In this publication the application of novel piezoelectric materials for energy harvesting on vibrating aircraft structures is investigated. These materials have significant advantages over conventional piezoelectric transducer materials like piezoceramics. In particular, biogenic materials in the form of wood-based materials and ferroelectrets in the form of irradiation cross-linked polypropylene are the subject of the investigation. The material characterization in terms of mechanical and electromechanical properties is shown for both material types. For the wood materials a compression test is used as the material has load-bearing properties. The ferroelectrets provide high compliances and are therefore investigated in a tensile test for material characterisation as well as in a four-point flexural test regarding its behaviour when glued to a dynamically bending surface. Additionally an FE-model of the material model for ferroelectrets is presented, which is validated by experimental results. An estimation of the power output is given for different concepts with both kinds of materials.
An optimized driving comfort with a low interior noise level is an important intention in the passenger car development process. The interior noise level caused by the dynamic interaction between the rolling tyre and the rough road surface and transmitted via the car-body is a significant component of the entire noise level. To reduce the road induced interior noise, in general, the chassis system has to be optimized. Passive measures often induces a trade-off between vehicle dynamics and driving comfort. To overcome this disadvantage in this paper, the development and realization of an active measure is proposed. For the purpose of active mechanical decoupling, an active control system is developed, the feasibility of the integration is investigated and its noise reduction potential is identified by vehicle tests. In a first step, a classical multi-channel and experimental-based structure-borne transfer path analysis of the full vehicle is realized to determine the dominant transfer paths. The concept for the active mount system (active mounts, multi-channel control system, sensors) is developed and parametrized by system level simulation. Mechanical components and power electronics of the active system are designed, manufactured and tested in the laboratory. Subsequently, the entire active system is integrated into the vehicle. The broadband adaptive feedforward algorithm is extended by certain measures in order to improve robustness and performance. Full vehicle tests are used to quantify the required specifications and the achieved effectiveness of the active vibration control system.
This work covers a novel concept for piezoelectric energy harvesting for the use in lightweight design. It is motivated by a structural strain excitation in an aircraft wing caused by a dynamic pressure. The concept uses piezoelectric electrets, also called ferroelectrets. Ferroelectrets are piezoelectric polymers that show a higher ecological compatibility and a much higher structural flexibility than piezoceramics. The used ferroelectret material for piezoelectric energy conversion is fluorinated ethylene propylene (FEP) assembled in a parallel-tunnel structure that provides high transversal piezoelectric δ31-coefficients. The transformation of strain energy is realized by a metallic mechanism converting a low strain amplitude with a high structural stress to a desired high strain amplitude. Due to low stresses required in the ferroelectret material, the metallic mechanism is designed in a very light way. An analytical model is presented to show the main design parameters and a finite element model is used with the goal of investigating the power output per total energy harvester mass. The model is eventually validated with experimental results. A power output of 344.2 nW and a ratio of power per mass of 302.6 μWkg−1 can be reached for a single harvester under a realistic quasistatic load. For a suggested cluster this can be increased up to 2.6 mW/m2 which is enough to power many devices with a low power consumption.
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