U.S. patent application number 11/983980 was filed with the patent office on 2011-03-03 for blast-resistant barrier.
Invention is credited to Raymond L. Goodson, James M. Lorenzo, Robert A. Pyles.
Application Number | 20110048219 11/983980 |
Document ID | / |
Family ID | 41016631 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110048219 |
Kind Code |
A1 |
Pyles; Robert A. ; et
al. |
March 3, 2011 |
Blast-resistant barrier
Abstract
A blast-resistant barrier comprising a plurality of units each
including a panel having a thickness of greater than 20 to less
than 40 millimeter is disclosed. The panel is in the form of a
monolithic polycarbonate sheet or laminate that is positioned
vertically between the source of a blast and the blast target, the
laminate including at least two polycarbonate sheets and an
optional image layer interposed therebetween. The panel is fixedly
attached to a frame which is firmly embedded in concrete in a
manner calculated to provide stiffness sufficient to absorb and
withstand external forces resulting from said blast. In a preferred
embodiment the panel includes at least two polycarbonate sheets
laminated one to the other, optionally including an image layer
interposed therebetween. In an additional embodiment, the frame is
anchored securely to the target enabling dissipation of the blast
force through the target's structure. The height of the
blast-resistant barrier is preferably proportional to the height of
the target.
Inventors: |
Pyles; Robert A.; (Bethel
Park, PA) ; Lorenzo; James M.; (Mars, PA) ;
Goodson; Raymond L.; (Sandy, UT) |
Family ID: |
41016631 |
Appl. No.: |
11/983980 |
Filed: |
November 13, 2007 |
Current U.S.
Class: |
89/36.01 ;
89/903; 89/917 |
Current CPC
Class: |
E04C 2/384 20130101;
F41H 5/24 20130101; F41H 5/013 20130101; E04C 2/20 20130101; F41H
5/0407 20130101; E04H 9/10 20130101 |
Class at
Publication: |
89/36.01 ;
89/903; 89/917 |
International
Class: |
F41H 5/02 20060101
F41H005/02 |
Claims
1. A blast-resistant barrier comprising one or more units each
including a panel fixedly attached to a frame, said panel being
greater than 20 and less than 40 millimeter in thickness and
including at least one polycarbonate sheet is vertically positioned
between the source of a blast and the blast target.
2. The barrier of claim 1 wherein said frame comprise at least one
member selected from the group consisting of carbon steel,
stainless steel and aluminum.
3. The barrier of claim 1 wherein said frame is grounded in
concrete.
4. The barrier of claim 1 wherein said frame is anchored in the
target.
5. The barrier of claim 1 wherein said panel is concave with its
hollow side fronting said source.
6. The barrier of claim 1 wherein said panel is in the form of a
monolithic polycarbonate sheet.
7. The barrier of claim 1 wherein said panel is in the form of a
laminate containing more than one polycarbonate sheet.
8. The barrier of claim 7 further comprising an image layer
interposed between said sheets.
9. The barrier of claim 8 wherein said image layer contains at
least one member selected from the group consisting of fabric,
photograph, paper, wire, screen, rod, bar, grass and plant.
10. The barrier of claim 9 wherein said member is encapsulated in a
polymeric resin compatible with said member and said
polycarbonate.
11. The barrier of claim 1 wherein at least one surface of said
panel is hard-coated.
12. The barrier of claim 1 wherein at least one surface of said
panel is embossed.
13. The barrier of claim 1 wherein said panel contains a
UV-stabilizer.
14. The barrier of claim 1 wherein said frame has a "C"
cross-section.
15. The barrier of claim 1 wherein said panel is fixedly attached
to said frame by a plurality of bolts.
16. The barrier of claim 1 wherein said panel is adhesively
attached to said frame.
17. The barrier of claim 1 wherein said panel contains at least two
polycarbonate sheets bonded one to the other by an adhesive.
