Phenomenological aspects of quasi-perfect pivots in metallic pantographic structures

This article discusses the results of the first attempts to print metal pantographic structures with perfect pivots, i.e. with rotational hinges connecting the two families of fibers composing the network without any stiffness. On the one hand, it is observed that perfect pivots do not behave as expected theoretically. On the other hand, the force measured during a bias extension test is a few orders of magnitude lower than that measured for pantographic structures with standard pivots (where a certain stiffness is associated to the interconnecting hinges). This leads to considering the pivots as quasi-perfect (non-zero stiffness, but neither the theoretical one which can be computed by means of the geometrical features of the pivot). Numerical simulations complete the analysis by showing how, by modulating the torsional stiffness of the pivots, it is possible to reproduce the force-displacement plot both in the case of standard pivots and with quasi-perfect ones.