copolyesters, suitable fibers are disclosed, for
example, in U. S.P. No.'s 3,975,487; 4,118,372; and 4,161,470. Tenaci ty ~ s
~of about 15 to about 30 g/d and preferably
about 20 to about 25 g/d, and tensile modulus of about 500 to 1500 g/d and
preferably about 1000 to about 1200 g/d are particularly desirable.
If a matrix material is employed in the practice of this invention, it may
comprise one or more thermosetting resins, or one or more thermoplastic
resins, or
a blend of such resins. The choice of a matrix material will depend on how the
bands are to be formed and used. The desired rigidity of the band and/or
ultimate
to container will greatly influence choice of matrix material. As used herein
"thermoplastic resins" are resins which can be heated and softened,. cooled
and
hardened a number of times without undergoing a basic alteration, and
"thermosetting resins" are resins which cannot be resoftened and reworked
after
molding, extruding or casting and which attain new,~irreversible properties
when
once set at a temperature which is critical to each resin.
The tensile modulus of the matrix,material in the bands) may be low
(flexible) or high (rigid), depending upon how the band is to be used. The key
requirement of the matrix material is that it be flexible enough to process at
whatever stage of the band-forming method it is added. In this regard,
thermosetting resins which are fully uncured or have been B-staged but not
fully
cured would probably process acceptably, as would fully cured thermosetting
resins which can be plied together with compatible adhesives. Heat added to
the
process would permit processing of higher modulus thermoplastic materials
which
are too rigid to process otherwise; the temperature "seen" by the material and
duration of exposure must be such that the material softens for processing
without
adversely affecting the impregnated fibers, if any.
With the foregoing in mind, thermosetting resins useful in the practice of
this invention may include, by way of illustration, bismaleimides, alkyds,
acrylics,
amino resins, urethanes, unsaturated polyesters, silicones, epoxies,
vinylesters and
3o mixtures thereof. Greater detail on usefirl thermosetting resins may be
found in
U.S.P. 5,330,820. Particularly preferred
CA 02271707 2004-04-30
28
thermosetting resins are the epoxies, polyesters and vinylesters, with an
epoxy
being the thermosetting resin of choice.
Thermoplastic resins for use in the practice of this invention may also vary
widely. Illustrative of useful thermoplastic resins are polylactones,
polyurethanes,
polycarbonates, polysulfones, polyether ether ketones, polyamides, polyesters,
poly(arylene oxides), poly(arylene sulfides), vinyl polymers, polyacrylics,
polyacrylates, polyolefins, ionomers, polyepichlorohydrins, polyetherimides,
liquid
crystal resins, and elastomers and copolymers and mixtures thereof. Greater
detail
on useful thermoplastic resins may be found in U.S.P. 5,330,820. Particularly
preferred low modulus thermoplastic
(elastomeric) resins are described in U.S.P. 4,820,568, in columns 6 and 7 ,
especially those produced commercially by the Shell
Chemical Co. which are described in the bulletin KR.ATON~fhermoplastic
Rubber", SC-68-81. Particularly preferred thermoplastic resins are the high
density, low density, and linear low density polyethylenes, alone or as
blends, as
described in U.S.P. 4,820,458. A broad range of elastomers may be used,
including natural rubber, styrene-butadiene copolymers, polyisoprene,
polychloroprene-butadiene-acryIonitrile copolymers, ER rubbers, EPDM rubbers,
and polybutylenes.
2o In the preferred embodiments of the invention, the matrix comprises a low
modulus polymeric matrix selected from the group consisting of a low density
polyethylene; a polyurethane; a flexible epoxy; a filled elastomer
vulcanizate; a
thermoplastic elastomer; and a modified nylon-6.
The proportion of matrix to filament in the bands is not critical and may
vary widely. In general, the matrix material forms from about 10 to about 90%
by
volume of the fibers, preferably about 10 to 80%, and most preferably about 10
to
3 0%.
If a matrix resin is used, it may be applied in a variety of ways to the
fiber,
e.g., encapsulation, impregnation, lamination, extrusion coating, solution
coating,
3o solvent coating. Effective techniques for forming coated fibrous layers
suitable for
* Trade-mark
CA 02271707 1999-OS-07
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29
use in the present invention are detailed in referenced U.S.P.'s 4,820,568 and
4,916,000.
The blast resistant bands can be made according to the following method
steps:
A. wrapping at least one flexible sheet comprising a high strength fiber
material around a mandrel in a plurality of layers under tension sufficient to
remove
voids between successive layers;
B. securing the layers of material together to form a substantially seamless
and at least partially rigid first band; and
to C. removing the band from the mandrel.
The wrapping tension typically is in the range of from about 0.1 to 50 pounds
per
linear inch, more preferably in the range of from about 2 to 50 pounds per
linear
inch, most preferably in the range of from about 2 to 20 pounds per linear
inch.
The fabric layers can be secured in a variety of ways; e.g., by heat and/or
pressure
bonding, heat shrinking, adhesives, staples, and sewing, as discussed above.
