STRUCTURAL ENERGETIC MATERIALS
BACKGROUND OF THE INVENTION Field of the Invention
The present invention relates generally to structural materials, and more particularly, to structural components, for use in airframes, platforms, or both, that will self-destruct when desired.
Description of Related Art
Military weapons designed for use in an urban terrain have the requirement of being benign so as to meet the mandate of minimum collateral damage and minimum casualties. A primary issue is the disposal of residual munition or an airframe after target engagement. Another need is to destroy the munition after use so that any sensitive subsystems, such as electronics, do not fall into enemy hands or into the possession of untrained civilians. Hence, the need exists for the ability to efficiently dispose of the weapon airframe after its mission is completed. Also, in the field of weapons development, particularly, munition weapons development, it is often necessary to provide a target munition for test-firing new weapons. Unmanned munitions which are remotely controlled are utilized for this purpose. When test-firing an anti-aircraft weapon, the outcome of the test is generally deemed successful when the target munition is completely destroyed. However, in a test-firing whose outcome is only partially successful, the target munition may remain airborne, and possibly, remote control of the target munition may be lost. In the latter case, an uncontrollable target munition may proceed along an undesirable course, often into a populated area, and it becomes beneficial to self-destruct the target munition before it crashes and harms the populated area.
Previously, explosives have been added to the target munition, such as a target aircraft, for self-destruction purposes. In this case, a plurality of explosives are added to unoccupied spaces within the target aircraft. Each explosive has a detonator associated with it to detonate the explosive from a remote location when desired. However, adding explosives to a target aircraft increases the overall weight of the aircraft and may provide
undesirable flight characteristics. Further, the spaces and locations available for adding explosives in a target aircraft may not provide adequate or complete destruction of the aircraft. Furthermore, in a partially successful test-firing of an anti-aircraft weapon, the explosives may become separated from the target aircraft or the detonators and may fall to earth in an unexploded state, thereby becoming a hazard to life in the vicinity.
SUMMARY OF THE INVENTION
It is an object of the invention to combine materials with higher structural capabilities with an energetic material to produce multifunctional material systems and structural components that can be self-destructed on command. Another object of the invention is to provide structural materials for use in weapon airframes, munitions, and other weapon platforms that will self-destruct when required, consuming the weapon and all its subsystems.
According to the invention, energetic materials are incorporated into structural materials to form a composite energetic structural material that has the desired structural properties of a munition, air vehicle airframe, or weapon platform, and the ability to self- destruct on command. In an embodiment of the present invention, an energetic structural material is disclosed having an outer layer, which may be an energetic, and a thermite- reactive substrate. The outer layer may be, for example, aluminum, magnesium teflon viton, or an aluminum structural foam filled with polymer bonded explosive, double base propellant, Tovex, or any combination thereof. The thermite-reactive substrate may be, for example, magnesium teflon viton, an aluminum structural foam filled with iron oxide or copper oxide, or any combination thereof.
In another embodiment of the invention, an energetic structural material is disclosed having an aluminum outer layer and an energetic substrate, wherein the outer layer encloses the energetic substrate. The energetic substrate is a polymer bonded explosive, double base propellant, magnesium teflon viton, an aluminum foam filled with Tovex, or any combination thereof.
In another embodiment of the invention, an energetic structural material is disclosed having a thermite reactive outer layer, such as magnesium teflon viton, and a substrate made of aluminum or aluminum foam.
An advantage of the invention is that the multifunctional material system, or composite material, has desired structural capabilities while minimizing the weight and volume necessary to self-destruct a munition, aircraft, or platform. Another advantage of the invention is that munitions, airframes, and/or platforms will self-destruct on command at an end of a mission with minimal damage to persons, property, and the environment.
Other objects, features, and advantages of the present invention will be apparent to those skilled in the relevant art from drawings and the description of the invention, which follows, or may be learned from the practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be further understood from the following description and the accompanying drawings, in which:
Fig. 1 depicts an energetic structural material according to an embodiment of the invention.
Fig. 2 depicts an energetic structural material according to another embodiment of the invention. Fig. 3 depicts an energetic structural material according to another embodiment of the invention.
DETAILED DESCRIPTION OF INVENTION
Energetic materials are those that produce energy when activated. This energy may take the form of heat, gas, light, sound, work, or any combination thereof. Energetic materials contain their own source of oxygen or other element capable of sustaining combustion, and do not require atmospheric oxygen for combustion. Therefore, many energetic materials will sustain combustion under water or in a vacuum. Energetics are classified into deflagrating energetic materials and detonating energetic materials.
Deflagrating energetic materials comprise igniter compositions, pyrotechnics, propellants, and thermal compositions. Detonating energetic materials comprise explosives.
