Patent Grant
7685922
The present invention relates to armor methodologies that implement ceramic material, more particularly to armor methodologies that implement discrete ceramic elements in combination with non-ceramic material.
Current military armor applications include land vehicles, air vehicles (e.g., aircraft and rotorcraft), stationary structures, and personnel. Other applications of armor systems are less common but may become more prevalent in the future, including marine vehicles (e.g., ships), unmanned air vehicles, unmanned marine vehicles, and missiles. Generally, the weight of an armor system is most critical for personnel/personal (e.g., helmet or body) armor.
Various armor constructions and configurations have been disclosed involving utilization of ceramic material. See, e.g., the following U.S. patents, each of which is incorporated herein by reference: deWitt, U.S. Pat. No. 7,067,031 B2, issued 27 Jun. 2006, entitled “Process for Making A Ceramic Armor Plate”; Cohen, U.S. Pat. No. 6,860,186 B2, issued 1 Mar. 2005, entitled “Ceramic Bodies and Ballistic Armor Incorporating the Same”; Mohr et al., U.S. Pat. No. 6,792,843 B2, issued 21 Sep. 2004, entitled “Armor-Plating Composite”; Ghiorse et al., U.S. Pat. No. 6,601,497 B2, issued 5 Aug. 2003, entitled “Armor with In-Plane Confinement of Ceramic Tiles”; Shih et al., U.S. Pat. No. 6,532,857 B1, issued 18 Mar. 2003, entitled “Ceramic Array Armor”; Lyons, U.S. Pat. No. 6,332,390 B1, issued 25 Dec. 2001, entitled “Ceramic Tile Armor with Enhanced Joint and Edge Protection”; Lyons et al., U.S. Pat. No. 6,253,655 B1, issued 3 Jul. 2001, entitled “Lightweight Armor with a Durable Spall Cover”; Lyons, U.S. Pat. No. 6,009,789, issued 4 Jan. 2000, entitled “Ceramic Tile Armor with Enhanced Joint and Edge Protection.”
The aforementioned Shih et al. disclose an armor system that includes an elastomeric matrix material and, encapsulated therein, plural ceramic tiles arrayed along a common surface and spaced apart from one another. The ceramic tiles disclosed by Shih et al. and others are characterized by a smooth and planar shape. In other words, ceramic tiles conventionally used for armor applications are even in thickness.
Ceramic armor material, as conventionally embodied, often fails when impacted by a projectile (e.g., a ballistic body such as small arms fire, or an explosive fragment such as shrapnel from a bomb blast). A recognized need in the armor-related arts is to improve the capability of a structure or structural component made of ceramic to withstand significant impact.
In view of the foregoing, it is an object of the present invention to provide a ceramic body that is suitable for use in an armor system and that is more impervious to projectile impact than are conventionally known ceramic bodies. A further object of the present invention is to provide an armor system that implements such superiorly impervious ceramic bodies.
A conventional ceramic element can fail for various reasons when subjected to projectile impact. One important failure mechanism involves the reflection of shock waves off of the back face of the conventional ceramic element; equivalently expressed, the shock waves reflect off of the interface between the conventional ceramic element's back face and the matrix material in which the conventional ceramic element is embedded. “Incident” shock waves, compressive in nature, are associated with the impact of the projectile on the ceramic tile. “Reflected” shock waves, tensile in nature, are associated with the reflection of the incident shock waves from the rear surface of the conventional ceramic element. The complex interaction of the incident shock waves and the reflected shock waves results in internal failure of the conventional ceramic element.
This kind of destructive interaction of incident and reflected shock waves is particularly marked in a conventional ceramic element because of the evenly thick geometry of the conventional ceramic element, commonly referred to as a ceramic “tile.” In a conventional ceramic element, the incident shock waves and the reflected shock waves each describe approximately planar patterns of propagation. The incident shock waves and the reflected shock waves tend to coincide both spatially and temporally, encountering each other so as to be concentrated in one or more approximately planar areas in the interior of the ceramic element. The high energy density characterizing each of these planar levels of shock wave concentration brings about failure of the ceramic material.
The present invention provides new and improved geometric shapes for ceramic elements. Disclosed herein are inventive ceramic elements of various shapes that are suitable for inclusion in armor material systems. Uniquely featured by an inventive ceramic element is a geometrically uneven character that results in attenuation of interaction between the incident shock waves and the reflected shock waves within the inventive ceramic element.
A fundamental feature of the present invention—regardless of whether according to “first-mode,” “second-mode,” or “hybrid-mode” inventive practice—is the non-parallelism of the front and back surfaces, or portions thereof, of the inventive ceramic element. Inventively prescribed textures and/or shapes impart front-and-back non-parallelism to the present invention's ceramic elements. When an inventive ceramic element is impacted by a projectile, the non-parallel character of the front and back faces, relative to each other, tends to reduce both the spatial coincidence and the temporal coincidence, and hence the deleterious effects, of the interactions between the incident shock waves and the reflected shock waves.
A conventional ceramic element typically has a flat parallelepiped or plate-like shape, with smooth and planar front and back faces that are parallel to each other. Upon impact by a projectile upon a conventional ceramic element, the resultant incident shock waves (commencing at the front face and generally directed toward the back face) and the consequent reflected shock waves (commencing at the back face and generally directed toward the front face) tend to meet each other inside the conventional ceramic element. Because of the relatively great number and intensities of these encounters between incident and reflected shock waves within the conventional ceramic element, the probability is relatively high of significant fracture of the conventional ceramic element.
In contrast, an inventive ceramic element is characterized by non-parallelism of the front and back faces. Upon impact by a projectile upon an inventive ceramic element, the resultant incident shock waves (commencing at the front face and generally directed toward the back face) and the consequent reflected shock waves (commencing at the back face and generally directed toward the front face) tend to both temporally and spatially diverge and thereby tend to avoid each other inside the conventional ceramic element. The reflected shock waves are incident shock waves that reflect from the back face; equivalently expressed, the reflected shock waves are incident shock waves that reflect from the interface between the back face and the matrix material in which the inventive ceramic element is embedded. Because of the relatively small number and intensities of these encounters between incident and reflected shock waves within the inventive ceramic element, the probability is relatively low of significant fracture of the inventive ceramic element. The sizes and shapes of the inventive ceramic elements are to some extent dictated by the threat(s) intended to be stopped by the inventive armor system.
