Patent Publication Number: US-2023160666-A1

Title: Composite Enclosure for Explosive Reactive Armor and Methods of Manufacturing the Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. Pat. Application Serial No. 17/376,563, filed on Jul. 15, 2021 by at least one common inventor, which is a division of U.S. Pat. Application Serial No. 15/910,139, filed on Mar. 2, 2018 by at least one common inventor, which claims the benefit of U.S. Provisional Pat. Application Serial No. 62/442,499, filed on Jan. 5, 2017 by at least one common inventor. Each of the aforementioned applications is incorporated by reference herein in its entirety. 
    
    
     GOVERNMENT INTEREST 
     The inventions described herein may be made, used, or licensed by or for the U.S. Government for U.S. Government purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to explosive reactive armor tiles and, more specifically, to an enclosure made of fiber composite material for such tiles and methods of manufacturing the same. 
     Description of the Background Art 
     Today’s military vehicles face more lethal and advanced threats than ever before. Chemical energy (CE) threats (such as shaped charges and explosively-formed projectiles) have seen increased usage in recent operations. Defeat of high performing CE threats on vehicles has until recently required heavy armors. The use of explosives in armor designs (explosive reactive armor or ERA) has the potential to significantly increase armor efficiency and effectiveness. Considerable weight savings in an armor design is attainable with the use of explosives and armor plates. However, the introduction of explosives to a vehicle brings many integration challenges. The containment of the explosive area on a vehicle is extremely critical. Excessive reactive armor explosions can damage the vehicle or introduce vulnerabilities to the vehicle by causing armor attachments to fail. 
     Explosive reactive armor includes an enclosure for housing armor plates and explosive. An enclosure with the armor plates and explosive mounted inside is called a reactive armor tile. The enclosure is a critical part of the integrated reactive armor tile design. It must be able to protect the explosive and armor materials from environmental exposure and to minimize the impact of the blast pressure generated by a reactive armor detonation on tiles adjacent to the detonation. An improperly contained explosion could cause secondary explosions or dislodging of adjacent reactive armor tiles. This would result in a larger than desired damage area. Therefore, a well-designed enclosure will prevent excessive damage from occurring in adjacent tiles. 
     Current designs of reactive armor enclosures used on combat vehicles are constructed from stainless steel and are heavy. An example of an existing baseline design of a combat vehicle ERA enclosure is constructed from 1.59 mm to 4.76 mm (0.0625 in. to 0.1875 in) thick stainless steel and weighs approximately 10 kg (22 lbs.). Enclosures of this type can add up to 2700 kg (approx. 6,000 lbs.) or more of integration weight to a combat-class vehicle, depending on the vehicle size and armor coverage area. The enclosure, however, provides minimal protection to the vehicle, and is therefore considered parasitic weight. As vehicle size and performance expectations continually increase, a heightened awareness has been given to lightweight integration designs. The reactive armor enclosures are significant integration weight drivers requiring weight reduction efforts. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems associated with the prior art by providing a fiber-reinforced composite explosive reactive armor (ERA) enclosure for an ERA tile and methods of manufacturing the same. The ERA enclosure is lightweight but strong, and thus, enables an ERA tile constructed therefrom to function appropriately in response to a CE threat and withstand detonations from neighboring ERA tiles. The lightweight ERA tiles also improve the dynamics of the armored vehicle to which they are applied. 
     An explosive reactive armor (ERA) enclosure according to one embodiment of the invention includes a bottom and a plurality of sidewalls extending from the bottom. The plurality of sidewalls are continuous with each other and with the bottom so as to define an internal volume. The sidewalls are formed from a fiber-reinforced composite material having a plurality of plies of fiber sheet material, where each of the plies forms a portion of each of the sidewalls and defines a sidewall seam in one the plurality of sidewalls. Additionally, a first sidewall seam defined by abutting edges of a first ply of the plurality of plies is offset from a second sidewall seam defined by abutting edges of a second ply. 
     In a particular embodiment, the first sidewall seam is located in a first sidewall of the plurality of sidewalls, and the second sidewall seam is located in a second sidewall of the plurality of sidewalls. In one example, the first and second sidewall seams are located near the middle of the first and the second sidewalls, respectively. In the case of a third ply, a third sidewall seam defined by abutting edges of the third ply is also located in the first sidewall (e.g., in the middle). 
     In another particular embodiment, the plurality of sidewalls are formed from at least six plies, and sidewall seams of adjacent plies are located in non-adjacent sidewalls. 
     In still another particular embodiment, at least some of the plurality of sidewalls are free of sidewall seams. 
     In yet another particular embodiment, the bottom of the enclosure is also formed from the plurality of plies, and each of the sidewalls is formed continuously with at least a portion of the bottom. 
