Determination of the elastic properties of randomly oriented shape memory alloy (SMA) discontinuous wires reinforced epoxy resin

A micromechanics modeling based on the equivalent fiber properties for SMA wires is developed for characterizing the elastic properties of randomly oriented SMA reinforced polymer composites using Mori-Tanaka method. The interface effect between the SMA wires and the matrix can be considered using the obtained transversely isotropic equivalent fibers. Representative volume elements (RVEs) with different shapes and sizes are employed in order to predict the elastic modulus of randomly oriented discontinuous SMA reinforced polymer composites. Experimental fiber pull-out and composite specimen tensile tests are performed in order to obtain the interfacial shear strength and validate the micromechanics results, respectively. The effect of some important parameters including aspect ratios of the wires, temperature and the pre-strain levels in the wires are investigated. The results showed that for higher aspect ratios of the wires (l/d = 35) there is 20% improvement in elastic modulus of the composite in comparison with the composites reinforced by wires with lower aspect ratio (l/d = 5). Moreover, pre-straining the SMA wires in martensite phase by 4%, caused 12% enhancement in the elastic modulus of the composite.