Development and Analysis-Driven Design Optimization of an SMA-Based Slat-Cove Filler for Airframe Noise Reduction in Transport Aircraft

In transport-class aircraft, multi-element high-lift systems are used to augment lift and improve stall characteristics at the low speeds and then nest tightly in the cruise configuration to minimize drag. The geometric discontinuities that exist during deployment, however, cause unsteady aerodynamics and significant acoustic noise. The flow characteristics, noise production mechanisms and notional concepts for mitigation of slat noise in particular have been studied extensively. The concept of a slat-cove filler (SCF) was previously introduced as an option to fill the cavity behind the deployed slat and reduce flow unsteadiness and associated noise. This work considers the experimental development and analysis-driven optimization of a functioning SCF incorporating superelastic shape memory alloy (SMA) materials. The SMA flexures permit the large deformations involved in the structural changes between the deployed and stowed configuration. One key design goal is minimization of actuation force needed to retract the slat-SCF assembly while satisfying constraints on the maximum SMA stress and on the SCF deflection under static aerodynamic pressure loads. A 2-D physical bench-top model was first constructed, after which an FEA model based on the physical prototype was created such that fully automated iterative analysis of the design could be performed. Several design variables associated with the current SCF configuration were considered, including SMA flexure thicknesses. Designs of experiment (DOE) were performed to investigate structural response to an aerodynamic pressure load and to slat retraction and deployment. The subsequent optimization process determined a design that minimized actuator forces while satisfying the required constraints.