     The ERA enclosure can also include a plurality of attachment structures formed in at least one of the first and second sidewalls, where the plurality of attachment structures is configured to couple the ERA enclosure to an armor element. More specifically, the plurality of attachment structures comprises a plurality of apertures configured to engage a mounting bracket, which itself is configured to mount the ERA enclosure to an armored vehicle body. In another more specific example, the plurality of attachment structures includes a plurality of apertures configured to secure at least a portion of an ERA component within the internal volume of the ERA enclosure. Still more specifically, at least some of the plurality of sidewalls are free of attachment structures, and each of the plurality of sidewalls that is free of attachment structures is also free of sidewall seams. 
     Another explosive reactive armor (ERA) enclosure includes a bottom and a plurality of sidewalls extending from the bottom, and at least one attachment structure formed in one or more of the sidewalls, where the attachment structure is configured to couple the ERA enclosure to vehicle armor. Additionally, the sidewalls define an interior volume in combination with the bottom, the sidewalls are continuously formed with each other and with the bottom, and the bottom and the plurality of sidewalls are formed from a fiber-reinforced composite material. 
     A method of manufacturing an ERA enclosure includes laying a first layer of fiber sheet material over a generally prismatic mold, laying a second layer of fiber sheet material over the first layer, infusing the first and the second layers with a resin, curing the resin to form a fiber-reinforced composite ERA enclosure, separating the ERA enclosure from the mold, and forming at least one attachment structure in the ERA enclosure, where the attachment structure is configured to secure the ERA enclosure to an armor element. The ERA enclosure includes a bottom and a plurality of sidewalls extending from the bottom, which are continuous and define an internal volume. 
     In a particular method, the first and second layers are shaped and oriented such that a first seam between edges of the first layer is offset from a second seam between edges of the second layer. In a more particular method, the step of laying the first layer includes laying the first layer of the fiber sheet material over the mold such that the first seam is disposed adjacent a first sidewall of the mold, and the step of laying the second layer of fiber sheet material includes laying the second layer over the mold such that the second seam is disposed adjacent a second sidewall of the mold. 
     In another particular method, the step of infusing the first and the second layers with resin includes positioning a vacuum bag over the mold, the first layer, and the second layer and applying vacuum to the vacuum bag to draw resin into the vacuum bag and into the first and the second layers. 
     Still another particular method includes applying pressure to the first and second layers prior to the step of curing the resin. In one more specific method, the step of applying pressure includes placing at least one exterior mold over the first and second layers. Still more particularly, the step includes installing a plurality of exterior molds around the perimeter of the second layer and applying a clamping force to the exterior molds. In another more specific method, the step of applying pressure to the first and the second layers includes applying pressure to form at least a portion of the attachment structure. More particularly still, the at least one attachment structure includes at least one relief on an exterior of the ERA enclosure, where the relief is configured to seat a mounting bracket for coupling the ERA enclosure to a body of an armored vehicle. 
     In yet another particular method, the step of forming at least one attachment structure in the ERA enclosure comprises forming a plurality of apertures in at least one sidewall of the ERA enclosure. More specifically, the plurality of apertures can be configured to secure an ERA component within the internal volume. Additionally or alternatively, the plurality of apertures can be configured to secure at least one mounting bracket to the ERA enclosure, where the mounting bracket is configured to secure the ERA enclosure to an armored vehicle body. 
     Still another particular method further includes a step of securing at least one ERA component within the ERA enclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with respect to the following figures, wherein like reference numbers indicate substantially-similar elements: 
         FIG.  1    is a perspective view showing fiber-reinforced composite explosive reactive armor (ERA) tiles according to the present invention mounted on an armored vehicle; 
         FIG.  2 A  is a perspective view showing a generally-prismatic mold used to manufacture a composite ERA enclosure of the present invention; 
         FIG.  2 B  shows a plurality of wrap layers according to the present invention for laying up on the mold of  FIG.  2 A ; 
         FIG.  2 C  is a perspective view showing a first wrap layer laid on the mold of  FIG.  2 A ; 
         FIG.  2 D  is a perspective view showing a second wrap layer laid on the mold of  FIG.  2 A ; 
         FIG.  2 E  is a perspective view showing the laid up mold of  FIG.  2 A  being prepared for resin infusion by bagging; 
         FIG.  2 F  is a bottom view of a bracket mold for applying over the bagged mold of  FIG.  2 E ; 
         FIG.  2 G  is a perspective view showing exterior molds applied over the laid-up, bagged mold of  FIG.  2 E ; 
         FIG.  3    is a perspective view showing a finished fiber-reinforced composite enclosure of the present invention and other elements of an ERA tile; 
         FIG.  4    is a view looking into the open end of enclosure; 
         FIG.  5    is a perspective view illustrating a resin transfer molding (RTM) apparatus used to manufacture ERA enclosures according to an alternative method of the present invention; 
         FIG.  6    is a flowchart summarizing one method for manufacturing an ERA enclosure of the present invention; 
         FIG.  7    is a flowchart summarizing another method for manufacturing an ERA enclosure of the present invention; and 
         FIG.  8    is a flowchart summarizing a method for performing the third steps (“Layup Wrap Layers”) of the methods of  FIGS.  6  and  7   . 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. In other instances, particulars of well-known components and manufacturing practices have been omitted to avoid unnecessarily obscuring the present invention. 
