Detection and time-of-arrival estimation of impact-induced waves in composite laminates

This work assesses experimentally three selected methods for estimating the time of arrival (TOA) of guided waves generated by impacts on a carbon fiber reinforced polymer plate-like structure. This is reached by the individual evaluation of the continuous wavelet transform (CWT), the modified energy ratio (MER), and the Akaike information criterion (AIC). Considering the anisotropic nature of the laminated structure, the propagation of guided waves within such thin-walled structure presents intricate challenges. The utilization of surface-bonded piezoceramic patch sensors aids to detect and measure wave propagation across the plate. The experiments involved impacting the plate at various positions using an impulse hammer and an impact gun, generating a comprehensive dataset encompassing signals captured by sensors placed at different locations. Our investigations have revealed that, with specific modifications, these methods offer effective means of estimating the TOA. In the CWT framework, the introduced frequency domain threshold crossing technique enhances precision in the TOA estimation. To address the slight delays in TOA estimations using the MER method, we refined the method by identifying the first local maximum that exceeds a predefined threshold. This enhancement significantly improves the method’s ability to estimate the TOA of sensor signals. Among the explored methods, the AIC stands out for its precise detection of initial impact-induced signal alterations. This method consists of two sequential steps, with the second step notably influencing its outcome. By incorporating local minima from the method-specific function, instead of relying solely on the global minimum, a significant improvement in estimation accuracy was observed in several cases. Nevertheless, our modification led to notably inaccurate estimates in certain cases, indicating instances where the estimates were significantly too early. These findings offer valuable insights into successful TOA estimation, facilitating potential applications such as impact localization and guiding further research in this domain.