Investigations on actuation characteristics and life cycle behaviour of CuAlNiMn shape memory alloy bimorph towards flappers for aerial robots

Highlights: • Investigations on the thermomechanical behavior of CuAlNiMn/polyimide composite bimorphs • Grain size of 150 nm with β′ (128) martensite phase • Enhanced actuation of the quaternary alloy with large displacement up to 5.4 mm • Load bearing capacity at 60 mg is low for lower voltage of 1 V. • The samples had a life of 20,000 cycles with 50% reduction in displacement. In this work, life cycle and thermomechanical behaviour for quaternary CuAlNiMn alloy, developed through thermal evaporation technique on flexible Kapton polyimide substrate were investigated. Scanning electron microscopic images displayed grains less than 150 nm without any porosity and crack. The thickness of the film was found to be around 6.6 μm, and the XRD profile revealed the presence of β′ (128) martensite peak. The austenite transformation temperature was As: 221 °C and Af: 226 °C as obtained from differential scanning calorimetry plots. Further, thermal images were recorded to analyse the heat transfer profile of the film during actuation at various points on the bimorph. The thermomechanical behaviour was studied by actuating the composite film through Joule heating under different loads of 30 mg, 45 mg and 60 mg. Parameters such as voltage and frequency were varied to analyse the actuation properties. The composite bimorph required less than 2 V to displace 4 mm under 60 mg load. The life of eight samples was recorded for more than 20,000 cycles, and the reliability of the film was investigated. The bimorph was further actuated by batteries to replicate the actuation and their suitability towards developing flappers for aerial robots.