Shape Memory Alloy (SMA) wires as activators in polymers & composites
The integration of pre-strained Shape Memory Alloy wires with small diameters in fibre reinforced polymer composites leads from the engineering structural materials to the so-called adaptive or smart composite materials.
Adaptive materials integrate actuating and sensing components, which are very often totally different materials, into a structural one. These materials or material systems can vary some of their properties and/or functions, such as stiffness, damping capacity or even shape, in response to an external or internal stimulus. It is obvious that not only their overall mechanical performance, but also their adaptive functions are significantly affected by the quality of the interfacial regions between their constituents.
Shape Memory Alloy (SMA) materials such as binary NiTi or ternary NiTiX (where X could be Cu, Co, Fe, Nb etc.) have the ability to recover their own original shape after a cycle, which includes cooling-deforming-heating with the simultaneous generation of mechanical work, a function related to a reversible transformation between different crystal structures, called austenite and martensite. Under constrained conditions, pre-strained SMA wires are prevented from regaining their original shape and thus high recovery stresses are generated. Henceforth, SMA materials are able to sense thermal, mechanical or electrical stimuli and, in response, to activate the host medium in a controllable fashion.
• Panagiotis Pappas
- “Transformation fatique and stress relaxation of shape memory alloy wires” byP Pappas, D Bollas, J Parthenios, V Dracopoulos and C Galiotis, Smart Mater. Struct. 16/6 (2007) 2560-2570 Download the paper (pdf)
- “Stress generation by shape memory alloy wires embedded in polymer composites” by D.Bollas, P.Pappas, J.Parthenios and C.Galiotis, Acta materialia, 55/16, 5489-5499 (2007) Download the paper (pdf)
- “Progress in Composites with Embedded Shape Memory Alloy Wires”by J. Schrooten, V. Michaud, J. Parthenios, G. C. Psarras, C. Galiotis, R. Gotthardt, J. A. Manson and J. Van Humbeeck, Materials Transactions (The Japan Institute of Metals), 43/5, 961-973 (2002) Download the paper (pdf)