IDENTIFICATION OF IMPACT DAMAGE ON A SANDWICH PLATE THROUGH NON LINEAR ELASTIC WAVE SPECTROSCOPY (NEWS) USING WAVELET ANALYSIS

摘要

In order to reduce the problems related to the detection of impact damage in composite structures, the development of new methodologies capable of localising and assessing impact damage are necessary. A possible answer at this problem is offered by an evolution of the Non linear Elastic Wave Spectroscopy (NEWS), a methodology developed for geophysics applications. The NEWS damage detection based technique consists in the analysis of spectrum of a signal acquired from the structure under investigation excited by a bi-harmonic signal. In pristine condition, the signal spectrum presents two picks at the excitation frequencies. In presence of damages, the material starts to behave non-linearly around the damage location, this behaviour shows up in the bi-harmonic excited signal spectrum as side bands of the excited frequencies. The magnitude and the number of the side bands are related to damage size and magnitude. In this study, experimental findings on a sandwich plate were compared in order to understand the sensitivity of the NEWS technique to impact damages. The results showed that the proposed methodology was capable of localising successfully the presence of impact damage and impact location and it can be used as a first assessment of the presence of damage in aircraft application where the presence of damage should be quickly estimated. Further research studies and methodology development are needed to assess the location, the magnitude and the type of damage.