Nonlinear elastic wave spectroscopy identification of impact damage on a sandwich plate

Fragility of composite material to impact loading limits their application in aircraft structures. There is the need to develop reliable monitoring devices capable of localizing and assessing impact damage. At this aim, a new technique, non-linear elastic wave spectroscopy (NEWS), developed for geophysics applications, is investigated and presented in this paper. The NEWS damage detection based technique consists in the analysis of the spectrum of a signal acquired from the structure under investigation excited by a bi-harmonic signal. In pristine conditions, the signal spectrum presents two picks at the excitation frequencies. In presence of damages, the material starts to behave non-linearly and sidebands and harmonics of the excited frequencies are generated. In this study, experimental findings on a sandwich plate are presented in order to understand the capability of the NEWS technique to detect impact damages. (C) 2005 Elsevier Ltd. All rights reserved.