Patent Abstract:
An interleaving hexagonal tile (AHT) is provided for incorporation onto a liner in an array for a personnel armor clothing article. The AHT includes a hexagonally-symmetric solid object composed of a homogeneous material. The object includes a geometry that has obverse and reverse planar surfaces parallel to each other. Each planar surface has triangularly disposed terminals. First and second triple sets of oblique surfaces are disposed between the obverse and reverse planar surfaces. A plurality of facets is disposed substantially perpendicular to the planar surfaces. The facets connect between edges of the planar surfaces and adjacent edges of the oblique surfaces. The first and second triple sets of oblique surfaces are disposed to alternate with each other.

Full Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND 
     The invention relates generally to tiles for body armor. In particular, the invention relates to interlocking tiles to provide protection from small arms fire with improved flexibility. 
     During combat and insurgency patrol, military personnel can be subject to small-arms fire from gun-fired projectile rounds, as well as blast and fragmentation from grenades, designed to attack flesh. Personnel struck by such weapons can suffer serious or even mortal injury. To reduce vulnerability to combatants from such lethal contacts, wearable personnel armor, such as a vest with resistant-fiber mesh, has been developed. Further improvements have integrated high strength intermediary materials to further absorb or deflect kinetic impacts. Such measures have added weight and reduced flexibility for personnel so clad. 
     Conventional tactical body armor within the United States armed forces consists of small arms protective insert (SAPI) and Enhanced SAPI (ESAPI) ceramic trauma plates. The plates vary in performance where the SAPI plates are capable of defeating M80 ball rounds and the ESAPI is capable of defeating 0.30 caliber M2AP rounds. The plates are inserted within an interceptor vest which is capable of stopping 9 mm×19 mm handgun bullets. Conventional ESAPI/SAPI plates are comparatively large and bulky, and additionally limit flexibility of the wearer. 
     SUMMARY 
     Conventional body armor yield disadvantages addressed by various exemplary embodiments of the present invention. In particular, various exemplary embodiments provide an angled hexagonal tile (AHT) to incorporate as an interleaving arrayed plurality for a personnel armor clothing article. The plurality for the array is adhered onto a liner substrate. The AHT includes a hexagonally-symmetric solid object composed of a homogeneous material. The object includes a geometry that has obverse and reverse planar surfaces parallel to each other and separated by a thickness. Each planar surface has triangularly disposed terminals. Each obverse terminal is angularly offset to an adjacent reverse terminal. 
     In exemplary embodiments, the terminals on each corresponding planar surface have a length between a vertex at a first terminal and a center-point between second and third terminals. A first triple set of obverse-facing oblique surfaces is disposed between the obverse and reverse planar surfaces. Each obverse-facing oblique surface connects an obverse center-point on the obverse planar surface and a corresponding reverse terminal on the reverse planar surface. A second triple set of reverse-facing oblique surfaces is disposed between the obverse and reverse planar surfaces. 
     Each reverse-facing oblique surface connects an obverse terminal on the obverse planar surface and a corresponding reverse center-point on the reverse planar surface. A plurality of facets is disposed substantially perpendicular to the planar surfaces. The facets connect between edges of the planar surfaces and adjacent edges of the oblique surfaces. The first and second triple sets of oblique surfaces are disposed to alternate with each other. 
     In various embodiments, the object is composed of ceramic. In alternate embodiments, the planar surfaces form a contiguous triangular arrangement of hexagons. In other embodiments, these surfaces form a triangular boundary terminated by elongated octagons. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which: 
         FIG. 1  is an isometric view of a first tile configuration; 
         FIG. 2  is an isometric view of an array of first tiles; 
         FIG. 3  is an isometric view of a second tile configuration; and 
         FIG. 4  is an isometric view of an array of second tiles. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     Exemplary embodiments provide an interlocking tile geometry that improves protection of a surface otherwise vulnerable to kinetic collision, such as from bullet impact. Such tiles can be arranged between substrate layers to provide contiguous yet flexible shock-absorbent material in a wearable clothing article, such as in a jacket to protect the wearer&#39;s torso. The layers can represent a variety of woven fabrics, such as aramid Kevlar® and high-modulus polyethylene Spectra®. 
