Patent Application
20070277914
The following detailed description of preferred embodiments can be read in connection with the accompanying drawings in which like numerals designate like elements and in which:
Patent Attorney's Docket No. 1017750-000896
An outer skin or shroud 30 encloses at least portions of the booster motor 20 and the penetrator 10, and provides an aerodynamic shape. The mounting structure holding the penetrator 10 to the rocket booster motor 20 and the shroud 30 must be capable of supporting the penetrator 10, especially during the boost phase (when the rocket is firing), but also to release the penetrator a target impact with a minimal loss of kinetic energy. Such mounting structures may include circular clamps or pads, one of which being illustrated as element 33.
The munition may further include a guidance and control unit 40 including an onboard computer and navigation system. The guidance and control unit 40 may further include sensors, such as accelerometers, to detect the lateral acceleration of the munition. Control vanes, such as nose wings 42 and tail fins 50, are controllable by the unit 40 to steer the bomb. The munition may further comprise a global positioning system (GPS) receiver 44.
According to the present invention, one or more structural components of a munition or munitions system can be formed, at least in part, by a composite material comprising a energetic material dispersed in a metallic binder material. The one or more structural components can be formed in their entirety by the composite material of the present invention. Alternatively, structural components can be formed as hybrid components partially formed of the composite material of the present invention, and partly formed from an unreactive material.
As illustrated in
The binder material 120 can be formed from any suitable metal or combination of metals and/or alloys. According to one embodiment, the binder material 120 comprises a metal or alloy that when combined with the reactive component (or components), the pressure used to compact and densify the structure is of magnitude below that causing autoignition of the reactive materials. According to a further embodiment, the binder material 120 comprises one or more of: bismuth, lead, tin, aluminum, magnesium, titanium, gallium, indium, and alloys thereof. By way of non-limiting example, suitable binder alloys include (percentages are by mass): 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60% Sn/40% Bi; 95% Bi/5% Sn; 55% Ge; 45% Al; 88.3% Al/11.7% Si; 92.5% Al/7.5% Si; and 95% Al/5% Is. In addition, the binder material 120 may optionally include one or more reinforcing elements or additives. Thus, the binder material 120 may optionally include one or more of: an organic material, an inorganic material, a metastable intermolecular compound, and/or a hydride. By way of non-limiting example, one suitable additive could be a polymeric material that releases a gas upon thermal decomposition. The composite can also be reinforced by adding one or more of the following organic and/or inorganic reinforcements: continuous fibers, chopped fibers, whiskers, filaments, a structural preform, a woven fibrous material, a dispersed particulate, or a nonwoven fibrous material. Other suitable reinforcements are contemplated.
The binder material 120 of the present invention may be provided with any suitable density. For example, the binder material 120 of the present invention may be provided with the density of at least about 10.0 g/cm3. According to a further embodiment, the binder material 120 of the present invention is provided with a density of about 1.7 g/cm3 to about 14.0 g/cm3.
Component 100 may contain any suitable energetic material 130, which is dispersed within the metallic binder material 120. The volumetric proportion of metal binder with respect to reactive materials may be in the range of 20 to 80%, with the remainder of the fragment being comprised of reactive materials. The detonable energetic material 130 may have any suitable morphology (i.e., powder, flake, crystal, etc.) or composition.