It is
most preferred that the securing step comprises the steps of contacting the
fiber
material with a resin matrix and consolidating the layers of high strength
fiber _ _
material and the resin matrix either on or off of the mandrel. The fiber
material can
be contacted with a resin matrix either before, during or after the wrapping
step.
2o Some of the ways in which this can be done are detailed further below. By
"consolidating" is meant combining the matrix material and the fiber network
into a
single unitary layer. Depending upon the type of matrix material and how it is
applied to the fibers, consolidation can occur via drying, cooling, pressure
or a
combination thereof, optionally in combination with application of an
adhesive.
"Consolidating" is also meant to encompass spot consolidation wherein the
faces
of a band are consolidated but the edges are not. In this fashion, the faces
can be
made rigid while the edges retain the ability to bend or be bent to permit
collapsing
or folding of the band. "Sheet" is meant to include a single fiber or roving
for
purposes of this invention.
3o In one preferred embodiment, the flexible sheet material is formed as
follows. Yarn bundles of from about 30 to about 2000 individual filaments of
less
CA 02271707 2004-04-30
than about i2 denier, and more preferably of about 100 individual filaments of
less
than about 7 denier, are supplied from a creel, and are led through guides and
a
spreader bar into a collimating comb just prior to coating. The collimating
comb
aligns the filaments coplanarly and in a substantially parallel, and
unidirectional
5 fashion. The filaments are then sandwiched between release papers, one of
which
is coated with a wet matrix resin. This system is then passed under a series
of
pressure rolls to complete the impregnation of the filaments. The top release
paper
is pulled off and rolled up on a take-up reel while the impregnated network of
filaments proceeds through a heated tunnel oven to remove solvent and then be
10 taken up. Alternatively, a single release paper coated with the wet matrix
resin can
be used to create the impregnated network of filaments. One such impregnated
network is referred to as unidirectional prepreg, tape or sheet material and
is one of
the preferred feed materials for making some of the bands in the examples
below,
hereafter, "unitape."
~5 In an alternate embodiment of this invention, two such impregnated
networks are continuously cross plied, preferably by cutting one of the
networks
into lengths that can be placed successively across the width of the other
network
in a 0°/90° orientation. This forms a continuous flexible sheet
of high strength
fiber material, hereafter referred to as "shield." See U.S.P. 5,173,13» .
20 (This flexible sheet (fibrous layer), optionally with film
as discussed below, can then be used to form one or more bands in accordance
with the methods of the present invention. This fibrous layer is sui~ciently
flexible
to wrap in accordance with the methods of the present-invention; it can then
be
made substantially rigid (per the drapability test), if desired, either by the
sheer
25 number of wraps or by the manner in which it is secured. The weight percent
of
fiber in the hoop direction of the band can be varied by varying the number
and the
orientation of the networks. One way to achieve varying weight percents of
fiber
in the hoop direction is to make a composite sheet from the cross plied
material
and one or more layers of unidirectional tape/material (see the examples which
30 follow). By way of example, two unidirectional sheets with one cross-plied
sheet
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31
forms an imbalanced fabric having about 75 weight percent fiber in the hoop
direction.
In another embodiment, one or more uncured thermosetting resin-
impregnated networks of high strength filaments are similarly formed into a
flexible
sheet for winding around a mandrel into a band or bands in accordance with the
present invention followed by curing (or spot curing) of the resin.
Film may optionally be used as one or more layers of the band(s),
preferably as an outer layer. The film, or films, can be added as the matrix
material
(lamination), with the matrix material or after the matrix material, as the
case may
1o be. When the film is added as the matrix material, it is preferably
simultaneously
wound with the fiber or fabric (network) onto a mandrel and subsequently
consolidated; the mandrel may optionally become part of the structure. The
film
thickness minimally is about 0:1 mil and may be as large as desired so long as
the
length is still sufficiently flexible to permit band formation. The preferred
film
thickness ranges from 0.1 to 50 mil, with 0.35 to 10 mil being most preferred.
Films can also be used on the surfaces of the bands for a variety of reasons,
e.g., to
vary frictional properties, to increase flame retardance, to increase chemical
resistance, to increase resistance to radiation degradation, and/or to prevent
-- dif~'usion of material into the matrix. The film may or may not adhere to
the band
2o depending on the choice of film, resin and filament. Heat and/or pressure
may
cause the desired adherence, or it may be necessary to use an adhesive which
is
heat or pressure sensitive between the film and the band to cause the desired
adherence. Examples of acceptable adhesives include polystyrene-polyisoprene-
polystyrene block copolymer, thermoplastic elastomers, thermoplastic and
thermosetting poiyurethanes, thermoplastic and thermosetting polysulfides, and
typical hot melt adhesives.
Films which may be used as matrix materials in the present invention
include thermoplastic polyolefinic films, thermoplastic elastomeric films,
crossiinked thermoplastic films, crosslinked elastomeric films, polyester
films,
3o polyamide films, fluorocarbon films, urethane films, polyvinylidene
chloride films,
polyvinyl chloride films and multilayer films. Homopolymers or copolymers of
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32
these films can be used, and the films may be unoriented, uniaxially oriented
or
biaxially oriented. The films may include pigments or plasticizers.
