Abstract
Abstract
A new model is proposed for bilayer cantilever beams consisting of shape memory alloy (SMA) and functionally graded material (FGM) layers and subjected to loading at the tip. The model accounts for tensile-compressive SMA behavior through the use of an appropriate set of constitutive relations and considers the deformation of the beam within the frame of the Timoshenko beam theory. The derivation of the model proceeds by first determining the correct sequence in which different solid phase structures develop within the SMA layer as the load is applied, resulting in the formation of distinct solid phase regions. The boundaries separating these regions are then located and used in deriving appropriate moment and shear force equations throughout a complete loading-unloading cycle. The model is capable of tracking the deviation of the neutral surface with respect to the mid-plane and the distribution of martensite in the beam as the load varies. The nonlinear variation of stress and strain in a cross section of the beam is also considered. Results of beam deflection and neutral surface deviation are presented and validated against finite element simulations of a 3D model of a beam consisting of a Nitinol and CNT-reinforced layers.