Abstract:
A blast mitigation mat which protects soldiers from an explosion and from the fire and toxic fumes that result. The mat may include a surface layer that includes traction component, an energy absorptive, metallic, non-flammable layer which can include a hollow metallic structure, and a finishing layer. The non-flammable layer is comprised of materials that melt rather than burn. The finishing layer can be mounted to the vehicle or other surfaces subject to blast impulses.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to blast mitigating devices. Specifically, the present invention is directed to a non-flammable blast mitigating mat to protect those in a vehicle. 
       BACKGROUND OF THE INVENTION 
       [0002]    Wars in Iraq and Afghanistan have subjected troops within combat vehicles to roadside improvised explosive devices (IED) which are cheap to make but are also highly potent. IEDs are very effective, in part, because they can be buried near the road and explode when a combat vehicle drives past, such that the energy of the blast is directed from the ground up through the under-carriage of the vehicle. In recent years combat vehicles have been shaped to help deflect the explosive percussions away from the undercarriage, thus reducing the amount of energy absorbed by the vehicle and its passengers. Since a vehicle cannot deflect all of the energy from an IED bomb blast, combat vehicles have also been designed with materials that absorb the force of the blast so that less of the blast is absorbed by the occupants. 
         [0003]    Currently, some combat vehicles are outfitted with blast mitigating mats. Traditionally, mats are placed on the vehicle floor where soldiers stand or sit and protect the lower extremities from damaging impulse loads. Existing mats, which are typically made from polymeric materials such as molded elastomer or foam, significantly reduce the risk of injury from a bomb blast itself. However, a secondary effect of the blast is fire. Unfortunately, the existing mats are inherently flammable, even when formulated with flame retardants. Many times the blast force ignites combustibles in the vehicle. Not only is there a risk from fire, but burning polymers typically emit toxic gases which are also hazardous to soldiers in the vehicle. As the occupants are frequently belted in place, the fire and smoke from a burning mat creates unacceptable life threatening conditions. Therefore, there is a need for a non-flammable blast mitigating mat. 
       SUMMARY OF THE INVENTION 
       [0004]    The current invention is a blast mitigation mat which protects soldiers from an explosion by absorbing the energy of a blast. Unlike existing mats which can burn and emit toxic gases, the current invention may melt but cannot burn; thus, it protects soldiers from fire and toxic fumes. The current invention, in one embodiment, consists of three layers: a surface layer, an absorbent layer which is primarily a hollow metallic structure, and a finishing layer. 
         [0005]    In one embodiment, the surface layer consists of a diamond tread nonskid plate for walking or standing. The absorbent layer consists of a non-flammable energy absorbing material such as aluminum foam or Nomex™ Honeycomb. The thickness, density, and material may be tuned for specific purposes. The absorbing material layer deforms to minimize the amount of energy transmitted to the occupant standing or sitting on the mat. The finishing layer consists of a metal plate which provides a means of attachment to the vehicle structure or floor. It is clear that such material may also be placed on other walls and structures which maybe exposed to blast pressure from explosives. 
         [0006]    The present invention is a mat for minimizing the effect of a blast impulse. The mat comprising; an upper plate, a hollow metallic core plate, and a mounting plate, wherein the upper plate is bonded to a first face of the hollow metallic core plate, the hollow metallic core plate at least five times thicker than the upper plate, and the mounting plate bonded to a second face of the hollow metallic core. 
         [0007]    The upper plate provides an anti-slip surface such as a diamond plate. The upper plate is bonded to the hollow metallic core plate by adhesives, welding or brazing. 
         [0008]    The hollow metallic core plate may be formed of a metallic foam. The metallic foam may be an open cell or closed cell foam. Alternatively, the hollow metallic core plate is formed of dimpled aluminum sheets, or an aluminum honeycomb. 
         [0009]    The core may comprise a uniform or non-uniform construction. It may be formed of a discontinuous foam so as to create pillars between the upper plate and the mounting plate. 
         [0010]    The present invention is a mat for minimizing the effect of a blast impulse, the mat comprising: an upper plate, a core plate, and a mounting plate. The core plate includes internal spaces formed by a honeycomb structure, the honeycomb structure absorbing force upon impact such that the mounting plate never experiences a force greater than the core plate crush strength. The core plate can be a Nomex™ honeycomb, an aluminum honeycomb or similar material have the required strength, energy absorption and flame retardation qualities. 