18. The barrier of claim 17 wherein the adhesive is thermoplastic
polyurethane.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a blast-resistant barrier
and in particular to a barrier comprising at least one
polycarbonate panel.
TECHNICAL BACKGROUND
[0002] Government and commercial buildings (e.g., hotels, casinos,
malls, airports and stadiums) have proven attractive targets for
bombing attacks throughout the world. The attacker, in most cases,
is a politically motivated terrorist using, as a weapon, a high
explosive device transported and detonated inside a vehicle
adjacent to the targeted building. The explosive device carried in
such vehicles is typically capable of generating a shock wave of
sufficient force as to shear the face off unprotected buildings,
leading to tremendous loss of life and property damage. The
resulting debris field surrounding the building is often several
feet thick blocking entrances. In addition, glass remnants dangle
precariously, potentially falling from great heights to the ground
in the slightest breeze. Consequently, both hazards hinder and
threaten the safety of emergency response teams as they attempt to
enter the damaged building to render aid to the injured.
[0003] The simplicity and stealth of vehicular weapons make them a
complex foe. It's virtually impossible to screen all the cars and
trucks that rumble past critical buildings. Defending against such
an explosive device involves keeping such vehicles at a distance
from vulnerable targets, often using Jersey barriers, blocks,
bollards and other concrete structures (U.S. Pat. Nos. 7,144,186
and 6,767,158, and U.S. Patent Application 2004/0261332). This can
be difficult where public roads pass immediately outside these
structures. Closure of roads, or protecting buildings with concrete
barriers is not always practical, it can be unsightly and is
generally undesirable.
[0004] Existing buildings rarely have blast resistant construction
and thus much emphasis has been placed on retrofits for windows to
mitigate glass hazards. The use of so-called safety glazing or
penetration-resistant glazing for windows, using multiple layers of
polycarbonate, glass, and other resinous materials is well known.
For example, glass-polycarbonate resin laminates adhering together
with ethylene-vinyl copolymers are described in U.S. Pat. No.
3,666,614. In U.S. Pat. No. 3,520,768, there are described
laminates of relatively thick glass having a comparatively thin
polycarbonate foil as the adhering material. Also relevant is U.S.
Pat. No. 4,027,072 that disclosed certain
polysiloxane-polycarbonate block copolymers as an adhesive in
preparing polycarbonate containing laminates. U.S. Pat. No.
3,624,238 concerns a bullet resistant laminated structure that
includes outer faces or plies of safety glass with an intermediary
ply formed of a polycarbonate resin. U.S. Pat. No. 4,312,903 deals
with an impact resistant double glazed structure made of glass and
polycarbonate and is concerned in particular with the thickness of
the layers of the laminated window panes, and their chemical
compositions.
[0005] U.S. Pat. No. 5,059,467 is concerned with a protective
ballistic panel including a first-impact, front layer and a second
rear layer, the layers being spaced from one another by a
semi-elastic material, defining a sealed space. The panel is used
as a personnel protective shield.
[0006] U.S. Pat. No. 6,266,926 describes a flexible apparatus that
is deployed by inflating a protective barrier adjacent to windows
to reduce the quantity of debris hazard in the event of an
explosion. U.S. Pat. No. 6,349,505 discloses a louver system
mounted adjacent to the inside and/or outside of a glass window and
reinforced using high elongation cables or straps attached to the
floor and ceiling. The louver system would immediately close upon
detection of an explosion, reducing the quantity of debris hazard
in the building.
[0007] U.S. Pat. No. 4,625,659 disclosed a bullet and explosion
proof window or door system comprising two spaced apart panels,
whereby the outer panel is spaced from a support soffit such that a
gap is formed for providing a ventilation channel. However,
peripheral portions of the panels are fitted with a security layer
in order to prevent projectiles from entering through the
ventilation gap. U.S. Pat. Nos. 6,177,368 and 4,642,255 disclosed
blast-resistant panels produced from PVC and woven fiberglass, and
polyvinyl acetal, glass and a fibrous layer encapsulated in the
polyvinyl acetal layer. U.S. Pat. No. 3,191,728 disclosed a barrier
consisting of welded metal strips, as protection for workers in
aircraft parking areas from the exhaust of jet engines.