By virtue of its unique geometric shape, an inventive ceramic element can control the propagation of shock waves associated with impact by a projectile. When an inventive ceramic element is impacted by a projectile, the inventive ceramic element controls the propagation of shock waves both within and behind the elastomeric matrix layer in which the inventive ceramic element is embedded. The inventive ceramic element slows down the propagation of shock wave energy so that, to the extent that the shock wave energy passes through the ceramic-embedded elastomeric matrix layer and reaches the backing layer (which is adjacent to and behind the ceramic-embedded elastomeric matrix layer), the backing layer is less susceptible to tearing or breaking.
Generally speaking, a backing in an armor system that is subjected to projectile impact fails upon the occurrence of either or both of the following circumstances: (i) the shock wave energy is so great that the backing cannot strain to a sufficient extent; (ii) the shock wave energy is so rapid (e.g., the backing is “pushed” so quickly) that the backing cannot strain at a sufficient rate. When the present invention's composite armor system, as typically embodied, is subjected to projectile impact, the time delay and reduced intensity of the shock waves that reach the backing permit the backing to sufficiently adapt, adjust and/or recover so to remain intact or at least substantially so.
As typically embodied, the present invention's layered composite material system of armor comprises a strike layer and a backing layer. The strike layer includes elastomeric matrix material and plural inventive ceramic-inclusive elements. The inventive ceramic-inclusive elements are embedded in the elastomeric matrix material and are arranged (e.g., in one or more rows and one or more columns) along a geometric plane corresponding to the front surface (initial strike surface) of the strike layer. More rigid than the strike layer, the backing layer is made of a rigid material such as a metallic (metal or metal alloy) material or a fiber-reinforced polymeric matrix material. Some inventive embodiments further comprise a spall-containment layer fronting the strike layer. The inventive ceramic-inclusive elements are geometrically configured in any of three inventive modes. The first inventive mode of ceramic-inclusive element has a flat front face and a textured back face. The second inventive mode of ceramic-inclusive element has a pyramidal front section and a prismatoidal (especially, prismoidal, e.g., truncated pyramidal or prismatic) body section. The hybrid mode of ceramic-inclusive element combines the textured back face geometry of the first inventive mode with the combined pyramidal-prismatoidal geometry of the second inventive mode.
Generally speaking, geometric terms used herein are defined as they are conventionally understood.
A “polyhedron” is a three-dimensional figure all of the faces (sides) of which are polygons.
A “prismatoid” is a polyhedron all of the vertices of which lie in one of two parallel planes. Types of prismatoids include pyramids and prismoids. Types of prismoids include pyramidal frustums and prisms.
A “pyramid” is a prismatoid having a polygonal base and at least three triangular faces that meet at a common point (“vertex” or, synonymously, “apex”). The apex, which is the common point of the triangular faces of a pyramid, lies in a first parallel plane of the pyramidal prismatoid; the polygonal base lies in a second parallel plane of the pyramidal prismatoid.
A “cone” is a geometric figure having a round (circular, elliptical, or oval) base, a vertex situated outside the plane of the base, and a continuously curved side narrowing to an apex (vertex). Geometrically speaking, a cone bears some analogy to a pyramid.
A “prismoid” is a prismatoid having two polygonal bases that have an equal number of sides. One polygonal bases lies in a first parallel plane of the pyramidal prismatoid; the other polygonal base lies in a second parallel plane of the pyramidal prismatoid. The lateral faces of a prismoid are quadrilaterals.
A “pyramidal frustum” (synonymously, “frustum of a pyramid”) is a prismoid the two polygonal bases of which are geometrically similar (but not geometrically congruent). Equivalently expressed, a pyramidal frustum is a “truncated pyramid,” i.e., a pyramid that is cut/sliced off below the apex along a plane parallel to the polygonal base of the pyramid. A pyramidal frustum can also be described as a “tapered prism,” i.e., a prism-like figure that is tapered (gradually decreases in size) from one polygonal base to the other polygonal base. The terms “truncated pyramid” and “tapered prism” are used synonymously herein with the term “pyramidal frustum.” A pyramidal frustum has a polygonal base and at least three trapezoidal faces that meet at the other polygonal base.
A “conical frustum” is a geometric figure that is a “truncated cone,” i.e., a cone that is cut/sliced off below the apex along a plane parallel to the round base of the cone. The terms “conical frustum,” “frustum of a cone”, and “truncated cone” are used synonymously herein. Geometrically speaking, a truncated cone bears some analogy to a truncated pyramid.
A “prism” is a prismoid the two polygonal bases of which are geometrically congruent. In other words, the two polygonal bases (which can also be referred to as the “ends” of the prism) are exactly the same size and shape, and the prism is the identical size and shape all the way through from one polygonal base to the other polygonal base. At least three parallelogram faces join the two polygonal bases.
The term “right” is used herein to describe terms such as “prismatoid,” “prismoid,” “pyramid,” “pyramidal frustum,” “cone,” “conical frustum,” and “prism.” The term “right” when used in such contexts connotes that a prismatoid is characterized, or approximately or generally characterized, by a geometric axis of symmetry, and that the axis is perpendicular to the one polygonal base (in the case of a pyramid) or the two polygonal bases (in the cases of a pyramidal frustum and a prism, each of which is a prismoid). All of the faces of a right prism are perpendicular to the polygonal bases.
A “regular pyramid” is a pyramid in which the polygonal base is a regular polygon. Similarly, a “regular prismoid” (e.g., “regular pyramidal frustum” or “regular prism”) is a prismoid in which the polygonal bases are regular polygons. A “regular polygon is a polygon all of the sides of which are equal length and all of the angles of which are equal size. Examples of regular polygons are regular triangles, regular quadrilaterals (parallelograms or rectangles), regular pentagons, regular hexagons, regular heptagons, regular octagons, etc.
