Design, manufacturing and testing of SMA-based smart and cellular structures

This work illustrates the design, manufacturing and testing of a novel concept of honeycomb made from Shape Memory Alloy (SMA). The aim of the work is to incorporate SMA into auxetic structure to create a new concept for a future deployable structure. An auxetic structure is a structure that exhibits a negative Poisson’s ratio effect. The auxetic structures involved in this work include re-entrant and chiral honeycombs. The honeycombs, which include hexagonal honeycomb, are manufactured using NiTiCu SMA ribbons. Tensile tests at room temperature were performed on the hexagonal and re-entrant honeycomb. Finite element simulations have been carried out for the honeycomb. Cellular Material Theory (CMT) has been used to describe the linear elastic behaviour of the honeycombs. Good agreement is observed between numerical nonlinear simulations and the experimental results. An analysis of the Poisson’s ratio effect of the honeycomb is also presented in this thesis. The work also involved describing the thermally induced transformation equivalent viscoelastic damping of NiTiCu SMA ribbon. The Dynamic Mechanical Analysis test has been carried out at different frequencies and temperatures, with increasing and decreasing temperature gradients. Thermally induced transformations (austenitic and martensitic) provide damping peaks at low frequency range excitations, while storage modulus is not affected by the harmonic pulsation. As the SMA ribbon increases its stiffness, the damping capacity reduces, and the loss factor drops dramatically at the austenite finish temperature.