Delamination/disbond propagation analysis in adhesively bonded composite joints using guided waves

ABSTRACT This paper investigates debonding and delamination assessment by means of Lamb waves in adhesively bonded composite joints. Adhesively bonded wide CFRP panels with initial delamination were subjected to fatigue loading. A segment of a group velocity dispersion curve was constructed for the plain panel and the bonded section. The fundamental asymmetrical Lamb wave mode (A0) was utilized to evaluate damage propagation. The depth of debonding/delamination and the extent of the damage within the bonded section were analyzed in relation to the group velocity change of the A0 mode. The results indicate that a suitable sensor placement and a proper frequency selection enable the assessment of the interface failure in the three-layer system. Based on the time delays, it was possible to distinguish delamination in the specific adherent. Metallographic analysis confirmed the depth of delamination propagation. Guided wave-based measurements were compared to and verified with ultrasonic A-scans. Additionally, RAPID algorithm was utilized to visualize damage extent with the first damage detection in 29.4 % of the fatigue life.