Delamination Identification of Laminated Composite Plates Using a Continuously Scanning Laser Doppler Vibrometer System

Abstract

Delamination frequently occurs in a laminated composite structure and can cause prominent local anomalies in curvature vibration shapes associated with vibration shapes of the composite structure. Spatially dense vibration shapes of a structure can be rapidly obtained by use of a continuously scanning laser Doppler vibrometer (CSLDV) system, which sweeps its laser spot over a vibrating surface of the structure. This paper extends two damage identification methods for beams to identify delamination in laminated composite plates using a CSLDV system. One method is based on the technique that a curvature vibration shape from a polynomial that fits a vibration shape of a damaged beam can well approximate an associated curvature vibration shape of an undamaged beam and local anomalies caused by structural damage can be identified by comparing the two curvature vibration shapes, and the other is based on the technique that a continuous wavelet transform can directly identify local anomalies in a curvature vibration shape caused by structural damage. In an experimental investigation, delamination identification results from the two methods were compared with that from a C-scan image of a composite plate with delamination.