Patent Publication Number: US-2011061522-A1

Title: Ballistic panel assemblies for use in body armor and method of forming ballistic panel assemblies

Description:
This application claims the priority of Provisional Application No. 61/172,303 filed Apr. 24, 2009, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to ballistic panel assemblies for use in body armor, body armor including such ballistic panel assemblies and methods of forming ballistic panel assemblies. These ballistic panel assemblies are also known as ballistic packages. 
     The following information is provided to assist the reader to understand the invention disclosed below and the environment in which it will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the present invention or the background of the present invention. The disclosure of all references cited herein are incorporated by reference. 
     Concealable body armor for protection from, for example, edged weapons, sharp objects and ballistic threats, has been available for several decades. Since the introduction of concealable body armor, ballistic materials have been improved greatly, resulting in relatively flexible, soft or pliant body armor and increased comfort for the user. Modern, lightweight concealable body armor often includes ballistic (or ballistic resistant) panels or packages formed from a number of polymeric materials such as KEVLAR® ballistic grade fibers/fabrics (formed from para-aramid synthetic fibers) available from E.I. du Pont de Nemours and Company of Wilmington, Del. USA. 
     Performance standards for ballistic panels are, for example, set forth in National Institute of Justice (NIJ) Standard-0101.06, “Ballistic Resistance of Body Armor”. NIJ Standard-0101.06 is a technical document that specifies the minimum performance requirements that equipment must meet to satisfy the requirements of criminal justice agencies and the methods that shall be used to test this performance. This standard is used to determine which body armor models meet the minimum performance requirements for inclusion on the NIJ Compliant Products List. 
     Although significant developments have been made in ballistic resistant body armor, it remains desirable to develop improved ballistic panel assemblies for use in body armor to satisfy current and future performance requirements, including those set forth in NIJ Standard-0101.06. 
     SUMMARY OF THE INVENTION 
     In one aspect, a ballistic panel assembly for use in body armor is provided, including at least one subassembly including at least one layer including fibers that extend from at least one side thereof and at least one edge guard encompassing at least a portion of the extending fibers. The ballistic panel assembly further includes a waterproof cover encasing the at least one subassembly. The cover includes a front section and a rear section. A waterproof seal is formed between the front section and the rear section around at least a portion of perimeters thereof adjacent to the at least one edge guard after the subassembly is placed between the front section and the rear section. The edge guard can, for example, include an adhesive tape. The waterproof seal can, for example, be formed between the front section and the rear section via a polymeric welding technique (for example, sonic or ultrasonic welding). 
     The at least one layer of the at least one subassembly can, for example, include a woven aramid fabric. In several embodiments, the at least one layer includes a woven para-aramid fabric. 
     The ballistic panel assembly can further include at least a first stitching around the entire perimeter of the subassembly through all layers of the subassembly. In several embodiments, the ballistic panel assembly also includes at least a second stitching around the entire perimeter of the subassembly through all layers of the subassembly. The second stitching is spaced from the first stitching. 
     In another aspect, a method of forming a ballistic panel assembly for use in body armor is provided, including: forming at least one subassembly including at least one layer including fibers that extend from at least one side thereof and at least one edge guard encompassing at least a portion of the extending fibers; and encasing the subassembly and the at least one edge guard within a waterproof cover. The cover includes a front section and a rear section. A waterproof seal is foamed between the front section and the rear section around at least a portion of perimeters thereof adjacent to the at least one edge guard after the subassembly is placed between the front section and the rear section. 
     In a further aspect, a ballistic panel assembly for use in body armor is provided, including at least one subassembly including at least one composite layer including a plurality of plies of a polymeric film and a plurality of plies formed form ultrahigh molecular weight polyethylene fibers. At least one ply of the polymeric film is alternated with a plurality of plies formed form ultrahigh molecular weight polyethylene fibers. In several embodiments, a single ply of the polymeric film is alternated with a plurality of plies formed form ultrahigh molecular weight polyethylene fibers. In a number of embodiments, the polymeric film is a polycarbonate film. The ballistic panel assembly can further include a waterproof cover encasing the at least one subassembly. 
