Damage identification in composites using built-in piezoelectrics

An identification method was developed that uses measured responses from piezoelectrics built into laminated composite beams to detect a delamination and estimate its size and location. This development involved both experimental and analytical work.;Experiments were performed using surface-mounted piezoceramics on composite beams with and without an artificial delamination. Some of these piezoceramics were used as actuators to dynamically excite specimens while others were used as sensors to measure strains. These experiments showed that a delamination changes the dynamic forced response. Therefore, when a measured response differs from an undamaged structure's baseline response, damage could exist and the identification procedure is run.;The identification procedure consists of a response comparator, a damage selector and a model. The model is run repeatedly to predict the changes in response due to different possible delaminations. After each run, the damage selector chooses the next assumed delamination size and location randomly, using an approach related to "simulated annealing" that improves agreement between the measured and calculated responses. The response comparator then compares these two responses using a weighted quadratic objective function. When the objective function is minimized, the responses agree, and the assumed delamination dimensions are also best estimates for the actual dimensions. The technique has been tested using measured responses and has successfully identified artificially implanted beam delaminations.