Numerical simulation of the propagation of Lamb waves and their interaction with defects in C-FRP laminates for non-destructive testing

Abstract

The constantly growing demand for cost-intensive lightweight structures is accompanied by an increased demand for reliable non-destructive testing (NDT) methods. Previous investigations have shown that Lamb Waves (LW) are very well suited for the use in Structural Health Monitoring (SHM) due to their relatively undamped propagation over long distances. Therefore the numerical modelling of a non-contact and automated system for non-destructive testing of C-FRP laminates was investigated in the present study. The method is based on the propagation of LW, which are excited by an actuator-driven piezo transducer and interact with defects in the structure. In contrast to classical Structural Health Monitoring, a scanning inspection system is used instead of a sensor permanently integrated into the structure to detect the measurement signals. For the representation of the wave propagation a three-dimensional simulation model with the commercial FEM software PZFlex was modelled. The wave interactions in defective C-FRP coupons are investigated and visualized through different output formats like A-, B- and C-Scans. Additionally the model allows the determination of the dispersion characteristics of the LW in the examined laminate. The validation of the numerical results was successfully carried out at different levels with the help of experimental investigations.