Reliability and limitations of Impact-Echo Method for Thickness Measurement of Orthotropic Composite Plates

In this paper, an Impact-Echo method has been used to numerically simulate low velocity impact of a steel ball on laminated composite plates in order to measure the plate s thickness. For the purpose of simulation, Ls-Dyna finite element code has been employed to express the behaviour of impact between steel ball and composite plates. Furthermore, a single node near the impact area has been chosen and its displacement was demonstrated during the impact time on a graph by the software. After that, displacement-time graph was transformed to amplitude-frequency domain graph by means of Fast Fourier Transform which was done by MATLAB software. The peak frequency was used to calculate the plate s thickness. The calculated thickness was verified by real plate thicknesses and this comparison shows an acceptable agreement between simulation and experimental results.