Poly(vinylidene fluoride), PVDF, as one of important polymeric materials with extensively scientific interests and technological applications, shows five crystalline polymorphs with α, β, γ, δ and e phases obtained by different processing methods. Among them, β phase PVDF presents outstanding electrical characteristics including piezo-, pyro-and ferroelectric properties. These electroactive properties are increasingly important in applications such as energy storage, spin valve devices, biomedicine, sensors and smart scaffolds. This article discusses the basic knowledge and character methods for PVDF fabrication and provides an overview of recent advances on the phase modification and recent applications of the β phase PVDF are reported. This study may provide an insight for the development and utilization for β phase PVDF nanofilms in future electronics.

https://www.mdpi.com/2073-4360/10/3/228/pdf

Properties and Applications of the β Phase Poly(vinylidene fluoride).

Vibrations of straight and curved composite beams: A review

Rotating composite beams and blades have a wide range of applications in various engineering structures such as wind turbines, industrial fans, and steam turbines. Therefore, proper understanding of such structures is of a great importance. As a result, the behavior of rotating composite beam structures has received a lot of attention. This paper presents a comprehensive review of scholarly articles about rotating composite beams as published in the past decades. The review addresses analytical, semi-analytical and numerical studies dealing with dynamical problems involving adaptive/smart/intelligent materials (e.g. piezoelectric materials, electrorheological fluids, shape memory alloys, etc.), damping and vibration control, advanced composite materials (e.g. functionally graded materials and nanocomposites), complicating effects and loadings (e.g. added mass, tapered beams, initial curve and twist, etc.), and experimental methods. Moreover, the influence of Vlasov or restrained warping, out-of-plane warping, transverse shear, arbitrary cross-sectional geometry, trapeze phenomena, swept tip, size-dependent effect, as well as other areas that have been considered in research, are reviewed in depth. The review concludes with a presentation of the remaining challenges and future research needs.

Dynamics, vibration and control of rotating composite beams and blades: A critical review

Polyvinylidene fluoride (PVDF) is known as a favorite polymer from the family of fluoropolymers due to its excellent piezoelectric properties, thermal stability, and mechanical strength. It has a good processability, and it also possess chemical resistance property to different materials such as different acids, bases, organic solvents, oil, and fat. The present study reveals an overview of the recent growth and development in the application perspective and modification of PVDF membranes, majorly focus on sensors and actuators, spin-valve devices, magnetoelectric materials, energy harvesting applications, tissue engineering, modeling engineering, and other biomedical engineering and devices. From an electronic point of view, ferroelectric polymers are insulating, polar, and possess a non-conjugated backbone; therefore, they are termed as highly insulating materials. The insulating polymers are most attractive for the study of charge transportation and storage. Such polymers also yield the best electrets for practical application because of their insulating properties and high concentration of deep trapping sites. Thus, the objective of this review is to present the physical, chemical, thermal, and mechanical properties of PVDF. This article also provides an intelligent direction in the progress of PVDF in different fields of science and technology.

Seung-Chan Choi

Papers

Vibration control of pre-twisted rotating composite thin-walled beams with piezoelectric fiber composites

Active damping of rotating composite thin-walled beams using MFC actuators and PVDF sensors