IMPACT DAMAGE MONITORING OF AIRCRAFT COMPOSITE STRUCTURES WITH PIEZOELECTRIC SENSORS

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In the present research, we have developed a real-time and automatic health monitoring method for smart composite structures with strain sensors, in order to improve the reliability and safety of composite structures. The conclusions obtained by the present study are summarized as follows:1. We have proposed a force identification method using an experimental transfer matrix, and identified the location and history of impact force from dynamic strain responses in composite laminates. The validity of the present method is verified through an impact test of CFRP stiffened panels with impulse hummer, and the location and history of impact force can be identified precisely in a few seconds after impact.2. A real-time damage monitoring method has been developed using the identified impact force history. It is shown that the damage occurrence can be predicted easily from the shape of the identified force history, where the shape of force history is smooth without damage while that has a sharp oscillation with damage.3. The experimental relationships between the impact energy and the maximum force, and between the maximum force and the damage size have been obtained in drop-weight test, which have a good agreement with predicted ones based on the finite element analysis. Delamination size predicted by the finite element analysis has also a good agreement with that observed experimentally by the ultrasonic C-scan image.