Usefi~l thermoplastic polyolefinic films include those of low density
polyethylene, high density polyethylene, linear low density polyethylene,
polybutylene; and copolymers of ethylene and propylene which are crystalline.
Polyester films which may be used include those of polyethylene terephthalate
and
polybutylene terephthalate.
Pressure can be applied by an interleaf material made from a plastic film
wrap which shrinks when the band is exposed to heat; acceptable materials for
this
1o application, by way of example, are polyethylene, polyvinyl chloride and
ethylene-
vinylacetate copolymers.
The temperatures and/or pressures to which the bands of the present
invention are exposed to cure the thermosetting resin or to cause adherence of
the
-.- networks to each other and optionally, to at least one sheet of film, vary
depending
upon the particular system used. For example, for extended chain polyethylene
filaments, temperatures range from about 20°C. to about 150°C.,
preferably from
about SO°C. to about 145°C., more preferably from about
80°C. to about 120°C,
depending on the type of matrix material selected. The pressures may range
from
about 10 psi (69 kPa) to about 10,000 psi (69,000 kPa). A pressure between
2o about 10 psi (69 kPa) and about 500 psi (3450 kPa), when combined with
temperatures below about 100°C. for a period of time less than about
1.0 min.,
may be used simply to cause adjacent filaments to stick together. Pressures
from
about 100 psi (690 kPa) to about 10,000 psi (69,000 kPa), when coupled with _
___
temperatures in the range of about 100°C. to about 155°C. for a
time of between
about 1 to about 5 min., may cause the filaments to deform and to compress
together (generally in a film-Iike shape). Pressures from about 100 psi (690
kPa)
to about 10,000 psi (69,000 kPa), when coupled with temperatures in the range
of
about 150°C. to about 155°C for a time of between 1 to S min.,
may cause the film
to become translucent or transparent. For polypropylene filaments, the upper
limitation of the temperature range would be about 10 to about 20°C.
higher than
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33
_. for ECPE filament. For aramid filaments, especially Kevlar filaments, the
temperature range would be about 149 to 205°C. (about 300 to
400°F.).
Pressure may be applied to the bands on the mandrel in a variety.of ways.
Shrink wrapping with plastic film wrap is mentioned above. Autoclaving is
another
way of applying pressure, in this case simultaneous with the application of
heat.
The exterior of each band maybe wrapped with a shrink wrappable material and
then exposed to temperatures which will shrink wrap the material and thus
apply
pressure to the band. The band can be shrink wrapped on the mandrel in its
hoop
direction which will consolidate the entire band, or the band can be shrink
wrapped
across its faces with material placed around the band wrapped mandrel
perpendicular to the hoop direction of the band; in the latter case, the edges
of the
band can remain unconsolidated while the faces are consolidated.
Many of the bands formed with fibrous layers utilizing elastomeric resin
systems, thermosetting resin systems, or resin systems wherein a thermoplastic
resin is combined with an elastomeric or thermosetting resin can be treated
with
pressure alone to consolidate the band. This is the preferred way of
consolidating
the band. However, many of the bands formed with continuous lengths/plies
utilizing thermoplastic resin systems can be treated with heat, alone or
combined
with pressure, to consolidate the band.
2o In the most preferred embodiments, each fibrous layer has an areal density
of from about 0.05 to about 0.15 kg/mz. The areal density per band ranges from
about 0.5 to about 40 kg/mz, preferably from about 1 to 20 kg/m2, and more
preferably from about 2 to about 10 kg/mz. In the embodiment where SPECTRA
SHIELD~ composite nonwoven fabric forms a fibrous layer, these areal densities
2s correspond to a number of fibrous layers per band ranging from about 10 to
about
400, preferably fromabout 20 to about 200, more preferably from about 40 to
about 100. In the three band cube design of the most preferred embodiment of
the
present invention, each face of the cube comprises two bands of blast
resistant
material, which effectively doubles the aforesaid ranges for each face of the
cube.
3o Where fibers other than high strength extended chain polyethylene, like
SPECTRA~ polyethylene fibers, are utilized the number of layers may need to be
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34
increased to achieve the high strength and modulus characteristics provided by
the
preferred embodiments.
The "pin" which passes through the loops may be soft: rope, roving,
unitape, shield (preferable more that 80 % of fiber in length direction of the
pin),
s braid, belts, fabric {preferably unbalanced with more than 50 wt. of yarns
in length
direction of pin), and combinations thereof. Unitape, shield and fabrics may
be
rolled up to form a cylinder. They may be stitched, taped or subjected to heat
and
pressure to achieve some consolidation. Matrix may or may not be present. The
preferred fibers for use in soft/flexible pins are selected from the group
consisting
to of extended chain polyolefin fibers, aramid fibers, polybenzoxazole fibers,
polybenzothiazole fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers,
liquid
copolyester fibers, polyamide fibers, glass fibers, carbon fibers, and
mixtures
thereof.
