Experimental and numerical study of wave dynamics in tensegrity columns

This work deals with the experimental testing and the numerical simulation of the impulsive dynamics of a tensegrity lattice. The analyzed system is a column made of ten regular tensegrity prisms, each composed of two solid triangular plates (bases), three cross bars, and three cross cables. Bars and bases are additively manufactured in a titanium alloy, through electron-beam melting, while cross cables are made of Spectra fibers and are added to the titanium structure afterward 3D-printing process. The experimental response of the examined tensegrity column under impact loading is studied by recording the waves traveling through the system by means of a Digital Image Correlation algorithm, which measures the axial displacements of the bases of each unit. We compare the experimental results with those obtained from numerical simulations performed by adopting two different nonlinear elastic models: one accounting for the presence of bending-stiff connections between the 3D-printed elements, and for the resulting mixed bending-stretching regime; the other one being a tensegrity model which describes a purely stretching response of the column. Such a comparison shows that the presence of bending-stiff connections may weaken the nonlinearity of the wave dynamics that is typical of tensegrity lattices with frictionless nodal connections. We also observe that a marked nonlinear behavior occurs in the case of pure-tensegrity response (no bending deformation) under small prestress.