Ceramic tile design improvement for conformal personal armor

Abstract

A tile to be used in an arrangement of identical tiles of an armor, the tile including an obverse face, a reverse face opposite the obverse face, and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of another tile, and a strike face region that is not overlapped by another tile, the first region and the second region being adjacent to the non-overlapped strike face region, the strike face region including a Y-shaped raised portion, a bulging section, and no other raised portion or recessed portion, and the reverse face including a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, a depression at a location corresponding to the location of the bulging section, and no other depression or raised portion.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to ceramic tiles for armor applications and in particular to ceramic tiles for being arranged in an imbricated pattern in an armor panel.BACKGROUND OF THE INVENTION

[0002] U.S. PATENT NO. 8,434,396 (incorporated by reference) discloses a ceramic tile design, which can be used to devise an imbricated arrangement of tiles integrated with ballistic fabric to realize an effective conformable personal armor panel to defeat rifle rounds. An armor system using the tiles of U.S. PATENT NO. 8,434,396 has earned a National Institute of Justice Certification as a Level III armor (Verco Materials, LLC, model UrbanShieldMH).

[0003] U.S. PATENT NO. 11,473,877 (incorporated by reference) discloses a curved ceramic tile design, which can be used to devise an imbricated arrangement of tiles integrated with ballistic fabric to realize an effective personal armor panel to defeat rifle rounds. U.S. PATENT NO. 11,473,877 discloses a ceramic tile design, which, when assembled with other tiles, forms an imbricated pattern that follows a curve. The tiles of U.S. PATENT NO. 11,473,877 are particularly useful for an armor panel that follows a small radius of curvature of a part of a human body such as the transition from the front torso to the side torso, and the outer regions of the upper arm.

[0004] Weight is an important factor for police operators who wear rifle armor protection, as excessive weight can become fatiguing and affect performance when the armor is worn for extended periods.

[0005] A tile design which has equivalent ballistic effectiveness, conformability, and multi-hit stopping capability of the tiles of the prior art with a markedly reduced weight is desirable. To accomplish said objectives U.S. PATENT NO. 12,000,680 (incorporated by reference) discloses a tile design with a reduced weight compared to the tiles disclosed in U.S. PATENT NO. 8,434,396. U.S. PATENT NO. 12,000,680 further proposes decreasing the tilt angle of the imbricated assembly of tiles so that the assembly of tiles covers more area of the wear surface, reducing the extent of tile overlap in specific locations, and making the thickness of the tile more uniform to accomplish said objectives.

[0006] The tile disclosed in U.S. PATENT NO. 12,000,680 has an obverse face, a reverse face opposite the obverse face, and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of another tile, and a strike face region that is not overlapped by another tile, the first region and the second region being adjacent to this non-overlapped region. The strike face region includes a Y-shaped raised portion and no other raised portion or recessed portion, and the reverse face includes a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, and no other depression or raised portion.

[0007] The tile disclosed in U.S. PATENT NO. 12,000,680 may be symmetric about a center line that divides the Y-shaped raised portion into two symmetric portions. The first region and the second region may each slope downwardly from the strike face region toward respective first and second peripheral boundaries and each may be overlapped by corresponding regions of a respective tile when the tile and the respective tiles are arranged in an imbricated arrangement.

[0008] The tile disclosed in U.S. PATENT NO. 12,000,680 may be made of sintered boron carbide, sintered silicon carbide, or aluminum oxide.

[0009] U.S. PATENT NO. 12,000,680 discloses that the Y-shaped raised portion may be raised high enough to intercept a projectile travelling at an oblique angle to protect a seam defined by a tile overlapping the first region or the second region.

[0010] U.S. PATENT NO. 12,000,680 discloses that the first region and the second region may slope at an inclination that would permit assembly of an imbricated arrangement of additional tiles, each additional tile being identical to the tile, and a first tile of the additional tiles overlaps the first region and a second tile of the additional tiles overlaps the second region.

