Non-Model-Based Identification of Delamination in 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 introduces a continuous scanning scheme for general quadrangular scan areas assigned on plates and 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 structure can well approximate an associated curvature vibration shape of an undamaged structure and local anomalies caused by structural damage can be identified by comparing the curvature vibration shape of the damaged structure with that from the polynomial fit, 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. The two methods yield corresponding damage indices and local anomalies in curvature vibration shapes can be identified in neighborhoods with high damage index values. Both numerical and experimental investigations on effectiveness of the two methods are conducted on a laminated composite plate with a delamination area. In the experimental investigation, delamination identification results from the two methods were compared with that from a C-scan image of the composite plate.

Operational modal analysis using lifted continuously scanning laser Doppler vibrometer measurements and its application to baseline-free structural damage identification

“…a r  à T is an r þ 1 ð Þ-dimensional coefficient vector. As pointed out in Xu et al (2014Xu et al ( , 2017 and Chen et al (2016Chen et al ( , 2017Chen et al ( , 2018b, an increase of r in equation ( 36) can improve approximation of p j to j , but one should avoid over-fitting j . To determine the proper value of r in equation ( 36), a fitting index and a convergence index in Xu et al (2017) can be defined by…”

Diagnostics Based on Continuous Scanning LDV Measurements and RASTAR Analysis Method

“…CSLDV techniques well-suit structural integrity analysis for damage detection and identification and, in fact, several papers are available to this account. CSLDV techniques were attempted to either cracked beams or plates embedding damages, and these researches can be read in [15][16][17][18][19][20][21][22][23][24][25][26][27]. One of the most distinctive features of all the CSLDV papers, cited in here, is the recovery of the ODS(s) as means for further investigation of damage detection and identification.…”

Vibration-Based In-Situ Detection and Quantification of Delamination in Composite Plates

“…The scanning laser Doppler vibrometer has been widely used for vibration response measurements [30,31,32]. For the actuators, various methods of exciting the monitored structures can be found in the literature, such as shakers [36,37,38], hammers [39], and speakers [40]. Moreover, several researchers have explored the capability of piezoelectric wafer active sensors (PWAS) transducers for vibration-based delamination detection [30,41,42,43].…”