Crosslink-tuned large-deformation behavior and fracture mode in buckypapers

Abstract

Strong physical and/or chemical inter-tube crosslinks play a vital role in carbon nanotube buckypapers and composites. However, both underlying mechanisms and regulation patterns remain poorly understood. Here, we employed the coarse-grained molecular dynamics simulations to investigate the nonlinear large-deformation behavior and the fracture mode of crosslinked buckypapers by considering both intrinsic intra- and inter-tube bond-breaking. A critical crosslink density ρc is found to divide the deformation mode of buckypaper into two regimes in uniaxial tension, i.e., the bending-dominated mode at ρ < ρc and the bending-stretching-bending three-stage one at ρ > ρc. This transition is attributed to the stress concentration and the intrinsic bond-breaking in large tensile deformations. In uniaxial compression, it is always bending-dominated, which is independent of crosslinks and compressive strain. Furthermore, there exists another critical crosslink density controlling the ductile-brittle transition of fracture mode of the strongly-crosslinked buckypaper, which is explained from the viewpoint of the collective hierarchical microstructural evolution. This study provides a profound understanding of crosslink effect on the buckypaper, which is of great significance for the optimization design and further practical applications of the promising material.