Bird strike event monitoring in a composite UAV wing using high speed optical fiber sensing system

In this study, high speed bird strikes on a composite structure were successfully monitored using optical fiber sensors. Four multiplexed optical fiber sensors in a single cable were surface-bonded on the leading edge of a composite UAV wing box. In order to acquire those high frequency signals, a newly developed interrogation system was used to process strain signals from four sensors simultaneously at a sampling frequency of 100 kHz. Before the bird strike tests, pre-impact tests using a rubber hammer were performed to verify the suitability of the FBG signal acquisitions. The pre-test data were used in the neural network training procedures to estimate the bird strike locations. Then, the bird strike tests were accomplished using dummy projectiles and a pneumatic gun. The one-pound dummy birds, made of gelatin, hit the leading edge with a maximum speed of 201 km/h. The impact signals were successfully recorded during the tests and their frequency characteristics were then analyzed. Finally, the strike locations were estimated with the neural network which was trained through the pre-tests. The average error was 33.6 mm.