In this project, we developed a passive, noise-based Structural Health Monitoring (SHM) technique for composite materials. The focus was on creating a reliable, power-efficient method suitable for use in harsh environments where access to power is restricted. Using a Piezoelectric Transducer (PZT) sensor, we captured the diffused wave field within the composite structure, allowing us to monitor its integrity without active excitation.

A key innovation in this project was the application of cross-correlation and a discrete wavelet transform de-noising technique. This approach enhances SHM accuracy by filtering out unwanted noise, thereby improving the clarity of B-Scan imaging for regions of interest. The method was validated through experiments involving an external noise source—compressed air, manually sprayed onto the sample. We then applied a cross-correlation analysis on out-of-plane displacement data collected from two locations on a Glass Fiber Reinforced Polymer (GFRP) sample. This analysis allowed us to retrieve the Green's function, demonstrating a strong correlation and confirming the method’s validity through comparison with active wave propagation. While the results were promising, challenges remain in achieving consistent wave field distribution and frequency stability across the composite. This project marks a significant step toward creating passive SHM systems for composite structures, offering a feasible solution for environments where continuous monitoring is critical but power sources are limited.