HK1146495A - Blast-resistant barrier - Google Patents

Description

Explosion-proof barrier

Technical Field

The present invention relates to blast resistant barriers, and in particular to barriers comprising at least one polycarbonate panel.

Technical Field

Government departments and commercial buildings (e.g., hotels, casinos, malls, airports, and stadiums) are all major targets of explosive assaults throughout the world. In most cases, the attacker is a politically motivated terrorist using highly explosive devices as weapons, transporting the devices through automobiles, and detonating inside the automobile upon approaching the target building. The explosive devices carried in such vehicles are typically capable of generating shock waves of sufficient intensity to lift the exterior facades of unprotected buildings, resulting in significant personal injury and loss of property. The resulting ruin field surrounds the building, typically several feet thick, blocking access. Moreover, the glass residues are suspended in the air and are dangerous, and may fall from a high position to a bottom surface in case of breeze. Thus, these hazards can hinder emergency teams and threaten the safety of emergency team personnel when they are about to enter a damaged building to rescue the injured person.

The simplicity and concealment of vehicle weapons make them a nuisance hazard. In fact, it is not possible to perform a security check on all cars and trucks that pass through important buildings. Means to combat such explosive devices include stopping vehicles at a distance from the vulnerable targets, often using new jersey fencing, blocks, piles and other concrete structures (us 7,144,186 and 6,767,158, us 2004/0261332). However, these measures are difficult to take when public roads pass right outside these building structures. Closing roads or protecting buildings with concrete barriers is not always practical and may be unattractive.

Existing buildings rarely have explosion-proof structures and so more emphasis has been placed on improving windows to mitigate the hazards presented by the glass. For the use of so-called safety glass or penetration-resistant glass for windows, multilayer structures using polycarbonate, glass and other resin materials are well known. For example, U.S. patent 3,666,614 describes glass-polycarbonate resin laminates adhered with ethylene-vinyl copolymers. In us patent 3,520,768, a laminate with a thicker glass and a thinner polycarbonate foil adhered to the glass is described. The relevant literature also includes U.S. patent 4,027,072, which discloses a polysiloxane-polycarbonate block copolymer as an adhesive for use in the preparation of polycarbonate-containing laminates. U.S. patent 3,624,238 relates to a ballistic resistant laminate structure comprising an outer surface or skin of safety glass and an intermediate layer formed of a polycarbonate resin. Us patent 4,312,903 relates to an impact resistant double glazing structure formed from glass and polycarbonate, and in particular to the thickness of the plies of the laminated glazing and their chemical composition.

Us 5,059,467 relates to a ballistic panel comprising a first impact resistant front layer and a second back layer separated from each other by a semi-elastomeric material forming a sealed space. The panel is used as a personal protective screen.

Us patent 6,266,926 describes a flexible device that is deployed by inflating a protective barrier adjacent a window to reduce the risk of debris in the event of an explosion. U.S. patent 6,349,505 discloses a skylight system mounted adjacent the interior and/or exterior of a glass window that is reinforced with high elongation cords or straps attached to the floor and ceiling. The skylight system closes immediately after an explosion is detected, reducing the damage caused by debris in the building.

U.S. patent 4,625,659 discloses a bullet and explosion resistant window or door system comprising two spaced apart panels wherein the outer panels are separated by a supporting soffit so that the gap thus formed provides a ventilation channel. However, the peripheral portions of the two panels are provided with a safety layer to prevent projectiles from entering the chamber through the ventilation gap. U.S. Pat. nos. 6,177,368 and 4,642,255 disclose blast-resistant panels produced from PVC and woven glass fibers, as well as polyvinyl acetal, glass and a layer of fibers encapsulated in a polyvinyl acetal layer. Us patent 3,191,728 discloses a barrier consisting of welded metal strips for protecting airport apron crews from jet engine exhaust gases.

Us patent 5,277,952 discloses a decorative, cracked, mirror-like glass sheet produced by bonding glass together with a polymer interlayer. U.S. patents 5,643,666, 5,894,048, 5,958,539, 5,998,028 and 6,025,069 disclose panels composed of a layered copolyester and containing a decorative interlayer and a high relief surface.

Protecting building facades by retrofitting has traditionally involved reinforcing walls. To make wall strengthening truly effective, it is common to perform invasive operations on the wall, which adversely affect the appearance of the structure and interfere with the use of the building. Accordingly, it is desirable to have a structure that is unobtrusive and easy to install, while also protecting the entire building from damage from on-board bomb attack.