     In still a further aspect, a ballistic panel assembly for use in body armor is provided, including at least one subassembly including a plurality of layers of material to form a strike face and a wear face and at least a first stitching around the entire perimeter of the subassembly through all layers of the subassembly. The ballistic panel assembly further includes a waterproof cover encasing the at least one subassembly. In several embodiments, the ballistic panel assembly further includes at least a second stitching around the entire perimeter of the subassembly through all layers of the subassembly. The second stitching is spaced from the first stitching. 
     The present invention, along with the attributes and attendant advantages thereof, will best be appreciated and understood in view of the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a top plan view of the front of an embodiment of an article of body armor of the present invention laid flat on a surface, wherein a front ballistic panel assembly interior to a vest carrier is shown in dashed lines. 
         FIG. 2  illustrates a top plan view of the rear of the article of body armor of  FIG. 1  wherein the body armor is laid flat on a surface and the rear closure sections of the opposing closure mechanisms are folded back, wherein a rear ballistic panel assembly interior to the vest carrier is shown in dashed lines. 
         FIG. 3A  illustrates a top plan view of an embodiment of a subassembly for use in forming a front ballistic panel assembly of the article of body armor of  FIG. 1 . 
         FIG. 3B  illustrates a top plan view of an embodiment of a subassembly for use in forming a rear ballistic panel assembly of the article of body armor of  FIG. 1 . 
         FIG. 3C  illustrates a cross-sectional view of the subassembly of  FIG. 3A  along line A-A thereof. 
         FIG. 3D  illustrates a top plan view of the front ballistic panel assembly. 
         FIG. 3E  illustrates a top plan view of the rear ballistic panel assembly. 
         FIG. 3F  illustrates a cross-sectional view of the ballistic panel assembly of  FIG. 3D  along line B-B thereof. 
         FIG. 4A  illustrates a top plan view of another embodiment of a subassembly for use in forming the front ballistic panel assembly of the article of body armor of  FIG. 1 . 
         FIG. 4B  illustrates a top plan view of another embodiment of a subassembly for use in forming the rear ballistic panel assembly of the article of body armor of  FIG. 1 . 
         FIG. 4C  illustrates a cross-sectional view of the subassembly of  FIG. 4A  along line A-A thereof. 
         FIG. 4D  illustrates a top plan view of the front ballistic panel assembly. 
         FIG. 4E  illustrates a top plan view of the rear ballistic panel assembly. 
         FIG. 4F  illustrates a cross-sectional view of the ballistic panel assembly of  FIG. 4D  along line B-B thereof. 
         FIG. 5A  illustrates a top plan view of another embodiment of a subassembly for use in forming the front ballistic panel assembly of the article of body armor of  FIG. 1 . 
         FIG. 5B  illustrates a top plan view of another embodiment of a subassembly for use in forming the rear ballistic panel assembly of the article of body armor of  FIG. 1 . 
         FIG. 5C  illustrates a cross-sectional view of the subassembly of  FIG. 5A  along line A-A thereof. 
         FIG. 5D  illustrates a top plan view of the front ballistic panel assembly. 
         FIG. 5E  illustrates a top plan view of the rear ballistic panel assembly. 
         FIG. 5F  illustrates a cross-sectional view of the ballistic panel assembly of  FIG. 5D  along line B-B thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, the present invention provides ballistic panel assemblies for use in body armor, body armor including such ballistic panel assemblies and methods of forming ballistic panel assemblies for use in body armor. 
     As used herein and in the appended claims, the singular forms “a,” “an”, and “the” include plural references unless the content clearly dictates otherwise. Thus, for example, reference to “a panel assembly” includes a plurality of such panel assemblies and equivalents thereof known to those skilled in the art, and so forth, and reference to “the panel assembly” is a reference to one or more such panel assemblies and equivalents thereof known to those skilled in the art, and so forth. 