       FIG.  1    is a perspective view showing a plurality of fiber-reinforced composite explosive reactive armor (ERA) tiles  102  mounted on the outside of an armored vehicle body  104  (e.g., a tank, personnel carrier, etc.). Nine ERA tiles  102  are shown mounted in a square (3 × 3) configuration. However, this configuration is merely exemplary, and ERA tiles  102  can be positioned differently according to vehicle and mission. 
     Each ERA tile  102  includes a fiber-reinforced composite enclosure  106  and a lid  108 . The sidewalls and bottom ( FIG.  3   ) of enclosure  106  define an interior volume (covered by lid  108 ) that houses explosive reactive armor components (e.g., armor plates, explosives, etc., not shown). First pluralities of fasteners  110  (e.g., rivets, threaded fasteners, etc.) are inserted through at least some of the sidewalls of each enclosure  106  to retain lid  108  thereon. Second pluralities of fasteners  112  (e.g., rivets, threaded fasteners, etc.) are also inserted through at least some of the sidewalls of enclosure  106  to mount and retain the ERA components therein. 
       FIG.  1    further shows that ERA tiles  102  are mounted to armored vehicle body  104  via mounting brackets  114  and mounting rails  116 . Mounting rails  116  comprise “C” channels in this embodiment and are affixed (e.g., by fasteners, welding, etc.) to armored vehicle body  104 . Each ERA tile  102  includes two mounting brackets  114  in this embodiment, which are positioned on opposing sidewalls of enclosure  106 . Each mounting bracket  114  is affixed to a sidewall of its respective enclosure  106  by a plurality of fasteners  118 . Mounting brackets  114  are “L” brackets, which extend past the bottom (back) of enclosure  106  and face inward relative to the enclosure  106 , to be able to slide into (e.g., vertically) the “C” channels of mounting rails  116 . While only the outside mounting brackets  114  of the left-most column of tiles  102  are shown in detail, the inside mounting brackets  114  are substantially similar thereto, but mirrored in orientation. Other means for mounting tiles  102  to armored body  104  are also possible. 
     In this embodiment, each enclosure  106  has interior dimensions of approximately 33 cm × 33 cm × 33 cm (13 in. × 13 in. × 13 in.) and is fabricated from a light-weight fiber composite material. These dimensions are only exemplary, however. For example, other reactive armor designs can utilize a shallower enclosure with a depth around 18 cm (approximately 7 inches). Examples of possible fiber materials used to construct enclosure  106  are fiberglass, aramid, and carbon. At appropriate wall thicknesses, the use of any of the three fibers provides significant weight savings in enclosure  106  over the prior art metal designs. However, harness satin weave or plain weave fiberglass fabrics of areal densities from 163 g/m 2  to 814 g/m 2  (4.8 oz/yd 2  to 24 oz/yd 2 ) have been found to provide particularly desirable enclosure characteristics as described below. 
       FIGS.  2 A- 2 G  graphically illustrate an exemplary method for manufacturing an ERA enclosure  106  according to the present invention.  FIG.  2 A  is a perspective view of a generally-prismatic mold  202  positioned on a workbench  204 . Mold  202  is cubic in this example and includes four sidewalls  206 ( 1 - 4 ), and a top wall  208 . Top wall  208  corresponds to the bottom of the completed enclosure  106 , whereas sidewalls  206 ( 1 - 4 ) correspond to the sidewalls of the completed enclosure  106 .  FIG.  2 A  shows the edges of mold  202  to be sharp for simplicity. However, it will be understood that such edges can be radiused to provide a smooth, arcuate transition between interior surfaces of the finished enclosure  106 . 
