In situ non-destructive evaluation of an aircraft UHF antenna radome based on pulse-echo ultrasonic propagation imaging

Most aircraft antennas are protected by radomes made of composite materials. However, antenna radome structures are easily damaged by external forces and internal manufacturing defects. To detect damage in the composite antenna radomes while in service, a full-field pulse-echo ultrasonic propagation imaging (PE UPI) system is proposed as an in situ non-destructive inspection technique, which is mobile inside a hangar. The radome is generally a double-curvature structure, and thus, a curvature compensation algorithm is also developed to increase damage visibility. The proposed hardware and software have been tested by detecting a resin rich region formed between the E-glass/epoxy plies. To visualize the damage, PE ultrasonic wave propagation imaging has been performed, and ultrasonic energy mapping has also been applied. A curvature compensating algorithm has been newly developed and compared for its performance in damage visibility improvement. To verify the size of the real defects of a UHF antenna radome, destructive testing has been performed by cutting the defect area, polishing the cross section and investigating the section using a 50× microscope. The results have shown the feasibility of the proposed PE UPI system and the inspection strategy as an in situ non-destructive evaluation technique for radome structures.