       FIG. 1  illustrates an embodiment of an article of body armor  10  of the present invention in which a body armor carrier is in the form of a vest  20  as, for example, described in PCT International Patent Application Publication No. WO 2007/046863, the disclosure of which is incorporated herein by reference. As set forth in International Publication No. WO 2007/046863, vest  20  can be used alone or in operative connection with a connected garment such as shirt (not shown). For example, an exterior shell fabric of the body armor can be sewn to the shirt. A user of body armor  10  first dons body armor  10  and then adjusts the fit of body armor vest  20  using one or more side closure mechanisms as described in International Publication No. WO 2007/046863 Lightweight outer carriers in the form of vests similar to vest  20  are available from Mine Safety Appliances Company (MSA) of Pittsburgh, Pa. under the mark MSA PARACLETE®. One skilled in the art appreciates that the ballistic panel assemblies of the present invention are suitable for use in many different configurations of body armor other than the configuration illustrated in  FIG. 1 . 
     As described above, body armor  10  includes ballistic panel assemblies or ballistic resistant panel assemblies that provide resistance to, for example, edged weapons, sharp objects, and ballistic threats. As illustrated with dashed lines in, for example,  FIG. 1A , vest  20  includes a generally contiguous (in coverage), flexible front ballistic panel assembly  200 . One skilled in the art appreciates that ballistic panel assembly  200  can be formed as one, integral section or assembly or as a plurality of separate sections or assemblies. However, the coverage provided by ballistic panel assembly  200  is preferably contiguous. Front ballistic panel assembly  200  includes side sections  210   a  and  210   b  adapted to extend around the side of a user. Ballistic panel assembly  200 , including side sections  210   a  and  210   b , is enclosed within an outer shell of fabric forming the front of carrier or vest  20 . As illustrated with dashed lines in, for example,  FIG. 2 , vest  20  also includes a generally contiguous (in coverage), flexible rear ballistic panel assembly  300 . Like front ballistic panel assembly  200 , rear ballistic panel assembly  300  can be formed as one section or assembly or as a plurality of separate sections or assemblies. Rear ballistic panel assembly  300  includes side sections  310   a  and  310   b  adapted to extend around the side of a user. Like ballistic panel assembly  200 , ballistic panel assembly  300 , including side sections  310   a  and  310   b , is enclosed within an outer shell of fabric forming the rear of carrier or vest  20 . 
       FIGS. 3A through 3F  illustrate one embodiment of a ballistic panel assembly or ballistic package of the present invention  FIG. 3A  illustrates a flexible subassembly  230  for use in forming front ballistic panel assembly  200 , while  FIG. 3B  illustrates a flexible subassembly  330  for use in forming rear ballistic panel assembly  300 . Subassemblies  230  and  330  are designed for Type II level of ballistic performance as set forth in Section 2.2 of NIJ Standard-0101.06. In the embodiment of  FIGS. 3A through 3F , each of front ballistic panel assembly  200  and rear ballistic panel assembly  300  is manufactured using generally the same materials and procedures and differ generally only in shape.  FIG. 3C  illustrates a cross-sectional view of subassembly  230  along line A-A of  FIG. 3A . A cross-section of subassembly  330  along line A-A of  FIG. 3B  (which is not shown) is identical to that of subassembly  230 . 
     As illustrated in  FIG. 3C , subassembly  230  (as well as subassembly  330 ) includes, for example, a multi-ply (for example, a 2-ply) layer  232  of an aramid fabric on the front, outer or strike face thereof. The term “aramid” is short for aromatic polyamide. In one embodiment, layer  232  included two plies of GOLD FLEX® material available from Honeywell, which is a roll product including four plies of unidirectional aramid fiber. Adjacent plies are oriented differently at angles orthogonal to each other (that is, at 0°/90°/0°/90°) and sandwiched in a thermoplastic film. No adhesive was placed between the plies of GOLD FLEX material. Without limitation to any particular mechanism of operation, layer  232  is believed to operate, at least in part, to alter the shape, deform or flatten a projectile or bullet impacting layer  232  so that it has less potential to penetrate any adjacent layer(s). 
     Adjacent to layer  232  is a layer  234  including a plurality of plies of, for example, an aramid fabric. In one embodiment, layer  234  included, for example, 17 plies of TWARON® woven fabric available from Teijin Aramid BV of Arnhem, The Netherlands. TWARON material is a very strong, light para-aramid (poly-paraphenylene terephthalamide), which has a high tensile strength and is thermally stable. TWARON fabrics also exhibit high impact and chemical resistance. No adhesive was used between the plies of TWARON fabric in layer  234 . Without limitation to any particular mechanism of operation, it is believed that the projectile or bullet is stopped within layer  234  as a result, at least in part, of elongation and breakage of the high tensile strength fibers of the TWARON fabric. 
