Energy absorbing and spall mitigating ammunition compartment liner cassette

An ammunition storage compartment includes a plurality of connected walls defining an interior region to store ammunition, wherein at least one of the walls includes an outer armor plate having an outer surface and an inner surface. A layer of energy absorbing material is located proximate the inner surface of the armor plate in the interior region. A spall mitigating panel is located inward of the layer of energy absorbing material in the interior region. At least one air gap is in between the layer of energy absorbing material and the spall mitigating panel.

BACKGROUND

Technical Field

The embodiments herein generally relate to compartments for ammunition stowage, and more particularly to a system for mitigating the risk of injury or damage resulting from penetration of the compartment by an overmatching threat.

Description of the Related Art

Military vehicles often carry defensive or offensive weapon systems. The ammunition for these weapon systems is often carried in specialized armored compartments. Ammunition stowed in combat vehicles poses a substantial vulnerability when subject to penetrating ballistic impacts. Although ammunition is typically stowed in armor-protected compartments, overmatching threats penetrating the compartment may result in violent ammunition fires, loss of vehicles, and loss of human life.

Large caliber ammunition compartments in existing armor vehicles are located externally relative to the crew compartment and employ blow-off panels. Upon overmatching threat penetration, the blow-off panels effectively release high temperature gases avoiding catastrophic loss of the entire vehicle and occupants. Yet, the stowed ammunition in the compartment is commonly destroyed.

SUMMARY

In view of the foregoing, an embodiment herein provides an ammunition storage compartment comprising a plurality of connected walls defining an interior region to store ammunition, wherein at least one of the walls comprises an outer armor plate having an outer surface and an inner surface; a layer of energy absorbing material located proximate the inner surface of the armor plate in the interior region; a spall mitigating panel located inward of the layer of energy absorbing material in the interior region; and at least one air gap in between the layer of energy absorbing material and the spall mitigating panel. The layer of energy absorbing material may comprise one of a plurality of energy-absorbing layers provided in between the spall mitigating panel and the inner surface of the outer armor plate.

The at least one air gap may be positioned in between one of the plurality of energy-absorbing layers and another panel selected from the plurality of energy-absorbing layers and the spall mitigating panel. The at least one air gap may comprise one of a plurality of air gaps, wherein a respective one of the plurality of air gaps is positioned in between each of the plurality of energy-absorbing layers and a neighboring one of the plurality of energy-absorbing layers and in between the spall mitigating panel and one of the plurality of energy-absorbing layers neighboring the spall mitigating panel. The layer of energy absorbing material may comprise any of high density polyethylene and rubber. The spall mitigating panel may comprise a plate comprising any of an aramid woven fabric and woven laminate encased in a resin.

Another embodiment provides a liner cassette comprising a frame having a first side and a second side, each of the first side and the second side having an inner surface, the frame defining a space between the inner surface of the first side of the frame and the inner surface of the second side of the frame; an energy absorbing layer positioned within the space; and a spall mitigating panel positioned within the space in between the energy absorbing layer and the second side.

The liner cassette may further comprise an air gap positioned in between the energy absorbing layer and the spall mitigating panel. The energy absorbing layer may comprise one of a plurality of energy absorbing layers positioned within the space in between the spall mitigating panel and the first side of the frame. The liner cassette may further comprise at least one air gap positioned in between one of the plurality of energy absorbing layers and another panel selected from the plurality of energy absorbing layers and the spall mitigating panel. The frame may define a first opening on the first side of the frame and a second opening on the second side of the frame such that the first opening is in registry with the second opening, wherein a first energy absorbing layer of the plurality of energy absorbing layers is positioned adjacent the first opening, wherein the spall mitigating panel is positioned adjacent the second opening, and wherein the plurality of energy absorbing layers, other than the first energy absorbing layer, are placed in between the first energy absorbing layer and the spall mitigating panel.

