Stress generation by shape memory alloy wires embedded in polymer composites

Single shape memory alloy (SMA) wires are capable of generating high compressive stresses under constrained conditions when they are thermally activated. In this work, the ability of single SMA wires to act as internal stress generators in fibrous polymer composite systems has been investigated. The stress fields recorded both at the specimen level and internally in the reinforcing fibers by means of Raman microscopy measurements have confirmed that SMA wires can serve as effective stress-actuators. The efficiency of stress generation depends on the wire alloy composition and level of prestrain prior to incorporation into the composite medium. The internal stress distribution in the composite fibers decayed from a position just above the wire surface to the edges of the specimen reaching zero at a distance of approximately 3000 pm. The maximum value of stress recorded in the fibers at a distance of approximately one wire radius was 227 MPa. The significance of these results in the design and operation of adaptive composites systems similar to those examined here is discussed. (c) 2007 Published by Elsevier Ltd on behalf of Acta Materialia Inc.