A molecular dynamics assisted insight on the enhancement of interfacial adhesion of carbon fiber with polypropylene matrix via a combination of surface functionalization and defect laden carbon nanotube coating

The low compatibility of traditional carbon fibers with thermoplastics results in an inferior interfacial interaction. Therefore, it prohibits full exploitation of low-cost thermoplastics like polypropylene in developing high-strength carbon fiber reinforced composites. In the present study, atomistic and mesoscopic molecular dynamics simulations are carried out to postulate enhancement in interfacial shear strength among amine terminated carbon fiber and polypropylene. Pristine and amine functionalized carbon nanotubes are coated to the amine terminated carbon fiber separately. The influence of Stone-Wales and Di-vacancy defects of carbon nanotubes, with their varying defect concentration, is investigated. Besides, maleic anhydride-grafted-styrene ethylene butylene styrene is used as a compatibilizer. Interaction energy among maleic anhydride-grafted-styrene ethylene butylene styrene and amine terminated carbon nanotubes increases with amine weight percentage over carbon nanotube. The highest optimal interaction energy is shown by carbon nanotube functionalized with 6 wt percent amine groups and having 3 Stone-Wales defects, which is ∼41% higher than that with pristine carbon nanotubes. The pull-out coarse-grain simulations of the amine terminated carbon fiber coated with such optimal carbon nanotubes displayed the highest interfacial shear strength of 31.11 MPa, and it was ∼106% higher than the composite reinforced with neat carbon fiber.