     The tile design corresponds to a hexagonally symmetric form to represent an angled hexagonal tile (AHT) geometry. The AHTs provide three advantages including: (a) angled interfaces that reduce interstitial vulnerability from conventional tiles, (b) force distribution enhances multi-impact capability by reduced damage propagation, and (c) adhesion to one surface of the AHTs to a flexible fabric facilitates flexibility with an integrated and contiguous area of body protection from blunt force trauma. 
       FIG. 1  shows an isometric view  100  of a first tile configuration  110  for an AFT. A compass rose  115  shows Cartesian orientation of the first AHT  110  with x and z directions representing the facial x-z plane parallel to the surface to be shielded, and y direction denoting thickness. View  100  shows an obverse planar surface  120  (normal upward relative to y) parallel to a reverse planar surface  125  (normal downward relative to y). These planar surfaces  120  and  125  reveal a contiguous regular tri-hexagonal form. 
     Triple upward-facing oblique rectangular wedges  130  concatenate alternatingly with counterpart triple downward-facing oblique rectangular wedges  135 . Obverse-adjacent triangular edge facets  140 ,  145 ,  150  and  155  interweave the wedges  130  and  135  with the obverse surface  120 . Similarly, reverse-adjacent triangular edge facets  160 ,  165 ,  170  and  175  interweave the wedges  130  and  135  with the reverse surface  125 . These triangular facets are substantially perpendicular to the planar surfaces  120  and  125  and thereby at least approximately parallel to y. The planar surfaces  120  and  125  feature three outward obtuse tips  180  flanked by six adjacent obtuse vertices  185 , such that three inverse divots  190  are disposed therebetween. Effectively, tips  180  and the divots  190  yield overlapping triangles that form a Star-of-David on the planar surface  120 . 
     Thickness of the tile  110  between the planar surfaces  120  and  125  is denoted as height H and for exemplary personnel armor can vary based on threat assessments. Expected thickness range between ¼ inch and ⅝ inch. The example height illustrated in view  100  constitutes 0.50 inch (1.27 cm). Distance along the obverse surface  120  between a first tip  180  and its opposite divot  190  on the obverse surface  120  is denoted as length L, which for exemplary personnel armor can vary between one inch and five inches, depending on requirements. The example length in view  100  measures 1.25 inch (3.175 cm). 
     The interface angle θ between the divot  190  on the obverse surface  120  and the adjacent tip  180  on the reverse surface  125  can vary from ten degrees to sixty degrees. The example angle in view  100  is 50.19442891° (0.87606 radian). The tips  180  on the obverse surface  120  and the tips  180  on the reverse surface  125  are angularly offset. In the configuration shown, this phase offset is 180° (π radians) between the corresponding obverse and reverse tips  180 . 
       FIG. 2  shows an isometric view  200  of an array  210  of the first AHTs  110  connected together by interleaving facets. The obverse surfaces  120  and select wedges  130  and  135  along the edge are illustrated. Of the seven tiles  110  depicted, the fore unit  220  presents one tip  180  facing right, with aft unit  230 , starboard unit  240  and port unit  250  sharing edges, along with a rear unit  260  behind the port unit  250 . Edge transitions along the obverse surfaces  120  include corners at tip-to-divot  270 , vertex-to-divot  275 , and vertices junction  280 . Fore and aft units  220  and  230  connect with the tip-to-divot  270 . 
     Fore and port units  220  and  250  connect with the tip-to-divot  275 . At their adjacent vertices  185 , the port, aft and rear units  230 ,  250  and  260  connect together at their common junction  280 . Similarly, complementary wedges  130  and  135  on adjacent tiles  110  face each other, as do triangular facets  140  with complements  150 , along with facets  145  with  155 , facets  160  with  170  and facets  165  with  175 . 
       FIG. 3  shows an isometric view  300  of a second tile configuration  310  for the AHT. A compass rose  315  shows orientation of the second AHT  310  similarly as rose  115 . View  300  shows an obverse planar surface  320  (normal upward relative to y) parallel to a reverse planar surface  325  (normal downward relative to y). These planar surfaces  320  and  325  reveal a contiguous triple elongated-octagon form. Triple upward-facing oblique rectangular wedges  330  concatenate alternatingly with counterpart triple downward-facing oblique rectangular wedges  335 . 
