Identifying Delamination in Composite Beams Using Built-In Piezoelectrics

Abstract

An investigation was performed on using piezoelectrics built into laminated composite structures to detect a delamination and estimate its size and location. Previously, a structural model was developed for predicting the output voltages from the sensors when a delaminated beam was excited by the actuators. In this sequel, a delamination identification method is presented which consists of the structural model, a response comparator and a damage selector. When damage is suspected, the structural model is run repeatedly to predict the changes in response due to different possible delaminations. During these runs, delamination sizes and locations are selected randomly by the damage selector, which is based on an approach similar to the "simulated annealing algorithm" that improves agreement between the measured and calculated responses. In the response comparator, the agreement is quantified by using a weighted quadratic objective function. When the objective function is minimized, the responses agree, and the assumed damage is also a best estimate for the actual delamination dimensions. The method has been tested using responses measured in the laboratory and has successfully identified artificially implanted beam delaminations.