Weakening effect of nickel catalyst particles on the mechanical strength of the carbon nanotube/carbon fiber junction

Carbon fiber reinforced composites have been accepted as a newly-developing structural material widely used in the automotive and aerospace industries owing to its lightweight and good mechanical performances. The growth of carbon nanotubes (CNTs), catalyzed by metal nanoparticles, on the fiber surface is a promising way to mitigate the stress concentration around the fibers but requires strong bonds between the tubes and the fiber surface. Yet, details regarding the fiber/CNT bonding remain largely unknown. In this work, ReaxFF based reactive molecular dynamic simulations have been performed to predict the grafting strength between single wall carbon nanotubes (SWCNTs) and graphene layers in the presence of pure and oxidized nickel nanoparticles. These multi-material interfaces were loaded in tension and mechanical properties were calculated. The system without nanoparticle shows the largest stress at failure whereas the presence of a pure nickel nanoparticle weakens the SWCNT/Graphene junction up to 50%, while the SWCNT/graphene junction remains strong in the presence of an oxidized nickel nanoparticle. A detailed analysis of the formation and breakage of chemical bonds between the carbon, oxygen, and nickel atoms during the tensile tests enables us to elucidate the roles of the nanoparticle on the failure mechanisms.

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