Other objects, advantages and features of the present invention will become apparent from the following detailed description of the present invention when considered in conjunction with the accompanying drawings.
The present invention will now be described, by way of example, with reference to the accompanying drawings, wherein like numbers indicate same or similar parts or components, and wherein:
Referring now to
According to typical first-mode inventive practice, front face 110 is flat. The term “flat,” as used herein to describe a surface, means at least approximately smooth (even) and level so as to at least substantially lie in a geometric plane. A flat surface manifests itself in two dimensions, e.g., length and width. Also according to typical first-mode inventive practice, as distinguished from front face 110, back face 120 is not flat. A non-flat surface manifests itself in three dimensions, e.g., length, width and height.
As shown in
Examples of a one-dimensionally textured back face 120, are shown in plan view in
Examples of a two-dimensionally textured back face 1202 are shown in plan view in
The profile views shown in
A one-dimensionally textured surface describes variation in height in one direction. According to typical inventive practice, a one-dimensionally textured back face 1201 describes a pattern of ridges 121 and grooves 122 that are parallel to and alternate with each other (e.g., ridge-groove-ridge-groove-ridge-groove, etc.).
Examples of a one-dimensionally textured back face 1201 include, but are not limited to: triangular ridges and triangular grooves, such as shown in
A two-dimensionally textured back face 1202 describes variation in height in two perpendicular directions. According to typical inventive practice, a two-dimensionally textured back face 1202 describes an array of protuberances 123 and indentations 124. For instance, many inventive embodiments of two-dimensionally textured back face 1202 having an arrangement of protuberances 123 and indentations 124 in parallel rows and perpendicular columns (i.e., wherein parallel columns are perpendicular to parallel rows), thus describing a kind of “egg crate” pattern.
Examples of a two-dimensionally textured back face 1202 surface include, but are not limited to: adjacent rows and columns of pyramidal protuberances, each having four triangular sides and a rectangular (e.g., square) base, such as shown in
Both one-dimensionally textured back faces 1201 and two-dimensionally textured back faces 1202 are characterized by elevated surface areas and depressed surface areas. The present invention's one-dimensionally textured back faces 1201 typically have ridges 121 and grooves 122. The present invention's two-dimensionally textured back faces 1202 typically have protuberances 123 and indentations 124. Inventive practice lends itself to wide latitude in configuring textured back faces 1201 and 1202.
Note, for instance, the diverse possible shapes of protuberances 123 and indentations 124 in an inventive two-dimensionally textured back faces 1202, such as exemplified in
Inventive first-mode practice usually provides an inventive ceramic element 100 having a flat front face 110 and a textured back face 120 corresponding to respective parallel geometric planes. As illustrated in
Although typical inventive practice provides for flatness of front face 110 and texturing of back face 120, the texturing (one-dimensional texturing and/or two-dimensional texturing) of both front face 110 and back face 120, such as depicted in
The present invention's back face 120 is normally embodied as having a regular pattern of elevations and depressions, regardless of whether the texture is one-dimensional or two-dimensional along the geometric plane of back face 120. Shown in
According to some inventive embodiments, the imparting of a fractal character to the texturing of back face 120 may prove particularly propitious in furthering the shock wave-ameliorative qualities of inventive practice. Fractal mathematics is well known, and various applications thereof have been disclosed in the public literature. See, e.g., Gipple et al. U.S. Pat. No. 6,663,803 B1 issued 16 Dec. 2003, entitled “Fabrication of a Fractally Attributively Delamination Resistive Composite Structure,” incorporated herein by reference, and Gipple et al. U.S. Pat. No. 6,333,092 B1 issued 25 Dec. 2001, “entitled Fractal Interfacial Enhancement of Composite Delamination Resistance,” incorporated herein by reference, which disclose composite laminate structures characterized by a fractal interfacial profile.
As exemplified in
Nevertheless, depending on the inventive embodiment, an inventive first-mode ceramic element 100 can describe practically any plan form, curved and/or curvilinear and/or rectilinear—for instance, triangle, non-rectangular quadrilateral (e.g., trapezoid or parallelogram), polygon having five sides or greater, circle, oval (e.g., ellipse or ellipsoid or irregular oval), or some combination thereof. The plan form of an inventive first-mode ceramic element 100 is secondary to its elevation form, which entails the nature and degree of parallelism between its front face 110 and its back face 120, and which represents the primary inventive focus that improves the physical shock wave mechanism concomitant impacting thereof by a projectile such as a bullet, missile, or explosive fragment.
There is considerable variability in inventive first-mode practice as to how a textured back face 120 can be configured in terms of the sizes, shapes, and relationships (e.g., separations) of the elevated surface areas and depressed surface areas. Inventive first-mode practice admits of a variety of textures of inventive back face 120, both one-dimensionally textured back face 1201 and two-dimensionally textured back face 1202. Although two-dimensionally textured back face 1202 is variously shown by way of example in
Some inventive embodiments combine indicia of one-dimensional and two-dimensional texturing of back face 120, for instance by providing at least a first surface portion representing one-dimensionally textured back face 1201 and at least a second surface portion representing two-dimensionally textured back face 1202. The ordinarily skilled artisan who reads the instant disclosure will recognize that the present invention's textured back face 120 can be embodied as having any of multifarious textures other than those that are illustrated herein by way of example.
A practitioner of the present invention should base his/her selection of the values of the various geometric parameters (including scale, shape, and spacing) of the texture of back face 120 on consideration of the following factors, among others: the modulus of the material; the speed of the shock wave; and, the thickness of the inventive ceramic element 100. The texture of back face 120 is preferably designed such that the reflections of the incident shock waves will be disrupted because of the locally angled or curved surfaces, and such that the timings of the reflections will be dispersed because the incident shock waves will encounter back face 120 at locally different times as they progress through the textured region of back face 120. The overall result, when an inventively configured ceramic element 100 is impacted by a projectile, is a damping effect on the incident and reflected shock waves.