     Mold  202  enables a plurality of plies of fiber sheet material to be sequentially laid up on it in the desired shape and then have resin infused (if necessary) and cured. Mold  202  is an interior mold in this example, meaning that the first ply applied to it will be the inner-most ply of the finished enclosure  106 . An inner mold is desirable because it provides better control over the dimensions and surface finish of the interior of enclosure  106 , thereby making fitting of the armor plates inside enclosure  106  easier and more uniform. Additionally, mold  202  is collapsible (separable) into three discrete sections along the dashed lines shown. The use of a collapsible mold  202  eliminates the need for a draft angle when removing the finished enclosure  106  therefrom. Mold  202  is formed from aluminum in this embodiment, although other materials (e.g., high-density foam, other metals, etc.) can be used instead. 
       FIG.  2 B  is a plan view showing a plurality of wrap layers  210 ( 1 - n ) that will be laid up on mold  202 . In this example, each wrap layer  210 ( 1 - n ) has the same shape, but can vary in size to account for the volume added to the mold  202  by previously-applied wrap layers  210 . In the present example, each enclosure  106  is formed from six wrap layers  210 ( 1 - 6 ) of plain (cross) weave, 24 oz/yd 2  (814 g/m 2 ) S-2 fiberglass sheet material. The first three wrap layers  210 ( 1 - 3 ) are all made in equal size. The last three wrap layers  210 ( 4 - 6 ) are also made in equal size, but larger than the first three wrap layers, to account for the increased volume resulting from laying up the first three wrap layers  210 ( 1 - 3 ) on mold  202 . 
     As shown by the dashed line on wrap layer  210 ( 1 ), each wrap layer  210 ( 1 - n ) includes a generally rectangular section  212  formed continuously with five triangular flaps  214 ( 1 - 5 ). Additionally, as shown on wrap layer  210 ( n ), each wrap layer  210 ( 1 - n ) is applied to mold  202  such that the regions  216 ( 1 - 5 ) of section  212  will form sidewalls of a finished enclosure  106 , and flaps  214 ( 1 - 5 ) will combine to form the bottom of an enclosure  106 . When a layer is laid up on mold, regions  216 ( 1 ) and  216 ( 5 ) abut and define a sidewall seam as described below. 
       FIG.  2 C  is a perspective view showing first wrap layer  210 ( 1 ) laid on mold  202  so that a sidewall seam  220  between rectangular regions  216 ( 1 ) and  216 ( 5 ) is positioned near the center of sidewall  206 ( 1 ) ( FIG.  2 A ) of mold  202 . Sidewall seam  220  is formed by a direct abutment of the outside edges of regions  216 ( 1 ) and  216 ( 5 ). Accordingly, the seam  220  of wrap layer  210 ( 1 ) will be away from corners of the completed enclosure  106  where high stress concentration are expected.  FIG.  2 C  also shows that the flaps  214 ( 1 - 5 ) of wrap layer  210 ( 1 ) are folded over top wall  208  of mold  202  so as to form a bottom of enclosure  106  with five seams  222 . Advantageously, the flaps  214 ( 1 - 5 ) provide continuity between the sidewalls and the bottom of enclosure  106 . Additionally, because there is only one sidewall seam  220 , there is high fabric continuity in the sidewalls of the completed enclosure  106 . Finally, the dashed lines denote bends/folds in continuous portions of fabric wrap layer  210 ( 1 ) over the edges of underlying mold  202 , but they are not seams. 
     To aid in applying wrap layer  210 ( 1 ) to mold  202 , a spray adhesive can be applied. For example, Super 77™ by 3M™ Corporation can be applied to temporarily hold wrap layer  210 ( 1 ) in position on mold  202  and does not compromise the strength of the resin subsequently infused into the wrap layers  210 . Use of Super 77™, however, is not required. Other spray adhesives can also be used. 
       FIG.  2 D  shows a second wrap layer  210 ( 2 ) laid up on mold  202  over first wrap layer  210 ( 1 ). Second wrap layer  210 ( 2 ) is laid up such that its sidewall seam  220  is offset from the sidewall seam  220  of first wrap layer  210 ( 1 ). More specifically, sidewall seam  220  of second wrap layer  210 ( 2 ) is positioned over back wall  206 ( 2 ) of mold  202 , i.e., opposite the sidewall seam  220  of the prior wrap layer. Flaps  214 ( 1 - 5 ) of second wrap layer  210 ( 2 ) are also folded down over top wall  208  of mold  202 , which will form a second ply of the bottom of the completed enclosure  106 . As before, a spray adhesive can be used to aid in the applique of second wrap layer  210 ( 2 ) over first wrap layer (1). 
     The remaining wrap layers  210 ( 3 - 6 ) are applied in alternation as illustrated in  FIGS.  2 C and  2 D  until mold  202  has all six plies laid up on it. That is, wrap layers  210 ( 3 ) and  210 ( 5 ) are applied to mold as illustrated in  FIG.  2 C , whereas wrap layers  210 ( 4 ) and  210 ( 6 ) are applied as shown in  FIG.  2 D . Thus, according to this example, only the front and back sidewalls  206 ( 1 ) and  206 ( 3 ) of mold  202  have sidewall seams  220  of wrap layers  210 ( 1 - 6 ) adjacent thereto. This layering approach provides fiber continuity across the corners of adjacent sidewalls and across corners between the bottom and sidewalls of the completed enclosure  106  in each ply/layer. 
