The return of commercial supersonic flight requires innovative solutions to be developed that meet noise and efficiency requirements for overland flight. To study such a possibility NASA is supporting a multi-disciplinary team of academic and industrial experts to explore the potential of activating small real-time geometric outer mold line reconfigurations to minimize boom signatures in response to changing ambient conditions, thereby enabling noise-compliant supersonic flight. The team will exploit recent advances in supersonic computational fluid dynamic methods, new noise prediction tools, and new design approaches to consider embedded highly energy-dense shape memory alloy (SMA) actuators for in situ adjustment of a supersonic aircraft leading to optimal low boom signature in different environments. On-board LIDAR measurements will provide information about the local atmosphere and will aide in the prediction of how loud the sonic boom will be just ahead of the aircraft. Small, distributed shape memory alloy actuators will then be used to modify the shape of the aircraft to affect a desired change in the pressure field to reduce sonic boom noise for the upcoming flight and atmospheric conditions. The presentation will focus on the development of the appropriate SMAs based on the requirement of reliable repeated actuation up to 100,000 thermal actuation cycles under high levels of stress. We will discuss the micromechanical modeling of such alloys, their modeling of fatigue and fracture and also the behavior of structural components embedded in morphing structures. Because precipitation can adjust their thermomechanical cyclic stability, phase transformation temperatures, and transformation strains, micromechanical modeling of SMAs will focus on the prediction of precipitation hardened behavior to capture their thermomechanical response. Moreover, a unified constitutive modeling approach will be described to capture the phenomena associated with the unique response of SMAs that include, pseudo-elasticity, shape memory effect, tension-compression asymmetry, partial transformation loops and transformation induced plasticity, evolving with actuation cycles and ultimately leading to damage accumulation and actuation fatigue failure.
