Composite enclosure for explosive reactive armor and methods of manufacturing the same

An explosive reactive armor (ERA) enclosure for an ERA tile includes a bottom and a plurality of sidewalls extending from the bottom, where the plurality of sidewalls are continuous with each other and with the bottom so as to define an internal volume. The plurality of sidewalls are formed from a fiber-reinforced composite material having a plurality of plies of fiber sheet material. Additionally, a sidewall seam defined by abutting edges of the first ply is offset from a sidewall seam defined by abutting edges of the second ply. Methods of manufacturing ERA enclosures, including applying wrap layers and forming attachment structures for securing the fiber-reinforced composite ERA enclosure to an armor element, are also described. The composite enclosure is inexpensive and lightweight and improves the dynamic capabilities of armored vehicles using such ERA tiles.

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.

DETAILED DESCRIPTION

FIG. 1is a perspective view showing a plurality of fiber-reinforced composite explosive reactive armor (ERA) tiles102mounted on the outside of an armored vehicle body104(e.g., a tank, personnel carrier, etc.). Nine ERA tiles102are shown mounted in a square (3×3) configuration. However, this configuration is merely exemplary, and ERA tiles102can be positioned differently according to vehicle and mission.

Each ERA tile102includes a fiber-reinforced composite enclosure106and a lid108. The sidewalls and bottom (FIG. 3) of enclosure106define an interior volume (covered by lid108) that houses explosive reactive armor components (e.g., armor plates, explosives, etc., not shown). First pluralities of fasteners110(e.g., rivets, threaded fasteners, etc.) are inserted through at least some of the sidewalls of each enclosure106to retain lid108thereon. Second pluralities of fasteners112(e.g., rivets, threaded fasteners, etc.) are also inserted through at least some of the sidewalls of enclosure106to mount and retain the ERA components therein.

FIG. 1further shows that ERA tiles102are mounted to armored vehicle body104via mounting brackets114and mounting rails116. Mounting rails116comprise “C” channels in this embodiment and are affixed (e.g., by fasteners, welding, etc.) to armored vehicle body104. Each ERA tile102includes two mounting brackets114in this embodiment, which are positioned on opposing sidewalls of enclosure106. Each mounting bracket114is affixed to a sidewall of its respective enclosure106by a plurality of fasteners118. Mounting brackets114are “L” brackets, which extend past the bottom (back) of enclosure106and face inward relative to the enclosure106, to be able to slide into (e.g., vertically) the “C” channels of mounting rails116. While only the outside mounting brackets114of the left-most column of tiles102are shown in detail, the inside mounting brackets114are substantially similar thereto, but mirrored in orientation. Other means for mounting tiles102to armored body104are also possible.

In this embodiment, each enclosure106has 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 enclosure106are fiberglass, aramid, and carbon. At appropriate wall thicknesses, the use of any of the three fibers provides significant weight savings in enclosure106over the prior art metal designs. However, harness satin weave or plain weave fiberglass fabrics of areal densities from 163 g/m2to 814 g/m2(4.8 oz/yd2to 24 oz/yd2) have been found to provide particularly desirable enclosure characteristics as described below.

FIGS. 2A-2Ggraphically illustrate an exemplary method for manufacturing an ERA enclosure106according to the present invention.FIG. 2Ais a perspective view of a generally-prismatic mold202positioned on a workbench204. Mold202is cubic in this example and includes four sidewalls206(1-4), and a top wall208. Top wall208corresponds to the bottom of the completed enclosure106, whereas sidewalls206(1-4) correspond to the sidewalls of the completed enclosure106.FIG. 2Ashows the edges of mold202to 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 enclosure106.

Mold202enables 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. Mold202is an interior mold in this example, meaning that the first ply applied to it will be the inner-most ply of the finished enclosure106. An inner mold is desirable because it provides better control over the dimensions and surface finish of the interior of enclosure106, thereby making fitting of the armor plates inside enclosure106easier and more uniform. Additionally, mold202is collapsible (separable) into three discrete sections along the dashed lines shown. The use of a collapsible mold202eliminates the need for a draft angle when removing the finished enclosure106therefrom. Mold202is formed from aluminum in this embodiment, although other materials (e.g., high-density foam, other metals, etc.) can be used instead.

FIG. 2Bis a plan view showing a plurality of wrap layers210(1-n) that will be laid up on mold202. In this example, each wrap layer210(1-n) has the same shape, but can vary in size to account for the volume added to the mold202by previously-applied wrap layers210. In the present example, each enclosure106is formed from six wrap layers210(1-6) of plain (cross) weave, 24 oz/yd2(814 g/m2) S-2 fiberglass sheet material. The first three wrap layers210(1-3) are all made in equal size. The last three wrap layers210(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 layers210(1-3) on mold202.

