Damage evaluation of complex composite structures using acousto-ultrasonic detection combined with phase-shifted fiber Bragg grating and dual-frequency based data processing

Structures consisting of composites with complex geometries are challenging to be precisely monitored. In this study, a hardware-software integrated acousto-ultrasonic detection is proposed using a highly sensitive phase-shifted fiber Bragg grating sensor and influence-resistant dual-frequency based data processing to evaluate damage within two typical complex composite structures that are composite propeller and composite T-joint. The optical fiber sensor with broad bandwidth and flexibility was fastened to the surface of complex structures, and ultrasonic signals with a sufficiently high signal-to-noise ratio were detected for the subsequent data processing. The maximum arrival time difference of the dual-frequency calculated by the correlation of the wavelet coefficients increased with the impact number on the propeller, and it was also proportional to the delamination length of the T-joint. The results imply that the proposed acousto-ultrasonic detection method is promising for the detection of various damages in complex composite structures.