Detection of local bonding failure damage by Digital Image Correlation technique

•Detectability of local adhesive bonding failure damage for the GFRP composite is examined with DIC measurement.•The damage-sensitive features based on the stress fields near the damage are determined.•Damages subjected to in-plane and out-of-plane loads are considered.•Sensitivity of the damage detectability to the applied loads is investigated. Detectability of bonding failure damage for GFRP(Glass-Fiber Reinforced Plastic) composite under in-plane and out-of-plane loads was investigated through the DIC(Digital Image Correlation) strain and deflection measurement. The damages were introduced to the tensile specimen and trailing edge of 100 kW wind turbine blade which were subject to in-plane and out-of-plane load, respectively. DIC measurements were performed over the tensile specimen surface and the blade surface, including the damage, respectively, with a 3D DIC system(ARAMIS 5M). Longitudinal and transverse strain profiles for the in-plane tensile specimen were determined, and the deflection profile and deflection, longitudinal and chordwise strain profile for the wind turbine blade were obtained. From these measurements, it was found that the dissimilarities, like local concentration and gradient, in the directional strain profiles were corresponded to the presence of the damage. Therefore, the bonding failure damages in the tensile specimen and wind turbine blade could be detected from the deflection and directional strain profile. Besides, in this study, sensitivity of these profiles to the applied loads was examined to determine an optimal load level for DIC measurement.