Performance of non-uniform functionally graded piezoelectric energy harvester beams

The appearance of functionally graded piezoelectric materials has solved the lamination problem of the conventional piezoelectric structures. Functionally graded piezoelectric materials are the new materials with unexplored capabilities. This article theoretically investigates the effects of non-uniformity on the performance of the functionally graded piezoelectric material cantilever beams subjected to harmonic excitation. The governing equations are derived based on Timoshenko and Euler–Bernoulli beam theories. The finite element method with the application of superconvergent element is employed here for the discretization and the vibration analysis of the system. This model is validated by comparing the numerical results with the experimental results of piezoelectric energy harvesters of conventional shapes available in the open literature. Parametric studies are carried out with respect to the effects of tapering ratios, the degree of non-uniformity, load resistance, and the volume fraction parameter on the electrical output power and the fundamental resonance frequency. It was observed that the application of diverging beams noticeably enhances the power output per mass of piezoelectric element extracted while decreases the natural frequency which is advantageous for scavenging energy from ambient surroundings. The results reveal that there is an optimal value for the non-homogeneous parameter leading to the maximized harvested energy under different operating conditions.