Nacre-inspired hierarchical framework enables tough and impact-monitoring epoxy nanocomposites

Multifunctional epoxy nanocomposites hold great promise for artificial structural materials across civil, industrial, and aerospace fields but were severely impeded by catastrophic brittleness under damage and lack of chemical activity resulting from highly cross-linked networks, leading to poor toughness and absent functionality. Herein, we report a facile yet efficient strategy for fabrication of graphene-encapsulated natural rubber frameworks through nanogroove-based freeze-casting technology, leading to highly tough hierarchically biomimetic epoxy nanocomposites. As judiciously elucidated by physicochemical and morphological characterizations, graphene sheets encapsulated natural rubber were bidirectionally aligned through ice crystals expelled from oriented nanogrooved surface to build hierarchical layered architecture with nanoasperities. Moreover, notable crack deflection derived from the "brick-mortar" structure in epoxy composite and nanoasperities debonding at the interlocking "hard-soft-hard" interface dissipate large amount of energy during fracture process, resulting in boosted fracture toughness. Accordingly, a synergistic performance enhancement is achieved, i. e., more than 3.32-fold increase in fracture toughness at low rubber content (4.3 wt%), and efficient real-time impact self-monitoring and evaluation. This work investigated for the first time the role of grapheneencapsulated natural rubber framework with nanoasperities structure in the reinforcement of epoxy nanocomposites. The design approach outlines a way for high-toughness, multifunctional and long-lasting materials for various engineering applications.