ACTIVE COMPOSITE MATERIALS BASED ON SHAPE MEMORY ALLOYS FOR THE DESIGN AND PROTOTYPING OF DEFORMABLE AERODYNAMIC SURFACES

Abstract

This thesis investigates the development of active composite materials integrating shape memory alloys (SMAs) for creating deformable aerodynamic surfaces, with a focus on automotive applications. The research addresses key challenges in SMA polymer composite design, including interfacial adhesion, thermal management, and shape morphing performance. A novel multi-material design approach is proposed, combining a stiff polymer substrate, soft silicone embedding layer for SMAs, and aluminum terminals. This configuration overcomes issues of interfacial delamination and matrix overheating. Comprehensive experimental characterization of SMA thermomechanical and electrical properties is conducted. Interfacial strength is evaluated through static and fatigue pullout tests under complex loading conditions. A multiphysics finite element model is developed, integrating SMA constitutive behavior, heat transfer, and fluid-structure interaction. The model accurately predicts shape morphing and stress development in the composites. Wind tunnel testing validates aerodynamic performance. Parametric studies explore the effects of SMA volume fraction, positioning, and activation temperature on deflection, stress, and fatigue life. The research culminates in prototyping and testing an active under-motor shield for the Fiat 500X, demonstrating significant shape morphing capabilities. The findings provide valuable insights for optimizing SMA-polymer composites, paving the way for their implementation in adaptive aerodynamic structures for automotive and aerospace applications.