Interfacial debonding detection in externally bonded bfrp reinforced concrete using stress wave-based sensing approach

Fibre-reinforced polymer (FRP) composite materials have been increasingly used for strengthening concrete members. The strengthening performance and structural capacity of FRP reinforced concrete (RC) structures are highly influenced by the interfacial bonding behaviour between FRP and concrete. A reliable technique for debonding detection, especially at its early age, is essential to ensure the strengthening efficacy and avoid premature failure of FRP RC structures. This study develops a stress wave-based sensing approach to quantitatively monitor the debonding process by using surface mounted piezoceramic-based transducers (also called as smart aggregates SAs). The scanning wave signals in swept frequency mode and single frequency mode were utilised in experimental and numerical methods, respectively. Both results showed that when the stress wave propagated through the FRP-concrete interface, the wave energy attenuation increased as the debonding developed. To quantify the debonding level and provide assessment of the interface condition, a wavelet packet-based debonding index was established and its validity was verified by the data retrieved from digital image correlation measurement. The proposed method has potential for fast determination or real-time monitoring of FRP-concrete interfacial debonding for both research and field applications.