Perhaps the best known thermal composition is thermite. Thermite is a generic name given to high temperature reactions between a metal and a metal oxide, for example, iron oxide or copper oxide, and aluminum. When a thermite composition is ignited or heated, it gives off heat as a result of the chemical combination of the metal with the oxygen of the metal oxide. The following thermite reaction is a single replacement reaction between iron(III) oxide and aluminum to produce aluminum oxide and elemental iron: Fe203 + 2AΪ → Al2 O3 + 2Ee + Heat
As the equation shows, this reaction releases heat energy and is thus considered exothermic. The standard enthalpy change in this reaction is -849 kJ/mol (DH° = -849 kJ/mol). Thus, 849 kJ of energy is released for every mole of iron(III) oxide that reacts. With such a large amount of energy being released, the temperatures produced can reach values estimated to be about 2,400 °C. Because the melting point of iron is 1530 °C, the iron produced in the reaction is actually formed in the liquid phase at temperatures well above a thousand degrees Celsius.
Igniter compositions are those that can be used to activate an energetic. Under normal conditions, some energetics, such as explosives, will not burn, but they will detonate if ignited. The explosive strength and brisance of igniter compositions are inferior to those of explosives, but they are sufficient to activate an explosive or other energetic. Because of the sensitivity of igniter compositions, they are often used in munitions for initiating and intensifying high-order explosions.
Plastic-bonded explosives ("PBX") are high explosives that have been formulated with an organic polymer that functions as a binder to produce PBX molding powder. These molding powders are pressed and machined for specialty applications. Examples of commercial plastic-bonded explosives include HMX, TATB, RDX, HNS, LX, PBX 9501, PBX 9502, PBX 9407, LX-15-0, LX-16-0, PBX 9404, LX-17-0, HiKel 800, LX-04-1, LX-17-1, LX-18-0, LX-07-0, LX-09-1, LX-10-1, and LX-14-0. PBX may be cast and cured or injection molded into a form having a consistency similar to that found in a
conventional pencil eraser. PBX dissolves in water and therefore, is often coated with a moisture-resistant sealant.
A double-base explosive, such as a colloid of nitrocellulose and nitroglycerin, is mixed and then cured into a consistency similar to that of Tupperware®. Subsequently, it may be extruded into a variety of large shaped fixtures, for example, in the shape of a sheet. Further, double-base explosives are not sensitive to water.
Magnesium teflon viton ("MTV"), is a thermite reactive composition that burns reasonably at ambient pressures and is impervious to water. Like a double-base explosive, MTV has a consistency similar to that of Tupperware®. Therefore, it also may be extruded into a variety of large shaped fixtures, for example, in the shape of a sheet.
Water-gel explosives, such as TOVEX, were developed to eliminate nitroglycerine as a basic ingredient in cartridged explosives. TOVEX is a high explosive which is safer and more inexpensive to manufacture, transport, store, and use than other materials such as dynamite. Metal foams, such as aluminum, steel, titanium, copper, or super-alloys, are cellular-metal compositions having 20-40% voids. Metal foams may be fabricating by utilizing an electrolysis process for the deposition of a metal onto a polymer foam precursor via electrolytic deposition. The use of cellular-metal compositions allows simultaneous optimization of many properties, such as, stiffness, strength, and overall weight. Because of this feature, metal foams are desirable for a wide range of engineering, including structural, applications.
Energetic materials are generally not capable of being used as a structural component on their own. The present invention incorporates an energetic material into a structural material to form a composite energetic structural material that has desired structural properties, such as strength, formability, and the ability to self-destruct.
Referring to Fig. 1, energetic structural material 100 is depicted according to an embodiment of the invention. Energetic structural material 100 has the form of a skinned porous metal foam which comprises skin 110 and ignition material 120. Skin 100 is an energetic, such as an explosive made of MTV or an aluminum foam filled with PBX, a double base propellant, or TOVEX. Alternatively, skin 100 may be made of only
aluminum. Ignition material 120 is a thermite compound made of an aluminum foam filled with iron oxide or copper oxide.
Referring to Fig. 2, energetic structural material 200 is depicted according to an embodiment of the invention. Energetic structural material 200 has the form of a sandwiched energetic which comprises skin 210 enclosing energetic material 220. Skin 210 is preferably made from a light weight material, such as aluminum. Energetic material 220 is PBX, double base propellant, or MTV. Alternatively, energetic material 220 may be made of an aluminum foam filled with TOVEX.
Referring to Fig. 3, energetic structural material 300 is depicted according to an embodiment of the invention. Energetic structural material 300 has the form of a skinned metal which comprises energetic skin 310 and material 320. Energetic skin 310 is made of MTV. Material 320 is a metal, preferably aluminum or an aluminum foam.
Energetic structural materials, according to the above embodiments, are ideally suited for forming, either singularly or in combination, munition, air vehicle airframe, or weapon platform structures. By incorporating energetic structural materials into munition, airframe, and platform structures, the structures possess desired structural properties, and the ability to self-destruct and to completely consume the structures and all subsystems.
While this invention has been described with reference to illustrative embodiments, it is to be understood that this description is not intended to be construed in a limiting sense. Modifications to and combinations of the illustrative embodiments will be apparent to persons skilled in the art upon reference to this description. It is to be further understood, therefore, that changes in the details of the embodiments of the present invention and additional embodiments of the present invention will be apparent to persons of ordinary skill in the art having reference to this description. It is contemplated that such changes and additional embodiments are within the spirit and true scope of the invention as claimed below.