Patent Publication Number: US-2012024138-A1

Title: Armor panels having strip-shaped protection elements

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure is related to armor panels. More particularly, the present disclosure is related to armor panels having strip-shaped protection elements. 
     2. Description of Related Art 
     Armor plates, assembled into protective, “Targets” have been used to protect buildings, vehicles, and people from projectiles. When used to protect buildings and vehicles, the armor plates have been made from variety of materials such as metal, ceramics, fiber composites, glass, and others materials. 
     Armor plates made of metal and many traditional ceramics have a high specific gravity, which because of their large weight is problematic when protecting people or vehicles. For example, adding heavy metal armor plates to vehicles reduces the speed and maneuverability of the vehicle, reduces the load bearing capability of the vehicle, reduces the range of the vehicle, and increases the operating costs for the vehicle, in part by requiring more expensive elements such as suspension, drive train, wheels and engine. Exotic material plates, such as traditional ceramics, fiber composites and glass, for personal protection devices, vehicles, and buildings undesirably add to costs of producing and maintaining armor. 
     Accordingly, there is a continuing need for armor panels of continuously decreasing weight sufficient to protect against threats found in active and potential theaters of operations, which are growing in lethality, while reducing the weight and cost of the armor panels. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     An armor panel having an impact face is provided. The armor panel includes at least one rigid absorbing layer and a high-tensile confining layer surrounding the at least one rigid absorbing layer. The at least one rigid absorbing layer has a plurality of strip-shaped protection elements that are adhered to one another along a plane substantially orthogonal to the impact face. 
     An armor panel is also provided that includes at least one rigid absorbing layer and a high-tensile confining layer surrounding the at least one rigid absorbing layer. The at least one rigid absorbing layer being formed of a material having a coefficient of thermal expansion substantially equal to zero and that, upon impact by a projectile, converts to a dilatant power at least in an area of impact. 
     A method of absorbing energy of a projectile is provided. The method includes the steps of impacting the projectile on an impact face of an armor panel to convert a first strip-shaped protection element of the armor panel into a dilatant powder and confining the dilatant powder via a confining layer and strip-shaped protection elements adhered to the first strip-shaped protection element along a plane substantially orthogonal to the impact face so that strain of the projectile on the dilatant powder causes an increased viscosity sufficient to absorb at least a portion of the energy of the projectile. 
     The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side, top perspective view of a vehicle having an exemplary embodiment of an armor panel according to the present disclosure; 
         FIG. 2  is a side, top perspective view of the armor panel of  FIG. 1 ; 
         FIG. 3  is a sectional view of the armor panel of  FIG. 2 , taken along lines  3 - 3 ; 
         FIG. 3A  is an elongated sectional view of the armor panel of  FIG. 2 , taken along lines  3 - 3 ; 
         FIG. 4  is a sectional view of the armor panel of  FIG. 2 , taken along lines  4 - 4 ; 
         FIG. 5  is a side, top perspective view of the armor panel of  FIG. 2  having an outer constraint layer removed; 
         FIG. 6  is an expanded view of a portion of the armor panel of  FIG. 5 ; 
         FIGS. 7A and 7B  are pictures that illustrate a comparison of fracture mechanisms between an example armor plate and an armor panel according to the present disclosure with the outer constraint layer removed; 
         FIG. 8  is a side top perspective view of an arrangement of armor panels, each having portions of the outer constraint layer removed; 
         FIG. 9  is a side, top perspective view of an alternate exemplary embodiment of an armor panel according to the present disclosure; 
         FIG. 10  is a sectional view of the armor panel of  FIG. 9 , taken along lines  10 - 10 ; 
         FIG. 11  is a sectional view of the armor panel of  FIG. 9 , taken along lines  11 - 11 ; 
         FIG. 12  is a side, top perspective view of an alternate exemplary embodiment of an armor panel according to the present disclosure; 
         FIG. 13  is a sectional view of the armor panel of  FIG. 12 , taken along lines  13 - 13 ; 
         FIG. 14  is a sectional view of the armor panel of  FIG. 12 , taken along lines  14 - 14 ; 
         FIG. 15  is a side, top expanded perspective view of the armor panel of  FIG. 12  having an outer constraint layer removed; 
         FIG. 16  is a side, top expanded perspective view of an alternate exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; 
         FIG. 17  is a side, top expanded perspective view of another alternate exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; and 
         FIG. 18  is a side, top perspective view of still another alternate exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; 
         FIG. 19  is an expanded view of the armor panel of  FIG. 18 , taken at circle  19 ; 
         FIG. 20  is a side, top view of another alternative exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; 
         FIG. 21  is a side, top expanded view of yet another alternative exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; 
         FIG. 22  is a side, top expanded view of yet another alternative exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; 
         FIG. 23  is an expanded view of the armor panel of  FIG. 22 , taken at circle  23 ; 
         FIG. 24  is a side, top expanded view of yet another alternative exemplary embodiment of an armor panel according to the present disclosure having an outer constraint layer removed; and 
         FIG. 25  is an expanded view of the armor panel of  FIG. 24 , taken at circle  25 . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Referring now to the drawings and in particular to  FIG. 1 , an exemplary embodiment of an armor panel according to the present disclosure is shown and is generally referred to herein by reference numeral  10 . Advantageously, armor panel  10  provides a light-weight energy absorbing projectile protection device. Armor panel  10  provides this light-weight protection capability by providing one or more strip-shaped layers within an outer constraint layer. 