[0008] U.S. Pat. No. 5,277,952 disclosed a decorative, cracked
mirrored, glass panels created from glass bonded together with a
polymeric interlayer. U.S. Pat. Nos. 5,643,666, 5,894,048,
5,958,539, 5,998,028 and 6,025,069 disclosed panels consisting of
laminated copolyester sheets and containing decorative interlayers
and high relief surfaces.
[0009] Retrofits to protect building facades have traditionally
involved strengthening of walls. To be truly effective,
wall-strengthening is often an invasive operation which adversely
affects the appearance of the structure and impacts building
operations. It is, therefore, desirable to have a structure that is
unobtrusive, easy to install, and at the same time protective of
the entire building from the devastating effects of a vehicular
bombing attack.
SUMMARY OF THE INVENTION
[0010] A blast-resistant barrier comprising a plurality of units
each including a panel having a thickness of greater than 20 to
less than 40 millimeter is disclosed. The panel is in the form of a
monolithic polycarbonate sheet or a laminate that is positioned
vertically between the source of a blast and the blast target, the
laminate including at least two polycarbonate sheets and an
optional image layer interposed therebetween. The panel is fixedly
attached to a frame which is firmly embedded in concrete in a
manner calculated to provide stiffness sufficient to absorb and
withstand external forces resulting from said blast.
[0011] In a preferred embodiment the panel includes at least two
polycarbonate sheets laminated one to the other, optionally
including an image layer interposed therebetween. In an additional
embodiment, the frame is anchored securely to the target enabling
dissipation of the blast force through the target's structure.
[0012] The height of the blast-resistant barrier is preferably
proportional to the height of the target.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The inventive panel comprise at least one monolithic,
preferably two or more superposed polycarbonate sheets that are
laminated and/or adhesively bonded one to the other to form a
laminate.
[0014] The inventive panel may optionally include at least one
image layer in the form of wood, stone, glass, textile, metal,
paper, plastic, plants, flowers or vegetation and their products
and each of these may be of any color. The image layer may be
laminated to or between any two of the layers. The thickness of the
panel is in the range of 20 to 40 millimeters.
[0015] In the embodiment where the panel includes a laminate it is
preferred that it includes a first polycarbonate sheet 10 to 20,
preferably 12-18 millimeter (mm) in thickness, a second
polycarbonate sheet 10 to 20, preferably 12-18 mm in thickness and
at least one image layer interposed between the first and second
sheets. Other embodiments entail a plurality of polycarbonate
sheets, typically three of four sheets of identical thicknesses or
differing thicknesses.
[0016] The several sheets making up the inventive panel may be
bonded one to the other by lamination or by the use of an adhesive.
A suitable adhesive layer includes 0.025'' thick A4700 Dureflex
polyurethane film, a product of Deerfield Urethane. It is
imperative that the adhesive be sufficiently heat resistant to
withstand the thermal conditions encountered in lamination without
degradation and distortion. Naturally, in circumstances where
transparency of the panel is desired, the adhesive must be
transparent.
[0017] In one embodiment of the invention, the panel may be
prepared by (a) providing a first polycarbonate sheet having a
thickness of 10 to 20 mm; and (b) providing a second polycarbonate
sheet having a thickness of 10 to 20 mm; and (c) placing at least
one image layer between the first and second sheets to form a
sandwiched structure and (d) pressing the structure at elevated
temperature for a time sufficient to form a laminate. Suitable
thermal conditions are generally 18 to 249.degree. C., preferably
32 to 227.degree. C. under pressure of 69 to 2069, preferably 448
to 662 kPa, for a time at maximum temperature and pressure of 0.1
to 20 preferably 0.1 to 5 most preferably 0.17 to 3 minutes.
