Modeling and testing of shape memory alloy chiral honeycomb structures

Shape memory alloy honeycombs are constitute a novel set of cellular structures developed by the authors using initially centersymmetric honeycomb configurations (hexagonal ones), and pseudo-plastic Nitinol ribbons as core. Chiral honeycomb structures feature a noncentresymmetric unit cell configuration, with rotational symmetry only and in-plane Poisson's ratio equal to -1. Nonlinear unit cell FE models of these chiral honeycombs have been developed using the formulation proposed by Auricchio et al. related to pseudo-elastic and superelastic SMA materials. The numerical results are compared with experimental ones from tensile tests of chiral honeycomb samples subjected to uniaxial tensile loading at full martensite phase, and analytical results from the model proposed by Prall and Lakes on hexachiral configurations. A working prototype of a deployable antenna made out hexachiiral cells with 1-way SMA ribbon is also described.