Contactless Damage Evaluation of a Rotating Carbon Fiber Propeller

There is a need for contactless health evaluation of curved propellers ranging from servicing drones to wind power plants. Structures that close upon themselves feature multiple paths for acoustic waves to travel which causes interference and reduces contrast. In addition, blade curvature makes it challenging to scan the structure in a contactless manner due to the difficulty to aim the laser beam. We introduce a technique that allows to scan a sample with a highly directed acoustic field. We show the feasibility of this approach by locating damage on a commercial drone propeller rotating at 1000 rpm.