Shape memory alloy wires turn composites into smart structures. Part II: manufacturing and properties

The manufacturing route and resulting properties of adaptive composites are presented in the second part of this European project report. Manufacturing was performed using a specially designed frame to pre-strain the SMA wires, embed them into Kevlar-epoxy prepregs, and maintain them during the curing process in an autoclave. Composite compounds were then tested for strain response, recovery stress response in a clamped-clamped configuration, as well as vibrational response. Through the understanding of the transformational behavior of constrained SMA wires, interesting and unique functional properties of SMA composites could be measured, explained and modeled. Large recovery stresses and as a consequence, a change in vibrational response in a clamped- clamped condition, or a reversible shape change in a free standing condition, could be generated by the SMA composites in a controllable way. These properties were dependent on composite design aspects and exhibited a reproducible and stable behavior, provided that the properties of the matrix, of the wires and the processing route were carefully optimized. In conclusion, the achievements of this effort in areas such as thermomechanics, transformational and vibrational behavior and durability of SMA based composites provide a first step towards a reliable materials design, and potentially an industrial application.