     At the end of the day, all armor suffers what is called either a complete or a partial penetration, in other words it is either partially or completely destroyed. In reviewing the need for improved armor systems, the present application has come to the conclusion through careful observation of defeated targets, that in order to defeat and stop a projectile, one must consider the materials properties and system mechanism in which the materials are placed in the time domain perspectives of the actual dynamic event. 
     Moreover, the present application has come to the conclusion that the properties of the materials and systems under the dynamic conditions and time domains are almost always dramatically different than the properties for these materials and systems at standard temperature and pressure (STP) or outside of these time domains. 
     Simply stated, the present application has concluded that the dynamic properties of the materials during the time domain of the impact are different from the static properties of these same materials. Too often, prior art armor performance has been interpreted by looking at the STP properties of the materials by observing the target before and after and not considering the several time domain events which actually take place. Advantageously, armor panel  10  of the present disclosure provides one or more strip-shaped layers within an outer constraint layer, which are believed to optimize the properties of the materials and systems under the dynamic conditions and time domains of the ballistic event. 
     During the small time domains of the ballistic impact, the present application has determined that the materials perform in surprising and unexpected ways for small time period. The materials can compress plastically by very large amounts, as much as 30 and 40%. The materials can decompose into different compositions for brief time periods and then recompose in their original form due to the small time domains and the failure of things to be able to move physically to accommodate the new formulation. The materials can fail as powders and or grains and suddenly expand as a dilatant powder under great strain and actually increase resistance to the projectiles. The materials can become almost liquidus or plastic in surprising ways. The thermal conductivity, the sonic velocity capacity, the hardness, the toughness, the modulus of rupture, the density and the cross section of the materials can all change dramatically. 
     The materials and design of prior art armor systems have failed to capitalize on these transient properties, while armor panel  10  has been configured to capitalize on these transient properties as is described in more detail herein below. 
     Armor panel  10  is substantially opaque and can find use in personal protection devices, vehicles, and buildings. For purposes of clarity, armor panel  10  is shown in use on a vehicle  12 , which is illustrated as a truck. Of course, it is contemplated by the present disclosure for armor panel  10  to find use on any vehicle  12  including, but not limited to, cars, boats, airplanes, watercraft, and any other vehicle that requires protection from threats. Further, it is contemplated by the present disclosure for panel  10  to find use on any fixed or portable building or personal protection device. 
     In some embodiments, armor panel  10  is used to protect a first portion  14  of vehicle  12 . Here, armor panel  10  is a single panel having a generally planar, polygonal shape, which generally matches the shape of portion  14 . However, it is contemplated by the present disclosure for panel  10  to have any desired shape and/or for more than one panel  10  to be arranged next to one another and/or on top of one another to protect first portion  14 , which can be any desired portion of vehicle  12 . 
     Armor panel  10  has a threat side  18  and safe side  20 . Threat side  18  is formed by a first plane defined through an x-axis and a y-axis, while safe side  20  is formed by a second plane defined through the x-axis and the y-axis. Threat side  18  and safe side  20  are generally parallel to one another and are offset from one another by a distance  22  along the z-axis. Distance  22  defines the thickness of armor panel  10  such that the z-axis is generally along the commonly assumed direction of flight of incoming projectiles. Armor testing and qualification is almost always performed in a worst case angle of impact, which is assumed to be orthogonal to the x and y axes of the impact plate where the travel of the projectile is along the z axis. 
     In use, armor panel  10  is arranged so that threat side  18  faces away from the item and/or person being protected (e.g., vehicle  12 ) and towards the direction of the threat, namely in the direction of the incoming projectile. Conversely, armor panel  10  is arranged so that safe side  20  faces towards the item and/or person being protected and away from the direction of the threat. In this manner, threat side  18  presents an impact or strike face  24  towards the threat. 
     As used herein, strike face  24  merely indicates the face or side of armor panel  10  that faces the direction of the incoming projectile. In some embodiments, strike face  24  may include one or more plates, but in other embodiments may not include any plates. 
     An exemplary embodiment of armor panel  10  is described in more detail with reference to  FIGS. 2 through 6 . 
     Armor panel  10  includes one or more outer constraint layers  30  (only one shown) that enclose the armor panel. In the illustrated embodiment, constraint layers  30  enclose armor panel  10  along all six sides of the panel. Of course, it is contemplated by the present disclosure for constraint layers  30  to enclose armor panel  10  along less than six sides of the panel. 
     Constraint layer  30  can be formed of any high-tensile material sufficient to provide six axes confinement of forces. By way of example, constraint layer  30 , which could be cast or potted or assembled, can be formed of metal, polymer, glass-reinforced polymer, fiber-reinforced polymer, carbon-reinforced polymer, ballistic fabrics such as those comprised of aramid fibers, Ultra High Molecular Weight Polyethelyne fibers, fiber glass, other high-tensile materials, or any combinations thereof. 
     When forming outer constraint layers  30  of ballistic fabrics, such as those formed using Ultra High Molecular Weight Polyethelyne fibers, which are commercially available under the tradenames DYNEEMA and SPECTRA, or aramid fibers, which are commercially available under the tradename KEVLAR, armor panel  10  can be wrapped with the fabric so that overlapping layers of fabric are positioned at impact face  24 . 
