Abstract
Composite materials have increasingly been used in construction and in the aerospace and automotive industries because they are lightweight, strong and corrosion resistant, and because their anisotropic properties can be controlled; maintenance costs are also low. However, there is a growing demand for improved composite materials which have ‘smart’ capabilities, that is, they are able to sense, actuate and respond to the surrounding environment. Shape-memory alloys (SMAs) possess sensing and actuating functions. Embedding SMAs into composite materials can create smart or intelligent composites. Amongst the commercially available SMAs, NiTi alloys – in the form of wires, ribbons or particles – are the most widely used because of their excellent mechanical properties and shape-memory performance. These materials have found application in broad fields of engineering and science as a result of their superior thermomechanical properties. Here we review the use of NiTi SMAs in applications such as vibration control, shape control, position control and adaptive stiffening.
Highlights
Composite materials are increasingly used in construction and in the aerospace and automotive industries because they are lightweight, strong and corrosion resistant and their anisotropic properties can be controlled.[1]
We present a concise review of the applications of NiTi Shape-memory alloys (SMAs) in composite materials and the ways in which their performance characteristics can be improved
When the deformed martensite is heated above austenite finish (Af), the SMA reverts to its original shape and, upon subsequent cooling, it returns to the deformed shape
Summary
Composite materials are increasingly used in construction and in the aerospace and automotive industries because they are lightweight, strong and corrosion resistant and their anisotropic properties can be controlled.[1]. Shape-memory effect (SME) is a phenomenon by which SMAs that have been permanently deformed can recover their original configuration after being heated above a certain transition temperature. SME is based on the reversible martensitic transformation of the SMA between an austenitic phase and a martensitic phase by the application of heat or stress.[8]. As-austenite start Af-austenite finish temperature (greater than Af) and another shape at low temperature (lower than Mf).[14] The SMA is severely deformed at a temperature below Mf. When the deformed martensite is heated above Af, the SMA reverts to its original shape and, upon subsequent cooling, it returns to the deformed shape. Pseudoelasticity ( known as superelasticity) is the ability of the NiTi SMA to return to its original shape upon loading after substantial deformation.[15] This functional property of NiTi SMAs is present at almost constant deformation and constant temperature (Figure 5)
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