Performance optimization and broadband design of piezoelectric energy harvesters based on isogeometric topology optimization framework

Energy harvesting is attracting considerable attention in devices that cannot replace exhausted batteries, where improving the energy harvesting efficiency of piezoelectric energy harvesters (PEHs) through different optimi-zation methods is always a research hotspot. This paper proposes an isogeometric topology optimization framework to implement the simultaneous optimization of fiber angles and piezoelectric material and reveal the feasibility of broadband design for PEHs. We deduce the isogeometric formulation of PEHs based on Kirchhoff plate theory and Hamilton's principle. The optimization formulations are established with minimum energy factor or maximum output power considered, and the distributions of fiber angles and piezoelectric material are respectively defined by the Heaviside Penalization of Discrete Material Optimization (HPDMO) model and the Piezoelectric Material with Penalization (PEMAP) model. The numerical results show that there is only a slight difference in the optimized designs of fiber angles between the static load and harmonic load when the objective function is the minimum energy factor. Furthermore, taking maximum output power as the objective function, resistance has a substantial effect on the optimized distributions of fiber angles and piezoelectric material, and there is an optimal resistance making the output power of the optimized design increase 9 times compared with the initial model. More important, by combining the designability of composite material, the proposed method is extended to the broadband design of PEHs. It is concluded that the optimized design can not only generate two resonance peaks in the predetermined frequency range but also the second-order output power amplitude is 14 times higher than that of the benchmark model.