The energetic material 130 may comprise a material, or combination of materials, which upon reaction, release enthalpic or work-producing energy. One example of such a reaction is called a “thermite” reaction. Such reactions can be generally characterized as a reaction between a metal oxide and a reducing metal which upon reaction produces a metal, a different oxide, and energy. There are numerous possible metal oxide and reducing metals which can be utilized to form such reaction products. Suitable combinations include but are not limited to, mixtures of aluminum and copper oxide, aluminum and tungsten oxide, magnesium hydride and copper oxide, magnesium hydride and tungsten oxide, tantalum and copper oxide, titanium hydride and copper oxide, and thin films of aluminum and copper oxide. A generalized formula for the stoichiometry of this reaction can be represented as follows:
MxOy+Mz=Mx+MzOy+Energy
wherein MxOy is any of several possible metal oxides, M, is any of several possible reducing metals, Mx is the metal liberated from the original metal oxide, and MzOy is a new metal oxide formed by the reaction. Thus, according to the principles of the present invention, the energetic material 130 may comprise any suitable combination of metal oxide and reducing metal which as described above. For purposes of illustration, suitable metal oxides include: La2O3, AgO, ThO2, SrO, ZrO2, UO2, BaO, CeO2, B2O3, SiO2, V2O5, Ta2O5, NiO, Ni2O3, Cr2O3, MoO3, P2O5, SnO2, WO2, WO3, Fe3O4, MoO3, NiO, CoO, Co3O4, Sb2O3, PbO, Fe2O3, Bi2O3, MnO2 Cu2O, and CuO. For purposes of illustration, suitable reducing metals include: Al, Zr, Th, Ca, Mg, U, B, Ce, Be, Ti, Ta, Hf, and La. The reducing metal may also be in the form of an alloy or intermetallic compound of the above. For purposes of illustration, the metal oxide is an oxide of a transition metal. According to another example, the metal oxide is a copper or tungsten oxide. According to another alternative example, the reducing metal comprises aluminum or an aluminum-containing compound.
As noted above, the energetic material components 130 may have any suitable morphology. Thus, the energetic material 130 may comprise a mixture of fine powders of one or more of the above-mentioned metal oxides and one or more of the reducing metals. This mixture of powders may be dispersed in the metal binder 20. According to certain embodiments, the metal binder 20 acts as a partial or complete source of metal fuel for the energetic, or thermite, reaction.
Alternatively, as schematically illustrated in
The structural component 100 of the present invention can be formed according to any suitable method or technique.
Generally speaking, a suitable method for forming a structural component of the present invention includes forming an energetic material, combining the energetic material with a metallic binder material to form a mixture, and shaping the combined energetic material and metallic binder material mixture to form a composite structural component.
The energetic material can be formed according to any suitable method or technique. For example, when the energetic material is in the form of a thin film, as mentioned above, the thin-film detonable energetic material can be formed as follows. The alternating layers of oxide and reducing metal are deposited on a substrate using a suitable technique, such as vacuum vapor deposition or magnetron sputtering. Other techniques include mechanical rolling and ball milling to produce layered structures that are structurally similar to those produce in vacuum deposition. The deposition or fabrication processes are controlled to provide the desired layer thickness, typically on the order of about 10 to about 1000 nm. The thin-film comprising the above-mentioned alternating layers is then removed form the substrate. Removable can be accomplished by a number of suitable techniques such as photoresist coated substrate lift-off, preferential dissolution of coated substrates, and thermal stock of coating and substrate to cause film delamination. According to one embodiment, the inherent strain at the interface between the substrate and the deposited thin film is such that the thin-film will flake off the substrate with minimal or no effort.
The removed layered material is then reduced in size; preferably, in a manner such that the pieces of thin-film having a reduced size are also substantially uniform. A number of suitable techniques can be utilized to accomplish this. For example, the pieces of thin-film removed from a substrate can be worked to pass them through a screen having a desired mesh size. By way of non-limiting example, a 25-60 size mesh screen can be utilized for this purpose. This accomplishes both objectives of reducing the size of the pieces of thin-film removed from the substrate, and rendering the size of these pieces substantially uniform.
