Interaction of Feature Guided Waves with Defects in Composite Structural Bends
Complex-shaped composite structures such as bends, stiffeners, and ribs are increasingly incorporated in aerospace applications because of their attractive mechanical properties and good moldability. However, damages like matrix cracking and delamination can be caused in these structures by stress concentration and out-of-plane impacts during the in-service use, consequently degrading the system integrity and reliability. Ultrasonic feature guided waves (FGW) can serve as promising candidates for their inspection as they can propagate along the feature long distances and potentially detect the possible defects. In this study, potential FGW modes have been identified in 90° carbon fiber/epoxy (CF/EP) quasi-isotropic bent plates by applying the Semi-Analytical Finite Element (SAFE) method. These modes show strong energy confinement in the bend region and have limited radiation to the adjacent plates, which are promising for the long-range inspection. The interaction of identified bend-guided waves with different types of defects is studied by the 3D Finite Element (FE) simulation. Their reflection coefficient spectra are calculated and the sensitivity to different defects is discussed. Preliminary experiments are also performed to validate the modeling results.