Experimental determination of dispersion diagrams over large frequency ranges for guided ultrasonic waves in fiber metal laminates

Fiber metal laminates (FMLs) are of high interest for lightweight structures as they combine the advantageous material properties of metals and fiber-reinforced polymers (FRPs). However, low-velocity impacts can lead to complex internal damage. Therefore, structural health monitoring with guided ultrasonic waves (GUWs) is a methodology to identify such damage. Numerical simulations form the basis for corresponding investigations, but experimental validation of dispersion diagrams over a wide frequency range is hardly found in the literature. In this work the dispersive relation of GUWs is experimentally determined for an FML made of carbon FRP and steel. For this purpose, multi-frequency excitation signals are used to generate GUWs and the resulting wave field is measured via laser scanning vibrometry. The data are processed by means of a non-uniform discrete 2d Fourier transform and analyzed in the frequency-wavenumber domain. The experimental data are in excellent agreement with data from a numerical solution of the analytical framework. In conclusion, this work presents a highly automatable method to experimentally determine dispersion diagrams of GUWs in FML over large frequency ranges with high accuracy.

Automated summary

In this work, the dispersive relation of guided ultrasonic waves (GUWs) in fiber metal laminates (FMLs) made of carbon FRP and steel is experimentally determined. Multi-frequency excitation signals and laser scanning vibrometry are used to measure the resulting wave field. The data are processed and analyzed in the frequency-wavenumber domain, showing excellent agreement with numerical solutions.