Synergistic Interfacial Reinforcement via Modulus Gradient and Cation–π Interactions for Recyclable Carbon Fiber Composites

ABSTRACT The effectiveness of carbon fiber reinforced polymers (CFRPs) is frequently limited by stress concentration, which arises from the substantial modulus disparity between the reinforcing fibers and the polymer matrix. To overcome this limitation, a modulus gradient interphase was designed by constructing a zinc oxide nanosheet@zeolitic imidazolate framework‐8 (ZnO‐Ns@ZIF‐8) nanoarray on the fiber surface. This interphase not only alleviated the modulus gap between carbon fibers and the polymer matrix but also increased fiber surface roughness and chemical activity. Furthermore, an electron‐rich indole group was incorporated as a π‐system into the PHT resin (In‐PHT), enabling cation–π interactions with Zn ²⁺ in ZIF‐8 and thus synergistically enhancing interfacial adhesion. As a result, CF@ZnO‐Ns@ZIF‐8/In‐PHT exhibited a tensile strength improvement of 62% and a wear rate decrease of 41% relative to the untreated control sample. Additionally, the acid‐degradable In‐PHT matrix allowed closed‐loop recycling of the fibers without substantial performance loss. This study presents a novel approach for fabricating durable, wear‐resistant, and sustainable CFRPs, with a focus on achieving significantly improved interfacial bonding.