Composite materials such as fiber metal laminates combine the advantages of metallic materials and fiber-reinforced polymers. Hence, these materials are of great interest for thin-walled structures in lightweight engineering. Due to the structure of these materials, damage to fiber metal laminate components occur more frequently inside the structure than with conventional materials. Since the detection of interlaminar damage is more complicated compared to external damage, it is one of the biggest challenges in the use of fiber metal laminates. One approach to detect this kinds of damage, is the use of guided ultrasonic waves, for example Lamb waves. To be able to perform such damage detection, knowledge about the propagation behavior of this kind of waves in fiber metal laminates is fundamental. Abrupt stiffness variations across the thickness of fiber metal laminates, resulting from the different material layers, lead to the question whether the known approaches for the propagation of guided ultrasonic waves in isotropic and transversely isotropic materials are applicable here. Therefore, the objective of this work is to investigate the propagation behavior of these guided ultrasonic waves in fiber-metal laminates over large frequency ranges. For this purpose, dispersion relations from finite element simulations are compared with experimental data and numerical solutions based on the analytical framework. The investigations are carried out using a fiber metal laminate consisting of steel and carbon fiber-reinforced polymers. Due to the orthotropy of the laminate, wave propagation in the fiber direction and perpendicular to it is considered. For the finite element simulations a linear two dimensional eigenvalue analysis is used. This method is especially suitable because it offers a very efficient modeling approach for this kind of application. The experimental data are based on measurements contained in previous publications by the authors. The comparison of the finite element simulations with the experimental data and the data from the analytical framework show that they are in good agreement. The results shown in this work serve to validate the numerical approach presented and allow for further, more complex simulations.
T. Barth, J. Wiedemann, T. Roloff, C. Hühne, M. Sinapius, N. Rauter
Investigations on Guided Ultrasonic Wave Dispersion Behavior in Fiber Metal Laminates Using Finite Element Eigenvalue Analysis
Proceedings in Applied Mathematics & Mechanics, 23, e202200149, (2023) [Link]