For large integrated composite structure, the replacement of parts may not be feasible. Thus, the ability to repair the composite structure is important for maintaining its airworthiness. Although adhesively bonded joints have been employed for the repair of secondary structures, the absence of a reliable non-destructive testing (NDT) method for detecting poor bond limits their application to primary structures. Our team has developed smart composite repair patch based on different sensor technologies for monitoring the quality of the repair at the time of application as well as the integrity of the repair patch during the life-time of the structure:

PZT based smart repair:

PZT transducers are designed in a ring shape to be attached to the primary structure surrounding the repair patch. Both baseline and baseline free methods based on guided waves are explored for damage detection in a step-sanded repair patch. Most of the diagnostic algorithm developed based of Lamb wave propagation requires baseline measurements taken at a reference state where no damage is present.

The limitation of baseline methods is that Lamb wave signals are affected by environmental and operational conditions of their host structures. Although baseline methods show higher reliability in damage localization, for monitoring repair patch, damage localization is secondary, and damage detection is of much higher importance. Therefore, our group have developed smart repair technologies for damage detection in the repair patch without the need for a baseline measurement.