Gold nanocomposites-based photoacoustic multimodal rebar micro-cracks detection

Photoacoustic technology has been extensively employed in ultrasonic monitoring for the evaluation of metal cracks. To facilitate distributed and quantitative monitoring of micro-cracks on steel bar surfaces, this study introduces an innovative approach that integrates photoacoustic excitation via a gold-poly (dimethyl siloxane) composite (Au-PDMS) with fiber optic sensing techniques. A 532 nm pulsed laser is utilized to excite the Au-PDMS composite, thereby generating broadband ultrasonic waves that stimulate an HRB400 rebar specimen. Simultaneously, a distributed fiber optic sensing system is strategically implemented on the rebar surface to capture the dynamic strain field induced by the interaction between ultrasonic waves and micro-cracks. By developing a parametric model of crack evolution, the ultrasonic response characteristics corresponding to varying crack opening-width are systematically analyzed, leading to the construction of a multi-parameter predictive model for quantitative crack identification. Experimental findings demonstrate that this methodology, which combines localized photoacoustic excitation with long-range distributed fiber optic sensing, achieves highly sensitive detection and characterization of micro-cracks. This approach offers a novel technical framework for distributed, non-destructive monitoring of large-scale civil engineering infrastructures.