Summary of The Invention

A blast resistant barrier is disclosed which comprises a plurality of cells, each cell comprising a panel having a thickness of greater than 20 mm to less than 40 mm. The panel is in the form of a monolithic polycarbonate sheet or laminate vertically disposed between an explosive source and an explosive target, the laminate comprising at least two polycarbonate sheets and an optional image layer sandwiched therebetween. The plate is fixed to a frame which is firmly embedded in the concrete in a suitable manner to provide sufficient rigidity to absorb and withstand the external forces caused by the explosion.

In a preferred embodiment, the panel comprises at least two polycarbonate sheets stacked on top of each other, optionally including an image layer sandwiched therebetween. In another embodiment, the frame is rigidly fixed to the target, enabling the explosive force to be distributed throughout the target structure. The height of the blast barrier is preferably proportional to the height of the target.

Detailed Description

The panel of the invention comprises at least one monolithic, preferably two or more, stacked polycarbonate sheets, which are stacked and/or adhered to each other to form a stack.

The panels of the invention may optionally include at least one image layer in the form of wood, stone, glass, fabric, metal, paper, plastic, plant, flower or vegetation and products derived therefrom, any of which may be of any color. The image layer may be laminated to the polycarbonate layer or sandwiched between any two polycarbonate layers. The thickness of the plate is in the range of 20-40 mm.

In embodiments where the panel comprises a laminate, it is preferred that the panel comprises a first polycarbonate sheet having a thickness of 10 to 20 mm, preferably 12 to 18 mm, a second polycarbonate sheet having a thickness of 10 to 20 mm, preferably 12 to 18 mm, and at least one image layer sandwiched between the first polycarbonate sheet and the second polycarbonate sheet. Other embodiments include multiple polycarbonate sheets, typically three or four sheets of the same or different thickness.

The several sheets that make up the panels of the invention may be adhered to one another by lamination or the use of an adhesive. Suitable adhesive layers include a 0.025 "thick a4700 Dureflex polyurethane film, a product of dierfield Urethane (Deerfield Urethane). The adhesive must have sufficient heat resistance to withstand the thermal conditions to which it will be subjected during lamination without degradation and deformation. Of course, in cases where transparency of the sheet is required, the adhesive must also be transparent.

In one embodiment of the invention, the plate may be prepared by: (a) providing a first polycarbonate sheet having a thickness of 10-20 millimeters; (b) providing a second polycarbonate sheet having a thickness of 10-20 millimeters; (c) placing at least one image layer between a first polycarbonate sheet and a second polycarbonate sheet to form a sandwich; (d) pressure is applied to the structure at an elevated temperature for a time sufficient to form a laminate. Suitable thermal conditions are generally 18-249 ℃, preferably 32-227 ℃, a pressure of 69-2069kPa, preferably 448-662kPa, and a time at the maximum temperature and pressure of 0.1-20 minutes, preferably 0.1-5 minutes, most preferably 0.17-3 minutes. Preferably, the temperature should not exceed 249 ℃ and the pressure should not exceed 2070kPa during the heat press bonding process, since under such conditions the polycarbonate sheet layer may be extruded as a registered image layer. It is preferred to apply pressure before heating. Optionally, the stack thus formed may be cooled at a pressure of 7 to 2065 kPa. In another embodiment, the laminate of the present invention further comprises a protective hardcoat layer.

Importantly, the first and second polycarbonate sheets are not necessarily the outermost sheets of the inventive panel. As mentioned above, the plate may comprise a plurality of sheets (layers) and several image layers on both sides of the image layer. However, the total thickness of the plate is required to be more than 20 mm and less than 40 mm. The panels are preferably 4 feet wide and 8 feet long, but the panels of the present invention are not limited to these dimensions.

The polycarbonate sheet may be transparent, translucent or opaque, respectively. Also, the respective transparencies or translucencies and colors of the polycarbonate sheets may be different from each other.

Polycarbonates are well known thermoplastic aromatic polymer resins (see German published Specification (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; especially the monograph of H.Schnell "polycarbonate Chemistry and Physics of Polycarbonates", Interscience publishers, New York City, New York State, 1964, incorporated herein by reference). The polycarbonates suitable according to the invention have a weight-average molecular weight of 8,000-200,000, preferably up to 80,000, and an intrinsic viscosity of 0.40 to 1.5 dl/g, measured in methylene chloride at 25 ℃. Preferably, the polycarbonate has a glass transition temperature of 145-148 ℃.