     In addition, when forming outer constraint layers  30  of ballistic fabrics, armor panel  10  can be wrapped with a first fabric layer that spans the safe side, the threat side, and two edges of the armor panel, and then with a second fabric layer that again spans the safe side and the threat side as well as the remaining two edges of the armor panel. 
     In this manner, the first and second outer constraint layers  30  cover all six faces of armor panel, with a double overlap of the fabric layers on the safe and threat sides  18 ,  20 . Of course, it is contemplated by the present disclosure for armor panel  10  to have more or less than the two fabric layers described above and/or for the fabric layers to overlap on faces other than the safe and threat sides  18 ,  20 . 
     In some embodiments, outer constraint layers  30  can be formed of structural aluminum plates with extension tabs (not shown) could be positioned around the structure and welded in each corner of armor panel  10 . Here, outer constraint layers  30  can be configured to introduce a hoop pre-stress around armor panel  10 . For example, the shrinkage of the aluminum weldment can be used to induce the hoop pre-stress of armor panel  10 . 
     In other embodiments, outer constraint layers  30  can include one or more steel bands (not shown) around one or more portions of armor panel  10 . Again, the steel bands can be configured to introduce a hoop pre-stress to armor panel  10 . For example, the steel band can be sized slightly smaller than armor panel  10  and can be secured around the armor panel using a heat expansion approaches to compression fit the steel band around the armor panel to provide lateral confinement. 
     In some embodiments, armor panel  10  can include a separate backing plate  32  adhered to safe side  20  by an adhesive layer  34 . In other embodiments, safe side  20  of panel  10  can be adhered or otherwise secured directly to the item and/or person being protected (e.g., vehicle  12 ). Adhesive layer  34  can be, for example, a layer of butyl adhesive, polyurethane, epoxy, polysulfide, polyvinylbutural, or any combinations thereof. 
     Enclosed within outer constraint layer  30  is at least one rigid impact absorbing layer  36 . Rigid impact absorbing layer  36  includes a plurality of strip-shaped protection elements  38 , which are adhered to one another along a plane that is orthogonal to impact face  24 . It has been determined by the present disclosure that adhering strip-shaped protection elements  38  to one another along the orthogonal plane ensures that the protection elements are secured to one another along their entire length and eliminates open spaces between the shaped protection elements, improving the ballistic performance of the armor panel against small projectiles and projectile fragments. 
     Prior art armor plates required the use of energy absorbing materials formed in the shape of “plates”, which have both a width (e.g., measured along the x-axis) and a length (e.g., measured along the y-axis) that were significantly larger than the thickness (e.g., measured along the z-axis). It has been determined by the present disclosure that such prior art armor plates are disadvantageous because they are sized to have their smallest dimension along the z-axis, which is the axis perpendicular to the impact face and is generally along the direction of flight of projectiles. In doing so, such prior art plates limit the ability of the layer to resist forces imposed by the impacting projectile. 
     In contrast, armor panel  10  includes rigid impact absorbing layer  36 , which is formed by strip-shaped protection elements  38 . As used herein, the term “strip-shaped” means that protection element  38  has its smallest dimension along an axis other than the z-axis, which is the axis perpendicular to impact face  24  and is generally along the direction of flight of projectiles. 
     In this manner, it has been determined by the present disclosure that strip-shaped protection elements  38  provide an enhanced resistance to bending along the direction of the flight incoming projectiles as compared to the prior art plates. 
     Stated another way, assuming that strip-shaped protection elements  38  have a length extending along the x-axis, a width extending along the y-axis, and a thickness extending along the z-axis, then the strip-shaped protection elements  38  have an z:x aspect ratio or an z:y aspect ratio that are equal to or greater than 1:1, preferably between about 2:1 and 60:1, more preferably between about 8:1 and 40:1, with between about 15:1 and 25:1 being the most preferred, and any subranges therebetween. 
     In the embodiment of armor panel  10  illustrated in  FIGS. 2 through 6 , the armor panel includes two rigid impact absorbing layers  36 , namely first layer  36 - 1  and second layer  36 - 2 . First layer  36 - 1  is formed by a plurality of strip-shaped protection elements  38  adhered to one another along an x:z plane that is orthogonal to impact face  24 , while second layer  36 - 2  is formed by a plurality of strip-shaped protection elements  38  adhered to one another along an y:z plane that is orthogonal to the impact face. 
     Thus in the illustrated embodiment, first and second layers  36 - 1 ,  36 - 2  are shown offset from one another by an angle θ that is equal to 90° (ninety degrees). It should be recognized that angle θ is illustrated as being equal to 90° by way of example only. Of course, it is contemplated by the present disclosure for armor panel  10 , when more than one rigid impact layer  36  is present, to have an angle θ between layers that is less than or greater than 90°. For example, it is contemplated by the present disclosure for angle θ to be in a range between from above 0° to 180°, and any angles therebetween. 
     It is also contemplated by the present disclosure for panel  10  to include as many rigid impact layers  36  as desired to meet a specific threat for which protection is desired. For example, panel  10  can include as few as one rigid impact layer  36  and as many as twenty or more rigid impact layers. 
