120 mm Prestressed Carbon Fiber/Thermoplastic Overwrapped Gun Tubes

The emphasis on lightweight large caliber weapons systems has placed the focus on the use of advanced composite materials. Using composite materials not only directly removes weight from the gun tube but also, by better balancing the tube, allows the use of smaller drive systems, thus further enhancing the system weight loss. Additionally, the use of high stiffness composites helps with pointing accuracy and to alleviate the dynamic strain phenomenon encountered with high velocity projectiles. Traditionally, there were two issues with composite jackets: the coefficient of thermal expansion mismatch between the steel substrate and the composite jacket causing a gap and the lack of favorable prestress in the jacket. Dealing with these issues greatly complicated the manufacturing process to the point where mass-producing the barrels would have been problematic at best. By using a thermoplastic resin, a cure on the fly process, and winding under tension, the manufacturability of the barrels has been greatly improved, the gap has been eliminated, and a favorable prestress has been achieved. Four 120 mm barrels have been manufactured using this process with IM7 fibers in a PEEK matrix and successfully test fired. The first barrel was not prestressed and was reported on previously. This paper will focus on the other three barrels. The design, manufacturing, and test firing of these barrels will be covered.