Morphing blades with embedded SMA strips: An experimental investigation

Analysis of the Aerodynamic and Structural Performance of a Cooling Fan with Morphing Blade

“…Starting from a 1.5 mm thick plane foil of material, the strips were cut to a dimension of 1.5 × 15 × 77 mm by means of electro-erosion machining. For the sake of brevity, the thermal characterization of the SMA strips which enables the evaluation of the transformation temperatures of the material and the thermomechanical treatment performed to memorize the shape, are not reported and more detail can be found in [16].…”

“…SMA strips were housed inside purpose-built slots in direct contact with the airflow and located in the range of about 50%-85% of the blade span. A detailed description of the blade structure is reported in [16].…”

“…SMA strips determine the airfoil deflection along the chordwise direction without being affected by the centrifugal force that works along the blade height. modification of the blade shape was continuously evaluated by means of digital image analysis techniques [16]. Figure 2 shows the comparison of the digital captures from the recorded video at the blade tip view for the blade shape at the initial condition (non-activated) and at the maximum deflection (activated).…”

“…For the intended application, the strips work against (i) polymeric matrix stiffness [16] and (ii) aerodynamic and centrifugal loads provided by operation of the cooling fan.…”

“…Thanks to the thermally-activated phase transformation of the SMAs elements, the blades change their shape and the local flow field, thus adjusting the performance of the cooling fan according to the thermal requests of the engine. Based on previous thermomechanical characterization of the SMA elements and experimental data collected from wind tunnel tests performed on a single blade [16], the present study is focused on the numerically-based analysis of the aerodynamic and structural behavior of morphing blades. The fan, composed of five morphing blades, was modeled by using the parametric solid modeler representation resulting from the three-dimensional blade surface captures obtained during the activation tests.…”