Due to carbon fiber's inherent structural properties, its weak interfacial bond with resin results in low interlaminar shear strength in untreated composites. Surface treatment is therefore essential. Primary methods include oxidation, deposition, electropolymerization, electrodeposition, and plasma treatment, detailed below.
Oxidation
Liquid-phase oxidation:
Direct medium oxidation: Complex process with high pollution; rarely used today.
Anodic oxidation: Industry-preferred method for effectiveness.
Gas-phase oxidation:
Simple and convenient but challenging to control.
Deposition
Performed in high-temperature environments, this method deposits metal halides as carbide films on fiber surfaces to achieve modification.
Electropolymerization
Carbon fiber acts as an anode in an electrolyte containing monomers (e.g., styrene, acrylonitrile). Generated radicals form macromolecular side chains on the fiber surface.
Electrodeposition
Similar to electropolymerization, this technique coats fibers with a polymer layer.
Plasma Treatment
Plasma types include thermal, non-thermal (most common), and hybrid plasma.
Core Purpose
Carbon fiber's smooth surface limits active bonding sites. Treatments apply coatings that create robust bonding interfaces with matrices, enhancing composite performance-a straightforward yet critical principle.
