Reference-free damage detection, localization and quantification in composite

Abstract

A reference-free damage detection, localization and quantification technique in a multi layered composite plate is proposed. It is reported that when A0 Lamb wave mode propa-gates the damage, time delay, attenuation and multiple reflections are occurred in the dam-age area. In this thesis, additional reflected waves from the damage due to multiple reflec-tions are used as a feature for characterizing the damage. First, the damage is identified by detecting the additional reflected waves from the damage area. Then, the location of the damage is estimated using combined pitch-catch and pulse-echo methods. Finally, the dam-age is quantified using a damage index defined as the ratio between the physical length of the damage and the wavelength of the A0 Lamb wave mode. The matching pursuit method is utilized for analyzing the obtained signal by decomposing overlapped waves and estimat-ing the parameters of each wave such as arrival time, driving frequency, amplitude, and so on. The proposed technique has an advantage that the damage can be characterized without reference data obtained from pristine condition of the monitored structure within a single path. The feasibility of the proposed technique is verified through numerical simulations and experimental tests. In numerical simulation, different damage models (length, material properties, and location) are investigated. In experimental tests, a Teflon tape inserted and impact-induced damage are characterized under temperature variations. The results are suggesting a reliable damage characterization in composites.