Theoretical and experimental investigation of guided wave temperature compensation for composite structures with different thicknesses

This study presents a novel framework for compensating temperature effects on guided waves in composite structures with different thicknesses, based on both theoretical and experimental investigations. The developed method proposes compensation factors that can be scalable to panels of different thicknesses for composite structures made from the same material. In the theoretical analysis, the relationship between the group velocity and amplitude versus the frequencies and thicknesses are determined by the semi-analytical finite element (SAFE) and tuning curve models. The effects of temperature on group velocity and amplitude are then examined through the acquisition of the temperature-dependent material properties obtained by mechanical tests. The theoretical analysis reveals a consistent trend regarding changes in group velocity and amplitude with temperature for the A0 mode within a specific frequency and thickness range. In the experimental investigation, a temperature database was established by collecting temperature signals from composite structures with a circular sensor layout. These structures possessed thicknesses of 2 mm, 4 mm, and 6 mm, with stacking sequence [0/45/−45/90]ns, n=2,4,6 leading to a quasi-isotropic material behaviour. The scalability of the compensation factors is confirmed by computing the factors for one panel and then applying them to the rest, resulting in effective compensation for temperature differences up to ± 30 °C. Furthermore, the performance of the scalable compensation factors is validated by successfully locating damage even when the current temperature is 30 °C lower than the baseline temperature. By scaling the temperature compensation factors at the panel thickness level and using dimensionless compensation factors derived from one thickness to another, the effect of temperature differences in composite panels with varying thicknesses are effectively compensated. This approach requires less baseline temperature data and enhances the damage localization performance, making it applicable to industrial applications where panels of different thicknesses are commonly utilized.