Balancing strength, ductility and multifunctionality in aluminum matrix composites (AMCs) represents a long-standing challenge because of the inherent trade-offs between mechanical performance and functional properties. Conventional reinforcement approaches using carbon nanotubes (CNTs) and graphene-based materials often suffer from agglomeration, weak interfacial bonding and insufficient load transfer, limiting their strengthening potential. To overcome these drawbacks, this study presents a gradient-laminated (GL) CNT + RGO hybrid/Al composite incorporating a 3D-interconnected hybrid network of CNTs and reduced graphene oxide (RGO) within a four-layer hierarchical design. This bio-inspired gradient architecture, fabricated by a dry-wet smart coating process followed by annealing, ensures uniform dispersion of the nanocarbon reinforcements and formation of robust interfacial bonds. The hybrid 3D CNT-RGO network not only strengthens the composite through improved load transfer, crack bridging and dislocation prevention, but also maintains high electrical and thermal conductivity by mitigating excessive electron and phonon scattering. As a result, the GL CNT + RGO hybrid/Al composite proposed in this study achieves a remarkable yield strength of ∼388 MPa, a tensile strength of ∼503 MPa and a uniform elongation of ∼22 %, significantly outperforming conventional AMCs. At room temperature, the composite exhibits a thermal conductivity of ∼280 W/m·K and an electrical conductivity of ∼88 % International Annealed Copper Standard (IACS), which decrease slightly to ∼ 260 W/m·K and 82 % IACS at 200 °C, demonstrating excellent multifunctional performance. The exceptional mechanical properties result from the synergistic strengthening mechanisms of grain boundary stabilization, high dislocation storage and optimized strengthening by nanocarbon networks. This study presents a scalable design strategy also integrating finite element simulations and experimental testing for next-generation high-performance AMCs, and provides a transformative route for applications requiring high strength, superior thermal management and excellent electrical conductivity, particularly in the aerospace, automotive and electronics industries.