The liner cassette may further comprise an air gap positioned in between each of the plurality of energy absorbing layers and a neighboring one of the plurality of energy absorbing layers and in between the spall mitigating panel and one of the plurality of energy absorbing layers neighboring the spall mitigating panel. Each of the plurality of energy absorbing layers may comprise a frontal area larger than the first opening and the spall mitigating panel comprises a frontal area larger than the second opening. Each of the plurality of energy absorbing layers and the spall mitigating panel may comprise a frontal area larger than the first opening and larger than the second opening. The frame may comprise an approximately U shaped cross section formed by approximately parallel lateral walls, each wall having an outer perimeter, and a bottom plate extending generally perpendicularly to the lateral walls, and wherein the plurality of energy absorbing layers and the spall mitigating panel are positioned in between the lateral walls. The energy absorbing layer may comprise any of high density polyethylene and rubber. The spall mitigating panel may comprise a plate comprising any of an aramid woven fabric and woven laminate encased in a resin.

In an embodiment, a sum defined by the added thicknesses of all of the plurality of energy absorbing panels and of the spall mitigating panel may be less than a dimension of the space between the inner surface of the first side of the frame and the inner surface of the second side of the frame, and wherein at least one of the plurality of energy absorbing panels is held loosely within the frame such that the at least one of the plurality of energy absorbing panels is configured to move relative to the frame in at least one direction in response to an impact by a fragment having a component of velocity in the at least one direction.

In another embodiment, a sum defined by the added thicknesses of all of the plurality of energy absorbing panels and of the spall mitigating panel may be less than a dimension of the space between the inner surface of the first side of the frame and the inner surface of the second side of the frame, wherein the frame defines a first opening on the first side of the frame and a second opening on the second side of the frame such that the first opening is in registry with the second opening, wherein a first energy absorbing panel of the plurality of energy absorbing panels is positioned adjacent the first opening, wherein the spall mitigating panel is positioned adjacent the second opening, wherein the plurality of energy absorbing panels, other than the first energy absorbing panel, are placed in between the first energy absorbing panel and the spall mitigating panel, and wherein at least the plurality of energy absorbing panels, other than the first energy absorbing panel, are held loosely within the frame such that at least the plurality of energy absorbing panels, other than the first energy absorbing panel, are configured to move relative to the frame. The plurality of energy absorbing panels may be held loosely within the frame such that the plurality of energy absorbing panels are configured to move relative to the frame.

DETAILED DESCRIPTION

Ammunition stowed in combat vehicles poses a substantial vulnerability when subject to penetrating ballistic impacts. Although ammunition is typically stowed in armor-protected compartments, overmatching threats penetrating the compartment may result in violent ammunition fires, loss of vehicles, and loss of human life. In particular, combat vehicles in threat environments have the potential to be affected by overmatching penetrating threats; e.g., shaped-charge jets embodied in rocket-propelled grenades or anti-tank guided missiles. In the event of an ammunition compartment incident, stowed ammunition typically responds in a violent energetic reaction potentially destroying all stowed ammunition resulting in loss of ammunition, vehicle and occupant crew. Stowed ammunition on the shaped-charge jet shotline will be affected by the jet. Whereas, the non-shotline stowed ammunition are damaged and react in response to spall fragment and ricochet. Ammunition stowed in existing combat vehicles are protected by external armor. In the event of overmatching threat penetration, the ammunition is not protected resulting in catastrophic loss to the ammunition, vehicle and occupants. The embodiments herein provide an energy absorbing and spall mitigating ammunition compartment cassette liner system. The embodiments herein significantly improve stowed ammunition survivability by absorbing and mitigating spall fragment ricochet effectively reducing the quantity of rounds responding with a violent reaction.

Referring now to the drawings, and more particularly toFIGS. 1 through 12, where similar reference characters denote corresponding features consistently throughout the figures, there are shown exemplary embodiments. In the descriptions provided herein, reference is made to various dimensions, shapes, and materials for the purposes of providing example approximate configurations of the various components. All given dimensions are example approximate dimensions, and all described shapes and materials are examples. However, the embodiments herein are not restricted to these particular dimensions, shapes, or materials.

