Detailed characterisation and evaluation of composite stiffener R-zones based on mono-pulse ultrasonic reflection behavior.

R-zones are important part of the skin-stiffener joint in composite panels. Owing to their complex geometric shapes, defect behaviour, and poor accessibility, it is difficult to perform non-destructive testing and evaluation of their defects. A new method based on reflection behaviour generated by mono-pulse ultrasonic (MU) waves in R-zones for characterising and evaluating their defects was developed.