It’s a fact of operating an aircraft, that the make noise. If you’re an aviator you might want to quiet your craft to avoid annoying people nearby, or you might even want to operate in stealth mode. It turns out that there are different sources of noise on a plane depending upon the phase of flight. A NASA study found that when landing, a gap between the wing and leading edge slats causes air to cavitate causing unnecessary noise. Blocking that hole would allow for quieter landings, but there was no material suitable for both normal flight and the landing. That is, until Texas A&M researchers devised a way to use a shape memory alloy to do it.
In addition to two different shape memory alloy configurations, the study looks at a more conventional fiberglass composite, although this would only work for a limited number of wing configurations.
Quite a bit of the paper is pretty high-octane math simulations, but if you are serious about quieting down your next winged drone design it might be worth wading through.
We don’t see many shape memory projects, but the technology is accessible. We recently saw a clever use of leading-edge slats in a scrappy experimental aircraft.