Modeling and design optimization of shape memory alloy-enabled building skins for adaptive ventilation

This paper presents a modeling and design study of shape memory alloy (SMA)-based skins that enable adaptive ventilation in buildings. The skins are formed by panels with attached SMA wires and can be periodically arranged to form a building envelope. When the environmental temperature is below the SMA austenitic transformation temperatures, the SMA wires are relaxed and the panel forms a closed surface, preventing circulation of exterior airflow into the building. When the environmental temperature exceeds such SMA transformation temperatures, the SMA wires contract and bend the panel to create an opening that enables circulation of airflow into the building. The response of the adaptive skins is evaluated through a thermomechanically coupled finite element model. The applied thermal loads are determined from published field measurements. Metallic materials and fiber-reinforced composites are explored as candidates for the panel. Genetic algorithms are employed for optimization, where the objective is that the panel exhibits a large opening when the environmental temperature exceeds a prescribed ideal temperature and stays closed otherwise. Optimization results show that two-layered composite panels with ply angles of 45°/−45° and thicknesses of 0.1/0.25 mm (layers ordered from the interior to the exterior side) display the most favorable performance.