         [0011]    The above summary of the various representative embodiments of the invention is not intended to describe each illustrated embodiment or every implementation of the invention. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices of the invention. The figures in the detailed description that follow more particularly exemplify these embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention can be completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
           [0013]      FIG. 1  is a perspective view of the present invention mat. 
           [0014]      FIG. 2  is a cross sectional view of the mat. 
           [0015]      FIG. 3  is a perspective view of the mat in  FIG. 1  after an energetic event. 
           [0016]      FIG. 4  is a cut-away view of the mat. 
           [0017]      FIG. 5  is a perspective view of the mat atop an ammunition container. 
           [0018]      FIG. 6  is a perspective view of the mat as an attachment to body armor. 
           [0019]      FIG. 7  is a perspective view of the mat installed on the floor of a vehicle 
           [0020]    While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Embodiments of the present invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the present invention is not intended to be limited to the specific terminology so selected. A person skilled in the relevant art will recognize that other equivalent parts can be employed and other methods developed without parting from the spirit and scope of the present invention. 
         [0022]    By manufacturing the mat entirely out of non-flammable materials, this mat improves upon existing mats because it reduces the force which is transmitted from the blast to nearby soldiers and eliminates the risk of a subsequent fire. In addition to being non-flammable, the structure can absorb large blasts while remaining lightweight. 
         [0023]    Referring to  FIG. 1 , in one embodiment, mat  100  is a blast mitigation surface that can absorb the impulse from an explosion. Mat  100  comprises a surface layer  102 , absorptive layer  104 , and a finishing layer  106 . In this embodiment, mat  100  is designed to be placed on the floor of a vehicle [See  FIG. 7 ]. Surface layer  102  of mat  100  can be approximately 3 mm thick and provides an anti-slip surface  108  for walking or standing. Anti-slip surface  108  is one embodiment is a diamond plate. Surface layer  102  is bonded, in this case adhesively, but could be welded or brazed, to absorptive layer  104 . In other embodiments, surface layer  102  can comprise different thicknesses or materials, depending on the application of mat  100 . 
         [0024]    Referring to  FIG. 1 , in the same embodiment, absorptive layer  104  is primarily a hollow metallic structure approximately 1 to 1.5 inches thick. Absorptive layer  104  is structured to absorb blast accelerations. The structure is composed of metallic ligaments or thin skins formed by foaming, casting, stamping, or drawing. Open-cell foams have a complex microstructure consisting of an interconnected network of ligaments that form along the edges of randomly packed cells that evolve during the foaming process. The core material may be discontinuous in the form of space pillars, but this is not necessary.  FIG. 1  shows absorptive layer  104  configured using an open cell aluminum foam, however one skilled in the art will recognize that other materials, metal or non-metal, may be used for absorptive layer  104 . 
         [0025]    Material selection for absorptive layer  104  is preferably a non-flammable material, such as for example, aluminum foam, Nomex™ or a metal honeycomb. Aluminum foam can be open cell or closed cell. Nomex™ honeycomb is made from Nomex™ paper—a form of paper based on Kevlar®, rather than cellulose fibers. It is widely used in fire retardant applications. Aluminum honeycomb produces one of the highest strength/weight ratios of any structural material. Various configurations of the aluminium foil which can lead to a variety of geometric cell shapes (usually hexagonal). Properties can also be controlled by varying the foil thickness and cell size. 
         [0026]    Finishing layer  106  is of similar thickness to surface layer  102 . In one embodiment it is designed to provide a means of attachment to the vehicle structure or floor. It may be attached to absorptive layer  104  in a manner similar to the way surface layer  102  is attached to the absorptive layer  104 . Finishing layer  106  may have apertures or other connecting elements to mount the blast mitigation surface to a structure. 