As shown by the dashed line on wrap layer210(1), each wrap layer210(1-n) includes a generally rectangular section212formed continuously with five triangular flaps214(1-5). Additionally, as shown on wrap layer210(n), each wrap layer210(1-n) is applied to mold202such that the regions216(1-5) of section212will form sidewalls of a finished enclosure106, and flaps214(1-5) will combine to form the bottom of an enclosure106. When a layer is laid up on mold, regions216(1) and216(5) abut and define a sidewall seam as described below.

FIG. 2Cis a perspective view showing first wrap layer210(1) laid on mold202so that a sidewall seam220between rectangular regions216(1) and216(5) is positioned near the center of sidewall206(1) (FIG. 2A) of mold202. Sidewall seam220is formed by a direct abutment of the outside edges of regions216(1) and216(5). Accordingly, the seam220of wrap layer210(1) will be away from corners of the completed enclosure106where high stress concentration are expected.FIG. 2Calso shows that the flaps214(1-5) of wrap layer210(1) are folded over top wall208of mold202so as to form a bottom of enclosure106with five seams222. Advantageously, the flaps214(1-5) provide continuity between the sidewalls and the bottom of enclosure106. Additionally, because there is only one sidewall seam220, there is high fabric continuity in the sidewalls of the completed enclosure106. Finally, the dashed lines denote bends/folds in continuous portions of fabric wrap layer210(1) over the edges of underlying mold202, but they are not seams.

To aid in applying wrap layer210(1) to mold202, a spray adhesive can be applied. For example, Super 77™ by 3M™ Corporation can be applied to temporarily hold wrap layer210(1) in position on mold202and does not compromise the strength of the resin subsequently infused into the wrap layers210. Use of Super 77™, however, is not required. Other spray adhesives can also be used.

FIG. 2Dshows a second wrap layer210(2) laid up on mold202over first wrap layer210(1). Second wrap layer210(2) is laid up such that its sidewall seam220is offset from the sidewall seam220of first wrap layer210(1). More specifically, sidewall seam220of second wrap layer210(2) is positioned over back wall206(2) of mold202, i.e., opposite the sidewall seam220of the prior wrap layer. Flaps214(1-5) of second wrap layer210(2) are also folded down over top wall208of mold202, which will form a second ply of the bottom of the completed enclosure106. As before, a spray adhesive can be used to aid in the applique of second wrap layer210(2) over first wrap layer (1).

The remaining wrap layers210(3-6) are applied in alternation as illustrated inFIGS. 2C and 2Duntil mold202has all six plies laid up on it. That is, wrap layers210(3) and210(5) are applied to mold as illustrated inFIG. 2C, whereas wrap layers210(4) and210(6) are applied as shown inFIG. 2D. Thus, according to this example, only the front and back sidewalls206(1) and206(3) of mold202have sidewall seams220of wrap layers210(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 enclosure106in each ply/layer.

FIG. 2Eshows mold202having six wrap layers210(1-6) applied thereto being prepared for resin infusion. An enclosure240(e.g., a vacuum bag, etc.) used for Vacuum Assisted Resin Transfer Molding (VARTM) is placed over mold202and/or workbench204and tightly secured (e.g., with tape, bands, etc.). Vacuum bag240includes a vacuum port242and a resin inlet port244. When it is time to infuse the resin, vacuum is applied to port242, which causes bag240shrink and conform to the laid-up mold202, and pull resin into bag240via port244. This, in turn, infuses the laid up wrap layers210(1-6) with resin causes good “wet-out” of the wrap layers210(1-6). Layers of peel ply and/or infusion media can also be applied between the outermost wrap layer210(6) and the vacuum bag240to 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. 2Fis a bottom view of an external bracket mold250, which is applied to the layup over top wall208of mold202and over vacuum bag240. Bracket mold250includes protrusions252that form reliefs for mounting brackets114in the portions of wrap layers210(1-6) adjacent mold sidewalls206(1) and206(3), which contain sidewall seams220. Bracket mold250can be formed from a rigid material, such as a metal, high-density foam, etc.