Criteria for a soft pin follows. The following is a relation between the
1s interrupted band/belt characteristics: (tensile strength of belt fiber
(Sf), number of
belt plies (np), number of ends in a ply (n~), yarn (end) denier (d), width of
a hinge-
strip (b)) on one side, and the soft pin (rope) parameters : (rope fiber
strength {S~),
rope denier (d~) on the other side. Rope strength N=S~ d~ )
(Sfx2xn~xdxnPxb)/4Sina= d~S~
2o The means of restriction for the rope not allowing it to move (slide)
through the pin-holes (hinges) (such as end-knots, friction) affect the angle
a, at
which the rope actually resists separation of the ends of the belt. The closer
the
knots to the end hinges and the tighter the knots, the smaller is angle a.
Higher
friction between the pin and the hinge surfaces leads to the similar trend.
The rigid
25 inserts for the hinges restrict their transversal contractions, and lead
also to smaller
a.
Angle a should not be too small, because when a. -~ o, the required rope
strength N = d~. S~ -~~. If the angle is too big the band will not fi~nction
properly,
allowing too much of a slack and showing inefficient participation in blast
30 containment.
CA 02271707 1999-OS-07
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The following is an example for calculating required strength of the rope.
Consider a belt constructed of 14 plies of SPECTRA SHIELD fabric.
Sf= 30 g/den, nP = 14 plies; the width of individual strip b = tin,
Then the required strength of the rope according to ( 1 ) is
5 N [lbs] =11,088 / Sin a , (2)
which leads to the following table:
a ° 5 10 15 30 45
N[lbs] 127,000 63,800 42,800 22,170 15,680
to Compare these numbers to the strength of 0.75 in diameter Spectra rope (d~=
162,OOOg;
Sf= 30 g/den i.e. Nr = 106,920 lbs).
This rope is sufficiently strong for this belt design, if a >_6° is
allowed ( for b 5 tin)
The "pin" for use in the present invention may be rigid, e.g., metals,
15 plastics, ceramics, wood, fiber-reinforced composites, and combinations
thereof. If
a metal is used, it can be selected from the group consisting of steel, steel
alloys,
aluminum, aluminum alloys, titanium, and titanium alloys. If a rigid, fiber-
reinforced composite is utilized, the reinforcing fiber preferably is selected
from the
group consisting of aluminum fibers, aluminum alloy fibers, titanium fibers,
2o titanium alloy fibers, steel fibers, steel alloy fibers, ceramic fibers,
extended chain
polyolefin fibers, aramid fibers, polybenzoxazole fibers; polybenzothiazole
fibers;
polyvinyl alcohol fibers, polyacrylonitrile fibers, liquid copolyester fibers,
polyamide fibers, and mixtures thereof. The reinforcing fiber should be
predominantly in the length direction.
25 Criteria for a rigid pin are as follows. For a symmetrical hinge
arrangement
the maximal bending moment is equal M""X = bq 2 /8
From equation for the maximal normal stress caused by the bending
a""" = M~/w~,
where wX = nd3/32 for a rod with circular cross section of diameter d, we have
3o condition of equal strength of the belt and the hinge pin connection
aB = bd 2 32/8n d3
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36
and the following criterion: d3 >_4qbz/nab ( 1
The second criterion for the pin follows from the condition of sufficient
shear strength
'Lb 1Cd 2/4 = Q,
where Q =qb/4, i. e.
d2 = qb/TBn (2)
Example: q = 22000 lb ; ae = 200ksi; tB = 100ksi ; b = 2 in
Criterion 1 : d >_ 0.824 in
Criterion 2 : d ? 0.375 in
to Examination of equations (1) and (2) indicates that the required pin
diameter
decreases as b decreases (and the number of loops increase for a given size of
opening). -
By blast mitigating material is meant any material that functionally improves
the resistance of the container to blast. The preferred blast mitigating
material
utilized in forming the container assemblies of the present invention are
polymeric
- foams; particulates, such as vermiculite; condensable gases, preferably non-
flammable; heat sink materials; foamed glass; microballoons; balloons;
bladders;
hollow spheres, preferably elastomeric such as basketballs and tennis balls;
wicking
fibers; and combinations thereof. These materials are used to surround the
2o explosive or explosive-carrying luggage within the blast resistant
container, and
mitigate the shock wave transmitted by an explosion.
Chemical explosions are characterized by a rapid self propagating
decomposition which liberates considerable heat and develops a sudden pressure
effect through the action of heat on the produced or adjacent gases. On a
weight
z5 basis, the heat of vaporization of water is similar to the heat liberated
by the
explosive. Provided that rapid heat transfer can be accomplished, water has
the
potential of greatly decreasing the blast overpressure. One technique to
achieve
the desired effect is to surround the explosive with heat sink materials.
