Health monitoring of smart structures using damage index sensors

Simple and inexpensive passive sensors that can monitor the peak strain or displacement of a critical structural member were developed. The developed sensors have an ability to quickly assess the degree of damage in a structure when a checkup is needed. The sensors need no power supply for monitoring. The peak values can be retrieved wirelessly if desired. In addition, they can be easily modified to measure other damage indexes such as maximum acceleration and force. The mechanism to memorize the peak strain or displacement values relies on the pure plastic extension of sensing section. The pure plastic extension of the sensing section is made possible by introducing elastic buckling. The peak value is detected by measuring a change in electric resistance, inductance or capacitance. In addition, introduction of an LC circuit intohe sensor enabled wireless retrieval of the data. Theoretical and experimental studies exhibit the feasibility of the developed sensors for structural health monitoring of smart structures.