       FIG.  2 E  shows mold  202  having six wrap layers  210 ( 1 - 6 ) applied thereto being prepared for resin infusion. An enclosure  240  (e.g., a vacuum bag, etc.) used for Vacuum Assisted Resin Transfer Molding (VARTM) is placed over mold  202  and/or workbench  204  and tightly secured (e.g., with tape, bands, etc.). Vacuum bag  240  includes a vacuum port  242  and a resin inlet port  244 . When it is time to infuse the resin, vacuum is applied to port  242 , which causes bag  240  shrink and conform to the laid-up mold  202 , and pull resin into bag  240  via port  244 . This, in turn, infuses the laid up wrap layers  210 ( 1 - 6 ) with resin causes good “wet-out” of the wrap layers  210 ( 1 - 6 ). Layers of peel ply and/or infusion media can also be applied between the outermost wrap layer  210 ( 6 ) and the vacuum bag  240  to improve resin flow and to facilitate removal of the vacuum bag after cure. The VARTM process enables very consistent part manufacturing and also contributes to higher fiber volume fraction at low cost. Optionally, double bagging can be used to ensure uniform pressure on the part and clamping force on the exterior molds (discussed below). 
       FIG.  2 F  is a bottom view of an external bracket mold  250 , which is applied to the layup over top wall  208  of mold  202  and over vacuum bag  240 . Bracket mold  250  includes protrusions  252  that form reliefs for mounting brackets  114  in the portions of wrap layers  210 ( 1 - 6 ) adjacent mold sidewalls  206 ( 1 ) and  206 ( 3 ), which contain sidewall seams  220 . Bracket mold  250  can be formed from a rigid material, such as a metal, high-density foam, etc. 
       FIG.  2 G  shows additional exterior molds  260  applied around the perimeter of mold  202  over vacuum bag  240 . Four exterior molds  260 ( 1 - 4 ) are applied, each wrapping around a respective corner of the layup. In this embodiment, exterior molds  260 ( 1 - 4 ) comprise four angle-brackets or caps made of rigid material, such as steel. Molds  260 ( 1 - 4 ) are clamped down circumferentially around mold  202  until a distance D between adjacent external molds  260 ( 1 - 2 ) reaches a predetermined value. Molds  260 ( 1 - 4 ) can be clamped down using, for example, C-clamps (not shown) installed between adjacent pairs of molds  260 ( 1 - 2 ),  260 ( 2 - 3 ),  260 ( 3 - 4 ), and  260 ( 4 - 1 ). High-strength tape  262  can be used to hold the exterior molds  260  in position after they are clamped to the desired pressure. 
     The use of exterior molds  260 , and bracket mold  250 , provide two benefits: 1) increasing the fiber volume fraction; and 2) improving the exterior surface finish. For example, molds  260 ( 1 - 4 ) are arcuate in the corners and, therefore, smooth and round the corners between the sidewalls of the finished enclosure  106 . Similarly, mold  250  functions to smooth and round corners between adjacent sidewalls and between sidewalls and bottom of the finished enclosure  106 . The gaps between molds  260 ( 1 - 4 ) and mold  250  allow routing of ports  242  and  244  therethrough. 
     When the predetermined distance D is reached, then the laminated wrap layers  210 ( 1 - 6 ) have been compressed to the desired aggregate wall thickness for enclosure  106  and resin can be infused (pulled) into the laid up wrap layers  210 ( 1 - n ) via port  244  by applying vacuum to port  242 . The inventors have found that epoxy is a desirable resin choice because of its hardness and resistance to fracture. For example, the two-part epoxy “SC-15” by Applied Poleramic, Inc. of Benicia, CA can be used. However, use of epoxy resin is not a requirement and other types of resins can be used instead. The resin-infused wrap layers  210  are then cured according to the resin employed (e.g., by heating, etc.). The molds  202 ,  250 , and  260 ( 1 - 4 ) allow the fibers in wrap layers  210  to maintain shape while the resin cures. 
     After the resin has cured sufficiently to retain its shape, the resulting fiber-reinforced composite enclosure  106  is separated from molds  250  and  260 ( 1 - 4 ), removed from the vacuum bag  140 , and separated from the mold  202 . Various attachment structures, such as pluralities of apertures  110  and  112  and apertures for mounting brackets  114  can then be formed in the enclosure  106  (e.g., by drilling, water-jet, etc.). Thereafter, ERA components (e.g., armor plates, supporting components, etc.) can be placed inside of enclosure  106  and secured thereto along with lid  108  to complete the ERA tile  102 . 
