Ultrasonic Guided Wave Based Damage Detection of Engine Composite Fan Blades

Engine composite fan blades are subjected to tremendous centrifugal and aerodynamic forces for long periods of time, resulting in blade cracking and delamination. Ultrasonic guided wave detection technology in structural health inspection technology has the advantages of wide coverage and high detection accuracy, and has a very high potential for application in the health monitoring of blades. However, the variable curvature and material anisotropy of the blade can affect the propagation of the guided wave, which in turn affects the accuracy of damage quantification and localization. In order to mitigate this effect, an ultrasonic guided wave detection method applicable to engine blade structures is proposed in this paper to localize and quantify the damage. The damage likelihood lines were determined based on the ratio of the damage index(DI) of the signals acquired by each pair of sensors, and the damage was localized by the intersection of multiple damage likelihood lines. The size of the damage was assessed as the mean value of the two largest damage factors. This method was validated on a test platform simulating the rotating operating environment of an engine blade, where damage was simulated by bonding a vacuum sealant to the blade. The results show that the proposed method for damage localization and quantification is effective and suitable for damage detection of composite blades.