[0011] An armor made with a plurality of tiles according to U.S. PATENT NO. 12,000,680 may have the tiles cooperatively arranged to realize a flexible body, each tile comprising an obverse face, a reverse face opposite the obverse face, and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of a respective tile from the plurality of tiles, and a strike face region that is not overlapped by another tile from the plurality of tiles, the first region and the second region being adjacent the non-overlapped strike face region, the strike face region including a Y-shaped raised portion and no other raised portion or recessed portion, and the reverse face including a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, and no other depression or raised portion. The first region and the second region may each slope downwardly from the strike face region toward respective first and second peripheral boundaries and each may be overlapped by a corresponding region on the reverse face of a respective tile from the plurality of tiles.

[0012] U.S. PATENT NO. 12,000,680 discloses that the armor may be configured as an armor blanket.

[0013] U.S. PATENT NO. 12,000,680 discloses that each tile in the armor may be wrapped in an epoxy-impregnated carbon fiber fabric, and the wrapped tiles may be arranged in an imbricated pattern and held in place by encapsulation in an adhesive-coated aramid fabric.

[0014] U.S. PATENT NO. 12,000,680 discloses that the first and the second regions of the tiles in the armor may be sloped to permit an arrangement that can follow a curved contour with a radius of curvature in the range of two to six inches.

[0015] U.S. PATENT NO. 12,000,680 discloses that each curved tile in the armor may have an edge to center thickness ratio in the range 0.49 to 0.90.

[0016] U.S. PATENT NO. 12,000,680 discloses that weight-saving was realized by forming a Y-shaped depression on the wear face of the tile (the side closest to the wearer) opposite a Y-shaped raised portion on the strike face region (the surface opposite the wear side, which is intended to intercept the projectile), and the edge-to-center thickness ratio was also increased to yield an imbricated pattern with more uniform ballistic performance at all locations along the imbricated pattern.

[0017] U.S. PATENT NO. 12,000,680 discloses that ballistic tests showed that while a 4.9 lb torso panel using sintered boron carbide tiles according to U.S. Patent No. 8,434,396 was ballistically sound against six M80 ball rounds shot at standard muzzle velocity, the same result was achieved with a 3.9 lb torso panel of the same coverage area using tiles disclosed therein with the same sintered boron carbide.SUMMARY OF THE INVENTION

[0018] A tile according to the present invention includes an obverse face, a reverse face opposite the obverse face, and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of another tile, and a strike face region that is not overlapped by another tile, the first region and the second region being adjacent to the non-overlapped strike face region, the strike face region including a Y-shaped raised portion, a bulging section, and no other raised portion or recessed portion, and the reverse face including a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, a depression corresponding to the location of the bulging section, and no other depression or raised portion.

[0019] In a tile according to the present invention, the bulging section may have a tear-shaped profile in the plan view.

[0020] In a tile according to the present invention, the bulging section may be positioned between diverging legs of the Y-shaped raised portion.

[0021] A tile according to the present invention may be symmetric about a center line that divides the Y-shaped raised portion into two symmetric portions.

[0022] In a tile according to the present invention, the first region and the second region each may slope downwardly from the strike face region toward respective first and second peripheral boundaries and each may be overlapped by corresponding regions of a respective tile when the tile and the respective tiles are arranged in an imbricated arrangement.

[0023] A tile according to the present invention may be based on sintered boron carbide, or sintered silicon carbide.

[0024] In a tile according to the present invention, the Y-shaped raised portion may be raised high enough to intercept a projectile travelling at an oblique angle to protect a seam defined by a tile overlapping the first region or the second region.

[0025] In a tile according to the present invention, the first region and the second region may slope at an inclination that would permit assembly of an imbricated arrangement of additional tiles, each additional tile being identical to the tile, and a first tile of the additional tiles overlapping the first region and a second tile of the additional tiles overlapping the second region.

[0026] A tile according to the present invention is configured so that the imbricated arrangement can follow a curved contour with a radius of curvature in the range of two to six inches.

[0027] A tile according to the present invention may have an edge to center thickness ratio in the range 0.49 to 0.90.

