Design and performance evaluation of soft morphing car-spoiler

Automotive wings are considered to be aerodynamic devices which have a significant effect on the driving, braking and cornering performances by influencing the flow of fluids around the vehicle without changing the weight of the vehicle. The wings have developed from having a fixed shape to multisectional wings in order to amplify the advantages of their aerodynamic effect in specific situations such as cornering and braking. However, the multi-sectional wings based on flaps, ailerons, and slats have to modify their surface or camber using hinged parts. These discrete sections create aerodynamic losses during shape changes. In this paper, a morphing car-spoiler based on a reinforced elastomer capable of continuous selfactuation throughout its surface was applied to a small-scale vehicle without slotted parts or mechanical elements. The designed morphing car-spoiler consists of a woven type Smart Soft Composite (SSC) which was made by weaving Shape Memory Alloy (SMA) wires and glass fibers embedded in a polydimethylsiloxane (PDMS) polymeric soft matrix. The phase transformation from martensite to austenite of the SMA wires creates an axial load in the longitudinal direction resulting in symmetric bending of the spoiler. Using an open-blowing type wind tunnel, tests were conducted on the stand-alone spoiler to verify its aerodynamic effects. Furthermore, to evaluate its performance in practice, the morphing car-spoiler was mounted on a small-scale vehicle and tested in a closed-type wind tunnel. Results show that the morphing car-spoiler generates a downforce which increases the normal tire adhesion and that it is possible to adapt its shape for various situations such as cornering and braking.