Referring toFIGS. 1 through 12, one of the examples disclosed herein is an energy-absorbing and spall-mitigating ammunition compartment liner cassette100that will substantially improve ammunition, combat vehicle, and crew or occupant survivability.

FIG. 1illustrates an ammunition storage compartment101comprising a plurality of connected walls150defining an interior region155to store ammunition103, wherein at least one of the walls comprises an outer armor plate124having an outer surface135and an inner surface136. A layer102of energy absorbing material is located proximate the inner surface136of the armor plate124in the interior region155, and a spall-mitigating panel104is located inward of the layer102of energy absorbing material in the interior region155.FIG. 2, with reference toFIG. 1, shows the layer102adjacent to the armor plate124. The layer102may be directly touching the armor plate124or may be offset by a predetermined distance away from the armor plate. At least one air gap108is configured in between the layer102of energy absorbing material and the spall-mitigating panel104.

The layer102of energy absorbing material may comprise one of a plurality of energy-absorbing layers102provided in between the spall-mitigating panel104and the inner surface136of the outer armor plate124.FIG. 3, with reference toFIGS. 1 and 2, illustrate that the layer102of energy absorbing material may comprise a plurality of energy-absorbing layers102. The at least one air gap108is positioned in between one of the plurality of energy-absorbing layers102and another panel selected from the plurality of energy-absorbing layers102and the spall-mitigating panel104. The at least one air gap108may comprise one of a plurality of air gaps108, wherein a respective one of the plurality of air gaps108is positioned in between each of the plurality of energy-absorbing layers102and a neighboring one of the plurality of energy-absorbing layers102and in between the spall-mitigating panel104and one of the plurality of energy-absorbing layers102neighboring the spall-mitigating panel104. The layer102of energy-absorbing material may comprise any of high density polyethylene and rubber. The spall-mitigating panel104may comprise a plate comprising any of an aramid woven fabric and woven laminate encased in a resin.

FIGS. 4A through 4D, with reference toFIGS. 1 through 3, illustrate various views of the layer102of energy absorbing. The layer102may comprise a substantially planar surface143on all sides of the layer102including the front, rear, left-side, right-side, top, and bottom. The layer102comprises a length L1and a width W1defining a first frontal area A1.FIGS. 5A through 5D, with reference toFIGS. 1 through 4D, illustrate various views of the spall-mitigating panel104. The panel104may comprise a substantially planar surface147on all sides of the panel104including the front, rear, left-side, right-side, top, and bottom. The panel104comprises a length L2and a width W2defining a second frontal area A2.

FIG. 6, with reference toFIGS. 1 through 5D, illustrates a frame106having a first side175and a second side176, each of the first side175and the second side176having an inner surface178. The frame106defines a space170between the inner surface177of the first side175of the frame106and the inner surface178of the second side176of the frame106, wherein the energy-absorbing layer102is positioned within the space170, and the spall-mitigating panel104is positioned within the space170in between the energy-absorbing layer102and the second side176.

The frame106defines a first opening126on the first side175of the frame106and a second opening128on the second side176of the frame106such that the first opening126is in registry with the second opening128, wherein a first energy-absorbing layer102aof the plurality of energy-absorbing layers102is positioned adjacent the first opening126, wherein the spall-mitigating panel104is positioned adjacent the second opening128, and wherein the plurality of energy-absorbing layers102, other than the first energy-absorbing layer102a, are placed in between the first energy-absorbing layer102aand the spall-mitigating panel104.

Each of the plurality of energy-absorbing layers102comprises a frontal area A1larger than the first opening126and the spall-mitigating panel104comprises a frontal area A2larger than the second opening128. Moreover, each of the plurality of energy-absorbing layers102and the spall-mitigating panel104comprises a frontal area A1, A2larger than the first opening126and larger than the second opening128.

