A numerical model for the analysis and simulation of electro-active paper

• Applicant: Professor Dr.-Ing. Sven Klinkel
• Subject Area: Applied Mechanics, Statics and Dynamics
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 393020662

In recent years, electro-active paper (EAPap) has emerged as an interesting alternative in the field of actuation devices. Similar to piezoelectric materials and dielectric elastomers, the material is deformed under the influence of an electric field. In contrast to these materials, no build-up of layers is necessary for an actuator device in order to enable a bending actuation. Since an ionic diffusion process occurs through the thickness of the paper, the actuator is mainly bent instead of being compressed as in piezo-ceramics and dielectric elastomers. The main advantage of this technology is that large bending deformations can be obtained for low voltage application. Other remarkable properties are lightweight and biodegradability, which opens up many possibilities for practical applications in the field of smart actuators.EAPap is a piezoelectric cellulose which is characterized by ordered regions consisting of chitosan chains. During the fabrication process, hydrogen chloride is injected in the material which gets attached to the ordered chitosan chains. Under the influence of an applied electric field, the chloride anions detach from the chitosan chains and migrate to the anode, converging towards a heterogeneous distribution of ionic mass and charge. Consequently, electrostatic forces and hydrostatic stresses are heterogeneously distributed over the thickness of the EAPap, which results in the bending of the actuator. In the literature, the phenomenological behavior is highly simplified with respect to the structural analysis by piezoelectric models. This research project aims for a numerical and phenomenological model, which captures the physical bending behavior of EAPap by considering the piezo effect as well as the diffusion of ions. Since EAPap is a rather thin structure, a shell formulation is derived as a starting point for the modeling. We seek for a model that incorporates the inhomogeneous ionic distribution by a so-called scaled boundary shell formulation. Additionally, it facilitates the computation of the highly non-linear strains through the thickness of the structure. An extension to electro-mechanical coupled problems is provided. We are aiming for a model that accounts for the bending actuation mechanism by describing the deformation of EAPap as a function of the ionic distribution. The model includes electrostatic forces as well as volumetric changes. Moreover, the time-dependent behavior is an additional focus of the project. In particular, a model for the ionic migration over time is proposed. For this purpose, the diffusion of ions is considered as a function of the applied external electric field. Finally, the project provides a simulation method for the development and refinement of EAPap actuators for realistic applications. This method may also be adapted conveniently to similar actuation principles as e.g. ionic polymer metal composites.

• DFG Programme: Research Grants