Optimizing dual-scale wettability of epoxy resin on large-tow carbon fiber via tension-driven capillary wicking

Benefiting from the cost-performance advantage, large-tow carbon fiber (LCF) is under the rapid development and shows great application potential in various products like wind turbine blade and hydrogen storage cylinder. However, the numerous and densely stacked monofilaments of LCF require further researches on wetting behavior, laying the foundation for improving the mechanical strength of composite. Here, the established strategy for optimizing the wettability of LCF at dual-scale reveals the microscopic wetting mechanism driven by surface energy and capillary wicking. Firstly, at microscale, the relationship between surface energy and dynamic wetting behavior of single fiber is accurately established by dynamic contact angle and molecular kinetic theory (MKT), and the positive correlation between wettability and interfacial strength is verified. At macroscale, the quantification of fiber bundle wettability is achieved by infiltration rate constant. Meanwhile, the overall wettability of fiber bundle is evaluated and improved through the capillary wicking theory and tension-driven optimization mechanism. Such mechanism is further validated by an increase in infiltration rate constant of 144.7% and composites tensile strength of 16.4%, demonstrating that tension-driven optimization mechanism opened viable opportunities and inspirations for the enhancement of mechanical properties in LCF reinforced polymers.