     Prior art glass “plates” are believed by the present disclosure to have three fracture stages; crushing, radial fractures, and late time concentric fractures. Upon initial impact, the material of the prior art glass plates is crushed into a powder. Then, fractures in the plate typically propagate radially outward from the point of impact. Finally, late time fractures, which are typically concentric, as they form a series of concentric circles or arcs around the point of impact, are formed. These concentric fractures propagate between the radial fractures. 
     Advantageously, and without wishing to be bound by any particular theory, it is believed that armor panel  10  having strip-shaped protection elements  38  minimizes the effect of the radial and concentric fracture mechanics, enhancing the confinement of the pulverized and dilatant powder. 
     For example, it is believed that strip-shaped protection elements  38  mitigate the propagation of cracks between adjacent protection elements due to the radial and concentric fractures being stopped or mitigated by the interface of the adherence of the strips to one another along the plane that is orthogonal to impact face  24 . 
     Referring now to  FIGS. 7A and 7B , images illustrating the fracture mechanism differences between prior art plate armor  110  and armor panel  10  are shown. In this example, plate armor  110  and armor panel  10  of significantly the same materials of construction and dimensions were exposed to significantly similar projectile impacts. The main difference between the construction of plate armor  110  and armor panel  10  was that plate armor  110  included layers in the shape of plates, while armor panel  10  was as described above with respect to the embodiment shown in  FIGS. 2 through 6 , namely having two rigid layers  36  of strip-shaped protection elements  38  offset from one another by an angle θ of 90°. 
     As shown in  FIG. 7A , plate armor  110  includes both radial and concentric fractures radiating outward to the outer edges of the armor. Thus, plate armor  110  has a well defined fracture area with a generally circular appearance and that has propagated to the outer edges of the armor plate. 
     In contrast, armor panel  10  illustrates a well defined fracture area having a generally cross-shaped appearance, which is believed to be present due to the offset of the two rigid layers  36  by the 90° angle θ. Here, the fracture area is focused in the cross-shaped area, while propagation of the fracture area outside of this cross-shaped area is minimized as compared to that in plate armor  110 . 
     Additionally, armor panel  10  is further believed to provide enhanced projectile energy absorbance through lateral confinement, namely along the x and/or y axes, of the fractured strip-shaped protection elements  38  due to the presence of the laterally adjacent strip-shaped protection elements. 
     At least some of the plurality of strip-shaped protection elements  38  are formed of one or more brittle materials such as, but not limited to, glass, ceramic, glass-ceramic, or polymers comprising one or more of these materials. 
     In some embodiments, strip-shaped protection elements  38  are made of glass-ceramic, which is a light weight material having a density of 2.55 grams per cubic centimeter and aids in minimizing the weight of armor panel  10 . Thus, glass-ceramic has a lower specific gravity than many other common materials such as technical ceramics like aluminum oxide, which has a specific gravity of about 3.9 grams per cubic centimeter. 
     Further, glass-ceramic has a coefficient of thermal expansion (CTE) that is substantially equal to zero. For example, many glass-ceramics have a CTE of 0.03*10 −7 /degree Celsius, which has been found useful in maintaining the longevity of armor panel  10  in the environments to which such panels are typically exposed and can be used to apply hoop pre-stress to the panel as discussed above. 
     The use of glass-ceramic has been found to be particularly cost effective by the present disclosure. More specifically, it has been found that a considerable amount of the glass-ceramic that is currently being manufactured is discarded due to optical defects, because of trimming and cutting to achieve the discrete shapes required for its intended uses. Advantageously, armor panel  10 , as an opaque armor device, does not require optical clarity such that the glass-ceramic that would otherwise be discarded due to optical defects can be used for strip-shaped protection elements  38 . Similarly, much of the glass-ceramic that would otherwise be discarded because of trimming and cutting can be used for strip-shaped protection elements  38 . 
     When armor panel  10  is subjected to sudden impact from a projectile, strip-shaped protection elements  38  formed of such materials in the area of impact are believed by the present disclosure to absorb, without wishing to be bound by any particular theory, the energy of the projectile in several ways. 
     First, the stress of the impact is believed by the present disclosure to result in plastic compression, possibly as large as 30% to 40%, of materials forming strip-shaped protection elements  38  at least in the area of impact. This compression is constrained by the strip-shaped protection elements  38  that are laterally adjacent to the impacted elements and by outer constraint layers  30  enclosing panel  10 . This compression is believed to assist in the absorption of a portion of the impact energy. 
     The stress of the impact is also believed by the present disclosure to result in the decomposition of the materials forming strip-shaped protection elements  38 , at least in the area of impact, for brief time periods and then recompose in their original form due to the small time domains and the failure of the materials to be able to move physically to accommodate the new formulation. This decomposition and recomposition are also believed to assist in the absorption of a portion of the impact energy. 
     Further, the stress of the impact is believed by the present disclosure to result in the materials forming strip-shaped protection elements  38 , at least in the area of impact to fail, becoming pulverized into individual grains. It is believed by the present disclosure that shear induced on the powder grains by the projectile causes an increase in the viscosity between the grains—a characteristic of dilatant material. More specifically, it is believed that the individual grains dilate and eventually lock together in the high shear region proximate the projectile when properly constrained by the adjacent strip-shaped protection elements  38  and outer constraint layers  30 . Once the impact event is completed and the high shear region is no longer present, the grains return to a flowable state of lower viscosity. 