Effective
heat sink materials include aqueous foams; aqueous solutions having antifreeze
3o therein such as glycerin, ethylene glycol; hydrated inorganic salts;
aqueous gels,
preferably reinforced; aqueous mists; wet sponges, preferably elastomeric; wet
CA 02271707 2004-04-30
37
profiled fibers; wet fabrics; wet felts; and combinations thereof. Aqueous
foams
are most preferred, especially aqueous foams having a density in the range of
from
about 0.01 to about 0.10 g/cm3, more preferably in the range of from about
0.03 to
about 0.08 g/cm3.
In general, aqueous foams, through a number of mechanisms, transform
energy of the explosion to heat energy within the aqueous phase. After an
explosion venting of gases occurs in most containers, and when the pressure
drops
below some critical value the collapsed foam expands again causing additional
slow
release of gases. The presence of these foams decreases the rate at which
energy is
to transmitted from the container to the surroundings, and thereby decreases
the
hazard. Aqueous foams for use with this invention are preferably prepared with
gases (foaming agents) which do not support combustion and that are
condensable.
$y condensable is meant that under pressure the gas will change phase from gas
to
liquid, simultaneously evolving their heat of condensation which heats the
aqueous
15 solution with which the gas has intimate contact. The gas selected for a
particular
application will depend on ambient temperature and on the pressure that the
container (within which the gas is placed) can withstand. Preferred gases
include
the hydrocarbons such as propane, butane (both isomers), and pentane(all
isomers);
carbon dioxide; inorganic gases such as ammonia,. sulfur dioxide;
fluorocarbons,
2o particularly the hydrochlorofluorocarbons and the hydrofluorocarbons, such
as, for
example, the GENETRON~ series of refrigerants commercially available from
AlliedSignal Inc. as set forth in the AlliedSignal GENETRON~ Products
Brochure, published January, 1995, and
combinations thereof. A preferred gas is isobutane, which can be condensed at
25 modest pressures, about 30 psi at room temperature. Mixtures of condensable
and
non-condensable gases can be used. For example, a mixture of isobutane and
tetrafluorornethane can be used for a room temperature application. The blast
overpressure would cause the isobutane to condense but the tetrafluoromethane
would remain gaseous. Preferred gases have low sonic velocities.
3o In order to rapidly dispense aqueous foams, it may be desirable to use a
gas
that does not condense in the pressurized canister, in combination with a
CA 02271707 1999-OS-07 '
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38
condensed gas. When a foam is dispensed, the remaining contents cool.
Consequently it is important to have a permanent gas present so that the
dispensing
rate does not slow down. Carbon dioxide, nitrogen, nitrous oxide or carbon
tetrafluoride could serve as such as gas. Gases which vaporize to provide
propellant action cool the canister during dispensing and the rate of
discharge
slows.
Considerations which are used for selection of foaming agent for an
aqueous foam can also be used in selection of condensable gases to be used as
the
blast mitigating material in collapsible containers (in the absence of aqueous
foam).
1o Such gases can conveniently be confined in bladders within the containers.
The following examples are presented to provide a more complete
understanding of the invention and are not to be construed as limitations
thereon.
In the examples, the following technical terms are used:
(a) "Area( Density" is the weight of a structure per unit area of the
structure in kg/m2. Panel area( density is determined by dividing the weight
of the
panel by the area of the panel. For a band having a polygonal cross-sectional
area,
area( density of each face is given by the weight of the face divided by the
surface
area of the face. In most cases, the area( density of all faces is the same,
and one
can refer to the area( density of the structure. However in some cases the
area(
2o density of the different faces is different. For a band having a circular
cross-
sectional area, area( density is determined by dividing the weight of the band
by the
exterior surface area of the band. For a cubic box container, the area(
density is the
area( density of each of the six panels forming the faces of the box and does
not
include the area( density of any hinges or pins.
{B) "Fiber Areal Density of a Composite" corresponds to the weight of the
fiber reinforcement pEr unit area of the composite.
(c) "Cso", a measure of blast resistance, is measured as the level of charge
(in ounces) that will rupture the container/tube 50 % of the time (where
C°
represents no failureslruptures and C,oo represents failure 100% of the time).
If
3o failure occurs at one level and not at the next lower level, the Cso is
calculated by
averaging the two levels.
CA 02271707 1999-OS-07
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39
In the examples that follow, the explosive used was C4, which is 90 percent
RDX (cyclo-1,3,5-trimethylene-2,4,6-trinitroamine) and 10 percent of a
plasticizer
(potyisobutylene), a product of Hitech Inc., and a class A explosive having a
shock
wave velocity of 8200 m/sec (26,900 ft/sec).
The specific techniques, conditions, materials, proportions and reported
data set forth to illustrate the principles of the invention are exemplary and
should
not be construed as limiting the scope of the invention.
EXAMPLE 1 -
All of the containers in this example were cube shaped and consisted of a
1o supporting shell around which three mutually perpendicular reinforcing
fiber/fabric
bands were wrapped. The cube had an inner side length of 1 S inches.
