Mechanical analysis of a growing carbon nanotube forest

Abstract

Carbon nanotube forests are vertically oriented and entangled tubes that grow normal to a given substrate. The excellent thermal, mechanical, and electronic properties of individual carbon nanotubes motivates their study. Herein, two and three dimensional finite element models are developed to perform a mechanical analysis and parametric growth studies of actively growing carbon nanotube forests. Nanotube growth rate distribution, orientation angle, and diameter are varied to examine their effects on the resulting forest morphology. Individual carbon nanotubes are modeled as linear frame elements interconnected at adjacent nodes. The van der Waals interaction between carbon nanotubes is modeled as bar elements. The fastest-growing carbon nanotube in the forest are restricted by surrounding tubes, thereby generating a compressive force that is transmitted to the base of the carbon nanotube. The slowest growing carbon nanotube transmits tensile forces. The simulated forest morphology exhibits a strong consistency with observed carbon nanotube forests whilst maintaining mechanical phenomena like buckling, translation and rotation as seen in electron micrographs. This modeling approach is a paradigm shift in the study of carbon nanotube forest growth mechanics and establishes a framework for further thermal and electrical analyses.