     Adjacent to layer  234  is a layer  236  of, for example, an aramid fabric that forms the back, inner or wear face of subassembly  230 . In one embodiment, layer  236  was a multi-ply (for example, a 4-ply) layer of GOLD FLEX material with no adhesive between the plies thereof. layer  236  can operate, at least in part, to limit deformation of the wear face of subassembly  230  upon a ballistic strike thereto to limit the amount of blunt force trauma experienced by a user of vest  20 . In that regard (and, once again, without limitation to any particular mechanism of operation), layer  236  can, for example, operate to distribute rearward propagating force from the projectile or bullet over the surface area thereof and assists in limiting backface deformation or backface signature (BFS) as defined in Section 3.8 of NIJ Standard-0101.06. In that regard, the allowable BFS is the greatest extent of indentation in a backing material caused by a nonperforating impact on tested armor. As set forth in Section 3.9 of NIJ Standard-0101.06, the backing material is a homogeneous block of nonhardening, oil-based modeling clay placed in contact with the back of the armor panel during ballistic testing. 
     As illustrated in  FIGS. 3A and 3B , each of subassemblies  230  and  330  includes stitching  240  and  340 , respectively, around the perimeter thereof. Each of stitching  240  and stitching  340  assists in maintaining the integrity (particularly under the conditioning requirement of NIJ Standard-0101.06 and in subsequent use) of subassemblies  230  and  330 , respectively, and improves the ballistic resistant performance thereof for strikes along the edge thereof. Unlike previously available ballistic panel subassemblies, the perimeter stitching of the present invention passes through all layers of subassemblies  230  and  330 . The perimeter stitching of the present invention improves, for example, BFS performance in the case of edge strikes. In one embodiment, the stitching was performed with Tex 90 nylon 6, 6 thread. The Tex size is 1/9 the denier size. In one embodiment, edge stitching  240  and  340  was positioned a distance “a” of approximately ½ inch from the edge of subassembly  230  and subassembly  330 , respectively. 
     As also illustrated in  FIGS. 3A and 3B , each of subassembly  230  and subassembly  330  also include generally orthogonal stitching therethrough in a quilt pattern  244  and  344 , respectively. In one embodiment, spacing “b” between adjacent stitching lines in the quilt pattern was approximately 1 inch. An angle α of the stitch lines was approximately 45° The quilt stitching was done with Tex 90 nylon 6, 6 thread. Quilt pattern stitching, for example, improves backface deformation or BFS by stiffening subassembly  230 . A closer quilt spacing b, can result in improved ballistic performance. However, a closer quilt spacing b is also associated with increased overall stiffness and thus less flexibility of the panel assembly. 
     In the illustrated embodiment, the lower edge of each of subassembly  230  and  330  was encompassed by an edge guard or trim  238  and  338 , respectively. In one embodiment, a tape such as duct tape (a vinyl, fabric-reinforced, pressure sensitive tape) was used for edge guard  238  and edge guard  338 . As illustrated in  FIGS. 3D through 3F , subassemblies  230  and  330  were each placed within a waterproof cover  250  and  350 , respectively, formed from a polymeric material which was sealed (for example, via sonic welding) around the perimeter thereof. In one embodiment, two sheets (cut to the appropriate size and shape) of a polymeric material such as polyurethane coated (on one side) nylon fabric were sonic welded around the perimeters thereof (to create a seal  252  and  352 ), leaving the bottom edge thereof unsealed. The polyurethane coated side faced inward on each of the front and rear. Subassemblies,  230  and  330  where then slid into the partially sealed covers  250  and  350 , respectively, through the unsealed bottom edges thereof. Subsequently, the bottom edges of covers  250  and  350  were sealed via, for example, a polymer welding technique such as sonic welding. 
     The inventors have discovered that extending fibers or filaments of, for example, woven fabrics used to form subassemblies  230  and  330  interfere with forming edge seals  252  and  352 . Application of edge guards or trims  238  and  338  to bottom edge (or other edge corresponding to the last edge of covers  250  and  350  to be sealed) of subassemblies  230  and  330 , respectively, prevents such interference and enables a waterproof seal. A waterproof seal of subassemblies  230  and  330  is important to maintaining the ballistic performance thereof. 
