Role of friction and geometry in tuning the bending stiffness of topologically interlocking materials

Topologically interlocking material (TIM) systems offer adjustable bending stiffness controlled by external pre-stress, as shown in previous studies. This study focuses on a specific TIM system comprised of truncated tetrahedral particles interconnected via tensioned wires. The fabrication process involves weaving nylon wires through 3D printed truncated tetrahedrons that have longitudinal and latitudinal through-holes. By varying the tension applied to the wires, one can systematically control the overall bending stiffness of the TIM system. We change the surface friction and the contact angle between adjacent particles at a fixed wire tension, to study experimentally how they affect the system’s bending response. We inform experiments with Level Set Discrete Element Method (LS-DEM) simulations, to correlate surface friction and contact area changes with the system’s bending modulus. The numerical model is shown to be predictive and could be used in the future to evaluate designs of TIMs.