Toughening by Design: Unveiling the Fracture Mechanisms of Nonlocal Lattice Materials

Abstract Lattice materials offer extraordinary opportunities for lightweight structural design, yet their practical application is often compromised by their propensity for brittle fracture originating from inherent defects. This study introduces a novel design strategy to overcome this limitation by incorporating nonlocal interactions into the lattice architecture. We investigate the fracture mechanics of two-dimensional lattice materials with and without nonlocal connections through a combination of finite element analysis and a node-based homogenization method. Our theoretical model accurately predicts the crack-tip displacement field, revealing significant deviations from classical continuum mechanics. The results strikingly demonstrate that nonlocal lattices exhibit superior stiffness, strength, and fracture toughness compared to their local counterparts. An energy-based analysis unveils the core toughening mechanism: nonlocal interactions effectively redistribute stress at the crack tip, leading to the formation of a larger plastic zone. This enhanced plasticity not only delays crack initiation by increasing the required energy for fracture but also elevates crack growth resistance by dissipating more energy during propagation. This work elucidates the fundamental role of nonlocality in enhancing fracture performance and provides a robust framework for designing tough, defect-tolerant lattice materials for high-performance applications.