Constructing Multiscale Interfaces With External Flexibility and Internal Rigidity in Carbon Fiber Composites: A <scp>MOF</scp> ‐On‐ <scp>MXene</scp> In Situ Growth Approach

ABSTRACT MXene materials have shown considerable promise for application in fiber interface modification. However, current research remains largely focused on MXene deposition methods, with relatively little attention given to modification techniques for MXene materials. During MXene deposition, interlaced agglomeration often occurs, causing voids on carbon fibers and weakening composite interfacial properties. Therefore, modifying MXene to prevent interlayer bonding is essential for improving interfacial performance. This study combines flexible, multi‐active‐group CD‐MOF with high‐strength MXene via in situ growth, synthesizing a modified “soft‐exterior, rigid‐interior” MXene‐MOF hybrid. An APTES‐MOF‐MXene‐MOF interlayer was further constructed. Characterizations (XPS, Raman, SEM) confirmed that the interlayer introduced oxygen‐containing groups, enhancing surface activity, roughness, and resin infiltration. The alternating soft–rigid structure also alleviated the modulus mismatch between fiber and resin, reducing stress concentration. Mechanical tests showed that the interlayer improved interlaminar shear, flexural, and tensile strengths by 58.94%, 34.91%, and 18.55%, respectively, along with enhanced dynamic thermomechanical properties. Failure behavior and interfacial mechanisms were investigated, demonstrating that this approach effectively suppresses MXene agglomeration and significantly enhances interfacial performance, offering a viable strategy for CFRTP improvement.