Modelling Shape Memory Effect in Hybrid Composite

Composite materials have been widely used in a large range of industrial applications, mainly because of their lightweight characteristics and high capability to increase strength and stiffness in certain directions, especially in unidirectional laminates. On the other hand, the unique thermomechanical behavior of Shape Memory Alloys (SMAs) has a set of remarkable properties resulting from microscopic phase transformation, allowing the possibility to design new devices that consider pseudoelasticity and shape memory effect (SME) [1,2]. In this study, a unidirectional composite made by SMA fibers embedded in an epoxy matrix is considered. Two different temperature cycles are modelled: first, the curing manufacture process is simulated [3], and then the applied temperature on the SMA fibers to induce the SME. The generalized plane strain state is assumed, and two approaches are used to model the interaction between fibers and matrix. A simplified 1D model, which considers fibers and matrix as springs in parallel, is introduced to evaluate the maximum recovery capability of the composite and a 2D equivalent cell model is used to represent a hexagonal array [4]. The Brinson constitutive model [5] and its modified version with the von Mises equivalent for general stress state [6,7] are applied for the SMA fibers, while the matrix is assumed linearly-elastic with properties defined as functions of the temperature. The maximum recoverable strain range is found to be function not only of the SMA maximum recoverable strain but also of the matrix and interface failures [8]. Results indicate a good correlation between both approaches, however the 2D model has the advantage to be able to computer interface stresses and nonuniform phase transformation. A comparison with the analytical single-fiber model is also carried out [9].