A sum defined by the added thicknesses of all of the plurality of energy-absorbing layers102and of the spall-mitigating panel104is less than a dimension of the space170between the inner surface177of the first side175of the frame106and the inner surface178of the second side176of the frame106, and wherein at least one of the plurality of energy-absorbing layers102is held loosely within the frame106such that the at least one of the plurality of energy-absorbing layers102is configured to move relative to the frame106in at least one direction in response to an impact by a fragment105having a component of velocity in the at least one direction.

At least the plurality of energy-absorbing layers102, other than the first energy-absorbing layer102a, are held loosely within the frame106such that at least the plurality of energy-absorbing layers102, other than the first energy-absorbing layer102a, are configured to move relative to the frame106. The plurality of energy-absorbing layers102may be held loosely within the frame106such that the plurality of energy-absorbing layers102are configured to move relative to the frame106.

As shown inFIG. 7, with reference toFIGS. 1 through 6, the frame106comprises an approximately U-shaped cross section formed by approximately parallel lateral walls118,120, each wall118,120having an outer perimeter, and a bottom plate122extending generally perpendicularly to the lateral walls118,120, and wherein the plurality of energy-absorbing layers102and the spall-mitigating panel104are positioned in between the lateral walls118,120. InFIGS. 7 and 8, with reference toFIGS. 1 through 6, the frame106comprises frame members110, which all have an approximately U-shaped cross-section formed by approximately parallel lateral walls118,120, each having an outer perimeter, and a bottom plate122extending generally perpendicularly to the lateral walls118,120between the outer perimeters of the lateral walls118,120.FIGS. 9A through 9B, with reference toFIGS. 1 through 8, illustrate perspective views of the frame106with the energy-absorbing layer102and spall-mitigating panel104installed therein and with respect to the first opening126and second opening128.FIG. 9C, with reference toFIGS. 1 through 9B, is a partially exploded view of the frame106containing the energy-absorbing layers102and spall-mitigating panel104, along with the frame members110surrounding the layers102and panel104.

An exemplary embodiment of the cassette100is comprised of a plurality of (e.g., eight, for example) layers102of high temperature energy absorbing elastomer capped with a half inch thick panel or layer104comprising KEVLAR® material, for example, assembled in a U-channel “cassette” frame106to form the cassette100to line internal ammunition compartment volume of the ammunition compartment101. The frame106may comprise 14-16 gauge steel, in one example. The cassette100is configured to mitigate overmatching shaped-charge threats, as described herein.

Upon overmatching threat penetration to the ammunition compartment, the cassette100as positioned within the ammunition compartment101, mitigates spall propagation, dampens and captures ricochet fragmentation internal to the compartment, and absorbs energy resulting in improved ammunition, vehicle, and crew or occupant survivability.

The cassette100mitigates spall propagation. Upon ballistic threat penetration to the ammunition compartment structure101, the main penetrator, channel material, back-face material, and eroded penetrator material enter the compartment101impacting and initiating or igniting stowed ammunition103). The ensuing energy release, or explosion, imparts substantial loading on the ammunition compartment structure often resulting in mechanical failure. The embodiment100reduces the dispersion of spall fragments by offering resistance through a stack of layers102acting as a loosely packed curtain ply capped with a panel104. In one example, the layers102may comprise eight ⅛-inch thickness energy absorbing rubber layers102. The panel104may comprise ½-inch thick KEVLAR® material. These materials strip-out some, but not all, of the spall fragments entering the ammunition compartment volume.

The cassette100dampens and captures ricochet of fragments105. In the confines of an ammunition compartment101, it has been experimentally determined that there is substantial fragment ricochet damage galling the interior ammunition compartment walls115. Conventionally, these ricochet fragmentation105could re-enter the compartment volume returning back to intact stowed ammunition103causing additional stowed ammunition reaction and fires. However, the cassette100provided by the embodiments herein protect stowed ammunition103from ricochet fragmentation105through damping and capturing of the ricochet fragmentation105. When the ammunition compartment101is penetrated by a shaped-charge jet or a penetrator, some fragments will penetrate the panel104and the layers102. As the fragments impact the interior walls115, they may ricochet back into the layers102. The layers102absorb ricochet fragment energy as the ricochet fragment105pulls on each ply of the plurality of layers102as a series of “loose curtains” until captured within the stack of layers102.