The materials of construction were as-follows. The supporting cubic shells --
were made of 0.25 inch thick plywood panels nailed onto 0.75 x 0.75 inch wood
molding strips running along the inside edges. The shells weighed about 3.20
kg.
One of the six sides of the cubic shell was left open, i.e., without any
plywood.
The bands were made of SPECTRA Unitape, a product of AlliedSignal, Inc. (a
parallel array of SPECTRA 1000T-a high performance extended chain polyethylene
fibers in a matrix of 20 wt.% of Shell KR.ATON D 1107 rubber, areal density of
about 0.0675 kg/m2, 9.6 end/inch, 1300 denier fiber, 240 filaments per fiber),
and
of SPECTRA SH>ELD fabric, also a commercial product of AlliedSignal, Inc., and
comprising a laminate of two plies of Unitape normal to each other and having
an
areal density of about 0.135 kg/m2, i.e., double that of the Unitape. In
addition a
woven SPECTRA fabric was used alone to form some bands. The fabric was
woven by Clark-Schwebel Inc., Anderson, NC 29622, as style 955, areal density
of
about 3.26 oz/yd2, SSx55 yarns/inch, plain weave, using SPECTRA 1000 yarn of
215 denier. 1000/215/3 SPECTRA sewing thread, i.e., three strands of SPECTRA
1000 yarn of 215 denier twisted into a sewing thread, made by Advance Fiber
Technology Corp., 15 Industrial Rd, Fairfield, NJ 07006. A woven KEVLAR~
fabric was also used alone to form some bands. This fabric was also woven by
3o Clark-Schwebel Inc., style 745, 13.6 oz/ydz, KEVLAR 129 fiber, 3000 denier,
17x17 yarns/inch, plain weave.
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Three identical containers, C 1-C3, were made in which each of the three
bands was continuous and removable to gain access to the inside (See FIGURES
8A-8F; note that the inner plywood shell is not shown). These containers were
made as controls for comparison with containers in which one of the three
bands
s was interrupted across its length, i.e., discontinuous, and could be opened
and
closed by insertion of a pin in a hinge - like closure mechanism.
The six sides of each cube shaped box are referred to as follows: open side
= front, the other five sides are top, bottom, left, right, and back,
respectively. For
the control boxes, C 1-C3, the inner band 11 was made in the following manner.
to Two wraps of a continuous strip of SPECTRA SHIELD fabric, 15 inches wide,
were made around the front, top, back, bottom, followed by 34 wraps of
SPECTRA Unitape, followed by 2 more wraps of SPECTRA SHIELD fabric.
This band was covered inside and out with a 2 mil thick film of linear low
density
polyethylene (LLDPE) to facilitate sliding of the band onto and off of the
shell.
1s The various plies were held together with double stick adhesive tape as
needed.
The middle band 12 consisted of two portions: a first, not removable portion
and a
second, removable portion. The first portion of band 12 was made of 4 wraps of
SPECTRA SHIELD fabric, 1 S inches wide, placed around the top, right, bottom,
and left side of the shell. The second, removable portion of band I2 consisted
of
zo two plies of SPECTRA SHIELD fabric, twenty-six plies of SPECTRA Unitape
and two more plies of SPECTRA SHIELD fabric. It was covered with LLDPE
film like band 11, and followed the wrap direction of the first portion of
band 12.
The outer band 13 was made of twenty-five wraps of SPECTRA fabric, 16 inches
wide, style 955, by Clark-Schwebel, spot stitched with 100/215/3 SPECTRA
25 thread and placed around the front, Left, back, and right side of the box.
Weights
of the three containers are set forth in Table 1.
Three additional containers, 1-3, which form part of the present invention,
were made as described above except that the inner bands 11', 11 ", 11"',
respectively (see FIGURES 11 A-11 C), could be opened across the front, open
side
30 of the plywood shell for access to the interior. An important feature of
these bands
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41
is that no fibers in the hoop direction, i.e., encircling the plywood shell,
were cut to
make them discontinuous and thus no strength was lost.
In a normal band any fiber follows a circular path around the container. In
the interruptedldiscontinuous bands, to be described, any fiber will follow a
path
s around the container to a given point and then change direction by 180
degrees and
loop back to the original point from the other side. To make such a band
SPECTRA Unitape, 1 S inches wide, was wrapped around two sections of PVC
pipe which were mounted parallel to each other in a rotating frame. The pipes
were 15 inches long, 1 inch inside diameter, 1.3 inches outside diameter, and
separated by about. 63 inches (far enough to make a band that could fit around
the
four 15-inch sides-o~the container and provide some overlap of the loops at
the
band's ends). Each of tl3e PVC pipes had been glued to a laminated panel of 4,
plies of KEVLAR fabric, 5.5 x 14:75 inches in size, using a vinylester resin
(SILMAR). The KEVLAR panels were directed towards each other. In order to
achieve the same areal density as in the control containers, 17 plies of
SPECTRA
Unitape, 15 inches wide, followed by two plies of SPECTRA SHIELD fabric, were
wrapped around the PVC pipes. These 1 S inch wide plies were separated on one
pipe into seven, approximately 2 inch wide strips. Each strip was gathered and
tied
into a one-inch wide loop around the pipe. On the other pipe, six centrally
located,
2o two inch wide strips, flanked by two one inch wide strips, were gathered in
similar
fashion. In this process, on each of the two pipes, for each of the sections
holding
a fiber bundle, a corresponding section was cleared of fibers. These sections
were
sawed out o that two half hinges were created. These could be interlocked and
connected by insertion of a pin in the remaining pipe sections. Note that no
fibers
were cut in the process of forming the hinges (except for the transverse
fibers of
the 2 plies of SPECTRA SHIELD fabric covering the Unitape) and thus no
strength was lost. The three containers of the present invention, 1-3, were
identical except for the pins for the hinges. The areal density of these three
- containers 1-3 is identical to that of the control containers C 1-C3.
