A FE2 based approach for multiscale modeling and design of energy harvesting devices

New technologies that aim at powering wireless sensor nodes by scavenging the energy from ambient vibrations can be a practical solution for some structural monitoring applications in the near future. However, structural weaknesses, stress concentrations and discontinuities may lead to the premature failure of energy harvesting devices, thereby jeopardizing the functionality of the smart monitoring infrastructure. Therefore, a performance-based approach is considered for the design of energy harvesters by resorting to concepts and tools largely exploited within the seismic engineering community. This study is especially focused on the calculation of the capacity curve of the device (i.e., pushover curve), which is obtained by applying a pattern of static forces into the corresponding non-linear finite element model. In doing so, the FE2 method is employed to compute stress and strain levels at the microscale in the most critical interfaces. The capabilities of this novel computational procedure are demonstrated by analyzing the response of a multilayer PVDF energy harvester. Stress stiffnening/softening nonlinear device response is analyzed emphasizing the role of micro and macro scale variables on the global behaviour.