| Abstract | Aircraft structures are susceptible to foreign object impacts, which may occur during manufacturing, maintenance and in-service. Sizes of these impacted objects especially during in-service can range from a small rock to a large bird. Common ways to detect such impacts are based on flight / ground crew observations and reports leading to close examinations of structures using non-destructive evaluation (NDE) techniques. If undetected these impact damages can grow during service loading and may be detrimental to flight safety. Therefore, timely detection of any signs of impact damages are critical such that proper maintenance actions can be taken. The aim is to develop methodologies using Structural Health Monitoring (SHM) techniques to detect and characterize foreign object impact events. In this experiment, a cut-out of an aluminum panel measuring 31 x 26 inches from an out-of-service aircraft was used. The panel was instrumented with four Lead Zirconate Titanate (PZT) sensors from Acellent Inc., as well as, four Acoustic Emission (AE) sensors from Mistras Inc. Impedance and susceptance measurements were acquired to assess the proper functionality of the PZT sensors before and after the impact events. Both the PZTs and the AE sensors were directly connected to a digital oscilloscope, without any amplification and / or filtering for acquiring raw data during the impact events. An instrumented multi-use tapper was designed and developed to calibrate the system, as well as, to record the impulse (impact force and time) during the impact events. The acquired data were processed using physics-based and machine learning techniques to detect and characterize the impact events. |
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