~ In container 1, the pin was a rigid steel rod, AERMET 100, HT 303769,
NOJ-7781-O1, from Carpenter Technology Corp., Carpenter Steel Division,
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4'
Reading , PA 19612, diameter of 1.01 inches, length of 15.75 inches, and
weight of
1646 gm (41.1 gm/cm).
In container 2, the pin was a flexible SPECTRA rope, Part Code
7102048SZZL, Maxibraid - Maxijacket, gray, from Yale Cordage Co., Rigging
Division, 100 Fore Street, Portland, ME 04101, 0.75 inch diameter cord, 67
inches
long, 307 gm (1.80 gm/cm) weight. This piece of rope was threaded through the
knuckles (loops) of the hinge, leaving equal excess on both sides. A double
knot
was made on one side of the hinge and left intact. A single knot was made on
the
other side as close as possible to the hinge after insertion of the rope. The
excess
to rope and knots were pushed into the box interior.
In container 3, the pin was made as follows. SPECTRA Unitape was
wrapped longitudinally around a 0.5 inch diameter aluminum rod: Fifteen plies
of --
Unitape, 10 inches wide normal to the fiber direction~and 46 inches long in
the fiber
direction, were wrapped around the 0.5 inch diameter aluminum rod, which was
15
inches long and centered, lengthwise, on the 46 inch long Unitape bundle. The
Unitape-wrap was held together by wrapping with electrical tape, except for 2 -
inches on either end of the aluminum rod. This two inch gap in tape increased
flexibility at either end of the rod so that the Unitape wrap could be folded
adjacent
to the rod portion. Weights were as follows: aluminum rod 136 gm, Unitape 304
2o gm, electrical tape 20 gm, total weight 460 gm (aluminum rod 3.57 gm/cm,
Unitape bundle 2.60-gm/cm). The pin was threaded through the knuckles (loops)
of the hinge, centering the wrapped aluminum rod portion in the knuckles of
the
hinge. The excess lengths of "pin" on either side of the hinge were folded
onto the
outside of the two sides of the box adjacent to the front portion containing
the
hinge. The weights of the containers, I-3, are set forth in Table 2.
The control containers/boxes, C1-C3, were tested against 1.5; 2.5 and 3.0
ounces of C4, respectively. All of the containers contained the explosion with
the
bands remaining intact; the plywood inner shell badly splintered.
Containers 1-3 of the present invention (with intenupted/discontinuous
3o bands connected with pins) were tested against 2.0 ounces of C4: Container
1,
which utilized the rigid steel pin, contained the explosion. No distortion of
the pin
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43
was noted. The PVC guide tubes were shattered. Container 2, which utilized the
SPECTRA rope, contained the explosion. No rope damage was noted, but again
the PVC guide tubes were shattered. Container 3, which utilized the SPECTRA
Unitape-wrapped aluminum rod, contained the explosion. The pin was somewhat
bent, and the PVC guide tubes were shattered.
It is anticipated that flounces of C4 would cause failure of the control
container. Assuming this result, a Cso of 3.5 ounces is calculated. The Cso
for
each of the containers with interrupted bands was greater than 2.0 ounces.
EXAMPLE 2
With reference to FIGURES 10A - 10E, a hardened aircraft luggage
container of the LD3 type was fabricated and tested. The container was a
rectangular box having dimensions of, approximately, 77 inches long x 56
inches
wide x 63 inches high. A step, approximately 21 inches long x 56 inches wide x
20
inches high,was created at the bottom of one side to facilitate band wrapping.
The
box was constructed of fiberglass/honeycomb sandwich panels, 0.5 inch thick,
with
a total of 95 lbs of the panel material used (part NSOSEC commercially
available
from Teklam. and comprising fiberglass/epoxy skins and NOMEX~ honeycomb).
The structural fiberglass/honeycomb shell had an opening, 40 inches x 40
inches,
on the front side. All plates were precut to the side dimensions and assembled
in
2o the box using hot-melt thermoplastic glue (#3789 Jet-Melt Adhesive, a
commercial _
product of the 3M Corporation). This shell addresses structural functions of
the
box since it retains its shape when fully loaded and permits loading and
unloading,
especially in a user-friendly manner.
