Patent Application
20110113950
1. Field of the Invention
The present invention relates to a composite material. In particular, the present invention relates to a composite material suitable for use as an armor.
2. Description of Related Art
In combat situations, such as in military, police, and/or armored transport operations, it is desirable to protect vehicles, such as tanks, personnel carriers, trucks, and the like, as well as the vehicle's contents from damage by enemy fire. Accordingly, such vehicles are known to have armor to reduce the likelihood that ballistic rounds or other such projectiles will penetrate the vehicle. If the rounds penetrate the vehicle, the occupants of the vehicle may be injured or the vehicle's ability to operate may be impaired. It may also be desirable for the armor to be able to survive multiple rounds striking the armor in close proximity to one another, so that the integrity of the vehicle is not compromised or is only minimally compromised. Moreover, it is generally desirable for armor to include a relatively hard outer layer that the round encounters first. The hard outer layer starts the projectile or round defeat sequence by increasing the projectile dwell time on the armor, thus slowing the projectile down, or by blunting or fracturing the projectile early in the penetration event.
While protecting the vehicle and its occupants is generally of primary importance, other factors may play a role in the design of armor for the vehicle. It is desirable for the vehicle to be as lightweight as possible. Generally, a vehicle's fuel consumption increases as the vehicle's weight increases. A heavier vehicle usually requires a heavier drive train than a lighter vehicle, which further increases weight. Increased weight may also reduce the mobility of the vehicle and, thus, reduce the utility of the vehicle in combat. As the weight of the vehicle's armor contributes to the overall weight of the vehicle, it is desirable for the vehicle's armor to be as lightweight as possible. Many known armor systems, while protecting the vehicle from ballistic damage, add significant weight to the vehicle and provide little or no additional structural strength to the vehicle.
It is also not desirable for the vehicle's armor to greatly increase the overall size of the vehicle (e.g., the vehicle's height, width, length, volume, and the like), so that existing transportation equipment (e.g., trucks, trailers, aircraft, and the like) are capable of transporting the vehicle. If the size of the vehicle is increased over previous vehicles, the existing transportation equipment may not be capable of transporting the vehicle, or the existing transportation equipment may be limited to carrying fewer vehicles per load. Additionally, it is desirable to maximize the internal volume of the vehicle to allow adequate space to house the crew and crew gear. Accordingly, armor having lower volumes generally result in vehicle designs having larger internal volumes. The overall size of the vehicle is also a factor in combat situations. Generally, smaller targets (i.e., smaller vehicles) are more difficult to hit with artillery, such as rockets, mortars, missiles, and the like. Thus, it is desirable for the vehicle's overall size to be smaller, rather than larger, to reduce the likelihood of an artillery hit.
It is also desirable that the vehicle's armor be durable. During combat and during travel between combat locations, the vehicle may encounter flying rocks, debris, shrapnel, and the like. If the armor is overly thin or brittle, it may not be capable of surviving impacts from such sources.
Cost is also a consideration in vehicle armor. Armor that uses exotic materials (e.g., laminated ceramics of boron carbide, silicon carbide, and alumina; fiberglass/epoxy laminates; fiberglass/phenolic laminates; and the like), or armor that has many components in difficult-to-produce configurations, may be quite effective in combat but may be unaffordable.
Other applications exist for materials that are suitable for use as armor. Specifically, such materials may also be suitable as wear-resistant materials in high-wear applications. For example, armor materials may be suitable for use in equipment used in oilfield and/or gasfield operations, such as in drill pipe fixtures.
There are many designs of materials that are useful as armors and that are well known in the art; however, considerable shortcomings remain.
There is a need for a composite structure that is useful as an armor.
Therefore, it is an object of the present invention to provide a composite structure that is useful as an armor.
These and other objects are achieved by providing, in one aspect, a composite material suitable for use as an armor, including a first layer of a metallic material, metallurgically bonded with the first layer. The second layer includes a matrix of the material of the first layer and a plurality of brittle particles dispersed in the matrix.
