Characterization of micro-scale creep deformation of an electro-active paper actuator

Abstract

The creep deformation process of an electro-active paper (EAPap) actuator wasinvestigated by adapting stepwise dead-weight loading. To understand the deformationmechanism of the EAPap film, including morphological and structural changes, variousloading conditions below yield strength were applied to cellophane EAPap. From thestructural observation, micro-dimples and micro-cracks were detected at applied load lowerthan 10% of yield strength, while they were not found in higher load conditions. It ishypothesized that only short and random fibers in the amorphous region may respond tothe applied stress at the low loading condition, not the fibers in the crystalline area. As aresult, deformation energy at the localized spot accumulated and created micro-defects atthe surface. Meanwhile, fibers in the crystalline region may sustain most of the loads ascreep load increases to a high level. Molecular chains in the fiber may rotate and elongatewith high load. Elongated fibers were observed only at a high level of load. From thestructural change as a function of applied load, a peak shift of crystal orientation wasobserved only in high load conditions by wide angle x-ray measurement. This mayconfirm that creep deformation could give rise to structure changes in EAPap.