Flexible CMC Structures for Propulsion Efficiency

Physical Sciences Inc (PSI) will fabricate high temperature spring preloaders for turbomachinery seals from our flexible Carbon fiber-reinforced Silicon Carbide (C/SiC) Ceramic Matrix Composite (CMC) system. The team will fabricate springs of different lengths, thicknesses, and stiffnesses with an accordion fold geometry and variable lengths. PSI will evaluate the springs’ mechanical performance at both ambient and elevated temperatures to model their mechanical response based on the different fabrication variables to meet NASA’s performance requirements for spring preloaders in turbomachinery sealing systems. Seals have historically been a major area of concern with propulsion systems, both turbines and hypersonics, to prevent leaks and uncontrolled changes in pressure of the flight system. Existing sealing systems for these applications have an upper use temperature of ~2000 °F. Combustors can reach temperatures upwards of 3000 °F in J-class turbine engines, well beyond the upper use temperature of metallic alloys. The High Mach Gas Turbine (HMGT) and Turbine Based Combined Cycle (TBCC) propulsion systems, currently being explored by NASA and AFRL for use in DARPA’s NextRS systems, will also require innovative higher temperature materials systems than metallic alloys can provide to reach the desired speeds. PSI’s flexible C/SiC CMCs are the most flexible CMCs available with active bend radii as small as 3.5” and tailorable stiffness. The flexible CMCs can be fabricated in complex geometries with bend radii as small as 1/16” for complex structures such as accordion fold spring preloaders. PSI’s Flexible CMC material has resilience in extended bend fatigue testing to a 3.5” radius in ambient environments for thousands of cycles. There is no measurable loss in the flexure of the material after the initial few cycles. PSI’s flexible CMCs have been tested under continuous actuation in highly aggressive oxidating environments at temperatures up to 5000 °F