In another aspect, the present invention provides an armor, including a first layer made of a material selected from the group consisting of titanium and titanium alloys and a second layer metallurgically bonded to the first layer. The second layer includes a matrix made of the material of the first layer and a plurality of particles dispersed in the matrix.
In yet another aspect of the present invention, a method for making a composite structure suitable for use as an armor from a workpiece of a metallic material is provided. The method includes the steps of plasticizing a fractional thickness of the workpiece using a friction stir process, introducing a plurality of brittle particles into the plasticized, fractional thickness of the workpiece, and dispersing the plurality of brittle particles into the plasticized, fractional thickness of the workpiece using the friction stir process.
The present invention provides significant advantages, including: (1) providing a material, useful as an armor, that is lighter in weight than conventional armor; (2) providing a material, useful as an armor, that occupies less volume than conventional armor; (3) providing a material, useful as an armor, that is less expensive to produce than conventional, light-weight armors; and (4) providing a lower-cost means for forming an integral, hard, outer layer on a metallic structure.
Additional objectives, features and advantages will be apparent in the written description which follows.
The novel features believed characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as, a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numerals denote(s) the first figure in which the respective reference numerals appear, wherein:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
It should be appreciated that the following terms and phrases are intended to have a particular meaning throughout the following detailed description: The term “composite structure” refers to a structure made from two or more constituent materials that remain separate and distinct on a macroscopic level while forming a single component. The term “brittle particles” is intended to refer to particles comprising a material that, when stressed, tend to fracture before any substantial plastic deformation takes place. The term “metallurgically bonded” refers to the bonding within metals, which involves the delocalized sharing of free electrons within a lattice of metal atoms. The term “mixture” is intended to refer to a chemical substance comprising two or more materials, in a homogeneous or heterogeneous association, without chemical bonding of elements and/or compounds, such that the materials retain their own individual properties and makeup.
The present invention represents to a composite material or structure suitable for use as a ballistic armor comprising a first layer of a metallic material and a second layer, such that the second layer is metallurgically bonded to the first layer along an interface. The second layer comprises a plurality of brittle particles dispersed in a matrix. The particles act to increase the outer layer hardness of the composite structure. Specifically, the matrix, which comprises the same material as the first layer, is metallurgically bonded to the first layer along the interface. In one embodiment, which is particularly useful as an armor, the first layer and the matrix comprise a metallic material having a specific gravity of at least about four grams per cubic centimeter. Preferably, the second layer is a mixture of the metallic material of the first layer and the plurality of particles. Moreover, it is preferable for the plurality of brittle particles to comprise chemical elements that do not readily chemically combine with the material of the matrix. While the structure of the present invention has many applications, the structure is particularly useful as an armor to inhibit the penetration of ballistic projectiles. In such armor applications, materials having a specific gravity of at least about four grams per cubic centimeter are particularly useful as the first layer and the matrix of the second layer.
Preferably, the structure of the present invention is produced using friction stir processing, in which a fractional thickness of a precursor, comprising a metallic material having a specific gravity of at least about four grams per cubic centimeter, is frictionally heated to a plastic but non-molten state by a rotating, non-consumable tool. The non-consumable tool disperses the plurality of brittle particles into the frictionally-heated, plastic portion of the precursor. Thus, the plurality of brittle particles is dispersed in a matrix of the frictionally-heated portion of the precursor. Upon cooling, the plurality of brittle particles dispersed in the matrix comprising the frictionally-heated portion of the precursor becomes the second layer. The fractional thickness of the precursor that was not heated to a plastic state by the rotating tool is the first layer, which is metallurgically bonded to the second layer.
