Design of pull-out stresses for prestrained SMA wire/polymer hybrid composites

Abstract

Shape memory alloy (SMA) materials possess many unique mechanical, thermal and thermal-mechanical properties that govern their temperature-dependent shape memory, superelastic and pseudoelastic effects. SMA actuators, in the forms of wire or strip embedded into polymer-based composite structures are able to control the structures' shape and stiffness in order to accommodate any environment impacts. Due to an intrinsic shape memory effect (SME) of prestrained SMA wires, additional recovery forces, which are able to alternate the dynamic and buckling properties of the structures, are generated upon heating. This heat is usually induced by a means of externally applied current. To fully use the benefit of the SME in SMA composite structures, understanding the interfacial bonding behaviour and stress transfer properties between the embedded SMA wires and matrix is crucial. In this paper, the wire pull-out properties of prestrained SMA wire/polymer composites subjected to different temperatures were experimentally studied. The results indicated that the critical debonding stress, that initiates fully debond at a bond interface between the SMA wire and matrix increased with increasing the externally applied current, and thus changing the phase condition in the wire. This phenomenon was due to the SME of the prestrained wires and can be interpreted by using a newly developed phase–stress–displacement diagram.