Delamination inspection in composite laminates with S0 Lamb wave using flexible macro-fiber composite transducers

Abstract

Delamination in composite laminates poses a serious threat to structural integrity in aerospace applications due to its potential to cause structural failure. Effective structural health monitoring (SHM) methods are needed to identify such damage. The objective of this paper is to measure and localize delamination in a glass fiber reinforced polymer (GFRP) cross-ply composite laminate based on the S0 Lamb wave detection method, using the Macro-Fiber Composite (MFC) as both actuator and receiver. To analyze the interaction behaviors between the excited S0 Lamb wave and delamination, the finite element models were established to simulate the Lamb wave propagation in composites, incorporating the local stiffness reduction method to model the delamination region. The simulation results indicate that the interaction behaviors between the excited S0 wave and the delamination occur mainly at the end of the delamination, and the generated new wave packets in the received signals can be used to identify the delamination. Furthermore, the S0 wave reflected from the end edge of delamination was used to localize the delamination. Reflection coefficients were found to vary significantly with delamination depth, and the delamination's longitudinal position was accurately localized using Time-of-Flight (ToF) extraction. Finally, a pitch-catch experiment with MFC transducers was conducted to detect an artificial delamination, demonstrating that it is a promising approach to inspect delamination accurately with end-edge reflected waves.