FIG. 2Gshows additional exterior molds260applied around the perimeter of mold202over vacuum bag240. Four exterior molds260(1-4) are applied, each wrapping around a respective corner of the layup. In this embodiment, exterior molds260(1-4) comprise four angle-brackets or caps made of rigid material, such as steel. Molds260(1-4) are clamped down circumferentially around mold202until a distance D between adjacent external molds260(1-2) reaches a predetermined value. Molds260(1-4) can be clamped down using, for example, C-clamps (not shown) installed between adjacent pairs of molds260(1-2),260(2-3),260(3-4), and260(4-1). High-strength tape262can be used to hold the exterior molds260in position after they are clamped to the desired pressure.

The use of exterior molds260, and bracket mold250, provide two benefits: 1) increasing the fiber volume fraction; and 2) improving the exterior surface finish. For example, molds260(1-4) are arcuate in the corners and, therefore, smooth and round the corners between the sidewalls of the finished enclosure106. Similarly, mold250functions to smooth and round corners between adjacent sidewalls and between sidewalls and bottom of the finished enclosure106. The gaps between molds260(1-4) and mold250allow routing of ports242and244therethrough.

When the predetermined distance D is reached, then the laminated wrap layers210(1-6) have been compressed to the desired aggregate wall thickness for enclosure106and resin can be infused (pulled) into the laid up wrap layers210(1-n) via port244by applying vacuum to port242. 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, Calif. 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 layers210are then cured according to the resin employed (e.g., by heating, etc.). The molds202,250, and260(1-4) allow the fibers in wrap layers210to maintain shape while the resin cures.

After the resin has cured sufficiently to retain its shape, the resulting fiber-reinforced composite enclosure106is separated from molds250and260(1-4), removed from the vacuum bag140, and separated from the mold202. Various attachment structures, such as pluralities of apertures110and112and apertures for mounting brackets114can then be formed in the enclosure106(e.g., by drilling, water-jet, etc.). Thereafter, ERA components (e.g., armor plates, supporting components, etc.) can be placed inside of enclosure106and secured thereto along with lid108to complete the ERA tile102.

FIG. 3shows a completed enclosure106ready to have, one or more ERA component(s)302, two mounting brackets114, and a lid108mounted thereto. Enclosure106includes four sidewalls306(1-4) corresponding to sidewalls206(1-4) of mold202, respectively, and a bottom308corresponding to top wall208of mold202. Sidewalls306(1-4) and bottom308are formed continuously and have arcuate corners to reduce stress concentration there.

During finishing of enclosure106, various pluralities of attachment structures are formed in its sidewalls306. For example, a plurality of apertures310are formed in each sidewall306near the opening of enclosure106. Apertures310align with complementary apertures311formed in a lip of lid108such that, after enclosure106is loaded with its ERA components302, lid108is secured to enclosure106by fixing fasteners110through apertures310and311. The inventors have found that using three rivets110per sidewall306is often sufficient to securely retains lid108in position even if a neighboring tile102detonates. However, additional or fewer fasteners can be employed if desired.

Second pluralities of apertures312are formed in sidewalls306(1) and306(3) such that fasteners112can be passed therethrough and into one or more ERA component(s)302(e.g., armor plates, etc.) to secure ERA component(s)302within enclosure302. Because of this connection, ERA component(s)302provide significant structural reinforcement to enclosure106and resist flexing and inward deformation of sidewalls306(1) and306(3) when a neighboring tile102detonates. Apertures312can also comprise ports for inserting foam into enclosure106. Expanding foam placed internally can also provide structural reinforcement to enclosure.

Third pluralities of apertures314are formed in sidewalls306(1) and306(3) as well. Apertures314are complementary to apertures316formed in mounting brackets114such that fasteners118(e.g., nuts and bolts, etc.) can be passed therethrough to secure mounting brackets114to enclosure106. As shown, mounting bracket114includes an outer L-bracket114A and a backing plate114B. L-bracket114A engages C-channels116(FIG. 1) and is secured to armored vehicle body104via fasteners passed through aperture(s)320. The backing plate114B is installed inside enclosure106and, in combination with L-bracket114A, sandwiches the associated sidewall306therebetween. Accordingly, mounting brackets114structurally re-inforce sidewalls306(1) and306(3).

Each of sidewalls306(1) and306(3) also includes a relief322(only relief for sidewall306(1) shown), which seats L-bracket114A generally flush with the outside of the respective sidewall. Relief322illustrates how the shape of the fiber composite enclosures106can be easily tailored in shape to accommodate the attachment provisions by making a geometric change to one or more external mold(s)250and/or260.