[0028] An armor according to the present invention includes a plurality of tiles cooperatively arranged to realize a flexible body, each tile comprising an obverse face, a reverse face opposite the obverse face, and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of a respective tile from the plurality of tiles, and a strike face region that is not overlapped by another tile from the plurality of tiles, the first region and the second region being adjacent to the non-overlapped strike face region, the strike face region including a Y-shaped raised portion, a bulging section, and no other raised portion or recessed portion, and the reverse face including a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, a depression corresponding to the location of the bulging section, and no other depression or raised portion.

[0029] In an armor according to the present invention, the bulging section of each tile may have a tear-shaped profile in the plan view.

[0030] In an armor according to the present invention, the bulging section of each tile may be positioned between diverging legs of the Y-shaped raised portion.

[0031] In armor according to the present invention, the first region and the second region of each tile slope downwardly from the strike face region toward respective first and second peripheral boundaries and each may be overlapped by a corresponding region on the reverse face of a respective tile from the plurality of tiles.

[0032] In an armor according to the present invention, the tiles may be comprised of sintered boron carbide, sintered silicon carbide.

[0033] An armor according to the present invention may be configured as an armor blanket.

[0034] In an armor according to the present invention, each tile may be wrapped in an epoxy-impregnated carbon fiber fabric, and the wrapped tiles are arranged in an imbricated pattern and held in place by encapsulation in an adhesive-coated aramid fabric.

[0035] In an armor according to the present invention, the Y-shaped raised portion of each tile may be raised high enough to intercept a projectile travelling at an oblique angle to protect a seam defined by a tile overlapping the first region or the second region.

[0036] In an armor according to the present invention, the first and the second regions of each tile may be sloped to permit an arrangement that can follow a curved contour with a radius of curvature in the range of two to six inches.

[0037] In an armor according to the present invention, each tile may have an edge to center thickness ratio in the range 0.49 to 0.9.

[0038] Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Fig. 1 shows top (having the strike face region) and side views, with dimensions indicated, of an example of a tile according to U.S. PATENT NO. 12,000,680. Fig. 2 shows top (having the strike face region) and side views, with dimensions indicated, of a curved tile according to U.S. PATENT NO. 12,000,680. Fig. 3 shows a perspective view of an obverse side of a tile according to U.S. PATENT NO. 12,000,680. Fig. 4 shows a perspective view of the reverse side of a tile according to U.S. PATENT NO. 12,000,680. Fig. 5a is a perspective view of the strike face region of a tile according to U.S. PATENT NO. 12,000,680 tilted at an angle corresponding to the angle at which the tile would be tilted (7°) when present in an imbricated arrangement. Fig. 5b is a perspective underside (opposite the strike face region) view of the tile of Fig. 5a. Fig. 5c is a top edge view of the tile of Fig. 5a. Fig. 5d is a side edge view of the tile of Fig. 5a. Fig. 5e is a bottom edge view of the tile of Fig. 5a. Fig. 6 shows four tiles according to Fig. 5a in an imbricated arrangement, the seam between the upper 3 and lower 4 tiles in a column of tiles being marked with letter H. Fig. 7 shows seven tiles according to Fig. 5a in an imbricated arrangement. Fig. 8 shows a side view of the arrangement of Fig. 7 with the angles of incline relative to the wear face contact surface shown. Fig. 9 shows a top view of the strike faces of the arrangement of Fig. 7 with tiles rendered semitransparent to show the extent of the overlap of the tiles. Fig. 10 shows thickness measurements at indicated locations on a 30 gram sintered boron carbide tile according to U.S. PATENT NO. 12,000,680. Fig. 11 is a plan view showing the strike face of a tile according to the present invention. Fig. 12 is a perspective view of the strike (obverse) face of the tile of Fig. 11. Fig. 13 is a perspective view of the reverse face of the tile of Fig. 11. Fig. 14 is a view of the bottom edge of the tile of Fig. 11. Fig. 15 is a view of the side edge of the tile of Fig. 11. Fig. 16 is a table showing the results of a ballistic test of a panel of tiles of U.S. PATENT NO. 12,000,680, referred to as the flat-center tile. Fig. 17 is a table showing the results of a ballistic test of a panel of tiles according to the present invention, referred to as the teardrop-center tile. Fig. 18 shows the strike face side of a ballistic panel, in which an imbricated pattern aramid-wrapped flat-center tiles (backed by sheets of ultra-high molecular weight polyethylene) may be seen, shot six times, with shots intended to impact the tile centers of six of the tiles. Fig. 19 shows the strike face side of a ballistic panel, in which an imbricated pattern of aramid-wrapped teardrop-center tiles (backed by sheets of ultra-high molecular weight polyethylene) may be seen, shot six times, with shots intended to impact the tile centers of six of the tiles. Fig. 20 is an illustration of the zone of tile pulverization of the six tiles shot as shown in Fig. 19, along with a best estimate of the location of impact (circular dot). Fig. 21a and Fig. 21b are strike face images of single tiles on separate identical ultra-high molecular weight backings shot at tile centers, Fig. 21a showing a flat-center tile and Fig. 21b showing a teardrop-center tile. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0040] Figs. 1 and 2 show the typical dimensions for a tile according U.S. PATENT NO. 12,000,680, which are six-sided with rounded corners with the length of the sides thereof being closer to equal. The tile seen in Figs. 1 and 2 may be symmetrical with respect to a center line CL that symmetrically divides a Y-shaped raised portion C (see Figs. 1 and 2) on the strike face region of the tile.

