A two‐dimensional analysis of the influence of delamination on the wave propagation in a fiber metal laminate

Abstract Structural Health Monitoring (SHM) of composite materials using Guided Ultrasonic Wave (GUW) represent a central research topic with a large range of application fields. One major concern in this context is the detection of hidden inter‐laminar damage such as delaminations in composites, as these cannot be detected by visual inspection [1]. Fiber Metal Laminate (FML) consist of different layers of metal (e.g. steel) and Fiber Reinforced Polymer (FRP) stacked on top of each other and belong to a new type of material system that has been insufficiently explored in the context of damage detection using GUW. Following the objective of damage detection using GUW, two dimensional numerical simulations of the wave propagation in FML composed of layers made from steel and Carbon Fiber Reinforced Polymer (CFRP) are conducted. In order to properly identify and describe the different phenomena occurring when the GUW encounter a delamination three kind of numerical models were considered: undamaged plate, damaged plate with symmetrically and off‐center placed delamination. As far as the modeling of delaminations, the present work is restricted to a zero‐thickness‐delamination generated by de‐merging nodes at the interface of the layers. Mode‐selective excitation (fundamental symmetric and anti‐symmetric mode wave) of the models was then applied and the B‐scan representations of the in‐plane and out‐of‐plane displacement fields were generated and compared. Effects such as reflection, transmission and mode conversion of the main wave are observed and analyzed. Thus, a singular phenomenon as the trapped mode wave can be clearly observed and interpreted.