CORNERSTONE RESEARCH GROUP INC — Department of Defense SBIR Phase II: A19-004

Description

Current and future armament systems would greatly benefit from large-caliber guns with reduced weight designs and longer life cycles. Although composites are the favored approach for these applications, simply replacing metal with composites is not feasible due to the operating conditions while firing. High use temperatures are the biggest challenge, but wear is also an issue, and changing the barrel mass has system-level consequences with regard to recoil and moment of inertia. A compromise solution is to make gun tubes with a steel core that has a composite overwrap. The steel surface addresses wear, the composite improves specific strength and stiffness, and the combined materials approach gives the designer flexibility in their tradeoff space between weight and system level issues like recoil. The compromise solution introduces a new problem in the form of CTE mismatch between the composite and the steel; however, in general, a steel tube overwrapped with composite is a promising option for light weighting future large caliber gun barrels as long as the composite can withstand the high temperatures associated with firings.   CRG proposes to reduce the weight of gun barrels for the Army with its proprietary MG resin systems and composites. CRG has developed a family of high temperature organic resins with excellent thermal stability, ultra-low flammability, high char yield, and practical processing called MG Resins. MG composites represent a new class of light weight, low-cost, easy-to-process high-temperature structural materials. The thermophysical performance of the materials is unique, and the chemistry is proprietary to CRG. MG Resin has been used to produce multiple product formats including low viscosity infusion resins, commercially produced prepreg, filled elastomer insulation, and syntactic foams. They enable the use of light weight composites in gun barrels, reducing weight and cost, while enhancing lifespan and robustness. CRG will select and mature an MG Resin with IM7 reinforcement by evaluating catalyst loading effect on cure and glass transition temperatures (Tg) to minimize CTE mismatch between steel gun barrels and composite materials. Finite element analysis will be used to optimize these conditions. Production will be scaled to support final product format(s) used for winding test articles and fabricated panels to support cryogenic and elevated mechanical testing.