Analysis To Mechanical Response Of Electro-active Polymer Membrane Transducer As Well As Its Optimization Design

As a kind of high molecular polymer, electro-active polymers (EAPs) can be explored and used in many fields. EAPs belong to the family of soft materials, possessing many excellent attributes such as good flexibility, lightweight and so on. When stimulied by chemical products or by voltage, the EAPs will bend flexibly or stretch intensely, acting like animal muscle. Due to this similarity, EAPs are called as artifical muscle. Actuators made of EAPs can convert electrical energy into mechanical energy directly. As a class of materials for electromechanical transduction, EAPs posses a unique combination of attributes:large deformation, fast response, high efficiency, low cost, and light weight.Due to these attributes, EAPs are promising for applications as transducers in cameras, robots, valves, pumps, energy harvesters and so on. In the family of EAPs, Dielectric elastomers (DEs) have gained so much attention. In the U.S.A, several typical actuators made of DEs have been fabricated and marketed as commercial products. The essential part of such actuators is a layer of dielectric elastomer membrane sandwiched between tow compliant electrodes. When subject to a voltage, the membrane will reduce its thickness while expand its area, converting electrical energy into mechanical energy. Instead of being used as actuators, DEs also can be used as energy harvesters. Unfortunately, the investigation on harvesting energy by DEs transducers is little so far.(1)Focuses on the large deformation analysis of electro-active polymers membrane-spring system. The system is constructed from attaching a disk in the middle of a circular dielectric membrane and then connecting the disk with a spring. The governing equations describing the large out-of-plane deformations of the membrane-spring system are formulated by combing the nonlinear theory of deformable dielectrics and thermodynamics. Then the governing equations are solved numerically by shooting method. The relations related to the displacement of the disk, the spring force, the applied voltage, and the parameters of spring including stiffness and initial length are illustrated. The results show the anticipated displacement of the disk can be achieved by adjusting the spring and the applied voltage individually or simultaneously, and the parameters of the spring, that is, stiffness and initial length, play an important role in the performance of the membrane-spring system. This configuration can be potentially used as a key part in valves. The results obtained in this part may provide some guidelines on designing and optimizing such valves.(2)The performance modes of energy harvesters made of DEs are discussed. Contrary to the mechanism of actuators, the energy harvesters can convert mechanical energy into electrical energy, functioning as a generator. The energy harvesters made of DEs are lightweight and have very high energy density, making them ideal candidates as portable energy sources. In addition to superior performance, DEs have two features that distinguish them from other energy-conversion materials:they are made from low cost materials that can be easily fabricated and they are compliant. DEs electrical energy generation is well suited to applications where electrical power must be produced from relatively large motions produced by wind and waves. In this part, the governing equations characterizing the large deformation of the dielectric elastomer membrane are derived based on the theory of deformable dielectrics. The membrane is susceptible to several modes of failure, including rupture, loss of tension, electrical breakdown, electro-mechanical instability etc. According to these failure modes, a closed loop is proposed to demonstrate the allowable performing range of the energy harvesters. This loop may be helpful to design and optimize the energy harvesters.