Investigations on the life cycle behavior of Cu-Al-Ni/polyimide shape memory alloy bi-morph at varying substrate thickness and actuation conditions

Abstract

In this work, a two-way displacing Cu-Al-Ni/Polyimide shape memory alloy bi-morph without any post processing has been developed. The forward stroke was achieved with shape memory effect and the return stroke was due to the influence of flexible polyimide substrate. A custom made setup with electrical heating was developed to investigate the life cycle of the bi-morph at different voltages, ranging from 2 V to 3 V. The austenite transformation temperatures of the bi-morph, was found to be As = 215 °C and Af = 240 °C. Shape recovery ratio was calculated and the shape memory alloy deposited on 75 μm thick polyimide sheet exhibited better recoverability than 50 μm thick sheets. Further, maximum displacement of 19 mm was observed from the edge of the bi-morph through plate heating. The effect of substrate thickness on the life cycle behavior of the bi-morph was investigated. The bi-morph showed minor signs of deformation when actuated at 0.5 Hz after 500 cycles. In addition the structural, morphological and thermal behavior of the SMA bi-morph has been investigated in detail. © 2016 The Author(s)