       FIG.  3    shows a completed enclosure  106  ready to have, one or more ERA component(s)  302 , two mounting brackets  114 , and a lid  108  mounted thereto. Enclosure  106  includes four sidewalls  306 ( 1 - 4 ) corresponding to sidewalls  206 ( 1 - 4 ) of mold  202 , respectively, and a bottom  308  corresponding to top wall  208  of mold  202 . Sidewalls  306 ( 1 - 4 ) and bottom  308  are formed continuously and have arcuate corners to reduce stress concentration there. 
     During finishing of enclosure  106 , various pluralities of attachment structures are formed in its sidewalls  306 . For example, a plurality of apertures  310  are formed in each sidewall  306  near the opening of enclosure  106 . Apertures  310  align with complementary apertures  311  formed in a lip of lid  108  such that, after enclosure  106  is loaded with its ERA components  302 , lid  108  is secured to enclosure  106  by fixing fasteners  110  through apertures  310  and  311 . The inventors have found that using three rivets  110  per sidewall  306  is often sufficient to securely retains lid  108  in position even if a neighboring tile  102  detonates. However, additional or fewer fasteners can be employed if desired. 
     Second pluralities of apertures  312  are formed in sidewalls  306 ( 1 ) and  306 ( 3 ) such that fasteners  112  can be passed therethrough and into one or more ERA component(s)  302  (e.g., armor plates, etc.) to secure ERA component(s)  302  within enclosure  302 . Because of this connection, ERA component(s)  302  provide significant structural reinforcement to enclosure  106  and resist flexing and inward deformation of sidewalls  306 ( 1 ) and  306 ( 3 ) when a neighboring tile  102  detonates. Apertures  312  can also comprise ports for inserting foam into enclosure  106 . Expanding foam placed internally can also provide structural reinforcement to enclosure. 
     Third pluralities of apertures  314  are formed in sidewalls  306 ( 1 ) and  306 ( 3 ) as well. Apertures  314  are complementary to apertures  316  formed in mounting brackets  114  such that fasteners  118  (e.g., nuts and bolts, etc.) can be passed therethrough to secure mounting brackets  114  to enclosure  106 . As shown, mounting bracket  114  includes an outer L-bracket  114 A and a backing plate  114 B. L-bracket  114 A engages C-channels  116  ( FIG.  1   ) and is secured to armored vehicle body  104  via fasteners passed through aperture(s)  320 . The backing plate  114 B is installed inside enclosure  106  and, in combination with L-bracket  114 A, sandwiches the associated sidewall  306  therebetween. Accordingly, mounting brackets  114  structurally reinforce sidewalls  306 ( 1 ) and  306 ( 3 ). 
     Each of sidewalls  306 ( 1 ) and  306 ( 3 ) also includes a relief  322  (only relief for sidewall  306 ( 1 ) shown), which seats L-bracket  114 A generally flush with the outside of the respective sidewall. Relief  322  illustrates how the shape of the fiber composite enclosures  106  can be easily tailored in shape to accommodate the attachment provisions by making a geometric change to one or more external mold(s)  250  and/or  260 . 
       FIG.  4    is a view of sidewalls  306 ( 1 - 4 ) and bottom  308  looking into the open end of enclosure  106 . As shown, sidewalls  306 ( 1 - 4 ) and bottom  308  are formed continuously and are 6-ply. Only sidewalls  306 ( 1 ) and  306 ( 3 ) include sidewall seams  220 . Additionally, sidewall seams  220  of adjacent plies are offset with respect to each other. More particularly, sidewall  306 ( 1 ) contains sidewall seams  220  of odd-numbered wrap layers (starting with the innermost layer corresponding to wrap layer  210 ( 1 )), whereas sidewall  306 ( 3 ) contains sidewall seams  220  of even-numbered wrap layers. Sidewalls  306 ( 2 ) and  306 ( 4 ) contain no sidewall seams  220 . 
