Radii structures with complex geometries are commonly encountered in carbon fiber reinforced plastic (CFRP) composites in aerospace components. How to improve the corresponding nondestructive testing quality on defects is one key issue for the assurance of load-bearing properties. In virtue of numerical modeling and wave propagation analysis

the difficulties of ultrasonic testing in CFRP radii were clarified. Due to the intrinsically elastic anisotropy of CFRP material

the layered structure and the curved surface

the normal incidence of ultrasonic wave could not be easily realized and the wave propagation path kinks seriously. Moreover

the structural noise is obvious and the acoustic coupling is difficult. In view of this problem

the research progress in study of phased array ultrasonic testing (PAUT) was summarized

especially for the radii with a varied cross-section in plate thickness

curvature and included angle. The development of PAUT probe

the ultrasonic imaging based on signal post-processing technique

and the research of solid flexible coupling medium and probe jig were emphasized

respectively. The remaining issues and the future development trend were analyzed.