[0041] Referring to Figs. 3 and 4, a tile 10 according to U.S. PATENT NO. 12,000,680 has an obverse face 12, a reverse face 14 opposite the obverse face, and an endless edge 16 between the obverse face 12 and the reverse face 14, the endless edge 16 being defined by a plurality of peripheral boundaries 18 connected by curved sections 20, wherein the obverse face 12 includes a first region 22 and a second region 24 each configured to be overlapped by a corresponding region 26, 28 of a reverse face of another tile, and a strike face region 30 that is not overlapped by another tile, the first region 22 and the second region 24 being adjacent this non-overlapped region of the strike face region 30, the strike face region including a Y-shaped raised portion 32 and no other raised portion or recessed portion, and the reverse face 14 including a Y-shaped depression 34 at a location corresponding to the location of the Y-shaped raised portion 32, and no other depression or raised portion.

[0042] Referring to Figs. 5a and 5e, a tile according to U.S. PATENT NO. 12,000,680 has a Y-shaped raised portion C (feature 32 in Fig. 3) on the strike face region (the strike face region faces away from the wearer's body), which provides coverage in an imbricated arrangement against projectiles oriented at oblique angles that would otherwise exploit an open gap between adjacent tiles (discussed further below with reference to Figs. 6 to 7).

[0043] In a tile design according to U.S. PATENT NO. 12,000,680, a Y-shaped depression D (Figs. 5b and 5c) on the wear face (the side which faces the wearer's body) is aligned beneath the Y-shaped raised portion C (Figs. 5a, 5d, 5c) on the strike face region. The Y-shaped depression D reduces the thickness of the tile in the regions of the Y-shaped raised portion C to that which is similar to the tile thicknesses at regions away from the Y-shaped raised portion. The provision of the Y-shaped depression D contributes to weight savings.

[0044] Referring to Fig. 6, at region H, the side edge of the upper tile 3 is partially recessed behind the rear side edge I (Figs. 5a and 5d) of part of the Y-shaped raised portion C of the lower tile 4. This arrangement provides an effective block against projectiles at various angles of trajectory oriented into this region of the imbricated assembly. Because of the lack of a tooth feature F, along with the depression D beneath the base region of the Y-shaped raised portion C, thicknesses (and weight) in this region are reduced compared to the design in U.S. PATENT NO. 8,434,396.