Polycarbonate sheets suitable for use in the present invention are commercially available. Sheets made from homopolycarbonates based on bisphenol a are preferred due to their good mechanical properties and excellent transparency. Such suitable sheets are commercially available under the MAKROLON trademark from Sheffield Plastics inc.

The image layer preferably comprises a fabric, wire, rod and/or stick, paper or photographic image, and vegetation such as grass, flowers, wheat and thatch. The image layer may display an image or design or may be solid-colored, and should have sufficient heat resistance, e.g. a sufficiently high melting temperature, to avoid any degradation or deformation during the preparation or processing of the panel. Preferably the image layer is substantially continuous. The image layer preferably has a thickness of from 0.0254 to 1.524 mm, preferably from 0.0254 to 0.05 mm, and most preferably 0.04 mm. However, depending on the available equipment, thinner or thicker polymer films may be used in the decorative image layer, and the thickness is only limited by function under such conditions.

In a preferred embodiment, the panel comprises at least one first image layer disposed between the first and second polycarbonate sheets and at least one second image layer disposed between the second and third polycarbonate sheets.

In one embodiment of the invention, the image layer comprises a fabric of textile fibers. The fabric may exhibit an image or pattern produced in the fabric by weaving or knitting techniques. The fabric may be textile fibres (i.e. fibres of natural, semi-synthetic or synthetic polymeric material). For example, the fabric may be made of: cotton, wool, silk, rayon (regenerated cellulose), polyesters 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 fibres should be high enough to avoid any degradation or deformation of the fabric during the preparation or processing of the laminate of the invention.

The fabric may be woven, spun bonded, knitted or prepared by methods well known in the fabric art, may be uncolored, e.g., white, or colored by conventional dyeing and printing techniques. Alternatively, the fabric may be produced from dyed yarns, or from threads and yarns from pigmented polymers. Preferably, the fabric present in the decorated laminate structure is substantially continuous, constituting a distinct image layer or laminate. In one embodiment of the invention, the image layer comprises metal wires, rods or rods. The metal cords may be formed by various techniques, resulting in a metal mesh fabric, screen or open mesh with high transparency. The wire, rod or bar may be woven, welded, knitted or manufactured by other methods well known in the art of wire manufacturing. The wires, rods and bars may be of any color. The metallic component of the image layer may be a different metallic material, such as copper, aluminum, stainless steel, galvanized steel, titanium, or the like, or combinations thereof. The metallic components of the image layer may be made of metallic thin wires, rods and bars having different cross-sectional areas and geometries, such as substantially circular, elliptical or relatively flat. The thickness or diameter of the wires, rods and bars is not critical. However, it is important that the metal surface be smooth to avoid propagating cracks that may weaken the panel. It is therefore advantageous to embed the metal surface in a polymeric material such as polyvinyl chloride, copolyester or polyurethane. The only requirement for this embodiment is that the polymeric material used to embed the metal surface has sufficient heat resistance so that thermal degradation or deformation does not occur during the sheet lamination and forming process.

In another embodiment, the plate may comprise an image layer of wires, rods or bars of reinforced polycarbonate. In another embodiment, the image layer comprises a printed or pigmented image. Preferably, the printed or pigmented image layer has opposite surfaces, wherein an image is printed on one of the surfaces, and/or the decorative image layer comprises a color. More than one printed or pigmented 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 three-dimensional or "embossed" appearance to the decorative image, or the formation of letters in the printed or colored image layers. One surface of each printed or pigmented image layer is attached to the first polycarbonate sheet so that the image or color can be seen through the first polycarbonate sheet without significant distortion. The printed or pigmented image layer may comprise any suitable polymeric material that is compatible with the materials used in the first and second polycarbonate sheets, inks or other materials used in making the laminate of the present invention. Preferably, the image layer comprises a polyvinyl chloride, copolyester, polycarbonate or polyurethane thermoplastic material.

In another embodiment, an image or color is printed on the bottom side of the image layer, in which case the polymer used to make the image layer is transparent.

The printed image may be prepared according to conventional photographic printing processes or using a digital database generated from the photographic image. Digitizing and storing the image may be accomplished by any method well known in the computer art, such as scanning.

