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Biocomposites based on thermoplastic polymers and natural fibers have recently been used in wind turbine blades, to replace non-biodegradable materials. In addition, carbon nanofillers, including carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), are being implemented to enhance the mechanical performance of composites. In this work, the Mori–Tanaka approach is used for homogenization of a polymer matrix reinforced by CNT and GNP nanofillers for the first homogenization, and then, for the second homogenization, the effective matrix was used with alfa and E-glass isotropic fibers. The objective is to study the influence of the volume fraction Vf and aspect ratio AR of nanofillers on the elastic properties of the composite. The inclusions are considered in a unidirectional and random orientation by using a computational method by Digimat-MF/FE and analytical approaches by Chamis, Hashin–Rosen and Halpin–Tsai. The results show that CNT- and GNP-reinforced nanocomposites have better performance than those without reinforcement. Additionally, by increasing the volume fraction and aspect ratio of nanofillers, Young’s modulus E increases and Poisson’s ratio ν decreases. In addition, the composites have enhanced mechanical characteristics in the longitudinal orientation for CNT- reinforced polymer and in the transversal orientation for GNP-reinforced polymer.

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.

The future trends of wind turbine blade materials are mostly centered around utilizing lighter materials with improved life cycle and low cost. In modern wind turbine blade, using green composite or biocomposite is a sustainable solution, especially for small wind turbine blade with natural fiber and biodegradable polymer. In this work, four natural fibers (Alfa, Flax, Sisal and Hemp) are used with Polypropylene (PP) thermoplastic polymer. The objective is to evaluate the elastic muduli of composite by two methods; Analytical Mori Tanaka theory and numerical with Digimat MF. The results show a good validation between the two methods. The comparison of the mechanical behaviour of the transversely isotropic of natural fibers indicate that the hemp have a good performance with high Young and shear modulus regarding to their low density, which can offer an excellent candidate for the manufacturing of small wind turbine blades in rural and isolated areas.

This paper presents and compares films made using the solution casting method with a mixture of poly (vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), graphene oxide (GO), and lead zirconate titanate (PZT). The Hummers' method synthesized GO. Scanning electron microscopy (SEM), Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and tensile testing were realized. The developed composite films were found to have a coherent distribution of PZT and GO in PVDF‐HFP. After that, a gradual improvement, such as an increase in the quantity of β phase, produces high piezoelectric performance. Also, the PVDF‐HFP polymer's thermal stability improved. When 0.1 wt% of PZT/GO was added, the melting temperature increased from 140 to 143°C, and the crystallization temperature from 109 to 113°C. PVDF‐HFP elastic modulus and tensile strength were also considerably reduced as PZT/GO increased. As a result, this has enabled us to develop composite films with important properties that can be used as piezoelectric materials for energy harvesting.

In the last few years, a lot of research focused on increasing of smart textiles products such as woven and knitted structures, which are able to show significant change in their mechanical properties (such as shape and stiffness), in a practical way in response to the stimuli. In this paper, we investigate the potential of a flexible piezoelectric film stuck onto three woven textile matrices: cotton, polyester/cotton, and Kermel, for harvesting mechanical energy from the textile and converting it into electrical energy. At first, a brief introduction of energy harvesting using the piezoelectric material and smart textile is presented. Furthermore, a basic model showing the operation of polyvinylidene fluoride with 33 mode is established. The second part is focused on standard approach model of energy harvesting based on resistive load and freestanding piezo-polymer for the examination of the performance of 33-mode polyvinylidene fluoride energy harvester and the prediction of harvested energy quantity. A power analytical model generated by a smart structure type polyvinylidene fluoride that can be stuck onto fabrics and flexible substrates is investigated. On the other hand, the effects of various substrates and the sticking of these substrates on the piezoelectric material are reported. Additionally, the output power density of this theoretical model of woven textile matrices could reach a value that was seven times higher than freestanding piezo-polymer. Three types of the substrates have been compared as function of excitation frequency and the compressive applied force.

The 3D printing technology used for small tidal and wind turbines has great potential to change and overcome certain weaknesses in traditional manufacturing techniques. In rural areas and isolated communities, small turbine systems could be locally fabricated and assembled by using additive manufacturing machines and also can be employed to decrease residential energy consumption. The objective of the paper is to study the thermomechanical performance of 3D printing of a small-scale tidal turbine blade and their process using Digimat-AM because more research efforts are needed in this area. In this work, the tidal turbine blade is printed by using the Selective Laser Sintering SLS method with Polyamide 12 (PA12) and Polyether ether ketone (PEEK) polymers reinforced by carbon beads (CB) and glass beads (GB). This research examines conceptual considerations of small tidal turbines including material properties and aerodynamic parameters. Once the finite element evaluation has been completed, the deflection, residual stresses, temperature distribution, and the deformed blade or warpage can be obtained. It is concluded that PA12-CB has warpage higher than PA12-GB by 3.78%, and PEEK-CB has warpage lower than PEEK-GB by 8.4%. Also, the warpage of PA12-CB is lower than PEEK-CB by 10.31%, and the warpage of PA12-GB is lower than PEEK-GB by 20.95%. Therefore, the lowest warpage is observed for PA12-GB. Finally, the results showed that 3D printing presents an excellent opportunity in the design and development of tidal energy systems in the future.