         [0027]    In operation of the embodiment above, absorptive layer  104  is comprised of aluminum foam which will not burn. Existing mats typically use a polymer such as polyurethane foam. Polymer based foams are susceptible to fire, even if coated with a fire resistive material. Referring to  FIG. 2 , when a combat vehicle drives over an IED the energy of the blast  107  is directed upward from through the undercarriage of the vehicle. The energy travels through the floor of the vehicle to finishing layer  106  of mat  100 . The energy further travels into absorptive layer  104 , which absorbs most of the energy and causes the aluminum foam to deform. The aluminum foam can heat up as it deforms. Because the absorptive layer is made of aluminum foam rather than polyurethane, the foam will not burn when it heats up; instead it will melt. By using a hollow metallic structure such as aluminum foam, the mat is able to absorb large blasts while remaining lightweight, durable, and importantly, non-flammable. 
         [0028]    In operation, referring to  FIG. 3 , mat  100  is shown after a simulated explosion. A soldier  110  is standing atop surface layer  102 . A mechanical device  112  exerts a sudden force upward through finishing layer  106 . Absorptive layer  104  absorbs most of the energy from  112  which causes it to deform. The deformation is greatest where soldier  110  has the most weight on surface layer  102 . Since absorbing layer  104  and surface layer  102  absorb most of the energy, less energy is transmitted to soldier  110  which drastically reduces injuries to the lower extremities. 
         [0029]    This concept is not limited to floor mats; additional embodiments of non-flammable blast mitigation mats may include mats for seats, walls, bulkheads, ceilings, ammunition compartments for ships and aircraft, and even protective gear such as helmets and body armor. 
         [0030]    Referring to another embodiment,  FIG. 4 , shows non-flammable blast mitigation mat  200  which is designed to cover walls. Surface layer  202  may be a thin layer of non-reflective coating. Absorptive layer  204  may be several inches thick. It may consist of aluminum foam, or the foam may be made with even stronger or heavier metals. Finishing layer  206  may be similar to the finishing layer  106  of the floor mat embodiment, allowing mat  200  to be attached to the wall via screws or other fasteners, or bonded to the wall with adhesives, welding, or brazing. 
         [0031]    Operably, energy from an explosive event impacts surface layer  202 . Absorptive layer  204  absorbs the majority of the blast energy causing the aluminum foam to deform and melt. Finishing layer  206  is attached to the exterior of a structure. Because absorptive layer  204  absorbs most of the blast energy, the structure remains standing long enough for its occupants to make a safe exit. After the explosion, mat  200  may be replaced by removing detaching finishing layer  206  from the structure. 
         [0032]    Referring to another embodiment,  FIG. 5 , shows non-flammable blast mitigation mat  300  which is designed for ammunition compartments. Surface layer  302  may consist of a thin layer of metal with handholds or hinges depending upon which area of the ammunition compartment the mat covers. Absorptive layer  304  may be aluminum or titanium foam several inches thick. Finishing layer  306  may be omitted if there is no need to attach the mat to another object. 
         [0033]    An explosive event may occur within ammunition compartment  312  or outside ammunition compartment  312 . Operably, when the explosion occurs outside ammunition compartment  312 , energy from an explosive event impacts surface layer  302 . Absorptive layer  304  absorbs the majority of the blast energy causing the aluminum foam to deform and melt. Finishing layer  306  prevents the melted foam from contacting the contents of ammunition compartment  312 . If ordinance within ammunition compartment  312  explodes, absorptive layer  304  absorbs the blast energy, preventing injury to nearby soldiers. 
         [0034]    Referring to another embodiment,  FIG. 6 , shows non-flammable blast mitigation mat  400  which is designed for body armor. Surface layer  402  may be a layer of Kevlar®. Absorptive layer  404  may be only a few millimeters thick. Absorptive layer  404  may be a carbon nanotube structure. Finishing layer  406  may be another layer of Kevlar®. An explosive event may be due to a bomb blast or bullet. Operably, energy from the blast strikes mat  400  and is transmitted through surface layer  402  and is absorbed by absorptive layer  404 . Absorptive layer  404  absorbs the energy of the blast and, in the case of a bullet, absorbs enough energy to slow down a bullet. Finishing layer  406 , made of Kevlar®, provides additional protection to stop any bullets that pierce absorptive layer  404 . 
         [0035]      FIG. 7  depicts the present invention mat  100  installed on the crew area of a military vehicle  160 . The mat  100  is laid in tile sheets and then held in place by mat strips  150 . The strips  150  overlap portions of the mat  100 . Fasteners  152  are used to attach the mat strip  150  to the base floor  154  of the military vehicle  160 .