Temperatures exceeding 249.degree. C. and pressures exceeding 2070
kPa are undesirable in hot press bonding since the sheet layers may
squeeze out of the aligned image layer. It is preferred to apply
pressure before the application of heat. Optionally the laminate
thus formed may be cooled at pressure between 7 and 2065 kPa. In
yet an additional embodiment the inventive laminate further
includes a protective hard-coat layer.
[0018] Importantly, the first and second sheets are not necessarily
the outermost sheets of the inventive panel. As noted above the
panel may contain a plurality of sheets (layers) on each side of
the image layer as well as several image layers. It is however
required that the total thickness of the panel be greater than 20
and less than 40 mm. The panel is preferably 4 feet wide and 8 feet
long but these are not limiting dimensions.
[0019] The polycarbonate sheets independently may be transparent,
translucent, or opaque. Moreover the sheets may differ one from the
others in their respective degrees of transparency or translucency
and color.
[0020] Polycarbonate is well known thermoplastic, aromatic
polymeric resin (see German Offenlegungsschriften 2,063,050;
1,561,518; 1,570,703; 2,211,956; 2,211,957 and 2,248,817; French
Patent 1,561,518; and in particular the monograph by H. Schnell,
"Chemistry and Physics of Polycarbonates", Interscience Publishers,
New York, N.Y., 1964, which is incorporated herein by reference).
The polycarbonate suitable in the context of the invention has
weight average molecular weight of 8,000 to 200,000, preferably up
to 80,000 and an intrinsic viscosity of 0.40 to 1.5 dl/g as
measured in methylene chloride at 25.degree. C. Preferably, the
glass transition temperature of polycarbonates ranges from 145 to
148.degree. C.
[0021] Polycarbonate sheets suitable in the context of the
invention are available in commerce. Preferable for their good
mechanical properties and excellent transparency are sheets made of
a homopolycarbonate based on bisphenol A.
[0022] Such suitable sheets are available under the MAKROLON
trademark from Sheffield Plastics Inc.; a Bayer MaterialScience
company.
[0023] The image layer(s) preferably includes fabric, metallic
wire, rod and/or bar, papers or photographic images, and
vegetation, such as grasses, flowers, wheat, and thatch. The image
layer may display images or designs or may be of a solid color and
should be sufficiently thermally resistant, e.g. of sufficiently
high melt temperature to avoid any degradation or distortion of the
image during the manufacture or processing of the panel.
Preferably, the image layer(s) are substantially continuous. The
thickness of the image layer is advantageously 0.0254 to 1.524 mm,
preferably 0.0254 to 0.05 mm, and is most preferably 0.04 mm.
However, polymeric films thinner or thicker may be used in the
decorative image layer depending on the equipment available, and
under such conditions the thickness is limited only by
functionality.
[0024] In a preferred embodiment the panel includes at least one
first image layer positioned between the first and the second
polycarbonate sheet and at least one second image layer positioned
between the second and the third polycarbonate sheet.
[0025] In one embodiment of the present invention, the image layer
comprises a fabric of textile fibers. The fabric may display images
or designs produced, e.g., by weaving or knitting techniques, in
the fabric. The fabrics may be textile fibers, (i.e., fibers of
natural-occurring, semi-synthetic or synthetic polymeric
materials). For example, the fabrics may be prepared from cotton,
wool, silk, rayon (regenerated cellulose), polyester such as
polyethylene terephthalate, synthetic polyamides such as nylon 66
and nylon 6, acrylic, methacrylic, and cellulose acetate fibers.
The melting point of the textile fibers should be sufficiently high
to avoid any degradation or distortion of the fabric during the
manufacture or processing of the laminate of the invention.
