Design Sensitivities of Response/Fatigue Life of Panels to Thermo-Acoustic Loads

The design of the panels of future reusable launch vehicles will represent a particularly challenging task as these structural components will be subjected to some thermal effects, potentially severe random acoustic excitations and will support a complex thermal protection system (TPS). The structural dynamic behavior of the combined system is expected to display a significant nonlinearity arising not only from the combination of the acoustic and thermal effects but also from the yielding character of the TPS. A methodology for the fast and accurate prediction of the fatigue life of such nonlinear structures, involving full finite element solutions, reduced order modeling, and random response and fatigue life prediction, is rapidly maturing. The focus of the present effort is then to take these important analysis capabilities to the next level, i.e. to an efficient design tool. This task will be accomplished through the formulation and implementation of the sensitivities of the fatigue life of the panels to their geometric/material properties, boundary conditions, TPS characteristics, etc. The Phase I effort will represent a proof-of-concept on panels without TPS. The Phase II will then proceed with the structural modeling/reduced order modeling of TPS and a complete validation of the proposed design sensitivity methodology.