Estimation of Impact Damage in C/C Composites by Drop Weight Tests (Wavelet Analysis of Impact Load)

Abstract

The evaluation of impact damage properties and strength of C/C composites is becoming important, due to its low impact strength. In this study, the impact damage is evaluated by using the impact load-deflection diagrams and absorbed energy of specimens on a drop weight impact test. The measured impact load is decomposed in approximation components and detail components by multiple-resolution analysis based upon the wavelet transform. And then the possibility of wavelet analysis for estimating the impact damage is studied. The results are as follows: (1) The Daubechies' wavelet is useful for smoothing the impact load signals by multiple resolution analysis in wavelet transform. (2) In the low impact energy that most of the damage does not occur, the approximation component result demanded by wavelet analysis accords with the wave pattern of numerical one that is removed free vibration component.