[0026] The fabric may be woven, spun-bonded, knitted, or prepared
by other processes well known in the textile trade and may be
uncolored, e.g., white, or colored by conventional dyeing and
printing techniques. Alternatively, the fabrics may be produced
from dyed yarn or from filaments and yarn derived from mass colored
polymers. Preferably, the fabrics present within the decorated
laminate structure are substantially continuous and constitute a
distinct image layer or laminate. In an embodiment of the
invention, the image layer comprises metallic wire, rod, or bar.
The metal wire may be formed by a variety of techniques to produce
metal mesh fabric, screens, or open mesh having high transparency.
The metal wire, rod or bar may be woven, welded, knitted, or
fabricated by means of other processes well known in the metal wire
fabrication art. The metallic wire, rod and bar may be of any
color. The metallic element of the image layer may be of different
metallic materials such copper, aluminum, stainless steel, steel,
galvanized steel, titanium, etc. or combinations thereof. The
metallic component of the image layer may be prepared from wire
filaments, rods and bars having various cross-sectional areas and
geometries, e.g., generally circular, oval or relatively flat. The
thickness or diameter of the wire, rod and bar is not critical. It
is however critical that the metallic surfaces are smooth so as
avoid creating of propagating cracks that may weaken the panel.
Hence, embedding the metallic surfaces in a polymeric material,
such as polyvinyl chloride, copolyester or polyurethane, may be
advantageous. The only requirement relative to this embodiment is
that the embedding polymeric materials have sufficient heat
resistance so as not to be thermally degraded or distorted by the
panel lamination and forming processes.
[0027] In an additional embodiment the panel may comprise an image
layer of wire, rod, or bar that reinforce the polycarbonate. In
further embodiment, the image layer comprises a printed or colored
image. Preferably, the printed or colored image layer has opposed
surfaces wherein an image is printed on one of the surfaces and/or
the decorative image layer contains coloration. More than one
printed or colored decorative image layer may be used in the
decorated laminate structure of the present invention. The use of
multiple decorative image layers may provide a 3-dimensional or
"floating" appearance to the decorative images or lettering in the
printed or colored image layers. Each of the printed or colored
image layers is joined to a first sheet on one of its surfaces such
that the image or coloration may be viewed through the first sheet
without significant distortion. The printed or colored image layer
may comprise any suitable polymeric material which is compatible
with the materials used for the first and second sheets, inks, or
other materials used in fabricating the laminate. Preferably, the
image layer comprises polyvinylchloride, copolyester, polycarbonate
or polyurethane thermoplastic.
[0028] In another embodiment, the image or coloration is printed on
the bottom side of the image layer in which case the polymer used
to prepare the image layer is transparent.
[0029] The printed image may be prepared according to conventional
photographic printing processes or with a digitized database
generated from a photographic image. Digitizing and storing the
image may be accomplished through any of a number of processes well
known in the computer art such as scanning.
[0030] In yet another embodiment, the image layer comprises
vegetation, such as grasses, thatch, flowers, for example rose
petals, wheat, grains, natural papers and others, such that the
natural color of vegetation is preserved. More than one image layer
comprising vegetation may be used in the decorated laminate
structure of the present invention. The use of multiple image
layers may provide a 3-dimensional or "floating" appearance to the
decorative vegetation in the image layers. Each of the image layers
is joined to a first sheet on one of its surfaces such that the
vegetation can be seen through the first sheet without significant
distortion.
[0031] The laminate structure may optionally comprise a protective
hard-coat layer, which is a transparent, hard, scratch-resistant or
abrasion resistant coating or layer laminated to the top surface of
the first sheet. Such coating may also increase the chemical
resistance of the laminate and provide an anti-graffiti surface.
The protective layer may be a bi-layer film comprising a protective
layer on top of a sheet layer. The protective layer is preferably
selected from the UV-cured or electron-beam-cured crosslinked
acrylic, vacuum-cured or UV-cured urethane, UV-cured or
electron-beam-cured silicon with acrylic or heat cured urethane or
plastisol. A layer of polyurethane may be applied over the exterior
surface to provide abrasion resistance. Alternatively, a biaxially
oriented polyethylene terephthalate, such as MYLAR.RTM. or a
TEFLON.RTM. film, such as TEDLAR.RTM. both available from DuPont
Chemical Company, may be laminated to the top surface of the first
sheet as a protective layer. More preferably, the protective layer
comprises a thermal-cured, UV-cured or electron-beam-cured silicon
to achieve glass appearance.
