Damage detection and identification in composite aircraft components

Commercial and military aircraft such as the V-22 Osprey are being constructed using substantial amounts of advanced light-weight composite materials. Impact damage as well as fatigue stress can cause internal delaminations leading to catastrophic part failure without prior visible warning. A reliable health monitor system can enable condition-based maintenance. This can significantly reduce life cycle costs by minimizing inspection time and effort, and by extending the useful life of new and aging aerospace structural components. In this paper we describe a smart structures approach for the detection and assessment of damage in critical composite structures. An array of piezoelectric transducers is attached to the structure for both actuation and sensing. The system actively interrogates the structure with wideband chirp excitation of multiple actuators. Statistical analysis of the changes in the vibration response is used to detect, localize, and assess the severity of damage in the structure. Damage is indicated when the vibration signatures differ from a known baseline condition. Pattern recognition techniques are employed to distinguish damage responses from those due to benign changes such as temperature or loading variations. This model-independent damage detection approach can be applied without extensive algorithm training. Tests were conducted in the fatigue test facility at Bell Helicopter on the V-22 pendulum yoke. Results presented here demonstrate that vibration signature analysis is a viable technique for in-situ damage detection of advanced composite aircraft components.