Composite aircraft debonding visualization by laser ultrasonic scanning excitation and integrated piezoelectric sensing

Abstract

Two aircraft wings made of carbon fiber-reinforced plastic material were inspected using the laser-based ultrasonic propagation imaging system for the visualization of manufacturing defect and damages of debonding mode. Hypotheses of the detection mechanism of composite debonding were presented and validated through the inspection results for the bonding lines of the composite wing structures. The inspection showed that the location, shape, and size of the poor bonding defect, artificial stringer tip debonding, and real skinspar debonding can be visualized and/or measured from the imaging results. The performance of the imaging system was found better than that of a manual ultrasonic C-scan in terms of spatial resolution and damage detectability. Another finding from the inspection was the occurrence of skin buckling between two riveted locations. Most importantly, the presence of structural elements or features such as spars, stringers, ribs, lugs, inspection windows, and even embedded PZT elements did not adversely affect the inspection.