Mechanical properties of carbon fiber reinforced epoxy resin treated by electrochemical process

ABSTRACT This research investigates the influence of electrochemical surface treatment on the mechanical properties of carbon fiber reinforced epoxy composites through systematic parameter optimization and comprehensive characterization. The study established optimal treatment conditions using ammonium bicarbonate electrolyte at 35°C, achieving enhanced interfacial properties through controlled surface modification. Surface characterization revealed the development of hierarchical surface features with primary grooves (0.5–1 μm width) and secondary nano-scale features (50–200 nm), accompanied by a significant increase in surface polarity from 0.20 to 0.41. XPS analysis demonstrated the successful introduction of oxygen-containing functional groups, with hydroxyl, carbonyl, and carboxyl groups showing particular prominence. The modification depth was confined to 200–300 nm, preserving the fiber’s core structure. Mechanical testing revealed substantial improvements in composite performance, evidenced by enhanced load transfer efficiency and a transition in failure modes. The treatment resulted in improved damage initiation stress (from 985 MPa to 1290 MPa) and initial linear modulus (from 135.2 GPa to 149.6 GPa). Additionally, the composite compressive modulus increased from 128.5 ± 3.8 GPa to 142.3 ± 4.2 GPa, representing a 10.7% improvement. Furthermore, surface roughness was significantly enhanced, with the arithmetic mean roughness (Ra) increasing from 8.2 ± 0.5 nm to 45.7 ± 2.3 nm.