Mechanical characterization and modeling of cyclic and time dependent behavior of a soft 3D printed photopolymer

TangoBlackPlus © (TB+) is a 3D printable photopolymer frequently employed in advanced materials, as additively manufactured biomimetic composites and metamaterials, or soft actuators based on shape memory effects. Thorough knowledge of its mechanical response is essential to identify constitutive laws for the modelling of innovative devices or fine tuning of simulations of the fracture process. In the present work we investigated the response of TB+ under different types of mechanical loading, including uniaxial tension at different strain rates, stepped stress relaxation and cyclic imposed loads. The experimental results were used to compare the predictive capabilities of different visco-plastic models. Among these, the Bergstrom-Boyce (BB) model showed the highest accuracy, as also verified through FE implementation, allowing prediction of large deformation, time-dependent response and residual strain resulting from cyclic loading.