Enhanced interphase between thermoplastic matrix and UHMWPE fiber sized with CNT-modified polydopamine coating

The fiber phase, matrix phase, and fiber/matrix interphase are different phases of fiber reinforced polymers (FRPs). FRP property such as mechanical strength is highly dependent on the adhesion level between the fiber and matrix for efficient load transfer. In this study, functionalized multiwalled carbon nanotubes (MWCNT) modified dopamine coating solution is coated on the fiber surface as additional sizing to enhance the interfacial bonding strength between ultra-high-molecular-weight polyethylene (UHMWPE) fiber and thermoplastic matrix (Elium®) which has resin infusion capability. The resultant of transverse fiber bundle tests shows that the polydopamine (PDA) coating of fiber with embedded 0.03% of MWCNT can improve the bonding strength of fiber/matrix about 42.50% compared with that of common composites. In contrast, the addition of carbon nanotubes into Elium® matrix shows a distinctly weaker bonding effect than the interphase between neat PDA coating and UHMWPE fiber. This discrepancy is because of densification of carbon nanotubes (CNT) forest grafted on the fiber surface during the nanocomposite coating process. When being compared to other surface modification process, CNT embedded dopamine surface modification is cost effective and less time consuming and has better performance than the modified matrix with the addition of CNTs.