Surface functionalization and CNT coating induced improved interfacial interactions of carbon fiber with polypropylene matrix: A molecular dynamics study

• MD used to assess impact of functionalization and CNT coating of carbon fibre (CF). • ‑NH 2 functionalized CF exhibited highest interaction energy than -OH and ‑COOH. • Pull-out simulations showed 126% increase in IFSS for 6 wt% ‑NH 2 functionalized CF. • Radial distributive function confirms interaction strength order: –NH 2 > –OH > –COOH. • ~112% increase in composite modulus with CNT coated 6 wt% ‑NH 2 functionalized CF. An in-depth study of interfacial interactions between carbon fiber (CF) and polypropylene (PP) matrix was carried out through a series of pull-out simulations using molecular dynamics (MD). CF surface was functionalized by grafting separately with 2, 4, and 6 wt% of –OH, –COOH and NH 2 groups to understand its impact on fiber–matrix interfacial properties. Besides CF grafting, the effect of carbon nanotube (CNT) presence on its surface, mimicking dip coating of CNTs over CF, was also studied. The addition of maleic anhydride-grafted-PP (MA-g-PP), was also investigated to assess its role in imparting interfacial interactions. Among the simulated composites, the one reinforced with 6 wt% –NH 2 grafted CF displayed a significant ~126% increase in IFSS compared to the composite having pristine CF, while the other reinforced with CNT coated and 6 wt% –NH 2 functionalized CF showed a ~112% increment. Composite with CNT coated CF alone exhibited IFSS ~35% higher than the composite with pristine CF. Furthermore, the Young’s and shear modulus of composites improved with both grafting percentage and CNT coating. Composite reinforced with CNT coated CF and CNT coated 6 wt% –NH 2 grafted CF displayed ~58 and ~112% increase in Young’s modulus compared to composite strengthened with pristine CF.