[0032] Lamination of the inventive panel is conventional. In one
laminating method a plywood laminating press that features
efficient heat transfer and even distribution of heat is preferably
used.
[0033] To augment the reduction in pressure, a vacuum may be
applied in order to remove trapped air between the layers. During
the bonding process, if necessary, the polycarbonate materials may
be bonded or fused together with the use of adhesive.
[0034] Preferably, the laminating method comprises hot press
bonding or cold press bonding. As is well known, hot press bonding
methods include, but are not limited to, hot steam, electric heat,
hot oil heated and other methods known in the art. Cold press
bonding methods include, but are not limited to, cold water and
glycol cooled method. The lamination may be performed either with
or without a vacuum press. Generally, the formation of bubbles in
the laminated panel is less likely if the air is evacuated prior to
applying heat and pressure. In any event it is critical that
sufficient pressure is applied to rid the system of air prior to
bonding. Following the hot press bonding, the bonded structure is
allowed to cool by being held at 10 to about 148.degree. C.
(50.degree. F. to about 298.degree. F.), preferably 21.1 to
32.2.degree. C. (70 to 90.degree. F.) and pressure of 7 to 2069
preferably 448 to 662 more preferably 552 to 662 most preferably
634 kPa until it cools below the glass transition temperature of
the polycarbonate. Optionally, in the course of press bonding
texture may be applied to one or both surfaces of the panel.
[0035] The frame to which the panel is fixedly attached is
preferably made of carbon steel, i.e. steels having up to about 2
percent carbon content, stainless steel or aluminum. For increased
durability and aesthetic appeal, frames of carbon steel may be
treated with corrosion resistant coatings and/or paints. Stainless
steels are preferred for outdoor applications because they are more
resistant to rusting and staining than carbon and low alloy steels,
thus maintaining their aesthetic appeal. It is imperative that in
the instances where the image layer is capable of absorbing
moisture, the edges of the panel are sealed to prevent wicking.
Suitable sealing may be by the application of silicone or by gluing
to the edge a thin polymeric film, e.g. polycarbonate film.
[0036] The steel frame comprise shaped members (e.g., a "C" cross
section shaped members) providing sufficient stiffness and strength
to absorb the external forces applied by the blast without major
distortion. The frame may be extended vertically at its bottom so
that the extensions can be embedded in reinforced concrete
foundation. As an alternative, the steel frame may be attached to
the steel skeleton of the target (e.g. building) in a manner to
dissipate the shock wave.
[0037] The panel may be attached to the frame by either a
structural adhesive or by a plurality of bolts. The bolts,
preferably shoulder bolts, are 0.75 to 1.25 inches, preferably 1.0
inch in diameter, with flat heads so that upon tightening, the bolt
head and nut place the area of the panel around the bolt hole in
compression without creating cracks or notches. The bolts may be
spaced 4 inches to 8 inches, preferably 6 inches, apart and offset
approximately 1.0 inch to 1.5 inches from the panel edge. The bolt
holes in the panel are preferably produced with smooth, elongated
edges to allow for thermal expansion and to mitigate stress. Rubber
or elastomeric washers or spacers may be used between the panel and
frame to further absorb impact energy and dampen forces transmitted
to the building.
[0038] The mechanical properties for the "C" section steel channels
preferably exhibit a final yield strength in tension of
approximately 300 MPa. Otherwise, for higher or lower modulus
materials such as aluminum, equivalent section properties are
preferably followed through use of thicker or thinner walls.
