Energy conversion of electrostrictive poly(vinylidene fluoride-co-hexafluoropropylene)/Graphene composites

This study investigates energy-conversion properties of the electrostrictive polymer, poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), filled with graphene nanosheets (GNPs). The composites (i.e., P(VDF-HFP) and GNPs) were fabricated by using the solution casting method. The dielectric constant of these electrostrictive materials was measured to observe the energy conversion property with different frequencies using an LCR meter. Their mechanical properties were measured using a photonic sensor with varying various input vibrations and electric fields to calculate their electrostrictive coefficients. These characterized results revealed that dielectric constants and electrostrictive coefficients were significantly increased when GNPs fillers were filled higher. For the electrical property, the generating current, which was measured across these polymer films, increased proportionally with respect to the adding GNPs. In this obtained result, the main finding of P(VDF-HFP)/GNPs composites is a promising electrostrictive material for applications of electromechanical energy conversions in many smart-material systems.

Electrostrictive polymer plates as electro-elastic material surfaces: Modeling, analysis, and simulation

In this article we discuss modeling of electrostrictive polymer plates as electro-elastic material surfaces. A complete direct approach is developed without the need to involve the three-dimensional formulation. Ponderomotive forces and couples as well as constitutive coupling by means of electrostriction are accounted for. We propose a rational formulation for the augmented free energy of electro-elastic material surfaces incorporating electrostriction by a multiplicative decomposition of the surface stretch tensor and an additive decomposition of the surface curvature tensor into elastic and electrical parts. Numerical results computed within the framework of this complete direct approach are compared to results computed with a method that requires the numerical integration of the three-dimensional augmented free energy through the thickness of the plate and to alternative formulations reported in the literature.

Analysis of Parametric Resonances in In-Plane Vibrations of Electrostrictive Hyperelastic Plates

Electrostriction is a recent actuation mechanism which is being explored for a variety of new micro- and millimeter scale devices along with macroscale applications such as artificial muscles. The general characteristics of these materials and the nature of actuation lend itself to possible production of very rich nonlinear dynamic behavior. In this work, principal parametric resonance of the second mode in in-plane vibrations of appropriately designed electrostrictive plates is investigated. The plates are made of an electrostrictive polymer whose mechanical response can be approximated by Mooney Rivlin model, and the induced strain is assumed to have quadratic dependence on the applied electric field. A finite element model (FEM) formulation is used to develop mode shapes of the linearized structure whose lowest two natural frequencies are designed to be close to be in 1:2 ratio. Using these two structural modes and the complete Lagrangian, a nonlinear two-mode model of the electrostrictive plate structure is developed. Application of a harmonic electric field results in in-plane parametric oscillations. The nonlinear response of the structure is studied using averaging on the two-mode model. The structure exhibits 1:2 internal resonance and large amplitude vibrations through the route of parametric excitation. The principal parametric resonance of the second mode is investigated in detail, and the time response of the averaged system is also computed at few frequencies to demonstrate stability of branches. Some results for the case of principal parametric resonance of the first mode are also presented.