Multilayered Graphene‐ PyC ‐Graphene Interface for Enhanced Mechanical, Tribological, EMI Shielding and Thermal Management Properties of Carbon Fiber/Phenolic Composites

ABSTRACT Carbon fiber reinforced phenolic resin composites (CF/PR) are promising for multifunctional structural applications but are limited by weak fiber‐matrix interfacial bonding. Herein, we report an interface engineering strategy to tailor the fiber/matrix interphase by constructing a multilayered graphene–pyrolytic carbon–graphene (GE‐PyC‐GE) structure on the carbon fiber surface via sequential CVD processes. The effects of this designed interphase on the microstructure, mechanical properties, tribological behavior, EMI shielding performance, and thermal conductivity were systematically investigated. Results show that the GE‐PyC‐GE multilayered interphase significantly enhances fiber‐matrix interlocking and load transfer efficiency. Compared with unmodified composites, the tensile strength increased by 43%, while the wear rate decreased by 68%. The abundant interfaces promote multiple reflections of electromagnetic waves, yielding a 45% enhancement in EMI shielding effectiveness (reaching 37 dB) in the X‐band. Additionally, reduced interfacial thermal resistance leads to a 33% improvement in thermal conductivity. This work demonstrates an effective interface engineering strategy for developing high‐performance multifunctional carbon fiber composites.