TEHNOMUS - New Technologies and Products in Machine Manufacturing Technologies 80 MECHANICAL TESTING OF ELASTOMERS FOR SENSOR AND ACTUATOR APPLICATIONS Vlad Cârlescu 1 , Vlad Stelian 2 , Gheorghe Prisăcaru 1, Dumitru Olaru 1 1 ”Gheorghe Asachi” Technical University of Iaşi, Faculty of Mechanical Engineering, Str. D. Mangeron 43, 700050, Iasi, Romania. e-mail: carlescu.vlad@yahoo.com 2 “Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41 A, 700487 Iasi, Romania. Abstract: Mechanical testing of soft materials, such as polymers, elastomers and bio- materials, presents considerable challenges that do not arise when characterizing metals and ceramics. Soft elastomers, mostly silicones and acrylics, are interesting candidates as dielectric materials in electroactive polymer (EAP) actuator technology [1]. In this paper we investigated the elastic properties of poly(dimethylsiloxane)-based elastomer films using various mechanical tests. Uniaxial tensile and compression tests were performed in room conditions in order to determine the elastic modulus that showed to have similar values for both tests. In order to investigate the membrane behavior, biaxially stress tests were performed by indentation of freestanding circular films with various spherical indenter sizes at loads up to 1 N. The load– deflection measurements showed a non-linear elastic response, typically for elastomers, that depends on span length and indenter size. Also, the load-displacement measurements of indentation of flat films showed a strong non-linearity. In this case, classical Hertz solution is not valid, so other constitutive models that account for non-linear elastic contact needed to be considered. Keywords: elastomers, mechanical tests, elastic modulus, EAP actuators 1. Introduction Polymers have many advantages such as low manufacturing cost, lightweight, compliant nature, fracture tolerant, can be made in different shape or size, easy handling etc. They are used in various applications including toys, footwear, electronics, coatings, paints, adhesives, tires, packing and encapsulating materials etc. It was showed that polymers can change their shape or size in response to various stimuli including chemical, thermal, pneumatic, optical, electric and magnetic. Recently, much attention has been paid to soft elastomers, mostly silicone and acrylic, as dielectric electroactive polymers (EAPs) in the field of novel actuator technology [1]. Dielectric elastomers (DEs) consist of a thin polymer film sandwich between two compliant electrodes. When a voltage is applied across the electrodes, the electrostatic forces from the opposite electric charges create a pressure, called Maxwell stress, which squeeze the film in thickness direction and expand it in area. Dielectric elastomer actuators (DEAs) showed good overall actuator performance such as linear and circular electric field-induced strain responses beyond 200%, high stress (up to 7.2 MPa), high elastic energy density of 3.4 J/cm 3 , good efficiency and high response speed in order of milliseconds [2],[3],[4]. DEs have also showed the capability to be used in sensors and generators applications [5],[6],[7]. The specific requirements for DE materials depend on the actuator type and its foreseen