     Obverse-adjacent triangular edge facets  340 ,  345 ,  350  and  355  interweave the wedges  330  and  335  with the obverse surface  320 . Similarly, reverse-adjacent triangular edge facets  360 ,  365 ,  370  and  375  interweave the wedges  330  and  335  with the reverse surface  325 . These obverse-adjacent and reverse-adjacent triangular facets are substantially parallel to y, and join at the intersections with their associated wedges  330  and  335 . The planar surfaces  320  and  325  feature three outward edges  380  joined at chamfered sides of the facets by three inward edges  390 . Effectively, centers of the outward edges  380  and the inward edges  390  yield overlapping triangles that form a Star-of-David on the planar surface  320 . 
       FIG. 4  shows an isometric view  400  of an array  410  of the second AHTs  310 . A compass rose  415  shows orientation of the assembly  410  with normal to the planar surfaces  320  parallel to the y-direction. The identified tiles  310  include left upper unit  420 , right upper unit  430 , center unit  440  and right lower unit  450 . Edges of units  430 ,  440  and  450  join together at a junction point  460  between the edges  380  and  390 . 
     Arrays  210  and  410  enable force absorption from kinetic impact onto obverse surfaces  120  and  320  by momentary flexing, coupled with the plastic deformation of individual tiles  110  and  310 . In particular, flexing constitutes angular separation of the respective constituent tiles  110  and  310  from their neighbors. For example for view  200 , striking the aft unit  230  causes its downward deflection in the −y direction (see rose  115 ). The adjacent units, including  220 ,  250  and  260 , are constrained laterally by their substrate layers (not shown), and thus deflect by tilting, while maintaining protection against subsequent impacts without serious gaps. 
     Type of AHT deformation depends on composition material. The AHT can be considered to be a homogeneous substantially isotropic material. Ceramic units, such as boron carbide (B 4 C) and silicon carbide (SiC), can fracture under high compressive and shear loads. Ceramic material can also include boron carbide derivatives, such as boron carbide nitride, poly(6-cyclooctenyldecaborane) and poly(6-norbornenyldecaborane). Other more ductile materials (e.g., metals) can plastically deform without shattering, but at lower yield strengths than typical for ceramics. 
     To enable the development of flexible body armor that reduces blunt force trauma from a projectile strike, reduces vulnerabilities from interstitial joints, benefits from decreased weight, and increases multi-hit capability over conventional designs. The force from bullet impact against an angled hexagonal tile matrix is distributed across multiple tiles while still enabling each individual tile to flex. In addition, the angled sides reduce the vulnerabilities of the joining seams, where the angled joints can either deflect or dissipate incident threats. 
     Based on desire to reduce weight, increase multi-hit capability, and enhance flexibility, the AHT has been designed to satisfy these requirements. The first AHT design modifies geometry relative to the second AHT design, thereby simplifying the production, lowering the cost, and minimizing the number of interface surfaces to improve the transmission of shock waves across each other, instead of the wearer. 
     The AHT objects can replace the conventional SAPI/ESAPI plates with the ceramic AHTs, forming equivalent surface area coverage but with fewer gaps for improved bodily protection. Preferably, the ceramic materials are composed of either boron carbide or silicon carbide, and can be manufactured to near theoretical maximum density to provide optimal material properties. Alternative ceramics can be used, including compositions that derive from boron carbide. 
     The ceramic AHT units are joined together in an array and adhered to a spall liner fabric substrate. After adhesion to the liner, the AHTs  110  and/or  310  can optionally be encapsulated within polyurea foam. This technique is described in U.S. Patent Application Publication 2012/0312150, incorporated by reference in its entirety. 
     The exemplary AHTs can be integrated into the body armor system similar to the current SAPI/ESAPI plates as inserts. For each exemplary first AHT  110 , the six peripheral faces  130  and  135  are angularly disposed in relation to the nominal hexagonal orientation, with each AHT  110  having three positively angled wedges  130  and three negatively angled wedges  135  alternating symmetrically back and forth along the periphery. 
     The adherence of the reverse surface  125  to the spall liner inhibits lateral tile movement. In response to kinetic impact, the AHTs  110  direct force on each neighboring tile through the angled wedges  130  and  135 , enabling the impact energy to be distributed across all of the AHTs  110 . The angled wedges also reduce the interstitial vulnerability at seams between tiles  110  by eliminating straight-through points. This similarly applies to the second AHT  310 . 
     While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.

Technology Classification (CPC): 5