Abstract: The development of high-performance structural-functional composites capable of reconciling mechanical robustness with multifunctional integration remains a critical challenge. Inspired by the hierarchical structure of nacre layers, we have created flexible ternary composites featuring an interpenetrating three-dimensional (3D) network of MXene (Ti₃C₂T_x), graphene nanosheets (GNs), and aramid nanofibers (ANF). This multiscale strategy synergistically combines hydrogen bonding and a nacre-mimetic hierarchical structure with a 3D interpenetrating network, enabled by GNs for interfacial lubrication to overcome the strength-toughness trade-off while facilitating multifunctionality. The optimized MXene-GNs/ANF (60 wt% MXene-GNs, 50:50 ratio, 28 μm thickness) achieves exceptional mechanical properties: tensile strength of 175.10 ± 3.80 MPa, strain at break of 18.56 % ± 0.78 %, toughness of 15.88 ± 0.60 MJ m^-3. Simultaneously, it shows an electromagnetic interference shielding effectiveness (EMI SE) of 36.4 dB (8.2-12.4 GHz) and in-plane thermal conductivity (TC) of 11.58 W m^-1 K^-1. Increasing the thickness to 65 μm further enhances EMI SE to 40.2 dB and TC to 23.21 W m^-1 K^-1, outperforming most reported analogues. The composite also exhibits excellent thermal stability, with no significant weight loss below 558 °C in the N₂ atmosphere, as well as multifunctional properties such as rapid Joule heating (∼160 °C at 4 V), environmental resilience, and flame-retardant fire alert. By harmonizing interfacial interactions and hierarchical structuring, this work provides a scalable route to advanced flexible materials for next-generation wearable electronics and extreme-environment applications requiring integrated mechanical durability EMI shielding, and thermal management.

Key words: MXene, Graphene nanosheets, Mechanical properties, EMI shielding, Thermal conductivity