The above-mentioned reduced-size pieces of thin layered film are then combined with metallic matrix or binder material to form a mixture. The metallic binder material can be selected from many of the above-mentioned binder materials. This combination can be accomplished by any suitable technique, such as milling or blending. Additives or additional components can be added to the mixture. As noted above, such additives or additional components may comprise one or more of: an organic material, and inorganic material, a metastable intermolecular compound, and/or a hydride In addition, one or more reinforcements may also be added. Such reinforcements may include organic and/or inorganic materials in the form of one or more of: continuous fibers, chopped fibers, whiskers, filaments, a structural preform, dispersed particulate, a woven fibrous material, or a nonwoven fibrous material. Optionally, the pieces of layered film, the metallic binder material, the above-mentioned additives and/or the above-mentioned reinforcements can be treated in a manner that functionalizes the surface(s) thereof, thereby promoting wetting of the pieces of thin-film in the matrix of metallic binder. Such treatments are per se known in the art. For example, the particles can be coated with a material that imparts a favorable surface energy thereto.
This mixture can then be shaped thereby forming a structural component having a desired geometrical configuration. The structural component can be shaped by any suitable technique, such as molding or casting, pressing, forging, cold isostatic pressing, hot isostatic pressing. As noted above, the structural component can be provided with any suitable geometry
As explained above, there are number of potential applications for a structural components according to principles of the present invention. Non-limiting exemplary weapons and/or weapons systems which may incorporate composite structural components formed according to the principles of the present invention include a BLU-109 warhead or other munition such as BLU-109/B, BLU-113, BLU-116, JASSM-1000, J-1000, and the JAST-1000.
One advantage of a structural component formed according to principles of the present invention is that both the composition and/or morphology of the reactive material 130 can be used to tailor the sensitivity of the reactive structural component to impact forces. While the total chemical energy content of the reactive material is primarily a function of the quantity of the reducing metal and metal oxide constituents, the rate at which that energy is released is a function of the arrangement of the reducing metal and metal oxide relative to one another. For instance, the greater the degree of mixing between the reducing metal and metal oxide components of the energetic material, the quicker the reaction that releases thermal energy will proceed. Consider the embodiment of the thin-film 132′ depicted in
Similarly, the timing of the release of chemical energy from a thin-film formed according to the principles of the present invention can also be controlled, at least to some degree, by the selection of materials, and their location, within a thin-film. For example, in the thin-film 132′ depicted in
Other advantages provided by the present invention can be attributed to the use of a metallic binder material 120, of the type described herein, in the formation of a structural component. First, the structural component can be provided with an increased density relative to structural components made from conventional materials. This increased density enhances the ballistic effects of the fragment on the target by imparting more kinetic energy thereto. The metallic binder material also may increase the structural integrity of the structural component thereby enhancing the same ballistic effects. This increased structural integrity also may enhance the ability of the structural component to withstand the shock loadings encountered during firing of the munition.
Still other advantages can be attained from the structural components of the present invention. During the blast, particles of the metallic binder material will likely exhibit a desirable nonideal gas-like behavior due to its high density, large molecular weight and heat transfer rates. Namely, momentum effects of the blast likely results in the particles of the metallic binder material lagging in velocity behind the lighter weight gas explosive products such as CO, CO2, N2, and H2O vapor, Similarly, heat transfer effects on the particles of the metallic binder material also lag behind. This desirable non-ideal behavior suggests that the sharpness of an overpressure peak during the initial will be somewhat attenuated due to thermal and kinetic energy storage of released binder particles. As the blast progresses, release of the kinetic and thermal energy stored by the particles of the metallic binder material will ideally result in an extension of the time at overpressure, thereby enhancing damage to the target. Many metallic binder materials, such as those discussed above, have relatively strong thermodynamic tendencies to react with oxygen in the air. Thus, particles of metallic binder material may impart a significant after burning component to the blast, further extending the overpressure in the time domain and the release of energy into the target. Any metallic binder material which is not consumed by after burning can be readily distributed into the target as a result of a successful reactive fragment impacts, thus increasing the likelihood of electrical short-circuiting if electrical components are housed within the target.
All numbers expressing quantities of ingredients, constituents, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term “about”. Notwithstanding that the numerical ranges and parameters setting forth, the broad scope of the subject matter presented herein are approximations, the, numerical values set forth are indicated as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective measurement techniques.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims.
