Multifunctional Carbon Fiber Composites via Interface-Engineered MXene-Polyurethane Hybrids: Synergistically Enhanced Mechanical, In Situ Damage Sensing, and EMI Shielding Properties

An organic–inorganic hybrid filler system comprising isocyanate-terminated polyurethane (PU) and hydroxyl-terminated MXene nanoplatelets was developed and incorporated into an epoxy (EP) matrix. The 0.1% MXene and 1% PU in the EP matrix resulted in a 25% and 60% increase in tensile and bending strength, respectively, compared to neat EP, attributed to the crack-pinning effect of MXene, shear yielding and plastic deformation of PU, and strong chemical bonding between PU and EP. Vacuum-assisted resin infusion (VARI) was used to infuse the modified EP into a carbon fiber (CF) preform, leading to a 104% and 79% improvement in bending strength and interlaminar shear strength (ILSS) for the 0.1%MXene-1%PU-EP/CF composite compared to the desized CF/EP. The uniform dispersion of conductive MXene nanosheets and the inherent conductivity of the CF skeleton resulted in a 123% and 25% increase in out-of-plane and in-plane electrical conductivity. The conductive MXene-PU hybrid network enabled highly sensitive and reliable in situ damage sensing capabilities. The 0.1%MXene-1%PU-EP/CF composite exhibited a maximum electromagnetic interference (EMI) shielding effectiveness (SE) of 27.8 dB, attributed to conductive loss, interfacial polarization, and dipole polarization mechanisms. This study demonstrates the effectiveness of hybridizing MXene and PU in simultaneously enhancing the mechanical, electrical, in situ damage sensing, and EMI shielding properties of carbon fiber reinforced polymer (CFRP) composites, providing valuable insights for future research in multifunctional composite materials.