Adaptive materials have the ability to change their shape due to external inputs and also produce outputs due to shape change. A careful placement of such materials can contribute to the improvement of aeronautical structures. Localized structural reinforcement on demand can lead to vibration reduction and flutter delay. Assuming that the adaptive system implementation presents a lower weight increase than the conventional structural reinforcement solution required to achieve the same performance, lower requirements on the lift production implies lower drag, lower fuel consumption, and lower costs. To this end, an experimental investigation on adaptive systems based on active aeroelastic aircraft structures with bending-torsion coupling properties is presented. Two techniques for vibration and flutter alleviation are studied and tested. The first one is based on the use of carbon composite spars with misaligned fibers. The second technique involves an active spar with a multi-cross section embedded with piezoelectric actuators. A wing was designed and manufactured for testing in a wind tunnel and subsequently implemented on a demonstrator platform for flight testing. Results show that a carefully designed misalignment of the fibers can lead to significant performance increase. The active system based on piezoelectric actuators with a linear controller exhibits significant improvements in aeroelastic performance compared to the passive system. The research findings lead us to conclude that significant vibration reduction and flutter envelope extension can be achieved using the proposed strategies.
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