A robust hybrid method for damage detection under varying environmental conditions

This paper presents a hybrid structural health monitoring (SHM) approach that combines the high damage sensitivity of guided waves with the temperature resilience of modal analysis, enabling damage detection in plates with varying material properties under different temperature conditions, without the need for extensive baseline data or temperature compensation. To validate this approach, a series of experiments were designed and carried out on plates equipped with four Piezoelectric transducers to actuate and receive guided waves to obtain the transmissibility functions (TFs) of structures under different temperature conditions ranging from 20°C to 60°C. The changes in correlation coefficients of TFs between the current and baseline states were selected as damage-sensitive features, with the Mahalanobis distance (MD) calculated as a damage indicator. The proposed method was experimentally verified on an aluminum plate (M1), a quasi-isotropic composite plate (M2), and an anisotropic curved composite plate (M3). Results demonstrate high accuracy in detecting damage at five different locations on the M1 plate, both inside and outside the sensor coverage area, over the temperature range of 20°C–60°C. Furthermore, the proposed method successfully detected damage on the M2 and M3 plates over temperature ranges of 20°C–40°C and 20°C–30°C, respectively. Finally, the performance of the proposed methodology was evaluated using an alternative actuator, thereby mitigating potential uncertainties arising from variations in sensor locations. This work highlights a practical and efficient SHM solution, offering accurate damage detection across variable environmental conditions with a simplified experimental setup and minimal baseline requirements.