In this regard, the cassette100absorbs energy. As the stowed ammunition103responds to the ballistic insults and contained energetics ignite, gaseous combustion products are generated from the energetic reaction at high rates. The gaseous product generation results in an increased pressure environment internal to the ammunition compartment101. Energy absorbing polymer material such as rubber in the layers102receives the first-order shock wave typically incident on the inner surfaces115allowing for a lengthened application on the interior surfaces115; hence, mitigating the initial shock loading to the structure of the compartment101while improving structural survivability.

Accordingly, the embodiments herein offer a departure from the configurations and functionalities of conventional ammunition compartments, which offer no specific means to capture ricochet, absorb energy, and mitigate spall fragment effects internal to the compartment

Potential uses for the cassette100include military platforms containing stowed ammunition to perform combat and logistics operations in hostile environments, ground combat vehicles, logistic systems, aircraft, and naval platforms. The cassette100may also be applied to logistic systems; e.g., transport vehicles, heavy haulers, trailers, and shipping containers. The cassette100may also be applied to naval vessels with stowed ammunition. Furthermore, any commercial ground vehicle, aircraft, ship, rail car, and logistics container stowing ammunition behind armor may also benefit from the cassette100.

Each of the cassette100and frame106may be assembled using any suitable manufacturing technique such as, for example, by using Tungsten Inert Gas (TIG) welding techniques. The cassette100was tested in verification tests as discussed below. Prototypes of cassettes100were fabricated for proof-of-principle verification tests with a circular pressure gauge port (not shown) for instrumentation purposes. Production cassettes100do not need or have the pressure gauge port.

Test Results: The effectiveness of the cassette100was experimentally verified quantifying improved ammunition survivability and reductions in stowed ammunition response via side-by-side comparative tests (without cassette100, then with cassette100). In summary, all ammunition103without the cassette100lining the ammunition compartment101initiated and were destroyed realizing a 0% survival rate when subjected to an overmatching shaped charge threat. Ammunition103protected by the cassette100lining the interior surfaces115of the ammunition compartment101realized a 62.5% survival rate; a marked improvement in the survivability of the ammunition103.

External armor124, shown inFIG. 10, with reference toFIGS. 1 through 9Cprovides a ballistic resistance by removing energy from the penetrator130and causing erosion/break-up of the penetrator130. This reduces energy applied to and entering the compartment101and the compartmented ammunition103. Examples of external armor124which may be used include Rolled homogeneous armor (RHA), ceramics, composites, and explosive reactive armor.

The energy absorbing polymer, such as the layer102, absorbs spall fragments impacting the side walls117and back face119of the compartment101, which is the interior surface of the compartment101facing the wall121of the compartment101initially impacted by the penetrator130, thus mitigating ricochet. Ricochet fragments105are found to be significant contributors to the destruction of compartmented ammunition103as shown by experiments using witness or inert receptors. Examples of suitable energy-absorbing material include high molecular weight polyethylene and extreme temperature silicone rubber.

FIG. 11, with reference toFIGS. 1 through 10, illustrates an example of an experimental ammunition compartment101. The ammunition compartment101used for the experimentation was 20 inches in length, 10 inches in width, and 15 inches in height. For the experimental testing, four cassettes100were fabricated in two sizes. One size, referred to as type 1, was intended to cover the shorter vertical walls of the ammunition compartment101. The second size, referred to as type 2, was intended to cover the longer vertical walls of the ammunition compartment101extending between the two type 1 cassettes covering the shorter vertical walls. In an example, the ammunition compartment101may utilize six cassettes100to line or cover all six internal surfaces115of the ammunition compartment101.

