The temperature effect on guided wave based structural health monitoring of composite structures

Abstract

In the field of aeronautics, ensuring the integrity of structures is important for aircraft safety, where structural health monitoring (SHM) serves as a technique for detecting and localizing damage in composite structures. In this thesis, the temperature effect on the guided wave-based SHM (GWSHM) for composite structures of different thicknesses is investigated. A sensitivity analysis of damage detection to temperature variations is first presented. A stochastic metamodel is developed by implementing Gaussian Process Regression and Monte Carlo sampling. Additionally, the sensitivity of the separation range is evaluated to determine how baseline and current temperature variations influence the system’s reliability. Following that, a framework for temperature compensation in composite structures of different thicknesses is investigated. The developed method proposes scalable compensation factors applicable to panels with varying thicknesses. The theoretical analysis involves establishing the relationship between the group velocity and amplitude versus the frequencies and thicknesses using the semi-analytical finite element and tuning curve models. Based on the theoretical analysis, experimental studies are conducted and the compensation factors are determined for three panels, demonstrating their transferability to other panels. Previous studies have focused on GWs generated by surface-mounted transducers. An extensive investigation has been carried out to explore the propagation of GWs generated by embedded transducers. Experiments have been carried out with the Laser Doppler Vibrometer to obtain the wavenumber, group velocity, and amplitude of the GWs generated by embedded transducers. It is demonstrated that the proposed methodology is scalable to other panels of different thicknesses for embedded transducers. This research provides the foundation for further analysis and application of the embedded transducers in GWSHM.