Reference is now made to
Inventive first-mode ceramic elements 100 are frequently practiced so that the inventive ceramic elements 100 are large enough that the inventive texturing of back face 120 imparts significant benefit in terms of determining shock wave propagation and interaction concomitant projectile impact. In contrast, inventive second-mode ceramic elements 200 are frequently practiced so that the inventive ceramic elements 200 are relatively small and are closely arranged so as to be tantamount to larger ceramic elements having qualities akin to those of inventive first-mode ceramic elements 100.
The shock wave attenuating attributes of an inventive second-mode ceramic element 200 array tend to be furthered when the inventive second-mode ceramic elements 200 are more tightly “packed” together, e.g., closely or contiguously arranged. The terms “areal density” and “areal packing density,” as used synonymously herein, denote mass per unit area, such as measured in the geometric plane of the front surface of an inventive composite armor system. The areal packing density of the inventive second-mode ceramic elements 200 should preferably be as complete as possible, minimizing small gaps between the inventive second-mode ceramic elements 200.
As shown in
The body section of an inventive second-mode or inventive hybrid-mode ceramic element has the geometric shape of a prismatoid having two parallel polygonal bases. Frequent inventive practice provides for second-mode or hybrid-mode ceramic elements having the geometric shape of a tapered prism (synonymously referred to herein as a truncated pyramid or a pyramidal frustum). Inventive practice sometimes provides for second-mode or hybrid-mode ceramic elements having the geometric shape of a prism, which is not tapered. A prism is a polyhedron having two congruent, parallel, opposite, polygonal bases and at least three parallelogram lateral faces. The lateral faces are formed by parallel straight lines connecting corresponding vertices of the bases. A tapered prism is a polyhedron having two similar, non-congruent, parallel, opposite, polygonal bases and at least three trapezoidal lateral faces. The lateral faces are formed by non-parallel straight lines connecting corresponding vertices of the bases. Otherwise expressed, a tapered prism is a prism that is gradually narrower or thinner toward one of the two bases.
The inventive second-mode ceramic element 200 depicted in side view in
Inventive ceramic element 200 is frequently embodied so as to be characterized by geometrical symmetry, for instance axial symmetry (with respect to a geometric axis a) or bilateral symmetry (with respect to a geometric plane passing through geometric axis a). A symmetrically configured inventive tapered-body ceramic element 200 is a regular polyhedral shape, characterized by axial or bilateral symmetry with respect to a geometric axis or plane passing through apex A. Nevertheless, symmetrical geometry is not necessary to inventive practice of ceramic element 200. For instance, the pyramidal front 240 can have unequal pyramidal faces 241 irregularly arranged so that apex A is “off-center,” e.g., skewed with respect to an imaginary central axis that extends through the tapered prismatic body section 250.
As shown in
Multifarious shapes of inventive tapered-body ceramic element 200 are possible in inventive practice, of which
Varieties and shapes differ among the inventive tapered-body ceramic elements 200 depicted in
The inventive hybrid-mode ceramic element 300 depicted in side view in
The textured back face 352 of inventive hybrid-mode ceramic element 300 is, practically speaking, the same textured surface as the textured back face 120 of inventive first-mode ceramic element 100, which is exemplified in
Inventive second-mode ceramic element 200 shown in
As distinguished from inventive tapered-body practice, inventive invertedly-tapered-body practice provides for angle β greater than ninety degrees and angle α less than ninety degrees. Inventive invertedly-tapered-body second-mode or third-mode practice is exemplified by
As distinguished from a tapered prismatic body 250, a “straight” (non-tapered) prismatic body 250R is purely prismatic. The tapered prismatic body 250 of typical inventive tapered-body practice consists of a polygonal back face 252 or 352 and at least three trapezoidal body faces 251. The straight (non-tapered) prismatic body 250R of typical inventive straight-body practice consists of a polygonal back face 252 or 352 and at least three rectangular body faces 251R. Frequent inventive practice provides for a geometric axis of symmetry (e.g., rotational or lateral symmetry), such as axis a shown in
Inventive second-mode elements 200 and 200R and inventive hybrid-mode elements 300 and 300R each have a rectilinear character. In contrast, with reference to
With reference to
According to typical inventive practice, elastic matrix material 1222 is an elastomeric material, such as a thermoset elastomer. The terms “elastomer” and “elastomeric,” as used herein, broadly refer to any material that is both polymeric and elastic, and are considered to include both natural (e.g., natural rubber) and synthetic (e.g., thermoset or thermoplastic) materials. Polyurethane and polyurea are two thermoset elastomers that will frequently be suitable for constituting the elastomeric matrix material 1222 in inventive practice, as polyurethane and polyurea are each characterized by high elongation-to-failure (strain-to-failure).
Illustrated in
Generally in inventive practice, the two essential layers of a inventive plural-layer armor system 1000 are the ceramic-embedded elastic matrix material layer 1002 and the backing layer 1001; in addition thereto, an inventive armor system 1000 can be embodied to include one or practically any plural number of additional layers or sub-layers of practically any material and configurational description, for instance metallic, fiber-reinforced polymer, or ceramic-embedded polymer. The inventive two-layer material armor system 10001′ shown in
As shown in
Accordingly, as shown in
The sole difference between the inventive three-layer material armor system 10001 shown in
The inventive second-mode ceramic elements 200 shown in
Upon subjection of an inventive composite material armor system 1000 to impact by a projectile (such as projectile 45 shown in
As previously pointed out herein, the spall-containment layer serves to contain flying debris, e.g., fragments of the projectile and/or the ceramic material.
The inventive ceramic element that is contacted by the projectile serves to blunt and/or break up the projectile. Moreover, as noted hereinabove and as further described hereinbelow, the contacted inventive ceramic element effects a physical mechanism that attenuates the shock waves internal to the inventive ceramic element, thereby reducing the extent of its fracture and improving its capability of blunting and/or breaking up the projectile. Furthermore, if and to the extent that the contacted inventive ceramic element fractures, it absorbs energy. If more than one inventive ceramic element is contacted by the projectile, each inventive ceramic element may behave similarly.
The elastic (e.g., elastomeric) matrix material absorbs energy and constrains the fractured inventive ceramic element(s), thereby imparting some continued, partial effectiveness of the fractured ceramic element(s). In addition, the elastic matrix material diffuses the shock resulting from the impact, thereby preventing the inventive ceramic elements near the impact area from fracturing; in this manner, the elastic matrix material preserves the ballistic capability of neighboring ceramic material for future impacts, i.e., a “multi-hit” capability.
