Effect of Carbon Fiber Fabric Oxidation in Polyamide 6 Based Composites

Background: One of the major issues of carbon fiber reinforced polymeric composites is the weak interface between the phases, that supports crack propagation and leads to premature mechanical failure. The paper presents a study involving carbon fiber compatibilization with the polymeric matrix via oxidative treatment and the effect that the modified carbon fiber fabric has on the mechanical performance of its polyamide 6 composites.

Methods: Thermoplastic polyamide 6 matrix/fabric based composites are obtained using carbon fiber fabric that is oxidized using K2Cr2O7/H2SO4 mixture in different reaction conditions. The oxidized carbon fiber surface is analysed using FTIR spectroscopy and the composite materials are mechanically tested in terms of tensile and flexural properties, the fracture cross section is analyzed by SEM and optical microscopy to evaluate the interface and the fracture mode.

Results: FTIR spectroscopy showed that higher temperature oxidation generates more functional groups on the carbon fiber surface that are able to interact with the polymer, enhancing the interface strength. Tensile and flexural tests showed significant improvement of strength and stiffness when using surface oxidized carbon fabric, results owned to the excellent bonding between the matrix and the fibers that compose the fabric, illustrated by SEM and optical microscopy analysis.

Conclusion: The obtained results prove that carbon fiber oxidation in certain condition is efficient for achieving stronger fiber/themoplastic matrix interface, by creating hydrogen bonding sites that prevent delamination and are able to improve the mechanical performance of the composites.