As shown inFIGS. 2 and 6, the energy-absorption and spall-mitigation cassette100may also include at least one air gap108between the energy-absorbing polymer layer102and the spall-mitigation panel104. The air gap108allows spall fragments to extend their conical trajectories; i.e., spread out more, before impacting the spall-mitigation panel104; thus, increasing the effective surface area for capture of the fragments by the spall-mitigating panel104. As the area widens, the specific energy or the energy per unit area is reduced on the spall-mitigation providing for a more effective reduction in spall impacts. The air gap8may be configured as a 1-inch gap, for example, according to some embodiments herein.

The spall-mitigation panel104may be, for example, a layer of composite armor. The spall-mitigation panel104is configured to reduce the number of fragments, from direct shaped-charge jet or penetrator interaction with the external armor124, entering the compartment101containing the ammunition103and to reduce the number of ricochet fragments105, which have had their energy reduced and less concentrated through interaction with the energy-absorbing polymer layer102and the air gap108, re-entering the compartment101containing the ammunition103.

The composite armor for the spall-mitigation panel104may be a woven laminate of aramid yarn in a ceramic, including thermoplastic and thermosetting polymer, or resin matrix. “Aramid” is the shortened form of “aromatic polyamide.” Examples of suitable fibers, yarns, or fabrics are KEVLAR® material, in particular KEVLAR® K29, TWARON®, and NOMEX® materials. In one exemplary embodiment, laminated woven fabric of KEVLAR® K29 available from E. I. du Pont de Nemours and Company, Delaware, USA, which is a para-aramid with the chemical name of poly(para-phenylene terephthalamide) embedded in a polyvinyl butyral (PVB) phenolic resin matrix may be used for the panel104.

The cassette100is provided with a cascade or stack of energy-absorbing polymer layers or panels102. In an example, eight energy-absorbing polymer layers102are provided. Each of the energy-absorbing polymer layers102may be about ⅛ inch thick and may be made of extreme temperature rubber. In other examples, the energy-absorbing polymer layers102may be fiber, yarn, or weave reinforced.

The air gaps108may be configured between the energy-absorbing polymer layers102themselves or between the energy-absorbing polymer layers102and the panel104. The energy-absorbing polymer layers102are loosely held in the frame106such that the energy-absorbing polymer layers102behave as a “loose curtain” to drag and pull energy from the spall fragments. In an example, the panel104has a thickness of about ½ inch.

A plurality of spall-mitigation and ricochet-energy-absorbing cassettes100may be inserted into the ammunition compartment101of the test rig107. In an example, four cassettes100are used to line the interior surfaces115of the ammunition compartment101. In other examples, six cassettes100may be used to line all interior surfaces115of the ammunition compartment101.

The cassette100includes a “window frame” like structure106, and in one example may be made of 1/16-inch mild steel U-shaped channels. The cassettes100fabricated for testing included two type 1 and two type 2 cassettes. The external dimensions of the two type 1 cassettes were 14¾ inch by 9¾ inch. The type 1 cassettes lined the shorter vertical sides of the ammunition compartment101. The external dimensions of the two type 2 cassettes were 14¾ inch by 16½ inch. The type 2 cassettes lined the longer vertical sides of the ammunition compartment101. The type 2 cassettes were each shorter than the length of the longer sides of the ammunition compartment101by the combined thicknesses of the type 1 cassettes. Both types of cassettes had the same thickness in the experimental fabrication. In an example, the cassettes100may comprise an overall or outside thickness of 1.75 inches. In an example, the cassettes100may have an inside thickness of 1.625 inches. The panel104may have a thickness of ½ inch.

As described with respect toFIGS. 7 and 8, the frame106may comprise a plurality of frame members110each of which may be made of a length of mild-steel U-shaped channels. The ends112of each frame member110may be cut at a 45° angle to permit proper joining of the individual frame members110to create the frame106. The ends112of the frame members110may be joined together by welding to form a quadrilateral frame106, such as a square or a rectangle, in some examples. The joints (not shown) between the ends112of the frame members110may be formed by forming a weld bead along all three sides of the frame members110. The completed frame106has openings126,128on either side of the frame106that are spaced apart by the inside thickness of the frame106. In an example, the frame members110may have a depth of about 0.9375 inch that may receive portions of the energy-absorbing elastomer layers102and the panel104. The frame members110may have an overall exterior height of about one inch, in an example.

