Investigation of sizing materials for carbon fiber reinforced thermoplastic composites

For the manufacturing of mechanically strong and lightweight composite aerostructures reinforcement materials (e.g. carbon fibers, CFs) are the most convenient way. Therefore, sizing of carbon fibers is crucial for guiding them into service by protecting the CF’s surface. In this study, a novel sizing agent was developed and effects of this sizing on CFs’ physicochemical as well as surface properties were investigated. The impact on the fiber-matrix interphase behavior was analyzed. Results reveal that the surface free energy of CF was increased from 5.67 mJ/m² to 13.13 mJ/m² through sizing by enhancing the wettability property of CF. In addition, surface topography analyses indicate that the surface roughness Ra is 3.70 ± 2.59 nm for neat CF; 1.01 ± 0.65 nm for Polyetherimide (PEI) sized CF; and 1.71 ± 1.14 nm for PEI-Polyether ether ketone (PEEK) sized CF. Finally, it was concluded that an increment in the wettability can be related with chemical changes on the fiber’s surface.