[0045] Referring to Fig. 7, the oblique coverage of the contacting geometry of the tiles (arrow in Fig. 7) is improved over the tiles of U.S. PATENT NO. 8,434,396 because of the higher elevation of the Y-shaped raised portion C.

[0046] Referring to Fig. 8, with tiles according U.S. PATENT NO. 12,000,680, the angle of the tiles in the imbricated pattern is shallower (for example, 7°) compared to tiles of U.S. PATENT NO. 8,434,396 (14°), which over the expanse of an armor panel, results in fewer tiles being needed for the same coverage area, acting to lower the weight of the panel.

[0047] Referring to Fig. 9, compared to tiles of U.S. PATENT NO. 8,434,396, when assembled in an imbricated pattern, the tile overlap with tiles of U.S. PATENT NO. 12,000,680 is less than the tile overlap with tiles of U.S. Patent No. 8,434,396. For example, the area percent overlap among six tiles in an imbricated pattern with the tiles of U.S. PATENT NO. 8,434,396 is 25.61 while it is 20.58 for the tiles of U.S. PATENT NO. 12,000,680, indicating that the tiles according to U.S. PATENT NO. 12,000,680 provide more coverage along the wear face per tile in an imbricated pattern, requiring fewer tiles for the same area coverage.

[0048] Referring to Fig. 10, thickness measurements were taken at the indicated locations of a 40 gram sintered boron carbide tile of U.S. PATENT NO. 8,434,396, and a 30 gram sintered boron carbide tile of U.S. PATENT NO. 12,000,680 (Fig. 10). The edge to center thickness ratio for the tile of U.S. PATENT NO. 8,434,396 range from 0.14 to 0.31, while for a tile of Fig. 10 (U.S. PATENT NO. 12,000,680) the edge to center thickness ratio range from 0.49 to 0.90, which is a substantial thickening of the edges relative to the center compared to the tile of U.S. PATENT NO. 8,434,396. Edge to center thickness ratio is the ratio of the measured thickness at an edge location to the thickness measured at the center.

[0049] Referring to Figs. 11-15, a ballistic tile 36 according to the present invention has all the features of the tile disclosed in U.S. PATENT NO. 12,000,680 (Figs. 1-10), and further includes an additional bulging section 38 located between the two legs of the Y-shaped raised portion 32 on the strike (obverse) side of the tile. The bulging section 38 has a teardrop-shaped profile in plan view, which is symmetric about axis CL. The teardrop-shaped profile has two diverging sides 40 that begin at a common origin 42 inside of the Y-shaped raised portion 32 and terminate at a curved side 44 outside of the Y-shaped raised portion 32. The diverging sides 40 may be straight, and the common origin 42 may be curved. The bulging section 38 has two sloping sides 46 each beginning at a respective side 40 and terminating at a curved section 50 that extends along the axis CL. The curved side 44 serves as the base of a partial (e.g. quarter) sphere section 48 of the bulging section 38, which meets and merges with the two sloping sides 46 to define a shape that resembles a tear drop convexly rising from the non-overlapped region of the strike face region 30 of the tile 36.

[0050] Referring to Fig. 13, a teardrop-shaped depression 52 is defined on the reverse side of the tile 36 located to coincide with the teardrop-shaped bulging section 38 of the obverse side of the tile 36.

[0051] For a commercial implementation, each tile may be wrapped with epoxy-impregnated carbon fiber fabric, and the epoxy may be set at elevated temperature and pressure. The wrapped tiles may be arranged in an imbricated pattern and held in place by encapsulation in adhesive-coated aramid fabric to make a tile pack (see Fig. 19) that may be sewn to sheets of ballistic fabric (e.g., aramid and / or high molecular weight polyethylene) to obtain a composite system that forms a torso-conformable rifle-protection armor panel (armor panel). The hardness of each ceramic tile at the strike face region acts to blunt and / or fracture the impacting projectile and absorb much of its kinetic energy, while the backing fabric arrests and captures the bullet or its fragments emerging from the locally pulverized ceramic tile.