In the fully assembled cassette100, the panel104is positioned against the lateral sides of the frame members110that define the opening128, such that the panel104is positioned adjacent to the opening128. The energy-absorbing elastomer layer102is positioned against the lateral sides of the frame members110that define the opening126, such that the energy-absorbing elastomer layer102is positioned adjacent to the opening126. There may be a 1/64th inch air gap108between the energy-absorbing elastomer layers102and between the panel104and the energy-absorbing elastomer layer102nearest the panel104. The cassette100is installed against the interior surface115of a wall of the ammunition compartment101, which may same a common structure as the exterior armor124of the ammunition compartment101, with the panel104facing toward the interior of the ammunition compartment101.

In an example implementation, the cassette100is an energy absorbing and spall mitigating cassette liner system or, more briefly, a cassette100that may be applied to the interior surfaces of a combat vehicle ammunition compartment. The cassettes100are integrated to the ammunition compartment101with a KEVLAR® surface of the panel104facing the interior of the ammunition compartment101.

In operation, as the overmatching threat munition130penetrates the exterior armor124, the stack of eight (for example) extreme temperature, energy-absorbing elastomer or rubber layers102allows initial spall fragments to spread in a conical pattern. Next, some spall fragments105will be absorbed by the panel104. The continuing penetrator130and spall fragments105will travel through the compartment101impacting both stowed ammunition103and cassettes100lining the interior surfaces115of the ammunition compartment101. The residual spall impacting cassettes100will now be absorbed by the panel104and the energy absorbing rubber layers102. Some fragments105will penetrate the cassette100ricocheting off the back face123of the compartment101, which is the interior surface of the compartment110opposite the surface121through which the penetrator130entered the compartment110. The spall fragments105will return into the layers102, which behaves as a “loose curtain” to drag and pull energy from returning spall fragments105. These effects culminate in a reduced ammunition response; i.e. fewer live rounds of ammunition103within the compartment101will ignite, and a reduced mechanical effect on the interior compartment surfaces115,121,123thus increasing the structural survivability of the ammunition compartment101and the vehicle (not shown) attached thereto. In the absence of the cassettes100, the spall fragments105would ricochet back into the compartment110damaging and igniting a greater number of the stowed ammunition103.

The embodiments herein increase ammunition survivability by absorbing and eliminating fragment ricochet internal to the ammunition compartment101upon overmatching threat penetration by a penetrator130. The layered energy absorbing elastomer layers102coupled with spall mitigation panels104are configured to reduce spall, capture ricochet, absorb energy, and mitigate fragments105returning to the ammunition compartment101and subsequently impacting stowed ammunition103. The layered energy-absorbing elastomer layers102behave with a “curtain” effect transferring ricochet spall fragment kinetic energy, and thus the spall fragment velocity, to work performed by the fragment105in displacing each layer102ultimately reducing the quantity of ricochet fragments105returning to the ammunition compartment101and impacting stowed ammunition103. The embodiments herein do not simply rely on anti-fratricide techniques to mitigate round-to-round propagation.

InFIG. 12, with reference toFIGS. 1 through 11, a second embodiment of a system200is provided. The exterior armor224forms the walls of the ammunition compartment101. The material of the exterior armor224is similar to the exterior arm24of the first embodiment. An energy-absorbing layer202lines the interior surface of the exterior armor224. A spall-mitigating, composite armor panel204is located inward of the energy-absorbing layer202in the interior of the ammunition compartment101such that the energy-absorbing layer202is located in between the exterior armor224and the composite armor panel204. An air gap208of about one inch, for example, separates the energy-absorbing layer202and the composite armor panel204.