In this paper, the fracture problem of a piezoelectric actuator consisting of a functionally graded piezoelectric material strip (FGPM strip) with a normal crack and a homogeneous layer by a transient thermal load combined with an electric load is considered. The thermo-electro-mechanical fields in the un-cracked laminate induced by the transient thermal load and the electric load are calculated. By using the superposition technique, the obtained normal stresses are used as the crack surface tractions with opposite sign to formulate the mixed boundary value problem. The integral transform techniques are employed to reduce the problem to the solution of a singular integral equation. We focused on the effect of the crack contact phenomenon on the stress intensity factors for the case of the pure electric load. Moreover, the effect of the difference between two kinds of the electric boundary conditions on the stress intensity factors and the reduction of ones by the electric load would be discussed.

Piezoelectric composites constitute one of the components for energy harvesting; they are more flexible than piezoelectric ceramics despite having a low output voltage problem. In this study, a new model was proposed for the finite element analysis of functionally graded composite (FGC) specimens composed of barium titanate particles and polyvinylidene fluoride-co-trifluoroethylene. Finite element analysis of energy harvesting showed that the FGC produced a higher output voltage than that of the homogeneous composite. This trend was consistent with the results of the piezoelectric coefficient measurement tests related to the energy harvesting of the actual fabricated FGC specimens. This study effectively shows that functionally graded structures enhance piezoelectric properties, thereby directing future structural design from an experimental and analytical point of view.

Chromium disilicide (CrSi₂) is generally known as a p-type degenerate semiconductor whose power factor can be improved by substitution of Al on the Si site. However, it has not been clarified why holes are majority carriers in pure CrSi₂ nor how the thermoelectric properties of CrSi_2−xAl_x depend on the temperature above 400 °C. In this paper, we prepared CrSi_2−xAl_x samples with x ranging from 0.00 to 0.20. The composition ratio in each sample measured by Wavelength-dispersive X-ray spectroscopy (WDX) showed that the sum of Si and Al to Cr was less than the stoichiometric ratio. The electronic density of states calculated by first principles calculation based on density functional theory revealed that the atomic vacancies on the Si sites, whose existence was implied by WDX, can supply holes. Comparing thermoelectric properties of the samples at 500 °C, the sample with nominal composition CrSi_1.96Al_0.04 showed the highest power factor 0.606 mW m⁻¹ K⁻².

In this paper, the dynamic fracture problem of a functionally graded piezoelectric material strip (FGPM strip) containing an infinite row of cracks normal to the interface between the FGPM strip and a homogeneous layer is considered. It is assumed that the electro-elastic properties of the FGPM strip vary exponentially in the thickness direction, and that the crack faces are under normal mechanical impact loadings. The integral transform techniques and the dislocation density function are employed to reduce the problem to the solution of a singular integral equation. The dynamic stress intensity factors of the internal cracks are computed and are presented as a function of the normalized time for the various values of the nonhomogeneous and geometric parameters.