[0052] As reported in U.S. PATENT NO. 12,000,680, an armor panel as described above, using an imbricated pattern of 30 g carbon-wrapped boron carbide tiles, and 2.3 psf of backing fabric (95 sheets of high molecular weight polyethylene fabric) was ballistically tested. A shot pattern, as shown in Figure 10 of that patent, was used so that over six shots, a variety of locations of the imbricated pattern were evaluated (e.g. tile center shots, two-tile overlap locations, and three-tile overlap locations) with six shots. The ballistic results in Figure 12 of that patent shows acceptable performance, based on the fact that there were no perforations and the back face signatures (dent into the flat clay block the panel was mounted on) were all below 44 mm.

[0053] Experience with the armor system reported in U.S. PATENT NO. 12,000,680 showed more uniform ballistic performance at all locations of the imbricated pattern than the armor system reported in U.S. PATENT NO.. 8,434,396, in which ballistic performance was generally better for shots at tile centers as compared locations of tile overlap.

[0054] While ballistic performance was found to be more uniform at all locations of the ballistic pattern for the armor system described in U.S. PATENT NO. 12,000,680, the weakest ballistic performance was generally seen for shots located at tile centers. The tile design according to the present invention was intended to improve ballistic performance at tile centers, while maintaining an identical tile weight (30 g).

[0055] Ballistic evaluation of six tile-center shots was performed on a panel based on tiles described in U.S. PATENT NO. 12,000,680, hereafter referred to as the flat-center tile, and a panel using tiles based on the present invention, hereafter referred to as the teardrop-center tile. Target points 1-6, shot in numerical sequence, were located at or close to the mouth of the Y-shaped feature of six tiles in the armor panel: two bottom tiles, two middle tiles and two top tiles (see, for example Figs. 18 and 19). Other than the two different tile designs, the construction of the panels were identical: Carbon fiber-wrapped 30 g boron carbide tiles in an imbricated pattern were held in place by adhesive-coated aramid fabric, backed by 2.06 psf (85 sheets) of high molecular weight polyethylene. These are fewer sheets of backing fabric than the 95 sheets reported in the ballistic test of the flat-center tile in U.S. PATENT NO. 12,000,680.

[0056] All tests were performed with the M80 ball round (the same projectile used for the NIJ 0101.06 Level 3 standard) at muzzle velocity (2780 ft / s). Test panels were mounted on a NIJ standard-specified flat clay surface at a specified temperature, and the depth of dent into the clay after the armor was shot was measured. This is referred to as the back face signature, and indicates the extent of blunt force trauma that would be experienced by the wearer of the armor. The NIJ 0101.06 standard requires back face signatures be less than 44 mm (or a statistical analysis of data is used to establish the passing criteria if a small number of back face signatures exceed 44 mm).

[0057] Fig. 16 shows the ballistic results for the flat-center tile. One of the projectiles perforated the armor. The average and standard deviation of the back face signature of the flat center tiles (omitting the perforating round) is 44.324 ± 8.783 mm. The back face signature on shot #2 of 55.86 mm, or alternately the perforation on shot 3, would cause this armor panel to fail the NIJ 0101.06 test.

[0058] Fig. 17 shows the ballistic results for the teardrop-center tile. For this panel, there were no perforations, and the average back face deformation was 32.175 ± 7.660 mm. These results would not be the cause of a test failure in a NIJ 0101.06 test (note that the standard test involves more than one armor panel). Thus, a tile according to the present invention shows a significant improvement over the tile of U.S. PATENT NO. 12,000,680.

[0059] Fig. 18 shows the strike face of the shot panel made up of flat-center tiles (from which the data in Fig. 16 was obtained). The zone of disruption of the aramid fabric is approximately of the same diameter as the M80 round (7.62 mm in diameter). Fig. 19 shows the strike face of the shot panel made up of teardrop-center tiles (from which the data in Fig. 17 was obtained). For most of the impacts, the zone of disruption of the fabric is significantly greater than the diameter of the round. These regions of fabric are torn apart as a result of spall of fine boron carbide debris in a direction opposite the direction of propagation of the bullet, tearing apart the aramid fabric.