       FIGS. 4A through 4F  illustrate another embodiment of a ballistic panel assembly suitable for use in the present invention.  FIG. 4A  illustrates a flexible subassembly  430  for use in forming front ballistic panel assembly  400  (which can be used in vest  20  as an alternative to ballistic panel assembly  200 ), while  FIG. 4B  illustrates a flexible subassembly  530  for use in forming rear ballistic panel assembly  500  (which can be used in vest  20  as an alternative to ballistic panel assembly  300 ). In the embodiment of  FIGS. 4A through 4F , each of ballistic panel assembly  400  and rear ballistic panel assembly  500  is manufactured using the same materials/procedures and differ generally only in shape.  FIG. 4C  illustrates a cross-sectional view of subassembly  430  along line A-A of  FIG. 4A . A cross-section of subassembly  530  along line A-A of  FIG. 4B  (which is not shown) is identical to that of subassembly  430 . 
     As illustrated in  FIG. 4C , subassembly  430  (as well as subassembly  530 ), for example, includes a multi-ply (for example, a 2-ply) layer  432  of an aramid fabric on the front, outer or strike face thereof. Subassemblies  430  and  530  are designed for a Type IIIA level of ballistic performance as set forth in Section 2.3 NIJ Standard-0101.06. In one embodiment, layer  432  included two plies of GOLD FLEX material. No adhesive was placed between the plies of GOLD FLEX material. Similar to layer  232 , layer  432  is believed to operate, at least in part, to alter the shape, deform or flatten a projectile or bullet impacting layer  432  so that it has less potential to penetrate any adjacent layer(s). 
     Adjacent to layer  432  is a layer  434  including, for example, a plurality of plies of an aramid fabric. In one embodiment, layer  434  included, for example, 14 plies of TWARON® fabric. No adhesive was used between the plies of TWARON fabric in layer  434 . The projectile or bullet is believed to be stopped within layer  434  as a result, at least in part, of elongation and breakage of the high tensile strength fibers of the TWARON fabric. 
     Adjacent to layer  434  is another layer  436  of, for example, an aramid fabric. In one embodiment, layer  436  was a multi-ply (for example, a 2-ply) layer of GOLD FLEX material with no adhesive between the plies thereof. Layer  436  can, for example, operate, at least in part, to limit deformation of the wear face (or “back deformation”) of subassembly  430  to limit the amount of blunt force trauma experienced by a user of vest  20 . Layer  436  is, for example, believed to assist in distributing rearward propagating force from the projectile or bullet over the surface area thereof. 
     Adjacent to layer  436  is another layer  437  of, for example, an aramid fabric forming the back, inner or wear surface of subassembly  430 . In one embodiment, layer  437  was a multi-ply layer (for example, a 10-ply layer) of GOLD FLEX material with no adhesive between the plies thereof. Layer  437  is, for example, believed to operate to further distribute rearward propagating force from the projectile or bullet over the surface area thereof to limiting backface deformation or BFS. 
     As illustrated in  FIGS. 4A and 4B , each of subassemblies  430  and  530  includes a first or outer perimeter stitching  440  and  540 , respectively, and a second or inner perimeter stitching  442  and  542 , respectively, around the perimeter and through all layers thereof. As described above, such perimeter stitching assists in maintaining the integrity of subassemblies  430  and  530 , respectively, and improves the ballistic resistant (for example, backface deformation or BFS) performance thereof for ballistic strikes along the edge thereof. A double row of stitching results, for example, in better BFS performance along the edge than a single row of stitching, but increases the stiffness along the edge or perimeter. In one embodiment, the stitching was performed with Tex 90 nylon 6, 6 thread. In one embodiment, each of edge stitching  440  and  540  was positioned a distance “a” of approximately ½ inch from the edge of subassembly  430  and subassembly  530 , respectively, and the spacing a′ between first edge stitching  440  and second edge stitching  442  (as well as between first edge stitching  540  and second edge stitching  542 ) was approximately 1 inch. 