Overall, the inventive panel is preferably placed at a distance of
at least 12 inches from the surface of the protected target to
avoid the polycarbonate panels striking the building while bending
as a result of being hit with the shock wave resulting from a
blast. Shorter distances may be used for lower threat levels or
smaller panels.
EXAMPLES
Example 1
[0039] A panel in the form of a laminate that includes a colored
textile was prepared. A hot press platen was preheated to
475.degree. F. The cold press platen temperature was set at
65.degree. F. Next the following were assembled in the following
order (top to bottom): steel press plate, Nomex pad (Nomex pressure
distribution pads), or another suitable medium to attain even
distribution of pressure, aluminum separation plate, release paper
(patina finish Ultra-cast release paper), 0.060'' polycarbonate
sheet, image layer in the form of textile (sheer nylon textile),
0.060'' polycarbonate sheet, release paper, aluminum separation
plate, Nomex pad, steel press plate.
[0040] A thermocouple was inserted in-between the first sheet of
polycarbonate and the textile. The assembly was then inserted in
the hot press, the press was closed and the pressure was increased
to 94 psi. The temperature was closely monitored until the
thermocouple read 420.degree. F. Once the temperature was reached,
the pressure was released and the press opened. The assembly was
then transferred to the cold press set to cold press platen
temperature of 65.degree. F. Next, the pressure in the cold press
was increased to 94 psi. This transfer and re-pressurizing was
completed in less than 3 minutes. The temperature was closely
monitored until the thermocouple read 90.degree. F. at which point
the decorated laminate structure was removed from the press.
Example 2
[0041] An additional panel in the form of a laminate was prepared.
A hot press platen was preheated to 475.degree. F. The cold press
platen temperature was set at 65.degree. F. Next the following were
assembled in the following order (top to bottom): steel press
plate, Nomex pad (Nomex pressure distribution pads), aluminum
separation plate, release paper (patina finish Ultra-cast release
paper), hard coated polycarbonate film (0.005'' thick film),
oriented with the hard-coat against the release paper, 0.118''
polycarbonate sheet, image layer in the form of textile, 0.118''
polycarbonate sheet, release paper, aluminum separation plate,
Nomex pad, and steel press plate. The "hard coat" used was a
flexible aliphatic polyurethane coating.
[0042] A thermocouple was inserted in-between the first sheet of
polycarbonate and the textile. The assembly was then inserted in
the hot press, the press was closed and the pressure was increased
to 94 psi. The temperature was closely monitored until the
thermocouple read 420.degree. F. At that temperature the pressure
was released and the press opened. The assembly was then split
between the first release paper and hard-coated polycarbonate film
and then transferred to the cold press (press platen temperature of
65.degree. F.) and the pressure in the cold press was increased to
94 psi. This transfer and re-pressurizing was completed in less
than 3 minutes. The temperature was closely monitored until the
thermocouple read 90.degree. F. at which point the laminate was
removed from the press. Surface finishes on the bottom of the
product were uniform and even.
Example 3
[0043] An additional panel in the form of a laminate that including
botanical matter with clear resin, flat texture, thatch reeds
embedded on multiple layers, and patina finish on both sides, was
prepared as follows: A hot press platen was preheated to
475.degree. F. The cold press platen temperature was set at
65.degree. F. Next the following were assembled in the following
order (top to bottom): steel press plate, Nomex pad (Nomex pressure
distribution pads), aluminum separation plate, release paper,
0.118'' polycarbonate sheet, thatch (thatch reeds), 0.236''
polycarbonate sheet, thatch, 0.118'' polycarbonate sheet, release
paper, aluminum separation plate, Nomex pad, and steel press
plate.