[0060] Analysis of tile remains of the flat-center tiles after bullet impacts at their centers showed a conical zone of ceramic extraction from the tile, with the diameter approximating the diameter of the bullet on the strike face, with the cone widening in cross sectional area with depth toward the wear face of the tile. The ceramic left behind was in the form of cracked shards of relatively coarse size. In contrast, analysis of the tile remains of the teardrop-center tiles after impacts at their centers shows removal of all regions of the teardrop dome at elevations below (toward the wear face of the tile) the point of impact. This was a much larger cross sectional area of removal, which was more cylindrical in nature with depth going from strike face to wear face surfaces of the tiles. The remaining ceramic was rubblized into comparatively smaller particles.

[0061] Fig. 20 is based on analyses of the teardrop-center tiles in Fig. 19. The colored zones of non-uniform shape drawn on the six images of tiles, are the regions in which pulverized and removed boron carbide was observed. The circular dot within this zone denotes a best estimate of the center of bullet impact. This dot was informed, in part, by the appearance of damage on the layers of ballistic fabric on the strike face of the fabric pack (which resides on the wear face of the aramid-wrapped imbricated array of ceramic tiles). The shape of the indicated pulverized zone showed some similarity to the zone of disruption of the strike face aramid fabric, but there were some differences. Depending on the topography of impact, the direction of high-energy ejecta, tearing apart the aramid fabric, may differ somewhat from the regions of the tile undergoing extensive pulverization.

[0062] As can be seen in Fig. 20, even though the shot impact locations were marked to be at the center of the tile, which corresponds to the highest elevation of the teardrop dome, the actual impact locations varied, as is typical in a ballistic test. This variation is useful for elucidating the mode of interaction of the bullet with the teardrop dome. The back face deformations in Fig. 19 are also marked next to each shot in Fig. 20. As can be seen in Fig. 19, shots 3, 4, and 6 impacted closest to the center of the dome (sphere section 48), and had the lowest back face signatures of the six shots. The zone of boron carbide pulverization was also largest for those shots. Shots 1 and 2 were close to the curved termination 44 of the dome back to a flat surface near the top of the tile. The zone of pulverization of these locations was relatively smaller. The interaction of the bullet with these locations is interpreted to approach behavior similar to that of the flat-center tile design. Shot 5 impacted in the well between the side edge of the teardrop protrusion 40 and the Y-shaped protrusion 32. This demonstrated a more intermediate back face behavior relative to the aforementioned shot locations.

[0063] Figs. 21a and 21b show single tiles of teardrop-center and flat-center tiles, respectively each mounted on identical backing fabrics. Both were mounted on a ballistic fabric pack of 120 sheets of high molecular weight polyethylene fabric. Both were impacted at tile centers by a single M80 ball round at muzzle velocity. As can be seen, the flat-center tile remained atop the fabric pack. However, the teardrop-center tile has been permanently embedded into the fabric pack. This illustrates the ability of the teardrop-center tile to distribute a significant amount of the force of the bullet over the entire tile, for enough time to bury the tile in the fabric backer.

[0064] It is well known in the materials sciences that the energy absorbed in the fracture of a brittle ceramic is equal to the energy required to form new surfaces as a result of the fracture (Griffith-Irwin theory). While the teardrop mound at the center of the tile was expected to distribute the initial concentrated load of the bullet over a wider area, these regions of the tile which were shifted laterally away from the bullet and of lower elevation, were not anticipated to provide resistance once the regions directly beneath the bullet were pulverized. What instead occurred was that a wide area of the tile away from the bullet was pulverized, in turn absorbing a notably greater amount of bullet energy than with a flat-center tile.

[0065] A tile according to the present invention may be curved as described in U.S. PATENT NO. 12,000,680, and assembled in an imbricated pattern in an armor as described in U.S. PATENT NO. 12,000,680.

