Effect of surface post-oxidation of epoxy-sized carbon fibre on interlaminar shear strength of the polyamide 66 composites

Epoxy-sized carbon fibre (ESCF) was modified by post-oxidation in air atmosphere at polyamide 66 matrix process temperature for enhancing the interfacial property of the composite. The influence of the post-oxidation on the fibre mechanical and bundling properties is negligible for protection of the reserved sizing. The optimal interlaminar shear strength value of the composite reinforced with the post-oxidation-modified ESCF for 15 min was remarkably enhanced to 80.4 MPa by 426%, compared to that reinforced with the pristine ESCF, and by 93% compared to that reinforced with nitrogen heat-treated ESCF. The interfacial property improvement is attributed to thermal stability improvement and newly generated functional groups of the carbon fibre surface, which not only improved the interaction between the fibre and sizing, but also enhanced the interfacial adhesion between the fibre and surrounding matrix.