The backing serves as a “catcher” to stop debris such as the broken pieces of the projectile and/or the ceramic material.
The elastic matrix material affords benefits other than those associated with projectile impact such as noted hereinabove. The elastic matrix material can serve as an adhesive for assembly of an inventive composite armor system 1000 and, due to its placement at the front thereof, can serve to protect the inventive ceramic elements from accidental damage during service (e.g., maintenance or repair).
The coupling of the inventive ceramic elements to the backing layer is generally an important aspect of inventive practice. In inventive first-mode ceramic element practice, the textured back face 120 of an inventive first-mode ceramic element 100 may not adhere to backing 1001 as well as desired if a conventional, unadulterated polymeric material (e.g., polyurethane or polyurea or some combination thereof) is used as the elastomeric matrix material 1222 of the ceramic-embedded elastomeric matrix layer 1002.
Instead of a conventional, unadulterated polymeric material, it may be advantageous to employ, as the elastomeric matrix material 1222, a filled polymeric material that incorporates metal filler particles and/or ceramic filler particles. Such a particle-filled elastomeric matrix material would represent a bonding material with higher stiffness (acoustic impedance) than would be necessary with flat back faces, such as those characterizing conventional ceramic elements, and such as those characterizing inventive second-mode ceramic elements 200.
Additionally or alternatively, a “leveling” fill material, such as a metallic material (e.g., aluminum) 99 shown in
With reference to
Reference is now made to
As shown in
As shown in
As shown in
In accordance with typical inventive composite armor systems such as shown in
With reference to
Ceramic-embedded heterogeneous polymeric matrix layer 9002 includes front-most sub-layer 9102, intermediate sub-layer 9202, and backmost sub-layer 9302. Like the inventive armor systems shown in
The sub-layers meet different performance requirements in furtherance of optimum performance of the armor system. Optimum performance is inventively obtained using polymeric materials exhibiting different properties in each of the three zones. The properties are engineered to manage the shock wave energy so as to reduce the damage in the vicinity of an impacted ceramic element, and so as to enhance the performance of the impacted ceramic element.
The front-most (strike-face) sub-layer, sub-layer 9102, consists of polymeric material 910. Polymeric material 910 serves to constrain the ceramic elements, contain spall, and limit lateral transmission of shock waves from ceramic elements to other, nearby ceramic elements. An example of a suitable polymeric material 910 for front-most sub-layer 9102 is a high elongation polyurea.
Behind front-most sub-layer 9102 is the intermediate sub-layer, sub-layer 9202, which is the ceramic-embedded polymeric matrix sub-layer. Intermediate sub-layer 9202 encompasses polymeric matrix material 920 and the ceramic elements, which are depicted as conventional ceramic elements 800 in
In intermediate sub-layer 9202, the interaction of the shock waves with the ceramic-polymer interfaces should be controlled precisely in order to balance transmission of shock waves into neighboring ceramic elements essentially in the following manner. On the one hand, the transmission of shock waves from impacted ceramic elements to proximate ceramic elements should be at energy levels sufficiently low to prevent damage to the proximate ceramic elements. On the other hand, the shock wave energy emanating from impacted ceramic elements should be as high as possible in order to disperse this impact energy over as large an area as possible.
Behind intermediate sub-layer 9202 is the backmost sub-layer, sub-layer 9302. Backmost sub-layer 9302 consists of polymeric material 930 and represents the region between the ceramic elements and the backing 1001. It is preferable that the acoustic impedance of polymeric material 930 be lower than that of the ceramic material and higher than that of the backing material, with a view toward permitting as much shock wave energy as possible to leave the ceramic elements without reflecting off of their back faces and causing destruction of the ceramic elements. An example of a suitable polymeric material 930 for backmost sub-layer 9302 is a higher modulus elastomer filled with solid particles (e.g., metal filler particles and/or ceramic filler particles) 939 such as shown in
The solid particulate quality of polymeric material 930 shown in
Inventive plural-layer armor systems are not necessarily embodied so as to have an entirely linear (straight) character, such as illustrated in
As illustrated in
The term “geometric plane,” as used herein specifically to indicate geometries relating to armor system layering (e.g., surfaces or interfaces of layers) or ceramic-inclusive element arrayal (e.g., front points or front surfaces of ceramic-inclusive elements of an array) in the context of inventive practice of plural-layer armor systems, broadly refers to a geometric plane that is straight in all directions or that is at least partially curved in at least one direction. Otherwise expressed, a “geometric plane,” in this specialized usage of the term, can be characterized by complete linearity, or by some degree of linearity and some degree of curvilinearity, or by complete curvilinearity. Regardless of the degree of curvature, if any, of an inventive armor system, its system layering and ceramic-inclusive element arrayal are configured so as to generally manifest parallelness, which can be expressed in terms of corresponding geometric planes.
Certain ceramic materials are known in the art to be suitable for use in armor applications. These conventional armor ceramics—which include aluminum oxide (commonly called “alumina”), silicon carbide, boron carbide, and titanium carbide—have been developed over the last thirty years or so, and represent the current state of the art. Inventive ceramic elements 100, 200, and 300 can each be made of any one, or any combination, of these “tried-and-true” conventional ceramic armor materials, with ceramic material preferences varying in accordance with particular inventive embodiments and applications. As alternatives to conventional ceramic materials, new materials may be suitable, and even advantageous, for some embodiments of the present invention. Inventive practice, such as of inventive armor systems 1000 and 9000, lends itself to use of diverse “ceramic-inclusive” materials.
One possibility for inventive practice of the inventive geometric ceramic elements, as an alternative to the above-mentioned conventional ceramic materials, is an aluminosilicate porcelain material. One of the present inventors, Curtis A. Martin, along with some colleagues of his, has investigated the possibility of using aluminosilicate porcelain as a ceramic armor material. Heretofore in conventional practice the above-noted conventional pure ceramic materials (aluminum oxide, silicon carbide, boron carbide, titanium carbide, etc.) have been relied upon for armor applications. Use of aluminosilicate porcelain is not known in the armor-related arts, as it has always been dismissed as an insufficiently strong ceramic material for use in armor applications.
