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

Due to low impact strength of C/C, it's important to evaluate impact damage properties and impact strength. In this study, the estimating method for impact damage is used to evaluate the relationship between the impact load and displacement, absorbed energy of C/C specimens on a drop weight impact test. The measured impact load is decomposed in approximation components and detail components by multiple resolution analysis in wavelet transform. 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 produce, the approximation component demanded by wavelet analysis accords with the wave pattern of the numerical computation result that is removed free vibration component.