In another embodiment, the image layer includes vegetation, such as grass, thatch, flowers (e.g., rose petals), wheat, grain, natural paper, and the like, such that the natural color of the vegetation is maintained. 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 three-dimensional or "embossed" appearance to the decorative vegetation in the image layer. One surface of each image layer is attached to the first polycarbonate sheet so that the vegetation is visible through the first polycarbonate sheet without significant distortion.

The laminate structure may optionally comprise a protective hard coating that is a clear, hard, scratch or abrasion resistant coating or layer laminated to the upper surface of the first polycarbonate sheet. These coatings may also improve the chemical resistance of the laminate, providing a scratch resistant surface. The protective layer may be a bilayer film comprising a protective layer on a sheet layer. The protective layer is preferably selected from uv-or electron beam-cured cross-linked acrylics, vacuum-or uv-cured urethanes, uv-or electron beam-cured silicones with acrylic groups, or heat-cured urethanes or plastisols. A polyurethane layer may be applied to the outer surface to provide abrasion resistance. Alternatively, biaxially oriented polyEthylene terephthalate, e.g. MYLAROr TEFLONFilms, e.g. TEDLAR(both available from DuPont Chemical Company) may be laminated as a protective layer on the upper surface of the first polycarbonate sheet. More preferably, the protective layer comprises a thermally, uv or e-beam cured silicone to achieve a glass appearance.

The lamination operation of the panels of the invention is conventional. In one lamination process, preferably a laminator is used, the apparatus being characterized by providing sufficient heat transfer and uniform heat distribution.

To increase the pressure drop, a vacuum may be applied to remove air trapped between the layers. During the bonding process, the polycarbonate materials may be bonded or fused together using an adhesive, if desired.

Preferably, the lamination process comprises hot or cold pressure bonding. As is well known, thermocompression bonding methods include, but are not limited to, hot steam, electric heat, hot oil heat, and other methods known in the art. Cold pressure bonding methods include, but are not limited to, cold water and glycol cooling methods. The lamination operation may be performed with or without vacuum pressing. Generally, if the air is evacuated prior to heating and pressurizing, it is less likely that air bubbles will form in the laminate. In any event, it is important to apply sufficient pressure to remove air from the system prior to bonding. After thermocompression bonding, the bonded structure is cooled by: maintaining the pressure at 10 ℃ to about 148 ℃ (50 DEG F to about 298 DEG F), preferably 21.1 to 32.2 ℃ (70-90 DEG F) and 7 to 2069kPa, preferably 448-. Optionally, the woven structure may be applied to one or both surfaces of the panel during the pressure bonding process.

The frame for the fixing plate is preferably made of carbon steel, i.e. steel containing at most about 2% carbon, stainless steel or aluminium. To improve durability and aesthetics, carbon steel frames may be treated with corrosion resistant coatings and/or lacquers. Stainless steel is preferred for outdoor applications because this material is less prone to rusting and discoloration than carbon steel and low alloy steel, thereby maintaining its aesthetic properties. In the case of an image layer that is hygroscopic, the edges of the plate must be sealed to prevent moisture exposure. A suitable sealing operation may be the application of silicone or glue to the edges of a thin polymer film, such as a polycarbonate film.

The steel frame includes shaped elements (e.g., "C" cross-section shaped elements) that provide sufficient rigidity and strength to absorb external forces generated by an explosion without significant deformation. The frame may extend vertically at its bottom so that the extended portion may be embedded in a reinforced concrete foundation. Alternatively, the steel frame may be attached to the steel frame of the object (i.e., the building) in a manner to disperse the shock waves.

The plate may be attached to the frame with structural adhesive or by a plurality of bolts. The bolts (preferably shoulder bolts) are 0.75-1.25 inches in diameter, preferably 1.0 inch, and have flat heads so that when tightened, the bolt heads and nuts tighten the area around the bolt holes in the plate without cracking or denting. The bolts may be spaced 4 inches to 8 inches, preferably 6 inches, from the plate edges by about 1.0 inch to 1.5 inches. The bolt holes in the plate preferably have smooth, elongated edges to withstand thermal expansion and relieve stresses. Rubber or elastomeric gaskets or spacers may be used between the panels and the frame to further absorb the impact energy and damping forces (dampen forces) transmitted to the building.