     The seam locations and armor attachment locations are selected to increase strength of the enclosure  106  in the hoop (perimeter) direction. For example, because sidewalls  306 ( 2 ) and  306 ( 4 ) contain no sidewalls seams  220  and are strong and flexible, they are resistant to inward inelastic deformation when a neighboring tile detonates. Additionally, when the ERA tile  102  including the enclosure  106  itself detonates, the sidewalls  306  flex outward before rupture. Their significant hoop strength (resistance to outward radial loading) absorbs much of the lateral blast energy before resin matrix breakdown and/or fiber breakage and, thus, limits damage to the neighboring tiles  102 . Sidewalls  306 ( 1 ) and  306 ( 3 ) include several sidewall seams  220  each and, therefore, would be more susceptible to resin matrix breakdown during flexion. However, sidewalls  306 ( 1 ) and  306 ( 3 ) are structurally reinforced internally by the ERA component(s)  302  and internally and externally by the mounting brackets  114 . Such reinforcement provides significant resistance to seam failure during neighboring tile detonations. Bottom  308  is also resistant to damage because it is mounted against armored vehicle body  104 . Thus, the performance requirements of enclosure  106  are not degraded by the introduction of seams, particularly sidewall seams  220 . 
     Of the three fiber sheet materials discussed herein (fiberglass, aramid, and carbon), testing has shown fiberglass to be the most efficient in terms of providing adequate blast protection for adjacent reactive tiles  102  at minimum weight. Carbon fiber enclosures were found to be quite brittle for the rapid blast loading of ERA. However, a combination of the materials may be used as well to achieve a balanced solution. 
     In testing, two enclosures were fabricated using heavier 814 g/m 2  (24 oz/yd 2 ) fiberglass fabric. The first enclosure had a wall thickness of 4.76 mm (0.1875 in.) and the second had a thickness of 3.18 mm (0.125 in). A third fiberglass enclosure was constructed utilizing 300 g/m2 (8.8 oz/yd 2 ) fabric sheets with a 4.76 mm wall thickness. The resulting enclosures weighed between 1.8 and 3.6 kg (approximately 4 and 8 lbs). These values are by way of example only and are not intended to be limiting. 
     Based on testing, it has been determined that enclosure  106  provides adequate blast protection from adjacent tiles with wall thicknesses as thin as 4.76 mm. Additionally, the 814 g/m 2  (24 oz/yd 2 ) fiberglass fabric sheet had better performance than the 300 g/m 2  (8.8 oz/yd 2 ) fiberglass fabric at this thickness. Because fewer wrap layers are needed with the heavier fabric, there is less reliance on resin matrix load transfer to resist damage and fracturing of the resin is reduced. Instead blast load is carried by tension in the heavier weight fibers. 
     Thus, the present invention provides fiber-reinforced composite enclosures for ERA tiles that are extremely lightweight compared to prior art steel enclosures, are able to resist detonations from neighboring tiles, and can be readily and inexpensively manufactured by VARTM without unique tooling. Accordingly, ERA tiles  102  can be provisioned for armored vehicles at lower cost, and because they are lightweight, the tiles  102  improve the dynamic loading and operability of such armored vehicles in theatre. Additionally, the composite enclosure  106  meets environmental testing requirements of MIL-STD 810. 
       FIG.  5    is a perspective view of an exterior mold  502  of a resin transfer molding (RTM) apparatus, which is used to infuse and cure the laid up mold  202  according to an alternative method of the invention. The interior cavity of exterior mold  502  defines a desired geometry for the external surface of enclosure  106 . Exterior mold  502  is placed over laid up mold  202 , and resin is pushed into the interstitial space between the two parts via inlet port  504 . When the resin is cured (e.g., by heating), exterior mold  502  and mold  202  are separated from enclosure  106 . RTM is often used in higher-production environments than VARTM and provides enclosures  106  with high quality bend radii (e.g., near the corners) and finish at a rapid throughput. 
       FIG.  5    illustrates how alterations can be made to the present invention without departing from its spirit and scope. Indeed, various alterations can be made. For example, pre-impregnated (pre-preg) fiber sheet material can be used. These pre-preg rolls of fabric contain the same fibers as described in previous embodiments, but already contain resin infused in the fiber. The use of pre-preg sheet material eliminates the need to infuse resin using the VARTM process. However, the desired number of layers can still be laid up on or in a mold, and then vacuum bagged to maintain the desired shape of the part during the curing process. This can be done with or without the use of external molds/brackets for maintaining shape. 
     As another option, pressure assisted curing (e.g., autoclave, etc.) can be utilized. For example, an autoclave provides uniform pressure around a part, in addition to heat, during curing, which provides a uniform exterior finish. Such uniform pressure can also be used to impart the desired external shape to the enclosure as an alternative, or in addition, to exterior molds. 
     As still another example, alternative wrap layers can be included in the enclosure. For example, one or more layer(s) in the shape of a “plus-sign” (+) can be laid up on mold  202  in addition to wrap layers  210 . The plus-sign layer can be applied with its center over the top wall  208  ( FIG.  2 A ) of mold  202  and its wings folded down over respective sidewalls  206 . The plus sign layer can be used to provide reinforcement for the bottom  308  of the resulting enclosure, which would be beneficial where enclosure  106  was mounted to a vehicle via bottom  308 . 
