ADAPTIVE SHOCK CONTROL BUMP WITH SHAPE MEMORY ALLOY WIRES ON A MORPHING SPOILER

Abstract

Conventional transport aircraft operate under transonic conditions in which the transonic shock leads to an increase in wave drag. Shock control bumps (SCBs) can mitigate the shock strength, leading to reduced drag. Preceding studies show the applicability of adaptive SCBs on morphing spoilers. However, with increasing airflow velocities the shock moves downstream, making it structurally challenging to realize sufficient curvature on the rear spoiler end. In this study, a morphing spoiler is structurally designed to form an adaptive SCB utilizing a shape memory alloy (SMA) actuator. A fiberglass composite structure is constructed to enable a form variable region, sufficiently stiff for handling aerodynamic loads but flexible enough for SMA actuation. To prevent the spoiler trailing edge lifting from the flap during bump deployment, a structural pre-bend is implemented on three regions. However, for SCB crest locations near the spoiler rear end, a strong pre-bend would be required, leading to significant contour deviations and waviness in clean configuration with retracted bump. An additional actuator combined with structural pre-bends can enable more downstream bump crest locations than a single spoiler actuator. Since installation space for this additional actuator may be limited, SMAs are considered in this work. In modeling the two-way effect of the SMA, a simplified methodology is utilized. Despite the observed stress limits within the SMA wire being exceeded, the results demonstrate potential and indicate the possible utility of SMA for adaptive shock control on aircraft spoilers.