Response Of Piezoelectric Composites Research Articles

Development of poly(vinylidene fluoride)/thermoplastic polyurethane/carbon black‐polypyrrole composites with enhanced piezoelectric properties

AbstractPoly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) composites filled with carbon‐black polypyrrole were prepared via melt compounding followed by compression molding and fused filament fabrication. CB‐PPy was added to the blends from 0 up to 15% to possible act as nucleating filler for PVDF β phase in order to increase its piezoelectric response. The influence of blending PVDF and TPU and of the addition of CB‐PPy on the overall crystallinity, content of β phase, and piezoelectric response of composites were investigated by differential scanning calorimetry (DSC), Fourier‐transformed infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and determination of the piezoelectric coefficient (d33). It was found that the addition of TPU to PVDF induced an increase of the crystallinity degree and content of β phase in PVDF. Moreover, although the degree of crystallinity of the composites decreased with the addition of CB‐PPy, the percentage of β phase in PVDF was increased. This effect is more significant in samples with filler concentration higher than 6 wt%. As expected, the d33 of the composites increased as the content of the β phase increased. Furthermore, 3D printed samples displayed lower content of β phase and reduced piezoelectric responses when compared to compression molded samples with same composition.

Interface energy effect on electromechanical response of piezoelectric composites with an arbitrary nano-inclusion under anti-plane shear

For piezoelectric composites with nano-inclusions, the interface energy around the nano-inclusions will play important roles in predicting the electromechanical response under different loadings. In this paper, the interface energy effect on the electromechanical response of piezoelectric composites with a coated nano-inclusion of arbitrary shape under anti-plane mechanical and in-plane electric loadings is studied, and the analytical solutions of the stress and electric displacement are presented. Combining the Laurent series expansion technique and conformal mapping method, the general solutions of complex potentials are expressed. The unknown coefficients are determined by satisfying the boundary conditions with consideration of surface/interface effect. Some examples such as triangle and quasi-square shapes of nano-inclusions are given to show the distribution of internal stress and electric field. It is found that the interface energy effect shows significant variation with the shapes of nano-inclusions, and the effect in the case of circular shape is the smallest. The interface effect on the stress and electric field at the inner and outer boundaries is also examined.

Design of micromachined self-focusing piezoelectric composite ultrasound transducer.

Based on the Fresnel half-wave band interference, a micromachined self-focusing piezoelectric composite ultrasound transducer was proposed in this paper. The theoretical analysis was deduced based on the concept of constructive interference of acoustic waves and electromechanical response of piezoelectric composites. The calculated and simulation results showed that it combined the advantages of composite transducer and plate self-focusing transducer, and can achieve high electromechanical coupling coefficient, low acoustic impedance, high intensity, short focal length and micro size. Because it was based on the micro-electromechanical systems, the fabrication process was accurate and controllable, which made it have good potential for interventional ultrasound imaging, cellular microstructure imaging, skin cancer detection and industrial nondestructive testing applications.

A general closed-form solution for the overall response of piezoelectric composites with periodic and random particulate microstructures

In this paper, we make use of a new iterative homogenization technique in finite electroelastostatics (Lopez-Pamies, 2014) to derive a closed-form solution for the overall response of two-phase piezoelectric composites with particulate microstructures. The calculations amount to solving a system of Riccati differential equations for the effective elastic, dielectric, and piezoelectric tensors of the composites, where the volume fraction of the inclusions plays the role of independent variable. The solution is valid for any choice of piezoelectric behaviors for the underlying matrix and inclusions, and any choice of the one- and two-point correlation functions describing the microstructure. In addition to discussing the key theoretical and practical features of the solution, its descriptive and predictive capabilities are illustrated via comparisons with a broad range of experimental data and full-field simulations (available from the literature) for composites with periodic and random distributions of inclusions of various shapes.