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

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