Aluminosilicate porcelain has a density of 2.4 g/cm3, significantly less than the densities of: silicon carbide (3.2 g/cm3); 90% alumina (high alumina porcelain) (3.6 g/cm3); 99% alumina (3.95 g/cm3); and, titanium diboride (4.5 g/cm3). Because it is advantageous in terms of weight, cost and availability, present inventor Martin believes that aluminosilicate porcelain may be worthy of consideration, generally, as an alternative ceramic armor material to the conventional ones.
Present inventor Martin and colleagues have demonstrated that aluminosilicate porcelain elements can be efficaciously implemented as embedded in an elastomeric layer of a plural-layer composite armor material system. They assembled four experimental armor systems in which conventionally shaped (rectangular flat plate) tiles were embedded in elastomeric matrix material adjacent to steel (rolled homogeneous armor, or “RHA”) backing material. Each armor system was tested under identical circumstances in a ballistic range using a 20 mm fragment-simulating projectile. The four armor systems were made so as to be characterized by equal areal densities of the respective ceramic elements, wherein areal density was defined as mass per unit area measured in the frontal geometric plane of the armor system.
In the first armor system, aluminosilicate porcelain tiles arrayed in a single geometric plane were embedded in an elastomeric matrix layer adjacent to a steel backing layer. In the second armor system, aluminosilicate porcelain tiles arrayed in two parallel geometric planes were embedded in an elastomeric matrix layer adjacent to a steel backing layer. In the third armor system, 90% aluminum oxide tiles arrayed in a single geometric plane were embedded in an elastomeric matrix layer adjacent to a steel backing layer. In the fourth armor system, 99% aluminum oxide tiles arrayed in a single geometric plane were embedded in an elastomeric matrix layer adjacent to a steel backing layer.
Since the four armor systems were designed to have equal areal densities of the respective ceramic tiles, the thicknesses of the ceramic tiles and corresponding elastomeric matrix layers were rendered differently in accordance with the different physical densities of the ceramic tiles. That is, the 90% alumina tiles and corresponding elastomeric matrix layer of the third armor system were slightly thicker than the 99% alumina tiles and corresponding elastomeric matrix layer of the fourth armor system. The aluminosilicate porcelain tiles and two corresponding elastomeric matrix layers of the second armor system were significantly thicker than the 90% alumina tiles and corresponding elastomeric matrix layer of the third armor system; similarly, the, aluminosilicate porcelain tiles and single corresponding elastomeric matrix layer of the first armor system were significantly thicker than the 90% alumina tiles and corresponding elastomeric matrix layer of the third armor system.
The ballistic performances of the four armor systems were tested and compared in terms of “V50,” which was defined as the velocity at which 50% of the projectiles impacting an armor system at its frontal side will be stopped by the armor system. Velocity V50 was normalized to a maximum value of one hundred. It was demonstrated that the first and second armor systems (i.e., the two armor systems implementing aluminosilicate porcelain tiles) exhibited performances comparable to those of the third and fourth armor systems (i.e., the two armor systems implementing alumina tiles). The first, third and fourth armor systems obtained respective Velocity V50 scores of approximately 100. The second armor system obtained a Velocity V50 score of approximately 95. The somewhat lower Velocity V50 score for the second armor system's double-layer aluminosilicate porcelain tile-embedded matrix system may suggest some configurational superiority thereto of the first armor system's single-layer aluminosilicate porcelain tile-embedded matrix system.
It was thus experimentally demonstrated that lower density ceramic material can be used in these kinds of armor systems, with effectiveness equal to that of conventional ceramic materials, by providing a thicker overall ceramic-embedded matrix layer at the same areal density of the ceramic material (which is tantamount to saying at the same mass or weight of the ceramic material). The increased thickness of the aluminosilicate porcelain ceramic-embedded matrix layer compensates for the lesser intrinsic ballistic armor effectiveness of aluminosilicate porcelain material as compared with conventional armor ceramic materials.
Another intriguing and innovative possibility for inventive practice, conceived and investigated by present inventor Curtis A. Martin and colleagues, is a two-phase composite ceramic material composition consisting of chromium diboride and aluminum oxide.
By way of background, it was demonstrated several years ago that a two-phase composite ceramic material composition consisting of titanium diboride and aluminum oxide can exhibit enhanced ballistic resistance, as compared with ballistic resistance exhibited by aluminum oxide alone; see Gary A. Gilde et al., “Processing Aluminum Oxide/Titanium Diboride Composites for Penetration Resistance,” Ceramic Engineering and Science Proceedings, volume 22, number 3, pages 331-342 (2001), incorporated herein by reference. A significant drawback of the titanium diboride-aluminum oxide composite material disclosed by Gilde et al. is the necessity to prepare this composition by hot pressing, thus limiting practical application due to reduced production capacity and higher production cost.
It was previously demonstrated that a two-phase composite ceramic material composition consisting of chromium diboride and aluminum oxide possesses enhanced mechanical properties, as compared with mechanical properties of chromium diboride alone or of aluminum oxide alone; see Inna G. Talmy et al., “Ceramics in the CrB2-Al2O3System,” Ceramic Transactions, volume 74, pages 261-272 (1996), incorporated herein by reference. Talmy et al. disclose an increase in toughness and hardness in various “intermediate” compositions of chromium diboride-aluminum oxide, as compared with pure aluminum oxide or pure chromium diboride.
Both Talmy et al. and Gilde et al. disclose the making of their respective ceramic-ceramic composite materials via hot pressing. In general, the necessity to prepare a composition by hot pressing represents a significant drawback of that composition, as this limits practical application because of reduced production capacity and higher production cost. There is an advantage of the chromium diboride-aluminum oxide composition disclosed by Talmy et al., vis-à-vis the titanium diboride-aluminum oxide composition disclosed by Gilde et al., namely, because of limited solid solubility in a chromium diboride-aluminum oxide system, the hot pressing temperature is reduced as compared with that of a titanium diboride-aluminum oxide system. Notwithstanding possible cost-saving advantage of lower hot pressing temperature, as a practical matter neither Talmy et al's chromium diboride-aluminum oxide material nor Gilde et al.'s titanium diboride-aluminum oxide material holds significant promise for armor applications.