[0066] Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

1. A tile comprising: an obverse face; a reverse face opposite the obverse face; and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of another tile, and a strike face region that is not overlapped by another tile, the first region and the second region being adjacent to the non-overlapped strike face region, the strike face region including a Y-shaped raised portion, a bulging section, and no other raised portion or recessed portion, and the reverse face including a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, a depression corresponding to the location of the bulging section, and no other depression or raised portion.

2. The tile of claim 1, wherein the bulging section has a tear-shaped profile in the plan view.

3. The tile of claim 1, wherein the bulging section is positioned between diverging legs of the Y-shaped raised portion.

4. The tile of claim 1, wherein the tile is symmetric about a center line that divides the Y-shaped raised portion into two symmetric portions.

5. The tile of claim 1, wherein the first region and the second region each slopes downwardly from the strike face region toward respective first and second peripheral boundaries and each is overlapped by corresponding regions of a respective tile when the tile and the respective tiles are arranged in an imbricated arrangement.

6. The tile of claim 1, wherein the tile is comprised of sintered boron carbide.

7. The tile of claim 1, wherein the tile is comprised of sintered silicon carbide.

8. The tile of claim 1, wherein the Y-shaped raised portion is raised high enough to intercept a projectile travelling at an oblique angle to protect a seam defined by a tile overlapping the first region or the second region.

9. The tile of claim 1, wherein the first region and the second region slope at an inclination that would permit assembly of an imbricated arrangement of additional tiles, each additional tile being identical to the tile, and a first tile of the additional tiles overlaps the first region and a second tile of the additional tiles overlaps the second region.

10. The tile of claim 1, wherein the imbricated arrangement can follow a curved contour with a radius of curvature in the range of two to six inches.

11. The tile of claim 1, wherein the tile has an edge to center thickness ratio in the range 0.49 to 0.90.

12. An armor comprising a plurality of tiles cooperatively arranged to realize a flexible body, each tile comprising an obverse face, a reverse face opposite the obverse face, and an endless edge between the obverse face and the reverse face, the endless edge being defined by a plurality of peripheral boundaries connected by curved sections, wherein the obverse face includes a first region and a second region each configured to be overlapped by a corresponding region of a reverse face of a respective tile from the plurality of tiles, and a strike face region that is not overlapped by another tile from the plurality of tiles, the first region and the second region being adjacent to the non-overlapped strike face region, the strike face region including a Y-shaped raised portion, a bulging section, and no other raised portion or recessed portion, and the reverse face including a Y-shaped depression at a location corresponding to the location of the Y-shaped raised portion, a depression corresponding to the location of the bulging section, and no other depression or raised portion.

13. The armor of claim 12, wherein the bulging section of each said tile has a tear-shaped profile in the plan view.

14. The armor of claim 12, wherein the bulging section of each said tile is positioned between diverging legs of the Y-shaped raised portion.

15. The armor of claim 12, wherein the first region and the second region each slopes downwardly from the strike face region toward respective first and second peripheral boundaries and each is overlapped by a corresponding region on the reverse face of a respective tile from the plurality of tiles.

16. The armor of claim 12, wherein the tiles may be comprised of sintered boron carbide.

17. The armor of claim 12, wherein the tiles may be comprised of sintered silicon carbide.

18. The armor of claim 12, wherein the armor arrangement is configured as an armor blanket.

19. The armor of claim 12, wherein each tile is wrapped in an epoxy-impregnated carbon fiber fabric, and the wrapped tiles are arranged in an imbricated pattern and held in place by encapsulation in an adhesive-coated aramid fabric.

20. The armor of claim 12, wherein the Y-shaped raised portion is raised high enough to intercept a projectile travelling at an oblique angle to protect a seam defined by a tile overlapping the first region or the second region.

21. The armor of claim 12, wherein the first and the second regions are sloped to permit an arrangement that can follow a curved contour with a radius of curvature in the range of two to six inches.

22. The armor of claim 12, wherein each tile has an edge to center thickness ratio in the range 0.49 to 0.9.

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