Proceedings PaperRecent progress in ferroic high-strain actuator materials
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The clamant need for field controlled high strain actuator materials in a multitude of emerging smart materials applications has lead to extensive studies over a very wide range of materials systems from ultra soft elastomers to exceedingly stiff martensitic metals. The capabilities which have been achieved and the basic strain mechanisms exploited to achieve high controlled deformation will be briefly reviewed. The focus of the talk will be upon the importance of ferroic systems, where incipient or full spontaneous ordering permits the achievement of strain levels which would otherwise be impossible in such stiff matrices. The struggle to discipline and control spontaneous ordering so as to achieve well controlled anhysteretic response will be discussed, drawing on the examples of the electron irradiation modified polyvinylidene fluoride:trifluoroethylene copolymer and the high strain high coupling response in the single crystal lead zinc niobate: lead titanate (PZN:PT) perovskites. It is interesting to note the common theme of engineering instability in domain and/or sub domain structures important in these two grossly dissimilar material systems and the manner in which this is carried forward in other ferroics. The final important question to be discussed is where these considerations lead for the design of the next generation of improved high strain actuator materials.