The mechanical properties of the "C" section steel channel are preferably exhibited with a final tensile yield strength of about 300mpa otherwise, for higher or lower modulus materials such as aluminum, the same section properties are preferably obtained by using thicker or thinner walls. In general, the panels of the present invention are preferably placed at least 12 inches from the surface of the protected target to avoid the polycarbonate panels from impacting the building under the action of the blast shock wave and bending due to the impact. For lower anti-terrorism levels or smaller panels, shorter distances may be used.

Examples

Example 1

A panel comprising a coloured fabric is prepared in the form of a laminate. The hot platen was preheated to 475 ° f. The cold platen temperature was set at 65 ° f. Then, the following components were assembled in the following order (from top to bottom): steel press plates, Nomex pads (Nomex pads) or other suitable media for achieving uniform pressure distribution, aluminum separator plates, separator paper (surface patination treated Ultra-cast separator paper), 0.060 "polycarbonate sheets, image layers in the form of fabrics (thin nylon fabric), 0.060" polycarbonate sheets, separator paper, aluminum separator plates, Nomex pads, steel press plates.

A thermocouple was inserted between the first polycarbonate sheet and the fabric. The assembly was then inserted into the hot press, which was closed and the pressure was raised to 94 psi. The temperature was closely monitored until the thermocouple reading was 420 ° f. Once this temperature was reached, the pressure was released and the hot press was opened. The assembly was then transferred to a cold press kit, with a cold press plate temperature of 65 ° f. The pressure in the cold press was then raised to 94 psi. The transfer and repressurization process is completed in less than 3 minutes. The temperature was closely monitored until the thermocouple read 90 ° f, at which time the decorated laminate structure was removed from the cold press.

Example 2

Another plate in the form of a stack is prepared. The hot platen was preheated to 475 ° f. The cold platen temperature was set at 65 ° f. Then, the following components were assembled in the following order (from top to bottom): steel press plates, nomex pads (nomex pressure distribution pads), aluminum separator plates, release paper (surface patized Ultra-cast release paper), polycarbonate films with a hard coating (0.005 "thick film) (hard coating against release paper), 0.118" polycarbonate sheets, image layers in the form of a fabric, 0.118 "polycarbonate sheets, release paper, aluminum separator plates, nomex pads and steel press plates. The "hard coating" used is a flexible aliphatic polyurethane coating.

A thermocouple was inserted between the first polycarbonate sheet and the fabric. The assembly was then inserted into the hot press, which was closed and the pressure was raised to 94 psi. The temperature was closely monitored until the thermocouple reading was 420 ° f. After this temperature is reached, the pressure is released and the hot press is opened. The assembly was then torn from between the first release paper and the hard coated polycarbonate film, and then transferred to a cold press (platen temperature 65 ° f), where the pressure was increased to 94 psi. The transfer and repressurization process is completed in less than 3 minutes. The temperature was closely monitored until the thermocouple read 90 ° f, at which time the laminate was removed from the cold press. The surface finish of the bottom of the product is consistent and uniform.

Example 3

Another laminated form of board was prepared as described below, comprising plant matter embedded in layers and transparent resin, flat texture, thatch comb (thatch reeds), both sides of the board being surface patination treated. The hot platen was preheated to 475 ° f. The cold platen temperature was set at 65 ° f. Then, the following components were assembled in the following order (from top to bottom): steel press plates, nomex pads (nomex pressure distribution pads), aluminum separator plates, release paper, 0.118 "polycarbonate sheets, thatch (thatch comb cracks), 0.236" polycarbonate sheets, thatch, 0.118 "polycarbonate sheets, release paper, aluminum separator plates, nomex pads, and steel press plates.

A thermocouple was inserted between the first couch grass and the 0.236 "polycarbonate sheet. The assembly was then inserted into the hot press, which was closed and the pressure was raised to 10 psi. The temperature was closely monitored until the thermocouple reading was 410 ° f. At this temperature, the pressure was raised to 30 psi. The temperature was closely monitored until the thermocouple reading was 420 ° f. At this temperature, the pressure was increased to 94 psi. The temperature was closely monitored until the thermocouple reading was 435 ° f. The pressure is then released and the hot press is opened. The assembly was then transferred to a cold press (platen temperature 65 ° f) where the pressure was increased to 94 psi. The transfer and repressurization process is completed in less than 3 minutes. The temperature was closely monitored until the thermocouple read 90 ° f, at which time the decorated laminate structure was removed from the cold press. The resulting laminate was heat fused around and over the entire circumference of the thatch, thereby providing a tight envelope. The surface finish of the bottom of the product is consistent and uniform.