     As also illustrated in  FIGS. 4A through 4C , a portion q (see  FIG. 4C ) of each of subassembly  430  and subassembly  530  also includes generally orthogonal stitching therethrough in a quilt pattern  444  and  544 , respectively. As illustrated in  FIG. 4C , portion q included layers  432 ,  434  and  436 . Layer  437  was not quilted. In one embodiment, spacing “b” between adjacent stitching lines in the quilt patterns was approximately 1 inch. An angle α of the stitch lines was approximately 45°. The quilt stitching was also done with Tex 90 nylon 6, 6 thread. As described above, a closer quilt spacing b, results in improved ballistic/BFS performance, but is associated with increased stiffness. Quilting portion q, but not layer  437  resulted in suitable BFS performance while maintaining sufficient flexibility. 
     As described in connection with subassemblies  230  and  330 , the lower edge of each of subassembly  430  and  530  was encompassed by an edge guard or trim  438  and  538 , respectively. In one embodiment, a tape such as duct tape was used as edge guards  438  and  538 . As illustrated in  FIGS. 4D through 4F , subassemblies  430  and  530  were each placed within a waterproof cover  450  and  550 , respectively, formed from a polymeric material which was sealed (for example, via sonic welding) around the perimeter thereof. In one embodiment, two sheets (cut to the appropriate shape) of a polyurethane coated (on one side) nylon fabric were sonic welded around the perimeters thereof (to create perimeter seals  452  and  552 ), leaving the bottom edge thereof unsealed. The polyurethane coated side faced inward on each of the front and rear. Subassemblies,  430  and  530  where then slid into covers  450  and  550 , respectively, through the unsealed bottom edge. Subsequently, the bottom edges of covers  450  and  550  were sealed via, for example, sonic welding. As described above, application of tape  438  and  538  to bottom edge (or other edge corresponding to the last edge of covers  450  and  550  to be sealed) of subassemblies  430  and  530 , respectively, prevents interference of fabric filaments in forming a waterproof seal. 
       FIGS. 5A through 5F  illustrate another embodiment of a ballistic panel assembly suitable for use in the present invention.  FIG. 5A  illustrates a flexible subassembly  630  for use in forming front ballistic panel assembly  600  (which can be used in vest  20  as an alternative to ballistic panel assembly  200 ), while  FIG. 5B  illustrates a flexible subassembly  730  for use in forming rear ballistic panel assembly  700  (which can be used in vest  20  as an alternative to ballistic panel assembly  300 ). Subassemblies  630  and  730  are designed for a Type IIIA level of ballistic performance as set forth in Section 2.3 NIJ Standard-0101.06. In the embodiment of  FIGS. 5A through 5F , front ballistic panel assembly  600  and rear ballistic panel assembly  700  are manufactured using generally the same materials/procedures and differ generally only in shape.  FIG. 5C  illustrates a cross-sectional view of subassembly  630  along line A-A of  FIG. 5A . A cross-section of subassembly  730  along line A-A of  FIG. 5B  (which is not shown) is identical to that of subassembly  630 . 
     As illustrated in  FIG. 5C , subassembly  630  (as well as subassembly  730 ) includes a layer  632  of a plurality of plies of a high-strength fabric on the outer or strike face thereof. In one embodiment, layer  632  included, for example, 20 plies of DYNEEMA® UD-SB31 composite material available from DSM Dyneema of Geleen, The Netherlands. The DYNEEMA UD-SB31 material is a “unidirectional” material in which the fibers (ultrahigh molecular weight polyethylene fibers) are laid parallel, in the same plane, rather than being woven together. Dyneema UD (unidirectional) materials are made of several layers of DYNEEMA fibers, with the direction of fibers in each layer at 90° to the direction of the fibers in the adjacent layers. Without limitation to any particular mechanism, the unidirectional configuration of the fibers in DYNEEMA UD materials is believed to allow the energy transferred from an impact of a bullet or other threat to be distributed along the fibers faster and more efficiently than in conventional woven fabrics. No adhesive was placed between the plies of DYNEEMA material. Layer  632  is believed to operate to both deform the projectile or bullet and to stop the projectile of bullet within layer  632 . 
