Load-transfer and failure behaviors of crosslinked interfaces in collagen-mimic carbon nanotube bundles

194Weak interface has been a long-standing bottleneck critically hindering the exploitation of the ultra-high stiffness and strength of carbon nanotubes (CNTs) as reinforcement materials. Inspired by the structure of collagen fibril, a covalently cross-linked interface design for ultra-strong CNT bundles has attracted a lot of attentions. In the present paper, molecular dynamics simulations were conducted to systematically study the load-transfer capacity and failure behaviors of the crosslinked interface, including the influence of crosslink type (length), density, and interface length. We found that a small number of covalent crosslinks can significantly enhance the interface stiffness and strength. The shorter crosslinks usually yield higher interface stiffness while the longer crosslinks generally produce higher interface strength. There are three major failure modes unveiled as the crosslink density and interface length vary, namely the abrupt interface failure, the gradual interface failure and the CNT break. A forth failure mode was also seen upon an optimal interface design, in which bond breaks propagate simultaneously and gradually in crosslinked interfaces and CNTs. The optimal design is highly desired in engineering applications since it can simultaneously provide superior stiffness, strength and toughness. These findings provide useful insights into the interface design of high-performance CNT fibers.