     It has been determined by the present disclosure that it is advantageous for armor panel  10  exhibit a high stiffness during the early microseconds of the ballistic event. Since a dilatant material response or a response with plastic deformation is desired, armor panel  10 , having strip-shaped protection elements  38 , at least in part, behaves like a spring. 
     Thus, armor panel  10  is configured so as to behave somewhat like a spring during the first several microseconds of the ballistic event where at least some of the materials are crushed, are compressed, and then bounce back dilatantly and the force resistance defined by stiffness factored by thickness at that point will work in our favor while the thickness will also build mightily in our favor by not failing so early on the bottom side by failing in tension and relieving the compressive forces by such failure. 
     It has been found by the present disclosure that the use of strip-shaped protection elements  38 , instead of the prior art plates, results in a tremendous advantage to greater columnar cross sections so long as containment is sufficient. Moreover, it has been found by the present disclosure that the use of strip-shaped protection elements  38 , instead of the prior art cylinders, in combination with constraint layer  30 , provides enhanced containment over prior art systems. 
     As an incoming round hits armor panel  10 , the dynamic event begins with the exertion of an enormous compressive force on first rigid impact absorbing layer  36 - 1 . During the first microseconds of the ballistic event, first rigid impact absorbing layer  36 - 1  is stiffly reinforced by second rigid impact absorbing layer  36 - 2 , and during this first period of time the materials of the first rigid impact absorbing layer will plastically compress, turn to powder or just compress, and then spring back dilatantly proportional to this combined stiffness. 
     If the energy of the incoming round exceeds the ability of first rigid impact absorbing layer  36 - 1  to restrain the projectile, some elements of the projectile will penetrate first rigid impact absorbing layer  36 - 1  and impact second rigid impact absorbing layer  36 - 2 . In this second time domain, the above noted process will be repeated with much reduced force and lethality. 
     Advantageously, the use of strip-shaped protection elements  38 , in combination with outer constraint layers  30 , are believed to increase the ability of armor panel  10  to constrain the grains formed by impact and therefore maximizing the dilatants characteristics. The maximization of the dilatants characteristics of pulverized strip-shaped protection elements  38  is believed to assist in the absorption of additional portions of the impact energy. 
     It should be recognized that strip-shaped protection elements  38  are disclosed above by way of example as being formed of glass-ceramic. However, it is contemplated by the present disclosure for strip-shaped protection elements  38  to be formed of any light weight material, namely those having a density of about 3 grams per cubic centimeter or less, which acts dilatantly upon impact. For example, it is contemplated by the present disclosure for strip-shaped protection elements  38  to be made of a hardened compound, such as resin or epoxy, which is filled with a plurality of reinforcing particles of size and distribution, such as a ternary distribution in size, such that the loading of particles in the compound is 60% or more and the reinforcing particles act dilatantly when impacted. 
     Armor plate  10  includes one or more adhesive-layers  40  between strip-shaped protection elements  38 , which bond the strip-shaped protection elements to one another. It is believed by the present disclosure that adhesive-layers  40  can, in some embodiments, assist in providing increased lateral resistance and confinement to the flow of the dilatant powders formed by strip-shaped protection elements  38  in the impact area. 
     Adhesive-layers  40  can be a very thin adhesive interlayer, typically about 0.025 inches, with layers as thin as 0.005 inches being contemplated. Of course, adhesive-layers  40  can have any desired thickness. 
     Preferably, the material of strip-shaped protection elements  38  and the material of adhesive-layers  40  are selected so that the protection elements have a lower coefficient of thermal expansion (CTE) than the adhesive-layers. In this manner, strip-shaped protection elements  38  can be held in compression by adhesive-layers  40 . Here, protection elements  38  and adhesive-layers  40  can be assembled together at a temperature higher than room temperature. The elevated temperature, combined with protection elements  38  having a lower CTE than adhesive-layers  40 , results in the adhesive-layers expanding more than the protection elements. Upon returning the assembly to room temperature, adhesive-layers  40  will contract more than protection elements  38 , which will mean that the protection elements are in a state of pre-compression and the adhesive-layers are in tension. In this manner, even when fractures of protection elements  38  occur, the cracks are held and bound tightly together. 
     Still further, it is contemplated by the present disclosure for strip-shaped protection elements  38  to be in a state of pre-compression by other means such as, but not limited to, thermal or chemical tempering of the strip-shaped protection elements before assembly with one another. 
     Accordingly, it has been found by the present disclosure that armor panel  10 , having outer constraint layer  30  and strip-shaped protection elements  38 , provides an energy absorbing system capable of defeating very heavy threats at lighter weights and lower cross sectional dimensions than previously possible using plated armor. 
     When armor panel  10  includes more than one rigid impact absorbing layer  36 , such as layers  36 - 1  and  36 - 2 , the incoming projectile begins by putting enormous compressive forces on first layer  36 - 1 , which, during the first microseconds of the impact event, will be stiffly reinforced by second layer  36 - 2 , and during this period of time the materials of the first layer will plastically compress, turn to powder, and then spring back dilatantly proportional to this stiffness. After failing, the projectile will impact second layer  36 - 2  and in this second time domain the routine will be repeated with a much reduced force and lethality. 
