Rate Sensitivity of Superelastic Column Buckling: An Experimental Study

The use of shape memory alloys (SMAs) in thin-walled honeycomb structures is a relatively new approach to realize high performance adaptive structures. Traditionally, honeycombs made from metals have been used in engineering structures due to their high specific stiffness and energy absorption properties. Incorporation of SMAs into honeycombs amplifies the bending dominated kinematics of the honeycomb structure and improves the thermal time constant of the SMA by increasing the surface-to-volume ratio of the material. Possible applications of SMA honeycombs range from reusable energy absorbers, to high stroke actuators, to deployable devices.

An experimental characterization of the thermo-mechanical response of NiTi honeycombs and corrugations is presented. Honeycomb specimens of varying geometries were fabricated from commercially available NiTi ribbon using a novel Nb-based brazing technique. A series of in-plane compression experiments are performed on the fabricated honeycombs, characterizing the shape memory cycle, the superelastic response, the shape memory thermal lag, the superelastic rate sensitivity, and effects of honeycomb geometry on performance. The buckling response of NiTi beams is also examined to better understand the interaction between the material instability found in NiTi and the structural instabilities commonly found in in-plane compression of honeycombs.