Identification and imaging of multi-defects on a complicated composite structure by ultrasonic guided wave

Combination of probabilistic damage imaging (PDI) algorithm and the fusion ultrasonic guided wave damage index can be used to detect the damage in a complicated composite structure with acceptable accuracy. However, the damage signatures associated with PDI algorithm cannot accurately identify multi-defects features such as the number, position and dimension information, which greatly restrict the inspection effect in real practice. In this paper, the damage shape factor βM of each damage-impaired path is optimized to enhance the resolution of PDI algorithm. Then, a modified probabilistic damage imaging (MPDI) algorithm with the βM is proposed to identify the multi-defects existed in the curved carbon/epoxy composite structures. The validity of the algorithm is firstly checked in the curved composite structures with the single defect. The MPDI with the βM is applied to identify the depth of defect. The obtained results show that the precision of different defects identification by the MPDI algorithm is much higher than that used by the PDI algorithm. The number, position and dimension of multi-defects existed in the curved composite structure are clearly imaged by the method. This study also verifies that the majorization of damage shape factor in the MPDI algorithm is practicable and necessary for better identification of multi-defects in composite structure. ●The fusion signal difference coefficient damage indices from the frequency domain are successfully used to detect and identify different types of defects in the monitoring zone.●The probabilistic damage imaging (PDI) algorithm associated with the fusion damage index is developed to detect the damage in the complicated composite structure.●The modified probabilistic damage imaging (MPDI) algorithm with the damage shape factor is proposed to identify the multi-defects existed in the curved composite structures.●The identification precision of different defects identified by the MPDI algorithm is higher than that used by the PDI algorithm.●The number, position and dimension level of multi-defects can be clearly imaged by the MPDI algorithm.