     Returning to  FIGS. 2 through 6 , armor panel  10  can include one or more layers, such as plate shaped layers  42 ,  46 ,  48 , in addition to the one or more rigid impact absorbing layer  36  as discussed herein below. 
     Armor panel  10  can include a first impact plate  42  secured to first rigid impact absorbing layer  36 - 1  by a suitable adhesive  44  such as, but not limited to, a thermoplastic polyurethane (TPU). First impact plate  42  can be formed of any desired material such as, but not limited to, metal, polymer, glass, glass-ceramic, polymers impregnated with one or more of these materials, or any combinations thereof. In a preferred embodiment, first impact plate  42  is made of polycarbonate. 
     In embodiments having multiple rigid impact absorbing layers  36 , the layers can be secured directly to one another or can have one or more intervening plates  46 . In the illustrated embodiment, armor panel includes two intervening plates  46  bonded to one another and to first and second layers  36 - 1 ,  36 - 2  by suitable adhesive  44 , which can be TPU as discussed above. 
     Intervening plates  46  can be formed of any desired material such as, but not limited to, metal, polymer, wood, glass, ceramics such as alumina, titanium diboride, silicon carbide, silicon nitride, boron carbide, plaster, glass-ceramic, an aramid reinforced polymer, an Ultra High Molecular Weight Polyethelyne reinforced polymer, a polymer impregnated with one or more of these materials, or any combinations thereof. In a preferred embodiment, intervening plates  46  are made of polycarbonate. 
     Armor panel  10  can also include one or more bottom plates  48  (only one shown) between the bottom most rigid impact absorbing layer  36  and outer constraint layers  30 . Bottom plate  48  is bonded to second layer  36 - 2  by suitable adhesive  44 , which can be TPU as discussed above. 
     Bottom plate  48  can be formed of any desired material such as, but not limited to, metal, polymer, wood, glass, ceramics, ballistic fabric, fiber glass, glass-ceramic, an aramid reinforced polymer, an Ultra High Molecular Weight Polyethelyne reinforced polymer, a polymer impregnated with one or more of these materials, or combinations thereof. In a preferred embodiment, bottom plate  48  is made of polycarbonate. 
     It should be recognized that armor panel  10  is described above by way of example including, when present, impact plate  42 , intervening plates  46 , and bottom plate  48  formed of the same material. Of course, it is contemplated by the present disclosure for plates  42 ,  46 , and  48  to be formed of the same or different materials. Similarly, armor panel  10  is described above by way of example including having the same adhesive  44  joining the plates  42 ,  46 ,  48  and layers  36 - 1 ,  36 - 2 . Of course, it is contemplated by the present disclosure for adhesive  44  at different locations within armor panel  10  to be formed of the same or different materials. 
     Advantageously, armor panel  10  can be configured so that it is reversible, namely so that either side the armor panel can be utilized as impact face  24 . Alternately, armor panel  10  can be configured so that it has a single direction of use, namely so that only one side the armor panel can be utilized as impact face  24 . 
     In embodiments where armor panel  10  includes backing plate  32 , the backing plate preferably assists in confining the dilatant powder by being resistant to dynamic compression and localized bending in the time frames of the ballistic event, and that is light weight. In the preferred embodiment, this plate is a high strength, light weight aramid reinforced polymer or an Ultra High Molecular Weight Polyethelyne reinforced polymer. 
     It has been observed by that backing plate  32 , when in use with armor panel  10  of the present disclosure, is loaded by the constrained dilatant powder and not by the projectile. For example, it has been observed that the diameter of the cavity formed by the projectile, which contains the powder, is about 2 to 3 times the diameter of the projectile. It is believed that this impact area of dilatant power spreads the load and reduces the chance of shear failure on backing plate  32 , allowing the backing plate to be more effective in energy absorption than in prior art armor plates. 
     Backing plate  32  can be formed of any desired material sufficient to absorb the load imposed by the constrained dilatant powder. For example, backing plate  32  can be formed from titanium, aluminum, or steel, or any alloys thereof, an aramid reinforced polymer, or an Ultra High Molecular Weight Polyethelyne reinforced polymer. 
     While aluminum and aluminum alloys are not as strong as titanium or steel, for the same areal density they can be almost 3 times thicker than steel and 1.7 times thicker than titanium because of their low density, and they can exhibit exceptional elongation before failure. Considering the effects of resistance to localized bending and the effectiveness of rear face confinement, backing plate  32  is, in some embodiments, formed of aluminum or aluminum alloy. 
     It has been determined by the present disclosure that aluminum and aluminum alloys can be prone to spalling, namely having flakes broken off, when used as backing plate  32 . Thus, in embodiments having backing plate  32  made of aluminum and/or aluminum alloys, the backing plate further includes a spall liner (not shown) of a traditional fiber reinforced plastic bonded to the aluminum to catch any extant spall. 
     In other embodiments, backing plate  32  can be formed by combination of a brittle polymer plate such as, but not limited to polymethyl methacrylate (PMMA), and relatively thin a plate, which functions as spall catcher. The thin plate can be formed of steel, fiber reinforced plastic composites such as Kevlar, Dyneema, S 2  fiber glass, or even a thin layer of polycarbonate. 