A significant advantage, recently discovered by present inventor Martin along with Inna G. Talmy and James Zaykoski, is the fact that some compositions of chromium diboride-aluminum oxide—especially, those that consist predominantly of aluminum oxide—can be pressureless sintered. Generally speaking, pressureless sintering is a less expensive processing methodology than hot pressing. With its promise of reduced cost and increased availability, Martin, Talmy, and Zaykoski's chromium diboride-aluminum oxide materials manufactured via pressureless sintering has greater potential than many materials manufactured via hot pressing. By virtue of this processing improvement (i.e., pressureless sintering production vice hot pressing production) and its favorable mechanical properties, a pressureless sintered chromium diboride-aluminum oxide system is an attractive material for use as armor (e.g., ballistic armor) ceramic, particularly in lieu of hot pressed materials.
The afore-noted conventional ceramic armor materials (e.g., aluminum oxide, silicon carbide, boron carbide, titanium carbide) represent pure ceramic materials. The afore-noted unconventional ceramic armor material (aluminosilicate porcelain), as well, represents a pure ceramic material. The afore-noted chromium diboride-aluminum oxide composition represents a completely ceramic composite material system consisting of two different pure ceramic material phases. Inventive practice does not require that the inventive ceramic elements be composed of a pure ceramic material or a completely ceramic composite material. Instead, according to inventive practice, the inventive ceramic elements can be composite articles that consist of at least one ceramic material and at least one non-ceramic material.
Although the present invention is typically practiced whereby the inventive ceramic elements are made of conventional ceramic armor material, inventive practice permits a wide variety of ceramic-inclusive material compositions for the inventive ceramic elements. The term “ceramic-inclusive material,” as used herein, denotes any material that includes at least one ceramic material. Generally as defined herein, a ceramic-inclusive material can fall into any of three categories, viz., (a) a ceramic material, (b) a ceramic-ceramic composite material, and (c) a ceramic-non-ceramic composite material. A ceramic material consists of a “pure” ceramic material, i.e., a single, completely ceramic material. A ceramic-ceramic composite material consists of at least two different ceramic materials. A ceramic-non-ceramic composite material consists of at least one ceramic material and at least one non-ceramic material. For instance, a ceramic-ceramic composite material can consist of three different ceramic materials. As another example, a ceramic-non-ceramic composite material can consist of two different ceramic materials and two different non-ceramic materials. And so on . . . .
In the realm of ceramic-non-ceramic composite materials, joint inventor Martin has conceived interesting possibilities of using, for ballistic armor applications, various types of composites that combine ceramic materials with metal materials, glass materials, and/or polymeric materials. Conventional ceramic armor materials do not lend themselves to preparation in complex shapes. In contrast, according to joint inventor Martin's conceptions, a reaction-bonded ceramic material such as reaction-bonded silicon nitride (RBSN) is prepared rather easily in a complex shape such as a helmet shape or vest shape, and the specially shaped reaction-bonded ceramic (e.g., RBSN) preform is then readily infiltrated with at least one selected non-ceramic infiltrator material from among one or more of three categories of non-ceramic infiltrator material, viz., (i) metal, (ii) polymeri (e.g., elastomer), and (iii) glass. Advantageously, such a ceramic-non-ceramic composite of Martin can exhibit reduced density, and therefore reduced weight, because it is constituted as if part of the ceramic material has been replaced with less dense material; in effect, a metal (especially, a light metal such as aluminum), a polymer (e.g., elastomer), or a glass has been substituted for a portion of the total volume of the ceramic.
Techniques are known for making certain kinds of ceramic-metal composites. One previously disclosed methodology for creating a ceramic-metal composite involves the combination of ceramic powder with a metal component through dispersion of ceramic powder into the melted metal component. Another previously disclosed methodology for preparing a ceramic-metal composite involves the partial sintering of ceramic material to obtain a porous ceramic body, followed by melt infiltration of the porous ceramic body with a metal.
The following United States patents, incorporated herein by reference, are instructive on methods for making ceramic-metal composite materials: Claussen et al. U.S. Pat. No. 6,573,210 B1 issued 3 Jun. 2003; Claussen et al. U.S. Pat. No. 6,051,277 issued 18 Apr. 2000; Claussen et al. U.S. Pat. No. 6,025,065 issued 15 Feb. 2000; Claussen U.S. Pat. No. 5,843,859 issued 1 Dec. 1998; Claussen U.S. Pat. No. 5,607,630 issued 4 Mar. 1997; Claussen U.S. Pat. No. 5,326,519 issued 5 Jul. 1994; Claussen et al. U.S. Pat. No. 5,158,916 issued 27 Oct. 1992; Claussen et al. U.S. Pat. No. 4,908,171 issued 13 Mar. 1990; Claussen et al. U.S. Pat. No. 4,900,492 issued 13 Feb. 1990; Claussen et al. U.S. Pat. No. Re. 32,449 reissued 30 Jun. 1987; Claussen et al. U.S. Pat. No. 4,525,464 issued 25 Jun. 1985; Aghajanian et al. U.S. Pat. No. 7,197,972 B2 issued 3 Apr. 2007; Benitsch U.S. Pat. No. 7,128,963 B2 issued 31 Oct. 2006; Aghajanian et al. U.S. Pat. No. 7,104,177 B1 issued 12 Sep. 2006; Aghajanian et al. U.S. Pat. No. 6,995,103 B2 issued 7 Feb. 2006; Aghajanian et al. U.S. Pat. No. 6,862,970 B2 issued 8 Mar. 2005; Karandikar et al. U.S. Patent Application Publication No. 2004/0238794 A1 published 2 Dec. 2004; McCormick et al. U.S. Pat. No. 6,805,034 B1 issued 19 Oct. 2004; McCormick et al. U.S. Pat. No. 6,609,452 B1 issued 26 Aug. 2003.
