Pitch-catch active sensing methods in structural health monitoring for aircraft structures

This study presents active sensing methods in structural health monitoring, for detecting cracks and debonds in metallic and composite structures, which can be potentially implemented into airframe structures. First, a pitch-catch method using a pair of piezoelectric actuator and sensor is introduced to generate a damage index which can be used to characterize damage at a known location. Tests on airbus fuselage panels are conducted to verify the method and damage index. The damage index relates changes in the energy content of a specific Lamb wave mode selected by group velocity analysis to the extent of damage. Second, an imaging method based on multiple pitch-catch information, a network of piezoelectric actuator/sensors, is presented for characterizing damage (location and size) without need for a structural or damage model. The imaging method with an autofocusing feature is applied to aluminum plates and a stiffened composite panel for method verification.