For actuation purposes active hybrid structures made of fiber reinforced polymers (FRP) and shape memory alloys
(SMA) enable substantial savings concerning weight, space and cost. Such structures allow realizing new functions
which are more or less impossible with commonly used systems consisting of the structure and the actuator as separated
elements, e.g. morphing winglets in aeronautics. But there are also some challenges that still need to be addressed. For
the successful application of SMA FRP composites a precise control of temperature is essential, as this is the activating
quantity to reach the required deformation of the structure without overloading the active material. However, a direct
measurement of the temperature is difficult due to the complete integration of SMA in the hybrid structure. Also the
deformation of the structure which depends on the temperature, the stiffness of the hybrid structure and external loads is
hard to determine. An opportunity for controlling the activation is provided by the special behavior of the electrical
resistance of SMA. During the phase transformation of the SMA - also causing the actuation travel - the resistance drops
with rising temperature. This behavior can be exploited for control purposes, especially as the electrical resistance can be
easily measured during the activation done by Joule heating. As shown in this contribution, theoretical modelling and
experimental tests provide a load-independent self-sensing control-concept of SMA-FRP-hybrid-structures.
Static vortex generators (VGs) are installed on different aircraft types. They generate vortices and interfuse the slow
boundary layer with the fast moving air above. Due to this energizing, a flow separation of the boundary layer can be
suppressed at high angles of attack. However the VGs cause a permanently increased drag over the whole flight cycle
reducing the cruise efficiency. This drawback is currently limiting the use of VGs. New active VGs, deployed only on
demand at low speed, can help to overcome this contradiction. Active hybrid structures, combining the actuation of
shape memory alloys (SMA) with fiber reinforced polymers (FRP) on the materials level, provide an actuation principle
with high lightweight potential and minimum space requirements. Being one of the first applications of active hybrid
structures from SMA and FRP, these active vortex generators help to demonstrate the advantages of this new technology.
A new design approach and experimental results of active VGs are presented based on the application of unique design
tools and advanced manufacturing approaches for these active hybrid structures. The experimental investigation of the
actuation focuses on the deflection potential and the dynamic response. Benchmark performance data such as a weight of
1.5g and a maximum thickness of only 1.8mm per vortex generator finally ensure a simple integration in the wing
structure.
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