High temperature composite projectile barrel

Abstract

A composite projectile barrel is disclosed comprising a polymer matrix composite outer shell that accommodates higher temperature loading. In one embodiment, the invention comprises an outer shell fabricated from carbon fibers and polyimide resin having a glass transition temperature greater than 500° F. In another embodiment, the resin mixture includes a plurality of sizes of aluminum particles, between about 0.1 microns and 10.0 microns in diameter and of approximately spherical shape, as a thermal conductive additive.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to two Provisional patent application No. 61 / 871,154 filed Aug. 28, 2013 and No. 61 / 873,771 filed Sep. 4, 2013. The entire disclosures of both provisional applications are hereby incorporated by reference and relied upon.BACKGROUND OF THE INVENTION[0002]Users have long desired lighter gun systems that remain durable and reliable. It is known to substitute relatively strong but lightweight materials—such as unreinforced and reinforced polymers, continuous glass fiber or carbon fiber composites—for various portions of the gun commonly fabricated from steel, aluminum, or other metals. Attention has focused on gun barrels, which constitute a large percentage of a gun's weight. It is known, for example, to fabricate a gun barrel having a steel inner liner surrounded by a carbon fiber reinforced polymer matrix composite (PMC) outer shell, incorporating a resin. This combination lightens the gun while retaining g...

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Benefits of technology

[0014]A composite projectile barrel is disclosed comprising a novel polymer matrix composite outer shell that accommodates higher temperature operation. In one embodiment, the invention comprises a barrel for directing the path of a dischargeable projectile including an inner liner defining an axial bore and an outer shell surrounding and in direct contact with the inner liner, said outer shell fabricated f

Problems solved by technology

When a composite barrel is subjected to high heat from rapid or prolonged firing, however, they are usually less durable than solid steel barrels.

Even with the addition of thermally conductive chopped carbon pitch, however, rapidly firing a gun fitted with a carbon fiber composite barrel may cause barrel temperatures to significantly exceed the use-temperature capability of epoxy resins.

At the Tg, the PMC softens significantly and the mechanical integrity of the composite barrel is compromised.

As the barrel is heated to even higher temperatures irreversible thermal decomposition of the cured epoxy matrix occurs and barrel structural integrity is further compromised.

Because all of these thermally conductive additives tend to strongly increase the viscosity of the resin, however, higher concentrations of the thermally conductive additive make the resin mixture more viscous, inhibiting complete coating of the carbon fiber tow with resin and making manufacturing more difficult and less consistent.

Additionally, high loadings of conductive additives generally diminish the mechanical properties (e.g., strength) of the composite.

Other resins having higher glass transition temperatures than epoxy exist, but they are generally more difficult to process and manufacture PMC articles with and are significantly more expensive than epoxies.

Although cured polyimide resins have superior thermal performance as compared to epoxy resins, many have relatively high toxicity from the solvents and monomers used in their manufacture.

The RP46 resin, however, at high enough solids concentration for manufacturing PMCs is semi-solid at room temperature; its high viscosity makes it very difficult to work with when “wet” winding fiber filament tows.

Another obstacle to using polyimide resins such as the P2SI® 635LM resin in filament winding applications relates to processing difficulties to cure a freshly-wound barrel.

When curing a wound gun barrel that inherently has minimal part “edges”, however, it has proven difficult to remove the volatile products and gasses because they tend to become trapped between the continual filament windings.

This problem is compounded whe

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