     Referring now to  FIG. 8 , a plurality of armor panels  10  are shown in relation to one other for protecting a large surface. Armor panels  10  can be arranged with respect to one another in any desired manner. For example, the plurality of armor panels  10  can be arranged so that the individual panels are rotated about the z-axis with respect to adjacent panels by ninety degrees. In this manner, the direction of first layer  36 - 1  and second layers  36 - 2  alternate with respect to one another. 
     An alternate exemplary embodiment of armor panel  10  according to the present disclosure is shown in  FIGS. 9 through 11 . In this embodiment, armor panel  10  includes a single rigid impact absorbing layer  36  within outer constraint layer  30 , where the rigid impact absorbing layer includes strip-shaped protection elements  38  and adhesive-layers  40  therebetween in the manner disclosed above. 
     Armor panel  10  further include first impact plate  42  secured to rigid impact absorbing layer  36  by suitable adhesive  44  such as, but not limited to, a thermoplastic polyurethane (TPU). First impact plate  42  can be formed of any desired material such as, but not limited to, metal, polymer, wood, an aramid reinforced polymer, an Ultra High Molecular Weight Polyethelyne reinforced polymer, ceramics, glass, glass-ceramic, polymers impregnated with one or more of these materials, or any combinations thereof. In a preferred embodiment, first impact plate  42  is made of polycarbonate. 
     Armor panel  10  includes one or more intervening plates  46  (two shown) bonded to one another and to rigid layer  36  by suitable adhesive  44  such as thermoplastic polyurethane (TPU). Armor panel  10  can also include one or more bottom plates  48  (only one shown). Intervening and bottom plates  46 ,  48  can be formed of any desired material such as, but not limited to, metal, polymer, wood, an aramid reinforced polymer, an Ultra High Molecular Weight Polyethelyne reinforced polymer, ceramics, glass, glass-ceramic, polymers impregnated with one or more of these materials, or any combinations thereof. In a preferred embodiment, intervening and bottom plates  46 ,  48  are each made of polycarbonate. 
     Armor panel  10  also includes, positioned between bottom plate  48  and intervening plates  46 , one or more brittle plates  50  in place of second layer  36 - 2  discussed above. Brittle plates  50  are, preferably, made of glass-ceramic, but could be ceramic, glass, PMMA, and are bonded to one another and to bottom plate  48  and the bottom most intervening plate  46  by suitable adhesive  44  such as TPU. 
     In some embodiments, armor panel  10  includes separate backing plate  32  adhered thereto by an adhesive layer  34 . In other embodiments, armor panel  10  can be adhered or otherwise secured directly to the item and/or person being protected. Adhesive layer  34  can be, for example, a layer of epoxy, polysulfide, butyl adhesive, or other suitable bonding agent. 
     Again, armor panel  10 , through the use of strip-shaped protection elements  38  within outer constraint layer  30  provides enhanced energy absorption as compared to prior art armor plates. 
     Another alternate exemplary embodiment of armor panel  10  according to the present disclosure is shown in  FIGS. 12 through 15  in which the armor panel  10  includes a single rigid impact absorbing layer  36  within outer constraint layer  30 . Again, rigid impact absorbing layer  36  includes strip-shaped protection elements  38  and adhesive-layers  40  therebetween in the manner disclosed above. 
     Armor panel  10  further includes first impact plate  42  secured to rigid impact absorbing layer  36  by suitable adhesive  44  and one or more intervening plates  46  (one shown) bonded to rigid layer  36  by suitable adhesive  44 . 
     In this embodiment, armor panel  10  includes, replaces both bottom plate  48  and second layer  36 - 2  discussed above with one or more brittle plates  50 . Preferably, brittle plate  50  is made of PMMA and is bonded to the bottom most intervening plate  46  by suitable adhesive  44 . Armor panel  10  can further includes separate backing plate  32  adhered thereto by an adhesive layer  34 . In other embodiments, armor panel  10  can be adhered or otherwise secured directly to the item and/or person being protected. 
     Again, armor panel  10 , through the use of strip-shaped protection elements  38  within outer constraint layer  30  provides enhanced energy absorption as compared to prior art armor plates. 
     Referring to  FIGS. 16 through 25  additional alternate exemplary embodiments of armor panel  10  according to the present disclosure are shown. 
     In  FIG. 16 , armor panel  10  is substantially identical to the embodiment illustrated in  FIGS. 2 through 6 . However, in this embodiment second layer  36 - 2  has a different height along the z-axis as compared to the height of first layer  36 - 1 . 
     Referring now to  FIG. 17 , another exemplary embodiment of armor panel  10  according to the present disclosure is shown. Here, armor panel  10  is substantially identical to the embodiment illustrated in  FIGS. 2 through 6 . However, in this embodiment first layer  36 - 1  has strip-shaped protection elements  38  within the layer having different heights along the z-axis. Specifically, first layer  36 - 1  includes first strip-shaped protection elements  38 - 1  that are shorter than second strip-shaped protection elements  38 - 2 . 
     In this embodiment, the outer constraint layers (not shown) is wrapped so as to conform to areas  54  defined above upper surface  56  of first strip-shaped protection elements  38 - 1  and between side edges  58 . In this manner, the outer constraint layers constrain protection elements  38 - 1 ,  38 - 1 . 
