A molecular perspective to analytical modeling that reveals new instabilities in dielectric elastomer transducers

摘要

We use a four-parameter material model for polymers - the Edward-Vilgis (EV) model, which models polymeric crosslinks, sliplinks, slippage and inextensibility to analyze dielectric elastomers (DEs). The EV model allows us to investigate the DE response from a molecular perspective, revealing new instabilities in DEs, primarily due to sliplinks. We compare the EV model with the Gent model - a crosslink-only model commonly used in the field of DE, on its ability to fit the non-linear stress-strain response of an acrylic elastomer (VHB 4905), which contains a significant amount of entanglements. We found that the EV model provided an excellent fit to the strain softening phenomenon at small to modest strains, which is missed by the Gent model. Slippage of sliplinks at these regions of strain produces slip resistance that contributed to enhance the resistance to applied forces. Subsequent slip relaxation due to the uncoiling of entanglements will lead to significant strain softening, giving the DE a higher susceptibility to mechanically and electro-mechanically-induced instabilities. From our analyses, we produced mechanical stability phase plots and electromechanical stability design plots, for elastomers of different sliplink-to-crosslink compositions. Such plots may serve as guides to develop dielectric elastomers with desired material properties and performances, and tailor to specific applications. (C) 2019 Elsevier Ltd. All rights reserved.