FIG. 4is a view of sidewalls306(1-4) and bottom308looking into the open end of enclosure106. As shown, sidewalls306(1-4) and bottom308are formed continuously and are 6-ply. Only sidewalls306(1) and306(3) include sidewall seams220. Additionally, sidewall seams220of adjacent plies are offset with respect to each other. More particularly, sidewall306(1) contains sidewall seams220of odd-numbered wrap layers (starting with the innermost layer corresponding to wrap layer210(1)), whereas sidewall306(3) contains sidewall seams220of even-numbered wrap layers. Sidewalls306(2) and306(4) contain no sidewall seams220.

The seam locations and armor attachment locations are selected to increase strength of the enclosure106in the hoop (perimeter) direction. For example, because sidewalls306(2) and306(4) contain no sidewalls seams220and are strong and flexible, they are resistant to inward inelastic deformation when a neighboring tile detonates. Additionally, when the ERA tile102including the enclosure106itself detonates, the sidewalls306flex 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 tiles102. Sidewalls306(1) and306(3) include several sidewall seams220each and, therefore, would be more susceptible to resin matrix breakdown during flexion. However, sidewalls306(1) and306(3) are structurally reinforced internally by the ERA component(s)302and internally and externally by the mounting brackets114. Such reinforcement provides significant resistance to seam failure during neighboring tile detonations. Bottom308is also resistant to damage because it is mounted against armored vehicle body104. Thus, the performance requirements of enclosure106are not degraded by the introduction of seams, particularly sidewall seams220.

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 tiles102at 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/m2(24 oz/yd2) 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/yd2) 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 enclosure106provides adequate blast protection from adjacent tiles with wall thicknesses as thin as 4.76 mm. Additionally, the 814 g/m2(24 oz/yd2) fiberglass fabric sheet had better performance than the 300 g/m2(8.8 oz/yd2) 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 tiles102can be provisioned for armored vehicles at lower cost, and because they are lightweight, the tiles102improve the dynamic loading and operability of such armored vehicles in theatre. Additionally, the composite enclosure106meets environmental testing requirements of MIL-STD810.

FIG. 5is a perspective view of an exterior mold502of a resin transfer molding (RTM) apparatus, which is used to infuse and cure the laid up mold202according to an alternative method of the invention. The interior cavity of exterior mold502defines a desired geometry for the external surface of enclosure106. Exterior mold502is placed over laid up mold202, and resin is pushed into the interstitial space between the two parts via inlet port504. When the resin is cured (e.g., by heating), exterior mold502and mold202are separated from enclosure106. RTM is often used in higher-production environments than VARTM and provides enclosures106with high quality bend radii (e.g., near the corners) and finish at a rapid throughput.

FIG. 5illustrates 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 mold202in addition to wrap layers210. The plus-sign layer can be applied with its center over the top wall208(FIG. 2A) of mold202and its wings folded down over respective sidewalls206. The plus sign layer can be used to provide reinforcement for the bottom308of the resulting enclosure, which would be beneficial where enclosure106was mounted to a vehicle via bottom308.

As yet another example, wrap layers210can 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 seams220of consecutive wrap layers210can be located in different sidewalls of enclosure106according 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. 6is a flowchart summarizing one method600for manufacturing an ERA enclosure according to the present invention. In a first step602, a mold is provided. In a second step604, a plurality of wrap layers are provided, and in a third step606, 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 step608, one or more vacuum bag(s) are applied over the laid-up mold, and in a fifth step610, one or more exterior molds are applied over the vacuum bag(s). In a sixth step612, vacuum is applied to the vacuum bag(s) to infuse (pull) resin into the laid-up wrap layers, and in a seventh step614, the resin is cured, for example, by baking. Then, in an eighth step616, the molds are removed from the enclosure. In a ninth step618, 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 step612(infuse resin) can be avoided if pre-impregnated wrap layers are provided in second step604.

FIG. 7is a flowchart summarizing another method700for manufacturing an ERA enclosure according to the present invention. In a first step702, an interior mold is provided. In a second step704, a plurality of wrap layers are provided, and in a third step706, the wrap layers are laid up on the mold. In a fourth step708, an exterior mold is applied over the laid-up interior mold. In a fifth step710, resin is infused (pushed) into the interstices between the interior and exterior molds, and in a sixth step712, the resin is cured. Then, in a seventh step714, the molds are removed from the enclosure, and in an eighth step716, attachment structures are formed in the enclosure, and the enclosure undergoes finishing as described above.

FIG. 8is a flowchart summarizing a method for performing the third steps606and706(“Layup Wrap Layers”) of methods600and700. In a first step802, 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 step804, 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 step806, it is determined if there are more wrap layers to apply. If so, the method returns to second step804. If not, then the method ends.