Phenomenological aspects of quasi-perfect pivots in metallic pantographic structures

Abstract

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.

Contact interactions in complex fibrous metamaterials

“…The constitutive micro-structural elements have been studied in detail for fully understanding their contribute to the global macroscopic deformation behavior of the structure. Specifically, we have examined the mechanics of pivots (as it has been already presented in [76,77]) and the interactions between the constituent fibers. In fact, in the available literature about pantographic structures the fibers of the two families have been always considered as non-interacting.…”

“…These values can be obtained by fitting the experimental data. Some problems related to the shear energy are discussed in [76]. An attempt to find a further form for shear energy, able to well reproduce the observed phenomenology, is being performed recently.…”

Parameter identification of a second-gradient model for the description of pantographic structures in dynamic regime

“…In this structure, two orthogonal groups of parallel beams are mutually connected by means of pivots. The pivots can be of two types: either perfect pivots (hinges) [40,41], or elastic cylinders [42][43][44][45]. Herein, we utilize pivots in the form of deformable cylinders.…”

Large in-plane elastic deformations of bi-pantographic fabrics: asymptotic homogenization and experimental validation

“…Polyamide powder was used as raw material. Possible use of metallic powders is to be investigated [50][51][52]. A picture obtained by optical microscopy showing the granularity of the printed polyamide is presented in Figure 4.…”