Morphing blades with embedded SMA strips: An experimental investigation

• Design of a morphing blade made up of polymeric matrices with embedded NiTi elements
• Development of a specifically designed shape setting treatment
• Comparison of thermoplastic polymeric compounds
• Study of blade changes by digital image analysis and CAD reconstruction
• Innovative 3D actual blade shape detection by means of a non-contact sensor

This paper focuses on the development and experimental testing of a composite blade for an automotive axial fan. A novel concept of morphing blade is proposed with the aim of replacing the conventional actuator systems. The structure is made up of a polymeric matrix equipped with NiTi shape memory alloy strips as active elements. The morphing blade changes its shape as the phase transformations of the strips are thermally activated by airflow. To study the morphing capability of the blade, together with the recovery behavior of the NiTi strips, four different polymeric compounds have been compared. Digital image analysis techniques have been performed to quantitatively analyze the blade deflections and to evaluate the most suitable polymeric matrix for the intended application. Finally, the blade shape modifications, which occur along the blade span during the activation cycles, have been reconstructed by three-dimensional non-contact surface detection. Results from the comparison between these two reverse engineering methods could provide a powerful support for the assessment of the aerodynamic performance of the morphing blade.

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