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9 April 2010 Radially expanding mechanism for dielectric elastomers
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Dielectric elastomer actuators (DEAs) offer numerous benefits as high displacement smart material actuators. The output of a DEA film is typically characterised by a large area expansion and a smaller transverse displacement. Consequently, their application is often limited by difficulties in resolving area expansion strain into a usable output. Certain DEAs also require pre-strain in order to achieve optimal performance. In this paper, Hoberman's radially expanding mechanism is used to form a novel DEA structure. The mechanism is composed of a number of repeating angulated scissor-links which resolve area expansion into a uniaxial displacement and have intrinsic pre-straining capabilities. This allows the Hoberman mechanism to be exploited as an actuator or as a pre-straining device. The stress distribution induced in the elastomer film when the mechanism is expanded was analysed using photoelasticity, which showed a 6 segment mechanism produces a significantly more uniform strain pattern compared to 4 segments. Prototype DEA mechanisms demonstrated that the Hoberman linkage does resolve area expansion strain into a uniaxial displacement (which can be linear or rotary) at the cost of mechanical friction losses. The 4 segment DEA prototype produced a maximum stroke of 3.13 mm (6.88% planar strain) with a tensile load of 1.46 N. The 6 segment DEA prototype demonstrated improved performance with a maximum stroke of 4.52 mm (7.51% planar strain) and a maximum rotation of 4.98°.
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A. T. Conn and J. M. Rossiter "Radially expanding mechanism for dielectric elastomers", Proc. SPIE 7642, Electroactive Polymer Actuators and Devices (EAPAD) 2010, 76420P (9 April 2010);

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