     As yet another example, wrap layers  210  can be formed from a fiber sheet material manufactured with more (or stronger) fibers located in the hoop (perimeter) direction of the resulting enclosure. Doing so can yield enclosures of adequate strength but that are lighter than other embodiments. 
     As still another example, composite enclosures can be manufactured using alternative molds and/or wrap layers of alternative shapes. For example, using an exterior mold in the shape of an open-top box, a first layer (which forms the outermost layer of the enclosure when removed from the exterior mold) is cut to a rectangle shape, placed in the mold, and wrapped around all four of the sides of the mold, leaving a seam along one of the wall/wall corners. A square piece of woven sheet is then placed in the bottom of the mold to create the bottom of the enclosure. An epoxy resin is then brushed onto the fibers. A second layer is cut in the shape of a “plus-sign” (+) and is placed in the bottom of the mold and folded up to create the sides. Again, resin is brushed onto the fibers. A third layer identical to the first layer is then laid up. This alternating pattern is continued until the desired total material thickness is achieved. 
     In yet another embodiment using an interior mold, a first layer of fiber sheet material is cut into the shape of a plus-sign and placed on the mold, and the sides folded down to create the walls. Resin is then brushed onto the fibers. A second layer in the shape of a rectangle is then wrapped around the side walls of the mold. Next, a square piece of woven sheet is placed on top of the mold to create the bottom of the enclosure. A third layer identical to the first layer is then applied over the second layer. This series of layers can be repeated until the desired total material thickness is achieved. A vacuum bag is then applied outside the mold to ensure proper/complete wet out of the fibers and shape conformity. 
     As still another example, the sidewall seams  220  of consecutive wrap layers  210  can be located in different sidewalls of enclosure  106  according to other schemes, such as in a predetermined order, clockwise, counterclockwise, etc. However, it is beneficial to limit the number, or eliminate, seams in sidewalls where there is no internal structural reinforcement. As yet another option, in any of the designs discussed herein, a strip of aramid fabric can also be added along one or more of the wall/wall corners and/or seams for added reinforcement. Similarly, other woven fabrics might be employed, such as ultra-high molecular weight polyethylene fibers such as available from Honeywell Spectra, Dyneema, etc. or an aramid fiber such as Kevlar™. 
       FIG.  6    is a flowchart summarizing one method  600  for manufacturing an ERA enclosure according to the present invention. In a first step  602 , a mold is provided. In a second step  604 , a plurality of wrap layers are provided, and in a third step  606 , the wrap layers are laid up on the mold (e.g., so the sidewall seam of each layer is offset with respect to adjacent layers, etc.). In a fourth step  608 , one or more vacuum bag(s) are applied over the laid-up mold, and in a fifth step  610 , one or more exterior molds are applied over the vacuum bag(s). In a sixth step  612 , vacuum is applied to the vacuum bag(s) to infuse (pull) resin into the laid-up wrap layers, and in a seventh step  614 , the resin is cured, for example, by baking. Then, in an eighth step  616 , the molds are removed from the enclosure. In a ninth step  618 , attachment structures (e.g., for mounting brackets, ERA components, lids, etc.) are formed in the enclosure, and the enclosure undergoes finishing (e.g., deburring, painting with a chemical agent resistive coating, etc.). Optionally, sixth step  612  (infuse resin) can be avoided if pre-impregnated wrap layers are provided in second step  604 . 
       FIG.  7    is a flowchart summarizing another method  700  for manufacturing an ERA enclosure according to the present invention. In a first step  702 , an interior mold is provided. In a second step  704 , a plurality of wrap layers are provided, and in a third step  706 , the wrap layers are laid up on the mold. In a fourth step  708 , an exterior mold is applied over the laid-up interior mold. In a fifth step  710 , resin is infused (pushed) into the interstices between the interior and exterior molds, and in a sixth step  712 , the resin is cured. Then, in a seventh step  714 , the molds are removed from the enclosure, and in an eighth step  716 , attachment structures are formed in the enclosure, and the enclosure undergoes finishing as described above. 
       FIG.  8    is a flowchart summarizing a method for performing the third steps  606  and  706  (“Layup Wrap Layers”) of methods  600  and  700 . In a first step  802 , a first wrap layer is laid on the mold so that its sidewall seam is located in a first sidewall of the enclosure. In a second step  804 , a second wrap layer is laid up so that its sidewall seam is at a location that is offset (e.g., in a different sidewall, etc.) from the sidewall seam location of the prior wrap layer. Then, in a third step  806 , it is determined if there are more wrap layers to apply. If so, the method returns to second step  804 . If not, then the method ends. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.