     In other embodiments, it is contemplated for a lower surface of the first impact plate (not shown) to be secured to an upper surface  52  of second strip-shaped protection elements  38 - 2  so as to define area  54  between the upper surface  56  of first strip-shaped protection elements  38 - 1  and the lower surface of the first impact plate. Here, area  54  is filled with any desired material having a higher or a lower density as compared to second strip-shaped protection elements  38 - 2 . 
     For example, area  54  can be filled with a material such as, but not limited to, glass, ceramic, resin compounds, epoxy compounds, or any combinations thereof. In some embodiments, the resin compounds or epoxy compounds can be filled with materials such as, but not limited to glass, glass ceramic, or any combinations thereof. 
     In both embodiments described with respect to  FIG. 17 , area  54 , either filled or constrained by layer  30 , presents a different density to incoming projectiles at first strip-shaped protection elements  38 - 1  as compared to second strip-shaped protection elements  38 - 2 . It is believed that the different density regions of armor panel  10  causes the incoming projectile to fracture, tumble, tilt or otherwise be made less effective, which allows the projectile to be more effectively managed by subsequent rigid impact absorbing layers  36 . 
     Referring to  FIGS. 18 and 19 , armor panel  10  is shown having an interlayer-strip  60  positioned between strip-shaped protection elements  38 . Preferably, interlayer-strip  60  is bonded to each strip-shaped protection elements  38  by an adhesive-layer (not shown) in the manner described above. 
     Interlayer-strips  60  can be formed of a material having density different than strip-shaped protection elements  38 . Again, it is believed that the different density regions of armor panel  10  causes the incoming projectile to fracture, tumble, tilt or otherwise be made less effective, which allows the projectile to be more effectively managed by subsequent rigid impact absorbing layers  36 . 
     Interlayer-strips  60  can be formed of any desired material such as, but not limited to, steel, titanium diboride (TiB 2 ), thermoplastic polyurethane (TPU), polymethyl methacrylate (PMMA), which is commercially available under many trade names, including, but not limited to, PLEXIGLAS and LUCITE, and others. 
     In some embodiments, interlayer-strips  60  are made of a hardened compound, such as resin or epoxy, which is filled with a plurality of reinforcing particles of size and distribution, such as a ternary distribution in size, such that the loading of particles in the compound is 60% or more and the reinforcing particles act dilatantly when impacted. 
     In other embodiments, interlayer-strips  60  are formed of a ductile material. As used herein, the term ductile material shall mean materials having a percent elongation of greater than about 1%, preferably greater than about 3%, with greater than about 5% being most preferred. 
     For example, it is contemplated by the present disclosure for interlayer-strips  60  to be formed of PMMA and has a percent elongation of about 5%. PMMA is also a generally lightweight material having a density of about 1.150 to about 1.190 g/cm 3 , which aids in minimizing the weight of armor panel  10 . Also, it is contemplated by the present disclosure for interlayer-strips  60  to be formed of TPU and has a percent elongation of about 100% or more. 
     In further embodiments, interlayer-strips  60  can be bonded to strip-shaped protection elements  38  so that the strip-shaped protection elements are in a state of pre-compression. For example, interlayer-strips  60  can be selected so as to have a higher CTE than strip-shaped protection elements  38  and armor panel  10  can be formed at an elevated temperature such that, upon cooling to ambient temperature, the interlayer-strips place the strip-shaped protection elements in a state of pre-compression. 
     Referring now to  FIG. 20 , armor panel  10  is illustrated having strip-shaped protection elements  38  that have a length along either the x-axis or the y-axis that is less than the entire length of the panel along that axis. It is believed that armor panel  10  having such shortened strip-shaped protection elements  38  further minimizes the effect of the radial and concentric fracture mechanics, enhancing the confinement of the pulverized and dilatant powder. 
     Additionally, it is believed that the use of such shortened strips  38 , when made of glass-ceramic, is particularly cost effective. Here, the shortened strips  38  makes use of glass-ceramic that would otherwise be discarded due to optical defects or because of trimming and cutting. 
     In  FIG. 21 , armor panel  10  is illustrated having strip-shaped protection elements  38  curved or bent about the z-axis in one or more directions. 
     Referring now to  FIGS. 22 through 25 , armor panel  10  is illustrated having strip-shaped protection elements  38  curved about the x-axis and/or the y-axis. Here, armor panel  10  can be secured to first portion  14  of vehicle  12  ( FIG. 1 ), where the first portion includes a curvature. Any plates, such as plates  48 , within these embodiments of armor panel  10  would be machined or molded to the desired surface curvature of portion  14  before being adhered to rigid impact absorbing layers  36 . 
     In the embodiment of  FIGS. 22 and 23 , strip-shaped protection elements  38  are cut or machined along their rear face  62 , either before or after being adhered to one another, to provide a surface curvature that matches the curvature of plates  48 . 
     In the embodiment of  FIGS. 24 and 25 , strip-shaped protection elements  38  are offset from one along their rear face  62  to provide the curvature that matches the curvature of plates  48   
     It should also be noted that the terms “first”, “second”, “third”, “upper”, “lower”, and the like may be used herein to modify various elements. These modifiers do not imply a spatial, sequential, or hierarchical order to the modified elements unless specifically stated. 
     While the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated, but that the disclosure will include all embodiments falling within the scope of the appended claims.