     Adjacent to layer  632  is a composite layer  634  including, alternating layers of a high-strength material (for example, an ultrahigh molecular weight polyethylene material such as DYNEEMA) and a high-strength polymeric film. In one embodiment, layers  634   a  of polycarbonate were alternated with a multi-ply (for example, a 2-ply) layers  634   b  of DYNEEMA UD-SB31 material. In one such embodiment, the were eight layers  634   a  of singly-ply polycarbonate alternated with eight layers  634   b  of 2-ply DYNEEMA material, for a total of 24 plies in layer  634 . The surface of layer  634  opposite the surface in contact with layer  632 , forms the inner or wear surface of subassembly  630 . Without limitation to any particular mechanism of operation, layer  634  is, for example, believed to distribute rearward propagating force from the projectile or bullet over the surface area thereof and assists in limiting backface deformation or BFS. 
     The inventors have discovered that alternate layers of polycarbonate and ultrahigh molecular weight polyethylene material (for example, DYNEEMA material), wherein a single ply of polycarbonate is alternated with a plurality of plies of DYNEEMA material, operate more effectively to limit backface deformation or BFS than alternate layers of polycarbonate and a single ply of DYNEEMA material. Alternating a single ply of polycarbonate with a plurality of plies of DYNEEMA material (for example, two plies) can also result in equivalent or better ballistic performance while using less material (and thus resulting in a thinner and lighter subassembly) than the case in which polycarbonate is alternated with a single ply of DYNEEMA material. Use of a polymeric material such as polycarbonate rather than only DYNEEMA material can, for example, save on fabrication costs as materials such as polycarbonate are less expensive than DYNEEMA material. 
     As illustrated in  FIGS. 5A and 5B , similar to subassemblies  430  and  530 , each of subassemblies  630  and  730  includes a first or outer perimeter stitching  640  and  740 , respectively, and as second or inner perimeter stitching  642  and  742 , respectively, around the perimeter thereof. As described above, such perimeter stitching assist in maintaining the integrity of subassemblies  630  and  730 , respectively, and improves the ballistic resistant performance thereof for strikes along the edge thereof. Once again, a double row of stitching results in improved ballistic performance along the edge, but increases the stiffness along the edge or perimeter. In one embodiment, the stitching was performed with Tex 90 nylon 6, 6 thread. In one embodiment, each of edge stitching  640  and  740  was positioned a distance “a” of approximately ½ inch from the edge of subassembly  630  and subassembly  730 , respectively, and the spacing a′ between first edge stitching  640  and second edge stitching  642  (as well as between first edge stitching  740  and second edge stitching  742 ) was approximately 1 inch. In the embodiment of  FIGS. 4A through 4F , no portion of subassemblies  630  or  730  was quilted. Subassemblies  630  and  730  were suitable to satisfy the backface deformation of BFS requirements of NIJ Standard-0101.06 without introducing the stiffness associated with quilt stitching. 
     As illustrated in  FIGS. 5D through 5F , subassemblies  630  and  730  were each placed within a waterproof cover  650  and  750 , respectively, formed from a polymeric material which was sealed (for example, via sonic welding) around the perimeter thereof. As described above, two sheets (cut to the appropriate shape) of a polyurethane coated (on one side) nylon fabric was sonic welded around the perimeters thereof (to create a seal  652  and  752 ), leaving the bottom edge thereof unsealed. The polyurethane coated side faced inward on each of the front and rear sides. Subassemblies,  630  and  730  where then slid into covers  650  and  750 , respectively, through the unsealed bottom edge. Subsequently, the bottom edges of covers  650  and  650  were sealed via, for example, sonic welding. 
     As described above, extending fibers or filaments from various layers of the subassemblies used in the present invention can interfere with the formation of a waterproof seal. Such extending fibers or filaments can, for example, be present in the case of woven fabrics. As there were no extending fibers or filaments from any layer of subassemblies  630  or  730 , no tape or other edge guard or trim was required in connection with subassemblies  630  or  730 . 
     Although the present invention has been described in detail in connection with the above embodiments and/or examples, it should be understood that such detail is illustrative and not restrictive, and that those skilled in the art can make variations without departing from the invention. The scope of the invention is indicated by the following claims rather than by the foregoing description. All changes and variations that come within the meaning and range of equivalency of the claims are to be embraced within their scope.