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Electroactive polymers have been widely used as smart material for actuators in recent years. Electromechanical applications are currently focused on energy harvesting and actuation, including the development of wireless portable electronic equipment autonomous and specific actuators such as artificial muscles. The problem to be solved is to make its devices the most efficient, as possible in terms of harvested energy and action. These two criteria are controlled by the permittivity of the electrostrictive polymer used, the Young’s modulus, and their dependence on frequency and level of stress. In the present paper, we presented a model describing the mechanical behaviour of electrostrictive polymers with taking into account the mechanical losses. Young’s modulus follows a linear function of strain and stress. However, when the elongation becomes higher, the data obtained from this strain linear trend and significant hysteresis loops appear the reflections on the existence of mechanical losses. In this work, to provide the analysis of the experimental observations, we utilized a theoretical model in order to define a constitutive law implying a representative relationship between stress and strain. After detailing this theoretical model, the simulation results are compared with experimental ones. The results show that hysteresis loss increases with the increase of frequency and strain amplitude. The model used here is in good agreement with the experimental results.

An approach to harvesting electrical energy from a mechanically excited piezoelectric element has been described. The topic of this paper studies the most important properties of piezoelectric polymer polyvinylidene fluoride (PVDF) in energy harvesting. We have chosen to develop a recovery application within the clothes. By the use of a piezoelectric energy harvester capable to convert the mechanical energy produced by the knee during walking to an electrical energy. This will be achieved by replacing the traditional textile of the kneepad with the one that is made of the technical textile based on acrylic knitted and PVDF as a patch stuck on the textile. Furthermore, PVDF has many unique features, such as excellent mechanical behavior, large strain without structure fatigue, which enables it to act strongly as the load bearing member, and corrosion resistance. The technical textile, functioning as multifunctional wearable human interfaces, is considered today as a useful tool in several energy fields. In this paper, a smart structure based on piezoelectric polymer (PVDF) has been presented, which a power analytical model, based on the frequency, the geometrical parameters and other factors were investigated. Furthermore, the set of numerical results illustrating the harvested power for a given size of the device has been performed and discussed and how this harvested power may be used as a source for a wearable device. Finally, the theory presented in this study can be used for the realization of other optimal designs, for a wearable sensor with low consumption and so on.

The use of piezoelectric nanocomposite in detection and actuation applications for the development of electromechanical microsystems (MEMS) has become quite common over the last decade. In this paper, we present a flexible piezoelectric nanocomposite films, composed of lead zirconate titanate (PZT) nanoparticles, embedded in poly(vinylidene-difluoride hexafluoro propylene) (PVdF-HFP) matrix. Piezoelectric and ferroelectric properties evolution is proportional to the evolution of the crystalline β-phase. The evaluation of the interactions between PZT and PVdF- HFP, performed by Fourier transform infrared spectroscopy (FTIR), revealed a dramatic improvement in these characteristics over pure PVdF-HFP, and attributed to a better crystallinity of the PVdF-HFP matrix and uniform distribution of nanoparticles. These films nanocomposites were done by solvent casting method, with various concentrations of PZT. Results of these experiments indicate that the investigated thin films nanocomposites are appropriate for various applications in energy storage and energy harvesting application.