Assessment of bonding defects in FRP reinforced structures via ultrasonic technique

Fiber reinforced polymer (FRP) composite systems are widely used for the rehabilitationof concrete structures such as building that need to resist to seismic loads,bridges that have to carry heavier traffic loads. The technique consists in bonding thecomposite plate to the concrete surface element in order to increase the flexural capacity.A proper attachment of the FRP plate to the concrete surface is necessary forthe efficiency of the load transfer between the reinforcement and the substrate. Inthis work, the quality of composite bonding is characterized through ultrasonic testing.The proposed technique is relative to a time domain analysis of the ultrasonicsignals and couples the Akaike Information Criterion (AIC), used as automatic onsetsignal detection, and the Equivalent Time-Length (ETL), used as an indicator of thequantity of energy propagating through the bonding. It has been tested both numericallyand experimentally, in vitro, using samples with imposed well- known defects.