An interface-enhanced discrete element model (I-DEM) of bio-inspired flexible protective structures

Natural organisms have evolved protective structures that help them survive environmental threats without sacrificing flexibility. While the discrete element method (DEM) has been used to model bio-inspired flexible protective structures, existing DEM models struggle with modeling interactions between elements of complex geometries and finite deformation, making them unsuitable for describing interfacial interlocking and associated failure mechanisms observed in experiments. Here, we propose an interface-enhanced DEM (I-DEM) model that brings about a number of advantages over the existing methods. First, contact-induced geometric nonlinearity is incorporated via a nonlinear interaction function to model interfacial interlocking. Second, finite deformation of interfacial material is taken into account in modeling interfacial failure. Furthermore, contact detection and processing algorithms are utilized to model collision and post-contact behaviors. The utility of I-DEM is demonstrated in modeling bio-inspired flexible protective structures across three distinct interfaces, evidencing its broad applicability to varied interface geometries. FEM simulations of scaled armor structures with segmented helmet and space shield are performed to demonstrate an increase in computational efficiency of the proposed I-DEM model by about four orders of magnitude for static analysis and by two orders of magnitude for dynamic analysis, with numerical discrepancies within about 10%, compared to FEM.