The blast containment function is primarily provided by three mutually
~5 reinforcing, perpendicular bands of commercially_available SPECTRA SHIELD
fabric (two continuous bands forming the middle and outer bands, and one
interrupted/discontinuous~band having a pin joint and forming the inner band).
The
interrupted band, covering the area of the opening in the shell, was
constructed of
14 layers of SPECTRA SHIELD fabric, 54 inches (4.5 ft) wide, thus overlapping
3o the width of the opening in the shell by approximately 7 inches on either
side. The
hinge connection was created by subdividing the end section (to 6 inches
depth)
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44
into 2 inch strips, by cutting between the parallel fibers in the hoop
direction.
These strips were each symetrically folded over from the sides with a double
stick
tape in the fold to make strips only 1 inch wide. Sections of PVC plastic
tubing
( 1.4 inches inside diameter and I inch wide) were fixed inside of each stcip,
thus
creating regular round openings through which the connecting pin (1.375 inches
diameter, AERMAT 100 rigid steel pin, 54 in long, weight of 27 lbs,
commercially
available from Carpenter Technology Corp., Carpenter Steel Division; Reading,
PA
19612) could be inserted. The interrupted inner band was prepared separately
from the box.
1o With reference to FIGURES IOA-and IOC, it can be seen that continuous
sub-bands, narrower in width than the box, were formed by directly winding on
the
box. Each of the sub-bands contained 14 wraps/layers of SPECTRA SHIELD
fabric. Sub-bands were wound directly on the box to either side of the access
opening in a front, top, back, bottom orientation (see FIGURE l0A), after
which
the interrupted inner band was placed over the box with the pin connection
across
the middle of the access opening. The pin was horizontal in position. Two
additional continuous sub-bands, similar to the others, were formed by
directly
winding on the box. These sub-bands were also located on either side of the
access
opening, but were wound in a front, side, back, side orientation (see FIGURE
lOC). These sub-bands were permanently attached to the box and to themselves
via double stick tape (similar to product 465, 2 mil Hitact ADH Transfer Tape,
commercially available from the 3M Corp.).
A triangular wedge of 0.125 inch thick aluminum (approximately 21 inches
long x 56 inches wide x 20 inches high, ends closed) was placed in the step
with its
base located to the exterior prior to wrapping the middle band. This wedge, in
conjunction with the stepped box, forms the truncated side of the aircraft LD3
container. The middle band was created by winding SPECTRA SHIELD fabric in
the side, top, side, bottom direction, to cover the corresponding (top and
bottom)
sections of the inner band. The middle band was permanently attached to the
box
3o since it does not interfere with the opening of the box. It was attached to
the box
with double stick tape, similar to that described above.
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The outer band was made removable. It was created by winding the full
width of SPECTRA SHIELD fabric, 54 inches, for 14 layers in the direction
side,
front, side, back. The outer band was placed on the container so that it could
be -
moved in the vertical direction. The height of this band causes it to come
down
5 past the wedge portion of the truncated side. For commercial application,
this
band would have height such that it would not extend below the wedge portion
of
the truncated side.
The integrity of the bands was achieved by periodically placing double-stick
tape, similar to that described above, between the layers of SPECTRA SHIELD
to fabric in the process of winding. Total amount of SPECTRA SHIELD fabric
used
in the box was 140 lbs.
The container is tested as follows. One pound of C4 is placed within a
piece of typical luggage. Other typical luggage pieces, which contain ordinary
passenger cothing and toiletry articles, are placed layer by layer within the
15 container until the container is about half full. The luggage containing
the C4
charge is then placed at the geometrical center of the container (box).
Additional
layers of typical luggage pieces are then added until the container is about
two-
thirds full. The container (box) is then assembled by fastening the inner band
with
the pin and sliding the outer. band into place. The C4 is then detonated. The
box is
2o expected to contain the blast successfully with no failure of the fiber
bands,
including the interrupted inner band (door) utilizing the pin-closure
mechanism.
From the foregoing description, one skilled in the art can easily ascertain
the essential characteristics of this invention, and without departing from
the spirit
and scope thereof, can make various changes and modifications of the invention
to
25 adapt it to various usages and conditions.
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46
Table 1
Control Container Weights (kg)
g __
Sample Outer Removable Inns Plywood shell Total
band middle band +4 plies shield
C 1 1.82 1.54 1.91 3.47 8.75
C2 1.77 1.55 1.90 3.50 8.71
C3 1.78 1.53 2.03 3.16 8.49
Table 2
Weights
of Containers
of the
Invention
(kg)
Container/ Outer Plywood Shell, Inner and Pin
band
Total Weight
Middle Band Assembly (no
pin)
___
1/ 1.81 kg 7.25 kg 1.65 kg
10.71 kg
2/ 1.72 kg 7.20 kg 0.31 kg
9.23 kg
3/ 1.79 kg 7.75 kg 0.46kg
10.00 kg
