Fiber rupture in sheared planar pantographic sheets: Numerical and experimental evidence

Pantographic sheets are metamaterials showing some interesting mechanical features. The mechanical behavior of planar pantographic sheets has been studied by means of second gradient continuum models, see [1,2]. In [3,4] an efficient numerical code has been developed by characterizing equilibrium configurations under imposed displacement boundary conditions as those minimizing a discrete Lagrangian deformation energy. Using this model, it is possible to design experimental setups and, qualitatively and quantitatively, predict the elastic behavior of specimens built by means of 3D printing technology. In the present paper we show the first available experimental evidence obtained for sheared pantographic specimens and we show how effective and predictive is the aforementioned code. Subsequently, a simple fiber rupture mechanism is postulated and added to the initially elastic model. By adding further constitutive parameters to the previous four elastic ones, the generalized numerical model is able to predict very well the observed rupture phenomena. The promising results obtained motivate further development of proposed numerical and theoretical models and the conception of more complex experimental setups.