In one particular embodiment wherein structure 101 is used as an armor, a thickness t of second layer 105 is within a range of about two percent of a total thickness T of structure 101 to about 20 percent of total thickness T of structure 101. The scope of the present invention, however, is not so limited. Rather, thickness t of second layer 105 may be only a miniscule portion of thickness T of structure 101, may approach thickness T, or may be any suitable portion of thickness T depending upon the implementation of structure 101. It should be noted, however, that thickness t of second layer 105 may vary across structure 101.
While structure 101 is illustrated in
Furthermore, it is preferable, in armor applications, for brittle particles 301 to comprise a volume fraction of second layer 105 within a range of about one percent to about 30 percent, although embodiments of structure 101 having other volume fractions of brittle particles may be very effective in armor applications. Accordingly, the scope of the present invention includes any suitable volume fraction of brittle particles 301 in second layer 105, depending upon the implementation. Moreover, the volume fraction of brittle particles entrained in second layer 105 may vary across structure 101, depending upon the implementation of structure 101. Preferably, matrix 303 has an average grain size that is smaller than an average grain size of first layer 103. It should also be noted that second layer 105, and, thus, matrix 303, may or may not extend continuously across a part or first layer 103, depending upon the implementation of structure 101.
Preferably, structure 101 is formed using a friction stir process. Generally, friction stir processes engage a rotating, non-consumable tool with a stationary workpiece to plasticize, but not melt, a fractional thickness of the workpiece. Typically, friction stir processes are used to weld adjacent portions of a workpiece. According to the present invention, however, a friction stir process is utilized to plasticize a fractional thickness of a workpiece and to disperse a plurality of brittle particles into the plasticized volume of the workpiece. It should be noted, however, that, while the friction stir tool is not designed to transfer material from the friction stir tool into the plasticized, fractional thickness of the workpiece, in some situations minute portions of the friction stir tool may indeed be transferred into the plasticized, fractional thickness of the workpiece. Thus, a friction stir tool of the present invention is considered “non-consumable”, even though minute portions of the tool are transferred into the plasticized, fractional thickness of the workpiece.
Specifically, as shown in
Still referring to
As disclosed above, the plurality of brittle particles is introduced into the plasticized portion of workpiece 411. In one particular embodiment, depicted in
Irrespective of the means for introducing the plurality of brittle particles into the plasticized portion of workpiece 411, according to the present invention, tool 401 is traversed across a desired area of workpiece 411 in which second layer 105 (shown in
It should be noted that, in some embodiments, friction stir processing refines the grain size of the metallic grains comprising the plasticized portion of workpiece 411. Accordingly, the resulting solid state portion 421 (and thus matrix 303) exhibits an average grain size that is less than an average grain size of first layer 103, since first layer 103 was not subjected to friction stir processing.
It should also be noted that the scope of the present invention is not limited to the particular configuration of tool 401. For example, in some embodiments, pin 405 may define circumferential threads or other such features to promote mixing of the plurality of particles into the plasticized portion of workpiece 411, to enhance the transfer of plasticized material of the workpiece from leading edge 415 of tool 401 toward trailing edge 417 of tool 401, and/or to generally enhance the friction stir process. Moreover, the particular shape of tool 401, shoulder 403, and/or pin 405 is implementation specific and, thus, shapes other than those shown in
Other means for introducing the plurality of brittle particles into the plasticized portion of a workpiece are contemplated by the present invention. For example, the plurality of brittle particles may be introduced into the plasticized portion of a workpiece via a passageway defined by a friction stir tool, such as friction stir welding tools 302, 402, 502, 602, 1102, or 1202 of commonly-assigned U.S. Pat. No. 6,543,671 to Hatten et al., entitled “Apparatus and Method for Friction Stir Welding Using Filler Material”, which is incorporated by reference herein for all purposes. Moreover, a workpiece or precursor, such as workpiece 411, may define or comprise other features for retaining the plurality of particles, such that the plurality of particles are incorporated into the plasticized portion of the workpiece or precursor by a friction stir processing tool, such as tool 401.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. It is apparent that an invention with significant advantages has been described and illustrated. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof.