[0044] A thermocouple was inserted in-between the first thatch and
0.236'' polycarbonate sheet. The assembly was then inserted in the
hot press, the press was closed and the pressure was increased to
10 psi. The temperature was closely monitored until the
thermocouple read 410.degree. F. At that temperature the pressure
was increased to 30 psi. The temperature was closely monitored
until the thermocouple read 420.degree. F. At that temperature the
pressure was increased to 94 psi. The temperature was closely
monitored until the thermocouple read 435.degree. F. Next, the
pressure was released and the press opened. The assembly was then
transferred to the cold press (press platen temperature of
65.degree. F.) and the pressure in the cold press was increased to
94 psi. This transfer and re-pressurizing was completed in less
than 3 minutes. The temperature was closely monitored until the
thermocouple read 90.degree. F. at which point the decorated
laminate structure was removed from the press. The resulting
laminate was thermally fused around and through the thatch,
resulting in its intimate encapsulation. Surface finishes on the
bottom of the product were uniform and even.
Example 4
[0045] A yet additional panel in the form of a laminate that
includes textile as the image layer, was prepared. In a clean room,
the sheet was unmasked, cleaned with 50/50% (by volume)
water/isopropyl solution, air dried and the static electricity was
removed from the sheet using deionized air. The following were
assembled on a table in order (top to bottom):
0.5''.times.4'.times.8' polycarbonate sheet, image layer (sheer
nylon textile), 0.025'' aliphatic TPU film (Deerfield A 4700),
0.5''.times.4'.times.8' polycarbonate sheet.
[0046] The assembly was then inserted into a vacuum bag which was
subsequently evacuated to 29'' of mercury. This vacuum was
maintained 1 hr prior to, and subsequently throughout, the
autoclaving cycle. The vacuum bag with its contents was then placed
in an autoclave and heated 2.5.degree. F./min for 96 min to
240.degree. F. At the same time the pressure was increased 3.8
psi/min to 171 psi over 45 minutes. The 240.degree. F. temperature
was then held for 90 min at 171 psi. Next, the vacuum bag was
gradually cooled at 2.0.degree. F./min to 105.degree. F., and the
pressure was then reduced at 3.8 psi/min to ambient. The assembly
was allowed to sit undisturbed for another hour. Finally the
assembly was removed from the vacuum bag.
Example 5
[0047] A virtual barrier structure produced in accordance with the
invention was tested in a ABAQUS computer model simulating
vehicular bomb blasts. The model simulated a blast using the
equivalent of 2000 pounds of trinitrotoluene (TNT) against a panel
wherein the panel was a 4' by 8' sheet of polycarbonate 25 to 35 mm
thick at distances of 100 feet, 80 feet and 50 feet, and against 2'
by 8' sheets of polycarbonate 25 mm thick at 80 feet, 50 feet and
40 feet from the blast resistant barrier. The data show that for
panels 4 by 8 feet the stand off distance (the distance from the
blast) should be greater than 50 feet. For panels 2 by 8 feet the
stand off distance should be greater than 40 ft.
TABLE-US-00001 TABLE 1 Wall Inward Force to Outward Force from
Thickness Structure Structure [mm] [N/(Unit Length)] [N/(Unit
Length)] 10 -14200 5400 15 -11900 12200 20 -9012 12943 25 -7810
12858 30 -7076 9489 35 -6788 5833 40 -9093 3961 45 -9587 2622 50
-9056 984 55 -7970 4263
[0048] Data presented in the above table show that for panels
having wall thickness of 10 to 20 mm, the inward force to the
structure is greater than 9,000 units. For panels having thickness
greater than 20 and less than 40 mm the inward force decreases
below 8,000 units. At wall thicknesses of 40 mm to 50 mm, the
inward force to the structure again tends to exceed 9,000 units.
While the performance of the panel at a wall thickness of 55 mm
increases, the thickness and inward force to the structure is
reduced again as a consequence of the added thickness and weight
stiffening the panel.
[0049] The above description is not to be construed as limiting the
invention, since those of ordinary skill in the art will realize
that various modifications, changes and substitutions can be made
in various materials and methods disclosed herein, without
departing from the spirit or the scope of the present inventive
discovery. Instead, the present invention is defined by the claims
appended hereto and the equivalents encompassed thereby.
* * * * *