Fellowship/Shulte: Novel Shape Memory Composites for Space Applications

Abstract Smart materials help to bridge the gap between our ability to manipulate information and to use that information to direct mechanical action. They simplify products, add features, improve performance, and increase reliability with relatively little mechanical complexity. They can sense and react to their environment autonomously and represent the future of aerospace technology. Shape memory polymers (SMPs) and Shape Memory Alloys (SMAs) are two classes of smart materials that offer mechanical action triggered by an external stimulus. S\IAs have the ability of reversibly changing shape depending on their temperature, stress or magnetic field. They can produce very high actuation strain (5-8% strain), stress (~100-400 MPa) and work output (~l 0 MJ/m3) as a result of reversible martensitic phase transformations. SMPs can undergo deformation at high temperatures, retain the defol111ed shape \vhen cooled, and return to its original, unaltered configuration upon heating above the glass transition temperature (up to 400% strain). The abilities of SMPs to fix a temporary shape and to recover an original shape in a controlled fashion through use of external stimuli (i.e., heat, electric field. magnetic field, irradiation) distinguish them from most conventional polymeric materials. Shape fixing and shape recovery reflect the various microstructural transformations and determine the extent to which SMPs can be practically used, and are, therefore, of both fundamental and practical importance. In contrast to SMAs. SMPs have a much lower density and have been demonstrated to recover strains on an order of magnitude higher than SMAs. Lightweight and inexpensive SMPs offer high recoverable strain upon activation but suffer from low strength, modulus (at high temperatures) and irreversible actuation. Embedding SMA wires in SMP matrix could increase the strength and provides an opportunity for reversible actuation. In this proposal, unique properties of SMA and SMPs will be utilized to design and fabricate S:VIA/SMP based shape memory composites (SMCs). The material and actuation prope11ies of this composite will be characterized and optimized for reversible actuation. The following objectives are proposed; I) Characterize fundamental material properties of SMPs and SMAs 2) Determine shape recovery strain and stress 3) Design and fabricate SMCs 4) Characterize the material properties of SMCs 5) Involve undemraduate student Rvan Schulte in research to contribute to the development of the technolo€!ical workforce 6) Enhance the quality of space-related research and education in Kentuckv 7) Establish a strong collaboration with NASA and University of Kentuckv The key outcomes from the proposed research are identi tied as (i) gaining fundamental knowledge on SMCs characteristics; (ii) enable the design and fabrication of affordable, reliable, durable, and maintainable SMC structures for various space applications, (iii) optimize the SMC response as a new multifunctional material; (iv) establish a strong collaboration bet\veen NASA and Lniversity of Kentucky, (v) involve Ryan Schulte, an undergraduate student, in research at the early stage of his academic life and (vi) contribute to the development of the Nation's technological \vorkforce of the future by attracting and retaining students in mechanical engineering discipline.