Design and optimization of variable stiffness piezoelectric energy harvesters

The use of curvilinear fiber in piezoelectric structures has become a hot spot in recent years. Nevertheless, the existing researches rarely execute curvilinear fiber optimization, especially considering topology optimization simultaneously. This paper proposes an isogeometric topology optimization based on the Heaviside filter to realize the simultaneous optimization of fiber orientation and topology structure for variable stiffness composite laminate (VSCL) energy harvesters. The isogeometric formulations of the VSCL energy harvesters are derived based on the Kirchhoff plate theory and Hamilton’s principle. Then, combined with the piezoelectric material with penalization (PEMAP) model, the optimization model taking the minimum energy factor as the objective function is established. For a bimorph VSCL energy harvester, the correctness of isogeometric formulations is verified, and the effect of strain energy constraint, curvature constraint, and initial fiber paths on the optimized designs is fully analyzed. Besides, the optimization process is extended to a multilayer VSCL energy harvester. More importantly, the harmonic vibration analysis is executed to test the energy harvesting characteristics of optimized designs. The results show that the present approach can improve energy harvesting efficiency from the fiber path and topology structure point of view, and the output power increases by 37.9% compared with the initial model.