A nacre mimicking layered composite consisting of multilayer graphene (MLG) flakes and copper is fabricated in this study by a two‐step process including cementation reaction and Joule heating via spark plasma sintering (SPS). In situ cementation reaction deposits copper nanodroplets on activated graphene flakes with the aid of reducer Magnesium metal. The copper‐coated graphene flakes are subjected to pressure and localized Joule heating, resulting in a hierarchical 3D architecture comprising of uniformly aligned graphene flakes firmly bonded together by intermediate copper layers. The lamellar microstructure is characterized by a heterogeneous variation of elastic modulus. The impact of this hierarchical structure on the composite's mechanical behavior is explored by indentation loading, revealing a four‐fold increase in the load bearing ability of MLG/Cu hybrid as compared to MLG monolith. The Nacre‐inspired MLG‐Cu hybrid exhibits work of indentation ≈22.4 mJ, which is 500% improvement over MLG monolith (≈3.7 mJ). Copper deposition on graphene significantly improves the inter‐layer adhesion and restricts the sliding, pull‐out, and delamination of graphene flakes. The intimate interfacial contact between the constituent layers of the 3D hybrid facilitates effective stress‐transfer, thereby improving the overall load‐bearing ability. The novel processing route proposed here can be applied to other 2D materials for developing bioinspired 3D architectures with superior mechanical properties for a wide range of applications.

An electrostatic spraying technique was used to synthesize 3D graphene foam (GrF)‐reinforced polyurethane (PU) composites. Glass transition temperature (Tg) of PU increased from 120 to 148 °C after 3.3 vol% GrF addition. Strong interfacial bonding accounts for the improvement in Tg of PU‐GrF composites. Energy dissipation behavior is probed at multiple load scales to examine the intrinsic and structural damping characteristic. Micro‐scale damping at 1 mN and 1,000 Hz exhibited loss tangent value (tan δ), which is 200% higher and 3 times faster than PU. Nano dynamic mechanical analysis of PU‐3.3 vol% GrF composite demonstrated up to 383% tan δ improvement than of PU at 5 μN dynamic load. Physical mechanisms including rippling effect and weak van der Waals forces in graphene account for the high energy dissipation of PU‐GrF composite. This study suggests that PU‐GrF nanocomposites have the potential to serve as a good damping material in vibrating systems. POLYM. COMPOS., 40:E1862–E1870, 2019. © 2018 Society of Plastics Engineers

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