Construction of a Stable Organic–Inorganic Double‐Locked Interphase to Achieve Structural‐Functional Integration of Carbon Fiber/Epoxy ( CF / EP ) Composites

ABSTRACT The development of carbon fiber‐reinforced polymer (CFRP) with integrated structural and functional performance is essential for advanced engineering applications. However, due to weak interfacial bonding and the trade‐off between conductivity and mechanical properties, achieving both high mechanical strength and efficient electromagnetic interference (EMI) shielding in CFRP continues to be challenging. Here, a stable organic–inorganic double‐locked interphase was constructed to address this challenge. Co 3 O 4 nanosheets were in situ grown to serve as rigid anchors for mechanical interlocking and multiple reflections of electromagnetic waves, while a polyaniline (PANI) nanolayer was subsequently deposited as a flexible buffer to enhance interfacial compatibility and conductivity. Compared with CF/EP, CF‐Co1.5@PANI/EP exhibited increases of 71.3%, 76.5%, 64.8%, and 89.5% in flexural strength, ILSS, IFSS, and EMI shielding effectiveness, respectively. This enhancement arises from the double‐locked interphase, which not only shifts the dominant fracture mechanism to cohesive failure but also provides a conductive network enriched with mobile charge carriers to dissipate electromagnetic waves. This study offers an innovative approach for designing high‐performance multifunctional CFRP, demonstrating its potential for applications in unmanned aerial vehicles (UAVs) and other advanced engineering fields.