Optimum piezoelectric patch positioning: A strain energy-based finite element approach

For the design of smart composite structures, the placement of piezoelectric patch transducers is a very important issue. For sensing and passive vibration damping applications, the electric charge and the generalized electromechanical coupling coefficient are important parameters. This article presents an approximative but efficient method for the calculation of the generalized coupling coefficient using finite element simulation results. A smart composite turbomachine blade serves as a test structure for the new method. The influence of different laminate integration layers, positions, rotation angles, patch size variations and performance benefits of increased allowable strain is tested with the new procedure. The efficient nature of the method allows for parametric placement studies or even exhaustive search to find the global positioning optimum for the structure under investigation. The proposed method is compared to state-of-the-art procedures for the calculation of the generalized electromechanical coupling factor. The 1:5 scale models of full carbon fabric/epoxy blades were manufactured with structurally integrated piezo modules. Two different piezo placement positions inside the blade were investigated experimentally. The coupling coefficient was determined and compared to the calculated values.