Influence of Fiber Surface Treatment on Hydrothermal Aging Behavior of a Woven Thermoplastic Laminate

A detailed investigation on the effects of hydrothermal aging on the mechanical and thermal performance of woven carbon-fiber-reinforced polyamide 6 (CF/PA6) laminates processed using hot compression molding is presented. A surface treatment with a polyurethane dispersion (PUD) agent is applied on CFs to enhance the interfacial bonding capability between the CF and PA6 matrix. The moisture uptake results indicate that untreated CF/PA6 laminates exhibit higher equilibrium moisture absorption ( M ∞ ), corrected diffusion coefficient ( D C ), and rate of diffusion ( k ) than treated CF/PA6 laminates, implying that the interface damage of untreated CF/PA6 laminates is more pronounced than that of treated CF/PA6 laminates. The mechanical performance of the CF/PA6 laminates reduces significantly after water absorption and hydrothermal aging. Nevertheless, PUD-treated composites exhibit higher remaining flexural property than the virgin composites, due to the improved durability of CF/PA6 interface, as verified by the scanning electron microscopy results. Dynamic mechanical properties (i.e., T g , storage modulus, and tan δ) of the treated CF/PA6 laminates degrade more slowly than those of the untreated CF/PA6 laminates. Finally, the relationships between flexural property retention and moisture absorption ratio (i.e., M t / M ∞ ), and between flexural property retention and tan δ for both types of CF/PA6 laminates are established.