The development of an 'active' surface using Shape Memory Alloys

Abstract

Recent years have witnessed a tremendous growth and significant advances in "smart" composites and "smart" composite structures. These smart composites integrate active elements such as sensors and actuators into a host structure to create improved or new functionalities through a clever choice of the active elements and/or a proper design of the structure. Such composites are able to sense a change in the environment and make a useful response by using an external feedback control system. Depending on their applications. smart composites usually make use of either the joint properties of the structure or the properties of the individual elements within the composites. The accumulation in the understanding of materials science and the rapid developments in computational capabilities have provided an even wider framework for the implementation of multi-functionality in composites and make "smart" composites "intelligent". This thesis is a contribution towards the global endeavour to innovate using smart structures to enhance our everyday lives. One of the phenomena of shape memory alloys. the shape memory effect was put to use in the development of an active surface. Here the pre-stressed shape memory alloy (in its de-twinned martensitic state) is surrounded or embedded in a non-SMA matrix material. This active surface can be used in a variety of applications that requires active shape control to change the shape of a flexible structure member such as a submarine stem, aerospace control surfaces and aircraft wings. An experimental protocol was developed to treat or stabilize shape memory alloys that are used as actuators within composite structures. Shape memory alloys exhibit complex behaviour during their quasi-plastic material response. The complex behaviour includes variability in yield values and the transformation region/range.