Unveiling the role of carbon fiber modulus on interfacial crystallization and mechanical properties of LM-PAEK composites

During the composites forming process, the carbon fiber surface can serve as heterogeneous nucleation sites to induce the formation of unique interfacial crystallization structures-a critical factor determining the final interfacial properties and overall mechanical performance of composites. However, current research has primarily focused on standard modulus carbon fibers (SMCF) or single type fiber systems, while systematic investigations into how carbon fibers with different moduli regulate matrix crystallization behavior through their surface characteristics and consequently affect composite mechanical properties remain insufficient. This study investigates the influence of carbon fibers with varying moduli on the crystallization behavior of a self-developed low-melting temperature poly (aryl ether ketone) (LM-PAEK) matrix and the mechanical properties of its composites. The results demonstrate that the surface characteristics of carbon fibers exhibit synergistic effects with modulus dependent interfacial crystallization behavior, collectively determining the interfacial bonding strength and failure modes of the composites. Notably, while high modulus carbon fibers (HMCF) and ultrahigh modulus carbon fibers (UHMCF) promote the formation of transcrystalline (TC) layer, their enhanced surface chemical inertness leads to weakened chemical bonding interactions, and significant changes in fiber surface structure create a competitive relationship between physical and chemical interactions. By clarifying the intrinsic connection between fiber modulus, matrix crystallization characteristics, and mechanical performance, this study provides important theoretical support and practical guidance for the efficient utilization of high modulus carbon fibers in high-performance thermoplastic composites and the optimization of interfacial design.