Finite Element Analysis of Three-Phase Piezoelectric Nanocomposites

Abstract

In recent years, traditional piezoelectric materials have been pushed to the limit in terms of performance because of countless novel applications. This has caused an increased interest in piezoelectric composites, which combine two or more constituent materials in order to create a material system that incorporates favorable attributes from each constituent. One or more of the constituents exhibits piezoelectric behavior, so that the composite has an effective electromechanical coupling. The composite material may also have enhanced properties such as stiffness, durability, and flexibility. Finite element analyses were conducted on a three-phase piezoelectric nanocomposite in order to investigate the effects of several design parameters on performance. The nanocomposite consisted of a polyimide matrix, beta-CN APB/ODPA, enhanced with single wall carbon nanotubes and PZT-5A particles. The polyimide and nan- otube phases were modeled as a single homogenized phase. This results in a two-phase nanocomposite that can be modeled entirely in the continuum domain. The material properties for the nano-reinforced matrix and PZT-5A were obtained from previous experimental efforts and from the literature. The finite element model consisted of a single representative volume element of the two-phase nanocomposite. Exact periodic boundary conditions were derived and used to minimize the analysis region. The effective mechanical, electrical, and piezoelectric properties were computed for a wide range of nanotube and PZT particle concentrations. A discrepancy was found between the experimental results from the literature and the computational results for the effective electrical properties. Several modified finite element models were developed to explore possible reasons for this discrepancy, and a hypothesis involving dispersion of the nanotubes was formulated as an attempt to explain the difference. The response of the nanocomposite under harmonic loading was also investigated using the finite element model. The effective properties were found to be highly dependent on the dielectric loss of the beta CN/SWNT matrix. It was also found that increasing the matrix loss enhanced piezoelectric performance up to a certain point. Exploiting this type of behavior could be an effective tool in designing piezoelectric composite materials.