Implementation of Carbon Fiber Composites in Rotorcraft Transmission Housing Applications

An investigation into the practical application of carbon fiber composites to replace cast Magnesium in rotorcraft transmission housings is presented. The primary focus of the effort was the production of risk reduction test articles abstracted from the RAH-66 main gearbox housing design. Advances in composite manufacturing technologies have yielded new processes and capabilities leading to the possible use of composite materials to replace metallic castings for a broad range of transmission applications. The composite materials selected as part of this study offer the opportunity to reduce weight and eliminate life limiting corrosion and fatigue concerns associated with metal castings. The study explores the utilization, performance and compatibility of several composite material forms including P4A (Programmable Powdered Preform Process for aerospace), triaxial braid, advanced compression molding compound, and low resin content prepreg fabrics. The integration of the various reinforcement forms was accomplished by using them in their dry fiber form in conjunction with the Resin Transfer Molding (RTM) process. The selected materials were evaluated both individually and as co-cured assemblages. Specific structural configurations abstracted from the RAH-66 transmission housing were selected as representing the highest risk features of the housing assembly. Each of the risk reduction sub-elements were evaluated and tested to validate specific performance characteristics.