Experimental determination of Lamb wave dispersion diagrams over large frequency ranges in fiber metal laminates

TL;DR

This paper presents an experimental method to accurately determine the dispersion diagrams of guided ultrasonic waves in fiber metal laminates across wide frequency ranges, validated against numerical models.

Contribution

It introduces a highly automatable experimental approach for measuring dispersion diagrams of GUWs in FMLs over large frequency ranges, filling a gap in existing literature.

Findings

Experimental dispersion diagrams match numerical solutions.

Method achieves high accuracy over broad frequency ranges.

Laser vibrometry effectively captures wave fields.

Abstract

Fiber metal laminates (FML) are of high interest for lightweight structures as they combine the advantageous material properties of metals and fiber-reinforced polymers. However, low-velocity impacts can lead to complex internal damage. Therefore, structural health monitoring with guided ultrasonic waves (GUW) 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 fiber-reinforced polymer 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.