WAVELET-BASED ACTIVE SENSING FOR QUANTITATIVE ASSESSMENT OF THROUGH-THICKNESS CRACK SIZE AND ANGLE IN COMPOSITE PLATES

摘要

Cost-effective and reliable damage detection is critical for utilization of composite materials. This paper utilizes PZT piezoelectric disks to excite the first symmetric Lamb wave (So mode). The interaction of Lamb wave mode with a through-thickness crack of different lengths and angles in [0/45/-45/90]_s CF/EP laminate plates is analyzed in terms of finite element method. This study contributes to the damage detection by developing an improved wavelet-based signal processing technique that enhances the visibility and interpretation of the Lamb wave signals related to defects. Based on the amount of energy dissipated by the damage, a damage index is defined as the function of an electric signal's attenuation for a limited time span and at the input frequency of the signal.