Fracture behavior of multi-phased nanomaterial reinforced interpenetrating polymeric composites

Interpenetrating phase composites (IPCs) rooting on triply periodic minimal surface architectures (TPMS) have attracted considerable attention owing to their exceptional mechanical properties. Fracture toughness under flexural loading is a critical parameter; however, it remains relatively underexplored for TPMS-based IPCs. In this work, IPCs incorporating a gyroid-structured TPMS lattice and a 2D-material-reinforced polymer matrix were fabricated via additive manufacturing, followed by an interpenetration process. 2D material fillers—MXene, graphene oxide, and graphene nanoplatelets—were individually incorporated into the polymer phase prior to the interpenetration process to fabricate 2D-material-reinforced IPCs (2D-IPCs). The resulting 2D-IPCs exhibited markedly superior fracture resistance compared to lattice/polymer IPCs. Comprehensive fractographic analysis was performed to elucidate the underlying fracture mechanisms. The findings indicate that the 2D‑IPCs exhibit hierarchical zigzag crack trajectories at three coupled scales—large (lattice‑guided), medium (epoxy‑mediated), and small (2D‑filler‑induced). TPMS architectures alter the crack propagation path, while the incorporated 2D materials activate additional toughening mechanisms during deformation, suppressing crack growth and promoting significant crack deflection—thereby enhancing material toughness. Furthermore, finite element modeling was employed to uncover the fracture initiation behavior in IPCs. This work provides new insights into tailoring the fracture properties of IPCs by engineering the reinforcement phase and optimizing constituent material properties.