A viscoelastic harvester-absorber for energy generation and vibration control

A vibration energy harvester harnesses the oscillatory movement and converts it into electrical energy. On the other hand, a (dynamic) vibration absorber dissipates the mechanical energy of a host structure (primary system). The proposal for a harvester-absorber device (HAD), comprinsing a piezoelectric element (conventional harvester) bonded with a viscoelastic layer and a steel constrained layer, is based on the dual purpose of generating energy and at the same time reducing the vibratory response of the primary system. Introducing a viscoelastic dissipative layer in a conventional harvester, also offers the advantage of simultaneously reducing wear on the piezoelectric element, thereby extending its lifespan and preventing fatigue-related breakage. The paper presents a model of a harvester-absorber built from a bimorph piezoelectric beam, a layer of viscoelastic material (E-A-R C1002-01PSA) and a beam of steel, which acts as a constrained layer. A lumped parameter model is proposed for the theoretical description of the HAD which is successfully used to experimentally determine its parameters. After that, and using the equivalent stiffness concept, the HAD was coupled to a free-free beam with two masses at its ends to study its perfomance over a real host structure. The inertance of the composite system and voltage/force frequency response function of the HAD were obtained and compared with experimental results. The accuracy of the results justifies and validate the model which has the advantage of simplicity and can contribute to reducing wear and increasing the lifespan of brittle piezoelectric structures.