Example 4

Another panel in the form of a laminate is prepared, which includes a fabric as the image layer. In a clean room, the sheet was masked off, washed with 50/50% (by volume) water/isopropanol solution, air dried, and the static electricity on the sheet was removed using deionized air. Then, the following components were assembled on the table in the following order (from top to bottom): 0.5 "X4 'X8' polycarbonate sheet, image layer (thin nylon fabric), 0.025" aliphatic TPU film (Dierfield A4700), 0.5 "X4 'X8' polycarbonate sheet.

The assembly was then inserted into a vacuum bag and then evacuated to 29 "mercury. The vacuum state is maintained for 1 hour before the high pressure processing cycle (autograding cycle), and then the vacuum state is maintained throughout the high pressure processing cycle. The vacuum bag and its contents were then placed in an autoclave and heated at a rate of 2.5F/min for 96 minutes to 240F. At the same time, the pressure was increased to 171psi at a rate of 3.8 psi/min over 45 minutes. Then, the temperature of 240 ° f was held at 171psi for 90 minutes. The vacuum bag was then slowly cooled to 105F at a rate of 2.0F/min, and the pressure was then reduced to ambient pressure at a rate of 3.8 psi/min. The assembly was held still for an additional 1 hour. Finally, the assembly is removed from the vacuum bag.

Example 5

The virtual barrier structure produced in accordance with the present invention was tested in an ABAQUS computer model simulating the detonation of a vehicle bomb. The model simulates a bomb equivalent to 2000 pounds of trinitrotoluene (TNT) to strike a panel of the present invention, where the panel is a4 'x 8' polycarbonate sheet with a thickness of 25-35 mm and the bomb is 100 feet, 80 feet and 50 feet from the blast barrier, or a 2 'x 8' polycarbonate sheet with a thickness of 25 mm and the bomb is 80 feet, 50 feet and 40 feet from the blast barrier. The data indicates that for a4 x8 foot panel, the standoff distance (distance from the explosive) should be greater than 50 feet. For a 2 x8 foot panel, the standoff distance should be greater than 40 feet.

TABLE 1

Wall thickness	Inward force on structure	External force from the structure
			[ mm ] of]	[ ox/(unit length)]	[ ox/(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

The data in the above table show that the inward force on the structure is greater than 9,000 units for panels with wall thicknesses of 10-20 mm. For plates with a thickness greater than 20 mm and less than 40 mm, the inward force is reduced to below 8,000 units. At wall thicknesses of 40-50 mm, the inward force on the structure again exceeds 9,000 units. While at a wall thickness of 55 mm the performance of the panel increases and the thickness and inward force on the structure again decreases, since the stiffness of the panel is increased by the increase in thickness and weight.

The above description should not be construed as limiting the invention since those of ordinary skill in the art will recognize that various modifications, alterations, and substitutions can be made to the various materials and methods disclosed in the present invention without departing from the spirit or scope of the invention. Rather, the invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims (18)

1. A blast barrier comprising one or more units, each of said units comprising a panel secured to a frame, said panel having a thickness greater than 20 mm and less than 40 mm, said panel comprising at least one polycarbonate sheet, said panel being vertically disposed between a source of an explosion and a target of the explosion.

2. The barrier of claim 1 wherein said frame comprises at least one component selected from the group consisting of: carbon steel, stainless steel, and aluminum.

3. The barrier of claim 1 wherein said frame is grounded into the concrete.

4. The barrier of claim 1 wherein said frame is secured in an object.

5. The barrier of claim 1 wherein said panel is concave with the concave surface facing 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 comprising more than one polycarbonate sheet.

8. The barrier of claim 7 further comprising an image layer disposed between said sheets.

9. The barrier of claim 8 wherein said image layer comprises at least one component selected from the group consisting of: fabric, photograph, paper, thread, screen, rod, stick, grass and plant.

10. The barrier of claim 9 wherein said composition is encapsulated in a polymeric resin compatible with said composition 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 comprises an ultraviolet 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 secured to said frame by a plurality of bolts.

16. The barrier of claim 1 wherein said panel is adhered to said frame.

17. The barrier of claim 1 wherein said panel comprises at least two polycarbonate sheets bonded to each other by an adhesive.

18. The barrier of claim 17 wherein said adhesive is a thermoplastic polyurethane.