The following two references disclose RBSN-metal composites. Nils Claussen et al., “Squeeze Cast β-Si3N4—Al Composites,” Advanced Engineering Materials, volume 4, number 3, pages 117-119 (2002), incorporated herein by reference, disclose infiltration (referred to by Claussen et al. as “squeeze casting”) of a conventional aluminum alloy into a porous reaction-bonded silicon nitride (Si3N4) preform to produce a β-Si3N4—Al composite exhibiting excellent mechanical properties. N. A. Travitzky and N. Claussen, “Microstructure and Properties of Metal Infiltrated RBSN Composites,” Journal Of The European Ceramics Society, volume 9, number 1, pages 61-65 (1992), incorporated herein by reference, disclose gas-pressure infiltration of RBSN with one of four different metallic materials—viz., aluminum (Al), with an aluminum alloy (Al—Mg—Si—Zn), titanium-aluminum (Ti—Al) intermetallic, and silicon (Si)—thus producing four different RBSN-metal composites.
A reaction-bonded silicon nitride (RBSN) “preform” can be prepared by forming a “green body” of silicon particles (e.g., by pressing or slip-casting), and then reacting the green body with nitrogen or nitrogen-bearing gas (such as ammonia), resulting in conversion of silicon particles to silicon nitride grains. The RBSN material perform thus produced is necessarily porous; it can never be pore-free (fully dense). It is possible to control the porosity (and therefore the density) of the RBSN by controlling the “green density.”
Claussen et al., Advanced Engineering Materials, prepared aluminum—silicon nitride composites, measured flexural strengths, and found that flexural strength was dramatically increased by infiltration of Si3N4 with Al. Present inventor Martin has conceived the infiltration into RBSN preforms of non-ceramic materials such as polymeric materials or glass materials. It is believed by Martin that the infiltration of such materials into RBSN preforms will yield similar increases in flexural strength. Moreover, regardless of whether the porosity of RBSN is filled with a metal, a glass, or a polymer, a pore-free material would result, having a lower overall density than fully dense silicon nitride, and having a significantly lower density than alumina.
Present inventor Martin believes that RBSN materials hold promise for armor applications. The silicon nitride grains in RBSN are interlocked and well-bonded; in fact, the bonding between the grains in RBSN is stronger than that of partially sintered ceramics. Based on the varying strengths for varying porosities of RBSN as reported by the afore-noted Claussen et al., Advanced Engineering Materials, the flexural strength of porous RBSN with more than 40% porosity can be over 250 Mpa, which is as strong as fully dense 90% alumina, a common armor material.
Accordingly, present inventor Martin's novel lightweight ceramic-non-ceramic-infiltrated RBSN preform composite materials, and novel methods of making same, are believed to be suitable for ballistic armor applications. Featured by Martin's new ceramic-non-ceramic composite materials is the infiltration of a metallic material and/or a polymeric material and/or a glass material into a reaction-bonded porous ceramic such as a reaction-bonded silicon nitride (“RBSN”). More specifically, previously unknown are Martin's RBSN-glass composites, RBSN-polymer composites, RBSN-glass-polymer composites, RBSN-metal-polymer composites, RBSN-metal-glass composites, and RBSN-metal-polymer-glass composites.
Infiltration of a reaction-bonded ceramic preform can be accomplished without great difficulty. To make a ceramic-metal-infiltrated RBSN preform composite, the impregnation of RBSN by a metal can be accomplished via pressure melt infiltration of a metallic (metal or metal alloy) material. Pressureless melt infiltration may be possible with the right surface chemistry. To make a polymer-metal-infiltrated RBSN preform composite, the impregnation of RBSN by a polymer can be accomplished via melt infiltration or vacuum/pressure infiltration of a thermoset polymeric material. To make a polymer-glass-infiltrated RBSN preform composite, the impregnation of RBSN by a glass can be accomplished via melt infiltration of a glass material.
The unique ceramic-non-ceramic-infiltrated RBSN preform composite—e.g., a ceramic-metal infiltrated RBSN preform composite or a ceramic-polymer infiltrated RBSN preform composite or a ceramic-glass infiltrated RBSN preform composite—may be particularly suitable for light weight armor applications (such as personal/personnel armor applications, e.g., body armor or armored helmets) for which weight is critical but at the same time the need exists to increase the level of protection to cover more aggressive fragments and other projectiles. Currently, ground troops are outfitted with a polymer composite helmet that is capable of stopping handgun threats.
In theory, a helmet made of a ceramic material could provide greater resistance to projectile impact than what is currently used. In practice, however, helmets represent especially difficult applications for ceramic armor because of both weight restriction and specialized shape. Ceramic armor materials of more advanced capability are prepared most often by hot pressing, a method that is not suitable for preparation of an article of complex shape such as a helmet. By comparison, reaction bonded silicon nitride can be prepared easily in a helmet shape, as evidenced by the current production of automotive turbocharger rotors and jet engine components. The helmet-shaped RBSN perform can be readily infiltrated with the selected (e.g., metal, polymer, or glass) material.
This application is related to the U.S. provisional patent application being concurrently filed herewith, hereby incorporated herein by reference, invention title “Ballistic Armor Methods, Systems and Materials,” joint inventors Curtis A. Martin, Gilbert F. Lee, Jeffrey J. Fedderly, David E. Johnson, David P. Owen, Rodney O. Peterson, Philip J. Dudt, James A. Zaykoski, and Inna G. Talmy. This application is also related to the U.S. nonprovisional patent application being concurrently filed herewith, hereby incorporated herein by reference, invention title “Ballistic Armor Methodology Using Low-Density Ceramic Material,” joint inventors Curtis A. Martin, David E. Johnson, David P. Owen, Rodney O. Peterson, and Philip J. Dudt.
The present invention, which is disclosed herein, is not to be limited by the embodiments described or illustrated herein, which are given by way of example and not of limitation. Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of the instant disclosure or from practice of the present invention. Various omissions, modifications and changes to the principles disclosed herein may be made by one skilled in the art without departing from the true scope and spirit of the present invention, which is indicated by the following claims.
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.
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